1

Features and possible mechanisms of long range D

retention in PFMrsquos(based on investigations carried out in RF)

Presented by

Valery Kurnaev

7-10 May 2007

ITPA DIV SOL meeting 7-10 May 2007 Garching Germany

2

Contributions presented by

bull YuMartynenko BNKolbasov AASkovoroda ASpitsin Kurchatov Research Centre

bull AAirapetov LBegrambekov AGolubeva OFadina APisarev PShigin MEPhI

bull VAlimov Institute of Physical Chemistry RAS

3

The evidence of long range D retention

Polycrystalline amp mixed materials

Long range effect at ion implantation was seen more than 40 years ago MGuseva

6 keV D is captured in the hot rolled W at depth of several microns In single crystal W D ins not captured in the bulk VAlimov et al in Hydrogen and helium recycling at PFC ed by AHassanein Kluwer Academic Publishers 2002 p131-143

In the CVD coatings of W2C and WC exposed to the D plasma at Tgt 400 K D atoms diffuse into the bulk and accumulate to 2 at at depths of several micrometers VAlimov

Carbon based materials

Deep penetration of deuterium into carbon fibre composite CF222 (up to 2-3 mm) after exposure to the PISCES-A plasma- B Emmoth M Rubel E Franconi Nucl Fusion 30 (1990) 1140

Tritium depth profiles in divertor tiles of JET have revealed that in the 2D (two-dimensional) CFC tiles about 40 of tritium was retained at depths larger than 1 mm to only few percent found at these depths in the 4D CFC tile from TFTR R-D Penzhorn N Bekris U Berndt JP Coad H Ziegler W Naumlgele J Nucl Mater 288 (2001) 170 R-D Penzhorn JP Coad N Bekris L Doerr M Friedrich W Pilz Fus Eng Des 56amp57 (2001) 105 N Bekris CH Skinner U Berndt CA Gentile M Glugla B Schweigel J Nucl Mater 313-316 (2003) 501

4

Surer deep hydrogen penetration in vanadium alloy

Hydrogen isotopes penetrate through the 07 mm sample of V-349Ga alloy to the non irradiated backside after stationary pulsed power plasma and 6-keV ions irradiation

0 50 100 1500

5

10

15

20

2

1

Con

cent

rati

on a

t

Depth nm

Hydrogen concentration profiles in V-349Ga alloy after exposition in stationary plasmaof PLAST installation (D= 2∙1025 m-2 Т = 4500С Е = 100 eV)

1 ndash irradiated side 2 - backside

(ERDA 2-MeV He+)

Preprint 64527 Kurchatov Institute

5

0 50 100 1500

1

2

3

2

1

Depth nm

Con

cent

rati

on a

t

Deuterium concentration profiles in V-349Ga alloy after irradiation with pulsed deuterium plasma (15 pulses 028 MJm2) 1 ndash backside 2 ndash irradiated side 3- non irradiated(ERDA 2-MeV He+)

0 50 100 1500

5

10

15

3

2

1

Con

cent

rati

on a

t

Depth nm

Hydrogen concentration profiles in V-349Ga alloy after irradiation with 6-keV H+ ions in ion accelerator ILU at dose 10 1023 м-2 and target temperature Т = 4500С 1 ndash irradiated side 2 - backside 3 ndash non irradiates sample(ERDA 2-MeV He+)

Surer deep hydrogen penetration in vanadium alloy (2)

6

0

200

400c

0

200

400b

Depth m

0

200

400а

Mic

roh

ard

nes

s k

gm

m2

0 100 200 300 400 100 0

Microhardness as a function of depth measured on samples cross section after stationary plasma irradiation ( ndash irradiated side - back side - before irradiation) а) V-10Ti-6Cr-005Zr ndash irradiation time 20 min (D= 22 1024 m-2)b) V-10Ti-6Cr-005Zr ndash irradiation time 1 hour (D= 64 1024 m-2) c) V-15Ti-10Cr-005Y - irradiation time 1 hour (D= 64 1024 m-2)

Hydrogen irradiation induceddeep strengthening

Stationary pulsed power hydrogen plasma and 6-keV H+ ions irradiation results in deep strengthening ndash a reason is hydrates formation which create compressive stress in material

Preprint 64527 Kurchatov Institute

Before irradiation

backside

7

0 1 2 3 4 510-2

10-1

100

101

0 1 2 3 4 510-2

10-1

100

101

a)

W2C + 10 at C

200 eV D plasma CVD coatings 2x1024 Dm2

D c

on

ce

ntr

atio

n [a

t

]

Texp

= 373 K T

exp = 433 K

Texp

= 503 K

b)

WC + 10 at C

Texp

= 413 K T

exp = 543 K

Texp

= 653 K T

exp = 813 K

D c

on

ce

ntr

atio

n [a

t

]

Depth [m]

NRA analysis of CVD W2C amp WC coatings (VAlimov et al)

At temperatures above 550 K D concentration in the bulk starts to decrease

Presumably deuterium is retained in carbon precipitates

8

Mechanisms of long range D transportYuMartynenko et al

Shock wave initiation

ion

Cascade of displacements

defects

Physical interpretation connected with generation and transport of dislocation loops under influence of surface layer tension generation of thermoelastic tension and shock waves that force diffusion of admixtures along interstitials and grain borders

9

But physical mechanisms are far from full understanding

For adequate explanation versatile investigations using novel experimental methods as well as intimate theoretical analysis are necessary

For chemical active C based materials with compound structure (CFC) the task is much more complicated and need very careful investigations

10

0 2 4 6 8 1010-3

10-2

10-1

100

101 200 eV D plasma CFC NB31 2x1024 Dm2

Texp

= 463 K T

exp = 673 K

Texp

= 773 K T

exp = 948 K

D c

once

ntra

tion

[at

]

Depth [m]

0( ) [1 erf( )]2

xC x C

Dt

Migration in the bulk obeys diffusion equation with D=D(Fluence Temp)

10 15 20 25 3010-17

10-15

10-13

10-11

10-9

10-7

NB31 200 eV D plasma (Magnetron)

Coe

ffici

ent o

f D m

igra

tion

[m2 s

]

1000Temperature [K-1]

LA Sedano et al (1998) NB11 Matrix N11 Matrix NB11 Fibres N11 Fibres

Values for the deuterium migration derived from the D depth profiles are in good agreement with data for intrinsic hydrogen diffusivity in the fibres Migration through pores along fibres with low activation energy may be considered as mechanism of deuterium penetration into the bulk of the CFC materials

Channels of D transport in CFC VAlimov et al

11

Fine grain graphite (as well as CFC) ndashtransparent for gases in principle

Penetrating gas flow via gas pressure for MPG-8 graphite (thickness 126 mm diameter 305 mm)

room temperature

Measured gas flux density j ~ σ P σ Ad

P ndashpressure A ndasharea d- thickness σ ndash specific gas permeability

σ = 5middot1015 mols for MPG-8

Flu

x m

ols

Pressure Pa

Graphite sheet behaves as capillary A=1m2 d =1cm P =1Pa 35middot1017 D2s

12

Influence of tokamak T-10 exposure on MPG-8 graphite permeability

MPG-8 membrane 18 mm thick cut off T-10 limiter demonstrated hydrogen permeability ~9middot1015 molmiddotc-1m-1Pa-1 - 2 times more than for ldquovirginrdquo graphite

Possible reason ndash graphite porosity increase after long term expose in tokamak

All attempts to increase MPG-8 permeability in lab plasma experiments failed

4 mm

Place of limiter tile used for the membrane

14

Comparison of lab experiments and tokamak exposed tile retention in CFC

TDS investigation of the samples CFC N11 implanted by deuterium ions in the laboratory setups (MEPhI) and high field side tile of Tore Supra

[1] Begrambekov L Brosset C Bucalossi J Delchambre E Gunn JP Grisolia C Lipa M Loarer T Mitteau R PMoner-Garbet P Pascal J-Y PShigin P Titov N Tsitrone E Vergazov S Zakharov A ldquoSurface modification and hydrogen isotope retention in CFC during plasma irradiation in the Tore Supra tokamakrdquo17th Internal Conference on Plasma Surface Interactions in Controlled Fusion Devices (PSI17) Hefei China May 22 ndash 26 2006

LABORATORY SAMPLE

TORE SUPRA TILE [1]

Particles deuterons deuterons

Ion energy 50 100 200

500 eV

10-100 eV (as well as low energy atoms molecules and charge exchange neutrals )

Ion flux density 1times1020 atm2s (1-2)times1019 atm2s

Fluence 5times1023 atm2 5times1023 atm2 (estimated)

Surface temperature 450-470 K up to 500-600 K

Retention ~07times1021 atm2 ~2times1022 atm2 (30 times higher)

15

Hydrogen retention via fluence in lab exp

1021 1022 1023 1024 10251020

1021

1022

Hyd

roge

n re

tent

ion

at

m2

Fluence atm2

B4C 100 eVH MPG-8 100 eVH MPG-8 1 keVH HPG99 1 keVH [1] HOPG 100 eVH HOPG 1 keVH

Ion flux density = 35x1020 at(secm2)

[2] L Begrambekov O Buzhinsky A Gordeev E Miljaeva P Leikin P Shigin TDS investigation of hydrogen retention in graphites and carbon based materials Physica scripta N108 (2004) p72-75

Possible underestimation of tokamak tile irradiation fluence hardly could seriously influence the presented data -hydrogen retention will not increase 30 times even for ~100 times higher fluence

16

Possible mechanisms of enhanced D

trapping under tokamak plasma irradiation

1 Presence of hydrogen in the Tore Supra tiles

TDS spectra of H2 and D2 for the as prepared CFC N11 samples irradiated in deuterium plasma

Ei = 100 eVat

Ji = 121020 atm2s

Ф = 451023 atm2

Presence of hydrogen in the CFC twice increases deuterium trapping at the expense of filling the hydrogen traps by deuterium due to isotope

exchange mechanism

Lab experiment

17

2 Trapping of deuterium activated by electron irradiation

[ Collaboration DRFC CEA-Cadarache ndash MEPhI ROSATOM 2007]

Thermal desorption of deuterium as D2

and as CD4 from CFC graphite under

ion and electron irradiationEi=100 eVat Ji=121020 atm2s

Ф=451023 atm2

Increase of deuterium retention along with irradiation time as well as deuterium retention under electron irradiation support an assumption about participation of D2

molecules from surrounding atmosphere in deuterium trapping into graphites Ion and electron irradiation act as a driving forces of the process

Plasma electron irradiation of CFC increased deuterium trapping 12 ndash 3 times depending on energy distribution of impinging deuterium particles

0 200 400 600 800 100000

05

10

15

Ret

entio

n x

1017

at

cm2

Energy eVat

CFC D2 (1020)

D2 electron irr

CFC D2 (2x1019)

electronirradiation

18

3 Transportation of deuterium into the material and trapping in the bulk of the tile

TDS analysis of the samples cut from different depth of the tile shows that more 10 of cumulative trapping collected in the bulk of tile

The samples of 1 ndash 2 mm thickness are usually used in the laboratory experiments The laboratory results could be compared

only to trapping in surface region of tokamak tile

4 Deuterium trapping in graphites irradiated by ion flux with wide energy distribution

Peculiarities of deuterium trapping in graphites exposed to plasma allows to expect an enhancement of retention in graphites irradiated by ion flux with wide energy distribution in tokamaks in comparison with graphites subjected to mono energy ion irradiation in laboratory

setups

19

5 Graphite surface irradiation during Helium Glow Discharge Conditioning

Helium ion bombardment leads to development of the surface relief and destruction of near surface layer As result trapping of deuterium during tokamak discharges should be enhanced

6 Graphite surface irradiation by oxygen impurities

Graphite irradiation by ions and atoms of oxygen impurities leads to accelerated surface destruction and develop the surface As a result trapping of deuterium ions and neutrals by graphite surface is probably more enhanced

20

Conclusion

bull The long range D retention in general is the very complicated physical (amp chemical) problem Many observed features of this phenomenon is not clear now

bull Complex and multiple-factor impact of PFM in tokamaks makes difficult distinguishing its influence on the LR hydrogen isotopes retention

bull Laboratory experiments with well defined impact parameters are crucially necessary

bull During last two years we mounted and calibrated a series of high vacuum installations with well controlled parameters for measurement of D retention in plasma exposed (as well in situ in simulators) samples and started comparative studies of samples radiated at different tokamaks and laboratory installations

21

Plansbull Investigations of samples irradiated in LENTA PR-2

PIN laboratory plasma facilities as well as in T-10 TEXTOR and Tore Supra tokamaks are now in progress

bull As there is very large scattering of the experimental data

on D retention careful measurements at D retention via fluxes (at high fluxes) and temperature in different irradiation facilities are under way

bull To pick up contribution of different factors on D retention step by step experimental investigations at varying definite factors (im flux density consequent and simultaneous irradiation with deuterium and helium broad energy spectra influence etc) are planned

bull Experimental measurements of neutron irradiation influence on hydrogen isotopes retention in PFM is now discussed

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21

2

Contributions presented by

bull YuMartynenko BNKolbasov AASkovoroda ASpitsin Kurchatov Research Centre

bull AAirapetov LBegrambekov AGolubeva OFadina APisarev PShigin MEPhI

bull VAlimov Institute of Physical Chemistry RAS

3

The evidence of long range D retention

Polycrystalline amp mixed materials

Long range effect at ion implantation was seen more than 40 years ago MGuseva

6 keV D is captured in the hot rolled W at depth of several microns In single crystal W D ins not captured in the bulk VAlimov et al in Hydrogen and helium recycling at PFC ed by AHassanein Kluwer Academic Publishers 2002 p131-143

In the CVD coatings of W2C and WC exposed to the D plasma at Tgt 400 K D atoms diffuse into the bulk and accumulate to 2 at at depths of several micrometers VAlimov

Carbon based materials

Deep penetration of deuterium into carbon fibre composite CF222 (up to 2-3 mm) after exposure to the PISCES-A plasma- B Emmoth M Rubel E Franconi Nucl Fusion 30 (1990) 1140

Tritium depth profiles in divertor tiles of JET have revealed that in the 2D (two-dimensional) CFC tiles about 40 of tritium was retained at depths larger than 1 mm to only few percent found at these depths in the 4D CFC tile from TFTR R-D Penzhorn N Bekris U Berndt JP Coad H Ziegler W Naumlgele J Nucl Mater 288 (2001) 170 R-D Penzhorn JP Coad N Bekris L Doerr M Friedrich W Pilz Fus Eng Des 56amp57 (2001) 105 N Bekris CH Skinner U Berndt CA Gentile M Glugla B Schweigel J Nucl Mater 313-316 (2003) 501

4

Surer deep hydrogen penetration in vanadium alloy

Hydrogen isotopes penetrate through the 07 mm sample of V-349Ga alloy to the non irradiated backside after stationary pulsed power plasma and 6-keV ions irradiation

0 50 100 1500

5

10

15

20

2

1

Con

cent

rati

on a

t

Depth nm

Hydrogen concentration profiles in V-349Ga alloy after exposition in stationary plasmaof PLAST installation (D= 2∙1025 m-2 Т = 4500С Е = 100 eV)

1 ndash irradiated side 2 - backside

(ERDA 2-MeV He+)

Preprint 64527 Kurchatov Institute

5

0 50 100 1500

1

2

3

2

1

Depth nm

Con

cent

rati

on a

t

Deuterium concentration profiles in V-349Ga alloy after irradiation with pulsed deuterium plasma (15 pulses 028 MJm2) 1 ndash backside 2 ndash irradiated side 3- non irradiated(ERDA 2-MeV He+)

0 50 100 1500

5

10

15

3

2

1

Con

cent

rati

on a

t

Depth nm

Hydrogen concentration profiles in V-349Ga alloy after irradiation with 6-keV H+ ions in ion accelerator ILU at dose 10 1023 м-2 and target temperature Т = 4500С 1 ndash irradiated side 2 - backside 3 ndash non irradiates sample(ERDA 2-MeV He+)

Surer deep hydrogen penetration in vanadium alloy (2)

6

0

200

400c

0

200

400b

Depth m

0

200

400а

Mic

roh

ard

nes

s k

gm

m2

0 100 200 300 400 100 0

Microhardness as a function of depth measured on samples cross section after stationary plasma irradiation ( ndash irradiated side - back side - before irradiation) а) V-10Ti-6Cr-005Zr ndash irradiation time 20 min (D= 22 1024 m-2)b) V-10Ti-6Cr-005Zr ndash irradiation time 1 hour (D= 64 1024 m-2) c) V-15Ti-10Cr-005Y - irradiation time 1 hour (D= 64 1024 m-2)

Hydrogen irradiation induceddeep strengthening

Stationary pulsed power hydrogen plasma and 6-keV H+ ions irradiation results in deep strengthening ndash a reason is hydrates formation which create compressive stress in material

Preprint 64527 Kurchatov Institute

Before irradiation

backside

7

0 1 2 3 4 510-2

10-1

100

101

0 1 2 3 4 510-2

10-1

100

101

a)

W2C + 10 at C

200 eV D plasma CVD coatings 2x1024 Dm2

D c

on

ce

ntr

atio

n [a

t

]

Texp

= 373 K T

exp = 433 K

Texp

= 503 K

b)

WC + 10 at C

Texp

= 413 K T

exp = 543 K

Texp

= 653 K T

exp = 813 K

D c

on

ce

ntr

atio

n [a

t

]

Depth [m]

NRA analysis of CVD W2C amp WC coatings (VAlimov et al)

At temperatures above 550 K D concentration in the bulk starts to decrease

Presumably deuterium is retained in carbon precipitates

8

Mechanisms of long range D transportYuMartynenko et al

Shock wave initiation

ion

Cascade of displacements

defects

Physical interpretation connected with generation and transport of dislocation loops under influence of surface layer tension generation of thermoelastic tension and shock waves that force diffusion of admixtures along interstitials and grain borders

9

But physical mechanisms are far from full understanding

For adequate explanation versatile investigations using novel experimental methods as well as intimate theoretical analysis are necessary

For chemical active C based materials with compound structure (CFC) the task is much more complicated and need very careful investigations

10

0 2 4 6 8 1010-3

10-2

10-1

100

101 200 eV D plasma CFC NB31 2x1024 Dm2

Texp

= 463 K T

exp = 673 K

Texp

= 773 K T

exp = 948 K

D c

once

ntra

tion

[at

]

Depth [m]

0( ) [1 erf( )]2

xC x C

Dt

Migration in the bulk obeys diffusion equation with D=D(Fluence Temp)

10 15 20 25 3010-17

10-15

10-13

10-11

10-9

10-7

NB31 200 eV D plasma (Magnetron)

Coe

ffici

ent o

f D m

igra

tion

[m2 s

]

1000Temperature [K-1]

LA Sedano et al (1998) NB11 Matrix N11 Matrix NB11 Fibres N11 Fibres

Values for the deuterium migration derived from the D depth profiles are in good agreement with data for intrinsic hydrogen diffusivity in the fibres Migration through pores along fibres with low activation energy may be considered as mechanism of deuterium penetration into the bulk of the CFC materials

Channels of D transport in CFC VAlimov et al

11

Fine grain graphite (as well as CFC) ndashtransparent for gases in principle

Penetrating gas flow via gas pressure for MPG-8 graphite (thickness 126 mm diameter 305 mm)

room temperature

Measured gas flux density j ~ σ P σ Ad

P ndashpressure A ndasharea d- thickness σ ndash specific gas permeability

σ = 5middot1015 mols for MPG-8

Flu

x m

ols

Pressure Pa

Graphite sheet behaves as capillary A=1m2 d =1cm P =1Pa 35middot1017 D2s

12

Influence of tokamak T-10 exposure on MPG-8 graphite permeability

MPG-8 membrane 18 mm thick cut off T-10 limiter demonstrated hydrogen permeability ~9middot1015 molmiddotc-1m-1Pa-1 - 2 times more than for ldquovirginrdquo graphite

Possible reason ndash graphite porosity increase after long term expose in tokamak

All attempts to increase MPG-8 permeability in lab plasma experiments failed

4 mm

Place of limiter tile used for the membrane

14

Comparison of lab experiments and tokamak exposed tile retention in CFC

TDS investigation of the samples CFC N11 implanted by deuterium ions in the laboratory setups (MEPhI) and high field side tile of Tore Supra

[1] Begrambekov L Brosset C Bucalossi J Delchambre E Gunn JP Grisolia C Lipa M Loarer T Mitteau R PMoner-Garbet P Pascal J-Y PShigin P Titov N Tsitrone E Vergazov S Zakharov A ldquoSurface modification and hydrogen isotope retention in CFC during plasma irradiation in the Tore Supra tokamakrdquo17th Internal Conference on Plasma Surface Interactions in Controlled Fusion Devices (PSI17) Hefei China May 22 ndash 26 2006

LABORATORY SAMPLE

TORE SUPRA TILE [1]

Particles deuterons deuterons

Ion energy 50 100 200

500 eV

10-100 eV (as well as low energy atoms molecules and charge exchange neutrals )

Ion flux density 1times1020 atm2s (1-2)times1019 atm2s

Fluence 5times1023 atm2 5times1023 atm2 (estimated)

Surface temperature 450-470 K up to 500-600 K

Retention ~07times1021 atm2 ~2times1022 atm2 (30 times higher)

15

Hydrogen retention via fluence in lab exp

1021 1022 1023 1024 10251020

1021

1022

Hyd

roge

n re

tent

ion

at

m2

Fluence atm2

B4C 100 eVH MPG-8 100 eVH MPG-8 1 keVH HPG99 1 keVH [1] HOPG 100 eVH HOPG 1 keVH

Ion flux density = 35x1020 at(secm2)

[2] L Begrambekov O Buzhinsky A Gordeev E Miljaeva P Leikin P Shigin TDS investigation of hydrogen retention in graphites and carbon based materials Physica scripta N108 (2004) p72-75

Possible underestimation of tokamak tile irradiation fluence hardly could seriously influence the presented data -hydrogen retention will not increase 30 times even for ~100 times higher fluence

16

Possible mechanisms of enhanced D

trapping under tokamak plasma irradiation

1 Presence of hydrogen in the Tore Supra tiles

TDS spectra of H2 and D2 for the as prepared CFC N11 samples irradiated in deuterium plasma

Ei = 100 eVat

Ji = 121020 atm2s

Ф = 451023 atm2

Presence of hydrogen in the CFC twice increases deuterium trapping at the expense of filling the hydrogen traps by deuterium due to isotope

exchange mechanism

Lab experiment

17

2 Trapping of deuterium activated by electron irradiation

[ Collaboration DRFC CEA-Cadarache ndash MEPhI ROSATOM 2007]

Thermal desorption of deuterium as D2

and as CD4 from CFC graphite under

ion and electron irradiationEi=100 eVat Ji=121020 atm2s

Ф=451023 atm2

Increase of deuterium retention along with irradiation time as well as deuterium retention under electron irradiation support an assumption about participation of D2

molecules from surrounding atmosphere in deuterium trapping into graphites Ion and electron irradiation act as a driving forces of the process

Plasma electron irradiation of CFC increased deuterium trapping 12 ndash 3 times depending on energy distribution of impinging deuterium particles

0 200 400 600 800 100000

05

10

15

Ret

entio

n x

1017

at

cm2

Energy eVat

CFC D2 (1020)

D2 electron irr

CFC D2 (2x1019)

electronirradiation

18

3 Transportation of deuterium into the material and trapping in the bulk of the tile

TDS analysis of the samples cut from different depth of the tile shows that more 10 of cumulative trapping collected in the bulk of tile

The samples of 1 ndash 2 mm thickness are usually used in the laboratory experiments The laboratory results could be compared

only to trapping in surface region of tokamak tile

4 Deuterium trapping in graphites irradiated by ion flux with wide energy distribution

Peculiarities of deuterium trapping in graphites exposed to plasma allows to expect an enhancement of retention in graphites irradiated by ion flux with wide energy distribution in tokamaks in comparison with graphites subjected to mono energy ion irradiation in laboratory

setups

19

5 Graphite surface irradiation during Helium Glow Discharge Conditioning

Helium ion bombardment leads to development of the surface relief and destruction of near surface layer As result trapping of deuterium during tokamak discharges should be enhanced

6 Graphite surface irradiation by oxygen impurities

Graphite irradiation by ions and atoms of oxygen impurities leads to accelerated surface destruction and develop the surface As a result trapping of deuterium ions and neutrals by graphite surface is probably more enhanced

20

Conclusion

bull The long range D retention in general is the very complicated physical (amp chemical) problem Many observed features of this phenomenon is not clear now

bull Complex and multiple-factor impact of PFM in tokamaks makes difficult distinguishing its influence on the LR hydrogen isotopes retention

bull Laboratory experiments with well defined impact parameters are crucially necessary

bull During last two years we mounted and calibrated a series of high vacuum installations with well controlled parameters for measurement of D retention in plasma exposed (as well in situ in simulators) samples and started comparative studies of samples radiated at different tokamaks and laboratory installations

21

Plansbull Investigations of samples irradiated in LENTA PR-2

PIN laboratory plasma facilities as well as in T-10 TEXTOR and Tore Supra tokamaks are now in progress

bull As there is very large scattering of the experimental data

on D retention careful measurements at D retention via fluxes (at high fluxes) and temperature in different irradiation facilities are under way

bull To pick up contribution of different factors on D retention step by step experimental investigations at varying definite factors (im flux density consequent and simultaneous irradiation with deuterium and helium broad energy spectra influence etc) are planned

bull Experimental measurements of neutron irradiation influence on hydrogen isotopes retention in PFM is now discussed

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21

3

The evidence of long range D retention

Polycrystalline amp mixed materials

Long range effect at ion implantation was seen more than 40 years ago MGuseva

6 keV D is captured in the hot rolled W at depth of several microns In single crystal W D ins not captured in the bulk VAlimov et al in Hydrogen and helium recycling at PFC ed by AHassanein Kluwer Academic Publishers 2002 p131-143

In the CVD coatings of W2C and WC exposed to the D plasma at Tgt 400 K D atoms diffuse into the bulk and accumulate to 2 at at depths of several micrometers VAlimov

Carbon based materials

Deep penetration of deuterium into carbon fibre composite CF222 (up to 2-3 mm) after exposure to the PISCES-A plasma- B Emmoth M Rubel E Franconi Nucl Fusion 30 (1990) 1140

Tritium depth profiles in divertor tiles of JET have revealed that in the 2D (two-dimensional) CFC tiles about 40 of tritium was retained at depths larger than 1 mm to only few percent found at these depths in the 4D CFC tile from TFTR R-D Penzhorn N Bekris U Berndt JP Coad H Ziegler W Naumlgele J Nucl Mater 288 (2001) 170 R-D Penzhorn JP Coad N Bekris L Doerr M Friedrich W Pilz Fus Eng Des 56amp57 (2001) 105 N Bekris CH Skinner U Berndt CA Gentile M Glugla B Schweigel J Nucl Mater 313-316 (2003) 501

4

Surer deep hydrogen penetration in vanadium alloy

Hydrogen isotopes penetrate through the 07 mm sample of V-349Ga alloy to the non irradiated backside after stationary pulsed power plasma and 6-keV ions irradiation

0 50 100 1500

5

10

15

20

2

1

Con

cent

rati

on a

t

Depth nm

Hydrogen concentration profiles in V-349Ga alloy after exposition in stationary plasmaof PLAST installation (D= 2∙1025 m-2 Т = 4500С Е = 100 eV)

1 ndash irradiated side 2 - backside

(ERDA 2-MeV He+)

Preprint 64527 Kurchatov Institute

5

0 50 100 1500

1

2

3

2

1

Depth nm

Con

cent

rati

on a

t

Deuterium concentration profiles in V-349Ga alloy after irradiation with pulsed deuterium plasma (15 pulses 028 MJm2) 1 ndash backside 2 ndash irradiated side 3- non irradiated(ERDA 2-MeV He+)

0 50 100 1500

5

10

15

3

2

1

Con

cent

rati

on a

t

Depth nm

Hydrogen concentration profiles in V-349Ga alloy after irradiation with 6-keV H+ ions in ion accelerator ILU at dose 10 1023 м-2 and target temperature Т = 4500С 1 ndash irradiated side 2 - backside 3 ndash non irradiates sample(ERDA 2-MeV He+)

Surer deep hydrogen penetration in vanadium alloy (2)

6

0

200

400c

0

200

400b

Depth m

0

200

400а

Mic

roh

ard

nes

s k

gm

m2

0 100 200 300 400 100 0

Microhardness as a function of depth measured on samples cross section after stationary plasma irradiation ( ndash irradiated side - back side - before irradiation) а) V-10Ti-6Cr-005Zr ndash irradiation time 20 min (D= 22 1024 m-2)b) V-10Ti-6Cr-005Zr ndash irradiation time 1 hour (D= 64 1024 m-2) c) V-15Ti-10Cr-005Y - irradiation time 1 hour (D= 64 1024 m-2)

Hydrogen irradiation induceddeep strengthening

Stationary pulsed power hydrogen plasma and 6-keV H+ ions irradiation results in deep strengthening ndash a reason is hydrates formation which create compressive stress in material

Preprint 64527 Kurchatov Institute

Before irradiation

backside

7

0 1 2 3 4 510-2

10-1

100

101

0 1 2 3 4 510-2

10-1

100

101

a)

W2C + 10 at C

200 eV D plasma CVD coatings 2x1024 Dm2

D c

on

ce

ntr

atio

n [a

t

]

Texp

= 373 K T

exp = 433 K

Texp

= 503 K

b)

WC + 10 at C

Texp

= 413 K T

exp = 543 K

Texp

= 653 K T

exp = 813 K

D c

on

ce

ntr

atio

n [a

t

]

Depth [m]

NRA analysis of CVD W2C amp WC coatings (VAlimov et al)

At temperatures above 550 K D concentration in the bulk starts to decrease

Presumably deuterium is retained in carbon precipitates

8

Mechanisms of long range D transportYuMartynenko et al

Shock wave initiation

ion

Cascade of displacements

defects

Physical interpretation connected with generation and transport of dislocation loops under influence of surface layer tension generation of thermoelastic tension and shock waves that force diffusion of admixtures along interstitials and grain borders

9

But physical mechanisms are far from full understanding

For adequate explanation versatile investigations using novel experimental methods as well as intimate theoretical analysis are necessary

For chemical active C based materials with compound structure (CFC) the task is much more complicated and need very careful investigations

10

0 2 4 6 8 1010-3

10-2

10-1

100

101 200 eV D plasma CFC NB31 2x1024 Dm2

Texp

= 463 K T

exp = 673 K

Texp

= 773 K T

exp = 948 K

D c

once

ntra

tion

[at

]

Depth [m]

0( ) [1 erf( )]2

xC x C

Dt

Migration in the bulk obeys diffusion equation with D=D(Fluence Temp)

10 15 20 25 3010-17

10-15

10-13

10-11

10-9

10-7

NB31 200 eV D plasma (Magnetron)

Coe

ffici

ent o

f D m

igra

tion

[m2 s

]

1000Temperature [K-1]

LA Sedano et al (1998) NB11 Matrix N11 Matrix NB11 Fibres N11 Fibres

Values for the deuterium migration derived from the D depth profiles are in good agreement with data for intrinsic hydrogen diffusivity in the fibres Migration through pores along fibres with low activation energy may be considered as mechanism of deuterium penetration into the bulk of the CFC materials

Channels of D transport in CFC VAlimov et al

11

Fine grain graphite (as well as CFC) ndashtransparent for gases in principle

Penetrating gas flow via gas pressure for MPG-8 graphite (thickness 126 mm diameter 305 mm)

room temperature

Measured gas flux density j ~ σ P σ Ad

P ndashpressure A ndasharea d- thickness σ ndash specific gas permeability

σ = 5middot1015 mols for MPG-8

Flu

x m

ols

Pressure Pa

Graphite sheet behaves as capillary A=1m2 d =1cm P =1Pa 35middot1017 D2s

12

Influence of tokamak T-10 exposure on MPG-8 graphite permeability

MPG-8 membrane 18 mm thick cut off T-10 limiter demonstrated hydrogen permeability ~9middot1015 molmiddotc-1m-1Pa-1 - 2 times more than for ldquovirginrdquo graphite

Possible reason ndash graphite porosity increase after long term expose in tokamak

All attempts to increase MPG-8 permeability in lab plasma experiments failed

4 mm

Place of limiter tile used for the membrane

14

Comparison of lab experiments and tokamak exposed tile retention in CFC

TDS investigation of the samples CFC N11 implanted by deuterium ions in the laboratory setups (MEPhI) and high field side tile of Tore Supra

[1] Begrambekov L Brosset C Bucalossi J Delchambre E Gunn JP Grisolia C Lipa M Loarer T Mitteau R PMoner-Garbet P Pascal J-Y PShigin P Titov N Tsitrone E Vergazov S Zakharov A ldquoSurface modification and hydrogen isotope retention in CFC during plasma irradiation in the Tore Supra tokamakrdquo17th Internal Conference on Plasma Surface Interactions in Controlled Fusion Devices (PSI17) Hefei China May 22 ndash 26 2006

LABORATORY SAMPLE

TORE SUPRA TILE [1]

Particles deuterons deuterons

Ion energy 50 100 200

500 eV

10-100 eV (as well as low energy atoms molecules and charge exchange neutrals )

Ion flux density 1times1020 atm2s (1-2)times1019 atm2s

Fluence 5times1023 atm2 5times1023 atm2 (estimated)

Surface temperature 450-470 K up to 500-600 K

Retention ~07times1021 atm2 ~2times1022 atm2 (30 times higher)

15

Hydrogen retention via fluence in lab exp

1021 1022 1023 1024 10251020

1021

1022

Hyd

roge

n re

tent

ion

at

m2

Fluence atm2

B4C 100 eVH MPG-8 100 eVH MPG-8 1 keVH HPG99 1 keVH [1] HOPG 100 eVH HOPG 1 keVH

Ion flux density = 35x1020 at(secm2)

[2] L Begrambekov O Buzhinsky A Gordeev E Miljaeva P Leikin P Shigin TDS investigation of hydrogen retention in graphites and carbon based materials Physica scripta N108 (2004) p72-75

Possible underestimation of tokamak tile irradiation fluence hardly could seriously influence the presented data -hydrogen retention will not increase 30 times even for ~100 times higher fluence

16

Possible mechanisms of enhanced D

trapping under tokamak plasma irradiation

1 Presence of hydrogen in the Tore Supra tiles

TDS spectra of H2 and D2 for the as prepared CFC N11 samples irradiated in deuterium plasma

Ei = 100 eVat

Ji = 121020 atm2s

Ф = 451023 atm2

Presence of hydrogen in the CFC twice increases deuterium trapping at the expense of filling the hydrogen traps by deuterium due to isotope

exchange mechanism

Lab experiment

17

2 Trapping of deuterium activated by electron irradiation

[ Collaboration DRFC CEA-Cadarache ndash MEPhI ROSATOM 2007]

Thermal desorption of deuterium as D2

and as CD4 from CFC graphite under

ion and electron irradiationEi=100 eVat Ji=121020 atm2s

Ф=451023 atm2

Increase of deuterium retention along with irradiation time as well as deuterium retention under electron irradiation support an assumption about participation of D2

molecules from surrounding atmosphere in deuterium trapping into graphites Ion and electron irradiation act as a driving forces of the process

Plasma electron irradiation of CFC increased deuterium trapping 12 ndash 3 times depending on energy distribution of impinging deuterium particles

0 200 400 600 800 100000

05

10

15

Ret

entio

n x

1017

at

cm2

Energy eVat

CFC D2 (1020)

D2 electron irr

CFC D2 (2x1019)

electronirradiation

18

3 Transportation of deuterium into the material and trapping in the bulk of the tile

TDS analysis of the samples cut from different depth of the tile shows that more 10 of cumulative trapping collected in the bulk of tile

The samples of 1 ndash 2 mm thickness are usually used in the laboratory experiments The laboratory results could be compared

only to trapping in surface region of tokamak tile

4 Deuterium trapping in graphites irradiated by ion flux with wide energy distribution

Peculiarities of deuterium trapping in graphites exposed to plasma allows to expect an enhancement of retention in graphites irradiated by ion flux with wide energy distribution in tokamaks in comparison with graphites subjected to mono energy ion irradiation in laboratory

setups

19

5 Graphite surface irradiation during Helium Glow Discharge Conditioning

Helium ion bombardment leads to development of the surface relief and destruction of near surface layer As result trapping of deuterium during tokamak discharges should be enhanced

6 Graphite surface irradiation by oxygen impurities

Graphite irradiation by ions and atoms of oxygen impurities leads to accelerated surface destruction and develop the surface As a result trapping of deuterium ions and neutrals by graphite surface is probably more enhanced

20

Conclusion

bull The long range D retention in general is the very complicated physical (amp chemical) problem Many observed features of this phenomenon is not clear now

bull Complex and multiple-factor impact of PFM in tokamaks makes difficult distinguishing its influence on the LR hydrogen isotopes retention

bull Laboratory experiments with well defined impact parameters are crucially necessary

bull During last two years we mounted and calibrated a series of high vacuum installations with well controlled parameters for measurement of D retention in plasma exposed (as well in situ in simulators) samples and started comparative studies of samples radiated at different tokamaks and laboratory installations

21

Plansbull Investigations of samples irradiated in LENTA PR-2

PIN laboratory plasma facilities as well as in T-10 TEXTOR and Tore Supra tokamaks are now in progress

bull As there is very large scattering of the experimental data

on D retention careful measurements at D retention via fluxes (at high fluxes) and temperature in different irradiation facilities are under way

bull To pick up contribution of different factors on D retention step by step experimental investigations at varying definite factors (im flux density consequent and simultaneous irradiation with deuterium and helium broad energy spectra influence etc) are planned

bull Experimental measurements of neutron irradiation influence on hydrogen isotopes retention in PFM is now discussed

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21

4

Surer deep hydrogen penetration in vanadium alloy

Hydrogen isotopes penetrate through the 07 mm sample of V-349Ga alloy to the non irradiated backside after stationary pulsed power plasma and 6-keV ions irradiation

0 50 100 1500

5

10

15

20

2

1

Con

cent

rati

on a

t

Depth nm

Hydrogen concentration profiles in V-349Ga alloy after exposition in stationary plasmaof PLAST installation (D= 2∙1025 m-2 Т = 4500С Е = 100 eV)

1 ndash irradiated side 2 - backside

(ERDA 2-MeV He+)

Preprint 64527 Kurchatov Institute

5

0 50 100 1500

1

2

3

2

1

Depth nm

Con

cent

rati

on a

t

Deuterium concentration profiles in V-349Ga alloy after irradiation with pulsed deuterium plasma (15 pulses 028 MJm2) 1 ndash backside 2 ndash irradiated side 3- non irradiated(ERDA 2-MeV He+)

0 50 100 1500

5

10

15

3

2

1

Con

cent

rati

on a

t

Depth nm

Hydrogen concentration profiles in V-349Ga alloy after irradiation with 6-keV H+ ions in ion accelerator ILU at dose 10 1023 м-2 and target temperature Т = 4500С 1 ndash irradiated side 2 - backside 3 ndash non irradiates sample(ERDA 2-MeV He+)

Surer deep hydrogen penetration in vanadium alloy (2)

6

0

200

400c

0

200

400b

Depth m

0

200

400а

Mic

roh

ard

nes

s k

gm

m2

0 100 200 300 400 100 0

Microhardness as a function of depth measured on samples cross section after stationary plasma irradiation ( ndash irradiated side - back side - before irradiation) а) V-10Ti-6Cr-005Zr ndash irradiation time 20 min (D= 22 1024 m-2)b) V-10Ti-6Cr-005Zr ndash irradiation time 1 hour (D= 64 1024 m-2) c) V-15Ti-10Cr-005Y - irradiation time 1 hour (D= 64 1024 m-2)

Hydrogen irradiation induceddeep strengthening

Stationary pulsed power hydrogen plasma and 6-keV H+ ions irradiation results in deep strengthening ndash a reason is hydrates formation which create compressive stress in material

Preprint 64527 Kurchatov Institute

Before irradiation

backside

7

0 1 2 3 4 510-2

10-1

100

101

0 1 2 3 4 510-2

10-1

100

101

a)

W2C + 10 at C

200 eV D plasma CVD coatings 2x1024 Dm2

D c

on

ce

ntr

atio

n [a

t

]

Texp

= 373 K T

exp = 433 K

Texp

= 503 K

b)

WC + 10 at C

Texp

= 413 K T

exp = 543 K

Texp

= 653 K T

exp = 813 K

D c

on

ce

ntr

atio

n [a

t

]

Depth [m]

NRA analysis of CVD W2C amp WC coatings (VAlimov et al)

At temperatures above 550 K D concentration in the bulk starts to decrease

Presumably deuterium is retained in carbon precipitates

8

Mechanisms of long range D transportYuMartynenko et al

Shock wave initiation

ion

Cascade of displacements

defects

Physical interpretation connected with generation and transport of dislocation loops under influence of surface layer tension generation of thermoelastic tension and shock waves that force diffusion of admixtures along interstitials and grain borders

9

But physical mechanisms are far from full understanding

For adequate explanation versatile investigations using novel experimental methods as well as intimate theoretical analysis are necessary

For chemical active C based materials with compound structure (CFC) the task is much more complicated and need very careful investigations

10

0 2 4 6 8 1010-3

10-2

10-1

100

101 200 eV D plasma CFC NB31 2x1024 Dm2

Texp

= 463 K T

exp = 673 K

Texp

= 773 K T

exp = 948 K

D c

once

ntra

tion

[at

]

Depth [m]

0( ) [1 erf( )]2

xC x C

Dt

Migration in the bulk obeys diffusion equation with D=D(Fluence Temp)

10 15 20 25 3010-17

10-15

10-13

10-11

10-9

10-7

NB31 200 eV D plasma (Magnetron)

Coe

ffici

ent o

f D m

igra

tion

[m2 s

]

1000Temperature [K-1]

LA Sedano et al (1998) NB11 Matrix N11 Matrix NB11 Fibres N11 Fibres

Values for the deuterium migration derived from the D depth profiles are in good agreement with data for intrinsic hydrogen diffusivity in the fibres Migration through pores along fibres with low activation energy may be considered as mechanism of deuterium penetration into the bulk of the CFC materials

Channels of D transport in CFC VAlimov et al

11

Fine grain graphite (as well as CFC) ndashtransparent for gases in principle

Penetrating gas flow via gas pressure for MPG-8 graphite (thickness 126 mm diameter 305 mm)

room temperature

Measured gas flux density j ~ σ P σ Ad

P ndashpressure A ndasharea d- thickness σ ndash specific gas permeability

σ = 5middot1015 mols for MPG-8

Flu

x m

ols

Pressure Pa

Graphite sheet behaves as capillary A=1m2 d =1cm P =1Pa 35middot1017 D2s

12

Influence of tokamak T-10 exposure on MPG-8 graphite permeability

MPG-8 membrane 18 mm thick cut off T-10 limiter demonstrated hydrogen permeability ~9middot1015 molmiddotc-1m-1Pa-1 - 2 times more than for ldquovirginrdquo graphite

Possible reason ndash graphite porosity increase after long term expose in tokamak

All attempts to increase MPG-8 permeability in lab plasma experiments failed

4 mm

Place of limiter tile used for the membrane

14

Comparison of lab experiments and tokamak exposed tile retention in CFC

TDS investigation of the samples CFC N11 implanted by deuterium ions in the laboratory setups (MEPhI) and high field side tile of Tore Supra

[1] Begrambekov L Brosset C Bucalossi J Delchambre E Gunn JP Grisolia C Lipa M Loarer T Mitteau R PMoner-Garbet P Pascal J-Y PShigin P Titov N Tsitrone E Vergazov S Zakharov A ldquoSurface modification and hydrogen isotope retention in CFC during plasma irradiation in the Tore Supra tokamakrdquo17th Internal Conference on Plasma Surface Interactions in Controlled Fusion Devices (PSI17) Hefei China May 22 ndash 26 2006

LABORATORY SAMPLE

TORE SUPRA TILE [1]

Particles deuterons deuterons

Ion energy 50 100 200

500 eV

10-100 eV (as well as low energy atoms molecules and charge exchange neutrals )

Ion flux density 1times1020 atm2s (1-2)times1019 atm2s

Fluence 5times1023 atm2 5times1023 atm2 (estimated)

Surface temperature 450-470 K up to 500-600 K

Retention ~07times1021 atm2 ~2times1022 atm2 (30 times higher)

15

Hydrogen retention via fluence in lab exp

1021 1022 1023 1024 10251020

1021

1022

Hyd

roge

n re

tent

ion

at

m2

Fluence atm2

B4C 100 eVH MPG-8 100 eVH MPG-8 1 keVH HPG99 1 keVH [1] HOPG 100 eVH HOPG 1 keVH

Ion flux density = 35x1020 at(secm2)

[2] L Begrambekov O Buzhinsky A Gordeev E Miljaeva P Leikin P Shigin TDS investigation of hydrogen retention in graphites and carbon based materials Physica scripta N108 (2004) p72-75

Possible underestimation of tokamak tile irradiation fluence hardly could seriously influence the presented data -hydrogen retention will not increase 30 times even for ~100 times higher fluence

16

Possible mechanisms of enhanced D

trapping under tokamak plasma irradiation

1 Presence of hydrogen in the Tore Supra tiles

TDS spectra of H2 and D2 for the as prepared CFC N11 samples irradiated in deuterium plasma

Ei = 100 eVat

Ji = 121020 atm2s

Ф = 451023 atm2

Presence of hydrogen in the CFC twice increases deuterium trapping at the expense of filling the hydrogen traps by deuterium due to isotope

exchange mechanism

Lab experiment

17

2 Trapping of deuterium activated by electron irradiation

[ Collaboration DRFC CEA-Cadarache ndash MEPhI ROSATOM 2007]

Thermal desorption of deuterium as D2

and as CD4 from CFC graphite under

ion and electron irradiationEi=100 eVat Ji=121020 atm2s

Ф=451023 atm2

Increase of deuterium retention along with irradiation time as well as deuterium retention under electron irradiation support an assumption about participation of D2

molecules from surrounding atmosphere in deuterium trapping into graphites Ion and electron irradiation act as a driving forces of the process

Plasma electron irradiation of CFC increased deuterium trapping 12 ndash 3 times depending on energy distribution of impinging deuterium particles

0 200 400 600 800 100000

05

10

15

Ret

entio

n x

1017

at

cm2

Energy eVat

CFC D2 (1020)

D2 electron irr

CFC D2 (2x1019)

electronirradiation

18

3 Transportation of deuterium into the material and trapping in the bulk of the tile

TDS analysis of the samples cut from different depth of the tile shows that more 10 of cumulative trapping collected in the bulk of tile

The samples of 1 ndash 2 mm thickness are usually used in the laboratory experiments The laboratory results could be compared

only to trapping in surface region of tokamak tile

4 Deuterium trapping in graphites irradiated by ion flux with wide energy distribution

Peculiarities of deuterium trapping in graphites exposed to plasma allows to expect an enhancement of retention in graphites irradiated by ion flux with wide energy distribution in tokamaks in comparison with graphites subjected to mono energy ion irradiation in laboratory

setups

19

5 Graphite surface irradiation during Helium Glow Discharge Conditioning

Helium ion bombardment leads to development of the surface relief and destruction of near surface layer As result trapping of deuterium during tokamak discharges should be enhanced

6 Graphite surface irradiation by oxygen impurities

Graphite irradiation by ions and atoms of oxygen impurities leads to accelerated surface destruction and develop the surface As a result trapping of deuterium ions and neutrals by graphite surface is probably more enhanced

20

Conclusion

bull The long range D retention in general is the very complicated physical (amp chemical) problem Many observed features of this phenomenon is not clear now

bull Complex and multiple-factor impact of PFM in tokamaks makes difficult distinguishing its influence on the LR hydrogen isotopes retention

bull Laboratory experiments with well defined impact parameters are crucially necessary

bull During last two years we mounted and calibrated a series of high vacuum installations with well controlled parameters for measurement of D retention in plasma exposed (as well in situ in simulators) samples and started comparative studies of samples radiated at different tokamaks and laboratory installations

21

Plansbull Investigations of samples irradiated in LENTA PR-2

PIN laboratory plasma facilities as well as in T-10 TEXTOR and Tore Supra tokamaks are now in progress

bull As there is very large scattering of the experimental data

on D retention careful measurements at D retention via fluxes (at high fluxes) and temperature in different irradiation facilities are under way

bull To pick up contribution of different factors on D retention step by step experimental investigations at varying definite factors (im flux density consequent and simultaneous irradiation with deuterium and helium broad energy spectra influence etc) are planned

bull Experimental measurements of neutron irradiation influence on hydrogen isotopes retention in PFM is now discussed

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21

5

0 50 100 1500

1

2

3

2

1

Depth nm

Con

cent

rati

on a

t

Deuterium concentration profiles in V-349Ga alloy after irradiation with pulsed deuterium plasma (15 pulses 028 MJm2) 1 ndash backside 2 ndash irradiated side 3- non irradiated(ERDA 2-MeV He+)

0 50 100 1500

5

10

15

3

2

1

Con

cent

rati

on a

t

Depth nm

Hydrogen concentration profiles in V-349Ga alloy after irradiation with 6-keV H+ ions in ion accelerator ILU at dose 10 1023 м-2 and target temperature Т = 4500С 1 ndash irradiated side 2 - backside 3 ndash non irradiates sample(ERDA 2-MeV He+)

Surer deep hydrogen penetration in vanadium alloy (2)

6

0

200

400c

0

200

400b

Depth m

0

200

400а

Mic

roh

ard

nes

s k

gm

m2

0 100 200 300 400 100 0

Microhardness as a function of depth measured on samples cross section after stationary plasma irradiation ( ndash irradiated side - back side - before irradiation) а) V-10Ti-6Cr-005Zr ndash irradiation time 20 min (D= 22 1024 m-2)b) V-10Ti-6Cr-005Zr ndash irradiation time 1 hour (D= 64 1024 m-2) c) V-15Ti-10Cr-005Y - irradiation time 1 hour (D= 64 1024 m-2)

Hydrogen irradiation induceddeep strengthening

Stationary pulsed power hydrogen plasma and 6-keV H+ ions irradiation results in deep strengthening ndash a reason is hydrates formation which create compressive stress in material

Preprint 64527 Kurchatov Institute

Before irradiation

backside

7

0 1 2 3 4 510-2

10-1

100

101

0 1 2 3 4 510-2

10-1

100

101

a)

W2C + 10 at C

200 eV D plasma CVD coatings 2x1024 Dm2

D c

on

ce

ntr

atio

n [a

t

]

Texp

= 373 K T

exp = 433 K

Texp

= 503 K

b)

WC + 10 at C

Texp

= 413 K T

exp = 543 K

Texp

= 653 K T

exp = 813 K

D c

on

ce

ntr

atio

n [a

t

]

Depth [m]

NRA analysis of CVD W2C amp WC coatings (VAlimov et al)

At temperatures above 550 K D concentration in the bulk starts to decrease

Presumably deuterium is retained in carbon precipitates

8

Mechanisms of long range D transportYuMartynenko et al

Shock wave initiation

ion

Cascade of displacements

defects

Physical interpretation connected with generation and transport of dislocation loops under influence of surface layer tension generation of thermoelastic tension and shock waves that force diffusion of admixtures along interstitials and grain borders

9

But physical mechanisms are far from full understanding

For adequate explanation versatile investigations using novel experimental methods as well as intimate theoretical analysis are necessary

For chemical active C based materials with compound structure (CFC) the task is much more complicated and need very careful investigations

10

0 2 4 6 8 1010-3

10-2

10-1

100

101 200 eV D plasma CFC NB31 2x1024 Dm2

Texp

= 463 K T

exp = 673 K

Texp

= 773 K T

exp = 948 K

D c

once

ntra

tion

[at

]

Depth [m]

0( ) [1 erf( )]2

xC x C

Dt

Migration in the bulk obeys diffusion equation with D=D(Fluence Temp)

10 15 20 25 3010-17

10-15

10-13

10-11

10-9

10-7

NB31 200 eV D plasma (Magnetron)

Coe

ffici

ent o

f D m

igra

tion

[m2 s

]

1000Temperature [K-1]

LA Sedano et al (1998) NB11 Matrix N11 Matrix NB11 Fibres N11 Fibres

Values for the deuterium migration derived from the D depth profiles are in good agreement with data for intrinsic hydrogen diffusivity in the fibres Migration through pores along fibres with low activation energy may be considered as mechanism of deuterium penetration into the bulk of the CFC materials

Channels of D transport in CFC VAlimov et al

11

Fine grain graphite (as well as CFC) ndashtransparent for gases in principle

Penetrating gas flow via gas pressure for MPG-8 graphite (thickness 126 mm diameter 305 mm)

room temperature

Measured gas flux density j ~ σ P σ Ad

P ndashpressure A ndasharea d- thickness σ ndash specific gas permeability

σ = 5middot1015 mols for MPG-8

Flu

x m

ols

Pressure Pa

Graphite sheet behaves as capillary A=1m2 d =1cm P =1Pa 35middot1017 D2s

12

Influence of tokamak T-10 exposure on MPG-8 graphite permeability

MPG-8 membrane 18 mm thick cut off T-10 limiter demonstrated hydrogen permeability ~9middot1015 molmiddotc-1m-1Pa-1 - 2 times more than for ldquovirginrdquo graphite

Possible reason ndash graphite porosity increase after long term expose in tokamak

All attempts to increase MPG-8 permeability in lab plasma experiments failed

4 mm

Place of limiter tile used for the membrane

14

Comparison of lab experiments and tokamak exposed tile retention in CFC

TDS investigation of the samples CFC N11 implanted by deuterium ions in the laboratory setups (MEPhI) and high field side tile of Tore Supra

[1] Begrambekov L Brosset C Bucalossi J Delchambre E Gunn JP Grisolia C Lipa M Loarer T Mitteau R PMoner-Garbet P Pascal J-Y PShigin P Titov N Tsitrone E Vergazov S Zakharov A ldquoSurface modification and hydrogen isotope retention in CFC during plasma irradiation in the Tore Supra tokamakrdquo17th Internal Conference on Plasma Surface Interactions in Controlled Fusion Devices (PSI17) Hefei China May 22 ndash 26 2006

LABORATORY SAMPLE

TORE SUPRA TILE [1]

Particles deuterons deuterons

Ion energy 50 100 200

500 eV

10-100 eV (as well as low energy atoms molecules and charge exchange neutrals )

Ion flux density 1times1020 atm2s (1-2)times1019 atm2s

Fluence 5times1023 atm2 5times1023 atm2 (estimated)

Surface temperature 450-470 K up to 500-600 K

Retention ~07times1021 atm2 ~2times1022 atm2 (30 times higher)

15

Hydrogen retention via fluence in lab exp

1021 1022 1023 1024 10251020

1021

1022

Hyd

roge

n re

tent

ion

at

m2

Fluence atm2

B4C 100 eVH MPG-8 100 eVH MPG-8 1 keVH HPG99 1 keVH [1] HOPG 100 eVH HOPG 1 keVH

Ion flux density = 35x1020 at(secm2)

[2] L Begrambekov O Buzhinsky A Gordeev E Miljaeva P Leikin P Shigin TDS investigation of hydrogen retention in graphites and carbon based materials Physica scripta N108 (2004) p72-75

Possible underestimation of tokamak tile irradiation fluence hardly could seriously influence the presented data -hydrogen retention will not increase 30 times even for ~100 times higher fluence

16

Possible mechanisms of enhanced D

trapping under tokamak plasma irradiation

1 Presence of hydrogen in the Tore Supra tiles

TDS spectra of H2 and D2 for the as prepared CFC N11 samples irradiated in deuterium plasma

Ei = 100 eVat

Ji = 121020 atm2s

Ф = 451023 atm2

Presence of hydrogen in the CFC twice increases deuterium trapping at the expense of filling the hydrogen traps by deuterium due to isotope

exchange mechanism

Lab experiment

17

2 Trapping of deuterium activated by electron irradiation

[ Collaboration DRFC CEA-Cadarache ndash MEPhI ROSATOM 2007]

Thermal desorption of deuterium as D2

and as CD4 from CFC graphite under

ion and electron irradiationEi=100 eVat Ji=121020 atm2s

Ф=451023 atm2

Increase of deuterium retention along with irradiation time as well as deuterium retention under electron irradiation support an assumption about participation of D2

molecules from surrounding atmosphere in deuterium trapping into graphites Ion and electron irradiation act as a driving forces of the process

Plasma electron irradiation of CFC increased deuterium trapping 12 ndash 3 times depending on energy distribution of impinging deuterium particles

0 200 400 600 800 100000

05

10

15

Ret

entio

n x

1017

at

cm2

Energy eVat

CFC D2 (1020)

D2 electron irr

CFC D2 (2x1019)

electronirradiation

18

3 Transportation of deuterium into the material and trapping in the bulk of the tile

TDS analysis of the samples cut from different depth of the tile shows that more 10 of cumulative trapping collected in the bulk of tile

The samples of 1 ndash 2 mm thickness are usually used in the laboratory experiments The laboratory results could be compared

only to trapping in surface region of tokamak tile

4 Deuterium trapping in graphites irradiated by ion flux with wide energy distribution

Peculiarities of deuterium trapping in graphites exposed to plasma allows to expect an enhancement of retention in graphites irradiated by ion flux with wide energy distribution in tokamaks in comparison with graphites subjected to mono energy ion irradiation in laboratory

setups

19

5 Graphite surface irradiation during Helium Glow Discharge Conditioning

Helium ion bombardment leads to development of the surface relief and destruction of near surface layer As result trapping of deuterium during tokamak discharges should be enhanced

6 Graphite surface irradiation by oxygen impurities

Graphite irradiation by ions and atoms of oxygen impurities leads to accelerated surface destruction and develop the surface As a result trapping of deuterium ions and neutrals by graphite surface is probably more enhanced

20

Conclusion

bull The long range D retention in general is the very complicated physical (amp chemical) problem Many observed features of this phenomenon is not clear now

bull Complex and multiple-factor impact of PFM in tokamaks makes difficult distinguishing its influence on the LR hydrogen isotopes retention

bull Laboratory experiments with well defined impact parameters are crucially necessary

bull During last two years we mounted and calibrated a series of high vacuum installations with well controlled parameters for measurement of D retention in plasma exposed (as well in situ in simulators) samples and started comparative studies of samples radiated at different tokamaks and laboratory installations

21

Plansbull Investigations of samples irradiated in LENTA PR-2

PIN laboratory plasma facilities as well as in T-10 TEXTOR and Tore Supra tokamaks are now in progress

bull As there is very large scattering of the experimental data

on D retention careful measurements at D retention via fluxes (at high fluxes) and temperature in different irradiation facilities are under way

bull To pick up contribution of different factors on D retention step by step experimental investigations at varying definite factors (im flux density consequent and simultaneous irradiation with deuterium and helium broad energy spectra influence etc) are planned

bull Experimental measurements of neutron irradiation influence on hydrogen isotopes retention in PFM is now discussed

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21

6

0

200

400c

0

200

400b

Depth m

0

200

400а

Mic

roh

ard

nes

s k

gm

m2

0 100 200 300 400 100 0

Microhardness as a function of depth measured on samples cross section after stationary plasma irradiation ( ndash irradiated side - back side - before irradiation) а) V-10Ti-6Cr-005Zr ndash irradiation time 20 min (D= 22 1024 m-2)b) V-10Ti-6Cr-005Zr ndash irradiation time 1 hour (D= 64 1024 m-2) c) V-15Ti-10Cr-005Y - irradiation time 1 hour (D= 64 1024 m-2)

Hydrogen irradiation induceddeep strengthening

Stationary pulsed power hydrogen plasma and 6-keV H+ ions irradiation results in deep strengthening ndash a reason is hydrates formation which create compressive stress in material

Preprint 64527 Kurchatov Institute

Before irradiation

backside

7

0 1 2 3 4 510-2

10-1

100

101

0 1 2 3 4 510-2

10-1

100

101

a)

W2C + 10 at C

200 eV D plasma CVD coatings 2x1024 Dm2

D c

on

ce

ntr

atio

n [a

t

]

Texp

= 373 K T

exp = 433 K

Texp

= 503 K

b)

WC + 10 at C

Texp

= 413 K T

exp = 543 K

Texp

= 653 K T

exp = 813 K

D c

on

ce

ntr

atio

n [a

t

]

Depth [m]

NRA analysis of CVD W2C amp WC coatings (VAlimov et al)

At temperatures above 550 K D concentration in the bulk starts to decrease

Presumably deuterium is retained in carbon precipitates

8

Mechanisms of long range D transportYuMartynenko et al

Shock wave initiation

ion

Cascade of displacements

defects

Physical interpretation connected with generation and transport of dislocation loops under influence of surface layer tension generation of thermoelastic tension and shock waves that force diffusion of admixtures along interstitials and grain borders

9

But physical mechanisms are far from full understanding

For adequate explanation versatile investigations using novel experimental methods as well as intimate theoretical analysis are necessary

For chemical active C based materials with compound structure (CFC) the task is much more complicated and need very careful investigations

10

0 2 4 6 8 1010-3

10-2

10-1

100

101 200 eV D plasma CFC NB31 2x1024 Dm2

Texp

= 463 K T

exp = 673 K

Texp

= 773 K T

exp = 948 K

D c

once

ntra

tion

[at

]

Depth [m]

0( ) [1 erf( )]2

xC x C

Dt

Migration in the bulk obeys diffusion equation with D=D(Fluence Temp)

10 15 20 25 3010-17

10-15

10-13

10-11

10-9

10-7

NB31 200 eV D plasma (Magnetron)

Coe

ffici

ent o

f D m

igra

tion

[m2 s

]

1000Temperature [K-1]

LA Sedano et al (1998) NB11 Matrix N11 Matrix NB11 Fibres N11 Fibres

Values for the deuterium migration derived from the D depth profiles are in good agreement with data for intrinsic hydrogen diffusivity in the fibres Migration through pores along fibres with low activation energy may be considered as mechanism of deuterium penetration into the bulk of the CFC materials

Channels of D transport in CFC VAlimov et al

11

Fine grain graphite (as well as CFC) ndashtransparent for gases in principle

Penetrating gas flow via gas pressure for MPG-8 graphite (thickness 126 mm diameter 305 mm)

room temperature

Measured gas flux density j ~ σ P σ Ad

P ndashpressure A ndasharea d- thickness σ ndash specific gas permeability

σ = 5middot1015 mols for MPG-8

Flu

x m

ols

Pressure Pa

Graphite sheet behaves as capillary A=1m2 d =1cm P =1Pa 35middot1017 D2s

12

Influence of tokamak T-10 exposure on MPG-8 graphite permeability

MPG-8 membrane 18 mm thick cut off T-10 limiter demonstrated hydrogen permeability ~9middot1015 molmiddotc-1m-1Pa-1 - 2 times more than for ldquovirginrdquo graphite

Possible reason ndash graphite porosity increase after long term expose in tokamak

All attempts to increase MPG-8 permeability in lab plasma experiments failed

4 mm

Place of limiter tile used for the membrane

14

Comparison of lab experiments and tokamak exposed tile retention in CFC

TDS investigation of the samples CFC N11 implanted by deuterium ions in the laboratory setups (MEPhI) and high field side tile of Tore Supra

[1] Begrambekov L Brosset C Bucalossi J Delchambre E Gunn JP Grisolia C Lipa M Loarer T Mitteau R PMoner-Garbet P Pascal J-Y PShigin P Titov N Tsitrone E Vergazov S Zakharov A ldquoSurface modification and hydrogen isotope retention in CFC during plasma irradiation in the Tore Supra tokamakrdquo17th Internal Conference on Plasma Surface Interactions in Controlled Fusion Devices (PSI17) Hefei China May 22 ndash 26 2006

LABORATORY SAMPLE

TORE SUPRA TILE [1]

Particles deuterons deuterons

Ion energy 50 100 200

500 eV

10-100 eV (as well as low energy atoms molecules and charge exchange neutrals )

Ion flux density 1times1020 atm2s (1-2)times1019 atm2s

Fluence 5times1023 atm2 5times1023 atm2 (estimated)

Surface temperature 450-470 K up to 500-600 K

Retention ~07times1021 atm2 ~2times1022 atm2 (30 times higher)

15

Hydrogen retention via fluence in lab exp

1021 1022 1023 1024 10251020

1021

1022

Hyd

roge

n re

tent

ion

at

m2

Fluence atm2

B4C 100 eVH MPG-8 100 eVH MPG-8 1 keVH HPG99 1 keVH [1] HOPG 100 eVH HOPG 1 keVH

Ion flux density = 35x1020 at(secm2)

[2] L Begrambekov O Buzhinsky A Gordeev E Miljaeva P Leikin P Shigin TDS investigation of hydrogen retention in graphites and carbon based materials Physica scripta N108 (2004) p72-75

Possible underestimation of tokamak tile irradiation fluence hardly could seriously influence the presented data -hydrogen retention will not increase 30 times even for ~100 times higher fluence

16

Possible mechanisms of enhanced D

trapping under tokamak plasma irradiation

1 Presence of hydrogen in the Tore Supra tiles

TDS spectra of H2 and D2 for the as prepared CFC N11 samples irradiated in deuterium plasma

Ei = 100 eVat

Ji = 121020 atm2s

Ф = 451023 atm2

Presence of hydrogen in the CFC twice increases deuterium trapping at the expense of filling the hydrogen traps by deuterium due to isotope

exchange mechanism

Lab experiment

17

2 Trapping of deuterium activated by electron irradiation

[ Collaboration DRFC CEA-Cadarache ndash MEPhI ROSATOM 2007]

Thermal desorption of deuterium as D2

and as CD4 from CFC graphite under

ion and electron irradiationEi=100 eVat Ji=121020 atm2s

Ф=451023 atm2

Increase of deuterium retention along with irradiation time as well as deuterium retention under electron irradiation support an assumption about participation of D2

molecules from surrounding atmosphere in deuterium trapping into graphites Ion and electron irradiation act as a driving forces of the process

Plasma electron irradiation of CFC increased deuterium trapping 12 ndash 3 times depending on energy distribution of impinging deuterium particles

0 200 400 600 800 100000

05

10

15

Ret

entio

n x

1017

at

cm2

Energy eVat

CFC D2 (1020)

D2 electron irr

CFC D2 (2x1019)

electronirradiation

18

3 Transportation of deuterium into the material and trapping in the bulk of the tile

TDS analysis of the samples cut from different depth of the tile shows that more 10 of cumulative trapping collected in the bulk of tile

The samples of 1 ndash 2 mm thickness are usually used in the laboratory experiments The laboratory results could be compared

only to trapping in surface region of tokamak tile

4 Deuterium trapping in graphites irradiated by ion flux with wide energy distribution

Peculiarities of deuterium trapping in graphites exposed to plasma allows to expect an enhancement of retention in graphites irradiated by ion flux with wide energy distribution in tokamaks in comparison with graphites subjected to mono energy ion irradiation in laboratory

setups

19

5 Graphite surface irradiation during Helium Glow Discharge Conditioning

Helium ion bombardment leads to development of the surface relief and destruction of near surface layer As result trapping of deuterium during tokamak discharges should be enhanced

6 Graphite surface irradiation by oxygen impurities

Graphite irradiation by ions and atoms of oxygen impurities leads to accelerated surface destruction and develop the surface As a result trapping of deuterium ions and neutrals by graphite surface is probably more enhanced

20

Conclusion

bull The long range D retention in general is the very complicated physical (amp chemical) problem Many observed features of this phenomenon is not clear now

bull Complex and multiple-factor impact of PFM in tokamaks makes difficult distinguishing its influence on the LR hydrogen isotopes retention

bull Laboratory experiments with well defined impact parameters are crucially necessary

bull During last two years we mounted and calibrated a series of high vacuum installations with well controlled parameters for measurement of D retention in plasma exposed (as well in situ in simulators) samples and started comparative studies of samples radiated at different tokamaks and laboratory installations

21

Plansbull Investigations of samples irradiated in LENTA PR-2

PIN laboratory plasma facilities as well as in T-10 TEXTOR and Tore Supra tokamaks are now in progress

bull As there is very large scattering of the experimental data

on D retention careful measurements at D retention via fluxes (at high fluxes) and temperature in different irradiation facilities are under way

bull To pick up contribution of different factors on D retention step by step experimental investigations at varying definite factors (im flux density consequent and simultaneous irradiation with deuterium and helium broad energy spectra influence etc) are planned

bull Experimental measurements of neutron irradiation influence on hydrogen isotopes retention in PFM is now discussed

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21

7

0 1 2 3 4 510-2

10-1

100

101

0 1 2 3 4 510-2

10-1

100

101

a)

W2C + 10 at C

200 eV D plasma CVD coatings 2x1024 Dm2

D c

on

ce

ntr

atio

n [a

t

]

Texp

= 373 K T

exp = 433 K

Texp

= 503 K

b)

WC + 10 at C

Texp

= 413 K T

exp = 543 K

Texp

= 653 K T

exp = 813 K

D c

on

ce

ntr

atio

n [a

t

]

Depth [m]

NRA analysis of CVD W2C amp WC coatings (VAlimov et al)

At temperatures above 550 K D concentration in the bulk starts to decrease

Presumably deuterium is retained in carbon precipitates

8

Mechanisms of long range D transportYuMartynenko et al

Shock wave initiation

ion

Cascade of displacements

defects

Physical interpretation connected with generation and transport of dislocation loops under influence of surface layer tension generation of thermoelastic tension and shock waves that force diffusion of admixtures along interstitials and grain borders

9

But physical mechanisms are far from full understanding

For adequate explanation versatile investigations using novel experimental methods as well as intimate theoretical analysis are necessary

For chemical active C based materials with compound structure (CFC) the task is much more complicated and need very careful investigations

10

0 2 4 6 8 1010-3

10-2

10-1

100

101 200 eV D plasma CFC NB31 2x1024 Dm2

Texp

= 463 K T

exp = 673 K

Texp

= 773 K T

exp = 948 K

D c

once

ntra

tion

[at

]

Depth [m]

0( ) [1 erf( )]2

xC x C

Dt

Migration in the bulk obeys diffusion equation with D=D(Fluence Temp)

10 15 20 25 3010-17

10-15

10-13

10-11

10-9

10-7

NB31 200 eV D plasma (Magnetron)

Coe

ffici

ent o

f D m

igra

tion

[m2 s

]

1000Temperature [K-1]

LA Sedano et al (1998) NB11 Matrix N11 Matrix NB11 Fibres N11 Fibres

Values for the deuterium migration derived from the D depth profiles are in good agreement with data for intrinsic hydrogen diffusivity in the fibres Migration through pores along fibres with low activation energy may be considered as mechanism of deuterium penetration into the bulk of the CFC materials

Channels of D transport in CFC VAlimov et al

11

Fine grain graphite (as well as CFC) ndashtransparent for gases in principle

Penetrating gas flow via gas pressure for MPG-8 graphite (thickness 126 mm diameter 305 mm)

room temperature

Measured gas flux density j ~ σ P σ Ad

P ndashpressure A ndasharea d- thickness σ ndash specific gas permeability

σ = 5middot1015 mols for MPG-8

Flu

x m

ols

Pressure Pa

Graphite sheet behaves as capillary A=1m2 d =1cm P =1Pa 35middot1017 D2s

12

Influence of tokamak T-10 exposure on MPG-8 graphite permeability

MPG-8 membrane 18 mm thick cut off T-10 limiter demonstrated hydrogen permeability ~9middot1015 molmiddotc-1m-1Pa-1 - 2 times more than for ldquovirginrdquo graphite

Possible reason ndash graphite porosity increase after long term expose in tokamak

All attempts to increase MPG-8 permeability in lab plasma experiments failed

4 mm

Place of limiter tile used for the membrane

14

Comparison of lab experiments and tokamak exposed tile retention in CFC

TDS investigation of the samples CFC N11 implanted by deuterium ions in the laboratory setups (MEPhI) and high field side tile of Tore Supra

[1] Begrambekov L Brosset C Bucalossi J Delchambre E Gunn JP Grisolia C Lipa M Loarer T Mitteau R PMoner-Garbet P Pascal J-Y PShigin P Titov N Tsitrone E Vergazov S Zakharov A ldquoSurface modification and hydrogen isotope retention in CFC during plasma irradiation in the Tore Supra tokamakrdquo17th Internal Conference on Plasma Surface Interactions in Controlled Fusion Devices (PSI17) Hefei China May 22 ndash 26 2006

LABORATORY SAMPLE

TORE SUPRA TILE [1]

Particles deuterons deuterons

Ion energy 50 100 200

500 eV

10-100 eV (as well as low energy atoms molecules and charge exchange neutrals )

Ion flux density 1times1020 atm2s (1-2)times1019 atm2s

Fluence 5times1023 atm2 5times1023 atm2 (estimated)

Surface temperature 450-470 K up to 500-600 K

Retention ~07times1021 atm2 ~2times1022 atm2 (30 times higher)

15

Hydrogen retention via fluence in lab exp

1021 1022 1023 1024 10251020

1021

1022

Hyd

roge

n re

tent

ion

at

m2

Fluence atm2

B4C 100 eVH MPG-8 100 eVH MPG-8 1 keVH HPG99 1 keVH [1] HOPG 100 eVH HOPG 1 keVH

Ion flux density = 35x1020 at(secm2)

[2] L Begrambekov O Buzhinsky A Gordeev E Miljaeva P Leikin P Shigin TDS investigation of hydrogen retention in graphites and carbon based materials Physica scripta N108 (2004) p72-75

Possible underestimation of tokamak tile irradiation fluence hardly could seriously influence the presented data -hydrogen retention will not increase 30 times even for ~100 times higher fluence

16

Possible mechanisms of enhanced D

trapping under tokamak plasma irradiation

1 Presence of hydrogen in the Tore Supra tiles

TDS spectra of H2 and D2 for the as prepared CFC N11 samples irradiated in deuterium plasma

Ei = 100 eVat

Ji = 121020 atm2s

Ф = 451023 atm2

Presence of hydrogen in the CFC twice increases deuterium trapping at the expense of filling the hydrogen traps by deuterium due to isotope

exchange mechanism

Lab experiment

17

2 Trapping of deuterium activated by electron irradiation

[ Collaboration DRFC CEA-Cadarache ndash MEPhI ROSATOM 2007]

Thermal desorption of deuterium as D2

and as CD4 from CFC graphite under

ion and electron irradiationEi=100 eVat Ji=121020 atm2s

Ф=451023 atm2

Increase of deuterium retention along with irradiation time as well as deuterium retention under electron irradiation support an assumption about participation of D2

molecules from surrounding atmosphere in deuterium trapping into graphites Ion and electron irradiation act as a driving forces of the process

Plasma electron irradiation of CFC increased deuterium trapping 12 ndash 3 times depending on energy distribution of impinging deuterium particles

0 200 400 600 800 100000

05

10

15

Ret

entio

n x

1017

at

cm2

Energy eVat

CFC D2 (1020)

D2 electron irr

CFC D2 (2x1019)

electronirradiation

18

3 Transportation of deuterium into the material and trapping in the bulk of the tile

TDS analysis of the samples cut from different depth of the tile shows that more 10 of cumulative trapping collected in the bulk of tile

The samples of 1 ndash 2 mm thickness are usually used in the laboratory experiments The laboratory results could be compared

only to trapping in surface region of tokamak tile

4 Deuterium trapping in graphites irradiated by ion flux with wide energy distribution

Peculiarities of deuterium trapping in graphites exposed to plasma allows to expect an enhancement of retention in graphites irradiated by ion flux with wide energy distribution in tokamaks in comparison with graphites subjected to mono energy ion irradiation in laboratory

setups

19

5 Graphite surface irradiation during Helium Glow Discharge Conditioning

Helium ion bombardment leads to development of the surface relief and destruction of near surface layer As result trapping of deuterium during tokamak discharges should be enhanced

6 Graphite surface irradiation by oxygen impurities

Graphite irradiation by ions and atoms of oxygen impurities leads to accelerated surface destruction and develop the surface As a result trapping of deuterium ions and neutrals by graphite surface is probably more enhanced

20

Conclusion

bull The long range D retention in general is the very complicated physical (amp chemical) problem Many observed features of this phenomenon is not clear now

bull Complex and multiple-factor impact of PFM in tokamaks makes difficult distinguishing its influence on the LR hydrogen isotopes retention

bull Laboratory experiments with well defined impact parameters are crucially necessary

bull During last two years we mounted and calibrated a series of high vacuum installations with well controlled parameters for measurement of D retention in plasma exposed (as well in situ in simulators) samples and started comparative studies of samples radiated at different tokamaks and laboratory installations

21

Plansbull Investigations of samples irradiated in LENTA PR-2

PIN laboratory plasma facilities as well as in T-10 TEXTOR and Tore Supra tokamaks are now in progress

bull As there is very large scattering of the experimental data

on D retention careful measurements at D retention via fluxes (at high fluxes) and temperature in different irradiation facilities are under way

bull To pick up contribution of different factors on D retention step by step experimental investigations at varying definite factors (im flux density consequent and simultaneous irradiation with deuterium and helium broad energy spectra influence etc) are planned

bull Experimental measurements of neutron irradiation influence on hydrogen isotopes retention in PFM is now discussed

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21

8

Mechanisms of long range D transportYuMartynenko et al

Shock wave initiation

ion

Cascade of displacements

defects

Physical interpretation connected with generation and transport of dislocation loops under influence of surface layer tension generation of thermoelastic tension and shock waves that force diffusion of admixtures along interstitials and grain borders

9

But physical mechanisms are far from full understanding

For adequate explanation versatile investigations using novel experimental methods as well as intimate theoretical analysis are necessary

For chemical active C based materials with compound structure (CFC) the task is much more complicated and need very careful investigations

10

0 2 4 6 8 1010-3

10-2

10-1

100

101 200 eV D plasma CFC NB31 2x1024 Dm2

Texp

= 463 K T

exp = 673 K

Texp

= 773 K T

exp = 948 K

D c

once

ntra

tion

[at

]

Depth [m]

0( ) [1 erf( )]2

xC x C

Dt

Migration in the bulk obeys diffusion equation with D=D(Fluence Temp)

10 15 20 25 3010-17

10-15

10-13

10-11

10-9

10-7

NB31 200 eV D plasma (Magnetron)

Coe

ffici

ent o

f D m

igra

tion

[m2 s

]

1000Temperature [K-1]

LA Sedano et al (1998) NB11 Matrix N11 Matrix NB11 Fibres N11 Fibres

Values for the deuterium migration derived from the D depth profiles are in good agreement with data for intrinsic hydrogen diffusivity in the fibres Migration through pores along fibres with low activation energy may be considered as mechanism of deuterium penetration into the bulk of the CFC materials

Channels of D transport in CFC VAlimov et al

11

Fine grain graphite (as well as CFC) ndashtransparent for gases in principle

Penetrating gas flow via gas pressure for MPG-8 graphite (thickness 126 mm diameter 305 mm)

room temperature

Measured gas flux density j ~ σ P σ Ad

P ndashpressure A ndasharea d- thickness σ ndash specific gas permeability

σ = 5middot1015 mols for MPG-8

Flu

x m

ols

Pressure Pa

Graphite sheet behaves as capillary A=1m2 d =1cm P =1Pa 35middot1017 D2s

12

Influence of tokamak T-10 exposure on MPG-8 graphite permeability

MPG-8 membrane 18 mm thick cut off T-10 limiter demonstrated hydrogen permeability ~9middot1015 molmiddotc-1m-1Pa-1 - 2 times more than for ldquovirginrdquo graphite

Possible reason ndash graphite porosity increase after long term expose in tokamak

All attempts to increase MPG-8 permeability in lab plasma experiments failed

4 mm

Place of limiter tile used for the membrane

14

Comparison of lab experiments and tokamak exposed tile retention in CFC

TDS investigation of the samples CFC N11 implanted by deuterium ions in the laboratory setups (MEPhI) and high field side tile of Tore Supra

[1] Begrambekov L Brosset C Bucalossi J Delchambre E Gunn JP Grisolia C Lipa M Loarer T Mitteau R PMoner-Garbet P Pascal J-Y PShigin P Titov N Tsitrone E Vergazov S Zakharov A ldquoSurface modification and hydrogen isotope retention in CFC during plasma irradiation in the Tore Supra tokamakrdquo17th Internal Conference on Plasma Surface Interactions in Controlled Fusion Devices (PSI17) Hefei China May 22 ndash 26 2006

LABORATORY SAMPLE

TORE SUPRA TILE [1]

Particles deuterons deuterons

Ion energy 50 100 200

500 eV

10-100 eV (as well as low energy atoms molecules and charge exchange neutrals )

Ion flux density 1times1020 atm2s (1-2)times1019 atm2s

Fluence 5times1023 atm2 5times1023 atm2 (estimated)

Surface temperature 450-470 K up to 500-600 K

Retention ~07times1021 atm2 ~2times1022 atm2 (30 times higher)

15

Hydrogen retention via fluence in lab exp

1021 1022 1023 1024 10251020

1021

1022

Hyd

roge

n re

tent

ion

at

m2

Fluence atm2

B4C 100 eVH MPG-8 100 eVH MPG-8 1 keVH HPG99 1 keVH [1] HOPG 100 eVH HOPG 1 keVH

Ion flux density = 35x1020 at(secm2)

[2] L Begrambekov O Buzhinsky A Gordeev E Miljaeva P Leikin P Shigin TDS investigation of hydrogen retention in graphites and carbon based materials Physica scripta N108 (2004) p72-75

Possible underestimation of tokamak tile irradiation fluence hardly could seriously influence the presented data -hydrogen retention will not increase 30 times even for ~100 times higher fluence

16

Possible mechanisms of enhanced D

trapping under tokamak plasma irradiation

1 Presence of hydrogen in the Tore Supra tiles

TDS spectra of H2 and D2 for the as prepared CFC N11 samples irradiated in deuterium plasma

Ei = 100 eVat

Ji = 121020 atm2s

Ф = 451023 atm2

Presence of hydrogen in the CFC twice increases deuterium trapping at the expense of filling the hydrogen traps by deuterium due to isotope

exchange mechanism

Lab experiment

17

2 Trapping of deuterium activated by electron irradiation

[ Collaboration DRFC CEA-Cadarache ndash MEPhI ROSATOM 2007]

Thermal desorption of deuterium as D2

and as CD4 from CFC graphite under

ion and electron irradiationEi=100 eVat Ji=121020 atm2s

Ф=451023 atm2

Increase of deuterium retention along with irradiation time as well as deuterium retention under electron irradiation support an assumption about participation of D2

molecules from surrounding atmosphere in deuterium trapping into graphites Ion and electron irradiation act as a driving forces of the process

Plasma electron irradiation of CFC increased deuterium trapping 12 ndash 3 times depending on energy distribution of impinging deuterium particles

0 200 400 600 800 100000

05

10

15

Ret

entio

n x

1017

at

cm2

Energy eVat

CFC D2 (1020)

D2 electron irr

CFC D2 (2x1019)

electronirradiation

18

3 Transportation of deuterium into the material and trapping in the bulk of the tile

TDS analysis of the samples cut from different depth of the tile shows that more 10 of cumulative trapping collected in the bulk of tile

The samples of 1 ndash 2 mm thickness are usually used in the laboratory experiments The laboratory results could be compared

only to trapping in surface region of tokamak tile

4 Deuterium trapping in graphites irradiated by ion flux with wide energy distribution

Peculiarities of deuterium trapping in graphites exposed to plasma allows to expect an enhancement of retention in graphites irradiated by ion flux with wide energy distribution in tokamaks in comparison with graphites subjected to mono energy ion irradiation in laboratory

setups

19

5 Graphite surface irradiation during Helium Glow Discharge Conditioning

Helium ion bombardment leads to development of the surface relief and destruction of near surface layer As result trapping of deuterium during tokamak discharges should be enhanced

6 Graphite surface irradiation by oxygen impurities

Graphite irradiation by ions and atoms of oxygen impurities leads to accelerated surface destruction and develop the surface As a result trapping of deuterium ions and neutrals by graphite surface is probably more enhanced

20

Conclusion

bull The long range D retention in general is the very complicated physical (amp chemical) problem Many observed features of this phenomenon is not clear now

bull Complex and multiple-factor impact of PFM in tokamaks makes difficult distinguishing its influence on the LR hydrogen isotopes retention

bull Laboratory experiments with well defined impact parameters are crucially necessary

bull During last two years we mounted and calibrated a series of high vacuum installations with well controlled parameters for measurement of D retention in plasma exposed (as well in situ in simulators) samples and started comparative studies of samples radiated at different tokamaks and laboratory installations

21

Plansbull Investigations of samples irradiated in LENTA PR-2

PIN laboratory plasma facilities as well as in T-10 TEXTOR and Tore Supra tokamaks are now in progress

bull As there is very large scattering of the experimental data

on D retention careful measurements at D retention via fluxes (at high fluxes) and temperature in different irradiation facilities are under way

bull To pick up contribution of different factors on D retention step by step experimental investigations at varying definite factors (im flux density consequent and simultaneous irradiation with deuterium and helium broad energy spectra influence etc) are planned

bull Experimental measurements of neutron irradiation influence on hydrogen isotopes retention in PFM is now discussed

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21

9

But physical mechanisms are far from full understanding

For adequate explanation versatile investigations using novel experimental methods as well as intimate theoretical analysis are necessary

For chemical active C based materials with compound structure (CFC) the task is much more complicated and need very careful investigations

10

0 2 4 6 8 1010-3

10-2

10-1

100

101 200 eV D plasma CFC NB31 2x1024 Dm2

Texp

= 463 K T

exp = 673 K

Texp

= 773 K T

exp = 948 K

D c

once

ntra

tion

[at

]

Depth [m]

0( ) [1 erf( )]2

xC x C

Dt

Migration in the bulk obeys diffusion equation with D=D(Fluence Temp)

10 15 20 25 3010-17

10-15

10-13

10-11

10-9

10-7

NB31 200 eV D plasma (Magnetron)

Coe

ffici

ent o

f D m

igra

tion

[m2 s

]

1000Temperature [K-1]

LA Sedano et al (1998) NB11 Matrix N11 Matrix NB11 Fibres N11 Fibres

Values for the deuterium migration derived from the D depth profiles are in good agreement with data for intrinsic hydrogen diffusivity in the fibres Migration through pores along fibres with low activation energy may be considered as mechanism of deuterium penetration into the bulk of the CFC materials

Channels of D transport in CFC VAlimov et al

11

Fine grain graphite (as well as CFC) ndashtransparent for gases in principle

Penetrating gas flow via gas pressure for MPG-8 graphite (thickness 126 mm diameter 305 mm)

room temperature

Measured gas flux density j ~ σ P σ Ad

P ndashpressure A ndasharea d- thickness σ ndash specific gas permeability

σ = 5middot1015 mols for MPG-8

Flu

x m

ols

Pressure Pa

Graphite sheet behaves as capillary A=1m2 d =1cm P =1Pa 35middot1017 D2s

12

Influence of tokamak T-10 exposure on MPG-8 graphite permeability

MPG-8 membrane 18 mm thick cut off T-10 limiter demonstrated hydrogen permeability ~9middot1015 molmiddotc-1m-1Pa-1 - 2 times more than for ldquovirginrdquo graphite

Possible reason ndash graphite porosity increase after long term expose in tokamak

All attempts to increase MPG-8 permeability in lab plasma experiments failed

4 mm

Place of limiter tile used for the membrane

14

Comparison of lab experiments and tokamak exposed tile retention in CFC

TDS investigation of the samples CFC N11 implanted by deuterium ions in the laboratory setups (MEPhI) and high field side tile of Tore Supra

[1] Begrambekov L Brosset C Bucalossi J Delchambre E Gunn JP Grisolia C Lipa M Loarer T Mitteau R PMoner-Garbet P Pascal J-Y PShigin P Titov N Tsitrone E Vergazov S Zakharov A ldquoSurface modification and hydrogen isotope retention in CFC during plasma irradiation in the Tore Supra tokamakrdquo17th Internal Conference on Plasma Surface Interactions in Controlled Fusion Devices (PSI17) Hefei China May 22 ndash 26 2006

LABORATORY SAMPLE

TORE SUPRA TILE [1]

Particles deuterons deuterons

Ion energy 50 100 200

500 eV

10-100 eV (as well as low energy atoms molecules and charge exchange neutrals )

Ion flux density 1times1020 atm2s (1-2)times1019 atm2s

Fluence 5times1023 atm2 5times1023 atm2 (estimated)

Surface temperature 450-470 K up to 500-600 K

Retention ~07times1021 atm2 ~2times1022 atm2 (30 times higher)

15

Hydrogen retention via fluence in lab exp

1021 1022 1023 1024 10251020

1021

1022

Hyd

roge

n re

tent

ion

at

m2

Fluence atm2

B4C 100 eVH MPG-8 100 eVH MPG-8 1 keVH HPG99 1 keVH [1] HOPG 100 eVH HOPG 1 keVH

Ion flux density = 35x1020 at(secm2)

[2] L Begrambekov O Buzhinsky A Gordeev E Miljaeva P Leikin P Shigin TDS investigation of hydrogen retention in graphites and carbon based materials Physica scripta N108 (2004) p72-75

Possible underestimation of tokamak tile irradiation fluence hardly could seriously influence the presented data -hydrogen retention will not increase 30 times even for ~100 times higher fluence

16

Possible mechanisms of enhanced D

trapping under tokamak plasma irradiation

1 Presence of hydrogen in the Tore Supra tiles

TDS spectra of H2 and D2 for the as prepared CFC N11 samples irradiated in deuterium plasma

Ei = 100 eVat

Ji = 121020 atm2s

Ф = 451023 atm2

Presence of hydrogen in the CFC twice increases deuterium trapping at the expense of filling the hydrogen traps by deuterium due to isotope

exchange mechanism

Lab experiment

17

2 Trapping of deuterium activated by electron irradiation

[ Collaboration DRFC CEA-Cadarache ndash MEPhI ROSATOM 2007]

Thermal desorption of deuterium as D2

and as CD4 from CFC graphite under

ion and electron irradiationEi=100 eVat Ji=121020 atm2s

Ф=451023 atm2

Increase of deuterium retention along with irradiation time as well as deuterium retention under electron irradiation support an assumption about participation of D2

molecules from surrounding atmosphere in deuterium trapping into graphites Ion and electron irradiation act as a driving forces of the process

Plasma electron irradiation of CFC increased deuterium trapping 12 ndash 3 times depending on energy distribution of impinging deuterium particles

0 200 400 600 800 100000

05

10

15

Ret

entio

n x

1017

at

cm2

Energy eVat

CFC D2 (1020)

D2 electron irr

CFC D2 (2x1019)

electronirradiation

18

3 Transportation of deuterium into the material and trapping in the bulk of the tile

TDS analysis of the samples cut from different depth of the tile shows that more 10 of cumulative trapping collected in the bulk of tile

The samples of 1 ndash 2 mm thickness are usually used in the laboratory experiments The laboratory results could be compared

only to trapping in surface region of tokamak tile

4 Deuterium trapping in graphites irradiated by ion flux with wide energy distribution

Peculiarities of deuterium trapping in graphites exposed to plasma allows to expect an enhancement of retention in graphites irradiated by ion flux with wide energy distribution in tokamaks in comparison with graphites subjected to mono energy ion irradiation in laboratory

setups

19

5 Graphite surface irradiation during Helium Glow Discharge Conditioning

Helium ion bombardment leads to development of the surface relief and destruction of near surface layer As result trapping of deuterium during tokamak discharges should be enhanced

6 Graphite surface irradiation by oxygen impurities

Graphite irradiation by ions and atoms of oxygen impurities leads to accelerated surface destruction and develop the surface As a result trapping of deuterium ions and neutrals by graphite surface is probably more enhanced

20

Conclusion

bull The long range D retention in general is the very complicated physical (amp chemical) problem Many observed features of this phenomenon is not clear now

bull Complex and multiple-factor impact of PFM in tokamaks makes difficult distinguishing its influence on the LR hydrogen isotopes retention

bull Laboratory experiments with well defined impact parameters are crucially necessary

bull During last two years we mounted and calibrated a series of high vacuum installations with well controlled parameters for measurement of D retention in plasma exposed (as well in situ in simulators) samples and started comparative studies of samples radiated at different tokamaks and laboratory installations

21

Plansbull Investigations of samples irradiated in LENTA PR-2

PIN laboratory plasma facilities as well as in T-10 TEXTOR and Tore Supra tokamaks are now in progress

bull As there is very large scattering of the experimental data

on D retention careful measurements at D retention via fluxes (at high fluxes) and temperature in different irradiation facilities are under way

bull To pick up contribution of different factors on D retention step by step experimental investigations at varying definite factors (im flux density consequent and simultaneous irradiation with deuterium and helium broad energy spectra influence etc) are planned

bull Experimental measurements of neutron irradiation influence on hydrogen isotopes retention in PFM is now discussed

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21

10

0 2 4 6 8 1010-3

10-2

10-1

100

101 200 eV D plasma CFC NB31 2x1024 Dm2

Texp

= 463 K T

exp = 673 K

Texp

= 773 K T

exp = 948 K

D c

once

ntra

tion

[at

]

Depth [m]

0( ) [1 erf( )]2

xC x C

Dt

Migration in the bulk obeys diffusion equation with D=D(Fluence Temp)

10 15 20 25 3010-17

10-15

10-13

10-11

10-9

10-7

NB31 200 eV D plasma (Magnetron)

Coe

ffici

ent o

f D m

igra

tion

[m2 s

]

1000Temperature [K-1]

LA Sedano et al (1998) NB11 Matrix N11 Matrix NB11 Fibres N11 Fibres

Values for the deuterium migration derived from the D depth profiles are in good agreement with data for intrinsic hydrogen diffusivity in the fibres Migration through pores along fibres with low activation energy may be considered as mechanism of deuterium penetration into the bulk of the CFC materials

Channels of D transport in CFC VAlimov et al

11

Fine grain graphite (as well as CFC) ndashtransparent for gases in principle

Penetrating gas flow via gas pressure for MPG-8 graphite (thickness 126 mm diameter 305 mm)

room temperature

Measured gas flux density j ~ σ P σ Ad

P ndashpressure A ndasharea d- thickness σ ndash specific gas permeability

σ = 5middot1015 mols for MPG-8

Flu

x m

ols

Pressure Pa

Graphite sheet behaves as capillary A=1m2 d =1cm P =1Pa 35middot1017 D2s

12

Influence of tokamak T-10 exposure on MPG-8 graphite permeability

MPG-8 membrane 18 mm thick cut off T-10 limiter demonstrated hydrogen permeability ~9middot1015 molmiddotc-1m-1Pa-1 - 2 times more than for ldquovirginrdquo graphite

Possible reason ndash graphite porosity increase after long term expose in tokamak

All attempts to increase MPG-8 permeability in lab plasma experiments failed

4 mm

Place of limiter tile used for the membrane

14

Comparison of lab experiments and tokamak exposed tile retention in CFC

TDS investigation of the samples CFC N11 implanted by deuterium ions in the laboratory setups (MEPhI) and high field side tile of Tore Supra

[1] Begrambekov L Brosset C Bucalossi J Delchambre E Gunn JP Grisolia C Lipa M Loarer T Mitteau R PMoner-Garbet P Pascal J-Y PShigin P Titov N Tsitrone E Vergazov S Zakharov A ldquoSurface modification and hydrogen isotope retention in CFC during plasma irradiation in the Tore Supra tokamakrdquo17th Internal Conference on Plasma Surface Interactions in Controlled Fusion Devices (PSI17) Hefei China May 22 ndash 26 2006

LABORATORY SAMPLE

TORE SUPRA TILE [1]

Particles deuterons deuterons

Ion energy 50 100 200

500 eV

10-100 eV (as well as low energy atoms molecules and charge exchange neutrals )

Ion flux density 1times1020 atm2s (1-2)times1019 atm2s

Fluence 5times1023 atm2 5times1023 atm2 (estimated)

Surface temperature 450-470 K up to 500-600 K

Retention ~07times1021 atm2 ~2times1022 atm2 (30 times higher)

15

Hydrogen retention via fluence in lab exp

1021 1022 1023 1024 10251020

1021

1022

Hyd

roge

n re

tent

ion

at

m2

Fluence atm2

B4C 100 eVH MPG-8 100 eVH MPG-8 1 keVH HPG99 1 keVH [1] HOPG 100 eVH HOPG 1 keVH

Ion flux density = 35x1020 at(secm2)

[2] L Begrambekov O Buzhinsky A Gordeev E Miljaeva P Leikin P Shigin TDS investigation of hydrogen retention in graphites and carbon based materials Physica scripta N108 (2004) p72-75

Possible underestimation of tokamak tile irradiation fluence hardly could seriously influence the presented data -hydrogen retention will not increase 30 times even for ~100 times higher fluence

16

Possible mechanisms of enhanced D

trapping under tokamak plasma irradiation

1 Presence of hydrogen in the Tore Supra tiles

TDS spectra of H2 and D2 for the as prepared CFC N11 samples irradiated in deuterium plasma

Ei = 100 eVat

Ji = 121020 atm2s

Ф = 451023 atm2

Presence of hydrogen in the CFC twice increases deuterium trapping at the expense of filling the hydrogen traps by deuterium due to isotope

exchange mechanism

Lab experiment

17

2 Trapping of deuterium activated by electron irradiation

[ Collaboration DRFC CEA-Cadarache ndash MEPhI ROSATOM 2007]

Thermal desorption of deuterium as D2

and as CD4 from CFC graphite under

ion and electron irradiationEi=100 eVat Ji=121020 atm2s

Ф=451023 atm2

Increase of deuterium retention along with irradiation time as well as deuterium retention under electron irradiation support an assumption about participation of D2

molecules from surrounding atmosphere in deuterium trapping into graphites Ion and electron irradiation act as a driving forces of the process

Plasma electron irradiation of CFC increased deuterium trapping 12 ndash 3 times depending on energy distribution of impinging deuterium particles

0 200 400 600 800 100000

05

10

15

Ret

entio

n x

1017

at

cm2

Energy eVat

CFC D2 (1020)

D2 electron irr

CFC D2 (2x1019)

electronirradiation

18

3 Transportation of deuterium into the material and trapping in the bulk of the tile

TDS analysis of the samples cut from different depth of the tile shows that more 10 of cumulative trapping collected in the bulk of tile

The samples of 1 ndash 2 mm thickness are usually used in the laboratory experiments The laboratory results could be compared

only to trapping in surface region of tokamak tile

4 Deuterium trapping in graphites irradiated by ion flux with wide energy distribution

Peculiarities of deuterium trapping in graphites exposed to plasma allows to expect an enhancement of retention in graphites irradiated by ion flux with wide energy distribution in tokamaks in comparison with graphites subjected to mono energy ion irradiation in laboratory

setups

19

5 Graphite surface irradiation during Helium Glow Discharge Conditioning

Helium ion bombardment leads to development of the surface relief and destruction of near surface layer As result trapping of deuterium during tokamak discharges should be enhanced

6 Graphite surface irradiation by oxygen impurities

Graphite irradiation by ions and atoms of oxygen impurities leads to accelerated surface destruction and develop the surface As a result trapping of deuterium ions and neutrals by graphite surface is probably more enhanced

20

Conclusion

bull The long range D retention in general is the very complicated physical (amp chemical) problem Many observed features of this phenomenon is not clear now

bull Complex and multiple-factor impact of PFM in tokamaks makes difficult distinguishing its influence on the LR hydrogen isotopes retention

bull Laboratory experiments with well defined impact parameters are crucially necessary

bull During last two years we mounted and calibrated a series of high vacuum installations with well controlled parameters for measurement of D retention in plasma exposed (as well in situ in simulators) samples and started comparative studies of samples radiated at different tokamaks and laboratory installations

21

Plansbull Investigations of samples irradiated in LENTA PR-2

PIN laboratory plasma facilities as well as in T-10 TEXTOR and Tore Supra tokamaks are now in progress

bull As there is very large scattering of the experimental data

on D retention careful measurements at D retention via fluxes (at high fluxes) and temperature in different irradiation facilities are under way

bull To pick up contribution of different factors on D retention step by step experimental investigations at varying definite factors (im flux density consequent and simultaneous irradiation with deuterium and helium broad energy spectra influence etc) are planned

bull Experimental measurements of neutron irradiation influence on hydrogen isotopes retention in PFM is now discussed

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21

11

Fine grain graphite (as well as CFC) ndashtransparent for gases in principle

Penetrating gas flow via gas pressure for MPG-8 graphite (thickness 126 mm diameter 305 mm)

room temperature

Measured gas flux density j ~ σ P σ Ad

P ndashpressure A ndasharea d- thickness σ ndash specific gas permeability

σ = 5middot1015 mols for MPG-8

Flu

x m

ols

Pressure Pa

Graphite sheet behaves as capillary A=1m2 d =1cm P =1Pa 35middot1017 D2s

12

Influence of tokamak T-10 exposure on MPG-8 graphite permeability

MPG-8 membrane 18 mm thick cut off T-10 limiter demonstrated hydrogen permeability ~9middot1015 molmiddotc-1m-1Pa-1 - 2 times more than for ldquovirginrdquo graphite

Possible reason ndash graphite porosity increase after long term expose in tokamak

All attempts to increase MPG-8 permeability in lab plasma experiments failed

4 mm

Place of limiter tile used for the membrane

14

Comparison of lab experiments and tokamak exposed tile retention in CFC

TDS investigation of the samples CFC N11 implanted by deuterium ions in the laboratory setups (MEPhI) and high field side tile of Tore Supra

[1] Begrambekov L Brosset C Bucalossi J Delchambre E Gunn JP Grisolia C Lipa M Loarer T Mitteau R PMoner-Garbet P Pascal J-Y PShigin P Titov N Tsitrone E Vergazov S Zakharov A ldquoSurface modification and hydrogen isotope retention in CFC during plasma irradiation in the Tore Supra tokamakrdquo17th Internal Conference on Plasma Surface Interactions in Controlled Fusion Devices (PSI17) Hefei China May 22 ndash 26 2006

LABORATORY SAMPLE

TORE SUPRA TILE [1]

Particles deuterons deuterons

Ion energy 50 100 200

500 eV

10-100 eV (as well as low energy atoms molecules and charge exchange neutrals )

Ion flux density 1times1020 atm2s (1-2)times1019 atm2s

Fluence 5times1023 atm2 5times1023 atm2 (estimated)

Surface temperature 450-470 K up to 500-600 K

Retention ~07times1021 atm2 ~2times1022 atm2 (30 times higher)

15

Hydrogen retention via fluence in lab exp

1021 1022 1023 1024 10251020

1021

1022

Hyd

roge

n re

tent

ion

at

m2

Fluence atm2

B4C 100 eVH MPG-8 100 eVH MPG-8 1 keVH HPG99 1 keVH [1] HOPG 100 eVH HOPG 1 keVH

Ion flux density = 35x1020 at(secm2)

[2] L Begrambekov O Buzhinsky A Gordeev E Miljaeva P Leikin P Shigin TDS investigation of hydrogen retention in graphites and carbon based materials Physica scripta N108 (2004) p72-75

Possible underestimation of tokamak tile irradiation fluence hardly could seriously influence the presented data -hydrogen retention will not increase 30 times even for ~100 times higher fluence

16

Possible mechanisms of enhanced D

trapping under tokamak plasma irradiation

1 Presence of hydrogen in the Tore Supra tiles

TDS spectra of H2 and D2 for the as prepared CFC N11 samples irradiated in deuterium plasma

Ei = 100 eVat

Ji = 121020 atm2s

Ф = 451023 atm2

Presence of hydrogen in the CFC twice increases deuterium trapping at the expense of filling the hydrogen traps by deuterium due to isotope

exchange mechanism

Lab experiment

17

2 Trapping of deuterium activated by electron irradiation

[ Collaboration DRFC CEA-Cadarache ndash MEPhI ROSATOM 2007]

Thermal desorption of deuterium as D2

and as CD4 from CFC graphite under

ion and electron irradiationEi=100 eVat Ji=121020 atm2s

Ф=451023 atm2

Increase of deuterium retention along with irradiation time as well as deuterium retention under electron irradiation support an assumption about participation of D2

molecules from surrounding atmosphere in deuterium trapping into graphites Ion and electron irradiation act as a driving forces of the process

Plasma electron irradiation of CFC increased deuterium trapping 12 ndash 3 times depending on energy distribution of impinging deuterium particles

0 200 400 600 800 100000

05

10

15

Ret

entio

n x

1017

at

cm2

Energy eVat

CFC D2 (1020)

D2 electron irr

CFC D2 (2x1019)

electronirradiation

18

3 Transportation of deuterium into the material and trapping in the bulk of the tile

TDS analysis of the samples cut from different depth of the tile shows that more 10 of cumulative trapping collected in the bulk of tile

The samples of 1 ndash 2 mm thickness are usually used in the laboratory experiments The laboratory results could be compared

only to trapping in surface region of tokamak tile

4 Deuterium trapping in graphites irradiated by ion flux with wide energy distribution

Peculiarities of deuterium trapping in graphites exposed to plasma allows to expect an enhancement of retention in graphites irradiated by ion flux with wide energy distribution in tokamaks in comparison with graphites subjected to mono energy ion irradiation in laboratory

setups

19

5 Graphite surface irradiation during Helium Glow Discharge Conditioning

Helium ion bombardment leads to development of the surface relief and destruction of near surface layer As result trapping of deuterium during tokamak discharges should be enhanced

6 Graphite surface irradiation by oxygen impurities

Graphite irradiation by ions and atoms of oxygen impurities leads to accelerated surface destruction and develop the surface As a result trapping of deuterium ions and neutrals by graphite surface is probably more enhanced

20

Conclusion

bull The long range D retention in general is the very complicated physical (amp chemical) problem Many observed features of this phenomenon is not clear now

bull Complex and multiple-factor impact of PFM in tokamaks makes difficult distinguishing its influence on the LR hydrogen isotopes retention

bull Laboratory experiments with well defined impact parameters are crucially necessary

bull During last two years we mounted and calibrated a series of high vacuum installations with well controlled parameters for measurement of D retention in plasma exposed (as well in situ in simulators) samples and started comparative studies of samples radiated at different tokamaks and laboratory installations

21

Plansbull Investigations of samples irradiated in LENTA PR-2

PIN laboratory plasma facilities as well as in T-10 TEXTOR and Tore Supra tokamaks are now in progress

bull As there is very large scattering of the experimental data

on D retention careful measurements at D retention via fluxes (at high fluxes) and temperature in different irradiation facilities are under way

bull To pick up contribution of different factors on D retention step by step experimental investigations at varying definite factors (im flux density consequent and simultaneous irradiation with deuterium and helium broad energy spectra influence etc) are planned

bull Experimental measurements of neutron irradiation influence on hydrogen isotopes retention in PFM is now discussed

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21

12

Influence of tokamak T-10 exposure on MPG-8 graphite permeability

MPG-8 membrane 18 mm thick cut off T-10 limiter demonstrated hydrogen permeability ~9middot1015 molmiddotc-1m-1Pa-1 - 2 times more than for ldquovirginrdquo graphite

Possible reason ndash graphite porosity increase after long term expose in tokamak

All attempts to increase MPG-8 permeability in lab plasma experiments failed

4 mm

Place of limiter tile used for the membrane

14

Comparison of lab experiments and tokamak exposed tile retention in CFC

TDS investigation of the samples CFC N11 implanted by deuterium ions in the laboratory setups (MEPhI) and high field side tile of Tore Supra

[1] Begrambekov L Brosset C Bucalossi J Delchambre E Gunn JP Grisolia C Lipa M Loarer T Mitteau R PMoner-Garbet P Pascal J-Y PShigin P Titov N Tsitrone E Vergazov S Zakharov A ldquoSurface modification and hydrogen isotope retention in CFC during plasma irradiation in the Tore Supra tokamakrdquo17th Internal Conference on Plasma Surface Interactions in Controlled Fusion Devices (PSI17) Hefei China May 22 ndash 26 2006

LABORATORY SAMPLE

TORE SUPRA TILE [1]

Particles deuterons deuterons

Ion energy 50 100 200

500 eV

10-100 eV (as well as low energy atoms molecules and charge exchange neutrals )

Ion flux density 1times1020 atm2s (1-2)times1019 atm2s

Fluence 5times1023 atm2 5times1023 atm2 (estimated)

Surface temperature 450-470 K up to 500-600 K

Retention ~07times1021 atm2 ~2times1022 atm2 (30 times higher)

15

Hydrogen retention via fluence in lab exp

1021 1022 1023 1024 10251020

1021

1022

Hyd

roge

n re

tent

ion

at

m2

Fluence atm2

B4C 100 eVH MPG-8 100 eVH MPG-8 1 keVH HPG99 1 keVH [1] HOPG 100 eVH HOPG 1 keVH

Ion flux density = 35x1020 at(secm2)

[2] L Begrambekov O Buzhinsky A Gordeev E Miljaeva P Leikin P Shigin TDS investigation of hydrogen retention in graphites and carbon based materials Physica scripta N108 (2004) p72-75

Possible underestimation of tokamak tile irradiation fluence hardly could seriously influence the presented data -hydrogen retention will not increase 30 times even for ~100 times higher fluence

16

Possible mechanisms of enhanced D

trapping under tokamak plasma irradiation

1 Presence of hydrogen in the Tore Supra tiles

TDS spectra of H2 and D2 for the as prepared CFC N11 samples irradiated in deuterium plasma

Ei = 100 eVat

Ji = 121020 atm2s

Ф = 451023 atm2

Presence of hydrogen in the CFC twice increases deuterium trapping at the expense of filling the hydrogen traps by deuterium due to isotope

exchange mechanism

Lab experiment

17

2 Trapping of deuterium activated by electron irradiation

[ Collaboration DRFC CEA-Cadarache ndash MEPhI ROSATOM 2007]

Thermal desorption of deuterium as D2

and as CD4 from CFC graphite under

ion and electron irradiationEi=100 eVat Ji=121020 atm2s

Ф=451023 atm2

Increase of deuterium retention along with irradiation time as well as deuterium retention under electron irradiation support an assumption about participation of D2

molecules from surrounding atmosphere in deuterium trapping into graphites Ion and electron irradiation act as a driving forces of the process

Plasma electron irradiation of CFC increased deuterium trapping 12 ndash 3 times depending on energy distribution of impinging deuterium particles

0 200 400 600 800 100000

05

10

15

Ret

entio

n x

1017

at

cm2

Energy eVat

CFC D2 (1020)

D2 electron irr

CFC D2 (2x1019)

electronirradiation

18

3 Transportation of deuterium into the material and trapping in the bulk of the tile

TDS analysis of the samples cut from different depth of the tile shows that more 10 of cumulative trapping collected in the bulk of tile

The samples of 1 ndash 2 mm thickness are usually used in the laboratory experiments The laboratory results could be compared

only to trapping in surface region of tokamak tile

4 Deuterium trapping in graphites irradiated by ion flux with wide energy distribution

Peculiarities of deuterium trapping in graphites exposed to plasma allows to expect an enhancement of retention in graphites irradiated by ion flux with wide energy distribution in tokamaks in comparison with graphites subjected to mono energy ion irradiation in laboratory

setups

19

5 Graphite surface irradiation during Helium Glow Discharge Conditioning

Helium ion bombardment leads to development of the surface relief and destruction of near surface layer As result trapping of deuterium during tokamak discharges should be enhanced

6 Graphite surface irradiation by oxygen impurities

Graphite irradiation by ions and atoms of oxygen impurities leads to accelerated surface destruction and develop the surface As a result trapping of deuterium ions and neutrals by graphite surface is probably more enhanced

20

Conclusion

bull The long range D retention in general is the very complicated physical (amp chemical) problem Many observed features of this phenomenon is not clear now

bull Complex and multiple-factor impact of PFM in tokamaks makes difficult distinguishing its influence on the LR hydrogen isotopes retention

bull Laboratory experiments with well defined impact parameters are crucially necessary

bull During last two years we mounted and calibrated a series of high vacuum installations with well controlled parameters for measurement of D retention in plasma exposed (as well in situ in simulators) samples and started comparative studies of samples radiated at different tokamaks and laboratory installations

21

Plansbull Investigations of samples irradiated in LENTA PR-2

PIN laboratory plasma facilities as well as in T-10 TEXTOR and Tore Supra tokamaks are now in progress

bull As there is very large scattering of the experimental data

on D retention careful measurements at D retention via fluxes (at high fluxes) and temperature in different irradiation facilities are under way

bull To pick up contribution of different factors on D retention step by step experimental investigations at varying definite factors (im flux density consequent and simultaneous irradiation with deuterium and helium broad energy spectra influence etc) are planned

bull Experimental measurements of neutron irradiation influence on hydrogen isotopes retention in PFM is now discussed

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21

14

Comparison of lab experiments and tokamak exposed tile retention in CFC

TDS investigation of the samples CFC N11 implanted by deuterium ions in the laboratory setups (MEPhI) and high field side tile of Tore Supra

[1] Begrambekov L Brosset C Bucalossi J Delchambre E Gunn JP Grisolia C Lipa M Loarer T Mitteau R PMoner-Garbet P Pascal J-Y PShigin P Titov N Tsitrone E Vergazov S Zakharov A ldquoSurface modification and hydrogen isotope retention in CFC during plasma irradiation in the Tore Supra tokamakrdquo17th Internal Conference on Plasma Surface Interactions in Controlled Fusion Devices (PSI17) Hefei China May 22 ndash 26 2006

LABORATORY SAMPLE

TORE SUPRA TILE [1]

Particles deuterons deuterons

Ion energy 50 100 200

500 eV

10-100 eV (as well as low energy atoms molecules and charge exchange neutrals )

Ion flux density 1times1020 atm2s (1-2)times1019 atm2s

Fluence 5times1023 atm2 5times1023 atm2 (estimated)

Surface temperature 450-470 K up to 500-600 K

Retention ~07times1021 atm2 ~2times1022 atm2 (30 times higher)

15

Hydrogen retention via fluence in lab exp

1021 1022 1023 1024 10251020

1021

1022

Hyd

roge

n re

tent

ion

at

m2

Fluence atm2

B4C 100 eVH MPG-8 100 eVH MPG-8 1 keVH HPG99 1 keVH [1] HOPG 100 eVH HOPG 1 keVH

Ion flux density = 35x1020 at(secm2)

[2] L Begrambekov O Buzhinsky A Gordeev E Miljaeva P Leikin P Shigin TDS investigation of hydrogen retention in graphites and carbon based materials Physica scripta N108 (2004) p72-75

Possible underestimation of tokamak tile irradiation fluence hardly could seriously influence the presented data -hydrogen retention will not increase 30 times even for ~100 times higher fluence

16

Possible mechanisms of enhanced D

trapping under tokamak plasma irradiation

1 Presence of hydrogen in the Tore Supra tiles

TDS spectra of H2 and D2 for the as prepared CFC N11 samples irradiated in deuterium plasma

Ei = 100 eVat

Ji = 121020 atm2s

Ф = 451023 atm2

Presence of hydrogen in the CFC twice increases deuterium trapping at the expense of filling the hydrogen traps by deuterium due to isotope

exchange mechanism

Lab experiment

17

2 Trapping of deuterium activated by electron irradiation

[ Collaboration DRFC CEA-Cadarache ndash MEPhI ROSATOM 2007]

Thermal desorption of deuterium as D2

and as CD4 from CFC graphite under

ion and electron irradiationEi=100 eVat Ji=121020 atm2s

Ф=451023 atm2

Increase of deuterium retention along with irradiation time as well as deuterium retention under electron irradiation support an assumption about participation of D2

molecules from surrounding atmosphere in deuterium trapping into graphites Ion and electron irradiation act as a driving forces of the process

Plasma electron irradiation of CFC increased deuterium trapping 12 ndash 3 times depending on energy distribution of impinging deuterium particles

0 200 400 600 800 100000

05

10

15

Ret

entio

n x

1017

at

cm2

Energy eVat

CFC D2 (1020)

D2 electron irr

CFC D2 (2x1019)

electronirradiation

18

3 Transportation of deuterium into the material and trapping in the bulk of the tile

TDS analysis of the samples cut from different depth of the tile shows that more 10 of cumulative trapping collected in the bulk of tile

The samples of 1 ndash 2 mm thickness are usually used in the laboratory experiments The laboratory results could be compared

only to trapping in surface region of tokamak tile

4 Deuterium trapping in graphites irradiated by ion flux with wide energy distribution

Peculiarities of deuterium trapping in graphites exposed to plasma allows to expect an enhancement of retention in graphites irradiated by ion flux with wide energy distribution in tokamaks in comparison with graphites subjected to mono energy ion irradiation in laboratory

setups

19

5 Graphite surface irradiation during Helium Glow Discharge Conditioning

Helium ion bombardment leads to development of the surface relief and destruction of near surface layer As result trapping of deuterium during tokamak discharges should be enhanced

6 Graphite surface irradiation by oxygen impurities

Graphite irradiation by ions and atoms of oxygen impurities leads to accelerated surface destruction and develop the surface As a result trapping of deuterium ions and neutrals by graphite surface is probably more enhanced

20

Conclusion

bull The long range D retention in general is the very complicated physical (amp chemical) problem Many observed features of this phenomenon is not clear now

bull Complex and multiple-factor impact of PFM in tokamaks makes difficult distinguishing its influence on the LR hydrogen isotopes retention

bull Laboratory experiments with well defined impact parameters are crucially necessary

bull During last two years we mounted and calibrated a series of high vacuum installations with well controlled parameters for measurement of D retention in plasma exposed (as well in situ in simulators) samples and started comparative studies of samples radiated at different tokamaks and laboratory installations

21

Plansbull Investigations of samples irradiated in LENTA PR-2

PIN laboratory plasma facilities as well as in T-10 TEXTOR and Tore Supra tokamaks are now in progress

bull As there is very large scattering of the experimental data

on D retention careful measurements at D retention via fluxes (at high fluxes) and temperature in different irradiation facilities are under way

bull To pick up contribution of different factors on D retention step by step experimental investigations at varying definite factors (im flux density consequent and simultaneous irradiation with deuterium and helium broad energy spectra influence etc) are planned

bull Experimental measurements of neutron irradiation influence on hydrogen isotopes retention in PFM is now discussed

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21

15

Hydrogen retention via fluence in lab exp

1021 1022 1023 1024 10251020

1021

1022

Hyd

roge

n re

tent

ion

at

m2

Fluence atm2

B4C 100 eVH MPG-8 100 eVH MPG-8 1 keVH HPG99 1 keVH [1] HOPG 100 eVH HOPG 1 keVH

Ion flux density = 35x1020 at(secm2)

[2] L Begrambekov O Buzhinsky A Gordeev E Miljaeva P Leikin P Shigin TDS investigation of hydrogen retention in graphites and carbon based materials Physica scripta N108 (2004) p72-75

Possible underestimation of tokamak tile irradiation fluence hardly could seriously influence the presented data -hydrogen retention will not increase 30 times even for ~100 times higher fluence

16

Possible mechanisms of enhanced D

trapping under tokamak plasma irradiation

1 Presence of hydrogen in the Tore Supra tiles

TDS spectra of H2 and D2 for the as prepared CFC N11 samples irradiated in deuterium plasma

Ei = 100 eVat

Ji = 121020 atm2s

Ф = 451023 atm2

Presence of hydrogen in the CFC twice increases deuterium trapping at the expense of filling the hydrogen traps by deuterium due to isotope

exchange mechanism

Lab experiment

17

2 Trapping of deuterium activated by electron irradiation

[ Collaboration DRFC CEA-Cadarache ndash MEPhI ROSATOM 2007]

Thermal desorption of deuterium as D2

and as CD4 from CFC graphite under

ion and electron irradiationEi=100 eVat Ji=121020 atm2s

Ф=451023 atm2

Increase of deuterium retention along with irradiation time as well as deuterium retention under electron irradiation support an assumption about participation of D2

molecules from surrounding atmosphere in deuterium trapping into graphites Ion and electron irradiation act as a driving forces of the process

Plasma electron irradiation of CFC increased deuterium trapping 12 ndash 3 times depending on energy distribution of impinging deuterium particles

0 200 400 600 800 100000

05

10

15

Ret

entio

n x

1017

at

cm2

Energy eVat

CFC D2 (1020)

D2 electron irr

CFC D2 (2x1019)

electronirradiation

18

3 Transportation of deuterium into the material and trapping in the bulk of the tile

TDS analysis of the samples cut from different depth of the tile shows that more 10 of cumulative trapping collected in the bulk of tile

The samples of 1 ndash 2 mm thickness are usually used in the laboratory experiments The laboratory results could be compared

only to trapping in surface region of tokamak tile

4 Deuterium trapping in graphites irradiated by ion flux with wide energy distribution

Peculiarities of deuterium trapping in graphites exposed to plasma allows to expect an enhancement of retention in graphites irradiated by ion flux with wide energy distribution in tokamaks in comparison with graphites subjected to mono energy ion irradiation in laboratory

setups

19

5 Graphite surface irradiation during Helium Glow Discharge Conditioning

Helium ion bombardment leads to development of the surface relief and destruction of near surface layer As result trapping of deuterium during tokamak discharges should be enhanced

6 Graphite surface irradiation by oxygen impurities

Graphite irradiation by ions and atoms of oxygen impurities leads to accelerated surface destruction and develop the surface As a result trapping of deuterium ions and neutrals by graphite surface is probably more enhanced

20

Conclusion

bull The long range D retention in general is the very complicated physical (amp chemical) problem Many observed features of this phenomenon is not clear now

bull Complex and multiple-factor impact of PFM in tokamaks makes difficult distinguishing its influence on the LR hydrogen isotopes retention

bull Laboratory experiments with well defined impact parameters are crucially necessary

bull During last two years we mounted and calibrated a series of high vacuum installations with well controlled parameters for measurement of D retention in plasma exposed (as well in situ in simulators) samples and started comparative studies of samples radiated at different tokamaks and laboratory installations

21

Plansbull Investigations of samples irradiated in LENTA PR-2

PIN laboratory plasma facilities as well as in T-10 TEXTOR and Tore Supra tokamaks are now in progress

bull As there is very large scattering of the experimental data

on D retention careful measurements at D retention via fluxes (at high fluxes) and temperature in different irradiation facilities are under way

bull To pick up contribution of different factors on D retention step by step experimental investigations at varying definite factors (im flux density consequent and simultaneous irradiation with deuterium and helium broad energy spectra influence etc) are planned

bull Experimental measurements of neutron irradiation influence on hydrogen isotopes retention in PFM is now discussed

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21

16

Possible mechanisms of enhanced D

trapping under tokamak plasma irradiation

1 Presence of hydrogen in the Tore Supra tiles

TDS spectra of H2 and D2 for the as prepared CFC N11 samples irradiated in deuterium plasma

Ei = 100 eVat

Ji = 121020 atm2s

Ф = 451023 atm2

Presence of hydrogen in the CFC twice increases deuterium trapping at the expense of filling the hydrogen traps by deuterium due to isotope

exchange mechanism

Lab experiment

17

2 Trapping of deuterium activated by electron irradiation

[ Collaboration DRFC CEA-Cadarache ndash MEPhI ROSATOM 2007]

Thermal desorption of deuterium as D2

and as CD4 from CFC graphite under

ion and electron irradiationEi=100 eVat Ji=121020 atm2s

Ф=451023 atm2

Increase of deuterium retention along with irradiation time as well as deuterium retention under electron irradiation support an assumption about participation of D2

molecules from surrounding atmosphere in deuterium trapping into graphites Ion and electron irradiation act as a driving forces of the process

Plasma electron irradiation of CFC increased deuterium trapping 12 ndash 3 times depending on energy distribution of impinging deuterium particles

0 200 400 600 800 100000

05

10

15

Ret

entio

n x

1017

at

cm2

Energy eVat

CFC D2 (1020)

D2 electron irr

CFC D2 (2x1019)

electronirradiation

18

3 Transportation of deuterium into the material and trapping in the bulk of the tile

TDS analysis of the samples cut from different depth of the tile shows that more 10 of cumulative trapping collected in the bulk of tile

The samples of 1 ndash 2 mm thickness are usually used in the laboratory experiments The laboratory results could be compared

only to trapping in surface region of tokamak tile

4 Deuterium trapping in graphites irradiated by ion flux with wide energy distribution

Peculiarities of deuterium trapping in graphites exposed to plasma allows to expect an enhancement of retention in graphites irradiated by ion flux with wide energy distribution in tokamaks in comparison with graphites subjected to mono energy ion irradiation in laboratory

setups

19

5 Graphite surface irradiation during Helium Glow Discharge Conditioning

Helium ion bombardment leads to development of the surface relief and destruction of near surface layer As result trapping of deuterium during tokamak discharges should be enhanced

6 Graphite surface irradiation by oxygen impurities

Graphite irradiation by ions and atoms of oxygen impurities leads to accelerated surface destruction and develop the surface As a result trapping of deuterium ions and neutrals by graphite surface is probably more enhanced

20

Conclusion

bull The long range D retention in general is the very complicated physical (amp chemical) problem Many observed features of this phenomenon is not clear now

bull Complex and multiple-factor impact of PFM in tokamaks makes difficult distinguishing its influence on the LR hydrogen isotopes retention

bull Laboratory experiments with well defined impact parameters are crucially necessary

bull During last two years we mounted and calibrated a series of high vacuum installations with well controlled parameters for measurement of D retention in plasma exposed (as well in situ in simulators) samples and started comparative studies of samples radiated at different tokamaks and laboratory installations

21

Plansbull Investigations of samples irradiated in LENTA PR-2

PIN laboratory plasma facilities as well as in T-10 TEXTOR and Tore Supra tokamaks are now in progress

bull As there is very large scattering of the experimental data

on D retention careful measurements at D retention via fluxes (at high fluxes) and temperature in different irradiation facilities are under way

bull To pick up contribution of different factors on D retention step by step experimental investigations at varying definite factors (im flux density consequent and simultaneous irradiation with deuterium and helium broad energy spectra influence etc) are planned

bull Experimental measurements of neutron irradiation influence on hydrogen isotopes retention in PFM is now discussed

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21

17

2 Trapping of deuterium activated by electron irradiation

[ Collaboration DRFC CEA-Cadarache ndash MEPhI ROSATOM 2007]

Thermal desorption of deuterium as D2

and as CD4 from CFC graphite under

ion and electron irradiationEi=100 eVat Ji=121020 atm2s

Ф=451023 atm2

Increase of deuterium retention along with irradiation time as well as deuterium retention under electron irradiation support an assumption about participation of D2

molecules from surrounding atmosphere in deuterium trapping into graphites Ion and electron irradiation act as a driving forces of the process

Plasma electron irradiation of CFC increased deuterium trapping 12 ndash 3 times depending on energy distribution of impinging deuterium particles

0 200 400 600 800 100000

05

10

15

Ret

entio

n x

1017

at

cm2

Energy eVat

CFC D2 (1020)

D2 electron irr

CFC D2 (2x1019)

electronirradiation

18

3 Transportation of deuterium into the material and trapping in the bulk of the tile

TDS analysis of the samples cut from different depth of the tile shows that more 10 of cumulative trapping collected in the bulk of tile

The samples of 1 ndash 2 mm thickness are usually used in the laboratory experiments The laboratory results could be compared

only to trapping in surface region of tokamak tile

4 Deuterium trapping in graphites irradiated by ion flux with wide energy distribution

Peculiarities of deuterium trapping in graphites exposed to plasma allows to expect an enhancement of retention in graphites irradiated by ion flux with wide energy distribution in tokamaks in comparison with graphites subjected to mono energy ion irradiation in laboratory

setups

19

5 Graphite surface irradiation during Helium Glow Discharge Conditioning

Helium ion bombardment leads to development of the surface relief and destruction of near surface layer As result trapping of deuterium during tokamak discharges should be enhanced

6 Graphite surface irradiation by oxygen impurities

Graphite irradiation by ions and atoms of oxygen impurities leads to accelerated surface destruction and develop the surface As a result trapping of deuterium ions and neutrals by graphite surface is probably more enhanced

20

Conclusion

bull The long range D retention in general is the very complicated physical (amp chemical) problem Many observed features of this phenomenon is not clear now

bull Complex and multiple-factor impact of PFM in tokamaks makes difficult distinguishing its influence on the LR hydrogen isotopes retention

bull Laboratory experiments with well defined impact parameters are crucially necessary

bull During last two years we mounted and calibrated a series of high vacuum installations with well controlled parameters for measurement of D retention in plasma exposed (as well in situ in simulators) samples and started comparative studies of samples radiated at different tokamaks and laboratory installations

21

Plansbull Investigations of samples irradiated in LENTA PR-2

PIN laboratory plasma facilities as well as in T-10 TEXTOR and Tore Supra tokamaks are now in progress

bull As there is very large scattering of the experimental data

on D retention careful measurements at D retention via fluxes (at high fluxes) and temperature in different irradiation facilities are under way

bull To pick up contribution of different factors on D retention step by step experimental investigations at varying definite factors (im flux density consequent and simultaneous irradiation with deuterium and helium broad energy spectra influence etc) are planned

bull Experimental measurements of neutron irradiation influence on hydrogen isotopes retention in PFM is now discussed

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21

18

3 Transportation of deuterium into the material and trapping in the bulk of the tile

TDS analysis of the samples cut from different depth of the tile shows that more 10 of cumulative trapping collected in the bulk of tile

The samples of 1 ndash 2 mm thickness are usually used in the laboratory experiments The laboratory results could be compared

only to trapping in surface region of tokamak tile

4 Deuterium trapping in graphites irradiated by ion flux with wide energy distribution

Peculiarities of deuterium trapping in graphites exposed to plasma allows to expect an enhancement of retention in graphites irradiated by ion flux with wide energy distribution in tokamaks in comparison with graphites subjected to mono energy ion irradiation in laboratory

setups

19

5 Graphite surface irradiation during Helium Glow Discharge Conditioning

Helium ion bombardment leads to development of the surface relief and destruction of near surface layer As result trapping of deuterium during tokamak discharges should be enhanced

6 Graphite surface irradiation by oxygen impurities

Graphite irradiation by ions and atoms of oxygen impurities leads to accelerated surface destruction and develop the surface As a result trapping of deuterium ions and neutrals by graphite surface is probably more enhanced

20

Conclusion

bull The long range D retention in general is the very complicated physical (amp chemical) problem Many observed features of this phenomenon is not clear now

bull Complex and multiple-factor impact of PFM in tokamaks makes difficult distinguishing its influence on the LR hydrogen isotopes retention

bull Laboratory experiments with well defined impact parameters are crucially necessary

bull During last two years we mounted and calibrated a series of high vacuum installations with well controlled parameters for measurement of D retention in plasma exposed (as well in situ in simulators) samples and started comparative studies of samples radiated at different tokamaks and laboratory installations

21

Plansbull Investigations of samples irradiated in LENTA PR-2

PIN laboratory plasma facilities as well as in T-10 TEXTOR and Tore Supra tokamaks are now in progress

bull As there is very large scattering of the experimental data

on D retention careful measurements at D retention via fluxes (at high fluxes) and temperature in different irradiation facilities are under way

bull To pick up contribution of different factors on D retention step by step experimental investigations at varying definite factors (im flux density consequent and simultaneous irradiation with deuterium and helium broad energy spectra influence etc) are planned

bull Experimental measurements of neutron irradiation influence on hydrogen isotopes retention in PFM is now discussed

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21

19

5 Graphite surface irradiation during Helium Glow Discharge Conditioning

Helium ion bombardment leads to development of the surface relief and destruction of near surface layer As result trapping of deuterium during tokamak discharges should be enhanced

6 Graphite surface irradiation by oxygen impurities

Graphite irradiation by ions and atoms of oxygen impurities leads to accelerated surface destruction and develop the surface As a result trapping of deuterium ions and neutrals by graphite surface is probably more enhanced

20

Conclusion

bull The long range D retention in general is the very complicated physical (amp chemical) problem Many observed features of this phenomenon is not clear now

bull Complex and multiple-factor impact of PFM in tokamaks makes difficult distinguishing its influence on the LR hydrogen isotopes retention

bull Laboratory experiments with well defined impact parameters are crucially necessary

bull During last two years we mounted and calibrated a series of high vacuum installations with well controlled parameters for measurement of D retention in plasma exposed (as well in situ in simulators) samples and started comparative studies of samples radiated at different tokamaks and laboratory installations

21

Plansbull Investigations of samples irradiated in LENTA PR-2

PIN laboratory plasma facilities as well as in T-10 TEXTOR and Tore Supra tokamaks are now in progress

bull As there is very large scattering of the experimental data

on D retention careful measurements at D retention via fluxes (at high fluxes) and temperature in different irradiation facilities are under way

bull To pick up contribution of different factors on D retention step by step experimental investigations at varying definite factors (im flux density consequent and simultaneous irradiation with deuterium and helium broad energy spectra influence etc) are planned

bull Experimental measurements of neutron irradiation influence on hydrogen isotopes retention in PFM is now discussed

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21

20

Conclusion

bull The long range D retention in general is the very complicated physical (amp chemical) problem Many observed features of this phenomenon is not clear now

bull Complex and multiple-factor impact of PFM in tokamaks makes difficult distinguishing its influence on the LR hydrogen isotopes retention

bull Laboratory experiments with well defined impact parameters are crucially necessary

bull During last two years we mounted and calibrated a series of high vacuum installations with well controlled parameters for measurement of D retention in plasma exposed (as well in situ in simulators) samples and started comparative studies of samples radiated at different tokamaks and laboratory installations

21

Plansbull Investigations of samples irradiated in LENTA PR-2

PIN laboratory plasma facilities as well as in T-10 TEXTOR and Tore Supra tokamaks are now in progress

bull As there is very large scattering of the experimental data

on D retention careful measurements at D retention via fluxes (at high fluxes) and temperature in different irradiation facilities are under way

bull To pick up contribution of different factors on D retention step by step experimental investigations at varying definite factors (im flux density consequent and simultaneous irradiation with deuterium and helium broad energy spectra influence etc) are planned

bull Experimental measurements of neutron irradiation influence on hydrogen isotopes retention in PFM is now discussed

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21

21

Plansbull Investigations of samples irradiated in LENTA PR-2

PIN laboratory plasma facilities as well as in T-10 TEXTOR and Tore Supra tokamaks are now in progress

bull As there is very large scattering of the experimental data

on D retention careful measurements at D retention via fluxes (at high fluxes) and temperature in different irradiation facilities are under way

bull To pick up contribution of different factors on D retention step by step experimental investigations at varying definite factors (im flux density consequent and simultaneous irradiation with deuterium and helium broad energy spectra influence etc) are planned

bull Experimental measurements of neutron irradiation influence on hydrogen isotopes retention in PFM is now discussed

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21