11

Confinement and MHD Confinement and MHD Stability in the Large Stability in the Large

Helical DeviceHelical Device

Osamu MotojimaOsamu MotojimaLHD Experimental Group LHD Experimental Group

National Institute for Fusion ScienceNational Institute for Fusion Science

IAEA2004, Vilamoura, Portugal, Nov. 1IAEA2004, Vilamoura, Portugal, Nov. 1, 2004, 2004

OV1OV1--44

22

Content of my paperContent of my paper

•• 1. Change of NIFS Organization 1. Change of NIFS Organization •• 2. MHD study2. MHD study•• 2.1. High beta experiment2.1. High beta experiment•• 2.2. Healing of magnetic island2.2. Healing of magnetic island•• 3. Extended operation regime in LHD3. Extended operation regime in LHD•• 3.1 Edge control by Local Island Divertor3.1 Edge control by Local Island Divertor•• 3.2 Control of radial electric field by shift of magnetic axi3.2 Control of radial electric field by shift of magnetic axiss•• 3.3 Density limit and radiation collapse3.3 Density limit and radiation collapse•• 3.4 Achievement of high ion temperature with NBI3.4 Achievement of high ion temperature with NBI•• 3.5 Long pulse operation with ECH3.5 Long pulse operation with ECH•• 4 Transport study4 Transport study•• 4.1 Properties of particle and heat transport4.1 Properties of particle and heat transport•• 4.2 Electron transport 4.2 Electron transport •• 5 Summary5 Summary

33

Big Challenge!Big Challenge!National Institute for Fusion Science (NIFS)National Institute for Fusion Science (NIFS)

joined a new organization in April, 2004joined a new organization in April, 2004““National Institutes of Natural Sciences (NINS)National Institutes of Natural Sciences (NINS)””

NIFS will be incorporated into a new academic agency, NIFS will be incorporated into a new academic agency, as an interas an inter--university research institute for universities all over Japanuniversity research institute for universities all over Japan

Together with Okazaki National Research Institutes Together with Okazaki National Research Institutes (Institute for Molecular Science, National Institute for Basic B(Institute for Molecular Science, National Institute for Basic Biology iology and National Institute for Physiological Sciences) and National Institute for Physiological Sciences) and National Astronomical Observatory of Japanand National Astronomical Observatory of Japan

Fusion, Astronomy, Materials, Biology, etc.Fusion, Astronomy, Materials, Biology, etc.

Okazaki National Research InstituteOkazaki National Research Institute•• Institute for Molecular ScienceInstitute for Molecular Science•• National Institute for Basic BiologyNational Institute for Basic Biology•• National Institute for Physiological SciencesNational Institute for Physiological Sciences

National Astronomical National Astronomical Observatory of JapanObservatory of Japan

National Institute National Institute for Fusion Sciencefor Fusion Science

•• IIncrease the activities ncrease the activities of mutual cof mutual collaboration and exchange programollaboration and exchange programwith domestic and international universities and institutionswith domestic and international universities and institutionsto develop individual research areas and new science categoriesto develop individual research areas and new science categories

•• Provide adequate research opportunities for Provide adequate research opportunities for scientistsscientists•• Work Work with Universities to educate with Universities to educate graduate studentsgraduate students

44

Objectives of NIFS/LHD ProjectObjectives of NIFS/LHD ProjectNational Institute for Fusion ScienceNational Institute for Fusion Science•• Established in May, 1989Established in May, 1989

An An interinter--university National Instituteuniversity National Institute to promote scientific research of to promote scientific research of fusion plasmas and their applicationfusion plasmas and their application

Report of National Council for Science and Technology in 1984 Report of National Council for Science and Technology in 1984 •• NIFS promotes experimental and theoretical research into fusionNIFS promotes experimental and theoretical research into fusion

and plasma physics using the worldand plasma physics using the world’’s largest s largest superconducting helical experiment, the Large Helical Device (LHsuperconducting helical experiment, the Large Helical Device (LHD)D)and by means of and by means of theoretical and simulation studiestheoretical and simulation studies

Based on the Heliotron, an original Japanese conceptBased on the Heliotron, an original Japanese concept•• Increased effort in Increased effort in fusion technologyfusion technology

5

Ground Design of Japanese Fusion ResearchGround Design of Japanese Fusion ResearchNow, role of NIFS is clear Now, role of NIFS is clear . Keep a close relation with universities . Increase collaboration as a center of excellence of fusion research. Increase educational function in cooperation with the Graduate University

for Advanced Studies

Reactor engineering Fusion sciencePlasma Science

Scientific Research Basis

ITER

Fusion Reactor

IFMIF Tokamak LHD Laser(Development) (Science)

Development

Science

Stratified Structure of Research towards Fusion Reactor

Working Group on Fusion Research Future Direction of National Fusion Research

Special Committee on Basic Issues Subdivision on Science Council for Science and Technology

6

External diameter 13.5 mPlasma major radius 3.9 mPlasma minor radius 0.6 mPlasma volume 30 m3

Magnetic field 3 TTotal weight 1,500 t

NBI NBI

Local Island Divertor

(LID)

ECR84 – 168 GHz

ICRF25-100 MHz

Plasma vacuum vessel

World largest superconducting coil systemMagnetic energy 1 GJCryogenic mass (-269 degree C) 850 tTolerance < 2mm

Present View!Large Helical Device

(LHD)

7

Mission of LHDMission of LHD

(a)(a) To realize To realize high nhigh nττEETT plasmas and to study transport plasmas and to study transport physics applicable to fusion plasmas,physics applicable to fusion plasmas,

(b)(b) To demonstrate To demonstrate high high ββ stable plasmasstable plasmas (<(<ββ> > ≥≥ 5 %) 5 %) and to study related physics,and to study related physics,

(c)(c) To develop physics and technology for To develop physics and technology for long pulselong pulse or or steady state operation and control using steady state operation and control using divertordivertor,,

(d)(d) To study To study energetic particle behaviorsenergetic particle behaviors to simulate a to simulate a particles in fusion plasmas,particles in fusion plasmas,

(e)(e) To increase To increase the physics understanding of toroidal the physics understanding of toroidal plasmasplasmas by an approach which is by an approach which is complementarycomplementary to to tokamakstokamaks

Physics Issues Contributing to Fusion ResearchPhysics Issues Contributing to Fusion Research

8

Stored energy has reached 1.3MJ comparable to big tokamaks. Electron temperature 10 keV Ion temperature 10 keVBeta 4.1 % Density 2.4x1020 m-3

Pulse length 756 s

Steady progress of plasma parametersSteady progress of plasma parameters

0

2

4

6

8

10

12

0

100

200

300

400

500

600

700

800

1 2 3 4 5 6 7

Electron temp.Ion temp.

Tem

pera

ture

(keV

)

Pulse length (s)

Experimental campaign

Pulse length

'98 '99 '00 '01 '02 '03

0

5

10

ECHICHNBI

Hea

ting

Pow

er(M

W)

0

0.5

1.0

0 10000 20000 30000 40000 50000

1st(1998)2nd(1998)3rd (1999)4th(2000)

5th(2001)6th(2002)7th(2003)S

tore

d E

nerg

y (M

J)

Shot Number

9

Beta value has reached 4.1%Beta value has reached 4.1%

LHD has been pushing beta

10

• Aspect ratio of plasma is optimized by controlling the central position of HC current

P oloidal Coils

Plasma

H-M HC-OHC-MHC-I

Helical Coil

Large Aspect Ratio

- Aspect-ratio of 5.8 ~ 8.3 is available in the Rax = 3.6 m configuration

- High aspect-ratio configuration has high rotational transform which restrains the plasma shift

Aspect-ratio (γ=n/m.ac/R=κε) Control in LHD

11

Scenario to achieve high β plasma in LHD

β(%)

MHD limit

transport limit

3.5 3.6 3.7 3.8 3.9 4.0Major radius of magnetic axis (m)

Transport improvement

inward shift outward shift

Small Shafranovshift (γ =1.22) Standard Shafranov

shift (γ =1.254) Smaller Shafranov shift (γ=1.22) has higher transport limit for a given heating power and better heating efficiency

Although it has lower beta limit than the standard configuration (γ=1.254)

0.0

0.1

0.2

0.3

0.4

0 1 2 3 4

shaf

rano

v_sh

ift [m

]

<beta_dia>t

γ =1.254

γ =1.22RT_NBI

RT_NBI

•• γ optimization to minimize Shafranov shift is a key

12

Beta value has reached 4.1%Beta value has reached 4.1%

. The core fluctuation (ex.n/m=1/2) disappears because of spontaneous generation of magnetic well

. Even edge fluctuation (n/m=1/1) is mitigated because of flattening of pressure gradient

High beta discharge at B=0.45T

Further progress expected

K.Y.Watanabe EX/3-3

13kinetic beta gradients at ρ=0.9 (ι/2π = 1) in <β>-dβ/dρ diagram.

Role and Function of BoundaryStudy on MHD stability limit of high beta plasma

γ=1.22(γ=n/m.ac/R=κε)

Te(Ti ): Thomsonne:FIR

0

4

8

12

0 1 2 3 4 <β

dia> (%)

Mercier

currentless m/n=1/1 unstable

γ/ωA =10-2

0.5x10-2

ρ=0.9 (ι~1)dβ

kin/dρ

Achieved beta is close to the m/n=1/1 ideal mode limit

Achieved beta significantly exceeds the Mercier limit

K.Y.Watanabe EX/3-3

. β values achieved significantly exceeds the Mercier limit and increases up to m/n=1/1 ideal MHD limit

14The improvement factor of effective energy confinement as a function of (a) beta value for the plasma with Rax=3.6m, B=0.45-1.75T and γ = 1.22 and

0.0

0.5

1.0

1.5

2.0

0 1 2 3 4

His

s95-

Dia

mag

<βdia

> (%)

(a)

low β high β

. Degradation of energy confinement due to high Degradation of energy confinement due to high ββ is not observedis not observed

Confinement property of high β regime

. H-factor with respect to the ISS95 scaling decreases as the β is increased

. This decrease is due to the possible reduction of ISS95 scaling at higher collisionality

K.Y.Watanabe EX/3-3B.J.Peterson EX/6-2

15(a) Time evolution of the Te profile with the n=1 external field. (b) Normalized coil current vs. island width (w) in vacuum (open circles) and in plasma (closed circles).

0

0.5

1

1.5

2

4 4.2 4.4 4.6

Shot 38937

T e (keV

)

1.35

1.25

1.15

1.05(after pellet)

R (m)

(a)healing of magnetic island

Healing of magnetic island. Magnetic island appearing after the pellet injection is healed by itself as the collisionality decreases

Low νb*high νb*

Magnetic island is growing

Magnetic island is healed

ms

Y.Nagayama EX/P5-14

0

0.1

0.2

0 0.1 0.2W

(m)

Wex

(m)

Vacuum Width

Island Width(β=0.77% plasma)

(b)

. Positive shear(ι /2π) plays an important role on MHD property of LHD

. Magnetic island existing in the vacuum field is healed, when the size of magnetic island is small (w<0.3a)

1616

Extended operation regime in LHDExtended operation regime in LHD•• Edge control by Local island divertor (LID)Edge control by Local island divertor (LID)•• Control of radial electric field by shift of Control of radial electric field by shift of

magnetic axismagnetic axis•• Density limit and radiation collapseDensity limit and radiation collapse•• Achievement of high ion temperature with NBIAchievement of high ion temperature with NBI•• Long pulse operation with ECHLong pulse operation with ECH

Transport studyTransport study•• Properties of particle and heat transportProperties of particle and heat transport•• Electron transportElectron transport

17

Energy Confinement and Targets of LHD

04.0*

16.071.0*

40.03/2

21.265.051.059.080.095 26.0−−−

−−

νβρτ∝

=τ

B

eISSE qaRnPB

10-3

10-2

10-1

100

10-3 10-2 10-1 100

W7-ASATFCHSH-EW7-ALHD R3.75LHD R3.6

τ Eex

p (s)

τE

ISS95 (s)

TokamaksELMy H-mode 10-5

10-4

10-3

10-2

10-1

100

101

102

10-1 100 101 102 103 104 105 106 107

Fusi

on tr

iple

pro

duct

n 0T

i0τ E

(1020

m-3

keV

s)

Operated Duration (s)

TRIAM-1M

JETJT-60U

DIII-D

LHD

min. hour day month

JT-60UJET

PrecedingHelical Dev.

Tokamaks

Q=1

Commercial ReactorIgnition

ITERLHD 2nd target

LHD 1st target

ToreSupra

International Stellarator Scaling 95 (ISS95)

A factor of 1.5 improvement of the energy confinement time τE over the ISS95Comparable to ITER ELMy H-mode

H.Yamada EX/1-5

18

Prevent radiation collapse

by impurity shielding effect

0

0.08

0 0.08

τ Eexp (s

)

τE

ISS95 (s)

LID config.

Helical divertorconfig.

(a)

-20

-10

0

10

20

3.8 3.9 4.0 4.1 4.2

E r(kV

/m)

R(m)

without MI(limiter config.)

with MI (LID config.)

MI X-point

(c)

0

1

2

3

4

3.8 4.0 4.2 4.4 4.6

T e (keV

)

R (m)

LID configuration

Produce edge Positive Er

Create sharp edge (large Te gradient) Confinement

improvement

. Basic function of LID demonstrated1) confinement improvement 2) prevent radiation collapse

0

1

2

3

4

5

6

0.0 0.5 1.0 1.5 2.0

Prad

(MW

)

Time(s)

with MI (LID config.)

without MI(limiter config.)

(b)

A.Komori EX/10-4, K.Ida EX/P4-6

LID

19

02468

1012

0 2 4 6 8 10 12 14

Ti (

keV

)

Pabs/ne (MW/1019m-3)

(a)

02468

1012

0 1 2 3 4

Ti &

Te (

keV

)

Time (sec)

Ti (ArXVII)

Te (ECE)R=3.822m

(b)

(a) Ion temperature as a function of the direct ion heating power normalized by the ion density in the plasma with Ar- and Ne-puff and (b) time evolution of electron and ion temperature in a low-density high-Z plasma.

at present: 3 tangential beam lines with 180keV/14MW H: electron heating Ar, Ne: ion heating

next year: one perpendicular beam line added with 40kev/3MWmore efficient central ion heating

• Central ion temperature increases up to 10keV with strong impurity puff

Study on high ion temperature

Y.Takeiri EX/P4-11

20

0.1

1

D(m

2 /sec

)

Te (keV)

0.5 1

(a)

Dedge

Dcore

-8

-4

0

4

8

1 10-dT

e/dr (keV/m)

V(m

/sec

)

Outward

Inward

Vedge

Vcore

(b)

(a) Electron temperature dependence of diffusion coefficient (b) convective velocity as a function of the temperature gradient

Particle transport in L-mode plasmas

. Consistent with Gyro Bohm

. Consistent with density profile measured in the steady state

. Te dependence (Te1.5)

Density profile is flat in the core region in LHDTransient transport analysis with gas puff

modulation is required to derive diffusion coefficient in the core

low Pnbi high Pnbi

Peaked ne Hollow ne

low Pnbi high Pnbi

Dedge ~ Te1.1+-0.14

Dcore ~ Te1.7+-0.9

K.Tanaka EX/P6-28

21

0

5

10

15

0 0.2 0.4 0.6 0.8 1χ cp =

(1+β

)χe (m

2 /s)

ITB

Powerbalance

(a)

ρ

LHDχ

e

-5

0

0 0.2 0.4 0.6 0.8 1

α

(b)

ρ

LHD

(a) The radial profiles of the electron heat diffusivity(b) Te dependence factor of χe, α, estimated by cold pulse propagation. The heat diffusivity estimated by

power balance is also plotted

Temperature dependenceTemperature dependenceαα= (T= (Tee//χχee)(d)(dχχee/dT/dTee))

Inside ITB : α < 0 negative Te dependenceOutside ITB : α > 0 positive Te dependence

Steady-state transport analysis Power balance χeTransient transport analysis Cold pulse propagation χe and dχe/dT

Heat transport in ITB plasma

. Significant reduction of thermal diffusivity inside the ITB is observed both in steady-state and transient transport analysis

S.Inagaki EX/P2-12, T.Shimozuma EX/P3-12

22

1. Plasma performance was improved remarkably through 7 experimental campaigns in these 6 years

2. Quality and amount of database increased remarkably for MHD and transport study

3. With NBI of 12MW, Te=4.5keV and Ti=10.1keV were obtained at <Ne>=3.5 × 1018m-3

4. With ECRH of 1.2MW, Te=10.2keV and Ti=2.0keVwere obtained at <Ne>=5.0 × 1018m-3

5. A maximum volume averaged β value of 4.1% was achieved without any serious MHD instability

6. Good confinement time of τE=0.36sec, large plasma energy of Wp=1.36MJ, and long plasma operation of 756sec were obtained, which showed the good capability of LHD plasmas

7. The global confinement characteristics show better propertiesthan the existing empirical scaling ISS95

8. The knowledge of transport, MHD, divertor and long pulse operation etc. is now rapidly increasing, which comes from the successful progress of physics experiments

9. The advantage of an SC device is becoming clearer especially when we try to perform the steady state experiments 50 thousand shots

OM7128

Obtained Physics and Achieved Parameters of LHD ExperimentsLHD

2323

•• steady state operationsteady state operation•• advanced plasma regimes advanced plasma regimes

(higher normalized plasma pressure: (higher normalized plasma pressure: ββ))•• control of power fluxes to wallscontrol of power fluxes to walls

ITER/DEMO oriented ITER/DEMO oriented

Strong accompanying physics programmes are needed in the partiesStrong accompanying physics programmes are needed in the parties during ITER during ITER construction and operation. Their functions should include, in pconstruction and operation. Their functions should include, in particular, to directly articular, to directly support ITER and to complement ITER outputs in the preparation osupport ITER and to complement ITER outputs in the preparation of DEMO. f DEMO.

The main functions in support to DEMO will be to explore operatiThe main functions in support to DEMO will be to explore operational regimes and issues onal regimes and issues complementary to those being addressed in ITER. In particular thcomplementary to those being addressed in ITER. In particular these will include:ese will include:

Joint Report of EU/JA Expert Group MeetingJoint Report of EU/JA Expert Group Meeting18th / 19th April 2004, Culham18th / 19th April 2004, Culham

ononA Broader Approach to Fusion PowerA Broader Approach to Fusion Power

2424

ContributorO.Motojima 1), K.Ida 1), K.Y.Watanabe 1), Y.Nagayama 1), A.Komori 1), T.Morisaki 1), B.J.Peterson 1), Y.Takeiri1), K.Ohkubo 1), K.Tanaka 1), T.Shimozuma 1), S.Inagaki 1), T.Kobuchi 1), S.Sakakibara 1), J.Miyazawa 1), N.Ohyabu 1), K.Narihara 1), K.Nishimura 1), M.Yoshinuma 1), S.Morita 1), T.Akiyama 1), N.Ashikawa 1), C.D.Beidler 2), M.Emoto 1), T.Fujita 3), T.Fukuda 4), H.Funaba 1), P.Goncharov 5), M.Goto 1), H.Idei 6), T.Ido 1), K.Ikeda 1), A.Isayama 3), M.Isobe 1), H.Igami 1), K.Itoh 1), O.Kaneko 1), K.Kawahata 1), H.Kawazome 7), S.Kubo 1), R.Kumazawa 1), S.Masuzaki 1), K.Matsuoka 1), T.Minami 1), S.Murakami 8), S.Muto 1), T.Mutoh 1), Y.Nakamura 1), H.Nakanishi 1), Y.Narushima 1), M.Nishiura 1), A.Nishizawa 1), N.Noda 1), T.Notake 9), H.Nozato10), S.Ohdachi 1), �Y.Oka 1), S.Okajima 11), M.Osakabe 1), T.Ozaki 1), A.Sagara 1), T.Saida 12), K.Saito 1), R.Sakamoto 1), Y.Sakamoto 3), M.Sasao 12), K.Sato 1), M.Sato 1), T.Seki 1), M.Shoji 1), S.Sudo 1), N.Takeuchi 9), N.Tamura 1), K.Toi 1), T.Tokuzawa 1), Y.Torii 9), K.Tsumori 1), T.Uda 1), A.Wakasa 13), T.Watari 1),H.Yamada 1),I.Yamada 1), S.Yamamoto 9), T.Yamamoto 9), K.Yamazaki 1), M.Yokoyama 1), Y.Yoshimura 1)

1) National Institute for Fusion Science, 322-6 Oroshi-cho, Toki-shi, 509-5292, Japan2) Max-Planck Institut fuer Plasmaphysik, Greifswald D-17491, Germany3) Japan Atomic Energy Research Institute, Naka, 311-0193, Japan4) Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871,5) Department of Fusion Science, School of Mathematical and Physical Science, Graduate University for Advanced

Studies, Hayama, 240-0193, Japan6) Research Institute for Applied Mechanics, Kyushu University, Kasuga, 816-8580, Japan7) Graduate School of Energy Science, Kyoto University, Uji 611-0011, Japan8) Department of Nuclear Engineering, Kyoto University, Kyoto 606-8501, Japan9) Department of Energy Engineering and Science, Nagoya University, 464-8603, Japan10) Graduate School of Frontier Sciences, The University of Tokyo 113-0033, Japan11) Chubu University, Kasugai, Aichi, 487-8501, Japan12) Graduate School of Engineering, Tohoku University, Sendai, 980-8579, Japan13) Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan

e-mail contact of main author: motojima@LHD.nifs.ac.jp