Quartz line ISOL target prototype: suppression factors obtained online – E. Bouquerel – 04/09/07 - CERN Quartz line ISOL target prototype: suppression

Quartz line ISOL target prototype: suppression factors Quartz line ISOL target prototype: suppression factors obtained online obtained online – E. Bouquerel – 04/09/07 - CERN– E. Bouquerel – 04/09/07 - CERN

Quartz line ISOL target Quartz line ISOL target prototype: suppression factors prototype: suppression factors

obtained onlineobtained online

E. Bouquerel, D. Carminati, R. Catherall, M. Eller, J. Lettry, S. Marzari, T. Stora and the ISOLDE Collaboration

CERN, CH-1211, Geneva, Switzerland

Workshop on Radioactive Ion Beam Purification:


• What do we want?– Delivering unprecedented pure beams of exotic n-

rich Cd and Zn.

• How?– Contaminant elements (produced alkalis such as

Rb, Cs and also In and Ga) are trapped by adding a quartz insert in the transfer line.


• Isothermal chromatography is applied to design a selective Transfer Line in an ISOL Target and Ion Source.

• For the production of noble gases, the less volatile elements are condensed in the transfer line.

Introduction

Zn80

Rb80

Kr80

Br80

Se80

As80

Ge80

Ga80

• The selective ionisation provided by laser (RILIS) suffers from isobaric contamination.

• In 1986 Kratz et al. showed that the quartz has the properties of delaying alkalis (130Cs).


• 2 main processes lead to the release of atoms from a target: diffusion and effusion

• Effusion consists of 3 important parameters:– Number of collisions (ncoll) with the surface of the materials

– The mean sticking time (ts) per collision (depending on temperature and desorption enthalpy)

– The mean flight time (tfly) between collisions (depending on the geometry, the mass and temperature)

Theory


• Frenkel equation:

• Exponential decay expression:

• Combination gives:

Theory

scollflyeff tntt )/(0

kTHs

adett

teNtN 0)(

Number of radioactive nuclei at time = 0

ln2 / t1/2 Half life of the nuclei

2/1

2ln

0

)(t

t

th

eff

etN

Nf

)()(ln )/(0

kTHcollth

adetnf

Estimation of suppression factor


• To efficiently trap alkalis, the transfer line must operate within a certain range of temperatures, then 2 prototypes has been designed with a controlled transfer line temperature:– From 700ºC to 1100 ºC (Version 1.0)– From 300 ºC to 800 ºC (Version 2.0)

• RIBO code allowed the estimation of the quartz dimensions to be used according to the number of collisions: 50mm long tube, 6mm diameter

• An ISOLDE UC2-C Target & Ion Source operate at temperature above 2000ºC: estimation of the heat flow mandatory to avoid the quartz to melt

Design of the transfer line


• Heat transfer equations…

qx heat flow rate (W), A1 section through which the heat is conducted (m2), dT/dL temperature gradient along the line (K/m) and k thermal conductivity (W/m.K)

qrad radiated heat flow (W). A2 is the area (m2), ε emissivity, σ Stefan-Boltzmann constant (σ = 5.67 X 10-8 W/m2. K4). Ts temperature of the surface, T0 temperature of the surrounding surface.

…and…• Simulation software: ANSYS Workbench 11.0

…have been used to estimate the temperature through the prototype.


dL

dTLAkLqx ).(.)( 1 ))(.(.).()(

4

0

4

2 TT LLALqsrad



Quartz insert to trap Alkalis

Thermal screens

Target

to W RILIS Cavity

Heating(Ta-resistor oven)

Q3

Heating(Ohmic)

Q4;T4

Temperatureread-out

(T3)

Heating(Ohmic)

Q1;T1

Heat Dissipation

(Ta radiator)Q2;T2

L=0cm

L=20cm


Thermal screens

Target

to W RILIS Cavity

Heating(Ta-resistor oven)

Q3

Heating(Ohmic)

Q4;T4

Temperatureread-out

(T3)

Heating(Ohmic)

Q1;T1

Heat Dissipation

(Ta radiator)Q2;T2

L=0cm

L=20cm

Quartz insert location

Target (T1= 2000˚C)

Transfer lineIon source(T4= 1650˚C)

Thermal screen

Thermocouple locationQuartz insert location

Target (T1= 2000˚C)

Transfer lineIon source(T4= 1650˚C)

Thermal screen

Thermocouple location

Schematic layout and temperature profile within the quartz transfer line (v.1.0)

S.Marzari



Heating(Ohmic)


Thermal screens

Target

to W RILIS Cavity

Heating(Ta-resistor

oven)

Heating(Ohmic)

Temperatureread-out

Heat Dissipation

(Ta radiator)

L=0cm

L=20cm

Heat Dissipation

(water cooling block)

Heating(Ohmic)


Thermal screens

Target

to W RILIS Cavity

Heating(Ta-resistor

oven)

Heating(Ohmic)

Temperatureread-out

Heat Dissipation

(Ta radiator)

L=0cm

L=20cm

Heat Dissipation


Heating(Ohmic)


Thermal screens

Target

to W RILIS Cavity

Heating(Ta-resistor

oven)

Heating(Ohmic)

Temperatureread-out

Heat Dissipation

(Ta radiator)

L=0cm

L=20cm

Heat Dissipation


Heating(Ohmic)


Thermal screens

Target

to W RILIS Cavity

Heating(Ta-resistor

oven)

Heating(Ohmic)

Temperatureread-out

Heat Dissipation

(Ta radiator)

L=0cm

L=20cm

Heat Dissipation


Cooling/heatingsystem

Quartz location

Target

To ion source

Proton beam


T1T2

Cooling/heatingsystem

Quartz location

Target

To ion source

Proton beam


T1T2

Schematic layout and temperature profile within the quartz transfer line (v.2.0)

E.Bouquerel



Quartz Transfer Line version 1.0(before the final assembly)

Quartz Transfer Line version 2.0


Online ResultsAlkali Suppression

– 80Rb suppressed by 4 orders of magnitude when compared to a standard UC2-C unit:

• 3.3x103 At/μC (transfer line at 400ºC); 1.8x108 At/μC (for standard unit)

– Significant quartz transfer line temperature effect on the 80Rb yields

1.00E+04

1.00E+05

1.00E+06

1.00E+07

0.0006 0.0008 0.001 0.0012

Quartz line temperature, 1/T (1/K)

Yie

ld (

At/

uC

)

Experiment



– 80Rb suppressed by 4 orders of magnitude when compared to a standard UC2-C unit:

• 3.3x103 At/μC (transfer line at 400ºC); 1.8x108 At/μC (for standard unit)

– Significant quartz transfer line temperature effect on the 80Rb yields

1.0E+04

1.0E+05

1.0E+06

1.0E+07

0.0006 0.0008 0.001 0.0012

Quartz line temperature, 1/T (1/K)

Yie

ld (

At/

uC

)

Theory

ExperimentΔHad ncoll t0 k

= 2.6 ± 0.3 eV = 240 (from RIBO)= 1ps= 1.38x1023 J.K-1


1.0E+03

1.0E+04

1.0E+05

0.01 0.1 1 10tdelay + 1/2 tcoll (s)

β c

ou

nt

pe

r t c

oll

ec

tio

n (

s-1

)

T=950 ºC; v1.0T=680 ºC; v1.0T=550 ºC; v2.0T=300 ºC; v2.0


– 142Cs suppressed by 4 orders of magnitude when compared to a standard UC2-C unit

– The suppression factor for 142Cs was insensitive to the quartz line temperature between 700ºC and 1100ºC

142Cs

1.0E+02

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1.0E+09

1.0E+10

0.01 0.1 1 10tdelay + 1/2 tcollection (s)

β c

ou

nt

pe

r t

colle

ctio

n (

s-1

)

142Cs-ISOLDE UCx-1700ºC

142Cs-quartz-680ºC


Online Results

The suppression factor for 142,126Cs seemed to be sensitive to a quartz line temperature between 300ºC and 550ºC

Isotope t1/2 (ms) Temp. (ºC) yield (At/uC)126Cs 9840 300 2.3x103

126Cs 9840 550 7.2x105

Isotope t1/2 (ms) Temp. (ºC) yield (At/uC)142Cs 1780 300 2.5x105

142Cs 1780 550 4.9x105

Alkali Suppression

Seen 1 week ago…


Online Results

1.E+05

1.E+06

1.E+07

7.0E-04 8.0E-04 9.0E-04 1.0E-03 1.1E-03

Quartz line Temperature, 1/T3 (1/K)

Yie

ld (

At/

μC

)

75Zn114In77Ga

Isotope Half Life (ms)80Rb 34000 3.3x103 1.8x108 5450046K 115200 6.5x105 5.4x107 808Li 840.3 1.7x105 3.9x107 230

142Cs 1780 2.5x105 1.5x108 600

Yield (atoms/μC)Quartz line T=300˚C

Standard ISOLDE Ucx T=1800˚C

Suppression factor

Other alkali suppression factors

Production of In, Zn, Ga and Sr

Isotope Half life (ms) TL Temperature (ºC) Yield (atoms/μC)75Zn 10200 700 7.3x106

77Ga 13200 700 9.9x105

114In 72000 700 2.7x105

77Ga 13200 300 4.8x104

96Sr 1070 300 1.5x104


Summary

• The quartz tube placed in a transfer line traps alkali contaminants by significant orders of magnitude

• Clear dependence of the 80Rb as a function of the quartz temperature

• Suppression factor for 80Rb has been estimated from effusion and sticking times and agreed with the experimental data

• 126,142Cs trapped and seemed dependent of the quartz for temperatures below 550ºC

• Temperature dependence of the line on the production of 114In


Future Investigations

• Design of a prototype having a quartz transfer line operating with a broader range of temperature (from 200ºC to 1200 ºC)

• Further investigations on experimental data could lead to physical models to deduce the suppression factor for the different other isotopes

• The use of other materials which could also suppress contaminants and located in a transfer line


References• E. Bouquerel, R. Catherall, M. Eller, J. Lettry, S. Marzari, T. Stora and the

ISOLDE Collaboration, “ Purification of a Zn Radioactive Ion Beam by alkali suppression in a quartz line target prototype” (European Phys. Journal A.) in press.

• S. Sundell, H. Ravn and the ISOLDE Collaboration, NIM B70 (1992) 160.• V.N.Fedosseev et al,”Development of the RILIS Research laboratory at

ISOLDE”, CERN-INTX-2006-015, INTC-I-065, 20.01.2006• K.L. Kratz et al., “The Beta-decay half-life of 13048Cd82 and its importance

for astrophysical r-process scenarios”, CERN-EP/86-189, 18 November 1986.• M. Santana Leitner, A Monte Carlo Code to Optimize the Production of

Radioactive Ion Beams by the ISOL Technique, PhD. Thesis, UPC-ETSEIB / CERN.

• M. Turrion Nieves, Private Communication – CERN.• Fundamentals of Heat and Mass Transfer Fifth Edition, Frank P Incropera,

David P DeWitt, John Wiley & Sons 2002, pp 53, pp 699.• http://www.ansys.com/products/workbench.asp.• ISOLDE target reference UC2020.

Documents

Quartz line ISOL target prototype: suppression factors obtained online – E. Bouquerel – 04/09/07 - CERN Quartz line ISOL target prototype: suppression