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:
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
• 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.
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
• 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).
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
• 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
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
• 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
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
• 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
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
• 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.
Design of the transfer line
dL
dTLAkLqx ).(.)( 1 ))(.(.).()(
4
0
4
2 TT LLALqsrad
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
Design of the transfer line
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
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
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
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
Design of the transfer line
Heating(Ohmic)
Quartz insert to trap Alkalis
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)
Quartz insert to trap Alkalis
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)
Quartz insert to trap Alkalis
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)
Quartz insert to trap Alkalis
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)
Cooling/heatingsystem
Quartz location
Target
To ion source
Proton beam
Thermocouple location
T1T2
Cooling/heatingsystem
Quartz location
Target
To ion source
Proton beam
Thermocouple location
T1T2
Schematic layout and temperature profile within the quartz transfer line (v.2.0)
E.Bouquerel
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
Design of the transfer line
Quartz Transfer Line version 1.0(before the final assembly)
Quartz Transfer Line version 2.0
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
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
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
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
1.0E+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
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
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
Online ResultsAlkali Suppression
– 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
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
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…
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
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
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
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
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
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
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
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.