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

2. Quartz line ISOL target prototype: suppression factors obtained online – 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.

3. Quartz line ISOL target prototype: suppression factors obtained online – 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 ( 130 Cs).

4. Quartz line ISOL target prototype: suppression factors obtained online – 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 (n coll ) with the surface of the materials –The mean sticking time (t s ) per collision (depending on temperature and desorption enthalpy) –The mean flight time (t fly ) between collisions (depending on the geometry, the mass and temperature) Theory

5. Quartz line ISOL target prototype: suppression factors obtained online – E. Bouquerel – 04/09/07 - CERN Frenkel equation: Exponential decay expression: Combination gives: Theory Number of radioactive nuclei at time = 0 ln2 / t 1/2 Half life of the nuclei Estimation of suppression factor

6. Quartz line ISOL target prototype: suppression factors obtained online – 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

7. Quartz line ISOL target prototype: suppression factors obtained online – E. Bouquerel – 04/09/07 - CERN Heat transfer equations… q x heat flow rate (W), A 1 section through which the heat is conducted (m2), dT/dL temperature gradient along the line (K/m) and k thermal conductivity (W/m.K) q rad radiated heat flow (W). A 2 is the area (m 2 ), ε emissivity, σ Stefan-Boltzmann constant (σ = 5.67 X 10-8 W/m 2. K 4 ). T s temperature of the surface, T 0 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

8. Quartz line ISOL target prototype: suppression factors obtained online – E. Bouquerel – 04/09/07 - CERN Design of the transfer line Schematic layout and temperature profile within the quartz transfer line (v.1.0) S.Marzari

9. Quartz line ISOL target prototype: suppression factors obtained online – E. Bouquerel – 04/09/07 - CERN Design of the transfer line Schematic layout and temperature profile within the quartz transfer line (v.2.0) E.Bouquerel

10. Quartz line ISOL target prototype: suppression factors obtained online – 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

11. Quartz line ISOL target prototype: suppression factors obtained online – E. Bouquerel – 04/09/07 - CERN Online Results Alkali Suppression – 80 Rb suppressed by 4 orders of magnitude when compared to a standard UC 2 -C unit: 3.3x10 3 At/μC (transfer line at 400ºC); 1.8x10 8 At/μC (for standard unit) –Significant quartz transfer line temperature effect on the 80 Rb yields

12. Quartz line ISOL target prototype: suppression factors obtained online – E. Bouquerel – 04/09/07 - CERN Online Results Alkali Suppression – 80 Rb suppressed by 4 orders of magnitude when compared to a standard UC 2 -C unit: 3.3x10 3 At/μC (transfer line at 400ºC); 1.8x10 8 At/μC (for standard unit) –Significant quartz transfer line temperature effect on the 80 Rb yields ΔH ad n coll t 0 k = 2.6 ± 0.3 eV = 240 (from RIBO) = 1ps = 1.38x10 23 J.K -1

13. Quartz line ISOL target prototype: suppression factors obtained online – E. Bouquerel – 04/09/07 - CERN Online Results Alkali Suppression – 142 Cs suppressed by 4 orders of magnitude when compared to a standard UC 2 -C unit –The suppression factor for 142 Cs was insensitive to the quartz line temperature between 700ºC and 1100ºC

14. Quartz line ISOL target prototype: suppression factors obtained online – E. Bouquerel – 04/09/07 - CERN Online Results The suppression factor for 142,126 Cs seemed to be sensitive to a quartz line temperature between 300ºC and 550ºC Isotopet 1/2 (ms)Temp. (ºC) yield (At/uC) 126 Cs9840 300 2.3x10 3 126 Cs9840 550 7.2x10 5 Isotopet 1/2 (ms)Temp. (ºC) yield (At/uC) 142 Cs1780 300 2.5x10 5 142 Cs1780 550 4.9x10 5 Alkali Suppression Seen 1 week ago…

15. Quartz line ISOL target prototype: suppression factors obtained online – E. Bouquerel – 04/09/07 - CERN Online Results Other alkali suppression factors Production of In, Zn, Ga and Sr

16. Quartz line ISOL target prototype: suppression factors obtained online – 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 80 Rb as a function of the quartz temperature Suppression factor for 80 Rb has been estimated from effusion and sticking times and agreed with the experimental data 126,142 Cs trapped and seemed dependent of the quartz for temperatures below 550ºC Temperature dependence of the line on the production of 114 In

17. Quartz line ISOL target prototype: suppression factors obtained online – 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

18. Quartz line ISOL target prototype: suppression factors obtained online – 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.http://www.ansys.com/products/workbench.asp ISOLDE target reference UC2020.