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Quartz line ISOL target prototype: suppression factors obtained online

Workshop on Radioactive Ion Beam Purification:. 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.

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Quartz line ISOL target prototype: suppression factors obtained online

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  1. Workshop on Radioactive Ion Beam Purification: 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

  2. 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. Rb80 Kr80 Br80 Se80 As80 Ge80 Ga80 Zn80 Introduction • 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. • 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).

  4. Theory • 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)

  5. Theory • Frenkel equation: • Exponential decay expression: • Combination gives: Half life of the nuclei ln2 / t1/2 Number of radioactive nuclei at time = 0 Estimation of suppression factor

  6. Design of the transfer line • 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

  7. 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.

  8. Design of the transfer line S.Marzari Schematic layout and temperature profile within the quartz transfer line (v.1.0)

  9. Design of the transfer line E.Bouquerel Schematic layout and temperature profile within the quartz transfer line (v.2.0)

  10. Design of the transfer line Quartz Transfer Line version 1.0 (before the final assembly) Quartz Transfer Line version 2.0

  11. Online Results Alkali 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

  12. Online Results Alkali 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 ΔHad ncoll t0 k = 2.6 ± 0.3 eV = 240 (from RIBO) = 1ps = 1.38x1023 J.K-1

  13. Online Results Alkali 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

  14. Online Results Alkali Suppression 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) 142Cs 1780 300 2.5x105 142Cs 1780 550 4.9x105 Seen 1 week ago… Isotope t1/2 (ms) Temp. (ºC) yield (At/uC) 126Cs 9840 300 2.3x103 126Cs 9840 550 7.2x105

  15. Online Results Other alkali suppression factors Production of In, Zn, Ga and Sr

  16. 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

  17. 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. 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.

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