Developments in target-ion source chemistry for ISOL facilities [Elektronische Ressource] / Carola Jost

Sujets

• Naturwissenschaften

Informations

• Publié par: johannes_gutenberg-universitat_mainz
• Publié le: 01 janvier 2010
• Nombre de lectures: 7
• Langue: English
• Poids de l'ouvrage: 2 Mo

Extrait

Developments in target – ion source chemistry
for ISOL facilities

















Dissertation
zur Erlangung des Grades
„Doktor der Naturwissenschaften“
im Promotionsfach Chemie
am Fachbereich Chemie, Pharmazie und Geowissenschaften (FB 09)
der Johannes Gutenberg-Universität
in Mainz



Carola Jost
Mainz, den 17.8.2010


1. Gutachter:
2. Gutachter:


Prüfungsdatum: 13.8.2010




































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Science is the topography of ignorance
Oliver Wendell Holmes, Sr.




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4 Table of Contents

0 Abstract

1 Introduction
1.1 Motivation
1.2 Aims and Objectives

2 Foundations / Literature
2.1 Production of RIBs – In-flight and ISOL
2.2 The ISOL method
2.2.1 Target
2.2.2 Transfer line
2.2.3 Ion sources
2.2.4 Beam purification
2.3 RIB facilities
2.3.1 ISOLDE
2.3.2 Oak Ridge
2.4 Adsorption
2.5 Thermochromatography
2.6 Nuclear Structure
2.6.1 Beta decay
2.6.1.1 Fermi theory
2.6.1.2 Fermi and Gamow-Teller transitions
2.6.2 Gamma decay
2.6.2.1 Order of multipoles
2.6.2.2 Electric and magnetic multipoles
2.6.3 Nuclear structure models
2.6.3.1 The shell model
2.6.3.2 Current models

3 Methods
3.1 TC
3.1.1 Experimental procedures at ISOLDE
3.1.2 Expetal procedures at TRIGA Mainz
3.1.3 Analysis
3.1.4 Adsorption enthalpies
3.2 On-line experiments
3.2.1 OR TIS
3.2.2 Yield measurements
3.2.3 Hold-up times
3.2.4 Adsorption materials
3.3 RIBO
3.4 Spectroscopy



5 4 Results and Discussion
4.1 Target-ion source development
4.1.1 Selective adsorption experiments
4.1.1.1 Ag
4.1.1.2 Group 12
4.1.1.3 Group 13
4.1.1.4 Group 14
4.1.1.5 Halogens
4.1.1.6 Noble gases
4.1.1.7 Alkali metals
4.1.1.8 Sr
4.1.2 Discussion of methods
4.1.3 Discussion of ISOLDE vs. OR
4.1.4 Summary
4.2 Spectroscopy

5 Conclusions

6 Bibliography

7 Acknowledgments


























6 Figures

Fig. 2.1 Nuclear reactions on uranium at ISOLDE 13
Fig. 2.2 ORNL standard target-ion source system 13
Fig. 2.3 Path of an atom travelling out of a foil target to the ion source 16
Fig. 2.4 Elastic reflection 17
Fig. 2.5 Diffuse reflection 18
Fig. 2.6 ISOLDE surface ion source 20
Fig. 2.7 ISOLDE FEBIAD ion source 22
Fig. 2.8 A and Z separation 23
Fig. 2.9 CERN accelerator layout 26
Fig. 2.10 ISOLDE facility layout 27
Fig. 2.11 Layout of the HRIBF at the ORNL 28
Fig. 2.12 Layout of the OLTF at the HRIBF 29
Fig. 2.13 2D depiction of the structure of crystalline quartz (a) and fused silica (b) 31
Fig. 2.14 Alkali atoms in a fused silica structure, before (a) and after annealing (b) 31
Fig. 2.15 Hydroxyl groups on silica surfaces 32
-Fig. 2.16 Transformation of a neutron into a proton by emission of a W boson 38
Fig. 2.17 Different potential gradients to describe the nuclear potential 42
Fig. 2.18 Depth of potential well for protons and neutrons 43
Fig. 3.1 Schematic of TC experiment setup 46
Fig. 3.2 Temperature gradient of ISOLDE 10-zone oven 46
Fig. 3.3 Temperature gradient of the Mainz TC oven 47
Fig. 3.4 γ-setup with 2cm collimator (not visible) and quartz tube 48
Fig. 3.5 Modified target ion source used for selective adsorption tests 53
Fig. 3.6 Temperature gradient from the target along the transfer line to the ion source 54
for different line heater currents
Fig. 3.7 Photograph of pressed-powder UC target 55 x
Fig. 3.8 Photograph of UC coated RVC fiber target 55 2
Fig. 3.9 SEM picture of uncoated and UC coated RVC fibers 56 2
Fig. 3.10 Schematic of the two component release model 58
Fig. 3.11 Beam current plotted continuously by WinDAQ data logger 60
89Fig. 3.12 Hold-up measurement on Rb with 1023 keV line 61
Fig. 3.13 Fit of hold-up curve for Ag, quartz low temperature 61
Fig. 3.14 Straight and partially blocked quartz tube 63
Fig. 3.15 Visualization of the RIBO model for the modified transfer line containing a
straight tube 65
Fig. 3.16 Release probabilities for particles in the bare Ta line, with a straight tube
inserted and with a partially blocked tube inserted 66
Fig. 3.17 Beam line LA1 (left) with tape station and γ-detectors 67
Fig. 4.1 Ag yields from pressed-powder target 71
Fig. 4.2 Comparison of Ag yield ratios with prediction from hold-up measurements 73
(Ta HT/ q LT)
Fig. 4.3 Comparison of Ag yield ratios with prediction from hold-up times (qHT/qLT) 73
Fig. 4.4 Zn yields 75
Fig. 4.5 Cd yields from pressed-powder target 76
Fig. 4.6 Ga yields from pressed-poet 77
Fig. 4.7 In yields from pressed-powder target 78
Fig. 4.8 Ge yields from pressed-poet 81
120Fig. 4.9 Hold-up behavior of Sn on high temperature Ta 82
-5Fig. 4.10 Equilibrium composition of the Ta-Br system at 10 mbar, from 200 to 2000° C 84
79Fig. 4.11 Hold-up behavior of Br on high temperature Ta 85
-5Fig. 4.12 Equilibrium composition of the Ta-I-system at 10 mbar, from 0 to 2000°C 86
Fig. 4.13 Xe yields from pressed-powder target 87


7 Fig. 4.14 Kr yields from pressed-powder and graphite fiber targets under different 88
transfer line conditions
Fig. 4.15 Comparison of Kr hold-up times from pressed-powder and fiber targets 89
Fig. 4.16 Carrier-free Cs and Cs containing a carrier on a quartz column 91
Fig. 4.17 Thermochromatogram of K on quartz with Mainz gradient oven 92
Fig. 4.18 Rb yields from graphite fiber target 94
Fig. 4.19 Hold-up curve of Rb on Ta, high temperature 96
65Fig. 4.20 Release curves of Cu ions released from a 30 mm W cavity after the laser 102
pulses for temperatures between 1400° C and 2300° C
Fig. 4.21 Section of the “laser on” γ spectra on mass 131, 800 to 900 keV 104
Fig. 4.22 Section of the “laser off” sum spectra on mass 131, 800 to 900 keV 104
Fig. 4.23 Section of the “laser on” sum spectra on mass 131, 2300 to 2500 keV 105
Fig. 4.24 Section of the “laser off” sum spectra on mass 131, 2300 to 2500 keV 105
Fig. 4.25: Section of the “laser on” sum spectra on mass 131, 2550 to 2750 keV 106
Fig. 4.26: Section of the “laser off” sum spectra on mass 131, 2550 to 2750 keV 106
Fig. 4.27: Section of the “laser on” sum spectra on mass 131, 3750 to 4000 keV 107
Fig. 4.28: Section of the “laser off” sum spectra on mass 131, 3750 to 4000 keV 107
Fig. 4.29: Section of the “laser on” sum spectra on mass 131, 5950 to 6200 keV 108
Fig. 4.30: Section of the “laser on” sum spectra on mass 131, 5950 to 6200 keV 108
131Fig. 4.31: Decay scheme of Cd as proposed by Hannawald et al. 110
131Fig. 4.32: Tentative level scheme for In 111






























8 Tables

Table 2.1: Beta decay types and their log ft values 40
Table 3.1: List of all nuclides used in thesis experiments 50
Table 3.2: Energies, charge states and max. current on target for tandem beams used 51
Table 3.3: Cycle times used for measurements of hold-up times with radioactive nuclides 60
Table 3.4: Dimensions of tubes used for adsorption materials 64
Table 3.5: Number of collisions on line surfaces with and without tubes inserted 65
Table 4.1: Average Ag hold-up times 69
Table 4.2: Adsorption enthalpies and deposition temperatures of Ag on quartz glass 69
Table 4.3: Adsorption enthalpies of Ag on different surfaces, from hold-up time 70
measurements and TC
Table 4.4: Ag yield ratios – predictions and experimental results 72
Table 4.5: TC results for group 12 elements 74
Table 4.6: In holdup times 79
Table 4.7: Comparison of experimental and calculated yield ratios fo