Characterization of solid D_1tn2 as a source material for ultracold neutrons (UCN) and development of a detector concept for the detection of protons from the neutron decay [Elektronische Ressource] / Axel Reimer Müller

¨ ¨TECHNISCHE UNIVERSITAT MUNCHEN
Physik Department Experimentalphysik E18
Characterization of solid D as source material for2
ultra cold neutrons and development of a detector
concept for the detection of protons from the
neutron decay¨ ¨TECHNISCHE UNIVERSITAT MUNCHEN
Physik Department Experimentalphysik E18
Characterization of solid D as source material for2
ultra cold neutrons and development of a detector
concept for the detection of protons from the
neutron decay
Axel Reimer Mu¨ller
Vollst¨andiger Abdruck der von der Fakult¨at fu¨r Physik
der Technischen Universit¨at Mu¨nchen
zur Erlangung des akademischen Grades eines
Doktors der Naturwissenschaften (Dr. rer. nat.)
genehmigten Dissertation.
Vorsitzender: Univ.-Prof. Dr. W. Weise
Pru¨fer der Dissertation: 1. Univ.-Prof. Dr. St. Paul
2. Univ.-Prof. Dr. W. Petry
Die Dissertation wurde am 09.09.2008 bei der Technischen Universit¨at Mu¨nchen
eingereicht und durch die Fakult¨at fu¨r Physik am 09.12.2008 angenommen.Contents
1 Introduction 23
1.1 Fundamental research with neutrons . . . . . . . . . . . . . . . . . . . 23
1.2 Ultra-cold neutrons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
1.3 Neutron decay in Standard Model . . . . . . . . . . . . . . . . . . . . . 26
1.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2 Towards a strong UCN source 29
2.1 UCN production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.1.1 ”Conventional” UCN production . . . . . . . . . . . . . . . . . 29
2.1.2 ”Superthermal” UCN production . . . . . . . . . . . . . . . . . 30
2.1.3 Superthermal production based on deuterium . . . . . . . . . . 31
2.2 Deuterium characterization. . . . . . . . . . . . . . . . . . . . . . . . . 35
2.2.1 Setup of the cubeD experiment . . . . . . . . . . . . . . . . . . 352
2.2.2 Visible light inspection . . . . . . . . . . . . . . . . . . . . . . . 39
2.2.3 Raman spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . 40
2.2.4 Neutron scattering . . . . . . . . . . . . . . . . . . . . . . . . . 41
2.3 cubeD , a test UCN source at the FRMII . . . . . . . . . . . . . . . . . 442
2.3.1 Setup at the FRMII . . . . . . . . . . . . . . . . . . . . . . . . 44
2.3.2 UCNs, VCNs and CNs . . . . . . . . . . . . . . . . . . . . . . . 46
2.4 Experimental Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
2.4.1 Visible light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
2.4.2 Raman spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . 52
2.4.3 Neutron scattering data . . . . . . . . . . . . . . . . . . . . . . 56
2.4.4 The dynamics of solid deuterium . . . . . . . . . . . . . . . . . 60
2.4.5 Influence on the design of UCN sources . . . . . . . . . . . . . . 61
2.4.6 Phonon and multiphonon contribution . . . . . . . . . . . . . . 63
2.4.7 Estimation of the UCN production from S(q,ω) . . . . . . . . . 65
2.4.8 UCN up-scattering losses in deuterium . . . . . . . . . . . . . . 70
2.4.9 Interpretation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
2.5 UCN production results . . . . . . . . . . . . . . . . . . . . . . . . . . 73
2.5.1 UCN versus VCN . . . . . . . . . . . . . . . . . . . . . . . . . . 74
2.5.2 UCN production in gaseous, liquid and solid D . . . . . . . . . 752
2.5.3 Effects of freezing and annealing . . . . . . . . . . . . . . . . . . 77
2.5.4 UCN production as function of ortho/para concentration . . . . 79
2.5.5 Cell thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
2.6 miniD converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 812
2.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
53 UCN guides 85
3.1 Methods to evaluate the transmission probability of UCN guides . . . . 86
3.1.1 The storage method . . . . . . . . . . . . . . . . . . . . . . . . 86
3.1.2 The two hole method . . . . . . . . . . . . . . . . . . . . . . . . 88
3.2 Sample tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
3.2.1 Samples for UCN valve characterization . . . . . . . . . . . . . 88
3.2.2 Possible UCN guide materials . . . . . . . . . . . . . . . . . . . 88
3.2.3 Electro polishing and discharge cleaning . . . . . . . . . . . . . 89
3.3 Beam measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
3.3.1 ”UCN valve” and ”storage method results” . . . . . . . . . . . . 89
3.3.2 Surface roughness, machined versus electro polished . . . . . . . 91
3.3.3 Efficiency of discharge cleaning . . . . . . . . . . . . . . . . . . 91
3.3.4 Different wall coatings on aluminum tubes . . . . . . . . . . . . 93
3.3.5 Temperature dependence . . . . . . . . . . . . . . . . . . . . . . 93
3.4 UCN transport simulation . . . . . . . . . . . . . . . . . . . . . . . . . 93
3.4.1 The U shaped baffle . . . . . . . . . . . . . . . . . . . . . . . . 94
3.4.2 Calibration of the simulation . . . . . . . . . . . . . . . . . . . . 95
3.4.3 cubeD data to extract f . . . . . . . . . . . . . . . . . . . . . . 962
3.5 Storage method and two hole method results . . . . . . . . . . . . . . . 98
3.6 Conclusion on the characterization of UCN guides . . . . . . . . . . . . 99
4 UCN storage for n-lifetime measurement 101
4.1 UCN trapping using material bottles . . . . . . . . . . . . . . . . . . . 101
4.2 UCN trapping in magnetic bottles . . . . . . . . . . . . . . . . . . . . . 102
4.2.1 Basic theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
4.2.2 Previous magnetic storage experiments . . . . . . . . . . . . . . 103
4.3 The PENeLOPE project . . . . . . . . . . . . . . . . . . . . . . . . . . 103
4.3.1 PENeLOPE storage container . . . . . . . . . . . . . . . . . . . 103
4.3.2 PENeLOPE neutron detection. . . . . . . . . . . . . . . . . . . 105
4.3.3 PENeLOPE proton detection . . . . . . . . . . . . . . . . . . . 105
5 Proton detection 109
5.1 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
5.2 Basic detector idea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
5.3 Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
5.3.1 Active area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
5.3.2 Proton interaction . . . . . . . . . . . . . . . . . . . . . . . . . 111
5.3.3 Light guiding structures . . . . . . . . . . . . . . . . . . . . . . 113
5.3.4 Stress calculations . . . . . . . . . . . . . . . . . . . . . . . . . 117
5.3.5 Temperature mapping . . . . . . . . . . . . . . . . . . . . . . . 120
5.4 Material requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
5.4.1 Scintillator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
5.4.2 Light guides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
5.4.3 Photon counting units . . . . . . . . . . . . . . . . . . . . . . . 121
5.5 Experimental data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
5.5.1 Low energy proton detection with scintillators . . . . . . . . . . 121
5.5.2 Low-temperature characterization . . . . . . . . . . . . . . . . . 122
65.5.3 The photon counting unit . . . . . . . . . . . . . . . . . . . . . 127
5.5.4 Thin film CsI scintillation counter . . . . . . . . . . . . . . . . . 128
5.6 Main detector concept . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
5.7 Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
6 Large area avalanche photodiodes (LAAPDs) 137
6.1 Basic information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
6.1.1 PiN diode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
6.1.2 APD diode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
6.2 Theoretical description . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
6.2.1 Internal gain. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
6.2.2 Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
6.3 LAAPD structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
6.3.1 Beveled edge type . . . . . . . . . . . . . . . . . . . . . . . . . . 143
6.3.2 Reach through type . . . . . . . . . . . . . . . . . . . . . . . . . 143
6.4 Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
6.4.1 Measurementoftheworkingparametersasfunctionoftemperature144
6.4.2 Gain and noise as function of T . . . . . . . . . . . . . . . . . . 146
6.4.3 Spectral response . . . . . . . . . . . . . . . . . . . . . . . . . . 150
6.5 Interpretation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
6.5.1 LAAPD performance at low temperature . . . . . . . . . . . . . 151
6.5.2 Beveled edge type versus reach through type . . . . . . . . . . . 152
7 paff accelerator 155
7.1 Setup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
7.1.1 Source part . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
7.1.2 Diagnostic and monitoring part . . . . . . . . . . . . . . . . . . 159
7.1.3 Diagnostic and beam-reduction part. . . . . . . . . . . . . . . . 161
7.1.4 e-beam part . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
7.1.5 Target part . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
7.2 Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
7.2.1 The effect of the potential distribution in the source . . . . . . . 164
7.2.2 The Einzel lens . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
7.2.3 Beam transport properties . . . . . . . . . . . . . . . . . . . . . 166
7.3 Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
7.3.1 Beam composition . . . . . . . . . . . . . . . . . . . . . . . . . 167
7.3.2 Beam intensity variations . . . . . . . . . . . . . . . . . . . . . 168
7.3.3 Beam energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
7.3.4 Beam profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
7.3.5 Beam monitoring system . . . . . . . . . . . . . . . . . . . . . . 173
7.3.6 Beam visualization . . . . . . . . . . . . . . . . . . . . . . . . . 174
7.3.7 Electron beam . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
7.4 Experimental application of paff . . . . . . . . . . . . . . . . . . . . . 177
7.4.1 aSPECT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
7.4.2 PENeLOPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
8 Summary 179
79 Outlook 181
10 Appendix 183
10.1 Oxisorb as converter material . . . . . . . . . . . . . . . . . . . . . . . 183
10.2 Inelastic neutron scattering . . . . . . . . . . . . . . . . . . . . . . . . 184
10.3 Two hole method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
10.4 electropolishing and discharge cleaning . . . . . . . . . . . . . . . . . . 189
10.4.1 Electropolishing . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
10.4.2 DC-discharge cleaning . . . . . . . . . . . . . . . . . . . . . . . 191
10.5 Mechanical and electropolishing . . . . . . . . . . . . . . . . . . . . . . 191
10.6 FRED versus an analytical calculation . . . . . . . . . . . . . . . . . . 192
10.7 Pree preparation of Hamamatsu LAAPDs for cooling tests . . . . . . . 194
10.8 Simulation results for the proton detector . . . . . . . . . . . . . . . . . 195
8List of Tables
1.1 Energy, velocity and wavelength for different neutron energy regions[1]. 23
1.2 Characteristic values for different material corresponding to UCN. . . . 25
1.3 Parametrization of the free neutron decay. . . . . . . . . . . . . . . . . 27
−12.1 Raman shifts in cm for rotational states of H , HD and D . . . . . . 412 2
2.2 Miller indices for hcp Bragg peaks of solid deuterium. . . . . . . . . . . 57
2.3 Comparison between different experimental predictions on σ . . . . . . 80x
3.1 Different samples used at the two hole method to measure the and f
values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
3.2 ComparisonbetweenthecubeD2 transmissiondataandtheFRED sim-
ulation of the cubeD2 setup. . . . . . . . . . . . . . . . . . . . . . . . . 97
3.3 Comparingtheresultsfromthestorage method andthetwo hole method
for the 2 m Nokado tube. . . . . . . . . . . . . . . . . . . . . . . . . . . 98
5.1 Scintillator materials and its properties.. . . . . . . . . . . . . . . . . . 111
5.2 CalculatedstressduetocooldownoftheCsIlayeronvariouslight-guide
materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
5.3 Calculated peak position in ADC channels for the different energy spec-
tra from the listed radioactive sources compared with the measured ones.127
6.1 List of specified operation parameter from the data sheets of the used
two LAAPD types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
7.1 Experiments for fundamental particle research dealing with proton de-
tection from the free neutron decay. . . . . . . . . . . . . . . . . . . . . 155
7.2 Requirements on the paff facility. . . . . . . . . . . . . . . . . . . . . 156
7.3 Influence of the lens voltage U on the beam focus position.. . . . . . 162lens
7.4 Relative correction factor for the intensity loss due to the divergent beam.166
7.5 Possible reactions of the ion beam atoms I with rest gas atoms X. . . . 169
10.1 Size distribution of the Oxisorb particles. . . . . . . . . . . . . . . . . . 184
10.2 Differences between Polished and Buffed Milled Finishes, Abrasive Grit
Numbers and Surface Roughness. . . . . . . . . . . . . . . . . . . . . . 193
10.3 Trapeze coverage with a thickness of t=10mm . . . . . . . . . . . . . . 195
10.4 Trapetze coverage with thickness t=3mm . . . . . . . . . . . . . . . . . 196
10.5 Coverage with circle segments thickness t=10mm . . . . . . . . . . . . 196
10.6 Circle coverage with segments thickness t=3mm. . . . . . . . . . . . . . 196
10.7 coverage with triangle and cuboids thickness t=10mm. . . . . . . . . . 196
10.8 Coverage with triangle and cuboids thickness t=3mm. . . . . . . . . . . 196
910