C Copyright 2015 Laura I. Bodine

c Copyright 2015 Laura I. Bodine Molecular Effects in Tritium Beta-Decay Neutrino-Mass Measurements Laura I. Bodine A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Washington 2015 Reading Committee: R. G. Hamish Robertson, Chair Jason Detwiler R. Jeffrey Wilkes Program Authorized to Offer Degree: Physics University of Washington Abstract Molecular Effects in Tritium Beta-Decay Neutrino-Mass Measurements Laura I. Bodine Chair of the Supervisory Committee: Professor R. G. Hamish Robertson Department of Physics An understanding of the molecular final state distribution is crucial to extracting a neutrino mass from molecular tritium-based experiments including the upcoming Karlsruhe Tritium Neutrino Mass Experiment. This dissertation studies molecular systematics for the upcoming neutrino mass measurements and discusses the mea- surement of molecular dissociation as a test of final state distribution calculations. TABLE OF CONTENTS Page List of Figures................................... iv List of Tables.................................... viii Glossary....................................... xi Chapter 1: Neutrino Mass...........................1 1.1 Introduction to Massive Neutrinos....................1 1.2 Neutrino mass in the standard model..................2 1.3 Neutrinoless double-beta decay.....................3 1.4 Astrophysics, cosmology and neutrino mass...............5 1.5 Direct neutrino mass experiments....................8 1.6 Future prospects for direct neutrino-mass experiments......... 10 Chapter 2: Molecular Tritium Decay and Neutrino Mass Measurements.. 15 2.1 Beta Decay and Neutrino Mass..................... 15 2.2 Molecular Final State Distribution................... 24 2.3 Conceptual model of the rotational-vibrational spectrum....... 32 2.4 Tests of tritium final-state calculations................. 44 Chapter 3: Tritium Recoil-Ion Mass Spectrometer.............. 63 3.1 Experimental Concept.......................... 63 3.2 Simulations................................ 66 3.3 Extracting the Branching Ratio..................... 75 3.4 Analytic Calculations........................... 78 3.5 Hardware considerations......................... 81 3.6 Statistical and Systematic Errors.................... 99 i Chapter 4: TRIMS Data Analysis....................... 106 4.1 Analysis parameters........................... 106 4.2 Data run plan............................... 107 4.3 Waveform Filtering............................ 110 4.4 Energy-vs-time-of-flight spectra..................... 117 4.5 Branching Ratio Analysis........................ 117 4.6 TRIMS run plan............................. 120 Chapter 5: Krypton Calibration........................ 123 5.1 Krypton decay scheme.......................... 123 5.2 Krypton in TRIMS............................ 125 5.3 Krypton source.............................. 128 5.4 Source Production............................ 130 5.5 Cell design................................. 134 5.6 Activation Run.............................. 140 5.7 Source characterization.......................... 140 5.8 TRIMS krypton spectra: First Light.................. 150 5.9 Outlook.................................. 151 Chapter 6: Discussion & Conclusions..................... 154 6.1 Theoretical uncertainty: toward validation of the calculations..... 154 6.2 Impact on KATRIN and other molecular-tritium-based neutrino mass experiments................................ 155 6.3 Summary................................. 168 Bibliography.................................... 171 Appendix A: TRIMS Software.......................... 189 Appendix B: TRIMS bake-out.......................... 194 B.1 Bake-out Method............................. 194 B.2 Component temperature ratings..................... 196 B.3 Pumping during bake-out........................ 198 B.4 Vacuum Monitoring during bake-out.................. 199 ii Appendix C: TRIMS Slow controls and Database............... 200 C.1 Slow Controls............................... 200 C.2 Database.................................. 200 Appendix D: TRIMS Power Requirements................... 209 iii LIST OF FIGURES Figure Number Page 1.1 Two neutrino and neutrinoless double-beta decay Feynman diagrams.4 1.2 Layout of the Karlsruhe Tritium Neutrino Experiment, the next-generation, tritium-beta-decay neutrino-mass experiment.............. 13 2.1 Tritium beta spectrum with 3 active neutrinos with masses mνi 1 eV for the case of no daughter excitation.................' 16 2.2 Energy levels relevant to atomic and molecular tritium decay..... 22 2.3 Molecular spectrum excited in the beta decay of T2 (J = 0) as calculated by Saenz et al. [1] (solid curve, red online) and by Fackler et al. [2] (dotted curve, blue online)..................... 26 2.4 Recoil kinetic energy imparted to a 3He daughter by the beta decay of an isolated tritium nucleus at rest.................... 35 2.5 Distributions of excitation energy in the ground-state rotational and vibrational manifold of 3HeT+ (left) and 3HeH+ (right) as calculated by Saenz et al. [1]. The expected value for the excitation energy in each case, based on kinematic considerations, is indicated by a vertical line. An excitation energy of 0 corresponds to a binding energy of 1.897 eV [3]. (Figure made by R. G. H. Robertson for reference [4].)..... 36 2.6 Calculated recoil excitation energy spectra from zero-point motion in the parent molecule (dotted curves, blue online), compared to the final- state distributions calculated by Saenz et al. [1] at 30 K (solid curves, red online)................................. 39 2.7 Sketch of potential curve for 3HeT+ showing the bound, quasibound, predissociative resonance and dissociative states............. 43 3.1 Schematic of the TRIMS detector with a sample decay......... 64 3.2 TRIMS Simulation showing the energy deposited in the active region of the ion detector versus time of flight for each ion species....... 67 3.3 Beta spectrum from decay of T2 in the TRIMS apparatus....... 70 iv 3.4 Beta energy spectrum after acceleration following the decay of T2 in the TRIMS apparatus.......................... 70 3.5 Ion energy spectrum from decay of T2 in the TRIMS apparatus... 71 3.6 Ion energy spectrum after acceleration following the decay of T2 in the TRIMS apparatus............................. 71 3.7 Ion energy deposition in the detector following the decay of T2 in the TRIMS apparatus............................. 72 3.8 Ion time of flight for simulated decays of T2 in the TRIMS apparatus 72 3.9 Reconstructed ion time of flight for simulated decays of T2 in the TRIMS apparatus............................. 73 3.10 Ion energy versus time of flight of 100k simulated decays of T2 and HT in the TRIMS apparatus with nominal parameters described in Table 3.1. The parabolic mass cuts are defined by the density profiles as described in sec. 4.5........................... 74 3.11 Ion energy versus time of flight spectrum for a high HT (30%) simulation of 100k events in the TRIMS apparatus.............. 76 3.12 Ion energy versus time of flight of 100k simulated decays of T2 and HT in the TRIMS apparatus with high HT parameters described in Table 3.1 77 3.13 Difference between simulated high and low HT contamination energy- vs-time-of-flight distributions with fiducial volume cuts applied.... 77 3.14 Schematic of resistive-feedback charge-sensitive preamplifier for TRIMS 84 3.15 Board layout of resistive-feedback charge-sensitive preamplifier for TRIMS. (Figure produced by D. A. Peterson for fabrication.).......... 85 3.16 TRIMS signal processing chain. The link between the preamp and digitizer is fiber-optic for high-voltage isolation; all other connections are copper.................................. 87 3.17 Engineering model section view of the acceleration chamber and detector mounts................................. 90 3.18 TRIMS vacuum system schematic.................... 91 3.19 Red lines are the predicted axial magnetic field from each coil and the sum. Blue dots are from a field survey done at 46 A that was scaled to 140 A. (Figure made by R. G. H. Robertson.)............ 96 3.20 Cut-away view of the TRIMS inventor model.............. 98 v 4.1 Typical calibration spectrum taken with an Am-241 source, detector 118088 and the ion-detector preamplifier and filtered with a 8 µs peaking time................................... 109 4.2 Sample pulser signal. On the x-axis, each bin is 4 ns. On the y-axis, each adc bin is 0.49 mV.......................... 110 4.3 Sample pulser signal shaped with a trapezoidal filter.......... 111 4.4 Sample pulser signal shaped with consecutive trapezoidal filters... 111 4.5 Linewidth (standard deviation) of pulser signal as a function of filter peaking time................................ 112 4.6 Timing resolution (Gaussian width) for pulser signal fanned out to two preamplifiers and digitizer channels................... 114 4.7 Timing filter efficiency.......................... 114 4.8 Energy spectrum created by 5-second runs at voltage settings between 1 mV (red) and 100 mV (purple)..................... 115 4.9 Linearity test of copper signal showing linear behavior. Line positions are from Gaussian fits to the pulser signal position for a set of pulser settings ranging from 1 mV (red, unresolved) to 100 mV (purple).. 115 4.10 Linearity test of fiber optic signal response showing quadratic behavior. Line positions are taken from Gaussian fits to the pulser signal position for a set of pulser settings ranging from 1 mV (red,

Load more