Toward a Measurement of the Neutrino Mass with Tritium: Ion Studies for the KATRIN and TRIMS Experiments

The KATRIN (KArlsruhe TRItium Neutrino) experiment aims to measure the effective neutrino mass with an unprecedented design sensitivity of 0.2 eV at the 90% confidence level by measuring the energy spectrum of electrons produced in tritium beta-decay. Magnetic fields guide charged particles through the energy-analyzing retarding spectrometers towards the main detector. In this process, ions produced from the decay and from scattering

processes, act as a background source as they further ionize residual gas and produce secondary electrons. Ion-blocking mechanisms are implemented in the transport section for which we found preferred settings and neutralization times. We monitor the small ion flux in the spectrometers by the current that they make by striking electrodes along the beamline and by electron generation by ion-impact in the spectrometer. We calibrated the monitoring devices and present their performance during the first neutrino mass campaigns. We demonstrated that it was safe to run the experiment without ion contamination at the

high tritium concentration used during neutrino mass measurements. The molecular final-state theory, used to calculate the beta-energy spectrum for the KATRIN

experiment, is validated by the TRIMS (Tritium Recoil-Ion Mass Spectrometer) experiment. The goal of the TRIMS experiment is to measure the molecular tritium beta-decay

branching ratio to the bound state 3HeT+ and resolve discrepancies between theory and experimental results. In this thesis we will discuss selected analysis projects done for the TRIMS experiment, including characterization of the ion detector to correct for energy-loss effects, and investigations of the beta-decay daughter ion energy spectrum.