Development of a Raman system for in-line monitoring of tritium at the Karlsruhe Tritium Neutrino (KATRIN) experiment

• Main Author: Lewis, Richard James
• Format: Dissertation
• Language: English
• Published: Swansea University 2007

The overall objective of this thesis was the development of a laser Raman spectroscopic system to monitor the purity of tritium injected into the Windowless Gaseous Tritium Source (WGTS) tube of the Karlsruhe Tritium Neutrino (KATRIN) experiment. KATRLN is a next-generation direct (beta decay endpoint) neutrino mass measurement experiment currently under construction at Forschungszentrum Karlsruhe (FZK) that is designed to improve the sensitivity in the measurement of the electron neutrino mass by an order of magnitude over the recent Mainz and Troitsk experiments, i.e. to reach a mass sensitivity of 0.2eV/c2 (90% C.L.). A definite measurement of the electron neutrino mass by KATRIN would be a discovery of profound importance for particle physics, astrophysics and cosmology. In order to minimise systematic errors in the determination of the electron neutrino mass, the purity of the tritium gas used as the beta decay source must be monitored continuously and to a minimum precision of about ±0.2%, with ±0.1% being an ideal-case 'gold standard'. A fibre-coupled laser Raman monitoring system (including complimentary Raman spectrum simulation and post-acquisition data processing software) has been developed and tested both off-line at Swansea University under low-laser power, high-pressure conditions, and in-line at the Test of Inner Loop (TILO) mock-up WGTS system at FZK. Both sets of measurements demonstrate that the minimum purity precision of ±0.2% can be met easily, and that it is probable that even the 'gold standard' of ±0.1% will be surpassed in near-future repeats of the in-line experimental runs.