Bochum 2018 – wissenschaftliches Programm
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HK: Fachverband Physik der Hadronen und Kerne
HK 52: Poster
HK 52.60: Poster
Donnerstag, 1. März 2018, 16:30–18:45, Audimax Foyer
Ray Optics Simulation of the KATRIN Rear Wall Illumination — •Benedikt Bieringer — Institut für Kernphysik, Münster, Deutschland
The KArlsruhe TRItium Neutrino (KATRIN) experiment is designed to measure the mass of the electron antineutrino from the shape of the tritium β-decay spectrum with a sensitivity of 0.2 eV/c2 (90 % CL). An electrostatic spectrometer of MAC-E filter type is used for the analysis of the decay electrons generated in the Windowless Gaseous Tritium Source (WGTS). The decaying tritium produces a plasma inside the WGTS with a high conductivity along the magnetic flux lines inside the source. Electrons that are emitted in the backward direction (away from the spectrometer) or reflected from the spectrometer because of not passing the high energy filter are magnetically guided and absorbed in the so-called rear wall (a gold-plated stainless steel disc). To prevent a net positive charge of the plasma, the rear wall can be illuminated homogeneously with UV light to produce photoelectrons which neutralize the plasma. For this purpose, a broad light spectrum is generated from a xenon short-arc lamp and then filtered using two dichroic beam splitters. The remaining beam with wavelengths between approx. 200 and 260 nm is enlarged using a refracting telescope. This illumination setup was optimized using 3D ray-tracing simulations performed with COMSOL to investigate the homogeneity of the illumination, the total intensity of the illumination and the size of the setup. The optimization process of the rear wall illumination setup is presented. This work is supported under BMBF contract number 05A17PM3.