Dresden 2017 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 62: Surface Dynamics
O 62.3: Poster
Dienstag, 21. März 2017, 18:30–20:30, P2-OG2
A test experiment to determine the long term behaviour of work function and quantum efficiency of gold surfaces — •Kerstin Schönung and KATRIN Collaboration — Max-Planck-Institut für Kernphysik, Postfach 10 39 80, 69029 Heidelberg
The KArlsruhe TRItium Neutrino experiment KATRIN will perform a model-independent measurement of the effective neutrino mass by examining the β-electron energy spectrum of a gaseous molecular tritium source (WGTS). To achieve the desired sensitivity of 0.2 eV/c2 (90 % C.L.) the plasma potential of the tritium gas must be temporally and spatially stable within 20 meV. In order to achieve this stringent stability requirement the work function of the so called Rear Wall, which terminates the tritium volume at its rear end and defines the plasma potential therein, must be known even more precisely. The temporal fluctuations must be investigated. In addition to the work function fluctuations, the charge of the plasma in the tritium source could increase over time by the remaining positive ions produced by the tritium decays. In order to prevent this charging and the subsequent inhomogeneity of the plasma potential, the gold surface of the Rear Wall will be used to emanate electrons by the photoelectric effect. For a proper design of the required light source the quantum efficiency of the Rear Wall surface and its stability has to be determined.
A new experiment which investigates both, the in-situ work function and the quantum efficiency of the Rear Wall surface, is currently built up at KIT. In addition to the setup, first results will be presented. We acknowledge the support of the BMBF (05A14VK2).