KATRIN background due to surface radioimpurities

The goal of the KArlsruhe TRItrium Neutrino (KATRIN) experiment is determination effective electron antineutrino mass with a sensitivity 0.2 eV/c2 at 90 % C.L.1. This can only be achieved very low background level in order 10 mcps2 detector region interest. A possible source are α-decays on inner surface KATRIN Main Spectrometer. Rydberg atoms, produced sputtering processes accompanying α-decays, not influenced by electric or magnetic fields and freely propagate inside vacuum Here, they ionized thermal radiation released electrons directly contribute to background. Two α-sources, 223Ra 228Th, were installed Spectrometer purpose temporarily increasing study α-decay induced processes. In this paper, we present generation mechanism measurements performed these two radioactive sources. Our results show clear correlation between α-activity spectrometer from volume spectrometer. key characteristics – dependency electrode offset potential, radial distribution could reproduced artificially These findings indicate high contribution events residual