Berlin 2018 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 18: Optical Analysis of Thin Films (Reflection, Ellipsometry, Raman, IR-DUV Spectroscopy, ...): Session I

DS 18.7: Vortrag

Mittwoch, 14. März 2018, 11:45–12:00, H 0111

A condensed Krypton conversion electron source with ellipsometry monitoring for the KATRIN experiment — •Stephan Dyba for the KATRIN-Collaboration — Institut für Kernphysik, WWU Münster

The KATRIN (KArlsruhe TRItium Neutrino) experiment will perform an ultra-precise measurement of the endpoint region of the energy spectrum of electrons from tritium β-decay to determine the neutrino mass with a sensitivity of 0.2 eV (90% C.L.). To achieve the required accuracy, the kinetic energy of the decay electrons is measured using a MAC-E filter type spectrometer. To characterize the transmission properties of the KATRIN main spectrometer a movable calibration source has been constructed, using mono-energetic conversion electrons from the decay of the ^83mKr isomer as a natural standard. For this purpose the radioactive krypton atoms from a ⁸³Rb generator are frozen onto a HOPG substrate at a temperature below 30 K. This Condensed Krypton Source (CKrS) uses sub-monolayer film thicknesses to provide decay electrons with a narrow line width and stable line position. The substrate is prepared by heating and laser ablation. The substrate with the sub-monolayer ^83mKr and condensing residual gas are monitored using PCSA type ellipsometry, where analyzer and the light detector are directly mounted near to the substrate under ultra-high vacuum in the cold environment. The whole system is movable to allow to freely position the source within the magnetic fluxtube of the experiment.

This project is supported by BMBF, contract number 05A11PM2.