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HK: Fachverband Hadronen und Kerne
HK 10: Accelerators and Instrumentation II
HK 10.4: Talk
Monday, March 16, 2009, 15:00–15:15, H-ZO 90
A large-area low-temperature proton detector for the neutron lifetime experiment PENeLOPE — •Christian Tietze, Igor Altarev, Heinz Angerer, Beatrice Franke, Erwin Gutsmiedl, Joachim Hartmann, Stefan Materne, Axel Reimer Mueller, Stephan Paul, and Rüdiger Picker — Physik-Department, Technische Universität München
The neutron lifetime τn is a quantity very important for fundamental physics and cosmology. The new experiment PENeLOPE shall determine τn by trapping ultra-cold neutrons in a magnetic multipole field and by gravitation. Their lifetime will be determined precisely by both, counting the remaining neutrons after one storage period and online measurements of the time distribution of the decay protons. It is planned to use a scintillation counter as proton detector; it shall consist of a thin CsI layer evaporated on a UV-transparent light guide. The signals will be read out with large-area avalanche photodiodes (LAAPDs). As the whole arrangement is situated next to superconducting coils of PENeLOPE, the detector has to work at high magnetic fields and cryogenic temperatures. Extensive investigations were performed to prove the feasibility of the setup. The gain of two different types of LAAPDs was measured down to 25 K and found to be nearly constant. Additionally, the temperature dependent light output of CsI was measured as well as its behaviour after exposition to humid air. The talk will cover further developments of the detector concept as well as its integration into the PENeLOPE cryostat. This work is supported by MLL, DFG and by the Cluster of Excellence EXC 153.