Münster 2017 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 26: Instrumentation V

HK 26.8: Vortrag

Dienstag, 28. März 2017, 16:00–16:15, F 102

Investigations of a self-made potential-free picoammeter for MCP-PMT lifetime measurements — •Daniel Miehling, Merlin Böhm, Albert Lehmann, Markus Pfaffinger, Samuel Stelter, and Fred Uhlig for the PANDA collaboration — Physikalisches Institut, Universität Erlangen-Nürnberg

π/K identification in the PANDA experiment at HESR/FAIR will be done with DIRC detectors. These detectors are located in a magnetic field of >1 Tesla. This and other reasons leave the usage of Microchannel-Plate Photomultipliers (MCP-PMTs) as the only option. A serious concern of MCP-PMTs is their lifetime. While the integrated anode charge (IAC) increases the quantum efficiency (QE) of these PMTs decreases due to an aging process caused by feedback ions. A setup in Erlangen measures and monitors the QE, while the MCP-PMTs are illuminated. However, the time the most recent MCP-PMTs take to age at PANDA DIRC photon rates is rather long (up to years). We intend to accelerate this process by increasing the light intensity during the illumination. Unfortunately the limited MCP-PMT rate stability causes the anode signals to saturate at high light intensities. Then it is not possible anymore to directly correlate the IAC and the QE decline, i.e. the damage of the photocathode (PC). This can be avoided by measuring the charge directly at the PC or at the first MCP in combination with the IAC. For this purpose a potential-free picoammeter is needed. Because such devices are either not existent or very expensive, a "self-made" picoammeter was built and tested. The results will be presented in this talk. - Funded by BMBF and GSI -