Bonn 2020 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 48: Instrumentation X

HK 48.2: Talk

Thursday, April 2, 2020, 14:30–14:45, J-HS C

A photoelectric-effect-based field calibration system for the Time Projection Chamber at the CBELSA/TAPS experiment — •Dimitri Schaab, Fabian Metzger, Markus Ball, Reinhard Beck, and Bernhard Ketzer — Helmholtz-Institut für Strahlen- und Kernphysik, Universität Bonn

The performance of a Time Projection Chamber (TPC) relies on a very good knowledge of the electric field inside the sensitive volume. This is crucial since deviations from a perfectly homogeneous drift field deteriorate the spatial resolution of the detector if they remain uncorrected. Reasons for these deviations are, on the one hand, static imperfections of the detector structure and, on the other hand, dynamic changes of the space charge inside the sensitive volume which mainly originate from fluctuations of the event rate.
For the new TPC for the CBELSA/TAPS experiment, a calibration system based on the one of the T2K experiment is being set up. With the help of a UV-laser, electrons are released via the photoelectric effect at well-known positions on the cathode. By the electric field, these electrons are guided towards the readout plane and show the integrated spatial distortions. The UV laser light is introduced into the TPC from the anode side through fibre bundles. Care was taken to achieve a uniform illumination of the cathode surface. In this scope, a small TPC (sTPC) has been designed and built in order to test the calibration system. The setup and first measurements will be presented.