Mainz 2022 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 6: Instrumentation III

HK 6.4: Vortrag

Montag, 28. März 2022, 14:45–15:00, HK-H5

A calibration system for a modular small-format TPC with GEM amplification — •Dmitri Schaab, Reinhard Beck, and Bernhard Ketzer for the CBELSA/TAPS collaboration — Helmholtz-Institut für Strahlen- und Kernphysik

The performance of a Time Projection Chamber (TPC) relies on a good knowledge of the electric field inside the sensitive volume. This is crucial since deviations from a homogeneous drift field, either due to mechanical imperfections or due to space charge effects at high particle rates, deteriorate the spatial resolution of the detector if they remain uncorrected. One calibration method is to release electrons via the photoelectric effect at well-known positions on the cathode. By the electric field, these electrons are guided across the drift region towards the readout plane and show the integrated spatial distortions. In addition, a drift velocity measurement is provided. This photoelectric calibration concept, first employed at the T2K experiment, was implemented on a small scale involving a test tracking detector and a pulsed UV-laser. The laser light is conditioned using an optical setup and fed into the detector with the help of a multimode fiber bundle. Calculations were made in order to provide a uniform illumination of the detector cathode. The photoelectric calibration system was implemented in a newly built small TPC (sTPC) with GEM amplification. Its fully modular design allows for spatially resolved studies of field distortions using different GEM configurations or readout geometries.

The development of the measurement setup as well as characterizing photoelectric measurements will be presented.