Mainz 2012 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 11: Instrumentation

HK 11.2: Vortrag

Montag, 19. März 2012, 17:00–17:15, P 2

Energy Calibration of a GEM-TPC Prototype — •Roman Schmitz — Helmholtz-Institut für Strahlen- und Kernphysik, Universität Bonn

A Time Projection Chamber (TPC) with Gas Electron Multiplier (GEM) readout has been developed with an inner/outer diameter of 105/300 mm and a total drift length of 725 mm. A triple GEM stack is used for gas charge amplification to reach sufficiently high gain. In addition the GEM stack provides an intrinsic strong secondary ion backflow suppression without the necessity for an ion gate, which opens the possibility to operate such a detector in a continuous mode even at high interaction rates. The anode of the prototype GEM-TPC consists of 10254 hexagonal pads with an outer radius of 1.5 mm which are read out by 42 front end cards based on the T2K/AFTER chip. The TPC is used to improve the inner tracking and vertexing of the FOPI experiment at GSI and serves as a full-scale prototype for the CBELSA/TAPS experiment. In order to perform an accurate channel-wise relative gain calibration and a total gain estimation, a ^83mKr source is used. Its gaseous form makes it perfectly suitable for this purpose and several conversion electron peaks between 9.4 keV and 41.55 keV enable gain calibration over a wide energy range. The short half-life of 1.83 h allows for normal detector operation after a short flushing period of about one hour. Details on source production, integration and first calibration results compared to calibration results obtained with cosmic rays are presented.
This work is supported by DFG SFB/TR 16.