Heidelberg 2015 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 13: Instrumentation 5

HK 13.4: Vortrag

Montag, 23. März 2015, 18:00–18:15, M/HS2

Ion backflow and energy resolution in micro-pattern gas detectors for the ALICE TPC — •Esther Bartsch, Alexander Grein, Michael Jung, Rainer Renfordt, and Harald Appelshäuser for the ALICE collaboration — Institut für Kernphysik, Goethe-Universität Frankfurt

For the upgrade of the Time Projection Chamber (TPC) of the ALICE experiment at the CERN LHC it is planned to replace the multiwire proportional readout chambers by Gas Electron Multiplier (GEM) stacks. The high interaction rate of 50 kHz foreseen for the Run 3 period of the LHC requires a readout scheme that can accommodate the 100 times higher rates. GEM-based readout chambers that can be operated in continuous mode are the prime candidate. To reduce the backflow of positive ions (IBF) into the detector volume several measures can be taken, such as optimization of the GEM voltages and transfer fields between the foils, and a systematic variation of the hole pitch. As alternative technology Micromegas (MICRO MEsh GAseous Structure) in addition to two GEM foils is also considered for gas amplification. Two dedicated test detectors, one for the characterization of triple and quadruple GEM stacks and one for the characterization of Micromegas, were set up at the IKF in Frankfurt. The results of systematic studies of the IBF and the energy resolution in several arrangements of GEM foils with different pitch sizes and in arrangements of Micromegas and GEM foils will be presented.

Supported by BMBF and the Helmholtz Association.