Münster 2002 – scientific programme
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HK: Physik der Hadronen und Kerne
HK 28: Instrumentation and Applications III
HK 28.6: Talk
Wednesday, March 13, 2002, 12:15–12:30, F
The Common GEM and Silicon Readout for the COMPASS Experiment [*] — •Boris Grube1, Rita De Masi1, Jan Friedrich1, Igor Konorov1, Stephan Paul1, Lars Schmitt1, Frank Simon1, Robert Wagner1, Michael Wiesmann1, and Bernhard Ketzer2 — 1TU München, Physik-Department E18, James-Franck-Straße, 85748 Garching, Germany — 2CERN, CH-1211 Genève 23, Switzerland
COMPASS is a fixed target experiment at the CERN SPS which uses GEM and Silicon detectors for small angle tracking. For both detector types the APV 25, a development of the CMS collaboration, was chosen as the frontend chip. The system utilizes the ’Multi’ readout mode of the APV, in which the chip sends three consecutive samples for each event. By calculating the ratios of the amplitudes of the different samples, it is possible to determine the position along the assumed pulse shape and thus to get precise timing information. The readout chain is based on reconfigurable logic in the form of Field Programmable Gate Arrays (FPGAs) and is designed to stand high trigger rates of up to 100 kHz. The analog signals of the APV are digitized by 10 bit ADCs. The digital signals are then processed and sparsified by a zero suppression logic. Because fluctuations of the baseline of the APV are observed, the data have to be corrected for this ’common mode noise’, before a threshold cut can be applied. This correction is performed in the hardware using a combination of averaging and histogramming. [*] This project is supported by the BMBF and the Maier-Leibnitz-Labor, Garching