Münster 2017 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 27: Poster

HK 27.95: Poster

Tuesday, March 28, 2017, 16:45–18:45, F Foyer

Signal time reconstruction for GEM detectors read out by the APV chip — •Rocio Reyes Ramos, Mikhail Mikhasenko, and Bernhard Ketzer — Universität Bonn, Helmholtz-Institut für Strahlen- und Kernphysik, 53115 Bonn, Germany

The APV25 chip is an analog sampling ASIC that preamplifies the signals on each of its 128 input channels and samples them into a 160-cell switched capacitor array. Upon reception of a trigger signal, the sample values corresponding to a predefined latency are multiplexed and sent to a pipelined ADC for digitization.

While the chip was designed for Silicon microstrip detectors for the CMS experiment, they are also used for COMPASS GEM detectors, where 3 samples on the leading edge of the signal separated by 25 ns are read out. A pulse-shape analysis technique is used to reconstruct the signal time from the three samples taking into account the known signal shape. The time calibration of the system is performed by scanning the signal shape using different latencies. It is based on calculating sample amplitude ratios as a function of the trigger latency, corrected by the relative phase of the synchronized trigger signal and the passage of the particle. A Gaussian fit is performed over slices perpendicular to the time axis. Finally a phenomenological function representing the signal shape is fitted over the Gaussian mean values.

Recent improvements of the method like smearing of digital values (considering resolution and dynamic range of the ADCs) and removing large signals (saturating the dynamic range of the chip) will be shown.

Supported by BMBF.