Göttingen 2012 – wissenschaftliches Programm

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T: Fachverband Teilchenphysik

T 58: Spurkammern: Gas

T 58.10: Vortrag

Montag, 27. Februar 2012, 19:05–19:20, VG 2.102

A GEM-TPC read-out based on the AFTER ASIC — •Sverre Dørheim — Technische Universität München

A Time Projection Chamber (TPC) with Gas Electron Multiplier (GEM) amplification opens up the possibility to operate such a detector at high interaction rates. This is due to the intrinsic suppression of ion back-flow of the GEM amplification stage. A GEM-TPC prototype was built and tested within the FOPI spectrometer at GSI where it also serves as an upgrade, improving vertex resolution and acceptance. It has a drift length of 728 mm and an inner (outer) radius of 52.5  (150) mm. The pad plane has 10254 hexagonal pickup electrodes with a radius of 1.5 mm which are read out using 42 front-end cards.

The electronics for the GEM TPC prototype has to fulfill three important requirements: low noise, buffering electron drift times up to 30 µs and high integration. A low noise allows the detector to run at a lower gain, reducing the number of ions drifting back. The front-end electronics, based on the AFTER ASIC, developed for the TPCs for the T2K experiment, satisfies all these requirements. The multiplexed analog differential output signals of the ASICs are digitized at 20 MHz by a custom made pipeline ADC, which also performs baseline subtraction, common mode correction and zero-suppression.

An overview of the detector hardware and first results on the performance will be presented with the main focus on the front-end electronics and the read-out chain. Supported by the BMBF, the DFG Cluster of Excellence "Universe" and the EU 7th framework program.