Darmstadt 2016 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 70: Instrumentation XX

HK 70.4: Talk

Friday, March 18, 2016, 15:00–15:15, S1/01 A3

Charge transfer in Gas Electron Multipliers — •Jonathan Ottnad, Markus Ball, and Bernhard Ketzer for the CBELSA/TAPS collaboration — HISKP, Bonn University, Nussallee 14-16, D-53115 Bonn

The operation of a Time Projection Chamber at high event rates requires an amplification structure which minimizes the backdrift of ions into the drift volume and at the same time maintains a good energy and spatial resolution. This can be achieved with the implementation of Gas Electron Multipliers (GEM), offering a continuous readout, a stable operation with sufficient charge amplification and an intrinsic suppression of the ions flowing back into the drift volume.

In order to optimize the operation parameters of a GEM based readout, various GEM geometries and different electric field settings inside a multi-GEM stack have been studied experimentally. The transfer efficiencies of electrons and ions have been measured and compared to the results of a microscopic simulation. An effective parametrization of the transfer efficiency is presented. It describes the charge transfer as a function of geometric parameters and the applied electric fields. From this, predictions for the transfer efficiency of electrons and the ion backflow suppression for a given GEM geometry and set of fields become possible.

Supported by SFB/TR16.