Darmstadt 2016 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 69: Instrumentation XIX

HK 69.4: Talk

Friday, March 18, 2016, 15:00–15:15, S1/01 A2

Describing charge transfer processes in GEM foils with a model based on electric flux calculations — •Viktor Ratza, Markus Ball, Bernhard Ketzer, and Jonathan Ottnad for the ALICE collaboration — Helmholtz-Institut für Strahlen- und Kernphysik, Bonn, Germany

With the planned upgrade of the ALICE Time Projection Chamber the current readout technology will be replaced by a Gas Electron Multiplier (GEM) - based readout technology in order to allow for a continuous operation at high interaction rates up to 50 kHz. A stack of four GEM stages has been chosen to achieve a suppression of the ion backflow below 1%, while maintaining a good energy resolution and guaranteeing a stable operation of the chamber. As the charge transfer between the GEM stages highly influences the energy resolution and the ion backflow, a detailed understanding of the transfer processes inside the GEM stack is mandatory in order to predict the performance of the detector.

Based on an analytic solution of the Poisson equation for a single GEM, expressions for the transfer efficiencies as a function of the GEM geometry can be deduced from calculations of the corresponding electric fields and electric fluxes. The model as well as the results will be presented and compared to simulations which include charge transfer processes in gases.

Supported by BMBF.