Bonn 2020 – scientific programme

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T: Fachverband Teilchenphysik

T 107: Combined instrumentation session I: Gaseous detectors (joint session HK/T)

T 107.3: Talk

Friday, April 3, 2020, 11:30–11:45, J-HS C

Charge transfer properties of a GEM stack – simulations and measurements — •Jan Paschek, Philip Hauer, Jonathan Ottnad, Markus Ball, and Bernhard Ketzer — Universität Bonn, Helmholtz-Institut für Strahlen- und Kernphysik, Bonn, Germany

Gas Electron Multipliers (GEM) are a micropatterned structure widely used as an amplification stage in gaseous detectors exposed to a high rate particle flux, e.g. Time Projection Chambers. Typically, a GEM consists of a polyimide foil which is coated with thin copper layers on both sides. Through a photolitographic process large numbers of holes are etched into this structure. In order to obtain the desired amplification a suitable voltage needs to be applied between both metal layers.

Typically, detectors consist of stacks of multiple GEM foils. The performance of a detector is highly influenced by the charge-transfer properties within the stack. To study these effects, a Monte-Carlo program simulating the charge transfer in a GEM stack using the frameworks Garfield++ and Ansys has been written. This program allows us to predict the properties of a GEM stack from the geometry of the GEM-foils and the applied fields. In order to verify the predictions a test detector has been assembled with a configuration corresponding to the quadruple GEM stack of the new readout chambers for the ALICE TPC. The talk will discuss the simulation program and compare the predictions to measurements with this test detector.

Supported by BMBF.