Sep 12 – 17, 2021
University of Birmingham
Europe/London timezone

Position reconstruction studies with GEM detectors and the charge-sensitive VMM3a ASIC

Sep 16, 2021, 10:41 AM
Teaching and Learning Building (University of Birmingham)

Teaching and Learning Building

University of Birmingham

Edgbaston Campus University of Birmingham B15 2TT UK


Lucian Scharenberg (CERN, University of Bonn (DE))


Gas Electron Multiplier (GEM) detectors are a prominent example of Micro-Pattern Gaseous Detectors (MPGDs). One of their main features is that they provide a good spatial resolution over large areas (square metre sized detector modules). When the interacting particle deposits energy inside the detector volume, primary electrons are created that drift towards the readout anode (here: 9 mm drift distance). During the drift, the electron cloud diffuses (sigma of 250 µm) over fine pitch granularity readout electrodes (here strips with 400 µm pitch). With such granularities, spatial resolutions of about 100 µm are achieved. Due to the charge spread over several readout electrodes, even better spatial resolutions can be achieved (around 40 µm with high-energy MIPs in COMPASS-like GEM detectors) by using position reconstruction algorithms, like for example the centre-of-gravity (COG) method.

To apply the COG method, multi-channel charge-sensitive readout electronics is needed. For the here presented studies, the VMM3a ASIC was used, which will be briefly introduced. It records the charge information and allows a self-triggered high-rate, position and energy-sensitive readout of large area particle detectors.

Due to the discretised readout structure, a bias is introduced in the reconstructed position, which was similarly observed with Multi-Wire Proportional Chambers (MWPCs), indicating that a pure usage of the COG method may not be the optimal choice. In this presentation, a simple modification of the COG method to mitigate the bias effect is shown and its applicability is discussed. Further, a hardware feature of the VMM3a is presented, which allows to recover otherwise lost charge information in its threshold-based self-triggered readout scheme and thus improves the position reconstruction.

Your name Lucian Scharenberg
Institute CERN, University of Bonn (DE)
Nationality German

Primary author

Lucian Scharenberg (CERN, University of Bonn (DE))


Antonija Utrobicic (CERN) Djunes Janssens (Vrije Universiteit Brussel (BE)) Dorothea Pfeiffer (CERN) Eraldo Oliveri (CERN) Florian Maximilian Brunbauer (CERN) Francisco Ignacio Garcia Fuentes (Helsinki Institute of Physics (FI)) Hans Muller (University of Bonn (DE)) Heikki Pulkkinen (Helsinki Institute of Physics (FI)) Hugo Natal da Luz (Universidade de Sao Paulo (BR)) Jerome Samarati (ESS - European Spallation Source (SE)) Jona Bortfeldt (Ludwig Maximilians Universitat (DE)) Karl Flöthner (HISKP-Uni-Bonn) Klaus Desch (University of Bonn) Leszek Ropelewski (CERN) Marek Hracek (Czech Technical University in Prague (CZ)) Marta Lisowska (University of Silesia (PL)) Michael Lupberger (University of Bonn (DE)) Miranda Van Stenis (CERN) Rob Veenhof (Uludag University (TR))

Presentation materials