Discharge reduction technologies for Micromegas detectors in high hadron flux environments

Abstract

R&D program on Micromegas detectors for high flux hadron environment is ongoing at CEA Saclay, lead by the COMPASS and CLAS12 groups. The goal is to reduce the discharge probability in presence of intense highly ionizing beam. In order to achieve full efficiency at the high flux of 5 × 10 7 hadrons/s foreseen at the COMPASSII experiment, a reduction of the spark rate by a factor 10 to 100 compared to the present COMPASS Micromegas detectors is needed. Two approaches have been followed. The first one is based on a pre-amplification stage with a GEM foil and the second one using resistive layers. To study and evaluate these solutions, two prototypes featuring an additional GEM foil were extensively studied, while six resistive detectors, including two of them featuring buried resistance scheme proposed by R. de Olivera et al., were built and tested. These detectors have been characterized at CERN during two periods of beam tests: one at the Proton-Synchrotron (PS) using of 0.3 to 3 GeV/c pion beam, and the other one during the RD51 test beam period at the Super-Proton-Synchrotron (SPS) using 200 GeV/c muons.The GEM pre-amplification solution matches the COMPASSII requirements and simulations successfully reproduce the results. The good performances of the resistive design open another promising alternative.

New pixelized Micromegas detector with low discharge rate for the COMPASS experiment

“…Efficiencies and spatial resolution measured with muon beam were very similar to classic bulk Micromegas detectors. These results are presented in detail in the present proceedings, in the contributions of M. Vandenbroucke [11] and S. Procureur [12].…”

“…This foil allows reducing the gain of the micro-mesh stage and thus reducing the discharge probability for the same total gain. Results from both solutions are presented extensively in these proceedings by M. Vandenbroucke [11] and S. Procureur [12].…”