Production and characterization of random electrode sectorization in GEM foils

Abstract

In triple-GEM detectors, the segmentation of GEM foils in electrically independent sectors allows reducing the probability of discharge damage to the detector and improving the detector rate capability. However, a segmented foil presents thin dead regions in the separation between two sectors and the segmentation pattern has to be manually aligned with the GEM hole pattern during the foil manufacturing, a procedure potentially sensitive to errors. We describe the production and characterization of triple-GEM detectors obtained with an innovative GEM foil segmentation technique, the “random hole segmentation”, that allows easier manufacturing of segmented GEM foils. The electrical stability to high voltage and the gain uniformity of a random-hole segmented triple-GEM prototype are measured. The results of a test beam on a prototype assembled for the Phase-2 GEM upgrade of the CMS experiment are also presented. A high statistics efficiency measurement shows that the random hole segmentation can limit the efficiency loss of the detector in the areas between two sectors, making it a viable alternative to blank segmentation for the GEM foil manufacturing of large-area detector systems.