Calculation and Measurement of the Interstrip Capacitance on the Readout Board of the GE2/1 GEM Detector

The Phase 2 upgrade of the CMS experiment at CERN will increase the luminosity by a factor of ten. In order to cope with the higher muon trigger rates from the increased luminosity, the GE2/1 gas electron multiplier (GEM) detector has been proposed. A critical factor in the design of this detector is the interstrip capacitance of the strips on the readout board (ROB); by decreasing the interstrip capacitance, the noise in the detector can be lowered, which consequently improves the signal-to-noise ratio. This presentation will report on the analytical calculations and measurements of the interstrip capacitance of twelve different configurations of strip dimensions that are proposed for the M1 and M4 modules of the GE2/1 detector. The results of these calculations successfully predict the behavior of the interstrip capacitance of strip designs with different dimensions and geometries. Measurements of the interstrip capacitance were made both with and without an opposing copper plane, which simulates the capacitance due to the third GEM foil in the detector. Additionally, equivalent noise charge (ENC) measurements were made for each sector, and show a linear correlation with the interstrip capacitance.