Assembly and test results of a 4-GEM detector

The development of Gas Electron Multiplier (GEM) detector at CERN has led to its extensive use in many present and planned future experiments in high energy physics. The advantages of the GEM detectors, compared to other gas detectors, are high particle detection rate, good position and energy resolution, low ion back flow (IBF) and stable operation in long run experiments. Triple GEM detectors with 3 GEM foils are commonly used in most of the experiments. We have reported a detailed test of a triple GEM detector recently. 4-GEM detectors with 4 GEM foils have the advantage of low IBF and low discharge probability. For this purpose, we have assembled a 4-GEM detector at VECC, Kolkata and tested. Here we report the assembly method and test results of the 4-GEM detector