Operational characteristics of a GEM-MSGC system for X-ray detection

This report outlines a recent study undertaken at CCLRC Rutherford Appleton Laboratory to evaluate the performance of a gas electron multiplier (GEM) coupled with a microstrip gas counter (MSGC). The parameters investigated during this study were effective gain, effective gain stability and energy resolution at 8.05 keV using Cu-K X-rays. These parameters were studied as a function of drift field, induction field, potential differences across the GEM holes and that across the MSGC anodes and cathodes. This report demonstrates that a single stage GEM can sustain effective gains up to 6000 whilst retaining adequate X-ray energy resolution. By utilising the MSGC as well as the GEM amplification these gains easily exceed 100,000 and allow the MSGC operation at much lower voltages. This report also demonstrates that the introduction of the GEM preamplification to the MSGC enables the operation of the latter at much higher effective gains (30,000) before any degradation in the X-ray energy resolution.