Effects of the induction-gap parameters on the signal in a double-GEM detector

A study of a dual-GEM detector coupled to a strip readout anode is described. The effects of the induction electric field and GEM-to-anode gap are presented, for an operation in atmospheric pressure Ar/CO2 (70/30) and Ar/CH4 (95/5). Visible gain and anode signal pulse-shapes, measured with 5.9 keV X-rays are presented for 1–6 mm wide induction gaps and for induction fields ranging up to 6 kV cm−1. The spatial distribution of the anode charge is provided for induction gaps of 2–12 mm. The results are useful for matching the detector parameters to the position recording circuit requirements.