Performance of a GEM detector with copper-less foils

In this paper we present results of systematic investigation of a GEM detector built of GEM foils and the drift electrode with mostly removed copper cladding, keeping in mind possible applications of such a detector to spectroscopic imaging of soft X-rays. Copper-less foils have been manufactured starting from the standard copper-clad foils and removing most of the copper but narrow strips forming 1 cm grid, and using adhesive chromium layer for detector bias distribution. Performance of the detector for various gas mixtures: Ar/CO₂ (70/30), Xe/CO₂ (90/10), Xe/TMA (95/5), and Kr/CO₂ (80/20) has been evaluated. Spatial distributions of gas gain and energy resolution were measured over entire detector area of 10 × 10 cm with a pixel size of 800 ×  μm. During consecutive tests a significant variation of the mean value of the gas gain and increase of its spread across the detector was observed. The spatial variation of the gas gain formed mosaic patterns with square cells corresponding to the grid formed by copper strips on the drift electrode and on GEM foils. The energy resolution was not affected and stayed uniform across the detector area regardless variation of the gas gain. The observed deterioration of the detector is attributed to specific parameters of the GEM foils and specific processing steps and it is not considered as showstopper in further development of a copper-less GEM detector.