First signals from indigenously produced GEM foils

Gas Electron Multiplier (GEM) detectors belong to the family of micro-pattern gas detectors (MPGD) which are advanced detectors for radiation detection in High Energy Physics (HEP) Experiments and imaging applications. These are high rate detectors, can provide high position resolution (< 50 µm) and can work in quite harsh radiation environment. They also have the advantage of being amenable to large area requirements which is often desired for the detectors in HEP experiments, such as those in PHENIX, ALICE, CBM, etc. GEM foils which is the main amplifying element of the GEM detector is composed of 50µm thin polyimide layer with 5µm copper layer on both its surfaces. Holes of ~50µm diameters are pierced all over the surface with a pitch of 140µm. A voltage of 400-500 V when applied across the two surfaces of the foil creates high electric field inside these holes. When placed in gas, the primary ionization electrons which passes through this holes initiate an avalanche of electrons thus multiplying the number of final electrons reaching the readout. Multiple planes of such amplification layers can be put together to achieve high gas gains. The production procedures for making such perforated foils are complex and there are only few places in the world where they are manufactured. An indigenous attempt has been made by ECIL, Hyderabad, to produce such foils for the first time. In this paper, we report the fabrication process and first test results of one such indigenously built GEM foil