Operation Of A Novel Large Area, High Gain, Single Stage Gaseous Electron Multiplier

The operation of a novel large area micro-patterned gaseous electron multiplier, made from a 125 micron thick copper claded kapton foil, the COBRA_125, is presented. The COBRA_125 is equiped with 3 independent electrodes which allow to establish 2 independent multiplication regions in a single micro-patterened gaseous electron mutiplier. We report on the operation of a COBRA_125 with an active area of 100x100mm(2). Charge gains above 104 and energy resolutions in the range 18%-20% were achieved in a mixture of Ar-CH4 (90%-10%) by irradiation with X-rays from Fe-55 source. Gain and energy resolutions were stable over the detector area, with maximum deviation from the average values of 8% and 15%, respectively.