The performance of the GPSC/MSGC hybrid detector with argon-xenon gas mixtures

The performance for X-ray spectrometry of Ar-Xe gas proportional scintillation counters using a CsI-coated microstrip plate in direct contact with the scintillation gas as a VUV photosensor is investigated for different argon-xenon mixtures. The GPSC/MSGC hybrid detectors filled with argon-xenon mixtures present superior performance when compared to those with pure argon and pure xenon-fillings. For these mixtures, the signal amplification due to the scintillation processes and the detector energy resolution may achieve values of 15-18 and 11-10%, respectively. Best energy resolutions can be achieved for mixtures with a broad range of xenon concentration, 20 to 70% Xe, being achieved for lower reduced electric fields in the scintillation region as the xenon concentration is reduced. As in pure argon or pure xenon gas-filling, the detector performance is limited by optical positive feedback resulting from additional scintillation produced in the electron avalanche processes around the MSP anodes. Best energy resolutions are achieved for positive feedback gains of about 1.1.