Micropattern gas detectors: the CMS MSGC project and gaseous pixel detector applications

We report recent results from the development and testing of two types of m icropattern gas detectors-micro-strip gas chambers and GEM-based devices wi th two types of pixel read-out. Thirty-two micro-strip gas chambers were te sted in a high intensity hadron beam as a milestone for CERN's Compact Muon Solenoid (CMS) experiment. The detectors were operated with voltage settin gs corresponding to 98% hit detection efficiency at CMS for a total high in tensity exposure period of 493 h. All of the requirements expected by the m ilestone-gain stability, number of lost strips, spark rate, etc.-were met, with wide margins. In a separate investigation, we have coupled PCB pixel r ead-out planes to GEM foils. In one case, 2 mm x 2 mm pixels were fanned ou t to individual discriminators and scalers to provide very fast (2 MHz/pixe l) read-out; this system has been used as an imaging device to provide diag nostic information in fusion experiments. The second type of device used sm aller pixels (200 mum squares) and a Flash-ADC read-out system to reconstru ct individual photoelectron tracks. The angular distribution of the tracks allows the polarisation direction of polarised X-ray sources to be identifi ed, with possible applications for future space experiments studying celest ial X-ray emissions. (C) 2001 Elsevier Science B.V. All rights reserved.