Development of microstrip gas chamber and application to imaging gamma-ray detector

Abstract

We have developed a microstrip gas chamber (MSGC) by using multi-chip technology which enables high-density assembly of bare LSI chips on a silicon board. Our MSGC was operated steadily with approximately 10 3 gain more than one week. An energy resolution of 15% (FWHM) for 5.9 keV x ray of 55 Fe was obtained. With a very thin polyimide substrate of 16 micrometers thickness, two interesting phenomena were observed; one is a strong dependence of gains on the back plane potential, and the other is little time variation of gains. A new type of MSGC with a guarding mask of a thin polyimide layer on the cathode edges has been examined to reduce incidental electrical discharges between anode and cathode strips. Furthermore, a new approach to reduce the resistivity of the substrate has been examined. By these approaches, the stability of the high gain operation of approximately 10 4 has been drastically improved. In addition, we discuss the possibility of the application of MSGC to the coded mask x-ray imaging detector for astrophysics.