NEW CONCEPTS FOR THE DESIGN OF LARGE-AREA GAS PROPORTIONAL SCINTILLATION-COUNTERS

New concepts are presented that allow the design of gas proportional s cintillation counters with large areas and medium size photomultiplier s. These designs are based on the compensation of the radial decrease of the scintillation light collected in the photomultiplier due to sol id angle and reflection effects, with a radial increase of the light p roduction due to a non-uniform electric field produced by a properly s haped curved grid. An implementation of these concepts based on a 2'' diameter photomultiplier is presented. It shows a pulse amplitude vari ation, along the radial position (0 to 10 mm) of less than 0.5%, and a n energy resolution of 8.0% for a broad 5.9keV X-ray beam entering the detector through the full 25mm diameter window.