THE APPLICATION OF THE CURVED-GRID TECHNIQUE TO A GAS PROPORTIONAL SCINTILLATION-COUNTER WITH A SMALL-DIAMETER PHOTO-MULTIPLIER TUBE

The curved-grid technique was developed to maintain the superior perfo rmance of large-area gas proportional scintillation counters (GPSCs) w ithout resorting to complex and bulky focusing systems or large photom ultiplier tubes (PMTs) for applications in energy-dispersive x-ray flu orescence analysis. The technique is a simple method to compensate for the variation in solid angle viewed by the PMT as a function of the r adial distance from the cylindrical axis of the detector. The feasibil ity of the technique is demonstrated in a GPSC, by measuring the energ y resolution as a function of entrance window diameter. With a properl y shaped curved grid, no degradation in detector energy resolution is observed even when the effective detector sensitive area is increased approximately six-fold. The maximum ratio of detector entrance window to PMT diameter achieved thus far is approximately 0.75.