Proportional Counter Photon Camera

A gas-filled proportional counter camera that images photon emitting sources was built and tested. This camera measures and displays the impact location of individual photons in an energy range between 1 and 150 keV and permits pulse shape and energy discrimination for background reduction. Possible fields of applications for this camera include nuclear medicine, nuclear physics, x-ray diffraction, and related areas. The signal processing of the camera is based on further improvements and simplifications of the risetime method as applied to multiwire position-sensitive counters. Materials inside the counter were selected so that the camera can be used over long periods of time without purification of the counter gas. The sensitive area of the camera is 200 × 200 mm2, and the size of each picture element is 1 × 1 mm2; thus 40,000 picture elements are resolved. Counting rates of up to 20,000 photons/s do not appreciably affect the spatial resolution. The camera has been tested only with low energy photons (<30 keV) to determine the properties and applicability of the camera; however, by use of high pressure (>10 atm) Xe counter gas, a useful detection efficiency (>30%) and good spatial resolution are expected for 150-keV photons.