X-ray photocathodes are used in a large number of X-ray imaging systems, mainly in the fields of astronomy and medical imaging. In most applications, X-ray photocathodes are used in conjunction with a microchannel plate (MCP) and a position- sensitive detector. Devices incorporating this combination are capable of imaging X-rays with very high spatial and temporal resolution. Many different X-ray photocathode materials have been developed to date. These materials have usually been alkali-halides (e.g., Csl or CsBr) and tend to be hygroscopic in nature. For this reason special handling and treatment of these materials is necessary to prevent them from degradation in the laboratory. In addition, X-ray imaging systems employing these materials as X-ray photocathodes suffer from low sensitivity and very poor energy resolution. The purpose of this work is to develop the semi-insulating semiconductor material thallium bromide (TlBr) for use as an X- ray photocathode. The development of this material would lead to a significant improvement in the utility of devices employing X- ray photocathodes.
