Evaluation Of X-Ray Transmission Photocathode Detection Issues In The Energy Range Of 8-30 Kev

At the National-Ignition-Facility (NIF) and other laser facilities, X-ray transmission photocathodes are used in streak cameras and pulse-dilation framing cameras with temporal resolution well below 100 ps. For X-ray imaging quality assurance, signal-to-noise ratios of at least a couple, and optimally higher, have to be achieved. The signal-to-noise ratio depends on the photon fluence and the Detective Quantum Efficiency (DQE). X-ray photocathodes are notoriously noisy, since they have large pulse height distributions, and their DQE is both material and photon-energy dependent. Furthermore, for high temporal resolution, in pulse dilation instruments space charge effects may further limit the achievable signal-to-noise ratio. Here, we look into details on what to consider when choosing photocathode materials to optimize the achievable signal-to-noise and touch on further potential improvements using structured photocathodes.