Avalanche Photodiodes as Fast X-ray Detectors

An avalanche photodiode (APD) detector provides a sub-nanosecond time resolution and an output rate of more than 10⁸ counts s^-1 of synchrotron X-rays. Moreover, the APD has the advantage of low noise. A review of recent developments of detectors using APD devices designed for X-ray experiments is presented in this paper. One of the detectors has an excellent time response of 100 ps resolution and a narrow width on its response function, 1.4 ns at 10^-5 maximum. The other consists of a stack of four diodes and has a transmission structure. The stacked detector improved the efficiency for X-rays, e.g. 55% at 16.53 keV. The output rates reached more than 10⁸ counts s^-1 per device.