500-MHz x-ray counting with a Si-APD and a fast-pulse processing system

Abstract

We introduce a counting system of up to 500 MHz for synchrotron x‐ray high‐rate measurements. A silicon avalanche photodiode detector was used in the counting system. The fast‐pulse circuit of the amplifier was designed with hybrid ICs to prepare an ASIC system for a large‐scale pixel array detector in near future. The fast amplifier consists of two cascading emitter‐followers using 10‐GHz band transistors. A count‐rate of 3.25×108 s−1 was then achieved using the system for 8‐keV x‐rays. However, a baseline shift by adopting AC‐coupling in the amplifier disturbed us to observe the maximum count of 4.49×108 s−1, determined by electron‐bunch filling into a ring accelerator. We also report that..