Towards a Counting Point Detector for Nanosecond Coherent X-ray Science

Abstract

We present the technical realization of a high-speed hard X-ray single-photon counting-detection scheme based on a commercial avalanche silicon photodiode and high-speed oscilloscope. The development is motivated by the need to perform pulse-resolved photon-correlation and pump-probe studies at synchrotron sources with densely packed pulse patterns that result in high repetition rate pulses on the order of hundreds of MHz. Commissioning experiments are performed at the 1C PAL-KRISS beamline at PLS-II of South Korea operating at a burst mode maximum repetition rate of 500 MHz. In such a high count-rate measurement, detector dead-time can lead to a distortion of counting statistics. We are able to model the counting behavior of our detector under these conditions with a detector dead-time comparable to time between X-ray pulses, implying that nanosecond X-ray photon correlation spectroscopy should be possible at diffraction-limited light sources.

Special Issue on Trends in Sub-Microsecond X-ray Science with Coherent Beams

“…Lee at al. reported on the technical realization of a high-speed hard X-ray single photon detection scheme at a synchrotron that delivers X-ray pulses at a repetition rate of 500 MHz [3]. Sung et al reported on the development of a single-shot coherent X-ray imaging instrument at Pohang Accelerator Laboratory that is optimized to perform XPCS, CDI, and coherent X-ray scattering experiments for pursuing ultrafast phenomena of nanoparticles [4].…”