High Resolution Photon Counting Detection System for Advanced Inelastic X-Ray Scattering Studies

Abstract

High brilliance and high spectral resolution of synchrotron sources and associated optics enable a large number of soft-X-ray spectroscopic studies such as inelastic X-ray scattering, which is becoming a technique of choice for the investigation of the electronic properties of complex materials. The resolution of the detection system in such experiments has to match the accuracy of the probe beam in order to take the full advantage of the performance of modern synchrotron sources. In this paper we describe our advanced photon counting detection system capable of simultaneously registering both position and time of individual photons with 2-dimensional spatial accuracy of < 50 mum and timing accuracy of < 130 ps FWHM. The open face, 25 mm active area detector consists of a Z-stack of microchannel plates and a cross delay line readout and has a dark count rate of only a few counts per second. The associated electronics allows event counting rates up to ~400 KHz with 10% dead time for randomly events. We present the results of our first measurements of delayed fluorescence from different materials performed at the Advanced Light Source. Time and angular resolved fluorescence measurements allowed us to separate images for the prompt elastically scattered and the delayed photons. The detector can also distinguish registration of electrons, ions or photons by variation of the potential on its input mesh. These results demonstrate the capabilities of our detection system, which is currently being integrated into an advanced time resolved X-ray emission spectroscopy system.