Sub-microsecond-resolved multi-speckle X-ray photon correlation spectroscopy with a pixel array detector

Small-angle X-ray photon correlation spectroscopy (XPCS) measurements spanning delay times from 826   ns to 52.8   s were performed using a photon-counting pixel array detector with a dynamic range of 0 – 3 (2   bits). Fine resolution and a wide dynamic range of time scales was achieved by combining two modes of operation of the detector: (i) continuous mode, where data acquisition and data readout are performed in parallel with a frame acquisition time of 19.36   µ s, and (ii) burst mode, where 12 frames are acquired with frame integration times of either 2.56   µ s   frame − 1 or 826   ns   frame − 1 followed by 3.49   ms or 1.16   ms, respectively, for readout. The applicability of the detector for performing multi-speckle XPCS was demonstrated by measuring the Brownian dynamics of 10   nm-radius gold and 57   nm-radius silica colloids in water at room temperature. In addition, the capability of the detector to faithfully record one- and two-photon counts was examined by comparing the statistical distribution of photon counts with expected probabilities from the negative binomial distribution. It was found that in burst mode the ratio of 2   s to 1   s is markedly smaller than predicted and that this is attributable to pixel-response dead-time.

Source: Journal of Synchrotron Radiation - August 2, 2018 Category: Physics Authors: Zhang, Q. Dufresne, E.M. Narayanan, S. Maj, P. Koziol, A. Szczygiel, R. Grybos, P. Sutton, M. Sandy, A.R. Tags: pixel array detector (PAD) X-ray photon correlation spectroscopy (XPCS) multi-speckle XPCS research papers Source Type: research