EPICS oscilloscope for time-resolved data acquisition

The Sector 7 undulator beamline (7 ID) of the Advanced Photon Source (APS) is dedicated to time-resolved X-ray research [1]. Silicon avalanche photodiodes (APDs) are used as the primary point detector for time-resolved Bragg diffraction experiments for their fast recovery time (<100 ns) and ability to observe single photon events. For experiments with high photon flux (≥105 photons/s) at the detector, however, deadtime corrections to the counting statistics become appreciable [2]. Common practice has been to attenuate the monochromatic beam entering the experimental hutch to an appropriately low flux [3]. For these high-flux experiments, an APD operated in proportional mode is a better detector choice due to a large dynamic range and linearity. With the ZT4212 ZTEC, EPICS based oscilloscope, the operating procedure to use an APD in proportional mode has been improved. This article shows the setup and operating procedure for this oscilloscope and demonstrates its application to measuring time-resolved rocking curves of laser excited semiconductors.