H. Mio, H. Amenitsch, W. Leingartner, and P. Laggner
Institute for Biophysics and X-ray Research, Austrian Academy of Sciences

A new PC-based histogramming data collection system for fast readout and on-line data display of one or more digitising units with the possibility to trigger external devices will be described. One of the major advantages of the proposed system is the short intrinsic dead time of only 170 ns which allows a count rate of 1 MHz with only 0,3 % losses assuming a Poisson distribution of the incident pulses. Furthermore the graphical Windows software and live display of acquired data allow an immediate user interaction with the experiment even during an active acquisition. Since the beamline is dedicated and designed to host a large variety of scanning and jump-relaxation sample stages (e.g. T-, p-, magnetic field, stopped- flow etc.) the control system has been developed on a uniform user surface (based upon LabView) to enable user-friendliness. The main advantage of this user surface is that the beamline scientist can configure the actual needs for the experiments based on a great variety of modules. On the other hand the valves, shutters, the radiation safety system and vacuum pressure interlocks are controlled via VME-crate and a PLC with network interface to the beamline-PC in order to guarantee the security for sensible instruments. The experience with the PC-board and associated software, which has been extensively used at the Austrian SWAX (small- and wide-angle X-ray scattering)-beamline at Elettra in Trieste during the last two years, an overview of the acquisition and control system, as well as some applications of it will be presented.

(posted 22-Oct-97 jw)