An Experiment Control and Data Acquisition System for the Biology Small-Angle X-Ray Scattering Station

Abstract

An experiment control and data acquisition system for experiments to be conducted at the Biology Small-Angle X-ray Scattering Station at the National Synchrotron Light Source is under development. The primary function of the system is to acquire and record x-ray diffraction patterns in time-slice (or time-frame) mode, where the basic average rate of data collection is 106 detected photons/second and the biological process under study can be divided up into ~101 - 103 separate time slices. Furthermore, the system must provide external sample stimuli which bring about the biological process and must coordinate these stimuli with the time slices. A multiprocessor system has been designed. The principle behind the system design is to use a commercially available computer system to perform the standard functions associated with experiment control and data acquisition, while partitioning off the non-standard functions onto auxiliary computer processors. This technique has led to a four-processor system in which interprocessor communication is accomplished by means of a multiported shared memory module. A discussion of the computer system components, both hardware and software, which make up the system is presented. The description of hardware includes the processors, peripheral devices, and special-purpose hardware components present in the system; the software description covers the computer programs, operating systems, and special-purpose software which execute within the system itself and extends to a brief description of the software utilized to develop experiment control and data acquisition programs for execution on the system.