Design and execution of data acquisition systems for inelastic neutron spectrometers

We present the design and implementation of the data acquisition and instrument control for two new state-of-the-art inelastic neutron scattering spectrometers at the NIST Center for Neutron Research. The data acquisition system for the High Flux Backscattering Spectrometer (HFBS) is a multi-processing setup of several COTS digital and analog VME modules and a Motorola 96000 digital signal processor to perform real-time histogramming of detected events. The data acquisition system for the Disk Chopper Spectrometer, also VME-based, is a hierarchy: the front end is a bank of custom field programmable gate array (FPGA)-based modules to timestamp individual events. The front end units feed a sequencing FPGA which then passes events to a Pentium VME CPU running soft-real-time Linux for processing into a detector-by-time channel histogram. Overall control for each instrument is administered through the actions of an autonomous "core" program on a Linux host computer. Users interact with the core through client GUIs written in the Tool Command Language (TCL).