We present details of the data acquisition system that will be used and supported at the SNS neutron scattering facility. The design satisfies the unique requirements of the instruments at SNS including high data rates up to 60 million events/second, a common hardware and software platform and remote viewing/control of experiments in progress. To meet the wide range of instrument requirements the SNS data acquisition system uses a combination of networked PCs and custom electronics. Within this distributed control environment, a control PC regulates the progress of an experiment while the actual control of hardware is accomplished by a number of satellite computers, with each satellite computer controlling a specific part of the instrumentís hardware. Hardware changes are handled automatically by the use of dynamic configuration files. Neutron scattering data is handled by one or more server class PCs configured as a cluster. The preprocessor cluster along with the detector electronics creates a virtual detector system whose hardware and software interface is common between all the SNS instruments. Each instrumentís computers operate on a private network behind a firewall computer that provides a secure public interface and a gateway for low bandwidth information. High bandwidth data files are handled on a separate read only data/file server. Control of the experiment is handled either through Python scripts or control GUIs. GUIs are easily constructed from a standard suite of custom C++ classes that incorporate the necessary communication and error handling codes. A number of other drivers and multithread applications have also been development for intelligent management of networking resources. Custom interface boards provide a detector interface capable of transferring data at 200 Mbytes/second along with the optical transmission of real time digital signals with less than 5 nsec. of jitter.
Abstract File: abstract00055.txt
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