In response to the need for additional data acquisition systems within the next two years, we have prepared an architecture based upon neutron scattering requirements, market trends, and developments within the Web community and the controls community. A preliminary version will be shown in a demonstration session.
To maximize software reuse and to minimize cost for software we want to exploit commercially successful products and the work of successful physics collaborations. The software will have three components: the user interface , the real-time process, and the data acquisition server. Today we envision a generic Web browser, VxWorks, and WindowsNT as these software elements, respectively. Popular Web browsers are available from Microsoft, Netscape, and Sunsoft for a wide variety of hardware platforms. WindowsNT is the industrial-strength version of the popular windowing system from Microsoft, and VxWorks is the real-time kernel used throughout the high-energy and nuclear physics community. Communication between the the real-time and the data acquisition server components is based upon the Experimental Physics and Industrial Control System (EPICS), which enjoys wide support in accelerator, telescope, and commercial controls.
At a minimum the data acquisition configuration consists of one microprocessor to handle the user interface and Web server functions, another microprocessor to handle the real-time event processing and histogram construction, memory to store the histograms, and a custom module to capture the data from a pulse of neutrons. A private network connects the readout controllers to the data acquisition server. Normally users control the experiment via the Internet from a third computer located in a data room, office, another laboratory, home, or hotel. If high-performance graphics are required, then the user may run directly on the data acquisition server.
Since VME/VXI hardware has been commercially viable over the past 15 years and since VME processor modules are available with all the latest and greatest microprocessor chips (PowerPC, Intel, Alpha, MIPS), we felt that our performance demands for today and the future could be satisfied with commercial equipment. Of course, a custom VME module will be required to time stamp and buffer events from our neutron scattering experiments. Following collaborative efforts with IPNS, we will use the flexible Argonne design to perform this function.
(posted 21-Oct-97 jw)