Initial Requirements

The SR User Facility at TRIUMF consists of four beamlines, each using a VAX and single CAMAC crate for data acquisition. The data acquisition system, MODAS, was developed by Dave Maden for the Time Differential SR (TD-SR) experiments performed at TRIUMF and PSI. [1,2] At TRIUMF, another distinctly different experiment type, Integral SR (I-SR), required a second component to MODAS. This was written by Syd Kreitzman.

The configuration of slow control instruments at TRIUMF changes for each experiment and often during an experiment. Since experiments last only one or two weeks, a slow control system which would provide easy online configuration changes was necessary, along with the ability to save and load configurations. Furthermore, the suite of available instruments is always growing. Rapid addition of new instrument drivers would also be necessary.

A library for client applications and, since much of MODAS is written in DCL, a command-line interface were required for integration with data acquisition. A user interface was required for viewing and modifying the configuration. A fully functional textual user interface was required for use of the system from a maximum number of terminals, including the all-important home PC. It was also necessary that there be multiple user interfaces and/or client programs concurrently.

Because of the complexity of many of the instruments in use, it was desired that multiple variables be available for setting and readback for each instrument. The system would therefore provide a generic way for new users to access simple variables, and for expert users and client programs to access the more complex functionality of an instrument. The attributes of variables would include polling (update rate), logging and alarm information. Each instrument could be locked for exclusive control by a client application. Possible communication interfaces would include: RS-232-C, GPIB and CAMAC, some instruments having both RS-232-C and GPIB capability.

There were several desires of those determining the initial requirements that were not considered necessary. These include: implementation of pseudo-instruments, portability, and distribution of applications. Pseudo-instruments are drivers that encapsulate multiple physical instruments.

Based on the experience of using CAMP in the field over the last year, several upgrades were necessary. These are described later in this text.