Upgraded Computer Hardware and Software for SSRL Beam Lines

- G. George

At present most beam lines at SSRL use aging MicroVAX III computers with DSP Q-bus CAMAC crate controllers, running VAX-motors and CAMVMS software. By modern standards, the MicroVAX computers are very slow. Furthermore the CAMAC hardware, while still adequate for most purposes, is approaching obsolescence. No modern computers use Q-bus, and DSP has discontinued production of their Q-bus based crate controllers.

This configuration will be upgraded to a Digital Alphastation 500/233 with a Kinetic Systems Grand Interconnect crate controller and new control software. An additional X-terminal for data analysis will also be present at each of thirteen experimental stations, which are planned to be upgraded during the upcoming run. The Alphastations will provide an approximate 200-fold increase in computing power compared to the current MicroVAX III systems. Initially, the Alphastations will use the Open-VMS operating system. The choice of computer (the Alphas can run Open-VMS, Digital UNIX or Windows NT) provides more flexibility than any other platform regarding future operating systems should a change from Open-VMS be desirable.

Kinetic Systems' Grand Interconnect crate controller provides a very high throughput, low-latency interface to CAMAC, and VXI crates. Using Grand Interconnect a large number of crates can be simultaneously controlled by a single computer. Initially, only the existing CAMAC crates will be used on most beam lines. Grand Interconnect provides an upgrade path in which VXI hardware can be gradually phased in while maintaining existing CAMAC units.

New beam line control software is currently under development by Martin George and was initiated as part of the Beam Line 9 project. It will replace the existing VAXmotors and CAMVMS software. This new software consists of a control program which is responsible for all aspects of beam line instrument control including data collection. This is combined with a number of utility programs including a sophisticated graphical user interface to assist in beam line setup.

All relevant beam line parameters, including such things as equations of motion for combination motors (e.g. monochromators) will be stored in simple ASCII files. This allows considerable flexibility, and should make beam line configuration and setup very straightforward, with the ability to define new experiments and new combination motors without the need for any new compiled code.

The two existing mainstream SSRL data collection programs, XAS-collect and Super, will be fully supported by the new system.

The new software has been designed from the outset with portability in mind, with minimal use of operating system dependent code. The initial implementation will be under Open-VMS, but a future move to Windows NT or to UNIX should not present a significant obstacle.

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December 2, 1996