The SLAC Beam Switchyard Control Computer

A computer system has been developed at SLAC in the beam switchyard for on-line beam transport control. The system consists of an SDS ´925´ computer and various specially designed interface devices. The system scans and records changes in interlocks and status signals; sets up, monitors, and maintains magnet currents and controls collimator and slit apertures. In addition to standard card and teletype input-output, the system has special panels for operator control of magnet currents and slit and collimator settings. A link to another computer provides for remote information access and control for experimenters. An important feature of the system is the operator oriented language which is provided for operator/computer interaction. The language is arranged so that an inadvertent action of the operator cannot adversely affect the computer program. A single computer instruction can vary a group of magnets simultaneously to change the beam energy while maintaining a given beam focussing condition. A fine-tune control has been provided so that the current in an arbitrary group can be controlled by a single switch. The operator can write instructions in the language which are synchronized in time to 1/360 of a second, and/or repeated at prescribed time intervals.