A Fast Protection System for Linear Acclerantors

The high beam current in the Los Alams Meson Physics Facility (LAMPF) accelerator constitutes a safety hazard to both personnel and equipment. It must be possible to inhibit beam injection rapidly and reliably in the event any condition occurs along the accelerator which will result in a beam spill. A hardware "fast protect" system based on transmission line principles has been developed which will provide a beam-inhibit signal in <10 μs after detection of an alarm condition anywhere along the 3000-ft length of the facility. The system also provides a permissive function to prevent beam injection, should the facility not be in a condition to accept beam. An indication that a shutdown occurred, along with an identification of the source which initiated it, is passed through an interface to the central control computer. The hardware is fail-safe to single component failures and features computer testing of the system integrity. Some details of the design, related to device-selection, ground-isolation, computer faultdetection, and provision for pulsing the rf out of the beam time are discussed. Comments relating to a prototype system installed on a computer-controlled electron linac are presented.