Arc Detection and Interlock Module for the Pep-ii Low Level Rf System*

A new arc detection and interlock generating module for the SLAC PEP-II low-level RF VXI-based system has been developed. The system is required to turn off the RF drive and high voltage power supply in the event of arcing in the cavity windows, klystron window, or circulator. Infrared photodiodes receive arc signals through radiation resistant optical fibers. Gain and bandwidth are selectable for each channel to allow tailoring response. The module also responds to interlock requests from other modules in the VXI system and communicates with the programmable logic controller (PLC) responsible for much of the low-level RF system's interlock functionality. 1 SPECIFICATION AND DESCRIPTION The PEP-II low-level RF system VXI-based Fast Interlock module (figure 1) performs several functions related to monitoring and protecting the RF system. The module serves as the sole VXI module responsible for transmitting any VXI module generated faults to trip the klystron high voltage system. Each Fast Interlock module resides in a VXI crate adjacent to each RF station. An additional hardware subsystem known as the ‘Local Panel’ has been configured to serve as an intermediary between the interlock handling subsystems of the VXI Fast Interlock module, the Allen-Bradley (Milwaukee, WI) PLC, and the high voltage power supply (HVPS) controller[1]. Figure 1. VXI Fast Interlock Module The Fast Interlock module communicates directly with the Local Panel and indirectly through it to the AllenBradley system and the high voltage power supply controller. *Work supported by U.S. Department of Energy Contract DE-AC03-76SF00515 Fiber optic cables monitor for high power arcing near the cavity windows and at the klystron and circulator.