Design and development of AR RF personnel protection and interlock system for RF Test with Access mode to RF cavities in ALS-U project at LBNL

The ALS-U project at LBNL is a major upgrade of the ALS involving a new Accumulator Ring (AR) and an upgraded Storage Ring (SR). The new AR RF System has one operational mode with beam and three test modes without beam. Another upgraded overarching Ring Personnel Protection Systems (PPS) covering both AR and SR ring enclosure areas is in place for personnel protection from ionizing radiation during beam operation and it is interfaced with AR RF PPS subsystem for status & control signals. In the RF Test with Access mode, the controlled access of authorized personnel is permitted to AR RF cavities area when it is powered below certain predetermined power limit without beam, for conducting low power RF leakage checks, tests. For that objective, an AR RF PPS power monitor & interlocks as described in this paper has been designed & developed for use in the Test with Access mode in order to ensure that potential exposure to harmful ionizing X-rays from RF cavity operating does not result in doses above the prescribed limits. The actual X ray dose rate data will also be experimentally surveyed at various RF cavity power levels. This paper presents the design features, circuits and construction of such AR RF PPS subsystem for accurately monitoring RF Cavity power and to break the interlocked chain to turn OFF the RF input drive to AR RF High Power Amplifiers (HPA) feeding RF cavities, if the RF cavity power exceeds such pre-determined power limits.