Dependable Implementation of the Beam Interlock Mechanism in CERN Power Converter Controllers

At CERN a Beam Interlock System (BIS) protects accelerators from accidental and uncontrolled release of beam energy, avoiding machine downtime. Throughout the accelerator complex numerous critical subsystems, including power converters, interact with the BIS indicating their readiness for operation with beam. Power converters play a vital role in establishing operational conditions, and an unmitigated power converter malfunction could lead to damage to the machine. For example a bending magnet converter set at an incorrect current would result in an incorrect field strength, and beam passing through this may impact and damage the machine. A fast and dependable Beam Interlock Mechanism is required between power converters and BIS, verifying that voltage and current levels are within tolerances. This paper describes the design and realisation of the Beam Interlock Mechanism, based on CERN's Function Generator Controller (FGC), the central processing unit power converter control. Particular emphasis is placed on the system architecture required to assure the integrity of the power converter parameters, and the protection of the CERN accelerator complex.