Evolution of the CERN LINAC 4 Intensity Interlock System Using a Generic, Real-Time Comparator in C++

During the commissioning phase of LINAC 4, three watchdog interlock systems were used to protect the accelerator and its equipment. These systems cut the beam if losses, calculated by combining the intensity measurements at various locations, exceed some predefined thresholds. While the existing systems were designed to be simple and robust to ensure safety, the future connection of the linac to the Proton Synchrotron Booster (PSB) requires new instances of these systems with additional requirements. Such requirements include the remote communication of the watchdogs with the intensity measurement systems to decouple any physical dependency between the two systems, and the arithmetical/logical combination of the measured data based on the watchdog location. As the Controls Interlocks Beam User (CIBU) hardware interface to the Beam Interlock Controller (BIC) is simple, the software part of the system can be re-designed to be application agnostic giving a single decision after performing a configurable set of comparisons. This paper describes the upgrade of the software of the existing watchdog interlock system to a generic comparator, enabling its usage for other applications.