High power proton beam imaging and real-time machine protection

Abstract A real-time optical imaging system has been developed and commissioned at the European Spallation Source (ESS) to monitor the high-power proton beam at the tuning beam dump, and provide machine protection. The system employs chromium-doped alumina (Chromox) luminescent screens imaged by radiation-shielded optics and a CMOS camera. Real-time FPGA-based processing extracts beam size and position, detects saturation, and generates machine-protection interlocks within the required pulse period. Thermo-mechanical modelling, benchmarked with ANSYS simulations, has defined safe operational limits for each beam mode and has verified screen survivability under nominal and off-normal conditions. During beam commissioning, the system accurately detected errant beam spots, quantified the photon yield and luminescence lifetime, and proved robust against radiation-induced artefacts. These results confirm that the system meets ESS machine-protection requirements while providing reliable beam diagnostics for routine operation.