New optics design of the Cherenkov threshold detectors at CERN

The performance of the Cherenkov threshold detectors (XCET) used in the secondary beam areas (SBA) at CERN is limited by their built-in optics. This study showcases an improved design using compound parabolic concentrators (CPCs) to reduce size and cost of the optics while optimizing the light collection efficiency. The detector was simulated with Geant4 over its full experimental range in terms of pressure, beam momentum, and particle type. The efficiency of the current design was found to be limited by the geometry of the parabolic mirror. The optimized CPC designs resulted in a size reduction of up to 54% and improved photon collection up to 67% compared to the original design when using CO2 as radiator gas and 276% when using R-218. These results highlight the advantages of using CPC and Monte Carlo simulations in the development of Cherenkov threshold detectors and may be useful for further improvements in the next generation of the XCET.