Cherenkovsensorer

Cherenkov sensors are devices that detect Cherenkov radiation, light emitted by charged particles when their velocity in a dielectric medium exceeds the phase velocity of light in that medium. The light is emitted in a cone with a characteristic angle, known as the Cherenkov angle, which is given by cos(theta_C) = 1/(β n), where β is the particle's speed as a fraction of c and n is the medium's refractive index. By collecting and timing the Cherenkov photons with an array of photodetectors, the particle's velocity can be determined, and when combined with momentum measurements, particle identification is achieved.

Common implementations include threshold Cherenkov detectors, which provide a yes/no indication of whether a particle's velocity exceeds a chosen threshold, and Ring Imaging Cherenkov (RICH) detectors, which image the Cherenkov light as rings to yield precise velocity measurements over a broad range. Time-of-Propagation (TOP) detectors and related variants use photon arrival times to improve discrimination. The detectors typically couple radiators such as ultrapure water, aerogel, or transparent solids to photodetectors like photomultiplier tubes or silicon photomultipliers, often with light guides and optics to shape and collect the light.

Applications are widespread in experimental high-energy physics, including particle identification in collider experiments and neutrino detectors. Examples include RICH systems in experiments such as LHCb and Belle II, water Cherenkov detectors in Super-Kamiokande, and Cherenkov-based systems in other large-scale neutrino and cosmic-ray experiments. IceCube uses Cherenkov light produced by high-energy charged particles in Antarctic ice to reconstruct events with a large volume of optical sensors.

Advantages of Cherenkov sensors include fast timing and relatively compact form factors for given PID performance, while limitations involve light yield dependent on the radiator, optical clarity, and calibration needs, as well as radiation hardness in some environments.