Development Of The Cherenkov-Type Diagnostic System To Study Runaway Electrons Within Tokamaks

Measurements of fast electrons produced in plasma a nd escaping from tokamak-type facilities are of particular interest for diagnostics, because such electrons deliver information about processes occurring inside bulk plasma. A team from the National Centre for Nuclear Research (NCBJ, former IPJ) proposed Cherenkov-type probes for measurements of fast electrons in tokamaks because of high spatial- and temporal-reso lution of such detectors. The paper presents feasibility and design studies o f the Cherenkov-type probes, a development of the measuring head constructions designed for di fferent tokamak devices. In order to lower an energy threshold of the electron detection the auth ors applied radiators with the highest values of the refractive index. Different radiator materia ls, such as aluminium nitride (AlN) and CVD diamond crystals were applied. Several versions of measuring heads and different manipulators, e.g., a movable vacuum-tight shaft or a fast-moving reciprocating probe, have been manufactured and used. The practical application of the Cherenkov probes required also a consideration of the optical fibres and photomultip liers spectral characteristics. In order to investigate an energy distribution of fast electron beams the multi-channel probes have been designed and manufactured.