Possibilities of alpha-particle diagnostics in future tokamaks using helium and lithium beam injection

The possibility of using active charge-exchange (CX) diagnostics based on helium and lithium beam injection to investigate the confined alpha-particle distribution function in future fusion experiments is considered. The required helium beam densities are determined by mathematic modeling of the physical processes (double CX, attenuation of the doping beam, and CX flow, taking into account the step processes). They are found to be approximately 1 A for a 40-keV beam for thermalized ('ash') alpha-particle diagnostics and 30 to 600 mA for a 0.35 to 0.65 MeV/amu HeH⁺ ion source for hot alpha-particle diagnostics. A ³He beam with energy of 500 keV (He⁺ ion source) and intensity of 0.1 to 3 A is proposed for measurement of the alpha-particle distribution function in the energy range of 0.2 to 2 MeV.