On the energy distribution of fast atoms emerging from Tokamak plasmas

Assuming rotational symmetry and a local Maxwellian (and thereby neglecting particle drifts) energy spectra have been calculated for 1) asymptotic conditions E/T0 >> 1, E/T0 << 1 (T0 = peak ion temperature) 2) model profiles for plasma density and temperature as well as neutral atom concentration. For plasmas extending several mean free paths in radius an energy is estimated around which T0 may be preferably obtained as the inverse logarithmic derivative of the flux spectrum. The results indicate that collection of a significant number of particles in the Maxwellian tail (E approximately> 8 T0) should allow a fairly accurate determination of T0 even if the hot region is separated from the outside by many mean free paths. (orig.)