Modification of atomic physics rates due to nonlocal electron parallel heat transport in divertor plasmas

The effect of steep temperature gradients on the rate of ionization of atomic hydrogen is studied numerically with the electron kinetic code 'FPI' [Phys. Rev. Lett. 72 (1994) 1208]. A set of cross sections ['Atomic and Plasma-Material Interaction data for fusion'. Supplement to the journal Nucl. Fusion 4 (1993)] has been used which gives the same rates of radiation, ionization and recombination as in the well known edge modeling codes 'UEDGE' and 'DEGAS' for Maxwellian electron energy distribution functions. For this purpose, 30 energy levels are included in the computation, as stepwise ionization is dominant. The enhancement of the ionization rate by non-Maxwellian effects in the colder part of the plasma is significant.