Stark broadening of hydrogen lines in low-density magnetized plasmas.

ABSTRACT

Stark broadening of hydrogen lines in the presence of a magnetic field is revisited, with emphasis on the role of the ion component under typical conditions of magnetized fusion devices. An impact theory for ions valid at low density (N_{e} < or approximately 10;{14} cm;{-3}) and taking into account the Zeeman degeneracy removal of the atomic states is developed. It is shown that the Stark widths of the Lorentz triplet components strongly depend on the magnetic field. The model is validated by a computer simulation method. For the lateral sigma components of Lyalpha , we show that the impact approximation still holds for densities as high as N_{e} approximately 10;{15} cm;{-3}. In contrast, for the central pi component as well as for the other lines from low principal quantum number, significant discrepancies between the proposed theory and the simulation results appear at high density. Application to Dalpha in tokamak divertor plasma conditions shows that, in this case, the quasistatic approximation becomes more relevant.