イオン源のイオン引出し孔附近におけるプラズマ界面の挙動

抄録

Behavior of the ion sheath near an aperture of ion source is investigated via a nonlinear Poisson equation for an electric potential function in a cylindrical coordinated system. On the assumptions of free electrons with Maxwellian distribution and trapped ions with zero temperature, the sheath criterion and under which the plasma boundary is concave are derived. These conditions are shown to depend on the aperture radius, wall potential U, electron temperature kTe and initial ion velocity. The ion current through an aperture with maximum radius is found to increase significantly when U_??_20kT_e. Behaviors of the potential and plasma boundary under various situations are also demonstrated by means of numerical calculations.