Electron beam effects on the spectroscopy of satellite lines in Aluminum X-pinch experiments

Aluminum wire X-pinch experiments performed at the Cornell University XP pulsed power generator and at the Lebedev Institute BIN generator show detailed high resolution spectra for satellilte lines of Li-like, Be-like, B-like, and C-like ions. These lines, which correspond to transitions originating from autoionizing levels, are observed in the direction of the anode with respect to the bright X-pinch cross point. The intensities of these satellites are much smaller or absent in the direction of the cathode. Such transitions are caused by collisions of ions with energetic electrons (5–15 keV) which are created by the inductive voltage drop between the cross point and the anode. A collisional-radiative model was constructed using a non-Maxwellian electron energy distribution consisting of a thermal Maxwellian part plus a Gaussian part to represent the high energy electron beam. The shapes of the observed satellite structures are consistent with the calculated spectrum for electron temperatures between 30–100 eV, and beam densities of about 10⁻⁷ times the plasma electron density.