Study of K absorption structures in a subcritical-density laser-produced plasma

The study of K line absorption by point-projection backlighting is presented for a laser-produced aluminum plasma at electronic densities below 5×1021 cm-3. The appearance of ionic species as a function of distance from the target is measured absolutely by the use of a knife edge as a spatial fiducial. These data are used to determine the gradient of the average charge as a function of space. A non-local-thermodynamic-equilibrium ionization model has been developed to determine temperature and densities consistent with this measure. Comparisons with hydrodynamic codes are presented, along with a discussion of the inferred temperature.