X-ray lasing in ablative capillary discharges

Abstract

In this presentation we summarize the results on lasing in the soft X-ray region as obtained with ablative capillary discharges at the Ruhr-University of Bochum. During the first half-cycle of the discharge the initial plasma is obtained from ablated wall material (polyacetal); in the second half-cycle a chain of hot plasma spots is produced in the neck regions of a m = 0 instability. Fully stripped carbon ions stream into the cold plasma outside the necks, and charge exchange with CIII ions results in population inversion between the n = 3 and n = 2 levels of CVI and thus in lasing at 18.22 nm. Modulation of the inner wall or of the return conductor influences the wavelength of the instability and via the number of inversion layers also the lasing spike. Its duration is measured to about 400 ps. The relevant charge exchange processes are also demonstrated with colliding laser produced plasmas.