No abstract

A capillary discharge has been developed to produce pulses of intense soft x-ray radiation of tens of nanoseconds duration. The soft x-ray photons were emitted in a plasma column resulting from polyethylene in capillary wall ablation. The spectrum was dominated by the C IV, C V, and C VI emission lines in the soft x-ray spectral range. The experimental value of the electrical circuit inductance has been measured and compared to the calculated one. The electron temperature was estimated to be higher than 50 eV from the plasma resistivity measurement. The time dependence of the electron density outside the capillary channel has been determined using spectroscopic measurement in the visible range. The time dependence of the electron temperature has been determined from the intensity ratio of C V and C VI emission lines, using a collisional radiative equilibrium code.

Time- and space-resolved measurements of an ablative polyethylene capillary discharge using a pinhole camera are presented in this paper. Measurements with and without a 0.1 µm thick polyimide filter allowed us to identify the soft x-ray production zones. The images show that the plasma, mainly composed of highly ionized carbon, was not detached from the capillary wall during the heating phase. This plasma behaviour does not favour the development of a recombination-pumped x-ray laser. For two capillary lengths, the plasma dynamics were observed at constant power density in a first run and at identical current waveform in a second run. In both cases, they were different and could induce errors on gain measurement when varying capillary lengths. To our knowledge, this is the first report of time-resolved pinhole images of ablative carbon capillary discharges used as soft x-ray sources.