Powerful microfocus x-ray and hard x-ray 1 MA x-pinch plasma source for imaging, spectroscopy, backlighting, and polarimetry

摘要

The x-ray emission of Ti, Fe, Mo, W, and Pt x-pinches are currently being studied at the Nevada Terawatt Facility z-pinch machine (0.9-1.0 MA, 100 ns). New x-ray diagnostics for time-resolved spectroscopy and imaging has been developed and used in x-pinch experiments. The total x-ray/ EUV yield was more than 10 kJ. The minimum x-ray pulse duration was 1.1 ns (Mo, W, Pt). For Ti, Mo and W pinches x-ray pulses occurred in two or three groups in the narrow time intervals after the start of the current. The most compact emitting region has been observed for a planar-loop Mo x-pinch (the number of hot spots ranging from 1-5 with a minimum size smaller than 30μm at λ<1.5-2 A). Strong jets were observed (Ti, Fe, Mo) directed toward the discharge axis, perpendicular to the wires. A structure of an x-pinch includes energetic electron beams directed toward the anode and along wires. The total beam energy increases from Ti to W. A pulse of hard x-ray radiation was observed moving upwards along the axial axis with an energy of several hundred keV (Mo). The size of this source was smaller than 1 mm. The measurements of temperature and density of x-pinch plasmas were based on theoretical modeling of K-shell Ti and L-shell Mo spectra (T_e=1.5 keV for Ti, 0.8 keV for Mo, N_e up to 2-Sxl0~(22) cm~(-3) with 1-10 % of hot electrons).