Dynamics of hot spots in the DPF-78 plasma focus from X-ray spectra and REB emission

Summary form only given, as follows. The X-ray emission from hot spots in the plasma focus DPF-78 (60 kV, 28 kJ, /spl tau//4=1.5 /spl mu/s) was investigated with the help of two X-ray quartz crystal spectrometers (looking side-on and end-on) of the Johann type and a 4 fold magnifying X-ray pinhole camera (side-on). In the experiments the working gas was chosen to be 300 Pa deuterium with 20 Pa argon admixture. X-ray spectra in the wavelength range from 3.55 /spl Aring/ to 4.0 /spl Aring/, including H-like and He-like argon lines, were recorded on Kodak DEF-2 film. From the spatially resolved spectra recorded side-on, a relative spectral shift between different hot spots of the same shot was often observed. The shift could be attributed to the Doppler shift. The maximum shift for the resonant line of He-like Argon (3.9488 /spl Aring/), emitted from two hot spots located on the anode axis with distances of about 16 and 19 mm from anode, was 9 m/spl Aring/. From spectral characteristics such as intensities and FWHM of Ar resonant and intercombination lines electron densities of up to 3/spl middot/10/sup 27/ m/sup -3/ were determined. Radial dimensions of the hot spots ranging from about 140 /spl mu/m to 300 /spl mu/m were found from pinhole pictures applying the penumbra method. Usually two pulses of relativistic electron beams (200 keV/spl les/E/spl les/600 keV) were observed using Cherenkov detectors in a magnetic spectrometer. The measured FWHM of the REB pulses ranges from 3 ns to about 10 ns. The characteristics of the time-integrated X-ray spectra and the time resolved REB spectra and their dependence on the composition of the filling gas are discussed.