Measurement and analysis of argon continuum radiation from a 12-CM diameter gas puff Z pinch at 6MA

Summary form only given. Absolute measurement of the free-bound (FB) continuum spectrum above the K-shell from atomic-number Z ges 10 Z-pinches can be a useful diagnostic tool to obtain the electron temperature and the ion density of a hot, radiating Z-pinch. These measurements are also of interest for benchmarking continuum radiation models associated with the use of this high-photon-energy radiation for radiation-matter interaction studies. In previous work, we described a curved crystal spectrometer modified to measure, absolutely, the argon FB spectrum from 5 to 10 keV emanating from the implosion of a 12-cm diam, shell-on-shell, argon-gas-puff Z pinch, driven by peak currents of ~6 MA with implosion times of 220-260 ns on the decade quad. Time averaged and time resolved electron temperatures were determined from the slope of the FB spectrum and the energy in the FB spectrum was compared with the total K-shell yield. Now, we review the diagnostic and discuss an improved absolute calibration. The new calibration results in ~10% of the total K-shell yield residing in the continuum above 4.4 keV, about a factor-of-three lower than previously reported. We present new calculations that relate the ion density, electron temperature and absolute continuum emission that account for radiative recombination on both bare and H-like ions. Using radial and axial scale lengths obtained from time-integrated pinhole-camera images, this expression is used to infer the time-averaged density of ions radiating in the FB continuum, which is then compared with ion densities determined using the line-ratio technique. Finally, these measurements are compared with results from a CRE-based model that includes radiation transport