Measurements of the K Continuum for Argon Z-Pinches

Summary form only given. While the characteristic "resonance" lines dominate the K-shell X-ray emission from Z pinches, the energy in the K continuum (free-bound and free-free transitions) can be significant. A simple model implies that the continuum could supply well over 10% of the K-shell yield if the plasma is warm enough and dense enough. We present here new measurements of the continuum strength for argon implosions. The data were taken at peak currents of 3.5 MA with implosion times exceeding 200 ns. Heavily filtered GaAs photoconductive detectors (PCD) were used as direct measures of the argon continuum above ~4 keV. Other major diagnostics included X-ray power sensors, calorimeters, time-integrated CCD spectra and CCD pinhole images. By combining the data from all of these instruments, we have derived the strength and temperature of the continuum as well as the yield in the K-lines using a self-consistent method. As implosion conditions changed, the changes seen in electron temperature (derived from K-line ratios) were not as large as the changes seen in the continuum temperature (derived from the PCDs). The yield in the continuum was close to a linear function of the K yield. The relative strength of the continuum does appear to depend on the detailed mass distributions produced by the 12 cm diameter nozzles used for these tests