Measurements of the Free-Bound Continuum for Argon Gas-Puff Implosions on the Decade Quad

Summary form only given. Free-bound (F-B) continuum spectra for argon gas-puff implosions on the Decade Quad are measured with a curved crystal spectrometer. Measurements are reported for implosions with two 12-cm diameter double-shell nozzles: one provided by Titan Corporation, San Leandro, CA and one provided by Alameda Applied Sciences Corporation (AASC), San Leandro, CA. These gas-puffs are driven by a peak current of 6 MA and have implosion times of 240 to 270 ns. A LiF crystal is used to disperse the photon spectrum, and an array of six silicon pin diodes is used to time-resolve the X-rays at energies ranging from 5.1 to 10.2 keV. The spectrometer is calibrated in photon energy by measuring lower energy He-like and H-like Ar lines on X-ray film. The pin diode measurements are corrected for filter transmission, crystal reflectivity, spectral dispersion, and detector sensitivity. The electron temperature at peak X-ray emission is 2.3 to 2.4 keV for the Titan nozzle, and the time-integrated temperature is 1.7 to 1.8 keV. For the AASC nozzle, peak X-ray emission is not well defined due to rapid nanosecond variations of the emitted radiation. The time-integrated electron temperature for this nozzle is 1.5 to 1.6 keV. Electron temperatures from the time-integrated measurements for both nozzles are in agreement with temperatures obtained from Ar K-shell line-ratio measurements. This diagnostic can be used to measure the electron temperature with a time resolution of a few ns. The integrated energy above 5 keV in the continuum spectrum is 5 to 7 kJ or nearly 25% of the total K-shell yield including the F-B continuum. This continuum intensity is consistent with an analytic model. The absolute intensity can be combined with measurements of the size of the radiating plasma to determine the electron density