Measurements of ion temperatures of Al wire arrays in short and long current pulse Z-pinches

The Doppler broadening of ion line profiles emitted by a Z-pinch plasma provides information about the thermalization of the implosion kinetic energy and the radiation efficiency of the pinch. Measurement of these line profiles is often complicated by source broadening in the instrument and opacity broadening of the emitted radiation. A high resolution concave crystal spectrometer in the Johann geometry was used to record the time averaged spectra of optical thin trace elements in the load. An imaging slit provided radially resolved but axially averaged spectra. Source broadening is overcome by imaging monochromatic x-rays emitted from all axial pinch positions to one point on the Rowland circle. The recording film is located on the Rowland circle whose radius is half the crystal radius and whose circumference is tangent to the center of the crystal. The spectral resolution of the spectrometer, λ/Δλ to approximately 1000, was measured with K radiation generated by a 10 keV electron beam incident on a Si or Al target. Measurements are reported for Al wire loads on both the Saturn and Double Eagle accelerators in both a short current pulse mode (60-100 ns) and a long pulse mode (125-225 ns). On Double Eagle we observed ion temperatures in the 3-5 keV range in the short pulse mode and 20-30 keV in the long pulse mode. On Saturn, on the other hand, we observed the larger values for both current modes.