Diagnosing Z pinches with pinhole imaging at various photon energies

Summary form only given. X-ray pinhole imaging, both time-resolved and time-integrated, has become a standard experimental method for assessing the quality of Z-pinch implosions. Usually, the detector(s) are filtered to emphasize certain regions of the X-ray spectrum and/or exclude others. In the present work, detailed multifrequency calculations of pinhole images of imploded Al wire array pinches for different assumed pinch conditions are carried out. The way different pinhole images recorded in different photon energy intervals correlate with pinch conditions potentially enhances the diagnostic value of this experimental technique. The assumed pinch conditions are based upon, but not limited to, inferred time-resolved profiles from Saturn shot 2706. Generally, in the presence of a sharp density gradient, the pinch diameters are larger when the images are from line emission rather than spectral regions dominated by the continuum. The diameter of the image as determined from different X-ray lines depends on both the energy of the lines and the temperature gradient present in the pinch. Therefore, better spectral resolution can be expected to yield more sensitive and comprehensive pinch diagnostics. The underlying physics governing these dependencies will also be explored.