Calculated evolution of side-on and end-on X-ray images of wire and gas puff implosions on Z

As J × B forces implode a Z-pinch load, a variety of phenomena that affect its radiative behavior may occur. These include snowplows and shocks, instabilities, amplification of initial load asymmetries, and high-density condensations (possibly caused by a local radiative collapse). On the axis, arrival of the main load mass occurs, but it may be preceded by a precursor plasma. An important aim of experimental diagnostics is to determine the degree and importance of such physical processes as a function of the properties of the load and the driving generator. X-ray spectroscopy and imaging are well-established components of most Z-pinch diagnostic suites. The purposes of the present work are to determine the x-ray signatures of some of these phenomena and to ascertain the x-ray energies that provide the clearest and least ambiguous indicators of these processes. To accomplish this, we have carried out radiation hydrodynamics calculations of argon gas puff and titanium wire array loads imploded on Sandia´s Z generator. These calculations provide a large database of x-ray spectra and images. Some clear image signatures are seen in the calculations. These include intensity enhancement near the outer edge of the pinch, which is characteristic of the heating and compression that occurs in the snowplowed region of the pinch prior to its final on-axis assembly. Spatial image intensity profiles in the lower energy x-rays are generally indicative of the density profile of the pinch. The profile of the image at different photon energies within the K-shell spectral region is related to the presence of an electron temperature gradient.