The Optimization of Iron K-Shell Yields on High Power Pulsed Generators

Summary form only given. To ionize moderate atomic number plasmas such as iron into the K-shell, rapid plasma heating rates are required. When a plasma shell is imploded, this heating ideally occurs when the accumulated implosion kinetic energy is suddenly thermalized on axis. In the earlier investigation of this process, aluminum was employed to calculate how efficiently the kinetic energy of implosion could be converted into K-shell X-rays as a function of the load mass and the maximum load implosion velocity. The results of these calculations were scaled to higher atomic number plasmas, but this scaling could not include the effects that kilovolt energy L-shell losses would have on the thermalization dynamics, and these losses become increasingly important as the atomic number of the imploding plasma increases. The dependence of iron K- and L-shell emissions on load mass and implosion velocity is investigated in this work by carrying out a series of similar calculations for iron plasma shell implosions as were done for aluminum. Plasma parameters for these calculations are set by first benchmarking them to a set of nested stainless steel wire array implosion experiments that were carried out on the Z generator at Sandia National Laboratories. Using these parameters, the implosion kinetic energies and load masses that are needed to achieve optimal production of iron K-shell emission are then determined, and the capability of the ZR or future generators to meet these requirements is assessed. How L-shell emission rates impact the ability of the plasma to ionize its way through the L-shell ionization stages and how these rates influence the K-shell X-ray conversion efficiency of iron are also determined as a function of load mass and implosion velocity