The physics of multi-kev emissions from Z-pinches at the Z accelerator

Summary form only given. The Z Accelerator is the world's most powerful x-ray source, producing >300 TW from a z-pinch load. A z pinch is produced when current from Z (up to 26 MA) is delivered to a wire array or gas puff load. Early in the current pulse, the wire array or gas puff begins to ionize and current flows through the resulting plasma (ablation phase). This flow of current produces a magnetic field, which, via the J×B force, drives the plasma to the axis (implosion phase). When the plasma reaches the axis, x-rays are emitted from the high energy density plasma (stagnation phase). Varying the design load allows for a broad range of experiments relevant for astrophysics, inertial confinement fusion studies, and z-pinch physics experiments.This presentation focuses on z-pinch physics experiments producing > 3keV emissions and the detailed physics that can be studied in the implosion and stagnation phases. The Magnetic Rayleigh Taylor instability, which can limit the production of x-rays, is observable during these phases, but can be mitigated with the use of high wire number arrays and nested wire arrays to enable high power emissions. High resolution spectra, yield measurements, and imaging data from various K-shell x-ray experiments have been used to verify theoretical scaling models, including the plasma conditions needed for efficient K-shell emission and the necessary load physics necessary to achieve these plasma conditions. The spectra have also been used to assess the implosion velocity via Doppler splitting, and the structure of the stagnated pinch, including opacity effects and temperature gradients. More recently, studies of the transition from thermal to non-thermal emissions from z-pinches have extended the range of photon energies produced to >10 keV. While the existing diagnostic suite at Z provides data up to ~ 25 keV, limited information is available > 10 keV. To better evaluate these emissions, new diagnostics have been developed. These new diagnostics include a hard x-ray pinhole camera capable of measuring 15-100 keV, a differential hard x-ray (DAHX) spectrometer for assessing 50-1000 keV emissions, and a high-resolution time-integrated crystal spectrometer (CRITRX). Details of these diagnostics and initial data collected >10keV will also be presented to illustrate trends in the emissions as the photon energy increases.