Photodiodes with x-ray sensitive photocathodes are commonly used as broadband x-ray detectors in fusion plasma diagnostics. We have measured the photocathode quantum efficiency between 1–500 Å of common photocathode materials including aluminum, copper, nickel, gold, three forms of carbon, chromium, and cesium iodide. We have also studied the effects of the experimental environment and long-term cathode aging on the measured quantum efficiencies. In addition, we have measured the x-ray mass-absorption coefficients of x-ray filter windows of Kimfoil, aluminum, polypropylene, and Formvar in energy regions where data were previously unavailable. Measurements between 1–50 Å were performed at the Los Alamos Scientific Laboratory’s low-energy x-ray calibration facility, while the measurements between 50–500 Å were performed at the National Bureau of Standard’s synchrotron ultraviolet radiation facility.
The Net resonance transitions were measured with sufficient precision to extend the spectroscopy of the Net isoelectronic sequence to Z = 40. Ab initio atomic-structure calculations and isoelectronic extrapolations are in agreement with the measured values. Atomic-structure calculations were used to interpret the Naand Mg-like satellite lines in the 2p-3s and 2p-3d regions in Se and Zr. The interpretation of the L-series satellites may prove important for future plasma diagnostics.
The interaction physics and hydrodynamic motion of thin-foil targets irradiated by long, low-flux Nd-laser pulses (3 nsec, 1012–1015 W/cm2) are studied experimentally and compared with theoretical models. Laser light absorption is high (80%–90%) and thin-foil targets are accelerated up to 107 cm/sec with good (20%) hydrodynamic efficiency in the 1012–1013 W/cm2 range. These results agree with a simple rocket ablation model. Details of thermal heat flow, both axially (related to ablation depth) and laterally (related to beam uniformity requirements), are also presented.
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