We discuss the characterization of a long-duration, broadband x-ray flux source forlaboratory astrophysics experiments. The experiments were done at the OMEGA EPhigh-power laser facility. This is a four-beam laser system that can deliver up to 4.4kJ of UV laser energy in pulses of 10 ns duration. By driving sequentially in time anarrangement of three copper hohlraums, i.e. one hohlraum at a time, we can produceand sustain a 90 eV radiation temperature x-ray flux at the source for 30 ns. Wecall this concept the “Gatling-Gun” x-ray source. It is important to characterize andmonitor the performance of the Gatling-Gun source since it is the x-ray flux thatactually drives the laboratory astrophysics experiments, not the laser beams. To thisend, we have field three diagnostics, namely VISAR, SOP and a gated grating spectrometer. The VISAR (velocity interferometry system for any reflector) is an opticallaser interferometry diagnostic that measures the speed of a shock launched by theGatling-Gun x-ray flux in an ablator; in turn, the shock speed relates to the radiationtemperature which is an important characteristic of the x-ray flux. The SOP is aStreaked Optical Pyrometer that can be used to extract the brightness temperatureof the shock front. The gated grating spectrometer records the spectral distributionof the broadband x-ray flux over a photon energy interval of almost 2 keV; this spectral information is important for understanding the experiment driven by the x-rayflux, it shows the thermalization of the x-ray field in the hohlraum, and provides yetanother method to determine the radiation temperature. These diagnostics requireadvanced data processing, modeling and interpretation. This MS thesis presents theseries of OMEGA EP experiments in which the diagnostics were fielded, the datarecorded, and the results obtained for the characterization and performance of theGatling-Gun x-ray source.
|Advisor:||Mancini, Roberto C.|
|Commitee:||Bach, Bernhard, Wiest, Lynda R.|
|School:||University of Nevada, Reno|
|School Location:||United States -- Nevada|
|Source:||MAI 82/7(E), Masters Abstracts International|
|Subjects:||Astrophysics, Plasma physics|
|Keywords:||Laboratory astrophysics, Photoionized plasma, PIE, Steady state|
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