Temperature Measurements in Radiative Shock Experiments.

Shock Wave;Physics;Science;Applied Physics

Visco, Anthony JohnPowell, Ken ;

University of Michigan

关键词: Shock Wave;    Physics;    Science;    Applied Physics;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/95965/tvisco_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

At signifcantly large pressures, shock waves can be driven that are so energetic that radiation starts to play an important role in the dynamics of the system. Radiativeshock waves are found in many astrophysical systems, including supernovae and explosive jets, but can also be created in large laser facilities, where pressures caused by laser ablation can easily be in the megabar range. Millimeter-scale targets are filled with a high-Z gas, in this case argon, and irradiated with beams from the Omega laser at the Laboratory for Laser Energetics, causing a shock wave to propagate in the gas at velocities high enough to be in the radiation flux dominated regime.In this thesis we discuss experiments to measure the temperature in the radiativeshock system. In one experiment the method of x-ray Thomson scattering was employed. This was the first time the technique was used in measuring radiative shock systems. Temperature measurements can be inferred from the detailed spectrum of radiation that has been scattered from the shocked plasma. The use of x-rays has the advantage of being able to penetrate the dense post shocked region. The application of this method to a radiative shock system is explained and a discussion of the measured temperature and its interpretation are discussed. The results of the measurement confirm experimentally the formation of an optically thin hot layer in the shock transition, indicating the shock is in the radiative regime. The experiment demonstrates the applicability of x-ray Thomson scattering for measuring radiative shock systems. In a second experiment, measurements of the self-emission from the dense shocked argon plasma were made using a streaked optical pyrometer. The inferred temperature is discussed, as are the difficulties in using optical frequencies, due to radiative effects from the shock wave.