Pressure Gradient Effects On Two-Dimensional Plasma Expansion.

Moon, S. ; Smith, R. F. ; Dunn, J. ; Keenan, R. ; Nilsen, J. ; Hunter, J. R. ; Filevich, J. ; Rocca, J. J. ; Marconi, M. C. ; Shlyaptsev, V. N.

Technical Information Center Oak Ridge Tennessee

关键词: Plasma density;    Pressure gradients;    Interferometry;    Electron density;    X-ray lasers;   

RP-ID  :  DE200515014567

学科分类：工程和技术（综合）

美国|英语

来源: National Technical Reports Library

【 摘 要 】

The electron density evolution of a laser-heated Al plasma is measured using a diffraction grating interferometer (DGI) at different times, relative to the peak of a 600ps plasma forming pulse. This gives an effective moving picture of how the plasma evolves in space and in time. The experimental results show pronounced two dimensional effects such as significant lateral transport and an on-axis density dip. We use 2-D hydrodynamic simulations in order to calculate the contributions of various physical mechanisms driving the plasma expansion. Density depressions have been observed before for high intensities laser drivers (pondermotive force) and for lower intensities were the pumping pulse lasts for several nanoseconds (coronal x-ray ray heating). For the plasma conditions explored here, simulations suggest that the on-axis density dip can be explained by rapid movement of material laterally due to the large pressure gradients set up by the tightly focused laser beam.