Shack-Hartmann Electron Densitometer (SHED): An Optical System for Diagnosing Free Electron Density in Laser-Produced Plasmas

Report No. ARL-TR-7868
Authors: Anthony R Valenzuela
Date/Pages: November 2016; 26 pages
Abstract: The Shack-Hartmann Electron Densitometer is a novel method to diagnose ultrashort pulse laserĂ¢??produced plasmas by measuring the phase change to a probe laser beam. Free electrons in a plasma cause distortions to the phasefront of a probe laser that is measured through a lenslet array onto a camera. This method allows for superior performance in measuring minute variations in the electron density in 2 dimensions with subpicosecond time resolution. The data taken demonstrated the ability to diagnose plasmas with densities of the order of 1019 cm-3 and show the temporal evolution of the plasma long after the driving laser pulse has left. The method can be further improved by enclosing the probe beam and adding a second axis to allow for tomographic reconstruction of the electron density in 3 dimensions.
Distribution: Approved for public release
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Last Update / Reviewed: November 1, 2016