Double-Pulse Laser-Driven Jets on OMEGA |
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| Authors: | S Sublett J P Knauer I V Igumenshchev A Frank D D Meyerhofer |
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| Institution: | (1) Laboratory for Laser Energetics, Rochester, NY 14623, USA;(2) Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA;(3) Laboratory for Laser Energetics, Rochester, NY 14623, USA;(4) Department of Physics and Astronomy, University of Rochester, Rochester, NY USA, 14627;(5) Laboratory for Laser Energetics, Rochester, NY 14623, USA;(6) Department of Physics and Astronomy, University of Rochester, Rochester, NY USA, 14627;(7) Department of Mechanical Engineering, University of Rochester, Rochester, NY USA, 14627 |
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| Abstract: | A double-pulse laser drive is used to create episodic supersonic plasma jets that propagate into a low density ambient medium.
These are among the first laser experiments to generate pulsed outflow. The temporal laser-intensity profile consists of two
1-ns square pulses separated by 9.6 ns. The laser is focused on a truncated conical plug made of medium Z material inserted into a high-Z washer. Unloading material from the plug is collimated within the cylindrical washer hole, then propagates into the low-Z foam medium. The resulting jet is denser than the ambient medium. Double-pulse jet evolution is compared to that driven by
a single laser pulse. The total drive energy is the same for both jets, as if a source with fixed energy generated a jet from
either one or two bursts. Radiographs taken at 100 ns show that a single-pulse jet was broader than the double-pulse jet,
as predicted by hydrodynamic simulations. Since the initial shock creating the jet is stronger when all the energy arrives
in a single pulse, the jet material impacts the ambient medium with higher initial velocity. Detailed comparisons between
single- and double-pulsed jet rheology and shock structure are presented. 2-D hydrodynamic simulations are compared to the
experimental radiographs.
PACS: 52.30.−q 41.75.Jv 42.62.−b 42.68.Sq 47.40.−x 47.56.+r |
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| Keywords: | Laser experiments Plasma jet Episodic outflow |
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