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Plasma Expansion Dynamics in Hydrogen Gas

Fort Peck Community College, 605 Indian Avenue, Poplar, MT 59255, USA
Department of Physics and Astronomy, University of Tennessee/University of Tennessee Space Institute, 411 B.H. Goethert Parkway, Tullahoma, TN 37388, USA
Author to whom correspondence should be addressed.
Atoms 2018, 6(3), 46;
Received: 13 July 2018 / Revised: 9 August 2018 / Accepted: 10 August 2018 / Published: 20 August 2018
(This article belongs to the Special Issue Stark Broadening of Spectral Lines in Plasmas)
Micro-plasma is generated in ultra-high-pure hydrogen gas, which fills the inside of a cell at a pressure of (1.08 ± 0.033) × 105 Pa by using a Q-switched neodymium-doped yttrium-aluminum-garnet (Nd:YAG) laser device operated at a fundamental wavelength of 1064 nm and a pulse duration of 14 ns. The micro-plasma emission spectra of the hydrogen Balmer alpha line, Hα, are recorded with a Czerny–Turner type spectrometer and an intensified charge-coupled device. The spectra are calibrated for wavelength and corrected for detector sensitivity. During the first few tens of nanoseconds after the initiation of optical breakdown, the significant Stark-broadened and Stark-shifted Hα lines mark the well-above hypersonic outward expansion. The vertical diameters of the spectrally resolved plasma images are measured for the determination of expansion speeds, which were found to decrease from 100 to 10 km/s for time delays of 10 to 35 ns. For time delays of 0.5 µs to 1 µs, the expansion speed of the plasma decreases to the speed of sound of 1.3 km/s in the near ambient temperature and pressure of the hydrogen gas. View Full-Text
Keywords: laser–plasma interactions; plasma dynamics and flow; hypersonic flows; Emission Spectra laser–plasma interactions; plasma dynamics and flow; hypersonic flows; Emission Spectra
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Gautam, G.; Parigger, C.G. Plasma Expansion Dynamics in Hydrogen Gas. Atoms 2018, 6, 46.

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