Abstract
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.
Highlights
In laser-induced plasma, the ambient gas can foster or diminish the plasma expansion.The pressure and type of gases influences the post-breakdown phenomena
The motivation behind this engineering and scientific research [5] extends to the measurement of phenomena that occur at hypersonic speeds to re-entry speeds that are in the Mach number range of 5–25 or above
The laser‐induced plasma expands at a well‐above hypersonic speed depending upon the
Summary
In laser-induced plasma, the ambient gas can foster or diminish the plasma expansion. The astrophysical interests include the interpretation of white dwarf photosphere absorption spectra by simulating the conditions of these selected stars in laboratory settings [2,3,4] and by exploring laser-induced plasma [4] with time-resolved laser spectroscopy The motivation behind this engineering and scientific research [5] extends to the measurement of phenomena that occur at hypersonic speeds to re-entry speeds that are in the Mach number range of 5–25 or above. 532 nm and the pulse width of 6.5 ns [8], show two distinct regions with higher intensity towards the plasma generateddirection in air atfor thetime standard temperature and images pressure show plasma jet laser propagation delays ambient of 25 ns to. Jet propagation dependsand on the threshold for the occurrence opticalabsorbed breakdown [9].plasma and the threshold irradiance type of gas,irradiance the gas pressure, the ratio ofofenergy in the for the occurrence of optical breakdown [9]
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