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Laser-produced spark test bed for plasma diagnostics
Hinnegan, Sarah
Hinnegan, Sarah
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2021
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Abstract
A laser-produced spark test bed for plasma diagnostics has been developed to investigate the complex processes involved in the development of a plasma spark. By using a pair of laser pulses to ionize the test gas, a plasma is produced that has a well-defined start time and repeatable characteristics. These diagnostics include time-resolved spectra in ultraviolet and visible, spectral line broadening, and continuum evolution. These measurements can be used to analyze plasma and electron temperatures and the evolution of the plasma species. Analysis of laser-produced sparks supports a collaborative investigation between the Colorado School of Mines and Los Alamos National Lab into how much energy from electrostatic discharges is delivered to a victim load. We use the fourth harmonic (λ = 266 nm) from a high-power Q-switched laser to pre-ionize the gas at the lens focus. This low-density plasma is heated by a high-energy second pulse at the fundamental (λ = 1064 nm) to produce a denser plasma through collisional ionization. The spark is produced in a vacuum chamber where the composition and pressure of the gas is controlled to simplify identification of plasma species as well as to compare the spectral measurements between different gases. High-speed imaging and precise camera triggering are used to produce time-resolved experimental imaging and spectroscopy measurements. The initial results from the direct spark imaging and spectral imaging demonstrate our ability to analyze plasma species evolution, broadband evolution, and spectral line broadening of sparks in various gas compositions and at controllable pressures through the lifetime of the sparks using the laser-produced spark test bed.
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