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Optical diagnostics of laser-produced aluminium plasmas under water

Walsh, N.; Costello, J. T.; Kelly, T. J.

Authors

N. Walsh

J. T. Costello

T. J. Kelly



Abstract

We report on the findings of double-pulse studies performed on an aluminium target submerged in water using Nd:YAG laser pulses. Shadowgraphy measurements were performed to examine the dynamic behaviour of the cavitation bubble that eventually forms some considerable time post-plasma ignition. These measurements were used to inform subsequent investigations designed to probe the bubble environment. The results of time-resolved imaging from within the cavitation bubble following irradiation by a second laser pulse reveal the full dynamic evolution of a plasma formed in such an environment. Rapid displacement of the plasma plume in a direction normal to the target surface followed by a diffusive outwards expansion is observed and a qualitative model is proposed to explain the observed behaviour. Line profiles of several ionic and atomic species were observed within the irradiated cavitation bubble. Electron densities were determined using the Stark broadening of the Al II line at 466.3 nm and electron temperatures inferred using the ratio of the Al II (466.3 nm) and Al I (396.15 nm) lines. Evidence of self-reversal of neutral emission lines was observed at times corresponding to growth and collapse phases of the cavitation bubble suggesting high population density for ground state atoms during these times.

Journal Article Type Article
Publication Date Jun 1, 2017
Journal Applied Physics B
Print ISSN 0946-2171
Electronic ISSN 1432-0649
Publisher Springer Verlag
Peer Reviewed Peer Reviewed
Volume 123
Issue 6
Article Number 179
APA6 Citation Walsh, N., Costello, J. T., & Kelly, T. J. (2017). Optical diagnostics of laser-produced aluminium plasmas under water. Applied physics. B, Lasers and optics, 123(6), doi:10.1007/s00340-017-6754-3
DOI https://doi.org/10.1007/s00340-017-6754-3
Publisher URL https://link.springer.com/article/10.1007/s00340-017-6754-3
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