Investigating the dynamics of laser induced sparks in atmospheric helium using Rayleigh and Thomson scattering

Journal Article · Wed Jan 07 00:00:00 EST 2015 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4905190· OSTI ID:22399197

Nedanovska, E.; Nersisyan, G.; Lewis, C. L. S.; Riley, D.; Graham, W. G. ^[1]; Morgan, T. J.; Hüwel, L. ^[2]; Murakami, T. ^[3]

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1. Department of Physics and Astronomy, Centre for Plasma Physics, Queen's University Belfast, Belfast BT71NN (United Kingdom)
2. Department of Physics, Wesleyan University, Middletown, Connecticut 06459 (United States)
3. Department of Energy Sciences, Tokyo Institute of Technology, Yokohama 2268502 (Japan)

We have used optical Rayleigh and Thomson scattering to investigate the expansion dynamics of laser induced plasma in atmospheric helium and to map its electron parameters both in time and space. The plasma is created using 9 ns duration, 140 mJ pulses from a Nd:YAG laser operating at 1064 nm, focused with a 10 cm focal length lens, and probed with 7 ns, 80 mJ, and 532 nm Nd:YAG laser pulses. Between 0.4 μs and 22.5 μs after breakdown, the electron density decreases from 3.3 × 10{sup 17 }cm{sup −3} to 9 × 10{sup 13 }cm{sup −3}, while the temperature drops from 3.2 eV to 0.1 eV. Spatially resolved Thomson scattering data recorded up to 17.5 μs reveal that during this time the laser induced plasma expands at a rate given by R ∼ t{sup 0.4} consistent with a non-radiative spherical blast wave. This data also indicate the development of a toroidal structure in the lateral profile of both electron temperature and density. Rayleigh scattering data show that the gas density decreases in the center of the expanding plasma with a central scattering peak reemerging after about 12 μs. We have utilized a zero dimensional kinetic global model to identify the dominant particle species versus delay time and this indicates that metastable helium and the He{sub 2}{sup +} molecular ion play an important role.

• OSTI ID: 22399197
• Journal Information: Journal of Applied Physics, Vol. 117, Issue 1; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BREAKDOWN
ELECTROMAGNETIC PULSES
ELECTRON DENSITY
ELECTRON TEMPERATURE
ELECTRONS
EV RANGE
HELIUM
HELIUM IONS
LASER-PRODUCED PLASMA
MOLECULAR IONS
NEODYMIUM LASERS
PLASMA EXPANSION
RAYLEIGH SCATTERING
THOMSON SCATTERING
TIME DELAY