Early-stage plasma dynamics with air ionization during ultrashort laser ablation of metal

Hu, Wenqian; Shin, Yung C.; King, Galen

doi:doi:10.1063/1.3633067

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Beyond Zeeman spectroscopy: Magnetic-field diagnostics with Stark-dominated line shapes

A recently suggested spectroscopic approach for magnetic-field determination in plasma is employed to measure magnetic fields in an expanding laser-produced plasma plume in an externally applied magnetic field. The approach enables the field determination in a diagnostically difficult regime for which the Zeeman-split patterns are not resolvable, as is often encountered under the conditions characteristic of high-energy-density plasmas. Here, such conditions occur in the high-density plasma nea...

Towards a fully kinetic 3D electromagnetic particle-in-cell model of streamer formation and dynamics in high-pressure electronegative gases

Streamer and leader formation in high pressure devices is dynamic process involving a broad range of physical phenomena. These include elastic and inelastic particle collisions in the gas, radiation generation, transport and absorption, and electrode interactions. Accurate modeling of these physical processes is essential for a number of applications, including high-current, laser-triggered gas switches. Towards this end, we present a new 3D implicit particle-in-cell simulation model of gas bre...

In this study, the early-stage plasma evolution generated by an ultrashort laser pulse is investigated through pump-probe shadowgraph measurements and simulations. The measurements are performed to show the evolution of the plasma front, while the simulation model is used to further investigate the evolution process and mechanism. Specifically, the laser pulse propagation in air is simulated using the beam propagation method with the slowly varying envelope approximation. The lattice dynamics, the electron dynamics and the multi-scattering event, and the evolution of charged particles (free electrons and ions), are simulated using a molecular dynamics method, a Monte Carlo method, and a particle-in-cell method, respectively. With this simulation model, the refractive index and plasma evolutions are calculated and compared with measured results to validate the simulation model. Different plasma expansion processes, caused by the air ionization, are found with the focal point slightly above and below the target. Air ionization occurs in both cases, but their primary mechanisms are shown to be different.

Article Outline

INTRODUCTION
METAL ABLATION
EARLY-STAGE PLASMA
AIR BREAKDOWN
PLUME PLASMA
SIMULATION SETUP AND VALIDATION
1. Simulation domain setup
2. Refractive index of laser spark in air
3. Plasma evolution in vacuum
4. Near surface plasma evolution in air
EARLY-STAGE PLASMA EVOLUTION AND AIR IONIZATION
1. Experimental and simulation results
2. Discussions
CONCLUSION

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KEYWORDS and PACS

Keywords

air, ionisation, laser ablation, molecular dynamics method, Monte Carlo methods, plasma density, plasma light propagation, plasma probes, plasma simulation, refractive index

PACS

52.38.Mf

Laser ablation
52.65.Pp

Monte Carlo methods
52.65.Rr

Particle-in-cell method
52.65.Yy

Molecular dynamics methods
52.25.Jm

Ionization of plasmas
52.25.Os

Emission, absorption, and scattering of electromagnetic radiation

ARTICLE DATA

Digital Object Identifier

http://dx.doi.org/10.1063/1.3633067

PUBLICATION DATA

ISSN

1070-664X (print)

1089-7674 (online)

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American Institute of Physics

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