Transparency of near-critical density plasmas under extreme laser intensities

We investigated transparency of near-critical plasma targets for highly intense incident lasers and discovered that beyond relativistic transparency, there exists an anomalous opacity regime, where the plasma target tend to be opaque at extreme light intensities. The unexpected phenomenon is found t...

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Bibliographic Details
Published in:New journal of physics 2018-05, Vol.20 (5), p.53043
Main Authors: Ji, Liangliang, Shen, Baifei, Zhang, Xiaomei
Format: Article
Language:English
Subjects:
Computer simulation
laser-plasma interaction
Luminous intensity
Opacity
particle-in-cell simulation
Physics
Plasmas (physics)
Propagation velocity
Relativism
Relativistic effects
relativistic transparency
Trapping
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Summary:We investigated transparency of near-critical plasma targets for highly intense incident lasers and discovered that beyond relativistic transparency, there exists an anomalous opacity regime, where the plasma target tend to be opaque at extreme light intensities. The unexpected phenomenon is found to originate from the trapping of ions under exotic conditions. We found out the propagation velocity and the amplitude of the laser-driven charge separation field in a large parameter range and derived the trapping probability of ions. The model successfully interpolates the emergence of anomalous opacity in simulations. The trend is more significant when radiation reaction comes into effect, leaving a transparency window in the intensity domain. Transparency of a plasma target defines the electron dynamics and thereby the emission mechanisms of gamma-photons in the ultra-relativistic regime. Our findings are not only of fundamental interest but also imply the proper mechanisms for generating desired electron/gamma sources.
ISSN:1367-2630
1367-2630
DOI:10.1088/1367-2630/aac24b