Polarization-Dependent Self-Injection by Above Threshold Ionization Heating in a Laser Wakefield Accelerator

We report on the experimental observation of a decreased self-injection threshold by using laser pulses with circular polarization in laser wakefield acceleration experiments in a nonpreformed plasma, compared to the usually employed linear polarization. A significantly higher electron beam charge w...

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Bibliographic Details
Published in:Physical review letters 2020-03, Vol.124 (11), p.114801-114801, Article 114801
Main Authors: Ma, Y, Seipt, D, Hussein, A E, Hakimi, S, Beier, N F, Hansen, S B, Hinojosa, J, Maksimchuk, A, Nees, J, Krushelnick, K, Thomas, A G R, Dollar, F
Format: Article
Language:English
Subjects:
Circular polarization
Electron beams
Ionization
Laser beam heating
Lasers
Linear polarization
Particle in cell technique
Plasma temperature
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Summary:We report on the experimental observation of a decreased self-injection threshold by using laser pulses with circular polarization in laser wakefield acceleration experiments in a nonpreformed plasma, compared to the usually employed linear polarization. A significantly higher electron beam charge was also observed for circular polarization compared to linear polarization over a wide range of parameters. Theoretical analysis and quasi-3D particle-in-cell simulations reveal that the self-injection and hence the laser wakefield acceleration is polarization dependent and indicate a different injection mechanism for circularly polarized laser pulses, originating from larger momentum gain by electrons during above threshold ionization. This enables electrons to meet the trapping condition more easily, and the resulting higher plasma temperature was confirmed via spectroscopy of the XUV plasma emission.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.124.114801