Robust relativistic electron mirrors in laser wakefields for enhanced Thomson backscattering

Mu, Jie and Li, Fei Yu and Zeng, Ming and Chen, Min and Sheng, Zheng-Ming and Zhang, Jie (2013) Robust relativistic electron mirrors in laser wakefields for enhanced Thomson backscattering. Applied Physics Letters, 103 (26). ISSN 0003-6951

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    Abstract

    By adopting an up-ramp density profile, we propose to generate relativistic electron mirrors from laser-driven underdense plasma waves, which are insensitive to finite thermal temperature within a certain range. Along the density ramp, premature wavebreaking due to thermal effects is shown to be well mitigated. Under sufficiently high amplitudes of wake excitation, overcritical dense electron mirrors can pile up when approaching the end of the up-ramp. The consequent mirror speed can be stably driven to the group velocity of the laser propagating in a corresponding uniform plasma. Compared with using purely uniform but thermal plasmas, the present thermal-insensitive mirrors can provide enhanced scattering efficiency and spectral upshift for a counter-propagating probe pulse. These observations are confirmed by multi-dimensional particle-in-cell simulations.