Plasma optical shutter in ultraintense laser-foil interaction

Wei, W. Q. and Yuan, X. H. and Fang, Y. and Ge, Z. Y. and Ge, X. L. and Yang, S. and Li, Y. F. and Liao, G. Q. and Zhang, Z. and Liu, F. and Chen, M. and Zhao, L. and Zhuo, H. B. and Li, Y. T. and Sheng, Z. M. and Zhang, J. (2017) Plasma optical shutter in ultraintense laser-foil interaction. Physics of Plasmas, 24 (11). 113111. ISSN 1070-664X

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    Abstract

    We report on a plasma optical shutter to reduce the intensity level of a nanosecond-duration pedestal of amplified spontaneous emission (ASE) using an ultrathin foil. The foil is ionized by the ASE prepulse and forms an expanding underdense preplasma, which enables the main laser pulse transmission, leading to an enhancement in temporal contrast. When such a plasma shutter is placed in front of a main target of interest, the preplasma profiles observed are similar to that produced from a single-layer reference target irradiated by a high-contrast laser, and can be finely tuned by varying the shutter thickness. Proton beams with significantly reduced divergence and higher flux density were measured experimentally using the double-foil design. The reduction in beam divergence is a characteristic signature of higher contrast laser production as a combined consequence of less target deformation and flatter sheath-acceleration field, as supported by the two-dimensional (2D) hydrodynamic and particle-in-cell simulations. The plasma shutter holds the promise to enhance the laser contrast and manipulate the preplasma conditions for application in high-field-physics experiments.