An analytical formalism is developed to study the nonlinear laser penetration through radiation pressure accelerated thin foils, employed to produce high energy ions. We include the effects of relativistic mass increase and nonuniform electron density compression due to the ponderomotive force in plasma permittivity. For foils like diamond the usual optimum foil thickness l _(opt) = λ_(Ln cr a 0) / ρn0 (where λL and a_0 are the wavelength and normalized amplitude of the laser), at which the ponderomotive force on electrons balances the space charge force due to the ions left behind, is significantly below the skin depth unless the laser intensity is excessively large and significant laser transmission through the foil reduces the radiation pressure on it. The reflection coefficient decreases with laser field strength, though the ponderomotive force led electron compression tends to raise it. The reflection coefficient also decreases significantly with foil velocity, which is a sensitive function of laser field strength and foil thickness.
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机译:发展了一种分析形式主义,以研究非线性激光穿透辐射压力加速的薄箔所产生的高能量离子。我们包括相对论质量增加和由于等离子体介电常数的质动力引起的不均匀电子密度压缩的影响。对于像金刚石这样的箔片,通常的最佳箔片厚度l _(opt)=λ_(Ln cr a 0)/ρn0(其中λL和a_0是激光的波长和归一化振幅),在电子上的磁势平衡空间除非激光强度过大并且激光通过箔的有效透射会降低其上的辐射压力,否则由于残留离子而产生的电荷力将大大低于集肤深度。反射系数随激光场强度而降低,尽管介电势导致电子压缩趋于提高。反射系数也随着箔速度而显着降低,这是激光场强度和箔厚度的敏感函数。
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