Malkin V M, Fisch N J
Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08544, USA.
Phys Rev Lett. 2007 Nov 16;99(20):205001. doi: 10.1103/PhysRevLett.99.205001. Epub 2007 Nov 12.
Powerful x-ray pulses might be compressed to even greater powers by means of backward Raman amplification in ultradense plasmas produced by ionizing condensed matter by the same pulses. The pulse durations contemplated are shorter than the time for complete smoothing of the crystal lattice by thermal motion of ions. Although inhomogeneities are generally thought to be deleterious to the Raman amplification, the relic lattice might, in fact, be useful for the Raman amplification. The x-ray frequency band gaps can suppress parasitic Raman scattering of amplified pulses, while enhanced dispersion of the x-ray group velocity near the gaps can delay self-phase-modulation instability, thereby enabling further amplification of the x rays.
强大的X射线脉冲可以通过在由相同脉冲电离凝聚态物质产生的超密等离子体中进行受激拉曼后向放大，被压缩到更高的功率。所设想的脉冲持续时间比离子热运动使晶格完全平滑所需的时间更短。虽然通常认为不均匀性对拉曼放大有害，但残余晶格实际上可能对拉曼放大有用。X射线频带隙可以抑制放大脉冲的寄生拉曼散射，而在频带隙附近增强的X射线群速度色散可以延迟自相位调制不稳定性，从而实现X射线的进一步放大。
