| Generation of monochromatic subfemtosecond X-rays at reflection of ultraviolet laser pulses from two moving towards each other relativistic bunches accelerated by ultrashort high intensity pulses are explored. Dependence of the frequency of obtained γ radiation on the flying mirrors velocities, thicknesses and concentrations are investigated. It was shown that at high frequencies the mirrors become partly transparent. The transparency is also determined by the intensity of the generated pulses. The process of reflection of highfrequency pulses is significantly influenced by Rayleigh -Tailor -like instabilities. The shortwave nonuniformity causes distortion of the reflecting surfaces and scattering of the waves. To avoid this undesirable effect, the bunches need to be reflected at early stage their formation. On the other hand, this leads to decrease of the reflected radiation frequency as at such stage of acceleration, their velocities are less than their highest values. In addition, decrease of the rapid growth of shortwave instabilities demand a high degree of homogeneity of the targets' initial densities and uniformity of the transverse distribution of the pulse intensities. There is also found such profile of the accelerator pulses, at which monochromaticity of the generated X-rays is increased |
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