Thomson scattering nonlinear

Fig. 11.1. Principle of the nonlinear Thomson scattering X-ray source. The nonlinear motion of the free plasma electrons oscillating in the strong electromagnetic laser held (ao) produces high harmonics of the fundamental laser light that can reach the X-ray spectral range. As ao is increased, the radiation becomes more collimated...

Fig. 11.4. Energy distribution functions of the radiation produced by nonlinear Thomson scattering in a laser field for two laser intensities. Radiation above 1 keV can be achieved for laser intensities larger than 1020 W/cm2...

Fig. 11.7. X-ray intensity as a function of the electronic density of the plasma and the laser strength parameter. The process of nonlinear Thomson scattering for the production of X-ray emission can be observed for the highest laser intensities and along the laser axis (ao = 5.6 for the two first figures)...

Nonlinear Thomson scattering can only be observed for the highest laser intensities, as shown in Fig. 11.7. As expected from the theory, when ao < 1, the nonlinear Thomson scattering vanishes and the collisional radiative processes from the thermal plasma prevail (Bremsstrahlung and radiative recombination). For ao > 1, these latter processes are still effective, as shown by the quadratic dependency on the electronic density of the plasma observed for 9 = 40°. However, this isotropic thermal emission remains less intense than the collimated nonlinear Thomson scattering emission and becomes detectable only at a large angle of observation (> 40°). 

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