Absorption of intense x-ray radiation in plasma by multiphoton inverse-bremsstrahlung

Summary form only given. The perspectives of powerful x-ray FELs¹, when the electron-field interaction energy over a x-ray wavelength comparable to electron rest energy, will open a new field of experimental studies ofnonlinear quantum-electrodynamics phenomena² in the shortwave domain of an external radiation. Among the fundamental processes of laser-plasma interaction, the inverse-bremsstrahlung absorption of an intense laser field in plasma is one of the contemporary problems that have applications ranging from plasma diagnostics to thermonuclear reactions and generation of intense x-ray radiation. Note that in the intense x-ray laser, an electron may gain relativistic energies absorbing even of a few hundred quanta, which makes it as an effective mechanism for laser-plasma heating. The theoretical description of this phenomenon in such superstrong radiation fields requires one to go beyond the scope of common Quantum Electrodynamics -Feynman diagrams corresponding to the perturbation theory.