Heating of strong turbulent plasma by laser radiation

Abstract

The high-power laser excites the electric field of the turbulent plasma strong enough to exceed the weak turbulence condition so that strong Langmuir turbulence develops. In this thesis, the heating of the electrons in strong Langmuir turbulent plasma by multiphoton absorption of the strong laser radiation is investigated. In the theory of strong Langmuir turbulence, the turbulent electric field is described by the form of Langmuir solution, which is formed as a result of modulational instability. A kinetic equation is derived from a quantum mechanical view point and the rate of change of the kinetic energy of the electron is calculated. The phenomenological collision frequency is found and compared with the effective collision frequency of multiphoton inverse Bremsstrahlung. It is found that the heating rate is proportional to $(nTe^3)^{\frac{1}{2}}$. $W_o\cdot$ Em/Eo where n, Te are electron density and electron temperature, and $W_o$, Eo the frequency and the amplitude of the electric field of the laser, and Em the amplitude of the turbulent electric field, respectively. And it is also found that the heating is more efficient than that of the inverse Bremsstrahlung when the electric field amplitude exceeds the value, $\pi^{\frac{5}{2}} \eta^{\frac{3}{2}} e^4/\sqrt{3} Te^{\frac{3}{2}}$.