Absorption of radiation in a magnetoplasma and application to the laser-fusion process

One mechanism for the generation of heat in the laser-fusion process is via inverse bremsstrahlung. Since it is desirable to maximize the amount of heat produced, it is thus of interest to investigate possibilities for increasing the absorption rate via the inverse bremsstrahlung process. Here we show that, in the presence of a magnetic field, the absorption rate can be either increased or decreased depending on the relative orientations of the polarization vector of the laser beam, the incident direction, and the magnetic field direction, and depending on the relative magnitudes of the electron\u27s average energy due to thermal and electric-field effects. In particular, for radiation incident along the magnetic direction, we show that the absorption of right-circularly- polarized radiation is decreased, whereas that of left-circularly-polarized radiation is increased, if we are in the weak-electric-field regime (thermal effects dominate). On the other hand, in the strong-electric-field regime, the rate of absorption of right-polarized radiation is greater than that of left. In addition, the right-polarized radiation will penetrate to a region of greater plasma density than the left, in the direction of the magnetic field. © 1980 The American Physical Society