Cooperative enhanced scattering from nonthermal theta-pinch plasmas

The conditions under which enhanced scattering of far-infrared laser radiation (337 to 119 μ) can be obtained from theta-pinch plasmas are investigated. The enhanced scattering cross-section results from above-thermal electron density fluctuations that can be produced only by nonthermal electrons in the plasma. The scattering cross section is derived for a plasma in a weak magnetic field (Ωc2≪ωp2) and "rigid rotor" distributions modeling the specific theta pinch plasma are used to calculate the actual cross section. The conditions under which this cross section can become greatly enhanced are then examined. Finally, various types of bremsstrahlung (free-free, magnetic, and nonmagnetic wave-wave) are compared with the scattered power. For typical laser power densities (10 W/cm2, the plasma must be considerably nonthermal for the scattered power to be dominant.