Nonlinear Absorption and Heating of Dense Plasmas.
Technical rept. Jun-Aug 73,
AIR FORCE ACADEMY COLO
Pagination or Media Count:
Absorption of laser radiation by dense plasmas is studied using the model of Dubois, Goldman, and McKinnis for saturation of the parametric decay instability. The basic model contains both linear and nonlinear absorption mechanisms. The nonlinear mechanism includes spectrum broadening, Landau damping, and mode coupling. Modifications have been made to investigate various density profiles and to include the increase in threshold intensity due to the presence of the nonuniform plasma. Physical parameters investigated are those characterizing an exploding aluminum wire plasma and the pinch region of a dense plasma focus both illuminated by a high intensity CO2 laser. Results indicate the previously noted increases in absorption due to the inclusion of the nonlinear saturation mechanism. The previously obtained increases in absorption with increasing density scale height and decreasing temperatures are also recovered. The former indicates end on illumination of the pinch region as the most favorable for heating. The general density results also show the absorption to be a strong function of the shape of the density profile. Modified author abstract
- Plasma Physics and Magnetohydrodynamics