THE PHYSICS OF MEGAJOULE, LARGE-SCALE, AND ULTRAFAST SHORT-SCALE LASER PLASMAS

Recent advances in laser science and technology have opened new possibilities for the study of high energy density plasma physics. The advances include techniques to control the laser spatial and temporal coherence, and the development of laser architectures and optical materials that have led to the demonstration of compact, short pulse (tau < 10(-12) sec) high brightness lasers, capable of irradiating plasmas with intensities > 10(18) W/cm2. Experiments with reduced laser coherence have shown a substantial decrease in laser-driven parametric instabilities and have extended the parameter range where inverse bremsstrahlung absorption is the dominant coupling process. Beam smoothing with short wavelength lasers should result in inverse bremsstrahlung dominated coupling in the irradiance parameter regimes of the millimeter scale-length plasmas envisioned for the megajoule class lasers for ignition and gain in inertial fusion. In addition new regimes of laser-plasma coupling will become experimentally accessible when plasmas are irradiated with I > 10(18) W/CM2 . Relativistic effects, extreme profile modification, and electrons heated to energies exceeding 1 MeV are several of the phenomena that are expected. Numerous applications in basic and applied plasma physics will result from these new capabilities.