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Session 1R - HIGH-INTENSITY, SHORT-PULSE LASER-PLASMA INTERACTIONS, FAST IGNITOR, AND BEAT WAVES.
MIXED session, Monday morning, November 06
Archibald/Cochran, 3rd floor, Tower
The formation of density channels in an underdense plasma has been studied as a function of the laser pulse length using the Janus laser at LLNL. The background density profile and the channel formed by the interaction pulse are measured using interferometry. For pulse lengths of less than 300 ps, the channels have a finite axial length and end short of the peak density (S. Wilks et al., Phys. Rev. Lett. 73), 2994 (1994).. As the pulse length is increased, the channel lengthens to the opposite side of the density profile and a situation can be obtained in which most of the beam propagates through the plasma within the vacuum propagation cone (P. Young et al., in press, Phys. Rev. Lett.(1995).). With a 300 ps Gaussian pulse, 80\ through the original focusing solid angle. The development of the channel has been time resolved, which illustrates the formation process. The channel formation is successfully modeled by two-dimensional hydrodynamic simulations. \hrule width4cm \vskip .1in * Work performed under the auspices of the U.S. Dept. of Energy by Lawrence Livermore National Laboratory under contract W-7405-ENG-48.