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(IFP/10) Update on Fast Ignition Experiments at Nova Petawatt

R. B. Stephens¹⁾, T. E. Cowan^2)*, R. R. Freeman³⁾, S. Hatchett²⁾, M. H. Key²⁾, J. A. Koch²⁾, R. W. Lee²⁾, A. MacKinnon²⁾, D. Pennington²⁾, R. Snavely²⁾, M. Tabak²⁾, and K. Yasuike^2)
 
1) General Atomics, San Diego, California USA
²⁾ Lawrence Livermore National Laboratory, Livermore, California USA
³⁾ University of California, Davis, Livermore, California USA
^* Present Address: General Atomics

Abstract.  The physics of fast ignition was studied on the PetaWatt laser facility at LLNL for $\sim$ 3 years, to May 1999. The previous report to this conference described experiments that demonstrated the efficient transfer of laser energy to relativistic electrons that penetrated into the target and heated to temperatures $\sim$ 1keV. Since then, we have looked at energy transfer and propagation in dense plasmas in considerably more detail. Measurements show that the relativistic electrons penetrate > 100$\mu$m into a CH foil in a collimated beam with a complex annular structure. Production of an energetic (up to 55 MeV) proton beam was also discovered. The protons are tightly bunched (< 40^oC spread) and are emitted normal to the back target surface, so can be accurately directed. This gives another promising possibility for delivery of the ignition pulse.

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