Laser plasma interactions in a relativistic parameter regime have been intensively investigated for studying the possibility of fast ignition in inertial confinement fusion ͑ICF͒. Using ultra-intense laser systems and particle-in-cell ͑PIC͒ simulation codes, relativistic laser light self-focusing, super hot electrons, ions, and neutron production, are studied. The experiments are performed with ultra-intense laser with 50 J energy, 0.5-1 ps pulse at 1053 nm laser wavelength at a laser intensity of 10 19 W/cm 2. Most of the laser shots are studied under preformed plasma conditions with a 100 m plasma scale length condition. In the study of laser pulse behavior in the preformed plasmas, a special mode has been observed which penetrated the preformed plasma all the way very close to the original planar target surface. On these shots, super hot electrons have been observed with its energy peak exceeding 1 MeV. The energy transport of the hot electrons has been studied with making use of K␣ emissions from a seeded metal layer in planar targets. The details of ion acceleration followed by beam fusion reaction have been studied with neutron spectrometers. Laser ponderomotive force self-focusing and hot electron generation have been applied to a compressed core to see the effect of heating by injecting 12 beams of 100 ps, 1 TW pulses.
When clusters of deuterium are irradiated with an intense, ultrafast laser pulse, the clusters explode, generating ions with kinetic energies high enough to produce nuclear-fusion events. Here we present experimental measurements of the dependence of the fusion yield of an exploding deuterium-cluster plasma on pulse energy up to the 10-J level for incident pulse durations of 100 fs and 1 ps. These energies correspond to peak vacuum intensities of 2 ϫ 10 20 and 2 ϫ 10 19 W/cm 2 , respectively. We also present measurements of the resulting plasma ion spectra that possess features indicative of a Coulomb explosion and discuss the yield scaling and its relation to previous findings based on the differences in laser focal geometry and pulse duration.
The back-reflected image of a 100 TW laser incident on a long scale length plasma is measured. The plasma is deliberately preformed on a solid planar target in a controlled way. Multiple highly intense spots are observed inside the original focal spot. These spots could be the experimental evidence for the laser beam relativistic filamentation in the plasma. Three-dimensional particle-in-cell (PIC) simulations for parameters close to the experimental values are performed. The experimental observations and the filamentation dynamics obtained in the PIC simulations are in a good agreement.
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