Observation of Energy Transfer between Identical-Frequency Laser Beams in a Flowing Plasma

Wharton, K. B.; Kirkwood, R. K.; Glenzer, S. H.; Estabrook, K. G.; Afeyan, Bedros; Cohen, B. I.; Moody, J. D.; Joshi, C.

doi:10.1103/physrevlett.81.2248

Cited by 48 publications

(30 citation statements)

References 27 publications

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“…Energy transfer between the two laser beams as well as plasma-wave and electronbeam enhancement are observed. The mechanism responsible for the energy transfer in this case differs from that studied in previous long-pulse and low-power crossedbeam experiments [9][10][11][12]. In our study, the mechanism was scattering from a stationary electron-density grating that was driven directly by optical interference, while in these previous experiments it was scattering from ion waves.…”

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confidence: 52%

“…It has been suggested theoretically [5] that this stochastic heating of electrons is ultimately responsible for the acceleration of multi-MeV energy beams of ions from laser-irradiated thin foils [6 -8]. In inertial fusion research, the electron heating and modification of the laser reflectivity that results from crossed laser beams [9][10][11][12] must be controlled in order to efficiently couple energy to the fusion target. High-intensity crossed beams are relevant to fastignition fusion research [13].…”

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confidence: 99%

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Laser-Energy Transfer and Enhancement of Plasma Waves and Electron Beams by Interfering High-Intensity Laser Pulses

et al. 2003

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confidence: 52%

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confidence: 99%

Laser-Energy Transfer and Enhancement of Plasma Waves and Electron Beams by Interfering High-Intensity Laser Pulses

et al. 2003

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“…This tuning mechanism takes advantage of the multiple laser beam interactions (28,29) with the plasma in the LEH area where all the beams cross. Transferring power into the inner beams, allows us to compensate for SRS losses of the inner beams.…”

Section: Symmetric Inertial Confinement Fusion Implosions At Ultra-himentioning

confidence: 99%

Symmetric Inertial Confinement Fusion Implosions at Ultra-High Laser Energies

Glenzer

MacGowan

Michel

et al. 2010

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Indirect-drive hohlraum experiments at the National Ignition Facility have demonstrated symmetric capsule implosions at unprecedented laser drive energies of 0.7 MJ. 192 simultaneously fired laser beams heat ignition emulate hohlraums to radiation temperatures of 3.3 million Kelvin compressing 1.8-millimeter capsules by the soft x rays produced by the hohlraum. Self-generated plasma-optics gratings on either end of the hohlraum tune the laser power distribution in the hohlraum producing symmetric x-ray drive as inferred from the shape of the capsule self-emission. These experiments indicate conditions suitable for compressing deuterium-tritium filled capsules with the goal to achieve burning fusion plasmas and energy gain in the laboratory.With completion (1) and commissioning (2) of the National Ignition Facility (NIF) the quest for producing a burning fusion plasma has begun (3, 4). The goal of these experiments is to compress matter to densities and temperatures higher than the interior of the sun (5-7) which will initiate nuclear fusion and burn of hydrogen isotopes (8-10). This technique holds promise to demonstrate a highly efficient carbon-free process that will burn milligram quantities of nuclear fuel on each laser shot for producing energy gain in the laboratory.The NIF (11) consists of 192 laser beams that have been arranged into cones of beams to irradiate a target from the top and bottom hemispheres. This "indirect-drive" laser geometry has been chosen for the first experiments to heat the interior of centimeter-scale cylindrical gold hohlraums (8,(12)(13)(14)(15) through laser entrance holes (LEH) on the top and bottom end of the cylinder (Fig. 1). Hohlraums act as radiation enclosures that convert the optical laser light into soft x-rays that are characterized by the radiation temperature T RAD . Present ignition designs operate at temperatures of 270 to 305 eV or 3.1 to 3.5 million K. The radiation field compresses a spherical fusion capsule mounted in the center of the hohlraum by x-ray ablation of the outer shell. The ablation process compresses the cryogenically prepared solid deuterium-tritium fuel layer in a spherical rocket implosion. In the final stages, the fuel reaches densities 1000-times solid and the central hot spot temperatures will approach 100 million K to initiate the nuclear burn process.We have symmetrically imploded 1.8-mm diameter fusion capsules in cryogenically fielded centimeter-scale hohlraums at 20 K. These experiments show efficient hohlraum heating to radiation temperatures of 3.3 million K. In addition, the large scale-length plasmas encountered in these experiments have allowed us to use self-generated plasma optics gratings (16) to control the radiation symmetry (17) and to achieve symmetric fusion capsule implosions.Figure 2 A shows the laser power at the frequency-tripled wavelength of 351 nm versus time for two different pulse shapes. These 11-ns and 16-ns long pulses heat 8.4-mm long, 4.6-mm diameter hohlraums with 20% helium, 80% hydrogen (atomic) mixtures and ...

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“…Resonant energy transfer via a zero-frequency ion wave has been the subject of much theoretical work [13,[17][18][19], and has recently been experimentally demonstrated for the first time [20]. Results from these previous experiments will be summarized below, along with new experimental results from beams with added frequency modulation.…”

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confidence: 99%