Progress in the shock-ignition inertial confinement fusion concept

W. Theobald, A. Casner, R. Nora, X. Ribeyre, M. Lafon, K.S. Anderson, R. Betti, R.S. Craxton, J.A. Delettrez, J.A. Frenje, V.Yu. Glebov, O.V. Gotchev (+15 others)
2013 EPJ Web of Conferences  
Shock-ignition experiments with peak laser intensities of ∼8 × 10 15 W/cm 2 were performed. D 2 -filled plastic shells were compressed on a low adiabat by 40 of the 60 OMEGA beams. The remaining 20 beams were delayed and tightly focused onto the imploding shell to generate a strong shock. Up to 35% backscattering of laser energy was measured at the highest intensity. Hard x-ray measurements reveal a relatively low hot-electron temperature of ∼40 keV, independent of intensity and spike onset
more » ... and spike onset time. Shock ignition (SI) is a two-step inertial confinement fusion concept in which a strong shock wave is launched at the end of the laser pulse to ignite the compressed core of a low-velocity implosion [1]. Two-step processes separate fuel assembly and ignition, relaxing driver requirements and promising high gains [1] [2] [3] . SI relies on highly shaped laser pulses that are within the pulse-shaping capabilities of currently operating laser systems like the National Ignition Facility (NIF) [4] . Proof-of-principle experiments can be carried out on the NIF [5]. This shows a promising route to high fusion gains at moderate laser energies. An intensity spike (∼3 × 10 15 to ∼10 16 W/cm 2 ) at the end of the laser pulse launches the ignitor shock, and the final fuel assembly develops a centrally peaked pressure profile, lowering the ignition threshold compared to standard isobaric assemblies [6] . Parametric plasma instabilities [7] such as stimulated Brillouin scattering (SBS), stimulated Raman scattering (SRS), and two-plasmon-decay (TPD) instability are of concern in an ignition target design. The instabilities increase the back-reflection of the laser light from the target, degrading the laserenergy coupling to the capsule. They increase the fraction of the laser energy transferred to suprathermal electrons-a potential source of preheat that could reduce the final core compression. Significant laserplasma instabilities can be expected during the high-intensity ignitor spike. Whether or not these are a
doi:10.1051/epjconf/20135903001 fatcat:3pywcr6cv5gd3onvrj2wvogrt4