Shock-tuned cryogenic-deuterium-tritium implosion performance on Omega

Abstract

Cryogenic-deuterium-tritium ͑DT͒ target compression experiments with low-adiabat ͑␣͒, multiple-shock drive pulses have been performed on the Omega Laser Facility ͓T. R. Boehly, D. L. Brown, R. S. Craxton et al., Opt. Commun. 133, 495 ͑1997͔͒ to demonstrate hydrodynamic-equivalent ignition performance. The multiple-shock drive pulse facilitates experimental shock tuning using an established cone-in-shell target platform ͓T. R. Boehly, R. Betti, T. R. Boehly et al., Phys. Plasmas 16, 056301 ͑2009͔͒. These shock-tuned drive pulses have been used to implode cryogenic-DT targets with peak implosion velocities of 3 ϫ 10 7 cm/ s at peak drive intensities of 8 ϫ 10 14 W / cm 2 . During a recent series of ␣ ϳ 2 implosions, one of the two necessary conditions for initiating a thermonuclear burn wave in a DT plasma was achieved: an areal density of approximately 300 mg/ cm 2 was inferred using the magnetic recoil spectrometer ͓J. A. Frenje, C. K. Li, F. H. Séguin et al., Phys. Plasmas 16, 042704 ͑2009͔͒. The other condition-a burn-averaged ion temperature ͗T i ͘ n of 8-10 keV-cannot be achieved on Omega because of the limited laser energy; the kinetic energy of the imploding shell is insufficient to heat the plasma to these temperatures. A ͗T i ͘ n of approximately 3.4 keV would be required to demonstrate ignition hydrodynamic equivalence ͓Betti et al., Phys. Plasmas 17, 058102 ͑2010͔͒. The ͗T i ͘ n reached during the recent series of ␣ ϳ 2 implosions was approximately 2 keV, limited primarily by laser-drive and target nonuniformities. Work is underway to improve drive and target symmetry for future experiments.

National Ignition Campaign Program Completion Report

“…This section briefly describes measurements of high areal densities in OMEGA cryogenic target implosions that give confidence in models of the DT compressibility under ignition-relevant conditions. As described in more detail below, LLE uses a triple picket laser pulse to compress cryogenic targets; areal densities of up to 300 mg/cm 2 have been demonstrated in OMEGA cryogenic target experiments [49,50]. Figure 3-14 shows a comparison of the measured areal densities with the predictions of 1D simulations using the LILAC hydrodynamic code [51].…”

Direct-drive inertial confinement fusion: A review

“…317 This made the targets less susceptible to vibration and easier to position accurately at TCC. On the shot that yielded 300 mg/cm 2 , the target offset was 10 lm.…”

“…Further success in increasing the areal density was reported in 2010 by Goncharov et al 42 and Sangster et al 317 Their targets ($860-lm-diam, 10-lm-thick CD shells surrounding an $65-lm-thick layer of DT ice) were irradiated with a triplepicket laser pulse with a peak intensity of $8 Â 10 14 W/cm 2 designed to put the fuel on an adiabat a $ 2. The areal density was determined from the energy loss of primary 14-MeV neutrons as they passed through the dense fuel.…”

Measurements of theT(t,2n)He4Neutron Spectrum at Low Reactant Energies from Inertial Confinement Implosions

“…A quantitative understanding of the tt neutron spectrum is also important to ICF. In particular, the tt spectrum overlaps with part of the downscattered neutron (DSn) spectrum, which is often used to diagnose areal density (R), an essential metric of implosion performance [9,10].…”

“…A quantitative understanding of the tt neutron spectrum is also important to ICF. In particular, the tt spectrum overlaps with part of the downscattered neutron (DSn) spectrum, which is often used to diagnose areal density (R), an essential metric of implosion performance [9,10].In this Letter, we present measurements of the neutron spectrum from the tt reaction that were carried out by using a variety of deuterium-tritium (DT) gas-filled capsule implosions at the OMEGA laser [1]. Using the implosion and diagnostic capabilities on OMEGA, the tt reaction was measured at a reactant center-of-mass (c.m.)…”