The minimum laser energy for ignition (black curve) and the corresponding minimum areal density (red curve) are plotted as functions of the implosion velocity for a design. Although the energy-scaled experiments on Omega (Ref. 7) with implosion velocities of do not scale to ignition with existing facilities, the minimum laser energy for ignition with the current energy-scaled experiments at is 1.5 MJ, well within the design envelope of the NIF. Future energy-scaled experiments at are expected to scale to ignition with a reasonable margin (much lower minimum ignition energy than the facility can produce).
A new direct-drive-ignition target design has been developed by Goncharov et al. (Ref. 22). (a) Details of the target and (b) the multiple-picket, multiple-shock drive pulse for this target. The design adiabat is approximately 2.
(a) The Omega energy-scaled version of the ignition-drive pulse from Fig. 2(b). This pulse was used to perform a shock-timing measurement using a spherical cone-in-shell target (Ref. 23). The third picket (at about 2 ns) is approximately 20% higher than designed. The third shock catches up with the first and second shocks too early, resulting in the coalesced shock in (b) at 2.7 ns (the green trace). The measured shock velocity is in excellent agreement with the 1D radiation-hydrocode prediction (blue trace).
(a) The DT-fuel-density distribution at peak burn for shot 55468 as predicted by the 2D radiation hydrocode DRACO using a measured offset of . (b) along radial lines of sight from the center of the hot spot is plotted as a function of the angle measured from the axis (red curve). The variation as a function of the polar angle is a factor of 3 and agrees well with the measured values listed in Table I. The black curve is an identical simulation for an offset of and shows that a single line-of-sight measurement using the MRS would provide a reasonable estimate of the average for such an implosion.
(a) The CPS1 and (b) CPS2 spectra for shot 55723 are fully saturated, i.e., the shape of the spectra is independent of . The MRS (c) deuteron spectrum shows the downscattered and primary yields leading to an inferred value of the of approximately .
The experimental is plotted as a function of the 1D-predicted for a variety of drive conditions and target designs.
The measured and predicted values for the on shot 55468.
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