Table 1 Status of the NOVA Technical Contract

Milestone

Issue

NIF Requirement

NTC Requirement

Achieved at CD-2 (6/94)

Achieved for CD-3 (11/96)

HLP-1

Laser coupling to hohlraum

Backscatter <20%

Backscatter <20%

Backscatter <10%

Backscatter 10% to 30% without smoothing; less with smoothing

HLP-2

Laser coupling at NIF temperatures

300 eV (recent targets are at 250 eV)

210–270 eV in different configurations

220–270 eV in different configurations

190 eV

HLP-3

Hohlraum plasma dynamics

Test low-Z liner and gas fill

Corner jet, wall ablation, and lined hohlraums

Limited testing

Lined hohlraums fail; gas filled at 0.1 nc retard closure

HLP-4

Drive symmetry

1% time average asymmetry, +/-15% time variation, <1 deg. bending, CR=25–35

2% time average asymmetry, +/-25% time variation, <1 deg. bending, CR=20

1% time average asymmetry, +/-25% time variation, <1 deg. bending, CR=7–15

1% time average asymmetry, +/-15% time 12 deg. bending, CR=10

HLP-5

Stimulated scattering in long-scale-length plasmas at 1–2 × 1015 W/cm3 Tc=3–4 keV, n/nc=0.07 to 0.25

L= 3–4 mm, f/8 scattering <10%

L= 2–3 mm, scattering <10–20%

L= 1 mm, scattering = 2–10%

L= 1 mm, scattering = 10–15%

HLP-6

Filamentation

Small

Small

No evidence

Evidence of forward spraying

HLP-7

X-ray conversion efficiency

70%

70%

70%

70%

HEP-1

Capsule hydro: increased pusher density, fuel density, with pulse-shaping contrast ratio; convergence ratio

700–1200 g/cm3 pusher, 45–75 g/cm3 fuel, 40–60 contrast ratio, CR=25–35

170–270 g/cm3 pusher, fuel, 11 contrast ratio; CR=24

170–270 g/cm3 pusher, 20–30 g/cm3 fuel, 11 contrast ratio; CR=24

140–170 g/cm3 pusher, 20–30 g/cm3 fuel, 8 contrast ratio; CR=24

HEP-2

Reduced growth of planar Rayleigh-Taylor instabilities

G=6–7 acceleration to breakup and 6–7 deceleration to mix

G=4–5 to breakup and 4–5 to mix

G=4–5 to breakup and 4–5 to mix

Extended results to multimode

HEP-3

Mix of fuel and pusher due to surface perturbations

G=6–7 defines surface finish requirement

G=4–5 to breakup and 4–5 to mix

G=4–5 to breakup and 4–5 to mix

G=4–5 to breakup and 4–5 to mix

HEP-4

Low convergence with growth factors and surface mode spectrum of NIF

CR=20 and G=6–7

CR=7–15 and G=4–5

CR=7–15 and G=4–5

CR=7–15 and G=4–5

HEP-5

High convergence with growth factors and surface mode spectrum of NIF

CR=25–35

CR up to 20, limited by number of NOVA beams

CR=10

CR=10

NOTE: CR = convergence ratio; G = e-foldings of growth; L = plasma scale length, nc = electron density at which laser light will no longer propagate.

confidence that might be gained by completion of this milestone is not sufficient to justify delaying the NIF program.

Motion of the hohlraum wall during the laser pulse can impair the symmetry of the radiation on the capsule and spoil the implosion. Motion of the laser spots and the small number of beams on NOVA allowed three-dimensional effects to complicate the results of experiments addressing this issue. Considering all the experimental parameters, the data that are available on that phenomenon are consistent with the NIF design but are not adequate to resolve the wall-motion issue on the NIF.



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement