Ignition target fabrication and fielding for the national ignition facility

Abstract

Abstract. Continued advances in the design of ignition targets have stimulating new development paths for target fabrication, with potentially important simplifications for fielding cryogenic ignition targets for the National Ignition Facility. Including graded dopants in ablators as well as optimizing capsule and fuel layer dimensions increase implosion stability. This has led to developments of micron-scale fill tubes to fill and field the targets. Rapid progress has been made in development of the graded dopant layers in capsules as well as their characterization, in fabrication methods for micro-fill-tubes, and in fuel fill control with these fill tubes. Phase-contrast x-ray radiography has allowed characterization of fuel layers in beryllium targets.

Cryogenic DT and D2 targets for inertial confinement fusion

“…The conceptual basis for the NIF cryogenic target system ͑NCTS͒ 28,38 is significantly different from the OMEGA CTHS. A Load, Layer, and Characterization System ͑LLCS͒ is being developed to operate just outside the NIF target chamber but mechanically integrated with the target inserter and target chamber.…”

The NIF Ignition Program: progress and planning

“…For the same initial capsule radius, the shock compressed ablator is at larger radius for a longer time for diamond than for Be, allowing it to absorb more of the drive. Currently, the fabrication technology for Be is more mature than for diamond, [9,10] therefore Be has been selected as the 'point design' for the 2010 ignition campaign. There continues to be excellent progress in the fabrication of these capsules 10 [11] and they will be reassessed in 2007.…”

“…These hohlraums were fabricated by co-sputtering materials on the inside two halves of a hohlraum mandrel that were rejoined during final assembly. An improved method of fabrication more suitable for routine production of ignition hohlraum assemblies, based on thin alternating layers of the high-Z materials, is under development by researchers at General Atomics [28].…”

“…The experimental 'tuning' campaigns will be conducted in two major phases, consistent with the facility commissioning, with operation at 0.35 MJ in early 2010, and up to 1 MJ in late 2010. The first phase will allow an assessment of target performance, under conditions relevant to 1 MJ targets, through the use of two types of targets; (a) '0.7-scale targets', where all target dimensions, the laser spot size and the laser pulse duration are reduced by a factor of 0.7, and the laser power is reduced by 0.5 6 , and (b) full size targets ('Scale-1'), where the laser pulse is not scaled, but may be truncated in time.…”

“…To allow margin for other errors, the capsule smoothness requirement is set to 30 nm rms in modes 15-1000 8. The mixture serves to fill in gaps in the absorption at particular x-ray wavelengths, thereby reducing the energy lost in heating the wall material, and improving the efficiency of re-emission, however, the propensity of U to oxidize makes the manufacture and longevity of these hohlraums challenging 9. The overall benefit of adding LEH shields is under assessment.…”