Steve Haan

The effects of fill tubes on the hydrodynamics of ignition targets and prospects for ignition

The notion of using a narrow bore fill tube to charge an ignition capsule in situ with deuterium-tritium (DT) fuel is very attractive because it eliminates the need for cryogenic transport of the target from the filling station to the target chamber, and in principle is one way of allowing any material to be considered as an ablator. We are using the radiation hydrocode HYDRA [M. M. Marinak et al., Phys. Plasmas 8, 2275 (2001)] in two dimensions to study the effect of fill tubes on graded copper-doped Be ignition capsule implosions. The capsule is ∼1.1-mm radius and driven at ∼300eV. Fill tubes are made of glass and range in diameter from 10–20μm. These are inserted between 5 and 40μm into the ablator surface, and a glue layer around the capsule ∼2-μm thick is included. The calculations are unusually demanding in that the flow is highly nonlinear from the outset, and very high angular resolution is necessary to capture the initial evolution of the tube, which is complex. Despite this complexity, the net r...

NIF Ignition Campaign Target Performance and Requirements: Status May 2012

Abstract The National Ignition Campaign (NIC) on the National Ignition Facility plans to use an indirectly driven spherical implosion to assemble and ignite a mass of D-T fuel. The NIC is currently in the process of conducting a variety of experiments using surrogate targets, meant to define various aspects of the future ignition experiment. Four platforms have been developed: Re-emit targets measure the symmetry of the early part of the pulse, keyhole targets measure the strength and time of shocks, symcap targets measure integrated performance and implosion symmetry, and ConA targets measure implosion velocity and ablator performance. Also, cryogenic layered capsules similar to the ignition design, containing a layer of either D-T or hydrodynamically equivalent tritium-rich fuel, are being fielded. These integrate the laser and target adjustments made during the tuning experiments and test the integrated performance with data on RhoR, temperature, yield, and other diagnostics. In an activity ongoing with these experiments, the point design for ignition is updated and modified as appropriate. This paper summarizes the target designs that are being used for the campaign, the results of the experimental campaign to date, and how the campaign has affected requirements for the eventual ignition experiment.

CHARACTERIZATION SPECIFICATIONS FOR BASELINE INDIRECT DRIVE NIF TARGETS

Abstract Successful ignition in NIF will require targets that meet stringent standards as to symmetry, composition, and dimensions. We describe here the current understanding of specifications for baseline indirect drive targets of each of the three types of ablators: beryllium, polyimide, and plasma polymer. These specifications include the range of values for all targets of each group, and the variation in value allowed in a specific target of that group. They cover all of the components which make up a target, and which are critical to an implosion: the hohlraum and its components — windows, capsule support foil and gas fill — and the shell and its DT ice layer. These specifications are preliminary and incomplete; they will necessarily evolve with design details and with increasing understanding of target dynamics. They are compiled here as a reference for the ICF community and a basis on which to plan future work: to fill in the gaps and to develop thenecessary characterization techniques. Future work will also include the requirements for direct drive targets.