Developing one-dimensional implosions for inertial confinement fusion science

J L Kline,R R Peterson,O A Hurricane,E S Dodd,R E Olson,P A Bradley,A B Zylstra,L F Berzak Hopkins,E L Dewald,A G Macphee,D Ho,G A Kyrala,T S Perry,L Yin,S H Batha,D C Wilson,A V Hamza,S Lepape,J E Ralph,N B Meezan,D J Strozzi,R J Leeper,A Nikroo,D A Callahan,D S Montgomery,T Cárdenas ,W Daughton ,Rahul Shah ,Brian Haines ,Monika M Biener ,Andrei N Simakov ,Juergen Biener ,Sunghwan Yi ,Elizabeth Merritt ,Tom Braun ,J Sater ,D E Hinkel ,B Kozioziemski

doi:10.1017/hpl.2016.43

Abstract

Experiments on the National Ignition Facility show that multi-dimensional effects currently dominate the implosion performance. Low mode implosion symmetry and hydrodynamic instabilities seeded by capsule mounting features appear to be two key limiting factors for implosion performance. One reason these factors have a large impact on the performance of inertial confinement fusion implosions is the high convergence required to achieve high fusion gains. To tackle these problems, a predictable implosion platform is needed meaning experiments must trade-off high gain for performance. LANL has adopted three main approaches to develop a one-dimensional (1D) implosion platform where 1D means measured yield over the 1D clean calculation. A high adiabat, low convergence platform is being developed using beryllium capsules enabling larger case-to-capsule ratios to improve symmetry. The second approach is liquid fuel layers using wetted foam targets. With liquid fuel layers, the implosion convergence can be controlled via the initial vapor pressure set by the target fielding temperature. The last method is double shell targets. For double shells, the smaller inner shell houses the DT fuel and the convergence of this cavity is relatively small compared to hot spot ignition. However, double shell targets have a different set of trade-off versus advantages. Details for each of these approaches are described.

Highlights

While progress towards laser-based indirect drive inertial confinement fusion (ICF) is being made[1,2,3], experimental results show challenges remain
The second approach uses Deuterium–Tritium (DT) liquid layered targets in which the convergence ratio is controlled by varying the initial mass in the central cavity of the capsule through the vapor pressure
The last approach uses double shell targets that are comprised of an inner shell filled with the DT fuel surrounded by an outer shell with a foam fill between the shells

Summary

Introduction

While progress towards laser-based indirect drive inertial confinement fusion (ICF) is being made[1,2,3], experimental results show challenges remain. The radiation symmetry and predictability of the hohlraum drive is expected to be in better agreement since the lasers should deposit their energy as designed If we do achieve a 1D like implosion, the step will be to move towards larger capsules to determine at which caseto-capsule ratio symmetry control for beryllium capsules degrades From those experiments, we can hydro-scale the target and get an estimate of how much energy would be needed to achieve ignition with the low radiation temperature, high case-to-capsule beryllium capsule target design

Liquid layers

Double shells

Conclusions