Exploration of Directly Driven Liquid Deuterium-Tritium Wetted Foam Designs for Burning Plasma and High Neutron Yield Applications

Project Overview

A Feasibility Study was performed to assess the potential risks and benefits of laser direct drive liquid deuterium-tritium (DT) wetted foam (WF) inertial confinement fusion (ICF) concepts for high-yield and burning plasma platforms on the National Ignition Facility (NIF). In this central hot spot approach, capsules consist of DT vapor surrounded by a liquid DT WF layer that serves as both the ablator and fuel. Experimental exploration of such concepts has only recently been realizable on the facility due to nascent target fabrication techniques and platform development. Two photon polymerization (2PP) additively manufactured (AM) capsules are being explored given the potential for unprecedented control over capsule properties; fabrication efforts focusing on prototyping and testing 2PP capsules suggest great promise for the approach. Cryogenic direct drive targets have been developed and demonstrated capability to support liquid DT designs. A NIF shot with a fully liquid filled thin-wall plastic capsule explored ablation properties of liquid deuterium and demonstrated laser coupling was better than preshot modeling expectations. Radiation-hydrodynamics models benchmarked to this new data suggest that high gain designs may be realizable with a NIF-scale direct drive facility, but the current polar direct drive (PDD) approach on NIF may not provide adequate coupling and drive uniformity to achieve ignition within existing facility capabilities. Benchmarking data with wetted foam capsules is desperately needed for further assessment. Experiments demonstrating the culmination of these fabrication, platform development, and model benchmarking efforts are scheduled in FY24 and will be supported through continuing and newly funded Lawrence Livermore National Laboratory and Los Alamos National Laboratory LDRD projects and the DOE INFUSE program.

Mission Impact

This project contributed to the advancement of several Lawrence Livermore National Laboratory and NNSA Core Competencies and Mission Focus Areas addressing high energy density science, high performance computing, and advanced additive manufacturing techniques. Through prototyping of 2PP capsules, demonstration of cryogenic PDD target platforms, and radiation-hydrodynamics model benchmarking, this work is an important step forward toward experimental realization of direct drive WF ICF concepts on the NIF. Such designs have the potential to greatly reduce target debris, reduce capsule manufacturing timelines/costs, and enhance facility flexibility for fielding ICF and burning plasma applications of interest to Stockpile Stewardship and Nuclear S&T while also developing inertial fusion energy (IFE) enabling technologies.

Publications, Presentations, and Patents

Garcia-Diaz, B. L., et al. " The ‘softer' side of fusion materials development." Advanced Materials and Processes Vol 181, No 06 (2023). https://static.asminternational.org/amp/202309/16/. LLNL IM#1081810.

G.E. Kemp, et al., "Polar direct drive DT wetted foam studies on the National Ignition Facility" (Presentation,12th International Conference on Inertial Fusion Sciences and Applications, Denver, CO, 2023). LLNL-PRES-854718.