Magnetically Assisted Ignition

Project Overview

Magnetized fusion fuel offers the possibility of improved performance and robustness for indirect drive implosions on the National Ignition Facility (NIF).

Runaway self-heating nuclear fusion requires the power production from D-T generated alphas reheating the fuel to exceed the losses from thermal conduction and radiation. Magnetizing the fusion fuel reduces electron thermal conduction losses (main loss in NIF ICF implosions) orthogonal to the direction of the B-field if the Hall parameter, wce tei ≥ 1, where wce is the electron cyclotron frequency and tei is the electron-ion collision time. The Braginskii formalism [Braginskii (1965)] for magnetized plasma heat transport shows that for a large Hall parameter and a simple unidirectional B-field the average electron thermal conductivity, k, decreases to 1/3 of the unmagnetized value [Ho (2016)].

The mission of this LDRD project was to quantify the performance improvement of a magnetized room-temperature gas-capsule implosion compared to an unmagnetized implosion. This required science and technology developments in target fabrication, target physics, and pulsed power. A previous LDRD ER project on magnetized NIF implosions focused primarily on simulations and showed that addition of a B-field to implosions close to the ignition threshold could be very effective at pushing these designs to ignition. These simulations showed that addition of the B-field has only minor effects on implosions far away from ignition. Nine NIF experiments comparing magnetized to unmagnetized implosions were performed as part of this project. The primary result is that application of a 26 T seed field leads to a 40% +/- 9% increase in ion temperature and a factor of 3 +/- 0.2 increase in neutron yield. The ion temperature and yield increase approximately match the simulated increases. However, the absolute yield in the simulations is about a factor of two above the measurements, and we are investigating the cause of this. This project benefitted from an LDRD feasibility study which demonstrated the ability to create a novel type of hohlraum using an alloy of Au and Ta which had high electrical resistivity, allowing the B-field to diffuse through the walls of the hohlraum and magnetize the fuel.

A second element of the LDRD project was to demonstrate the cryogenic aspects of fielding a magnetized cryo-layered implosion on NIF. This includes demonstrating the slow growth of a DT ice layer with a pulsed-power electrical coil wrapped around the hohlraum and demonstrating that the DT ice layer continues to meet the required specifications during the rapid several-microseconds magnetization time. Detailed thermal simulations show that an ignition-quality ice layer can be obtained with the coil; an experimental test of this will be conducted by the program as part of demonstrating a magnetized DT layered implosion on NIF. During magnetization, when current is run through the conductor surrounding the hohlraum, eddy currents in the hohlraum wall increase the wall temperature by up to 500 K at the highest B-field of 50 T and radiate heat onto the capsule, rapidly increasing the capsule temperature. COMSOL simulations show that there is no impact of this sudden heating on the carefully grown ice layer. A surrogate experiment designed to test this modeling will continue as a program effort.

Mission Impact

Solving the problems defined in this SI required cross-cutting S&T in high- energy-density science, advanced materials, innovation in target platforms, and the development of new diagnostics. In addition to the ignition science, this project creates opportunities to test magneto-hydrodynamic (MHD) and thermal transport models in radiation-hydrodynamic codes currently used for simulations in the ICF and WCI programs at LLNL. The MHD physics and its coupling to heat transport are currently not well tested against experiment. Finally, the amplified B-field in the imploded core provides a mini-laboratory for exploring fundamental atomic physics in ultra-high fields.

Publications, Presentations, and Patents

Alison Engwall et al. 2019. "High-resistivity Metal Alloy Coatings Fabricated With Physical Vapor Deposition." U.S. Patent Application 62/928968, filed October 31, 2019. Applicant: Lawrence Livermore National Security, LLC. LLNL Ref.: IL-13488.

Engwall, A. M. et al. 2021. "Effect of Substrate Tilt on Sputter-Deposited AuTa Films." Appl. Surf. Sci. 547, 149010 (2021); doi: 10.1016/j.apsusc.2021.149010.

Bayu Aji, L. B. et al. 2021. "Sputtered Au-Ta films with Tunable Electrical Resistivity.'' J. Phys. D: Appl. Phys. 54, 075303 (2021); doi: 10.1088/1361-6463/abc501.

Moody, J. D. 2021. "Boosting Inertial-Confinement-Fusion Yield with Magnetized Fuel." American Physical Society, Physics 14, 51 (2021); doi: 10.1103/Physics.14.51.

Moody, J. D. et al. 2020. "Transient Magnetic Field Diffusion Considerations Relevant to Magnetically Assisted Indirect Drive Inertial Confinement Fusion." Phys. Plasmas 27, 112711 (2020); doi: 10.1063/5.0022722. NEEDS HTML HELP

Ivanov, V. V. et al. 2021. "Generation of Strong Magnetic Fields For Magnetized Plasma Experiments at the 1-MA Pulsed Power Machine." Matter Radiat. Extremes 6, 046901 (2021); doi: 10.1063/5.0042863.

Walsh, C. A. et al. 2020. "Magnetized Directly-Driven ICF Capsules: Increased Instability Growth from Non-Uniform Laser Drive." Nucl. Fusion 60 106006 (2020); doi: 10.1088/1741-4326/abab52.

Walsh, C. A. et al. 2021. "Updated Magnetized Transport Coefficients: Impact on Laser-Plasmas with Self-Generated or Applied Magnetic Field." Nucl. Fusion 61,116025 (2021); doi: 10.1088/1741-4326/ac25c1.

Sio, H. et al. 2021. "Diagnosing Plasma Magnetization in Inertial Confinement Fusion Implosions Using Secondary Deuterium-Tritium Reactions." Rev. Sci. Instrum. 92, 043543 (2021); doi: 10.1063/5.0043381.

Morita, H. et al. 2021. "Dynamics of Laser-Generated Magnetic Fields Using Long Laser Pulses." Phys. Rev. E 103, 033201 (2021); doi: 10.1103/PhysRevE.103.033201.

Bradford, P. et al. 2021. "Measuring Magnetic Fields in Laser-Driven Coils with Dual-Axis Proton Deflectometry." Plasma Phys. Control. Fusion 63, 084008 (2021); doi: 10.1088/1361-6587/ac0bca.

Walsh, C. A. 2022. "Magnetized Ablative Rayleigh-Taylor Instability in 3-D." Phys. Rev. E 105, 025206 (2022); doi: 10.1103/PhysRevE.105.025206.

Moody, J. D. et al. 2022. "The Magnetized Indirect Drive Project on the National Ignition Facility." Journal of Fusion Energy 41:7 (2022); doi: 10.1007/s10894-022-00319-7.

Walsh, C. A. 2022. "Magnetized ICF Implosions: Scaling of Temperature and Yield Enhancement." Phys. Plasmas 29, 042701 (2022); doi: 10.1063/5.0081915.

Bae, J. 2021. "Gold-Tantalum Alloy Films Deposited by High-Density-Plasma Magnetron Sputtering." J. Appl. Phys. 130, 165301 (2021); doi: 10.1063/5.0050901.

Baker, A. A. et al. 2022. "Tantalum Suboxide Films with Tunable Composition and Electrical Resistivity Deposited by Reactive Magnetron Sputtering." Coatings 12, 917 (2022); doi: 10.3390/coatings12070917.

Moody, J. D. et al. 2022. "Increased Ion Temperature and Neutron Yield Observed in Magnetized Indirectly Driven D2-Filled Capsule Implosions on the National Ignition Facility." Phys. Rev. Lett. 129, 195002 (2022); doi: 10.1103/physrevlett.129.195002.

Engwall, A.M. et al. "Energetic Condensation of Ultra-Thick Films and Coatings." Invited talk, XXV International Conference on Ion-Surface Interactions (ISI-2021).Virtual. August 2021.

Ho, D. et al. “Implosion Magnetohydrodynamics for ICF: New Physics and Capsule Designs. ” Presentation, 62nd Annual Meeting of the APS Division of Plasma Physics. Virtual. November 2020. CO05.00011.

Moody, J. D. et al. "Magnetically-Assisted Ignition Project on the National Ignition Facility." Presentation, 61st Annual Meeting of the APS Division of Plasma Physics, Fort Lauderdale, FL. October 2019. TO6.00004.

Strozzi, D. J. et al. "NIF Hohlraum Modeling for Magnetically-Assisted Ignition." Presentation, 61st Annual Meeting of the APS Division of Plasma Physics, Fort Lauderdale, FL. October 2019. TO6.00005.

Zimmerman G. B. et al. "Novel MHD features in Indirect- and Direct-Drive Magnetized ICF Implosions." Presentation, 61st Annual Meeting of the APS Division of Plasma Physics. Fort Lauderdale, FL. October 2019. TO6.00006.

J. D. Moody et al. "Progress in Hohlraum Experiments and Plans for Magnetized HED Science." Presentation, Conference on High Intensity Laser and Attosecond Science, Tel-Aviv, Israel. December 2019.

Sio, H. et al. "Diagnosing Plasma Magnetization in Inertial Confinement Fusion (ICF) Implosions using Secondary DT Reactions." Presentation, 23rd Topical Conference on High Temperature Plasma Diagnostics, Virtual. December 2020.

Strozzi, D. J. et al. 2020. "Magnetically Assisted Ignition on NIF." Presentation, Z-Net Conference, San Diego, CA. January 2020.

Sio, H. et al. "Magnetized Inertial Confinement Fusion (ICF) Implosion Development at the National Ignition Facility (NIF)." First Z-Net-US Workshop, La Jolla, CA. January 2020.

Strozzi, D. J. et al. "Design of First Magnetized Hohlraum-Driven Implosions on NIF." Presentation, 62nd Annual Meeting of the APS Division of Plasma Physics, Virtual. November 2020. CO5.00008.

Moody, J. D. et al. "Development of a Magnetically-Assisted Ignition Experimental Platform for the National Ignition Facility." Presentation, 62nd Annual Meeting of the APS Division of Plasma Physics. Virtual. November 2020. CO5.00009.

Ho, D. et al. "Implosion Magnetohydrodynamics for ICF: New Physics and Capsule Designs." Presentation, 62nd Annual Meeting of the APS Division of Plasma Physics, Virtual. November 2020. CO5.000011.

Walsh, C. et al. "Investigating the Suppression of Burn in a Magnetized ICF Plasma." Presentation, 62nd Annual Meeting of the APS Division of Plasma Physics, Virtual. November 2020. CO5.000013.

Moody, J. D. et al. "Progress on the Magnetized Ignition Experimental Platform for the National Ignition Facility." Presentation, 63rd Annual Meeting of the APS Division of Plasma Physics, Pittsburgh, PA. November 2021. UO04.00007.

Sio, H. et al. "Secondary DT Neutron Spectra in Magnetized Indirect-Drive Implosions." Presentation, 63rd Annual Meeting of the APS Division of Plasma Physics, Pittsburgh, PA. November 2021. UO04.00009.

Strozzi, D. J. "First Magnetized Hohlraum-Driven Implosions on the NIF." Presentation, 63rd Annual Meeting of the APS Division of Plasma Physics, Pittsburgh, PA. November 2021. UO04.00008.

Zimmerman, G. et al. "Magnetized ICF: Role of E-Thermal Conductivity on Imploding Shock and High-Yield Capsule Designs." Presentation, 63rd Annual Meeting of the APS Division of Plasma Physics, Pittsburgh, PA. November 2021. UO04.00010.

O'Neill, S. T. et al. "Modelling Burn Physics in a Magnetized ICF Plasma." Presentation, 63rd Annual Meeting of the APS Division of Plasma Physics, Pittsburgh, PA. November 2021. UO04.00012.

Bayu Aji, L. B. et al. "A Combinatorial Approach to Developing Sputter-Deposited Heavy-Metal Alloy Films for ICF Applications." Presentation, International Conference on Metallurgical Coatings and Thin Films (ICMCTF-22). San Diego, CA. May 2022.

Kucheyev, S. O. et al. "Target Erosion Effects During HiPIMS Deposition of Ultrathick Au-Ta Alloy Films." Presentation, International Conference on Metallurgical Coatings and Thin Films (ICMCTF-22). San Diego, CA. May 2022.

Engwall, A. et al."Fabrication of Au-Ta Hohlraums for Magnetically-Assisted Ignition Targets." Presentation, Target Fabrication Specialist Meeting, Los Alamos National Laboratory. Virtual. June 2022.

Kucheyev, S. O. et al. "Overview of Plasma-Assisted Deposition Research for Laser Targets at LLNL." Presentation, Target Fabrication Specialist Meeting, Los Alamos National Laboratory. Virtual. June 2022.

Bayu Aji, L. B. et al. "Novel Alloys for Magnetized Ignition Hohlraums." Presentation, Target Fabrication Specialist Meeting Los Alamos National Laboratory. Virtual. June 2022.