On December 5, 2022, an indirect drive fusion implosion on the National Ignition Facility (NIF) achieved a target gain G_{target} of 1.5. This is the first laboratory demonstration of exceeding "scientific breakeven" (or G_{target}>1) where 2.05 MJ of 351 nm laser light produced 3.1 MJ of total fusion yield, a result which significantly exceeds the Lawson criterion for fusion ignition as reported in a previous NIF implosion [H. Abu-Shawareb et al. (Indirect Drive ICF Collaboration), Phys. Rev. Lett. 129, 075001 (2022)PRLTAO0031-900710.1103/PhysRevLett.129.075001]. This achievement is the culmination of more than five decades of research and gives proof that laboratory fusion, based on fundamental physics principles, is possible. This Letter reports on the target, laser, design, and experimental advancements that led to this result.

In Fiscal Year 2019 (FY19), Lawrence Livermore National Laboratory’s (LLNL’s) High- Energy-Density Physics (HED) and Indirect Drive Inertial Confinement Fusion (ICF-ID) programs conducted numerous campaigns on the OMEGA and OMEGA-EP (EP) laser systems. This was the 21st year of National Lab collaborative experiments at OMEGA since the Nova Laser at LLNL shut down in 1999, building upon prior collaborations. In FY19 overall, these LLNL programs led 488 target shots, with 259 shots using just the OMEGA laser system and 229 shots using just the EP laser system. Approximately 33% of the total number of shots (84 OMEGA shots and 79 EP shots) supported the Indirect Drive Inertial Confinement Fusion Campaign. The remaining 67% (175 OMEGA-only shots and 150 EP-only shots) were dedicated to experiments for High-Energy-Density Physics. Highlights of the various HED and ICF-ID campaigns are summarized in the following reports. In addition to these experiments, LLNL Principal Investigators (PIs) led a variety of Laboratory Basic Science campaigns using OMEGA and EP, including 80 target shots using just OMEGA, 68 shots using just EP, and 7 Joint shots using both lasers together. The highlights of these are also summarized, following the ICF and HED campaigns. Overall, LLNL PIs led a total of 636 shots at LLE in FY 2019. In addition, LLNL PIs supported 7 NLUF shots on Omega and 32 NLUF shots on EP in collaboration with the academic community.

The Capseed campaign goal is to measure shock front velocity non-uniformities in Inertial Confinement Fusion (ICF) ablator materials and quantify the level of non-uniformity caused by intrinsic effects. This is done using the Omega High Resolution Velocimeter (OHRV) to obtain velocity maps of the optically reflecting shock front following release of the ablator material into either PMMA for the warm experiments or cryogenic deuterium for the cryo experiments. For the three half-days in FY17 the focus was twofold: complete measurements on the impact of oxygen heterogeneity and oxygen mitigation layers for glow discharge polymer (GDP), and begin measuring velocity non-uniformities on deep release from Be, GDP, and highdensity carbon (HDC) into D2 with improved velocity sensitivity.

Hydrodynamic mix of the ablator into the DT fuel layer and hot spot can be a critical performance limitation in inertial confinement fusion implosions. This mix results in increased radiation loss, cooling of the hot spot, and reduced neutron yield. To quantify the level of mix, we have developed a simple model that infers the level of contamination using the ratio of the measured x-ray emission to the neutron yield. The principal source for the performance limitation of the “low-foot” class of implosions appears to have been mix. Lower convergence “high-foot” implosions are found to be less susceptible to mix, allowing velocities of >380 km/s to be achieved.

Alpha-particle self-heating, the process of deuterium–tritium fusion reaction products depositing their kinetic energy locally within a fusion reaction region and thus increasing the temperature in the reacting region, is essential for achieving ignition in a fusion system. Here, we report new inertial confinement fusion experiments where the alpha-particle heating of the plasma is dominant with the fusion yield produced exceeding the fusion yield from the work done on the fuel (pressure times volume change) by a factor of two or more. These experiments have achieved the highest yield (26 ± 0.5 kJ) and stagnation pressures (≍220 ± 40 Gbar) of any facility-based inertial confinement fusion experiments, although they are still short of the pressures required for ignition on the National Ignition Facility (∼300–400 Gbar). These experiments put us in a new part of parameter space that has not been extensively studied so far because it lies between the no-alpha-particle-deposition regime and ignition.

In FY16, LLNL’s High-Energy-Density Physics (HED) and Indirect Drive Inertial Confinement Fusion (ICF-ID) programs conducted several campaigns on the OMEGA laser system and on the EP laser system, as well as campaigns that used the OMEGA and EP beams jointly. Overall, these LLNL programs led 430 target shots in FY16, with 304 shots using just the OMEGA laser system, and 126 shots using just the EP laser system. Approximately 21% of the total number of shots (77 OMEGA shots and 14 EP shots) supported the Indirect Drive Inertial Confinement Fusion Campaign (ICF-ID). The remaining 79% (227 OMEGA shots and 112 EP shots) were dedicated to experiments for High-Energy-Density Physics (HED). Highlights of the various HED and ICF campaigns are summarized in the following reports. In addition to these experiments, LLNL Principal Investigators led a variety of Laboratory Basic Science campaigns using OMEGA and EP, including 81 target shots using just OMEGA and 42 shots using just EP. The highlights of these are also summarized, following the ICF and HED campaigns. Overall, LLNL PIs led a total of 553 shots at LLE in FY 2016. In addition, LLNL PIs also supported 57 NLUF shots on Omega and 31 NLUF shots on EP, in collaboration with the academic community.

In FY15, LLNL’s High-Energy-Density Physics (HED) and Indirect Drive Inertial Confinement Fusion (ICF-ID) programs conducted several campaigns on the OMEGA laser system and on the EP laser system, as well as campaigns that used the OMEGA and EP beams jointly. Overall these LLNL programs led 468 target shots in FY15, with 315 shots using just the OMEGA laser system, 145 shots using just the EP laser system, and 8 Joint shots using Omega and EP together. Approximately 25% of the total number of shots (56 OMEGA shots and 67 EP shots, including the 8 Joint shots) supported the Indirect Drive Inertial Confinement Fusion Campaign (ICF-ID). The remaining 75% (267 OMEGA shots and 86 EP shots) were dedicated to experiments for High-Energy-Density Physics (HED). Highlights of the various HED and ICF campaigns are summarized in the following reports.

Experiments have recently been conducted at the National Ignition Facility utilizing inertial confinement fusion capsule ablators that are 175 and 165  μm in thickness, 10% and 15% thinner, respectively, than the nominal thickness capsule used throughout the high foot and most of the National Ignition Campaign. These three-shock, high-adiabat, high-foot implosions have demonstrated good performance, with higher velocity and better symmetry control at lower laser powers and energies than their nominal thickness ablator counterparts. Little to no hydrodynamic mix into the DT hot spot has been observed despite the higher velocities and reduced depth for possible instability feedthrough. Early results have shown good repeatability, with up to 1/2 the neutron yield coming from α-particle self-heating.

We report on the first layered deuterium-tritium (DT) capsule implosions indirectly driven by a "high-foot" laser pulse that were fielded in depleted uranium hohlraums at the National Ignition Facility. Recently, high-foot implosions have demonstrated improved resistance to ablation-front Rayleigh-Taylor instability induced mixing of ablator material into the DT hot spot [Hurricane et al., Nature (London) 506, 343 (2014)]. Uranium hohlraums provide a higher albedo and thus an increased drive equivalent to an additional 25 TW laser power at the peak of the drive compared to standard gold hohlraums leading to higher implosion velocity. Additionally, we observe an improved hot-spot shape closer to round which indicates enhanced drive from the waist. In contrast to findings in the National Ignition Campaign, now all of our highest performing experiments have been done in uranium hohlraums and achieved total yields approaching 10^{16} neutrons where more than 50% of the yield was due to additional heating of alpha particles stopping in the DT fuel.

by the Advanced Radiographic Capability laser ([Formula: see text] kJ, 10 ps) can deliver significantly higher spatiotemporal resolution [M. P. Hill et al., Rev. Sci. Instrum. 92, 033535 (2021)], especially in high-opacity samples. Initial experiments revealed problematic brightness and spectral gradients from this source, but by radiographing a set of diamond-turned, 105 µm-thick Pb test objects and supported by simulations using the 3D Monte Carlo code GEANT4, these geometry-dependent gradients across the field of view are quantified and mitigation strategies are assessed. In addition to significantly enhancing the modulation transfer function compared to the existing system, image stacking from multiple layers of image plate is shown to almost double the signal to noise ratio that will reduce uncertainties in future dynamic strength experiments.

In FY14, LLNL’s High-Energy-Density Physics (HED) and Indirect Drive Inertial Confinement Fusion (ICF-ID) programs conducted several campaigns on the OMEGA laser system and on the EP laser system, as well as campaigns that used the OMEGA and EP beams jointly. Overall these LLNL programs led 324 target shots in FY14, with 246 shots using just the OMEGA laser system, 62 shots using just the EP laser system, and 16 Joint shots using Omega and EP together. Approximately 31% of the total number of shots (62 OMEGA shots, 42 EP shots) shots supported the Indirect Drive Inertial Confinement Fusion Campaign (ICF-ID). The remaining 69% (200 OMEGA shots and 36 EP shots, including the 16 Joint shots) were dedicated to experiments for High- Energy-Density Physics (HED). Highlights of the various HED and ICF campaigns are summarized in the following reports.

EP shots) supported the Indirect Drive Inertial Confinement Fusion Campaign. The remaining 67% (175 OMEGA-only shots and 150 EP-only shots) were dedicated to experiments for High-Energy-Density Physics. Highlights of the various HED and ICF-ID campaigns are summarized in the following reports. In addition to these experiments, LLNL Principal Investigators (PIs) led a variety of Laboratory Basic Science campaigns using OMEGA and EP, including 80 target shots using just OMEGA, 68 shots using just EP, and 7 Joint shots using both lasers together. The highlights of these are also summarized, following the ICF and HED campaigns. Overall, LLNL PIs led a total of 636 shots at LLE in FY 2019. In addition, LLNL PIs supported 7 NLUF shots on Omega and 32 NLUF shots on EP in collaboration with the academic community.

The x-ray laser is now being used at LLNL as a tool for measuring the behaviors of hot dense plasmas. In particular, we have used the 155{Angstrom} yttrium laser to study transient plasmas by both radiography and moire deflectrometry. These techniques have been used to probe long scale length plasmas at electron densities exceeding 10{sup 22}cm{sup {minus}3}. Recent advances in multilayer technology have made it possible to directly image ion densities in directly driven thin foils to an accuracy of 1--2 {mu}m. In addition, we have constructed an x-ray laser Mach-Zehnder interferometer using multilayer beam-splitters. This interferometer yields direct 2D projections of electron densities in plasmas with micron spatial resolution. In addition, this interferometer can be used to measure spectral line shapes to high accuracy. Among the subject plasmas under study are laser irradiated planar targets, gold hohlraums, and x-ray lasers themselves.

Collisionally pumped soft x-ray lasers now operate over a wavelength range extending from 35 to 300 Å. These well-characterized sources have high peak brightness (GeV blackbody temperature) and narrow bandwidth making them ideal for x-ray imaging and interferometry. We will describe experiments which have used the yttrium neon-like x-ray laser operating at 155 Å to probe plasmas at electron densities exceeding 4×1021 cm−3. The short pulse duration of this x-ray laser (∼150 ps) has made it possible to image directly driven thin foils with 1–2 μm spatial resolution. Advances in multilayer mirrors and beam splitters have now also made it possible to develop x-ray laser interferometers. We will describe initial experiments to probe plasmas relevant to ICF using x-ray laser interferometry. The progress in the development of short pulse x-ray lasers (∼30 ps) which are ultimately necessary to extend x-ray laser diagnostic techniques to higher densities will also be presented.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation L. B. Da Silva, T. W. Barbee, R. Cauble, P. Celliers, J. Harder, S. Libby, H. R. Lee, R. A. London, D. L. Matthews, S. Mrowka, J. C. Moreno, D. Ress, J. E. Trebes, A. Wan, F. Weber; X‐ray lasers for imaging and plasma diagnostics. AIP Conf. Proc. 1 May 1995; 332 (1): 553–558. https://doi.org/10.1063/1.47989 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search