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Sep 30

Modulated deuteron spectra observed with the magnetic recoil neutron spectrometer at the National Ignition Facility

Bao Nguyen, Yousef Lawrence, Christopher Wink, Timothy Mark Johnson, Niels Vanderloo, Benjamin Reichelt, Amber Hennessy, Daniel Thomas Casey, Dave Schlossberg, Nathan Masters, et al.

Journal of Plasma Physics5 days agoControl & Diagnostics AI, Modeling & Simulation Inertial Fusion & HEDP

The Magnetic Recoil Spectrometer (MRS) at the National Ignition Facility is used to measure the neutron spectrum from deuterium–tritium-fuelled inertial confinement fusion implosions via neutron–deuteron elastic scattering and magnetic dispersion of recoil deuterons. From the MRS-determined neutron spectrum, the yield ( upper Y Subscript n Y n $Y_n$ ), apparent ion temperature ( upper T Subscript i T i $T_i$ ) and areal density ( rho upper R ρ R $\rho R$ ) are determined. However, anomalous energy modulations in recoil deuterons have been observed in several high-yield indirect drive experiments ( upper Y Subscript n Baseline tilde 10 Superscript 16 Baseline minus 10 Superscript 18 Y n ∼ 10 16 − 10 18 $Y_n\sim 10^{16}{-}10^{18}$ ). These observations raise concerns about their potential impact on the MRS-inferred performance metrics. Analytic calculations and particle-in-cell simulations are used to examine the possible beam–plasma instabilities, which indicate the two-stream instability as a plausible mechanism behind energy modulations. Based on a statistical analysis of synthetic deuteron spectra, the modulation-induced errors are found to be within the errors of the determined upper Y Subscript n Y n $Y_n$ , upper T Subscript i T i $T_i$ and rho upper R ρ R $\rho R$ values and thus do not have a significant impact on the MRS measurement.

Imperial College LondonLawrence Livermore National LaboratoryLos Alamos National LaboratoryMassachusetts Institute of TechnologyGeneral Atomics

Sep 17

Indirect-Drive Fusion Target Design for Commercial Fusion Energy

C. R. Weber, A. L. Kritcher, S. Bhandarkar, T. Briggs, T. Chapman, T. M. Fears, B. A. Hammel, D. D. -M. Ho, O. Hurricane, B. Kozioziemski, et al.

arXiv (physics.plasm-ph)Sep 17, 2026Fusion Plant Engineering AI, Modeling & Simulation Inertial Fusion & HEDP

This paper presents the physics basis for commercially relevant laser indirect-drive (LID) (radiation-driven) inertial fusion energy (IFE) using a 10 MJ laser driver. To date, this approach, proven at the National Ignition Facility (NIF), remains the first and only controlled fusion method to demonstrate the key physics required for fusion energy production, including a self-sustained burning plasma, substantially de-risking the path to commercial fusion energy. Building directly on these results, we present scaled designs to larger target sizes and fusion gains relevant for commercial power generation ($G\sim 26$--$43$). The designs remain close to experimentally demonstrated ignition physics, modifying target components to improve scalability, manufacturability, and cost-effectiveness for fusion energy applications while preserving ignition-relevant implosion physics and fusion power plant compatibility. The baseline platform retains a high-density carbon ablator and clean cryogenic DT fuel layering while extending ignition platforms to substantially larger fuel masses (exceeding 10 times that of current ignition experiments at the NIF) and higher burn fractions ($\sim$40\%) with total areal densities at stagnation of $\sim$3~g/cm$^2$. Benchmarked simulations anchored to NIF ignition experiments (using HYDRA and LASNEX) predict that these designs achieve robust ignition and propagating burn at substantially higher fusion yields (265--427~MJ) with significant ignition margin (2--4$\times$ relative to NIF) against hydrodynamic instabilities and representative power-plant non-idealities, including low-mode asymmetry, polycrystalline DT ice roughness, HDC ablator voids, and target-support and fill-hole perturbations. We also show that implosion symmetry and laser-plasma interactions (LPI) can be controlled with our novel multi-beam configuration using thousands of laser beam-lines.

Lawrence Livermore National LaboratoryInertia

Aug 11

Modeling stimulated Brillouin backscatter from the inner laser cones during indirect-drive inertial confinement fusion experiments at the National Ignition Facility

A. J. Kemp, T. Chapman, L. Divol, D. P. Higginson, E. Kur, N. Lemos, S. MacLaren, P. Michel, D. J. Strozzi, G. B. Zimmerman

Physics of PlasmasAug 11, 2026AI, Modeling & Simulation Inertial Fusion & HEDP

We report progress modeling stimulated Brillouin scatter (SBS) at the National Ignition Facility (NIF). For indirect-drive, ignition-relevant hohlraum experiments, backward SBS light is a long-standing concern due to its potential for damaging laser optics as well as affecting the symmetry of the x-ray field that drives capsule implosions. To model SBS, we use maps of underdense plasma conditions, i.e., temperatures, densities, materials, charge states, and flows, from hydrodynamics simulations of the hohlraum to run backscatter simulations with the code pF3D [Berger et al., Phys. Plasmas 26, 012709 (2019)]; the latter calculates propagation of incident- and backscattered light of a NIF quad in the paraxial approximation. For the inner cone quads, in designs that utilize significant wavelength detuning, i.e., those that use cross-beam energy transfer to control implosion symmetry, this approach typically has overestimated both the peak power and the duration of SBS measured in experiments. In this work, we discuss how multi-species hydrodynamics simulations can lead to better agreement with experiments through changes to the simulated plasma conditions and the resulting SBS growth rates. Specifically, we discuss SBS reflectivity in the 23° and 30° inner cone quads, compare simulated spectra to FABS measured ones, and discuss how the time history of the backscattered light is related to the absorption/refraction of the incoming light off density features in the hohlraum plasma.

Lawrence Livermore National Laboratory

X-ray diagnostics, analysis, verification, and exploration (xDAVE) code for the prediction and interpretation of x-ray Thomson scattering experiments

Hannah M. Bellenbaum, Dave A. Chapman, Maximilian P. Böhme, Thomas Gawne, Sebastian Schwalbe, Willow M. Martin, Michael Bussmann, Dirk O. Gericke, Uwe Hernandez Acosta, Jan Vorberger, et al.

Physics of PlasmasAug 11, 2026Control & Diagnostics AI, Modeling & Simulation Inertial Fusion & HEDP

X-ray Thomson scattering (XRTS) is a common diagnostic used in the warm dense matter (WDM) regime to estimate plasma parameters like density, temperature, and charge state. Experimental analysis typically relies on a forward model to obtain estimates for these parameters, as the measured spectrum is a convolution of the dynamic structure factor (DSF) and the source-instrument function. The Chihara decomposition, where the spectrum is separated into contributions from bound and free electrons, is commonly used to estimate DSFs in the WDM regime, as it allows for the fast calculation of DSFs and therefore can easily be applied in a large-scale parameter optimization. Due to the limited availability of XRTS codes, we present “x-ray diagnostics, analysis, verification, and exploration”, a code designed to quickly estimate DSFs using the Chihara decomposition and analyze experimental spectra. The code is validated by re-analyzing an experiment with isochorically heated beryllium at the OMEGA Laser Facility. In addition, we demonstrate the applicability of the code to plan experiments and predict scattering spectra through the coupling to a ray-tracing code. Finally, the importance of accounting for the energy-dependence of spectrometer instrument functions is demonstrated by comparing ray-tracing simulations to the standard convolution for strongly compressed beryllium experiments at the National Ignition Facility, similar to previously published results.

First Light FusionLawrence Livermore National Laboratory

Aug 10

Size scaling of acceleration phase energetics and its effects on direct-drive DT-layered implosions

D. Patel, R. Betti, V. Gopalaswamy, A. Lees, D. Cao, R. C. Shah

Physics of PlasmasAug 10, 2026AI, Modeling & Simulation Inertial Fusion & HEDP

A fundamental question in inertial confinement fusion is how implosion performance, and therefore ignition thresholds and fusion gain, evolve with target size. In laser-driven direct drive fusion, the scaling of laser-drive performance with size is critical to this evolution and to extrapolating results from the 30-kJ OMEGA laser-fusion experiments to ignition-class facilities such as the National Ignition Facility. Beyond the well-known adverse effects of cross-beam energy transfer (CBET) on drive performance, here we demonstrate that effects related to the non-scaling physics of thermal conduction and electron–ion energy equilibration exert an influence on drive behavior with scale that equals or surpasses that of CBET. We find that a significant portion of the lost implosion performance with increasing scale is due to the loss of shell implosion velocity. Furthermore, we show that while modest modifications to hydro-scaled designs can recover most of the lost implosion velocity, a full hydro-equivalent performance extrapolation is difficult to achieve without CBET mitigation or subcooling below the triple point of DT.

University of Rochester