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Sep 1

Modeling hohlraum wall expansion with higher-moment multi-species fluid model

C. D. Decker, C. J. Bruulsema, W. A. Farmer, J. Harte, D. P. Higginson, A. J. Kemp, W. Riedel, J. S. Ross, D. J. Strozzi, G. Zimmerman

Physics of PlasmasSep 1, 2026AI, Modeling & Simulation Inertial Fusion & HEDP

We examine the validity of a multi-species 13-moment fluid approach to modeling hohlraum wall expansion occurring in inertial confinement fusion targets used at the National Ignition Facility. We compare our simulation to experiments conducted at the Omega laser facility [Pape et al., Phys. Rev. Lett. 124, 025003 (2020)], which produced counter-propagating gold–carbon plasmas, a phenomenon arising during hohlraum wall expansion. The two experiments we use to benchmark this fluid model produced counter-propagating gold–carbon plasmas in (1) vacuum and (2) a helium atmosphere. We find that simulations using this advanced fluid model replicate certain aspects of the vacuum experiment, such as material interpenetration, and distinct anisotropic gold and carbon ion temperatures are not captured with single-species lower-moment fluid models. However, our simulations underpredict the temperature of scarce gold ions that penetrate deep into the carbon—a phenomenon potentially requiring a kinetic treatment to model. When applied to the helium gas filled experiment, this advanced fluid model matches the amount of material mixing and gold stagnation point but overpredicts ion temperatures in the gold. Finally, we examine the applicability of single fluid models (as well as lower-order multi-species models) by comparing simulated plasma quantities vs the helium gas-fill density. As expected, we find the models converge as the helium gas density is increased. We find that for gas-fill densities larger than 0.6 mg/cm3 the single fluid model gives similar bulk plasma densities and temperatures as the multi-fluid 13-moment model. However, for gas-fill densities lower than 1.0 mg/cm3, simulations show substantial low-z material mixing in the gold—requiring multi-species modeling. Moreover, accurately modeling the low-z mixing to within 30% requires the full multi-species 13-moment fluid model.

Lawrence Livermore National Laboratory

Aug 24

Helical jets driven by a ring of laser irradiation

Kian Orr, Brandon K. Russell, Kirill Lezhnin, Yang Zhang, Geoffrey Pomraning, Petros Tzeferacos, Hantao Ji, Lan Gao

arXiv (physics.plasm-ph)Aug 24, 2026AI, Modeling & Simulation Inertial Fusion & HEDP

Plasma jets are formed in various astrophysical systems as plasma is rapidly ejected from a source, with a subset of these jets being magnetized and having a helical structure. Here, we demonstrate that helical jets may be formed using a ring of laser pulses that arrive on planar foils sequentially with increasing energy. The formation of the jets and their properties, including kinetic helicity, are studied through a set of three-dimensional magneto-hydrodynamics simulations with conditions informed by the parameters of the OMEGA laser facility. We find that jets with a higher degree of helicity may be generated under realistic experimental conditions when compared to a uniform jet. Synthetic x-ray and Thomson scattering diagnostics computed from simulated data demonstrate that the helical jet provides a unique fingerprint in both its morphology and plasma parameters. This laboratory helical jet platform may allow for controlled experimental study of the dynamics of helical plasma structures and, through interaction with other jets or targets, can allow for studies of shear-driven turbulence and mixing relevant to interactions between astrophysical jets and ambient clouds or crosswind.

Princeton UniversityUniversity of RochesterPrinceton Plasma Physics Laboratory

Aug 19

Informing spectral models for dense plasmas with K-edge absorption measurements of warm dense copper

T. Cordova, E. V. Marley, D. A. Chin, R. A. London, S. B. Hansen, S. M. Vinko, J. E. Pask, H. A. Scott, H. P. Le, D. Aberg, et al.

arXiv (physics.plasm-ph)Aug 19, 2026Inertial Fusion & HEDP

Warm dense matter remains a challenging regime to characterize experimentally and to model with predictive accuracy. Recent experimental platforms have been developed to generate, characterize, and diagnose uniform warm dense matter, enabling detailed comparisons with models. Here, we present experiments conducted at the OMEGA laser facility that compress and heat a buried layer target to warm dense matter conditions, where the targets are heated to temperatures of approximately 20 eV and compressed to densities of 25 g/cm^3. We probe the warm dense plasma using x-ray absorption spectroscopy, using the K-edge and bound-bound absorption features to constrain the temperature and charge state distribution of the plasma. We compare these measurements with two types of models: collisional-radiative models with detailed electronic structure and ad-hoc density effects, and a multi-ion model based on density functional theory in combination with excited-state projector augmented-wave potentials. Neither approach fully reproduces the observed data, We show that the broad structure and position of the K-edge region can be modeled using density functional theory in combination with excited-state projector augmented-wave potentials. The density functional theory results are contrasted with a collisional-radiative model approach that incorporates ad-hoc density effects, which show incomplete agreement with the experimental observations, highlighting a need for improved density-dependent atomic modeling in warm dense plasmas.

University of California San DiegoUniversity of OxfordUniversity of RochesterSandia National LaboratoryLawrence Livermore National Laboratory

Aug 17

A theoretical model for quantifying the imprinting sensitivity of direct-drive inertial confinement fusion implosions

Dongxue Liu, Jiaqin Dong, Yunxing Liu, Zhiyu HE He, Wei Wang, Yuqiu Gu, Xiuguang Huang, Jian Zheng

Nuclear FusionAug 17, 2026AI, Modeling & Simulation Inertial Fusion & HEDP

To quantify the sensitivity of diverse implosion designs to laser imprinting, we developed an equivalent perturbation model that maps laser imprinting as the initial target surface perturbation. By incorporating imperfections in target fabrication and thermal smoothing in the plasma, the model shows a reduced implosion sensitivity to laser imprinting, extending the analysis beyond geometric irradiation. The imprinting sensitivity threshold is defined as δh_{proxy}/δh{tar}(0)= 0.1, where δh_{proxy} is the imprinting amplitude and δh{tar}(0) is the initial target perturbation amplitude. Radiation-hydrodynamics simulations confirm that whenδh_{proxy}/δh{tar}(0)< 0.1, variations in nonlinear onset time and adiabat remain within 12\% of that with δh{tar}(0) alone. Moreover, the imprinting sensitivity is supported by OMEGA experiments. Overall, for linear perturbations of medium-to-high modes in direct-drive, the model enhances our physical understanding of how laser and target perturbations evolve and serves as a simplified tool to optimize implosion performance.

University of Science and Technology China

Aug 11

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

Jul 7

Inferring performance metrics for laser direct drive experiments on OMEGA

V. Gopalaswamy, L. Ceurvorst, A. Lees, D. Patel, J. P. Knauer, R. C. Shah, R. Betti

Physics of PlasmasJul 7, 2026Control & Diagnostics AI, Modeling & Simulation Inertial Fusion & HEDP

Quantifying performance improvements on the OMEGA laser facility requires robust inference of established no-alpha performance metrics, which requires, at minimum, a model to infer the shocked fuel mass and pressure of the confined fusion plasma. In this work, we describe the methodology used to infer performance metrics on OMEGA and present the current state-of-the art model used to infer these metrics from OMEGA experiments. In particular, since neutron images of cryogenic implosions are not available on OMEGA at present, we present how x-ray sizes are determined on OMEGA using a Gaussian Process regression model and how the neutron production region's size is inferred from them. We end by benchmarking the model using synthetic data and 1-D LILAC simulations and test its experimental self-consistency across available x-ray diagnostic channels.

University of RochesterLaboratory for Laser Energetics