Recent Publications

Quantum effects in plasmas

M. Bonitz, H. Kählert, D. Krimans, C. Makait, P. Hamann, J. Vorberger, Zh. Moldabekov, S. X. Hu, V. V. Karasiev, D. Kraus, et al.

The year 2025 has been designated by UNESCO as the International Year of Quantum Science and Technology. One hundred and twenty-five years ago, Max Planck's discovery of radiation quanta started the quantum era, and 100 years ago, quantum mechanics was developed by Schrödinger, Heisenberg, Bohr, Pauli, Dirac, Born, Fermi, and many others. By now, quantum mechanics is the theoretical foundation of most fields of physics and chemistry, and it is the basis for modern nanotechnology. How about plasma physics? How important are quantum effects in plasmas? In what experiments are quantum effects observed, and where do they govern the behavior of plasmas? How can these effects be treated theoretically and via computer simulations? Starting with a brief historical overview, we discuss the broad parameter range that is the characteristic of plasmas and outline where quantum effects are relevant. This is the case primarily for warm dense matter and inertial fusion plasmas. We provide an overview of the theoretical quantum methods that are available for these dense plasmas and how their respective advantages can be combined in order to achieve predictive capability. The key is a downfolding approach that is based on first-principles simulations.

Moments in time: Numerical analysis of a method for time-resolved neutron spectroscopy

C. B. Stuart, B. Appelbe, A. J. Crilly, C. Forrest, A. DeVault, M. Gatu Johnson, B. J. Lahmann, D. Schlossberg, S. P. Regan, G. Gregori

Time-resolved neutron information is essential for understanding the dynamics of inertial confinement fusion (ICF) implosions, providing key indicators that distinguish igniting from non-igniting plasmas and revealing the underlying causes of shot-to-shot performance variations. The moments method framework offers a practical pathway to extract such temporally resolved quantities using only a small number of neutron time-of-flight detectors. For example, one only needs four detectors to extract the burn-averaged rate of change of ion temperature, a well-defined physically useful quantity. In this work, we evaluate and validate the moments method across several levels of complexity. We first employ a controlled toy model to test the foundational assumptions and mathematical structure of the approach. We then demonstrate that the method generalizes to realistic one-dimensional simulation data of direct drive implosions with a 25 kJ laser driver that include time-dependent ion temperature evolution and hydrodynamic burn dynamics. Together, these results establish the moments method as an experimentally accessible and robust tool for extracting unique and independent information such as the burn-averaged rates of change of fluid velocity and ion temperature with time from neutron time-of-flight measurements, broadening the diagnostic capability of existing neutron detector systems. Fielding this diagnostic on ICF campaigns would improve our understanding of failure modes, helping to determine causes for improved or reduced performance during implosions, informing future target and laser drive design.

Hall-MHD in driven turbulence FLASH simulations

A. Mohapatra, E. C. Hansen, A. Reyes, A. F. A. Bott, E. G. Blackman, P. Tzeferacos

The origin of magnetic fields in turbulent astrophysical systems has long been a central problem in plasma astrophysics. Fluctuation dynamos are a class of field amplification mechanisms that occur in turbulent magnetohydrodynamics whereby stochastically forced motions of plasma at sufficiently high magnetic Reynolds numbers exponentially amplify magnetic energy. For steady forcing, such dynamos saturate with magnetic energies at a sizable fraction of the turbulent kinetic energy. Although fluctuation dynamo is widely studied within the framework of resistive magnetohydrodynamics (MHD) and driven-turbulence numerical simulations, this work explores the difference when the Hall term is included in the magneto-fluid's generalized Ohm's law. The inclusion is motivated in part by recent high energy-density plasma experiments studying fluctuation dynamo that are governed by an extended magnetohydrodynamics (xMHD) ansatz, which includes the Hall term. We first discuss the details of the Hall-MHD implementation in the FLASH code, the tool we use to model xMHD fluctuation dynamo. We then investigate the influence of the Hall term on the fluctuation dynamo in a three-dimensional periodic box, driven with stochastic forcing at the box scale. We compare cases with a Hall term of varying magnitude to no-Hall cases with respect to the magnetic field growth rate, saturation level, and magnetic field structure. The Hall-MHD fluctuation dynamo is found to saturate at lower magnetic energies and with fewer small-scale magnetic structures than the no-Hall cases. Both findings are consistent with the interpretation that the Hall term acts as an additional, non-linear transport term, akin to an enhanced turbulent diffusivity.

Hot-spot pressure evolution in inertial confinement fusion implosions

V. N. Goncharov, D. Cao, T. J. B. Collins, R. C. Shah, A. Shvydky

Pressure in the central hot-spot region plays a key role in determining ignition conditions in inertial confinement fusion implosions. This paper investigates the evolution of hot-spot pressure during the deceleration phase. Mass ablation from the inner shell surface increases the hot-spot size, causing the pressure phs to rise faster with hot-spot convergence than predicted by the adiabatic scaling ∼Rhs−5, where Rhs is the hot-spot radius. In contrast, radiation cooling reduces phs. By analyzing the balance between radiation and mass ablation, we relate the maximum phs, relative to the adiabatic scaling, to the hot-spot properties. Beyond the well-established role of bringing most of the fuel mass into the hot spot, mass ablation increases the peak pressure by approximately 60% relative to rigid-piston compression to the same final volume, an effect that has not been included in previous studies. In addition, in hydrodynamically scaled designs, where pressure and temperature are held constant, the pressure reduction due to radiation losses changes with the size as eΠ, where Π∼Rhs0.8. Therefore, neglecting radiation losses when scaling inertial confinement fusion performance to larger systems can lead to overly optimistic projections.

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

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.

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.

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.

Limitations of post accelerating ion beams using the snowplow field in a near-critical density target

Davide Terzani, Stepan S. Bulanov, Lieselotte Obst-Huebl, Carlo Benedetti, Franklin Dollar, Eric Esarey, Axel Huebl, Aodhan McIlvenny, John Palastro, Jessica Shaw, et al.

Laser-matter interaction at relativistic intensities is central to almost every scientific case for multi-PW laser facilities. In particular, the progress in laser-driven ion acceleration brings this interaction closer to multiple applications, ranging from material science to biomedical research. One of the most important questions regarding ion acceleration is how to obtain high charge ion beams with relativistic energies. Increasing laser energy and intensity usually leads to a number of limitations on maximum achievable ion energies rooted in the fundamental properties of charged particle interaction with strong electromagnetic fields. Following advances in staged laser-plasma electron acceleration, staged ion acceleration could offer a path to relativistic energies. Here, such scheme is explored and the possibility of scaling the acceleration of ion beams to relativistic energies is discussed.

Superpermeation and Compression Through Vanadium Foil

Joshua Ruby, Zachary Robinson, W. Udo. Schröder, Matthew Sharpe

Multi-petawatt physics at new and future laser user facilities

Jonathan D. Zuegel, Antonino Di Piazza, Karl M. Krushelnick, Daniele Margarone

The mini-conference on Multi-Petawatt Physics at New and Future Laser User Facilities, held at the 2024 Annual Meeting of the American Physical Society Division of Plasma Physics, updated worldwide progress at the frontier of multi-petawatt physics, including theoretical, computational, experimental, and technical advances.

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

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.

Energy-optimized scaling laws for self-guided laser wakefield accelerators

Petr Valenta, Marcel Lamač, Kyle G. Miller, Brandon K. Russell, Gabriele M. Grittani, Alec G. R. Thomas, Sergei V. Bulanov

Laser wakefield acceleration promises compact electron accelerators for applications in medicine, industry, and fundamental science. Yet, despite rapid progress, accurately predicting the electron energy attainable in a given experimental configuration and the acceleration length required to reach it remains an open challenge. Here we use Bayesian optimization combined with advanced particle-in-cell simulation techniques to determine the maximum electron energy that a self-guided laser wakefield accelerator driven by a laser of a given energy and wavelength can produce. By systematically optimizing the accelerator performance across a range of laser energies and wavelengths, we derive energy-optimized scaling laws. These scaling laws yield the highest electron energy over the shortest acceleration length possible, are expressed solely in terms of laser energy and wavelength, and are accompanied by the complete set of laser and plasma parameters required to enable the scaling. The resulting scaling laws provide practical guidance for designing state-of-the-art laser wakefield acceleration experiments operating at their fundamental performance limits.

Transforming Water Detritiation: Process Design and AI-Driven Material Selection

Rashad Ahmadov, Joshua Ruby, Mark Wittman, Zachary Robinson, Matthew Sharpe

Updating the Gas Chromatography Methodology for Measuring Hydrogen Isotopologues at the Laboratory for Laser Energetics

Matthew Sharpe

Experimental demonstration of Flying-Focus enhanced Thomson scattering

E. Gerstmayr, C. Mariani, R. Fitzgarrald, M. VanDusen-Gross, C. Berger, Q. Chen, A. Di Piazza, M. S. Formanek, D. H. Froula, C. G. R. Geddes, et al.

We report the experimental demonstration of a spatiotemporally engineered "Flying-Focus" laser pulse for enhanced x-ray generation in relativistic Thomson scattering. A combination of longitudinal chromatic aberration, angular dispersion, and group delay dispersion was applied to an ultrashort relativistically intense laser pulse to control the motion of its focal point. Precise tuning of the group delay dispersion was used to match the velocity of the focus to the trajectory of a counterpropagating electron bunch, produced by a laser wakefield accelerator. This prolonged the Thomson scattering interaction while reducing nonlinear effects, leading to an enhanced x-ray yield. The approach has the potential to increase the spectral density and brightness of the x-ray beam by orders of magnitude compared to equivalent focusing without spatiotemporal control. This experiment establishes a new technique for structured-light control at high intensity, demonstrating the realization of dynamic intensity structures that enhance light-matter interactions and for the generation of ultra-bright radiation sources.

Study of shock wave dynamics in strong magnetic fields

Z. J. Minaker, V. V. Ivanov, R. C. Mancini, L. S. Leal, A. V. Maximov

Shock waves in magnetized plasmas are central in many astrophysical systems, yet laboratory measurements have remained limited by 10–20 T. This work studies the dynamics of shock waves without and with magnetic fields as strong as 100–150 T generated by the 1 MA pulsed power machine. A shock wave in hydrogen was produced by a 0.8 ns laser pulse with intensity of 5 × 1014 W/cm2. Laser imaging diagnostics including multi-frame and two-color interferometry, shadowgraphy, and schlieren imaging providing sub-nanosecond temporal and 10 μm spatial resolution of shock wave evolution. The density of hydrogen gas was in the range of (2–10) × 1018 cm−3. Results show that without an applied magnetic field, shock waves expand symmetrically with velocities up to 1600 km/s. For shock waves in a magnetic field there is suppressed radial expansion perpendicular to the B-field and enhanced azimuthal expansion parallel to the B-field. In hydrogen, a laser-initiated ionization wave formed ahead of the shock waves. Plasma instability was observed on the front of the shock wave in the magnetic field. MHD simulations confirm that magnetic fields modify the shock wave conditions, with velocity anisotropy scaling with field strength, establishing a laboratory platform to study magnetically mediated and collisionless shock wave physics.

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

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.