Faraday rotation measurements in high-energy-density physics (HEDP) experiments using division-of-amplitude methods often suffer from image defects caused by registration errors. To address this, we developed a sub-degree Faraday rotation amplification and measurement system based on division-of-focal-plane polarimeters. Our approach utilizes Fresnel reflections from quartz glass surfaces to enhance polarization rotation, with adjustable magnification controlled by the incident angle. Experimental results demonstrate that this system eliminates registration errors while improving Faraday rotation image quality. The system achieves a high magnification factor k = -29.5 and a measurement standard deviation of 2.6 × 10-2°. The evaluation of plasma self-emission indicates that its impact on the experimental results is negligible, introducing a relative measurement error of less than 0.3%. Its compatibility with Mach-Zehnder interferometers enables direct magnetic field measurements in HEDP experiments.

Electronic response properties of high-energy density (HED) systems influence planetary structure, drive evolution of fusion targets, and underpin diagnostics in laboratory astrophysics. Real-time time-dependent density functional theory (TDDFT) offers a versatile modeling framework capable of accurately predicting the dynamic response of HED materials—including free–free, bound–free, and bound–bound contributions without requiring ad hoc state partitioning; capturing both collective and non-collective behavior; and applying within the linear-response regime and beyond. We review the theoretical formalism of real-time TDDFT as applied to HED systems, provide a practical tutorial for computing relevant response properties (dynamic structure factors, conductivity, and stopping power), and comment on avenues for further development of this powerful computational method in service of HED science.

"Simulation Techniques for High-Intensity Laser-Plasma Interactions"

X-ray Free Electron Laser (XFEL) facilities offer unprecedented opportunities to advance instrumentation for studying matter under extreme conditions. In this study, we harnessed the enhanced x-ray capabilities of XFELs to demonstrate dark field imaging in laser-driven experiments at XFEL facilities. Utilizing a Talbot x-ray interferometer, we simultaneously captured transmission, dark-field, and differential phase contrast radiographs of laser-driven metallic foils. Our work showcases the feasibility of single-shot grating-based Talbot x-ray dark-field imaging in pump-probe experiments at XFEL facilities, opening doors to a wide range of hard x-ray imaging applications in material science and high-energy density physics.

Laser wakefield acceleration (LWFA) has enabled generation of high-energy electron beams and radiation sources, which are of great importance in high-energy density physics. However, identifying the optimal laser-plasma parameters—particularly variations in laser pulse duration and focal spot size—is crucial for producing not only high-charge, high-energy electron beams but also high-brightness, high-flux betatron radiation. In this study, we investigated the optimum laser parameters for generating high-charge electron beams and betatron radiation in subcritical density plasmas (SCDP). Three-dimensional particle-in-cell (3D-PIC) simulations show that a 550 TW laser pulse can generate electron beams with charges of several tens of nanocoulombs (nC) and energies up to 500 MeV. Furthermore, these electron beams produce high-brightness x-ray radiation, achieving a peak brightness of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:mn>1.6</a:mn> <a:mo>×</a:mo> <a:msup> <a:mrow> <a:mn>10</a:mn> </a:mrow> <a:mrow> <a:mn>22</a:mn> </a:mrow> </a:msup> <a:mtext> </a:mtext> <a:mtext> </a:mtext> <a:mi>photons</a:mi> <a:mo>/</a:mo> <a:mo stretchy="false">(</a:mo> <a:mi mathvariant="normal">s</a:mi> <a:mtext> </a:mtext> <a:msup> <a:mrow> <a:mi>mm</a:mi> </a:mrow> <a:mrow> <a:mn>2</a:mn> </a:mrow> </a:msup> <a:mtext> </a:mtext> <a:msup> <a:mrow> <a:mi>mrad</a:mi> </a:mrow> <a:mrow> <a:mn>2</a:mn> </a:mrow> </a:msup> </a:mrow> </a:math> 0.1% BW) at 10 keV, with a total photon number reaching <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mn>4</e:mn> <e:mo>×</e:mo> <e:msup> <e:mn>10</e:mn> <e:mn>12</e:mn> </e:msup> </e:math> (energy <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:mo>&gt;</g:mo> </g:math> 1 keV).

Relativistic electron beams produced by intense lasers over short distances have important applications in high energy density physics and medical technologies. Vacuum laser acceleration with plasma mirrors asinjectors has garnered substantial research interest recently. However, a persistent challenge remains unresolved that electrons inevitably detach from the laser acceleration phase due to velocity mismatch. Here, we employ flying focus lasers to address this limitation. Through three-dimensional particle-in-cell simulations, we demonstrate that flying focus lasers can achieve a substantial enhancement in relativistic electron charge yield compared to conventional Gaussian lasers. This improvement stems from two key attributes: (1) the subluminal propagation velocity of the peak intensity keeps a larger electron population synchronized within the longitudinal ponderomotive acceleration region, and (2) flying focus lasers sustain higher magnitudes of the longitudinal ponderomotive force over longer distances in comparison to Gaussian lasers. This approach offers high-charge relativistic electron sources ideal for demanding applications such as high-flux Thomson scattering and radiography.

FLASH is a widely available radiation magnetohydrodynamics code used for astrophysics, laboratory plasma science, high energy density physics, and inertial confinement fusion (ICF). Increasing interest in magnetically driven inertial confinement fusion, including Pacific fusion's development of a 60 MA demonstration system designed to achieve facility gain, motivates the improvement and validation of FLASH for modeling magnetically driven ICF concepts, such as MagLIF, at ignition scale. Here, we present a collection of six validation benchmarks from experiments at the Z Pulsed Power Facility and theoretical and simulation studies of scaling MagLIF to high currents. The benchmarks range in complexity from focused experiments of linear hydrodynamic instabilities to fully integrated MagLIF fusion experiments. With the latest addition of physics capabilities, FLASH now obtains good agreement with the experimental data, theoretical results, and leading ICF target design simulation code results across all six benchmarks. These results establish confidence in FLASH as a useful tool for designing magnetically driven ICF targets on facilities like Z and Pacific fusion's upcoming 60 MA Demonstration System.

As the archetypal strong solid, the response of diamond shock compressed to multimegabar stresses is important for fundamental science and for numerical simulations of wave profiles for applications in high energy density physics experiments. Previous experiments and analysis [Winey et al., Phys. Rev. B 101, 184105 (2020)] have shown that the commonly used hydrodynamic assumption is invalid for diamond shock compressed to stresses below melt and an elastic–inelastic description is needed. Here, we present a phenomenological material model for calculating wave profiles in shock compressed diamond single crystals that incorporates this description. Also, to support the modeling effort, we carried out wave profile measurements on shock compressed diamond single crystals at the Sandia Z facility to augment previous measurements. Wave profiles for [100] and [111] diamond calculated using the material model provide a good match to the elastic–inelastic response (observed two-wave structure) measured at ∼325 and ∼360 GPa. Furthermore, the calculated peak stresses for single (overdriven) waves provide a good match to the measured Hugoniot states for stresses reaching ∼700 GPa, which is near melting conditions. The present results show that the diamond single crystal response at multimegabar shock stresses is characteristic of a brittle solid—pressure-dependent strength and strength loss due to inelastic deformation.

Abstract In previous studies, the pulsed strong magnetic fields generated by the laser-driven coils were usually overestimated. One of the reasons is that the self-generated magnetic field and the coil-induced magnetic field exhibit different power-law decay behaviors with respect to probe distance. We design an insulated coil target to measure the net coil-produced magnetic field, and to accurately infer the magnetic field inside a magnetized hohlraum. A magnetic field is generated by laser irradiation on a capacitor-coil target featuring an x-ray maze structure. The gold hohlraum inside the coil is slitted to eliminate the diamagnetic current and enable the external magnetic field to penetrate the gold hohlraum. To delay the closure of the slit, an x-ray maze is designed between the two capacitor plates. In this work, a pulsed magnetic field with a peak strength over 500 T is generated in the magnetized hohlraum using 1053 nm lasers with pulse length of 2 ns and energy of above 1.6 kJ. An energy conversion efficiency of ∼8% from laser energy to magnetic field energy was achieved. This work provides technical support for magnetized high-energy-density physics research.

In high energy density physics, the demand for precise detection of nanosecond-level fast physical processes is high. Ga:ZnO (GZO), GaN, and other fast scintillators are widely used in pulsed signal detection. However, many of them, especially wide-bandgap materials, still face issues of low luminous intensity and significant self-absorption. Therefore, an enhanced method was proposed to tune the wavelength of materials via coating perovskite quantum dot (QD) films. Three-layer samples based on GZO were primarily investigated and characterized. Radioluminescence (RL) spectra from each face of the samples, as well as their decay times, were obtained. Lower temperatures further enhanced the luminous intensity of the samples. Its overall luminous intensity increased by 2.7 times at 60 K compared to room temperature. The changes in the RL processes caused by perovskite QD and low temperatures were discussed using the light tuning and transporting model. In addition, an experiment under a pico-second electron beam was conducted to verify their pulse response and decay time. Accordingly, the samples were successfully applied in beam state monitoring of nanosecond pulsed proton beams, which indicates that GZO wafer coating with perovskite QD films has broad application prospects in pulsed radiation detection.

In high energy density physics (HEDP) and inertial confinement fusion (ICF), predictive modeling is complicated by uncertainty in parameters that characterize various aspects of the modeled system, such as those characterizing material properties, equation of state (EOS), opacities, and initial conditions. Typically, however, these parameters are not directly observable. What is observed instead is a time sequence of radiographic projections using X-rays. In this work, we define a set of sparse hydrodynamic features derived from the outgoing shock profile and outer material edge, which can be obtained from radiographic measurements, to directly infer such parameters. Our machine learning (ML)-based methodology involves a pipeline of two architectures, a radiograph-to-features network (R2FNet) and a features-to-parameters network (F2PNet), that are trained independently and later combined to approximate a posterior distribution for the parameters from radiographs. We show that the machine learning architectures are able to accurately infer initial conditions and EOS parameters, and that the estimated parameters can be used in a hydrodynamics code to obtain density fields, shocks, and material interfaces that satisfy thermodynamic and hydrodynamic consistency. Finally, we demonstrate that features resulting from an unknown EOS model can be successfully mapped onto parameters of a chosen analytical EOS model, implying that network predictions are learning physics, with a degree of invariance to the underlying choice of EOS model. To the best of our knowledge, our framework is the first demonstration of recovering both thermodynamic and hydrodynamic consistent density fields from noisy radiographs.

The University of New Mexico, in collaboration with the Naval Research Laboratory, has developed and characterized a fast rise time air-insulated linear transformer driver (LTD) for use in high power microwave (HPM), high energy density physics (HEDP), as well as shock physics experiments. The LTD cavity is a fast rise time—high current pulsed power rectangular device that is composed of four “wings” each containing three bricks, situated on the perimeter of a central spool containing the load. Each brick has two distinct capacitors and a rail switch composed of a six-by-six arrangement of spherical electrodes. This paper provides a full characterization of the device with relevant operational parameters, experimental results of load currents from various loads at various voltages, and currents and timing relationships from individual bricks and wings.

Ultrafast laser systems, those with a pulse duration on the order of picoseconds or less, have enabled advancements in a wide variety of fields. Of particular interest to this work, these laser systems are the key component to many High Energy Density (HED) physics experiments. Despite this, previous studies on the shape of the laser pulse within the HED community have focused primarily on pulse duration due to the relationship between pulse duration and peak intensity, while leaving the femtosecond scale structure of the pulse shape largely unstudied. To broaden the variety of potential pulses available for study, a method of reliably adjusting the pulse shape at the femtosecond scale using sub-nanometer resolution Direct Phase Control has been developed. This paper examines the capabilities of this new method compared to more commonplace dispersion-based pulse shaping methods. It also will detail the capabilities of the core algorithm driving this technique when used in conjunction with the WIZZLER and DAZZLER instruments that are common in high intensity laser labs. Performance of the method and instrumentation is examined using data taken with a single shot FROG system. Finally, some discussion is given to possible applications on how the Direct Phase Control pulse shaping technique will be implemented in the future.

High-order harmonic generation (HHG) plays a key role in producing coherent extreme ultraviolet (EUV) and x-ray radiation, which is crucial for applications in attosecond science and high-energy density physics. The intensity and order of high-order harmonics are crucial for advancing their applications. In this paper, a scheme is proposed to generate harmonics by the relativistic oscillating mirror (ROM) based on the energy exchange between electron and excited plasma wave by Landau damping, which employs dual laser pulses to sequentially excite the plasma surface electron oscillation to enhance the intensity and order of harmonics. Through theory and numerical analysis, we discover that our scheme significantly enhances the intensity of higher-order harmonics by an order of magnitude compared to typical harmonic generation methods of the same energy, and observe the higher-order harmonics. Furthermore, we investigate the essential factors affecting energy exchange in Landau damping and find that there exists an optimal pulse interval and energy ratio to maximize the energy exchange. The scheme based on Landau damping for generating high-order harmonics offers an alternative perspective for advancing HHG research and applications.

The study of beam–plasma interactions is important in many research fields, such as astrophysics, inertial confinement fusion, and high-energy density physics. Considering the significant impact of electromagnetic fields on the evolution of beam–plasma systems, comprehensive three-dimensional modeling of the system is needed. In this work, a relativistic three-dimensional electromagnetic particle-in-cell code IBMP3D is developed for the investigations of beam transport in plasmas. To save the computation time and achieve a fast simulation, a dynamic array data structure combined with particle sorting is designed in the code. Benchmarks between IBMP3D and the codes EPOCH and WarpX are presented for the transport of relativistic electron beams in plasmas, including the beam self-focusing effect, the excitation of the self-modulation, and current filamentation instabilities. While good agreements in the simulation results are found, a significant reduction in the computation time is achieved for the code IBMP3D.

The last decade has shown the great potential that X-ray Free Electron Lasers (FEL) have to study High Energy Density (HED) physics. Experiments at FELs have made significant breakthroughs in Shock Physics and Dynamic Diffraction, Dense Plasma Physics and Warm Dense Matter Science, using techniques such as isochoric heating, inelastic scattering, small angle scattering and X-ray diffraction. In addition, and complementary to these techniques, the coherent properties of the FEL beam can be used to image HED samples with high fidelity. We present new imaging diagnostics and techniques developed at the Matter in Extreme Conditions (MEC) instrument at Linac Coherent Light Source (LCLS) over the last few years. We show results in Phase Contrast Imaging geometry, where the X-ray beam propagates from the target to a camera revealing its phase, as well as in Direct Imaging geometry, where a real image of the sample plane is produced in the camera with a spatial resolution down to 200 nm. Last, we show an implementation of the Talbot Imaging method allowing both X-ray phase and intensity measurements change introduced by a target with sub-micron resolution.

Laser beam smoothing is a key element to enhance laser plasma hydrodynamic coupling in the context of high energy density physics experiments carried out in Inertial Confinement Fusion Facilities. Here, we experimentally study the effects of different polarization smoothing implementations on the Stimulated Brillouin Backscattering (B-SBS) and the transmission of a laser beam using the LULI2000 laser facility. First, we show that the polarization state (linear or circular) has no effect on B-SBS and transmission. We also show that under our experimental conditions, both the statistical average laser power carried by the speckle spots and their statistical average shape provide information on the effectiveness of the laser beam smoothing configuration. These findings open new paths for the optimization of high-power laser beam smoothing techniques on existing and future laser facilities.

Abstract Micro-cones so far mainly used for high energy density physics research have been proven to have an effective control on the fast electrons in the context of fast ignition research. In this paper we demonstrate by performing three-dimensional particle-in-cell simulations that an ultra-high intensity laser pulse can be intensified 28 times at the interaction with plastic micro-cones. The extreme intensities of the focused laser which are reached at the interaction with the plastic micro-cones are important in the plasma and nuclear physics investigations of dark matter, non-linear quantum electrodynamics, and fission–fusion experiments to study the N=126 waiting point for better understanding of the universe. Furthermore, we observe that micro-cones can shorten ultra-high intensity laser pulses both in time and space. The highest intensification of the incident laser pulse varies in time but not in position being localized very close to the rear side of the micro-cone tip. Therefore, the micro-cone can be a useful device in relativistic plasma optics.

In this paper, we apply the potential flow theory to study the Rayleigh–Taylor instability at an imploding interface associated with the Bell–Plesset effects in the cylindrical geometry. The coupled equations to describe the motion of the interface are numerically solved to understand how the physical properties of the external medium and the driving pressure affect its instability. Generally, the viscosity inhibits the interfacial motion. With higher viscosity, namely, smaller Re, the acceleration of interfacial motion is particularly inhibited, while the radius and velocity is slightly suppressed, leading to the amplitude for all modes being slowed down uniformly. On the contrary, the radius possesses pure oscillations with the presence of elasticity. For the perturbed amplitudes in the linear regime, the larger modes are accompanied by the higher frequency of oscillation but the smaller amplitude. In addition, there is a single mode that excites the largest perturbation in the elastic phase, and the perturbation is significantly suppressed when the mode is sufficiently large. Smaller values of driven pressure cause the faster rate of decay, and the perturbation will be more easily suppressed at the lower modes. When the pressure is large enough, the perturbation grows rapidly with increasing modes and is difficult to be suppressed. The above conclusions provide a deeper understanding of the mechanistic interactions between material properties and dynamic stability in high energy density physics.

Abstract Multi-keV x-rays are essential for diagnostic applications in inertial confinement fusion and high energy density physics. In this paper, enhancement of the multi-keV x-ray emission is achieved by using a low-coherence green laser to irradiate Ti foil targets at a fractional bandwidth of 0.6%. Compared to the widely used narrowband lasers, the above broadband laser generated 17%–23% more intense He-like alpha x-rays of Ti in the experiments at laser intensities of 4–6 × 1014 W cm-2. The improved laser absorption due to the reduction of stimulated Brillouin scattering introduced by the bandwidth is responsible for the enhancement of x-ray emission. The results suggest a promising application of broadband lasers on x-ray generations and further diagnostics.