High Energy Density Physics最新文献

The possibility of utilizing defected C₃N monolayers as the electrodes of supercapacitors (SCs) was investigated in the current study by performing DFT computations. A single-vacancy C₃N monolayer (SC₃NML), a double-vacancy C₃N monolayer (DC₃NM) and a pure C₃N monolayer (PC₃NML) were investigated. The charge plots, quantum capacitance (QC) and the density of state of SC₃NML, DC₃NM and PC₃NML were also studied. Based on the results, the QC of SC₃NML and DC₃NM at voltages between -0.80 and 0.80 V was more compared to the QC of PC₃NML. It was possible to use SC₃NML as a negative electrode and DC₃NM as a positive electrode, both of which were p-type semi-conductors. The stored charge in the SC₃NML and DC₃NM was higher compared to the stored charge in PC₃NML at voltages 0 to 0.8 V. The charge stored in DC₃NM was higher than the stored charge in SC₃NML and PC₃NML. Finally, DC₃NML layer can be regarded as an encouraging electrode for application in SCs.

The spin effects on the propagation characteristic of circularly polarized electromagnetic (EM) wave in high density strongly magnetized plasma are discussed based on the the classical hydrodynamical model of relativistic spin plasma. The dielectric coefficients for right-hand circularly polarized (RCP) and left-hand circularly polarized (LCP) waves are obtained. Results show that the spin effects can affect the propagation characteristic of circularly polarized EM wave dramatically. Provided the spin effect is strong enough, LCP waves can also propagate in the magnetized over-dense plasma, while RCP waves may not. The strength of spin effects can be enhanced by increasing the plasma density or/and EM wave intensity.

Measurement of the areal density and velocity of the carbon ablator shell during peak burn in inertial confinement fusion give powerful information on the state of the ablator and where in the trajectory of implosion it reaches peak burn. Detailed comparison of the absolute densities and velocities of the carbon in implosions has been prevented by the limited ability to resolve shot-to-shot variation within a shot series or within a campaign. A new approach using a single, ultra fast ($\sim$10 ps) gamma ray channel can massively reduce uncertainties and will provide insights on improvements to target and drive variables. Small improvements in these experimental design parameters may result in much greater yields.

Laser-driven “inverted corona” fusion targets have attracted interest as a low-convergence neutron source and platform for studying kinetic physics. The scheme consists of a hollow or gas-filled spherical shell made of deuterated plastic. The shell has one or more laser entrance holes (LEH), resembling a spherical hohlraum. The laser passes through the LEH’s and illuminates the interior surface of the shell, ablating a plasma that travels inward towards the target center. Long ion mean free paths in the converging plasma can lead to significant interpenetration, atomic mix, and other kinetic effects. In this work we report on numerical simulations of inverted corona targets using the kinetic-ion, fluid–electron hybrid particle-in-cell (PIC) approach in 2D RZ geometry. 2D simulations suggest that shape effects do not have a significant impact on plasma evolution and observed yield trends are primarily the result of 1D kinetic mix mechanisms. Simulations are also compared against available experimental data recorded at the OMEGA laser facility. In particular, synthetic x-ray emission images show good qualitative agreement with experimental results, albeit with an apparent timing discrepancy for the two-sided vacuum target. More generally, we demonstrate the potential of hybrid-PIC simulations for full-system modeling and experimental design, including collisional absorption of laser energy, plasma evolution, mix, and fusion burn.

The distorted-wave with exchange (DWE) method is employed to evaluate electron impact ionization cross sections in dense electron–ion plasmas. Bound and continuum electron wave functions are obtained from a non-relativistic average-atom code. Plots of DWE cross sections are presented for $1s$ electrons in Li and Be plasmas and $2p$ electrons in Na and Mg plasmas. For each of these elements, cross sections are evaluated at metallic density in a range of temperatures from 10 to 100 eV and at their respective melting points. Resonances in the cross sections appear near the incident energy threshold at high temperatures. The origin of these resonances is discussed. In general, the distorted wave (DW) method without exchange is found to be a good approximation to the DWE method for electron impact ionization calculations. In the resonance region, however, exchange effects are found to be very important and cannot be neglected.

We developed a PIC code using new load balancing technique, in which the lower load processes help the higher load processes. A test calculation indicates more than 10 times faster than that without load balancing. Large scale 3-d calculations indicate the formation of central current whose density is close to critical density, supported by the magnetic field inside the channel.

Sandia National Laboratories has been operating the Mykonos linear transformer driver (LTD) in a five-cavity configuration since 2014. The machine operates at 1 MA output current, 500 kV output voltage, with a 10–90% current rise time of 85 ns, which enables small scale physics and engineering pulsed power experiments. Mykonos provides hands-on pulsed power experimental training for students and staff alongside senior Sandia scientists in an environment that is more accessible than the Z Facility. Over the years, we have fielded and accumulated a wide variety of optical, x-ray and electrical diagnostics and we are preparing to open this facility to outside users. Here, we are presenting the pulsed power and diagnostic capability of Mykonos as well as some recent experiments that have been performed on the facility. The goal of this publication is to attract researchers across the pulsed power and high energy density (HED) community to collaborate with Sandia on exciting, innovative science and to train the next generation of researchers for the National Nuclear Security Agency (NNSA) and the nation. As such, we have established a Mykonos Academic Access Program (MAAP) as part of ZNetUS to enable academic utilization of the Mykonos Pulsed Power Facility.

Ultra-thin targets (less than 10 nm), such as graphene, can be irradiated with relativistic intensity lasers to generate energetic ions. However, the laser prepulse can prematurely destroy these targets and significantly influence the final ion energies. Due to the limitations of the conventional hydrodynamic model, simulating the interaction between ultra-thin targets and a prepulse is infeasible. To overcome this issue, we propose a hybrid simulation technique in this study. This technique involves simulating the target-prepulse interaction using molecular dynamics (MD) simulation, which is then combined with the particle-in-cell simulation for the target-main pulse interaction, in order to accurately model the entire laser-target interaction dynamics. A realistic, experimentally measured laser intensity profile for the prepulse is used for the MD simulation, and the particle energies from this hybrid simulation are found to be in good agreement with the experiment.

Global microphysics models are required for the modelling of high-energy-density physics (HEDP) experiments, the improvement of which are critical to the path to inertial fusion energy. This work presents further developments to the atomic and microphysics code, SpK, part of the numerical modelling suite of Imperial College London and First Light Fusion. We extend the capabilities of SpK to allow the calculation of the equation of state (EoS). The detailed configuration accounting calculations are interpolated into finite-temperature Thomas–Fermi calculations at high coupling to form the electronic component of the model. The Cowan model provides the ionic contribution, modified to approximate the physics of diatomic molecular dissociation. By utilising bonding corrections and performing a Maxwell construction, SpK captures the EoS from states ranging from the zero-pressure solid, through the liquid–vapour coexistence region and into plasma states. This global approach offers the benefit of capturing electronic shell structure over large regions of parameter space, building highly-resolved tables in minutes on a simple desktop. We present shock Hugoniot and off-Hugoniot calculations for a number of materials, comparing SpK to other models and experimental data. We also apply EoS and opacity data generated by SpK in integrated simulations of indirectly-driven capsule implosions, highlighting physical sensitivities to the choice of EoS models.

Magnetic reconnection, a critical process in plasma physics, involves the reconnection of magnetic field lines, leading to the release of energy and acceleration of particles. This phenomenon is pivotal across various fields such as astrophysics, fusion energy research, and space weather forecasting. In this study, we conducted an experiment on magnetic reconnection using a laser-driven micro-coil to generate bi-directional currents. Analysis of the ion energy distribution from the reconnection outflow revealed that the maximum energy for each ion species correlates with a common gyroradius within the reconnection field, with spectral shapes across different ion species — excluding protons — showing uniformity after normalization by the square of their charge-to-mass ratio. These findings align with the hypothesis of large-scale magnetic field turbulence at the acceleration site, indicative of a strongly driven magnetic reconnection system.