Matter and Radiation at Extremes
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当前目录 第9卷 第1期

Ke Lan a)
Author Affiliations
Abstract
Institute of Applied Physics and Computational Mathematics, Beijing 100094, China and HEDPS, Center for Applied Physics and Technology, and College of Engineering, Peking University, Beijing 100871, China
Matter and Radiation at Extremes
2024, 9(1): 013001
Author Affiliations
Abstract
1 University of Texas at Austin, Austin, Texas 78712, USA
2 SUPA Department of Physics, University of Strathclyde, Glasgow, Scotland G4 0NG, United Kingdom
3 Tau Systems, Inc., Austin, Texas 78701, USA
4 Lawrence Livermore National Laboratory, Livermore, California 94550, USA
5 Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
6 Brookhaven National Laboratory, Upton, New York 11973, USA
7 Ludwig-Maximilians-Universität, Munich, Germany
An intense laser pulse focused onto a plasma can excite nonlinear plasma waves. Under appropriate conditions, electrons from the background plasma are trapped in the plasma wave and accelerated to ultra-relativistic velocities. This scheme is called a laser wakefield accelerator. In this work, we present results from a laser wakefield acceleration experiment using a petawatt-class laser to excite the wakefields as well as nanoparticles to assist the injection of electrons into the accelerating phase of the wakefields. We find that a 10-cm-long, nanoparticle-assisted laser wakefield accelerator can generate 340 pC, 10 ± 1.86 GeV electron bunches with a 3.4 GeV rms convolved energy spread and a 0.9 mrad rms divergence. It can also produce bunches with lower energies in the 4–6 GeV range.
Matter and Radiation at Extremes
2024, 9(1): 014001
Author Affiliations
Abstract
1 Laboratory of Computational Physics, Institute of Applied Physics and Computational Mathematics, Beijing 10088, China
2 Institute of Applied Physics and Computational Mathematics, Beijing 10088, China
Extrapolation of implosion performance between different laser energy scales is investigated for indirect drive through a semi-hydro-equivalent design. Since radiation transport is non-hydro-equivalent, the peak radiation temperature of the hohlraum and the ablation velocity of the capsule ablator are not scale-invariant when the sizes of the hohlraum and the capsule are scale-varied. A semi-hydro-equivalent design method that keeps the implosion velocity Vi, adiabat αF, and PL/Rhc2 (where PL is the laser power and Rhc is the hohlraum and capsule scale length) scale-invariant, is proposed to create hydrodynamically similar implosions. The semi-hydro-equivalent design and the scaled implosion performance are investigated for the 100 kJ Laser Facility (100 kJ-scale) and the National Ignition Facility (NIF-scale) with about 2 MJ laser energy. It is found that the one-dimensional implosion performance is approximately hydro-equivalent when Vi and αF are kept the same. Owing to the non-hydro-equivalent radiation transport, the yield-over-clean without α-particle heating (YOCnoα) is slightly lower at 100 kJ-scale than at NIF-scale for the same scaled radiation asymmetry or the same initial perturbation of the hydrodynamic instability. The overall scaled two-dimensional implosion performance is slightly lower at 100 kJ-scale. The general Lawson criterion factor scales as χnoα2DS1.06±0.04 (where S is the scale-variation factor) for the semi-hydro-equivalent implosion design with a moderate YOCnoα. Our study indicates that χnoα ≈ 0.379 is the minimum requirement for the 100 kJ-scale implosion to demonstrate the ability to achieve marginal ignition at NIF-scale.
Matter and Radiation at Extremes
2024, 9(1): 015601
Author Affiliations
Abstract
Shanghai Institute of Laser Plasma, CAEP, Shanghai 201899, People’s Republic of China
The use of broadband laser technology is a novel approach for inhibiting processes related to laser plasma interactions (LPIs). In this study, several preliminary experiments into broadband-laser-driven LPIs are carried out using a newly established hundreds-of-joules broadband second-harmonic-generation laser facility. Through direct comparison with LPI results for a traditional narrowband laser, the actual LPI-suppression effect of the broadband laser is shown. The broadband laser had a clear suppressive effect on both back-stimulated Raman scattering and back-stimulated Brillouin scattering at laser intensities below 1 × 1015 W cm-2. An abnormal hot-electron phenomenon is also investigated, using targets of different thicknesses.
Matter and Radiation at Extremes
2024, 9(1): 015602
Author Affiliations
Abstract
1 Department of Physics, National University of Defense Technology, Hunan, China
2 ETSI Aeronáutica y del Espacio, Universidad Politécnica de Madrid, Madrid, Spain
3 Department of Nuclear Science and Technology, National University of Defense Technology, Hunan, China
The Brown–Preston–Singleton (BPS) stopping power model is added to our previously developed hybrid code to model ion beam–plasma interaction. Hybrid simulations show that both resistive field and ion scattering effects are important for proton beam transport in a solid target, in which they compete with each other. When the target is not completely ionized, the self-generated resistive field effect dominates over the ion scattering effect. However, when the target is completely ionized, this situation is reversed. Moreover, it is found that Ohmic heating is important for higher current densities and materials with high resistivity. The energy fraction deposited as Ohmic heating can be as high as 20%–30%. Typical ion divergences with half-angles of about 5°–10° will modify the proton energy deposition substantially and should be taken into account.
Matter and Radiation at Extremes
2024, 9(1): 015603
Author Affiliations
Abstract
HEDPS, CAPT, College of Engineering and School of Physics, Peking University, Beijing 100871, People’s Republic of China
In traditional finite-temperature Kohn–Sham density functional theory (KSDFT), the partial occupation of a large number of high-energy KS eigenstates restricts the use of first-principles molecular dynamics methods at extremely high temperatures. However, stochastic density functional theory (SDFT) can overcome this limitation. Recently, SDFT and the related mixed stochastic–deterministic density functional theory, based on a plane-wave basis set, have been implemented in the first-principles electronic structure software ABACUS [Q. Liu and M. Chen, Phys. Rev. B 106, 125132 (2022)]. In this study, we combine SDFT with the Born–Oppenheimer molecular dynamics method to investigate systems with temperatures ranging from a few tens of eV to 1000 eV. Importantly, we train machine-learning-based interatomic models using the SDFT data and employ these deep potential models to simulate large-scale systems with long trajectories. Subsequently, we compute and analyze the structural properties, dynamic properties, and transport coefficients of warm dense matter.
Matter and Radiation at Extremes
2024, 9(1): 015604
Author Affiliations
Abstract
P.N. Lebedev Physical Institute of Russian Academy of Sciences, Leninskii Prospect 53, Moscow 119991, Russia
A time-dependent analytical solution is found for the velocity of a plane ionization wave generated under nanosecond laser pulse action on the surface of a flat layer of low-Z porous substance with density less than the critical density of the produced plasma. With corrections for the two-dimensional nature of the problem when a laser beam of finite radius interacts with a flat target, this solution is in quantitative agreement with measurements of ionization wave velocity in various experiments. The solution compared with experimental data covering wide ranges of performance conditions, namely, (3–8) × 1014 W cm-2 for laser pulse intensity, 0.3–3 ns for pulse duration, 0.35–0.53 μm for laser wavelength, 100–1000 μm for laser beam radius, 380–950 μm for layer thickness, 4.5–12 mg cm-3 for average density of porous substance, and 1–25 μm for average pore size. The parameters of the laser beam that ensure the generation of a plane ionization wave in a layer of subcritical porous matter are determined for the problem statements and are found to meet the requirements of practical applications.
Matter and Radiation at Extremes
2024, 9(1): 016601
Author Affiliations
Abstract
1 Department of Radiation and Chemical Physics, Institute of Physics, Czech Academy of Sciences, Na Slovance 2, 182 21 Prague 8, Czech Republic
2 Laser Plasma Department, Institute of Plasma Physics, Czech Academy of Sciences, Za Slovankou 3, 182 00 Prague 8, Czech Republic
3 Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University in Prague, V Holešovičkách 2, 180 00 Prague 8, Czech Republic
4 Department of Physical Electronics, Faculty of Nuclear Science and Engineering Physics, Czech Technical University in Prague, V Holešovičkách 2, 180 00 Prague 8, Czech Republic
5 Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, 01328 Dresden, Germany
6 DESY Photon Science, Notkestraße 85, D-22607 Hamburg, Germany
7 Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, UMR 7590 – UPMC/CNRS/IRD/MNHN, Sorbonne Université, 4 place Jussieu, 75005 Paris, France
8 Department of Physics, Faculty of Electrical Engineering, Czech Technical University in Prague, Technická 2, 166 27 Prague 6, Czech Republic
9 Center for Soft Nanoscience, University of Münster, Busso-Peus-Straße 10, D-48149 Münster, Germany
We report on an experiment performed at the FLASH2 free-electron laser (FEL) aimed at producing warm dense matter via soft x-ray isochoric heating. In the experiment, we focus on study of the ions emitted during the soft x-ray ablation process using time-of-flight electron multipliers and a shifted Maxwell–Boltzmann velocity distribution model. We find that most emitted ions are thermal, but that some impurities chemisorbed on the target surface, such as protons, are accelerated by the electrostatic field created in the plasma by escaped electrons. The morphology of the complex crater structure indicates the presence of several ion groups with varying temperatures. We find that the ion sound velocity is controlled by the ion temperature and show how the ion yield depends on the FEL radiation attenuation length in different materials.
Matter and Radiation at Extremes
2024, 9(1): 016602
Author Affiliations
Abstract
1 Department of Modern Mechanics, University of Science and Technology of China, Hefei 230026, China
2 Deep Space Exploration Laboratory, Hefei 230026, China
3 Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang 621900, China
4 Institute of Applied Physics and Computational Mathematics, Beijing 100094, China
5 Department of Plasma Physics and Fusion Engineering, University of Science and Technology of China, Hefei, Anhui 230026, China
6 Collaborative Innovation Center of IFSA (CICIFSA), Shanghai Jiao Tong University, Shanghai 200240, China
7 CAS Center for Excellence in Ultra-intense Laser Science, Shanghai 201800, China
The evolution of ablative Rayleigh–Taylor instability (ARTI) induced by single-mode stationary and time-varying perturbations in heat flux is studied numerically in two dimensions. Compared with the stationary case, time-varying heat-flux perturbation mitigates ARTI growth because of the enhanced thermal smoothing induced by the wave-like traveling heat flux. A resonance is found to form when the phase velocity of the heat-flux perturbation matches the average sound speed in the ablation region. In the resonant regime, the coherent density and temperature fluctuations enhance the electron thermal conduction in the ablation region and lead to larger ablation pressure and effective acceleration, which consequently yield higher linear growth rate and saturated bubble velocity. The enhanced effective acceleration offers increased implosion velocity but can also compromise the integrity of inertial confinement fusion shells by causing faster ARTI growth.
Matter and Radiation at Extremes
2024, 9(1): 016603
Author Affiliations
Abstract
1 Center for High Pressure Science (CHiPS), State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China
2 School of Materials Science and Engineering, Henan University of Technology, Zhengzhou 450001, China
3 Department of Chemistry, State University of New York at Buffalo, Buffalo, New York 14260-3000, USA
4 Physics Department and EHU Quantum Center, University of the Basque Country, UPV/EHU, 48080 Bilbao, Spain
5 Donostia International Physics Center (DIPC), 20018 Donostia, Spain
6 Centro de Física de Materiales CFM, Centro Mixto CSIC-UPV/EHU, 20018 Donostia, Spain
7 Extreme Conditions Physics Research Team, College of Physics and Electronic Information, Inner Mongolia Minzu University, Tongliao 028043, China
Since the discovery of hydride superconductors, a significant challenge has been to reduce the pressure required for their stabilization. In this context, we propose that alloying could be an effective strategy to achieve this. We focus on a series of alloyed hydrides with the AMH6 composition, which can be made via alloying A15 AH3 (A = Al or Ga) with M (M = a group ⅢB or IVB metal), and study their behavior under pressure. Seven of them are predicted to maintain the A15-type structure, similar to AH3 under pressure, providing a platform for studying the effects of alloying on the stability and superconductivity of AH3. Among these, the A15-type phases of AlZrH6 and AlHfH6 are found to be thermodynamically stable in the pressure ranges of 40–150 and 30–181 GPa, respectively. Furthermore, they remain dynamically stable at even lower pressures, as low as 13 GPa for AlZrH6 and 6 GPa for AlHfH6. These pressures are significantly lower than that required for stabilizing A15 AlH3. Additionally, the introduction of Zr or Hf increases the electronic density of states at the Fermi level compared with AlH3. This enhancement leads to higher critical temperatures (Tc) of 75 and 76 K for AlZrH6 and AlHfH6 at 20 and 10 GPa, respectively. In the case of GaMH6 alloys, where M represents Sc, Ti, Zr, or Hf, these metals reinforce the stability of the A15-type structure and reduce the lowest thermodynamically stable pressure for GaH3 from 160 GPa to 116, 95, 80, and 85 GPa, respectively. Particularly noteworthy are the A15-type GaMH6 alloys, which remain dynamically stable at low pressures of 97, 28, 5, and 6 GPa, simultaneously exhibiting high Tc of 88, 39, 70, and 49 K at 100, 35, 10, and 10 GPa, respectively. Overall, these findings enrich the family of A15-type superconductors and provide insights for the future exploration of high-temperature hydride superconductors that can be stabilized at lower pressures.
Matter and Radiation at Extremes
2024, 9(1): 018401

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