- 标题
- 摘要
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- 实验方案
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Impact of asymmetries on fuel performance in inertial confinement fusion
摘要： Low-mode asymmetries prevent effective compression, con?nement, and heating of the fuel in inertial con?nement fusion (ICF) implosions, and their control is essential to achieving ignition. Ion temperatures (Tion) in ICF experiments are inferred from the broadening of primary neutron spectra. Directional motion (?ow) of the fuel at burn also impacts broadening and will lead to arti?cially in?ated “Tion” values. Flow due to low-mode asymmetries is expected to give rise to line-of-sight variations in measured Tion. We report on intentionally asymmetrically driven experiments at the OMEGA laser facility designed to test the ability to accurately predict and measure line-of-sight differences in apparent Tion due to low-mode asymmetry-seeded ?ows. Contrasted to CHIMERA and xRAGE simulations, the measurements demonstrate how all asymmetry seeds have to be considered to fully capture the ?ow ?eld in an implosion. In particular, ?ow induced by the stalk that holds the target is found to interfere with the seeded asymmetry. A substantial stalk-seeded asymmetry in the areal density of the implosion is also observed.
关键词： CHIMERA,xRAGE simulations,OMEGA laser facility,inertial con?nement fusion,ion temperatures,low-mode asymmetries
更新于2025-09-23 15:21:21
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Suppression of amplitude modulation induced by polarization mode dispersion using a multi-degree-of-freedom fiber filter
摘要： Polarization mode dispersion (PMD) in ?bers for high-power lasers can induce signi?cant frequency modulation to amplitude modulation (FM-to-AM) conversion. However, existing techniques are not suf?ciently ?exible to achieve ef?cient compensation for such FM-to-AM conversion. By analyzing the nonuniform transmission spectrum caused by PMD, we found that the large-scale envelope of the transmission spectrum has more serious impacts on the amount of AM. In order to suppress the PMD-induced FM-to-AM conversion, we propose a novel tunable spectral ?lter with multiple degrees of freedom based on a half-wave plate, a nematic liquid crystal, and an axis-rotated polarization-maintaining ?ber. Peak wavelength, free spectral range (FSR), and modulation depth of the ?lter are decoupled and can be controlled independently, which is veri?ed through both simulations and experiments. The ?lter is utilized to compensate for the PMD-induced FM-to-AM conversion in the front end of a high-power laser facility. The results indicate that, for a pulse with phase-modulation frequency of 22.82 GHz, the FM-to-AM conversion could be reduced from 18% to 3.2% within a short time and maintained below 6.5% for 3 h. The proposed ?lter is also promising for other applications that require ?exible spectral control such as high-speed channel selection in optical communication networks.
关键词： laser facility,laser systems,optimization,high-power laser,laser facility and engineering,advanced laser technology and applications,?ber laser and applications,modeling,design
更新于2025-09-23 15:21:01
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Proton acceleration via the TNSA mechanism using a smoothed laser focus
摘要： In this work, we present the results of an experiment aiming at proton acceleration using a focus with a homogeneous intensity distribution, called smoothed focus. To achieve this goal, we implemented a phase plate before the pre-amplifier of the Petawatt High-Energy Laser for Heavy Ion EXperiments laser facility. The phase plate was used for the first time at a high-power short-pulse laser. Demonstrating a low divergent ion beam was the main goal of this work. Numerical simulations using the particle-in-cell code Extendable PIC Open Collaboration estimated a 2–5 times reduction in the angular divergence of the proton beam using a phase plate due to a smoother sheath at the rear side of the target. However, the reduction in the angular divergence was not sensible according to the experimental data. A positive point is that the spectrum of protons that are generated with the smoothed beam is shifted toward lower energies, provided that the laser absorption is kept in check, compared to the Gaussian proton spectrum. Moreover, the number of protons that are generated with the smoothed beam is higher than the ones generated with the Gaussian beam.
关键词： smoothed laser focus,proton acceleration,phase plate,TNSA mechanism,PHELIX laser facility
更新于2025-09-23 15:19:57
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Ultra clean manufacturing techniques for final optics assembly in high-power laser facility
摘要： Cleanliness control is one of the most important processes for final optics assembly (FOA) in high-power laser systems. In this paper, an "Ultra Clean Manufacturing (UCM)" concept is put forward for the first time to satisfy the cleanliness requirements for FOA. First, the challenges and requirements for cleanliness in FOA are introduced and the concept of UCM is proposed. Significant surface cleaning technologies for mechanical parts and optics are then expounded. Finally, surface cleanliness control techniques, such as "gas knife" and "laser cleaning", are developed as online cleaning methods for the surface cleanliness in FOA.
关键词： high-power laser facility,cleanness control,contamination,Ultra-clean manufacturing,final optics assembly
更新于2025-09-16 10:30:52
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Optimized x-ray sources for x-ray diffraction measurements at the Omega Laser Facility
摘要： The use of x-ray diffraction (XRD) measurements in laser-driven dynamic compression experiments at high-power laser facilities is becoming increasingly common. Diffraction allows one to probe in situ the transformations occurring at the atomic level at extreme conditions of pressure, temperature, and time scale. In these measurements, the x-ray source is generated by irradiation of a solid foil. Under certain laser drive conditions, quasimonochromatic He-α radiation is generated. Careful analysis of the x-ray source plasma spectra reveals that this radiation is not a single line emission and that monochromaticity is highly dependent on the laser irradiance. In this work, we analyze how the spectra emitted by laser-irradiated copper, germanium, and iron foils at the Omega Laser vary depending on different laser drive conditions and discuss the implications for XRD experiments.
关键词： laser irradiance,x-ray diffraction,Omega Laser Facility,quasimonochromatic He-α radiation,laser-driven dynamic compression
更新于2025-09-12 10:27:22
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Effective electromagnetic shielding with multi-layer structure material on Shenguang laser facility
摘要： Electromagnetic pulses (EMPs) with high intensity and frequency bandwidth can be generated during the intensive laser irradiating solid targets in inertial confinement fusion (ICF). To shield the EMPs radiation and hence protect various diagnostics in and outside the target chamber, we designed a multi-layer structure material to shield the EMPs and demonstrate experimentally and numerically shielding performance of the material structure. The thickness of the multi-layer structure material has a great influence on the EMPs shielding. It is shown that, with the increase of the material thickness, the better shielding performance is obtained, and the material structure with polytetrafluoroethylene (PTFE) of 0.5 mm, copper of 0.4 mm and lead of 2.4 mm reduces 448 times compared the maximum value of EMPs voltage to that without shielded. The design of multi-layer structure material for EMPs shielding provides a promising way to reduce EMPs radiation, which is extremely useful for the diagnostics protection and signal processing in ICF.
关键词： inertial confinement fusion,Shenguang laser facility,electromagnetic pulse,shielding
更新于2025-09-12 10:27:22
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Investigation on laser plasma instability of the outer ring beams on SGIII laser facility
摘要： In order to study the laser plasma instabilities (LPIs) in the context of some novel six-side laser-driven indirect designs like the six-cylinder-port hohlraum and the three-axis cylindrical hohlraum, where the laser beams inject in hohlraum with a large angle. LPI experiments in cylindrical hohlraum with only outer beams were designed and performed based on the current laser arrangement condition of SGIII laser facility for the first time. Stimulated Brillouin backscatter (SBS) was found to be the dominant instability with high instantaneous reflectivity in experiments. A typical feature was obtained in the time-resolved spectra of SBS, which maintained similar for different laser intensities of the interaction beam. The experimental data are analyzed by the hydrodynamic simulations combined with HLIP code, which is based on the ray-tracing model. By analysis of experimental data, it is argued that the mixture of gas and Au in the region of their interface is important to SBS, which indicates the need for the mixture model between the filled gas and the high Z plasma from hohlraum wall in the hydrodynamic simulations. Nonlinear saturation of SBS as well as the smoothed beam are also discussed here. Our effective considerations of the ions pervasion effect and the smoothed beam provide utilitarian ways for improvement of the current ray-tracing method.
关键词： laser plasma instabilities,hydrodynamic simulations,stimulated Brillouin backscatter,ray-tracing model,SGIII laser facility
更新于2025-09-09 09:28:46