arXiv subjects

R. X. Li

Publications and source records attributed to R. X. Li.

5 recordsLinked to original sources

arXiv2026

Impact of ion-beam stopping power on proton-boron fusion yield in the pitcher-catcher scheme driven by ultra-intense laser

The effect of stopping power on proton-boron fusion is investigated for a proton beam propagating through boron plasma. Due to the stopping power, the electron temperature of the boron target rises as the proton beam deposits energy. Consequently, a feedback mechanism becomes significant when the trailing part of the beam propagates into the preheated plasma. By coupling this phenomenon with the proton-boron fusion process, fusion yields are systematically investigated by varying the central energy of the proton beam, as well as the thickness and density of the boron target. It is found that, under the influence of stopping power, the optimal central energy for fusion deviates from the intrinsic 672 keV resonance and shifts to approximately 900 keV. Moreover, the present results are substantiated by particle-in-cell simulations, which provides a valuable reference for subsequent high-yield hydrogen-boron fusion.

physics.plasm-ph↗

arXiv2024

Tracing Rayleigh-Taylor instability from measured periodic modulation in laser driven proton beams

Rayleigh-Taylor (RT) instability occurs in a variety of scenario as a consequence of fluids of different densities pushing against the density gradient. For example, it is expected to occur in the ion acceleration of solid density targets driven by high intensity lasers and is crucial for the acceleration process. Yet, it is essential to understand the dynamics of the RT instability, a typical way to measure this phenomenon requires sophisticated diagnostics such as streak X ray radiography. Here, we report on experimental observation on periodic modulation in the energy spectrum of laser accelerated proton beams. Interestingly, theoretical model and two-dimensional particle-in-cell simulations, in good agreement with the experimental finding, indicated that such modulation is associated with periodic modulated electron density induced by transverse Rayleigh-Taylor-like instability. Furthermore, the correlation between the RT instability and the ion acceleration provides an interpretation to trace the development of the RT instability from the modulated proton spectrum. Our results thus suggest a possible tool to diagnose the evolution of the RT instability, and may have implications for further understanding for the accelerating mechanisms as well as optimization strategies for laser driven ion acceleration.

physics.plasm-ph↗

arXiv2023

Dilution induced magnetic localization in Rb(Co$_{1-x}$Ni$_{x}$)$_{2}$Se$_{2}$ single crystals

We report experimental studies on a series of Rb(Co$_{1-x}$Ni$_{x}$)$_{2}$Se$_{2}$ (0.02 $\leq x \leq $ 0.9) powder and single crystal samples using x-ray diffraction, neutron diffraction, magnetic susceptibility, and electronic transport measurements. All compositions are metallic and adopt the body-centered tetragonal structure with $I4/mmm$ space group. Anisotropic magnetic susceptibilities measured on single crystal samples suggest that Rb(Co$_{1-x}$Ni$_{x}$)$_{2}$Se$_{2}$ undergo an evolution from ferromagnetism to antiferromagnetism, and finally to paramagnetism with increasing Ni concentration. Neutron diffraction measurements on the samples with $x$ = 0.1, 0.4, and 0.6 reveal an $A$-type antiferromagnetic order with moments lying in the $ab$ plane. The moment size changes from 0.69 ($x=0.1$) to 2.80$μ_B$ ($x=0.6$) per Co ions. Our results demonstrate that dilution of the magnetic Co ions by substitution of nonmagnetic Ni ions induces magnetic localization and evolution from itinerant to localized magnetism in Rb(Co$_{1-x}$Ni$_{x}$)$_{2}$Se$_{2}$.

cond-mat.str-el↗

arXiv2022

Acceleration of 60 MeV proton beams in the commissioning experiment of SULF-10 PW laser

We report the experimental results of the commissioning phase in the 10 PW laser beamline of Shanghai Superintense Ultrafast Laser Facility (SULF). The peak power reaches 2.4 PW on target without the last amplifying during the experiment. The laser energy of 72\pm 9 J is directed to a focal spot of ~6 μm diameter (FWHM) in 30 fs pulse duration, yielding a focused peak intensity around 2.0 \times 10^{21} W/cm^2. First laser-proton acceleration experiment is performed using plain copper and plastic targets. High-energy proton beams with maximum cut-off energy up to 62.5 MeV are achieved using copper foils at the optimum target thickness of 4 μm via target normal sheath acceleration (TNSA). For plastic targets of tens of nanometers thick, the proton cut-off energy is approximately 20 MeV, showing ring-like or filamented density distributions. These experimental results reflect the capabilities of the SULF-10 PW beamline, e.g., both ultrahigh intensity and relatively good beam contrast. Further optimization for these key parameters is underway, where peak laser intensities of 10^{22}-10^{23} W/cm^2 are anticipated to support various experiments on extreme field physics.

physics.plasm-ph↗

arXiv2019

A New Injection and Acceleration Scheme of Positrons in the Laser-Plasma Bubble Regime

A novel approach for positron injection and acceleration in laser driven plasma wakefield is proposed. A theoretical model is developed and confirmed through PIC simulation. One ring-shaped beam and one co-axially propagating Gaussian beam drive wakefields in a preformed plasma volume filled with both electrons and positrons. The laser's ponderomotive force as well as the charge separation force in the front bucket of the first bubble are utilized to provide the transverse momenta of injected positrons and those positrons can be trapped by the focusing field and then accelerated by the wakefield. The simulation shows that a relatively high-charge, quasi-monoenergetic positron beams can be obtained.

physics.plasm-ph↗