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Parametric study of ultra-intense laser interaction with uniform and nano-porous near-critical plasmas
摘要： Responses of the uniform near-critical plasma (UNCP) and nano-porous near-critical plasma (NPNCP) upon interaction with a short-intense laser have been scrutinized using two-dimensional (2D) particle-in-cell simulations. Maximum proton energy variation by the deposition of uniform and nano-porous layers in front of a solid target for a wide range of laser intensities (normalized amplitude a0 = 5–25) and average densities of the front layer ne = 0.3 ? 3nc (where nc is the critical density) has been parametrically studied. It is found that the proton maximum energy for the front layers with sub-10 μm thicknesses is independent of the target porosity and density. However, in the relatively thick targets, the nano-porous structure decreases the laser energy absorption and, subsequently, the maximum proton energy compared to the uniform one. The results indicate that by employing UNCPs instead of NPNCPs, at the moderate laser intensity, the maximum proton energy reveals a 23% enhancement. This increment could be explained by rapid self-focusing of the laser pulse and dominant direct laser electron acceleration regime on the well-formed plasma channel in the UNCP layer. However, in the case of NPNCPs, the laser scattering from the plasma structure makes it less intense and more disordered, which influences the efficient laser energy coupling to the electrons.
关键词： proton acceleration,near-critical plasmas,particle-in-cell simulations,ultra-intense laser,laser-plasma interaction
更新于2025-09-23 15:21:01
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Enhancement of proton acceleration and conversion efficiency by double laser pulses plasma interactions
摘要： We report an ef?cient scheme to improve the proton acceleration and energy conversion ef?ciency by using double laser pulses with foil interaction. We ?nd a signi?cant increase in the peak energy, the total number, and the maximum energy of the accelerated protons for the double laser pulses with foil interaction compared to those in the single laser pulse case, while the total laser energy is kept constant. The role of the ?rst pulse (pre-pulse) is to change the target electron distribution and reduce the re?ection of succeeding laser pulse and hence enhance the laser absorption so that more energy of the second laser pulse (main pulse) is converted into the particle energy. The main pulse preferentially accelerates the slower electrons located deeper in the plasma, and it also accelerates the fast electrons due to volumetric heating. Finally, the protons are accelerated to high energy due to the laser break-out afterburner, when the target becomes relativistically transparent to the laser pulse.
关键词： proton acceleration,laser-plasma interaction,double laser pulses,energy conversion efficiency
更新于2025-09-23 15:19:57
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Generation and modulation of terahertz gradient force in the interactions of two-color laser pulses with magnetized plasmas
摘要： Terahertz (THz) waves, as far-infrared light, offer new opportunities for the optical trapping and manipulation of single cells, in contrast to the other light sources. We present an efficient scheme to flexibly control multiple THz field distribution patterns generated by the laser–plasma interaction in a magnetized plasma. An analytical THz radiation field and two-dimensional particle-in-cell simulation are constructed to verify the feasibility of the scheme. Modulation of the THz gradient force and the energy flux by an asymmetrical THz field is investigated for the purpose of trapping and manipulating particles and cells. In particular, the stabilities of flexibly controlled THz radiation are investigated carefully in the form of the strong and short laser and super-strong magnetic field induced significant spatial structure instabilities and frequency instabilities of terahertz radiation.
关键词： Terahertz waves,laser–plasma interaction,optical trapping,magnetized plasmas,THz gradient force
更新于2025-09-23 15:19:57
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Pump depletion and hot-electron generation in long-density-scale-length plasma with shock-ignition high-intensity laser
摘要： Two-dimensional particle-in-cell simulations for laser plasma interaction with laser intensity of 1016 W/cm2, plasma density range of 0.01–0.28nc, and scale length of 230–330 μm showed signi?cant pump depletion of the laser energy due to stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) in the low-density region (ne = 0.01–0.2nc). The simulations identi?ed hot electrons generated by SRS in the low-density region with moderate energy and by two-plasmon-decay near ne = 0.25nc with higher energy. The overall hot electron temperature (46 keV) and conversion ef?ciency (3%) were consistent with the experiment’s measurements. The simulations also showed arti?cially reducing SBS would lead to stronger SRS and a softer hot-electron spectrum.
关键词： pump depletion,two-plasmon-decay,stimulated Raman scattering,stimulated Brillouin scattering,laser plasma interaction,hot-electron generation
更新于2025-09-23 15:19:57
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Investigation of Light-sail and Hole-boring Radiation Pressure Accelerations upon the Interaction of Ultra-intense Laser Pulses with Thin Targets
摘要： The radiation pressure acceleration (RPA) scheme with a circularly polarized laser pulse is well-known to provide an efficient generation of intense, energetic quasi-monochromatic ion beams. Depending on the thickness of targets, the RPA appears in two distinct modes: the light-sail (LS) RPA, which develops in ultrathin targets, and the hole-boring (HB) RPA, which develops in relatively thick targets. In this work, we investigated the ion acceleration dynamics of the LS-RPA and the HB-RPA through a fully relativistic particle-in-cell (PIC) simulation. The transition and competition between LS- and HB-RPA modes are investigated with suitable explanations of a one-dimensional (1D) theoretical model. To check the validity of the 1D results and investigate the multi-dimensional effects, two-dimensional simulations are also carried out. The present work may provide a deeper understanding of RPA and useful guidelines for generating high-quality and high-fluence ion beams.
关键词： Ion acceleration,Radiation pressure acceleration,Laser-plasma interaction,Particle-in-cell simulation
更新于2025-09-23 15:19:57
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Experimental investigation on nuclear reactions using a laser-accelerated proton and deuteron beam
摘要： We report an experimental investigation on nuclear reactions using an intense, ultra-short laser-accelerated proton and deuteron beam generated by the interaction of 25 fs, 150 TW Ti: sapphire laser pulse with normal thin foils and foils containing deuterium atoms. The production of a positron-emitting short-lived 11C radio-isotope from the interaction of protons and deuterium ions with a solid boron palette by means of 11B (p, n)11C and 10B (d, n)11C nuclear reactions was studied. The maximum radioactivity in the optimized laser irradiation condition was found to be 5.2 kBq per laser shot, which corresponds to ～9 × 106 atoms of 11C isotopes using the 11B (p, n)11C reaction. The relative ef?ciency of 11C production using a proton and deuteron beam was also explored experimentally. About 30 % enhancement in 11C activity was observed with CD2 coated targets. It was also found that because of the relatively low deuteron energy threshold of the reaction 10B (d, n)11C, even the low energy part of the accelerated deuterons in the spectrum can be used for ef?cient 11C production. In the same setup, the proton-induced fusion reaction in the boron target (p + 5B11 ? 3α + 8.7 MeV) was also studied. The resultant fusion yield and alpha particle energy spectrum was measured.
关键词： p?11B fusion,laser particle acceleration,positron emission tomography (PET) isotopes,laser driven ion acceleration,laser plasma interaction,laser induced nuclear reactions,high intensity lasers
更新于2025-09-19 17:13:59
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Laser-Plasma Interaction Experiment for Solar Burst Studies
摘要： A new experimental platform based on laser-plasma interaction is proposed to explore the fundamental processes of wave coupling at the origin of interplanetary radio emissions. It is applied to the study of electromagnetic (EM) emission at twice the plasma frequency (2ωp) observed during solar bursts and thought to result from the coalescence of two Langmuir waves (LWs). In the interplanetary medium, the first LW is excited by electron beams, while the second is generated by electrostatic decay of Langmuir waves. In the present experiment, instead of an electron beam, an energetic laser propagating through a plasma excites the primary LW, with characteristics close to those at near-Earth orbit. The EM radiation at 2ωp is observed at different angles. Its intensity, spectral evolution, and polarization confirm the LW-coalescence scenario.
关键词： electromagnetic emission,plasma frequency,solar bursts,Langmuir waves,laser-plasma interaction
更新于2025-09-19 17:13:59
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Laser reflection as a catalyst for direct laser acceleration in multipicosecond laser-plasma interaction
摘要： We demonstrate that laser reflection acts as a catalyst for superponderomotive electron production in the preplasma formed by relativistic multipicosecond lasers incident on solid density targets. In 1D particle-in-cell simulations, high energy electron production proceeds via two stages of direct laser acceleration: an initial stochastic backward stage and a final nonstochastic forward stage. The initial stochastic stage, driven by the reflected laser pulse, provides the preacceleration needed to enable the final stage to be nonstochastic. Energy gain in the electrostatic potential, which has been frequently considered to enhance stochastic heating, is only of secondary importance. The mechanism underlying the production of high energy electrons by laser pulses incident on solid density targets is of direct relevance to applications involving multipicosecond laser-plasma interactions.
关键词： particle-in-cell simulations,superponderomotive electron production,direct laser acceleration,laser reflection,multipicosecond laser-plasma interaction
更新于2025-09-19 17:13:59
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Gamma photons and electron-positron pairs from ultra-intense laser-matter interaction: A comparative study of proposed configurations
摘要： High-energy γ-photon generation via nonlinear Compton scattering and electron–positron pair creation via the Breit–Wheeler process driven by laser–plasma interaction are modeled, and a number of mechanisms are proposed. Owing to the small cross section, these processes require both an ultra-intense laser field and a relativistic electron bunch. The extreme conditions for such scenarios can be achieved through recent developments in laser technology. Photon emission via nonlinear Thomson and Compton scattering has been observed experimentally. High-energy positron beams generated via a multiphoton process have recently been observed too. This paper reviews the principles of γ-ray emission and e+e? pair creation in the context of laser–plasma interaction. Several proposed experimental setups for γ-ray emission and e+e? pair creation by ultra-intense laser pulses are compared in terms of their efficiency and the quality of the γ-photon and positron beams produced for ultrashort (15 fs) and longer (150 fs) multi-petawatt laser beams.
关键词： electron–positron pair creation,nonlinear Compton scattering,γ-photon generation,Breit–Wheeler process,laser–plasma interaction
更新于2025-09-19 17:13:59
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The experimental investigation of the <i>hohlraum</i> energetics of two-entrance holes spherical <i>hohlraum</i> at the 100 kJ level laser facility
摘要： The two-laser entrance hole (LEH) spherical hohlraum energetic experiments with all 48 laser beams and two laser pulse shapes at the 100 kJ level laser facility were investigated. In this work, the time-resolved radiation temperature measured by multi-angle x-ray diodes agreed well with LARED simulations, and the peak radiation temperature was up to 260 eV with the laser power of 45 TW. Meanwhile, the backscattered laser energy fraction was less than 5% in the majority of shots, which proposed a low level of laser–plasma interaction (LPI) effect in the spherical hohlraum. However, in the shaped pulse shots with capsules, the stimulated Raman scattering (SRS) of smaller incident angle lasers was signi?cantly increased to 15%. The measured SRS spectrum and LARED simulations showed that the increase in the LPI effects caused by the ablated CH plasma was around 0.1Nc (Nc is the critical density). In summary, according to the experimental results, the x-ray conversion ef?ciency of the vacuum spherical hohlraum was 85%–88% in 3 ns square pulses and 89%–93% in 3.6 ns shaped pulses. It was closer to that of the two-LEH cylindrical hohlraum at the Shen-Guang and NIF facilities.
关键词： LARED simulations,laser-plasma interaction,x-ray conversion efficiency,hohlraum energetics,spherical hohlraum
更新于2025-09-19 17:13:59