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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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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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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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Laser-Plasma Accelerated Protons: Energy Increase in Gas-Mixtures Using High Mass Number Atomic Species
摘要： The idea of using a gas-mixture comprising atoms with a high mass number in order to increase proton energies in laser induced plasma acceleration at critical density is investigated by means of 2D PIC (Particle-In-Cell) simulations. Comparing and discussing the case of a pure hydrogen plasma and that of a plasma containing higher mass number species with a small percentage of hydrogen, we demonstrate that the mixture enhances the energies of the accelerated protons. We also show that using a gas-mixture introduces the possibility of using the densities ratio in order to change the relative acceleration of the species.
关键词： laser wake-field acceleration (LWFA),proton acceleration,gas-mixture,high density gas-jet
更新于2025-09-19 17:13:59
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Optimization of laser parameters for proton acceleration using double laser pulses in TNSA mechanism
摘要： The energy of protons accelerated by ultra-intense lasers in the target normal sheath acceleration (TNSA) mechanism can be greatly enhanced by the laser parameter optimization. We propose to investigate the optimization of laser parameters for proton acceleration using double laser pulses in TNSA mechanism. The sheath field generation at the rear side of the target is significantly affected by the introduction of second laser pulse in TNSA mechanism, and consequently, the energy of the accelerated protons is also modified. The second laser pulse was introduced with different delays to study its impact on proton acceleration. Our study shows that the interplay of laser intensity and pulse duration of both laser pulses affects the proton acceleration. It was found that the proton maximum energy is the function of both laser intensity and pulse duration. A number of simulations have been performed to obtain maximum proton energy data under different combinations of laser intensity and pulse duration for the two laser pulses. The simulation results account for the underline physics for the proton bunch energy and the sheath field as a function of pulse intensity and pulse delay.
关键词： proton acceleration,ultrashort laser pulse,Laser–plasma interaction
更新于2025-09-16 10:30:52
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Effect of Small Focus on Electron Heating and Proton Acceleration in Ultrarelativistic Laser-Solid Interactions
摘要： Acceleration of particles from the interaction of ultraintense laser pulses up to 5 × 1021 W cm?2 with thin foils is investigated experimentally. The electron beam parameters varied with decreasing spot size, not just laser intensity, resulting in reduced temperatures and divergence. In particular, the temperature saturated due to insufficient acceleration length in the tightly focused spot. These dependencies affected the sheath-accelerated protons, which showed poorer spot-size scaling than widely used scaling laws. It is therefore shown that maximizing laser intensity by using very small foci has reducing returns for some applications.
关键词： proton acceleration,focal spot size,ultrarelativistic laser-solid interactions,electron heating,laser intensity
更新于2025-09-16 10:30:52
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Proton acceleration by collisionless shocks using a supersonic H <sub/>2</sub> gas-jet target and high-power infrared laser pulses
摘要： For most laser-driven ion acceleration applications, a well-characterized intense ion beam with a low divergence and a controllable energy spectrum produced at a high repetition rate is needed. Gas-jet targets have given promising results in simulations, and they have several technical advantages for high-repetition-rate lasers. In this work, we report on proton acceleration to energies up to 6 MeV using a supersonic H2 gas-jet target at the LULI PICO2000 laser facility. The experimental results are compared with the plasma hydrodynamics and the particle-in-cell simulations to identify the acceleration mechanisms at play.
关键词： supersonic H2 gas-jet target,collisionless shocks,proton acceleration,high-power infrared laser pulses
更新于2025-09-12 10:27:22
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Proton acceleration due to laser plasma interactions from mass-limited spherical targets
摘要： The proton acceleration processes involved in the interaction of an ultrashort circularly polarized laser with a near-critical density spherical target are investigated in this paper using three dimensional particles in cell simulations. Both the target size and the target density are varied to understand their influence on the accelerated beam of protons. The target is efficiently heated by relativistic transparency, and a complicated interplay is observed between the participating interaction processes. The electron heating and recirculations help in the formation of shocks which exert a further push to the protons accelerated by the electrostatic sheath formed due to the ponderomotive force. A maximum peak proton energy of about 40 MeV is observed, which is the result of the cumulative effects of various acceleration mechanisms. Electron jets are observed in the forward laser direction for the larger target size, which suppresses the energy of the proton beams.
关键词： spherical targets,laser plasma interactions,electrostatic sheath,electron heating,proton acceleration,relativistic transparency,ponderomotive force,shock formation
更新于2025-09-12 10:27:22
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Design and optimization of a laser-PIXE beamline for material science applications
摘要： Multi-MeV proton beams can be generated by irradiating thin solid foils with ultra-intense (>1018 W/cm2) short laser pulses. Several of their characteristics, such as high bunch charge and short pulse duration, make them a complementary alternative to conventional radio frequency-based accelerators. A potential material science application is the chemical analysis of cultural heritage (CH) artifacts. The complete chemistry of the bulk material (ceramics, metals) can be retrieved through sophisticated nuclear techniques such as particle-induced X-ray emission (PIXE). Recently, the use of laser-generated proton beams was introduced as diagnostics in material science (laser-PIXE or laser-driven PIXE): Coupling laser-generated proton sources to conventional beam steering devices successfully enhances the capture and transport of the laser-accelerated beam. This leads to a reduction of the high divergence and broad energy spread at the source. The design of our hybrid beamline is composed of an energy selector, followed by permanent quadrupole magnets aiming for better control and manipulation of the final proton beam parameters. This allows tailoring both, mean proton energy and spot sizes, yet keeping the system compact. We performed a theoretical study optimizing a beamline for laser-PIXE applications. Our design enables monochromatizing the beam and shaping its final spot size. We obtain spot sizes ranging between a fraction of mm up to cm scale at a fraction of nC proton charge per shot. These results pave the way for a versatile and tunable laser-PIXE at a multi-Hz repetition rate using modern commercially available laser systems.
关键词： hybrid beamline and beam manipulation,laser-PIXE,Cultural heritage,particle induced X-ray emission (PIXE),laser-driven proton acceleration,ion beam analysis
更新于2025-09-12 10:27:22
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Characterization of laser-driven proton acceleration from water microdroplets
摘要： We report on a proton acceleration experiment in which high-intensity laser pulses with a wavelength of 0.4 μm and with varying temporal intensity contrast have been used to irradiate water droplets of 20 μm diameter. Such droplets are a reliable and easy-to-implement type of target for proton acceleration experiments with the potential to be used at very high repetition rates. We have investigated the influence of the laser’s angle of incidence by moving the droplet along the laser polarization axis. this position, which is coupled with the angle of incidence, has a crucial impact on the maximum proton energy. Central irradiation leads to an inefficient coupling of the laser energy into hot electrons, resulting in a low maximum proton energy. the introduction of a controlled pre-pulse produces an enhancement of hot electron generation in this geometry and therefore higher proton energies. However, two-dimensional particle-in-cell simulations support our experimental results confirming, that even slightly higher proton energies are achieved under grazing laser incidence when no additional pre-plasma is present. illuminating a droplet under grazing incidence generates a stream of hot electrons that flows along the droplet’s surface due to self-generated electric and magnetic fields and ultimately generates a strong electric field responsible for proton acceleration. The interaction conditions were monitored with the help of an ultra-short optical probe laser, with which the plasma expansion could be observed.
关键词： high-intensity laser pulses,water microdroplets,particle-in-cell simulations,laser-driven,proton acceleration
更新于2025-09-11 14:15:04