Laser Plasma Research Articles

Single-backlighter time-framed X-ray imaging diagnostics of laser plasma using a quasi-coaxial multi-channel Kirkpatrick–Baez microscope

The time-resolved backlight imaging of plasma is crucial for diagnosing density-dependent plasma information. It requires a high-intensity X-ray source and efficient optics. We propose a quasi-coaxial, multi-channel Kirkpatrick–Baez (KB) structure that realizes high-brightness illumination. The angles between the observation axes of neighboring images were significantly reduced. An X-ray multilayer was optimized to enable the system to simultaneously function at two quasi-monochromatic energies to observe the plasma regions of varying densities. Eight-frame high-spatiotemporal-resolution images were obtained with an X-ray backlighter in ShenGuang-III prototype laser facility. This study reports the optical design, multilayer fabrication, and experiments of the proposed microscope.

Generation of highly stable electron beam via the control of hydrodynamic instability

By employing the stabilizer in the supersonic gas nozzle to produce the plasma density profile with a sharp downramp, we have experimentally demonstrated highly stable electron beam acceleration based on the shock injection mechanism in laser wakefield acceleration with the use of a compact Ti:sapphire laser. A quasi-monoenergetic electron beam with a peak energy of 315 MeV ± 12.5 MeV per shot is generated. The electron pointing fluctuations are less than 1 mrad, which is a significant improvement over previous results. This is due to the precise control of the target density distribution and the relative distance between the shock and the laser focal position. The Particle-in-cell simulations demonstrate the sensitivity of electron acceleration to the target profile, while the computational fluid dynamics prove the stabilizer’s effect on gas formation. Further developments of this scheme have the potential to deliver a high repetition rate gas target. The corresponding reproducibility of the accelerated electron beam paves the way for the realisation of compact laser plasma accelerators and the potential application of free electron lasers.

Precise control of sine laser pulse and plasma for enhancing electron acceleration efficiency

Precise control of sine laser pulse and plasma for enhancing electron acceleration efficiency

Laser Synthesis and Photocatalytic Properties of Bismuth Oxyhalides Nanoparticles.

Photocatalysis offers a powerful approach for water purification from toxic organics, hydrogen production, biosolids processing, and the conversion of CO2 into useful products. Further advancements in photocatalytic technologies depend on the development of novel, highly efficient catalysts and optimized synthesis methods. This study aimed to develop a laser synthesis technique for bismuth oxyhalide nanoparticles (NPs) as efficient and multifunctional photocatalysts. Laser ablation of a Bi target in a solution containing halogen salt precursors, followed by laser plasma treatment of the resulting colloid, yielded crystalline bismuth oxyhalides (BixOyXz, where X = Cl, Br, or I) NPs without the need for additional annealing. The composition, structure, morphology, and optical properties of the synthesized BixOyXz (X = Cl, Br, I) NPs were characterized using XRD analysis, electron microscopy, Raman spectroscopy, and UV-Vis spectroscopy. The effect of the halogen on the photocatalytic activity of the double oxides was investigated. The materials exhibited high photocatalytic activity in the degradation of persistent model pollutants like Rhodamine B, tetracycline, and phenol. Furthermore, the BixOyXz NPs demonstrated good efficiency and high yield in the selective oxidation of 5-hydroxymethylfurfural (5-HMF) to 2,5-furandicarboxylic acid (FDCA). The obtained results highlight the promising potential of this laser synthesis approach for producing high-performance bismuth oxyhalide photocatalysts.

Experimental Study on the Propulsion Performance of Laser Ablation Induced Pulsed Plasma

This study investigates the influence of electromagnetic fields on the propulsion performance of laser plasma propulsion. Based on the principle of pulsed plasma thrusters, an electromagnetic field is utilized to accelerate laser plasma, achieving enhanced propulsion performance. This approach represents a novel method for the electromagnetic enhancement of laser propulsion performance. In this paper, pulsed plasma thrusters induced by laser ablation are employed. The generated plasma is subjected to the Lorentz force under the influence of an electromagnetic field to obtain higher speed, thus increasing impulse and specific impulse. An experimental platform for laser-ablation plasma electromagnetic acceleration was constructed to explore the enhancement effect of discharge characteristics and propulsion performance. The results demonstrate that increased laser energy has little effect on discharge characteristics, while the trend of propulsion performance parameters initially rises and then declines. After coupling the electromagnetic field, the propulsion performance is significantly enhanced, with stronger electromagnetic fields yielding more pronounced effects.

Influence of Laser Micro-Texturing and Plasma Treatment on Adhesive Bonding Properties of WC-Co Carbides with Steel.

This article presents research on advanced surface preparation methods for sintered carbides (WC-Co, grade B2) commonly used in the tool industry, particularly in the context of bonding these materials with C45 steel using adhesives. Sintered carbides are widely used due to their high hardness, wear resistance, and good ductility, making them ideal for manufacturing tools operating in harsh conditions. Traditional bonding methods, such as brazing and welding, often result in stresses and cracks. Adhesive bonding has therefore emerged as an effective alternative to mitigate these challenges. The research focuses on comparing the results obtained through modern surface treatment techniques, such as laser micro-texturing and plasma treatment, with traditional methods like grinding, abrasive blasting, and electrolytic etching. The influence of these methods on adhesion properties and the strength of adhesive bonds was evaluated through mechanical tests, including static shear and pull-off tests. An approximately 50% increase in the mechanical strength of adhesive joints was observed for surfaces treated with low-temperature plasma (operating voltage: 18 kV, flow of gasses: 20 l/min., treatment time: 60 s) and laser micro-texturing (infrared fiber laser, wavelength: 1064 nm (±5 nm), power: 20 W), as compared to mechanical grinding. The shear strength of the adhesive joints was equal to 32 MPa and 30 MPa on average in the case of treatment with low-temperature plasma made of helium and argon, respectively. The highest strength of an adhesive joint was equal to 34.5 MPa on average in the case of laser micro-texturing.

Preparation and Characterisation of CdO@Au Nanoparticles by Hybrid System Using Laser Ablation and Plasma Jet Methods for Cytotoxicity Against Rat Embryonic Fibroblast Cell Line

The purpose of the research is to see if cadmium oxide@gold (CdO@Au) nanoparticles produced using the laser ablation and plasma jet method in deionised water (DW) solution could be a viable alternative to typical materials in cytotoxicity of rat embryonic fibroblast (REF) normal cell line. The cadmium nanoparticle core was prepared using a Q-switched Nd:YAG laser at a wavelength of 1,064 nm, with laser pulse energies varying between 800 mJ and 1,000 mJ over 500 shots. Gold nanoparticles shell prepared using atmospheric pressure plasma jet. The structural analysis process used X-ray diffraction (XRD) and UV-vis absorption spectroscopy to study the surface plasmon resonance (SPR) to follow the fast changes in the nanoparticles (NPs) colloidal solutions brought on by the interaction between Au sheets and CdO core. From UV-visible transmittance and absorbance spectra, it was observed that the transmittance pattern that can be obtained decreases. At the same time, the energy gap increases with the increase of laser energy, and this may be due to the increase in absorption. The XRD investigation revealed that the polycrystalline structure of CdO@Au NPs and their preferred orientation along (111) direction. The normal REF cell line was employed in the study to investigate the cytotoxicity of CdO@Au nanoparticles. After 48 h of exposure, the CdO@Au NPs displayed the maximum toxicity at a concentration of 100%.

Design and implementation of the first proton beam transport line in VEGA-3 Petawatt laser system

Laser–Plasma ion acceleration is acquiring importance on a daily basis due to incipient applicability in certain research fields. However, the energy and divergence control of these brilliant sources can be considered a bottleneck in the development of some applications. In this work, we present the commissioning of a compact proton beamline based on a triplet of quadrupoles dedicated to focus and collect short and energetic pulses, open to the user community. The focused proton beam characterization has been carried out by imaging of scintillation detectors with different particle filters. Experimental results have been compared with numerical simulations performed with Monte Carlo code (MCNP6) and TSTEP that have been used to retrieve the deposited energy, the particle tracking, and the particle distribution in different focal configurations, respectively. Charges of nC ( protons with energies up to 17.25 MeV) have been measured at the focal planes reducing the beam to spot sizes of a few millimetres in RMS (root mean square). The percentage fluctuation of the transported charges values has been studied. Finally, the beam rigidity has been measured by transverse moving of the quadrupoles and subsequent beam centroid shift, allowing to cross correlate the deflected energy with the energy ranges resulting from the filtering process.

Microstructure and wear behavior of AISI 316L austenitic stainless steel coating fabricated by laser cladding and plasma nitriding

Microstructure and wear behavior of AISI 316L austenitic stainless steel coating fabricated by laser cladding and plasma nitriding

Proton rings from late-forming ballistic sheath fields

Many laser-driven ion experiments have seen ring-like patterns in the proton angular distribution across a wide array of laser and target parameters. These rings can impede measurement due to the small acceptance angle of detectors and often inhibit potential applications. A myriad of explanations for their formation have been proposed, yet most studies attribute them to some aspect of the laser–plasma interaction. Using 3D particle-in-cell simulations, we show that late-forming strong radial electric fields can arise due to charge separation while the beam is in flight, long after the laser–plasma interaction. These fields can accelerate ions to significant divergences (≈10°) as they propagate away from the target. We compare our results to a recent experiment where a high intensity, short pulse laser (I0≈1021 W/cm2, τ≈30 fs) was incident upon thin (≈1 μm) liquid crystal targets. Our simulations capture all the main features of the experimental results—namely, robust ring formation and larger rings for higher energy protons. In addition, we show that rings do not form for sufficiently short preplasma scale lengths. Finally, we develop a phenomenological model to describe the spatiotemporal structure of the radial electric field and use this to explain the proton rings' energy and preplasma dependencies.

Advances in laser-based bremsstrahlung x-ray sources. I. Optimizing laser-accelerated electrons

In this work, we have performed a suite of kinetic simulations of relativistic laser–plasma interaction under settings relevant to recent and planned experiments on a variety of laser systems. The goal of the study is to illuminate the physics of laser–target coupling and to provide guidance for how to optimize these sources for applications. It is shown that the production of relativistic electrons is maximized when conditions of relativistic induced transparency (RIT) in dense plasmas can be achieved over a large interaction volume at the time of arrival of most intense part of the laser pulse. RIT is shown to enhance both the numbers of relativistic electrons and the energies of the electrons, leading to an increased x-ray dose. A variety of approaches to enhancing laser–target coupling are considered. These include optimizing the effects of low-density pre-plasma (arising either from finite laser pedestal or from the use of foam coatings) and of modifying the laser focusing geometry to reduce effects of filamentation and self-focusing. Evidence of a novel approach to achieving stable laser propagation over distances of tens of micrometers in a plasma gradient is also presented. These conditions coincide with plasma and laser conditions explored in recent experiments on the Omega EP laser system and compare favorably with an analytic criterion for stable laser propagation in relativistically underdense plasma obtained from a nonlinear Wentzel–Kramers–Brillouin analysis.

PLLA honeycombs activated by plasma and high-energy excimer laser for stem cell support

In this study, we constructed and activated honeycomb structures on perfluorinated substrates subjected to KrF laser treatment (wavelength 248 nm). We selected the biopolymer poly L-lactic acid (PLLA) as the honeycomb material, which was dissolved in a mixture of chloroform/methanol. A micropattern of a plasma-treated perfluorethyleneperopylene (FEP) substrate was prepared by improved phase separation during dip-coating. The PLLA micropattern was subsequently treated with an excimer laser with a laser fluence of 10 mJ.cm-2 and with a different number of laser pulses. Alternatively, plasma exposure can be used as a secondary treatment. The surface morphologies of the pristine and laser-treated PLLA patterns were studied using atomic force and scanning electron microscopy. The surface chemistry was analyzed using energy-dispersive spectroscopy and X-ray photoelectron spectroscopy. In addition, the metabolic activity of adipose stem cells was evaluated using the MTS test, and cell numbers in selected samples were determined. The morphology of cells growing in the honeycomb-like pattern was studied in detail using fluorescence microscopy. In all, we used a combination of honeycomb pattern (HCP) laser treatment and plasma treatment to construct an optimal scaffold for adipose stem cell culture.

(Invited) Rethinking Diffusion Media for Polymer Electrolyte Fuel Cells: Replacing Fluoropolymers and Engineering Microstructures

Diffusion media are performance-defining components in polymer electrolyte fuel cells, where they are responsible for multiple critical functions including providing an open porous structure for multiphase mass transport, a solid scaffold for electron and heat transport, and cushioning mechanical compression of the cell1. State-of-the-art materials are composed of an arrangement of two layers, namely a carbon fiber substrate and a microporous layer that have been engineered to sustain the complex performance requirements of the electrochemical cell. However, to date, the microstructure (e.g. pore size distribution) and surface chemistry (e.g. coating distribution, local wettability) of standard materials have not been precisely engineered which has motivated intensive research to optimize existing material sets. To improve water management, new methods aimed to introduce low capillary pressure pathways for the water to leave the cell. A non-exhaustive list of examples include the use of laser perforation2, plasma modifications3, or grafting with patterned wettability4. While these approaches have shown promising results, the addition of multiple steps onto the existing manufacturing pipelines results in higher manufacturing costs. Thus, developing methodologies that can readily fabricate precisely controlled microstructures and wetting properties from the bottom-up, while using low-cost and scalable manufacturing approaches, is an appealing avenue to further advance the technology.In this lecture, I will first review the state-of-the-art in diffusion media research and highlight key challenges. Second, I will introduce the pressing need to find alternative hydrophobic coatings to prevalent per- and polyfluoroalkyl molecules such as polytetrafluoroethylene and fluorinated ethylene propylene, as they bioaccumulate and their derivatives are damaging to living organisms5, resulting in a prospective ban6. Our group investigates the application of uniformly-distributed, thin-film coatings based on siloxanes, silanes and hydrocarbons. I will discuss the correlation between the chemical composition of these coatings, their intrinsic wetting properties, and ultimately their impact on single cell performance. Additionally, I will discuss strategies to replace fluoropolymers in conventional microporous layer inks and pastes. Third and finally, I will introduce a new approach based on non-solvent induced phase separation (NIPS) to manufacture diffusion media with controlled three-dimensional structures7. Using NIPS, we can synthesize microstructurally diverse porous media, including isoporous, pore size gradients, and structures with bimodal pore size distributions8,9. I will discuss the correlation between the diffusion media microstructure prepared with NIPS and the resulting performance in single cells. Using these methods, we aim to integrate the combined functions of carbon fiber substrates and microporous layers in a single material concept, thereby decreasing complexity and costs. References Mathias, M. F., Roth, J., Fleming, J. & Lehnert, W. Diffusion media materials and characterisation. in Handbook of Fuel Cells (John Wiley & Sons, Ltd, 2010). doi:10.1002/9780470974001.f303046.Csoklich, C., Xu, H., Marone, F., Schmidt, T. J. & Büchi, F. N. Laser Structured Gas Diffusion Layers for Improved Water Transport and Fuel Cell Performance. ACS Appl. Energy Mater. 4, 12808–12818 (2021).Zahiri, B. et al. Through-plane wettability tuning of fibrous carbon layers via O2 plasma treatment for enhanced water management. Appl. Surf. Sci. 458, 32–42 (2018).Forner-Cuenca, A. et al. Engineered Water Highways in Fuel Cells: Radiation Grafting of Gas Diffusion Layers. Adv. Mater. 27, 6317–6322 (2015).Ackerman Grunfeld, D. et al. Underestimated burden of per- and polyfluoroalkyl substances in global surface waters and groundwaters. Nat. Geosci. 17, 340–346 (2024).Tyrrell, N. D. A Proposal That Would Ban Manufacture, Supply, and Use of All Fluoropolymers and Most Fluorinated Reagents within the Entire EU. Org. Process Res. Dev. 27, 1422–1426 (2023).Non‐Solvent Induced Phase Separation Enables Designer Redox Flow Battery Electrodes - Wan - 2021 - Advanced Materials - Wiley Online Library. https://onlinelibrary.wiley.com/doi/full/10.1002/adma.202006716.Jacquemond, R. R. et al. Microstructural engineering of high-power redox flow battery electrodes via non-solvent induced phase separation. Cell Rep. Phys. Sci. 3, 100943 (2022).Wan, C. T.-C., Jacquemond, R. R., Chiang, Y.-M., Forner-Cuenca, A. & Brushett, F. R. Engineering Redox Flow Battery Electrodes with Spatially Varying Porosity Using Non-Solvent-Induced Phase Separation. Energy Technol. 11, 2300137 (2023).

Simulation of laser plasma wakefield acceleration with external injection based on Bayesian optimization

Abstract In laser wakefield acceleration (LWFA), injecting an external electron beam at certain energy is a promising approach to achieving high-quality electron beam with low energy spread and low emittance. In this paper, the process of laser wakefield acceleration with an external injection at 10 pC has been studied in simulations. A Bayesian optimization method is used to optimize the key laser and plasma parameters, so that the electron beam is accelerated to the expected energy with a small emittance and energy spread growth. The effect of rising edge of the plasma on the transverse properties of the electron beam is simulated and optimized in order to ensure that the external electron beam is injected into the plasma without significant emittance growth. Finally, a high-quality electron beam with an energy of 1.5 GeV, the normalized transverse emittance of 0.5 mm·mrad and the relative energy spread of 0.5% at 10 pC is obtained.

Boosting of fusion reactions initiated by laser accelerated proton beam in a non-thermal neutral and non-neutral proton-boron plasma

In this paper we explore the possibility of boosting the reactivity of non-thermal proton-boron fusion triggered by an external proton beam in a plasma at densities near and lower than solid density and temperature characteristic to laser plasma interaction. Suprathermal protons generated by collisions with alpha particles, as well as energetic protons created by the beam protons that do not undergo fusion during the stopping down in the bulk plasma, are accounted for. In addition, we conduct calculations for non-neutral plasma, motivated by recent suggestion that the number of fusion events in such system may be increased.

Effects of laser cladding and plasma nitriding on microstructure and properties of Cu-Al alloy

Effects of laser cladding and plasma nitriding on microstructure and properties of Cu-Al alloy

Generation of 10 kT axial magnetic fields using multiple conventional laser beams: A sensitivity study for kJ PW-class laser facilities

Strong multi-kilotesla magnetic fields have various applications in high-energy density science and laboratory astrophysics, but they are not readily available. In our previous work [Y. Shi et al., Phys. Rev. Lett. 130, 155101 (2023)], we developed a novel approach for generating such fields using multiple conventional laser beams with a twist in the pointing direction. This method is particularly well-suited for multi-kilojoule petawatt-class laser systems like SG-II UP, which are designed with multiple linearly polarized beamlets. Utilizing three-dimensional kinetic particle-in-cell simulations, we examine critical factors for a proof-of-principle experiment, such as laser polarization, relative pulse delay, phase offset, pointing stability, and target configuration, and their impact on magnetic field generation. Our general conclusion is that the approach is very robust and can be realized under a wide range of laser parameters and plasma conditions. We also provide an in-depth analysis of the axial magnetic field configuration, azimuthal electron current, and electron and ion orbital angular momentum densities. Supported by a simple model, our analysis shows that the axial magnetic field decays owing to the expansion of hot electrons.

Ion motion in strongly magnetized cluster laser plasma

Abstract This paper investigates the interaction of high intensity, circularly polarized, short laser pulses with heavy cluster plasma through analytical modeling and numerical simulations. The optimal parameters were found for the generation of several GigaGs quasi-stationary magnetic field by using the upgraded analytical model and detailed 3D PIC simulations. It is confirmed that a field of such strength slows down the thermal expansion of the cluster core in the direction transverse to the laser beam axis, which can be used in nuclear physics. The generated inward shocks produce ion core compression, which is relevant to nuclear fusion. The electrostatic interaction between the rotating laser field, electrons and ions leads to an ion spiral density distribution in the cluster’s transversal plane, which is absent in a cluster irradiated by linearly polarized pulses with the same parameters.

Characterization of optical depth for laser produced plasma extreme ultraviolet source

This study investigates the emission mechanism of laser-produced plasma extreme ultraviolet source (LPP-EUV). In the experiment, the EUV radiation is generated by a 1064 nm laser interacting with slab Sn target. The EUV emission is characterized by EUV energy monitors and an EUV spectrometer. The dependency of CE on laser intensity and plasma relative optical depth is explored by a plasma emission-absorption layer model. The dependency is confirmed by an optical interferometry measurement of plasma electron density for the first time. Our work provides a method for characterizing and optimizing the optical depth of laser driven EUV source.

Optical ionization effects in kHz laser wakefield acceleration with few-cycle pulses

We present significant advances in laser wakefield acceleration (LWFA) operating at a 1 kHz repetition rate, employing a sub-TW, few-femtosecond laser and a continuously flowing hydrogen gas target. We conducted a comprehensive study assessing how the nature of the gas within the target influences accelerator performance. This work confirms and elucidates the superior performance of hydrogen in LWFA driven by few-cycle, low-energy laser pulses. Our system generates quasimonoenergetic electron bunches with energies up to 10 MeV, bunch charges of 2 pC, and angular divergences of 15 mrad. Notably, our scheme relying on differential pumping enables continuous operation at kHz repetition rates, contrasting with previous systems that operated in burst mode to achieve similar beam properties. Particle-in-cell simulations explain hydrogen's superior performances: the ionization effects in nitrogen and helium distort the laser pulse, negatively impacting the accelerator performance. These effects are strongly mitigated in hydrogen plasma, thereby enhancing beam quality. This analysis represents a significant step forward in optimizing and understanding kHz LWFA. It underscores the critical role of hydrogen and the imperative need to develop hydrogen-compatible target systems capable of managing high repetition rates, as exemplified by our differential pumping system. These advances lay the groundwork for further developments in high-repetition-rate laser plasma accelerator technology. Published by the American Physical Society 2024