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Investigation the effect of laser ablation parameters in a liquid in order to reduce the pulse energy during laser shock peening
摘要： The features of laser shock peening technology was studied in relation to the physical processes occurring during and after laser treatment. The effect of laser parameters on the results of the process was investigated. It was shown that the reduce of the diameter of the laser spot while maintaining the intensity leads to a decrease in the effect of LSP. This phenomenon was studied from the point of view of the features of plastic deformation at various sizes of the treatment zone using the standard model for the LSP process. Besides the features of the development of a plasma plume during laser ablation in a liquid are considered. It was shown that the liquid determines the geometry of the plume evolution and the shock wave caused by it. The process parameters used and the results obtained are important for the development of low-energy LSP technology.
关键词： Surface treatment,Laser shock peening,Laser-produced plasmas,Laser ablation in liquid,Nickel alloys,Laser pulses,Lasers
更新于2025-09-23 15:21:01
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Laser-produced plasmas as drivers of laboratory collisionless quasi-parallel shocks
摘要： The creation of a repeatable collisionless quasi-parallel shock in the laboratory would provide a valuable platform for experimental studies of space and astrophysical shocks. However, conducting such an experiment presents substantial challenges. Scaling the results of hybrid simulations of quasi-parallel shock formation to the laboratory highlights the experimentally demanding combination of dense, fast, and magnetized background and driver plasmas required. One possible driver for such experiments is high-energy laser-produced plasmas (LPPs). Preliminary experiments at the University of California, Los Angeles, have explored LPPs as drivers of quasi-parallel shocks by combining the Phoenix Laser Laboratory [Niemann et al., J. Instrum. 7, P03010 (2012)] with a large plasma device [Gekelman et al., Rev. Sci. Instrum. 87, 025105 (2016)]. Beam instabilities and waves characteristic of the early stages of shock formation are observed, but spatial dispersion of the laser-produced plasma prematurely terminates the process. This result is illustrated by experimental measurements and Monte Carlo calculations of LPP density dispersion. The experimentally validated Monte Carlo model is then applied to evaluate several possible approaches to mitigating LPP dispersion in future experiments.
关键词： beam instabilities,collisionless quasi-parallel shocks,plasma dispersion,laser-produced plasmas,Monte Carlo calculations
更新于2025-09-23 15:21:01
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Absolute stimulated Raman side scatter in direct-drive laser-produced plasmas
摘要： Production of suprathermal electrons by stimulated Raman scattering (SRS) is a principal concern for contemporary direct-drive inertial confinement fusion experiments at the National Ignition Facility and similar systems since such electrons penetrate and preheat the target core, preventing efficient implosion. The higher temperatures and longer scale lengths in these experiments favor SRS over two-plasmon decay, which predominated in earlier experiments. In particular, current experiments are expected to exceed the threshold for absolute Raman side scatter, which would then dominate the interaction since it grows temporally until saturated by nonlinear mechanisms such as hot-electron production. Until recently, analyses of SRS side scatter have treated the case of a single laser beam incident on a plasma, but the direct-drive approach to laser fusion employs a multitude of beams to drive the implosion. Here, we present an analysis that can be applied to an arbitrary number of beams with varied angles of incidence and polarizations. In the case of a single beam, it allows a physically motivated derivation and verification of an analytic threshold formula. In the general case of multiple beams and arbitrary orientation and polarizations, the threshold is found by numerical integration of a set of first-order linear partial differential equations.
关键词： direct-drive,stimulated Raman scattering,inertial confinement fusion,laser-produced plasmas,suprathermal electrons
更新于2025-09-23 15:21:01
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Time-dependent optimization of laser-produced molecular plasmas through high-order harmonic generation
摘要： Analysis and characterization of laser-produced plasmas (LPPs) require the advanced methods for determination of different multiparticle component formation and spreading. Time-resolved high-order harmonic generation (HHG) in spreading LPPs allows determining optimal conditions for this process. One of the most important parameters of HHG in LPP is the delay between the heating and driving pulses. We demonstrate that the optimization of delays allows achieving the maximal harmonic yields in LPP created on the surfaces of the solid targets possessing different molar masses (m). The optimal delays (t) for B4C, ZnO, GaP, GaAs, and Ag2S plasmas were determined to be approximately 200, 300, 350, 500, and 700 ns, respectively. These variations of delays correspond to the t1(m)0.5 dependence for different materials. We demonstrate the applicability of the proposed method for analysis of the resonance-enhanced harmonics in atomic and molecular plasmas (Mo and MoS2) and for studies of large perovskite aggregates as potential emitters of harmonics. This diagnostic technique can also be applied to the analysis of the presence of different nanostructures in LPPs through HHG with a high spatiotemporal resolution.
关键词： perovskite aggregates,laser-produced plasmas,molar masses,time-resolved,high-order harmonic generation,optimization,nanostructures,resonance-enhanced harmonics
更新于2025-09-19 17:13:59
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Calculation of the extreme-ultraviolet radiation conversion efficiency for a laser-produced tin plasma source
摘要： This article presents the calculation results on the conversion efficiency (CE) of 1.064 μm laser-produced plasmas (LPPs) extreme-ultraviolet (EUV) tin (Sn) light sources with the Gaussian and a triangular-flat-topped like laser pulse temporal shapes. The computational model includes a collisional-radiative model and 1D hydrodynamics code that predicts reported experimental and theoretical results on the CE of 1.064 μm and 10.6 μm LPP EUV sources with the planar and mass-limited spherical Sn targets. The calculations for the case of a spherical target reveal that an optimum triangular-flat-topped like laser pulse generates a higher CE compared to the Gaussian pulse, especially, for the longer laser pulse duration than ~30 ns. The study demonstrated that a rising intensity rate of the laser pulse has a vital role to optimize the CE as well as to prolong the in-band (13.5 ± 0.135 nm) spectral emission of a small Sn spherical target. The model predicts a ~30 ns rising time duration for a linearly increasing intensity of triangular-flat-topped 1.064 μm laser pulse is necessary to obtain a maximum CE with a typical ~40 μm diameter liquid Sn droplet.
关键词： Extreme-ultraviolet lithography,Collisional-radiative model,Laser-produced plasmas,Radiation-hydrodynamics,Highly-charged tin spectra
更新于2025-09-19 17:13:59
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Experimental Observation of Ion–Ion Acoustic Instability Associated with Collisionless Shocks in Laser-produced Plasmas
摘要： We report experimental evidence of ion–ion acoustic instability in laser-produced astrophysically relevant plasma. Irradiation of a copper foil with a short (2 ps) intense (1017 W cm?2) laser pulse generates dense hot plasma, whose expansion into the rare?ed preplasma generates the electrostatic collisionless shock. A shock-re?ected ion beam penetrates through the shock upstream excites the ion–ion acoustic instability. The shock oscillation electric ?eld and the instability ?lamentary modulation are monitored by proton radiography. Particle-in-cell and particle-tracing simulations reproduce the experimental observation.
关键词： Laboratory astrophysics,collisionless shocks,laser-produced plasmas,ion–ion acoustic instability
更新于2025-09-19 17:13:59
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Resonance Enhancement in Laser-Produced Plasmas (Concepts and Applications) || Front Matter
摘要： The motivation in writing this book is to show the most recent findings of newly emerged field of resonance-enhanced high-order harmonic generation (HHG) using the laser pulses propagating through the narrow and extended laser-produced plasma plumes. It becomes obvious that the developments in this field are aimed for improvement of harmonic yield through precise study of resonance effects during fine-tuning of driving pulses to the resonances. The purpose of writing this book is to acquaint the readers with the most advanced, recently developed methods of plasma harmonics generation at the conditions of coincidence of some harmonics, autoionizing states, and some ionic transitions possessing strong oscillator strengths. This book demonstrates how one can improve the plasma harmonic technique using this approach.
关键词： extreme ultraviolet,plasma harmonics,laser-produced plasmas,high-order harmonic generation,resonance enhancement,XUV,nonlinear optics,HHG
更新于2025-09-19 17:13:59
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Laser-Induced Breakdown Spectroscopy Assisted by Machine Learning for Plastics/Polymers Identification
摘要： In the present work, Laser-Induced Breakdown Spectroscopy (LIBS) is used for the discrimination/identification of different plastic/polymeric samples having the same polymeric matrix but containing different additives (as e.g., fillers, flame retardants, etc.). For the classification of the different plastic samples, some machine learning algorithms were employed for the analysis of the LIBS spectroscopic data, such as the Principal Component Analysis (PCA) and the Linear Discriminant Analysis (LDA). The combination of LIBS technique with these machine learning algorithmic approaches, in particular the latter, provided excellent classification results, achieving identification accuracies as high as 100%. It seems that machine learning paves the way towards the application of LIBS technique for identification/discrimination issues of plastics and polymers and eventually of other classes of organic materials. Machine learning assisted LIBS can be a simple to use, efficient and powerful tool for sorting and recycling purposes.
关键词： laser-induced breakdown,polymers,LIBS,machine learning,identification of polymers,laser produced plasmas
更新于2025-09-16 10:30:52
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Laser-Produced Magnetic-Rayleigh-Taylor Unstable Plasma Slabs in a 20?T Magnetic Field
摘要： Magnetized laser-produced plasmas are central to many novel laboratory astrophysics and inertial confinement fusion studies, as well as in industrial applications. Here we provide the first complete description of the three-dimensional dynamics of a laser-driven plasma plume expanding in a 20 T transverse magnetic field. The plasma is collimated by the magnetic field into a slender, rapidly elongating slab, whose plasma-vacuum interface is unstable to the growth of the 'classical,' fluidlike magnetized Rayleigh-Taylor instability.
关键词： plasma dynamics,magnetic field,Rayleigh-Taylor instability,laser-produced plasmas
更新于2025-09-16 10:30:52
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Versitile X-ray diagnostics of laser-produced high-temperature plasmas using an ultra-high luminosity spectrometer
摘要： Versitile diagnostics of high-temperature magnesium laser-produced plasmas is performed using an ultra-high luminosity X-ray focusing crystal spectrometer. The plasmas are produced by focusing nanosecond laser pulses (0.53 mm, 1 J, 2 ns) on a massive magnesium target. The absolute intensities and X-ray yields are measured for the resonance lines of H- and He-like ions (spectral range: D?l = 8 –10 ?), the electron temperature of plasmas is determined (range: Te = 200 – 550 eV), and the behaviour of these parameters is established in a broad range of laser pulse energy EL (10 mJ – 1 J). This approach permits the parameters of laser-plasma radiation sources to be monitored in real time in a wide intensity range (difference in intensity: over 104) and in a broad range of plasma parameters.
关键词： laser-produced plasmas,X-ray spectrometers,high-temperature plasma diagnostics,X-ray spectroscopy and metrology,multiply charged ions
更新于2025-09-16 10:30:52