The characteristic of the lateral interaction of two plasma plumes in $Ar$ background gas at high pressures was reported in recent publication [Yadav {\it et. al.}, J. Phys. D: Appl. Phys. {\bf 50}, 053421 (2017)]. Further we have investigated the interaction characteristics of plumes in $He$, $Ne$, $Ar$ and $Xe$ background gases to see the effect of mass on the interaction. The present work illustrate the applicability of the present model for theoretical understanding of dynamics, structure, density variation, shock wave formations and their interactions of two propagating plasma plumes in a wide range of ambient conditions. The formation of interaction region, geometrical shape and strength of the shock fronts and subsequent regular and Mach reflections in accordance with the nature and pressure of ambient gas are successfully captured in the simulations. The observed results are supported by the reported experimental observations under identical conditions.
An experimental investigation of laser produced colliding plasma of aluminium target in the presence of external magnetic field in vacuum is done. Characteristic parameters and line emission of plasma plume in the presence of magnetic field are compared with those for field free case. Axial expansion of the plasma is slowed down in the presence of magnetic field as compared to the field free case. Contrary to the field free case no sharp interaction zone is observed. Higher electron temperature and increased ionic line emission from singly as well as doubly ionized aluminium can be attributed …
The electron density is one of the crucial parameters in plasma plume, which plays a major role in producing the key reactive species required for biological and industrial applications. In this work, experiments are performed to estimate the spatial variation of plasma density in a steady plume. The time-resolved images obtained from the ICCD camera, plume current measurements are utilized for estimating the plasma density. We observed the plasma density increases from the glass nozzle to the plume tip. This increase in plasma density is due to the combined effect of reduction of drift veloci…
In order to optimize the parameters of the plasma plume for atmospheric pressure plasma applications such as biological and industrial applications, it is highly necessary to thoroughly understand its characteristics. In this paper, various diagnostic techniques are discussed to characterize the atmospheric pressure plasma plume. The major emphasis of this work is to utilize possibly simple methods, low complexity in post data analysis and obtain in-situ information. The parameters of the plasma plume such as spatial variation of gas temperature, electron excitation temperature, plume velocity…
We have carried out a 3D ideal-MHD (Magnetohydrodynamic) simulation to study the evolution of laser generated plasma plume in a moderate external magnetic field (0.13 T) oriented perpendicular to the flow direction of the plasma plume. The simulation shows that the plasma plume pushes the external magnetic field lines outward in the direction of the expansion. This leads to compression and bending of the magnetic field lines.The force resulting from the change in shape and the density of magnetic field lines opposes the expansion of the plume. An elliptic layer of shocked plasma is formed at t…
We generated and characterized plasma with single and double picosecond laser pulses in order to study the plume dynamics and to control the plasma properties. The double-pulse scheme was found to be superior for the generation of a homogeneous plasma. The lateral expansion was prominent for irradiation schemes wherein energy of the first pulse is lower/equal to that of the second pulse. While the velocities of the fast and slow species were found to be nearly equal, the emission counts corresponding to slow species are larger for single pulse compared to the double pulse.
In the present work, we report the dynamics and geometrical features of the plasma plume formed by the laser ablation of copper and graphite (carbon) targets in the presence of different transverse magnetic field. This work emphasizes on the effect of atomic mass of the plume species on the diamagnetic behaviour and geometrical aspect of the expanding plasma plume in the magnetic field. The time-resolved analysis of the simultaneously captured two directional images in orthogonal to the expansion axis is carried out for the comparative study of projected three-dimensional structure of copper a…
During periods of strong magnetic activity, cold dense plasma from the plasmasphere typically forms a plume extending towards the dayside magnetopause, eventually reaching it. In this work, we present a large-scale two-dimensional fully kinetic Particle-In-Cell simulation of a reconnecting magnetopause hit by a propagating plasmaspheric plume. The simulation is designed so that it undergoes four distinct phases: initial unsteady state, steady state prior to plume arrival at the magnetospause, plume interaction and steady state once the plume is well engulfed in the reconnection site. We show t…
Composition analysis of LiF-C thin film for neutral and ionic contributions in Front Ablation (FA) and Back Ablation (BA) geometries in vacuum and 2\times10-1 mbar argon has been done. Temporal evolution of ionic to neutral ratio and neutral abundance for both the geometries has been estimated. For neutral abundance, two approaches viz Atomic Data and Analysis Structure (ADAS) analysis as well as integrated intensity ratio of Li I 670.1 nm and Li I 610.3 nm lines assuming LTE conditions are explored. The present attempt will be interesting from the view point of understanding the evolution of …
We describe the measurements to control the morphology and hence the characteristics of a picosecond laser produced chromium plasma plume upon double-pulse (DP) irradiation compared to its single-pulse (SP) counterpart. DP schemes are realized by employing two geometries wherein the inter-pulse delay ($τ_p$) in the collinear geometry and the spatial separation ($Δx$) are the control parameters for schemes DP$_1$ and DP$_2$ respectively. The aspect ratio (plume length/plume width) decreases upon increasing parameters such as pressure, delay between pulses and the energy of the second pulse in D…
Time-varying diamagnetism in laser-produced plasma moving across the transverse magnetic field with different field strengths has been studied using fast imaging and magnetic probe. The emphasis of the present work is on the development of suitable B-dot probe and quantitative analysis of induced diamagnetic field in an expanding plasma plume. A Helmholtz coil associated with pulsed power system is used to produce uniform magnetic field of different strengths. Helmholtz coil allowed the plume imaging along the magnetic field lines, which gives the direct structural information of the induced d…
Laser ablation plasma thrusters are an emerging space propulsion concept that provides promise for lightweight payload delivery. Predicting the lifetime and performance of these thrusters hinges on a comprehensive characterization of the expansion dynamics of the ablated plasma plume. While state-of-the-art techniques for simulating plasmas are often particle-based, a grid-based direct kinetic solver confers advantages in such a transient and inhomogeneous problem by eliminating statistical noise. A direct kinetic solver including interparticle collisions is employed on a plume expansion model…
In this work a method based on self-mixing interferometry (SMI) is presented for probing the concentration of plasma plumes induced by multi-pulse laser ablation. An analytical model is developed to interpret the single-arm interferometric signal in terms of plasma electron number density. Its time dependence follows a power-law scaling which is determined by concurrent effects of plume accumulation and propagation. The model has been applied for the experimental study of plume formation at variable laser pulse frequencies on different materials. The plume expansion dynamics has been observed …
A self-consistent model is presented for performing steady-state fully kinetic Particle-in-Cell simulations of magnetised plasma plumes. An energy-based electron reflection prevents the numerical pump instability associated with a typical open-outflow boundary, and is shown to be sufficiently general that both the plume kinetics and plasma potential demonstrate domain independence (within 4%). This is upheld by non-stationary Robin-type boundary conditions on the Poisson's equation, coupled to a capacitive circuit that allows physical evolution of the downstream potential drop in the transient…
We study the steady-state expansion of a collisionless, electrostatic, quasi-neutral plasma plume into vacuum, with a fluid model. We analyze approximate semi-analytical solutions, that can be used in lieu of much more expensive numerical solutions. In particular, we focus on the earlier studies presented in Parks and Katz (1979), Korsun and Tverdokhlebova (1997), and Ashkenazy and Fruchtman (2001). By calculating the error with respect to the numerical solution, we can judge the range of validity for each solution. Moreover, we introduce a generalization of earlier models that has a wider ran…
Large-amplitude current-driven instabilities in hollow cathode plumes can generate energetic ions responsible for cathode sputtering and spacecraft degradation. A 2D2V (two dimensions each in configuration [D] and velocity [V] spaces) grid-based Vlasov--Poisson (direct kinetic) solver is used to study their growth and saturation, which comprises four stages: linear growth, quasilinear resonance, nonlinear fill-in, and saturated turbulence. The linear modal growth rate, nonlinear saturation process, and ion velocity and energy distribution features in the turbulent regime are analyzed. Backstre…
First-principles kinetic simulations are used to investigate magnetic field generation processes in expanding ablated plasmas relevant to laser-driven foils and hohlraums. In addition to Biermann-battery-generated magnetic fields, strong filamentary magnetic filaments are found to grow in the corona of single expanding plasma plumes; such filaments are observed to dominate Biermann fields at sufficiently large focal radius, reaching saturation values of $\sim$ 100 T at National Ignition Facility-like drive conditions. The filamentary fields result from the ion Weibel instability driven by rela…
The electron cross-field transport by the induced azimuthal electric field in a Hall thruster exhibits the mobility scaled by $1/B$. This study investigates parameters affecting this transport over a Hall thruster's distinct regions, such as the ionization, acceleration, and plume region. The main focus is on the nonzero equilibrium azimuthal electric field induced by an azimuthally inhomogeneous neutral supply. A fast Fourier transform analysis of the plasma structure reveals that the wavenumber $k$ of the azimuthal plasma structure increases from $k=2$, which is the input condition, to $k=4$…
We carry out simulations of laser plasmas generated during UV nanosecond pulsed laser ablation of the chalcogens selenium (Se) and tellurium (Te), and compare the results to experiments. We take advantage of a 2D-axisymmetric, adaptive Cartesian Mesh (ACM) framework that enables plume simulations out to centimeter distances over tens of microseconds. Our model and computational technique enable comparison to laser-plasma applications where the long-term behavior of the plume is of primary interest, such as pulsed laser synthesis and modification of materials. An effective plasma absorption ter…
In this work, solid targets made from boron and boron nitride (BN) materials are ablated by a nanosecond pulsed laser at sub-atmospheric pressures of nitrogen and helium gases. Excited species in the ablation plume from the target are probed with spatiotemporally resolved optical emission spectroscopy (OES). Evaluation of chemical composition in the plasma plume revealed that for both boron-rich targets, emission from BN molecules is always observed in nitrogen-rich environments. In addition, BN molecules also present when ablating a boron nitride target in helium gas -- an indication that BN …
Recent experiments have demonstrated magnetic reconnection between colliding plasma plumes, where the reconnecting magnetic fields were self-generated in the plasma by the Biermann battery effect. Using fully kinetic 3-D simulations, we show the full evolution of the magnetic fields and plasma in these experiments including self-consistent magnetic field generation about the expanding plume. The collision of the two plasmas drives the formation of a current sheet, where reconnection occurs in a strongly time-and space-dependent manner, demonstrating a new 3-D reconnection mechanism. Specifical…
The Particle-in-Cell (PIC) method was used to study two different ion thruster concepts - Stationary Plasma Thrusters (SPT) and High Efficiency Multistage Plasma Thrusters (HEMP-T), in particular the plasma properties in the discharge chamber due to the different magnetic field configurations. Special attention was paid to the simulation of plasma particle fluxes on the thrusters channel surfaces. In both cases, PIC proved itself as a powerful tool, delivering important insight into the basic physics of the different thruster concepts. The simulations demonstrated that the new HEMP thruster co…
The stabilization of ``rigid'' flute and ballooning modes $m = 1$ in an axisymmetric mirror trap with the help of an ideally conducting lateral both in the presence and in the absence of end MHD anchors is studied. The calculations were performed for an anisotropic plasma in a model that simulates the pressure distribution during the injection of beams of fast neutral atoms into the magnetic field minimum at a right angle to the trap axis. It was assumed that the lateral wall has the shape of a cylinder with a variable radius, so that on an enlarged scale it repeats the shape of the plasma col…
We present the results of an experiment on plasma generation via laser ablation at 10^12 W/cm^2 of power intensity and in a nanosecond domain. Prompt electrons emission and complex plasma plume fragmentation were simultaneously observed for the first time in this laser intensity regime, along with a double electron temperature inside the plasma bulk surviving for a long time to the plume expansion. 1D PIC simulations are in agreement with experimental data as long as the emission of initial prompt electrons is considered. This assumption results to be the key to explain all the other experimen…
Experimental characterization and comparison of the temporal features of plasma produced by ultrafast (100 fs, 800 nm) and short-pulse (7ns, 1064 nm) laser pulses from a high purity nickel and zinc targets, expanding into a nitrogen background, are presented. The experiment is carried out under a wide pressure range of 10^-6 to 10^2 Torr, where the plume intensity is found to increase rapidly when the pressure approaches 1 Torr. Electron temperature (Te) is calculated from OES and is found to be independent of pressure for ultrafast excitation, whereas an enhancement in Te is observed around m…
An axial-azimuthal two-dimensional Hall thruster discharge model was developed for analyzing gradient drift instability (GDI) and cross-field electron transport enhancement induced solely by the GDI. A hybrid particle-fluid model was used for the partially ionized plasma, where the inertialess electron fluid in the quasineutral plasma was assumed. A nonoscillatory numerical method was proposed for the potential solver in the electron fluid model to avoid numerical instability and analyze the physics of GDI accurately. A simulation is performed for a 1 kW-class anode-layer-type Hall thruster, a…
In this article we report acceleration observed for ions in a forward ablation geometry of 50 nm thick nickel film coated on a glass plate under nanosecond laser ablation. A detailed study with varying background pressure and laser energy of time of flight (TOF) spectra of ionic and other neutral transitions from plasma is undertaken. The results indicate that TOF spectra recorded for different neutral transitions exhibit different dynamical behavior (the slower peak of the neutral emission becomes faster with background pressure). Similar observation is seen for the ionic species as well. The…
Control of Magnetic Reconnection in High Energy Density Plasmas
University of Michigan（密歇根大学）；Princeton University（普林斯顿大学）；Boston University（波士顿大学）；Institute for Advanced Study（高等研究院）；Lawrence Livermore National Laboratory（劳伦斯利弗莫尔国家实验室）；University of Rochester（罗切斯特大学）
We demonstrate a Wiley-McClaren Time of Flight Mass Spectrometer modified to allow direct extraction of ions from a laser-induced plasma. Unlike many other methods that utilize mass spectrometry to investigate laser-induced plasmas, no collisional cooling or further ionization of the plasma is required prior to acceleration, allowing measurements of the plasma ion composition to be obtained directly. Furthermore, we show using the laser ablation of gadolinium as an example that we are able to obtain the translational energy distribution of the plasma directly and infer information about the re…
Fast magnetic reconnection was observed between magnetized laser-produced plasmas at the National Ignition Facility. Two highly-elongated plasma plumes were produced by tiling two rows of lasers, with magnetic fields generated in each plume by the Biermann battery effect. Detailed magnetic field observations, obtained from proton radiography using a D$^3$He capsule implosion, reveal reconnection occurring in an extended, quasi-1D current sheet with large aspect ratio $\sim 100$. The 1-D geometry allowed a rigorous and unique reconstruction of the magnetic field, which showed a reconnection cur…
We present experimental measurements of a pulsed plasma gun, using two-colour imaging laser interferometry and spatially resolved Thomson scattering. Interferometry measurements give an electron density $n_e\approx2.7\times10^{17}$ cm$^{-3}$ at the centre of the plasma plume, at 5 mm from the plasma gun nozzle. The Thomson scattered light is collected from two probing angles allowed us to simultaneously measure the collective and non-collective spectrum of the electron feature from the same spatial locations. The inferred electron densities from the location of the electron plasma waves is in …
We report a technique of proton deflectometry which uses a grid and an in situ reference x-ray grid image for precise measurements of magnetic fields in high-energy density plasmas. A D$^3$He fusion implosion provides a bright point-source of both protons and x-rays, which is split into beamlets by a mesh grid. The protons undergo deflections as they propagate through the plasma region of interest, whereas the x-rays travel along straight lines. The x-ray image therefore provides a zero-deflection reference image. The line-integrated magnetic fields are inferred from the shifts of beamlets bet…
The comprehensive suite of scientific instruments with high temporal resolution measurements on the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft allowed studies of the structure and properties of the dayside magnetosphere of Mars. The dayside plasma envelope was found on first Mars orbiters (Vaisberg et al., 1976, Gringauz et al., 1976), but only the high temporal and mass resolutions of MAVEN instruments allowed investigations of the structure and processes of plasma of the dayside magnetosphere, the plasma layer which exists between shocked solar wind and ionosphere (Vaisberg et…
We report the modifications of compressional Mach cone propagation characteristics due to \textcolor{black}{the} polarization force acting on micron size dust particles embedded in a non-uniform plasma. We solve the hydrodynamic fluid equations for highly charged dust particles to investigate the Mach cone by incorporating the polarization force in the momentum equation and observe the structural change on lateral wakes at different polarization force for a given Mach number and Epstein drag force. We also notice that the maximum amplitude of normalized dust density perturbation decreases with…
Laser-induced breakdown spectroscopy (LIBS) show enhancement in its signal, when the laser-induced plasma is confined/decelerated under the effect of an external steady magnetic field or in a small cavity. An enhancement in LIBS signal has been observed ~2 times in the case of magnetic confinement. Combination of magnetic and spatial confinement provide enhancement by an order of magnitude. Theoretical analysis of the decelerated plasma has been found in agreement with the experimental observations. The enhancement in LIBS signal is found dependent on the efficiency of plasma confinement as we…
The magnetic field produced by planets with active dynamos, like the Earth, can exert sufficient pressure to oppose supersonic stellar wind plasmas, leading to the formation of a standing bow shock upstream of the magnetopause, or pressure-balance surface. Scaled laboratory experiments studying the interaction of an inflowing solar wind analog with a strong, external magnetic field are a promising new way to study magnetospheric physics and to complement existing models, although reaching regimes favorable for magnetized shock formation is experimentally challenging. This paper presents experi…
The RF plasma slit jet, which produces 150 mm wide streaming plasma outside the jet body, exhibits exciting self-organization phenomena that resemble the self-organized patterns of dielectric barrier discharge (DBD) filaments. Similarly, as in DBD, the filaments are surrounded by an inhibition zone that does not allow two filaments to come closer to each other. With fast camera imaging, we observed the filamentary character of the discharge in all the studied gas feeds (Ar, Ar/N$_2$, and Ar/O$_2$). Still, the visual appearance of the filaments in the plasma and their interaction with a dielect…
The energy distribution functions of ions in the cathodic arc plasma using composite AlCr cathodes were measured as a function of the background gas pressure in the range 0.5 to 3.5 Pa for different cathode compositions and gas atmospheres. The most abundant aluminium ions were Al$^{+}$ regardless of the background gas species, whereas Cr$^{2+}$ ions were dominating in Ar and N$_2$ and Cr$^{+}$ in O$_2$ atmospheres. The energy distributions of the aluminium and chromium ions typically consisted of a high-energy fraction due to acceleration in the expanding plasma plume from the cathode spot an…
Shocks in supersonic flows offer both a high-density and sharp density gradients that can be used, for instance,for gradient injection in laser-plasma accelerators. We report on a parametric study of oblique shocks created by inserting a straight axisymmetric section at the end of a supersonic "de Laval" nozzle. The impact of different parameters such as throat diameter and straight section length is studied through computational fluid dynamics (CFD) simulations. Experimental characterizations of a shocked nozzle are compared to CFD simulations and found to be in good agreement. We then introd…
Supersonic gas jets produced by converging-diverging (C-D) nozzles are commonly used as targets for laser-plasma acceleration (LPA) experiments. A major point of interest for these targets is the gas density at the region of interaction where the laser ionizes the gas plume to create a plasma, providing the acceleration structure. Tuning the density profiles at this interaction region is crucial to LPA optimization. A "flat-top" density profile is desired at this line of interaction to control laser propagation and high energy electron acceleration, while a short high-density profile is often …
