Fundamental Plasma Physics最新文献

Superior lifetime stability for the microplasma device developed by decorating nanodiamonds (nDs) on laser induced graphene (LIG) is reported. Upon overwhelming the difficulty of poor stability in graphene, the nD-LIG displays exceptional lifetime stability of 1770s verified at an applied voltage of 340 V. But, the lifetime stability of LIG is only 718 s at the same applied voltage. Therefore, the nD-LIG with enhanced lifetime stability have pronounced prospective as cathodes in microplasma device applications.

This study deals with the surface modification of polymer films utilizing a custom designed cost- effective dielectric barrier discharge (DBD) plasma produced in air at reduced pressure. We comprehensively examine diverse aspects of surface modification, encompassing electrical discharge characterization, optical signal analysis, contact angle measurements, and surface morphology assessment. Our observations unveiled the presence of distinctive filamentary streamer-based micro-discharges during the DBD process, with a power consumption of approximately 5.64 W and an electron density of 3.4 × 10¹¹ cm⁻³. Optical emission spectroscopy identifies multiple emission peaks attributed to nitrogen emissions. Notably, plasma treatment substantially reduced the water contact angle and augmented surface energy on polypropylene (PP) and polyethylene terephthalate (PET) films. Surface morphology analysis illustrated an increase in surface roughness following plasma treatment. Intriguingly, the initial rapid alterations in wettability and surface morphology attained equilibrium after approximately 30 s of treatment. This study highlights atmospheric DBD plasma's effectiveness in customizing polymer surfaces, improving wettability and roughness, offering promising applications for enhanced adhesion and wetting.

We consider a visco-resistive magnetohydrodynamic modelling of a steady-state incompressible tokamak plasma with a prescribed toroidal current drive, featuring constant resistivity η and viscosity ν. It is shown that the plasma velocity root-mean-square behaves as $\eta f\left(H\right)$ as long as the inertial term remains negligible, where H stands for the Hartmann number $H\equiv {\left(\eta \nu \right)}^{-1/2}$, and that $f\left(H\right)$ exhibits power-law behaviours in the limits $H\ll 1$ and $H\gg 1$. In the latter limit, we establish that $f\left(H\right)$ scales as $H^{1/4}$, which is consistent with numerical results.

We show that the wakefield driven by fast electrons inside the nanowire when irradiated with an ultra-short relativistic laser pulse strips atoms to a higher charge state. Using particle-in-cell simulations, we demonstrate that the charge state agrees with the barrier suppression threshold of the wakefield and reaches a higher value via collision. The ionisation of gold nanowires occurs only via collisional-damped wakefield. We found that the collisional ionisation of high-Z nanowires depends on the onset of the z pinch. These results suggest a different ionisation mechanism of the structured target in the subfemtosecond regime.

This study assesses the plasma sheath formation on the night side of the Moon when exposed to highly energetic ambient plasma. The calculations indicate that the secondary electron emission (SEE) due to highly energetic plasma electrons leads to the formation of the inverse sheath around the positively charged lunar surface on the night side, where a traditional Debye sheath with a high negative surface potential is anticipated. Analytical formulation of Debye sheath and inverse sheath formation is given considering Maxwellian plasma and secondary electrons and cold ions. For a given SEE yield, a temperature regime is predicted where the inverse sheath is possible.

A comprehensive overview is presented of recent theoretical advancements and observational manifestations of a relatively new type of electrostatic solitary wave (ESW), known as supersoliton or supersolitary wave (SSW). These nonlinear structures are characterized by a distorted pulse-shaped electrostatic potential excitations, deviating from the standard (“sech²”-like) form generally expected from solitonic pulses. In Space plasmas, in particular, e.g. in magnetospheric observations, SSWs may be associated with a characteristic wiggly bipolar electric field waveform. It has been shown that a three-component configuration is essential, as a minimum requirement for SSWs to occur in a plasma.

Various spacecraft missions have recorded evidence of “non-conventional” electrostatic solitary waves (pulses) such as wiggly bipolar pulses, offset bipolar pulses, and monopolar pairs. This review article aims to present the current state of the art in this fascinating new theme, first outlining the basic framework for the modeling of such “exotic” ESWs and then putting forward a correlation between SSW structures with certain non-standard bipolar electric field forms observed in planetary magnetospheres.

We studied the γ-ray emission from laser interactions with structured targets of Al and Au. Bremsstrahlung and Non-linear Compton Scattering (NCS) emission are considered for the γ-ray emission using the open source 2-D PIC code EPOCH. Different shapes of the target generated additional hot electrons, which helps to enhance the photon energy in individual cases. The enhancement of photon energy is due to the target's shape and the hot electrons. Hot electron generation and their dynamics, like refluxing behavior, are crucial phenomena in thin targets. This study uses four different shapes of Al and Au targets. The relative strength of emissions from both bremsstrahlung and NCS are compared. The shape of the target enhances the γ-ray energy, electron energy, and emitted photon number and improves the electron beam divergence. The effect of each target shape on hot electrons refluxing behavior and the role of the electric and magnetic fields are discussed in detail.

Thermal plasma is one of the upcoming powerful tools used for materials processing. It covers a wide range of technological applications such as synthesis of various refractory ceramic materials, metals and alloys, deposition of coatings, high temperature processing of materials as well as disintegration of waste materials. Representative technologically important material systems viz rare earth hexaboride (e.g. GdB₆) and carbonaceous materials are focus of the present manuscript. Both the material systems have been processed using DC thermal plasma route and characterized thoroughly for structural, morphological, surface properties using XRD, TEM, XPS respectively. Morphology of GdB₆ has been tailored by varying plasma parameters during synthesis. Further, these GdB₆ powder were investigated for electron emission performance using Field Electron Emission and maximum current density of 0.5 mA/cm² was noted for the nanocrystalline GdB₆ sample. Feasibility of thermal plasmas for production of nanocrystalline GdB₆ and processing of a bio-waste to obtain technologically important carbonaceous materials has also been explored.

High-order harmonic generation is a nonlinear optical frequency conversion process that occurs during intense ultrafast laser-matter interaction. At the Advanced Laser Light Source laboratory, we use ultrafast laser pulses having diverse wavelengths, spanning visible, near- and mid-infrared ranges, to generate high-order harmonics from laser-ablated plumes in the extreme ultraviolet or soft X-ray region of the electromagnetic spectrum. The Advanced Laser Light Source Laboratory is situated within the Énergie Matériaux Télécommunications Center of the Institut national de la recherche scientifique in Montréal, Quebec, Canada. We focus on generating bright and broadband harmonics by exploiting various types of ultrafast resonances in different species within the laser-ablated plume, and use them for applications in ultrafast spectroscopy, imaging, and AMO science. We are also actively exploring previously unknown physics governing the harmonic generation from different resonances. In this review article, we provide an overview of the recent advancements made in these directions.

Despite the undoubted importance of having fairly simple analytical expressions for the refractive indices of wave modes in a magnetoactive plasma, such expressions are known only in some particular cases. For electron waves with frequencies much higher than the lower hybrid resonance frequency, such an expression is known only for whistler waves in a dense plasma when the electron plasma frequency significantly exceeds the electron cyclotron frequency. In this Letter, we propose simple operational expressions for the refractive indices of all four electron modes in a magnetoactive plasma, namely, the fast magnetosonic, also called whistler mode, the slow extraordinary mode, the ordinary mode, and the fast extraordinary mode. The form of these expressions does not depend on the value of the ratio of plasma frequency to cyclotron frequency.