在美国国家聚变科学研究所的线性ECR等离子体装置HYPER-I中，我们观察到了旋转磁化等离子体中稳态涡旋结构的自发形成。该涡旋在其中心出现一个深的密度腔，即等离子体孔，并被确定为粘性流体中的耗散涡旋（Burgers涡旋）[1]。由涡量分布和离子流场估算的运动粘度比经典值高4个数量级，这可能是由于德拜屏蔽不足或准中性破缺所致.在这里，我们提出的潜在的测量结果和评估准中性打破。结果表明，该势具有钟形轴对称结构，其最大值超过5 Te。用泊松方程计算了准中性破缺程度，其值比实验室常用等离子体的值大3个数量级。这种准中性破缺产生的强电场驱动等离子体空穴的超声速旋转。应该提到的是，在等离子体孔的周围区域中的准中性破缺的程度与通常的实验室等离子体相当。因此，等离子体空穴可以看作是由准中性等离子体包围的非中性核结构。研究非中性等离子体和准中性等离子体的连通结构，特别是它们之间的界面层的涨落是一个很有意义的课题。我们的初步观察表明，在界面层中存在明显的波动。[1]K. Nagaoka，A. Okamoto，S. Yoshimura，M. Kono和M. Y. Tanaka，Phys. Rev. Lett. 89（2002）075001
英文摘要：
We have observed spontaneous formation of a stationary vortex structure in a rotating magnetized plasma produced in a linear ECR plasma device named HYPER-I at National Institute for Fusion Science. The vortex appears with a deep density-cavity, plasma hole, in its center, and is identified as a dissipative vortex in viscous fluids (Burgers vortex) [1]. The kinematic viscosity estimated from the vorticity profile and the ion flow field is 4 orders of magnitude higher than the classical value, which may be attributable to insufficiency of the Debye shielding or the breaking of quasi-neutrality. Here we present the results of potential measurements and the evaluation of quasi-neutrality breaking. It is revealed that the potential has a bell-shaped axisymmetric structure localized inside the core region, in which its maximum value exceeds 5 Te. Using Poisson's equation, degree of quasi-neutrality breaking is evaluated, which shows 3 orders of magnitude larger than that of usual laboratory plasma. The strong electric field produced by this quasi-neutrality breaking drives the supersonic rotation of the plasma hole. It should be mentioned that the degree of quasi-neutrality breaking in the ambient region of the plasma hole is comparable to that of usual laboratory plasma. Hence the plasma hole can be considered as the structure of a nonneutral core surrounded by a quasi-neutral plasma. It is of great interest to study the fluctuations associated with the connected structure of the nonneutral and the quasi-neutral plasma, especially the interfacial layer in between. Our preliminary observation shows that the pronounced fluctuations exist in the interfacial layer. [1] K. Nagaoka, A. Okamoto, S. Yoshimura, M. Kono, and M. Y. Tanaka, Phys. Rev. Lett. 89 (2002) 075001
Propagation of right-hand circularly polarized laser into highly magnetized over-dense collisional plasma is analytically studied from basic equations. Highly magnetized plasma with density of 10^23 cm^-3 is efficiently heated from 100 eV to 1 keV within depth of around 20 μ{m} in one nanosecond by Nd:YAG laser with moderate irradiance of around 10^14 Wcm^-2.
Hamiltonian formulations of quasilinear theory are presented for the cases of uniform and nonuniform magnetized plasmas. First, the standard quasilinear theory of Kennel and Engelmann (1966) is reviewed and reinterpreted in terms of a general Hamiltonian formulation. Within this Hamiltonian representation, we present the transition from two-dimensional quasilinear diffusion in a spatially uniform magnetized background plasma to three-dimensional quasilinear diffusion in a spatially nonuniform magnetized background plasma based on our previous work Brizard_Chan (2001,2004). The resulting quasil…
A charged particle moving through a plasma experiences a friction force that commonly acts antiparallel to its velocity. It was recently predicted that in strongly magnetized plasmas, in which the plasma particle gyro-frequency exceeds the plasma frequency, the friction also includes a transverse component that is perpendicular to both the velocity and Lorentz force. Here, this prediction is confirmed using molecular dynamics simulations, and it is shown that the relative magnitude of the transverse component increases with plasma coupling strength. This result influences single particle motio…
A solution to the Boltzmann equation is obtained for a magnetized plasma with non-degenerate electrons and ions by Chapman-Enskog method. To obtain an approximate solution, the Sonine polynomials up to the third-order approximation are used. Fully ionized plasma is considered. We obtained more accurately the components for the diffusion, thermal diffusion and diffusion thermoeffect tensors in comparison with previous publications on this subject.
In this paper, we obtain the dispersion relation for the lower-hybrid oscillations/waves in a cold magnetized electron-positron-ion (e-p-i) plasma. It is found that the frequency of the lower-hybrid oscillations in an e-p-i plasma is approximate $1/\sqrt{3}$ times the frequency of lower-hybrid oscillations in an electron-ion (e-i) plasma, provided the plasma density is high, and the equilibrium densities of the positron and the ion are balanced. The present work may have some relevance for laboratory/astrophysical e-p-i plasmas.
We present experimental data providing evidence for the formation of transient ($\sim 20~μ$s) plasmas that are simultaneously weakly magnetized (i.e., Hall magnetization parameter $ωτ> 1$) and dominated by thermal pressure (i.e., ratio of thermal-to-magnetic pressure $β> 1$). Particle collisional mean free paths are an appreciable fraction of the overall system size. These plasmas are formed via the head-on merging of two plasmas launched by magnetized coaxial guns. The ratio $λ_{gun}=μ_0 I_{gun}/ψ_{gun}$ of gun current $I_{gun}$ to applied magnetic flux $ψ_{gun}$ is an experimental knob for e…
Topological Langmuir-Cyclotron Wave (TLCW) is a recently identified topological surface excitation in magnetized plasmas. We show that TLCW originates from the topological phase transition at the Langmuir wave-cyclotron wave resonance. By isofrequency surface analysis and 2D and 3D time-dependent simulations, we demonstrate that the TLCW can propagate robustly along complex phase transition interfaces in a unidirectional manner and without scattering. Because of these desirable features, the TLCW could be explored as an effective mechanism to drive current and flow in magnetized plasmas. The a…
Magnetothermodynamics (MTD) is the study of compression and expansion of magnetized plasma with an eye towards identifying equations of state for magneto-inertial fusion experiments. We present recent results from SSX experiments on the thermodynamics of compressed magnetized plasmas. In these experiments, we generate twisted flux ropes of magnetized, relaxed plasma accelerated from one end of a $1.5~m$ long copper flux conserver, and observe their compression in a closed conducting boundary installed at the other end. Plasma parameters are measured during compression. The instances of ion hea…
Laser produced high-energy-density plasmas may contain strong magnetic fields that affect the energy transport, which can be nonlocal. Models which describe the magnetized nonlocal transport are formally complicated and based on many approximations. This paper presents a more straightforward approach to the description of the electron transport in this regime, based on the extension of a reduced entropic model. The calculated magnetized heat fluxes are compared with the known asymptotic limits and applied for studying of a magnetized nonocal plasma thermalization.
The radial characteristic of a partially magnetized plasma column created by a hot cathode filament is presented. It is found that in the absence of magnetic field, plasma potential and density varies similarly according to Boltzmann distribution. However as the magnetic field increases, a clear divergence is seen as plasma density becomes more pronounced in the centre whereas a corresponding minima is observed in plasma potential; thus limiting the radial diffusion of positive ions towards the grounded sidewalls. A phenomenological model based on short-circuiting effect is developed, which fa…
It is shown that the transport in low temperature, collisional, bounded plasma is enhanced by instabilities at high magnetic field. While the magnetic field confines the electrons in a stable plasma, the instability completely destroys the confinement such that the transport becomes independent of the magnetic field in the highly magnetized limit. An analytical expression of the instability-enhanced collision frequency is proposed, based on a magnetic field independent edge-to-center density ratio.
We investigate the formation of collisionless magnetized shocks triggered by the interaction between magnetized plasma flows and miniature-sized (order of plasma kinetic-scales) magnetic obstacles resorting to massively parallel, full particle-in-cell simulations, including the electron kinetics. The critical obstacle size to generate a compressed plasma region ahead of these objects is determined by independently varying the magnitude of the dipolar magnetic moment and the plasma magnetization. We find that the effective size of the obstacle depends on the relative orientation between the dip…
The ability to separate large volumes of mixed species based on atomic mass appears desirable for a variety of emerging applications with high societal impact. One possibility to meet this objective consists in leveraging mass differential effects in rotating plasmas. Beyond conventional centrifugation, rotating plasmas offer in principle additional ways to separate elements based on mass. Single ion orbits show that ion radial mass separation in a uniform magnetized plasma column can be achieved by applying a tailored electric potential profile across the column, or by driving a rotating magn…
In this work we introduce, for the first time, as far as we know, a complete self-consist kinetic model for collisional transport in the nonextensive statistics, i.e., the generalization of the ordinary Maxwell-Boltmzann statistics according to the Tsallis entropy. Starting only from the definition of this entropy, we derive the kinetic model, find its solutions for the electrons in a strongly magnetized plasmas, and calculate the respective transport coefficients in order to set the closed fluid equations. The results are further applied to model heat transport in space plasmas and the cold p…
In a two-ion-species plasma with disparate ion masses, heavy ions tend to concentrate in the low-temperature region of collisionally magnetized plasma and in the high-temperature region of collisionally unmagnetized plasma, respectively. Moreover, collisional magnetization can be determined as the ratio of the light ion gyrofrequency to the collision frequency of light and heavy ion species, and the behavior of this effect in the intermediate regime of partially magnetized plasma is predominantly dependent on this Hall parameter. Multi-ion cross-field transport has been described before in the…
Nonlinear ion-acoustic waves are analyzed in a non-relativistic magnetized quantum plasma with arbitrary degeneracy of electrons. Quantum statistics is taken into account by means of the equation of state for ideal fermions at arbitrary temperature. Quantum diffraction is described by a modified Bohm potential consistent with finite temperature quantum kinetic theory in the long wavelength limit. The dispersion relation of the obliquely propagating electrostatic waves in magnetized quantum plasma with arbitrary degeneracy of electrons is obtained. Using the reductive perturbation method, the c…
When turbulent structures split more frequently before they decay, persistent turbulence forms in neutral fluid shear flows. Whether this concept can be extended to linear magnetized plasmas is investigated here and compared to the behavior of the pipe flow. With increasing control parameter the dynamics in the magnetized plasmas is known to undergo several changes from a quasiperiodic to a phase locked to a weakly turbulent regime. When the phase-locked regime breaks down, the splitting time approaches the decreasing lifetime reflecting self-sustained turbulence, as known from the pipe flow.
Deposition of thin films that are resistant to aggressive environment conditions, using the High-power impulse magnetron sputtering (HIPIMS) technique, represents a technological challenge. To establish the optimal operating conditions it is desirable to know the lifetime of the magnetized plasma at the end of the pulsed cathode current. The table-top system we developed allows one to measure the lifetime for all operating HiPIMS types, both for short and long pulses, based on the rapid increase of the current when applying a voltage pulse with very short rise time, up to a value which depends…
A theoretical model is presented to study characteristics of dust acoustic shock in a viscous, magnetized and rotating dusty plasma at both fast and slow time scales. By employing reductive perturbation technique the nonlinear Zakharov--Kuznetsov (ZK) equation has been derived for both cases when dust is inactive and dynamic (fast and slow time scales). Both electrons and ions are considered to follow kappa/Cairns distribution. It is observed that the viscosity in both cases when dust is in background and active plays as a key role in dissipation for the propagation of acoustic shock. Magnetic…
The friction force on a test particle traveling through a plasma that is both strongly coupled and strongly magnetized is studied using molecular dynamics simulations. In addition to the usual stopping power component aligned antiparallel to the velocity, a transverse component that is perpendicular to both the velocity and Lorentz force is observed. This component, which was recently discovered in weakly coupled plasmas, is found to increase in both absolute and relative magnitude in the strongly coupled regime. Strong coupling is also observed to induce a third component of the friction forc…
Plasmas have been recently studied as topological materials. However, a comprehensive picture of topological phases and topological phase transitions in cold magnetized plasmas is still missing. Here we systematically map out all the topological phases and establish the bulk-edge correspondence in cold magnetized plasmas. We find that for the linear eigenmodes, there are 10 topological phases in the parameter space of density $n$, magnetic field $B$, and parallel wavenumber $k_{z}$, separated by the surfaces of Langmuir wave-L wave resonance, Langmuir wave-cyclotron wave resonance, and zero ma…
We consider backscattering of laser pulses in strongly-magnetized plasma mediated by kinetic magnetohydrodynamic waves. Magnetized low-frequency scattering, which can occur when the external magnetic field is neither perpendicular nor parallel to the laser propagation direction, provides an instability growth rate higher than Raman scattering and a frequency downshift comparable to Brillouin scattering. In addition to the high growth rate, which allows smaller plasmas, and the 0.1-2\% frequency downshift, which permits a wide range of pump sources, MLF scattering is an ideal candidate for ampl…
Terahertz (THz) radiation by beating of two laser beams in a groove density and magnetized hot plasma is discussed theoretically. In this mechanism, the ponderomotive force leads to a nonlinear oscillatory current that resonantly excites THz radiation at the frequency upper hybrid. It is interesting to find that the maximum THz radiation in the various electron temperature, therefore, exited an optimum temperature for the parameters such as beating frequency, transverse distance from lasers beam center and strength of the static magnetic field that THz radiation can be maximized.
A new transverse mode in a two-stream magnetized quantum plasma is studied by means of a quantum hydrodynamic model, under non-relativistic and ideal Fermi gas assumptions. It is found that Fermi pressure effects induce a minimum cutoff wavelength for instability, unlike the classical case which is unstable for larger wavenumbers. The external magnetic field is also shown to produce a stabilizing effect. Conditions for the applicability of the model and specific parameters for experimental observations are thoroughly discussed.
Propagation and scattering of lasers present new phenomena and applications when the plasma medium becomes strongly magnetized. With mega-Gauss magnetic fields, scattering of optical lasers already becomes manifestly anisotropic. Special angles exist where coherent laser scattering is either enhanced or suppressed, as we demonstrate using a cold-fluid model. Consequently, by aiming laser beams at special angles, one may be able to optimize laser-plasma coupling in magnetized implosion experiments. In addition, magnetized scattering can be exploited to improve the performance of plasma-based la…
Arched magnetized structures are a common occurrence in space and laboratory plasmas. Results from a laboratory experiment on spatio-temporal evolution of an arched magnetized plasma ($β\approx 10^{-3}$, Lundquist number $\approx 10^{4}$, plasma radius/ion gyroradius $\approx 20$) in a sheared magnetic configuration are presented. The experiment is designed to model conditions relevant to the formation and destabilization of similar structures in the solar atmosphere. The magnitude of a nearly horizontal overlying magnetic field was varied to study its effects on the writhe and twist of the ar…
The properties of obliquely propagating dissipative electron-acoustic solitary waves (OPdEASWs) have been investigated in a magnetized collisional superthermal plasma consisting of inertial cold electrons, inertialess hot electrons featuring kappa-distribution and static ions via the fluid dynamical approach. By using the reductive perturbation technique, a nonlinear Schamel equation that governs the nonlinear features of OPdEASWS is obtained. The solitary wave solution of the Schamel equation is used to examine the basic features of small, but finite amplitude OPdEASWs in such a magnetized co…
Behaviors of positively charged fine particles in a cross field sheath between magnetized double plasmas
研究了等离子体参数对带电微粒悬浮位置的影响。在水平磁场垂直分隔的不同电势的磁化双等离子体之间的交叉场鞘层中，粒子上的电荷变为正电荷，因为从下部高电势等离子体流动的离子电流超过从上部低电势等离子体穿过磁场的电子电流。通过测量由外部振荡电场驱动的粒子的共振频率，估计粒子上的电荷为10 e ~ 2的量级。粒子悬浮位置的变化可以用电荷的变化来解释。
Strongly magnetizing a plasma adds a range of waves that do not exist in unmagnetized plasmas and enlarges the laser-plasma interaction (LPI) landscape. In this paper, we use particle-in-cell (PIC) simulations to investigate strongly magnetized LPI in one dimension under conditions relevant for magneto-inertial fusion experiments, focusing on a regime where the electron-cyclotron frequency is greater than the plasma frequency and the magnetic field is at an oblique angle with respect to the wave vectors. We show that when electron-cyclotron-like hybrid wave frequency is about half the laser fr…
We identify the desired characteristics and parameters of a beta>1 magnetized plasma, possibly with highly tangled, open field lines, that could be a suitable target to be compressed to fusion conditions by a spherically imploding plasma liner [S. C. Hsu et al., IEEE Trans. Plasma Sci. 40, 1287 (2012)] formed by merging hypersonic plasma jets. This concept is known as plasma-jet-driven magneto-inertial fusion (PJMIF). We set requirements on the target and liner such that (a) compressional heating dominates over thermal transport in the target, and (b) magnetic amplification due to compression …
Large amplitude waves in magnetized plasmas, generated either by external pumps or internal instabilities, can scatter via three-waves interactions. While three-wave scatterings in either forward or backward geometry are well-known, what happens when waves propagate at angles with one another in magnetized plasmas remains largely unknown, mainly due to the analytical difficulty of this problem. In this paper, we overcome this analytical difficulty and find a convenient formula for three-wave coupling coefficients in cold, uniform, magnetized plasmas in the most general geometry. This is achiev…
We report experimental results on the injection of a magnetized plasma jet into a transverse background magnetic field in the HelCat linear plasma device at the University of New Mexico [M. Gilmore et al., J. Plasma Phys. 81, 345810104 (2015)]. After the plasma jet leaves the plasma-gun muzzle, a tension force arising from an increasing curvature of the background magnetic field induces in the jet a sheared axial-flow gradient above the theoretical kink-stabilization threshold. We observe that this emergent sheared axial flow stabilizes the n=1 kink mode in the jet, whereas a kink instability …
The self-diffusion phenomenon in a two-dimensional dusty plasma at extremely strong (effective) magnetic fields is studied experimentally and by means of molecular dynamics simulations. In the experiment the high magnetic field is introduced by rotating the particle cloud and observing the particle trajectories in a co-rotating frame, which allows reaching effective magnetic fields up to 3000 Tesla. The experimental results confirm the predictions of the simulations: (i) super-diffusive behavior is found at intermediate time-scales and (ii) the dependence of the self-diffusion coefficient on t…
A magnetic field was recently shown to enhance field-parallel heat conduction in a strongly correlated plasma whereas cross-field conduction is reduced. Here we show that in such plasmas, the magnetic field has the additional effect of inhibiting the isotropization process between field-parallel and cross-field temperature components thus leading to the emergence of strong and long-lived temperature anisotropies when the plasma is locally perturbed. An extended heat equation is shown to describe this process accurately.
