共查询到20条相似文献,搜索用时 218 毫秒
1.
XIE Bai-Song 《理论物理通讯》2006,46(4):735-738
Some new approaches for nonlinear force-free magnetic field are presented and new exact solutions are found analytically. Examples are given and some implications of results to astrophysical solar plasmas as well as tokamak or/and spheromak plasmas are discussed. 相似文献
2.
XIE Bai-Song 《理论物理通讯》2006,46(3):561-562
Two new solutions for non-constant-α force-free magnetic field are found analytically. Implications of the results to astrophysical solar plasmas as well tokamak plasmas are discussed. 相似文献
3.
采用理想磁流体力学模型,给出合理的二维(r, θ)质量注入边界条件,对丝阵Z箍缩早期消融等离子体的动力学过程进行了二维(r, θ)数值模拟研究,得到消融等离子体各参量以及磁场的二维时空分布.模拟结果表明,消融等离子体的运动包括四个主要阶段:首先向轴漂移,然后在轴线处滞止并形成先驱等离子体柱,随后先驱等离子体柱被压缩,最后缓慢膨胀.计算了不同丝阵半径和丝间距情况下消融等离子体到轴速度以及消融质量占丝阵总质量的份额,它们的变化规律与实验结果基本符合.通过
关键词:
丝阵Z箍缩
理想磁流体
消融等离子体 相似文献
4.
Effects of q-profiles of a weak magnetic shear on energetic ion excited q=1 mode in tokamak plasmas 下载免费PDF全文
In this paper, we study the effect of safety factor profiles, particularly with a very weak magnetic shear, on the m/n = 1mode excited by energetic ions in tokamak plasmas. It is found that the profile plays a significant role in the onset of the mode, and the thresholds for the instability are also derived. The numerical results for configurations with conventional or reversed non monotonic magnetic shears are discussed. The effects of radial location of rational surfaces, edge q value, and flatness of q-profile on the energetic ion excited mode are further analyzed in detail. 相似文献
5.
Multigrid methods can solve some classes of elliptic and parabolic equations to accuracy below the truncation error with a work-cost equivalent to a few residual calculations – so-called “textbook” multigrid efficiency. We investigate methods to solve the system of equations that arise in time dependent magnetohydrodynamics (MHD) simulations with textbook multigrid efficiency. We apply multigrid techniques such as geometric interpolation, full approximate storage, Gauss–Seidel smoothers, and defect correction for fully implicit, nonlinear, second-order finite volume discretizations of MHD. We apply these methods to a standard resistive MHD benchmark problem, the GEM reconnection problem, and add a strong magnetic guide field, which is a critical characteristic of magnetically confined fusion plasmas. We show that our multigrid methods can achieve near textbook efficiency on fully implicit resistive MHD simulations. 相似文献
6.
Observation of disruptions in tokamak plasma under the influence of resonant helical magnetic fields
Summary Disruptive instabilities were investigated in the small-tokamak TBR-1 during the application of resonant helical magnetic
fields created by external helical windings. Indications were found that the main triggering mechanism of the disruption was
the rapid increase of them=2/n=1 mode which, apparently after reaching a certain amplitude, interacts with other resistive modes: the internal 1/1 mode
in the case of a major disruption, or with higherm components, as the 3/1 or 4/1, in the case of minor disruptions. After the coupling, the growth of the associated islands
would create a chaotic field line distribution in the region between the corresponding rational magnetic surfaces which caused
the gross particle transport and, finally, destroyed the confinement. In addition, investigations on higherZ
eff discharges in which a mixture of helium and hydrogen was used resulted in much more unstable plasmas but apparently did not
alter the basic characteristics of the disruptions.
The authors of this paper have agreed to not receive the proofs for correction. 相似文献
7.
Summary The role of neutron spectrometry is discussed as a diagnostics of plasmas of compact ignition experiments. The situation with
regard to instrumentation (including diagnostic capabilities and limitations) is reviewed on the basis of existing experience
and new solutions are proposed as required by compact-plasma observations. Especially, the question of time resolution is
addressed and a dedicated spectrometer system is devised to make use of the high neutron fluxes expected for the nuclear-burn
phase of compact plasmas. It is shown that a system of three neutron spectrometers can provide adequate data on ion temperature
of D and DT plasmas over a range of plasma conditions of interest and with the required accuracy. The diagnostic output from
this neutron spectrometer system is presented especially with regard to flash ignition studies. 相似文献
8.
Thomson散射诊断技术的新进展 总被引:1,自引:0,他引:1
Thomson散射是一种主动而无干扰地对等离子体进行诊断的方法.它能够以较高的时空分辨率测量等离子体的参数,如电子与离子温度、密度以及等离子体的膨胀速度、电离程度、热流等参数.文章从Thomson散射基本概念出发,介绍了Thomson散射诊断方法在研究激光与等离子体相互作用中的重要意义,并分别介绍了近年来Thomson散射诊断技术的新进展,如对高Z等离子体、两种离子种类的等离子体、多种形态等离子体以及高密度等离子体的研究.文章最后对国内Thomson散射诊断技术的发展状况进行了简述. 相似文献
9.
G. Gorini J. Källne F. Ognissanto M. Tardocchi L. Ballabio L. Giacomelli C. Hellesen A. Hjalmarsson 《Few-Body Systems》2008,44(1-4):57-60
Ion reactions and elastic scatterings in fusion plasmas of H and He nuclides are discussed as they can be observed in the neutron emission spectrum (NES). New calculations are presented on radio-frequency driven multi-step processes in 3HeD plasmas involving knock-on scattering whose relative importance is discussed besides use for new plasma studies. 相似文献
10.
11.
Gorelenkov NN 《Physical review letters》2005,95(26):265003
A new type of global shear Alfvén eigenmode is found in tokamak plasmas where the mode localization is in the region intersecting the Alfvén continuum. The eigenmode is formed by the coupling of two solutions from two adjacent gaps (akin to potential wells) in the shear Alfvén continuum. For tokamak plasmas with reversed magnetic shear, it is shown that the toroidicity-induced solution tunnels through the continuum to match the ellipticity-induced Alfvén eigenmode so that the resulting solution is continuous at the point of resonance with the continuum. The existence of these double-gap Alfvén eigenmodes allows for potentially new ways of coupling edge fields to the plasma core in conditions where the core region is conventionally considered inaccessible. Implications include new approaches to heating and current drive in fusion plasmas as well as its possible use as a core diagnostic in burning plasmas. 相似文献
12.
13.
14.
N. L. Tsintsadze L. N. Tsintsadze A. Hussain G. Murtaza 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,64(2-3):447-452
A general quantum dispersion equation for electron-positron(hole)-ion quantum plasmas is derived and studied for some interesting cases. In an electron-positron-ion degenerate Fermi gas, with or without the Madelung term, a new type of zero sound waves are found. Whereas in an electron-hole-ion plasmas a new longitudinal quantum waves are revealed, which have no analogies in quantum electron-ion plasmas. The excitation of these quantum waves by a low-density monoenergetic straight electron beam is examined. Furthermore, the Korteweg-de Vries (KdV) equation for novel quantum waves is derived and the contribution of the Madelung term in the formation of the KdV solitons is discussed. 相似文献
15.
G.E. Morfill A.V. Ivlev M. Rubin-Zuzic C.A. Knapek R. Pompl T. Antonova H.M. Thomas 《Applied physics. B, Lasers and optics》2007,89(4):527-534
Complex (dusty) plasmas are a unique system for studying all sorts of dynamical processes at the most elementary individual
particle level. Microparticles in complex plasmas can be easily viewed and manipulated. Moreover, collective processes in
the strong coupling regime can be virtually undamped (in contrast to colloidal suspensions) and hence full dynamical information
can be obtained at all the relevant time scales. Therefore, investigations of dynamical phenomena in complex plasmas can provide
important insights into major generic processes governing the behavior of other strong coupling particle systems. In this
article we focus on the kinetics of self-organization observed in small clusters as well as extended crystals, and report
on some new findings that illustrate significant interdisciplinary potential of complex plasma studies.
PACS 52.27.Lw 相似文献
16.
John I.B. Wilson 《Contemporary Physics》2013,54(1):57-59
Most of the universe is in. the plasma state and for a long time astrophysicists have been making measurements on extraterrestrial plasmas. More recently high temperature plasmas have been produced in the laboratory and this has led to the development of new techniques for the determination of plasma parameters. This article describes the more important techniques which are being used for measurements on laboratory plasmas. High temperature plasmas are extremely difficult to contain for times of only a few milliseconds. Consequently it is essential for any successful technique to be able to provide adequate resolution in time so that the mechanisms controlling the growth and decay of the plasma may be understood. 相似文献
17.
H. Kersten H. Deutsch E. Stoffels W.W. Stoffels G.M.W. Kroesen R. Hippler 《等离子体物理论文集》2001,41(6):598-609
The research effort in the area of dusty plasmas initially aimed at avoiding particle formation and controlling the contamination level in industrial reactors. Nowadays, dusty plasmas have grown into a vast field and new applications of plasma‐processed dust particles are emerging. There is demand for particles with special properties, and for particle‐seeded composite materials. Low‐pressure plasmas offer a unique possibility of confinement, control and fine tailoring of particle properties. The role of plasma technology in treatment and surface modification of powder grains is reviewed and illustrated with examples. The interaction between plasma and injected micro‐disperse powder particles can also be used as a diagnostic tool for the study of plasma surface processes. 相似文献
18.
J. Röpcke S. Welzel N. Lang F. Hempel L. Gatilova O. Guaitella A. Rousseau P.B. Davies 《Applied physics. B, Lasers and optics》2008,92(3):335-341
Within the last decade mid-infrared absorption spectroscopy between 3 and 20 μm, known as infrared laser absorption spectroscopy
(IRLAS) and based on tuneable semiconductor lasers, namely lead salt diode lasers, often called tuneable diode lasers (TDL),
and quantum cascade lasers (QCL) has progressed considerably as a powerful diagnostic technique for in situ studies of the
fundamental physics and chemistry of molecular plasmas. The increasing interest in processing plasmas containing hydrocarbons,
fluorocarbons, organo-silicon and boron compounds has lead to further applications of IRLAS because most of these compounds
and their decomposition products are infrared active. IRLAS provides a means of determining the absolute concentrations of
the ground states of stable and transient molecular species, which is of particular importance for the investigation of reaction
kinetics. Since plasmas with molecular feed gases are used in many applications such as thin film deposition, semiconductor
processing, surface activation and cleaning, and materials and waste treatment, this has stimulated the adaptation of infrared
spectroscopic techniques to industrial requirements. The recent development of QCLs offers an attractive new option for the
monitoring and control of industrial plasma processes as well as for highly time-resolved studies on the kinetics of plasma
processes.
The aim of the present article is twofold: (i) to review recent achievements in our understanding of molecular phenomena in
plasmas using TDLs and (ii) to report on selected new applications of QCLs in the mid-infrared.
PACS 07.57.Ty; 52.70.Kz; 52.80.-s 相似文献
19.
P. Chessa M. Galimberti A. Giulietti D. Giulietti L. A. Gizzi P. Mora 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(2):153-156
It is well established that, at sub-relativistic intensities, the absorption of laser light by underdense plasmas decreases
with increasing pulse intensity as interaction enters a non-linear regime. On the other hand, as the relativistic interaction
regime is reached, further absorption mechanisms can be activated which can account for a substantial energy transfer. Using
the particle code WAKE, we performed numerical simulations of the relativistic interaction of intense laser pulses with underdense
plasmas in conditions that can be experimentally tested. Our simulations show that, while the relativistic laser intensity
generates a population of fast electrons, a considerable fraction of the pulse energy goes into a population of thermal electrons. These findings open new possibilities for a direct observation of relativistic interaction processes using high
resolution soft X-ray techniques. 相似文献
20.
Blades M.W. Banks P. Gill C. Huang D. LeBlanc C. Liang D. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1991,19(6):1090-1113
The use of weakly ionized plasmas as spectroscopic sources for materials sampling and analysis is reviewed. Plasma sources currently used for this purpose include direct-current and alternating-current plasmas, inductively coupled plasmas, microwave-induced plasmas, surface-wave plasmas, capacitively coupled plasmas, capacitive microwave plasmas, glow discharges, flowing afterglows, theta pinch discharges, exploding films and wires, and laser-produced plasmas. The authors give a summary of relevant characteristics of some of the plasma sources. Included are the source, common method of application, approximate detection limit for that method, applicability for solid sampling, susceptibility to matrix effects, approximate cost, and the most common usage for the method 相似文献