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通过求解二维热输运方程,数值分析了横越单磁岛的热输运现象。仅有背景加热时,当磁岛宽度小于临界磁岛宽度时,磁岛对能量约束影响不明显;当磁岛宽度大于临界磁岛宽度时,磁岛降低的能量损失随着磁岛宽度呈线性增大,有效径向热导系数在磁岛区域呈高斯分布且最大值在有理面处。当等离子体背景加热与ECRH共同加热时,ECRH对磁岛区域的温度分布及能量约束均有别于背景热源,这为进一步研究ECRH抑制撕裂模的问题提供了基础。     

反常输运与非线性自持磁岛的自洽分析

从沿磁力线的等离子体电流与粒子径向输运相关的新经典ＭＨＤ型的广义欧姆定律出发，提出了分析反常输运与非线性自持磁岛的自洽理论模型，基于该模型导出了反常扩散系数及反常电子热导。结果表明，非线性磁岛链可由磁岛调制的反常输动维持，反过来又通过磁岛短路效应维持反常输运。     

托卡马克等离子体中q=2面附近的磁流体驰豫现象

本文在采用一维圆柱输运模型来摸拟托卡马克等离子体欧姆加热时,考虑了杂质辐射与磁岛演变的耦合作用。我们发现,在一定参数条件下,m/n=2/1的磁岛宽度及相应于q=2面附近的电子温度会产生驰豫振荡。本文主要讨论了出现这种驰豫现象的原因及其对增强托卡马克约束的意义。     

稀疏膨胀过程中几何位形对于电子非局域热传导的影响

发展了考虑一维柱对称、球对称位型下流体演化的Fokker-Planck程序, 在流体力学极限下对程序进行了校验. 利用程序模拟研究了球对称位型、平板位型下等离子体在自由稀疏演化过程中电子热流的非局域热输运行为, 分析了几何位型对电子非局域热传导的影响. 非局域卷积理论的计算研究发现, 稀疏过程中空间的几何效应会减小外向电子热输运的非局域性.     

Al0.22Ga0.78N/GaN二维电子气中的弱局域和反弱局域效应

通过磁输运测量研究了Al_0.22Ga_0.78N/GaN二维电子气的电子相干散射中的弱局域和反弱局域化现象.在外加弱磁场的情况下，该系统表现出正-负磁阻的变化，说明在Al_0.22Ga_0.78N/GaN异质结中存在晶体场引起的电子自旋-轨道散射.同时讨论了二维电子气中不同的散射时间对温度的依赖关系，实验得到的非弹性散射时间与温度成反比，表明非弹性散射机理主要来源于小能量转移的电子-电子散射. 关键词： 二维电子气 弱局域 磁阻     

磁场下非对称T型量子波导的电子输运行为

运用模匹配方法和求解单电子薛定谔方程,来演示非对称T型磁量子结构的电子输运性质.结果表明,结构因子和磁势垒都能改变电子散射模数,电子输运谱因此变得复杂而丰富,散射区域出现了完全局域态和磁边缘态.在特定的结构参数和磁场强度下,能观测到宽谷、尖峰、共振透射和共振反射等电子输运现象,即可以通过调节磁场大小和结构参数来实现波矢过滤. 关键词： 介观体系 电子输运 磁效应     

Heusler合金Cu2VAl磁性及输运性质的研究

对Heusler合金Cu2VAl多晶甩带样品进行了磁性与输运性质方面的研究.实验发现Cu2VAl在温度T为210K附近发生铁磁-顺磁相变,为弱铁磁体.输运性质的测量表明在7.2K时电阻因局域杂质超导相变而发生突变,电子和声子之间的散射是主要的散射机理.居里温度Tc以下存在侧跃导致的反常霍尔效应,并且7K附近的相变导致霍尔电阻率发生异常.     

飞秒激光等离子体中电子热传导现象的数值模拟

采用相对论电磁粒子模拟程序研究了飞秒激光等离子体相互作用中产生的电流密度、电场和自生磁场的发展演化过程。介绍了电子的非局域热输运的基本特性以及激光加热过程中温度烧蚀前沿稠密等离子体子区的预热效应、临界面附近的限流效应,以及冕区的反扩散与限流效应,得到了经典Spitzer-Harm理论描述的电子热传导随自生磁场的演化情形。数值模拟表明:在线性强激光作用下,由于电子初始时刻的无规则热运动,在等离子体上激发电磁不稳定性,而不稳定性激发的强电磁场使电子束在非常短的距离内沉积能量,同时对在激光有质动力推开电子时形成的超热电子能量输运产生抑制作用。     

EAST 电子回旋共振加热效果的数值模拟和分析

为了给EAST 电子回旋共振加热物理实验提供理论依据和模拟预测,从电子热输运方程出发,运用 CRONOS 输运程序对不同等离子体和波参数下,电子回旋加热效果进行了数值模拟计算。给出不同电子回旋波功率、入射角、电子密度和纵场等参数对电子回旋加热效果的影响,预测在不同参数下,电子温度、等离子体总内能和能量约束时间的变化,分析了其原因,并与实验结果进行了初步的比较。     

EAST电子回旋共振加热效果的数值模拟和分析

为了给EAST电子回旋共振加热物理实验提供理论依据和模拟预测,从电子热输运方程出发,运用CRONOS输运程序对不同等离子体和波参数下,电子回旋加热效果进行了数值模拟计算。给出不同电子回旋波功率、入射角、电子密度和纵场等参数对电子回旋加热效果的影响,预测在不同参数下,电子温度、等离子体总内能和能量约束时间的变化,分析了其原因,并与实验结果进行了初步的比较。     

Low-threshold parametric decay instabilities in the experiments on the electron cyclotron resonance heating in tokamaks and stellarators

The experimental conditions have been analyzed for a significant reduction of the threshold of the reflective parametric decay instabilities under electron cyclotron resonance heating (ECRH) of a plasma in magnetic devices in the absence of the upper hybrid resonance for the pump wave. The role of the nonmonotonic profile of the plasma density near the O point of the magnetic island, which allows for the localization of ion Bernstein waves in the direction of the density gradient and the suppression of convective losses from the decay region has been discussed. It has been shown that the threshold of the instability of the induced backscattering near the local maximum of the density profile is decreased by four orders of magnitude and is easily exceeded in present-day ECRH experiments at a power of several hundred kilowatts.     

Wave-particle decorrelation and transport of anisotropic turbulence in collisionless plasmas

Comprehensive analysis of the largest first-principles simulations to date shows that stochastic wave-particle decorrelation is the dominant mechanism responsible for electron heat transport driven by electron temperature gradient turbulence with extended radial streamers. The transport is proportional to the local fluctuation intensity, and phase-space island overlap leads to a diffusive process with a time scale comparable to the wave-particle decorrelation time, determined by the fluctuation spectral width. This kinetic time scale is much shorter than the fluid time scale of eddy mixing.     

Observation of reduced heat transport inside the magnetic island O point in the large helical device

Evidence for a reduction of heat transport inside the magnetic island O point is observed from the propagation of a cold pulse produced by a tracer encapsulated solid pellet in the Large Helical Device. A small peak and slow propagation of the cold pulse are observed inside the island. A significant result is that electron heat diffusivity inside the island is estimated to be 0.2 m(2)/s which is smaller than that outside the island by an order of magnitude.     

Reconstruction of heat flux profile on the HL-2A divertor plate with a three-dimensional analysis model

A three-dimensional analysis model based on the finite element method (FEM) is developed, which can derive the evolution and distribution characteristics of heat flux deposited on the divertor plate from the surface temperature measured by infrared thermography diagnostics. The numerical simulations of surface heating due to localized power bursts and the power deposition calculations demonstrate that this analysis can provide accurate results and useful information about localized hot spots compared with the normal one- and two-dimensional calculations. In this paper, the details of this three-dimensional analysis are presented, and some results in ohmic heating and electron cyclotron resonant heating (ECRH) discharge on HL-2A are given.     

X-Ray Measurements during Whistler-Mode Electron Cyclotron Resonance Plasma Startup and Heating in an Axisymmetric Magnetic Mirror

New measurements and analyses of whistler-mode electron cyclotron resonant heating (ECRH) startup and heating in an axisymmetric magnetic mirror are presented. Experimental studies of startup are presented which include the effects of initial neutral gas pressure on density and energy buildup rates, the effects of electron-beam-generated seed plasma on startup times, and a possible density threshold for the absolute whistler instability. Results of two types of analyses are presented. The first is a Fokker-Planck finite-element simulation the principal result of which is the prediction of the creation of a sloshing electron velocity distribution in the first 10 ?s after microwave power is applied. The second simulation uses rate equations to predict buildup, with rate coefficients based on a model sloshing-electron distribution function. Both results are consistent with experimental observations. Measurements of X-ray emission provided information about plasma transport, the sloshing electron spatial distribution, and the hot-electron average energy. The foil ratio technique gave average energies of 1-3 keV during whistler-mode ECRH, in agreement with afterglow measurements of hot electron decay. Possible applications of whistler-mode ECRH plasma production and heating are for plasma soft X-ray sources and plasma potential modification in tandem mirror machines.     

Numerical Modeling on Heat Transport Across Stochastic Magnetic Field

The heat diffusion across the stochastic magnetic field is studied numerically. The stochastic field is generated by the overlap of two magnetic islands. The parameter w/w_c, is found tobe an important parameter in charactering the transport, where w is the magnetic island width, and w_c is the critical island width for flattening the electron temperature across an island. For w/w_c < 1, the enhanced radial heat diffusivity χ_r is proportional to the parallel heat diffusivity χ_∥, and the heat transport is dominated by the additive effect of individual islands. For w/w_c > 3, χ_r is also proportional to χ_∥ and the additional degradation of the energy confinement due to stochastic magnetic field becomes apparent. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Quenching of the nonlocal electron heat transport by large external magnetic fields in a laser-produced plasma measured with imaging thomson scattering

We present a direct measurement of the quenching of nonlocal heat transport in a laser-produced plasma by applying large external magnetic fields (>10 T). The temporally resolved Thomson-scattering measurements of the electron temperature profile show that the heat front propagation transverse to a high-power laser beam is slowed resulting in extremely strong local heating. We find agreement with hydrodynamic modeling when including a magnetic field model that self-consistently evolves the fields in the plasma.     

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利用调制送气过程中观察到的冷脉冲传播,研究了在HL-2A装置欧姆放电条件下的电子热输运。从扰动输运方程出发,分析了电子热输运过程,利用在实验中获得的数据,进行了曲线拟合和数值计算,得到了在HL-2A装置欧姆放电条件下强场侧电子热输运系数的分布特征为χ=15-14(1-r2)2m2.s-1。