离子温度梯度模湍流的带状流最小自由度模型

在离子温度梯度模(ITG)湍流背景中,通过最小自由度模型中模耦合方式产生带状流,对此模型做了动力学稳定性分析及数值求解.并在此基础上初步探讨了湍流中漂移波与带状流的能量转移,以及雷诺协强与带状流的关系. 关键词： 等离子体 离子温度梯度模 湍流 带状流     

负磁剪切等离子体中离子温度梯度驱动不稳定性分析

采用打靶法,数值求解了在负磁剪切托卡马克等离子体中离子温度梯度驱动的复本征模方程.数值计算表明,环向旋转剪切流可以整体上改变剪切板η_i不稳定性.在等离子体极小q磁面附近的芯部区域,环向剪切流有稳定η_i模的作用.     

环形等离子体中电子温度梯度不稳定性的粒子模拟

用粒子模拟方法求解描述环形等离子体中电子温度梯度静电模的回旋动力学方程.方程采用圆磁通面的轴对称环形几何系统，考虑了有限拉摩半径、电子渡越频率k_∥v _∥以及环形漂移(曲率和磁场梯度)运动w_D(v²_⊥,v ²_∥,θ)的效应.简述了粒子模拟的基本方法.采用了四阶变步长积分格式，使计算省时、简便.讨论了模的基本特征 , 并且给出了临界梯度对电子温度与离子温度之 关键词： 电子温度梯度不稳定性 粒子模拟 变步长积分格式 临界梯度     

逆磁效应对交换模湍流产生的带状流的影响

运用并扩展了Guzdar等人提出的一种简单的低维模型, 讨论了交换模湍流中的非线性逆磁效应对带状流产生的影响,通过对非线性演化方程的数值计算,得到如下结论：逆磁效应能抑制通常的（雷诺胁强驱动的）极化非线性效应,由此导致带状流的阻尼. 关键词： 托卡马克等离子体 交换模湍流 带状流 逆磁效应     

Y3Fe5-xMnxO12的磁结构和磁性能

对多晶Y₃Fe₃Fe_5-xMn_xO₁₂(x=0.05和0.09),得到300K下的中子衍射曲线。发现当x=0.05时,Mn³⁺离子占据16a和24d位置的几率分别为0.72和0.28;当x=0.09时,Mn³⁺离子全部占据16a位置;还得到两种组分16a和24d位置各自的磁矩值。在外磁场(800—10KOe)下测量Y₃Fe_5-xMn_xO₁₂(x=0—0.11)的磁化曲线,温度范围是1.5—300K。得到饱和磁矩值;并利用趋近饱和定律确定1.5K下的磁晶各向异性常数k₁值,发现|k₁|值随含锰量增加而减小。 关键词：     

非均匀磁场和杂质磁场对自旋1系统量子关联的影响

通过负值度和测量诱导的扰动, 研究了非均匀磁场和杂质磁场对自旋为1的Heisenberg系统量子关联的影响. 研究发现非均匀磁场的增加会降低纠缠, 但也可用来产生纠缠, 并且会提高临界非线性作用K_c的值, 测量诱导的扰动的临界磁场要高于负值度的临界磁场, 而且测量诱导的扰动不会随着非线性作用|K| 的减小而消失, 它能全面反映量子关联的存在. 研究还发现, 不同杂质磁场对测量诱导的扰动的影响彼此间无交叉. 杂质磁场下, 相互作用|J| 必须小于非线性作用|K| 才会有纠缠存在, 但是测量诱导的扰动却可以在相互作用|J| 大于非线性作用|K| 时依然存在, |J| 与|K| 相同时只是测量诱导的扰动的最小取值点. 此外, 系统粒子数目对量子关联也具有重要影响.     

基于谱估计方法的等离子体湍流三波耦合数据处理算法

基于数字谱分析技术求解波耦合方程,进而计算与三波相互作用相关联的线性耦合系数和能量转移,以此开发了数据处理程序用于研究HL-2A 装置等离子体边缘湍流中的非线性能量传递过程。介绍了算法设计和开发的主要思想。应用该程序对与带状流相关的一次放电的实验数据进行了数据处理研究。结果表明,带状流是由等离子体湍流的能量逆级联所驱动的。     

极化激元系统时间演化的量子涨落特性和非经典统计行为

将极化激元系统约化成模型单模光子-TO声子有效相互作用系统， 在此基础上以解析形式讨论了系统的力学量、压缩态、量子涨落特性以及亚泊松分布等非经典效应的动力学演化行为.结果表明，光子场与极化波量子场彼此交换能量过程随时间演化呈振荡性质，光子场和声子场都可以演化成压缩态，其二阶压缩度随时间演化成复杂周期振荡特性，这种非经典特性是非线性相互作用的结果并且以k₁项和k₂项同时存在并相互关联为前提.而此时光子和声子统计分布随时间演化呈现介于超Poison分布和亚Poison分布之间复杂周期振荡的新结果，非线性作用k₁项和k₂项对这种非经典统计行为都有贡献. 关键词： 极化激元系统动力学演化 单模光场-TO声子有效模型哈密顿量 量子涨落与压缩态 亚泊松分布     

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基于Hasegawa-Wakatani湍流模型,数值模拟了托卡马克边缘等离子体中漂移波湍流和相关的反常粒子输运.从等离子体动量守恒方程出发导出了不采用常规的布辛涅斯克近似的带状流方程,论证了大振幅密度扰动和湍性粒子流对激发带状流的贡献可等效地对应于低阶负粘滞阻尼效果.数值模拟表明,大振幅密度扰动的非线性大大增强了带状流饱和振幅,从而有效抑制了湍性粒子输运.研究结果阐明了托卡马克边缘等离子体大振幅密度扰动的非线性对驱动等离子体旋转、动量输运和带状流的重要性.     

等离子体填充盘荷波导高频特性分析

从麦克斯韦方程和流体理论出发，推导了填充磁化等离子体慢波结构的基本方程.在大磁场情况下，对等离子体填充盘荷波导的色散特性和耦合阻抗作了研究，结果表明填充等离子体使色散曲线上移，耦合阻抗提高.等离子体填充产生出模式谱非常丰富的周期性低频等离子体模式(TG模式).当等离子体密度增加到一定程度后，场模TM₀₁模的频率范围和TG₀₁模的频率范围相近，两个模式互相耦合产生出新的混合模G₁,G₂.如果相对论行波管工作在混合模上，将会产生新的工作机理. 关键词： 盘荷波导 等离子体填充 色散特性 相对论行波管     

Role of the zonal flow in multi-scale multi-mode turbulence with small-scale shear flow in tokamak plasmas

The structural characteristics of zonal flows and their roles in the nonlinear interaction of multi-scale multi-mode turbulence are investigated numerically via a self-consistent Landau-fluid model. The multi-mode turbulence here is composed of a shorter wavelength electromagnetic (EM) ion temperature gradient (ITG) mode and a Kelvin-Helmholtz (KH) instability with long wavelengths excited by externally imposed small-scale shear flows. For strong shear flow, a prominent periodic intermittency of fluctuation intensity except for dominant ITG component is revealed in turbulence evolution, which onset time depends on the ion temperature gradient and the shear flow amplitudes corresponding to different KH instabilities. It is identified that the intermittency phenomenon results from the zonal flow dynamics, which is mainly generated by the KH mode and back-reacts on it. It is demonstrated that the odd symmetric components of zonal flow (same symmetry as the external flow) make the radial parity of the KH mode alteration through adjusting the drift velocities at two sides of the resonant surface so that the KH mode becomes bursty first. Afterwards, the ITG intermittency follows due to nonlinear mode coupling. Parametric dependences of the features of the intermittency are elaborated. Finally, associated turbulent heat transport is evaluated.     

Generation and stability of zonal flows in ion-temperature-gradient mode turbulence

We address the mechanisms underlying zonal flow generation and stability in turbulent systems driven by the electrostatic ion-temperature-gradient (ITG) mode. In the case of zonal flow stability, we show the poloidal flows typical of numerical simulations become unstable when they exceed a critical level. Near marginal stability of the linear ITG mode, the system can generate zonal flows that are sufficiently weak to remain stable and sufficiently strong to suppress the linear ITG mode. This stable region corresponds to the parameter regime of the nonlinear Dimits up-shift.     

Quasilinear analysis of the zonal flow back-reaction on ion-temperature-gradient mode turbulence

There is strong evidence in favor of zonal flow suppression in the Ion-Temperature-Gradient (ITG) mode turbulence, specifically close to the linear stability threshold. The present Letter attempts to analytically calculate the effects of zonal flow suppression of the ITG turbulence by deriving a modified dispersion relation including the back-reaction of the zonal flows on the ITG turbulence based on the quasilinear theory. The results are manifested in a reduction of the linear growth rate and an increase in the effective linear ITG threshold.     

Change of zonal flow spectra in the JIPP T-IIU tokamak plasmas

When Ohmically heated low-density plasmas are additionally heated by higher-harmonics ion-cyclotron-range-of frequency heating, heated by neutral beam injection, or strongly gas puffed, the intensity of zonal flows in the geodesic acoustic mode frequency range in the tokamak core plasma decreases sharply and that of low-frequency zonal flow grows drastically. This is accompanied by a damping of the drift wave propagating in the electron diamagnetic drift direction, turbulence by trapped electron mode (TEM), and the increase of the mode propagating to ion diamagnetic drift direction (ITG). In the half-radius region, TEM and high-frequency zonal flows remain intense in both OH and heated phases. ITG and low-frequency zonal flows grow in heated plasmas, suggesting a strong coupling between ITG and low-frequency zonal flow.     

Nonlinear refractive index of RECOB (RE = Gd and La) crystals

The Z-scan technique is employed to obtain the nonlinear refractive index (n ₂) of the Ca₄REO(BO₃)₃ (RECOB, where RE = Gd and La) single crystals using 30 fs laser pulses centered at 780 nm for the two orthogonal orientations determined by the optical axes (X and Z) relative to the direction of propagation of the laser beam (k//Y// crystallographic b-axis). The large values of n ₂ indicate that both GdCOB and LaCOB are potential hosts for Yb:RECOB lasers operating in the Kerr-lens mode locking (KLM) regime.     

第Ⅰ种强度不对称三态叠加多模叠加态光场N次方Y压缩—第一正交相位分量的压缩情况

根据量子力学中的线性叠加原理,构造了由三个强度不等的多模相干态光场|{Z_j^(A)}>_q、|{Z_j^(B)}>_q和|{Z_j^(C)}>_q的线性叠加所组成的第Ⅰ种强度不对称三态叠加多模叠加态光场|ψ_l^(ABC)>_q.利用多模压缩态理论,研究了态|ψ_l^(ABC)>_q的第一正交方分量(即磁场分量)的广义非线性等幂次N次方Y压缩特性.结果发现:①在上述各多模相干态光场中各模的强度和各模的初始相位各不相等的情况下,态|ψ_l^(ABC)>_q的第一正交分量-磁场分量在一定的条件下,总可呈现出周期性变化的、任意等幂次的N次方Y压缩效应;②当上述各多模相干态光场的强度和各模的初始相位相等时,态|ψ_l^(ABC)>_q的磁场分量的N次方Y压缩现象消失,态|ψ_l^(ABC)>_q可恒处于等幂次N-Y最小测不准态.     

Nonlinear saturation of trapped electron modes via perpendicular particle diffusion

In magnetized fusion plasmas, trapped electron mode (TEM) turbulence constitutes, together with ion temperature gradient (ITG) turbulence, the dominant source of anomalous transport on ion scales. While ITG modes are known to saturate via nonlinear zonal flow generation, this mechanism is shown to be of little importance for TEM turbulence in the parameter regime explored here. Instead, a careful analysis of the statistical properties of the ExB nonlinearity in the context of gyrokinetic turbulence simulations reveals that perpendicular particle diffusion is the dominant saturation mechanism. These findings allow for the construction of a rather realistic quasilinear model of TEM induced transport.     

Inversion of the cyclotron resonance data in cadmium

The cyclotron resonance data for the third band lens in cadmium is inverted, using a spherical mapping procedure, to obtain a point for point value of the electron velocity |V_k| for different k points on the lens. The results are compared with the |V_k| deduced from an analysis of the magnetic surface states data.     

Zonal flow dynamics and control of turbulent transport in stellarators

The relation between magnetic geometry and the level of ion-temperature-gradient (ITG) driven turbulence in stellarators is explored through gyrokinetic theory and direct linear and nonlinear simulations. It is found that the ITG radial heat flux is sensitive to details of the magnetic configuration that can be understood in terms of the linear behavior of zonal flows. The results throw light on the question of how the optimization of neoclassical confinement is related to the reduction of turbulence.