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根据第二类气球模理论,在托卡马克中诸如不稳定漂移波类的环形局部模将在径向呈现源于环形性的对称性自发破缺。以流体离子温度梯度模模型方程为例,解出在准环坐标系中由对称性自发破缺产生的二维局部模本征模式。在略去边带效应后,它成为具有径向位移修正的平板模式。由位移修正离子温度梯度模式导出了种子平行雷诺胁强,而它在传统的(无位移修正的)平板模式下被证明为零。     

The intermittent excitation of geodesic acoustic mode by resonant Instanton of electron drift wave envelope in L-mode discharge near tokamak edge

There are two distinct phases in the evolution of drift wave envelope in the presence of zonal flow. A long-lived standing wave phase, which we call the Caviton, and a short-lived traveling wave phase (in radial direction) we call the Instanton. Several abrupt phenomena observed in tokamaks, such as intermittent excitation of geodesic acoustic mode (GAM) shown in this paper, could be attributed to the sudden and fast radial motion of Instanton. The composite drift wave—zonal flow system evolves at the two well-separate scales:the micro-scale and the meso-scale. The eigenmode equation of the model defines the zero-order (micro-scale) variation; it is solved by making use of the two-dimensional (2D) weakly asymmetric ballooning theory (WABT), a theory suitable for modes localized to rational surface like drift waves, and then refined by shifted inverse power method, an iterative finite difference method. The next order is the equation of electron drift wave (EDW) envelope (containing group velocity of EDW) which is modulated by the zonal flow generated by Reynolds stress of EDW. This equation is coupled to the zonal flow equation, and numerically solved in spatiotemporal representation; the results are displayed in self-explanatory graphs. One observes a strong correlation between the Caviton-Instanton transition and the zero-crossing of radial group velocity of EDW. The calculation brings out the defining characteristics of the Instanton:it begins as a linear traveling wave right after the transition. Then, it evolves to a nonlinear stage with increasing frequency all the way to 20 kHz. The modulation to Reynolds stress in zonal flow equation brought in by the nonlinear Instanton will cause resonant excitation to GAM. The intermittency is shown due to the random phase mixing between multiple central rational surfaces in the reaction region.     

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在文献[1]中,通过分析实验上观察到的测地声模的小密度-电位比与测地声模谐波定级的自洽性,论证了测地声模是在转向点附近一种“蝌蚪状”的定域结构,但没有给出导致这种结构的物理机制.从随机媒质对波传播产生定域化的角度进行了探讨,采用测地声模由漂移波湍流参量激发的产生模型,计算了随机定域化导致的也是文献[1]所关注的相干长度.讨论了与实验观测比较的有关问题.     

轴对称环状静电模的漂移波湍流参量激发理论研究

本文所论述的轴对称环状静电模是指环形磁约束等离子体(如托卡马克)中环向模数为零的近理想静电流体模,它包含有测地声模和基频率与之较低的声模;也含有所谓的‘近零频带状流’.本文根据冷离子流体模型在圆形磁面构成的准环坐标系中的表示,对涉及以上三种模式的漂移波湍流参量激发理论,在一级环形效应近似下,进行了系统讨论,并证明了带状流的四个新命题.利用对漂移波能谱的参数化描写,注意到由漂移波能谱径向有限宽度所引发的特性,如波能传播量的双Landau奇点,揭示了有限宽度对径向δ谱所得结果的重要修正:如,对近零频带状流和测地声模的参量激发条件带来的严格限制.此外,还讨论了密度带状流在高q条件下被激发的可能性.本文选用合理的物理参数.采用图示方法详细地讨论了有关的数值结果.分析表明,测地声模和近零频带状流的参量激发不可能发生在同一小半径处;如果测地声模被参量激发,也应能观察到密度带状流.     

托卡马克的反常电子输运定标律

本文假设导致托卡马克反常电子输运的主要机制为由温度梯度所驱动的重整化电子磁漂移波。通过求解动力学过程自洽地导出了反常电子输运系数的定标律:D^(T)=(c/ω_pe)²{((v_e/qR)²/2π+(v_{c/2)²)^1/2-vc/2}。它在数值上与现有实验给出的AIcator定标律符合。在无碰撞(vc→0)情况下与Ohkawa定标津一致。同时分析了该定标律与Alcator定标律的偏离,并由此讨论了强磁场欧姆加热托卡马克达到热核点火的可能性。 关键词：}     

托卡马克二维局部模的第三类气球理论

采用二维气球表象,在已有第一类和第二类气球理论的基础上,构造了第三类气球理论。与第一类气球理论相比,扩展了后者因受可解性条件限制的适用范围;与第二类气球理论相比,因容纳了“坏曲率”效应而获得具有更高增长率的解,故与采用初值数值模拟方法所得的结果更具可比性。本文以流体型离子温度梯度模为例,用第三类气球理论求解了二维本征值问题,计算了所选剖面参数下的本征频率和模式结构,并与前两种理论所得的结果进行了比较和讨论;也讨论了该理论对实现托卡马克高约束的意义。     

电子磁漂移波的静电修正问题

本文对为什么在托卡马克输运中电子表现为反常而离子表现为经典提出了一种解释。 关键词：