共查询到19条相似文献,搜索用时 93 毫秒
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本文在共振螺旋场(RHF)条件下,对撕裂模的时间演化过程进行了数值计算。在等离子体内部磁扰动与外加RHF的相位差不同时,分析了撕裂模的不同发展过程和结果。认为RHF可以最终改变托卡马克中的饱和磁岛宽度。 相似文献
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大破裂限定了托卡马克的运行。实验指出,撕裂模或者说磁岛的发展是这种大破裂的主要原因。考虑到无感电流驱动效应,我们重新推导了电阻撕裂模的三维非线性方程组?数值计算表明,跟随磁岛旋转的RF波电流驱动有效地抑制磁岛的发展。 相似文献
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本文研究了熔融织构块材和单晶YBa2Cu3O7在液氮温区63-75K的磁驰豫性质。在此温区常数ωa是与温度相关的,平均有效结合能作为电流密度的函数和Zeldov模型一致。 相似文献
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基于磁流体理论利用CIP方法数值对电阻磁流体中的磁岛演化动力学行为进行了长时间模拟。研究发现,磁岛饱和后流体演化并未结束,磁场重联将导致流体的宏观剪切流动。这一物理图象可用于解释托卡马克等离子体L-H模转换过程中观察到的磁流体行为。 相似文献
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锯齿振荡是托卡马克装置上常见的磁流体不稳定性之一.先进实验超导托卡马克(experimental advanced superconducting Tokamak,EAST)装置放电中观察到外加共振磁扰动(resonant magnetic perturbation,RMP)会影响锯齿振荡行为.本文研究了环向模数n=2的RMP对锯齿周期的影响.通过RMP线圈相位差扫描实验发现,当RMP上下线圈(n=2)相位差ΔφUL发生变化时,扰动场的谱型发生变化,锯齿周期和崩塌幅度也随之发生明显的改变.单流体电阻磁流体力学(MARS-F)程序分析表明,在相同实验条件下,当RMP上下线圈(n=2)相位差为ΔφUL=270°时,等离子体芯部区域的响应最强,此时锯齿周期和幅度最小.锯齿行为的改变可能与RMP引起的快离子损失相关.该研究利用RMP上下线圈(n=2)实现对锯齿行为的有效调控,有利于未来EAST发展高比压放电条件下的大锯齿自动控制技术. 相似文献
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Evolution of the current density profile associated with magnetic island formation of an m/n=2/1 tearing mode was measured using a motional Stark effect (MSE) diagnostic for the first time in the JT-60U tokamak. With the island growth, the current density profile turned flat at the radial region of the island, followed by an appearance of a hollow structure. As the island shrank, the flat region became narrower, and it finally diminished after the disappearance of the island. The fluctuation of the local poloidal magnetic field from MSE showed a strong correlation with a slow island rotation. This indicates that the observed deformation in the current density profile is localized at the island O point. 相似文献
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在HT-7装置上建立了一套高速CCD可见光成像诊断,测量了边界等离子体的可见光辐射成像.在HT-7装置放电中,首次观察到在等离子体边界区域存在一条极向旋转的可见光辐射带,由CCD诊断系统得到其极向旋转的频率为858Hz.根据多道Hα阵列测量得到极向旋转频率为952Hz.多道磁探针信号测量发现,等离子体内部存在m/n=3/1的电磁模,该模的旋转频率为972Hz.从电子回旋辐射诊断系统得到的电子温度剖面发现该模的磁岛宽度约为2.5cm. 相似文献
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在HT-7装置上建立了一套高速CCD可见光成像诊断,测量了边界等离子体的可见光辐射成像。在HT-7装置放电中,首次观察到在等离子体边界区域存在一条极向旋转的可见光辐射带,由CCD诊断系统得到其极向旋转的频率为858Hz。根据多道Hα阵列测量得到极向旋转频率为952Hz。多道磁探针信号测量发现,等离子体内部存在m/n=3/1的电磁模,该模的旋转频率为972Hz。从电子回旋辐射诊断系统得到的电子温度剖面发现该模的磁岛宽度约为2.5cm。 相似文献
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Small-scale quasicoherent oscillations of the x-ray emissivity and magnetic field perturbations are observed in the T-10 tokamak during abrupt growth of the m=2, n=1 magnetohydrodynamic modes at the density limit disruption. Analysis indicates a possible link between the small-scale oscillations and nonthermal electron beams induced around the X points of the m=2, n=1 magnetic island during reconnection of magnetic field lines at the disruption instability. 相似文献
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Zernicke polynomials method was first used in HT-7 tomography. Combining the characteristics of the soft X-ray imaging system in HT-7 tokamak, some of the technical consideration in applicating the tomography method are reported in this Letter. Through analyzing experimental soft X-ray data of a typical discharge with m=1 mode superimposed on sawtooth, it is shown that in the mid-mode and precursor phases, the central magnetic surface structure is composed of a hot core and a small magnetic island. In the crash phase, the hot core is obviously pushed outside and evolves into a crescent. The magnetic island is large. In addition, we compared the reconstructions obtained with Zernicke polynomials method and the Fourier-Bessel expansion method. The comparison result shows that as the magnetic island is large, Zernicke polynomials method seems more suitable to reconstruct the central plasma emissivity distribution on HT-7 tokamak. At last, through analyzing the oscillation amplitude and island size of the m=1 mode superimposed on sawtooth, it is thought that the large oscillation amplitude is due to large pressure gradient at the vicinity of inversion surface. 相似文献
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In the TCV tokamak, the m/n = 2/1 island is observed in low-density discharges with central electron-cyclotron current drive. The evolution of its width has two distinct growth phases, one of which can be linked to a "conventional" tearing mode driven unstable by the current profile and the other to a neoclassical tearing mode driven by a perturbation of the bootstrap current. The TCV results provide the first clear observation of such a destabilization mechanism and reconcile the theory of conventional and neoclassical tearing modes, which differ only in the dominant driving term. 相似文献
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结合HL-1装置的条件,采用撕裂模的准线性理论,研究了托克马克中导体壁对m=2/n=1扰动模的稳定作用。着重研究了导体壁位置,等离子体电流分布,等离子体位形对这种稳定效应的影响。结果表明,共振面的位置与壁的稳定作用有密切关系,存q_a接近于2的位形中,m=2的撕裂模扰动可以被靠近等离子体的导体壁完全抑制。导体壁的稳定效应与等离子体电流分布相联系,在一些现实的电流分布中,只要适当地压低等离子体边界区的电流密度,壁的稳定效应会更加显现出来。 相似文献
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The behavior of magnetohydrodynamic phenomena associated with disruptions of ohmically heated density limit discharges (qa=3.9) in the TEXTOR tokamak has been investigated in detail. A minor disruption is demonstrated to be only due to an tn = 2 mode instability, possibly due to the magnetic reconnection of an m=2 island. When the m = 2 mode oscillations cease, the internal m = 1 kink mode instability is drastically enhanced at once, twisting the plasma core considerably. If the twisting is too strong, the twisted plasma core is inevitably displaced to the outside and brings cold plasma to the central region, leading to the energy quench at a major disruption. 相似文献
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Maraschek M Gantenbein G Yu Q Zohm H Günter S Leuterer F Manini A;ECRH Group;ASDEX Upgrade Team 《Physical review letters》2007,98(2):025005
The efficiency of generating a helical current in magnetic islands for the purpose of suppression of neoclassical tearing modes (NTMs) by electron cyclotron current drive (ECCD) is studied experimentally in the ASDEX Upgrade tokamak. It is found that the efficiency of generating helical current by continuous current drive in a rotating island drops drastically as the width 2d of the co-ECCD driven current becomes larger than the island width W. However, by modulating the co-ECCD in phase with the rotating islands O point, the efficiency can be recovered. The results are in good agreement with theoretical calculations taking into account the equilibration of the externally driven current on the island flux surfaces. The result is especially important for large next-step fusion devices, such as ITER, where 2d>W is expected to be unavoidable during NTM suppression, suggesting that modulation capability should be foreseen. 相似文献