共查询到19条相似文献,搜索用时 140 毫秒
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徐茵 《核聚变与等离子体物理》1989,9(2):78-85,120
本文对托卡马克位形,用动力理论研究了非均匀热等离子体的ICRF快波模转换及有关的阻尼机制。结果表明,对于多种离子成分的等离子体,在离子-离子混杂共振层和二次谐波回旋共振层附近,存在快波和离子伯恩斯坦波(IBW)之间的模转换;模转换层附近的色散关系与k_(?),离子种类浓度以及等离子体密度有明显的相关性。适当选择这些参数可大大改善快波能量的吸收和吸收的局域性。而在一种离子成分的等离子体中、无模转换过程发生。 相似文献
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ICRF快波模转换及快波传播 总被引:1,自引:1,他引:0
本文通过分析离子回旋频段(ICRF)快波在模转换区传播的物理过程,导出了一个新的快波近似——完全快波近似二阶波方程。数值计算表明,它能给出与求解高阶方程非常一致的结果,尤其是在弱回旋阻尼(k_1较小)情况下,完全快波近似比快波近似有更满意的结果。最后讨论了二次谐波加热和少数成份离子加热的实例。 相似文献
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解析给出环形ηi模包括离子通行共振、磁漂移共振以及有限拉莫半径效应的局部和非局部完全动力色散关系,通过比较局非局部描述下环形ηi模增长率的大小,指出了局部近似适用的参数范围。 相似文献
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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. 相似文献
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采用等离子体分层模型,利用WKB近似研究了离子回旋共振加热(ICRH)天线发射谱n||对离子回旋波在托卡马克等离子体的表面功率反射系数、吸收衰减的影响,数值模拟了不同天线发射谱n||条件下快波少数离子加热的效果.模拟结果表明,当其它实验参数一定时,ICRH天线发射合适的n||能提高天线与等离子体的耦合效率,增强少数离子加热的效果. 相似文献
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基于外部谐振腔可以实现两基频激光的高效和频转换,通常可以采用泵浦不消耗近似(PUA)或小信号近似(SSA)来理论模拟实验结果。然而当基频光功率相近且转换效率较高时,此两种近似的误差就会变得不可接受,然而三波耦合波方程(TWCE)解析解通常需要进行椭圆积分,直接数值求解就变得简单易行。本文首先基于龙格-库塔方法求解准相位匹配下的TWEC,并与PUA和SSA下的解析解进行比较分析,确定了两种近似的适用条件;最后基于该精确数值解结合腔模理论对外腔高效和频对腔模线型的影响进行了研究。 相似文献
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刘玉魁 《核聚变与等离子体物理》1993,13(4):1-10
本文在直住几何位形下用线性化动力论得到了离子能量吸收及吸收特征长度的解析表示式,离子能量吸收的主要物理机制是回旋阻尼,波与离子的共振吸收条件是ω-lωci=kⅡνⅡ,其中ω和ωci分别是波的频率和离子回旋频率,kⅡ和vⅡ是平行于主磁场方向的波矢和离子速度的分量,l为整数。在等离子体参量慢变化的假定下,也得到了能量吸收半宽度的表示式。结合托卡马克的各种具体情况分别讨论了各种离子回旋共振加热模式的... 相似文献
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In the up-to-date ray tracing study of electron cyclotron resonance heating (ECRH) of fusion plasmas, energy absorption effect has never been considered into the wave trajectory computation. Thus all the work has been done in real space so far. In this paper we consider coupling of energy absorption to wave trajectory for the first time, and numerically solve the formal complex Hamilton equations in complex space, then take the real-space-projected wave trajectories and group velocities to be the corresponding concrete ones. It is shown that both ordinary wave and extraordinary wave injected from the inner side of the tokamak plasmas approach the electron cyclotron resonance surface step by step and their group velocities become exceedingly small as they move toward this surface. Those clearly show that the resonance between the electron cyclotron waves and the fusion plasmas takes place in the electron cyclotron resonance region, which is just the case the ECRH experimental results and the plasma kinetic theory of waves demonstrate. 相似文献
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本文采用多组态Dirac-Hartree-Fock方法研究了温稠密等离子体环境中Al12+离子的光电离过程. 等离子体效应采用SM屏蔽势来模拟(Stanton和Murillo在2015年提出). 计算中固定标度温度1.3eV,在强耦合等离子体环境下,研究了等离子体密度对能级,连续态波函数以及光电离截面的影响. 通过与相同等离子体条件下的Debye-Hückel模型势计算的光电离截面对比,发现两种模型对应的结果中未同时出现势形共振峰,这是由于本文采用的屏蔽模型包含等离子体简并、有限温度对动能的梯度修正和量子交换关联效应,对光电离截面的大小和共振结构具有显著影响. 相似文献
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The amplification mechanism of extra-ordinary mode radiation in the presence of kinetic Alfvén wave turbulence driven by an
electron beam is studied. It is shown that plasma maser process may be responsible for the amplification of the extra-ordinary
mode through up-conversion of turbulent energy via nonlinear wave particle interaction. The relevance of this investigation
to space plasmas is discussed. 相似文献
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《Physics letters. A》2020,384(25):126462
The effects of dust charge gradient (DCG) force and polarization force have been investigated on the properties of dust acoustic wave (DAW) and linear Jeans instability in strongly coupled dusty plasma. In the kinetic regime, DCG and polarization forces modify the DAW mode and couple with compressional viscoelastic wave mode. The Jeans instability criterion and critical wavenumber have been modified due to DCG force, polarization force and strong coupling effects. The results have been discussed in the warm photodisassociation region and in the laboratory complex plasmas. The strong correlation effect and the charge variation parameter stabilize the growth rate of Jeans instability. But, the polarization parameter stabilize the growth rate for positively charged dust grains and destabilize for negatively charged dust grains. The implications of charge gradient and polarization parameters are discussed for lower and higher charges in the laboratory complex plasma which decreases the growth of the propagating DAW. 相似文献
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Amagishi Y. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1992,20(6):622-625
A laboratory experiment has been performed in connection with interesting phenomena in space plasmas such as geomagnetic pulsations in the magnetosphere or particle acceleration by the kinetic Alfven wave in field-aligned currents of the auroral circuit. Fast waves or MHD surface waves in a cylindrical finite-β plasma have been observed to be mode converted into kinetic Alfven waves at the Alfven resonance layer. The surface waves were excited using small loop antennas located at the edge of the inhomogeneous plasma to simulate those on the magnetosphere or plasmapause 相似文献
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Analytical approximations are used to clarify the effect of Larmour radius on rf ponderomotive forces and on poloidal flows induced by them in tokamak plasmas. The electromagnetic force is expressed as a sum of a gradient part and of a wave momentum transfer force, which is proportional to wave dissipation. The first part, called the gradient electromagnetic stress force, is combined with fluid dynamic (Reynolds) stress force, and gyroviscosity is included into viscosity force to model finite ion Larmour radius effects in the momentum response to the rf fields in plasmas. The expressions for the relative magnitude of different forces for kinetic Alfven waves and fast waves are derived. 相似文献
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A theoretical study is made on the amplification mechanism of electrostatic Bernstein mode wave in presence of kinetic Alfven wave turbulence in a magnetized plasma on the basis of plasma-maser interaction. It is shown that a test high frequency electrostativ Bernstein mode wave is unstable in the presence of low frequency kinetic Alfven wave turbulence. The growth rate of the Bernstein wave vanishes only in an unmagnetized plasma. Because of the universal existence of the kinetic Alfven waves in large scale plasmas, the results have potential importance in space and astrophysical radiation processes. 相似文献
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A theoretical study is made on the generation mechanism of Langmuir mode wave in the presence of kinetic Alfvén wave turbulence
in a magnetized plasma on the basis of plasma-maser interaction. It is shown that a test high frequency Langmuir mode wave
is unstable in the presence of low frequency kinetic Alfvén wave turbulence. The growth of the Langmuir wave occurs due to
direct and polarization coupling terms. Because of the universal existence of the kinetic Alfvén waves in large scale plasmas,
the results have potential importance in space and astrophysical radiation processes. 相似文献