Alfven eigenmode properties and dynamics in the TJ-II stellarator
Alfven eigenmode properties and dynamics in the TJ-II stellarator
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DOI：
10.1088/0029-5515/52/12/123004
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发表时间：
2012-12-01
期刊：
影响因子：
3.3
通讯作者：
Yamamoto, S.
中科院分区：
文献类型：
--
作者：
Melnikov, A. V.;Eliseev, L. G.;Yamamoto, S.
在TJ-II仿星器中，用重离子束探针（HIBP）和Langmuir探针（LP）和Mirnov探针（MP）研究了中性束注入（NBI）加热等离子体中的Alfven本态模式（AEs）。HIBP在整个等离子体半径范围内检测ae，空间分辨率约为1 cm。在频率为50 kHz < f(AE) < 300 kHz的等离子体密度n(e)、电势phi和极向磁场B-pol中检测到AE引起的振荡。LP， MP和HIBP数据显示ae的特定分支具有高水平的一致性。在具有不同径向位置的ae分支中检测到极向模态波矢量k（theta）、模态数m （m < 8）和传播速度V-theta接近30 km s（-1）。当NBI加注导致密度增加时，声发射频率下降，与Alfven定律f（AE）预测的结果相似，与n(e)（-1/2）相似。在声发射频率衰减过程中，观察到以下新的声发射特征：(i)极向波矢量k（theta）和模态数m保持不变；（ii） B-pol、n(e)和电位振荡之间的交叉相位保持不变，每个声发射分支都有一个单独的值；（iii） V-theta与声发射频率成比例地减小。AEs与体（热）等离子体的相互作用在静电湍流粒子通量谱中产生了明显的准相干峰。不同的声发射分支对粒子通量的贡献不同：向外、向内和零，这取决于e -pol和n(e)振荡之间的相位关系，这是每个分支所特有的。与MHD模态模型的比较表明，一些更突出的频率分支可以被识别为径向扩展的螺旋ae。
Alfven eigenmodes (AEs) were studied in neutral beam injection (NBI) heated plasmas in the TJ-II stellarator using a heavy ion beam probe (HIBP) in the core, and by Langmuir (LP) and Mirnov probes (MP) at the edge. AEs were detected over the whole plasma radius by the HIBP with a spatial resolution of about 1 cm. AE-induced oscillations were detected in the plasma density n(e), electric potential phi and poloidal magnetic field B-pol with frequencies 50 kHz < f(AE) < 300 kHz. The LP, MP and HIBP data showed a high level of coherency for specific branches of AEs. Poloidal mode wave-vectors k(theta), mode numbers m (m < 8) and propagation velocities V-theta similar to 30 km s(-1) were detected for various branches of AEs, having different radial locations. When the density rose due to NBI fuelling, the AE frequency decreased as predicted by the Alfven law f(AE) similar to n(e)(-1/2). During the AE frequency decay the following new AE features were observed: (i) the poloidal wave-vector k(theta) and mode number m remained constant, (ii) the cross-phases between the oscillations in B-pol, n(e) and electric potential remained constant, having an individual value for each AE branch, (iii) V-theta decreased proportional to the AE frequency. The interaction of the AEs with the bulk (thermal) plasma resulted in clearly pronounced quasi-coherent peaks in the electrostatic turbulent particle flux spectra. Various AE branches exhibited different contributions to the particle flux: outward, inward and also zero, depending on the phase relations between the oscillations in E-pol and n(e), which are specific for each branch. A comparison with MHD mode modelling indicated that some of the more prominent frequency branches can be identified as radially extended helical AEs.