MHD Database for Design of Quasi-axisymmetric Stellarator

准轴对称仿星器设计的 MHD 数据库

基本信息

批准号：
12480128
负责人：
MATSUOKA Keisuke
金额：
$ 2.88万
依托单位：
Natiomal Institute for Fusion Science
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

项目摘要

MHD stability of quasi-axisymmetric stellarator CHS-qa is estimated by referring to CHS experimental data and by using computer codes. Although magnetic configurations of CHS-qa and CHS (low aspect ratio heliotron / torsatron) are different, stability criteria should be available for both configurations. Mercier criterion on the local interchange mode has been widely used as a guideline for evaluating MHD stability of CHS and LHD, because both machines are of a magnetic hill even in the finite J3 configuration, which makes the configurations possibly unstable against ideal interchange modes. Experimental results of CHS showed that finite <β> plasmas, where instabilities are expected from Mercier criterion, did not show any deleterious effect on the stored energy. Recent CHS experiments again confirmed this result for more strongly inward shift of vacuum magnetic axis than before, where the magnetic hill becomes stronger. This was also confirmed recently in LHD experiments. The important conclusion is that it is not necessary to take serious account of Mercier criterion in evaluating MHD stability of CHS-qa. In CHS-qa plasmas with finite <β>, the bootstrap current flows in the direction to augment the vacuum rotational transform. The current might excite tearing modes and external kink modes, where m=2/n=l mode is the most dangerous one. By inducing Ohmic and beam driven currents in CHS, MHD modes with m=2/n=l have been studied. Again there is no deleterious effect on the plasma performance. Because the resonant surface of m=2/n=l can not exist in vacuum in CHS, the external kink mode can not be simulated in the experiment. The mode has been analyzed by using Terpsichore and CAS3D codes in CHS-qa. The plasma is stable up to <β> of 2.5 - 3%. The ballooning mode has been analyzed with Terpsichore WBAL and Cobra codes, giving stability <β> of up to about 3%.

准轴对称恒星CHS-QA的MHD稳定性是通过参考CHS实验数据和使用计算机代码来估计的。尽管CHS-QA和CHS（低纵横比Heliotron / Torsatron）的磁性构型不同，但应用于两种配置的稳定性标准。本地交换模式上的Mercier标准已被广泛用作评估CHS和LHD的MHD稳定性的指南，因为这两台机器即使在有限的J3配置中都具有磁性山丘，这使得配置可能在理想的交换模式下不稳定。 CHS的实验结果表明，从Mercier标准中预期不稳定性的有限等离子体对存储的能量没有任何有害作用。最近的CHS实验再次证实了这一结果，使真空磁轴的内向移位比以前更强烈，在该磁磁山变得更强。 LHD实验最近也证实了这一点。重要的结论是，在评估CHS-QA的MHD稳定性时，不必认真考虑Mercier标准。在具有有限<β>的CHS-QA平原中，引导电流朝向增强真空旋转变换的方向流动。电流可能会激发撕裂模式和外部纠结模式，其中M = 2/N = L模式是最危险的。通过诱导的欧姆和光束驱动电流，已研究了M = 2/N = L的MHD模式。同样，对等离子体性能没有有害影响。由于在CHS中真空中不存在M = 2/N = L的谐振表面，因此在实验中无法模拟外部扭结模式。该模式已通过在CHS-QA中使用Terpichore和Cas3D代码进行了分析。血浆的稳定性为2.5-3％。已经用Terpichore Wbal和Cobra代码分析了气囊模式，稳定性<β>最高约为3％。