Study on Stabilization of Resistive Wall Modes in RFP's with the use of Rotating Helical Field

使用旋转螺旋场稳定 RFP 中的电阻壁模式的研究

• 批准号: 13680558
• 负责人: MASAMUNE Sadao
• 金额: $ 2.05万
• 依托单位: KYOTO INSTITUTE OF TECHNOLOGY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2001
• 资助国家: 日本
• 起止时间: 2001 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13680558/
• 关键词: Reversed Field Pinch; Tearing Mode (Instability); External Kink Mode (Instability); Resistive Wall Modes; Rotating Resonant Helical Field; Mode Rotation; Plasma Rotation; Control of MHD Mode Dynamics; モード安定化; 磁気閉じ込め核融合; MHD不安定性; 回転ヘリカル磁場; テアリン

Three critical MHD issues are to be addressed in the course of development of a reversed field pinch (RFP) fusion reactor. The first one is the internal tearing mode that plays essential roles in the RFP dynamics. In future RFP's inevitably equipped with resistive wall, control or suppression of this mode remains very important. The other two are ideal kink modes that grow with the time scale of field penetration time of the wall. Internal kink modes are unstable for flat current profile, while external kinks become unstable for peaked current profile. In STE-2 RFP [R/a=0.4m/0.1m], efforts have been made to actively control the resistive wall modes with resonant rotating helical field (RHF). The machine has been operated only with a SS vacuum vessel whose field penetration time(tw) is about 0.15 ms.Typical plasma current is 60 kA with discharge duration of 0.7 ms. In low pinch parameter (8) regime where θ=2, core resonant modes (with m=1/n=8,9) growing with time scale of tw are identif … More ied as the resistive wall tearing modes. When operated in high ? Regime (θ>2), m=1/n=3,4 modes grow with time scale of tw, and these are identified as resistive wall kink modes. We have installed pulsed oscillators so that RHF can be applied with constant amplitude during RFP discharge duration. The frequency can be changed from 10 kHz to 30 kHz, with maximum current of 1 kA. The perturbation amplitude of radial component at the edge [Bm] is about 15G (for helical current of 1 kA) at f=1O kHz, while it decreases to 5 G at f=30 kHz. The resonant surface of or interest lies near r/a=0.4, and the perturbation amplitude there is 4 G even at f=25 kHz, which would produce the magnetic island with the width of 10 % of the minor radius. In standard RFP plasmas in STE-2, the dominant m=1/n=8 and lower (n<8) modes are almost locked to the wall, while the higher modes (n>9) sometimes rotate in the opposite direction to the plasma current (CTR direction). When we apply the RHF, the resonant mode tends to rotate in the same direction as the applied RHF. The mode rotation velocity is lower than the applied RHF. In addition to the resonant m=l/n=8 mode, rotation of the neighboring m=l modes and m=0 modes also, are influenced by the RHF. When we increase the parturbation amplitude higher than 0.6% (to as high as 1%), a clear mode rotation can be seen in raw data of magnetic fluctuations. In addition, the pitch parameter θ sometimes tends to increase to higher than 2.5. In this high-θ regime, the resonant mode sometimes rotates at the same velocity as the applied RHF. The time-averaged fluctuation level of the dominant mode reduces by 30-50%. The lower level of core resonant modes indicates less active RFP dynamo, consistent with the higher θ trend. Although the plasma current increases and the discharge resistance decreases, no appreciable improvement is evident in RFP characteristics, which may be due to the lack of sufficient equilibraium control with increased plasma current. The present results have shown the possible use of RHF for the control of tearing modes with resistive wall. Less

在反场箍缩聚变堆的研制过程中，需要解决三个关键的磁流体动力学问题。第一种是内部撕裂模式，它在RFP动态中起着至关重要的作用。在未来的RFP的不可避免地配备了电阻墙，控制或抑制这种模式仍然非常重要。另外两个是理想的扭结模式，增长的时间尺度的场穿透时间的墙壁。内部扭结模式是不稳定的平坦的电流分布，而外部扭结变得不稳定的峰值电流分布。在STE-2 RFP [R/a=0.4m/0.1m]中，我们采用共振旋转螺旋场（RHF）对阻性壁模进行了主动控制。实验装置采用不锈钢真空室，其场穿透时间（tw）约为0.15ms，典型等离子体电流为60 kA，放电持续时间为0.7ms，在θ=2的低箍缩参数（8）区，发现了随时间尺度tw增长的芯共振模（m=1/n= 8，9），并发现了它们之间的相互作用。 ...更多信息 即电阻性壁撕裂模式。在高？当θ>2时，m=1/n= 3，4模随时间增长，这些模被认为是阻性壁扭结模。我们已经安装了脉冲振荡器，以便RHF可以在RFP放电期间以恒定的幅度施加。频率可在10 kHz至30 kHz之间变化，最大电流为1 kA。在f= 10 kHz时，边缘处径向分量的扰动幅度[Bm]约为15 G（对于1 kA的螺旋电流），而在f=30 kHz时，它减小到5 G。共振面位于r/a=0.4附近，在f=25 kHz时，微扰振幅为4G，产生的磁岛宽度为短半径的10%。在STE-2中的标准RFP等离子体中，占主导地位的m=1/n=8和较低（n<8）模式几乎被锁定在壁上，而较高模式（n>9）有时在与等离子体电流相反的方向（CTR方向）上旋转。当我们施加RHF时，谐振模式倾向于在与所施加的RHF相同的方向上旋转。模式旋转速度低于所施加的RHF。除了共振m= 1/n=8模之外，相邻m= 1模和m=0模的旋转也受到RHF的影响。当扰动幅度大于0.6%（高达1%）时，在磁涨落的原始数据中可以看到明显的模旋转。此外，间距参数θ有时倾向于增加到高于2.5。在这种高θ区，谐振模式有时以与所施加的RHF相同的速度旋转。主模的时均起伏水平降低了30- 50%。较低水平的核心谐振模式表明RFP发电机活动较少，与较高的θ趋势一致。虽然等离子体电流增加，放电电阻降低，没有明显的改善是显而易见的RFP特性，这可能是由于缺乏足够的平衡控制与增加等离子体电流。本文的结果表明，RHF可以用来控制有阻壁的撕裂模。少

项目成果

S. Maki, S. Masamune et al: "Diffusion Process of Fast Electrons in a Reversed Field Pinch"J. Phys. Soc. Jpn.. 71,7. 1680-1683 (2002)

S. Maki、S. Masamune 等人：“反向场收缩中快电子的扩散过程”J。

政宗貞男(分担執筆): "電気学会技術報告「プラズマイオン注入法とその応用」"電気学会. 60 (2001)

Sadao Masamune（合著者）：“IEEJ技术报告“等离子体离子注入方法及其应用””IEEJ 60（2001）。

S. Maki, S. Masamune et al: "Formation Mechanism of Reversed Toroidal Current in an RFP"J. Phys. Soc. Jpn.. 70,2. 415-420 (2001)

S. Maki, S. Masamune 等：“RFP 中反向环形电流的形成机制”J。

S. Masamune, M. Iida et al.: "Control of RFP Dynamics with Rotating Helical Fields"Proc. 18th IAEA Fusion Energy Conference. IAEA-F1-CN-77/EXP3/11. (2001)

S. Masamune、M. Iida 等人：“旋转螺旋场的 RFP 动力学控制”Proc。

S.Masamune, M.Iida: "Control of RFP dynamics using external helical fields"Mem.Fac.Eng.and Design, Kyoto Institute of Technology. Vol.50. 37-54 (2002)

S.Masamune、M.Iida：“使用外部螺旋场控制 RFP 动力学”Mem.Fac.Eng.and Design，京都工业大学。