CONTROL OF RFP DYNAMICS WITH HELICAL FIELDS

使用螺旋场控制 RFP 动力学

• 批准号: 10680459
• 负责人: MASAMUNE Sadao
• 金额: $ 1.79万
• 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: 1998
• 资助国家: 日本
• 起止时间: 1998 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10680459/
• 关键词: reversed field pinch; tearing modes; external kink modes; resistive wall modes; rotating helical field; plasma rotation; mode rotation; 抵抗性シェル不安定性; ヘリカル磁場; プラズマフロー(流れ); 磁気島

Control of the dynamics of reversed field pinches (RFPs) is one of the urgent issues for the improvements of RFP experiments. In RFPs with a resistive wall, both resistive and ideal modes can become unstable in the time scale of field penetration time of the wall. The growth of core resonant tearing modes would result in highly stochastic magnetic field, leading to significant degradation. Theories have predicted that the growth of tearing modes or their saturation amplitudes can be reduced by toroidal rotation of the plasma.In this research project, first attempts have been made to drive magnetic fluctuation mode and/or plasma rotation using rotating M/N=1/8 resonant helical field, where M (N) is the poloidal (toroidal) mode number of the applied field.In standard STE-2 (R/α=0.4m/0.1m) discharges with only the vacuum vessel whose time constant TィイD2wィエD2?0.15 ms, the plasma current IィイD2pィエD2 is around 60 kA with discharge duration TィイD2dィエD2 around 0.7 ms. The discharge resistance is … More about 50% higher than with a close-fitting copper shell of 2 ms time constant, and TィイD2dィエD2 shorter by about 30-40%. After attaining the RFP configuration, the magnetic fluctuations grow whose dominant toroidal mode number n appears to be 8, maintaining the structure for the rest of discharge. The m/n=1/8 mode is the tearing mode whose resonant surface is located at r/α〜0.4. The toroidally rotating helical field (RHF) was applied with two pairs of helical coils together with alternating current sources with a phase difference of π/2. The frequency was 10-20kHz, and the toroidal phase velocity of the rotating field was 4-7 km/s. Since we have used LC damping oscillation to obtain the alternating current in the present research project, effective duration of RHF is restricted to not longer than 0.3-0.4ms. The amplitude of the RHF |BィイD2rαィエD2| is defined as an average peak value from the second to the fifth peak values measured inside the vessel. The RHF was applied at t=0.3 ms, with f〜15 kHz and relative amplitude |BィイD2rαィエD2|/BィイD2θαィエD2 of 0.5%, where BィイD2θαィエD2 is the edge poloidal field. The amplitude of magnetic fluctuations is reduced, and, furthermore, the fluctuations rotate toroidally in the direction of the applied RHF for the amplitude level higher than 0.4%. The phase velocity of magnetic fluctuations is slightly lower than that of the RHF. The time evolution of the n=7, 8, 9 mode amplitudes with the RHF of relative amplitude of 0.5% shows that the growth of these mode amplitudes is suppressed transiently for 0.2-0.3 ms, and, moreover, the amplitudes are reduced for the rest of the discharge.It is the first demonstration in the RFP of the direct interaction between the rotating M=1 helical field with inherent m=1 core resonant tearing modes. Less

反向场箍缩（RFP）的动力学控制是RFP实验改进中亟待解决的问题之一。在具有电阻壁的RFP中，电阻模式和理想模式在壁的场穿透时间的时间尺度上都可能变得不稳定。纤芯共振撕裂模的增长将导致高度随机的磁场，导致显著的退化。理论预言等离子体的环形旋转可以抑制撕裂模的增长或其饱和振幅，本研究首次尝试用旋转M/N=1/8的共振螺旋场驱动磁涨落模和/或等离子体旋转，在标准STE-2（R/α=0.4m/0.1m）放电中，仅使用时间常数T_（max）= D_（2 w）= D_（2 w）= D_（2 w）的真空室，在真空室中放电时，在真空室中放电的模数为M（N），在真空室中放电的模数为M（N）。0.15 ms时，等离子体电流I D2 p D2约为60 kA，放电持续时间T D2 d D2约为0.7 ms。 ...更多信息 比具有2 ms时间常数的紧密配合的铜壳高约50%，并且T_（max）D2 d_（max）D2短约30- 40%。在获得RFP配置后，磁波动增长，其占主导地位的环形模式数n似乎是8，保持结构的其余放电。m/n=1/8模是撕裂模，其共振面位于r/α = 0.4处。利用两对螺旋线圈和相位差为π/2的交流电源施加环形旋转螺旋场（RHF）。频率为10- 20 kHz，旋转场的环向相速度为4-7 km/s。由于本课题采用LC阻尼振荡获得交流电流，因此RHF的有效持续时间被限制为不超过0.3-0.4ms。RHF的振幅|B β-D 2 r α-β-D 2|将在血管内测量的第二峰值至第五峰值的平均峰值定义为第一峰值。射频频率为t= 0.3ms，频率为15 kHz，相对振幅为10 kHz，|B β-D 2 r α-β-D 2|/B极化D2θα极化D2为0.5%，其中B极化D2θα极化D2为边缘极向场。磁波动的幅度减小，并且，此外，对于高于0.4%的幅度水平，波动在所施加的RHF的方向上环形地旋转。磁涨落的相速度略低于RHF的相速度。在相对振幅为0.5%的RHF下，n=7，8，9模振幅随时间的演化表明，这些模振幅的增长在0.2- 0.3ms内被瞬时抑制，而且，这是RFP中第一次证明旋转M=1螺旋场与固有m=1螺旋场之间的直接相互作用。1芯共振撕裂模。少

项目成果

S. Masamune: "Stability of Resistive Shell Modes in the RFP Surrounded by Helical Current"J. Phys. Soc. Jpn.. 68. 2161-2163 (1999)

S. Masamune：“螺旋电流环绕 RFP 中电阻壳模式的稳定性”J。

S. Masamune: "Control of RFP Dynamics with External Helical Fields"Fusion Energy 1998 (Proc. 17th IAEA Fusion Energy Conf.). 3. 919-922 (1999)

S. Masamune：“利用外部螺旋场控制 RFP 动力学”聚变能源 1998（第 17 届国际原子能机构聚变能源会议）。

S.Masamune: "Stability of Resistive Shell Modes in the RFP Surrounded by Helical Current"J.Phys.Soc.Jpn.. 68(7). 2161-2163 (1999)

S.Masamune：“螺旋电流包围的 RFP 中电阻壳模式的稳定性”J.Phys.Soc.Jpn.. 68(7)。