Establishment and practical use of the diagnosis technique to identify the non-axisymmetric fusion plasma boundary shape in the peripheral magnetic field region

2014 Fiscal Year Final Research Report

• Project/Area Number: 24561019
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Nuclear fusion studies
• Research Institution: Hokkaido University
• Principal Investigator: ITAGAKI Masafumi 北海道大学, 工学(系)研究科(研究院), 特任教授 (30281786)
• Co-Investigator(Kenkyū-buntansha): MATSUMOTO Yutaka 北海道大学, 大学院工学研究院, 助教 (40360929)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: 核融合プラズマ / 周辺磁場構造 / 最外殻磁気面 / 磁気センサー / コーシー条件面 / 非軸対称 / 渦電流 / 特異値分解

Outline of Final Research Achievements

The Cauchy condition surface (CCS) method, which identifies the plasma boundary shape using external magnetic sensor signals, has been applied not only to axisymmetric tokamaks but also to the LHD, a non-axisymmetric helical device. Using the twisted CCS, the numerical accuracy in the reconstructed field has been improved. In the singular value (SV) decomposition process employed in the CCS method, a gap is found in the SVs. If all the SVs smaller than the gap threshold are eliminated, the required number of sensors can be significantly reduced without losing the solution accuracy.
For some cases in the CCS analyses the effect of eddy current on the vacuum vessel (VV) cannot be neglected. To overcome this difficulty, boundary integrals of the eddy current along the VV are added to the CCS method formulation. The capability of the method is demonstrated for the RELAX device. The above techniques developed in the present series of works are applicable to many fusion devices.

Free Research Field

核融合