Showing papers by "Hiroaki Tsutsui published in 2021"
TL;DR: In this paper, a ray-tracing technique was used to overcome the reflection effect in a small tokamak device PHiX using Raysect and CHERAB python libraries.
Abstract: In a small tokamak, the visible light emission is observed and used to investigate plasmas’ behavior with a fast visible camera. However, the reflected light causes a systemic error in measuring visible light emitted from the plasma. In this paper, we managed to overcome the reflection effect with the ray-tracing technique which is utilized in a synthetic diagnostic platform of the small tokamak device PHiX at Tokyo Institute of Technology using Raysect and CHERAB python libraries. We successfully evaluated the amount of reflected light and obtained tomographic reconstruction images from simulated and experimental data with the TikhonovPhillips regularization and the L-curve method to choose an optimal regularization parameter. We also proposed to project the contour of a reconstruction image onto a camera image to validate tomography results.
2 citations
TL;DR: In this article, saddle coils are proposed as coils with a stabilizing effect of a vertical plasma position, which comes from an average magnetic field along a magnetic field line, and experiments to stabilize the vertical position of the plasma are carried out in a small tokamak device.
Abstract: Saddle coils (SCs) are proposed as coils with a stabilizing effect of a vertical plasma position. This effect comes from an average magnetic field along a magnetic field line. Magnetic field line tracing was performed to investigate the structure and the quantitative values of the averaged magnetic field generated by SCs and toroidal magnetic field coils (TFCs). Experiments to stabilize the vertical position of the plasma were also carried out in a small tokamak device, PHiX. It was experimentally demonstrated that the averaged magnetic field generated with SCs and TFCs could stabilize the vertically unstable plasmas. In addition, three-dimensional equilibrium calculation using VMEC suggested that the plasmas were vertically elongated on the toroidal average when the vertical positions were stabilized by SCs. From the above results, it was shown that the non-axisymmetric magnetic fields generated by SCs could realize the plasmas with stable vertical position and an elongated cross-section.
1 citations