Spontaneous transition of the plasma confinement mode was observed in thehelical-axis heliotron device 'Heliotron J' for three different plasma heating schemes, i.e.ECH-only, NBI-only and the combination of EC...Spontaneous transition of the plasma confinement mode was observed in thehelical-axis heliotron device 'Heliotron J' for three different plasma heating schemes, i.e.ECH-only, NBI-only and the combination of ECH and NBI. The transition seems to occur above a certaincritical density. In addition to the confinement transition, a spontaneous shift of the hittingposition of the divertor plasma flux on the wall was observed. This shift could be related with thechange of the edge field topology caused by non-inductive toroidal currents.展开更多
The efficiency of energetic ion confinement is reduced in a tokamak plasma by the non-axisymmetric field, namely the ripple field. The ripple field is produced by a finite number of toroidal field coils. It is affecte...The efficiency of energetic ion confinement is reduced in a tokamak plasma by the non-axisymmetric field, namely the ripple field. The ripple field is produced by a finite number of toroidal field coils. It is affected by the non-axisymmetric finite beta effect. The three-dimensional MHD equilibrium calculation code VMEC is used to analyze the non-axisymmetric finite beta effect in a ripple tokamak. In the VMEC code, the flux coordinates are used, so the calculation region is limited to the area of plasma. To calculate the orbit outside the plasma, we develop a field calculation code, which is based on the Biot-Savart law. The details of the method and results are described in this paper.展开更多
A fast video camera is verified to be a powerful t0ol for observation of filaments/blobs near the last closed flux surface （LCFS）. In order to extract the fluctuation component from the raw data of the fast camera, ...A fast video camera is verified to be a powerful t0ol for observation of filaments/blobs near the last closed flux surface （LCFS）. In order to extract the fluctuation component from the raw data of the fast camera, a pre-processing technique, sliding time window averaging subtraction （STWAS） has been developed to remove the background of slowly varying emission from the bulk plasma. By using this pre-processing technique, the fast camera data are analyzed. A method to identify the filaments in the pre-processed image is also discussed.展开更多
基金The project partially supported by the Grant-in-Aid for Science Research of MEXT in Japan and by the Collaboration Program of the Laboratory for Complex Energy ProcessesIAEKyoto University
文摘Spontaneous transition of the plasma confinement mode was observed in thehelical-axis heliotron device 'Heliotron J' for three different plasma heating schemes, i.e.ECH-only, NBI-only and the combination of ECH and NBI. The transition seems to occur above a certaincritical density. In addition to the confinement transition, a spontaneous shift of the hittingposition of the divertor plasma flux on the wall was observed. This shift could be related with thechange of the edge field topology caused by non-inductive toroidal currents.
基金performed with the support and backing of the NIFS Collaborative Research Program
文摘The efficiency of energetic ion confinement is reduced in a tokamak plasma by the non-axisymmetric field, namely the ripple field. The ripple field is produced by a finite number of toroidal field coils. It is affected by the non-axisymmetric finite beta effect. The three-dimensional MHD equilibrium calculation code VMEC is used to analyze the non-axisymmetric finite beta effect in a ripple tokamak. In the VMEC code, the flux coordinates are used, so the calculation region is limited to the area of plasma. To calculate the orbit outside the plasma, we develop a field calculation code, which is based on the Biot-Savart law. The details of the method and results are described in this paper.
文摘A fast video camera is verified to be a powerful t0ol for observation of filaments/blobs near the last closed flux surface （LCFS）. In order to extract the fluctuation component from the raw data of the fast camera, a pre-processing technique, sliding time window averaging subtraction （STWAS） has been developed to remove the background of slowly varying emission from the bulk plasma. By using this pre-processing technique, the fast camera data are analyzed. A method to identify the filaments in the pre-processed image is also discussed.
