Figure 4

(a) Flux surface at the pellet injection toroidal section (#11.5) and representative magnetic field lines observed from the camera on the 3D model drawn by “Blender”. (b) Superimposed image of fluctuation structure and typical magnetic field lines. Different magnetic field lines are stacked with different tilt angles in the depth direction of the camera’s line of sight. (c) A schematic of the analysis procedure for localizing fluctuation. (d) A typical distribution of scoring parameter s, projected on the R-Z plane from x–y coordinates, at the toroidal section of the pellet injection port with a 3 mm spatial resolution. Only the points with s > 0.5 are shown as color here. (e) Time evolution of parameter s for a single, identical fluctuation. The color of points represents the s value, as well as (d). The circles indicate the ablation cloud of the pellet. While the fluctuation propagates around the pellet, the pellet itself does not move so much compared with the motion of the fluctuation structure. Note that the field line location where the fluctuation exists can be projected on the poloidal cross-section of the pellet injection port, as shown in (c). The detail of the three-dimensional motion of fluctuation is discussed in Figs. 5 and 6.