1. Stereoscopic Pellet Imaging
Motivation
Pellet injection during previous campaigns has revealed the presence of striated structure during the evolution of the pellet ablation. Furthermore, this striated structure has qualitatively different behavior during L-Mode and H-Mode operation. L-Mode shots have striations that move in both the positive and negative ion diamagnetic velocity. Striations in H-Mode move purely in the negative ion diamagnetic drift direction.
Shot

2. Stereoscopic Pellet Imaging
Mid Plane
42.4 inches
9.56”
Camera Views
Pellet Trajectory
Idea
Using the stereoscopic imaging system recently developed for C-Mod, we would like to image a large number of pellet shots during different modes of plasma operation to gather three dimensional data on the ablation process and evolution of the striations, and determine what effect the background plasma conditions have on the striations. This data will be compared with poloidal flows determined by gyro kinetic simulations to determine if any correlation exists.
9.56”

3. Stereoscopic Pellet Imaging
Expected Results
Observation of growth of Raleigh-Taylor instability that drives striation formation
Stereoscopic imaging should be able to discern whether the cloud is rotating prior to the striation formation, and determine the rotation rate.
Parks Predicts that the rotation rate, and instability frequency should go like:
Determine whether striation formation has a temporal or spatial scaling
The Parks instability theory predicts that the frequency of striation emission should be independent of the position of the pellet.
If the striation motion is a function of the local poloidal flows in the plasma then distribution of the striation velocities will be correlated with the structure of the poloidal flows.
Observe scaling of poloidal flows.
Theory and Gyro-kinetic simulations indicate that the magnitude of poloidal flows should go like