Our experimental design starts with an adaptation of shot 187219 with higher upper triangularity, reduced pressure, and increased Bt and Ip, maintaining the same ITER-similar lower-single-null shape. This experiment obtained large type-1 ELMs, which is a primary goal. Here, we propose experiments at low density and high heating power to generate large ELMs, and later scanning towards lower triangularity and higher collisionality to mimic the original target shot (still at higher field). We will require the 150L beam with high voltage operation and short off-phases (notches) for the operation of both diagnostics. Operation at higher magnetic field (2T Bt) is planned to maximize the Stark Splitting of the beam emission which improves the signal-to-noise ratio of the Jr measurements.
To study the ELM and turbulence characteristics, we will adjust collisionality, torque, and triangularity. These modifications will have a direct impact on the pedestal height and dynamics, turbulence drive, bootstrap current formation, and the rotation stabilization of the pedestal’s MHD and turbulent characteristics.
The rough shot design involves generating a stable version of shot 187219 (with the previously described modifications) and doing a minor current sweep to calibrate. Next, we will attempt a higher-power H-mode, during which co-current beams are replace by counter current beams halfway through the shot to obtain a scan in torque while keeping the total heating power constant. This initial shot will be repeated 1-2 times to obtain a spatial scan via the BES motorized fiber array. A full-field Bt=2.15T may be attempted next. Then, a series of shots with reducing triangularity will be performed, still with the beam-swap. Finally, we will reset to high-triangularity and increase density via puffing until we reach an analog of shot 196494 (but in Deuterium, with higher field/current). If time permits, we will finally reduce the field and current to attempt to mimic 196494 and obtain an accurate isotope comparison.