Plasma Response to n=3 Magnetic Perturbations in Noninductive Hybrid Plasmas in the DIII-D Tokamak
ORAL
Abstract
3D magnetic perturbations (MPs) are effective in suppressing Type-I and Grassy ELMs in DIII-D noninductive Hybrid plasmas over a wide range of q95 (5.2-7.5) and beam torque (6 -0.2 Nm) with minimal confinement degradation (\beta$_{N}$\approx3.2, H$_{98}$\approx1.2)$. Recent experiments elucidate the role of the plasma response to n= 3 MPs that is responsible for the effectiveness of ELM suppression in this regime. Scans of the n= 3 applied spectrum were performed using the new ASIPP Super Supplies and by comparing the plasma response to even/odd parity and single row I-coil configurations. Even parity is poor at driving plasma response and for ELM suppression, consistent with model predictions. All other coil configurations showed strong amplification by the plasma, $\approx4x$ larger than for the $\beta$_{N}$\approx1.8$ ITER inductive scenario, consistent with predictions from linear MHD modeling. These results reveal the beneficial role of high beta and elevated q$_{95}$ for the suppression of ELMs by MPs in Advanced Tokamak scenarios.
*Work supported under USDOE Agreement DE-AC02-09CH11466, DE-FC02-04ER54698, DE-FG02-08ER54984.
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