Impact of EC location and timing on the stability and performance of the zero torque ITER Baseline Scenario in DIII-D
Abstract
Scans of EC deposition at zero input torque in recent ITER Baseline Scenario (IBS) Demonstration discharges show that power deposition in the region of the q =2 surface is prone to causing (not suppressing) 2/1 modes, due to its impact on the local Teped. The maximum stable Teped is inversely proportional to li, which points to a first order dependence of the stability on the global current profile (J) shape. The local minimum in J near q =2 is higher later in the shot, when li is lower, and the equilibrium can sustain a higher Teped without crossing the stability boundary. Local Te impacts both the bootstrap current and the resistivity, therefore both the outer and inner layer physics, affecting the Δ' and the Δ' critical for instability. An in-shot dynamic scan of EC deposition from core to edge decreases H98y2 by 17% and τE by 30%, due to loss of heating efficiency. This calls into question the compatibility of direct EC stabilization with achieving ITER's performance goals. 0-D simulations show that the zero torque IBS shots with core ECH project to the ITER goals (Q =10, Pfus = 550 MW, with heating power Pheat = 70 MW, compatible with the ITER hardware), and indicate the trade-offs between density, field, pressure and gain.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- 2019
- Bibcode:
- 2019APS..DPPJO5003T