Stability boundaries and development of the ITER baseline scenario
Abstract
Plasmas stable to m/n=2/1 tearing modes (TMs), in the ITER baseline scenario (IBS) with ITER similar Ip/aBT, have been demonstrated in DIII-D, evolving to stationary conditions. Previous studies showed the possibility that long pulse IBS plasmas might be susceptible to TMs. However within a defined stability boundary, most of these longer duration discharges have achieved stationary conditions (δτduration<=7.5 s and <=11τR) with high Co-beam torque and without the need for ECCD. To mitigate 2/1 TMs at reduced torque, broad ECCD deposition was found to be most effective when positioned near the q=3/2 flux surface, although a subset of low torque pulses were also obtained without ECCD. The DIII D internal coils (I coils) were used to achieve ELM suppression in IBS plasmas with ECCD at q95=3.15 for durations up to 1 s with only the upper row of I coils, providing a broad n=3 spectrum. Conditions stable to n=1 tearing modes in IBS discharges and the effect of Zeff, density, and other parameters are discussed.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- October 2012
- Bibcode:
- 2012APS..DPPUO7009J