Progress towards high performance, steady-state Spherical Torus
Abstract
The Spherical Torus is exploring the benefits of modifying the field line structure from that in more moderate aspect ratio devices. For an ST-based Component Test Facility and, ultimately a Demo device, it is essential to develop high performance, steady-state operational scenarios. The scientific issues are energy confinement, MHD stability at high beta, non-inductive sustainment, power and particle handling and solenoid-free start-up. NSTX has demonstrated CTF-relevant discharges with 60% non-inductively driven current sustained over a resistive skin-time, and a product β_NH_89P approaching 15 at 0.8 MA plasma current. At 1.2 MA, the plasma βT has reached 35%. In future, NSTX will be exploring advanced regimes with 100% non-inductively driven current, βT up to 40% and βN up to 8 which are sustained much longer than the skin-time. Modeling shows that this can be facilitated by some device improvements, including increasing the plasma elongation at high triangularity, active stabilization of resistive wall modes power and particle control using advanced walls and off-axis current drive using EBW. In addition to coaxial helicity injection, solenoid-free start-up concepts utilizing external poloidal field coils are being pursued on NSTX.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- October 2003
- Bibcode:
- 2003APS..DPPKO1001O