A Comparison of Plasma Performance Between Single-Null and Double-Null Configurations During Elming H-Mode
Tokamak plasma performance generally improves with increased shaping of the plasma cross section, such as higher elongation and higher triangularity. The stronger shaping, especially higher triangularity, leads to changes in the magnetic topology of the divertor. Because there are engineering and divertor physics issues associated with changes in the details of the divertor flux geometry, especially as the configuration transitions from a single-null (SN) divertor to a marginally balanced double-null (DN) divertor, we have undertaken a systematic evaluation of the plasma characteristics as the magnetic geometry is varied, particularly with respect to (1) energy confinement, (2) the response of the plasma to deuterium gas fueling, (3) the operational density range for the ELMing H-mode, and (4) heat flux sharing by the diverters. To quantify the degree of divertor imbalance (or equivalently, to what degree the shape is double-null or single-null), we define a parameter DRSEP. DRSEP is taken as the radial distance between the upper divertor separatrix and the lower divertor separatrix, as determined at the outboard midplane. For example, if DRSEP=O, the configuration is a magnetically balanced DN; if DRSEP = +1.0 cm, the divertor configuration is biased toward the upper divertor. Three examples are shown in Fig. 1. In the following discussions, VB drift is directed toward the lower divertor.
- Research Organization:
- General Atomics, San Diego, CA (US)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC03-99ER54463; W-7405-ENG-48; AC04-94AL85000; FG03-86ER53225
- OSTI ID:
- 766942
- Report Number(s):
- GA-A23155; TRN: US0110519
- Resource Relation:
- Conference: 26th European Physical Society Conference on Controlled Fusion and Plasma Physics, Maastricht (NL), 06/14/1999--06/18/1999; Other Information: PBD: 1 Jul 1999
- Country of Publication:
- United States
- Language:
- English
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