TRANSFORMERLESS OPERATION OF DIII-D WITH HIGH BOOTSTRAP FRACTION
OAK-B135 The authors have initiated an experimental program to address some of the questions associated with operation of a tokamak with high bootstrap current fraction under high performance conditions, without assistance from a transformer. In these discharges they have maintained stationary (or slowly improving) conditions for > 2.2 s at {beta}{sub N} {approx} {beta}{sub p} {approx} 2.8. Significant current overdrive, with dI/dt > 50 kA/s and zero or negative voltage, is sustained for over 0.7 s. The overdrive condition is usually ended with the appearance of MHD activity, which alters the profiles and reduces the bootstrap current. Characteristically these plasmas have 65%-80% bootstrap current, 25%-30% NBCD, and 5%-10% ECCD. Fully noninductive operation is essential for steady-state tokamaks. For efficient operation, the bootstrap current fraction must be close to 100%, allowing for a small additional ({approx} 10%) external current drive capability to be used for control. In such plasmas the current and pressure profiles are rightly coupled because J(r) is entirely determined by p(r) (or more accurately by the kinetic profiles). The pressure gradient in turn is determined by transport coefficients which depend on the poloidal field profile.
- Research Organization:
- General Atomics, San Diego, CA (United States)
- Sponsoring Organization:
- (US)
- DOE Contract Number:
- AC03-99ER54463
- OSTI ID:
- 821384
- Resource Relation:
- Conference: 30TH European Physical Society Conference on Controlled fusion and Plasma Physics, St. Petersburg (RU), 07/07/2003--07/11/2003; Other Information: PBD: 1 Jul 2003
- Country of Publication:
- United States
- Language:
- English
Similar Records
Progress toward fully noninductive, high beta conditions in DIII-D
Noninductive Current Drive and Steady-State Operation in JT-60U