Confinement and stability of VH-mode discharges in the DIII-D tokamak
A regime of very high confinement (VH-mode) has been observed in neutral beam-heated deuterium discharges in the DIII-D tokamak with thermal energy confinement times up to [approx]3.6 times that predicted by the ITER-89P L-mode scaling and 2 times that predicted by ELM-free H-mode thermal confinement scalings. This high confinement has led to increased plasma performance, n[sub D] (0)T[sub i](0)[tau][sub E] = 2 [times] 10[sup 20] m[sup [minus]3] keV sec with I[sub p] = 1.6 MA, B[sub T] = 2.1 T, Z[sub eff] [le] 2. Detailed transport analysis shows a correspondence between the large decrease in thermal diffusivity in the region 0.75 [le] [rho] [le] 0.9 and the development of a strong shear in the radial electric field in the same region. This suggests that stabilization of turbulence by sheared E [times] B flow is responsible for the improved confinement in VH-mode. A substantial fraction of the edge plasma entering the second regime of stability may also contribute to the increase in confinement. The duration of the VH-mode phase has been lengthened by feedback controlling the input power to limit plasma beta.
- Research Organization:
- General Atomics, San Diego, CA (United States)
- Sponsoring Organization:
- DOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC03-89ER51114; AC05-84OR21400; W-7405-ENG-48
- OSTI ID:
- 6701568
- Report Number(s):
- GA-A-21092; CONF-9209290--7; ON: DE93008988
- Country of Publication:
- United States
- Language:
- English
Similar Records
Investigations of VH-mode in DIII-D and JET
Recent VH-mode results on DIII-D
Related Subjects
700310* -- Plasma Confinement-- (1992-)
CLOSED PLASMA DEVICES
CONFINEMENT
CONFINEMENT TIME
DIVERTORS
DOUBLET-3 DEVICE
EDGE LOCALIZED MODES
H-MODE PLASMA CONFINEMENT
INSTABILITY
PLASMA CONFINEMENT
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
STABILITY
THERMONUCLEAR DEVICES
TOKAMAK DEVICES