Nondimensional transport scaling in the Tokamak Fusion Test Reactor: Is tokamak transport Bohm or gyro-Bohm?

Journal Article · Fri Jan 01 00:00:00 EST 1993 · Physics of Fluids. B, Plasma Physics

DOI:https://doi.org/10.1063/1.860534· OSTI ID:6989883

Perkins, F. W.; Barnes, Cris W.; Johnson, D. W.; Scott, S. D.; Zarnstorff, M. C.; Bell, M. G.; Bell, R. E.; Bush, C. E.; Grek, B.; Hill, K. W.; Mansfield, D. K.; Park, H.; Ramsey, A. T.; Schivell, J.; Stratton, B. C.; Synakowski, E.

General plasma physics principles state that power flow Q(r) through a magnetic surface in a tokamak should scale as Q(r) = {32π² Rr³T_e² c n_ea/[eB (a ²₋r²)²]} F(ρ*,β,ν*,r/a,q,s,r/R,...) where the arguments of F are local, nondimensional plasma parameters and nondimensional gradients. This paper reports an experimental determination of how F varies with normalized gyroradius ρ*≡(2T _eMi ]) ^1/2 c/eBa and collisionality ν*≡(R/r)^3/2 qRν _e(m_e / 2T_e)^1/2 for discharges prepared so that other nondimensional parameters remain close to constant. Tokamak Fusion Test Reactor (TFTR) [D. M. Meade] [ital et al]., in [ital Plasma Physics and Controlled Nuclear Fusion Research], 1990, Proceedings of the 13th International Conference, Washington (International Atomic Energy Agency, Vienna, 1991), [Vol. 1, p. 9] L-mode data show F to be independent of ρ* and numerically small, corresponding to Bohm scaling with a small multiplicative constant. By contrast, most theories predict gyro-Bohm scaling: F∝ρ*. Bohm scaling implies that the largest scale size for microinstability turbulence depends on machine size. Analysis of a collisionality scan finds Bohm-normalized power flow to be independent of collisionality. Implications for future theory, experiment, and reactor extrapolations are discussed.

• Sponsoring Organization: USDOE
• DOE Contract Number: AC02-76CH03073
• OSTI ID: 6989883
• Journal Information: Physics of Fluids. B, Plasma Physics, Vol. 5, Issue 2; ISSN 0899-8221: PFBPEI
• Publisher: American Institute of Physics
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
TFTR TOKAMAK
PLASMA MICROINSTABILITIES
SCALING LAWS
MAGNETIC SURFACES
PLASMA CONFINEMENT
THERMONUCLEAR REACTORS
TRANSPORT THEORY
TURBULENCE
CLOSED PLASMA DEVICES
CONFINEMENT
INSTABILITY
MAGNETIC FIELD CONFIGURATIONS
PLASMA INSTABILITY
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
700310* - Plasma Confinement- (1992-)
700340 - Plasma Waves
Oscillations
& Instabilities- (1992-)