NONDIMENSIONAL TRANSPORT SCALING IN THE TOKAMAK FUSION TEST REACTOR - IS TOKAMAK TRANSPORT BOHM OR GYRO-BOHM

General plasma physics principles state that power flow Q(r) through a magnetic surface in a tokamak should scale as Q(r) = {32pi2Rr3T(e)2c n(e)a/[eB(a2 - r2)2]} F(rho*,beta,nu*,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 rho* = (2T(e)M(i)1/2c/eBa and collisionality nu* = (R/r)3/2qRnu(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 et al., in 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 rho* and numerically small, corresponding to Bohm scaling with a small multiplicative constant. By contrast, most theories predict gyro-Bohm scaling: F is-proportional-to rho*. 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.