ROLE OF CORE TOROIDAL ROTATION ON THE H-MODE RADIAL ELECTRIC-FIELD SHEAR, TURBULENCE, AND CONFINEMENT AS STUDIED BY MAGNETIC BRAKING IN THEDIII-D TOKAMAK

''Magnetic braking'' of the plasma toroidal rotation in the high confi nement H mode by applied resonant, low m,n=1 static error fields is us ed in DIII-D [Nucl. Fusion 31, 875 (1991)] as an independent control t o evaluate the E(r)XB stabilization of microturbulence in the plasma c ore. In the core (rho less than or similar to 0.9) of a tokamak, the r adial electric field and its shear are dominated by toroidal rotation. The fundamental quantity for shear stabilization of microturbulence i s shear in the velocity of the fluctuations v(perpendicular to) approx imate to E(r)XB/B.B which in the core is upsilon(perpendicular to) app roximate to upsilon(phi)B(theta)/B-phi. With magnetic braking greatly decreasing the toroidal rotation and thus reducing the core radial ele ctric field and shear, far infrared (FIR) measurements of density micr oturbulence show downshifting in frequency near rho less than or simil ar to 0.8 as a result of the reduced Doppler shift (omega approximate to k(theta)E(r)/B-phi) and a factor of 2 increase in the turbulence le vel (n/n)(2) in the period between edge localized modes (ELMs). There is also a large reduction in turbulence at an ELM which tends to compe nsate for the increase in turbulence with reduced radial electric fiel d shear between ELMs. No significant change is found in H-mode plasma energy, confinement time, internal inductance l(i), density profile, T -e profile, or T-i profile. Good H-mode confinement is maintained by t he edge (rho greater than or similar to 0.95) transport barrier where the reversed edge E(r) and high edge E(r) shear remain unchanged.