Bw. Rice et al., THE FORMATION AND EVOLUTION OF NEGATIVE CENTRAL MAGNETIC SHEAR CURRENT PROFILES ON DIII-D, Plasma physics and controlled fusion, 38(6), 1996, pp. 869-881
Using the combination of early neutral beam injection, ramping of the
plasma current, low electron density and controlled L-H transitions, r
obust discharges with negative central magnetic shear are reproducibly
obtained on the DIII-D tokamak. The effects of these factors on the f
ormation and evolution of the q profile during the initial phase of th
ese discharges are documented. Details of the evolution of the inverte
d q profile are obtained from measurements of the internal field pitch
using a 16-channel motional Stark effect (MSE) system. Time-dependent
MSE data are used to directly construct the profile of the toroidal e
lectric field and allow a straightforward calculation of the non-induc
tive current density profile.