Session CO3 - NSTX and Other ST.
ORAL session, Monday afternoon, November 15
Room 204/205, SCC
The National Spherical Torus Experiment (NSTX) resumed operation in February 2004 and completed in July a program of experiments which expanded its operating space and contributed to resolving issues both for the design of future ST devices and in toroidal magnetic confinement physics. Improvements in plasma control have led to the achievement of higher plasma elongation, \kappa = 2.6 and normalized current, I_N = I_p/aB_T = 6.9 MA/m \cdot T. By optimizing the current ramp-up, gas puffing and neutral beam power waveforms, reliable early transitions to the H-mode have been obtained, which improved confinement and broadened the pressure profiles, permitting the achievement of very high beta, \beta_T = 34%, determined by EFIT from external magnetic and kinetic profile data and corroborated by analysis with TRANSP. These improvements have led to the achievement of 1MA pulses with 1s duration that were not limited by the available transformer flux. First measurements have also been obtained with the MSE diagnostic. The features of the NSTX operating space and characteristics of the high-\beta plasmas will be discussed. This work supported by DOE Contract Number DE-AC02-76CH03073