High beta, Long Pulse, Bootstrap Sustained Scenarios on the National Spherical Torus Experiment (NSTX)

National Spherical Torus Experiment (Project) ; Gates, D. A.

Princeton University. Plasma Physics Laboratory.

关键词: Bootstrap Current;    70 Plasma Physics And Fusion Technology;    Spherical Torus;    Current Density;    Elongation;   

DOI  :  10.2172/812084
RP-ID  :  PPPL-3791
RP-ID  :  AC02-76CH03073
RP-ID  :  812084

美国|英语

来源: UNT Digital Library

【 摘 要 】

Long-pulse, high-beta scenarios have been established on the National Spherical Torus Experiment (NSTX). Beta(sub)t(always equal to 2{mu}(sub)0{center_dot}

/B{sup 2}(sub)t0) {approx} 35% has been achieved during transient discharges. The machine improvements that lead to these results, including error field reduction and high-temperature bakeout of plasma-facing components are described. The highest Beta(sub)t plasmas have high triangularity (delta = 0.8) and elongation (k = 2.0) at low-aspect ratio A always equal to R/a = 1.4. The strong shaping permits large values of normalized current, I(sub)N(always equal to I(sub)p /(aB(sub)t0)) approximately equal to 6 while maintaining moderate values of q(sub)95 = 4. Long-pulse discharges up to 1 sec in duration have been achieved with substantial bootstrap current. The total noninductive current drive can be as high as 60%, comprised of 50% bootstrap current and {approx}10% neutral-beam current drive. The confinement enhancement factor H89P is in excess of 2.7. Beta(sub)N * H(sub)89P approximately or greater than 15 has been maintained for 8 * tau(sub)E {approx} 1.6 * tau(sub)CR, where tau(sub)CR is the relaxation time of the first radial moment of the toroidal current density. The ion temperature for these plasmas is significantly higher than that predicted by neoclassical theory.