Speaker
Dr
Sang-hee Hahn
(Korea, Republic of)
Description
The realization of a wide variety of plasma shapes with varying plasma current density profiles places challenging demands on the vertical control system. In particular the bootstrap current scales quadratically with elongation at fixed normalized β_N = β_TaB_T/I_p where I_p is the plasma current, B_T is the toroidal field, and β_T = P/(B_T^2/2μ_0) and P is the volume averaged plasma pressure. The plasma elongation is controlled by the action of coils that generally act to produce a field shape with an index of curvature that is closer to vertical instability as the elongation is increased. In devices such as KSTAR, EAST and ITER, the superconducting coils are separated from the plasma by conducting structures that limit the plasma response time to changes in the coil currents. Fast control of the plasma vertical motion, essential for stable operation at high elongation and disruption avoidance, can be accomplished with coils internal to the vacuum vessel in these devices. Shape control systems in tokamaks are generally based upon equilibrium analysis that does not lend itself well to fast control and in particular cannot produce a reliable time derivative of the vertical position. The simple analysis of standard integrated magnetic signals to produce a vertical position (z) signal can be incapable of yielding a derivative term (dz/dt) that has sufficient signal-to-noise ratio to be adequate for control. Employing the difference of up-down symmetric un-integrated voltage loops can provide better signal to noise for dz/dt. The results of using the voltage loop-based sensors in the KSTAR and EAST fast vertical control system in their upcoming runs will be presented. In particular, the efficacy of employing these diagnostics in the fast control loop to achieve greater plasma elongation over a range of plasma internal inductance will be examined.
This research was supported by U.S. DOE contract DE-AC02-09CH11466
| Country or International Organisation | USA |
|---|---|
| Paper Number | PPC/P8-17 |
Primary author
Dr
Dennis Mueller
(Princeton Plasma Physics Laboratory)
Co-authors
Dr
Bingjia Xiao
(Institute of Plasma Sciences, Chinese Academy of Sciences)
Dr
David Gates
(PPPL)
Dr
Egemen Kolemen
(PPPL)
Dr
Jonathan Menard
(Princeton Plasma Physics Laboratory)
Dr
Nichloas Eidietis
(General Atomics)
Dr
Sang-hee Hahn
(Korea, Republic of)
Dr
Si-woo Yoon
(National Fusion Research Institute)
Dr
Stefan Gerhardt
(Princeton Plasma Physics Laboratory)
Dr
Steven Sabbagh
(Columbia University)
Dr
Young-Seok Park
(Columbia University)
