Speaker
Dr
Steven Sabbagh
(Columbia University)
Description
Neoclassical Toroidal Viscosity (NTV) due to non-ambipolar particle diffusion occurs in tokamaks due to low magnitude (dB/B0 ~10-3) three-dimensional (3D) applied magnetic fields, used for positive purposes including alteration of the plasma rotation profile, Vt, to stabilize MHD modes and for ELM suppression. As ITER and future devices will use 3D fields for these purposes, it is important to accurately quantify NTV effects over key plasma and 3D field variations. The present work quantitatively analyzes and compares a formidable combination of NTV databases from two tokamak devices of significantly different aspect ratio. These data allows testing of NTV theory over a broad range of plasma variables including aspect ratio, q95, collisionality, gyroradius, plasma rotation speed and profile, as well as 3D field strength and spectrum. Isolation of the NTV torque profile, TNTV, is accomplished by applying the 3D field faster than the plasma momentum diffusion time. A dedicated international experiment was run in late 2015 to measure the NTV profile this way for the first time in the KSTAR superconducting tokamak at medium aspect ratio (A = 3.5). Over 360 variations of the parameters mentioned above were produced. These results are compared to new analysis of complementary experimental results from the extensive NTV database of low A = 1.3 NSTX plasmas. The NSTX experiments yield unique information in plasmas with computed displacements smaller than the ion banana width, showing that finite-orbit effects will average TNTV over such spatial scales. In KSTAR, six different 3D field spectra were run, including dominantly n = 2, n = 1 field pitch-aligned, n = 1 field pitch non-aligned configurations, and their superposition. As expected by theory, the measured rotation profile change due to the 3D field, delVt, does not change sign, and is close to zero near the plasma boundary. All cases show broader delVt than found in NSTX. The change to the relative pitch alignment of the applied 3D field yielded a clear and unexpected result: the non-pitch-aligned field configuration produced a stronger change to the Vt profile than the pitch-aligned case. The delVt is global and non-resonant, with no strong indication of localized resonant effects, similar to NSTX results in different field configurations. Supported by US DOE contracts DE-FG02-99ER54524 and DE-AC02-09CH11466.
| Country or International Organization | USA |
|---|---|
| Paper Number | EX/P4-33 |
Primary author
Dr
Steven Sabbagh
(Columbia University)
Co-authors
Dr
Benoit LeBlanc
(PPPL)
Dr
Jayhyun Kim
(National Fusion Research Institute)
Dr
Jinseok Ko
(National Fusion Research Institute)
Dr
John Berkery
(Columbia University)
Dr
Jongha Lee
(National Fusion Research Institude)
Dr
K. C. Shaing
(Engineering Physics Department, University of Wisconsin)
Dr
Ron Bell
(PPPL)
Dr
Sang-hee Hahn
(National Fusion Research Institute)
Dr
Stefan Gerhardt
(Princeton Plasma Physics Laboratory)
Dr
Won Ha Ko
(Korea, Republic of)
Dr
Yongkyoon In
(National Fusion Research Institute)
Dr
Young-Seok Park
(Columbia University)
Dr
YoungMu Jeon
(National Fusion Research Institute)
Dr
Youwen Sun
(Institute of Plasma Physics, Chinese Academy of Scienses)
