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Non-monotonic radial structures of fluctuating temperatures and densities associated with fishbone activities in KSTAR

Authors :
Wonjun Lee
Jaewook Kim
Semin Joung
G. J. Choi
J. Kim
M. Woo
T. Rhee
K. D. Lee
J. G. Bak
J. S. Kang
Y.-C. Ghim
Source :
Physics of Plasmas. 30:022502
Publication Year :
2023
Publisher :
AIP Publishing, 2023.

Abstract

General characteristics of a fishbone mode in KSTAR are investigated. Fishbone activities are observed with a Mirnov coil, an electron cyclotron emission radiometer (from the core to the edge of plasmas) and an beam emission spectroscopy system (core or edge plasmas) which are measuring fluctuations of poloidal magnetic fields, electron temperatures, and densities, respectively. Temporal evolutions of these fluctuations are similar to the observations from other tokamaks. An interesting and notable feature found in KSTAR fishbone modes is that radial coherence structures of electron temperature and density with respect to magnetic fluctuations are non-monotonic that they have a local minimum at [Formula: see text] and a maximum at [Formula: see text] in addition to the usual global peak near the q = 1 surface, where r/ a is the normalized minor radius and q is the safety factor. Furthermore, the associated temporal evolution of the electron temperatures in slow-time scale, i.e., less than 1 kHz, with the fishbone activities show that there exist a drop in temperature or increase in temperature depending on inside or outside the q = 1 surface, respectively, from the core to the edge plasmas except that there are almost no temperature changes in the intermediate region which seems to be correlated with the non-monotonic coherence profile. Such a non-monotonic structure and the slow temporal evolution of temperatures are explained with barely trapped resonating fast ions with the banana orbit widths of the order of the minor radius, so that they transit the core and the edge regions simultaneously without trespassing the mid-plane intermediate region.

Subjects

Subjects :
Condensed Matter Physics

Details

ISSN :
10897674 and 1070664X
Volume :
30
Database :
OpenAIRE
Journal :
Physics of Plasmas
Accession number :
edsair.doi...........9fdce8503a2296894e56add6f8fe4b6e
Full Text :
https://doi.org/10.1063/5.0134354