Speaker
Jun-Gyo Bak
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1048.pdf
Experimental investigations on plasma current quench during disruptions
in the KSTAR tokamak
Jun Gyo Bak, Heung Su Kim, Sang Hee Hahn, Jahyun Kim, Hyun Seok Kim, Jeong Won Lee
and KSTAR team
National Fusion Research Institute (NFRI), Daejeon, Korea
The study on the plasma current quench in the phase of disruptions are carried out for the
plasma current Ip0 of 0.4 -1.0 MA in the KSTAR tokamak. The disruption data in the
experimental campaign of 2012 - 2017 are used for the study. Firstly, the relationship between
instantaneous current quench rate (ICQR) and the pre-disrupted plasma current Ip,pred is
investigated by using the ICQR obtained from the time derivative of plasma current at the phase
of current quench (CQ). The magnitude of the ICQR is up to ~ 200 MA/s and the increment of
the ICQR becomes smaller for higher value of Ip,pred, which means that the relationship between
ICQR and Ip,pred is not linear. Secondly, several linear (or averaged) current quench rates
(LCQRs) are evaluated from the linear fits for several ranges (for an example, 90 % - 60 %
level of Ip0) in the time evolution of plasma current during the CQ, and the best linear fit for
evaluating the LCQR can be selected from the comparison between the ICQR and the LCQRs.
From the investigation of the CQRs, the minimum current quench time is evaluated as ~ 2 ms.
Thirdly, the characteristics of the toroidal vessel current IVC and eddy current IPS induced on
the passive stabilizer as a conducting shell used for plasma control are investigated by using
experimental data in the phase of the CQ. The magnitude of IVC is up to ~ 60 % of Ip,disrup. There
is a correlation between the CQR and magnitudes of both IVC and IPS. In addition, the vertical
growth rate and shrink rate of plasma size during the vertical displacement events (VDEs) are
investigated by using the EFIT reconstructed data in the phase of the CQ. There is a weak linear
correlation between the vertical growth rate and the shrink rate of plasma size.
In this work, the results from the further investigations on plasma current quench during
disruptions in the KSTAR comparing to the previous work presented at the 44th EPS meeting,
together with behaviors during the VDE in the phase of the CQ, are reported.
