Speaker
Jong-Gu Kwak
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P1.1006.pdf
Measurement of the beam slowing-down time at neutral beam heated
KSTAR deuterium plasma
Jong-Gu Kwak1, Y.S. Lee1
1
National Fusion Research Institute, Daejeon, Korea
Fusion product alpha particle whose energy is about 3.5 MeV is used to sustain the fusion
reaction after the ignition, so behaviour of the fast ion confinement is one of key issues at the
burning fusion plasma. As the KSTAR plasma performance is improved with neutral heating
power(~5 MW) and operational boundary of the H-mode discharge is extended over MHD
no-wall limit(βN~4) with higher stored energy region, the confinement of fast ions with
injected energy of 100 keV neutral beam is also important as well as increasing thermal ion
confinement with the plasma current. Recent KSTAR experimental campaign also showed
the fully non-inductive discharge with high betap(βp ~3), which is one of promising
candidate scenarios of steady state operation at KSTAR. It is explained by the enhancement
of fast ion confinement with reducing TAE(Toroidal Alfen Eigenmode) activity. In addition,
because there is a lot of production of fast neutrons coming from via D(d,n)3He reaction in
neutral beam heated plasma, the neutron flux could be used for characterizing the
confinement time of energetic particle at deuterium plasma by applying blip beam or
measuring the absolute flux value, but in this study, the blank beam with 10 msec which is
routinely used for other plasma diagnostic is used for estimating the confinement time of
energetic particle. In this presentation, we also report on the estimating beam slowing down
time at various KSTAR discharges including ITB(Internal Transport Barrier) and high betap
using blank beam method as well as its feasibility test of blank beam method.
