Speaker
Hyung-Ho Lee
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1055.pdf
Circuit Analysis of Nested Current Element to Explain Ohmic Current
Diffusion in Tokamak Plasmas
ByoungHo Park1, H. H. Lee1
1
National Fusion Research Institute, Daejeon, Korea
A seemingly simple question sometimes is not that simple to answer in simple way. The
direction of current diffusion in the tokamak is one example. The inductive Ohmic current
when the central solenoid current is varying, we all know that the effects are start from
outside to inside. The answer may given by the wave propagation and skin depth effect but if
you compare the system size of the tokamak with the wave length caused by the central
solenoid current variation, the answer should be given in a simpler way. The most simple and
successful description of the start up of the tokamak operation is the circuit theory. The
circuit theory does not miss any essential feature of the tokamak start up in this aspect.
Therefore this question also should be able to be answered by circuit model. Each circuit
comprised in the circuit model does not direct information of distance from the CS coils they
just communicate each other through the mutual inductance. How do they know which one is
higher rank? This work is inspired by the following statement:
At the very moment of CS coils current are varied the loop voltages applied on any closed
paths surrounding the center stack are the same. Therefore all closed paths start to build
current on their paths and at the same time they are screening the induced electric field or
loop voltage each other by mutually interacting through the mutual inductance. They seem to
be equal when we write down them in a circuit model.
We modeled the tokamak current consists of nested circuit elements conformal with the flux
surface and we found that the matrix of mutual inductance of circuit model has specific
symmetry. Intuitive explanation of this question and analysis of some of KSTAR Ohmic
discharges are studied.
