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Kim, H.-S.*; Jeon, Y. M.*; Na, Y.-S.*; Ghim, Y.-C.*; Ahn, J.-W.*; Yoon, S. W.*; Bak, J. G.*; Bae, Y. S.*; Kim, J. S.*; Joung, M.*; et al.
Nuclear Fusion, 54(8), p.083012_1 - 083012_11, 2014/08
Times Cited Count：8 Percentile：37.63(Physics, Fluids & Plasmas)We evaluate the characteristics of global energy confinement in KSTAR (
) quantitatively by comparing it with multi-machine scalings, by deriving multiple regression equations for the L- and the H-mode plasmas, and evaluating confinement enhancement of the H-mode phase compared with the L-mode phase in each discharge. From the KSTAR database, of L-mode plasmas exhibits 
s to 
s and of H-mode plasmas 
s to 
s. The multiple regression equations derived by statistical analysis present the similar dependency on PL and slightly higher dependency on IP compared with the multi-machine scalings, however the dependency on elongation 
in both L- and H-mode plasmas draw the negative power dependency of 
and 
for H-mode and for L- mode database, respectively on the contrary to the positive dependency in all multi-machine empirical scalings. Although the reason is not clear yet, two possibilities are addressed. One is that the wall condition of KSTAR was not clean enough. The other is that striking points on the divertor plate were uncontrolled. For these reasons, as increases, the impurities from the wall can penetrate into plasmas easily. As a consequence, the confinement is degraded on the contrary to the expectation of multi-machine scalings.
Miyata, Yoshiaki; Hahn, S. H.*; Suzuki, Takahiro; Ide, Shunsuke; Chung, J.*; Bak, J. G.*; Ko, W. H.*
Physics of Plasmas, 21(3), p.032502_1 - 032502_11, 2014/03
Times Cited Count：9 Percentile：41.77(Physics, Fluids & Plasmas)Cauchy condition surface (CCS) method is a numerical approach to reconstruct the plasma boundary precisely and calculate the quantities related to plasma shape using small number of magnetic diagnostics in real time. It has been applied to the KSTAR plasma in order to establish the plasma shape reconstruction with the high elongation of plasma shape and the large effect of eddy current flowing in the structure for the first time. Calculations have been performed to validate the plasma shape reconstruction in 2012 KSTAR experimental campaign. Comparison between the CCS calculation and non-magnetic measurements revealed that the CCS calculation can reconstruct the accurate plasma shape even with a small Ip. The application of CCS calculation to the KSTAR plasma and the validation results of the plasma shape reconstruction are reported.
Bae, Y. S.*; Na, Y. S.*; Oh, Y. K.*; Kwon, M.*; Bak, J. S.*; Lee, G. S.*; Jeong, J. H.*; Park, S. I.*; Cho, M. H.*; Namkung, W.*; et al.
Fusion Science and Technology, 52(2), p.321 - 333, 2007/08
Times Cited Count：23 Percentile：81.77(Nuclear Science & Technology)An 84-GHz, 500-kW gyrotron system have been installed at KSTAR, and the initial test of the gyrotron has been carried out with 20 
sec-pulse and an output RF power of 500 kW. The launcher system having with a highly flexible steering mirror was fabricated and would inject 500-kW rf power into the KSTAR plasma. KSTAR will employ 170-GHz EC current drive (CD) in ITER-relevant experiments such as the suppression of the neoclassical tearing modes and the creation of an electron internal transport barrier. A JAEA 170-GHz, 1-MW gyrotron on loan in accordance with a Korea-Japan fusion collaboration agreement, and it will be used for the 170-GHz, 1-MW ECCD system in 2010. This paper describes the current status of the installation and initial conditioning tests of the 84-GHz gyrotron system as well as the development plan of the 170-GHz ECH and CD system. Also, this paper discusses the CD efficiency and the steering range of the second-harmonic X-mode injection.
Bizen, Teruhiko*; Tanaka, Takashi*; Asano, Yoshihiro; Kim, D. E.*; Bak, J. S.*; Lee, H. S.*; Kitamura, Hideo*
Nuclear Instruments and Methods in Physics Research A, 467-468(Part1), p.185 - 189, 2001/07
Times Cited Count：40 Percentile：92.11(Instruments & Instrumentation)no abstracts in English
Miyata, Yoshiaki; Hahn, S. H.*; Suzuki, Takahiro; Ide, Shunsuke; Chung, J.*; Bak, J. G.*; Ko, W. H.*
no journal, ,
The plasma shape reconstruction is essential for plasma equilibrium control and detailed physics analysis. Various methods to reconstruct a plasma shape have been developed for many tokamaks. Cauchy Condition Surface (CCS) method has reconstructed a plasma shape using the magnetic measurements in JT-60U. The CCS calculation can reconstruct the outermost magnetic surface, and calculate the eddy currents induced in the toroidal structure and the quantities related to plasma shape such as the Shafranov lambda, the safety factor and so on. In this presentation, the demonstration of real-time plasma shape reconstruction by the CCS calculation in KSTAR is discussed.
