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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.
Jeong, J. H.*; Bae, Y. S.*; Joung, M.*; Kim, H. J.*; Park, S. I.*; Han, W. S.*; Kim, J. S.*; Yang, H. L.*; Kwak, J. G.*; Sakamoto, Keishi; et al.
Fusion Engineering and Design, 88(5), p.380 - 387, 2013/06
Times Cited Count：3 Percentile：25.73(Nuclear Science & Technology)Yang, H. L.*; Kim, Y. S.*; Park, Y. M.*; Bae, Y. S.*; Kim, H. K.*; Kim, K. M.*; Lee, K. S.*; Kim, H. T.*; Bang, E. N.*; Joung, M.*; et al.
Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03
Because the 2010 operation of Korea Superconducting Tokamak Advanced Research (KSTAR) mainly aims to achieve strongly elongated and diverted plasma, all the necessary hardware systems to provide an essential circumstance for the plasma shaping were newly installed and upgraded in 2010. In this paper, general configuration of the upgraded systems described earlier will be outlined. Moreover, several key performances and test results of the systems will be also reported in summary.
Stober, J.*; Jackson, G. L.*; Ascasibar, E.*; Bae, Y.-S.*; Bucalossi, J.*; Cappa, A.*; Casper, T.*; Cho, M. H.*; Gribov, Y.*; Granucci, G.*; et al.
Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2010/10
Na, Y. S.*; Suzuki, Takahiro; Ide, Shunsuke; Mueller, D.*; Kim, J. H.*; Miyata, Yoshiaki; Kim, S. H.*; Kim, H. S.*; Jeon, Y. M.*; Bae, Y. S.*; et al.
no journal, ,
Development of advanced scenarios, an important experimental goal for the KSTAR project, has just begun. Target plasmas were successfully produced using large bore plasma and early divertor formation which exhibit low internal inductance with low magnetic shear at the centre and no sawtooth instability. Auxilliary heating during the current rampup phase was employed to slow the inductive current diffusion to the centre of the plasma. With respect to hybrid scenario development, so-called "Ip-overshoot" method being used in JET is applied for tailoring magnetic shear at reduced plasma current for higher poloidal beta and bootstrap current fraction. The confinement characteristics of these scenarios are investigated. Transport modeling is performed self-consistently with an integrated simulation package incorporating plasma equilibrium, transport, heating and current drive. Firstly, the current rampup phase is simulated and its impact on the target q-profile is addressed. Secondly, energy confinement of flattop phases is discussed. In addition, the non-inductive current drive fraction including the bootstrap current fraction is calculated. Lastly, these scenarios are compared with advanced scenarios developed in other tokamak devices and future directions in achieving advanced regimes are discussed.
Sasaki, Miyuki; Sanada, Yukihisa; Lee, E.*; Joung, S.*; Ji, Y.-Y.*
no journal, ,
Since the Fukushima Daiichi Nuclear Power Plant accident, some types of radiation monitoring have been conducted in Japan. Walking surveys and unmanned helicopter surveys have been conducted around the FDNPP to the ambient dose equivalent rates (air dose rate). The airborne radiation survey (ARS) by unmanned helicopter has the advantage of measuring large areas including forests. However, ARS has lower measurement resolution than walking surveys. Sasaki et al. constructed an artificial neural network (ANN) to convert ARS data into air dose rates at 1 m above ground level using data accumulated after the accident (Ref). It has been reported that the conversion using ANNs can convert to values closer to those measured on the ground than the conventional method. Showing that the ANN constructed from the Fukushima experience can be applied to detectors other than the radiation detector used to construct the ANN will greatly contribute to the future development of ARS. In this study, we investigated how to apply radiation measurement data acquired with a detector different from the radiation detector used to acquire the training data to an ANN that has already been constructed.
Joung, S.*; Ji, Y.-Y.*; Choi, Y.*; Lee, E.*; Ji, W.*; Sasaki, Miyuki; Ochi, Kotaro; Sanada, Yukihisa
no journal, ,
KAERI (Korea Atomic Energy Research Institute) has developed the MARK A1 aerial survey system for unmanned aerial vehicles for use in contaminated areas. The MARK A1 system consists of a CZT detector, signal processing unit, and positioning and interface units to a PC on the ground. To validate the effectiveness of the detectors, field tests were conducted in high dose rate environments near the Fukushima Daiichi Nuclear Power Station. The JAEA and KAERI detectors were each mounted on an unmanned helicopter to make measurements at different altitudes. For both systems, the air dose rates obtained from the airborne survey gave results with a similar trend to the air dose rates obtained from the walking survey. Therefore, it is expected that MARK A1 can be used to quickly scan large and highly contaminated areas that are difficult for humans to access in the event of a nuclear accident.
