Article
Physics, Fluids & Plasmas
Jaemin Seo, Y. S. Na, B. Kim, C. Y. Lee, M. S. Park, S. J. Park, Y. H. Lee
Summary: This work proposes a new feedforward control scheme for normalized beta (beta (N)) in tokamak plasmas, using deep reinforcement learning to optimize an artificial decision-making agent. The success and limitations of this approach are analyzed through a series of KSTAR experiments, suggesting a future research path for this area of study.
Article
Nuclear Science & Technology
T. Q. Jia, K. Y. He, D. L. Chen, J. P. Qian, X. Gu, B. Shen, Y. W. Sun, T. H. Shi, Y. Wang, B. Zhang, X. Z. Gong
Summary: This article presents the measurement method of the diamagnetic flux for poloidal beta and energy content of EAST based on diamagnetic loops. The error sources can be compensated with the diamagnetic loop and the compensation loop signals. The experimental results show a good response between the diamagnetic flux measurements and the rapid stored energy drop induced by edge localized modes (ELMs).
FUSION ENGINEERING AND DESIGN
(2022)
Article
Physics, Fluids & Plasmas
H. Shin, J. Hwang, Y. Han, G. Shin, H. Lee, K. -B. Chai, Wonho Choe
Summary: In this study, we demonstrate successful ELM suppression and mitigation using an argon-seeded discharge and a three-row resonant magnetic perturbation configuration in KSTAR. The heat flux on the divertor target was reduced by argon seeding, and the particle flux on both targets was significantly reduced. The divertor heat load was further reduced during the RMP grassy-ELM regime, and a highly localized radiation zone near the X-point was observed during divertor detachment.
Article
Physics, Fluids & Plasmas
S. G. Lee, J. Seol, H. H. Lee
Summary: This study investigates the toroidal rotation dynamics of KSTAR ohmic plasmas without any external torque sources. It is found that the toroidal rotation velocity increases as the plasma density rises, while the measured radial electric field is generally negative and its magnitude increases with the density. The study introduces a theoretical picture to explain the relation between the radial electric field and the toroidal rotation.
Article
Physics, Fluids & Plasmas
J. Chung, S-H Hahn, H. Han, J. Kang, H. S. Kim, Y. M. Jeon, J. Ko, K. D. Lee, W. H. Ko, S. H. Seo, J. H. Lee, J-W Juhn, M. W. Lee, M. H. Woo, Y. W. Cho, S. W. Yoon
Summary: In the ITB experiment at KSTAR, access to ITB was experimentally achieved with about 3 MW of NBI power using the upper single null (USN) condition. The key control parameters of the experiment are the vertical position of the plasma and the location of the outboard striking point, controlled through shape-control and striking-point control to maintain the ITB performance.
Article
Physics, Fluids & Plasmas
J. Seo, Y. -S. Na, B. Kim, C. Y. Lee, M. S. Park, S. J. Park, Y. H. Lee
Summary: This work develops an AI algorithm for tokamak operation design, which can control multiple plasma parameters simultaneously to achieve different targets. The AI is trained using reinforcement learning technique in a data-driven tokamak simulator to find the best action policy for higher reward. The algorithm has been successfully demonstrated in achieving the target plasma states in a real experiment.
Article
Physics, Fluids & Plasmas
S. M. Yang, J. -K. Park, H. S. Kim, M. Podesta, J. S. Kang, T. Rhee
Summary: This study investigates the optimization of the poloidal spectrum of the 3D field to enhance fast ion confinement during edge localized mode (ELM) suppression. The results highlight the potential of edge localization of the resonant fields to enhance the performance of fusion reactors.
Article
Physics, Multidisciplinary
Jeongwon Lee, Hyun-Tae Kim, Jayhyun Kim, Sang-hee Hahn, June-Woo Juhn, JuHyuk Jang, Jun-Gyo Bak, SooHyun Son, Mi Jung, YoungHwa An, Yong-Su Na, Si-Woo Yoon
Summary: An electron cyclotron heating (ECH) power absorption model, DYON-EC, was developed and validated against KSTAR ECH-assist start-up experiments. The absorbed ECH power was calculated based on electron density, temperature, and hardware settings, with consideration of wave parameter changes due to wall reflection. The DYON-EC model successfully reproduced multiple KSTAR EC-assisted discharges using optimized simulation settings, confirming its validity.
Article
Nuclear Science & Technology
Jaesic Hong, In-Sik Woo, Seung-Ju Lee, Myungkyu Kim, Kwang-Pyo Kim, Kaprai Park
Summary: Korea Superconducting Tokamak Advanced Research (KSTAR) has three interlock systems: Supervisory Interlock System (SIS), Fast Interlock System (FIS), and Personal Safety Interlock (PSI). The SIS and FIS have undergone optimization and modifications since 2009 to improve efficiency and machine protection.
FUSION ENGINEERING AND DESIGN
(2023)
Article
Energy & Fuels
Antonio Castaldo, Raffaele Albanese, Roberto Ambrosino, Flavio Crisanti
Summary: This paper presents important research in the field of nuclear fusion regarding the power exhaust problem. The study includes detailed descriptions and demonstrations of plasma scenarios for standard and alternative configurations in the Divertor Tokamak Test (DTT) tokamak, showcasing the flexibility of the machine.
Article
Nuclear Science & Technology
Jong-ha Lee, Seung Ju Lee, Ha Jin Kim, Sang Hee Hahn, Ichihiro Yamada, H. Funaba
Summary: This paper presents a prototype real-time Thomson scattering system that successfully transferred electron temperature data to the KSTAR plasma control system. The system utilizes a 155-channel 5 GS/s digitizer and applies pulse fitting and Fast Fourier Transformation (FFT) method to remove noise from the signals. A neural-network analysis method is employed for plasma parameter calculation. The data transfer was achieved within 50 ms.
FUSION ENGINEERING AND DESIGN
(2023)
Article
Physics, Fluids & Plasmas
Kimin Kim, Jisung Kang, Hyunseok Kim, Sumin Yi, Jeongwon Yoo, Minjun Choi, Tongnyeol Rhee, Junghee Kim, Myungwon Lee, Won-Ha Ko, Jaemin Kwon
Summary: We report the observation of improved confinement discharge in a magnetic braking experiment in the KSTAR tokamak. The improved confinement is achieved through reduced toroidal plasma rotation and significant reduction of edge localized modes (ELMs) induced by non-axisymmetric magnetic field. The modifications in multi-channel transport result in improved fast ion confinement and sustain thermal confinement against degradation in the 3D field experiment.
Article
Physics, Fluids & Plasmas
C. Y. Lee, J. Seo, S. J. Park, J. G. Lee, S. K. Kim, B. Kim, C. S. Byun, Y. S. Lee, J. W. Gwak, J. Kang, L. Jung, H. -S. Kim, S. -H. Hong, Yong-Su Na
Summary: A newly developed integrated code suite called TRIASSIC is reported for simulation and computation of a tokamak reactor. The suite consists of existing plasma simulation codes, with modularized components and good agreement with experimental measurements in validation conducted on 50 stationary plasma phases from 30 KSTAR discharges.
Article
Nuclear Science & Technology
B. Na, J. Kang, M. W. Lee, L. Jung, S. H. Hahn, J. W. Yoo, J. H. Jeong, J. Ko, C. Sung
Summary: This article reports on the neutral beam deposition profile of each neutral beam source in KSTAR. The accurate estimation and reconstruction of the neutral beam deposition profile is crucial for the main heating and current drive source in KSTAR. Through a fully non-inductive discharge experiment, the researchers derived the reconstructed beam-driven current and quantitatively interpreted the beam-driven deposition profile per each beam source by comparing with numerical beam modeling.
FUSION ENGINEERING AND DESIGN
(2022)
Article
Physics, Fluids & Plasmas
S. M. Yang, J. -K. Park, Y. S. Na, Y. In, H. Hahn, J. W. Jeon, J. W. Yoo, W. H. Ko, K. D. Lee, J. H. Lee, J. W. Lee, S. C. Hong, Y. J. Shi, N. C. Logan, Q. Hu, G. J. Choi
Summary: This study investigates the sensitivity of error field threshold in global parameters and toroidal harmonics dependence in KSTAR L-mode plasmas. The results show a non-monotonic correlation between error field threshold and density, which can be attributed to a modification of existing theoretical scaling in SOC and the influence of plasma rotation.
