Accurate plasma shape control is the basis of tokamak plasma experiments and physical research. Modeling of the linearized control response of plasma shape and position has been widely used for shape controller design in the last several years. But it usually contains much of the uncertainty, such as structured uncertainties and unmodeled dynamics. EAST tokamak plasma shape controller design is also based on a linear rigid plasma response model which integrated within a Matlab-based toolset known as TokSys. Meanwhile the PID control approach is currently used for EAST plasma shape control. This leads to strong coupling between different parameters describing the plasma shape. To handle these problems, a H_infinity robust control scheme for EAST multi-input multi-output (MIMO) shape control has been proposed. First, the plasma response is modeled as the linearized rigid RZIp model. Then, the controller design technique is introduced with two main stages: 1) loop shaping is used to shape the nominal plant singular values to give desired open-loop properties at frequencies of high and low loop gain; 2) a normalized coprime factorization and H_infinity technique is used to decouple the most relevant control channels and minimize the tracking errors. Finally, the simulation results show that the H_infinity robust controller combines good robust stability margins, speed of response, dynamic tracking characteristics, and closed-loop decoupling for EAST plasma shape control.
The optimum scheme for geometric phase measurement in EAST Tokamak is proposed in this paper. The theoretical values of geometric phase for the probe beams of EAST Polarimeter-Interferometer (POINT) system are calculated by path integration in parameter space. Meanwhile, the influences of some controllable parameters on geometric phase are evaluated. The feasibility and challenge of distinguishing geometric effect in the POINT signal are also assessed in detail.
Evolution of electron temperature, electron density and its fluctuation with high spatial and temporal resolutions are presented for the cold pulse propagation induced by super-sonic molecular beam injection (SMBI) in ohmic plasmas in the EAST tokamak. The non-local heat transport occurs for discharges with plasma current $I_p$=450 kA ($q_{95}\sim5.55$), and electron density $n_{e0}$ below a critical value of $(1.35\pm0.25)\times10^{19}~\mathrm{m^{-3}}$. In contrary to the response of core electron temperature and electron density (roughly 10 ms after SMBI), the electron density fluctuation in…
University of Science and Technology of China（中国科学技术大学）
A model for tokamak discharge through deep learning has been done on a superconducting long-pulse tokamak (EAST). This model can use the control signals (i.e. Neutral Beam Injection (NBI), Ion Cyclotron Resonance Heating (ICRH), etc) to model normal discharge without the need for doing real experiments. By using the data-driven methodology, we exploit the temporal sequence of control signals for a large set of EAST discharges to develop a deep learning model for modeling discharge diagnostic signals, such as electron density $n_{e}$, store energy $W_{mhd}$ and loop voltage $V_{loop}$. Comparin…
The characteristics of wall recycling with different divertor configurations were investigated in this study, focusing on the observations of the spatial distributions of deuterium atomic emissions in the Balmer series (D_α, D_β, D_γ, and D_δ) with different magnetic field configurations in the Experimental Advanced Superconducting Tokamak. The observed D_α and D_β emissions were primarily relatively close to the divertor targets, while the D_γ and D_δ emissions were primarily relatively close to the X-point. The distributions of the emissions close to the divertor targets and X-point changed …
In this work, a purely data-driven discharge prediction model was developed and tested without integrating any data or results from simulations. The model was developed based on the experimental data from the Experimental Advanced Superconducting Tokamak (EAST) campaign 2010-2020 discharges and can predict the actual plasma current $I_{p}$, normalized beta $β_{n}$, toroidal beta $β_{t}$, beta poloidal $β_{p}$, electron density $n_{e}$, store energy $W_{mhd}$, loop voltage $V_{loop}$, elongation at plasma boundary $κ$, internal inductance $l_{i}$, q at magnetic axis $q_{0}$, and q at 95% flux s…
Nitrogen-induced ELM suppression and confinement improvement in the EAST tokamak with a full metal wall
School of the Gifted Young, University of Science and Technology of China（中国科学技术大学少年班）；Institute of Plasma Physics, Chinese Academy of Sciences（中国科学院等离子体物理研究所）；School of Nuclear Science and Technology, University of Science and Technology of China（中国科学技术大学核科学与技术学院）；Southwestern Institute of Physics（西南物理研究所）
Quasi-periodic Pedestal Burst Instabilities (PBIs), featuring alternative turbulence suppression and bursts, have been clearly identified by various edge diagnostics during I-mode to H-mode transition in the EAST Tokamak. The radial distribution of the phase perturbation caused by PBI shows that PBI is localized in the pedestal. Prior to each PBI, a significant increase of density gradient close to the pedestal top can be clearly distinguished, then the turbulence burst is generated, accompanied by the relaxation of the density profile, and then induces an outward particle flux. The relative d…
The tearing mode, a large-scale MHD instability in tokamak, typically disrupts the equilibrium magnetic surfaces, leads to the formation of magnetic islands, and reduces core electron temperature and density, thus resulting in significant energy losses and may even cause discharge termination. This process is unacceptable for ITER. Therefore, the accurate identification of a magnetic island in real time is crucial for the effective control of the tearing mode in ITER in the future. In this study, based on the characteristics induced by tearing modes, an attention-aware convolutional neural net…
Compact torus injection is considered as a high promising approach to realize central fueling in the future tokamak device. Recently, a compact torus injection system has been developed for the Experimental Advanced Superconducting Tokamak, and the preliminary results have been carried out. In the typical discharges of the early stage, the velocity, electron density and particles number of the CT can reach 56.0 km/s, 8.73*10^20 m^(-3) and 2.4*10^18 (for helium), respectively. A continuous increase in CT density during acceleration was observed in the experiment, which may be due to the plasma …
A space-resolved visible spectrometer system using compact endoscopic optics for full vertical profile measurement of impurity line emissions in superconducting EAST tokamak
First Observation of Fishbone-Driven Zonal Flows with Fine Reversed Structure in Tokamak Plasmas
School of Nuclear Science and Technology, University of Science and Technology of China（中国科学技术大学核科学与技术学院）；Institute of Plasma Physics, Chinese Academy of Sciences（中国科学院等离子体物理研究所）
VEQDB: A Compact and Reconstructible Multi-Device Tokamak Equilibrium Database
Beijing VeloAlpha Technology Co., Ltd.（北京维洛阿尔法科技有限公司）；Key Laboratory of Materials Modification by Beams of the Ministry of Education, School of Physics, Dalian University of Technology（大连理工大学物理学院光束材料改性教育部重点实验室）
Electromagnetic turbulence in EAST plasmas with internal transport barrier
CAS Key Laboratory of Frontier Physics in Controlled Nuclear Fusion, School of Nuclear Sciences and Technology, University of Science and Technology of China（中国科学院前沿物理国家重点实验室，核科学与技术学院，中国科学技术大学）；Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）；Department of Physics and Astronomy, University of California, Irvine（加州大学尔湾分校物理与天文学系）
本研究通过全局非线性电磁 gyrokinetic 模拟，揭示弱反剪切 EAST 托卡马克 ITB 区域的电磁湍流特性，发现电磁效应可抑制高频 ITG 模、增强带状流剪切以降低热导率，为准确计算输运系数提供关键依据。
Plasma response to resonant magnetic perturbations (RMPs) near the pedestal top is crucial for accessing edge localized modes (ELMs) suppression in tokamaks. Since radial location of rotation zero-crossing plays a key role in determining the threshold for field penetration of RMP, plasma response may be different in low input torque plasmas. In this work, the linear MHD code MARS-F is applied to reveal the dependence of plasma response to RMP on rotation zero-crossing by a scan of rotation profiles based on an EAST equilibrium. It is shown that the plasma response is enhanced when zero-crossin…
