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17 pages, 4260 KiB

Open AccessArticle

Model-Based Optimization of the Field-Null Configuration for Robust Plasma Breakdown on the HL-3 Tokamak

by Muwen He, Bin Yang, Yihang Chen, Xinliang Xu, Xiaobo Zhu, Jiaqi Yang, Jiang Sun, Panle Liu, Bo Li and Xiaoquan Ji

Appl. Sci. 2025, 15(4), 2175; https://doi.org/10.3390/app15042175 - 18 Feb 2025

Abstract

This paper introduces a self-consistent field-null optimization algorithm of a poloidal magnetic field that precisely accounts for the influence of vacuum vessel eddy currents. Building on existing poloidal field (PF) coil currents, the algorithm can refine these waveforms to achieve various target field-null configurations. Firstly, based on the TokSys toolbox, a response model, including the PF coils and vacuum vessel circuits for the HL-3 tokamak, is developed under the MATLAB^® and Simulink^™ framework. The resistivity parameters of the model are calibrated using experimental data obtained from single-coil discharge tests. Subsequently, an iterative method was employed to simultaneously solve the dynamic field-null optimization problem within a specified spatial region and precisely account for the effect of passive eddy currents. Typically,

|B_{⊥}| \leq 1 G

within a large area can be obtained with this iterative scheme, which can be stably sustained for over 15 milliseconds to ensure the robustness of breakdown. Finally, a low-pass filtered PID controller is applied to the model to achieve precise control of the PF coils currents, confirming the feasibility of implementing the proposed algorithm in real experiments. Full article

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9 pages, 3295 KiB

Open AccessArticle

Upgrade of Thomson Scattering Diagnostic on HL-2A

by Wenping Guo, Yuan Huang, Chunhua Liu, Zhen Feng, Zhipei Hou, Wenyan Zhai, Hisamichi Funaba, Ichihiro Yamada, Yonggao Li and Zhongbin Shi

Instruments 2023, 7(1), 12; https://doi.org/10.3390/instruments7010012 - 6 Mar 2023

Cited by 1 | Viewed by 2269

Abstract

The Thomson scattering diagnostic of the HL-2A tokamak device was upgraded to improve its multi-point diagnostic capability, including new collection optics, fibers bundles, and data analysis code. The small old collection lens was replaced by a six-piece lens with a Cooke optical design. The aperture of its first standard sphere face is 310.125 mm, which successfully increases the amount of collected scattering light by about three times. The new collection optic module allows for up to twenty-six spatial points. A kind of Y-type fiber bundle has also been used to ensure that the fiber end-face matches the image of the laser beam exactly. Additionally, the new data analysis code can provide preview results in seconds. Finally, the multi-point

T_{e}

diagnostic ability has been significantly improved. Full article

(This article belongs to the Special Issue Feature Papers in Instruments 2021–2022)

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16 pages, 10133 KiB

Open AccessArticle

Development of a Radio-Frequency Quadrupole Accelerator for the HL-2A/2M Tokamak Diagnostic System

by Shuo Liu, Yaxia Wei, Yuanrong Lu, Zhi Wang, Meiyun Han, Tianhao Wei, Yin Xia, Haipeng Li, Shuli Gao and Pengfei Zheng

Appl. Sci. 2022, 12(8), 4031; https://doi.org/10.3390/app12084031 - 15 Apr 2022

Cited by 5 | Viewed by 2069

Abstract

In order to figure out the migration and deposition of impurities on the first wall of HL-2A/2M tokamak, Peking University and Southwestern Institute of Physics are co-developing a deuteron RFQ as part of the in situ ion-beam diagnostic for the material. The RFQ, which operates at 162.5 MHz, is designed to accelerate a 10-mA deuteron beam from 40 keV up to 1.5 MeV. Key design considerations and the final design parameters are presented. The RFQ has been conditioned at a 1% duty factor for 80 h at RF cavity power of 55 kW. The specific shunt impedance of the cavity is 221 kΩ·m by measuring the bremsstrahlung spectrum. The intrinsic Q-value after the high-power tests measured by the Ring-Down method is 13,780. Beam commissioning has been taken place during the first half of 2021, and the beam measurements include beam current and energy of ²H⁺ ion. A 10 mA ²H⁺ beam was successfully accelerated through the RFQ. Full article

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11 pages, 2856 KiB

Open AccessArticle

H-Mode Power Threshold Studies on MAST

by Yasmin Andrew, Jan-Peter Bähner, Ronan Battle and Tomas Jirman

Plasma 2019, 2(3), 328-338; https://doi.org/10.3390/plasma2030024 - 19 Jul 2019

Cited by 9 | Viewed by 5919

Abstract

Analysis of the L–H and H–L transition power thresholds (P_th) and pedestal parameters are presented for the mega ampere spherical tokamak (MAST). The dependencies of P_th on the average, core plasma electron density, X-point height, and plasma current are described. Increasing X-point distance from the divertor floor over 10–12 cm is found to increase P_th by a factor of three, while X-point heights greater than this have no further influence. The X-point height dependence of P_th is also observed to be sensitive to the plasma current. An I_p decrease from 0.77 MA to 0.65 MA, is observed to lower P_th by a factor of three across the X-point height scan and increases the maximum X-point height at which P_th stops increasing by 3 cm. Finally, a comparison of the experimental results with the predictions by the finite beta drift wave model is made, which provides a reasonable condition for the transition into and out of the H-mode. Full article

(This article belongs to the Special Issue Magnetic Confinement Fusion)

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