Radiation-driven<i>m</i>  =  2 island formation and dynamics near density limit in experimental advanced superconducting tokamak ohmic plasma

Xu, Liqing; Duan, Yanmin; Chen, Kaiyun; Zhao, Hengyu; Luo, Zhenping; Zheng, Zhen; Liu, Yong; Liu, Haiqing; Chen, Ying‐Jie; Yuan, Yifei; Hu, Liqun; Du, Haifeng; Shi, Tonghui

doi:10.1088/1741-4326/aa7f91

Cited by 18 publications

(31 citation statements)

References 28 publications

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“…8, as suggested by previous studies. [18] Figure 9 shows that the reconstructed signals match well with the measured signals.…”

Section: Sawtooth-like Internal Disruptionmentioning

confidence: 60%

Gaussian process tomography based on Bayesian data analysis for soft x-ray and AXUV diagnostics on EAST*

Yan

et al. 2020

Chinese Phys. B

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This work presents the Gaussian process tomography (GPT) based on Bayesian data analysis and its applications in soft x-ray (SXR) and absolute extreme ultraviolet spectroscopy (AXUV) diagnostics on experimental advanced superconducting tokamak (EAST). This is the first application of the GPT method in the AXUV diagnostic system in fusion devices. It is found that even if only horizontal detector arrays are used to reconstruct the two-dimensional (2D) distribution of SXR and AXUV emissivity fields, the GPT method performs robustly and extremely fast, which enables the GPT method to provide real-time feedback on impurity transport and fast magnetohydrodynamics (MHD) events. By reconstructing SXR emissivity in the poloidal cross section on EAST, an m/n = 1/1 internal kink mode has been observed, and the plasma redistribution due to the kink mode is clearly visible in the reconstructions, where m is the poloidal mode number and n is the toroidal mode number. Sawtooth-like internal disruptions extended throughout the entire plasma core and mainly driven by the m/n = 2/1 mode have been acquired. During the sawtooth-like internal disruption crash phase, the conversion from an m = 2 mode to an m = 1 mode is observed. Using the reconstructed AXUV emissivity field we were able to observe the process of impurity accumulated in the plasma core and the mitigation of core impurity due to neon injection in the plasma edge. The data from all other diagnostics involved in the analysis shows that the reconstructions from AXUV measurements are reliable.

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“…8, as suggested by previous studies. [18] Figure 9 shows that the reconstructed signals match well with the measured signals.…”

Section: Sawtooth-like Internal Disruptionmentioning

confidence: 60%

Gaussian process tomography based on Bayesian data analysis for soft x-ray and AXUV diagnostics on EAST*

Yan

et al. 2020

Chinese Phys. B

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“…Experiments have found some correlations between the impurity radiation and the tearing mode (TM) growth, ASDEX-Upgrade shows the low temperature and localized impurity radiation inside the growing magnetic island during the current contraction phase [1], and the similar connection between enhanced radiation and enlarged island width is observed in NSTX [2]. Besides, EAST experiments demonstrate the m = 2 (m is the poloidal mode number) island formation when the radiative cooling exceeds the ohmic heating [3]. Those experimental observation contribute to supporting the impurity radiation as a driven mechanism of TM but without more detail, JET experiments show the TM onset induced by unstable shrinking (broadening) current profile as a consequence of temperature edge cooling (central hollowing) from radiation loss [4].…”

Section: Introductionmentioning

confidence: 86%

“…The impurity level is sufficiently low to avoid triggering the fast major disruption such as in a massive gas injection (MGI) process [15], while sufficiently high to excite the resistive tearing modes as in recent EAST experiments [11]. The impurity penetrates inward mainly through diffusion and convection as governed by equation (3). A constant isotropic diffusion coefficient D = 10m 2 /s is adopted in the simulation, which is larger than the typical EAST experimental value, i.e.…”

Section: Nimrod/kprad Model and Simulation Setupmentioning

confidence: 99%

Magnetic island formation and rotation braking induced by low-Z impurity penetration in an EAST plasma

Zeng¹,

Zhu²,

Zhou³

et al. 2022

Preprint

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Recent observations of the successive formations of the 4/1, 3/1, and 2/1 magnetic islands as well as the subsequent braking of the 2/1 mode during a low-Z impurity penetration process in EAST experiments are well reproduced in our 3D resistive MHD simulations. The enhanced parallel current perturbation induced by impurity radiation predominately contributes to the tearing mode growth, and the 2/1 island rotation is mainly damped by the impurity accumulation as results of the influence from high n modes.

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“…Such studies on plasma radiation have been carried out, including bremsstrahlung, recombination radiation, cyclotron radiation and line radiation. [16,[26][27][28][29][30][31][32][33][34] It is worth mentioning that the line radiation comes mainly from the impurity radiation in the tokamak plasmas. Gates et al found that islands could be driven by the plasma radiation and this performance was consistent with the density limit.…”

Section: Introductionmentioning

confidence: 99%

“…[29] An m = 2 island induced by the plasma radiation was explored in EAST ap-proaching to the density limit when the loss of plasma radiation is more than the ohmic heating input. [30] Besides, Hu et al numerically studied plasma radiation response and MHD destabilization by a 3D-code JOREK and observed that the mode growth was propelled by the current, leading to the collapse in core temperature. [31] Furthermore, Salzedas et al advanced a new theory that MHD instabilities could be induced by plasma radiation.…”

Section: Introductionmentioning

confidence: 99%

Effects of plasma radiation on the nonlinear evolution of neo-classical tearing modes in tokamak plasmas with reversed magnetic shear

Jiang 姜,

Wang 王,

Wei 魏

et al. 2023

Chinese Phys. B

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Effects of plasma radiation on the nonlinear evolution of neo-classical double tearing modes (NDTMs) in tokamak plasmas with reversed magnetic shear are numerically investigated based on a set of reduced magnetohydrodynamics (MHD) equations. Cases with different separations △ rs =|r s2-r s1| between the two same rational surfaces are considered. In the small △ rs cases, the plasma radiation destabilizes the NDTMs and makes the kinetic energy still grow gradually in the late nonlinear phase. Moreover, the NDTM harmonics with high mode numbers reach a high level in the presence of plasma radiation, forming a broad spectrum of MHD perturbations that induces a radially broadened region of MHD turbulence. As a result, the profiles of safety factor also enter a nonlinear oscillation phase. In the intermediate △ rs case, the plasma radiation can advance the explosive burst of kinetic energy that results from the fast driven reconnection in between the two rational surfaces, because it can further promote the destabilizing effects of bootstrap current perturbation on magnetic island near the outer rational surfaces. In the large △ rs case, through destabilizing the outer islands significantly, the plasma radiation can even induce the explosive burst in the reversed magnetic shear configuration where the burst cannot be induced in the absence of plasma radiation.

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Radiation-drivenm = 2 island formation and dynamics near density limit in experimental advanced superconducting tokamak ohmic plasma

Cited by 18 publications

References 28 publications

Gaussian process tomography based on Bayesian data analysis for soft x-ray and AXUV diagnostics on EAST*

Gaussian process tomography based on Bayesian data analysis for soft x-ray and AXUV diagnostics on EAST*

Magnetic island formation and rotation braking induced by low-Z impurity penetration in an EAST plasma

Effects of plasma radiation on the nonlinear evolution of neo-classical tearing modes in tokamak plasmas with reversed magnetic shear

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