Runaway electron dynamics in Experimental Advanced Superconducting Tokamak helium plasmas

Luo, Chenxi; Zhang, Long; Zhu, Xiaoyan; Tang, Tian; Qiu, Zhiyong; Lin, Shiyao; Zhang, Tao; Liu, Hai Qing; Shi, Tonghui; Zhang, Bin; Ding, Rui; Wang, Qiao‐Chun; Gao, Wei; Ti, Ang; Zhao, Hai Lin; Zhou, Tian-Fu; Qian, J.; Sun, Yehuan; Liu, Bo; Zang, Qing; Ye, Jie; Liang, Yun-Feng; Gao, Xiang

doi:10.1088/1674-1056/acac12

Cited by 2 publications

(1 citation statement)

References 34 publications

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“…[ U loop (V) /n e ( 10 19 m −3 )] increases with time, and satisfies the condition for abundant EEs generation on EAST [31,32]. According to the database of EAST discharge experiments, the threshold value of E loop /E c is in the range of 3 ∼ 5, which is favourable for the generation of abundant EEs.…”

Section: Experimental Setup and Observationsmentioning

confidence: 67%

Bursting core-localized ellipticity-induced Alfvén eigenmodes driven by energetic electrons during EAST ohmic discharges

Su,

Lan,

Zhou

et al. 2024

Nucl. Fusion

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A series of high-frequency (400~1000 kHz) bursting core-localized Alfvén instabilities have been observed during ohmic discharges in EAST tokamak. The instability trigger favours the discharge conditions of low toroidal magnetic field and low electron density. The toroidal mode numbers are mainly n=2~3 and they propagate in the ion diamagnetic drift (co-current) direction. These modes are radially localized in the range of ρ_tor=0.2~0.35 based on Doppler BackScatter (DBS) measurement. They are identified as ellipticity-induced Alfvén eigenmodes (EAEs) occurring at q=1 rational surfaces by magnetohydrodynamics (MHD) simulations using the realistic geometry and plasma profiles. The EAEs show regular bursts with ~10 milliseconds duration along with the mode frequency chirping downwards and upwards rapidly. It is also found that sawtooth events can interrupt the growth and evolution of the EAEs, causing the modes to disappear immediately. Passing energetic electrons (EEs) that move much faster than Alfvén velocity are responsible for the destabilization of these EAEs, which attribute to the fact that the large poloidal and toroidal frequencies mostly cancel each other and satisfy the EAE resonance condition with primary energy exchange. These novel experimental results of the wave-particle interaction between EAEs and EEs are helpful for extrapolating alpha particle physics that are characterized by small orbit width with respect to machine size in future fusion reactors.

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Section: Experimental Setup and Observationsmentioning

confidence: 67%

Bursting core-localized ellipticity-induced Alfvén eigenmodes driven by energetic electrons during EAST ohmic discharges

Su,

Lan,

Zhou

et al. 2024

Nucl. Fusion

View full text Add to dashboard Cite

show abstract

Toroidal Alfvén eigenmodes excited by energetic electrons in EAST low-density ohmic plasmas

Zhu,

Qiu,

Bao

et al. 2024

Nucl. Fusion

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Operation in the quiescent regime with abundant trapped energetic electrons (EEs) has been achieved during the current flattop in EAST low-density Ohmic plasmas. This was facilitated by increasing the electron density to a specified level and subsequently reducing it slowly, resulting in the accumulation of a sufficient number of trapped EEs within the energy range of 150–250 keV. During the phase of decreasing electron density, toroidal Alfvén eigenmodes (TAEs) were observed to be excited by these EEs, with frequencies falling within the range of about 100–300 kHz. The experimental parameters were carefully set to satisfy the resonance conditions for TAE excitation by EEs, aligning well with predictions from ideal MHD theory. Statistical analysis indicated different density dependencies between the frequencies of TAEs and the Alfvén frequencies, due to their different radial excitation positions. The radial positions of the TAEs were found to be influenced by the energy distribution and the evolution of trapped EEs, which in turn were affected by the decay rate of electron density and loop voltage. Measurements of Hard X-rays (HXR) confirmed an energy distribution characterized by a “bump-on-tail” shape, with the TAEs observed near the energy bump. Theoretical considerations also demonstrate the possibility that the e-TAE can be driven unstable under this experiment condition even if the mode does not rotate in the electron-diamagnetic drift direction.

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Runaway electron dynamics in Experimental Advanced Superconducting Tokamak helium plasmas

Cited by 2 publications

References 34 publications

Bursting core-localized ellipticity-induced Alfvén eigenmodes driven by energetic electrons during EAST ohmic discharges

Bursting core-localized ellipticity-induced Alfvén eigenmodes driven by energetic electrons during EAST ohmic discharges

Toroidal Alfvén eigenmodes excited by energetic electrons in EAST low-density ohmic plasmas

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