Upgrade of the Mirnov probe arrays on the J-TEXT tokamak

Guo, Daojing; Hu, Qiming; Li, Da; Shen, Chengshuo; Wang, Nengchao; Huang, Zhuo; Huang, Mingxiang; Ding, Yonghua; Xu, Guo Sheng; Yu, Q.; Tang, Yuejin; Zhuang, G.

doi:10.1063/1.4996360

Cited by 23 publications

(22 citation statements)

References 11 publications

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“…MHD activity can be studied by the upgraded Mirnov probes, including poloidal and toroidal mode evolutions [34]. The toroidal probe array consists of 16 probe modules distributed uniformly in the toroidal direction at θ = −45°.…”

Section: Key Diagnosticsmentioning

confidence: 99%

The impact of an m/n = 2/1 locked mode on the disruption process during a massive gas injection shutdown on J-TEXT

et al. 2019

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Locked modes (LMs) will be one of the major causes of disruptions in the ITER tokamak. Disruption mitigation systems (DMSs), such as massive gas injection (MGI) or shattered pellet injection (SPI), are expected to be deployed in pre-disruption discharges with large pre-existing locked modes. A series of target plasmas with an m/n = 2/1 locked mode induced by resonant magnetic perturbation (RMP) penetration was terminated by an MGI on the J-TEXT tokamak. The penetration of the injected impurities during the process was diagnosed using a fast frame visible camera and a multi-channel polarimeter-interferometer (POLARIS) in combination. The electron temperature evolution during thermal quench (TQ) is also shown in detail. It is found that both the phase and width of the 2/1 mode have an effect on MGI shutdown dynamics. When the mode is larger than the critical width, the penetration depth and assimilation of impurities can be enhanced during pre-TQ, leading to a faster quenching process if the relative phase between the O-point of the 2/1 mode and the MGI valve is ∆φ = +90°. Conversely, the penetration depth and assimilation of impurities are suppressed, leading to a slower TQ when the relative phase is ∆φ = −90°. The toroidal radiation asymmetry is worse with the locked mode. The results suggest that the 3D effect between the injected impurities and the 2/1 locked mode is important during the disruption mitigation process.

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Section: Key Diagnosticsmentioning

confidence: 99%

The impact of an m/n = 2/1 locked mode on the disruption process during a massive gas injection shutdown on J-TEXT

et al. 2019

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“…Array 1 is installed at ϕ Mir1 = 258.75° with 24 modules measuring both the poloidal and radial magnetic fields. In the fall of 2017, array 2 was installed at ϕ Mir2 = 56.25° with 48 modules [22].…”

Section: Methodsmentioning

confidence: 99%

Formation of the non-axisymmetric helical current driven by a biased electrode in the scrape-off layer on J-TEXT

et al. 2019

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Resonant magnetic perturbations (RMPs), which change the magnetic topology, have been applied to control the edge-localized modes (ELMs) in many tokamak experiments. The non-axisymmetric helical currents induced by lower hybrid waves in the scrape-off layer (SOL) were observed to impact the magnetic topology profoundly and mitigated ELMs strongly in EAST (Liang et al 2013 Phys. Rev. Lett. 110 235002). In this paper, we present electrode biasing in the SOL as an alternative method to drive the non-axisymmetric helical currents in J-TEXT. A significant SOL current (e.g. ~150 A) was induced through the electrode with a biasing voltage of +200 V. The measured magnetic fields perturbed by the biasing current are consistent with those calculated from the helical currents flowing along the opened magnetic field lines in the SOL. This consistency reveals that the biased electrode induced non-axisymmetric helical currents in the SOL. The 3/1 component of the RMP field generated by the non-axisymmetric helical current can reach 13 Gauss kA−1 at the last closed flux surface. This indicates that the non-axisymmetric helical currents driven by biasing in the SOL might be an attractive new method for producing an RMP field and hence for controlling plasma instabilities such as ELMs.

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“…There are two poloidal arrays of 2D Mirnov coils and one array of 24 coils (arranged in a circular shape) for the detection of MHD activities [20,23]. The electron cyclotron emission (ECE) diagnostic system consists of a 16-channel heterodyne ECE detecting unit and a new 8-channel W-band detecting unit, which covers a large portion of the plasma and has a temporal resolution of 2 μs and a spatial resolution of less than 1.5 cm [24,25].…”

Section: Methodsmentioning

confidence: 99%

Study of MHD mode and cooling process during disruptions triggered by impurities injection in J-TEXT

Huang¹,

Chen²,

Hu³

et al. 2018

Nucl. Fusion

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The injection of a large amount of impurities is one of the possible ways of mitigating disruption in large-scale tokamaks. The deposition of impurities at the center of the plasma is the key to the radiation of plasma energy and suppression of runaway. The interaction of the gas jet with the rational surfaces has been studied by scanning the plasma current. The experimental results show that the injection of a massive amount of argon can cool the plasma from the edge to the core region, and the cooling process is accompanied by different magnetohydrodynamic (MHD) modes when the gas jet reaches the corresponding rational surfaces. It is observed that with different edge safety factors and electron density, gas injection can induce different poloidal modes at first. Then, the poloidal mode traverses to lower m (where m is the poloidal mode number) MHD activities until a 2/1 mode is initiated and a thermal quench is started. The experimental results show that the penetration of a gas jet across the rational surfaces is faster in the plasmas with pre-existing large 2/1 tearing modes, which indicates that the 2/1 mode plays an important role in the penetration process. Disruptions triggered by supersonic molecular beam injection display a slower cooling process compared with massive gas injection, which can be divided into four stages. The dominant poloidal mode transition from m = 3 to m = 2 is associated with electron temperature recovery.

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Upgrade of the Mirnov probe arrays on the J-TEXT tokamak

Cited by 23 publications

References 11 publications

The impact of an m/n = 2/1 locked mode on the disruption process during a massive gas injection shutdown on J-TEXT

The impact of an m/n = 2/1 locked mode on the disruption process during a massive gas injection shutdown on J-TEXT

Formation of the non-axisymmetric helical current driven by a biased electrode in the scrape-off layer on J-TEXT

Study of MHD mode and cooling process during disruptions triggered by impurities injection in J-TEXT

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