Analysis of electron temperature, impurity transport and MHD activity with multi-energy soft x-ray diagnostic in EAST tokamak

Lan, H.; Xu, Guosheng; Tritz, K.

doi:10.1088/2058-6272/aa8cbf

Cited by 4 publications

(1 citation statement)

References 38 publications

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“…During this period, the pedestal profiles evolve, as shown in figure 3. The pedestal electron temperature T e increases slightly after switching on the LHW power (figure 3(d)), probably due to the LHW-induced electron heating, as measured by an edge tangential multiplyenergy soft-X array system 184.5 mm above the outer midplane at a temporal resolution of 10 kHz and spatial resolution of ∼1 cm [19,20], absolutely calibrated with the Thomson scattering data which has a much lower temporal resolution (5 Hz). Figure 3(a) shows pedestal density profiles measured by an X-mode frequency-sweeping (32-110 GHz, cover Q/V/ W band) reflectometer at a temporal resolution of 50 μs [22], averaged over ±150 μs for each profile.…”

Section: Pedestal Profile Evolution During Elm Pacingmentioning

confidence: 99%

Pace making of edge localized modes with low-hybrid-wave power pulses in the EAST superconducting tokamak

Yang

Wan

et al. 2019

Plasma Phys. Control. Fusion

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Pace making of the edge-localized modes (ELMs) by low-hybrid-wave (LHW) power modulation has been observed in the EAST superconducting tokamak when the modulation frequency is sufficiently close to the natural-ELM frequency, i.e. within ±30%f ELM . The highest pace-making frequency obtained so far is 120 Hz. The ELM triggering is typically delayed by 1-2 ms relative to the LHW power rising edge, during which the pedestal profiles evolve. The mechanism of the synchronized triggering of ELMs was found due to the LHW-induced pedestal density pumpout. A previous study indicates that LHW generates field-aligned helical current filaments in the scrape-off layer (SOL) (Liang et al 2013 Phys. Rev. Lett. 110 235002), which produces three-dimensional (3D) magnetic topology change at the plasma edge similar to the effect of the resonant magnetic perturbations. The observed pedestal density pumpout, local flattening of the density gradient near the separatrix and steepening near the pedestal top may be induced by the 3D effect. Pedestal linear stability analysis using ELITE code indicates that the pedestal is approaching the peeling-ballooning stability boundary as the profile is getting steep near the pedestal top until the ELM is triggered. The power threshold for the ELM pacing with 2.45 GHz LHW is ∼1 MW.

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Section: Pedestal Profile Evolution During Elm Pacingmentioning

confidence: 99%

Pace making of edge localized modes with low-hybrid-wave power pulses in the EAST superconducting tokamak

Yang

Wan

et al. 2019

Plasma Phys. Control. Fusion

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Experimental observation of coexisting electromagnetic fluctuations correlating with the inter-ELM pedestal evolution on EAST

Lan

Chen

et al. 2019

Physics of Plasmas

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Correlations between the edge fluctuations and the pedestal evolution during the relatively large edge localized mode (ELM) cycles at high pedestal normalized electron collisionality (νe,ped* > 1) on the EAST tokamak are investigated. Not only the edge electrostatic coherent mode (ECM, ∼50 kHz) and the low frequency magnetic coherent mode (MCM, ∼32 kHz) but also a high frequency electromagnetic mode (HFM, >150 kHz) are observed to be coexisting between ELMs. After the ELM crash, the pedestal electron temperature recovered faster than the pedestal electron density. It is found that the saturation of the ECM coincides more with the saturation of the pedestal electron density, while the saturation of the HFM and MCM coincides more with the saturation of the pedestal electron temperature. In addition, the characteristics of the electromagnetic fluctuations (the HFM and MCM) are studied in detail: the HFM propagates in the electron diamagnetic drift direction in the laboratory frame with an average poloidal wave number of k¯θHFM≈0.17 cm−1, while the MCM propagates in the ion diamagnetic drift direction in the laboratory frame with k¯θMCM ≈ 0.12 cm−1 and the toroidal mode number of n = 1. Furthermore, both the HFM and MCM have inward average radial wave numbers of k¯RHFM≈0.13 cm−1 and k¯RMCM≈4.64 cm−1. The bispectral analysis shows that the HFM and MCM have strong nonlinear interactions. The HFM is clearly observed on both low and high field side Mirnov coils, which might suggest a feature beyond a ballooning type instability, e.g., the kinetic ballooning mode. These studies may contribute to a better understanding of the pedestal evolution.

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Modular bolometric/soft x-ray diagnostic in Sino-UNIted Spherical Tokamak

Yang

Wang

Tan

et al. 2021

Review of Scientific Instruments

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A bolometer/soft x-ray diagnostic based on modular absolute extreme ultraviolet photodiodes has been built to obtain the local emission profile of a poloidal cross section in Sino-UNIted Spherical Tokamak (SUNIST). The system consists of seven photodiode arrays of 112 channels located around the low field side of a poloidal cross section. All arrays are mounted into 81 × 36 × 33 mm3 modules, which could be installed flexibly on the wall of the vacuum vessel. Tungsten shields with adjustable pinholes restrict the radiation flux. Compact flexible printed circuits with multilayer copper polygon poured on both sides are designed to transmit signals with electronic noise, which is reduced to less than 1/10 before. A two-stage transimpedance amplifier array of 700 kHz bandwidth is fixed on the atmosphere side of a vacuum electrical feedthrough and is powered by battery packs. A synchronized switch shuts down the circuit to reduce the heat production and increase the battery life. A line-integrated radiation emission profile with 2 cm spatial resolution and temporal resolution up to 2 µs is obtained, and the local emission profile of SUNIST is reconstructed with the help of a newly developed tomography scheme for movable detector modules.

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Analysis of electron temperature, impurity transport and MHD activity with multi-energy soft x-ray diagnostic in EAST tokamak

Cited by 4 publications

References 38 publications

Pace making of edge localized modes with low-hybrid-wave power pulses in the EAST superconducting tokamak

Pace making of edge localized modes with low-hybrid-wave power pulses in the EAST superconducting tokamak

Experimental observation of coexisting electromagnetic fluctuations correlating with the inter-ELM pedestal evolution on EAST

Modular bolometric/soft x-ray diagnostic in Sino-UNIted Spherical Tokamak

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