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The penetration of an edge-localized mode (ELM) into an internal transport barrier (ITB) plasma has been studied on the EAST tokamak with a flat central safety factor profile q(0) ∼ 1 recently. The experiment indicates that when the ELM inward penetration radius reaches the ITB foot region, a significant influence on the ITB plasma is manifested, leading to the shrinking or collapse of the ITB on the EAST tokamak. Observations suggest that the onset of large ELM penetration, which extremely reduces the pedestal temperature and density, can trigger the collapse of the ITB, by means of the off-axis sawtooth on the EAST tokamak. The off-axis sawtooth events contribute to a further decrement in the core stored energy after a larger ELM crash in the pedestal region. The reversal surface of the off-axis sawtooth is situated around the ITB foot. The delay time between the ELM penetration reached to the ITB foot and the followed off-axis sawtooth collapse is about 2–3 ms. It is also found that the expanding of ITB is related to the net heating power. Mechanism of ITB collapse from ELM penetration to the off-axis sawtooth triggered is not yet clear. Experimental results for understanding ELM penetration in ITB plasmas are summarized and discussed.

The I-mode is a promising tokamak operational regime characterized by a high energy confinement and the absence of type-I edge localized modes (ELMs). However, I-mode plasmas occasionally exhibit small ELM-like events known as pedestal relaxation events (PREs), transiently elevating the heat flux on the divertor targets. These PREs have been observed on ASDEX Upgrade (AUG) and Alcator C-Mod. In this work, BOUT++ simulation using the AUG experimental equilibrium and profiles are conducted. The three-field simulation yields a stable outcome, indicating that the PRE profile is peeling and ballooning (P-B) mode stable. In the six-field nonlinear simulations, an I-mode PRE was successfully reproduced in both a qualitative and near-quantitative sense, with PRE characteristics, including time scales, weakly coherent mode (WCM) frequency, and four eigenfrequencies of precursor oscillations (75, 50, 35 and 16 kHz), all exhibiting excellent agreement with experimental observations. Based on the dominant toroidal mode numbers, the entire evolution can be divided into three phases. The first phase is dominated by drift-wave, exhibiting clear WCM characteristics. During the second phase, when the collapse begins to develop, cross-phase analysis reveals a value close to π / 2 between the potential and electron temperature perturbations, indicating that the interchange mode acts as the direct trigger of the PRE. Further analysis of turbulence and transport confirms that the triggering region is located within the area of WCM turbulence. This work proposes a physical picture of the PRE in which drift-wave turbulence evolves into interchange modes, ultimately leading to a pedestal collapse.

Pedestal turbulence spreading into a crape-off layer (SOL) can be used to explain the experimentally observed strong pedestal-SOL coupling and is expected to be important for the broadening of divertor deposition profiles in future devices (Xu et al 2019 Nucl. Fusion 59 126039). In the EAST tokamak, it is found that an electromagnetic (EM) mode in the pedestal region can spread into the SOL and broaden the divertor particle flux width. Multi-channel fluctuation reflectometry is used to measure the density fluctuations at the plasma edge. The EM mode rotates in the electron diamagnetic drift direction in the lab frame with a frequency range of [40–90] kHz, toroidal mode number n= 12–13 and poloidal wavenumber kθ = 0.41 cm−1. The mode amplitude peaks around the maximum of the pedestal density gradient. As the mode amplitude increases, the reflectometry channel in the SOL can clearly capture the mode. This result suggests that the EM mode is excited in the pedestal gradient region and spreads into the SOL. It is further found that the particle flux deposition profile in the divertor is broadened as the EM mode appears.

The edge coherent mode (ECM) is considered a highly attractive pedestal mode because it extends the duration of edge-localized modes and increases particle and impurity transport without significantly affecting energy transport. Moreover, it operates compatibly with high-performance plasma discharges. The ECM can also be detected using Langmuir probes on the divertor target plate, indicating that it extends from the pedestal region into the SOL and resulting in a connection to the divertor target plate via magnetic field lines. In this work, the distribution of ECM on divertor target plates is investigated by analyzing 215 upper single null discharges on the EAST tokamak. The coherence analysis of plasma fluctuations between the electron cyclotron emission signal in the pedestal region of the outer midplane and the ion saturation current measured by Langmuir probes in the divertor region reveals that the ECM is hardly detected by the divertor probe close to the outer strike point but can be observed at far SOL. This finding indicates the presence of an ECM quiescent region near the SOL on the divertor plate, and the extent of the quiescent region in the poloidal flux coordinate (Δ) has been statistically analyzed. A pronounced relationship between Δ and triangularity (δ) has been observed, that is Δ increasing with δ. Further analysis reveals that this relationship can be attributed to the average magnetic shear in the SOL. This result is consistent with the physical picture, which states that strong magnetic shear close to X-point significantly squeezes the cross-section of flux tubes down to scales dominated by collisions.

The improved energy confinement mode (I-mode) is widely considered as an important operation regime for ITER. I-mode implementation depends on the specified basic plasma parameters and certain operation conditions, which are discovered by statistical plasma characteristics from a large number of I-mode discharges on a tokamak. The extraction process of I-mode plasma characteristics is complicated, time-consuming, and limited to the sampling rate of the measured signals. Experimental observation of the I-mode is accompanied by the appearance of a weakly coherent mode (WCM). However, it takes much time to accurately scan and quantify WCM characteristics when analyzing many I-mode discharges. Recently, a neural network identification method was developed as an I-mode detector to traverse a whole database as a replacement for manual identification. Two fully connected neural network models were trained with the spectrum of propagation velocity of density perturbation from Doppler backward scattering and the electron density measured by a polarimeter-interferometer system with the experimental advanced superconducting tokamak I-mode database. An accuracy of 98.30% in identifying WCMs in I-mode discharges is achieved with the WCM classification model. In addition, the regime classification model was also utilized to successfully distinguish between the low confinement mode (L-mode), I-mode, and high confinement mode (H-mode) with 96.03% accuracy. Finally, ablation experiments were performed on the regime classifiers, showing that there is potential for further performance improvement with future use of RNN model.

This paper reports the recent observation of a weakly coherent mode (WCM) within a conventional reflectometer on EAST and successfully determines its poloidal wavenumber range. During the transition from the L-mode to I-mode, the line-averaged density remains nearly unchanged while a significant change is observed in the electron cyclotron emission (ECE) signals at the boundary. The difference between the signals for the two channels at the edge increased, coinciding with the appearance of the WCM and a simultaneous rise in the boundary electron temperature. Further investigation unveiled the modulating role of edge temperature ring oscillation (ETRO) (Liu et al 2020 Nucl. Fusion 60 126016) on high-frequency density fluctuations. Statistical results unveil an inverse relationship between the centeral frequency of the WCM and q 95. Simulation results provide additional insights, demonstrating that the simulated ‘WCM’ in the density fluctuations aligns with experimental data in terms of center frequency. Additionally, the radial distribution of the simulated ‘WCM’ closely corresponds to regions with the strongest electron temperature gradients. Finally, through a cross-correlation analysis of the simulated fluctuations, the following phase relationship for the wavenumber range of ‘WCM’ was observed: αT~e>αn~i∼αϕ~>αT~i .

Background Appetitive traits in childhood such as food responsiveness and enjoyment of food have been associated with body mass index (BMI) in later childhood. However, data on appetitive traits during infancy in relation to BMI in later childhood are sparse. We aimed to relate appetitive traits in infancy to subsequent BMI and weight gain up to 24 months of age. Methods Data of 210 infants from the Singapore GUSTO mother-offspring cohort was obtained. The Baby Eating Behavior Questionnaire (BEBQ) and the Child Eating Behavior Questionnaire (CEBQ) were administered to mothers when their offspring were aged 3 and 12 months respectively. Height and weight of offspring were measured at ages 3, 6, 9,12,15,18 and 24 months. The association of appetitive traits with both BMI z-score and weight gain were evaluated using multivariate linear regression. Results Food responsiveness at 3 months was associated with higher BMI from 6 months up to 15 months of age ( p  < 0.01) and with greater weight gain between 3 and 6 months of age ( p  = 0.012). Slowness in eating and satiety responsiveness at 3 months was significantly associated with lower BMI at 6 months ( p  < 0.01) and with less weight gain between 3 to 6 months of age ( p  = 0.034). None of the appetitive traits at 12 months were significantly associated with BMI or weight gain over any time period. Conclusion Early assessment of appetitive traits at 3 months of age but not at 12 months of age was associated with BMI and weight gain over the first two years of life. Trial registration Clinical Trials identifier NCT01174875