MARFE movement and density fluctuations after deuterium pellet injections in H-mode plasmas on EAST tokamak

Hou, Jilei; Chen, Yue; Zuo, Guizhong; Hu, Jiansheng; Mao, Shifeng; Yuan, Xiaolin; Huang, Jia; Wu, Mingfu; Xu, Liqing; Zhao, Hailin; Yuan, Jiahu; Wang, Shouxin; Liu, Haiqing; Meng, Lingyi; Shi, Tongyu; Li, Pan; Li, Jiangang

doi:10.1088/1361-6587/ac6048

Cited by 4 publications

(3 citation statements)

References 40 publications

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“…Each pellet takes on a cylindrical shape, possessing a diameter and length of 2 mm, and encapsulating an estimated 3.8 × 10 20 atoms. The injection process is subject to a maximum velocity constraint of 100 m s −1 and a frequency ceiling of 10 Hz [23].…”

Section: Methodsmentioning

confidence: 99%

Observation of local density increase during pellet homogenization on EAST

Huang,

Zhang,

Zhang

et al. 2023

Nucl. Fusion

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By combining the X-mode polarized lower and upper cut-off reflections obtained from the density profile reflectometer, we have successfully attained a comprehensive density profile spanning from the edge to the core region in pellet injection (PI) experiments on EAST. During the homogenization process after PI on EAST, an innovative method was introduced to quantify the local density increase. This approach employed the distinctive ‘dual-reflection’ phenomenon observed in the EAST microwave reflectometer, encompassing measurements of both the X-mode lower and upper cut-off frequencies. Furthermore, experimental investigations were carried out on EAST to comprehensively explore the parallel and poloidal expansion of the high-density pellet cloud. Notably, this study marks the first instance of measuring expansion velocities of pellet materials in both parallel and poloidal directions on EAST. A comparative analysis was performed initially between these experimental measurements and simulation results obtained from the HPI2 code, marking a pivotal stride towards enhancing its applicability in EAST.

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Section: Methodsmentioning

confidence: 99%

Observation of local density increase during pellet homogenization on EAST

Huang,

Zhang,

Zhang

et al. 2023

Nucl. Fusion

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“…[26] In EAST's pellet injection discharges, the MARFE becomes unstable and moves when the symmetry of heat flow on the two sides of it is broken. [27] The experiment on J-TEXT shows that localized current shrinkage happens before MARFE causes disruption. [9] The above results show that there is no unified physical model to use single or few plasma parameters to give warnings of MARFE movement.…”

Section: Introductionmentioning

confidence: 99%

Prediction of multifaceted asymmetric radiation from the edge movement in density-limit disruptive plasmas on Experimental Advanced Superconducting Tokamak using random forest

Hou

Luo

et al. 2023

Chinese Phys. B

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MARFE movement which can cause density limit disruption is often encountered during high density operation on many tokamaks. Therefore, identifying and predicting MARFE movement is meaningful to mitigate or avoid density limit disruption for the steady-state high-density plasma operation. A machine learning method named Random Forest (RF) has been used to predict the MARFE movement based on the density ramp-up experiment in the 2022’s first campaign of EAST. The RF model shows that besides Greenwald fraction which is the ratio of plasma density and Greenwald density limit, dβ p /dt, H 98 and dW mhd /dt relatively important parameters for MARFE-movement prediction. Applying the RF model on test discharges, the test results show that the successful alarm rate for MARFE movement causing density limit disruption reaches ~85% with a minimum alarm time of ~40 ms and mean alarm time of ~700 ms. At the same time, the false alarm rate for non-disruptive and non-density-limit disruptive discharges can be kept below 5%. These results provide a reference to the prediction of MARFE movement in high density plasmas, which can help the avoidance or mitigation of density limit disruption in future fusion reactors.

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“…In addition, the pellet injection system on EAST are capable of injecting the pellet both from the high field side (HFS) and the low field side (LFS) at a velocity of 100-300 m•s −1 with a maximum injection frequency of 10 Hz. [17] PI is also the preferred injection method for the future fusion reactors such as ITER. This method requires a highly integrated pellet injection system that applies vacuum, low-temperature, and high-pressure technologies.…”

Section: Introductionmentioning

confidence: 99%

Simulation of deuterium pellet ablation and deposition in the EAST tokamak with HPI2 code

Li 李,

Zhang 张,

Hou 侯

et al. 2024

Chinese Phys. B

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Pellet injection is a primary method for fueling the plasma in magnetic confinement devices. For that goal the knowledge of pellet ablation and deposition profiles are critical. In the present study, the pellet fueling code HPI2 was used to predict the ablation and deposition profiles of deuterium pellets injected into a typical H-mode discharge on EAST tokamak. Pellet ablation and deposition profiles were evaluated for various pellet injection locations, with the aim to optimize the pellet injection to obtain a deep fueling depth. In this study, we investigated the effect of the injection angle on the deposition depth of the pellet at different velocities and sizes. The ablation and deposition of the injected pellet were mainly studied at each injection position for three different injection angles: 0°, 45°, and 60°. The pellet injection on the high field side (HFS) can achieve a more ideal deposition depth than on the low field side (LFS). Among these angles, horizontal injection on the middle plane is relatively better on either the HFS or the LFS. When the injection location is 0.468 m below the middle plane on the HFS or 0.40 m above the middle plane of the LFS, it can achieve a similar deposition depth to the one of its corresponding side. When the pre-cooling effect is taken into account, the deposition depth was predicted to increase only slightly when the pellet was launched from the HFS. The findings of this study will serve as a reference for the update of pellet injection systems for EAST tokamak.

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MARFE movement and density fluctuations after deuterium pellet injections in H-mode plasmas on EAST tokamak

Cited by 4 publications

References 40 publications

Observation of local density increase during pellet homogenization on EAST

Observation of local density increase during pellet homogenization on EAST

Prediction of multifaceted asymmetric radiation from the edge movement in density-limit disruptive plasmas on Experimental Advanced Superconducting Tokamak using random forest

Simulation of deuterium pellet ablation and deposition in the EAST tokamak with HPI2 code

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