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Featured researches published by D. W. Huang.


Review of Scientific Instruments | 2014

Upgraded high time-resolved x-ray imaging crystal spectroscopy system for J-TEXT ohmic plasmas

Wei Jin; Z. Y. Chen; D. W. Huang; Q. L. Li; W. Yan; Y. H. Luo; S. G. Lee; Y.J. Shi; Yunhui Huang; R. H. Tong; Z. J. Yang; B. Rao; Yonghua Ding; G. Zhuang

This paper presents the upgraded x-ray imaging crystal spectrometer (XICS) system on Joint Texas Experimental Tokamak (J-TEXT) tokamak and the latest experimental results obtained in last campaign. With 500 Hz frame rate of the new Pilatus detector and 5 cm × 10 cm spherically bent crystal, the XICS system can provide core electron temperature (Te), core ion temperature (Ti), and plasma toroidal rotation (VΦ) with a maximum temporal resolution of 2 ms for J-TEXT pure ohmic plasmas. These parameters with high temporal resolution are very useful in tokamak plasma research, especially for rapidly changed physical processes. The experimental results from the upgraded XICS system are presented.


Review of Scientific Instruments | 2014

Designing of the massive gas injection valve for the joint Texas experimental tokamak

Y. H. Luo; Z. Y. Chen; Y. Tang; S.Y. Wang; W. G. Ba; Y. N. Wei; T K Ma; D. W. Huang; R. H. Tong; W. Yan; P. Geng; J. Shao; G. Zhuang

In order to mitigate the negative effects of the plasma disruption a massive gas injection (MGI) valve is designed for the joint Texas experimental tokamak. The MGI valve is based on the eddy-current repulsion mechanism. It has a fueling volume of 30 ml. The piston of the MGI valve is made by non-ferromagnetic material, so it can be installed close to the vacuum vessel which has a strong toroidal magnetic field. A diode is use to prevent current oscillation in the discharge circuit. The drive coil of the valve is installed outside the gas chamber. The opening characteristics and the gas flow of the MGI valve have been tested by a 60 l vacuum chamber. Owing to the large electromagnetic force the reaction time of the valve is shorter than 0.3 ms. Duration for the opening of the MGI valve is in the order of 10 ms.


Review of Scientific Instruments | 2014

Hard X-ray spatial array diagnostics on Joint Texas Experimental Tokamak

D. W. Huang; Z. Y. Chen; Y. H. Luo; R. H. Tong; W. Yan; Wei Jin; G. Zhuang

A spatially distributed hard X-ray detection array has been developed to diagnose the loss of runaway electron with toroidal and poloidal resolution. The hard X-ray radiation in the energy ranges of 0.3-1 MeV resulted from runaway electrons can be measured. The detection array consists of 12 CdTe detectors which are arranged surrounding the tokamak. It is found that most runaway electrons which transport to plasma boundary tend to loss on limiters. The application of electrode biasing probe resulted in enhancement of local runaway loss. Resonant magnetic perturbations enhanced the runaway electrons diffusion and showed an asymmetric poloidal loss rate.


Nuclear Fusion | 2016

Simulation of runaway electrons, transport affected by J-TEXT resonant magnetic perturbation

Z.H. Jiang; X H Wang; Z.Y. Chen; D. W. Huang; X.F. Sun; T. Xu; G. Zhuang

The topology of a magnetic field and transport properties of runaway electrons can be changed by a resonant magnetic perturbation field. The J-TEXT magnetic topology can be effectively altered via static resonant magnetic perturbation (SRMP) and dynamic resonant magnetic perturbation (DRMP). This paper studies the effect of resonant magnetic perturbation (RMP) on the confinement of runaway electrons via simulating their drift orbits in the magnetic perturbation field and calculating the orbit losses for different runaway initial energies and different runaway electrons, initial locations. The model adopted is based on Hamiltonian guiding center equations for runaway electrons, and the J-TEXT magnetic turbulences and RMP are taken into account. The simulation indicates that the loss rate of runaway electrons is sensitive to the radial position of electrons. The loss of energetic runaway beam is dominated by the shrinkage of the confinement region. Outside the shrinkage region of the runaway electrons are lost rapidly. Inside the shrinkage region the runaway beam is confined very well and is less sensitive to the magnetic perturbation. The experimental result on the response of runaway transport to the application RMP indicates that the loss of runaway electrons is dominated by the shrinkage of the confinement region, other than the external magnetic perturbation.


Nuclear Fusion | 2016

The behavior of runaway current in massive gas injection fast shutdown plasmas in J-TEXT

Z.Y. Chen; D. W. Huang; Y.H. Luo; Y. Tang; Y B Dong; L. Zeng; R. H. Tong; S.Y. Wang; Y. N. Wei; X H Wang; Xiang Jian; J. C. Li; X. Q. Zhang; B. Rao; W. Yan; T K Ma; Qiming Hu; Z. J. Yang; L. Gao; Yonghua Ding; Zhanhui Wang; Ming Zhang; G. Zhuang; Yuan Pan; Z.H. Jiang

Runaway currents following disruptions have an important effect on the first wall in current tokamaks and will be more severe in next generation tokamaks. The behavior of runaway currents in massive gas injection (MGI) induced disruptions have been investigated in the J-TEXT tokamak. The cold front induced by the gas jet penetrates helically along field lines, preferentially toward the high field side and stops at a location near the q = 2 surface before the disruption. When the cold front reaches the q = 2 surface it initiates magnetohydrodynamic activities and results in disruption. It is found that the MGI of He or Ne results in runaway free shutdown in a large range of gas injections. Mixture injection of He and Ar (90% He and 10%Ar) consistently results in runaway free shutdown. A moderate amount of Ar injection could produce significant runaway current. The maximum runaway energy in the runaway plateau is estimated using a simplified model which neglects the drag forces and other energy loss mechanisms. The maximum runaway energy increases with decreasing runaway current. Imaging of the runaway beam using a soft x-ray array during the runaway current plateau indicates that the runaway beam is located in the center of the plasma. Resonant magnetic perturbation (RMP) is applied to reduce the runaway current successfully during the disruption phase in a small scale tokamak, J-TEXT. When the runaway current builds up, the application of RMP cannot decouple the runaway beam due to the lower sensitivity of the energetic runaway electrons to the magnetic perturbation.


Review of Scientific Instruments | 2014

Wavelength calibration of x-ray imaging crystal spectrometer on Joint Texas Experimental Tokamak.

W. Yan; Z. Y. Chen; Wei Jin; D. W. Huang; Yonghua Ding; J. C. Li; X. Q. Zhang; S. G. Lee; Y.J. Shi; G. Zhuang

The wavelength calibration of x-ray imaging crystal spectrometer is a key issue for the measurements of plasma rotation. For the lack of available standard radiation source near 3.95 Å and there is no other diagnostics to measure the core rotation for inter-calibration, an indirect method by using tokamak plasma itself has been applied on joint Texas experimental tokamak. It is found that the core toroidal rotation velocity is not zero during locked mode phase. This is consistent with the observation of small oscillations on soft x-ray signals and electron cyclotron emission during locked-mode phase.


Review of Scientific Instruments | 2016

Observation of runaway electrons by infrared camera in J-TEXT

R. H. Tong; Z.Y. Chen; Ming Zhang; D. W. Huang; W. Yan; G. Zhuang

When the energy of confined runaway electrons approaches several tens of MeV, the runaway electrons can emit synchrotron radiation in the range of infrared wavelength. An infrared camera working in the wavelength of 3-5 μm has been developed to study the runaway electrons in the Joint Texas Experimental Tokamak (J-TEXT). The camera is located in the equatorial plane looking tangentially into the direction of electron approach. The runaway electron beam inside the plasma has been observed at the flattop phase. With a fast acquisition of the camera, the behavior of runaway electron beam has been observed directly during the runaway current plateau following the massive gas injection triggered disruptions.


Nuclear Fusion | 2016

Enhancement of runaway production by resonant magnetic perturbation on J-TEXT

Z.Y. Chen; D. W. Huang; V.A. Izzo; R. H. Tong; Z.H. Jiang; Qiming Hu; Y. N. Wei; W. Yan; B. Rao; S.Y. Wang; T K Ma; S.C. Li; Z. J. Yang; D.H. Ding; Zhanhui Wang; Ming Zhang; G. Zhuang; Yuan Pan; J-Text Team

The suppression of runaways following disruptions is key for the safe operation of ITER. The massive gas injection (MGI) has been developed to mitigate heat loads, electromagnetic forces and runaway electrons (REs) during disruptions. However, MGI may not completely prevent the generation of REs during disruptions on ITER. Resonant magnetic perturbation (RMP) has been applied to suppress runaway generation during disruptions on several machines. It was found that strong RMP results in the enhancement of runaway production instead of runaway suppression on J-TEXT. The runaway current was about 50% pre-disruption plasma current in argon induced reference disruptions. With moderate RMP, the runway current decreased to below 30% pre-disruption plasma current. The runaway current plateaus reach 80% of the pre-disruptive current when strong RMP was applied. Strong RMP may induce large size magnetic islands that could confine more runaway seed during disruptions. This has important implications for runaway suppression on large machines.


Review of Scientific Instruments | 2018

Vertical fast electron bremsstrahlung diagnostic on J-TEXT tokamak

H. Y. Yang; Zihao Chen; D. W. Huang; R. H. Tong; W. Yan; Y. N. Wei; Z. F. Lin; A. J. Dai; H. L. Gao; Xiaolei Wang; Yuansheng Li; Wenju Li; Yunhui Huang; J. Hu; D. Q. Wang; Z. J. Yang; Z. H. Jiang

Fast electron bremsstrahlung (FEB) emission during Ohmic discharge experiments on the Joint Texas Experimental Tokamak (J-TEXT) has been measured by a recently developed vertical multi-channel FEB diagnostic based on CdZnTe detectors. There are 5 sight lines to observe the vertical emission of fast electrons at the high-field side with a spatial resolution of 5 cm. The FEB emission in the energy range of 30-300 keV can be measured. The generation of fast electrons accelerated by loop voltage has been confirmed during the early phase of discharge by analyzing the signals of FEB emission. The runaway electron beam instabilities have been observed with the FEB diagnostic on J-TEXT.


Review of Scientific Instruments | 2016

Measurement of the internal magnetic fluctuation by the transport of runaways on J-TEXT

Z.Y. Chen; D. W. Huang; R. H. Tong; W. Yan; Y. N. Wei; T K Ma; Z.H. Jiang; X. Q. Zhang; Z. P. Chen; Z. J. Yang; G. Zhuang

The measurement of internal magnetic fluctuation is important for the study of transport in tokamak plasmas. The runaway electron transport induced by the sawtooth crash can be used to obtain the internal magnetic fluctuation. Inversed sawtooth-like activities on hard x-ray (HXR) fluxes following sawtooth activities were observed after the application of electrode biasing on J-TEXT tokamak. The runaway diffusion coefficient Dr is deduced to be about 30 m2/s according to the time delay of HXR flux peaks to the sawtooth crashes. The averaged value of normalized magnetic fluctuation in the discharges with electrode biasing was increased to the order of 1 × 10-4.

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R. H. Tong

Huazhong University of Science and Technology

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W. Yan

Huazhong University of Science and Technology

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G. Zhuang

Huazhong University of Science and Technology

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Y. N. Wei

Huazhong University of Science and Technology

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T K Ma

Huazhong University of Science and Technology

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Z. Y. Chen

Huazhong University of Science and Technology

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S.Y. Wang

Huazhong University of Science and Technology

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Z. J. Yang

Huazhong University of Science and Technology

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Z.Y. Chen

Huazhong University of Science and Technology

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Z.H. Jiang

Huazhong University of Science and Technology

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