Table of Content

15 June 2019, Volume 39 Issue 2

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Plasma Physics

Observation of edge localized mode mitigation with plasma vertical jogs in HL-2A tokamak

WU Na, CHEN Shao-yong, TANG Chang-jian, SONG Xian-ming, YANG Ceng-chen, YU De-liang, XU Jian-qiang, HL-2A Team

2019, 39(2):  97-103.  DOI: 10.16568/j.0254-6086.201902001

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The plasma vertical jogging is performed by adding the square wave perturbation into horizontal field in HL-2A experiments. Edge localized mode (ELM) mitigation is observed when plasma moves upward vertically. The research finds that the plasma column expands due to formation of new edge closed flux surfaces during the upward moving, and then the pedestal widens. In addition, the recycling of working gas and impurity both increase during the ELM mitigation. The expansion of plasma column and the increasing of impurity and recycling of working gas may be the main physical factors of ELM mitigation. This work provides some reference for ELM control in future fusion devices.

Analysis and prediction of disruption induced by vertical instability on EAST

TAN Sheng-jun, ZHANG Yang, YE Min-you, ZHANG Xiao-dong, LIU Lei, LUO Zheng-ping, GONG Xian-zu

2019, 39(2):  104-111.  DOI: 10.16568/j.0254-6086.201902002

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From the 2016 EAST experiments, 119 disruption discharge data were selected to analyze the cause of the disruption and it was found that about 60% of the disruption was caused directly by the vertical instability and resulted in larger halo current and bigger electromagnetic stress that might damage the device. The reason for the disruption caused by vertical instability (hereinafter VID) (72 runs) was carefully examined in order to explain its characteristics. In addition, a prediction model based on univariate (vertical displacement) and two-dimensional variables (vertical displacement, and vertical displacement growth rate) is established for VID burst prediction. Off-line tests showed that the prediction model based on two-dimensional variables can give a disruption warning signal 20 ms before disruption, with a success rate of 93%.

Numerical simulation of magnetohydrodynamic rectangular duct flow with flow inducing strips on parallel conducting walls

XU Chao, MAO Jie, YIN Yue-guang, WANG Hao

2019, 39(2):  112-118.  DOI: 10.16568/j.0254-6086.201902003

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In order to investigate the effect of the flow inducing strips at wall on turbulent magnetohydrodynamic (MHD) flow, the liquid metal turbulent flow in a conducting rectangular duct with flow inducing strips at the centre of the parallel wall and in a standard conducting rectangular duct subjected to a uniform transverse magnetic field has been investigated numerically using our independently developed fluid-solid coupled MHD solver with low magnetic Reynolds number in OpenFOAM. Coherent structure model of large eddy simulation has been used in the simulation. The results show that the interaction between an external transverse uniform magnetic field and a flowing conducting fluid produces a Lorentz force opposite to the flowing direction, which can suppress the fluctuation of the turbulent flow. Furthermore, the suppressing effect is stronger with the increasing of the Hartmann number. With weak wall conductance ratio, the MHD turbulent flows in both ducts are transformed into laminar flow at Re=16350 and Ha=212. The wall friction coefficient increases with the increase of the Hartmann number. The flow inducing strips located at the centre of the parallel wall generate the transverse velocity and motivate turbulence. But its duct wall friction coefficient is a little bit higher than that in a standard rectangular duct.

Simulation of deposition characteristics on plasma facing components

WANG Ya-lei, CAI Lai-zhong, HU Wan-peng

2019, 39(2):  119-126.  DOI: 10.16568/j.0254-6086.201902004

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In this paper, the deposition characteristics of plasma facing components (PFCs) in plasma environment are simulated by using PEGASUS software with particle simulation method. The results show that the PFCs’ geometry, surface roughness, angle of incidence, and flux have a significant effect on the deposition. The influence of incident energy on deposition is small when the energy is small and sputtering is negligible. The smaller the roughness is, the smaller the deposition amount will be. With the same roughness, different contours can also cause large changes in deposition, and it is more possible to reduce deposition when the contour structures are conformable. This simulation is of great significance for investigating on interactions between plasma and PFCs, and analyzing the influence of tile gap dimensions, tile processing technology and plasma parameters on the deposition behaviors of PFCs.

Nuclear Fusion Engineering and Technology

Simulation on heat transfer of new type lower divertor in EAST

XU Hou-chang, LI Lei, YAO Da-mao, ZHOU Zi-bo, CAO Lei, Xu Tie-jun, HAN Le, ZI Peng-fei

2019, 39(2):  127-133.  DOI: 10.16568/j.0254-6086.201902005

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A new water-cooled tungsten lower divertor was designed to replace the present carbon lower divertor in EAST to fit the heat flux up to 10MW·m^-2 under a 400s long pulse and high β H-mode plasma operation. Based on the heat transfer simulation of the lower divertor, an advanced water-cooled structure for the lower divertor was proposed after several cooling structures were studied. According to the analysis, the divertor model of EAST which meets the requirements of heat transfer is established.

Development of the HL-2A pulse step modulation high voltage power supply control system

LI Chun-lin, WANG Ying-qiao, YAO Lie-ying,MAO Xiao-hui, LI Qing, ZHOU Pei-hai, CHENG Yong

2019, 39(2):  134-138.  DOI: 10.16568/j.0254-6086.201902006

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The research of high voltage power supply control system on HL-2A tokamak based on the pulse step modulation technology was introduced. Based on the digital signal processing technology and the field programmable gate array technology (DSP & FPGA), the control system controls 112 SPS (sample per second) modules and outputs the stable voltage according to certain control mode. DSP is responsible for data transmission, communication and control algorithms, and so on, and FPGA uses its powerful logic function to output the desired pulse. Through the programming, simulation and debugging of the program, the experimental results show that the characteristics of the control system meet the design requirements.

Pulse power control system design based on FPGA and Labview

LI Jia-qiang, HUANG Zi-bin, FENG Hu-lin, PAN Shen-min, WANG Deng-hui

2019, 39(2):  139-143.  DOI: 10.16568/j.0254-6086.201902007

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The design and implementation of pulse power control system for magnetic confinement plasma, using the field programmable gate array (FPGA) technology are presented. Virtual instrument technology, embedded control technology, serial communication technology, and optical isolation technology are used to improve the system's anti-jamming performance and programmability, and to realize logic interlock, parameter setting and remote monitoring among multiple pulse power modules. The control system is specifically composed of the upper computer interface programmed by Labview (Laboratory Virtual Instrument Engineering Workbench), lower-level machine programmed by Verilog HDL (Hardware Description Language) and dedicated photoelectric isolation conversion circuit, which is used to implement timing control of multiple pulse power supply and discharge. The experiment proves that the system is stable and has good performance under complex electromagnetic environment.

Topology design and ripple suppression of 14T MRI superconducting magnet power supply

PENG Cheng-wei1, 2, GAO Ge1, SHENG Zhi-cai1, ZHOU Yu1, 2

2019, 39(2):  144-150.  DOI: 10.16568/j.0254-6086.201902008

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According to the requirements of load stability of a power supply (low voltage of 3V, current of 1500A, and current ripple less than 1ppm) for the 14T MRI (magnetic resonance imaging) magnet (inductance 307H and a connection impedance of 2mΩ), based on the problems of common topology, a topology suitable for the operation of this large inductance superconducting magnet is proposed. The topology is a combination of multi-stage processing, passive filtering and active filtering. The power topology is presented in sequence from the input stage, the intermediate conversion stage and the output stage, and the role of the topology design of each part in the suppression of the load current ripple is highlighted. Finally, Matlab simulation analysis is carried out to verify the rationality of the topology design.

Effects of deuterium plasma pre-irradiation on the thermal shock resistance of HERF W-Y2O3 alloy

TAN Yang, LIAN You-yun, FENG Fan, CHEN Zhe, WANG Jian-bao, LIU Xiang

2019, 39(2):  151-157.  DOI: 10.16568/j.0254-6086.201902009

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The transient thermal shock resistance experiments of W-Y₂O₃ alloy before and after deuterium plasma irradiation were carried out on the 60kW Electronic-beam Materials testing Scenario (EMS-60) under the absorbed power density from 0.22GW·m^-2 to 0.44GW·m^-2. The consequences indicated that, low energy deuterium irradiation did not reduce the cracking thresholds of the W-Y₂O₃ alloy for both the forging plane (perpendicular to the forging axis) and its cross section plane (parallel to the forging axis), while the forging plane showed higher cracking threshold, surpassing 0.33GW·m^-2. By comprehensive consideration, the transient thermal shock resistance and deuterium plasma irradiation behaviors of the high energy rate forging W-Y₂O₃, the forging plane may be more suitable for facing plasma.

Experiment and analytical simulation of fatigue properties of TIG welding and electron beam welding of RAFM steel

ZHOU Hai-bao, LIU Su-mei, SUN Jin-xin, GUO Liang-liang, XIA Jun-fu, WEI Fei

2019, 39(2):  158-164.  DOI: 10.16568/j.0254-6086.201902010

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The anti-fatigue simulation of Tungsten Inert Gas (TIG) welding and electron beam welding of reduced activation ferrite martensite (RAFM) steel was carried out by using ANSYS. Two types of RAFM steel specimens of TIG welding joint and electron beam welding joint were also tested by SDS200 electro-hydraulic servo fatigue testing machine. The fatigue performance of the weld joint both on TIG welding and electron beam welding was tested by applying the same gradient load. Comparison with experimental results shows that electron beam welding is superior to TIG welding, but under certain load, TIG welding can be used instead of electron beam welding.

Study on the fracture properties of SS316LN jacket for CFETR central solenoid model coil

LI Xiang-bin, JIN Huan, YANG Dong-Sheng, QIN Jing-gang

2019, 39(2):  165-168.  DOI: 10.16568/j.0254-6086.201902011

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Fracture properties of SS316LN tube of cable in conduit conductor (CICC) of fusion reactor central solenoid (CS) model coil is studied. The test results show that the SS316LN circle in square tube has low fatigue crack growth rate performance and the fracture toughness is decreased a lot after cold working and aging heat treatment. The results provide data reference for the design and performance analysis of superconducting coils in future nuclear fusion reactor.

Experimental study on treatment of plutonium-containing wastewater based on modified co-precipitation method

YU Meng-jun, LV Xian-jin, LI Shun

2019, 39(2):  169-174.  DOI: 10.16568/j.0254-6086.201902012

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By using the co-precipitation method, a large number of sequencing batch experiments for plutonium-containing wastewater were carried out by changing the original conditions of the sedimentation process. The experimental data show that the order of adding KMnO₄, iron containing adsorbent and NaOH influences significantly the adsorbing of plutonium. The order of first adding KMnO₄, adjusting pondus hydrogenii (pH) and then adding the adsorbent in experiments has the best effect on the plutonium adsorption. When the pH of plutonium-containing wastewater is about 10, FeCl₃ and FeCl₂ mixed reagent showed better adsorption ability and rate than FeSO₄ and Fe₂(SO₄)₃ mixed reagent, FeSO₄ reagent. At the different proportion of FeCl₃ and FeCl₂, the effect on the settlement of plutonium may also be affected. The improved process can promote 20% for the settling of plutonium in radioactive waste water, and the time needed for sedimentation reduced to 1/5 of the original.

Decomposition simulation of hexogen composites embedded with carbon nanotubes induced by electric field

WEI Li-lai, MIAO Feng

2019, 39(2):  175-180.  DOI: 10.16568/j.0254-6086.201902013

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The decomposition process of energetic materials is studied using the electric field as an ignition condition. Using hexogen (RDX) single crystal structure, a composite structure model of RDX embedded in carbon nanotubes (CNTs) was constructed, and the response of the material under external electric field is simulated with reactive molecular dynamics (ReaxFF MD) simulation. The results show that the composite structure can form a reaction hot spot with CNT as the center under the uniform electric field along the CNT tube. With the growth of the hot spot, a self-issued combustion layer is formed, which can decompose the whole system.

Non-Fusion Plasma Applications

Numerical simulation of magnetic pole sputtering of a cylindrical anode layer hall thruster

LI Ping-chuan, TANG De-li, ZHAO Jie, ZHANG Fan

2019, 39(2):  181-187.  DOI: 10.16568/j.0254-6086.201901014

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A three dimensional particle in cell (PIC) model is applied to simulate discharge and sputtering process in Hall thruster with solid and hollow inner magnetic poles. The influences of discharge power and magnetic field on ion sputtering degree are investigated and analyzed. Simulation results reveal that the discharge efficiency of thruster with solid inner pole is higher, while operation conditions of high voltage and intense magnetic field are beneficial for reducing sputtering degree for thruster with hollow inner pole. For the design of long-lifetime and high-power Hall thruster, hollow cathode structure and a proper ratio of E/B should be taken into consideration.

Effect of atmospheric pressure plasma jet treatment on seed germination rate and root length of mustard

Lü Xiao-gui, WANG Peng, LI Min, LI Feng-min

2019, 39(2):  188-192.  DOI: 10.16568/j.0254-6086.201902015

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The effect of atmospheric pressure plasma jet treatment on seed germination rate and roots length of mustard was studied. Seed germination rates and root lengths of mustard seeds treated by plasma jet with different voltage and different time were compared with reference groups. The results show that seed growth is certainly promoted by plasma jet treatment with the discharge voltage of 1.6kV and processing time of 120s and 30s, while seed growth is significantly inhibited by treatment with 2.2kV and 120s or the discharge voltage of 2.8kV.