Table of Content

15 March 2019, Volume 39 Issue 1

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Plasma Physics

Optimization for the data analysis of the microwave Doppler reflectometer

WEN Jie, SHI Zhong-bing, ZHONG Wu-lv, LIANG An-shu, JIANG Min, SHI Pei-wan, YANG Ceng-chen, CHEN Wei, FANG Kai-rui, LIU Ze-tian

2019, 39(1):  1-8.  DOI: 10.16568/j.0254-6086.201901001

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Combining with the analysis of Doppler spectrum, a new method, named symmetric-asymmetric spectrum (SAS) analysis is put forward based on dual Gauss fitting. A power spectrum is mainly composed of symmetric spectrum and asymmetric spectrum. The symmetric spectrum is principally decided by plasma cutoff density fluctuations, which can modulate the detecting signals, while the asymmetric spectrum is primarily determined by poloidal density fluctuations of k _⊥=2k₀sinθ turbulence. Compared with the commonly used method of spectral center of gravity (COG) and δ-phase method, SAS analysis not only improves the accuracy of the Doppler frequency shift measurements, but also provides the plasma density fluctuations of poloidal k_⊥ turbulence and cutoff.

Investigation of energetic ion losses due to localized magnetic perturbations in tokamak

WANG Jie, XIANG Dong, CAO Jin-jia, GONG Xue-yu

2019, 39(1):  9-14.  DOI: 10.16568/j.0254-6086.201901002

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Based on ORBIT code of a guiding center motion of single particle, the loss of energetic ions in different radial positions of tokamak plasma is studied by using test particle simulation method. The results show that the local magnetic perturbations can cause loss of many energetic ions near the central region of the plasma, but they have little effect on the ion loss near the plasma boundary, assuming that the local field is mainly located near a magnetic surface and its toroidal field is similar to the ripple field. These energetic ions are trapped ions, and the greater their pitch angle is, the easier they lose. In addition, the radial position of the local field that causes the maximum loss rate of energetic ions is usually offset from the initial radial position of these loss ions, and this shift is closely related to the energy of these ions. When the local field appears in certain locations, the ions of lower energy have some loss, but the ions higher energy does not lose.

Experimental analysis of EAST neutral beam counter-injection under different plasma current platform

LIU Cheng-yue, CHEN Mei-xia, WU Bin, SONG Feng-quan

2019, 39(1):  15-20.  DOI: 10.16568/j.0254-6086.201901003

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Comparative analysis of EAST neutral beam counter-injection experiment is carried out with the same beam parameters and different plasma current platforms. At the same time, the NUBEAM code is used to analyze beam current drive, power deposition, beam power deposition profile and beam energy loss, in order to optimize background plasma parameters. The results show that the higher current platform is more advantageous to the effect of beam on plasma, more effectively improving the background plasma temperature, beam-drive current, plasma rotation as well as the quality of plasma confinement.

Experimental study of electron beam based on microwave electron cyclotron resonance plasma cathode

LI Liang, LIU Yi-fei, CHEN Long-wei, WANG Gong, LIU Ming, REN Zhao-xing, LIU Bing-shan, ZHAO Guang-heng

2019, 39(1):  21-27.  DOI: 10.16568/j.0254-6086.201901004

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The generation and control of microwave electron cyclotron resonance (ECR) plasma cathode electron beam is studied experimentally. A complete set of discharge, electron beam extraction, focusing and measuring system was set up. The characteristics and performance of microwave ECR plasmas as electron beam extraction source were studied by measuring the current of water cooling target and the beam spot size on the target. Experimental results indicated that both microwave input power and accelerating voltage are conducive to improving electron beam current. The influence of gas pressure on the electron beam current was complex. With the increase of gas pressure, the electron beam current is characterized by decreasing first and then increasing. The extracted electron current of microwave ECR plasma cathode can reach 75mA at gas pressure of 7×10⁻⁴Pa, and the energy of the electron beam can reach 9keV. The energy utilization can reach 0.6. By adjusting the current of the focusing coil, the diameter of electron beam spot is reduced from 20mm to 13mm and the electron beam current keeps the value unchanged.

Nuclear Fusion Engineering and Technology

Simulation analysis and experiment of high frequency transformation of pulse step modulation high voltage power supply

ZHOU Pei-hai, LI Qing, MAO Xiao-hui, WANG Ya-li, LI Chun-lin

2019, 39(1):  28-33.  DOI: 10.16568/j.0254-6086.201901005

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In order to improve the physical experimental parameters of the HL-2A tokamak, the new high-power supply for the auxiliary heating systems need higher stability, faster response, higher power factor, shorter protective time, higher voltage, more flexible control, higher frequency and much less energy discharged to this equipment than the old one when the load is arcing. The high voltage power supply adopts the pulse step modulation (PSM) technology and mainly consists of 28 modules with 4 adjustable modules and 24 uncontrollable switch modules connected in series. The output voltage can be adjusted continuously in 0~20kV and the switch frequency maximum can reach 20 kHz. The results of simulation and experiment show that the operating parameters of the power supply can reach 20kV/200A and meet the experimental requirements.

Design of vacuum pumping and fuelling control system based on experimental physics and industrial control system

YUAN Xiao-lin, CHEN Yao, LI Jian-gang, HU Jian-sheng, ZHOU Yao, HOU Ji-lei, HUANG Ming

2019, 39(1):  34-40.  DOI: 10.16568/j.0254-6086.201901006

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Supervisory control and data acquisition (SCADA) framework of bottom layer and top layer, interlock protection, operational mode and system implementation were described. In bottom layer, vacuum pumping system and fuelling system are adopted to two different topological structures of optical fiber ring network. The top layer uses the experimental physical and industrial control system (EPICS) architecture to meet the requirements of the large-scale scientific facility. The topological structure of optical fiber ring network and EPICS framework are combined to develop the largely distributed SCADA system. Test results show that the control system is stable and reliable. The SCADA system provides not only reliable support for EAST, but also a good reference for developing other SCADA system of large-scale scientific facility in the future.

Progress of research and design of microwave diagnostics on CFETR

QU Hao, HAN Xiang, GAO Xiang, ZHANG Tao, WANG Yu-min, YANG Yao, LI Gong-shun

2019, 39(1):  41-47.  DOI: 10.16568/j.0254-6086.201901007

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Based on parameters of the recent zero-dimensional design of CFETR the research and design for microwave diagnostics are conducted. The reflectometry system works with a combination of both O-mode and X-mode. Besides, the measurement is conducted on high field side and low field side simultaneously in order to obtain the entire density profile. O-mode of the first harmonic of electron cyclotron emission (ECE) is used to measure the core electron temperature profile while X-mode measurement of the second harmonic can provide the edge temperature profile. In order to verify the applicability of the new technique on CFETR, a multi-band coupler based on the frequency select surfaces has been developed on EAST to offer the feasible solution for the multi-band coupling technical requirement on CFETR.

Study on the effect of fin structure on heat transfer performance of hypervapotron structure

LIU Qi, MAO Shi-feng, WANG Zhong-wei, LIU Xu-feng, YE Min-you

2019, 39(1):  48-54.  DOI: 10.16568/j.0254-6086.201901008

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Based on the computational fluid dynamic code ANSYS CFX, the inhomogeneous Eulerian- Eulerian multiphase model coupled with RPI (Rensselaer Polytechnic Institute) boiling model is adopted to simulate the subcooled boiling two-phase flow of hypervapotron structure, and the effects of different fin structures on the heat transfer performance of hypervapotron structures are compared. The results show that under high heat flux conditions, the heat transfer performance of the triangular fin structure is better than the rectangular fin structure. Triangular 4×3 to the flow geometry has the best heat transfer performance. Rectangular 4×3 geometry is greatly affected by the flow rate due to the obstruction of the fins making the flow rate to be lower and the heat transfer performance will be getting worse. Triangular 4×3 against the flow geometry make the fluid in the cavity to maintain a large degree of turbulence due to the small cavity between the fins and the adverse effects of counter-flow fins on the mainstream, so the fin area has a good heat transfer performance, but due to the impeding effect of the counter-flow fin on the fluid, the fluid velocity in the slot is getting lower and lower, as the result, the heat transfer performance on the sidewall far away from the fin area is getting worse.

Analysis for welding of 1/32 vacuum vessel sector of future fusion engineering test reactor

FAN Xiao-song, WU Jie-feng, LIU Zhi-hong, GU Yong-qi

2019, 39(1):  55-61.  DOI: 10.16568/j.0254-6086.201901009

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The welding process of the first 1/32 sector in the 1/8 section research and development project of the future fusion engineering test reactor vacuum vessel (VV) was analyzed. In the numerical simulation, the inherent strain method was used to compare and design the welding tools for 1/32 sector. Meanwhile, the trend of welding deformation and the amount of deformation were predicted by the simulation model. The displacements of the control points in the welding process are consistent with the numerical simulation results. The design of the welding tools and the application of the pre-compensation in the welding process are effective in improving manufacturing accuracy of the 1/32 VV sector.

Experimental study on the lithium film flow in horizontal magnetic fields

LIU Bai-qi, YANG Juan-cheng, QI Tian-yu, REN Dong-wei, NI Ming-jiu

2019, 39(1):  62-67.  DOI: 10.16568/j.0254-6086.201901010

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An experimental station, consisting of the magnet, the lithium flow loop, the dynamical circulation system, the heating system and the measure system, has been designed to study the liquid lithium film flow under a horizontal magnetic field. After the parts of the experimental facility are fabricated well and moved into the laboratory, the experiment station is assembled and tested on-site. At last, the experimental station is completed after the solid lithium is filled in and melted. Then, some experiments are conducted, including the lithium spreading performance on stainless-steel surface, the lithium film flow patterns under varying Reynolds numbers, and the MHD effects on the lithium film flow. The result shows that the liquid lithium film could spread well on the stainless steel which had been wetted by lithium sufficiently, and the horizontal magnetic field could steady the film flow pattern and restrain the surface wave of the film on the magnetic direction.

Numerical simulation on fatigue behavior of copper interlayer of divertor under ELM heat shock

LIU Shi-min, HUANG Sheng-hong

2019, 39(1):  68-75.  DOI: 10.16568/j.0254-6086.201901011

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With the finite element software, comprehensive numerical simulations on thermal/mechanical response and fatigue behaviors of divertor monoblock Cu interlayer under combined loads of high heat flux (HHF) and edge localized modes (ELMs) were conducted. The results show that: (1) the plastic damages induced by transient heat shock of ELMs will be coupled with damage by HHF loads in interlayer of copper; (2) under the combined loads of HHF and ELMs, the fatigue life of the interlayer continues to decrease and the magnitude of the decrease is nonlinearly increased with the peak and time-averaged heat flux of the ELMs; (3) the fatigue life reduction of the interlayer more sensitive to the peak heat flux and frequency of ELMs under the same time-averaged heat flux conditions.

Design and analysis of large aperture background field magnets

YANG Hao-jun, LU Kun, RONG Jian

2019, 39(1):  76-82.  DOI: 10.16568/j.0254-6086.201901012

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A design scheme of large aperture field magnet is provided based on the design requirements of the China Fusion Engineering Testing Reactor (CFETR) joints. Using the background field magnet to get the corresponding magnetic field data, the influence of the magnet parameter on the magnetic field is compared, and the corresponding magnetic field data are obtained. Gandalf program was used to simulate the shunt temperature of CFETR field magnet under operating conditions. Considering the hydrodynamic performance of liquid helium, Gandalf program was used to simulate the quench behavior of superconducting strands and to estimate the more accurate minimum quenching energy. The minimum quench value can be used as the Q₀ value inputted into the program to obtain hot spot temperature value. The analysis shows that the design meets the requirements for the production of high temperature superconducting magnets and provide reliable basis for manufacture and experiments.

Non-Fusion Plasma Applications

Research on plasma formation of ionized seeds under the influence of gunpowder gas

LI Jun, MAO Bao-quan, BAI Xiang-hua, ZHONG Meng-chun, ZHU Rui

2019, 39(1):  83-88.  DOI: 10.16568/j.0254-6086.201901013

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In order to study the plasma generation of ionized seeds under the action of gunpowder gas, a mathematical model under the condition of closed bomb (constant volume) was established, and a plasma test system was designed. Experiments were carried out with a certain type of artillery propellant and different kinds of ionized seeds. The results show that the ionized seeds can generate plasma under the action of gunpowder gas, and the electron densities are 2.25×10¹⁸m⁻³ and 4.63×10¹⁸m⁻³ after adding potassium salt and barium salt, respectively. The strontium salt ionization effect is better than the potassium salt. Under the test conditions, the simulation results are roughly in agreement with the test data.

Investigation of the carbon films by Ar/CCl4 plasma jet driven with dual-frequency power under atmospheric pressure

ZHANG Ya-dong, YUAN Qiang-hua, YAN Gui-qin, WANG Yong, LI Yang

2019, 39(1):  89-96.  DOI: 10.16568/j.0254-6086.201901014

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Amorphous carbon films were prepared on silicon substrate by changing RF power under the driving of dual-frequency Ar/CCl4 plasma jet at atmospheric pressure, and the corresponding numerical simulation was carried out by the program. The influence of the density, temperature, electric field, potential and angular distribution of electrons and ions on the morphology of carbon material samples at different powers was obtained. The prediction of the trend of the sample and the analysis of its causes, and the comparison with the experimental results were conducted. The results indicate that for the dual-frequency atmospheric pressure plasma, the radio frequency can control the energy and reaction intensity of the plasma independently, and can control the product relatively, which provides an important experimental basis for preparing the thin film morphology.