Table of Content

15 June 2017, Volume 37 Issue 2

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Plasma Physics

Negative viscosity damping of zonal flows in tokamak edge turbulence

HU Shi-lin1, LI Ji-quan1, 2

2017, 37(2):  125-130.  DOI: 10.16568/j.0254-6086.201702001

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Drift wave turbulence and associated particle transport are simulated based on Hasegawa- Wakatani turbulence model in tokamak edge plasmas. A zonal flow equation without assuming conventional Boussinesq approximation is derived from the plasma momentum conservation. Meanwhile, it is justified that the contribution of the large-amplitude density fluctuation as well as the turbulent particle flux to the zonal flow dynamics may be effectively equivalent to a low-order negative viscosity damping. Simulations show that the nonlinearity of large-amplitude density fluctuation can greatly enhance the zonal flow saturated amplitude, so that turbulent particle transport is dramatically suppressed. The results elucidate the importance of the nonlinearity of large-amplitude density fluctuation in driving plasma rotation, momentum transport and zonal flow generation in tokamak edge plasmas.

Influence of electric current caused by magnetic island rotation on neoclassical tearing modes

WANG Feng, QU Hong-peng

2017, 37(2):  131-136.  DOI: 10.16568/j.0254-6086.201702002

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The parallel current distribution caused by magnetic island rotation and its influence on the neoclassical tearing modes(NTMs) evolution are investigated analytically by using ion banana orbit central coordinate and average operator. The results show that if this perturbed current is considered and island rotation frequency ω=ω_*i, the bootstrap current term in NTMs evolution equation weakened by ion-banana-orbit-width (FBW) effect mostly recovers; while ω=ω_*e, the bootstrap current term can be reduced dramatically by the effect. This means that the perturbed current caused by magnetic island rotation can enlarge or weaken the FBW weakening effect on bootstrap current driven term when magnetic island rotation direction is different.

Effect of turbulence Reynolds stress and density perturbation on poloidal momentum transport

GUO Dong, NIE Lin, WU Yi-fan, YUAN Bo-da,LONG Ting, KE Rui, GONG Shao-bo, XU Min

2017, 37(2):  137-143.  DOI: 10.16568/j.0254-6086.201702003

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In HL-2A tokamak, the profile of turbulent Reynolds stress and the cross-phase between and was measured around the last closed flux surface. The result shows that the Reynolds stress is mainly determined by the cross-phase between and although the amplitude of and influence the amplitude of Reynolds stress. Besides, ohmic discharge and ECRH L-mode discharge show that radial particle flux caused by density perturbation has an important effect on the poloidal momentum flux. Its value is comparable to that of Reynolds stress. This indicates that the contribution of particle transport in the analysis of the turbulent momentum transport must be considered.

Application of quartz crystal microbalance on HL-2A tokamak

ZENG Xiao-xiao, CAI Lai-zhong, WU Ting

2017, 37(2):  144-151.  DOI: 10.16568/j.0254-6086.201702004

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A set of quartz crystal microbalance (QCM) was installed in HL-2A tokamak to measure the material deposition of carbon and its compounds. In the experiments, the mass deposited in each shot is usually in the magnitude of 0.1~10μg, an increase or decrease of the mass deposited could be induced by re-erosion and sputtering, which needs further investigation. The results also indicate that more mass can be deposited on the QCM after disruption. In addition, the average thickness of deposited layer in each shot is estimated to be 10nm in HL-2A tokamak.

Nuclear Fusion Engineering and Technology

Acceleration of real-time equilibrium reconstruction on HL-2A device

LING Fei, XIA Fan, MA Rui

2017, 37(2):  152-158.  DOI: 10.16568/j.0254-6086.201702005

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The HL-2A equilibrium reconstruction subsystem with grid dimension 33×33 didn’t meet the control accuracy and speed for the HL-2M tokamak, so a new equilibrium reconstruction subsystem with grid dimension 129×129 was developed. This subsystem can run a time slice in 600?s by solving the G-S function and reconstructing some algorithm of calculating some parameters and meet the requirements of the control system about real-time and accuracy on HL-2A and HL-2M tokamak.

GPU parallelization of HL-2A plasma real-time equilibrium reconstruction

MA Rui, XIA Fan, LING Fei, LI Jia-xian

2017, 37(2):  159-166.  DOI: 10.16568/j.0254-6086.201702006

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The GPU parallel algorithms of the HL-2A plasma real-time equilibrium reconstruction including parallel processing of G-S equation, an algorithm solving the tri-diagonal linear system efficiently in parallel, the computation of the flux on grid boundary points and some parallel speed-up for middle-scale matrix multiplication on GPU, were intoduced. After the parallelization, an equilibrium reconstruction iteration needs around 575μs with a 129×129 grid.

Activation calculation analysis for China helium cooled ceramic breeder test blanket system

CAO Qi-xiang1, ZHAO Feng-chao1, WU Xing-hua1,WANG Xiao-yu1, FENG Kai-ming1, Michael Loughlin2

2017, 37(2):  167-172.  DOI: 10.16568/j.0254-6086.201702007

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Using the Monte Carlo particle transport code MCNP and the European inventory code FISPACT-2007, activation calculation analysis for China helium cooled ceramic breeder test blanket module (CN HCCB TBM) and its ancillary systems (together called HCCB TBS) has been carried out based on the latest design of HCCB TBM and neutronic C-lite model provided by ITER. The radioactivity, afterheat and contact dose rate of the various structure components have been obtained and discussed. The results show that the total radioactivity and afterheat of HCCB TBM are 2.348×10¹⁶ Bq and 5.826 kW at shut down respectively. Activation calculation results can be used as the basic input data for other analyses of HCCB TBS, including safety analysis, maintenance, radwaste management, etc.

Numerical modeling packing structures of Li4SiO4 pebble bed for HCCB-TBM

GONG Bao-ping, FENG Yong-jin, LIU Yang, LIAO Hong-bing, WANG Xiao-yu, FENG Kai-ming

2017, 37(2):  173-180.  DOI: 10.16568/j.0254-6086.201702008

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The packing structures of pebble bed under the influence of gravity were studied initially by discrete element method simulation. The results indicate that both the friction coefficient and the restitution coefficient have a great influence on the final packing structure of pebble bed. When the friction coefficient is small, the effects of friction coefficient on the packing structure of pebble bed play a major role. When the friction coefficient is larger, the impacts of restitution coefficient on the packing structure of pebble bed play an important role. There is a transition of pebbles distribution from the regular distribution close to the container walls to the uniformly random distribution in the interior region of the pebble bed. The local packing factor of pebble bed shows an oscillation profile. The amplitude of the oscillation reduces gradually with the increase of distance to the container wall. The distribution of local packing factor presents a wall effect obviously. The packing structures of pebble beds obtained in this work can be used to build a random packing model of pebble bed for the studies of thermal properties of pebble bed and the flow characteristics of purge gas.

Influence of shape on copper base central solenoid’s cooling effect

HUANG Zhuo-cheng, LUO Tian-yong, ZHANG Guo-shu, LIU Jian

2017, 37(2):  181-187.  DOI: 10.16568/j.0254-6086.201702009

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Software of Fluent and ANSYS workbench were used to analysis fluid and thermal coupling in water-cooled copper solenoid coil combining the theory of computational fluid dynamics and finite element analysis. The relationship of inside wall temperature along with the curvature angle and surface angle in water-cooled copper base solenoid coil was obtained. Comparing CS maximum temperatures, average temperatures and minimum temperatures in export and interface of the three different flow channel shape (circle, elliptic, 3 leaf type) under the same condition, it was found that the flow shape will affect the CS heat exchange seriously, elliptical shape solenoid and trifoliate shape solenoid both have better cooling effect compared with circular shape solenoid, for example average wall surface temperature decreased nearly 70℃, the highest temperature on pipe wall and control within the 100℃, the maximum temperature difference is controlled within 60℃.

Thermal fatigue failure behavior on Be/Cu joint of ITER first wall after enhanced heat flux test

LIU Dan-hua, WANG Ping-huai, LI Qian, YANG Bo, JIN Fan-ya, CHEN Ji-ming, ITERBing-Bi-Bao-Ceng-Qu

2017, 37(2):  188-193.  DOI: 10.16568/j.0254-6086.201702010

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The ITER first wall mock-ups fabricated by joining CuCrZr and 316L(N) stainless steel with explosion welding, machining cooling channel, and then bonding Be tiles on CuCrZr interface with a hot isocratic press technology were subject to high heat flux test, the ultrasonic testing result of mock-up revealed that some larger defects on Be/Cu joint localized on the central area in mock-up. The defects located on Be/Cu interface were inspected by cutting sampling, combined with optical microscope, SEM observation and EDS, analyzing the possible reason what the defects caused by, leading to the first wall manufacturing technology optimization and better material choice.

EAST共振磁扰动线圈电源响应延迟分析及优化

CHEN Kun, GAO Ge

2017, 37(2):  194-198.  DOI: 10.16568/j.0254-6086.201702011

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In order to improve response speed and output characteristics of resonant magnetic perturbations (RMP) coil power supply of EAST tokamak, the response time delay is analyzed and optimized. Time delay that is caused by symmetrical rules sampling and single polarity PWM is amply analyzed and quantitatively determined. And multiple sampling & tardive updating is proposed to improve inverter response delay. The experimental data demonstrates that response time delay is decreased from 206μs to 70μs by the method, which meets the requirement of EAST experiments.

Optimal design of RMP coil power supply in EAST

SONG De-yong, GAO Ge, FU Peng, CHENG Zhi-cai

2017, 37(2):  199-203.  DOI: 10.16568/j.0254-6086.201702012

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According to the requirements of research on edge localized mode (ELM) and other phenomena in EAST, the resonant magnetic perturbation (RMP) coil power supply should have higher current-carrying capability, faster response speed and lower output voltage ripple. The optimal scheme about topology and major loop’s parameters is designed, and theoretical calculation, simulation results based on MATLAB and test results are given, the results show that the optimal scheme can perform better.

AC insulation monitoring technology for EAST fast control power supply

HUANG Hai-hong, CAO Yu-xi, WANG Hai-xin

2017, 37(2):  204-209.  DOI: 10.16568/j.0254-6086.201702013

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In order to ensure the stable operation of EAST fast control power supply, a new AC insulation monitoring technique, suitable for the high-frequency and high-voltage working environment of EAST fast control power supply, was presented. The unbalanced bridge of resistance was applied to cause changes in the partial voltage of the resistances by alternately switching, then voltages were collected real-time, and the value of insulation resistance could be calculated. The simulation platform based on Simulink was built to carry out real-time insulation monitoring analysis with ~220V and output of EAST fast control power supply as voltage input, and the waveforms were consistent with the expected. Through experimental verification, the new method can accurately complete the insulation monitoring of 220V AC input, and can work well in the fast control power supply field, where the accuracy of insulation monitoring is achieved.

Feedback control system of PSM high voltage power supply

LONG Chao-lei, WANG Yang-qiao, YAO Lie-ying, WANG Ya-li, LI Qing, MAO Xiao-hui, Li-wei-bin, REN Qing-hua

2017, 37(2):  210-214.  DOI: 10.16568/j.0254-6086.201702014

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The control system of the PSM high voltage power supply in the HL-2A tokamak power supply was presented. The control system based on DSP & FPGA, including parts of driving, communication, computation and feedback, generated 112 pulses to make IGBT modules turn on or off quickly in order to keep the output voltage steady. The upper computer was based on VB and could set experimental parameters then communicated to DSP by CAN BUS. DSP & FPGA completed the computation and feedback. The composing and debugging of software code and the testing of the whole system were accomplished. The results showed that the control system meets the requirements.

Vacuum performance analysis of EAST in-vessel viewing system

XU Lie-zhi, YAO Da-mao, ZHOU Zi-bo, CAO Lei, YU Yao-wei, DU Liang, EAST Contributors

2017, 37(2):  215-219.  DOI: 10.16568/j.0254-6086.201702015

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The structure and operating procedure of the vacuum performance of in-vessel viewing system (IVVS) are introduced. The outgassing rate materials used for IVVS ware tested to evaluate if the system vacuum properties meet EAST vacuum environment requirements. The ultimate pressure provided by the tank for IVVS is 3.37×10^-3Pa under effective pumping speed of 1064L•s^–1. Analyses and optimization was made to improve the system vacuum properties, and finally the ultimate pressure is declined to a certain range of 1×10^-4Pa under the same pumping speed by replacing lower outgassing rate materials, bake-processing of IVVS and more optimized structure. After optimization, the vacuum performance of the system is obviously improved that can meet the requirements of vacuum environment accepted by EAST. Furthermore, the ultimate pressure can be still promoted by adding a set of cryopump to the vacuum pumping system in the tank.

New control system of divertor power supply system based on JRFT

WAN Kuan-hong, CHEN Zhi, ZHENG Wei, ZHANG Ming, ZHENG Guo-zhen, LI Yang

2017, 37(2):  220-225.  DOI: 10.16568/j.0254-6086.201702016

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To achieve plasma control for complicated experiments, a new control system of divertor power system using J-TEXT real-time framework (JRTF) is designed and implemented. JRTF is a flexible real-time software framework designed for the implementation of real-time control systems on J-TEXT tokamak. It adopted the experiences of present power supply control systems and accorded with its control features. JRTF was compatible with the central control system and other systems. JRTF is compatible with ITER standard PFC hardware and ITER CODAC Core software. The new control system was applied to J-TEXT and the result shows that the new control system offers good control effects and real-time performance.

Electrode layout simulation for JAEA 10A multi-cusp source discharge

LIAO Peng, YIN Mao-wei, WU Yong-cun

2017, 37(2):  226-231.  DOI: 10.16568/j.0254-6086.201702017

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The JAEA 10A multi-cusp source discharge is simulated by the self-developed full 3D PIC/MCC software. The influence of the electrode layout on H^- volume generation efficiency was analyzed. The simulation shows that with a certain discharging power, the crosswise drifting from high energy electrons will weaken relatively when the number of electrodes decreases, then the uniform H? beam will be obtained. However, the lower electrodes lead to a lower generation efficiency of the H^- volume. When the electrodes are close to magnetic filtering region, the crosswise drifting will be strengthen relatively and the H^- volume generation efficiency is quite low. With changing the number of electrodes, the high H^- volume generation efficiency and the good space uniformity couldn’t be obtained together. The electrodes far away from magnetic filtering region are the best choice.

Influence of helium state on electrical properties of room temperature insulation breaks for superconducting tokamak

FANG Lin-lin, PAN Huan-jiang, ZHU Yin-feng, WU Cheng, CAO Yi, CHEN Huang

2017, 37(2):  232-235.  DOI: 10.16568/j.0254-6086.201702018

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To reveal the influence of helium state on the electrical properties of room temperature insulation breaks (RTIB) for a superconducting tokamak, a test platform used to perform high voltage-leakage current experiments was established. And using the test platform the high voltage-leakage current experiments of room temperature insulation breaks for a superconducting tokamak under static and flow rate of 0.65g•s^-1 helium gas environment were performed. The results show that the room temperature insulation breaks for a superconducting tokamak under the two Helium states can fulfill the operating requirements.

Non-Fusion Plasma Applications

NO removal from coal-combustion flue gas with dielectric barrier discharge non-thermal plasma

GUO Bin, LUAN Tao

2017, 37(2):  236-243.  DOI: 10.16568/j.0254-6086.201702019

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Reducing NO from exhaust gas was studied with dielectric barrier discharge (DBD) non-thermal plasma (NTP) generator. The measures to increase DBD denitration efficiency were analyzed. The DBD generator was used in either a mode where flue gas was directed through the discharge zone (direct oxidation), or a mode where produced ozonized air was injected in the flue gas stream (indirect oxidation). Following the approach of increasing energy efficiency, it can successfully seek a measure to increase denitration efficiency and reduce reactor energy consumption, so as to realize the purpose of saving energy and actual value of DBDP-based denitration. The result showed that denitrification efficiency is higher than the efficiency of desulfurization under whether direct oxidation or indirect oxidation. And indirect oxidation can greatly reduce power consumption. The removal efficiency of NO can be improved by the addition of ammonia.

Technology on spheroidization chromium powders with inductively coupled thermal plasma

CHEN Lun-jiang, CHEN Wen-bo, LIU Chuan-dong, CHENG Chang-ming, TONG Hong-hui

2017, 37(2):  244-248.  DOI: 10.16568/j.0254-6086.201702020

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In order to improve the powders’ liquidity and explore the preparation processing of spherical powder, irregular shaped chromium powders were prepared for spherical powders using inductively coupled thermal plasma (ICTP) as a heating source. The factor of powders’ feeding rate which could influence the spheroidization efficiency and liquidity of spherical powder was studied. The micro morphology and flow-ability of the powders were characterized with the metallographic microscope and hall flow meters, respectively. The results showed that the vast majority of powders was spheroidized after plasma treatment. For the particle size of Cr powders between 200 and 300 mesh, the liquidity of spheroidized powder was enhanced and the spheroidization efficiency was also increased with the increased feeding rate. But when the feeding rate was 35g/min, its liquidity and spheroidizaton efficiency were about 56.18s/50g and 85.6% respectively which both reached the best effect.