Table of Content

15 June 2018, Volume 38 Issue 2

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Plasma Physics

Experimental study on the asymmetry of implosion hot spot based on multi-channel Kirkpatrick-Baez microscope

DONG Jian-jun, DENG Ke-li, WANG Qiang-qiang, RENG Kuan,CAO Zhu-rong, JIANG Shao-en

2018, 2(2):  125-129.  DOI: 10.16568/j.0254-6086.201802001

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The details of the implosion compression hot spot was detected by the multi-channel Kirkpatrick- Baez microscope with high spatial resolution of about 3μm. The X-ray self emission of the hot spot is measured along the two orthogonal directions of the equator and the polar, and the spatial distribution of the two dimensional X-ray intensity is obtained. The X-ray image data show that the equatorial asymmetry component of the hot spot is larger than that of the polar about 8%. The P2 component in polar is 2μm larger than that in the equatorial region. This results show that the polar compressing of the hot spot is stronger than that in the equatorial region. It indicates that the radiation driven in polar region is stronger than that in the equatorial region, which causes the shape of the hot spot to be oblate at the implosion stagnation.

Development of the poloidal charge exchange spectroscopy in the HL-2A tokamak

WANG Jie, LIU Liang, HE Xiao-xue, CHEN Wen-jin, WEI Yan-ling, YU De-liang

2018, 2(2):  130-137.  DOI: 10.16568/j.0254-6086.201802002

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A poloidal charge exchange recombination spectroscopy (CXRS) was introduced in HL-2A tokamak, observing CⅥ spectral line (C5+, n=8→7, λ=529.06 nm). Two sets of optic lenses are installed inside the vacuum chamber, one is placed close to the NBI port to observe both the active and passive spectra; the other is at the other side to observe simply the passive spectra. A laser beam with wavelength λ~532nm is used as the reference. The ion temperature is obtained by the Doppler broadening of CⅥ line, and the sightlines cover the range of major radius from 1.91 to 2.02m. The edge transport barrier has been observed at plasma edge around R~2.00m during H-mode discharge with NBI heating.

Coupling of supersonic molecular beam injection model with the fluid transport code

WANG Ya-hui1, 2, GUO Wen-feng1, WANG Zhan-hui3,WAN Di4, REN Qi-long1, CHEN Jia-le1, SUN Ai-ping1

2018, 2(2):  138-143. 

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Adding supersonic molecular beam injection (SMBI) model to the fluid transport code ONETWO provides important particle source and electron and ion heat source. SMBI model is added to ONETWO physical model and the TPSMBI code is modified and coupled to ONETWO code. The coupled ONETWO code has been used to simulate the source terms of gas puffing and SMBI. Adding SMBI model to the ONETWO code will not only provide an important tool for the relevant experimental analysis, but also provide an important source of particle and energy for the physical design of future devices such as the China Fusion Engineering Experiment Reactor.

Numerical simulation and analysis of electron cyclotron resonance heating effect on EAST

WEI Wei, LI Miao-hui, WANG Xiao-jie

2018, 2(2):  144-151.  DOI: 10.16568/j.0254-6086.201802004

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In order to provide theoretical reference and predictions for relevant physical experiments of electron cyclotron resonance heating (ECRH) on EAST, based on the electron transport equation, some numerical simulations of heating effect of ECRH in different plasma and electron cyclotron wave (ECW) parameters were carried out by using CRONOS transport simulation code. The dependences of the heating effect on ECW power, injection angle, electron density and toroidal magnetic field are given. The electron temperature, total internal energy and energy confinement time for different parameters are predicted and analyzed. Finally, the preliminary comparisons of simulation results and experimental results are discussed.

Analysis of beam characteristics of the radio frequency ion source

Zhao Miao, LEI Guang-jiu, LI Ming, XIE Wei-min, ZHANG Xian-ming

2018, 2(2):  152-157.  DOI: 10.16568/j.0254-6086.201802005

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A radiofrequency (RF) ion source with beam power of 1 MW is developed for the neutral beam injector on the HL-2A tokamak. At present, this ion source can deliver a 35keV/12.4A hydrogen ion beam for 100 ms on the test-bed, reaching 44% of its design beam power. The proton proportion of the beam is 79%. The energy density profile of beam is measured with infrared imaging technique for beam characteristic evaluation. It is found that at a transportation distance of 1.3 m the beam density profile obeys a Gaussian distribution. The optimum beam perveance is about 1.689×10^–6A•V^-3/2 and it varies slightly with the RF power. According to the experimental results, some related measures have been taken to improve the beam performances of the ion source.

Spectroscopic measurement for ion beam components of radio-frequency ion source

XIE Wei-min, LI Ming, ZHAO Miao

2018, 2(2):  158-162.  DOI: 10.16568/j.0254-6086.201802006

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A radiofrequency (RF) ion source with beam power of 1 MW is developed for the neutral beam injector on the HL-2A tokamak. At present, this ion source can deliver a 35keV/12.4A hydrogen ion beam for 100 ms on the test-bed, reaching 44 % of its design beam power. The proton proportion of the beam is 79%. On the RF test platform, the ion source beam composition proportion is measured by using the spectrum of Doppler frequency shift, and the relationships between the beam composition proportion and the beam current from RF ion source are contrasted. The analysis of experimental data indicates that the ion flow compositions of H⁺ ₁, H⁺ ₂ and H⁺ ₃ are 75%, 18% and 7%, respectively, under the condition of 10A beam current. When the beam current increases from 3.3A to 10.4A, the composition proportion of H⁺ ₁ rises from 37% to 78% while H⁺ ₃ falls from 19% to 9%.

Nuclear Fusion Engineering and Technology

Research of turn to turn insulation for HL-2M toroidal field coils

QIU Yin, LI Guang-sheng, ZHOU Hui, SHAN Ya-nong, YANG Qing-wei

2018, 2(2):  163-169.  DOI: 10.16568/j.0254-6086.201802007

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HL-2M tokamak adopts the demountable toroidal field coils (TFCs) structure in order to assemble the vacuum vessel chamber and poloidal field coils (PFCs) integrally. TFCs are subjected to high shear force, which require high electrical performance and adhesive strength between the inter turn insulation and the copper plate. Baking and curing impregnated glass cloth and epoxy glass cloth under different pressure, then adhesive properties have been researched by shear tests. The results show that there are some differences in the adhesive properties between the turn to turn insulation and the copper plate under different structural combinations and different pressures. Appropriate structural combination and pressure of hot baking and curing were selected for TFCs.

Analyzing the deposition layer on the carbon tiles of HL-2A with laser-induced breakdown spectroscopy

WANG Zhen-zhong, CAI Lai-zhong, LIU Ping, LIU Min-Jia, Imran Muhammad, DING Hong-bin

2018, 2(2):  170-176.  DOI: 10.16568/j.0254-6086.201802008

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The graphite tiles, located at the lower divertor and the fixed limiter of HL-2A tokamak, were measured with ex-situ laser-induced breakdown spectroscopy (LIBS). The deposition behavior on HL-2A was presented by analyzing different elements including C, Fe, Si, H and D within the tiles and their distributions on depth in different tiles. Comparing with the results obtained with time of flight secondary ion mass spectrometry (TOF-SIMS), the depth profiles show well consistency. According to the effective number of deposition layer erased by the laser, the average laser ablation rate is estimated to be 270nm/pulse.

Studies on structural parameters influencing the cooling performance of HL-2M divertor target plat

LU Yong, CAI Li-jun, HUANG Yun-cong, LIU Jian, LIU Yu-xiang, ZHENG Guo-yao

2018, 2(2):  177-183.  DOI: 10.16568/j.0254-6086.201802009

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The maximum temperature of the graphite tile and heat sink plate is employed as the main
optimization goals. Based on heat conduction and convective heat exchange equations, some key design
parameters of HL-2M divertor, such as the thickness of the graphite tile, the center position and the diameter of
the cooling channel, the contacting thermal resistance of the interface between the graphite tile and the heat sink,
etc are simulated and optimized, utilizing CFX software. The results show that the thickness of the graphite tile
about 25mm is the best for HL-2M divertor cooling performance; the cooling performance of the divertor
decreases slightly when the distance from the center of the cooling channel in the heat sink to the graphite surface
increases, exhibiting an approximate linear correlation; the divertor cooling performance is improved slightly
when the diameter of cooling channel increases, the cooling performance of divertor is improved when the
contacting thermal transfer coefficient of the interface between the graphite tile and the heat sink plate increases,
but the thermal impact on the heat sink plate is more severe.

Neutronics design and analysis of helium cooled solid blanket for superconductor CFETR

ZHAO Feng-chao, FENG Kai-ming, CAO Qi-xiang, LI Zai-xin, ZHANG Guo-shu

2018, 2(2):  184-191.  DOI: 10.16568/j.0254-6086.201802010

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According to the design requirements of the China fusion engineering testing reactor (CFETR), neutronics design and analysis of helium cooled solid blanket (HCSB) for CFETR has been performed with MCNP code. The neutronics design and analysis results show that HCSB design with U-shaped breeding unit meets the tritium self-efficiency requirement. The calculation CFETR tritium breeding ratio with HCSB is 1.243. And the maximum area at mid-plane that can be used for auxiliary heating and diagnostic is about 11.43m².

Forming die dimensional design and experimental research of the fusion reactor vacuum vessel shells

HUANG Yun-cong, RAN Hong, HOU Ji-lai, CAO Zeng, SONG Bin-bin, TANG Le

2018, 2(2):  192-198.  DOI: 10.16568/j.0254-6086.201802011

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According to ITER vacuum vessel manufacturing standard, China fusion engineering test reactor (CFETR) vacuum vessel shells forming was pre-studied at room temperature. Firstly, the empirical formula was used to calculate the forming die dimension of the vacuum vessel shell which was mostly determined by the mechanical properties of material. Then, the bending process was simulated with finite element software for three nearby values in which the optimal profile errors of the shell meet the demand of ±1.5mm. Finally, the optimal dimensional values of the molds were confirmed to guide the forming experiment study. The actual profile errors, the thickness reduction, the maximum spring back and deformation were measured in the experiment. The results are in reasonable agreement with the finite element analysis data, verifying the suitability of the forming die design.

Thermal stress and elastic-plastic structural analysis of the ITER first wall beryllium-copper interface defects

LENG Zhen, CHEN Ji-ming, WANG Kun, KANG Wei-shan, HUANG Pan

2018, 2(2):  199-204.  DOI: 10.16568/j.0254-6086.201802012

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In order to guarantee the performance of the first wall beryllium copper connection under the ITER operation, the high heat flux test (HHFT) should be taken to evaluate the effects of defects, and then determine the acceptable defect size. Aiming at such test, using enhanced heat load (EHF) first wall small module, the temperature field and elastic-plastic structural analysis have been taken to study the effects of Be/CuCrZr interface defects under the high heat flux test condition. Analysis results show that the location and the size of Be/CuCrZr interface defects have a direct impact on local elastic-plastic strain, which affects thermal fatigue performance of the module; the bigger the defects, the greater the influence; marginal type defects is greater than the influence of the center type defects.

Analysis of the beryllium-copper connection interface of ITER first wall

LI Zhan-feng, CHEN Ji-ming, WANG Ping-huai, JIN Fan-ya

2018, 2(2):  205-210.  DOI: 10.16568/j.0254-6086.201802013

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Be and CuCrZr alloys for ITER first wall are connected by the thermal isostatic pressure diffusion
bonding technique, and partial connectors that completed the diffusion connection are annealed. Using ultrasonic
nondestructive testing of all connectors, defects in the Be-Cu connection interface of unannealed connector are
observed. In order to analyze the cause of the defect in the diffusion interface, a sample from the defect zone of
the connector was selected and analyzed with the interface microanalysis. By observing the micromorphology and
analyzing the change of alloying elements in the diffusion layer of the interface, it was found that the thickness of
the Cu-Ti diffusion layer and the thickness of the Ti layer in the Be-Cu diffusion interface after annealing were
increased. The probability of the formation of the brittle phase between the Be and the Cu elements in the middle
layer was reduced. The thickness of the whole diffusion layer became larger and the range of diffusion was larger.
The experimental results show that the annealing process can change the structure of Be-Cu thermal isostatic
pressure diffusion layer and expand the range of diffusion bonding.

Comparison and selection of coconut activated carbon for cryopump

JIANG Tao, CAO Jian-yong, LEI Guang-jiu, YANG Xian-fu

2018, 2(2):  211-215.  DOI: 10.16568/j.0254-6086.201802014

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In order to select a suitable absorbing material for cryopump in the nuclear fusion field, one comparison experiment was performed and four candidate coconut activated carbon samples were used. The microstructure of materials was studied with scanning electron microscopy. The adsorption properties of the samples were measured with the specific surface and pore size analyzer, the specific surface area and the pore volume of different pore size were obtained. Based on the comparison results, the suitable samples were found. Some useful information is provided for the coconut activated carbon selection of cryopump in the nuclear fusion field.

Calculation and measurement for passive filter impedance-frequency characteristic of tokamak magnet power supply

QU Jun, LI Ji, MAO Hua-feng, WU Ya-nan

2018, 2(2):  216-220.  DOI: 10.16568/j.0254-6086.201802015

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According to the operation modes of passive filters, the impedance characteristic of single-tuned and high-pass filter was deduced under equivalent frequency deviation, and a high-precision measuring method was proposed. The effectiveness of the two methods is validated during the experimental test of ITER poloidal field power supply. The conclusion would offer useful theoretical and engineering references for ITER reactive power compensation and harmonic filtering system.

Analysis and simulation of output ripple formation of SC-200 proton accelerator transport magnet coils power supply

ZHOU Yu, HUANG Yi-bin, GUO Fei, SUN Hao-zhang, ZHANG Jian, GUAN Rui

2018, 2(2):  221-227.  DOI: 10.16568/j.0254-6086.201802016

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The main circuit topology and technical requirements of current source used in proton therapy accelerator transport dipole magnet is presented. The requirements for the magnet power supply are that output current accuracy is less than 25ppm and the current ripple is less than 25ppm. The output current ripple of the power supply is composed of low and high frequency components. The formation mechanism of the output current ripple is analyzed and computed in detail. It is obtained that Pulse Width Modulation (PWM) current tracking control based on the impulse control principle can effectively eliminate the influence of low frequency ripple on the output current. Meanwhile, two methods are used for quantitative mathematical analysis of the high frequency ripple. The quantitative conclusions and formulas of computation are achieved. With the help of AnsoftSimplorer power electronic simulation software, the correctness of the conclusions and formulas is verified. Corresponding strategies for ripple suppression are proposed.

Study on operation and management of measurement and control systems on HL-2M tokamak

ZHAO Li, LUO Cui-wen, SONG Xian-ming, XIA Fan, CHEN Liao-yuan

2018, 2(2):  228-235.  DOI: 10.16568/j.0254-6086.201802017

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According to current engineering operation experiences and the new measurement and control (M&C) requirements for HL-2M tokamak, referring to the ITER control, data acquisition and communication standard, the operation and management of HL-2M M&C are focused on in this paper. Through the configuration and management for all plant systems, high performance networks architecture, physical data storage system design and expansion, operation status monitoring and alarm control system, an integrated system management platform for HL-2M tokamak M&C is created. This study is targeted on the optimization of the experimental signal quality, realization of effective real-time signal transmission, enhancement of automatic management level, and guarantee of equipments and data in the experimental process and with high feasibility.

Analysis on differences of design rules for Class 1, Class 2 and Class 3 components in RCC-MR 2007

LI Guo-qing1, WANG Wen-hua1, LI Yu-fang1, LI Xiang-bin2,LUO Feng1, WU Feng-feng1, LIU Fu-gui1

2018, 2(2):  236-242.  DOI: 10.16568/j.0254-6086.201802018

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Design and construction rules for mechanical components of nuclear installations (RCC-MR 2007) code are prescribed for design and manufacture of components or parts that form plasma chamber first confinement barrier and some system related components in ITER Project. On the base of contents of RCC-MR 2007, the differences of general requirements, materials, design rules and analysis rules for component behavior among Class 1 components, Class 2 components and Class 3 components are analyzed and compared. The differences of design requirements for shells, piping, box structures, heat exchanger elements, valves, and bellows among three Classes are also analyzed and compared.

Non-Fusion Plasma Applications

Study on movements of particles in thermal plasma induced by radio frequency induction

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

2018, 2(2):  243-248.  DOI: 10.16568/j.0254-6086.201802019

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A two-dimensional axisymmetric model of radio frequency (RF) inductively produced plasma is created, and the trajectory of particles in argon thermal plasma is calculated with ANSYS FLUENT software. Then the influence of powder size and carrier gas flow rate on the forces acting on the particles is studied in detail. The results show that the trajectories of small particles are disorganized due to the influence of recirculation zone while the movements of lager particles are dominantly controlled by gravity. Adjusting carrier gas flow can make more particles be heated sufficiently and to be melted, consequently, the spheroidization rate of particle is increased.