Table of Content

15 September 2019, Volume 39 Issue 3

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Plasma Physics

Research on minor disruptions in Keda torus experiment

HU Jin-tong, LI Hong, LI Zi-chao, Yolbarsop Adil, WU Yan-qi,WANG Hao-xuan, ZHUANG Ge, LIU Wan-dong

2019, 39(3):  193-200.  DOI: 10.16568/j.0254-6086.201903001

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In experiments of Keda torus experiment (KTX), a reversed field pinch magnetic confinement device, significant plasma displacement and the following minor disruption phenomenon were observed and studied. Its main feature is the slow outward plasma displacement before the minor disruption and rapid moving backward in a hundred microseconds after the minor disruption, reaching a stable configuration again, indicating by the data of the hydrogen-α spectrum, soft X-ray radiation and magnetic probe. At the same time, the minor disruption is accompanied by the disturbance of the m=1 boundary magnetic field, the rapid variation of the eddy currents on the stabilization shell, and the enhancement of the hydrogen-α spectrum and soft X-ray radiation. Based on the analysis and statistics of KTX minor disruption experimental data, the linear relationship between rebound displacement and plasma displacement is obtained. In this paper, a phenomenological circuit model is established for plasma current distribution and stable shell eddy currents, and the conclusion is consistent with the experimental results. It is determined that the rapidly changing eddy current on the stable shell is an important factor for restoring equilibrium after a minor disruption.

Design and development of the Langmuir probe for ITER divertor

ZHAO Wei1, JIN Yu-zhong1, ZHOU Hong-xia1,ZHONG Guang-wu1, NIE Lin1, LIU Chun-jia2

2019, 39(3):  201-207.  DOI: 10.16568/j.0254-6086.201903002

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Physics requirements analysis and structure design of ITER divertor Langmuir probes are performed, and the installation height range of probe relative to the surface of the divertor monoblock is determined. Temperature field and stress field under steady state heat load of Langmuir probe are obtained by the structure design and the thermal and mechanical simulation. The maximum temperature of probe is lower than that of divertor monoblock, and the stress of Langmuir probe is lower than the yield strength of the material. At the same time, probe manufacture and connection technology are explored and developed. The forged tungsten material is selected initially to make probe body and tungsten shield. The aluminum oxide ceramic is used between the probe body and the tungsten shield for insulation, and special technology is used for bonding probe body, ceramic and tungsten shield.

Preliminary neutronics analysis of neutron shielding for CFETR with 2GW fusion power

LI Jie1, 2, ZHANG Jie2, QIU Yang1, 2, LIU Chang-le1, LIU Xiao-gang1, GAO Xiang1

2019, 39(3):  208-214.  DOI: 10.16568/j.0254-6086.201903003

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Using a one-dimensional (1D) neutronics model, the neutronics performance in the China fusion engineering test reactor (CFETR) with latest design dimensions of vacuum vessel is calculated under the 2GW fusion power. The shielding effect of neutron reflecting material ZrH₂ on neutrons is calculated, and it is found that the 20cm reflector can shield 94.3% neutron fluence and 94.9% neutron nuclear heat. Meanwhile, the minimum shield blanket thickness corresponding to different neutron wall loads is calculated when CFETR is operated at 10FPY (full power year) and 20FPY. The results show that the minimum shield blanket thickness are 44cm, 53cm, and 65cm corresponding to the neutron wall loads with 1.0MW·m⁻², 1.5MW·m⁻², and 2.5MW·m⁻² respectively after the device is operated at 10 FPY; whereas the shielding blanket needs to be thicker in the radial direction to meet the neutron shielding requirements after the device is operated at 20FPY. The optimized size of the shielding blanket provides a significant reference for the design of CFETR advanced blanket.

Design of a new photoelectric detection system for fast-ion D_α diagnostic on EAST

LIU Dong-mei1, LUO Fan1, CHANG Jia-feng2, HUANG Juan2, XIONG Kui3, ZHOU Feng3, YUE Chang-xi3, LI Zhi-cheng3

2019, 39(3):  215-220.  DOI: 10.16568/j.0254-6086.201903004

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The D_α signal photoelectric detection system with high temporal and spatial resolution consists of 16 channels, each channel consists of a photomultiplier tube (PMT) and a current amplifier based on a sapphire material instead of a conventional printed circuit board. In order to enable the detection of the fast-ion D_α (FIDA) signal from other light sources of the same spectral range when a neutral beam is injected, the system parameters were designed with a total photon-to-voltage gain of 5.0×10⁹, the current amplifier with a current-to-voltage gain of 106V/A and a −3dB bandwidth at 500kHz. The EAST discharge experiment showed that the FIDA signal was well detected by this photoelectric detection system and the fast-ion properties were deduced from the Doppler shift spectrum of the D_α light.

Research on reliability of EAST upper divertor targets under halo currents

ZHANG Yang1, 2, QIN Shi-jun1, CAO Lei1, CHEN Da-long1, YAO Da-mao1

2019, 39(3):  221-226.  DOI: 10.16568/j.0254-6086.201903005

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Using the Gaussian mixture model of halo current peak distribution and the limit state equation of targets structure, the reliability of EAST upper divertor targets was studied with the Monte Carlo method. The results showed EAST upper divertor targets had extremely high reliability under halo currents, which provided references for the research on reliability of EAST upper divertor and CFETR.

Nuclear Fusion Engineering and Technology

Design and simulation analysis of filament power supply for MW neutral beam heating system of HL-2A tokamak

CHENG Ji-dong, WEI Hui-ling, YU Pei-xuan, CAO Jian-yong

2019, 39(3):  227-231.  DOI: 10.16568/j.0254-6086.201903006

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The main circuit topology, control hardware and control sequence of the cathode filament power supply for the HL-2A neutral beam heating system was introduced. Feedback control simulation of main circuit of filament power supply is carried out through MATLAB simulation software. It is found that the ripple factor is about 1%when the current is about 1000A, and the ripple coefficient increases to 3% when the current drops to 200A. Without the AC filter reactor in series L₁ and parallel harmonic filter LC in the low level control cabinet, the output current ripple coefficient becomes larger obviously. It shows that L₁ and LC not only absorb harmonic current, but also filter the chopper waveform after AC voltage regulation to make the output waveform smoother.

Research on forging and manufacturing process of HL-2M vacuum vessel support trunnion

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

2019, 39(3):  232-237.  DOI: 10.16568/j.0254-6086.201903007

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The manufacturing process of integral special-shaped forgings of the HL-2M vacuum vessel support trunnion was introduced, and the material testing was conducted by cutting the samples from the forging body. The test results show that the yield strength of the surface and core position of the trunnion forgings are 1100MPa and 1057MPa respectively, the grain size grade of those two positions can be up to grade 4, and all mechanical performance parameters can meet the design requirements.

Influence of interlayer’s thickness on Be/CuCrZr HIP diffusion bonding joints performance

WEI Zheng-xing1, CHEN Ji-ming1, WANG Ping-huai1,QIANG Jian-bing2, CHEN Yan-yu1, LI Qian1

2019, 39(3):  238-242.  DOI: 10.16568/j.0254-6086.201903008

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Beryllium (PVD coated on Ti, 10μm, Cu, 10μm), different thickness of oxygen-free cooper (OFC) sheets as transitionlayer and CuCrZr/316L(N) explosive bi-metallic plates are bonded by hot isostatic pressing (HIP), optical microscope, scanning electron microscope(SEM), Electron Probe Micro-analyzer(EPMA), X-ray diffraction( XRD), shearing tests are used to verify the diffusion bonding performance. Results turn out to be all kinds of mock-ups successfully bonded, no any cracks have been found in the diffusion bonding interface, three different kinds of diffusion layers are found between titanium and copper which are CuTi₂、CuTi and Cu₄Ti, respectively. The thicker of the OFC layer is, the better the shearing testing performance is.

Effect of annealing on Ti/CuCrZr HIP interface

CHEN Yan-yu1, WANG Ping-huai1, WANG Ying-min2, CHEN Ji-ming1, WU Ji-hong1

2019, 39(3):  243-248.  DOI: 10.16568/j.0254-6086.201903009

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As the ITER first wall Be/CuCrZr hot isostatic pressing (HIP) bonding intermediate transition layer, Ti/Cu layer can form a multi-layer intermediate metal phase, and defects such as cracks occur between the Ti/Cu metal phases. CuCrZr was used instead of Be, and a number of CuCrZr/Ti/Cu/CuCrZr joints were fabricated by the same HIP process as Be/CuCrZr to analyze the Ti/Cu joints. The effects of stress relief annealing on joint strength and defect distribution of the joints unannealed, annealed at 400°C and 500°C respectively were studied. The results show that three layers of Ti/Cu diffusion layers are formed on both sides of the intermediate titanium layer, namely Cu₄Ti, CuTi and CuTi₂. The thickness of Cu₄Ti on the pure copper side is thicker than that on the CuCrZr side, so that the crack is almost entirely distributed at the junction of Cu₄Ti and CuTi on the pure copper side where brittle fracture is easy to occur in the tensile samples. As the annealing temperature increases, the generation and propagation of cracks decreases.

Design of field monitoring system for ITER poloidal field power supply based on EtherCAT

YANG Ya-long1, 2, 3, LIU Wei1, 2, 3, GAO Ge1, HONG De-jian 1, 2

2019, 39(3):  249-255.  DOI: 10.16568/j.0254-6086.201903010

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According to the high real-time and high-reliability control requirements of ITER high-power poloidal field power supply, the industrial Ethernet field bus EtherCAT (Ethernet Control Automation Technology) with high real-time communication performance is selected to design the ITER poloidal field power field layer monitoring system. Due to the characteristics of large size and distributed distribution of the ITER poloidal field power supply device, as well as to ensure high reliability data transmission, the reliability of two kinds of EtherCAT ring network redundancy topologies are compared, and the EtherCAT ring network redundancy topology where the last station in slave station unit is an extension module converting E-BUS to 100BASE-TX/FX is more reliable and is adopted to design the structure of the poloidal field power supply monitoring system. The configuration software TwinCAT (The Windows Control and Automation Technology) is used to configure the system, and Human Machine Interfaces with functions such as visual display and control of live signals are drawn by this software. The experimental tests and operation demonstrate that the system can preferably realize real-time monitoring of hundreds of analog and digital signals on the field layer, and meet the high real-time and reliability control requirements of the ITER poloidal field power supply.

Development of the optimization design workflow for thermal shield based on parametric model

ZHU Zi-yang1, YE Min-you1, MAO Shi-feng1, LIU Xu-feng2

2019, 39(3):  256-264.  DOI: 10.16568/j.0254-6086.201903011

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In the integrated design framework provided in the CFETR integration design platform (CIDP), a workflow that can efficiently optimize the design of the vacuum vessel thermal shield (VVTS) was developed based on the parametric model. In the workflow, according to the geometry parameters of the parametric model of the VVTS, automatic modeling and finite element analysis in CAD/CAE software like CATIA and ANSYS can be driven by OPTIMUS software. The response surface model and sensitivity analysis are then used to determine the parameters which are closely related to the objective optimization. The optimized design parameters of the VVTS, which satisfy the design criterion, can be obtained by further optimization workflow. The application of the workflow is demonstrated by an example, where the safety requirement during plasma disruption events is considered. While the stress obtained by electromagnetic- structural analysis can meet the design criteria, the mass of the VVTS is minimized to reduce the construction cost and improve economics.

Enhanced heat transfer performances of subcooled water flow boiling in fusion reactor divertor

LIU Ping, WANG Peng-tong, DING Wen-long, LUO Chen-hui

2019, 39(3):  265-269.  DOI: 10.16568/j.0254-6086.201903012

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By using Fluent software with the Eulerian multiphase model and Non-equilibrium boiling model, the subcooled flow boiling heat transfers was numerically simulated in the plain upward vertical tubes under the condition of one-side heating. The influences of the different mass flux, inlet temperatures and heat flux on the heat transfer coefficient, the void fraction and heat transfer deterioration were investigated.

Development of arc detector with large dynamic range and digital control

ZHOU Xian-ming, LU Bo

2019, 39(3):  270-275.  DOI: 10.16568/j.0254-6086.201903013

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A new arc detector with ultra wide dynamic range was developed based on three gain adjustable amplifiers and microcontroller for the RF (radio frequency) windows in the high-power microwave heating systems on HL-2A/M tokamak. The gain is digitally adjustable with 8 levels in the main amplifier and the protection threshold is adjustable from 0 to 5V with accuracy of 20mV. Both the gain and threshold are remotely controlled with the help of a microcontroller. The measured maximum response time is 2.56μs. The arcing detectors work properly in different level of background light and in complicated electromagnetic environment.

Analysis and comparison of low activation characteristics of nuclear structural material SIMP steel

LI Xia1, 2, LIU Song-lin1, ZHANG Xiao-kang1, 2, YAN Wei3, WANG Zhi-guang4

2019, 39(3):  276-281.  DOI: 10.16568/j.0254-6086.201903014

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The activation properties of SIMP steel have been simulated under the conditions of the water cooled ceramic breeder (WCCB) blanket for China Fusion Engineering Test Reactor (CFETR) by coupling of the MCNP (Monte Carlo N-Particle Transport Code) and FISPACT activation code. The simulation results of specific activity, decay heat, contact dose rate and radiation damage of SIMP steel have been fully compared with other RAFM steel such as EUROFER-97, F82H and so on. The comparisons show that the SIMP has good activation performance corresponding to low activation performance of RAFM. It is conclusion that the SIMP can be chosen as one candidate structural material used for future fusion reactor blanket.

Non-Fusion Plasma Applications

Study of magnetic insulation with uniform charge density

YIN Mao-wei, SUN Yuan, WEI Jia-jun, ZHANG Yu-ting, LI Yu-lin, LIAO Peng

2019, 39(3):  282-288.  DOI: 10.16568/j.0254-6086.201903015

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With the uniform charge density in the magnetically insulated transmission line (MITL) of parallel plate, a laminar flow model with pressure balance and a new model without the assumption of laminar flow and pressure balance are solved analytically, respectively. The results of laminar flow model and non-laminar flow model are compared. It is shown that the charge density is smaller and electric field, magnetic field on anode is bigger in laminar flow model as without radial velocity of electrons. Then, the result of particle-in-cell simulation is compared for the two theories and shows that the accuracy of non-laminar model is higher than laminar model. Finally, the pressure balance equation and two models of laminar and non-laminar with the uniform charge density have been promoted to coaxial MITL and cone MITL.