Table of Content

15 September 2024, Volume 44 Issue 3

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Nuclear Fusion Engineering

Research on loop flow control of HL-3 poloidal field power supply

YAO Ju-kun, LI Wei-bin, WU Yi, ZHENG Xue

2024, 44(3):  249-255.  DOI: 10.16568/j.0254-6086.202403001

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In order to achieve the HL-3 plasma configuration control without dead zone, the poloidal field (PF) power supply needs to have four-quadrant circulating current operation capability with the controllable and fast zero-crossing characteristics. Based on the topology and load characteristics of the HL-3 poloidal field power supply, the circulation mathematical model of the four-quadrant power supply is deduced and a circulation control strategy is proposed by real time conduction angle modulation of the thyristor. The PSIM is used to verify the correctness and reliability of the strategy, and the simulation results show that the load current could cross the zero point quickly and smoothly under different control requirements, and dead zone of the circulating current is less than 2ms, which provides a guarantee for the stable control of the advanced plasma discharge in the HL-3 tokamak. 

Improvement and test of the optical path of ECRH No.1 upper launcher on HL-3 tokamak

ZHENG Wan-xin, YE Ji-ruo, CHEN Gang-yu, ZHANG Feng, HUANG Mei

2024, 44(3):  256-261.  DOI: 10.16568/j.0254-6086.202403002

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For different purposes of plasma experiments in HL-3 tokamak, three sets of launchers are designed for the electron cyclotron resonance heating system. The No.1 upper launcher contains two microwave beams. Its main function is to control the instability of MHD and suppress the new classical tearing mode (NTM) in real time. To control and suppress NTM in real-time, it is necessary to rely on the launcher to quickly change the injection angle, and then inject microwave to magnetic island. In response to the problems in the previous optical path design, the focusing mirror of No.1 upper launcher has been redesigned and processed. The performance of the launcher was tested using a laser simulated microwave on an optics testing platform. The fastest change time for the left and right motors of the tested launcher to operate at full range (injection angle −15° to −80°) is 189.875ms and 189.5ms. The test results show that the launcher control is accurate and fast, which meets the requirements for experimental use of the device. 

Analysis of the seismic response spectrum of the HL-3 carbon-based first wall 

TANG Le, CAI Li-jun, LU Yong, YUAN Ying-long, HOU Ji-lai, ZHANG Long, LIU Kuan-cheng, LAI Chun-lin

2024, 44(3):  262-266.  DOI: 10.16568/j.0254-6086.202403003

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The response spectrum analysis of the HL-3 carbon-based first wall under seismic condition is performed. The model containing the basic components of the host system is established, and the dynamics characteristics of the first wall system are achieved through the modal analysis. The response spectrum method is adopted for the seismic analysis of the first wall model, and the formation and stress distribution of the first wall structure under the seismic condition is obtained. The analysis results show that the carbon-based first wall meets the safety requirements of structural design. 

Preliminary structure design and analysis of CFETR ECRH system launcher

ZHANG Li-yuan, WANG Xiao-jie , WU Da-jun , TANG Yun-ying , WANG Han-lin, LIU Fu-kun

2024, 44(3):  267-274.  DOI: 10.16568/j.0254-6086.202403004

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The electron cyclotron resonance heating (ECRH) is an essential auxiliary heating and current driving method for the Chinese Fusion Engineering Testing Reactor (CFETR) to achieve scientific mission. The launcher is one of the core components of the ECRH system. In order to obtain the optimal current drive efficiency of the plasma, the preliminary structure design of ECCD system upper launchers is carried out from five aspects: overall layout, propagation of beam, convergence and launch of beams, neutron shielding, and maintenance scheme. A method of multibeam convergence is adopted for the ECCD launcher, and therefore two sets of 9-beam microwave powers inject into the resonance layer of the plasma through the compact upper port of the CFETR. Using a port-plug structure for the launcher design is beneficial to neutron shield and remote handing maintenance. The effective active cooling schemes for the launcher mirror have been designed via fluid-thermal-solid coupling simulation. The above analysis and design lay a foundation for the further detailed engineering design of ECRH launchers. 

Design of CFETR divertor cryo-pump pumping system and calculation of effective pumping speed

ZHANG Xi-yang , XU Tie-jun , YAO Da-mao

2024, 44(3):  275-281.  DOI: 10.16568/j.0254-6086.202403005

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CFETR has put forward the concept of hybrid divertor-blanket. The lower part of the divertor is occupied by the breeding blanket. The divertor pumping channel is designed in the breeding blanket to meet the engineering design requirements that the effective extraction flow of the divertor is 250Pa·m³ ·s^-1 . Based on the vacuum flow conductance calculation theory, the divertor cryo-pump pumping system is designed, and the flow conductance of the divertor cryo-pump pumping system and the effective pumping speed of a single cryo-pump at the inlet of the divertor pumping channel under different section shapes are calculated and compared. It is more reasonable to design a square section pumping channel in the breeding blanket, which can meet both the exclude impurities requirements and the strength requirements of the breeding blanket. When the square section size is 350mm×350mm, the flow conductance of the divertor cryo-pump pumping system is 12.08m³ ·s^-1 , the effective pumping speed of a single cryo-pump at the inlet of the divertor pumping channel is 9.905m³ ·s^-1 , 26 cryo-pumps can meet the exclude impurities requirements, and if one lower window is equipped with 2 cryo-pumps, the cryo-pumps occupy altogether 13 lower windows. Based on the theoretical formula, the cryo-pump pumping system of the divertor is designed and the exclude impurities ability of the divertor is evaluated, which provides a theoretical basis and reference for the subsequent optimization of the divertor pumping channel and evaluation of the effective pumping speed of CFETR. 

Design of water-cooling structure for spherical tokamak magnet based on the Fluent 

LI Ning, XU Hao , YANG Qing-xi , CHEN Jian , CHEN Shi-lin, LU Kun

2024, 44(3):  282-289.  DOI: 10.16568/j.0254-6086.202403006

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Numerical simulations of fluid flow and heat transfer within the magnet of the SUNIST-2 spherical tokamak was conducted with the Fluent, and the design of water-cooling structure of the magnet was optimized. Based on the SUNIST-2 specific operational conditions, the simulation analyses of the magnet's water-cooling system performance are performed under various flow rates and different inlet temperatures, for comparing the cooling efficiency and pressure drop under each condition. The results indicate that the optimized magnet water-cooling structure scheme significantly enhances the stability and safety of the magnet under actual operational conditions, which was validated through pressure drop tests on the water-cooling structure of the fabricated magnet. 

Design and application of alignment and metrology datum control network upgrade scheme on EAST 

GU Yong-qi, ZHENG Yuan-yang , YUAN Zhong , WANG Jun , WEI Wen-qi

2024, 44(3):  290-296.  DOI: 10.16568/j.0254-6086.202403007

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To obtain higher plasma operating parameters and longer running time, the EAST has been upgraded. The upgrade scheme of alignment and metrology datum control network on EAST is introduced. The number of fiducial points is increased, and the layout of the fiducial points is optimized. Horizontal level and multi-station laser tracker are used for multi-path measurement of the internal and external datum control network, and SA software is used to carry out 3D deviation analysis and calculation of the unified space metrology network (USMN). Through measurement data analysis, the average measurement uncertainty of all fiducial points is 0.039mm and the maximum measurement uncertainty is 0.176mm, which are better than the design requirements of average measurement uncertainty of 0.15mm and maximum measurement uncertainty of 0.20mm, meeting the installation requirements of new divertors and key components in EAST upgrading. 

Design and analysis of high temperature cooling water system for CRAFT NNBI beam source 

XIA Wen-ying, YANG Lei , HU Chun-dong , GUO Bin , ZHU Li-li , LI Wei-bao

2024, 44(3):  297-303.  DOI: 10.16568/j.0254-6086.202403008

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The preliminary design and thermal-hydraulic analysis of the Negative Neutral Beam Injection (NNBI) cooling water system in the Comprehensive Research Facility for Fusion Technology (CRAFT) is presented. The thermal-hydraulic model is established by Flowmaster software, and the precise temperature control is realized with Proportional-Integral-Differential (PID) control. The simulation results show that the temperature, pressure drop and temperature control accuracy meet the beam source constant temperature water supply system operation requirements that the water temperature is within 150~200℃ with the control accuracy of 0.5℃. The results will provide reference for thermal and hydraulic analysis and temperature control of NNBI cooling water system. 

Development of high current and refrequency pulse supply power system for compact torus core fueling device 

LI Yun-hai , YE Yang , TANG Liang-hao, TAN Ming-sheng , TONG Yi , YANG Rong , XIE Xiao-feng , DENG Tian-bai , KONG De-feng , TAO Jun

2024, 44(3):  304-311.  DOI: 10.16568/j.0254-6086.202403009

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Compact torus injection (CTI) technology is an effective means to realize core fueling in fusion device. A set of high current and repetition rate pulse power supply system is designed to realize the CTI. By deducing the lumped parameter calculation formula of the equivalent RLC second-order discharge circuit, the calculation formula of key parameters such as the peak value of discharge current and half wave period is obtained, and the basic parameters of the four-way pulse power supply are designed. The parameters are modeled and simulated, and the simulation waveform and the result parameters are given. The key discharge switch components are analyzed and selected, and the low-inductive installation structure of power supply is designed The discharge test of the power supply was carried out on the full-superconducting tokamak-compact torus injection device (EAST-CTI). The remote control software was used to flexibly set parameters and control the working time sequence of the power supply. The actual discharge waveform and output current parameters were in good agreement with the theoretical calculation and simulation. The peak current of the power supply exceeds 300kA and the repetition rate is 2Hz, which indicates that the designed power supply system can be effectively applied to the CTI device and has good engineering practical value. 

Research on heat transfer enhancement by inserting twisted band in the first wall of the helium cooled ceramic breeder blanket  

YANG Yu-xiang, WANG Zi-jing, LEI Ming-zhun

2024, 44(3):  312-317.  DOI: 10.16568/j.0254-6086.202403010

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To address the issue of insufficient heat transfer capacity in the first wall (FW) of the helium-cooled ceramic breeder blanket, a twisted band was inserted into the cooling pipe to investigate enhanced heat transfer. Thermal fluid analysis on the first wall was conducted using principles from engineering fluid mechanics theory and CFD software. The impact of different parameters related to twisted band on heat transfer under identical operating conditions was examined. The simulation indicates that twisting band effectively enhances heat transfer capability in the first wall. Optimal heat transfer performance is achieved with a band thickness of 3mm, bandwidth of 11mm and twisting rate of 2.5. This configuration leads to an average increase in inner wall heat transfer coefficient by 7.9% while reducing structural temperature rise by 8.6%.

Test and analysis on outgassing performance of insulation material G10 for future fusion reactor 

JI Hai-biao, XING Yin-long, WU Jie-feng, LIU Zhi-hong , WEN Wei, LIN Xiao-dong

2024, 44(3):  318-322.  DOI: 10.16568/j.0254-6086.202403011

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A test platform for the outgassing rate of the insulation material sample G10 in CFETR was designed and built, and the outgassing rates of two G10 materials were measured to provide the reference for the selection of insulation material G10 for future fusion reactor. 

Development of samarium-cobalt permanent magnet flowmeter and the velocity measurement of lead-lithium natural convection loop 

ZHAO Yao, SUN Zhen-chao, ZHANG Xiu-jie, PAN Chuan-jie, WANG Lei

2024, 44(3):  323-327.  DOI: 10.16568/j.0254-6086.202403012

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A development process for the samarium-cobalt permanent magnet flowmeter is presented, consisting of material selection, structure design, operation principle and internal magnetic field distribution. The calibrated average velocity by the commercial flowmeter in the gallium-indium-tin high temperature scouring loop is about 1.8 times of the measured value by the samarium-cobalt permanent magnet flowmeter. The calibrated formula is applied to the velocity measurement of lead-lithium natural convection loop and compared with the simulation of commercial software ANSYS Fluent. The error between them is about 23.3%, and is analyzed. It can be determined that the velocity range of lead-lithium natural convection loop is from 0.05m·s^-1 to 0.06m·s^-1 through the experiment and analysis. 

Plasma Physics

Observation of high-frequency magnetohydrodynamics instability in HL-3 Ohmic plasmas

YANG Qiu-lei, CHEN Wei, ZHANG Jie, CHENG Shi-kui, LIANG Shao-yong, ZHANG Yi-po, HL- Experimental Team

2024, 44(3):  328-333.  DOI: 10.16568/j.0254-6086.202403013

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This article describes the experimental observation obtained from HL-3 Ohmic plasma, using magnetic probe diagnostics. This measurement reveals the presence of two type high-frequency magnetohydrodynamics (MHD) instability in plasma. During the plasma start-up phase, the current rise is inhibited at t≈40ms and sodium iodide (NaI) detector measures enhancement of runaway electrons. At the same time magnetic probe diagnostics measure multi-branch upward-swept high-frequency MHD instability with a frequency range of f  is 20~400kHz. The results indicate that the instability, which is related to enhancement of runaway electrons, inhibits the plasma current rise with a loss of about 7% volt-second. When the plasma current and density are in climbing stage, magnetic probe diagnostics detects a downward-swept high-frequency MHD instability with a frequency range of f  is 110~160kHz. The frequency of instability is proportional to the core Alfvén frequency, which lies in the toroidal Alfvén eigenmode (TAE) frequency range. The plasma discharge is terminated as the instability evolves. The study of the high-frequency MHD instability has important reference for the subsequent discharge of HL-3 tokamak and the initial discharge of ITER in future. 

Experimental study of the SOL blob spatio-temporal characteristics in HL-2A tokamak 

ZHU You-jing , CHENG Jun , YAN Long-wen , WANG Wei-ce , HUANG Zhi-hui , WU Na , XU Yu-hong , SHI Zhong-bing , JI Xiao-quan , ZHONG Wu-lü , XU Min

2024, 44(3):  334-342.  DOI: 10.16568/j.0254-6086.202403014

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The spectral characteristics of the scrape-off layer (SOL) electrostatic fluctuations and blob dynamics have been studied by using two Langmuir probe arrays toroidally separated by 2100mm in HL-2A tokamak. The experimental results demonstrated that the fluctuation along the magnetic field line has the significant toroidal long-range correlation and the estimated parallel wavenumber is almost zero. These characteristics are well consistent with the theoretically predicated interchange instability. An E×B shear layer close to 1.0cm width forms just outside the LCFS during the ECRH, which has the ability to stretch the passing blobs. Conditional average analysis shows the potential difference in one blob increases by up to 40%~60% in ECRH, compared to that in Ohmically-heated plasma, which is much larger than the variation of blob poloidal size (20%~30%). This experimental finding presented here reveals that the increased internal potential differenceis the main cause for driving the blobs to move outward quickly. Therefore, this study provides an alternative interpretation for the additionally intermittent transport observed in ECRH and could help understand the behind physics on blob radial velocity scaling and find suitable control methods for suppression of the blob convective transport in future. 

Quantitative description of the spreading properties in ion temperature gradient driven turbulence 

TIAN Hui, LI Ji-quan

2024, 44(3):  343-350.  DOI: 10.16568/j.0254-6086.202403015

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The spreading properties of ion temperature gradient (ITG) driven turbulence in a shearless slab geometry are numerically simulated by using the gyrokinetic model. A quantitative description method on the turbulence spreading is proposed by defining the effective turbulence spreading distance. The parametric dependence of turbulence spreading properties on the magnetic field configuration factor and the characteristic length of ion temperature gradient is quantitatively discussed. The results show that the intensity of turbulence spreading increases with the decrease of the poloidal magnetic field. As the characteristic length of ion temperature gradient increases, turbulence spreading weakens. Particularly, the role of zonal flows in turbulence spreading is investigated by comparing the spreading characteristics in ITG and ETG turbulence and ITG turbulence under different collision damping. The simulation results show that zonal flows have a significant suppression effect on turbulence spreading under the model discussed in this paper. 

Simulation on the impact of diamagnetic drift on edge localized modes

ZHOU Yu-jie, HAO Guang-zhou, ZHU Yi-ren, XUE Miao

2024, 44(3):  351-358.  DOI: 10.16568/j.0254-6086.202403016

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In this study, numerical investigations on the effect of diamagnetic drift on ELMs are conducted using the BOUT++ three-field model, with a focus on the hybrid scenario in the HL-3 tokamak. The results show that diamagnetic drift has a significant stabilizing effect on ELMs, especially on the ballooning modes with high toroidal mode numbers, which lead to the most unstable modes transition from ballooning modes with high toroidal mode numbers to peeling modes with low toroidal numbers. Furthermore, the study reveals that the variation in the radial distribution of diamagnetic drift induces deformation in the ELM mode structure. Analysis of the ELM size shows diamagnetic drift can reduce the amplitude of ELM bursts, which is beneficial for the control of ELMs in HL-3 hybrid scenario. 

The isotope effect on ion temperature gradient mode in CFQS

QIN Cheng, HUANG Jie, LI Mo-shan

2024, 44(3):  359-366.  DOI: 10.16568/j.0254-6086.202403017

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Based on Chinese First Quasi-axisymmetric Stellarator (CFQS), we carry out the study of isotope effect on ion temperature gradient (ITG) mode in quasi-axisymmetric stellarator by using the gyrokinetic Vlasov simulation code GKV. The simulation results show that there is an obvious isotope effect on ITG in CFQS. The growth rate of ITG decreases significantly with the increase of the mass of hydrogen isotope. To scan the plasma parameters in CFQS, such as the content of the heavier hydrogen isotope in the mixed plasma, density gradient, and ion-to-electron temperature ratio, we study impact of these parameters on isotope effect. Otherwise, we also study the isotope effect of ITG in different toroidal angles and different radial positions of CFQS, and the results reveal the isotope effect of ITG is universal in CFQS. 

Influence of Soret and Dufour effect coupling on double diffusion of deuterium concentration and temperature in HL-2A diverter target plate 

SHAO Li-hua, LIU Ze-kang, LI Zai-xin, CAI Lai-zhong

2024, 44(3):  367-372.  DOI: 10.16568/j.0254-6086.202403018

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The JD-CF program with the Soret and Dufour coupling models was used to study the effects of deuterium particle concentration, temperature, and retention versus time in the HL-2A divertor target plate material under L-mode and H-mode discharges. The results indicate that the Soret and Dufour effects will have a certain impact on the concentration distribution, temperature distribution, and deuterium retention at different positions in different materials under the L/H mode discharges, with a maximum change rate of about 10%. Soret and Dufour effects have a more significant impact on RAFM steel under H-mode discharges than on L-mode discharges, and a more significant impact on RAFM steel than tungsten. The results have certain reference value for studying edge plasma transport, fusion reactor fuel recycling, tritium retention, and inventory.