Table of Content

15 June 2024, Volume 44 Issue 2

Previous Issue    Next Issue

Nuclear Fusion Engineering

Development of a CO₂ laser collective scattering system on HL-2A tokamak

WEN Ruo-nan, YAO Ke, LIU Yi, XU Yu-hong, SHI Zhong-bin, ZHONG Wu-lü

2024, 44(2):  125-132.  DOI: 10.16568/j.0254-6086.202402001

Asbtract ( )   PDF (4411KB) ( )  

References | Related Articles | Metrics

A CO₂ laser coherent scattering diagnostic system was successfully developed on the HL-2A tokamak. The tangential optical path layout which can improve the spatial resolution of the system and a dual-channel homodyne detection design were adopted. The two channels can simultaneously measure the small-scale turbulent changes of the plasma core (ρ≈0.28) with wavenumber in the range of 10~45cm⁻¹. The wave number resolution is ±3cm⁻¹ and the time resolution is 0.5μs. The system can provide important data for the study of plasma core transport. In addition, the main beam and the local oscillator beam of the diagnostic system pass through the plasma at the same time, which can also detect various large-scale plasma fluctuations in the core. The analysis of the diagnostic signals indicates that the system can accurately respond to the evolution of the small-scale turbulence in the plasma core, and also provide useful information for studying the macro-instability in the core area of plasma.

Numerical simulation analysis of the heat exchange of W/Cu module in the divertor 

ZHANG Xiao-qiang, LU Bi-wei, LIU Jia-qin, SUN Fei, WU Yu-cheng

2024, 44(2):  133-140.  DOI: 10.16568/j.0254-6086.202402002

Asbtract ( )   PDF (6737KB) ( )  

References | Related Articles | Metrics

The steady-state thermal simulation on the flat plate W/Cu module in the divertor was carried out by theoretical formula and CFX software, respectively, and the profiles in temperature and stress fields of the W/Cu module under different heat fluxes were obtained. The convective heat transfer coefficient is about 52304 W·(m²·K)^-1 by formula, and is about 35168~52186W·(m²·K)^-1 by CFX software. In addition, the temperature profiles of the W/Cu module obtained by the two steady-state thermal analysis methods are similar. Under the heat flux of 20 MW·m^‒2, the results of temperature field and stress field of the W/Cu module are beyond the allowable range of the corresponding materials, which seriously affected the stable operation of the divertor.

Preliminary study on low frequency drift mode database and its machine learning on the HL-2A tokamak

SHEN Yong, DONG Jia-qi, LI Jia, HAN Ming-kun, SHEN Yu-hang, ZHANG Xiao-ran, LIU Jia-yan, WANG Zhan-hui, LI Ji-quan

2024, 44(2):  141-148.  DOI: 10.16568/j.0254-6086.202402003

Asbtract ( )   PDF (4031KB) ( )  

References | Related Articles | Metrics

In order to explore the establishment of the HL-2A/3 experimental drift wave mode database and take it as the sample data, through the machine learning method, the artificial neural network is used to predict the occurrence and intensity of drift wave mode instability on tokamak discharge and then offer the supporting conditions to realize the real-time control of the HL-2A/3 plasma. A basic database of low frequency drift wave modes is constructed based on the calculation results for the case of four primary parameters (h, e, q, s). Then, based on the back propagation neural network (BP network) and the support vector machine (SVM) models, the neural network modeling and programming experiments were carried out, respectively, which verified the feasibility of intelligent prediction of ion temperature gradient (ITG)\trapped electron modes (TEM) instability of HL-2A tokamak. The preliminary results show that by further expanding the database by including all the sensitive parameters, accelerating the training speed of BP network, or adopting more complex models such as deep learning, the ultimate target of drift wave mode prediction can be finally achieved.

Research on HL-2A fishbone mode recognition algorithm based on deep learning

ZHU Xiao-bo, XIA Fan, YANG Zong-yu, LIU Feng-wu, GONG Xin-wen, LIU Yu-hang, ZHANG Yi, SHI Pei-wan, CHEN Wei, YU Li-ming, CHEN Zheng-wei, ZHONG Wu-lü

2024, 44(2):  149-156.  DOI: 10.16568/j.0254-6086.202402004

Asbtract ( )   PDF (5919KB) ( )  

References | Related Articles | Metrics

Based on the deep learning method, a set of fishbone mode (FB) recognition algorithm was developed on the HL-2A tokamak. The algorithm uses 858 shot discharge data (780 for training and 78 for verification) and about 463800 data slices for training and verification, and obtains a convolutional neural network mainly composed of convolutional layer, residual connection layer and fully connected layer. In order to measure the recognition ability of the algorithm, the algorithm was used to scan and identify the 780 discharge data, and a total of 86820 FB slices were identified, of which 4327 were misidentified, and the false alarm rate was 4.75%. In the actual 97145 FB slices, 10325 slices were missed, and the corresponding false negative rate was 10.63%, and the overall recognition accuracy rate reached 94.26%. The false positive rate and false negative rate can meet the accuracy requirements of FB recognition.

Safety interlock and remote monitoring of phase contrast imaging system on HL-2A tokamak

GONG Shao-bo, YU Yi, WANG Zhi-bing, WANG Hua-jie, YUAN Jin-bang, LIU Hao, WU Ting, LONG Ting, CHEN Yi-hang, KE Rui, NIE Lin, WANG Zhan-hui, SUN Ai-ping, XU Min

2024, 44(2):  157-162.  DOI: 10.16568/j.0254-6086.202402005

Asbtract ( )   PDF (3327KB) ( )  

References | Related Articles | Metrics

An electronically controlled safety shutter is introduced into the optical path of the phase contrast imaging system to control the laser output, and a delay circuit is used to achieve the synchronous triggering of the safety shutter and HL-2A discharge to ensure the safe operation of the diagnostic system. The temporal response of the safety shutter is 26ms with an error of 1ms. The four-quadrant sensor is used to realize the real-time monitoring of the laser beam spot position, and obtain the vertical and horizontal vibration data of the HL-2A tokamak. The electronically controlled shutter technology and laser real-time monitoring system developed in this research can not only raise greatly the safety and reliability of the phase contrast imaging system, but are of great significance to the development and optimization of the diagnostic systems on HL-2A and HL-3 tokamak.

Numerical study on gas and powder flow characteristics of helium cooled solid blanket tritium breeding pebble bed

WANG Kai-song, LIU Ming-zong, WANG Jian

2024, 44(2):  163-169.  DOI: 10.16568/j.0254-6086.202402006

Asbtract ( )   PDF (3098KB) ( )  

References | Related Articles | Metrics

Based on the coupled analysis method of computational fluid dynamics and discrete element method, the flow characteristics such as the velocity distribution and outlet of the helium-cooled solid proliferating blanket pebble bed were studied, as well as the changes in the velocity of the broken lithium orthosilicate powder over time and the variation of the powder quantity with the helium gas inlet flow rate. The results show that the normalized helium velocity with the helium inlet flow rate is independent of the inlet flow rate in the direction of helium flow, with larger changes in velocity near the edge of the pebble bed and smaller changes in the middle of the pebble bed, while the normalized velocity of the powder has little to do with the inlet flow rate and will gradually stabilize with the sweeping time; for small particle size powders, the higher the gas flow rate, the easier to be blown out of the pebble bed, while for large size powders, due to their large volume, there are blockages in the pebble bed.

Correction of poloidal position in microwave imaging diagnostics based on ray-tracing

GAO Yuan, YANG Zhou-jun, ZHANG Zhi-chao, LUO Qiang, JIN Zi-yang, GAO Li, PAN Yuan

2024, 44(2):  170-176.  DOI: 10.16568/j.0254-6086.202402007

Asbtract ( )   PDF (2904KB) ( )  

References | Related Articles | Metrics

The influence of the plasma is studied in the quasi-optical design of microwave imaging diagnostics. The ray-tracing method is used to calculate the poloidal imaging position of ECEI diagnostic with J-TEXT experimental parameters. It is found that when the focusing position is located on the high-field side and the plasma density is high, the actual imaging position deviates greatly from the position of quasi-optical design. This correction will not only improve the reliability of diagnostic, but also provide a reference for analysis of signal, optimization of diagnostic operation interval and imaging optical design.

Preload analysis of screw bolt joints on 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(2):  177-182.  DOI: 10.16568/j.0254-6086.202402008

Asbtract ( )   PDF (2689KB) ( )  

References | Related Articles | Metrics

The bolt preload of the HL-3 carbon-based first wall basic module at high temperature was analyzed, and the stress distribution of the first-wall structure and the variation of bolt pretension force was obtained, which provides the data support for the on-site installation of the first-wall structure.

Development of the monitoring and alarm system for key parameters of RF-driven negative ion source neutral beam

WANG Ze, HU Chun-dong, XIE Ya-hong, LIU Wei, CUI Qing-long, ZHAO Yuan-zhe, XU Yong-jian, BAN Ting, DUAN Lian

2024, 44(2):  183-190.  DOI: 10.16568/j.0254-6086.202402009

Asbtract ( )   PDF (4207KB) ( )  

References | Related Articles | Metrics

To effectively solve the problems of decentralized monitoring and untimely alarm of key parameters in RF-Driven negative ion source experiments, a monitoring and alarm system based on EPICS control system architecture for key parameters of RF-driven negative ion source neutral beam was designed and developed. The monitoring and alarm interface is realized through Phoebus integrated developing platform, and the cross-platform integration of EPICS, LabVIEW, and PLC is realized by Channel Access (CA) protocol and s7nodave device driver module. At present, the system has run normally in the RF-driven negative ion source experiment, which not only realizes the visual real-time monitoring, failure alarm, and failure tracking of the key parameters of neutral beam injection but also provides a reliable guarantee for the normal operation of the RF-driven negative ion source neutral beam experiment.

Research on virtual simulation of motion trajectory of remote handling manipulator in a tokamak

CHEN Xiao-lu, LI Peng-yuan, WEI Hai-hong, XU Wan-yun, CHEN Hui

2024, 44(2):  191-197.  DOI: 10.16568/j.0254-6086.202402010

Asbtract ( )   PDF (6675KB) ( )  

References | Related Articles | Metrics

Aimed at the motion trajectory problem of remote handling in a tokamak, a three-dimensional scene simulation platform, based on MATLAB and V-REP (Virtual Robot Experimentation Platform), was built for the vacuum vessel maintenance robot. The D-H (Denavit-Hartenberg) parameter was established to analyze the kinematics of manipulator, and the reachable workspace of manipulator was obtained by Monte-Carlo method. The high-order polynomial interpolation method was applied to plan a smooth and continuous interpolation curve for the motion trajectory simulation of the CFETR (China Fusion Engineering Test Reactor) vacuum vessel remote handling, which obtains the simulation curve of the manipulator end. The angular velocity and torque of each joint change smoothly, and the maximum value does not exceed the design value of the robot, which proved the correctness of the algorithm and the feasibility of the trajectory planning to a certain extent. The simulation results showed that the manipulator can adapt to the complex environment inside the vacuum vessel, and can effectively plan the motion trajectory that meets the requirements of the established space task. It is positive significance for the application and trajectory planning of remote handling in a tokamak.

Effect of sheath capacitance on the I-V characteristics of fast sweeping double Langmuir probe

SUN Hai-gang, JIN Cheng-yao, ZHANG Wei, JIANG Di, YIP Chi-Shung

2024, 44(2):  198-205.  DOI: 10.16568/j.0254-6086.202402011

Asbtract ( )   PDF (6434KB) ( )  

References | Related Articles | Metrics

A 500kHz asymmetric fast sweeping double probe system based on multi-dipole confined hot cathode discharge was constructed to experimentally investigate the effect of capacitance on measurement results. The results of fast sweeping asymmetric Langmuir double probe with different size effected by the ion saturation current and sheath current at different sweeping frequency are compared and analysed. This research provides a reference and guide for the selection and application of fast sweeping asymmetric double probes at different sweeping frequency.

Study on dependence of tungsten primary crack on pulse width time under transient heat flow

QU Miao, YAN Sha

2024, 44(2):  206-213.  DOI: 10.16568/j.0254-6086.202402012

Asbtract ( )   PDF (3867KB) ( )  

References | Related Articles | Metrics

In order to study the dependence of the crack behavior of tungsten under transient heat flow on the time distribution of heat source parameters, the pure tungsten samples have been irradiated by transient heat flow with pulse width t of 80ns, 1ms, 5ms at different energy densities E and pulse numbers. Two types of cracks on the tungsten surface were observed, including primary and secondary cracks. The primary cracks can be assorted as branch and network ones according to their patterns. By analyzing the characteristic quantities of primary cracks, it was found that when the surface temperature rise caused by thermal pulses with different pulse widths is similar, the shorter the pulse width, the higher the density of primary cracks. Considering the ductile-to-brittle transition property of W, an ideal elasto-plastic mechanics model is adopted in the thermodynamic finite element model, which is used to calculate the distribution and evolution of surface temperature and stress on tungsten under heat pulse irradiation with three kinds of pulse width. It is found that the differences of strain rate magnitude caused by the changes of pulse width can reflect the mechanical properties of materials. The shorter the pulse width, the stronger the brittleness of the material, leading to changes in the characteristics of primary cracks. Combining experimental and computational results, Et^‒3/2 is proposed to characterize the relative size of primary crack network density under thermal pulse irradiation with pulse width ranging from 100 ns to several ms.

Plasma Physics

Experimental observation and simulation study of beta-induced Alfvén eigenmodes in the HL-2A tokamak 

YIN Gang, BAO Jian, CHEN Wei

2024, 44(2):  214-221.  DOI: 10.16568/j.0254-6086.202402013

Asbtract ( )   PDF (7888KB) ( )  

References | Related Articles | Metrics

Based on the experimental observations of beta-induced Alfvén eigenmodes (BAE) in the HL-2A tokamak, the simulation study of BAE has been conducted using the eigenvalue program GAM-solver. The simulated results find that the frequency of BAE is in the range of about 50~70kHz, which increases with the increase of toroidal mode numbers (n). These simulation results are consistent with the experimental observations. Moreover, the mode frequency of BAE with n=3 has been predicted using GAM-solver, and the effects of the main parameters, such as ion-beta (β_i), electron temperature (T_e), and ion temperature (T_i), on the mode frequency of BAE have been studied. The results show that the frequency of the BAE mode is proportional to the square root of β_i; the increase of T_e and T_i will increase the frequency of the accumulation point of the BAE continuum spectrum. The structures of the continuum spectrum and the BAE mode are insensitive to T_e and T_i. The mode frequency increases with the increase of T_e and T_i, which is consistent with the accumulation point frequency of BAE, and the frequency of BAE is more sensitive to T_i.

Research on visible imaging system of plasma boundary on EAST

CHEN Ming, SHEN Biao, Shinichiro Kado, CHEN Da-long, ZHANG Heng, GUO Bi-hao, HUANG Yao, CAI Fu-rui, XIAO Bing-jia

2024, 44(2):  222-228.  DOI: 10.16568/j.0254-6086.202402014

Asbtract ( )   PDF (4657KB) ( )  

References | Related Articles | Metrics

In this paper, a set of high-precision folding optical system for H_a band is designed to observe the plasma boundary features, which achieves a resolution of 4 mm in the full field of view. Based on the local features of the image and the camera model, an optical plasma boundary reconstruction algorithm was developed and validated on EAST for plasma control points at the midplane of the high field side. The evolution of control points for optical reconstructions over time is in good agreement with the results of magnetic equilibrium reconstructions.

Research on plasma boundary recognition algorithm based on HL-2A optical imaging system

HE Meng-yuan, JI Xiao-quan, GAO Jin-ming, SUN Teng-fei, LIANG Shao-yong, WANG Ao

2024, 44(2):  229-235.  DOI: 10.16568/j.0254-6086.202402015

Asbtract ( )   PDF (2319KB) ( )  

References | Related Articles | Metrics

Based on the HL-2A Tokamak optical imaging system, an algorithm for plasma boundary reconstruction is designed, which has the advantages of fast operation speed and outstanding robustness to various noise signals. Firstly, the optical image is processed by the basic algorithm of digital image processing, then the plasma boundary coordinates in the image are extracted and fitted. Finally, the actual coordinates of plasma boundary are obtained by coordinate transformation, that is, the reconstructed plasma boundary. Comparing the optical reconstructed plasma boundary with the last closed flux surface by EFIT, the average errors of the high and low field side boundaries are about 8.5mm at midplane, and the overall average error is 11mm. The average time to identify each image on the experimental hardware equipment and software platform is 3ms. The proposed algorithm is expected to be used in plasma configuration identification and control under the current experimental results. It is consistent with EFIT qualitatively and quantitatively. In addition, it is not affected by magnetic field, and has excellent stability and robustness.

Design and sensitivity analysis of advanced snowflake divertor on HL-3 tokamak

LI Shi-min, WANG Zhan-hui, WANG Zhi-bin, HUANG Bo, LUO Yi-ming, WU Xue-ke, FU Cai-long, Kunlun integrated simulation and design Group

2024, 44(2):  236-241.  DOI: 10.16568/j.0254-6086.202402016

Asbtract ( )   PDF (5199KB) ( )  

References | Related Articles | Metrics

The configuration of the HL-3 snowflake divertor by using the EFIT program was designed, and the sensitivity of the snowflake configuration of HL-3 tokamak on the individual lower poloidal field (PF) coil current was studied. It was found that when the individual lower PF coil current only changes by 1%, the standard snowflake divertor immediately changes to a snowflake plus configuration or snowflake minus configuration, and when the individual lower PF current changes above 8.8%, the snowflake minus configuration can reach a equilibrium configuration with a large deviation, while the convergence result is difficult to be obtained under the snowflake plus configuration.

Experimental verification of laser-induced fluorescence based on the velocity distribution of helium ash in multi-dipole device 

JIANG Di, YIP Chi-Shung, JIN Chen-yao, ZHANG Wei, XU Guo-sheng, WANG Liang

2024, 44(2):  242-248.  DOI: 10.16568/j.0254-6086.202402017

Asbtract ( )   PDF (2023KB) ( )  

References | Related Articles | Metrics

The multi-dipole chamber is applied in this paper to simulate the existence of helium neutral particles near the divertor of a fusion reactor. Laser-induced fluorescence diagnostic is used to directly measure the velocity distribution of helium neutral particles. Additionally, the calibration of the measuring area's wavelength and the broadening of the diode laser's tunable range are discussed in detail. A feasible laser-induced fluorescence diagnosis technology scheme suitable for the divertor area of a future fusion reactor to measure the velocity distribution of helium neutral particles and detect helium ash elimination is promoted.