Development of a real-time magnetic island reconstruction system based on PCIe platform for HL-2A tokamak

A real-time magnetic island reconstruction(MIR) system based on PCI express platform for HL-2 A tokamak is introduced. The front-end analog circuit and high performance analog-to-digital converters complete high-precision synchronous sampling of 18 channel Mirnov signals, and the application of PCIe platform and direct memory access technology enables high speed data transmission between graphics processing unit and field programmable gate array(FPGA).FPGA, as a mainstream high speed parallelizable computing tool, was used to implement the MIR algorithm, while a parameter table is established in an external double data rate SDRAM to improve the computational efficiency. The software of the MIR system is developed with Compute Unified Device Architecture 8.0 in Centos 6 system, which mainly realizes driver development, data transmission, network communication, parameter calculation and system control. This system has been tested in HL-2 A plasma discharge experiment, and the reconstructed magnetic island structure can achieve a spatial resolution of 1.02 cm while the time resolution can reach 2 ms.     

Design of the HL-2M power supply control system

The power supply control system is one of the most important local control systems of HL-2M tokamak. The power supply system of HL-2M is composed of four flywheel generator sets with total capacity of 600 MVA, all the magnetic field coil power supplies and high voltage power supplies of auxiliary heating system. The control system of power supply should make sure the large amount of on-site equipment and facilities to operate steadily and reliably.This paper presents the architecture of HL-2M control system and four kinds of established control networks. It describes how the power supply control system is built by using the established hardware structures and software agreements. Specially, it is focused on introducing an application of real-time technology based on the reflective shared memory and the fully digital compact solution for controlling the high power converters. Otherwise, a scheme which adopts PROFINET and Sequence of Events technology to carry out the intellect interlock control system is given.     

A multi-channel real-time digital integrator for magnetic diagnostics in HL-2A tokamak

A novel full-digital integrator has been developed for the magnetic diagnostics in HL-2A. Based on the pipeline processing of the field-programmable gate array and high-speed PCI extensions for instrumentation platform, the digital integrator has realized octal-channel10-k Hz real-time integration and data transmission. In order to reduce the integration drift, a 24-bit analog-todigital converter and simple analog processing circuits are applied for high-precision sampling, while certain correction algorithms are used to minimize the drift. With simple and highly integrated circuits and high-performance digital processor, the digital integrator is of high stability and functional expansibility which greatly simplifies the operation procedure. The digital integrator has been tested in the plasma discharge experiments, and the experimental results have confirmed that the drift performance and accuracy of the digital integrator could fully meet the requirements of HL-2A.     

Magnetic configuration flexibility of snowflake divertor for HL-2M

HL-2M (Li, 2013 [1]) is a tokamak device that is under construction. Based on the magnetic coils design of HL-2M, four kinds of divertor configurations are calculated by CORSICA code (Pearlstein et al., 2001 [2]) with the same main plasma parameters, which are standard divertor, exact snowflake divertor, snowflake-plus divertor and snowflake-minus divertor configurations. The potential properties of these divertors are analyzed and presented in this paper: low poloidal field area around X-point, connection length from outside mid-plane to the primary X-point, target plate design and magnetic field shear. The results show that the snowflake configurations not only can reduce the heat load at divertor target plates, but also may improve the magneto-hydrodynamic stability by stronger magnetic shear at the edge. A new divertor configuration, named “tripod divertor”, is designed by adjusting the positions of the two X-points according to plasma parameters and magnetic coils current of HL-2M.     

大功率脉冲磁场电源系统

描述了中国环流器2号A(HL-2A)装置磁场电源系统,介绍了电源的控制系统和实验结果。磁场电源总脉冲容量近250 MVA,一次放电脉冲释能1 300 MJ,其中单套电源的最高直流电压为3510 V,最大电流为45 kA,均以脉冲方式运行,脉冲时间5 s,重复周期10 min。电源主回路主要由飞轮脉冲发电机、晶闸管变流设备、硅整流器等组成。采用了硅整流器直接并联、电流平衡、恒角移相控制、整流器全关断检测、先进的监控和脉冲高压强流检测等技术措施。实验表明,磁场电源的性能指标能够满足装置实验的要求。     

Tomography of emissivity for Doppler coherence imaging spectroscopy diagnostic in HL-2A

A newly developed Doppler coherence imaging spectroscopy(CIS) technique has been implemented in the HL-2 A tokamak for carbon impurity emissivity and flow measurement. In CIS diagnostics, the emissivity and flow profiles inside the plasma are measured by a camera from the line-integrated emissivity and line-averaged flow, respectively. A standard inference method, called tomographic inversion, is necessary. Such an inversion is relatively challenging due to the ill-conditioned nature. In this article, we report the recent application and comparison of two different tomography algorithms, Gaussian process tomography and Tikhonov tomography, on light intensity measured by CIS, including feasibility and benchmark studies.Finally, the tomographic results for real measurement data in HL-2A are presented.     

Comparing simulated and experimental spectral line splitting in visible spectroscopy diagnostics in the HL-2A tokamak

We established the passive-visible spectroscopy diagnostics(P-VSD) and active-VSD(A-VSD)spectral splitting models for the HL-2A tokamak. Spectral splitting due to the influence of electromagnetic fields on the spectra in VSD is studied. Zeeman splitting induced by the magnetic field(B) is used to distinguish reflected light overlap in the divertor for P-VSD. Stark splitting caused by the Lorentz electric field(E_Lorentz) from the neutral beam injection particle’s interaction with the m...     

The Power Supply System for HL-2A Tokamak＇s Magnetic Field

The highpower pulsed power supply system for the magnetic field of the HL-2A Tokamak is described in this paper. The total output power of its eight magnetic field power supply units of nearly 250 MW. Their highest DC output voltage and current are 3510 V and 45 kA, respectively. All the units are operated in a pulsed mode. The pulse duration is 5 s, and the cyclic period is 15 min. The power supply system consists mainly of pulsed flywheel motor generators, rectifying transformers, thyristor converters, diode rectifiers and switches. The system incorporates many key technologies-supply equalization with two generators and four diode bridges, constant-angle phase triggers with a wide frequency range, current equalization, a status detector for the high current 6-phase converter, and advanced monitoring based on a programmable logic computer and engineering parameter measurement. The experimental results show that the performance of the power supply system satisfies the requirements of HL-2A experiments very well.     

Fuelling and Diagnostics with Pellet Injection in the HL-1M Tokamak

The pellet injection experiments for fuelling and diagnostics have been carried out on the HL-1M tokamak. The eight-pellet injector was installed on HL-1M. A reliable monitordetector and camera system was set up to take initial pellet photographs and measure the initial pellet speed and size. High fuelling efficiency of 60 % - 100 % and a density profile with a peaking factor of 1.8 - 2.0 were obtained. The maximum density close to 10^14/cm^3 in HL-1M was achieved with newly optimized combined fuelling techniques. Two typical models of pellet ablation have been utilized for simulative calculation of the ablation rates in HL-1M. In comparison with the distribution of the measured Hα emission intensity from the digital data of the CCD camera, the experimental result seems more optimistic for core fuelling than theoretical predictions by the two models. The safety factor profile q（r） has been extracted from the information provided by the CCD camera during the pellet injection. The reliability of the measured results depends mainly on the calibration of the imaging space position. Based on the calibration, the measured q-profile becomes more reasonable than those published previously for the same shot number and same photograph.     

Development of the HL-2M digital pulse analysis system

A digital pulse analysis system is an important diagnostic system in nuclear physics experimental research. In response to the demand for reflecting the particle state in a nuclear physics experiment, we have designed and developed a real-time digital pulse analysis system and applied it to the digital nuclear pulse waveform discrimination of different detectors in the HL-2 M tokamak. The system is based on the peripheral component interconnect extensions for instrumentation(PXI) platform, while its software was written in LABVIEW. The key technologies involved in the system implementation include digital pulse analysis technology,digital discrimination technology, pulse height analysis technology, etc. The system has been applied to the plastic scintillator detector at the Neutron Source Lab of the University of Science and Technology of China. And the experimental results indicate that the system can discriminate between neutron(n) particles and gamma(γ) particles well when used to measure the plastic scintillator detector.     

中国环流器二号A(HL-2A)装置物理设计

文章是关于中国环流器二号A(HL-2A)装置物理设计的总结报告,包括以下几方面的内容:分析计算等离子体截面变形及由截面拉长引起的垂直不稳定性,提出对HL-2A极向磁场线圈电流和控制系统的要求;研究通过中性束注入加热(NBI)和低混杂波电流驱动(LHCD)实现等离子体剖面控制,模拟并设计HL-2A的高性能的运行模式;分析HL-2A先进约束位形(RS位形)下的磁流体力学不稳定性,为实现高性能模式稳态运行的等离子体控制指出方向;同时,利用数值模拟分析HL-2A偏滤器等离子体性能,为偏滤器的改进提供依据。     

Development of a data acquisition and control system for the International Thermonuclear Experimental Reactor neutron flux monitor

To satisfy high-precision, wide-range, and real-time neutron flux measurement requirements by the International Thermonuclear Experimental Reactor(ITER), a data acquisition and control system based on fission chamber detectors and fast controller technology, has been developed for neutron flux monitor in ITER Equatorial Port #7. The signal processing units which are based on a field programmable gate array and the PXI Express platform are designed to realize the neutron flux measurement with 1 ms time resolution and a fast response less than 0.2 ms,together with real-time timestamps provided by a timing board. The application of the widerange algorithm allows the system to measure up to 10~(10) cps with a relative error of less than 5%.Furthermore, the system is managed and controlled by a software based on the Experimental Physics and Industrial Control System, compliant with COntrol, Data Access and Communication architecture.     

Optimization of the optical system for electron cyclotron emission imaging diagnostics on the HL-2A tokamak

The optical system of the electron cyclotron emission imaging diagnostics on the HL-2A tokamak has been optimized in both the narrow zoom pattern and the wide zoom pattern. The two main features of the improved optical system are(1) larger coverage of the measurement region in the plasma and(2) a flatter imaging surface. The new optics has good focal characteristics over the whole plasma cross section. The curvature of the field of the image surface(ΔR between the core channel and the edge channel) is within 5.3 cm in the narrow zoom pattern and 6.7 cm in the wide zoom pattern after optimization, whereas the values with the present optics were 23 cm in the narrow zoom pattern and 15 cm in the wide zoom pattern. The optics will be fabricated, tested and installed on the HL-2A tokamak before the next experimental campaign.     

Recent Development of Data Acquisition System on HL-2A

This paper introduced recent development of data acquisition system(DAS) on the HL-2A tokamak. The existing DAS has to be remodeled because of the evident improvement on HL-2A itself and the increasing amount of corresponding experimental data. First, the experimental network on HL-2A Tokamak as a communication center is described in detail. Secondly, "The File's Format & Criterion of Experimental Data on HL-2A Tokamak" as the core of the new software is also presented. Thirdly, not only a multi-screen image display system on HL-2A is discussed, but also the build-up of a new display wall system is dealt with. Finally, on the graphical WINDOWS platform and on the basis of the new Data File's Format & Criterion, the new software on HL-2A is described, including a new multi-layer database management program, a real-time processing program, a common interactive analytic processing program and a data post-processing program, which is now under development.     

Conceptual design of 5 MW-NBI injector for HL-2 M tokamak

The HL-2 M tokamak is now under construction in Southwestern Institute of Physics in China. As one of the main auxiliary heating systems for HL-2 M tokamak, a new NBI beam line with 5 MW NBI power, 42° injection angle, based on 4 sets of 80 kV/45 A/5 s bucket ion sources with geometrical beam focus, is conceptually designed with geometrical calculation and engineering simulations. The preliminary structure and layout of key components including ion sources, neutralizers, ion dumps, deflection magnet, beam edge scraper, long pulse calorimeter target, short pulse calorimeter target, injection port and beam drift duct are determined. The magnetic shielding of the stray field of HL-2 M tokamak is analyzed. Beam power transmission efficiency is calculated with geometrical algorithm. The ratio of neutral beam injection power to ion beam power is as high as 48%.     

Research on the real-time signal conditioning method for dispersion interferometer in HL-2M

A new CO₂ laser dispersion interferometer has been developed in the HL-2M tokamak to measure the electron density. In order to meet the needs of high-precision measurement, a data acquisition system with real-time signal conditioning (RSC) method is proposed. It can eliminate part of the impacts of environmental factors, such as mechanical vibration, light path changes, and plasma refraction effect during experiments. In harsh environments, the system can measure the line-integrated density with a high precision of 2 × 10¹⁸ m⁻² with the RSC method. The system has been tested in a recent HL-2A experimental campaign, and the results show that the RSC method plays an important role in the plasma electron density measurement.     

A novel digital neutron flux monitor for international thermonuclear experimental reactor

A novel full-digital real-time neutron flux monitor(NFM) has been developed for the International Thermonuclear Experimental Reactor.A measurement range of 10~9 counts per second is achieved with 3 different sensitive fission chambers.The Counting mode and Campbelling mode have been combined as a means to achieve higher measurement range.The system is based on high speed as well as parallel and pipeline processing of the field programmable gate array and has the ability to upload raw-data of analog-to-digital converter in real-time through the PXIe platform.With the advantages of the measurement range,real time performance and the ability of raw-data uploading,the digital NFM has been tested in HL-2 A experiments and reflected good experimental performance.     

Integrated data analysis on the electron temperature profile of HL-2A with the Bayesian probability inference method

Data analysis on tokamak plasmas is mainly based on various diagnostic systems, which are usually modularized and independent of each other. This leads to a large amount of data not being fully and effectively exploited so that it is not conducive to revealing the deep physical mechanism. In this work, Bayesian probability inference with machine learning methods have been applied to the electron cyclotron emission and Thomson scattering diagnostic systems on HL-2A/2M, and the effects of integrated data analysis (IDA) on the electron temperature of HL-2A with Bayesian probability inference are demonstrated. A program is developed to infer the whole electron temperature profile with a confidence interval, and the program can be applied in online analysis. The IDA results show that the full profile of the electron temperature can be obtained and the diagnostic information is more comprehensive and abundant with IDA. The inference models for electron temperature analysis are established and the developed programs will serve as an experimental data analysis tool for HL-2A/2M in the near future.     

中国环流器二号A装置工程与实验进展

介绍了中国环流器二号A(简称HL-2A)装置上关键聚变工程技术取得的新进展及在磁约束聚变科学若干关键课题研究取得的重要实验成果,特别是在HL-2A装置上成功实现了偏滤器位形下具有边缘局域模的高约束模式运行,是我国磁约束聚变实验研究史上具有里程碑意义的重大进展,使我国的磁约束聚变科学和等离子体物理实验研究进入了一个崭新的阶段。     

中国环流器二号A装置工程与实验进展

介绍了中国环流器二号A(简称HL-2A)装置上关键聚变工程技术取得的新进展及在磁约束聚变科学若干关键课题研究取得的重要实验成果,特别是在HL-2A装置上成功实现了偏滤器位形下具有边缘局域模的高约束模式运行,是我国磁约束聚变实验研究史上具有里程碑意义的重大进展,使我国的磁约束聚变科学和等离子体物理实验研究进入了一个崭新的阶段。