50 kV全数字化电子枪高压电源设计

本文介绍了一种基于DSP的全数字化电子枪高压电源,该电源的特点是采用全数字化反馈电路、通过PID算法实现闭环控制。采用频率较高的谐振逆变电路,减小了谐振元件、变压器的体积。电源因采用电流耦合型分布式高压变压器及整流电路,提高了效率、减少了分布参数及可使高压整流电路工作在无油的环境中。该电源已成功用于辐照加速器电子枪栅控高压电源系统中。     

EAST-NBI抑制极电源IGBT串联技术的研究

中性束注入器(Neutral Beam Injector,NBI)是东方超环(Experimental Advanced Superconducting Tokamak,EAST)核聚变实验装置辅助加热的重要组成部分。目前NBI离子源引出系统采用四电极结构,即加速电极、梯度电极、抑制电极和地电极。抑制极电源是为其中的抑制电极提供负电位的高压直流电源。根据抑制极电源输出特性的要求,输出端采用串联绝缘栅双极型晶体管(Insulated Gate Bipolar Transistor,IGBT)作为调制开关。为研究IGBT串联技术对均压效果和抑制极电源输出特性的影响,采用PSpice软件对IGBT开关进行了建模,并进行了不同电路参数下的仿真。仿真表明:一定条件下,电阻电容二极管(Resistance Capacitance Diode,RCD)缓冲电路中电容参数对动态均压效果和电源关断特性具有决定性影响,缓冲电阻影响电容的放电时间及放电电流峰值。最后给出了相应的实验测试结果。该研究结果可以明确缓冲电路参数与均压效果以及抑制极电源开关特性之间的定量关系,为抑制极电源开关特性的进一步优化及其与加速极电源的特性匹配提供数据指导,对于NBI离子源的安全稳定运行具有重要意义。     

Transient Process of Stray Capacitance for PSM High Voltage Power System

At present, based on the features of Pulse Step Modulator (PSM) technology in high voltage power supply (HVPS) is applied to drive the auxiliary heating system in domestic and foreign Tokomak facility. Before design of PSM HVPS, it is necessary to consider the effect of stray parameter existed in HVPS on the dynamic process of HVPS and load. In this paper, based on PSM technology 50 kV HVPS have been completed which is built for EAST auxiliary heating system and the relationship between the stray capacitance and leakage impedance respectively existed in the oil isolation transformer and dry multi-secondary winding transformer is discussed. Finally a stray parameters electrical circuit model of HVPS is presented. At last, from the results of experiment,it is consistent with the results of simulation.     

Quench detection of fast plasma events for the JT-60SA central solenoid

The JT-60 is planned to be modified to a full-superconducting tokamak referred to as the JT-60 Super Advanced (JT-60SA). The maximum temperature of the magnet during its quench might reach the temperature of higher than several hundreds Kelvin that will damage the superconducting magnet itself. The high precision quench detection system, therefore, is one of the key technologies in the superconducting magnet protection system.The pick-up coil method, which is using voltage taps to detect the normal voltage, is used for the quench detection of the JT-60SA superconducting magnet system. The disk-shaped pick-up coils are inserted in the central solenoid (CS) module to compensate the inductive voltage. In the previous study, the quench detection system requires a large number of pick-up coils. The reliability of quench detection system would be higher by simplifying the detection system such as reducing the number of pick-up coils. Simplifying the quench detection system is also important to reduce the total cost of the protection system. Hence the design method is improved by increasing optimizing parameters. The improved design method can reduce the number of pick-up coils without reducing the sensitivity of detection; consequently the protection system can be designed with higher reliability and lower cost. The applicability of the disk-shaped pick-up coil for quench detection system is evaluated by the two dimensional analysis. In the previous study, however, the analysis model only took into account the CS, EF (equilibrium field) coils and plasma. Therefore, applicability of the disk-shaped pick-up coil for the quench detection system remains open question because the fast plasma events, such as disruption, mini collapse and ELM (edge localized mode), directly influences on the voltage of pick-up coil making the quench signal undetectable. Consequently, a new analysis model proposed in the present paper was designed to avoid this difficulty by introducing the passive coil series such as vacuum vessel and stabilizer. The influence of fast plasma events is absorbed by passive coil series like real system, and the evaluation of applicability can be examined in detail. The analysis results show that the disk-shaped pick-up coil is applicable whenever the standard operation, disruption, mini collapse and ELM.     

Further on integrator circuit analogy for natural convection

This research is an extension of the previous work on the development of an integrator (RC) circuit analogy for natural convection. This analogy has been proven experimentally as well as by numerical simulations. Additional Rayleigh-Bénard convection numerical simulations were performed to investigate ΔT (temperature difference between source and sink) dependence of the thermal resistance of a natural convection system. Our results suggest that analogous to voltage dependent resistor (VDR) in electrical engineering, ΔT dependent thermal resistance is observed in natural convection system. This ΔT dependent thermal resistance leads to a variable time constant. Moreover, this research also suggests that for a natural convection system, in addition to the thermal capacitance a kinetic energy capacitance also exists. The relative contribution of kinetic energy capacitance depends on Rayleigh number. These results provide significant step forward towards development of a new inexpensive modeling and transient analysis tool for a natural convection system.     

EWB软件仿真分析探测器-电流灵敏前置放大器

利用虚拟电子工作平台(EWB)软件仿真分析一个中子注量率时空分布的探测系统中应用的电流灵敏前置放大器电路,避免了复杂的数学理论计算,得到了直观的结果,为其调试工作提供了参考依据。介绍了在EWB上探测器信号源的模拟,仿真分析探测器输出回路RC、隔直交流耦合电容、传输电缆长度对该电流灵敏前置放大器输出电压信号的影响情况。     

Tunable biasing magnetic field design of ferrite tuner for ICRF heating system in EAST

Ion cyclotron range of frequency(ICRF) heating has been used in tokamaks as one of the most successful auxiliary heating tools and has been adopted in the EAST. However, the antenna load will fluctuate with the change of plasma parameters in the ICRF heating process. To ensure the steady operation of the ICRF heating system in the EAST, fast ferrite tuner(FFT) has been carried out to achieve real-time impedance matching. For the requirements of the FFT impedance matching system, the magnet system of the ferrite tuner(FT) was designed by numerical simulations and experimental analysis, where the biasing magnetic circuit and alternating magnetic circuit were the key researched parts of the ferrite magnet. The integral design goal of the FT magnetic circuit is that DC bias magnetic field is 2000 Gs and alternating magnetic field is±400 Gs. In the FTT, E-type magnetic circuit was adopted. Ferrite material is Nd Fe B with a thickness of 30 mm by setting the working point of Nd Fe B, and the ampere turn of excitation coil is 25 through the theoretical calculation and simulation analysis. The coil inductance to generate alternating magnetic field is about 7 m H. Eddy-current effect has been analyzed, while the magnetic field distribution has been measured by a Hall probe in the medium plane of the biasing magnet. Finally, the test results show the good performance of the biasing magnet satisfying the design and operating requirements of the FFT.     

共面栅碲锌镉探测器读出电路设计及性能研究

为有效读出共面栅碲锌镉(CPG-CZT)探测器的核脉冲信号,本文结合CPG-CZT探测器工作原理及国内外研究,设计了可用于CPG-CZT探测器的读出电路,主要包括高压偏置电路、前置放大电路、增益调节及减法电路。为研究读出电路性能,本文测试了各单元电路的性能及探测系统能量分辨率随偏置电压、增益调节电路中两路信号的相对增益G的变化规律。结果表明：高压偏置电路两路输出偏压与输入偏置电压的相关系数R²均为0.998;前置放大电路输出噪声为5 mV;增益调节及减法电路输出信号噪声为10 mV;输入偏置电压、相对增益G的变化均会影响探测系统能量分辨率,当偏置电压为-1650 V、相对增益G为0.7时对¹³⁷Cs源产生的γ射线能量分辨率最佳,可达3.65%,且无明显拖尾现象。     

Paralleling Inverters Study of EAST Vertical Stability Coil Power Supply

Experimental advanced superconducting tokamak vertical stability (VS) coil power supply is a large capacity single phase inverter power supply. To meet the requirement of large current and fast response, multi-inverters in parallel is presented, which based on carrier phase-shifted modulation technology. In parallel inverter system, the disperse circuit parameters and phase-shift carriers between parallel inverter units will cause circulating current, which contains fundamental component and a large number of harmonic components. In this paper, the model of circulating current is analyzed when VS coil power supply is working in voltage given mode, and an instantaneous current sharing control strategy is proposed based on the combination of current sharing inductor and instantaneous circulating current feedback control. Parallel inverter units are connected together through current sharing inductors which can change the impedance characteristic of the circulating impedance and well restrain the high-frequency circulating current. Then, the real part of the circulating impedance will be increased and the ability to restrain the low-frequency circulating current will be advanced by introducing virtual resistance, which is realized in the instantaneous circulating current feedback routine. The designations of the current sharing inductor and the virtual resistance are provided. The results of simulation and experiment verify that this current-sharing strategy is available and efficient.     

Measurement of transient neutral gas puff pressure in the NUDT_IPPTx by a fast ionization gauge

A gas injector was designed for the 400 J/pulse prototype of the planar inductive pulsed plasma thruster (IPPT) developed by the National University of Defense Technology (NUDT_IPPTx). As the gas puff distribution over the coil surface is critical to the NUDT_IPPTx functioning efficiently, a fast ionization gauge was developed to investigate the neutral gas pressure profiles to seek the critical time when the thruster is ignited. The gauge was calibrated for argon by using a capacitance manometer. Time-resolved pressure profiles have been acquired in the condition of the gas puff mass matching with the discharge energy and the drive coil parameters of the NUDT_IPPTx. It is demonstrated that the gas injector can supply a gas puff with a sufficiently steep (d_p/d_t ≈ 770 kPa s^-1 ) leading and trailing edge, and the gas puff can be compressed against the drive coil as expected. The critical ignition moment is considered to appear at some instant between 525 μs and 650μs after the valve trigger.     

Methane conversion using a dielectric barrier discharge reactor at atmospheric pressure for hydrogen production

In the present paper,we carried out a theoretical study of dielectric barrier discharge (DBD) filled with pure methane gas.The homogeneous discharge model used in this work includes a plasma chemistry unit,an electrical circuit,and the Boltzmann equation.The model was applied to the case of a sinusoidal voltage at a period frequency of 50 kHz and under a gas pressure of 600 Torr.We investigated the temporal variation of electrical and kinetic discharge parameters such as plasma and dielectric voltages,the discharge current density,electric field,deposited power density,and the species concentration.We also checked the physical model validity by comparing its results with experimental work.According to the results discussed herein,the dielectric capacitance is the parameter that has the greatest effect on the methane conversion and H2/CH4 ratio.This work enriches the knowledge for the improvement of DBD for CH4 conversion and hydrogen production.     

Experimental study of a low-pressure hybrid RF discharge

Experimental study of the low-pressure hybrid RF discharge with both inductive and capacitive channels was carried out. The RF power unit consists of inductor(antenna) and capacitor plates connected in parallel to the same RF power source. A separating capacitor Csepis included into the circuit between the antenna ends and the lead connected to the discharge capacitor plate in order to prevent the closing of the capacitive circuit through direct current by inductor and to control the contribution of capacitive channel to discharge sustaining. It is shown that at low power of the RF power source, power coupling to the discharge mainly occurs through the capacitive channel. Increasing the power of the RF power source increases the power coupled in the inductive channel, electron density, and current flowing through the capacitive channel. This leads to increasing voltage drop on the separating capacitor and partial cutoff of the capacitive channel. At separating capacitance values below certain value(below 50 pF in the present experiments), the self-bias of the loaded plate of the discharge capacitor becomes positive indicating that the thickness of the electrode sheath of the loaded electrode decreases compared to thickness of the sheath of the grounded electrode. The thickness of the space-charge sheath of the grounded electrode decreases with increasing power coupled to the plasma. At separating capacitance below 50 pF, higher harmonics of the RF voltage and current are actively generated in the capacitive discharge channel. Increasing the separating capacitance leads to decreasing electron density, increasing effective electron temperature and more effective RF energy coupling to plasma due to increasing relative importance of the capacitive discharge channel.     

Transient electrical behaviour of the ITER TF coils during fast discharge and two fault cases

Improvements of high voltage design criteria and quality assurance for ITER coils are indispensable taking into account the problems occurred during high voltage tests of the ITER TF model coil. One important aspect to consider is the transient electrical behaviour because fast changes of voltages may cause local overloading and destruction of the insulation system. This paper will present the calculation of the terminal voltages within the ITER TF coil system and the voltage stress of the insulation within an individual ITER TF coil for the fast discharge and two fault cases. Proposals for the high voltage tests are discussed based on the calculated voltage stress of the two fault cases and the experiences gained during the ITER TF Model Coil test to ensure appropriate dielectric quality of the ITER TF coils.     

Simulation and test results of low-order band harmonic filters to decrease resonance phenomenon in the KSTAR power system

The superconducting magnet power supply which supplies superconducting magnet coil (SC) with the power to generate plasma during a KSTAR experiment for nuclear fusion research is a nonlinear load. Characteristic harmonics are generally produced since it converts AC to DC using 6 or 12 pulsed operation. However, non-characteristic harmonics or inter-harmonics are generated according to output control characteristics. Also, 95% out of the power generated from superconducting magnet coil is reactive power. Therefore, harmonic and reactive power occurring during operation have some bad influences such as voltage drop, voltage distortion and decrease in power factor on the KSTAR power system, and reactive power compensator (RPC) & harmonic filter (HF) system which is able to compensate harmonic and reactive power at the same time was established and has been operated [1]. However, out of non-characteristic harmonics and inter-harmonics caused by output control characteristics of superconducting magnet power supply, the more compensation volume of the RPC & HF system increases, the more voltage distortion with harmonic expansion is caused by harmonics in a low-order band due to the parallel resonance in a low-order band between the KSTAR power system and the RPC & HF system. As a result, it has serious effect on the injection capacity restriction of the RPC & HF system, the unstable operation control of superconducting magnet coil, and the operation of main cooling facilities. This paper presents reasons of the resonance phenomenon of the KSTAR power system and suggests a design plan of additional facilities for stable operation of the KSTAR power system, and proves their effects through the simulation and test results.     

线缆X射线瞬态响应的电路模型计算

建立了同轴电缆和腔体内带保护层导线、裸导线X射线瞬态辐照响应的电路计算模型,该模型考虑了X射线辐照线缆时电子的运动规律及瞬态响应的产生机理,适用于瞬态响应的规律研究和工程预估。结合实例,介绍了计算模型中电流源、电容参数的物理意义及其计算方法,采用该模型计算了同轴屏蔽电缆的X射线瞬态响应,并与数值计算结果进行了比较。结果表明,电容的计算是采用电路模型计算响应的关键,采用衰减法计算的电子射程更适合计算电容。     

Effects of packing particles on the partial discharge behavior and the electrical characterization of oxygen PBRs

Packed-bed reactors(PBRs) hold great promise for environmental applications, but a deeper understanding of the behavior of plasma discharge within PBRs is required. To this end, a partial-discharge alternative equivalent circuit for PBRs was established in this work. Dielectric particles(glass beads or glass sand) were used to place focus on the effects of the particle size and shape on the partial discharge behavior of the oxygen PBRs. Some electrical characterizations were explored(e.g. the effective dielectric capacitance, partial discharge coefficient, and corrected burning voltage) that may differ from long-standing interpretations.The findings indicate that the suppressive effect of surface discharge on filament discharge is stronger with the decrease of the particle size. For partial discharge, the effective dielectric capacitance is always less than the dielectric capacitance. The corrected burning voltage and partial discharge tendency increase with the decrease of the particle size. As compared to an empty reactor, the average electric field in the PBR was found to be improved by 3–4 times, and the ozone energy efficiency and production were promoted by more than 20% and 15%,respectively. The plasma processing capacity can therefore be improved by choosing a relatively large size or a complex, irregularly-shaped packing material that is suitable for the discharge gap.     

功率MOS器件SEB、SEGR测量系统的研制

研制了功率MOS器件单粒子烧毁、单粒子栅穿辐照效应实验用的电流测量及电源系统,该系统由栅极电源电路、极电源电路、漏极RC振荡电路和DUT栅极触发电路组成,具有栅（漏）极电压偏置、电流测量、过流保护、电容电阻选择等功能,经实验验证,本系统工作性能稳定可靠。     

混合模式低噪声3 kV高压直流电源设计

高压直流电源是电离室等核辐射探测器的关键部件。针对需要3 kV左右高压的电离室,本文研制了0～3 kV连续可调的低噪声、高效率、小体积及高稳定性的高压直流电源。该高压直流电源系统采用线性与开关混合模式设计,兼顾了转换效率与低噪声。核心部分升压转换部分采用线性罗耶谐振电路与高频变压器实现,保证足够低的高压电源输出纹波。罗耶谐振电路的供电电源则由边沿时间控制型超低噪声开关稳压器LT1534提供,从而实现了混合模式高压直流电源的设计。高压直流电源输出部分采用二阶RC滤波电路进一步降低了输出电压的纹波。实测输出电压范围为0～3 kV,静态功耗为0.4 W,3 kV输出时纹波为16.55 mV,由此可知该电源可用于低噪声的核辐射探测器供电场合。     

LLC谐振恒流恒压高压充电电源技术研究

高压充电电源输出电压的稳定性是脉冲调制器的关键技术指标,需对其进行研究,以提高其输出稳定性。基于激磁电感、谐振电感、谐振电容（LLC）谐振变换器的工作原理,根据LLC等效电路得到了LLC谐振电路的电压增益曲线,分析了LLC谐振变换器工作区间的特性,提出了平面绝缘芯变压器的选择依据和设计方法,通过测量实际变压器得到变压器的参数;根据变压器参数选择了LLC谐振变换器谐振频率和工作频率,并通过LLC谐振变换器电路的推导,详细计算了高压充电电源输出电压的纹波幅值。结果显示,计算结果优于设计指标。经实验验证,叠层磁芯LLC谐振变换器高压充电电源的稳定性能达到了设计要求。     

Numerical and experimental analysis of AC loss for CFETR CS model coil

The central solenoid (CS) is an important com ponent of China Fusion Engineering Test Reactor,for producing,forming and stabilizing plasma in the superconducting tokamak.It is a complicated work to design and manufacture the large superconducting CS magnet,so it is meaningful to design a central solenoid model coil (CSMC) and analyze its electromagnetic properties in advance.In this paper,the structure,design parameters and magnetic field distribution of the CS model coil are dis cussed.The peak power of radial and axial turn conductors and time bucket loss are analyzed by using piecewise-linear method.The CSMC AC loss with different Nb3Sn CICCs and AC loss of ITER CS coil are compared.The special electrometric method to measure AC loss of the CS model coil for fu ture reference is presented.