Investigation of Vacuum Arc Voltage Characteristics Under Different Axial Magnetic Field Profiles

Characteristics of the arc voltage under different profiles of axial magnetic field were investigated experimentally in a detachable vacuum chamber with five pairs of specially designed electrodes generating both bell-shaped and saddle-shaped mafnetic field profile. The arc column and cathode spot images were photographed by a high speed digital camera. The dependence of the arc voltage on arcing evolution is analyzed. It is indicated that the axial magnetic field profile could affect the arc behaviors significantly, and the arc voltage is closely related to the arc light intensity.     

Typical Motion and Extinction Characteristics of the Secondary Arcs Associated with Half-Wavelength Transmission Lines

Secondary arc discharge is a complicated physical phenomenon and one of the key fundamental issues associated with ultra high voltage （UHV） half-wavelength transmission lines （HWTL）. With the establishment of a physicM simulation platform for the HWTLs, experiments were carried out regarding the motion and extinction characteristics of secondary arcs. The cathode arc root and the anode arc root were found to show an obvious polarity effect while the arc column was moving in a spirM, due to their different motion mechanisms. The extinction behavior was also recorded and experiments were designed with different compensation conditions. Results show that the arcing time can be greatly reduced if there exists an electrical compensation network. The research provides fundamentals for understanding the physics involved, especially the motion and extinction mechanisms of the secondary arcs.     

Prediction of Equivalent Electrical Parameters of Dielectric Barrier Discharge Load Using a Neural Network

A reliable,efficient and economical power supply for dielectric barrier discharge(DBD)is essential for its industrial applications.However,the equivalent load parameters complicate the design of power supply as they are variable and varied nonlinearly in response to varied voltage and power.In this paper the equivalent electrical parameters of DBD are predicted using a neural network,which is beneficial for the design of power supply and helps to investigate how the electrical parameters influence the equivalent load parameters.The electrical parameters including voltage and power are determined to be the inputs of the neural network model,as these two parameters greatly influence the discharge type and the equivalent DBD load parameters which are the outputs of the model.The voltage and power are decoupled with pulse density modulation(PDM)and hence the impact of the two electrical parameters is discussed individually.The neural network model is trained with the back-propagation(BP)algorithm.The obtained neural network model is evaluated by the relative error,and the prediction has a good agreement with the practical values obtained in experiments.     

Dynamic physical characteristics of DC arc on arcing horn for HVDC grounding electrode line

The dynamic physical characteristics of a DC arc on an arcing horn for a high voltage direct current(HVDC) grounding electrode line are significantly different from those of the switching device arc,secondary arc,AC fault arc and pantograph-catenary arc.In this work,an experimental platform for the DC arc on the arcing horn was built,and mechanisms of the arc column short circuit and arc root movement were studied.This work further analyzes the characteristics and mechanisms of the arc motion wh...     

抗辐射加固高压NMOS器件的单粒子烧毁效应研究

由于施加高栅极工作电压,使得器件容易发生重离子辐射损伤效应,其中,重大的重离子辐射损伤效应是单粒子栅穿效应（SEGR）和单粒子烧毁效应（SEB）。本文介绍了抗辐射加固高压SOI NMOS器件的单粒子烧毁效应。基于抗辐射加固版图和p型离子注入工艺,对高压器件进行抗辐射加固,提高器件的抗单粒子烧毁能力,并根据电路中器件的电特性规范,设计和选择关键器件参数。通过仿真和实验结果研究了单粒子烧毁效应。实验结果表明,抗辐射加固器件在单粒子辐照情况下,实现了24 V的高漏极工作电压,线性能量传输（LET）阈值为835 MeV·cm2/mg。     

Theory on dynamic matching with adjustable capacitors for the ICRF system of ASDEX Upgrade

The coupling of electromagnetic waves in the Ion Cyclotron Range of Frequencies (ICRF) is an important method to heat magnetically confined plasmas. Changing plasma conditions, which originate from processes like L-mode to H-mode transition or gas puffing, vary the load impedance of the ICRF antennas. To optimize the power transfer from the radio frequency (RF) generators to the antennas and consequently to the plasma, as well as to protect the RF sources against too high reflected power, a system that matches (i.e. transforms) the antenna input impedance to the impedance required by the generator is necessary. At ASDEX Upgrade this matching system consists of two stub tuners for each antenna, which match the antenna impedance for a value preset before the discharge. The length of the stubs cannot be changed fast enough to compensate plasma variations even on the moderate timescale of the confinement time in ASDEX Upgrade. The use of 3 dB-couplers allows operation even with varying load, at the cost of a reduced power to the plasma.When adjustable capacitors are applied in parallel to the stubs, dynamic matching becomes possible on the tens of ms timescale. The paper describes first the calculation of the required capacitance using transmission line theory. In a second model a minimum search algorithm finds, for a given antenna impedance, the length of the stubs needed for matching, now including the initial values of the capacitors. For the chosen pre-match point in the Smith chart, the range of impedances around this point is calculated for which the voltage standing wave ratio (VSWR) can be lowered below a minimum value by readjusting the capacitors within their maximum and minimum values. The matching range is thereby significantly larger than without the application of adjustable capacitors, at least with a frequency of 30 MHz and 36.5 MHz.     

A novel fault current limiter topology design based on liquid metal current limiter

The liquid metal current limiter (LMCL) is regarded as a viable solution for reducing the fault current in a power grid. But demonstrating the liquid metal arc plasma self-pinching process of the resistive wall, and reducing the erosion of the LMCL are challenging, not only theoretically, but also practically. In this work, a novel LMCL is designed with a resistive wall that can be connected to the current-limiting circuit inside the cavity. Specifically, a novel fault current limiter (FCL) topology is put forward where the novel LMCL is combined with a fast switch and current-limiting reactor. Further, the liquid metal self-pinch effect is modeled mathematically in three dimensions, and the gas-liquid two-phase dynamic diagrams under different short-circuit currents are obtained by simulation. The simulation results indicate that with the increase of current, the time for the liquid metal-free surface to begin depressing is reduced, and the position of the depression also changes. Different kinds of bubbles formed by the depressions gradually extend, squeeze, and break. With the increase of current, the liquid metal takes less time to break, but breaks still occur at the edge of the channel, forming arc plasma. Finally, relevant experiments are conducted for the novel FCL topology. The arcing process and current transfer process are analyzed in particular. Comparisons of the peak arc voltage, arcing time, current limiting efficiency, and electrode erosion are presented. The results demonstrate that the arc voltage of the novel FCL topology is reduced by more than 4.5 times and the arcing time is reduced by more than 12%. The erosions of the liquid metal and electrodes are reduced. Moreover, the current limiting efficiency of the novel FCL topology is improved by 1%‒5%. This work lays a foundation for the topology and optimal design of the LMCL.     

Electrical treeing behaviors in silicone rubber under an impulse voltage considering high temperature

In this paper,work was conducted to reveal electrical tree behaviors(initiation and propagation)of silicone rubber(SIR) under an impulse voltage with high temperature.Impulse frequencies ranging from 10 Hz to 1 k Hz were applied and the temperature was controlled between 30 °C and 90 °C.Experimental results show that tree initiation voltage decreases with increasing pulse frequency,and the descending amplitude is different in different frequency bands.As the pulse frequency increases,more frequent partial discharges occur in the channel,increasing the tree growth rate and the final shape intensity.As for temperature,the initiation voltage decreases and the tree shape becomes denser as the temperature gets higher.Based on differential scanning calorimetry results,we believe that partial segment relaxation of SIR at high temperature leads to a decrease in the initiation voltage.However,the tree growth rate decreases with increasing temperature.Carbonization deposition in the channel under high temperature was observed under microscope and proven by Raman analysis.Different tree growth models considering tree channel characteristics are proposed.It is believed that increasing the conductivity in the tree channel restrains the partial discharge,holding back the tree growth at high temperature.     

典型DC/DC电源变换器电离辐射效应研究

研究了典型DC/DC电源变换器辐照后不同输出负载、不同输入电压等测试条件下,DC/DC电源变换器输出电压等参数变化情况与辐照剂量之间的关系.研究结果表明,DC/DC电源变换器输出电压衰减程度随输出负载功率增大;输入电压变化对输出电压特性的影响程度较小.     

Coupling model of AC filter branch in SF6 circuit breaker during the break process

In this paper, a coupling model of the AC filter branch circuit with the arc plasma in the circuit breaker was built to investigate the arcing process considering the harmonic current. The comparisons among the current at power frequency (50 Hz), power frequency combining the 11th harmonic and power frequency combining the 24th harmonic show that the high-order harmonic current would lead to higher decreasing rate of current before current-zero period. In addition, the influence of arc on the amplitude of high-order harmonic current is not negligible. Thus, the coupling of arc with AC filter branch circuit is quite necessary in the numerical modeling of the circuit breaker in the AC filter branch at the high voltage direct current converter station.     

棒位探测器电源系统比例复数积分控制策略研究

单相逆变器在核电厂棒位检测系统中工作于电压源模式,其负载棒位探测器通常等效为阻感性负载,而阻感性负载连接至逆变器输出端不能稳定地输出正弦电压。为此,本文针对单相逆变器棒位探测器电源系统提出了一种比例复数积分（PCI）控制策略,并给出控制器参数设计方法。首先,基于系统的频域模型推导出电流环比例积分（PI）控制器和电压环PCI控制器参数解析式,并考虑负载参数对系统稳定性的影响。然后,设定期望的电流环和电压环开环截止频率和相位裕度,通过本文方法解析计算PI和PCI控制器参数。最后,通过MATLAB仿真验证了本文方法能够使阻感性负载下的单相逆变器得到稳定的输出电压与输出电流,且输出电流谐波畸变率（THD）<0.3%。该方法可以为单相逆变器棒位探测器电源系统控制提供指导。     

Design principles for handmade electrical insulation of superconducting joints in W7-X

The superconducting magnet system of the Wendelstein 7-X (W7-X) experiment consists of 50 non-planar and 20 planar coils, 121 bus bars and 14 current leads. The connection between bus bars, coils and current leads will be provided by 198 joints. The joints have to be insulated manually during the assembly of the machine in constraint positions and a tight environment. In general the insulation is based on glass tapes impregnated with epoxy resin and special G10 insulating pieces embedded in the glass tape insulation. In critical areas Kapton^®-foils are embedded in the insulation. All types of insulation were qualified at mock-ups in a 1:1 model of the expected environment in W7-X. The qualification programme comprises thermal cycling between room temperature and 77 K and high voltage tests under air, under vacuum and under reduced pressure (Paschen test). The paper describes the main principles used for different types of handmade Paschen-tight insulations in W7-X and the visual and electrical tests during and after assembly.     

线性稳压器不同偏置下电离总剂量及剂量率效应

为对工作在空间电离环境中稳压器的电离总剂量及剂量率效应进行研究,选择一种常用的低压差线性稳压器进行了不同偏置的高低剂量率的电离辐照和退火实验。结合电路特征和电离辐射效应,对线性稳压器产生蜕变的原因进行分析。结果显示,器件输出电压、线性调整率、负载调整率等关键参数在电离辐射环境下发生不同程度变化。在零偏条件下,低剂量率（LDR）下损伤明显大于高剂量率（HDR）条件,表现出低剂量率损伤增强效应;而在工作偏置条件下,高剂量率辐照损伤大于低剂量率的,退火实验中,发生损伤恢复现象,表现为时间相关效应。在整个辐照和退火过程中,零偏置损伤比工作偏置损伤大。     

Thermal analysis and optimization of the EAST ICRH antenna

The ion cyclotron resonance of frequency heating(ICRH) plays an important role in plasma heating.Two ICRH antennas were designed and applied on the EAST tokamak.In order to meet the requirement imposed by high-power and long-pulse operation of EAST in the future,an active cooling system is mandatory to be designed to remove the heat load deposited on the components.Thermal analyses for high heat-load components have been carried out,which presented clear temperature distribution on each component and provided the reference data to do the optimization.Meanwhile,heat pipes were designed to satisfy the high requirement imposed by a Faraday shield and lateral limiter.     

Experimental Study of Reversely Switched Dynistor Discharge Based on Gap Breakdown Load

Breakdown characteristics of a gap breakdown load was investigated in this study, and a Reversely Switched Dynistor (RSD) discharge circuit was designed based on the load. Based on the characteristics of the load the RSD discharge circuit was improved and optimized. The volume of the magnetic switch was reduced. To protect the thyristor and RSD, a diode was anti-parallely connected with the thyristor, which reduced the time requirement when a power voltage was applied to RSD. Experimental results show the circuit designed in this study can switch a high voltage and high current smoothly, and allows the power voltage to change in a wider range.     

Development of Radiation Hard ${rm N}^{+}$-on-P Silicon Microstrip Sensors for Super LHC

Radiation tolerance up to 10¹⁵ 1-MeV n_eq/cm² is required for the silicon microstrip sensors to be operated at the Super LHC experiment. As a candidate for such sensors, we are investigating non-inverting n⁺-on-p sensors. We manufactured sample sensors of 1 times 1 cm in 4" and 6" processes with implementing different interstrip electrical isolation structures. Industrial high resistive p-type wafers from FZ and MCZ growth are tested. They are different in crystal orientations lang100rang and lang111rang with different wafer resistivities. The sensors were irradiated with 70-MeV protons and characterized in views of the leakage current increase, noise figures, electrical strip isolation, full depletion voltage evolution, and charge collection efficiency.     

Formation Process of Intermittent Molten Bridge Between Au-Plated Contacts at Super Low Breaking Velocity

This paper presents the molten bridge behaviors of Au-plated material at super low breaking velocity conditions by introducing our new designed test rig.The typical waveforms of the contact voltage and contact force during breaking are investigated under the load of 5-25 V/0.2-1 A and velocity of 25-150 nm/s.It is shown that the intermittent molten bridge is formed from the competition of multitude contact a-spots for current distribution and the solidliquid mixing characteristics of a molten bridge.Also,it is proved that the bridge is not composed by the completed melted metal by using FEM thermal simulation and the voltage-temperature relation.The observed surface morphology reveals that the scattered and stacked melted regions are attributed to the intermittent bridge.Finally,the effects of breaking velocity and electrical load on bridge length and duration are also analyzed.     

Design of improved compact decoupler based on adjustable capacitor for EAST-ICRF antenna

The Ion Cyclotron Radio Frequency (ICRF) heating antenna on EAST adopts a decoupling device to constrain power coupling among the radiation straps, which was discovered shortcomings such as long size, poor contact, and etc. In order to improve these weak points, a new type decoupler with terminal-loaded tunable capacitor is designed to replace the previous design. Besides the capability of the tunable admittance parameters of decoupler, the withstand voltage of the capacitor is the most significant consideration for working under high power. Therefore, the theoretical analysis carefully elaborates the capacitor withstand voltage, and the detailed analytical equations and criteria for design are given. After the comparative analysis of theoretical calculation and 3D simulation results, the decoupler design scheme is finalized. The capacitor-loaded decoupler has been successfully adopted for ICRF antenna at port N on EAST, and achieved the optimization of adjacent port isolation from −22 to −58 dB at 37 MHz without plasma to restrict mutual coupling. The new design of the decoupler has greatly improved its compactness and automatic adjustment performance, and could be good solution for the decoupling network of ICRF antennas.     

Cyclic testing of shear keys for the ITER magnet system

Shear keys are to be used to support the out-of-plane loading of the toroidal field (TF) coils during a plasma pulse in ITER. At the inner intercoil structures (IIS) a set of poloidal shear keys is used to take the shear load at each connection between adjacent TF coils. Solid circular keys have been selected as reference. At the outer intercoil structures (OIS) adjustable conical shear keys and friction joint based shear panels are used to take the shear load. Low voltage electrical insulation is required at the flanges of the IIS and OIS, plus for all the bolts, poloidal keys and adjustable keys. This electrical insulation has to withstand large compression associated with some shear or slippage. A ceramic coating was selected for this purpose. The main scope of the experimental campaign was the mechanical testing of the shear keys and the electrical insulation in operational conditions relevant to ITER. Both keys were made of Inconel 718, provided with a ceramic alumina coating and inserted into flanges made of cast AISI 316 LN. The adjustable conical shear key was pre-loaded at room temperature and subject to cyclic shear loads of 2.5 MN for a large number of cycles (about 30,000) at cryogenic temperature (77 K). The conical key and the alumina coating remained undamaged after the test. Another test campaign was then performed with higher shear loads (up to 3 MN) to reach a sufficient safety margin even with the friction effect due to the pre-load. A set of 15,000 cycles were completed followed by some cycles at higher loads to reach the ultimate limit, which is the shear load to be experienced by the key in case of a poloidal field (PF) coil short.     

Structure Design and Test Research on the Electrical Properties of High Voltage Instrumentation Cables for the Fusion Reactor

The HV instrumentation cable is an important route for the signals transmission from the superconducting magnets to the control system, it should be long term operated at around 4.2 K and withstand the high voltage over several dozens of kilo volts during the failure operational contrition, meanwhile the cable should be flexible enough to assemble and arrange to the magnet system. According to the instrumentation cable technical requirement, one new type instrumentation cable was designed, after the electrical properties under high voltage were verified in ASIPP lab, the new type instrumentation cables fully meet the technical requirement.