Study on volt-ampere characteristics of solar array arcs in LEO spacecraft

The primary and secondary arcs volt-ampere characteristics of low earth orbit solar arrays are studied in this research. Using three gallium-arsenide solar cell samples, the gap lengths of the solar cell are set to 1, 2, and 3 mm. First, the primary arc voltage characteristics of a solar array are analyzed. It is found that two steps are involved in the primary arc voltages, which are 116 and 22 V according to our experiment and are independent of the electrostatic discharge current and the gap lengths. By comparing with the arc pattern, we determined that current chopping may be the reason for the stepped arc voltage. Then, the characteristics of the secondary arc of the solar array are demonstrated. The study shows that the secondary arc voltage values increase with the gap length. In the case of the same cell with a fixed gap length, the voltage of the secondary arc increases with the string current. Finally, the relationship between the secondary arc voltage and the gap length is obtained which helps the string voltage and the gap length selection for system design.     

Electrical and optical characteristics of atmospheric helium jet array plasma

In this paper, a honeycomb structure jet array with seven jet units was adopted to generate plasmas. Both the average discharge power and the emission intensity of the main excited species increase with increasing applied voltage. There are three stages of discharge evolution at different applied voltages: initial discharge, uniform discharge and strong coupling discharge.The spatial distribution of the emission intensity of the excited species can be divided into three categories: growth class, weakening class and variation class. The gas temperature along the whole plasma plume at different applied voltages is maintained at around 320K and can be widely used in heat-labile applications.     

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.     

Study on electrostatic discharge (ESD) characteristics of ultra-thin dielectric film

Electrostatic discharge (ESD) event usually destroys the electrical properties of dielectric films, resulting in product failure. In this work, the breakdown characteristic of machine mode (MM) ESD on three different nano size films of head gimble assemble are obtained experimentally. The breakdown voltage and thickness parameters show a positive proportional relationship, but they are generally very low and have large discrete characteristics (∼30%). The maximum and minimum breakdown voltages of the tested samples are 1.08 V and 0.46 V, which are far lower than the requirement of the current standard (25 V). In addition, the judgment criterion of product damage is given, and the relationship between discharge voltage polarity, initial resistance and breakdown voltage is studied. Finally, the theoretical analysis of the breakdown characteristic law has been given.     

0.4mm像素X射线阵列探测器的设计

描述了一种像素大小为0.4mm的X射线阵列探测器系统的设计,探测器以闪烁陶瓷材料Gd2 O2S:Tb耦合光电二极管阵列构成,可应用于几十到100keV的X射线数字辐射成像系统,可作为无损检测技术研究平台中的探测器系统.介绍了探测器的信号处理方法,给出了用该系统获取的实际图像.     

Effect of dilution gas composition on the evolution of graphite electrode characteristics in the spark gap switch

As the widely implemented electrode material, graphite has the characteristic of sublimation by the thermal shock of the switching arc, and the produced carbon vapor is easy to condense into carbon powders and deposit in the switch. The impact of the type of dilution gas in a mixture of20% oxygen and 80% dilution gas on the sublimation and oxidation characteristics of the graphite electrode is investigated. It is found that when nitrogen dilution gas was replaced by argon, the heat flux to the electrodes decreased, which led to a 63% reduction of graphite sublimation. At the same time, the cooling rate of the arc was slower in argon, which promotes oxidation of the carbon vapor. The residual solid carbon can be reduced by 70%–85% by using argon as the dilution gas. Consequently, it is demonstrated that the stability and working life of the switch could be increased by appropriate selection of the dilution gas.     

磁驱动旋转电弧运动图像及弧电压脉动的实验研究

磁驱动旋转电弧产生扩散电弧等离子体过程中有许多有趣的物理现象。本文利用高速摄影技术研究了大气压条件下、非均匀磁场中、大尺度磁驱动旋转氩电弧的电弧结构；在一定的弧电流和外磁场条件下，电弧的平面形状表现为不断发展和增长的螺旋结构，电弧螺旋结构的破裂往往产生于阴极附近的等离子体射流。采用图像分析的方法计算了外部磁场作用下阳极斑点沿弧室内壁的移动频率，分析了磁驱动旋转电弧运动过程中的弧电压脉动现象。结合电弧图像分析和电弧电压脉动及其FFT分析得出：电弧电压的大幅波动与多层电弧螺旋结构破裂和重建相关，而电弧电压的小幅波动则是弧根小幅跳动引起电弧拉长和收缩的结果。     

The Effect of High-Pressure Arc Discharge Plasma on the Degradation of Chlorpyrifos

A study is conducted to determine the effect of a kind of high-pressure arc discharge plasma on the degradation rate and kinetic equations of chlorpyrifos in different solvents with the treated times and concentrations as variables. The degradation rate was sorted in different solvents as water, methanol, acetone and then acetoacetate. The tendencies of the degradation rates with treated time in water and methanol were optimally fitted with first-order kinetics equations while those in acetone and acetoacetate were fitted with zeroth-order kinetics equations. The difference was attributed to the stronger polarity of water and methanol. The weak correlation of the degradation rates with time was mainly because the high-temperature of the arc discharge tube and the chemically-active species generated by the discharge. The degradation half-life was extended with increase of chlorpyrifos concentration. A degradation half-life less than 3 min was achieved for chlorpyrifos in water and methanol when the initial concentration was less than 300 μg/ml.     

Study of generation characteristics of glow-type atmospheric-pressure plasma jet based on DC discharge in air

In order to form an atmospheric-pressure plasma jet without airflow, a needle–ring electrode structure is proposed in this paper. When heteropolar potentials are applied to a needle and a ring, a marked electric field strength enhancement around the needle's pointed end has been found. When the same potential is applied to both the needle and the ring, the lateral electric field strength for the needle can be weakened. By using the above two methods, an increase of the difference between the pointed end electric field strength and the lateral one is achieved and stable plasma jets are formed. A symmetrical space electric field distribution is established at the pointed end of the needles when several sets of heteropolar needle–ring electrodes are uniformly arranged, which is conducive to forming a uniform array plasma jet. Under DC discharge conditions, a safe and stable plasma jet of high density and an array plasma jet are successfully achieved.     

硅多条阵列探测器多路电荷灵敏前置放大器研制

本文简要介绍了应用于阵列探测器特别是硅多条阵列探测器的高密度多路前置放大器和前端电子学的发展现状、工作原理、设计要求和设计思路.同时,介绍了一套新开发的用于硅多条探测器中的48路电荷灵敏前置放大器的电路设计和实际测量结果,它具有低成本、高密度、好于1%的能量分辨和良好的长期稳定性.     

新型晶体阵列探测器在MicroPET中的应用

PET因为采用了符合探测的原理,所以可得到高分辨率的图像。将这项技术应用于小动物的各项研究之中,就开发出了MicroPET系统。MicroPET在生物学、医学和药学等方面具有重大的意义。简述了MicroPET的研究意义和发展历史,并以加州大学洛杉矶分校研制的MicroPET样机为例,介绍了MicroPET及其新型晶体阵列探测器的结构、原理和发展方向。     

The Effect of Flow Distribution on the Concentration of NO Produced by Pulsed Arc Discharge

As a new method to cure acute respiratory distress syndrome （ARDS）, high blood pressure and some illnesses related to the lung, NO has recently received more attention. Thermal plasmas produced by arc discharge can create medical NO, but the concentration of NO2 produced by arc discharge must be controlled simultaneously. This paper investigates the characteristics and regulations of NO production at different flow distribution by pulsed arc discharge in dry air with a special pulsed power, The experimental results show that the flow distribution has a considerable effect on the NO concentration, the stabilization of NO. The production of NO2 could be controlled and the ratio of NO2/NO was decreased to about 10% in the arc discharge. Therefore, the arc discharge could produce stable inhaled NO for medical treatment by changing the flow distribution.     

基于辐射探测器阵列的单个γ源定位方法

采用探测器阵列并通过数据的自动处理实现辐射源的定位,是信息时代物联网工程对辐射信息监控的基本要求。为此,本文初步讨论了数学分析法、数学统计法和邻近探测器数据比较法三种定位方法,并采用MCNP5软件对通道内单个γ源的一维定位监控进行了数值仿真分析。结果表明,数学分析法和数学统计法的定位能力均优于工程上常用的邻近探测器数据比较法,前者需要的探测器数量少,但在多个探测器存在时误差随探测器组合而产生较大的变化。数学统计法需要多个探测器形成阵列,但定位精度很高,可用于大剂量或重要放射性部件的精确位置监控。     

Temperature and Nitric Oxide Generation in a Pulsed Arc Discharge Plasma

Nitric oxide （NO） is increasingly being used in medical treatments of high blood pressure, acute respiratory distress syndrome and other illnesses related to the lungs. Currently a NO inhalation system consists of a gas cylinder of N2 mixed with a high concentration of NO. This arrangement is potentially risky due to the possibility of an accidental leak of NO from the cylinder. The presence of NO in the air leads to the formation of nitric dioxide （NO2）, which is toxic to the lungs. Therefore, an on-site generator of NO would be highly desirable for medical doctors to use with patients with lung disease.
To develop the NO inhalation system without a gas cylinder, which would include a high concentration of NO, NAMIHIRA et al have recently reported on the production of NO from room air using a pulsed arc discharge. In the present work, the temperature of the pulsed arc discharge plasma used to generate NO was measured to optimize the discharge condition. The results of the temperature measurements showed the temperature of the pulsed arc discharge plasma reached about 10,000 K immediately after discharge initiation and gradually decreased over tens of microseconds. In addition, it was found that NO was formed in a discharge plasma having temperatures higher than 9,000 K and a smaller input energy into the discharge plasma generates NO more efficiently than a larger one.     

Analysis of Effects of the Arc Voltage on Arc Discharges in a Cathode Ion Source of Neutral Beam Injector

A hot cathode bucket ion source is used for the EAST(experimental advanced superconducting tokamak)neutral beam injector.The thermal electrons emitted from the surface of the cathode are extracted and accelerated by the electric field formed by the arc voltage,which is applied between the arc chamber of the ion source and the cathode.This paper analyzes the effects of arc voltage on the arc discharge in a hot cathode high current ion source.     

Ion property and electrical characteristics of 60 MHz very-high-frequency magnetron discharge at low pressure

The pre-ionized 60 MHz very-high-frequency (VHF) magnetron discharge at low pressure, assisted by inductively coupled plasma (ICP) discharge, was developed. The measurement of ion flux density and ion energy to the substrate was carried out by a retarding field energy analyzer. The electric characteristics of discharge were also investigated by voltage–current probe technique. It was found that by reducing the discharge pressure of VHF magnetron discharge from 5 to 1 Pa, the ion flux density increased about four times, meanwhile the ion energy also increased doubly. The electric characteristics of discharge also showed that a little improvement of sputtering effectiveness was achieved by reducing discharge pressure. Therefore, the deposition property of VHF (60 MHz) magnetron sputtering can be improved by reducing the discharge pressure using the ICP-assisted pre-ionized discharge.     

The influence of grounded electrode positions on the evolution and characteristics of an atmospheric pressure argon plasma jet

An atmospheric pressure plasma jet (APPJ) in Ar with various grounded electrode arrangements is employed to investigate the effects of electrode arrangement on the characteristics of the APPJ.Electrical and optical methods are used to characterize the plasma properties.The discharge modes of the APPJ with respect to applied voltage are studied for grounded electrodepositions of 10 mm,40 mm and 80 mm,respectively,and the main discharge and plasma parameters are investigated.It is shown that an increase in the distance between the grounded electrode and high-voltage electrode results in a change in the discharge modes and discharge parameters.The discharges transit from having two discharge modes,dielectric barrier discharge (DBD) and jet,to having three,corona,DBD and jet,with increase in the distance from the grounded to the high-voltage electrodes.The maximum length of the APPJ reaches 3.8 cm at an applied voltage of 8 kV.The discharge power and transferred charges and spectral line intensities for species in the APPJ are influenced by the positions of the grounded electrode,while there is no obvious difference in the values of the electron excited temperature (EET) for the three grounded electrode positions.     

Degradation prediction of a γ-ray radiation dosimeter using InGaP solar cells in a primary containment vessel of the Fukushima Daiichi Nuclear Power Station

ABSTRACT

Indium gallium phosphide (InGaP) solar cell with a superior high-radiation resistance is expected to be a powerful candidate for a dosimeter under a high-radiation dose rate environment. In this study, in order to predict the lifetime as the dosimeter using the InGaP solar cell, we clarify the effect of minority-carrier diffusion length (L) on a radiation-induced current as a dose signal in the InGaP solar cell by irradiation tests and empirical calculations. In the irradiation tests, the short-circuit current density (J_sc) as a function of the γ-ray dose rate is measured to estimate the L for the InGaP solar cell by irradiation tests. The operational lifetime as a detector using the InGaP solar cell under various dose rates is estimated by using the empirical calculations based on the relation between the L and absorbed dose. The results suggest that the dosimeter using InGaP solar cell is able to be used during more than 10 h in the primary containment vessel of the Fukushima Daiichi Nuclear Power Plant and it has a high potential of being a radiation-resistant dosimeter that would contribute to the decommissioning.     

Improvement of Spatial Uniformity of Nanosecond-Pulse Diffuse Discharges in a Multi-Needle-to-Plane Gap

Large-scale non-thermal plasmas generated by nanosecond-pulse discharges have been used in various applications, including surface treatment, biomedical treatment, flow con?trol etc. In this paper, atmospheric-pressure diffuse discharge was produced by a homemade nanosecond-pulse generator with a full width at half maximum of 100 ns and a rise time of 70 ns. In order to increase the discharge area, multi-needle electrodes with a 3×3 array were designed. The electrical characteristics of the diffuse discharge array and optical images were investigated by the voltage-current waveforms and discharge images. The experimental results showed that the intensity of diffuse discharges in the center was significantly weaker than those at the margins, resulting in an inhomogeneous spatial uniformity in the diffuse discharge array. Simulation of the electric field showed that the inhomogeneous spatial uniformity was caused by the non-uniform distribution of the electric field in the diffuse discharge array. Moreover, the spatial uniformity of the diffuse discharge array could be improved by increasing the length of the needle in the centre of the array. Finally, the experimental results confirmed the simulation results, and the spatial uniformity of the nanosecond-pulse diffuse discharge array was signi?cantly improved.     

Investigation on discharge characteristics of a coaxial dielectric barrier discharge reactor driven by AC and ns power sources

A coaxial dielectric barrier discharge(DBD) reactor with double layer dielectric barriers has been developed for exhaust gas treatment and excited either by AC power or nanosecond(ns)pulse to generate atmospheric pressure plasma. The comparative study on the discharge characteristics of the discharge uniformity, power deposition, energy efficiency, and operation temperature between AC and ns pulsed coaxial DBD is carried out in terms of optical and electrical characteristics and operation temperature for optimizing the coaxial DBD reactor performance. The voltages across the air gap and dielectric layer and the conduction and displacement currents are extracted from the applied voltages and measured currents of AC and ns pulsed coaxial DBDs for the calculation of the power depositions and energy efficiencies through an equivalent electrical model. The discharge uniformity and operating temperature of the coaxial DBD reactor are monitored and analyzed by optical images and infrared camera. A heat conduction model is used to calculate the temperature of the internal quartz tube. It is found that the ns pulsed coaxial DBD has a much higher instantaneous power deposition in plasma, a lower total power consumption, and a higher energy efficiency compared with that excited by AC power and is more homogeneous and stable. The temperature of the outside wall of the AC and ns pulse excited coaxial DBD reaches 158 ℃ and 64.3 ℃ after 900 s operation, respectively.The experimental results on the comparison of the discharge characteristics of coaxial DBDs excited by different powers are significant for understanding of the mechanism of DBDs,reducing energy loss, and optimizing the performance of coaxial DBD in industrial applications.