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.     

Study on the plasma generation characteristics of an induction-triggered coaxial pulsed plasma thruster

At present,spark plugs are used to trigger discharge in pulsed plasma thrusters (PPT),which are known to be life-limiting components due to plasma corrosion and carbon deposition.A strong electric field could be formed in a cathode triple junction (CTJ) to achieve a trigger function under vacuum conditions.We propose an induction-triggered electrode structure on the basis of the CTJ trigger principle.The induction-triggered electrode structure could increase the electric field strength of the CTJ without changing the voltage between electrodes,contributing to a reduction in the electrode breakdown voltage.Additionally,it can maintain the plasma generation effect when the breakdown voltage is reduced in the discharge experiments.The induction-triggered electrode structure could ensure an effective trigger when the ablation distance of Teflon increases,and the magnetic field produced by the discharge current could further improve the plasma density and propagation velocity.The induction-triggered coaxial PPT we propose has a simplified trigger structure,and it is an effective attempt to optimize the micro-satellite thruster.     

Understanding the changing mechanism of arc characteristics in ultrasound-magnetic field coaxial hybrid gas tungsten arc welding

Ultrasound-magnetic field coaxial hybrid Gas Tungsten Arc Welding (U-M-GTAW) is proposed as a means to control arc characteristics. The arc characteristics and the mechanism to change them, in an ultrasound-magnetic field coaxial hybrid GTAW, were studied by both experimental and theoretical analyses. The results showed that a periodic rotation and compression of the arc shape were obtained in U-M-GTAW and the arc energy was also enhanced. The most obvious compression of the arc shape in U-M-GTAW was obtained, compared with GTAW, M-GTAW and U-GTAW. At the same time, a periodic rotation of the arc was observed in U-M-GTAW. The geometric parameters of the arc shape in U-M-GTAW are reduced more than double compared with traditional GTAW. The arc voltage in the hybrid GTAW was increased, especially in the U-M-GTAW. The electromagnetic force and acoustic radiation force were the main factors for the change of arc characteristics in the U-M-GTAW.     

板状燃料组件非线性振动特性

设计1个能模拟堆芯燃料组件工作环境和力学边界条件的台架,研究板状燃料组件的非线性振动行为。对安装在振动台上的系统进行白噪声随机激励,得到燃料组件响应-激励关系不同方向、不同介质、不同振级共42种工况的系列曲线。试验结果表明:随着激励振级加大,板状燃料组件的第一阶共振频率减小;板状燃料组件在水中的第一阶共振频率远比在空气中的小,且非线性特性仍呈软弹簧特性;板状燃料组件在环境中的振动阻尼大,能大大抑制抗震响应。     

The characteristics of negative corona discharge and radio interference at different altitudes based on coaxial wire-cylinder gap

The corona discharge from transmission lines in high-altitude areas is more severe than at lower altitudes. The radio interference caused thereby is a key factor to be considered when designing transmission lines. To study the influence of altitude on negative corona characteristics, an experimental platform comprising a movable small corona cage was established: experiments were conducted at four altitudes in the range of 1120-4320 m, and data on the corona current pulse and radio interference ...     

ALICE实验中同轴电缆的信号传输特性的研究

在ALICE实验中,将大量采用同轴电缆作为信号传输线.采用分布参数电路理论,对同轴电缆的信号传输特性进行了分析.同时,从同轴电缆的特征阻抗、反射波损耗、阻抗匹配这三个特性进行分析,探讨了在ALICE实验中如何保证实验数据在传输中的精确性,并提出了一些技术上的建议.     

Dose-voltage dependence of coaxial Bremsstrahlung diodes

The relation ∝ IV^2.65 is widely used to estimate the on-axis radiation-dose rate for flash X-ray sources, as a function of diode current, I, and voltage, V, 1 m downstream of an optimized bremsstrahlung target. This relation is valid only for pencil beams. In this paper, we show that for diodes having beams with finite spatial and angular extent, this relation can still be used if the power 2.65 is modified. Using particle-in-cell and radiation-transport codes, this modification is evaluated for a diode proposed for the 20-MeV HERMES III accelerator that is currently under construction. Predictions of the calculational model are compared with measurements obtained from experiments on the existing 3-MeV HELIA accelerator and are found to be in good agreement. These results are characteristic of finite-area coaxial diodes in general and show the trend of the deviation from 2.65 for such sources.     

Development of a coaxial tapered electromagnetic shock tube for beam-plasma non-linear interaction experiments

A coaxial electromagnetic shock tube was developed to produce a non-ideal plasma target with Γ ∼ 0.1 (Γ: Plasma coupling constant) for non-linear interaction experiments between ion beams and plasmas. To evaluate the shock velocity, we photographed the trajectory of the shock front along the tube by a streak camera. From these measurements, we found that the shock waves are strong enough to produce a non-ideal plasma in the tube. To reduce the plasma thickness for the stopping power measurements, the effective diameter of the tube was reduced by using a tapered section. The effects of the tapered section on the shock velocity and the shape of the shock front were examined. Using a 30 tapered section, the shock velocity was increased up to 54 km/s compared with 47 km/s for a straight tube.     

Vibrations of two coaxial cylindrical shells containing fluid

This paper considers the vibrational behavior of two long, elastic, coaxial cylindrical shells containing (or conveying) fluid. Both exact and approximate formulas for the added (attached, virtual) mass of the fluid are derived. The method of analysis is illustrated using appropriate shell equations.     

Turbulence measurements and calculations of non-isothermal coaxial jets

In the present study, non-isothermal coaxial jets are numerically investigated and the turbulence quantities calculated with a second order closure model are compared with the experimental results and the validity is examined.     

N型HPGe同轴探测器的研制

本文介绍N型高纯锗同轴探测器的特点、制备方法及其性能。我们研制成的N型同轴探测器的体积为88cm~3,相对效率约为19％,它对_(60)Co 1.33MeV γ射线的能量分辨率为2.60keV,峰康比为34。     

Vibrational analysis of the superphenix internal shells

The geometry of the internal shells of Superphenix is somewhat complicated; they are mainly axisymmetric with some special parts, like pumps and heat exchanger crossing, non-axisymmetric. The flow leaving the reactor core or the heat exchanger strikes some of these shells and induces vibrations. Owing to the expected long life of the plant, without the possibility of intervention on the shells, it is necessary to verify that the vibrational level is sufficiently low and that there is no risk of fatigue. A first estimate of the vibrational level has been calculated. This paper explains the formalism used and describes the main steps of the calculation: (a) estimation of the fluctuating pressures; (b) calculation of the structural resonances, taking into account the sodium effects; and (c) estimation of the resulting vibrational amplitude. A short review of the experimental work planned to verify and validate the calculation results is presented.     

Vibrational conductivity approach to high-frequency dynamics

An approach in which a heat conduction equation is used to model high-frequency vibration propagation in complex structures is offered. A direct method is used to identify the parameters of the approach. In particular, the vibrational temperature turns out to be equal to the sum of the acceleration spectral densities in three orthogonal directions. The other parameters are determined through averaged structural mechanical characteristics and some generalized spectra. The accuracy of the approach is discussed, and the vibration fields of a cylinder and a half-space subjected to periodic acoustic impulses are computed.     

Coupled-mode theory of coaxial gyrotron with two electron beams

Results of coupled-mode theory for the study on coaxial gyrotron with two electron beams (CGTB) are given. The beam–wave interactions of single-mode and dual-mode CGTB are discussed in details. Compared with the coaxial gyrotron with one beam (CGOB), the dual-mode CGTB has distinguished advantages: the fundamental and high harmonic can be enhanced due to the coupling between two beams.     

单通道电子倍增器的性能测试

对一种国产单通道电子倍增器的单电子脉冲高度分布、坪特性、增益特性、随电子能量变化的相对效率及暗噪声分布进行了测试;确定了倍增器的最佳工作参数。倍增器输出幅度在10mV左右,脉冲上升时间小于15ns,坪宽超过500V,增益大于10~7,在电子能量为500eV左右时有较高的探测效率,暗噪声小于0.22脉冲/s。