Characteristic of a triple-cathode vacuum arc plasma source

In order to generate a better ion beam, a triple-cathode vacuum arc plasma source has been developed. Three plasma generators in the vacuum arc plasma source are equally located on a circle. Each generator initiated by means of a high-voltage breakdown between the cathode and the anode could be operated separately or simultaneously. The arc plasma expands from the cathode spot region in vacuum. In order to study the behaviors of expanding plasma plume generated in the vacuum arc plasma source, a Langmuir probe array is employed to measure the saturated ion current of the vacuum arc plasma source. The time-dependence profiles of the saturated current density of the triple vacuum arc plasma source operated separately and simultaneously are given. Furthermore, the plasma characteristic of this vacuum arc plasma source is also presented in the paper.     

基于圆弧限位的压电发电装置

提出一种基于圆弧限位压电发电装置来提高发电能力及可靠性。介绍了该装置的结构及工作原理,建立了其机电能量转换模型。通过模拟仿真分析获得了压电振子厚度比（基板与总厚度比）对最小限位圆弧半径及能量、及压电振子厚度和限位圆弧半径对电压及能量的影响规律。结果表明,最小限位圆弧半径随厚度比的增加而线性减小,且存在共同的最佳厚度比（0.35）使不同厚度压电振子的输出电压和能量最大;在最佳厚度比时,输出电压和能量随压电振子厚度增加或限位圆弧半径降低而增加。制作了一组限位圆弧半径不等的发电装置,并进行了相关试验测试。结果表明,压电振子的最大输出电压（变形量）仅与限位圆弧半径有关,故采用最小限位圆弧半径可同时获得最大的发电能力和较高的可靠性。     

A robust design in hardfacing using a plasma transfer arc

This paper presents the use of the Taguchi-regression method in developing the optimal plasma transferred arc welding (PTAW) process for obtaining high hardfacing quality characteristics. An “optimal” process means that the best performance characteristic would be produced while the least number of process parameters are involved. In the experimental tests, the surface hardening process is conducted using Cobalt-based and Nickel-based powdery metal materials together with L₁₈ orthogonal arrays. The dependent variable, wear, obeys the-smaller-the-better quality characteristic, and the performance statistics, the signal-to-noise ratios (SNRs), are obtainable. The experimental results show that the most efficient process parameters based on analysis of variance are set as follows: hardfacing material, the accelerating voltage, the powder feed rate , and the pre-heat treatment temperature. They account for almost 90% of the total variance of wear. Under the optimal setting, the average error rates for using Taguchi and Taguchi-regression methods are 7.05 and 5.50%, respectively. The outcome of the experiment indicates that predicted values of the optimal setting fit well with the actual data. The reproducibility of the optimal plasma transfer arc hardfacing is obtained from the experimental data of the confirmation run. A reliable analysis based on the results from plasma transfer arc hardfacing conditions can be achieved through the Taguchi-regression method.     

同轴等离子体发生器电弧运动轨迹数值分析与计算

为了计算针对外加轴向磁场的同轴等离子体发生器内等离子电弧的运行轨迹和旋转速度,采用了数值分析方法。首先采用通道模型计算了电弧半径;将电弧等效为刚体,根据电弧稳态旋转阻力力矩与电磁力矩平衡原理建立了其稳态运行的数学模型,然后通过采用禁忌搜索算法计算了其转速。研究结果表明:粒子的空间运行轨迹为近似平面抛物线以阴极为对称轴旋转形成的空间迹线。此外,实验结果证明了理论工作的有效性和正确性。     

Surface plasma source with saddle antenna radio frequency plasma generator

A prototype RF H(-) surface plasma source (SPS) with saddle (SA) RF antenna is developed which will provide better power efficiency for high pulsed and average current, higher brightness with longer lifetime and higher reliability. Several versions of new plasma generators with small AlN discharge chambers and different antennas and magnetic field configurations were tested in the plasma source test stand. A prototype SA SPS was installed in the Spallation Neutron Source (SNS) ion source test stand with a larger, normal-sized SNS AlN chamber that achieved unanalyzed peak currents of up to 67 mA with an apparent efficiency up to 1.6 mA∕kW. Control experiments with H(-) beam produced by SNS SPS with internal and external antennas were conducted. A new version of the RF triggering plasma gun has been designed. A saddle antenna SPS with water cooling is fabricated for high duty factor testing.     

水再约束等离子弧切割的改进

针对现有水再约束等离子弧加工中存在容易断弧等问题，提出了把水射流“焦平面”与被切割工件上表面重合的水再约束方案，并分析了该方案中再约束水流量对弧柱稳定性及切口质量的影响。     

An electric arc in a helium flow in a high-current plasmatron

Experimental studies of an electric arc in a helium flow are described. A generalized dependence of the electric field on the determining criteria has been obtained on the basis of the experimental data, and a plasmatron has been designed on the basis of the technique developed. Its thermal efficiency is 0.68–0.74, and the mass-averaged temperature of the helium flow is T = 3700–4200 K. The plasmatron can be used in various technological processes involving energy conversion.     

An ultrawideband Gigawatt pulse generator

An ultrawideband pulse generator consists of a bipolar voltage pulse generator, a four-channel power divider, and a flat (2×2) equally spaced equal-amplitude antenna array. Characteristics of the ultrawide-band radiation at the excitation of the antenna array by bipolar pulses with a±200-kV voltage amplitude, ≈3.5-ns duration, and 100-Hz pulse repetition rate are given. The peak power of the vertically polarized radiation is 1.3 GW.     

基于DDE的火力发电机组经济运行在线监测系统

针对发电机组经济运行的实际情况．介绍了DDE(Dyrlamlc Data Exchange．动态数据交换)的概念及其在在线监测系统开发中的应用。实践证明．通过对软件系统的结构规划，运用DDE技术可以大大提高软件的开发效率。     

Development of a plasma generator for a long pulse ion source for neutral beam injectors

A plasma generator for a long pulse H(+)/D(+) ion source has been developed. The plasma generator was designed to produce 65 A H(+)/D(+) beams at an energy of 120 keV from an ion extraction area of 12 cm in width and 45 cm in length. Configuration of the plasma generator is a multi-cusp bucket type with SmCo permanent magnets. Dimension of a plasma chamber is 25 cm in width, 59 cm in length, and 32.5 cm in depth. The plasma generator was designed and fabricated at Japan Atomic Energy Agency. Source plasma generation and beam extraction tests for hydrogen coupling with an accelerator of the KSTAR ion source have been performed at the KSTAR neutral beam test stand under the agreement of Japan-Korea collaborative experiment. Spatial uniformity of the source plasma at the extraction region was measured using Langmuir probes and ±7% of the deviation from an averaged ion saturation current density was obtained. A long pulse test of the plasma generation up to 200 s with an arc discharge power of 70 kW has been successfully demonstrated. The arc discharge power satisfies the requirement of the beam production for the KSTAR NBI. A 70 keV, 41 A, 5 s hydrogen ion beam has been extracted with a high arc efficiency of 0.9 -1.1 A/kW at a beam extraction experiment. A deuteron yield of 77% was measured even at a low beam current density of 73 mA/cm(2).     

Electromagnetic arc path control in robot plasma welding

Arc welding has always presented a challenge to robot operation. Variations in joint fit-up, positional welding requirements and the high levels of welder skill demanded by transient changes in operating conditions are just some of the variables with which any arc welding robot must cope. The article examines how an inertia-less high-frequency weaving technique using a novel deflector system can solve many of these problems even for high speed seam tracking.     

An approach to design and fabrication of a piezo-actuated microdroplet generator

In this research, a piezo-actuated microdroplet printing device for drop on demand (DOD) is studied. Microdroplet devices are used in applications such as inkjet printing, rapid prototyping, and production of metal powder. An experimental device is designed and manufactured, in which the fluctuation of a flexible diaphragm–by a piezoelectric element–pushes the liquid out of the nozzle and produces droplets. The deflection of diaphragm due to different voltages is investigated by analytical and experimental study. In experiments, beside deflection voltage, the effect of suction and compression time and nozzle diameter on droplet size, droplet velocity, satellite droplets, and cutoff length is also investigated. High-speed camera is used to take photo of the formation of droplets. In order to calculate droplet diameter and velocity, outputs of high-speed camera are processed by MATLAB R2008a. Results obtained by analytical and experimental are in good agreement with each other and could be used to control droplet properties. It is shown that the device is able to produce droplet of diameter from 450 to 1,000 μm. Velocity of droplet can be also controlled in a range of about 0.2 to 1.4 m/s. The repeatability is investigated by ink printing on a paper attached to a rotary table.     

A high-current plasma generator based on a hollow cathode for high-power electric propulsions

A construction diagram and procedure for independent tests of the new hollow cathode, created at the Keldysh Research Center, being capable of ensuring an emission current of about 100 A, and meeting the main requirements, imposed on thermoemission cathodes of high-power ion thrusters, are considered. Results of the independent tests are given and dependences of the discharge voltage on the discharge current in a discharge-current range of 20–120 A are obtained. The temperatures of the cathode construction elements in stationary operation modes are measured.     

电弧喷涂技术及进展

电弧喷涂是一种有发展前景的表面工程技术。这里简要介绍了电弧喷涂的原理、技术特点、设备、喷涂丝材、应用、以及发展方向。     

Status of the plasma generator of the superconducting proton linac

In the framework of the superconducting proton linac (SPL) study at CERN, a new non-cesiated H(-) plasma generator driven by an external 2 MHz RF antenna has been developed and successfully operated at repetition rates of 50 Hz, pulse lengths of up to 3 ms, and average RF powers of up to 3 kW. The coupling efficiency of RF power into the plasma was determined by the cooling water temperatures and the analysis of the RF forward and reflected power and the antenna current and amounts to 50%-60%. The plasma resistance increases between 10 kW and 40 kW RF power from about 0.45 Ω to 0.65 Ω. Measurements of RF power dissipated in the ferrites and the magnets on a test bench show a 5-fold decrease of the power losses for the magnets when they are contained in a Cu box, thus validating the strategy of shielding the magnets with a high electrical conductivity material. An air cooling system was installed in the SPL plasma generator to control the temperatures of the ferrites despite hysteresis losses of several Watts.     

Shunting arc plasma source for pure carbon ion beam

A plasma source is developed using a coaxial shunting arc plasma gun to extract a pure carbon ion beam. The pure carbon ion beam is a new type of deposition system for diamond and other carbon materials. Our plasma device generates pure carbon plasma from solid-state carbon material without using a hydrocarbon gas such as methane gas, and the plasma does not contain any hydrogen. The ion saturation current of the discharge measured by a double probe is about 0.2 mA∕mm(2) at the peak of the pulse.     

Magnetic multipole line-cusp plasma generator for neutral beam injectors

The magnetic multipole line-cusp device developed by MacKenzie and associates has been adapted for use as a neutral beam ion source. It has produced high-density, large volume, quiescent, uniform hydrogen plasmas, which makes it a potential candidate for use as a plasma generator for neutral beam injectors. The device is a water-cooled cylindrical copper discharge chamber (25 cm in diameter by 36 cm long) with one end enclosed by a set of extraction grids with a 15-cm-diam multi-aperture pattern. The chamber wall serves as an anode and is surrounded by an external system of rare-earth cobalt magnets arranged in a line-cusp geometry of 12 cusps; plasma is produced by electron emission from a hot cathode assembly. This source has achieved extracted beam currents of 12 A at 18.5 kV, radial plasma density uniformities of +/-5% over a 15-cm diameter, noise levels of less than +/-0.5%, and arc efficiencies (beam current/arc power) of 0.6 A/kW.     

Angular distribution of plasma in the vacuum arc ion source

This paper presents measurements of the angular distribution of the plasma components and different charge states of metal ions generated by a MEVVA-type ion source and measured by a time-of-flight mass-spectrometer. The experiments were performed for different cathode materials (Al, Cu, and Ti) and for different parameters of the vacuum arc discharge. The results are compared with prior results reported by other authors. The influence of different discharge parameters on the angular distribution in a vacuum arc source is discussed.     

System identification of controlled pulse keyhole plasma arc welding process

The development of closed-loop control systems is one of the most effective ways to improve the stability of the keyhole status during keyhole plasma arc welding (K-PAW). Due to the disadvantages of the "one-pulse-one-keyhole" technology based on the conventional square current waveform, the controlled pulse welding current waveform is newly applied to control the keyhole open and close periodically. In order to realize the real-time control on the keyhole behavior with this advanced current waveform, welding experiments and system identification are conducted based on the classical control theory. One complete welding cycle can be divided into 3 periods. The keyhole establishing time is the most important time variable, which determines the keyhole behavior and welding process stability. At the same time, the averaged efflux plasma arc voltage during one pulse cycle can reflect the real keyhole dimension and status in a real-time manner. Therefore, two single-input-single-output (SISO) systems are proposed, in which keyhole establishing time and keyhole average dimension are taken as the system controlled variables respectively. Welding experiments are designed with the peak current varying randomly. Experiments show that the keyhole establishing time changes in an opposite direction to the varied peak current, and the averaged efflux plasma arc voltage varies with the same trend as the peak current. Based on the least squares technique and F test of classical system identification, second order difference equation for keyhole establishing time/peak current system and first order difference equation for keyhole average dimension/peak current system are obtained. It is proved that the calculated data by the two mathematical expressions are well matched with the measured data. The proposed research provides mathematical expressions and theoretical analysis to develop closed-loop systems for the controlled pulse K-PAW.