Optical guiding of intense laser pulses by fast Z-pinch discharge

We have proposed the optical guiding of intense laser pulses by fast Z-pinch for channel-guided laser wakefield acceleration (LWFA). The method has been developed based on capillary discharge-pumped X-ray laser technique. A discharge through preionized helium gas driven by a current of 4.8 kA with a rise time of 15 ns proved able to produce a uniform guiding channel with good reproducibility, less than the time jitter of 1.8 ns. The observed guiding channel formation process was corroborated by 1D-MHD simulation. With this new guiding method, an intense Ti-sapphire laser pulse (λ = 790 nm, 2.2 TW, 90 fs, 1 × 10¹⁷ W/cm²) was transported through the channel over a distance of 2 cm, corresponding to 12.5 times the Rayleigh length. © 2001 Scripta Technica, Electr Eng Jpn, 136(3): 19–27, 2001     

脉冲等离子体反应器放电特性研究

脉冲放电等离子体被广泛用于气态污染物处理的研究,放电参数直接影响反应器内等离子体状态,进而影响污染物的去除效果,研究不同条件下的放电特性可为脉冲等离子体技术的应用提供参考.本文利用线板式脉冲等离子体反应器, BPFN型高压脉冲电源供电, 研究了电源电容、极板间距及介质阻挡对放电特性的影响.结果表明:增大电源电容可以有效地提高电源能量效率;增大极板间距,峰值电压VP增大,峰值电流IP减小,脉宽减小,波形更加理想;陶瓷板阻挡放电可解决间隙火花放电,使脉冲电晕放电空间分布均匀,在大范围内提高电源能量效率.     

Electric field measurement just beneath a surface discharge by optical‐waveguide pockels sensors

Although surface discharges are one of the principal kinds of phenomena associated with faults in electrical apparatus, they have not yet been fully elucidated. Electric field measurements in and around a corona streamer during the creeping advance of a surface discharge are very helpful in analyzing discharges. Pockels crystals have been used in the optical measurement of electric fields, and an optical waveguide technique has been successfully used to miniaturize the sensors. Electric field measurements are made just beneath a surface discharge with an optical waveguide Pockels sensor installed on a PMMA plate and output signals expressing the development of the discharge are obtained. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(2): 28–34, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10185     

Laser‐induced discharge in a rod–plane electrode in the presence of a negative dc electric field

Discharge induction experiments were performed between a plate and a rod on a plate electrode configuration with a gap length of 1 m using a high‐power CO₂ laser and a dc voltage generator. The electrodes are parallel planes. Each plate electrode consists of a central flat part having a diameter of 3 m with a circular edge on a cross section. The length of the rod is 10 cm. A chain of plasma beads of length 10 cm was created on the tip of the rod by the CO₂ laser and used for artificial triggering of negative high‐voltage sparkover. The behavior of streamer, leader, and return stroke was observed by an image converter camera. It was found that a positive upward traveling leader can be triggered from the tip of the rod on the lower plane to the upper plane by the chain of plasma beads created by the CO₂ laser. This apparatus is useful for study for realization of laser‐induced lightning. © 2000 Scripta Technica, Electr Eng Jpn, 132(4): 19–27, 2000     

Calculation of magnetic near field generated by the contact discharge of an ESD gun

An ESD (electrostatic discharge) testing is specified in the IEC 61000‐4‐2, in which the detailed waveform of the discharge current injected by an ESD gun is prescribed. However, due to lack of understanding of the discharge process, it is difficult to confirm whether or not the IEC current waveform can be injected onto actual equipment. We thus previously proposed an equivalent circuit model for the ESD gun based on its geometrical structure, and showed decisive factors for the discharge current. In this study, in order to confirm the feasibility of the above equivalent circuit model, we measured with a 6‐GHz wide‐band digital oscilloscope the discharge current through an SMA connector and the resultant magnetic near field for the contact discharge of an ESD gun. As a result, we found that both measured waveforms approximately agree with those calculated from our equivalent circuit model. We then measured with respect to charge voltages the magnetic near fields for the contact discharge of the ESD gun to the ground, which revealed that the measured waveform around the first peak is in fair agreement with the calculated one. Furthermore, we found that the magnetic field peak increases with increasing charge voltage, whose dependence can be predicted from our equivalent model. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(1): 17–24, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20194     

Enhancement of wave and acceleration of electron in plasma in the external field

This paper investigates the enhancement of Langmuir and ion-acoustic wave and the acceleration of the electron in collisionless plasma, in the presence of an external transverse field. Based on hydrodynamic equations, an equation formulizing the parametric instability was derived. Furthermore, the formula for ponderomotive force and the expression that describes the electron acceleration were obtained. The results show that Langmuir and ion-acoustic wave are enhanced and the charged particles can be accelerated by the coupling of wave-wave. In addition, it can be concluded that ponderomotive force, due to the coupling of the external field (pump) to the Langmuir wave (ion-acoustic wave), is the driving force to excite the parametric instability and comprises the high-and low-frequency components. __________ Translated from Chinese Journal of Radio Science, 2007, 22(1): 38–42 [译自: 电波科学学报]     

基于磁脉冲压缩的DBD高频双极性纳秒脉冲发生器的设计及其放电特性

作为高压高重复频率脉冲电压发生器的开关器件,磁开关的耐压、通流能力以及寿命远高于半导体开关,因而适用作为介质阻挡放电(DBD)激励电源的开关。为研究双极性高频下DBD等离子体放电特性,提出高频双极性磁脉冲压缩系统。首先,阐释通过全桥逆变电路、脉冲变压器和磁开关产生双极性脉冲的原理,并叙述该系统关键器件的设计;其次,利用PSpice仿真软件研究电路关键参数对输出波形的影响规律,测试电阻性负载电压波形,并与仿真结果进行对比分析。测试结果表明,通过双极性磁脉冲压缩系统,能够在负载两端输出的纳秒脉冲电压具有以下参数:幅值在5~13k V可调,上升沿100ns左右,重复频率可高至几千Hz。最后,针对高频双极性下的放电现象进行研究,结合DBD放电模型和放电图片探索高频双极性脉冲电压下放电特性与频率的关系,充实了高频放电理论研究。     

Generation of a large area thermal induction plasma by applying a 50 kHz magnetic field

Inductively coupled radio frequency plasmas are gradually becoming an important source of high-temperature and high-reactivity plasmas for processing new functional materials or for removal of unwanted substances. Spatially wider plasmas are required for higher rate, more uniform processing in the future. Although low MHz frequencies have been usually used for induction plasmas, an attempt to expand the high temperature plasma fields was made by superimposing lower frequency 50-kHz magnetic fields on the DC plasma discharge to obtain a small source plasma. Because the penetration depth in such a low frequency field is as long as a few hundred mm, a larger radius plasma can be expected. As a first step, we have investigated the operating conditions under which a stable low frequency plasma is generated, based on theoretical calculations that include the time dependent rate equations for heat transfer and fluid flow in conjunction with the Maxwell electro-magnetic equations. Results showed that the minimum necessary power for expanding a small DC plasma to a wider plasma 100 mm in diameter by applying a 50-kHz magnetic field, is about 130 kW at 0. 1-MPa pressure. This power level is recognized to be within the available range in existing high-power oscillator systems. Measurements were carried out of the time variation of the spectral emission from the plasma immediately after superimposing the 50-kHz magnetic field upon a small area plasma generated with DC power of 1.5 kW at a pressure of 0.01 MPa in Ar gas. At a low power level of about 60 kW, the small plasma starts to expand in the radial direction, and finally, converges to a new wider plasma with 100 mm diameter. FFT analysis of the oscillograph showed that during the transient state, a period fluctuation in light emission occurs at a few tens of Hz reflecting the thermal time constant of a few tens of ms, besides the power frequency of 41.7 kHz. The plasma temperature was estimated by using the spectroscopic line intensities from neutral Ar atoms, as between 8,000 and 11,000 K. A uniformly distributed temperature field was successfully produced by applying the 50-kHz magnetic field, as expected. © 1998 Scripta Technica, Electr Eng Jpn, 123 (4): 48–57, 1998     

均匀磁场强化磁性液体导热系数实验研究

将封有聚α-烯烃合成油基磁性液体的两玻璃管放置于磁场中,为消除磁场力、重力所引起的磁性液体自然对流的影响,消除端部效应,研制了磁性液体在均匀磁场中瞬态双热线导热系数的实验测量系统.实验测量了均匀磁场对不同体积浓度的磁性液体导热系数的影响.结果显示,均匀磁场显著强化磁性液体的导热系数,其导热系数随磁场强度的增加而近似线性...     

烟气脱硝的低温等离子体放电形式的述评

本文对各种低温等离子体放电形式脱除烟气中NOx的效应进行述评,指出这些低温等离子体处理烟气技术要能走向实际应用,首要课题是必须降低能耗,提高NOx脱除效率。     

胶囊内窥镜新型外磁场驱动系统模型与仿真

为了克服传统推进式和被动式内窥镜在医用检查时存在的不足,提出了一种由三个同轴圆线圈和两对平行鞍线圈组成的胶囊内窥镜新型外磁场驱动模型。胶囊内窥镜内部嵌入NdFeB永磁体,通过控制外部线圈的电流来驱动永磁体,带动内窥镜在体内运动。在实验过程中,运用ANSOFT电磁场仿真软件分别对三个同轴圆线圈和鞍线圈的磁场分布进行了分析,结果表明,该模块能够产生三维匀强磁场,符合驱动无线胶囊内窥镜在体内运动的要求,并且结构简单紧凑,可控性高,有利于提高检测效率。     

Oscillation wavelength shift characters of a semiconductor laser in a magnetic field: Observation by using a beat note

In papers published previously, we discussed the oscillation wavelength shift of a semiconductor laser in a magnetic field at room temperature. Observations were carried out by means of a monochromator that was able to measure the oscillation wavelength shift in a steady state only and that was subject to a certain degree of measurement error. In this work, we used the beat note between two semiconductor lasers as a means of observing the wavelength shift. This method reduces the overall measurement error to about one tenth that obtained when using the monochromator and enables us to observe the time dependence of the wavelength shift, after establishing a magnetic field. The observed wavelength shift was delayed in comparison with the square of the magnetic flux density, which is proportional to the wavelength shift in a steady state. The delay was about 0.07 s, which is much longer than we actually expected, when changing the temperature in an active layer. © 1998 Scripta Technica. Electr Eng Jpn, 122(3): 46–54, 1998     

Flow characteristics of a cold helium arc-jet plasma along open field lines

We experimentally study plasma parameters including ion acoustic Mach number of expanding cold helium plasma jet with an electron temperature of less than 1 eV flowing along open field lines. It is experimentally found that the ion Mach number increases from 1 to 3, and that the plasma potential decreases by about 1 V. We discuss the experimental results based on a quasi one-dimensional flow model in which the plasma is assumed to be quasi-neutral and in a state of thermodynamic equilibrium. Our model describes the ion acceleration, the axial profiles of the potential drop, and the electron temperature/density. The model also shows that the helium ions are accelerated both by the electric field and by the increasing cross-sectional area of the transonic flow. After the ion acceleration, the ion Mach number decreases and the electron temperature increases. These phenomena are discussed in terms of a shock wave. It is noted that the electron density decreases even in the shock wave. This is discussed in terms of rapid recombination because of the low electron temperature. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Characteristic measurement of discharge current injected by the air discharge of an ESD gun onto a ground

An immunity testing method for electrostatic discharge (ESD) is being specified in IEC 61000‐4‐2, in which the contact discharge of an ESD gun is being normally specified. Air discharge testing is known to be a severe immunity test compared to contact discharge testing, while the discharge current injected is not well reproduced. Grasping the behavior of the current injected by the air discharge would be helpful in establishing the worst‐case ESD immunity testing. We previously measured the discharge currents for air discharge testing onto the IEC‐recommended current transducer with a commercially available ESD gun, and showed that there exists a specific relationship of Ip·tr^ξ/V_c=constant (ξ=0.75), between rise time tr and current peak Ip. The current transducer, however, has a frequency‐dependent transfer impedance which should affect the measured current waveform. In this study, we investigated whether the above‐mentioned specific relationship can be obtained for air discharge of an ESD gun onto a ground that assumes a metal enclosure of electronic equipment under test. A method was presented for estimating the discharge current from simultaneously measured magnetic fields with two magnetic field probes regardless of the distance between the gun discharge‐point and the probe position. This method was validated for contact discharge of an ESD gun to an SMA connector. With this method, we estimated the discharge currents injected onto a ground for air discharge testing of an ESD gun with intentionally fast and slow approaches. As a result, we could confirm a specific relationship between rise time tr and current peak Ip of Ip·tr^ξ/V_c=constant with ξ=0.57 independent of charge voltages and gun approaches. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 158(4): 51– 59, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20454     

斜框型磁流体发电机中临界磁场的研究应用

磁流体发电是一种高效、低污染的发电技术,相对于其他发电方式,磁流体发电具有输出功率大、结构紧凑的优点,在短时、高功率电源领域运用有着不可替代的性能优势。认为斜框型磁流体发电机中的电流在一定磁场范围内会产生饱和,并就这一问题首次提出了临界磁场理论并推导出临界磁场的方程式。临界磁场的提出,是在研究磁流体发电机的通道性能问题上提出了新的思路,有利于超导磁体在磁流体发电机上应用问题的研究。     

Formation of a negative impulse discharge induced by an XeCl excimer laser in a long rod‐to‐rod electrode gap in air

Negative discharge induction experiments were performed with a rod‐to‐rod electrode configuration having a gap length of 0.8 m using a high‐power XeCl excimer laser of maximum output energy of 2 J/pulse and an impulse generator of maximum voltage of 1.2 MV. Development of a leader in the laser‐ionized plasma channel was observed by using an image converter camera. When an XeCl excimer laser is applied at a carefully controlled instant, the guiding effect for an impulse discharge is optimized. Three main results were obtained. First, the discharge started near the focal point and then developed bidirectionally toward the high‐voltage electrode and the grounded electrode. Midgap leaders were frequently observed. Second, it was observed that the lifetime of the laser‐ionized plasma channel was about 1 μs. Third, the discharge processes were classified into six stages. The mechanism of the streamer and leader propagation is discussed. © 2000 Scripta Technica, Electr Eng Jpn, 134(2): 11–18, 2001     

用于室温磁制冷机的高场强永磁磁路设计

把基于磁热效应的室温磁制冷技术应用到空调及家用冰箱上,除了开发出具有巨磁热效应的磁致冷材料(磁工质)外,高场强永磁磁路的设计与制造也是其关键。由于在空调及家用冰箱上采用结构复杂、价钱昂贵的超导磁体或电磁铁是不合适的,而传统永磁体回路的设计方法很难使永磁体产生较高的场强。本文在中空圆柱型磁场源(hollowcylindricalfluxsource)的基础上,设计出了用于室温磁制冷机(往复式和旋转式)的高场强永磁磁路,在磁路工作气隙为20mm时,工作气隙中心的场强分别为1 86T和1 97T。     

Inactivation property of microorganisms in water irradiated by atmospheric‐pressure plasma using dielectric barrier discharge

Microorganisms in water were inactivated by irradiating with an atmospheric‐pressure plasma generated by a dielectric barrier discharge. To understand the inactivation mechanism of microorganisms, the actions due to irradiation with plasma discharge, heating, and chemical reaction are studied. We compare the buffer gases helium and argon in generating the atmospheric‐pressure plasma. The results indicate that the inactivation with the helium as buffer gas is higher than with argon. It is found that the inactivation ratio at different reactor volumes depends on the density of microorganisms in water. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Portable application of thermal plasma and arc discharge for waste treatment,thermal spraying and surface treatment

Thermal plasma and arc discharge have numerous useful characteristics related to their high temperature and intense radiation. Many applications have been developed. Recently, a portable twin‐torch plasma arc furnace for waste treatment, thermal spraying torches, steam plasma torches, and surface treatment of low‐pressure arc was developed. This paper describes the recent development of a portable application of thermal plasma and arc discharge. The portable device can treat wastes and perform thermal spraying and surface treatments on site. This technology is expected to become more attractive. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Halbach阵列同心式磁力齿轮磁场全局解析法分析

针对Halbach阵列同心式磁力齿轮这种内外转子非接触传递的传动装置,运用全局解析法对磁力齿轮内外两层气隙磁场进行分析计算.求解场域划分为内外转子永磁体、内外两层气隙和调磁定子的槽形区域,各子区域的拉普拉斯方程和泊松方程通过边界连续条件建立联系.得到内外两层气隙区域的矢量磁位磁通密度解析表达式,并用计算了内外转子电磁转矩,将气隙磁场波形和内外转子电磁转矩波形分别与二维有限元法计算波形作比较,结果吻合,证明了方法的正确性和有效性.