共查询到20条相似文献,搜索用时 15 毫秒
1.
S. V. Bordusov 《Journal of Applied Spectroscopy》2002,69(1):126-129
Using the method of optical emission spectroscopy, the dynamics of the development and extinction of a pulsating SHF discharge, its time instability, and the ranges of stable pressurerelated operation of a resonatortype SHF plasmatron on the basis of an annular waveguideslit applicator were investigated. It is found that at the pressures of CF4 and its mixtures with oxygen optimal for breakdown a virtually complete lack of reproducibility of the signals of the components of the emission spectrum (in particular, of the FI 703.7nm line) from pulse to pulse of the discharge has been established. A discharge in oxygen in the investigated range of pressures and powers is characterized by a good repetition of the form of the pulses of the emission spectrum line (considered in relation to the OI 844.6nm line). 相似文献
2.
真空弧离子源在真空镀膜、材料表面改性、真空大电流开关、加速器离子注入等领域有广泛应用,目前国内外对真空弧放电等离子体的研究主要针对纯金属或合金电极,对含氢电极的研究和公开报道较少.本文利用高时空分辨的四分幅图像诊断系统,结合氢和钛原子特征线单色器件,研究了含氢钛电极的真空弧微秒级脉冲放电等离子体的轴向和径向时空分布特性.研究表明:在真空击穿阶段,阳极区域发光更为明显,阳极电极解吸附释放的氢原子是引发击穿的主要放电介质;在真空弧阶段,阴极-绝缘-真空三结合点处产生圆锥状阴极斑,喷射出大量的等离子体以维持弧放电,同时电极内壁非阴极斑区域也有少量等离子体产生,等离子体中H原子的轴向和径向空间分布均比Ti原子均匀. 相似文献
3.
大功率多磁极会切场离子源的弧放电特性分析 总被引:1,自引:0,他引:1
为了在HL-2A上实现3MW的中性束注入, 我院自主研制了直径为260mm, 高度为240mm的大功率多磁极会切场离子源. 目前, 它的性能已达到并超过了最初设计指标, 放电脉冲为1s时, 最大离子流密度为0.44A/cm2; 放电脉冲为3s时, 等离子体离子流密度0.24A/cm2; 等离子体非均匀性都在5%—7%范围之内. 目前, 它是我国国内等离子体密度最高, 放电功率最大的长脉冲桶式离子源. 本文通过实验数据与理论相结合的方式对弧放电特性进行分析. 相似文献
4.
Although plasma torches have been commercially available for about 50 years, areas such as plasma gun design, process efficiency,
reproducibility, plasma stability, torch lives etc. have remained mostly unattended. Recent torch developments have been focusing
on the basic understanding of the plasma column and its dynamics inside the plasma torch, the interaction of plasma jet and
the powders, the interaction of the plasma jet with surroundings and the impingement of the jet on the substrate. Two of the
major causes of erratic and poor performance of a variety of thermal plasma processes are currently identified as the fluctuations
arising out of the arc root movement on the electrodes inside the plasma torch and the fluid dynamic instabilities arising
out of entrainment of the air into the plasma jet. This paper reviews the current state of understanding of these fluctuations
as well as the dynamics of arc root movement in plasma torches. The work done at the author’s laboratory on studying the fluctuations
in arc voltage, arc current, acoustic emissions and optical emissions are also presented. These fluctuations are observed
to be chaotic and interrelated. Real time monitoring and controlling the arc instabilities through chaos characterization
parameters can greatly contribute to the understanding of electrode erosion as well as improvement of plasma torch lifetime. 相似文献
5.
阿贝尔逆变换数据处理算法在电弧诊断中的应用 总被引:1,自引:0,他引:1
提出了一种由等离子体辐射投影值重建发射系数的阿贝尔逆变换数据处理算法。采用计算简单、变换精度高的Bockasten插值方法实现阿贝尔逆变换积分方程的离散化。在阿贝尔逆变换前,运用傅里叶变换频域低通滤波去除实验数据中的噪声,通过多项式插值弥补数据采样率过低、提高空间分辨力,并对投影数据进行对称化处理以消除数据偏离对称对结果的影响。运用此算法对实验数据进行处理,得到电流200 A、弧长5 mm电弧温度在阴极下方0.5 mm处最高,超过22000 K,与文献中结果一致。该算法能够有效地克服噪声对变换结果的影响,运算速度快、计算精度高、稳定性好,处理大量数据时具有明显的优势。 相似文献
6.
气体火花开关是脉冲功率装置中最常用的关键器件。电极烧蚀作为脉冲功率开关中的难点问题,会引起开关自击穿电压降低、触发抖动增大及开关寿命降低,已成为制约气体开关发展和应用的一个瓶颈。本文回顾梳理了国内外学者针对电极烧蚀问题进行的一系列研究,从电极烧蚀理论和实验研究成果两个方面,介绍了电极烧蚀的基本机制及仿真模型,归纳了影响开关电极烧蚀的因素以及电极耐烧蚀材料的研究进展,最后讨论了电极烧蚀研究面临的问题以及优化电极材料抗烧蚀性能的方向。
相似文献7.
采用Mo,WCu和W分别作为三种气体火花开关的主电极材料,进行放电条件下电极烧蚀实验,研究开关电极烧蚀率和烧蚀形貌,分析电极烧蚀特征。结果表明,Mo,WCu和W开关的主电极烧蚀率分别为3.32×10-2 C-1·m-2,2.63×10-2 C-1·m-2和1.74×10-2 C-1·m-2,W开关主电极烧蚀率最小。实验后开关的主电极中心烧蚀严重,呈现明显裂纹和烧蚀坑。Mo主电极表面呈现明显熔融态,阴极表面形成大量裂纹(宽度达10μm)和孔隙(孔径达10μm);WCu和W主电极表面形成少量圆球状W突起(粒径达20μm及以上)。开关外壳内壁沉积了喷溅颗粒。WCu开关外壳沉积颗粒较大(粒径达10μm),Mo开关外壳沉积颗粒居中(粒径为2μm),W开关外壳沉积颗粒最小(近1μm)。因此可优先选用具有优异抗烧蚀性能的W作为气体火花开关电极材料。 相似文献
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9.
We study both theoretically and experimentally the possibilities of detecting malignant tumor inside a human body using near-field microwave probing. Our theoretical analysis is based on the developed theory of near-field diagnostics of plane-layered media. We verified this theory experimentally under controlled conditions of water-medium probing. Model calculations of recorded tumor contrast as a function of the size and depth of the tumor are performed. Two-dimensional images of an object imitating the tumor are obtained for different depths of object immersion in water. 相似文献
10.
《等离子体物理论文集》2017,57(9):395-403
An arc plasma can present various forms under the influence of an external magnetic field. In this study, a magnetically rotating arc plasma generator has been developed to produce three arc modes, namely rigid arc, distorted arc, and diffuse arc, which are obtained by controlling the gas flow rate. The evolution of these arc modes are experimentally studied and discussed. Results show that, as the gas flow rate increases, the arc mode is first transformed from the rigid to the distorted mode, and then to the diffuse mode. Comparisons show that the location of the arc attachment is a key factor in determining the rigid and distorted modes. The diffuse arc is observed under larger gas flow rates, but the completely diffuse arc can exist only within a narrow range of gas flow rates. Compared to the distorted arc, the diffuse arc has not only better stability but also a wider high‐temperature plasma zone, which indicates that the diffuse mode may be more useful in industry. 相似文献
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12.
Study on 3-D arc plasma fields with holographic interferometry 总被引:2,自引:0,他引:2
In this paper,serveral temperature(refractive index)fields which are de-scribed by different kinds of functions are reconstructed by computer simulations based onholographic tomography theory.The obtained results are compared and analyzed.We de-signed a special multibeam holographic system in which the disturbance from the intense arclight can be filtered.With the system multidirectional holographic interferograms of arc fieldscan be taken simultaneously.We also calculate the quantitative distributions of temperature,the number density of particles and ionicity at a typical section of the argon arc field from theexperimeantal data. 相似文献
13.
Numerical modelling of a direct current non-transferred thermal plasma torch for optimal performance
A laminar steady-state 2D axisymmetric model of a direct current (DC) thermal plasma torch using a magneto-hydrodynamic approach has been developed. The model takes into account the entire torch system comprising the plasma gas injection, the inner region of the torch, and the jet exiting into the ambient environment. Numerical results are obtained for two different power inputs chosen from published experimental data. The temperature predictions at the torch exit are found in good agreement with experimental results. Velocity analysis of the plasma jet has been presented and the impact of electromagnetic force on jet velocity is analysed. The Lorentz force arising due to the coupling of fluid motion and electromagnetic forces shoots up the jet velocity to significantly high values near the cathode tip. Temperature and velocity profiles are in good agreement with the characteristics of a long laminar plasma jet. An operating value of heat transfer coefficient (h) has been suggested for optimal torch operation, thus ensuring a low anode erosion rate and acceptable thermal efficiency. The argon torch has the maximum temperature and longest jet length among the plasma gases considered. 相似文献
14.
In this paper a theoretical study is initiated to observe the utility of directional spectral estimation techniques for ‘arc array’ geometries. We examine the suitability of a 15 ° arc transducer geometry for multibeam bathymetric applications. This geometry is tested using the Bartlett method for varying arc and linear arrays of 30-elements. We also examine ‘high resolution techniques’ such as the Maximum Likelihood (ML) method and the Maximum Entropy (ME) methods (different orders), for 16-element arrays of 15 ° arc. The superiority of the high resolution methods is seen by examining the beam patterns of the 15 ° arc array under multiple source/interference conditions, i.e. the situation for rough terrain or artefactcreating conditions. Furthermore, the 15 ° arc array geometry is found to be useful for multifrequency applications at different operating wavelengths, which is useful for underwater bathymetric applications. 相似文献
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16.
A cathodic arc plasma source equipped with a curved magnetic duct to filter macro-particles was used to study plasma diffusion and transport in the duct. We determine the optimal duct bias, at which the magnetic duct produces the maximum plasma output, for titanium cathodic arc plasma at 50, 100 and 150 A arc current, and we investigate the parametric effects of the arc current and guiding magnetic field on the optimal duct bias. The optimal bias decreases as the guiding magnetic field increases from 0.01 to 0.04T and is almost independent of the guiding magnetic field when the magnetic field strength ranges from 0.04 to 0.06T, the upper limit for our equipment. The optimal duct bias at 0.04T guiding magnetic field decreases with increasing arc current. 相似文献
17.
《等离子体物理论文集》2017,57(2):58-66
Plasma jets from conventional non‐transferred arc plasma devices are usually operated in turbulent flows at atmospheric pressure. In this paper, a novel non‐transferred arc plasma device with multiple cathodes is introduced to produce long, laminar plasma jets at atmospheric pressure. A pure helium atmosphere is used to produce a laminar plasma jet with a maximum length of >60 cm. The influence of gas components, arc currents, anode nozzle diameter, and gas flow rate on the jet characteristics is experimentally studied. The results reveal that the length of the plasma jet increases with increasing helium content and arc current but decreases with increasing nozzle diameter. As the gas flow rate increases, the length of the plasma jet initially increases and then decreases. Accordingly, the plasma jet is transformed from a laminar state to a transitional state and finally to a turbulent state. Furthermore, the anode arc root behaviours corresponding to different plasma jet flows are studied. In conclusion, the multiple stationary arc roots that exist on the anode just inside the nozzle entrance are favourable for the generation of a laminar plasma jet in this device. 相似文献
18.
采用Mo,WCu和W分别作为三种气体火花开关的主电极材料,进行放电条件下电极烧蚀实验,研究开关电极烧蚀率和烧蚀形貌,分析电极烧蚀特征。结果表明,Mo,WCu和W开关的主电极烧蚀率分别为3.3210-2 C-1m-2, 2.6310-2 C-1m-2和1.710-2 C-1m-2,W开关主电极烧蚀率最小。实验后开关的主电极中心烧蚀严重,呈现明显裂纹和烧蚀坑。Mo主电极表面呈现明显熔融态,阴极表面形成大量裂纹(宽度达10 m)和孔隙(孔径达10 m);WCu和W主电极表面形成少量圆球状W突起(粒径达20 m及以上)。开关外壳内壁沉积了喷溅颗粒。WCu开关外壳沉积颗粒较大(粒径达10 m),Mo开关外壳沉积颗粒居中(粒径为2 m),W开关外壳沉积颗粒最小(近1 m)。因此可优先选用具有优异抗烧蚀性能的W作为气体火花开关电极材料。 相似文献
19.