Transition of Discharge Mode of a Local Hollow Cathode Discharge

The discharge characteristics of hollow cathode discharge in argon in a cylindrical cavity are investigated experi- mentally. The voltage-current （V - I） characteristics and the light emission are measured. It is found that the discharge plasma is localized inside the hollow cavity, with an extensive Faraday dark space between the cathode and the anode. The discharge develops from predischarge to abnormal glow discharge, the hollow cathode effect （HCE） and a hybrid mode as the discharge current increases. The onset of the HCE is found for the first time by the transition from abnormal glow discharge together with a significant decrease in the slope of the V - I curve which shows a positive differential resistivity. The voltage increases proportionally with the current when the HCE is reached.     

Experimental data on the initiation of a pseudospark discharge

In connection with the development of a pseudospark switch for copper vapor lasers, several long endurance tests at repetition rates between 50 Hz and 7 kHz have been performed during the past years. These tests give some clues to the basic phenomena that are involved in the current build-up of a pseudospark discharge, especially as concerns the interaction of gas and surface effects. According to these results, current flow is initiated by a glow discharge in such a way that the positive column penetrates into the hollow cathode; forming a virtual anode. When the current reaches a threshold value <100 A, the electric field produced in the cathode fall of the glow discharge is sufficient for the formation of cathode spots in the cathode backspace. The spots act as electron emitters and carry the discharge current up to approximately 1 kA, where large area emission processes at the front side of the cathode might become important     

Breakdown formation in a transient hollow cathode discharge-astatistical study

Discharge formation at low pressure is found to be greatly influenced in the presence of a suitable hollow cathode region. The formation of a moving virtual anode which extends the anode potential to within the hollow cathode region is thought to be responsible for the enhanced ionization growth which subsequently leads to gas breakdown. In this paper, the spatial evolution of the local potential in the discharge region of a pulsed hollow cathode discharge has been measured in a range of pressures with two different cathode apertures. An extensive data set has been collected and analyzed using a statistical technique. From the characteristic of the statistical distribution of the data, unique features associated with the role of hollow cathode at the different stages of discharge formation have been identified. It was found that the influence of the hollow cathode region is strongest in the start of ionization growth and in the final change over to high current breakdown     

Operational characteristics of a plasma cathode with a grid stabilization in a two-stage ion source

The discharge characteristics and the parameters of the cathode plasma in a two-stage ion source with a grid plasma cathode and a magnetic trap in the anode region are investigated. It is shown that an increase in the gas pressure and the accompanying increase in the reverse ion current in the bipolar diode between the cathode and anode plasmas lead to an increase in the cathode plasma potential and a transition of the cathode into the regime of electron emission from the open plasma boundary. The dependence of the ion current extracted from the anode plasma on the area of the exit aperture of the hollow cathode and the mesh size of the grid plasma cathode is explained. The conditions at which the ion emission current from the anode plasma is maximum are determined. The potential difference at the bipolar diode is measured by using the probe method. It is shown that, when the gas pressures reaches a critical value determined by the mesh size of the grid plasma cathode, the discharge passes into a contracted operating mode, in which the ion current extracted from the anode plasma decreases severalfold.     

A Modified Version of the Grimm's Glow Discharge Lamp for Use as a Demountable Hollow Cathode Emission Source. II. The Current Intensity-Voltage Characteristic Curves

The dependence of resulting voltage on applied current intensity in a modified commercially available hollow cathode lamp is determined in the case of aluminium, copper and graphite cathodic materials in an extended range of argon carrier gas pressures and for five different cathode - anode distances. Experimental results show that the modified emission source affords high stability discharge in a wide range of experimental parameters.     

赝火花开关放电的蒙特卡罗粒子模拟

采用粒子模拟和蒙特卡罗相结合的方法,应用静电求解模型,对赝火花开关初始放电过程进行了模拟。赝火花开关初始放电过程主要由汤森放电过程、等离子体形成、空心阴极效应和场致发射引发主放电组成;等离子体形成和空心阴极效应对赝火花开关的发展导通具有至关重要的作用。改变赝火花开关工作参数,如气压、电极孔径、阳极电压和阴极腔中初始粒子密度,研究其对赝火花开关电子峰值电流形成时间的影响。结果表明:随着气压、电极孔径、阳极电压和初始粒子密度的增大,赝火花开关电子峰值电流形成时间减小。     

Measurements on electron beams in pulsed hollow-cathode discharges

Two different regimes of electron beams have been reported in the pulsed hollow cathode discharge-a low-current, high-energy beam, and a relatively high-current beam of low energy. The high-energy beam is related to the hollow cathode geometry and is found to be present even in the absence of subsequent gas breakdown, while the low-energy beam is always associated with voltage breakdown. Detailed measurements of the spatial and temporal distribution of the electron beam transported beyond a semitransparent anode associated with gas breakdown are reported. In particular, a high-energy component is observed after electrical breakdown. Low-energy electron beams are observed to be transported beyond the anode throughout the main discharge period     

Time evolution of hollow cathode ionization processes in the finalbreakdown phase of a transient hollow cathode discharge

The enhanced ionization processes taking place inside the hollow cathode region (HCR) of a transient hollow cathode discharge (THCD) are essential events which lead to final electrical breakdown. This ionization growth is permanently assisted by a virtual anode moving in the anode-cathode gap (A-K gap), which extends the anode potential to within the hollow cathode region. In the paper, the ionization growth inside the HCR under the enhanced field due to the close proximity of the anode potential has been studied using a statistical technique in a range of pressures, with three different cathode apertures. Statistical time distributions of an extensive experimental data set are analyzed to understand the mechanisms involved in the final stages, just before electric breakdown     

Plasma nitriding of low alloy steels at floating and cathodic potentials

The low alloy steels were nitrided in the plasma atmosphere generated by using hollow cathode discharge. For comparison, specimens of 40 Cr steel were in two different potential states. One kind is isolated from cathode and anode between them the discharge was created. The other kind is placed on the plate which is connected to the cathode. The nitriding was carried out at different temperatures. The surface morphology, phase of compound layers and microhardness profiles were analyzed. The optical microscopy observation and X-ray diffraction showed that the compound layers were formed in all experiments. The results of the nitriding treatment are weakly dependent on the potentials applied on the specimens.     

氮气中空心阴极放电条纹的发光特性

利用发射光谱法,在氮气环境下研究了圆柱型空心阴极放电条纹的特性。测量得到了气压为20 Pa,放电电流为1.3 mA时条纹区的发射光谱,结果表明发射光谱主要为氮分子的第一正带系(B3П_g →A3П_u)和 第二正带系(C3П_u→B3П_g )。利用双原子光谱发射理论,计算得到了氮分子振动温度的空间分布特性。结果表明光谱线强度呈周期性分布,明纹中心处的谱线强度高于暗纹中心处的谱线强度。明纹中心处的N₂分子振动温度为3 500～4 400 K,并且从阴极到阳极,明纹中心处光谱线强度和分子振动温度逐渐下降。同时测量得到了放电电流为1.0和1.5 mA时的发光条纹特性,研究了放电电流对条纹特性的影响。随着放电电流的增加,明纹中心处的分子振动温度升高,条纹间距增加。另外,利用测量得到的发光条纹,计算得到了条纹区的平均约化电场强度为44～49 m-1·Pa-1,并且由阴极向阳极逐渐降低。对于揭示气体放电中发光条纹的形成机理和促进空心阴极放电的稳定性有重要的参考价值。     

赝火花开关放电的蒙特卡罗粒子模拟

采用粒子模拟和蒙特卡罗相结合的方法,应用静电求解模型,对赝火花开关初始放电过程进行了模拟。赝火花开关初始放电过程主要由汤森放电过程、等离子体形成、空心阴极效应和场致发射引发主放电组成;等离子体形成和空心阴极效应对赝火花开关的发展导通具有至关重要的作用。改变赝火花开关工作参数,如气压、电极孔径、阳极电压和阴极腔中初始粒子密度,研究其对赝火花开关电子峰值电流形成时间的影响。结果表明：随着气压、电极孔径、阳极电压和初始粒子密度的增大,赝火花开关电子峰值电流形成时间减小。     

Observations of vacuum spark dynamics from its X-ray emission

The behavior of a medium energy (~1 kJ) pulse-power-driven vacuum spark is shown to depend on the electrode material and form of the anode in otherwise similar conditions of operation. The dynamical evolution of the discharge is followed from its soft X-ray emission. The electrode materials compared are titanium and aluminum with a form of anode that is tubular or conical. The use of a tubular anode favors a more uniform sheath and a better formation of a dense Z-pinch and the ensuing hot spots are found to be at least twice as bright. The position of the brightest spots differs according to the material and the electrode shape, and is found to coincide with the shape of the sheath. The energy output is measured and the density of the plasma in the hot spots may be calculated     

Density Distribution of Plasma Species in a Hollow Cathode Arc Discharge for Coating Application

The plasma of a hollow cathode arc discharge (argon/titanium) was studied by emission spectro-scopy and probe measurements. The behavior of the relative particle concentrations of the different heavy plasma components as well as the concentration and temperature of the electrons was determined as function of the vertical distance from the anode crucible. Abel-inverted radial distributions of the relative level populations for TiI (neutral titanium), TiII (singly ionized titanium), Ar I and ArII are presented. Further measurements characterize the influence of the discharge current on the relative level population.     

空心阴极放电条纹特性的光谱诊断

利用发射光谱法,研究了圆柱型空心阴极放电条纹的特性.测量了条纹区的发射光谱,在此基础E计算得到r电子激发温度、相对电子密度和电子平均能量的空间分布特性.结果表明条纹区的光强、电子激发温度和电子密度均呈非等幅的周期性变化.与暗纹中心处相比,明纹中心具有较高的电子激发温度和较低的电子密度.由阴极向阳极,明纹中心处的电子激发温度幅值逐渐减小.此外,条纹区的电子激发温度随着电流的增加而增加.     

空气中空心阴极不同放电模式下的发光特性

为了进一步揭示空心阴极放电中放电模式的转换机制,特别是空心阴极放电过程中自脉冲的形成机理,利用柱型空心阴极放电结构,在空气环境下研究了放电处于不同模式时的发光特性。测量得到了不同放电模式下的伏安特性曲线、放电发光图像、自脉冲阶段的脉冲波形等。实验结果表明随着放电电流的增加放电分为汤生放电模式、自脉冲放电模式、正常辉光放电模式和反常辉光放电模式。虽然所用电源为直流电源,但在自脉冲放电阶段电流和电压随时间呈周期性变化。实验结果表明在不同的放电模式下具有不同的发光特性。在由汤生放电转换为自脉冲放电模式和由自脉冲模式转换为正常辉光放电模式过程中,放电腔的径向中心处和轴向孔口附近均存在光强的突变。实验同时在200～700 nm范围内测量得到了不同电流时的发射光谱。结果表明发射光谱主要集中在330～450 nm,主要包括氮分子的第二正带系(C3Π_u→B3Π_g )和氮分子离子的第一负带系（B2Σ+_u→X2Σ+_g）。其中氮分子离子第一负带系具有较强的发射光谱。由于B2Σ+_u激发电位较高,因此该谱带较强发射光谱的存在表明空心阴极放电较其他放电形式更容易获得高激发态粒子和高能量电子。在650～700 nm附近存在一弱的发光谱带,主要为氮分子的第一正带发射谱（B3Π_g→A3Σ+_u）。在此基础上根据双原子光谱发射理论,结合氮分子第二正带系的三组顺序组带：Δν=-1,-2和-3,利用玻尔兹曼斜率法计算得到了不同放电模式下氮气的分子振动温度。结果表明在实验电流范围内分子振动温度在3 300 K左右,随着电流的增加而升高,并且在自脉冲消失时存在一突变迅速增强。由于电子能量、电子密度与分子振动温度密切相关,因此该结果也表明随着放电电流的增加电子平均能量和电子密度不断增加,当脉冲消失时,电子平均能量和电子密度出现跃变升高。最后,对空心阴极放电中自脉冲的形成机理进行了讨论,结果表明自脉冲放电源于放电模式的转换。     

电极构形对形成大面积放电均匀性影响

设计并制作了空心阴极、钮扣阴极、针阴极和条形阴极,利用CCD照相,在5cm×5cm口径范围内,分别对四种阴极放电的空间均匀性进行了研究。实验表明,在预电离电压800V,主放电电压3kV和气体气压约30Pa的条件下,利用空心阴极放电,能够获得空间较为均匀的放电等离子体。放电等离子体可以用作普克尔盒电光开关的等离子体电极。     

空气介质阻挡放电单个微放电通道发光强度及振动激发温度的空间分布

通过清洗放电方法,在平行平板介质阻挡空气放电中得到了单个稳定的微放电通道（又称放电丝）.测量了从瞬时阳极到瞬时阴极单个放电丝的发光强度及振动激发温度的空间分布.研究表明：在外加电压的每半周中放电丝发光呈现杯型分布,杯底位于瞬时阴极处;振动温度在两平行板间隙的中心处最高而在瞬时阳极处最低. 关键词： 介质阻挡放电 微放电通道 振动温度     

Accelerating voltage and electron temperature in a FXR discharge

X-ray quantum energies as well as electron temperatures in different parts of the discharge column in a flash X-ray (FXR) discharge have been estimated. It is found that the energy of the X-radiation is about 16 keV very near the cathode surface and about 30 keV at the anode during the first pinching of the discharge column (Initial voltage 20 kV). The electron temperature in the column is found to be 2 to 2.5 keV during the pinch interval, thereafter it rapidly decreases. A dark space is localized to a region just outside the anode surface. This dark region follows the anode when the inter-electrode spacing is varied.     

电极构形对形成大面积放电均匀性影响

 设计并制作了空心阴极、钮扣阴极、针阴极和条形阴极，利用CCD照相，在5cm×5cm口径范围内，分别对四种阴极放电的空间均匀性进行了研究。实验表明，在预电离电压800V，主放电电压3kV和气体气压约30Pa的条件下，利用空心阴极放电，能够获得空间较为均匀的放电等离子体。放电等离子体可以用作普克尔盒电光开关的等离子体电极。     

High current density spotless vacuum arc as a glow discharge

Vacuum discharge burning between a broad cathode and a point anode made of Mo, Cu, and Cd has been studied. This discharge operates in anode vapors and shows major arc characteristics, although no craters were examined on the cathode. The secondary electron emission is involved to explain current transport within the cathode region. This discharge is interpreted as a high density low voltage glow discharge. Having discussed the present and previous findings, the conclusion has been drawn that the secondary electron emission and “hump of potential” are dominant in the vacuum arc cathode spot