Untersuchung der Prozesse in der aktiven Zone der Hohlkatodenbogenentladung I. Die Energieverteilungsfunktion der Elektronen,die Anregungs- und Ionisationsgeschwindigkeit

In this paper the processes of excitation and ionization inside the cathode of a hollow cathode are discharge will be studied. The electron energy distribution function is calculated from the kinetic equation. For this we take into account the following processes: elastic and inelastic collisions of electrons with atoms, Coulomb interaction between emitted fast electrons and electrons of the plasma.     

Intensitätshysterese der Photoemission von Multialkalikathoden bei 77 °K

In a preceding paper it was reported on the photoemission of multialkali photocathodes with temperatures of about 77 °K, where nonlinearities, discontinuities and hystereses of the emission current were observed when the wave length and the intensity of the light was varied. In the following a detailed account is given on measurements of hystereses with alternating light intensities. Furtherly the absorption of the photocathodes was measured, while the emission current was at a discontinuity with a jump of the current by a factor of two and more. The absorption was independent of the jumps. From this and from a detailed discussion of the intensity hystereses it can be concluded an independence of the effect of: a) the primary interaction of the light with the cathode, b) the conduction mechanism of electrons through the cathode (for then otherwise a band gap of 7.05 eV should follow), c) the potentialstep at the cathode surface. Observed quantum yields of 100% are not due to electron multiplication by the initial energy of the excited photoelectrons but seem to indicate an exciton mechanism and/or field effect, the latter being quite different from the Malter effect. The intensity at which the upward jump occurs increases by a factor of ten when the cathode temperature rises by 0.36 °K. This temperature sensitivity is interesting in application as radiation detector.     

Zur Theorie der Rückstreuung

Electrons emitted from a cathode, are partially backscattered to the cathode surface by collisions with gas molecules. No equilibrium between electrons, gas and field is presumed for a theoretical treatment of this process, in contrary to the conception of Thomson [1]; instead of it the effect of single collisions is investigated assuming isotropy of scattering. The collision numbers, which may be calculated from successive integral transforms, are shown to form a monotone decreasing sequence. In the field-free case the collision numbers and the back diffusion rates for the first collisions may be explicitely stated; the convergence of this method is rather poor, however. A model for back diffusion in an electric field, whereby the effect of primary collisions only is considered, is completely treatable. The results depend on the angular and energy-distribution of the emitted electrons. A comparison with other formulas and with experimental results for back scattering shows a better agreement between the latter and our equations than in the case of the Thomson-Loeb relation. The consequences on the theory of cathode fall are briefly discussed.     

Emission of electrons from mim systems: Energy distributions

In this part of our study we measured energy distributionsN(E) andN(E _X ) of electrons emitted from sandwich cathodes, and their basic temperature (at 300, 200 and 80 K) and voltage dependences. From the distributionN(E) at 80 K we calculated the mean free path of electrons in cathode and the effective temperature of distribution. The anomalous emission (beginning at small leakage voltages) was observed and its energy distribution measured, too. From the graphs it can be seen that some electrons acquire energy 2–5 eV during their transition through the sandwich cathode.     

单晶LaB_6热阴极稳定性研究

介绍了用于１＋１／２射频腔中的ＬａＢ＿６热阴极电子枪的结构，通过分析电子枪阴极的热平衡关系和高温、强射频场条件下的阴极电流发射情况，给出了ＬａＢ＿６热阴极电子枪的热平衡和发射电流的关系曲线，并对阴极稳定性问题进行了仔细研究。     

Örtliche Relaxation der Elektronen-Energieverteilung in hohen elektrischen Feldern

The motion of electrons in high electric fields is of particular interest due to its special experimental phenomena and its problems in theoretical treatment. We examine the spatial relaxation of electron energy distributions theoretically and experimentally. In the theory we assume a negligible elastic energy loss and a simple model for the inelastic collisions. The distribution function can be separated in two factors depending either on the kinetic energyε or on the total energyX=g3+Φ (Φ: potential energy). In application to the energy relaxation we calculate the relaxation of a humped initial energy distribution to a smoothed equilibrium distribution. The corresponding experiment was performed in the positive column of an argon plasma at a pressure of 3.6 · 10^?3 Torr. We measured the electron energy distribution as a function of distance from the cathode with a Langmuir probe using the second derivative method. Good agreement was found between the experimental and theoretical distributions.     

Der Einfluß der Wärmeleitung zur Kathode im elektrischen Feldbogen

For various cathode metalsKesaev has measured the arc lifetime as a function of current. RecentlyKingdon, assuming the field emission theory could not explain these experiments, suggested that the secondary electron emission produced by positive ions through a diffusion-controlled neutralization process determines the cathode mechanism. In this paper another assumption is made, based on the field emission theory: the cathode needs a minimal energy-supply for evaporation in order to maintain a higher vapourpressure and ion density near the cathode. For the mercury cathode this assumption seems to be valid. The temperature of the cathode spot and the voltage drop in front of it, for Bi, Pb, Zn, Tl, Cd, In, Sn, Cu, is not yet exactly known. Therefore the validity of the assumption made, concerning these materials can only be proved qualitatively.     

Pulsed cathode heating method

A pulsed-mode heating method has been developed and tested for a 1-in.-diameter cathode which reduces the average filament power by over an order of magnitude. The method allows cyclic operation with a few seconds of peak cathode temperature, which allows many microsecond-duration electron pulses to be fired at the peak cathode temperature in each cycle. For a 2-in.-diameter 0.125-in.-thick LaB₆ cathode, the saving is just as great. A 1.68-mF capacitor at 6 kV can cycle the larger cathode from 494° to 1800°C and back in 120 s. The energy requirement is 30.2 kJ, which is an average power of 252 W. This is still a saving of over an order of magnitude from the case of steady heating. The same cathode thickness as in the 1-in. case is assumed in this prediction     

大面积环状LaB6阴极

 介绍了一种用于管状电子束发射的大面积LaB₆阴极电子源，其阴极发射面积为115 mm²，LaB₆发射体用钼作基底，在LaB₆与钼之间用耐高温的碳化物粘合剂填充以防止LaB₆与钼发生反应。采用电子束轰击的方式加热LaB₆发射体，当阴极温度为1 873 K时，加热功率为173 W，直流发射电流密度达到40 A/cm²。与用石墨加热LaB₆发射体相比，该电子源加热功率降低了66%。阴极在室温下反复暴露于大气后其发射性能稳定。     

深紫外激光光发射与热发射电子显微镜在热扩散阴极研究中的应用

对热扩散阴极表面微区发射状态进行原位观察和分析一直是热阴极研究的重要课题.本文着重介绍深紫外激光光发射电子/热发射电子显微镜的基本原理及其在热扩散阴极研究中的典型实例.系统配备了高温激活所用的加热装置,样品可被加热至1400℃.系统具有光发射电子、阴极热发射电子、光发射电子和阴极热发射电子联合三种电子成像模式.应用表明,对于热扩散阴极而言,深紫外激光光发射电子像适于呈现阴极表面的微观结构形貌;热发射电子像适于反映阴极表面的本征热电子发射及均匀性;光电子和热电子联合成像适于对阴极表面的有效发射点做出精确定位.     

Temperature Dependence of Retrograde Velocity of Vacuum Arcs in Magnetic Fields

Retrograde velocity of vacuum arcs in transverse magnetic fields is known to depend on, among other things, the magnetic induction, the arc current, the electrode spacing, the cathode material, and the cathode surface condition, and was also found to depend on the cathode temperature. Using the optical method, the retrograde velocity was measured as a function of the cathode temperature with copper, aluminum, and stainless steel as cathode materials. The optical measurement shows that by increasing the cathode temperature, the arc velocity decreases. It appears that with the increase in the cathode temperature, the decrease of the arc velocity is related to the increase of the cathode crater radius. The experimentally measured temperature dependence of the retrograde velocity of vacuum arcs can be explained by the ion jet model for retrograde motion of vacuum arcs [10]. The relative decrease of retrograde velocity as a function of the cathode temperature calculated according to this model agrees quantitatively with the reported measurements.     

Zur elektronischen Struktur ungeordneter eindimensionaler Systeme. II. Verlauf der Streuparameter als Funktion der Energie

Statements on the energy dependence of the three scattering parameters are made for general energy dependent and non-local potentials used in a preceding paper [1] in a one-dimensional model for the electronic structure of disordered systems. All results are also valid in the relativistic case. The possible types for the behaviour of the wave function within the gaps and the form of the scattering parameters for δ-potentials are discussed.     

Study of Intense Electron Beams Produced by High-Voltage Pulsed Glow Discharges

We report the generation of high-current-density (20 A/cm2) pulsed electron beams from high-voltage (48-100 kV) glow discharges using cathodes 7.5 cm in diameter. The pulse duration was determined by the energy of the pulse generator and varied between 0.2 ?s and several microseconds, depending on the discharge current. The largest electron beam current (900 A) was obtained with an oxidized aluminum cathode in a helium-oxygen atmosphere. An oxidized magnesium cathode produced similar results, and a molybdenum cathode operated at considerably lower currents. A small-diameter (<1 mm) well-collimated beam of energetic electrons of very high current density (>1 kA/cm2) was also observed to develop in the center of the discharge. Electrostatic probe measurements show that the negative glow plasma density and the electron beam current have a similar spatial distribution. Electron temperatures of 1-1.5 eV were measured at 7 cm from the cathode. The plasma density (8.5 · 1011 cm-3 at 450 A) was found to depend linearly on the discharge current. In discharges at high currents a denser and higher temperature plasma region was observed to develop at approximately 20 cm from the cathode. We have modeled the process of electron beam generation and predicted the energy distribution of the electron beam. More than 95 percent of the electron beam energy is calculated to be within 10 percent of that corresponding to the discharge voltage.     

微空心阴极放电时空特性

为了揭示微空心阴极放电的放电机理,利用流体模型研究了矩形微空心阴极放电的时间和空间分布特性。在氩气环境下计算得到了压强为1.3×10~4Pa时电流、电势、电场、电子和离子密度等随时间的发展变化。结果表明,整个放电过程分为四个阶段,即预放电阶段、电场由轴向向径向转换阶段、电流缓慢增长向空心阴极效应过渡阶段和稳态放电阶段。稳态放电时出现明显的空心阴极效应,阴极位降区存在很高的径向电场和较高的电子平均能量,而负辉区径向电场很弱,电子平均能量较低,电子和离子密度峰值出现在负辉区,二者数值基本相等,而在阴极位降区离子密度远高于电子密度。     

碳纤维阴极对输出脉宽及能量的影响

 在反射三极管实验平台上，通过浸渍碘化铯(CsI)碳纤维阴极与不锈钢阴极实验对比，研究了碳纤维阴极对虚阴极振荡器输出微波脉宽及能量的影响。实验得出碳纤维阴极虚阴极振荡器输出微波脉宽约200 ns，较不锈钢阴极虚阴极振荡器增加了30%；对输出微波脉宽面积近似积分，得出碳纤维阴极虚阴极振荡器与不锈钢阴极虚阴极振荡器的输出微波脉宽面积比值约为2.273，表明碳纤维阴极虚阴极振荡器输出微波能量是不锈钢阴极虚阴极振荡器的2倍左右。分析认为碳纤维阴极的材料特性及其综合发射机制导致阴阳极间等离子体膨胀速度及温度降低，延缓了阴阳极间隙的闭合，从而增加了输出微波脉宽，提高了微波输出能量。     

Mass analysis of fast ions from a glow discharge in a binary mixture

The ratios of the various ions do not correspond to those of the neutral species or to the ratios of the ionic components in the negative column [1]. The results indicate that charge transfer in the cathode dark space causes altered energy distribution and a mass spectrum for the fast ions passing to the cathode from the negative column.I am indebted to Dr. A. V. Bondarenko for direction in this work.     

Messungen von Anregungstemperaturen in der Hochstromhohlkathode

Measurements of excitation temperatures in the negative glow light of a high-current hollow cathode discharge lamp with a gas temperature of about 1,500 °K have shown values forT _a of approximately 5,000 °K, when the atomic spectral lines are used as indicator. However, from ionic lines a temperature of 30,000–100,000 °K is deduced depending on the nature of the discharge gas. This big difference indicates that there is no Maxwell distribution in the hollow cathode discharge. A possible explanation could be that two energetically distinct types of electrons take part in ionisation and recombination respectively.     

大直径钪酸盐阴极发射特性

 为获得kA级热发射电子束,研制了直径为100 mm钪酸盐热阴极组件,并建立了适应大面积热阴极实验环境的2 MV 注入器试验平台。实验在二极管真空3.7×10^-5 Pa、二极管电压1.95 MV、脉宽120 ns（FWHM）、阴极温度1 120 ℃时,获得最大收集电流1 038 A,发射电流密度约13 A/cm²。实验结果表明,工作状态下阴极发射能力与激活温度、系统真空度关系密切。     

A lithium ion battery using nanostructured Sn-C anode, LiFePO4 cathode and polyethylene oxide-based electrolyte

In this work we report a lithium ion battery based on a nanostructured Sn-C anode, an improved lithium iron phosphate, LiFePO₄, cathode and a polyethylene oxide-based electrolyte. The battery has a solid-like configuration, high safety and can operate at room temperature with a stable capacity of the order of 120 mAh g^− 1 at a voltage of 2.8 V. These properties candidate the battery as very appealing energy accumulation system suitable for environmentally friendly, safe, applications.     

轰击阴极的重粒子能量分布

采用蒙特卡罗模拟对氮辉光放电等离子体中轰击极阴的重粒子（N2^ ,N^ ,Nf及N2f）能量分布随放电参数的变化规律进行了研究。结果表明：阴极臂前诸粒子的能量分布取决于粒子被加速的能量和碰撞频率,能量较低的快原子Nf的密度比高能粒子N^ 的密度最近两个量级。在活性氮粒子（N^ ,Nf）产率最高的放电条件下,适当降低放电气压,提高阴极位降和气体温度,有利于两种活性氮粒子（N^ ,Nf）达到阴极。