Electronic excitation of the matrix during drift of excess electrons through solid xenon

It is shown experimentally that the exciton luminescence λ=172 nm) quantum yield excited by excess electrons drifting through solid xenon at 77 K in fields of 10 kV/cm amounts to 20±5 per electron and that luminescence takes place during the entire drift process. A CW bulky discharge through solid xenon (with a current up to 20 A/cm²) is realized, and intense visible luminescence due to excitation of impurities by electron impacts is observed. The prospects for using solid rare gases as matrices for studying processes in low-temperature plasmas and for creating effective electric energy converters in the vacuum ultraviolet range are discussed.     

Ultrahot electron formation under excess electron drift through solid Xe

The formation of "hot" (8 eV) electrons under excess electron drift in a moderate electrostatic field through solid xenon has been experimentally proved by observation of secondary electrons emitted from the photocathode. At T=77 K and U=1000 V one drifting electron produces about 20 (172 nm) photons, the efficiency of electric field-to-vacuum ultraviolet emission conversion is 15% tending to grow with temperature. A self-sustained electric discharge has been generated in solid Xe using a three-electrode cell with a zinc cathode.     

Photoemission from solid surfaces in intense laser fields

We present a Floquet analysis of photoemission of electrons from a solid surface due to its interaction with a laser beam. The method we use is based on a three-dimensional quasifree electron model. The model takes account of the changes in the effective mass of the electron inside and outside the solid and in the reflected and refracted beams due to the presence of the surface. It is shown that the photoemission of electrons from the solid surface may take place not only with no absorption of photons but also along with the emission of extra photons.     

Selection and design of the secondary electron channel of the time-of-flight mass spectrometer

Computer simulation is carried out for selecting a compact electron-optical system of the channel for detecting secondary electrons formed during the interaction of xenon atoms or ions with energy of 1-30 keV with Xe atoms. The solid angle of passage of secondary electron beams in a wide range of their initial energies is calculated. The energy spectrum of secondary electrons with various energies is determined by constructing their deceleration curve.     

An easy way to prepare pressurized glass inserts for MAS rotors

A novel technique to prepare pressurized glass insert samples for MAS rotors is described. In this technique, a small drop of epoxy is added to the tip of a piston and the gas is squeezed into the insert by pressing the piston. The amount of gas, i.e., pressure, in the sample can be controlled by the overall length of an insert test tube. As examples, (129)Xe NMR spectra taken from samples containing xenon gas, xenon gas and liquid crystal, and xenon gas, liquid crystal and porous solid, are shown. In principle, the method is feasible for making any kind of samples into glass inserts.     

电子束空间极限电流的非线性理论研究

从电子束一维稳态传输的电势非线性Poisson方程出发,推导了圆柱波导内实心束和环形束空间极限电流与电子入射电势的依赖关系,给出了数值求解方法和解的特征,分析比较了数值计算与现有解析公式及粒子模拟的结果.考虑电子的横向运动,对数值方法进行了二维修正,计算结果与粒子模拟结果具有很好的一致性.说明利用数值方法计算电子电势非线性微分方程能够得到更精确的电子束在圆柱波导内的空间极限电流;另外,对其他形状的波导,尤其是难以得到解析式的情况,根据实际几何结构设置边界条件,数值方法可以方便地给出束流传输特性,对设计新型结构的高功率微波器件提供理论指导. 关键词： 相对论电子束 圆柱波导 空间极限电流 束流传输     

An electronspectroscopic study of adsorbate structure

The ultraviolet photoelectron spectra of xenon adsorbed on crystals of (100) nickel and (110) iron have been measured as a function of xenon coverage. It is shown that the total current in the xenon peaks is a measure of the xenon coverage but that the attenuation of the electrons from the metal substrate is dependent on the packing density of xenon on the surface. Previous measurements by Auger electron spectroscopy are compared and it is shown that the mean free path of 16 eV electrons from the d-bands of nickel and iron is 2.75 times that of 60 eV Auger electrons. The data allows the calculation according to a slab model of a mean thickness of a xenon monolayer. This is interpreted as a measure of the packing density of xenon localized on metal lattices of varying dimensions. The UPS spectrum for xenon on (110) iron shows a marked broadening of the xenon peaks as compared to (100) nickel. This is interpreted as due to variation in relaxation energy over adsorbate states on the iron surface arising from xenon atoms in offsite positions.     

Emission characteristics and electron kinetic coefficients of the plasma of a transverse volume discharge initiated in a mixture of heavy inert gases with chlorine molecules

The results of studying the radiation due to argon, krypton, and xenon monochloride bands, as well as to the bands of chlorine molecules, from the plasma of a transverse Ar-Kr-Xe-Cl₂ volume discharge are reported. The working mixture of a pulse radiation source is optimized with regard to its pressure and elemental composition and parameters of an excitation system. By numerically solving the Boltzmann kinetic equation for the electron energy distribution function, the transport characteristics of plasma electrons and discharge power specific losses are found for different values of the reduced electric field strength. The plasma parameters are simulated for the quaternary mixture, which is most appropriate for a multiwave UV-VUV source. Qualitative analysis is conducted for the most important electron processes in the multicomponent plasma that govern the joint formation of argon, krypton, and xenon monochlorides in the transverse discharge.     

Waves in plasma formed by above-threshold ionization of gas atoms

In the regime of above-threshold ionization of gas atom in the field of laser radiation, plasma with photoelectron distribution consisting of peaks at discrete energy values is formed. It is shown that the number of longitudinal waves in such plasma coincides with the number of peaks in the distribution function. When peaks practically don't overlap, the dispersion law of each wave in the region of short waves is determined by electrons from the corresponding peak. In this case the phase and group velocities of the waves are close to the electron velocity, which corresponds to the peak maximum. It is possible to talk about such waves as an electronic sound, since the perturbations of the electron density mainly arise due to pressure perturbations. When the peaks are narrow, but having a finite width, the Cherenkov damping of waves is exponentially small. Numerical calculations the dispersion laws for of the two and four waves in photoionized xenon plasma, in which the electron distribution function consists of two or four narrow peaks are given.     

X-ray transitions from antiprotonic noble gases

The onset of antiprotonic X-ray transitions at high principal quantum numbers and the occurrence of electronic X-rays in antiprotonic argon, krypton, and xenon has been analyzed with the help of Multiconfiguration Dirac-Fock calculations. The shell-by-shell ionisation by Auger electron emission, characterised by appearance and disappearance of X-ray lines, is followed through the antiprotonic cascade by considering transition and binding energies of both the antiproton and the remaining electrons. Electronic lines could be attributed partly to specific states of the antiprotonic atom de-excitation.     

布里渊区角顶附近的费米面的计算

本文提出在布里渊区角顶近旁费米面的计算,考虑晶格周期场作用和电子间交换能作用费米面电子能级随费米面增加存在一个极小值。以铝金属为具体对象作了数值计算。     

新型反馈式轴向同轴虚阴极振荡器

提出一种利用低磁场导引环形电子束在同轴波导内轴向激励虚阴极振荡的新型虚阴极振荡器.利用反馈式结构,使虚阴极在由反馈环、阳极箔和同轴波导构成的高品质因子准谐振腔内形成.作用腔内环形电子束激励同轴波导TM₀₁模式,在相对低品质因子的同轴提取区转化为TEM主模输出.用25维KARAT粒子模拟软件研究得到束波功率转换效率12%,输出微波平均27 GW,中心频率38 GHz. 关键词： 环形电子束 轴向导引磁场 同轴波导 反馈环     

新型反馈式轴向同轴虚阴极振荡器

从电子束一维稳态传输的电势非线性Poisson方程出发,推导了圆柱波导内实心束和环形束空间极限电流与电子入射电势的依赖关系,给出了数值求解方法和解的特征,分析比较了数值计算与现有解析公式及粒子模拟的结果.考虑电子的横向运动,对数值方法进行了二维修正,计算结果与粒子模拟结果具有很好的一致性.说明利用数值方法计算电子电势非线性微分方程能够得到更精确的电子束在圆柱波导内的空间极限电流;另外,对其他形状的波导,尤其是难以得到解析式的情况,根据实际几何结构设置边界条件,数值方法可以方便地给出束流传输特性,对设计新型结构的高功率微波器件提供理论指导.     

脉冲氙灯放电过程分析与实验测定

脉冲氙灯是一种新型光源,利用量子理论以及气体放电理论分析了脉冲氙灯放电过程,设计了放电测试系统,实验测定了放电过程中的电压、电流和光脉冲信号。结果表明：在预电离阶段自由电子浓度较低,能量较低;气体放电阶段灯内形成电子崩,使得自由电子浓度的增大,放电电流迅速上升,电压下降;离子复合时释放出光子形成光脉冲,氙灯脉冲的光能量输出和光谱特性与复合电子能量、氙气复合能级相关,而当输入能量与氙灯的能耗不一致的时候,将导致充电电容反复充放电,而使电路产生振荡。对于分析脉冲氙灯放电过程,优化放电回路参数设计和脉冲氙灯的生产具有重要意义。     

Bremsstrahlung,Cerenkovstrahlung und Übergangsstrahlung in einer dünnen Schicht

We present a formula for the coherent emission of Bremsstrahlung, Cerenkov radiation and transition radiation of a single electron traversing a thin foil at an oblique angle of incidence and changing its velocity (direction or amount) inside the foil. As an example we consider the bombardment of silicon foils with 50 keV electrons. The statistical scattering of the electrons inside the foil is taken into account by means of a measured scattering pattern.     

On the mechanism of the runaway of electrons in a gas: The upper branch of the paschen curve

Basing on the simulation results, it is shown that the Townsend mechanism of electron multiplication in a gas at sufficiently large interelectrode distances is valid at least up to such large values of E/p at which relativistic electrons are generated. Correspondingly, the runaway electron producing in a gas is determined not by the local criteria accepted presently, but by the ratio of interelectrode distance and the characteristic electron multiplication length. It is shown that the critical discharge voltage U, at which the runaway electrons appear in a given gas, is a function of the product of the interelectrode distance by the gas pressure. This function (U-pd dependence) defines not only well-known Paschen curve but also an additional branch, which describes the absence of a self-sustained discharge at a high voltages sufficiently rapidly supplied across the electrodes. Critical discharge voltage dependence for helium and xenon are presented.     

An injector of xenon macroscopic pellets for quenching the fusion reaction in a tokamak

An injector for the formation of solid xenon pellets and their injection into the tokamak plasma is designed on the basis of a light-gas gun. Experimental results and calculations on production of xenon pellets with a diameter of 4 mm and a length of up to 25 mm directly inside of the barrel are presented.     

Magnetic-dipole vortex generation by propagation of ultraintense and ultrashort laser pulses in moderate-density plasmas

A magnetic-dipole vortex is generated in the behind of an ultraintense and ultrashort laser pulse in a near critical density plasma. The vortex is self-sustained by its magnetic field pressure which expels background electrons, and resulting sheath field accelerates electrons to drive high amplitude electric current inside the vortex. The electron energy spectra shows nonthermal distribution with relatively high energy. The vortex is stable for a long period since it is in the electromagnetic equilibrium, whose structure and characteristics are explained by a simple analytical model.     

Decay times of the intrinsic luminescence band (1750 Å) of solid Xe

Thin films of solid xenon have been excited by a pulsed electron beam with electron energies of 300 eV and pulse lengths down to 5 nsec at low current. For the main luminescence band of solid xenon (λ ≈ 1750 Å) two decay times have been observed. The short decay time (3 ± 1 nsec) is independent of temperature between 4 K and 30 K, whereas the long decay time decreases from 900 ± 50 nsec at 4 K to 150 ± 50 nsec at 30 K.     

A proposed ablation laser

A new type of eximer laser is proposed; it involves the simultaneous sublimation and excitation of a frozen film by means of a relativistic electron beam. Calculated beam requirements for noble gases are ～ 10 kA/cm² of 400 kV electrons for periods of 2 to 12 ns. Predicted advantages of this laser are high gain and the elimination of wavelength limiting optical windows. Preliminary experimental fluorescence spectra have been obtained from xenon films. The emission from the solid phase consists primarily of two 100 Å wide bands centered at 1690 Å and 1730 Å the fluorescence lifetimes are 4 ± 2 ns for both bands.