Diffraction of an electromagnetic wave from an infinitely long slit in an infinite metallic sheet

The diffraction of anE-polarized and anH-polarized wave by an imperfectly conducting slit (on which impedance boundary conditions are imposed) in an infinite metallic plane is investigated. The two independent problems are solved by using integral transforms, the Wiener-Hopf technique and asymptotic approximations. It is found that the diffracted field consists of the sum of fields produced by the two edges of the planes formed by the slit and a field due to the interaction of the two edges.     

The energy operator for infinite statistics

We construct the energy operator for particles obeying infinite statistics defined by aq-deformation of the Heisenberg algebra.The aim of this paper is to construct the energy operator for particles which obey the so-called infinite statistics defined by theq-deformation of the Heisenberg algebra. This topic was studied in the previous article [1], where a conjecture was formulated concerning the form of the energy operator. Our main result is a proof of this conjecture in a slightly modified form (cf. Remark 1).     

The measured energy loss of high energy electrons in aluminum

The energy distributions of electrons of about 54, 75 and 97 Mev have been measured before and after passing through aluminum absorbers of thicknesses ranging from 0.730 to 5.574 gm/cm². The electrons were accelerated by the LINAC of the Naval Postgraduate School. The most probable energy losses agree with the theory ofBlunck andWestphal for all thicknesses; the half widths of the distributions agree with theory except for large thicknesses, where they exceed the theoretical values. These results are in contrast to those ofBreuer, which indicate systematically large half widths and most probable energy losses which are greater than theory for thicknesses greater than about 2 gm/cm². Since our data agree with those ofBreuer, the difference occurs in the treatment of the theory.     

The optimization of electrostatic energy selection systems for low energy electrons

Design criteria are presented which allow electrostatic energy selection systems to be optimized to give the highest currents for electron beams having a low mean energy (? 500 eV) and a small energy spread (? 30 meV). Limitations in various parts of the system are discussed and a relationship between the current delivered by the system and the energy spread is presented. Different types and sizes for the energy selectors in these systems are considered and the best results are obtained with hemispherical deflectors. The advantage of using, within reasonable limits, a large selector with small image sizes is also demonstrated.     

The measured energy loss of high energy electrons in various metals

The energy distribution of electrons of about 53, 75 and 93 MeV has been measured before and after passing through Be, Sn and Gd absorbers of various thicknesses. Earlier data for Al, Cu and Pb absorbers are reviewed. The electrons were accelerated by the LINAC of the Naval Postgraduate School. The most probable energy loss and the half widths agree with the theory of Blunck and Westphal. An improved semi-empirical formula for the most probable energy loss is presented.     

The binding energy of electrons in supercritical atoms

In a supercritical atom, the most tightly bound electrons do not occupy bound-state eigenfunctions of the Dirac Hamiltonian. We discuss the binding energy of supercritical atoms in the light of this fact. We derive an expression for the binding energy which relates the supercritical and the undercritical cases in a smooth fashion.     

The energy spectrum of electrons in a crystal

The principal theorems concerning these characters are presented.     

Collisionless self-consistent trapping of electrons into a nonstationary potential well: Dynamics of trapped electrons

The subject of investigation is the early stage of self-consistent trapping of electrons into a potential well that forms during the development of aperiodic Pierce instability. An analytical estimate for threshold gap δ_th = d _th/λ_D (λ_D is the Debye beam length) above which the trapping begins is derived. The nonlinear dynamics and distribution function of trapped electrons are studied in detail using a numerical method ((E, K) code). It is found that the trapped particles produce a localized steep-edge bunch, which “dangles” around between the electrodes, causing potential oscillations. Trapped electrons render the well shallower. Some of the particles in the bunch are shown to periodically escape to the electrodes. As a result, the potential oscillation amplitude fades away and the mean depth of the well increases.     

Effect of positive muon trapping by dislocations

Aluminum was deformed at room temperature so that vacancies are annealed out and only dislocations are remained. The muon spin depolarization rate was found to be decreased as the temperature is raised. This indicates that some trapping-detrapping occur. Fitting the spin relaxation to the calculated spin relaxation function for the trapping-detrapping model, the values of the activation energy for the trapping rate and detrapping rate and of the depolarization rate at the trapping are found to be 25 meV, 66 meV, and 0.24 sec^–1, respectively for the best fit. This indicates that positive muons diffuse to dislocations and diffuse along dislocation lines and are trapped at a jog of the dislocation, and detrap from the jog.     

Current switch by coherent trapping of electrons in quantum dots

We propose a new transport mechanism through tunnel-coupled quantum dots based on the coherent population trapping effect. Coupling to an excited level by the coherent radiation of two microwaves can lead to an extremely narrow current antiresonance. The effect can be used to determine interdot dephasing rates and is a mechanism for a very sensitive, optically controlled current switch.     

The measured energy loss of high energy electrons in copper and lead

The energy distributions of electrons of about 53, 75 and 93 MeV have been measured before and after passing through copper absorber of thickness up to 5.726 g/cm² and lead absorbers of thickness up to 2.825 g/cm². Earlier data for aluminum absorbers are reviewed. The electrons were accelerated by the LINAC of the Naval Postgraduate School. The most probable energy losses agree with the theory of Blunck and Westphal for all thicknesses; the half widths agree except for large thicknesses, where they are smaller than theoretical values for lead, in agreement for copper, and larger for aluminum. Large numbers of electrons of energy less than 30 MeV are observed in the distributions of transmitted electrons, particularly for thick absorbers and higher values of atomic number. These are apparently the result of multiple processes in the absorbers.     

The elastic scattering of low energy electrons from Xenon

Calculations are presented of angular distributions for electrons elastically scattered from xenon in the energy range 5.5 to 10 eV. The potential describing the xenon atom is determined by the X_α-approximation. The relative dependence with energy of the differential cross section at 30° scattering angle has been calculated in the range 30 to 200 eV. The theoretical results are in very good agreement with experimental data.     

捕获电子对低杂波与电子回旋波的协同效应的影响

电子回旋波和低杂波的协同效应可有效地提高两只波的电流驱动效率.本文数值研究了捕获电子效应对电子回旋波和低杂波协同的影响.结果显示,随着捕获角的增大,双波协同驱动电流会减小,且协同因子也会明显减小,即捕获角对两只波协同驱动流的影响要比其对单独驱动电流的影响更加敏感.通过加宽低杂波共振区可减弱电子回旋波电流驱动对捕获角的依赖,同时发现随着电子回旋波功率的增加,捕获角对电子回旋波电流驱动的影响也会变小.     

高能电子束韧致辐射特性的理论研究

高能电子束轰击金属靶会产生韧致辐射X射线,为优化韧致辐射X射线品质,需要研究如何获取最佳辐射效率等韧致辐射规律.结合理论分析,并采用MCNP/4C对10,20?MeV电子的韧致辐射规律进行了模拟研究.讨论了不同靶材料产生的韧致辐射效率、角分布、能谱分布、准直锥孔内辐射效率等问题.通过对不同靶材料韧致辐射的模拟研究,给出了不同厚度靶与光子效率、注量分布、出射电子与角分布的关系与规律.由此得到不同靶材料对于10,20?MeV电子在最优韧致辐射效率下的一些边界条件与规律. 关键词： 韧致辐射 最佳效率 角分布 能谱     

Equilibrium state and free energy of an infinite mode dicke maser model

For an infinite mode Dicke maser model, we show that the infimum of the free energy over a class of translation-invariant product states is attained for a quasi-free state. Furthermore, the thermodynamic limit of the free energy is proved to exist and equals the quasi-free solution.     

二维环状无限深势阱中的朗道能级

对于带电粒子在磁场中的运动,在各种教科书上都有详细的阐述,但是对于限制在二维无限深势阱的带电粒子,现在流行的各种量子力学教科书上都没有阐述.本文主要讨论二维无限深势阱中的能级和朗道能级.     

Magnetic exchange energy of two-dimensional electrons

The exchange energy of a two-dimensional electron gas was evaluated exactly in the presence of a magnetic field when only the lowest Landau level is occupied fractionally.