HL-2A 装置偏滤器改造的初步设计

根据HL- 2A 装置的结构特点, 提出了HL- 2A 装置偏滤器系统改造的基本方向。对HL- 2A 极向场线圈系统进行了优化设计, 计算了单零平衡位形, 进行了开放式偏滤器的结构设计, 并对新的偏滤器系统进行了热分析和结构分析。结果表明, 新的偏滤器系统新的偏滤器系统能够满足具有一定拉长比和三角形变的等离子体放电要求。     

Impurities in type-II-staggered InAs/AℓSb superlattices

The physics of impurities in Type-II staggered superlattices is reviewed, with emphasis on changes of doping character, such as shallow to deep and deep to false-valence transitions, that can result from altering layer thicknesses. It is shown how some impurities can change their doping characters from "deep acceptors" (semi-insulating) to shallow donors (n-type) as functions of layer thicknesses in superlattices such as InAs/AℓSb. A particularly important case is an Aℓ_Sb antisite defect in an AℓSb layer of an InAs/AℓSb superlattice. This defect is a deep trap or "deep acceptor" in AℓSb, and a remote donor in some superlattices, depending on the layer thicknesses. It can, by itself, control the electron gas density in a superlattice structure, and so can play an important role in the development of high-speed field-effect transistors.     

On a certain method of solving nonlinear differential equations

A new method of exactly solving nonlinear differential partial equations is developed. This method is applied to an equation of a potential flow of compressible gas. A new solution is obtained in the supersonic region, which may be treated as an analogon of a nonlinear stationary wave.Partially supported by NSF contract INT 73-20002A01.     

Determining a quantum state by means of a single apparatus

The unknown state rho of a quantum system S is determined by letting it interact with an auxiliary system A, the initial state of which is known. A one-to-one mapping can thus be realized between the density matrix rho and the probabilities of the occurrence of the eigenvalues of a single and factorized observable of S+A, so that rho can be determined by repeated measurements using a single apparatus. If S and A are spins, it suffices to measure simultaneously their z components after a controlled interaction. The most robust setups are determined in this case for an initially pure or a completely disordered state of A. They involve an Ising or anisotropic Heisenberg coupling and an external field.     

Attractors and characteristic exponents

A natural definition of an attractor as an invariant measure is given (based on the ergodic theory of axiom A diffeomorphisms) and some results are proved which support this definition. It is also proved that if an attractor has every characteristic exponent less than zero in a set of nonzero measure, then the support set of the attractor is an asymptotic stable periodic orbit.     

Quantization from an exponential distribution of infinitesimal action

A statistical model of quantization based on an exponential distribution of infinitesimal action is proposed. A trajectory which does not extremize the action along an infinitesimal short segment of path is allowed to occur with a very small probability following an exponential law. Planck’s constant is argued to give the average deviation from the infinitesimal stationary action.     

Waveguide electro-optic modulator in fused silica fabricated by femtosecond laser direct writing and thermal poling

An integrated electro-optic waveguide modulator is demonstrated in bulk fused silica. A Mach-Zehnder interferometer waveguide structure is fabricated by direct writing with a femtosecond laser followed by thermal poling. A 20 degrees electro-optic phase shift is achieved at an operating wavelength of 1.55 microm with an applied voltage of 400 V and an interaction length of 25.6 mm, which correspond to an estimated effective electro-optic coefficient of 0.17 pm/V for the TE-polarized mode.     

TE_(02)模式W波段三次谐波回旋管腔体设计

设计了用于W波段三次谐波回旋管的带有iris结构的开放式谐振腔。采用低损耗圆对称模式TE_(02)工作。起振电流为2.9A,欧姆效率67%。PIC数值模拟结果表明,TE_(02)模式在iris谐振腔中可以实现稳定的W波段三次谐波单模振荡。当电压为45kV、电流为4A、横纵速度比为1.5时,可以获得25.7kW功率输出,对应的工作效率为14.3%。     

Indeterministic Objects in the Category of Effect Algebras and the Passage to the Semiclassical Limit

We consider a category of effect algebras and formulate an abstract-hidden variables problem for an object of this category. A notion of indeterministic object is introduced as of an object which induces a Kochen–Specker-type contradiction. A sufficient condition for an object to be indeterministic is derived. An abstract algebraic point of view on a no-hidden variables example constructed by Mermin is given. The notion of a passage to the semiclassical limit is analyzed and refined.     

A model for vibrational properties of the atomic interface in A/B fcc metals

The motivation of this theoretical work is to introduce a model calculation for the elastic waves scattering and coherent phonon transport at an atomic nanojunction between face-centered cubic (fcc) leads. The model system A/B consists of two perfect semi-infinite fcc leads A and B, oriented in the same direction and joined by an atomic interface. It is applied to the system Cu/Ni and its inverse Ni/Cu. A theoretical approach based on the matching method is used to study the dynamics of the system A/B.     

Combined exciton–electron excitation in quantum wells with a two-dimensional electron gas of low density

A combined exciton–cyclotron resonance is found in the photoluminescence excitation and reflectivity spectra of semiconductor quantum wells with an electron gas of low density. In external magnetic fields an incident photon creates an exciton in the ground state and simultaneously excites an electron between Landau levels. A theoretical model is developed and suggests the dominating contribution of the exchange exciton–electron interaction.     

Bow shock formation in a complex plasma

A bow shock is observed in a two-dimensional supersonic flow of charged microparticles in a complex plasma. A thin conducting needle is used to make a potential barrier as an obstacle for the particle flow in the complex plasma. The flow is generated and the flow velocity is controlled by changing a tilt angle of the device under the gravitational force. A void, microparticle-free region, is formed around the potential barrier surrounding the obstacle. The flow is bent around the leading edge of the void and forms an arcuate structure when the flow is supersonic. The structure is characterized by the bow shock as confirmed by a polytropic hydrodynamic theory as well as numerical simulation.     

Diode laser extended cavity for broad-range fast ramping

A novel design for an extended-cavity diode laser is presented. The cavity contains an electro-optic prism for synchronous tuning of the cavity length and the grating's incident angle. A simple analysis of the cavity is presented. Experimental results are reported that show mode-hop-free tuning over more than 10 GHz with high linearity and reproducibility. To the authors' knowledge, this is the first demonstration of mode-hop-free tuning of an extended cavity over several free spectral intervals with an electro-optic crystal.     

Theoretical calculations of dissociative adsorption of CH4 on an Ir(111) surface

The activation energy for chemisorption of CH(4) at an Ir(111) surface is determined using density functional theory combined with an estimate of the long range dispersion interaction. The results are found to be in good agreement with published results of bulb and beam experiments analyzed with a precursor model. A surprisingly large surface relaxation is found where an Ir surface atom is displaced outwards by as much as 0.6 A. A strongly bound molecular state at kinks and adatoms involving eta(2)-H,H bonding was also found.     

Low-cost wavelength measurement based on a macrobending single-mode fiber

A low-cost all-fiber wavelength measurement technique is proposed and demonstrated. A macrobending standard single-mode fiber is developed as an edge filter with an optimal design and simple surface processing. A ratiometric wavelength measurement system employing the developed macrobending fiber filter demonstrates a resolution of approximately 10 pm in a wavelength range from 1,500 to 1,560 nm with ease of assembly and calibration.     

Simple Millimeter Wave Dielectric Disc Filter with Very Flat Passband Characteristic

A particular fitter design suitable for millimeter- and submillimeter-waves is presented. By mounting equally spaced dielectric discs of identical thickness inside an overmoded circular waveguide very flat bandpass-filters with a relative bandwidth of about ±6% can be achieved. Normalized to the guided wavelength the air spacing corresponds to 1/4, 3/4, ... whereas the thickness of the dielectric disc is an integer multiple of 1/2. This particular design is possible for an odd number of discs only. A design example shows 19 GHz bandwidth at 150 GHz. A typical application is side-band filtering for radiometers at plasma experiments.     

一种光电数字传声器的设计

本文介绍了一种新颖光电传声器的设计，它不采用Ａ／Ｄ转换器而直接输出数字信号，文中介绍了与传声器有关的光学扫描系统，光栅探测器的工作原理和设计参数。     

Growth of three-shell onionlike bimetallic nanoparticles

We show by molecular dynamics simulations on three systems (B/A=Pd/Ag, Cu/Ag, and Ni/Ag) that three-shell metallic nanoparticles made by a core of a metal A, an intermediate shell of metal B and an external shell of metal A (A-B-A nanoparticles) can be grown by deposition of B atoms onto an A core. The growth of the intermediate B shell is triggered by the fact that the most favorable positions for isolated B impurities inside A clusters are located just one layer below the cluster surface.     

O− emission from 12CaO·7Al2O3 and MSZ composite and its application for silicon oxidation

The solid electrolyte 12CaO·7Al₂O₃ (C12A7) is an interesting material where an atomic oxygen radical anion (O⁻) can be emitted from the C12A7 to vacuum when it is heated to 1000 K under an applied electric field (100 V/cm). However, the mechanical strength of the C12A7 is not enough for an application study. In order to enhance the mechanical strength of the C12A7, a magnesia-stabilized zirconia (MSZ) support C12A7 film composite was developed, and ion emission from the MSZ/C12A7 composite was investigated. The MSZ/C12A7 composite showed O⁻ emission and also electron emission. The generated O⁻ was applied to a silicon sample to confirm its oxidation ability. Even though the surface temperature is less than 383 K, SiO₂ film formation was achieved.This O⁻ oxidation method is applicable for low-temperature and low-damage silicon oxidation processes.     

The Connection of the Asymptotics of the Far Field of a Jet with the Velocity Profile at an Orifice

Doklady Physics - A submerged nonswirling jet of a viscous incompressible fluid issuing from an orifice is considered under the boundary layer approximation. A connection of an unknown constant in...