摘要:

By defining the Hamiltonian function in an electron optical system the canonical aberration theory has been developed in the up to fifth‐order approximation. Therefore, the canonical position and momentum aberrations can be expressed by eikonal functions and equivalently by Poisson brackets. Consequently, all fifth‐order canonical aberration coefficients for rotationally symmetrical electron optical systems have been derived at any arbitrary observation planes.

ISSN:0021-8979    

DOI:10.1063/1.346928

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

In a 2N‐pole electromagnetic system, defining the electron optical Hamiltonian function, we have derived both general algebraic expressions (arbitraryN) and special numerical formulas (N=3,4,5,6,7) for different aberrations from lower to higher order (i.e., the order ofN−1,N+1, 2N−3, 2N−1, 3N−5). The so‐called canonical aberration theory in electromagnetic multipoles has thus been developed, which allows us to deduce angular dependencies of different aberrations and to examine the possibility for spherical correction of a round lens by using multipoles.

ISSN:0021-8979    

DOI:10.1063/1.346929

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Dependencies of photoluminescence in five membered heterocyclic conducting polymers on heteroatoms and temperature are studied. Luminescence intensity of poly(3‐alkylthiophene)s increases with temperature and luminescence intensity of poly(3‐alkylfuran)s is slightly enhanced with increasing temperature. However, luminescence intensity of poly(3‐hexylselenophene) is even suppressed with temperature. These difference of properties among heterocyclic conducting polymers with different heteroatoms can be interpreted in terms of the difference of steric hindrance effect between heteroatoms and alkyl side chain and the interchain interaction which influence on the dynamics of excited species and recombination.

ISSN:0021-8979    

DOI:10.1063/1.346930

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Electrons moving in circular orbits and colliding with gas atoms interact with a circular electromagnetic mode. Applying the linearized Boltzmann equation, the known nonresonant‐stimulated bremsstrahlung and the near‐resonance Landau effect are obtained. We predict that resonant electrons moving with angular velocity equal to the azimuthal phase velocity of the electromagnetic wave can exchange energy with the wave if the momentum transfer cross section for an electron‐atom collision is velocity dependent. Amplification is obtained if the momentum transfer cross section has a positive slope.

ISSN:0021-8979    

DOI:10.1063/1.346931

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Thin conducting foils focus charged particle beams through image charges induced on the foils. Such focusing has led to the suggestion that foils be used to transport intense, relativistic electron beams in high‐energy accelerators. This paper examines some of the limitations of foil focusing including sensitivity to the beam parameters, emittance growth from anharmonic focusing, and beam stability in multifoil transport. The analysis is based on a thin‐lens electrostatic treatment of paraxial beams.

ISSN:0021-8979    

DOI:10.1063/1.346932

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Two problems are studied. First, a new method is presented for calculating the electromagnetic field in two conjoined conducting half‐spaces in the presence of current sources in either or both half‐spaces. The method allows the two half‐spaces to differ in the conductivity, permeability, and permittivity. The full Maxwell’s equations are used; the quasistatic results may be derived as a particular limit. The method is unique in that it depends only on the solution of two variables; the components of the magnetic fieldBz, and the currentJz, normal to the interface between the half‐spaces. The second problem involves the determination of the fields induced by a current source in one half‐space with an arbitrary 3D inhomogeneity in the other. New, coupled integral equations for the fields are written down strictly in terms ofBz,Jz, and the external current source. The same formalism, used to generate the new integral equations, is also shown to yield the standard dyadic volume integral representations. Finally, it is shown that the formalism is a useful way of deriving various asymptotic results. The weak scattering limit (the Born approximation) is derived as an example.

ISSN:0021-8979    

DOI:10.1063/1.346933

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A theory is developed to model diffraction and Bremsstrahlung radiation from a loop and a disk of charge in a cylindrical pipe with multiple step changes in wall radius supporting all azimuthally symmetric transverse magnetic modes. The beam kinetics are assumedapriori. A correction in phase due to the abrupt change in beam velocity is incorporated at each step change in wall radius. A longitudinal coupling impedance based on energy and power considerations is employed. Loop charge radiation from cavity and collimator geometries is examined. By suitably choosing the loop charge radius, the energy backscattered in the beam tunnel problem can be minimized. The loading effects of the cavity onto the beam is sensitive to its length.

ISSN:0021-8979    

DOI:10.1063/1.346934

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Second‐order nonlinear optical properties of a newly synthesized dye‐attached polymer (3R) were investigated. The dye has a conjugated diazo structure, and the &bgr;&mgr;g(&bgr;: second‐order molecular hyperpolarizability, &mgr;g: dipole moment in the ground state) is larger than five times that of a monoazo dye (2R). The second‐order nonlinear coefficient (&khgr;(2)) of a 3R polymer is also greater than that of a 2R polymer throughout the fundamental wavelength of 1.06 &mgr;m and between from 1.50 to 1.70 &mgr;m when the polymers are electrically poled. For both polymers, the &khgr;(2)dependence on the fundamental wavelength corresponds to the absorption spectrum, which is explained by two‐photon resonance near the absorption maxima. The attainable &khgr;(2)of the polymers deviates from the theoretical linear relationship with the dye content when it is high. This indicates that the dipolar interaction increases as the dye content rises.

ISSN:0021-8979    

DOI:10.1063/1.346935

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Infrared waveguides have been made by isothermal evaporation diffusion of HgTe on a ZnTe substrate and characterized at 10.6 &mgr;m bym‐lines analysis. Refractive index profiles deduced from this analysis are correlated to the composition ones measured with a microprobe. As a result, we obtain the refractive index of the alloy as a function of the zinc concentration ranging from 0.2 to 1. Direct measurement of the substrate refractive index gives a value 2.60 to 2.65, results in slight disagreement with the previous data.

ISSN:0021-8979    

DOI:10.1063/1.347189

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We present a mode field analysis of the second‐harmonic electromagnetic wave that radiates from a nonlinear core bounded by a dielectric cladding. With this analysis the ultimate performance of the organic crystal‐cored single‐mode optical fiber waveguide as a guided‐wave frequency doubler is evaluated through the solution of nonlinear parametric equations derived from Maxwell’s equations under some assumptions. As a phase‐matching scheme we consider a Cerenkov approach because of advantages in actual device applications, in which the phase matching is achievable between the fundamental guided LP01mode and the second‐harmonic radiation (leaky) mode. Calculated results for organic cores made of benzil, 4‐(N, N‐dimethyl‐amino)‐3‐acetamidonitrobenzen, 2‐methyl‐4‐nitroaniline, and 4’‐nitrobenzilidene‐3‐acetoamino‐4‐metxianiline provide useful data for designing an efficient fiber‐optic wavelength converter utilizing nonlinear parametric processes. A detailed comparison is made between results for infinite and finite cladding thicknesses.

ISSN:0021-8979    

DOI:10.1063/1.346915

出版商:AIP    

年代:1990

数据来源: AIP