回旋速调管注波互作用瞬态非线性理论与模型研究

本文利用自洽非线性理论对回旋速调管放大器中的电子注-波互作用进行了时域瞬态分析,建立了多腔回旋速调管非线性理论,给出了相应的电子运动方程和复数形式的互作用瞬态场方程.探讨了调制腔、中间腔、和输出腔中注-波互作用的模型和研究方法,考虑了电子速度零散对注-波互作用的影响.最后利用FORTRAN语言给出并分析了一支Kα波段四腔回旋速调管注-波互作用的数值计算结果,经与实验值和PIC模拟结果相比较,三者较为符合. 关键词： 回旋速调管 电子注-波互作用 瞬态非线性理论     

An Unmagnetized Plasma-Loaded Relativistic Backward-Wave Oscillator: Experiment and Simulation

Reported in this paper are the results of an experiment to produce high-power microwave radiation from a gas-filled backward wave oscillator (BWO) driven by a relativistic electron beam without external guiding magnetic field. A peak power for background gas pressure at 5.25 mTorr has been observed as argon pressure from 0.75 mTorr to 15 mTorr. Operating frequency of the oscillator has been measured at 9.6 ± 0.4 GHz. The results of PIC simulation are in good agreement with the experimental results. A reasonable explanation is given for experimental results by PIC simulation.     

Polyhedral variation and the projected Hartree-Fock approximation

A generalization of the Hartree-Fock approach is considered. The axially symmetric intrinsic state is oriented in a finite number of spatial directions, and a variational calculation is performed in the resulting subspace. A parametric representation of matrix elements between the rotated states is introduced. Some simple, as well as more complex polyhedral configurations are chosen. Calculations are carried out for ²⁰Ne, ²⁴Mg and ²⁸Si and the results are compared and analyzed. The case of ²⁴Mg is of particular interest, and the results are consistent with the observation that the intrinsic state should actually be non-axially symmetric.     

Susceptibility and electric dipole in metal C 60 compounds

The permanent electric dipole moment of metal atom-C₆₀ compounds is measured. A column (alkali) and a row (transition metals) of the periodic table are systematically investigated. Most of the experimental results are obtained at high temperature when the atom is mobile on the C₆₀ cage. For a given example (NaC₆₀), the dipole moment is also measured by a different method at low temperature and both results are consistent. For alkali, the results are compared to ab initio calculations. A good agreement is obtained, both for absolute values and for the evolution of the bonding in the alkali column. For transition metals, the relative values of the dipole moments are in qualitative agreement with the ionic character of the compounds.     

Polarization effects and work function differences for transition metal surfaces: A perturbation LCAO MO approach

An analytical LCAO MO perturbation model has been developed for treating the polarization p-d contributions to the internal surface dipole moments of transition metal surfaces. The results are applied for treating changes in work functions (Ø) under chemisorption. The main conclusions are as follows. (1) Chemisorption of electropositive A (such as alkali metals) will always decrease Ø on all surfaces. (2) Chemisorption of electronegative A (such as H or halogens) can result in either increase or decrease in Ø depending on the nature of A and M. The smallest differences in A vs. M electronegativity are most likely to produce the paradoxical change ΔØ<0. The results obtained agree with experiment.     

Scaling properties of diffusion-limited reactions on fractal and euclidean geometries

We review our scaling results for the diffusion-limited reactions A + A 0 and A+B0 on Euclidean and fractal geometries. These scaling results embody the anomalies that are observed in these reactions in low dimensions; we collect these observations under a single phenomenological umbrella. Although we are not able to fix all the exponents in our scaling expressions from first principles, we establish bounds that bracket the observed numerical results.     

Multi-band spectra of odd and even nuclei of the s-d shell

The energy levels of^{21, 23}Na,^{22, 23}Ne,^{24, 28}Mg and^{25, 29}Al are obtained by mixing various bands using the projected deformed Hartree-Fock (DHF) method. Solutions having minimum energies are found to be prolate for all the nuclei considered here. Higher bands are obtained either by considering particle-hole excitations or oblate solutions. These various bands are mixed using the projection method and care has been taken to orthogonalize the bands. The interactions used in this study are those given by Kuo, Preedom-Wildenthal (PW) and WHMK interactions. The last one seems to give good results for most of the nuclei considered here. Not only are the lowest bands well-reproduced but the second lowest bands agree reasonably well in most nuclei. The third lowest ones obtained in some nuclei are not yet observed as complete bands. However, K obtained for the third band seems to be correct. A comparison with shell model calculations—which are numerically exhausting—shows similar results for the lowest band. However, the agreement of the second band varies from nucleus to nucleus. A comparison between matrix elements of the interactions is made to analyze the results.     

Theoretical and experimental investigations on the deposition rate and processes of parallel incident laser-induced CVD

A theoretical analysis of and experimental observations on a parallel incident laser-induced deposition rate are reported. Our theory predicts that the maximum deposition rate depends on the photo-traveling length, the scattering cross section of the reactant gases and their partial pressure. This result is applied to SiO₂ deposition using monosilane and nitrous oxide for reactant gases, and is compared with experimental results. We show that the deposition rate of SiO₂ films as a function of the incident light power and the partial pressure of reactant gases predicted by the present theory well explains our experimental results. A supply-limitation phenomenon of the reactant gases and a method of estimating deposition efficiencies are also discussed.     

Elastic differential cross sections and analyzing powers for p+40,42,44,48Ca at 0.8 GeV

Differential cross sections and analyzing powers for the elastic scattering of 800 MeV polarized protons from ^40,42,44,48Ca are reported. A first-order, spin-dependent KMT optical potential analysis is presented from which the rms radii of the neutron densities are deduced. A comparison of these results with other determinations and with various theoretical predictions is given.     

Gibbs states and equilibrium states for finitely presented dynamical systems

We studyfinitely presented dynamical systems (which generalize Axiom A systems) and show that the notions of equilibrium states and Gibbs states (for Hölder continuous functions) are equivalent. Our results extend those of Ruelle, Haydn, and others on Axiom A dynamical systems and statistical mechanics.     

Charge transfer and chemical shifts in zincblende compounds

Charge transfer and chemical shifts for some zincblende compounds are calculated using the electrostatic model of Shevchik et al.^3,4. A comparison of the results obtained from Phillips ionicities, the bond orbital model of Harrison and ionicities, recently proposed⁹, is performed. The predictions from the latter scale are in sufficient agreement with the experimental data. Additionally chemical shifts for some zincblende compounds are predicted, for which experimental data are not available.     

Properties and current-voltage characteristics of discharges in waveguide gas lasers

The paper deals with the properties andI-V characteristics of discharges in narrow capillaries used, for example, for He−Ne waveguide lasers. It has been observed that discharges in He−Ne waveguide lasers are unstable because of the strongly falling characteristic. A theory is presented which assumes that at low currents wall charges restrict the positive column to a narrow plasma channel and are the main reason for the observed falling characteristic. A numerical evaluation for helium gives results which agree well with experimental data.     

Exact solutions of anisotropic diffusion-limited reactions with coagulation and annihilation

We report exact results for one-dimensional reaction-diffusion modelsA+Ainert,A+AA, andA+Binert, where in the latter case like particles coagulate on encounters and move as clusters. Our study emphasizes anisotropy of hopping rates; no changes in universal properties are found, due to anisotropy, in all three reactions. The method of solution employs mapping onto a model of coagulating positive integer charges. The dynamical rules are synchronous, cellular-automaton type. All the asymptotic large-time results for particle densities are consistent, in the framework of universality, with other model results with different dynamical rules, when available in the literature.     

Measurement of number density of lead and thallium see-through hollow cathode discharges with a high resolution Fabry–Pérot spectrometer and by conventional atomic absorption

A see-through hollow cathode lamp, or galvatron, is investigated. A novel method is presented for the measurement of an atomic absorption profile using a quasi-continuum source created by the combination of two line sources and a high-resolution Fabry–Pérot interferometer coupled to a spectrometer. Number densities are calculated from the resulting absorption profiles by the peak absorption coefficient relationship and compare well with results obtained from high-resolution emission measurements. Number densities are also determined for the lead ³ P ₁ metastable state and thallium ² P _1/2 ^o ground state by conventional atomic absorption. A hollow cathode lamp is used as an emission source and is set at a relatively low current to approximate as a line source relative to the galvatron. Due to the relative line widths of the source and absorber, only the lead metastable state results compare to results obtained by saturated fluorescence. PACS 52.25.Tx; 32.70.Jz; 07.60.Ly     

Analysis of equation of state and thermodynamic functions for trans-decahydronaphthalene up to 200~MPa and 446~K

This paper develops a modified Tait equation of state(EOS) for trans-decahydronaphthalene with four parameters A,B,V0 and P0 being treated as linear functions of temperature.The coefficients contained in these functions are determined through fitting the experimental compression data in the literature between 293 K and 446 K and at pressures from 10 to 200 MPa.Expressions for the thermal expansivity,isothermal compressibility and thermodynamic quantities are deduced and the numerical results are analytically derived.The numerical results show that the precision of the modified Tait EOS developed in this paper is superior to the EOS in the literature.     

A reduced-scale railway noise barrier's insertion loss and absorption coefficients: comparison of field measurements and predictions

In situ testing determined the insertion loss (IL) and absorption coefficients of a candidate absorptive noise barrier (soundwall) to abate railway noise for residents of Anaheim, CA. A 4000 m barrier is proposed south of the tracks, but residential areas to the north have expressed concerns that barrier reflections will increase their noise exposure. To address these concerns, a 3.66 m high by 14.6 m long demonstration barrier was built in the parking lot of Edison Field, Anaheim, as part of a public open house, thereby allowing for acoustical measurements.Insertion loss (IL) was measured in third-octave bands assuming 1/2-scale construction. The IL for three, scaled railway noise sub-sources (rail/wheel interface, locomotive, and train horn) was measured at six, scaled distances. The highest total, A-weighted IL, after corrections for finite-barrier and point-source speaker effects was 22 dB(A) for rail/wheel noise, 18 dB(A) for locomotive noise, and 20 dB(A) for train horn noise. These results can be compared favourably to IL predictions made using algorithms from the US Federal Rail Administration (FRA) noise assessment guidelines. For the actual barrier installation, shielded residential receivers located south of the project are expected to see their future noise exposures reduced from an unmitigated 78 CNEL to 65 CNEL.Absorption coefficients were measured using time delay spectrometry. At lower frequencies, measured absorption coefficients were notably less than the reverberation room results advertised in the manufacturer's literature, but generally conformed with impedance tube results. At higher frequencies the correspondence between measured absorption coefficients and reverberation room results was much improved. For the actual barrier installation, unshielded residential receivers to the north are expected to experience noise exposure increases of less than 1 dB(A). This factor of increase is consistent with a finding of no impact when assessed using FRA guidelines for allowable increases of noise exposure.     

Photoemission and electronic structure of Mo,Ru and Amorphous MoRuB and MoRuP

The electronic structures of molybdenum, ruthenium and amorphous Mo₄₈ Ru₃₂ B₂₀ and Mo₄₀ Ru₄₀ P₂₀ are investigated by the XPS and UPS techniques. The experimental results of pure elements are in agreement with previous band calculations. The valence bands of the amorphous alloys are quite comparable to those obtained from pure Mo and Ru assuming hypothetical alloys. For the investigated alloys, the electronic DOS's at the Fermi level are intermediate between those of transition metal components. The disordering on the band structure, due to alloying effects, is found to be larger for the phosphorus based alloy than for the boron one. A qualitative band model can explain the various observed properties; the experimental results are also discussed in relation with the atomic volumes.     

On the quantification of OH*, CH*, and C2* chemiluminescence in flames

Absolute concentrations of all important chemiluminescent species, OH–A, CH–A, CH–B, and C₂-d have been measured for the first time in methane-oxygen flames at low pressure. The optical detection system for chemiluminescence measurements has been calibrated with Rayleigh and Raman scattering of a cw laser, with the latter approach yielding superior results. The measured ratio between the concentration of CH–B and CH–A suggests that the electronically excited CH* is formed close to thermal equilibrium. Introduction of different rate constants for reactions leading to CH–A and CH–B were not necessary to explain the experimental results. Results are compared with a recent numerical model. Deviations in profile shape and peak positions are relatively small for stoichiometric flames, but become more pronounced in richer mixtures. Larger discrepancies are observed for the absolute concentrations, depending on the chemiluminescent species and the stoichiometry. In an attempt to find an alternative method for the quantification of chemiluminescent species, MIR-CRDS has been performed around 3.9 μm. While H₂O and OH–X could be measured, the sensitivity was not high enough to detect the low sub-ppb concentration of OH–A—in part due to the limited reflectivity of mirrors in the MIR, in part due to a significant background of hot H₂O lines.     

Factorial moments and short range correlation at relativistic energies

We present the results on cumulant moments obtained from horizontally and vertically averaged factorial moments for the shower particles, produced in³²S-emulsion at 200 A GeV,¹⁶O-emulsion at 200 A GeV,¹⁶O-emulsion at 60 A GeV,²⁸Si-emulsion at 14.5 A GeV and proton-emulsion at 800 GeV. Except the cumulants of order two, all other moments are consistent with zero within their statistical uncertainties. The strength of correlation length for each beam is higher than the previously observed values.     

Simultaneous radiative and conductive heat transfer in non-gray media

Steady-state energy transfer through non-gray radiating and conducting media enclosed by black walls of unequal temperature is studied. A rectangular Milne-Eddington type relation is used to describe the frequency dependence of the absorption coefficient. Temperature distributions and total heat transfer results are presented for materials which absorb radiation (a) of low frequency, (b) of high frequency, (c) within a finite band width, and (d) of all frequencies (gray). The influence of optical thickness (τ₀) and conduction to a radiation interaction parameter (N) are examined and the results for non-gray materials are compared with those for a gray analysis. Exact results are compared with those determined by using the optically-thin and the optically-thick approximations, as well as with those evaluated for purely conductive and purely radiative transfer.