摘要:

The basic principles of electron backscattering from atoms and solids in the energy range 10 to 100 keV are reviewed. The total backscattering from thin self‐supporting films, from bulk solids, and from thin surface films on supporting bulk solids is discussed as well as the angular distribution of the backscattered electron intensity for normal and for oblique incidence of the primary beam. The results of theoretical models are compared with experimental results. Contrast mechanisms in scanning electron microscopy based on electron backscattering and the influence of diffraction effects are described. Finally the thickness determination of thin films by electron backscattering and by other methods is reviewed.

ISSN:0021-8979    

DOI:10.1063/1.331005

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The earlier theory of maser noise was based on Nyquist’s expression for thermal noise. We present here an alternate approach based on the Callen‐Welton expression for thermal noise. It is shown that available noise power measurements in high‐gain masers cannot discriminate between the two approaches. The noise figure and the system noise temperature are calculated for the two points of view.

ISSN:0021-8979    

DOI:10.1063/1.331078

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The Pd‐doped SnO2thin film detector for gaseous components has been developed, whose detection is based on the fact that the adsorption and desorption of gases cause the remarkable change in electrical resistivity of the semiconductor. This property of SnO2film is applicable to the preferential detector for gaseous components, especially ethanol gas. SnO2thin film was prepared on the polished ferrite substrate which SiO was precoated. Both the preparation and the precoating were done by vacuum deposition. Subsequently the oxidation for SnO2film in air was done at 500–550 °C for 30–60 min. The rise rate and fall rate of temperature were 2.5 and 1.7 °C/min, respectively. The thickness of SnO2film was about 0.3–0.35 &mgr;m.

ISSN:0021-8979    

DOI:10.1063/1.331079

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

A versatile vibrating‐sample magnetometer has been developed which measures the magnetization of metal hydrides as a function of magnetic field, hydrogen pressure (up to 6 MPa), and composition, temperature, and time. For the ferromagnetic NdCo5Hxsystem, magnetic properties of well‐defined hydrides and hydride‐phase transformations are studied by this method. The existence of a hydrogen‐rich phase in the NdCo5Hxsystem, the &ggr; phase, is indicated by the temperature dependence of magnetization under the influence of high pressure hydrogen.

ISSN:0021-8979    

DOI:10.1063/1.331080

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The elastic constantsC11,C33,C44,C13of oriented poly propylene films are measured with Brillouin scattering and are compared with the elastic constants obtained from extruded poly propylene rods. The photoelastic constantsp12,p13, andp31of the extruded rod samples are measured by comparison to a poly(methylmethacrylate) reference scatterer. In the film samples, the relative values of the photoelastic constantsp11,p33,p13, andp31are measured by comparison of the quasilongitudinal and quasitransverse intensities at several directions of sound propagation. Within the experimental error,p13,p31, andp12are found to be unaffected by extrusion or stretching.p11andp33are found to change in relation top31in the film samples. The results are interpreted by considering the chain morphology and the theory of photoelastic interaction. The changes in the Brillouin intensities are due to changes in the elastic constants, rather than the photoelastic constants.

ISSN:0021-8979    

DOI:10.1063/1.331081

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The fields induced in a conducting sphere of resistivity, &eegr;, placed in a strong, steady magnetic fieldBaz⁁, and a small oscillatory magnetic field (in thexyplane) of magnitudeB&ohgr;have been calculated approximately forB&ohgr;/Ba≪1 andBa/ne&eegr; ≪1, wherenis the number density. The conducting sphere is assumed to have a uniform resistivity and number density and the ions are assumed immobile. It has been shown that: (a) If the applied oscillatory field is linearly polarized, the magnetic field induced in the conducting sphere has a rotating component for which &ohgr; is parallel toBaz⁁. (b) If the applied oscillatory field is rotating (circularly polarized), its penetration in the conducting sphere is enhanced or impeded with respect to the classical skin effect depending on whether the sense of rotation is parallel or antiparallel toBaz⁁. These results are consistent with the experimental observation in the rotating field plasma experiments.

ISSN:0021-8979    

DOI:10.1063/1.331082

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The ion recovery efficiency of a transverse magnetic field monochromatic direct recovery device intended for intense neutral beams is examined theoretically by solving a Poisson–Vlasov equation. An optimum in recovery efficiency is obtained for finite ion current density and excess initial speed.

ISSN:0021-8979    

DOI:10.1063/1.331083

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

A number of tetrode electrode designs are considered. An improvement resulting in 425% more brightness with 26% less source plasma is suggested from the results of solutions of the Poisson–Vlasov equations.

ISSN:0021-8979    

DOI:10.1063/1.331084

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Recovery of a pulsed electron beam diode operating in the 50 A/cm2range has been studied using an inductive storage source producing two∼150 kV pulses with pulse‐to‐pulse separation ranging from 10–500 &mgr;sec. The diode cannot instantaneously support a second voltage pulse because of the short circuit provided by the interelectrode plasma associated with the first pulse. The properties of this plasma, including its effective lifetime, have been studied. The diode is observed to recover for pulse separation times≳100 &mgr;sec. The results can be extended to repetitively pulsed electron beam generation as needed in many physics experiments such as those related to beam propagation in gases, opening switches, and laser phenomenon.

ISSN:0021-8979    

DOI:10.1063/1.331085

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Light reflection from rough spheres being large compared to the incident wavelength is considered—the resulting reflection pattern is identical to that one produced by randomly oriented convex particles. Only the limiting case of short wavelengths is treated; that means the laws of geometrical optics are assumed to be valid. It turns out that the decisive quantity is the probability distributionP(&bgr;) of the directions of the surface normal vectors. The resulting differential cross section shows the following behavior: with growing roughness the cross section flattens for moderate scattering angles, whereas a rise occurs in the region of backscattering. The resulting formula can be inverted: from the measured cross section the probability distributionP(&bgr;) can be calculated by means of an integral transformation.

ISSN:0021-8979    

DOI:10.1063/1.331086

出版商:AIP    

年代:1982

数据来源: AIP