摘要:

The classical crystallographic equations used in deducing structure from peak positions, peak widths, and integrated intensities of x‐ray scattering are facile enough, but they involve assumptions that are not valid for extremely small crystallites. An alternate approach more generally valid is to use the Debye interference function. These two different approaches have been compared, using as examples a diamond crystallite containing three unit cells on a side (∼10.7 Å) and one containing ten unit cells on a side (∼35 Å).

ISSN:0021-8979    

DOI:10.1063/1.1713726

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

A method is given for the determination of the electromagnetic fields excited in accelerator cavities by a bunched beam of charged particles passing through the cavities. The electric and magnetic fields within a cavity are determined by solving a ``coupled regions'' problem, where the regions consist of a coaxial cavity and a cylindrical waveguide coupled through a gap. Numerical results are obtained by use of a digital computer for a few configurations representing linear accelerator cavities with drift tubes. The results are presented as a series of normalized curves of pertinent electrical quantities; they should give a clear qualitative picture of the effects of beam loading in linear accelerator cavities. Owing to space limitations, only the fundamental resonance excited by the fundamental beam harmonic was investigated in any detail. The general expressions advanced in this paper can be used to investigate higher‐order resonances excited by higher‐order beam harmonics.

ISSN:0021-8979    

DOI:10.1063/1.1713727

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

An experimental research program has demonstrated that the high‐voltage performance of a vacuum gap can be improved by the simple expedient of coating the cathode surface with a suitable thin insulating film. Steady voltages ranging to 340 kV were obtained with 5‐mm gaps composed of 15‐cm‐diam Rogowski electrodes. Simultaneously the average gap currents were suppressed to the 10−8to 10−10A range. Further, it was shown that an insulating film on the anode can be severely detrimental to gap performance. Experiments were performed, at voltages up to 380 kV, involving 12 different film materials. Film thicknesses ranged from 0.2 to 135 &mgr; and film resistivities ranged from 1011to 1019&OHgr;‐cm. The dielectric constants were between 1.7 and 3.5, except for one at 90. Based upon the experimental results and their interpretation, a tentative set of specifications can be given for a good cathode film: (1) resistivity of at least 1011&OHgr;‐cm; (2) dielectric constant in the range 1.5 to 4; (3) dielectric strength of at least 106V/cm; (4) film thickness between 10 and 25 &mgr;; (5) mechanically hard and smooth with high abrasion resistance and high adhesion strength; (6) no gas bubbles within the film. If bubbles are unavoidable they must be substantially smaller than the film thickness; (7) low vapor pressure; (8) the cathode substrate should be of a highly polished metal suitable for quality deposition of the desired film material.

ISSN:0021-8979    

DOI:10.1063/1.1713728

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The construction details and output characteristics of a high‐power GaAs junction laser are described. With the diode cooled to 20°K, continuous coherent optical power outputs up to 3.1 W have been obtained. This output was achieved with power efficiency of 46%. The coherent spectral output at several power levels well above threshold is shown. High resolution measurements of the spectral output place an upper limit of 310 Mc/sec upon the laser linewidth.

ISSN:0021-8979    

DOI:10.1063/1.1713729

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The Chapman‐Enskog solution of the Boltzmann equation is used to obtain theoretical data for the viscosity of gaseous cesium, including the effects of up to 10% ionization. Results are presented for the viscosity of ionized cesium at pressures of 10−2, 10−3, 10−4, and 10−5atm in the temperature range 1000°–3500°K, and for unionized cesium over the same range. The viscosity of the 10% ionized gas is found to be about 20% lower than that of unionized cesium under the same conditions.

ISSN:0021-8979    

DOI:10.1063/1.1713730

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The effectiveness of cataphoretic purification of neon was investigated in conjunction with work on breakdown potentials in neon below the Paschen minimum. The extreme sensitivity, resulting from the Penning effect, of the breakdown potential in neon to the presence of traces of argon was used as an indicator of the degree of purity of the neon. Under the conditions of this experiment the limit of sensitivity for argon was about 1:107. With a discharge current of 125 mA in a helically wound Pyrex tube 1.6‐cm o.d. and 2 m long, original concentrations of argon in neon of 50 ppm and 2%±1% were decreased to ≤0.1 and ≤1 ppm, respectively.

ISSN:0021-8979    

DOI:10.1063/1.1713731

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The diffusion equations of momentum, heat, and mass are solved for spiral flows of incompressible viscous fluids. General exact solutions for the steady‐state distributions of velocity, temperature, and concentration are obtained through the use of the similarity transformation technique. Also described are two typical boundary conditions which may be applied to determine the integration constants in the general exact solutions.

ISSN:0021-8979    

DOI:10.1063/1.1713732

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The saturation magnetostriction constants of single‐crystal Gd have been measured from 4.2° to 340°K with a strain gauge technique. A marked change in slope of &lgr;Awas observed near 220°K; this is the temperature region where the easy direction of magnetization in Gd shifts from thecaxis to a cone around thecaxis. The constant &lgr;Cshows a definite maximum near 130°K.

ISSN:0021-8979    

DOI:10.1063/1.1713733

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

Magnetic, crystallographic, and preparative data are reported on the system {Y2.75Bi0.25} Fe5−xAlxO12for values ofxto 1.50. For largexthere appear to be differences in 0°K magnetic moment between this system and the straight yttrium analog, which imply that the replacement of Y3+by the larger Bi3+ions favors occupation of the tetrahedral sites by the smaller Al3+ions. The replacement of Y3+by Bi3+ions leads to the reduction of the preparation temperature of aluminum substituted iron garnets by about 350°C.

ISSN:0021-8979    

DOI:10.1063/1.1713734

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

Experiments were performed to investigate the tensile properties of gold films of thickness ranging from 2000 to 50 000 Å, deposited on rocksalt cleavage surfaces at temperatures from 40°–300°C. The grain size, which varied from about 200 Å to single crystals, has little influence on the early stages of the stress‐strain curve which is characterised by an extremely high work‐hardening rate and small total strain at fracture. The extent of plastic deformation is greater in monocrystalline films than in fine‐grained polycrystalline ones. It is inferred that surface defects play an important role in determining the observed fracture stresses of the films.

ISSN:0021-8979    

DOI:10.1063/1.1713735

出版商:AIP    

年代:1964

数据来源: AIP