摘要:

Large single crystals of calcium niobate Ca(NbO3)2, grown by the Cˇzochralski technique, are transparent and can be doped with rare earth or transition metal ions. Laser action has been observed in calcium niobate doped with trivalent neodymium, holmium, praseodymium, erbium, and thulium.

ISSN:0021-8979    

DOI:10.1063/1.1729154

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Exo‐electron glow curves for an oxide surface on aluminum have two principal peaks. The analysis supports the theory of thermostimulatedexo‐electrons originating in traps below the conduction band. The aluminum oxide surface had two types of traps, both approximately one electron volt below the conduction band, and attempt‐to‐escape frequencies of 4×1010sec−1and 4×109sec−1.

ISSN:0021-8979    

DOI:10.1063/1.1729155

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A quantitative analysis of pulse sizes recorded in an air Geiger counter at 200 Torr was made, relating counting rates of various pulse types at different sensitivities and potentials along the counting plateau. Using this information and a determination of the onset of the self‐counting potential, data concerning counts, pulse size, distance of pulse propagation down the tube, and pulse velocities were obtained for pressures of 100, 200, 300, and 400 Torr. Triggering on the steep rise of the electrical pulse stimulated by &agr; particles at one end of the counter, the time of passage of the luminous pulse from one photomultiplier located at the &agr; particle gun, and a second viewing of the counter at a given distance along the axis could be recorded on an oscillograph screen. Large fluctuations of number of ions per pulse, distance of propagation down the tube, and velocities were noted. All these quantities increased with potential as the onset of steady corona was approached. There was a close correlation between pulse size, distance of propagation, and velocity. These are readily accounted for by the number of ions and photoionizing photons created in the avalanches produced by the initial triggering event.

ISSN:0021-8979    

DOI:10.1063/1.1729156

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

It has been known for many years that cylindrical plasma columns subjected to a transverse electric field exhibit dipole resonance effects. Very little attention has been given to the modification of this phenomenon by a magnetic field. This paper gives a theory for the splitting of the resonance that occurs under these conditions and describes experiments carried out using mercury‐vapor discharges at a pressure of about 1 &mgr; Hg to verify the theoretical prediction. Good agreement was obtained for magnetic fields giving an electron cyclotron frequency up to about half the geometric mean‐resonant frequency, and it is suggested that the effect provides a useful diagnostic technique for the measurement of mean electron density and magnetic field in discharge columns.

ISSN:0021-8979    

DOI:10.1063/1.1729157

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The design and construction of a superconducting solenoid generating a magnetic field of high homogeneity is discussed. The design is based on the Garrett mathematical description of a magnetic field produced from a set of axially symmetric coils. The experimental results for a 1.75 in. i.d. solenoid, operating at either 10 or 24 kg and possessing end‐correcting coils in an arrangement determined by theory, indicate a central field homogeneity of 1/105over about 1 in. at 10 kg and 0.75 in. at 24 kg. At approximately 9.4 kg it was possible to clearly resolve the three chemically shifted proton NMR peaks of ethyl alcohol. This result indicated a homogeneity of 1/106over the sample at a single point in the accessible field volume.

ISSN:0021-8979    

DOI:10.1063/1.1729158

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A method is given for calculating the potential distribution of a system consisting of two coaxial cylinders, each of unit radius, separated by a distance of 2aalong the axis. The potentials of the left‐ and right‐hand cylinders are taken as −1 and +1, respectively. The problem can be solved if the potential &phgr;(1,z) onr= 1 or its inverse Fourier sine transformA(&lgr;) is obtained. The dual integral equations forA(&lgr;) are derived from the boundary condition on the cylinders and the continuity condition of the potential and of its normal derivative on the gap (r= 1, |z|≤a) between the cylinders. The solutionA(&lgr;) is expressed by the following series:A(&lgr;)=2&pgr;J0(&lgr;a)&lgr;+n=1∞anJ2n(&lgr;a)&lgr;.The coefficientsanin this series satisfy an infinite set of linear equations. The values ofanfor several values of the half‐gap lengthaare calculated by successive approximations and are shown in a table.

ISSN:0021-8979    

DOI:10.1063/1.1729159

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The mixing of the first four axial‐mode frequencies of a ruby laser in a bulk, room temperature, CdSe crystal to obtain microwave beat frequencies in the 1–5 Gc/sec range is described. A photoconductive mixing analysis based on a monomolecular recombination process is found to give excellent agreement with the experimental data. The beat frequency power was found to vary as the square of the dc bias voltage applied across the crystal, the square of the incident light power, and inversely as the square of the beat frequency. A minimum lifetime of 10−9sec, a cross section of 1.3×10−16cm2, a modulation index of 0.2, and a maximum beat frequency power of 0.2 mW were obtained in the experiments.

ISSN:0021-8979    

DOI:10.1063/1.1729160

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Emission from most practical electron sources is nonuniform over the emitting area. Ordinary metallic surfaces are polycrystalline and their emission comes from many different small crystal facets whose work functions can vary over a wide range of values. As an example, the range of work functions of tungsten goes from a low of 4.3 eV for the (116) face to a high of 5.9 eV for the (110) face. Substantially improved uniformity of work function and current density would result if the entire emitting surface contained only a single‐crystal plane. The use of a single crystal as a means of obtaining such a surface is costly and wasteful since its unique bulk properties are superfluous and do not in any way contribute towards the improved performance. Even more important, using a single crystal inherently limits one to planar geometries.Many polycrystalline materials of arbitrary shape, among them the refractory metals, when prepared by chemical vapor deposition can be made to exhibit a high degree of uniaxial crystal orientation with their preferred axis centered about the direction of growth. Given proper treatment after deposition, the surface of such materials predominantly consists of a single‐crystal plane.In this paper, X‐ray, optical, and thermionic‐emission measurements are described which were made on vapor‐deposited tungsten prepared by the hydrogen reduction of tungsten hexafluoride. By comparing volt‐ampere characteristics of high‐vacuum diodes, one of which contains a conventional tungsten filament and the other a chemically vapor deposited one, of identical dimensions, it is found that there is an expected improvement in emission uniformity due to the uniaxial grain orientation in the latter.By a similar comparison of cesium‐neutralized energy‐converter diodes, it is shown that the improved surface uniformity results in significantly improved power quadrant characteristics.

ISSN:0021-8979    

DOI:10.1063/1.1729161

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Discharge currents which flow in carefully distilled hexane on the removal of the applied potential were investigated for predischarge stresses ranging from 10–750 kV/cm. The duration and shape of the discharge characteristics were found to depend on the electrode material, on the surface state of the cathode, and on the predischarge stress. It is believed that the discharge currents are the result of a redistribution of charges in the gap in the absence of an external field. Using a model based on the theory of simple diffusion within a liquid bulk, an equation is developed which shows good agreement with the experimental results.

ISSN:0021-8979    

DOI:10.1063/1.1729162

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

An expression for the output power of a laser in terms of the measured single‐pass gain is discussed for two cases: homogeneously and inhomogeneously broadened spectral lines. The results are applied to the 6328‐Å laser line in the helium‐neon mixture, but only an order‐of‐magnitude calculation is possible because of the lack of data. Finally, several of the assumptions made during the derivation are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1729163

出版商:AIP    

年代:1963

数据来源: AIP