摘要:

The CdS x‐ray detector is compared with the photo‐multiplier x‐ray detector. Reduced to the same solid angle the sensitivity of the CdS x‐ray detector is of the same order of magnitude as the sensitivity of the photo‐multiplier x‐ray detector. As the internal amplification of the primarily released electron currents in CdS is of the order 103to 104compared with the amplification in the multiplier tube of ½×106the conversion process of x‐ray quanta in slow electrons in CdS must be more efficient than the corresponding processes in the combination crystal phosphor screen photo‐multiplier. Calibration curves show a linear relation between photo‐current and intensity of x‐rays at low irradiation levels. At high irradiation saturation effects occur. Oscilloscope curves of the response at 60 x‐ray pulses per second are given. At strong irradiation the photo‐current over a long time increases in a completely reversible way. X‐ray intensities as low as 150 quanta CuK&agr;per second are registered with a circuit employing a WL 759 trigger tube.

ISSN:0021-8979    

DOI:10.1063/1.1699661

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

The diffraction of a plane electromagnetic wave by an infinitely long, perfectly conducting cylinder has been treated by a variational method (see the two papers by H. Levine and J. Schwinger). The incident field is assumed to be polarized in the direction of the cylinder axis, and thus the entire field is of two‐dimensional nature. This formulation yields an expression for the diffracted cylindrical wave amplitude, at distances from the cylinder large compared to its transverse dimension and the wave‐length, which is stationary relative to small independent variations of the surface currents arising from plane‐wave excitation along a pair of directions in space; furthermore, the stationary form of the diffracted amplitude is independent of the scale of the surface currents. In accordance with a theorem of Levine and Schwinger, the total plane‐wave scattering cross section is simply related to the diffracted cylindrical wave amplitude in the direction of incidence. To examine the high frequency behavior of the cross section, the surface current induced by a plane wave is taken different from zero only on the illuminated part of the cylinder, where its value is derived from the tangential component of the incident magnetic field. The resulting cross section is obtained and is shown to approach 4awhenkaapproaches infinity (k=2&pgr;÷wave‐length,aequals the radius of cylinder).

ISSN:0021-8979    

DOI:10.1063/1.1699662

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

It is suggested that when the air temperature increases upward an efficient and economical method for modifying low temperatures near the ground is to force air downward through vertical stacks from the relatively warm air aloft. Theory is developed which shows that the necessary power per unit mass is mainly a function of the air velocity in the stack. The energy required by this method is compared with the energy required to heat the air originally near the ground, and it is shown that under a strong temperature inversion the power method requires considerably less energy than the heating method.

ISSN:0021-8979    

DOI:10.1063/1.1699663

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

A general expression is derived for the effective attenuation of circular electric (TE01) waves owing to mode conversions in a section of wave guide whose shape deviates slightly in any specified manner from a perfect circular cylinder. Numerical predictions are in good agreement with experiment for the special case of transmission through an elliptically deformed section of pipe. The effect of random distortions in a long wave guide line is analyzed in terms of the mean‐square values of the Fourier coefficients describing the distortions; and from the general formulas it appears that the mode conversion losses depend in large measure upon the statistical distribution of the various types of distortion. Under certain rather arbitrary simplifying assumptions about this distribution, it is calculated that mode conversions in a 4.732‐inch copper pipe whose radius deviates by 1 mil r.m.s. from that of an average cylinder will increase the attenuation of theTE01mode at 3.2 cm by an amount equal to 8 percent of the theoretical copper losses. The dependence on frequency of mode conversion losses in such a guide is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1699664

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

The wettability of crystals, glasses, and even of water itself can be temporarily decreased by bringing ions of high polarizability into their surfaces. Base exchange experiments are described where the hydrogen ions present in the surface layers of bentonite (a clay mineral of high exchange capacity) and of a soda‐lime glass are replaced by different cations. This substitution seems to have no particular effect on the hydrophilic and rheological properties of the carriers as long as their surfaces are kept in contact with water. After drying, however, the surfaces which contain ions of high polarizability become hydrophobic, at least temporarily. A porous clay film will no longer absorb water instantaneously after having been treated with Ni2+, Mn2+, Hg2+, or similar ions with incomplete outer electron shells. Contact angles with water up to 70° could be observed for a short period for Hg2+and Pb2+clays.Glass capillary tubes which have been treated with non‐noble gas‐type ions show a capillary rise which is much smaller than that observed with the tubes which have been treated with HCl and water only. This depression of the capillary rise, too, is temporary and can be observed only if the glass wall has been thoroughly dried previous to the experiment and if the capillary rise is measured in the upward direction.An explanation is presented for these and allied phenomena on the basis of the polarization of ions in the strongly asymmetrical forcefields of interfaces. The experiments are correlated with the hysteresis of the contact angle and with observations concerning adhesion phenomena and catalytic activities of heavy metal ions at interfaces.

ISSN:0021-8979    

DOI:10.1063/1.1699665

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

Measurements are reported on the distribution of ionization in depth of aluminum produced by steady beams of two and three million‐volt electrons. The variation of cathode‐ray current density in a plane transverse to the beam, the effect on this transverse distribution of additional aluminum scattering foils, and a practical method of cathode‐ray dosage computation are given.

ISSN:0021-8979    

DOI:10.1063/1.1699666

出版商:AIP    

年代:1950

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1699667

出版商:AIP    

年代:1950

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1699668

出版商:AIP    

年代:1950

数据来源: AIP