摘要:

The use of photographic emulsions to record the spatial distributions and the intensity of radiation in spectroscopy, x‐ray diffraction, astronomy, and other fields is hampered by the sensitivity of the characteristic curve to development and exposure conditions. The deflection of a microphotometer or microdensitometer of conventional design cannot be made directly proportional to the intensity of radiation which is incident upon the element of area of the film or plate at the time of exposure.The recording microdensitometer described herein incorporates a device, termed a function transformer, which automatically and continuously converts densitometer deflection values to exposure values, and two pen and ink recorders. One recorder produces a direct exposure trace, while the other records the usual densitometer trace. An integrator permits the integrated exposure to be evaluated for any desired portion of the plate or film.The apparatus described can be used with any film or plate to which a suitable calibrating exposure has been applied and over the area of which the characteristic curve is sufficiently uniform.

ISSN:0034-6748    

DOI:10.1063/1.1745856

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

For the investigation of radiations of high energies, one can place a magnetic field between two cloud chambers. For a given flux of radiation to be observed, the air gap of the magnet in this arrangement can be made much smaller than when a cloud chamber is mounted between the pole pieces of a magnet. For small gap lengths, a permanent magnet is capable of producing a strong magnetic field. In order to assure most efficient distribution of the magnetic alloy used, model experiments were performed. A calculation shows that, if the variables are chosen appropriately, a single constant can be adjusted so that all the experimental results can be fitted to a universal function within a few percent. By means of a coordinate transformation of the universal function, one can predict field intensities or determine optimum constructions of a large variety of permanent magnets. Reasonable accuracy can be expected as long as the ratio of gap length to linear dimension of the pole faces is less than 1/4. The method has been applied to the construction of a large permanent magnet to be used for a study of the anomalous scattering of cosmic‐ray mesons.

ISSN:0034-6748    

DOI:10.1063/1.1745857

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

A centrifuge rotor constructed of steel and Duralumin ST‐14 weighing 4.93 kilograms and having a radius of 65 mm to the center of the standard centrifuge cell, which contains the material to be centrifuged, is suspended magnetically in a high vacuum (pressure less than 10−5mm Hg). The rotor is driven to running speed by an air turbine below the vacuum chamber. The turbine is connected to the rotor by a small steel shaft along the axis of rotation and passing through vacuum‐tight oil glands into the vacuum chamber. When the rotor reaches operating speed, the shaft is disconnected and the rotor is allowed to coast freely during the sedimentation experiment. This is possible because of the very small deceleration of the rotor (less than a 0.1 revolution per sec per hour). As a result the temperature and rotor speed not only can be measured accurately, but can be maintained very nearly constant. The ultracentrifuge has been used both for rates of sedimentation measurements and for sedimentation equilibrium measurements, but is especially suited for the latter.

ISSN:0034-6748    

DOI:10.1063/1.1745858

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

An apparatus is described for the partitioning of exhaled air into seven separate fractions beginning with the earliest portion of upper respiratory air and continuing to the terminal fraction of deep‐lung air. The same volumetric fractions from successive exhalations are collected over a test period of any practical duration. This apparatus has been employed for the study of lung retention of inhaled particulate matter with particular reference to the separate estimate of upper respiratory retention and penetration to and deposition of particulate matter in alveolar spaces. The apparatus is employed with a mechanical respirator of the Drinker type, which fixes the respiratory pattern at any desired frequency and tidal volume.

ISSN:0034-6748    

DOI:10.1063/1.1745859

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

The procedure used to design the 60‐in. cyclotron oscillator at Berkeley is described. The procedure consists in assuming the cyclotron and associated circuits to be oscillating on one of normal modes of vibration of the electrical circuit and adjusting the circuit so that the proper voltages to drive the oscillator tube are obtained. The procedure is illustrated by numerical examples taken from the original design data.

ISSN:0034-6748    

DOI:10.1063/1.1745860

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

The existence of a ring‐shaped constriction in the electron beam of a thin lens beta‐ray spectrometer is demonstrated experimentally by a photographic film method. Making use of a photographic mapping of the beam, an annular baffle is designed. Optimum relations between annular width, solid angle, and counter window diameter are investigated. A comparison of this type of baffle system with the original baffle system shows that at 2.5 percent resolution the spectrometer transmission may be increased by a factor of two by the use of an annular aperture in the region of beam constriction.

ISSN:0034-6748    

DOI:10.1063/1.1745861

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

Accurate neutralization of the earth's magnetic fieldBeover a long cylindrical region is necessary to extend the energy range of a magnetic‐lens spectrometer to electrons of very low energy. Axial conductors spaced 45° apart on the surface of a circular cylinder of radiusaare used to approximate a cos&thgr; distribution. The conductors at &pgr;/2 are missing since cos&thgr; vanishes. There are 1/√2 as many conductors at ±&pgr;/4 and ±3&pgr;/4 as at 0 and &pgr;. In the plane transverse to the length of the cylinder, the radial variation of the compensating field is given approximately by the termBe(r/a)6cos6&thgr;. Beta‐rays of a few kilovolts energy, which reach a maximum radiusa/2, experience an average residual field of about 0.1 percent ofBewhich produces a deflection of about 0.1 mm for a one‐meter spectrometer. The construction of the coils is described.

ISSN:0034-6748    

DOI:10.1063/1.1745862

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

A description is given of a flash illumination source of very high peak intensity which has been recently developed in this laboratory for use in conjunction with Kerr cell and image converter type cameras.The electrical circuit of the unit permits three standard commercial flash tubes of the Egerton type to be operated simultaneously using only one energy storage capacitor, one trigger circuit, and a single high voltage power supply.A comparison is made between the circuit of the present unit and those of previous flash illumination sources particularly with regard to (a) peak flash intensity, (b) effective flash duration, (c) efficiency of conversion of the total stored electrical energy into useful light output, and (d) reliability of triggering.Possible modifications of the present unit to enable it to be used as a flash source in the conventional ``open shutter‐single flash'' photographic technique are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1745842

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

The design of an improved electrometer circuit, which will compensate for voltage fluctuations and random emission changes, is described. The selection of suitable electrometer tubes is discussed.

ISSN:0034-6748    

DOI:10.1063/1.1745843

出版商:AIP    

年代:1951

数据来源: AIP

摘要:

Small but accurately shaped prolate spheroids of ferromagnetic substances, almost uniformly magnetized by direct current in a large coaxial solenoid, are subjected to alternating axial applied magnetic fields produced by high frequency current in a smaller coaxial solenoid. Measurements of the impedance of this high frequency coil with a specially designed Maxwell bridge, give, as the driving frequency is varied through the frequency of mechanical resonance in the fundamental mode of longitudinal vibration of the center‐supported spheroid, precise data for analyzing the distribution of electromagnetic driving forces and of magnetic, electrical, and mechanical losses by a theory to be given elsewhere. Since the spheroid dimensions are about 10 millimeters for length and one millimeter for diameter, the resonant frequencies of interest are near 300 kilocycles per second. Optical measurements of vibration amplitude, possible in principle, have not yet been effectuated.

ISSN:0034-6748    

DOI:10.1063/1.1745844

出版商:AIP    

年代:1951

数据来源: AIP