摘要:

The design and construction of a cylindrical proportional counter 36 in. long, 12 in. i.d. is described, and its performance as a spectrometer for studying soft radiations from radioactive samples of low specific activity is given. The counter tank is operated in an axial magnetic field of 2500 gauss to constrain beta rays to helical paths. A line width of 3.4% (&Dgr;E/E) is obtained for 625‐kev electrons from a Cs137source mounted on a thin film placed within the tank. Simple theory would predict 2.2%. Beta spectra are readily obtained with sources having total activities less than 10 m&mgr;C.

ISSN:0034-6748    

DOI:10.1063/1.1716946

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

A simple super‐regenerative oscillator that produces a coherent signal at the magnetic resonance frequency of a sample in its coil is described in theory and in practice. A cw oscillator is phase locked to the super‐regenerative oscillator and the signal which results follows variations in the frequency of magnetic resonance, owing to variations of the field, within less than 5 parts in 103; the signal produced is adequately monochromatic and stable enough to be used for magnetic resonance experiments with high resolution. The requirements for time and temperature stabilization of the magnet are very greatly relaxed.

ISSN:0034-6748    

DOI:10.1063/1.1716947

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

A practical spectrometer for the observation of high‐resolution proton magnetic resonance spectra at 30 Mc is described. Field modulation is imposed in such a way that ``sideband'' responses are observed, and this enables lock‐in detection to be used, giving increased stability to the baseline of the records. Spectra are displayed by slowly sweeping the modulation frequency and thus are calibrated directly in frequency. The radio‐frequency source is a proton controlled super‐regenerative oscillator, whose frequency follows variations of the electromagnet field. This reduces the effects of field drift and instability, allowing relatively slow scanning speeds to be used in recording the spectra.

ISSN:0034-6748    

DOI:10.1063/1.1716901

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

A high‐precision Zeeman modulated microwave spectrometer was developed to measure the rotational fine structure of oxygen. The transitions lie between 50 and 65 kMc. Direct measurement of the line widths was made at pressures from 20 to 500 &mgr;. The Zeeman components were resolved and compared with the theoretical expectation for theN−=3 line. Twelve lines were measured to better than 0.01 Mc and 11‐line breadth parameters were measured to 0.1 Mc/mm. Of particular interest is the use of transistor circuits to achieve design simplification and improvement.

ISSN:0034-6748    

DOI:10.1063/1.1716902

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

An apparatus for the observation of low‐energy electron diffraction patterns on a fluorescent screen is described. The diffracted electrons pass through a pair of grids and then are accelerated by a potential difference of the order of 103v to excite the fluorescent screen. The equipment is designed for high vacuum, and pressures below 2×10−10mm Hg have been maintained. Different gases can be introduced at low controlled pressures (10−9to 10−7mm Hg), and diffraction patterns produced by adsorbed layers can be photographed and studied. Typical diffraction patterns from a clean (111) face of a nickel crystal and from oxygen adsorbed upon this face are reproduced here.

ISSN:0034-6748    

DOI:10.1063/1.1716903

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

A description is given of a high‐speed bolometer intended for measuring the radiation from nuclear fireballs. The bolometer is made by successive depositions of an insulating layer and a gold sensing element upon a copper block which serves as a heat sink. An analysis of the bolometer's performance indicates that it has a response time of approximately 50 &mgr;sec.

ISSN:0034-6748    

DOI:10.1063/1.1716904

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

In the present paper a description is given of the design of an apparatus for measuring flow birefringence; the pertinent theory has been published previously [Physica22, 1197 (1956); J. Polymer Sci.23, 181 (1957)]. In this apparatus glass cylinders are used, instead of the usual metal cylinders. A slow convention stream which moves parallel to the cylinder axis, removes part of the frictional heat generated in the annular gap. In that way a rising temperature distribution throughout the cross section of the gap, as was described by Y. Bjo¨rnsta˚hl [Z. Physik119, 245 (1942)], is prevented. This temperature distribution, as is well known, causes the divergence of the light beam and, consequently, reflection at the walls of the cylinders. However, in the apparatus described in this paper, no reflections occur and, as a consequence, the appearance of a parasitic double refraction is avoided.Some results of measurements on solutions of cellulose nitrate in cyclohexanone are communicated.

ISSN:0034-6748    

DOI:10.1063/1.1716905

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

A platinum filament covered with a mixture of oxides has been used to replace the tungsten filament in the RCA model EMU‐2 electron microscope. This unit originally was used on an Akashi electron microscope. Since the filament operates at a low temperature, evaporation of the filament itself is very slow. The electron source is very small. The drift of illumination is small and the field of illumination is quite uniform.

ISSN:0034-6748    

DOI:10.1063/1.1716906

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

Equipment is described for maintaining pressures of 100 000 atmos at temperatures in excess of 2000°C for long periods of time. The equipment makes use of conical Carboloy pistons that push into each end of a specially shaped Carboloy chamber. Both chamber and pistons receive lateral support from stressed binding rings. Axial motion of the conical pistons in and out of the chamber is accomplished (while still maintaining a pressure seal) by the use of a specially shaped sandwich gasket made up of naturally occurring pyrophyllite and a steel cone. The arrangement gives a multistaging effect in a single stage. Pyrophyllite in addition to its use in the gasket is also used as pressure transmitting medium, thermal insulation, and electrical insulation. The sample is heated by passage of an electric current through a metal or graphite tube. Methods of pressure and temperature calibration as well as construction details are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1716907

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

A precision apparatus for applying liquid in uniform droplets to test surfaces has been described. The mean diameter of the droplets can be varied from 0.045 to 0.450 mm.

ISSN:0034-6748    

DOI:10.1063/1.1716908

出版商:AIP    

年代:1960

数据来源: AIP