摘要:

A feature of the method described is that it involves neither temperature nor heat‐flow measurements. The procedure consists merely of taking a stop‐watch reading (over a few minutes) and finding a value on a calibration chart. The two flat ends of a cylindrical sample, about 18 mm in diameter and 1–30 mm in length, are put in contact with two silver plates which are kept at constant temperatures by means of two boiling liquids of suitable boiling points,viz.differing by about 10–20°C. The time is measured in which a quantity of heat flows, in the steady state, through the sample. This quantity is determined very simply by the quantity of liquid evaporated at the ``cold'' end and which is collected as a condensate. In practice, two calibrated samples are measured first and a calibration line is plotted from which the thermal resistance of subsequent samples can be found at a glance. It is then not necessary to know the exact boiling points of the two liquids, nor the absolute amount of evaporated liquid, nor its heat of vaporization. A measurement takes about 15 min and the error is not more than ±3%. The construction of the apparatus and the performance of measurements in the temperature range of from 20 to 200°C are described in detail. Moreover this article shows a new way of measuring the conductivity of very small samples (e.g., small single crystals).

ISSN:0034-6748    

DOI:10.1063/1.1718523

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The development of an arc‐image system for crystal growth, and techniques for obtaining continuous growth of single crystals under controlled atmospheres, are described. Crystals grown include rutile, sapphire, ruby, stabilized zirconia, and ferrites.

ISSN:0034-6748    

DOI:10.1063/1.1718524

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A multiplication phenomenon caused by fission fragments has been observed in 300 &OHgr;‐cm gold surface barrier detectors when operated at bias voltages greater than 100 V. This phenomenon occurs only for fission fragments that penetrate beyond some threshold depth for multiplication, and the threshold depth is found to decrease with increasing bias voltage. However, the effect could also be due to the surface properties of the detector making the depth correlation fortuitous. An analysis in terms of a threshold depth indicates that the multiplication may be due to a hole rather than an electron effect. No multiplication was observed for alpha particles with the same electric fields. P‐n diffused junction detectors operated at similar average electric field strengths did not show any multiplication effects.

ISSN:0034-6748    

DOI:10.1063/1.1718525

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

This article describes a new aluminum oxide humidity sensing element. The element was developed primarily for use in radiosonde weather measuring equipment. It has a fast response over the entire humidity range and through a broad temperature range of −80 to +135°F. By using specially designed testers, measurements can be made which were previously unobtainable. The elements are small and lightweight, can be made inexpensively of readily available materials, and can be mass produced.

ISSN:0034-6748    

DOI:10.1063/1.1718526

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

An apparatus is described for the determination of Young's modulus from thin‐rod resonance behavior. The apparatus differs from previously described equipment in that it is capable of operating at temperatures over 2000°C while providing a vacuum or an inert atmosphere around the sample. The transducers operate at ambient temperature and are loosely coupled to the specimen under test by fine tungsten wires. Provision is also made for optical measurement of the thermal expansion of the sample.

ISSN:0034-6748    

DOI:10.1063/1.1718527

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A device has been constructed for measuring the changes in internal energy of metals and alloys during deformation. The basis of the method is the quantitative utilization of the heat released in the sample to vaporize a pure liquid under equilibrium conditions, and measurement of the volume of gas produced. The liquids which have been used are N2, CCl2F2, and CCl3F, having boiling points of −196, −30, and 24°C, respectively.

ISSN:0034-6748    

DOI:10.1063/1.1718528

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A device is described which can be used to weld tungsten, tantalum, and molybdenum. The general problem of fabricating tantalum process equipment from tantalum sheet is discussed.

ISSN:0034-6748    

DOI:10.1063/1.1718529

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A systematic study was made of methods of increasing the light collection efficiency of scintillation counters. Various reflectors, surface treatment of the scintillator, relative geometries of scintillator and photodiode, and light pipes were tried, using plastic scintillator cubes, 3 and 6 in. on a side, and right circular cylinders, 3 in. in diameter by 3 in. in length and 6 in. in diameter by 6 in. in length. The maximum factors by which light output could be increased, relative to a polished scintillator, were about 2.8 for 6‐in. scintillators and 3.3 for 3‐in. scintillators without the use of light pipes, and 5.0 for a 3‐in. scintillator with light pipe. The fraction of light trapped in a right circular cylinder by total internal reflection is derived as a function of index of refraction, as are the percentages of light coming out the ends and sides of a cylinder.

ISSN:0034-6748    

DOI:10.1063/1.1718530

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A detector has been devised which contains in different regions liquid scintillators of different spectral emission characteristics, thus enabling signals arising in those regions to be distinguished from each other. The spatial discrimination so achieved can be applied to problems of low level &bgr;−counting in which it is desired to reduce the background due to gamma rays. A study was made of five liquid scintillators, four of which have emission maxima in the range 4310 to 4660 Å and one with its maximum at 3640 Å, and various optical filter‐scintillation combinations were tested. The beta, gamma discrimination possibilities of the color scheme were examined in a preliminary manner using C14as the &bgr;−source and Cs137as the source of gamma rays.

ISSN:0034-6748    

DOI:10.1063/1.1718531

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Two types of vacuum‐tight joint have been developed for articulation of the connecting lines of a mercury manometer. The design and construction of each joint are described. The cylinder type has a seal around the circumference of a tube. The exit tube of the cylinder joint can be moved in a plane normal to the joint axis. The ball‐and‐socket type has a seal around the equator of the ball. The exit tube of the ball‐and‐socket joint can be deflected 15°. The joints are packed with Teflon and they remain vacuum tight without causing excessive resistance to movement.

ISSN:0034-6748    

DOI:10.1063/1.1718532

出版商:AIP    

年代:1963

数据来源: AIP