摘要:

A low‐temperature x‐ray goniometer for use between liquid nitrogen temperature and approximately −100°C has been designed for use with a Weissenberg camera, General Electric powder camera, or a Geiger counter system. The crystal is mounted on a goniometer head inside a vertical cylindrical stainless‐steel Dewar, and is irradiated through a polystyrene tip at the lower end of the Dewar. The crystal is cooled by conduction through the goniometer head, which is silver‐soldered to the base of a liquid nitrogen chamber inside and concentric with the outer wall of the Dewar. The Dewar vacuum is maintained by an oil diffusion pump and a forepump, through a rotating seal and the post which supports the goniometer.The Weissenberg camera mounts on a carriage and is driven by a 60‐rpm reversing motor which also rotates the Dewar and crystal.The carriage driving screws may be uncoupled from the motor shaft, and a Geiger counter spectrometer may be mounted on the carriage in place of the camera. The carriage is also adaptable for holding a G.E. powder camera.A General Electric CA‐7 x‐ray tube mounted horizontally supplies the x‐ray beam.

ISSN:0034-6748    

DOI:10.1063/1.1770608

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A new type of scintillation spectrometer is described. It is designed to suppress signals arising from incident photons that are not completely absorbed in the primary detecting NaI(Tl) crystal. When an undesired signal is detected by means of a cluster of NaI(Tl) crystals surrounding the primary crystal, it is removed through the discriminating action of an anticoincidence electronic gate. Under conditions of good discrimination, this type of arrangement offers the advantage of yielding the gamma‐ray spectrum directly without any interpretation of results which might become laborious, particularly if the incident gamma radiation has a complex spectrum. Results are presented that illustrate the discrimination action of the device by means of photographic representations of the scintillation gamma‐ray spectra of Cs137and Na22.

ISSN:0034-6748    

DOI:10.1063/1.1770609

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A recording system is described which measures the electromotive force generated by slowly responding linear‐type thermopiles. A means is provided for compensating electrically for the zero signal drift so that the thermopile may be used conveniently under rather unstable thermal surroundings. A twin phototube arranged in a feedback type amplification circuit is used as a receiver for the light beam reflected from the mirror of a sensitive galvanometer connected in series with the thermopile. The current from the feedback circuit which automatically keeps the galvanometer essentially at its zero signal position is directly proportional to the thermopile signal. This current may be measured by a conventional microammeter or an automatically recording meter if desired.

ISSN:0034-6748    

DOI:10.1063/1.1770610

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The use of cylindrical mirrors made of bent plate glass results in a rear‐illumination system for cloud chambers that is compact and gives good contrast with more than adequate light intensity. A small balloon‐borne cloud chamber using this system requires only 6 j of energy for the light, using a lens opening off/40. The mirrors are made in an inexpensive way from plate glass by heating the glass and allowing it to sag into a mold of the proper shape.

ISSN:0034-6748    

DOI:10.1063/1.1770611

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

In order to be able to study effectively the flammability characteristics of mixtures of hydrocarbon vapors and air, a surge generator, oscillograph, and associated equipment have been designed to deliver suitable ignition sparks and to study their characteristics. The duration, energy content, and wave shape of these sparks have been measured and studied to determine the effect that these spark parameters might have on the ignition process.

ISSN:0034-6748    

DOI:10.1063/1.1770612

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A current integrator is described which will integrate currents in the range 10−10to−5ampere. It is shown that the circuit is inherently capable of a better performance than previous integrators. The instrument can be easily calibrated and has a stability of the order of 0.1 percent.

ISSN:0034-6748    

DOI:10.1063/1.1770613

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A new method has been developed for studying the effect of temperature on the crystal structure of metals and alloys. In this method, a long wire specimen is held for a desired period of time in a known thermal gradient and is subsequently quenched and examined at room temperature by x‐ray diffraction. A special x‐ray camera is used, by means of which any point along the length of the specimen can be irradiated. The diffracted rays are registered on a cylindrical film in the usual way. This technique offers substantial savings in treating time and has the advantage of subjecting the specimen to all temperatures within the range of treatment.The method has been applied to the study of ordering phenomena in several binary systems. Debye‐Scherrer evidence for the existence of divariant equilibrium between ordered and disordered phases, has been found in several alloys of nonstoichiometric composition. A study of the copper‐gold system has yielded data which allow the quantitative location of the (order+disorder) field boundaries near CuAu.

ISSN:0034-6748    

DOI:10.1063/1.1770614

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Four different instruments are described in this paper. Three have been or are being used in studies of electron ejection from metal surfaces by positive ions. A fourth has been used in the study of the ion optics employed and in studies of ionization and dissociation of diatomic molecules by electron impact. Basic design features and performance characteristics are discussed with particular emphasis placed upon the steps taken to assure proper ion‐beam characteristics at the final focus. Experimental procedures are also described among which those having to do with the vacuum and adsorption of gas on the target are considered to be especially important. Auxiliary apparatus and the determinations of contact potential and work function are discussed briefly. The interpretation of data obtained with these instruments is also examined.

ISSN:0034-6748    

DOI:10.1063/1.1770615

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

An electric hygrometer of the Dunmore type has been constructed so reduced in size as to fit inside the end of a hypodermic needle. A special indicating circuit is required because of the small current permissible across the hygroscopic film. Relative humidities associated with surfaces as small as 0.001 square inch have been measured.

ISSN:0034-6748    

DOI:10.1063/1.1770616

出版商:AIP    

年代:1953

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1770617

出版商:AIP    

年代:1953

数据来源: AIP