摘要:

The treatment of a soot coating with a hydrocarbon solvent compacts the coat so that fine lines may be drawn in it with little force. The line resolution available is somewhat better than that of ordinary photographic films. Enlargements up to fifty times the size of the original record may be usefully employed.

ISSN:0034-6748    

DOI:10.1063/1.1745533

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

A simple modification is described for converting a Perkin‐Elmer Infra‐Red Spectrophotometer to double beam operation for direct recording of percent transmissionversuswave‐length. A phase discrimination system is used, requiring no changes in the optical system, and no sacrifice of versatility or ease of prism interchange. A complete spectrum over the rocksalt region may be obtained in 25 minutes with good resolution, and with no attention from an operator. Samples as small as 1×6 mm can be studied. The system is readily adaptable to other spectrophotometers, including those in the visual and ultraviolet range, the only limitation being sufficiently rapid response by the detector.

ISSN:0034-6748    

DOI:10.1063/1.1745534

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

The first‐order focusing properties of a magnetic spectrograph similar to that of Siegbahn and Svartholm, but differing in that both source and collector lie outside the field, are investigated. The parameters of the analogous thick lens optical system are derived. General expressions for image distance, astigmatism, magnification, solid angle, dispersion, and resolution of lines with a spread in momentum are obtained. Factors affecting the compromise between intensity and resolution are discussed. The possibility of increasing resolution without loss of intensity by introducing some astigmatism is considered. Second‐order effects have not been included since they are thought to be of the same order as corrections for the fringing field. The first approximation proved adequate for the design of an instrument in which satisfactory focusing was obtained by simple empirical adjustments.

ISSN:0034-6748    

DOI:10.1063/1.1745535

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

A scintillation gamma‐ray spectrometer has been developed, which is of particular use for the study of isotopes of low specific activity and in which the energies of the gamma‐rays are identified from the pulse height distributions of the recoil electrons produced in an activated NaI crystal. The Compton distributions are easily recognized, and a study of the gamma‐radiation of Co60and I131shows a proportionality to exist between the total light output per scintillation and the energy of the corresponding secondary beta‐ray particle. The noise level of the RCA 5819 photo‐multiplier, as used in this test, corresponded to an energy on the pulse height scale of less than 20 kev. A brief description is given of a new type of differential pulse height analyzer which has been developed for work of this type.

ISSN:0034-6748    

DOI:10.1063/1.1745536

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

A simple oscillating circuit with a special feed‐back circuit is employed as a tool for the search for and detailed analysis of nuclear paramagnetic absorption lines. The sensitivity approaches the optimum for a given noise band width and particularly useful is the ease of conducting slow, continuous changes of frequency while recording the output data. Spectra having several components at scattered frequencies are thus displayed. Line shapes are unambiguously recorded because of the absence of sensitivity to dispersion. Using protons in water, or solutions containing Li7, the device can be used as a versatile and extremely precise meter for measuring magnetic field strengths in the range from about 100 to 25,000 oersteds with a minimum of auxiliary equipment.

ISSN:0034-6748    

DOI:10.1063/1.1745537

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

A technique is discussed for utilizing photographic plate detectors in an evacuated camera, containing an appropriate radiator, to make precise determinations of the range distributions of the disintegration products of slow neutron reactions. The same technique is applied to the problem of measuring neutron energies by making range measurements on the forward recoil protons projected by fast neutrons from a thin polyethylene radiator. As an indication of the accuracy attainable with photographic plates when used in this manner, determinations have been carried out for theQvalues of the Li6(n,&agr;)H3reaction and the B10(n,&agr;)Li7reaction.

ISSN:0034-6748    

DOI:10.1063/1.1745538

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

An integrator has been constructed which is capable of computing the yield of nuclear reactions produced by radiation of intensity that varies arbitrarily with time. By combining the appropriate number of such machines the yield resulting from a series of consecutive reactions may be found.While the emphasis in this paper is on applications involving the yield of radioactive isotopes produced by a pile or other source of radiation, the instrument may be used to calculate temperatures in thermodynamic problems, voltages and currents in electrical networks, and so on, wherever the quantity (x) to be determined is governed by the differential equationdx/dt=−&lgr;x+f(t),f(t)being a given function of the time, and &lgr; a known constant.

ISSN:0034-6748    

DOI:10.1063/1.1745539

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

The relative slow neutron sensitivities of &bgr;‐sensitive emulsions, x‐ray film‐indium foil combinations, and boron‐loaded plates were investigated. Since the detection efficiency depends upon the neutron energy, experiments were made with epithermal, thermal, and cold neutrons. &bgr;‐sensitive emulsions and x‐ray‐indium combinations are about equally useful for the detection of epithermal neutrons. B10loaded plates, which are best for the detection of thermal and cold neutrons, have the following advantages: very low neutron intensities can be measured by microscopic counting of &agr;‐tracks, neutrons can be counted in the presence of &bgr;‐and &ggr;‐radiation, the number of &agr;‐tracks is essentially independent of the development conditions, and a wide range of neutron intensities can be measured with a single plate.

ISSN:0034-6748    

DOI:10.1063/1.1745540

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

A microcalorimeter suitable for measuring the energy of easily absorbed nuclear radiations is described. The calorimeter is an isothermal type operating at the temperature of liquid nitrogen and using the rate of vaporization of nitrogen under constant pressure as a measure of the heat input. The calorimeter is fairly simple to construct and to operate and has a short equilibration period. Heat inputs to the calorimeter as low as 7×10−6cal./sec. can be measured with an accuracy of one percent.

ISSN:0034-6748    

DOI:10.1063/1.1745541

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

A study of plateau slopes of self‐quenching Geiger‐Mu¨ller counters shows that no quenching vapor tested produced flat characteristics. On the assumption that the slopes were given by spurious counts arising from the gas discharge phenomena, a study was made of the controlling factors. Neither the quenching gas nor the vehicular gas positive ions were found to be significant. A study of the negative ions produced by molecular dissociation of the quenching gas at the cathode, and electron attachment in the body of the gas shows that these factors are directly correlated with the slopes of the plateau characteristics.

ISSN:0034-6748    

DOI:10.1063/1.1745542

出版商:AIP    

年代:1950

数据来源: AIP