摘要:

An x‐ray diffractometer operating in vacuum has been designed and constructed to study metals sensitive to oxygen and nitrogen contamination at elevated temperature. The instrument operates in a vacuum of 2×10−6mm Hg in which the partial pressure of oxygen and nitrogen is several orders of magnitude lower than the total pressure. The specimen is heated by radiation from a resistance‐type furnace to 1200°C. With this instrument it is possible to obtain lattice parameters which are accurate to one part in forty thousand. The thermal expansion of titanium has been investigated up to 650°C. Between room temperature and 400°C the expansion coefficients in directions perpendicular and parallel to thecaxis are 9.41×10−6and 11.18×10−6/°C, respectively. For a random polycrystalline sample, the mean expansion coefficient is 10.0×10−6/°C.

ISSN:0034-6748    

DOI:10.1063/1.1717685

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A differential Pirani gauge has been developed for the measurement of the difference between the dynamic pressure and static pressure in a rarefied gas. Pressure differential to the accuracy of 0.01 &mgr; Hg can be maintained at 1 &mgr; Hg ambient pressure.

ISSN:0034-6748    

DOI:10.1063/1.1717686

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A new, high speed instrument for mapping the magnitude of a variable, such as temperature, vibrational amplitude, radiation, height, etc., at different positions on a surface is described. This instrument records the values of the variable as broken line segments on a two‐dimensional map. The position and length of each line segment represent the position and associated average value of the variable during the recording of that particular line segment. Visible density of the map is greater within regions of greater line length so that a qualitative picture is obtained at a glance. A quantitative measurement can be obtained from the map with a ruler. The present instrument was designed for application to heat transfer testing of nuclear fuel elements. However, the method may have applications in any field where it is desirable to superimpose a quantitative record on a qualitative picture.

ISSN:0034-6748    

DOI:10.1063/1.1717687

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A new focusing vacuum monochromator is described which incorporates features making available a simple and flexible double monochromator with a single control. The focusing is provided with a linear motion coupled to a nearly balanced linkage system which, coupled to the grating, satisfies the conditions of the Rowland mount. Entrance and exit slits, variable in width, are offset to either side of the plane of the Rowland circle, which is of one‐meter diameter. Transparent window valves allow isolating the lamp and detector chamber from the monochromator, maintaining vacuum while making visual or near uv checks through the instrument. A filter wheel is built in to obviate some of the difficulty with scattered radiation when the instrument is used singly. Two units have been built and mounted as to allow changeover to the double system. The latter has yet to be tried but, used individually, they make nice instruments.

ISSN:0034-6748    

DOI:10.1063/1.1717688

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A brief discussion is presented of the occurrence of spurious negative dissipation factors, which appear to correspond to negative resistances, in the measurement of three terminal low loss specimens. The origin of these negative values is traced to series resistance in the guard ring lead and a technique, involving the use of a four electrode specimen, is described which obviates the need for extremely low resistance electrodes and leads.

ISSN:0034-6748    

DOI:10.1063/1.1717689

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A system which automatically processes optical excitation data is described. This system is capable of producing data faster and of better quality than the old method. The apparent cross section for excitation by electron impact of a particular state is proportional to the light intensity of a radiative transition from this level divided by the product of the electron beam current times pressure. The light intensity is measured from the output current of a photomultiplier tube. When the pressure in the collision chamber is maintained constant, the apparent cross section is proportional to the ratio of photomultiplier current to electron beam current. This ratio is continuously computed by an analog divider while the electron accelerating voltage power supply is slowly swept through its range by a motor and gear reduction system so as to give a visual display of the excitation function on an oscilloscope. Permanent records of the function are made by photographing the trace. Absolute values of the excitation function can be obtained by calibration against a standard lamp. In order to suppress noise and light signals not originating in the collision chamber, the light beam from the collision chamber is square wave modulated; this then is converted into a sinusoidal wave by means of a tuned amplifier. This in turn is rectified by a phase‐sensitive detector which produces a dc voltage proportional to the signal light intensity. Circuits of the phase‐sensitive detector and modulation unit are presented.

ISSN:0034-6748    

DOI:10.1063/1.1717690

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A description is given of an apparatus for thermoluminescence experiments with the following special features: a constant rate of warming with time obtained through a suitable cam; light detection making use of phase rectification to reject noise; a special furnace to record ``glow current curves'' simultaneously. Also, the possibility of ``flattening'' the spectral response of a photomultiplier (between 2000 and 6000 Å) is investigated and the method of calculating a suitable optical filter is outlined. The performance of the apparatus was quite satisfactory, in spite of the rather simple and relatively inexpensive construction of each part.

ISSN:0034-6748    

DOI:10.1063/1.1717691

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A photoelectric detector system has been constructed which triggers a photographic flash lamp whenever a random, heavily ionizing event appears in a low pressure helium diffusion cloud chamber. 83–93% event detection efficiency for alpha‐particle recoils of at least 1.8 MeV kinetic energy occurring in a 10‐in. chamber was obtained by reflecting constant intensity light from the vapor condensation along the path of a charged particle recoil into a light pipe system arranged so that five electron multiplier phototubes each viewed about one‐fifth the chamber area. The equipment and operation are described and comments are made on the detection efficiency.

ISSN:0034-6748    

DOI:10.1063/1.1717692

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

In this paper we illustrate the design of rubber Soller slit collimators suitable for work in neutron spectrometry, at present in use at our Laboratory. Experimental tests performed on the collimators proved the rubber lamellae to be very effective as collimating material. The performance of these collimators is that to be expected on the basis of the ``Gaussian approximation'' applied to the attenuation of a neutron beam proceeding through the typical elements of a crystal spectrometer. The simplicity of construction and the performance of these collimators lead us to recommend their use in the field of neutron spectrometry.

ISSN:0034-6748    

DOI:10.1063/1.1717693

出版商:AIP    

年代:1962

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1717695

出版商:AIP    

年代:1962

数据来源: AIP