摘要:

The instrument described here is designed to measure, indicate, record, and control the level of liquefied gases inside a closed vessel. It is especially designed for use at low temperatures with liquefied gases such as nitrogen, oxygen, hydrogen, and helium. It operates on a capacitance principle, and makes use of the difference in dielectric constants of the liquid and vapor. The sensing element is a cylindrical capacitor whose capacitance is a function of the height of the liquid column. The sensing capacitor is one element of an automatically balanced bridge which both indicates and records the liquid level. An over‐all accuracy of ±1.0 percent has been obtained. The sensitivity is adequate for use where the difference in dielectric constants of the liquid and vapor is 0.05 or greater. The instrument also incorporates a control function and supplies a controlled air pressure to a pneumatically operated valve for maintaining the level at a predetermined point.

ISSN:0034-6748    

DOI:10.1063/1.1771000

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

A rotating mirror is the basic element in the highest‐speed cameras of both the framing and sweeping image types. The factor of merit of these cameras is determined mainly by the peripheral speed of the mirror. The turbine drive described here will spin the best‐quality steel mirror up to its bursting speed. Flat mirrors with faces 17.5 mm wide by 21 mm perpendicular to the rotational axis are operated regularly at 10 000 rps. A camera designed to use these turbines and to take pictures at the rate of 3 500 000 fps, (frames per second) with an exposure time of 0.1 &mgr;sec, is illustrated.

ISSN:0034-6748    

DOI:10.1063/1.1771001

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

A radiometer is described which like the switching type cancels gain fluctuation effects by a comparison method, but which has approximately 3 db greater sensitivity.

ISSN:0034-6748    

DOI:10.1063/1.1771002

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

In the determination of crystal structures from x‐ray data, mathematical equations are frequently used for which there are no physical analogs available. The introduction of physical analogs is advantageous because they assign a physical significance to the mathematics and, also, because they make possible the use of apparatus which either aids or replaces the long computations. In this paper a description is given of an optical device which produces as photographic records the results of the mathematical processes known as convolutions. Since there are several kinds of convolutions, and since the device is very versatile, the particular types of convolutions for which the apparatus is adaptable are the well‐known Patterson projection and, also, the mixed projections. The illustrations that are furnished should aid in the understanding of some of the more recently developed methods of structure determination. The apparatus is constructed of materials readily available in any laboratory.

ISSN:0034-6748    

DOI:10.1063/1.1771003

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

A scintillation pair spectrometer involving the use of three NaI(Tl) crystals has been developed which has a high rejection of all unwanted pulses. As in the usual scintillation pair spectrometer, the gamma rays pass into a center crystal and the pair events are selected by detecting the two annihilation quanta in two side crystals. High rejection of unwanted coincidences is obtained by using a cathode‐ray tube differential discriminator set on the photoelectron peaks of the annihilation quanta in the side crystals, along with coincidence circuits of moderately good resolution (0.15 &mgr;sec). In this way pair distributions from Na24(1.38 and 2.76 Mev) and Co60(1.17 and 1.33) have been observed with almost no background. The apparatus has also been found useful in many other scintillation counter applications involving energy differentiation and coincidence counting.

ISSN:0034-6748    

DOI:10.1063/1.1771004

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

It is shown that the push‐pull mode of oscillation of a conventional two‐dee cyclotron can be described in terms of a ground potential surface between the dees. Unbalance in dee voltages arising from changes in capacitance or inductance of one dee system can be interpreted as a shift of the position of the ground surface. The predictions of the theory have been checked experimentally. The effects on a self‐excited type of cyclotron oscillator are discussed. The principal value of the concept is that it enables the cyclotron operator to predict easily the electrical implications of a particular adjustment.

ISSN:0034-6748    

DOI:10.1063/1.1771005

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

The spectrum of pulse heights from a stilbene scintillation counter exposed to approximately monoenergetic neutrons is subject to a number of inherent distortions. It is shown that the neutron energy and intensity can be determined rather simply by proper analysis of the experimental data. The reduction of background by various types of collimation is described.

ISSN:0034-6748    

DOI:10.1063/1.1771006

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

A cathode‐follower circuit of very high‐input impedance using ordinary tubes is described. At the coaxial cable input, the capacitance to ground is less than 0.3&mgr;&mgr;f from below 100 to above 5×104cps. The magnitude of the input resistance is more than 4×109ohms from below 100 to 4700 cps; above 3200 cps, its sign is negative and it decreases with frequency. A comparison of theoretical and experimental results is given and a stable modification of the circuit discussed with which it is possible to obtain zero or negative input capacitance.

ISSN:0034-6748    

DOI:10.1063/1.1771007

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

An electronic integrator suitable for measuring ionization currents down to 10−11ampere is described. The instrument simultaneously displays both the instantaneous value of the current and the total charge received. Automatic recycling is achieved with the aid of a contact mounted on the movement of a standard meter. Substantial lengths of coaxial cable with standard connectors may be connected to the input without producing unduly large leakage currents or changing the calibration, so that remote operation of the integrator is feasible.

ISSN:0034-6748    

DOI:10.1063/1.1771008

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

A stable, convenient system for low‐level counting of radon is described. The system permits a precision of ±1 percent with an efficiency of about 80 percent. The lower limit of measurement is the amount of radon in equilibrium with about 10−14gram of radium. A vibrating reed electrometer is used to amplify slow pulses obtained from an ionization chamber operated at 300 volts. The cumulative pulse count is recorded by a mechanical register following amplification of the output of the electrometer. Special care in construction and selection of the ion chamber materials permits an alpha background as low as 15 cph for a 4‐liter volume. Chemical pretreatment of the gases is unnecessary for most samples.

ISSN:0034-6748    

DOI:10.1063/1.1771009

出版商:AIP    

年代:1954

数据来源: AIP