摘要:

Quantitative considerations of the effects of fluid motion on the cooling of self‐heated thermistors are essential to their efficient application in many instruments. The investigations reported here were undertaken for the purpose of ascertaining these effects and obtaining useful expressions with which to describe them. Expressions for the time constant, sensitivity, and dissipation factor are derived, and their significance is demonstrated in qualitative considerations of practical instrumentation problems.

ISSN:0034-6748    

DOI:10.1063/1.1717658

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The electrical resistivity of polycrystalline lead and the resistance of soldered contacts to the lead have been measured at 1.16 and 4.2°K in magnetic fields up to 7000 gauss. The thermal conductance of a simple lead heat switch was measured in both the normal and the superconducting states in fields up to 3000 gauss in the temperature range of 0.15–0.5°K. Assuming the best linear fit for the temperature dependence for the conductivity of the normal state, the ratio of the thermal conductance of the switch (lead plus contacts) in the 3000‐gauss normal state to that of the superconducting state was found to be (T/K°)−2.3, however, the numerical factor varied strongly with magnitude and orientation of the field. As a magnetic field was slowly removed from the superconducting lead, heating corresponding to the irreversible exit of trapped flux was observed. The design of lead thermal switches is discussed.

ISSN:0034-6748    

DOI:10.1063/1.1717659

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A modified piezoelectric device is described for measuring dynamic and static forces which is simpler and more sensitive than the standard devices. The standard piezoelectric interferometers, piezocapacitance devices, etc., utilize displacement of the resonant frequency of piezoelectric substances under applied loads; the present device makes use of the relation between the magnitude of a dynamic or static force applied to a piezoelectric specimen and its electromechanical coupling factor. Comparison with the standard devices shows: sensitivity of the present device is about 2 magnitudes higher in case of small forces (tenth of grams) and sensitivity is equal in case of large loads (tons).

ISSN:0034-6748    

DOI:10.1063/1.1717660

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A Be ``single crystal'' filter was used to eliminate higher‐order contamination in the thermal neutron energy range from the monochromatic beam of a single crystal neutron spectrometer employing Ge(111) as monochromator. It is shown that 6.4‐cm Be crystal filter is sufficient to suppress higher order contamination to less than 0.5% in the neutron energy range ∼0.02–0.06 ev and the attenuation of the primary beam is a factor of 2–3 in this energy range.

ISSN:0034-6748    

DOI:10.1063/1.1717661

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

An electrochemical device for measuring oxygen in gases is described which utilizes a gold indicator electrode and a cadmium reference. Filled with electrolyte and encapsulated with a thin polyethylene membrane, this cell gives a current proportional to the oxygen partial pressure. The unit requires no power or polarizing voltage and can operate unattended for relatively long periods of time. Functional characteristics of the device are discussed in order to suggest potential applications.

ISSN:0034-6748    

DOI:10.1063/1.1717662

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The measured characteristics (pressure‐voltage, current‐voltage, and efficiency) of an ion drag pump using razor edge emitters are reported and comparisons made with theory. The advantages of this pump over one using corona point emitters are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1717663

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Imaging techniques and apparatus have been developed for measurement of thermal conductivity of small size samples at temperatures from 1000°C to the melting point of the material. Details of the method for heating the sample in an electric arc imaging furnace, measuring the temperature distribution over the sample surface with an optical pyrometer, and measuring the heat flux leaving the back of the sample with a thermopile are given. A computational procedure is described suitable for machine computer use.

ISSN:0034-6748    

DOI:10.1063/1.1717664

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Construction and performance criteria of a stroboscope, based upon the pulsed operation of Hall effect generators, are presented with special reference to the properties of evaporated thin films of indium antimonide. A high‐frequency periodic magnetic field of arbitrary waveshape is converted by the stroboscope into a low‐frequency replica of the input signal. This is accomplished by sampling the magnetic field by means of synchronized narrow rectangular current pulses applied to the Hall plate. These current pulses are phase modulated allowing the magnetic field to be scanned point by point thus producing an output voltage which, after integration, is a lower frequency synthesis of the input signal. The advantages of the stroboscope include a linearity between input and output signals to better than 1% and good frequency response between 100 cps and 5 Mc. Hall effect stroboscopes built in this manner also have superior properties as noise discriminators. They will not respond to ambient magnetic fields, except those of the same frequency as the input signal or its harmonics. The advantages of pulsed operation of thin film Hall effect devices in semiconductors with charge carriers having a short relaxation time are shown to be greatly improved sensitivities to small magnetic fields because of the greater peak current densities applicable to the film without any attendant Joule heating.

ISSN:0034-6748    

DOI:10.1063/1.1717665

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

An analysis method for the output of a multichannel analyzer is described. The data are fitted by a least squares computer program that will determine the area under Gaussian distributions which may be only partially resolved or separated. Mathematical considerations are discussed. Examples of various fits are shown illustrating the capabilities and some of the operational difficulties involved.

ISSN:0034-6748    

DOI:10.1063/1.1717666

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A direct‐reading magnetometer, based on the Faraday effect and designed to measure steady magnetic fields ranging to 180 kilogauss, is described. The magneto‐optic rotations are produced in a block of optical glass 1.23 cm thick and are read by a phase comparison technique. Rotations of the order of 0.1°(= 100 gauss) can be detected.

ISSN:0034-6748    

DOI:10.1063/1.1717667

出版商:AIP    

年代:1962

数据来源: AIP