摘要:

A holographic interferometer suitable for the precise measurement of heat transfer is described. In this instrument interference occurs between beams which have traversed the same optical components and hence these components need not be of high quality. Compared with the conventional Mach‐Zehnder interferometer, the present instrument is less expensive and simpler to construct, and yet the two interferometers yield comparable accuracy. For illustration, the holographic interferometer is used to study the free convection thermal boundary layer on a heated isothermal vertical flat plate. The results are in good agreement with an existing theory.

ISSN:0034-6748    

DOI:10.1063/1.1685000

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A relatively simple and versatile differential scattering molecular beam apparatus for nonalkali systems is described in which a low temperature semiconductor bolometer is used as detector. Details are given on vacuum facilities, beam sources, and detector element. A few examples of measurements on rare gases are given and the possibilities of the apparatus discussed.

ISSN:0034-6748    

DOI:10.1063/1.1685001

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A device, based on the heat pipe principle, is described in an application as a thermal switch at very low temperatures. The presence or absence of a high purity liquefied gas in the heat pipe is the basis for the switch being on or off.

ISSN:0034-6748    

DOI:10.1063/1.1685002

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A technique for preparation of cathodes consisting of a tantalum LaB6coated ribbon has been successfully tested. The cathode has shown good performances in high density gas discharge tube (as ion lasers) operations.

ISSN:0034-6748    

DOI:10.1063/1.1685003

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Single‐ and double‐channel laser triggered switches in high pressure gas have been designed and operated in the voltage range from 1 to more than 3 MV. Jitter times of <1 to 3 nsec were observed in most cases. Gas pressures of 10.5 and 21 kg·cm−2were used. The gases were either 100% nitrogen or various mixtures of N2, SF6, and Ar. Significant accomplishments were (1) the simultaneous firing of four stages of a Marx generator by an optically divided laser beam, (2) up to 40% reduction in the risetime observed in the output pulse from a multimegavolt dc generator when switched into a load through two simultaneously laser triggered channels, and (3) the design and operation of a laser triggered, dc charged switch at more than 3 MV with subnanosecond jitter.

ISSN:0034-6748    

DOI:10.1063/1.1685004

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

An apparatus is described for measuring the diffuse reflectance and/or fluorescence of small (15–30 mg) granulated or powdered samples of solid materials. The sample rests in the horizontal plane, thus requiring no special mounting procedure. Input light is provided by a quartz‐iodine lamp through a monochromator having a range of wavelengths from 350 to 800 nm. A photomultiplier measures the light scattered from the diffusely reflecting walls of the sample chamber. The optical absorption spectrum of &ggr;‐irradiated lithium fluoride powder is shown as an example of performance, obtained in a study of the possible applicability of LiFM‐,R2‐, andN2‐band absorption for radiation dosimetry purposes.

ISSN:0034-6748    

DOI:10.1063/1.1685005

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A concentric heat pipe oven is described, which serves as an oven with a highly homogeneous temperature distribution as required by such applications as crystal growing, thermal treatment of materials, and radiation standards. The design is simpler than conventional ovens with similar temperature stability and homogeneity. The temperature control is replaced by a pressure control. This device is used in a modification of the heat pipe oven that generates homogeneous mixtures of a vapor (such as a metal vapor) and an inert gas at well defined total pressure, partial pressure, temperature, and optical path length. All the features of the previously described heat pipe oven are maintained with the additional option that allows quantitative total and partial pressure measurements without relying on vapor pressure curves.

ISSN:0034-6748    

DOI:10.1063/1.1685006

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The sensitiveness of a balance is directly proportional to the lever arm and inversely proportional to the product of the distance of the axis of oscillation to the center of mass by the mass of the moving system. However, as the load increases, the central knife's edge and its support deform elastically, changing the line of contact to a surface with a larger frictional torque, decreasing the responsiveness of the balance to small increments of load. This is the main cause of loss of responsiveness as the load increases. It is possible to change the sensitiveness by means of a chain hung from an annular knife placed below the central knife, the other end of which can be raised or lowered. The elastic deformation of the central knife's edge and its support is avoided by turning the central knife's edge upward and making it touch lightly hard surfaces, supporting magnetically the weight of the moving system, thereby practically maintaining zero load responsiveness for all loads. By means of a servomechanism the beam is kept balanced and a suppressed zero record is made with a pen on a wide roll of paper which moves at uniform speed. It is thus possible to register the loss of mass of higher mammalians due to loss of water and metabolic processes.

ISSN:0034-6748    

DOI:10.1063/1.1685007

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A simple, quick, contactless, and accurate method for the measurement of electrical conductivity of a semiconductor slab is presented in this paper. The method is based on the study of transmission of circularly polarized TE11mode of microwave propagation in circular waveguide. Conductivity of n‐type germanium and silicon samples and its temperature variation in the range 293–140 K have been successfully studied.

ISSN:0034-6748    

DOI:10.1063/1.1685008

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A unique computer controlled automatic system for measuring the conductivity and Hall effect in semiconducting samples is described. The system features a small process control computer which runs a temperature programmable liquid helium Dewar, a magnet, and a data acquisition system. Fifty temperature points can be preprogrammed in any desired distribution over the range 4.2–400 K. The control computer ensures that the system is virtually foolproof in terms of operator blunder and system malfunction. Data acquisition is on punched paper tape with hard copy output. Data, converted from paper tape to cards, are analyzed by a high speed computer. Turnaround times (from sample loading to full analysis of data) of as low as 6 h have been achieved.

ISSN:0034-6748    

DOI:10.1063/1.1685009

出版商:AIP    

年代:1971

数据来源: AIP