摘要:

The expression of the functionf(&lgr;) defining the transmission of a mechanical monochromator with helical slots when the incident neutron beam is limited by a Soller collimator has been calculated. The influence of the total reflection from the collimator walls upon the functionf(&lgr;) was also studied. The paper describes a mechanical monochromator with helical slots devised for the suppression of the higher‐order Bragg reflections from a crystal. Measurements with this monochromator have served to check the calculations.

ISSN:0034-6748    

DOI:10.1063/1.1717348

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

An experimental method for measuring scintillation decay times of the order of nanoseconds is described. The method involves a repetitive time selection technique; i.e., in a sense, it is the electronic equivalent of the original Becquerel phosphoroscope. The complete circuitry is shown and some illustrative results are given.

ISSN:0034-6748    

DOI:10.1063/1.1717349

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A high pressure electrical cell is described consisting of tapered Carboloy pistons supported by a pyrophyllite pellet. The pistons are heavily work hardened. A calibration is obtained based on the barium transition at 59 kb, the bismuth transition at 90 kb, and an extrapolation of Bridgman's data. The pressure range is to 500 kb under favorable circumstances. New fixed points include a discontinuous rise in resistance of lead at 161 kb, a discontinuous rise in resistance of barium at 147 kb, a discontinuous rise in the resistance of rubidium at 193 kb, a maximum in the resistance of calcium at 370–75 kb, and a maximum in the resistance of rubidium at 425 kb. In addition, there is a discontinuous rise in resistance of iron at 133 kb which is consistent with the shock wave pressure point found at 131 kb and 37°C.

ISSN:0034-6748    

DOI:10.1063/1.1717350

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

The error of an ``immersed'' thermocouple due to heat leaks through the thermocouple wires has been estimated by means of a simple model. The error is shown to decrease exponentially with quantityL1/l1, whereL1is the ``immersion'' depth of the thermocouple andl1is a characteristic length depending on thermocouple parameters and the mode of heat transfer. It is shown that large errors generally arise if such a thermocouple is used in vacuum. Calculations for specific cases are given.

ISSN:0034-6748    

DOI:10.1063/1.1717351

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A new precision analyzer yields digital readout of probability or probability density for random waveforms at low audio frequencies. A preamplifier‐limiter conveniently increases a half‐volt slicing interval to 20 v or more, and a sample‐hold circuit permits the slicer to work slowly and accurately. The use of analog computer techniques permits convenient assembly of such instruments from inexpensive commercial plug‐in amplifiers and decimal counters. Some statistical theory is also presented.

ISSN:0034-6748    

DOI:10.1063/1.1717352

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A simple apparatus is described whereby any quantity of CO2up to several moles can be converted to methane in one step by catalytic hydrogenation using a ruthenium catalyst. The conversion is very rapid, the entire operation being carried out in about 3 hours. The over‐all yield is greater than 98%, and the methane is of high purity.

ISSN:0034-6748    

DOI:10.1063/1.1717353

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A device was constructed to photograph, on motion picture film, the etching behavior of zinc monocrystals. This apparatus consists of: (1) a transparent cell to hold sample and etchant; (2) a microscope with vertical illuminator; and (3) a motion picture camera driven by an electric motor. Several sequences of these pictures are reproduced, showing the continuous formation of spiral‐like etch patterns.

ISSN:0034-6748    

DOI:10.1063/1.1717354

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A sampling technique for generating Gaussian noise having a uniform power spectral density from approximately 0.1 cps to 5 kc is described. In principle one could extend the uniform power spectral density property at both ends of the spectrum. The only nonlinear circuit required to implement the technique is a simple high level sampling circuit. Random noise is periodically sampled in order to generate a pulse train having short pulse durations and statistically independent pulse amplitudes. The random pulse train is then applied to a low pass filter in order to produce a Gaussianly distributed output as is predicted by the central limit theorem of probability. The technique is also useful for studying periodic overlapping impulse noise.

ISSN:0034-6748    

DOI:10.1063/1.1717355

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A transducer has been developed to measure intense, transient heat levels. This transducer was designed to operate at close range in the heat environment generated by the Polaris missile at launch, but its use is readily adaptable to other similar requirements. Its main features as a transducer for measurement of thermal power are: (1) broad spectral sensitivity, (2) fast transient response (less than 1 msec for 63% response for the transducer described, while the inherent response time of the material is less than 12 &mgr;sec), (3) ability to withstand intense heat levels for short periods (600 w/in.2for 0.5 sec), (4) continued use for succeeding tests without need for recalibration, and (5) ease of installation, requiring a minimum in circuitry to record the heat levels. The transducer consists of a pyroelectric ceramic disk placed in a shock isolation mount. The ceramic disks used were either barium titanate or lead zirconate‐titanate, depending upon the thermal power level.

ISSN:0034-6748    

DOI:10.1063/1.1717356

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A description is given of a torsion pendulum and associated apparatus which have been employed in measuring internal friction and modulus changes due to dislocations. The pendulum is contained in an evacuated chamber. One specimen chamber is used for temperatures between 80° and 400°K and another for the range 290° to 1000°K. Decrements above 4×10−5have been observed at maximum strain amplitudes in the range 2×10−7to 2×10−4. Modulus changes may be measured within 1 part in 104. The specimens may be plastically deformedin situat temperature. A method is described for making measurements with an elastic torsional bias stress on the specimen.

ISSN:0034-6748    

DOI:10.1063/1.1717357

出版商:AIP    

年代:1961

数据来源: AIP