摘要:

An apparatus for the study of the instability of a layer of mercury heated from below and subjected to the simultaneous action of a magnetic field and rotation is described. The equipment is designed to examine the mode of convection and the dependence of the critical Rayleigh number (=&agr;g&bgr;cd4/&kgr;&ngr;, wheregdenotes the acceleration due to gravity, &bgr;cthe critical adverse temperature gradient, &agr; the depth of the layer, &kgr; the thermometric conductivity, &ngr; the kinematic viscosity, and &agr; the coefficient of volume expansion) for the onset of instability on the values of nondimensional parametersQ1(=&sgr;H2d2/&pgr;2&rgr;&ngr;, whereHis the strength of the magnetic field, &sgr; the electrical conductivity, and &rgr; the density of fluid) andT1(=4&OHgr;2d4/&pgr;4&ngr;2, where &OHgr; denotes the angular velocity of rotation), the features proven to be essential in such studies.By using a reconditioned cyclotron magnet as a part of the experimental arrangement, this apparatus covers wide ranges of parametersQ1(from 10 to 106) andT1(from 105to 1010).Typical results that can be obtained by this apparatus are discussed with a few illustrative examples.

ISSN:0034-6748    

DOI:10.1063/1.1715950

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

TypeE1 Ilford emulsions loaded with specks of Li6glass were studied for the measurement of neutron spectra from ∼50 to 1000 kev. The method is independent of the neutron directions. Resolutions of about 200 kev were obtained. Calibrations were made by exposure to monoergic neutrons at several energies, and the method was tested by neutron spectra determined independently from fission and ``long counter'' data. The theory of the reduction of track data to neutron spectra is given. The results look promising for application to the measurement of neutron spectra in fast critical assemblies and for similar problems.

ISSN:0034-6748    

DOI:10.1063/1.1715951

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A method is presented for observing electron resonance absorption on an oscilloscope screen by usingbotha magnetic field modulation and a klystron frequency modulation. This is distinguished from the usual system of keeping the klystron frequency fixed and modulating the magnetic field by the fact that the apparent line width observed on the oscilloscope is narrower than that observable by a single (magnetic or frequency) modulation. An equation is derived relating the apparent line width (double modulation) to the true line width (single modulation). Reductions by a factor of 17 can be easily obtained. As a result paramagnetic absorption lines ordinarily too wide to be observed within the width of the resonant cavity containing the sample can be observed within the cavity resonance. It is believed that this double modulation system might be advantageous in oscilloscope searching for new paramagnetic absorptions.

ISSN:0034-6748    

DOI:10.1063/1.1715952

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

This paper describes a method of fabricating cavity resonators having very low temperature frequency dependence and also describes a means of building pressure insensitive cavity resonators. Simple schemes of compensation using invar walls with steel or brass end plates forTE011cavity resonators are found to be unsatisfactory due to hysteresis type effects. With the arrangement described fixed frequency resonators are obtained having stable temperature‐frequency coefficients less than ±0.2 ppm/°C and pressure‐frequency characteristics of less than 0.003 ppm/mbar.

ISSN:0034-6748    

DOI:10.1063/1.1715953

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A nuclear magnetic resonance spectrometer has been constructed and its performance at 12 and 43 gauss is discussed. The magnetic field is obtained with an end corrected solenoid powered by batteries. The best resolution obtained is 10 microgauss at 12 gauss and 20 microgauss at 43 gauss over a 30 cm3sample. A twin‐T bridge and a synchronous detector are employed for the nuclear resonance detection. Some of the measurements for which this instrument is suited are described and the results of relaxation time measurements for ethanol‐water mixtures are presented.

ISSN:0034-6748    

DOI:10.1063/1.1715954

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

An instrument that quantitatively records and integrates solar radiation has been developed and put into operation. This instrument, called a spectroheliometer, records and integrates automatically from sunrise to sunset. Total radiation is measured in addition to sampling radiation in five distinct spectral regions: 3095–3260 A, 3410–3630 A, 3865–4150 A, 4420–4900 A, and 5385–6295 A. Solar power in these bands as low as 10−5watt per cm2has been quantitatively measured. The band widths intercepted are accurate to ±15 A with an estimated ±5 to 8% maximum error in determining absolute solar power and energy.

ISSN:0034-6748    

DOI:10.1063/1.1715955

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A large‐volume high‐pressure proportional counter used in a study of the ionization energy losses of mu mesons is described. The details of construction for operation at approximately one hundred atmospheres pressure are given.

ISSN:0034-6748    

DOI:10.1063/1.1715956

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A device for the precise measurement of small (<10°) liquid‐solid contact angles is described. The technique is a variation of the tilting plate method. Measurements of the contact angle of benzene on polyethylene at 25°C indicate that a precision of ±0.1° is readily attainable.

ISSN:0034-6748    

DOI:10.1063/1.1715957

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

The possible advantages are discussed of a resistance thermometer made with a metallic element of low Debye characteristic temperature and very high purity, e.g., ratio of residual resistance to ice‐point resistance of 10−4. Measurements on the electrical resistance of commercially available indium wire from 3 to 300°K suggest that it may be a useful thermometer as it remains temperature sensitive down to its superconducting transition at 3.41°K, because of its high purity and &tgr; ∼100°K.

ISSN:0034-6748    

DOI:10.1063/1.1715958

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

An all metal apparatus designed for density measurements on liquefied gases is described. The metal construction enabled its use with corrosive materials, and also allowed measurements to be made to moderate pressures. It consists of a pycnometer, temperature control device, and gas handling system. While this apparatus was particularly designed for density work it was used for vapor pressure determinations with slight modification. The design and construction is detailed and its use with liquid fluorine outlined.

ISSN:0034-6748    

DOI:10.1063/1.1715959

出版商:AIP    

年代:1957

数据来源: AIP