摘要:

An improved instrument has been designed and constructed for the measurement of the linear decomposition and sublimation rates of solid substances. This instrument, which is provided with automatic recording devices, eliminates many of the shortcomings of the earlier prototypes and makes possible the determination of linear rates with a precision of 1%. Important new features include (1) an integral heating element and thermocouple assembly; (2) stainless‐steel and Plexiglas construction throughout; (3) heavy, solid‐copper electrical‐conductor supports for the heating element; and (4) a precision position‐sensing potentiometer. The use of cut strands of Plexiglas 55 is recommended for periodic standardization and calibration of the instrument.

ISSN:0034-6748    

DOI:10.1063/1.1716204

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A method of measuring the velocity amplitude of sound waves propagated in hollow tubes is described. A conducting quartz fiber is stretched across a cross section of the tube where the latter is pervaded by the magnetic field of a permanent magnet. The potential difference across the oscillating fiber is recorded on an oscilloscope. Velocity amplitudes have been measured for frequencies up to about 20 000 cps. An approximate relation is derived for the velocity amplitude as a function of the generated potential. It has been found that the method is much freer from disturbances over the above frequency range than a similar method in which the cooling effect by the sound wave on a current heated wire or fiber is used. Some observations made during the production of quartz fibers sputtered with gold are reported.

ISSN:0034-6748    

DOI:10.1063/1.1716205

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A vapor pressure apparatus has been developed which has certain manipulative and accuracy advantages over the well‐known isoteniscope. A reliable criterion for complete degassing is inherent in the apparatus. Since degassing is required only once for a series of determinations at various temperatures, the apparatus is well adapted where the amount of sample is limited. The useful temperature range of this apparatus is between the freezing point of mercury (−38.9°C) and the temperature at which the vapor pressure of mercury becomes appreciable (∼0.1 mm at 80°C). The apparatus may not be used if the sample reacts chemically with mercury.

ISSN:0034-6748    

DOI:10.1063/1.1716206

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

This paper describes a circuit for identifying protons, deuterons, and tritons. The identification is accomplished by obtaining the product of the energy and the initial space rate of energy loss. The product is modified so that each type of particle gives a unique result in the form of an output pulse having an amplitude nearly proportional to the mass of the particle. The circuit as given is capable of handling input pulses as narrow as 1 &mgr;sec, although shorter pulses may be used if some test features are eliminated. The multiplying operation is performed by QK‐329 tubes, using the principle of difference of squares.

ISSN:0034-6748    

DOI:10.1063/1.1716207

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Neutrons, produced by the reaction H3(d,n)He4, gave proton recoils in nuclear emulsion whose ranges were used to obtain a calibration point on the range‐energy relation. The range for 13.94±0.10‐Mev protons in emulsion of density 3.815 g/cm3is 995.9±2.1 &mgr;.

ISSN:0034-6748    

DOI:10.1063/1.1716208

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Efficiencies for monoenergetic gamma rays, emanating from an axial point source and incident on sodium iodide crystals of 1.5 in. diameter and of various heights, have been calculated by numerical integration methods. The crystals considered are right circular cylinders of heights 0.125, 0.25, 0.375, 0.50, 0.75, 1.5, 2.0, and 3.0 in. Seventeen photon energies in the range from 0.025 to 10.0 Mev were used. Fourteen distances from source to crystal face in the range 0.1 to 50.0 cm were used. Efficiencies for crystals of diameters other than 1.5 in. may be obtained from these results. Relative photoelectric efficiencies were not calculated.

ISSN:0034-6748    

DOI:10.1063/1.1716209

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A new instrument is described which enables nondestructive measurements to be made of film and overlay thicknesses. It utilizes the change in electrical impedance of a composite sample resulting from differences in the thickness of the material being measured to cut off a swept‐frequency oscillator at a frequency determined by that thickness. Operating frequencies from 200 kc to 20 Mc have been used with frequency‐sweep widths, or deviations, up to 10% to measure overlay thicknesses ranging from 0.00005 to 0.007 in. on composite samples in which the conductivity‐to‐permeability ratio of the base and overlay differ by at least a factor of two. Equations are developed to illustrate the conditions for which a reactance‐tube oscillator is employed in a unique manner to make the measurement automatic.

ISSN:0034-6748    

DOI:10.1063/1.1716210

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

An apparatus is described for the measurement of the energy and angular distribution of protons from (&ggr;,p) reactions. A method is presented for obtaining energy spread of 3% for protons of 3 to 15 Mev with a NaI scintillator of 1‐in. diam aperture. Energy calibration of the detector with monoenergetic protons gives an energyvspulse‐height line having an intercept of 0.46±0.10 Mev. The ratio of &agr; particle to proton energy for equal pulse heights is found to be 1.93±0.04 for 4.48‐Mev &agr; particles. A CsI scintillator, similarly mounted, yields an intercept of −0.17±0.15 Mev and an &agr;‐proton energy ratio of 1.66±0.07 for 5.3‐Mev &agr; particles. A modification of the phoswich to provide discrimination against electrons is described.

ISSN:0034-6748    

DOI:10.1063/1.1716211

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A two crystal x‐ray spectrometer which is able to scan continuously through Bragg angles of 10°–45° has been put into operation. The appropriate angular changes of the components, first pointed out by Allison, are effected through a planetary gear system. The unit in use is adapted to a Norelco goniometer.

ISSN:0034-6748    

DOI:10.1063/1.1716212

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A furnace for the growth of naphthalene (mp 80°C) and anthracene (mp 217°C) crystals from the melt by the Bridgman method is described. Crystals up to 15 mm diam by 3 ft may be grown. The furnace is simple in construction, and very convenient and reliable in operation.

ISSN:0034-6748    

DOI:10.1063/1.1716213

出版商:AIP    

年代:1958

数据来源: AIP