摘要:

This method is based on the application of Stokes's law, and its aim is to measure the coefficient of viscosity of transparent viscous liquids. The method is to allow air bubbles of maximum diameter to evolve by a manometer system from the bottom to top of a liquid placed in an adjacent adjoining glass cell.

ISSN:0034-6748    

DOI:10.1063/1.1741180

出版商:AIP    

年代:1948

数据来源: AIP

摘要:

An autographic stress relaxometer has been designed and constructed for studying the relaxation of the stress of a polymer film elongated to constant length. The force‐measuring element is a linear variable differential transformer which measures the distortion of a flexible steel ring and drives a recorder. The sample is elongated to the desired length automatically, and the correct length is maintained by means of a second differential transformer.

ISSN:0034-6748    

DOI:10.1063/1.1741181

出版商:AIP    

年代:1948

数据来源: AIP

摘要:

Practical information is given concerning the calibration of an instrument called the ellipsometer, which is used to measure thicknesses from one angstrom unit up to many thousands angstrom units of transparent films deposited on polished metal slides. The instrument is a half‐shadow instrument taking advantage of the ellipticity of polarized light reflected from film‐coated metallic surfaces. The half‐shadow is produced by depositing a different thickness of transparent material on the lower and upper part of the slides, or by evaporating directly on the lower part of chromium slides a thin layer of gold.

ISSN:0034-6748    

DOI:10.1063/1.1741182

出版商:AIP    

年代:1948

数据来源: AIP

摘要:

Measurements of the collection of electrons in BF3due to alpha‐particle ionization pulses are described. Comparison of pulse heights showed that 1.33 as much energy is required to produce an ion pair in BF3as in argon. The mean drift distance of an electron before capture in BF3at 76 cm varies from 1.25 cm at anE/Pof 5 (volts/cm/cm of Hg) to 7.25 cm at an E/P of 20. The drift velocity is observed and varies from 0.5×106cm/sec. to 2.5×106cm/sec. over the range of E/P used. The method of preparation of pure BF3is described.

ISSN:0034-6748    

DOI:10.1063/1.1741183

出版商:AIP    

年代:1948

数据来源: AIP

摘要:

The evidence for a general relationship between the speed of a diffusion pump and the molecular weight of the gas being pumped is reviewed. Experiments are described which show that when pumps are operated at their normal ratings, the speeds for hydrogen and helium may be considerably lower than for nitrogen, and it is established that this is due to the relative ease with which the lighter molecules diffuse from the fore‐vacuum to the high vacuum side of the jet. The speeds of diffusion pumps for different gases are not in fixed ratios, but in ratios which depend upon the fore‐vacuum pressure and the heat input to the pump boiler. At heater wattages exceeding twice normal the inverse (M)½law may sometimes be obeyed.

ISSN:0034-6748    

DOI:10.1063/1.1741184

出版商:AIP    

年代:1948

数据来源: AIP

摘要:

Characteristics of a gamma‐ray counter making use of a 3000‐megacycle gas discharge in a coaxial mode cavity resonator are described. The breakdown of a discharge in gases at these frequencies does not depend upon secondary effects. Since the breakdown is not controlled by positive ions, shorter breakdown and resolving times than those of a Geiger‐Mu¨ller counter are realized. In the high frequency discharge, ambipolar diffusion is the controlling factor in loss of electrons. A d.c. clearing field is superimposed on the a.c. field to eliminate electrons rapidly. A quenching agent is present to suppress electron emission from positive ion bombardment of the walls. The discharge is extinguished by reducing the magnetron power electronically. The plateau and sensitivity characteristics are similar to those of a Geiger‐Mu¨ller counter.

ISSN:0034-6748    

DOI:10.1063/1.1741185

出版商:AIP    

年代:1948

数据来源: AIP

摘要:

A description is given of a 1‐meter focus vacuum grating spectrometer for the infra‐red which is distinguished by its versatility and compactness of design. The vacuum container is tubular in form and all optical parts are mounted on a carriage which is readily retractable from the case for adjustment. A novel feature is the use of a sine screw drive which gives a linear wave‐length scale. A representative spectrum tracing is given.

ISSN:0034-6748    

DOI:10.1063/1.1741186

出版商:AIP    

年代:1948

数据来源: AIP

摘要:

Electron multipliers similar to the type described by J. S. Allen are being used as counters for low energy protons. Multipliers with electrodes made from soft beryllium copper count protons in the energy range 5 kev to 10 kev with an efficiency between 80 percent and 100 percent. Efficiencies of about 100 percent have been obtained with a radioactive alpha‐source and about 0.2 percent with a RdTh gamma‐source.

ISSN:0034-6748    

DOI:10.1063/1.1741187

出版商:AIP    

年代:1948

数据来源: AIP

摘要:

An automatic recording instrument which permits the direct comparison of the x‐ray diffraction patterns of two separate powder samples has been constructed through suitable modification of a commercial North American Philips Geiger counter x‐ray diffraction spectrometer. Some of the experimental results obtained with the new instrument are shown, and possible applications to qualitative and quantitative analysis indicated.

ISSN:0034-6748    

DOI:10.1063/1.1741188

出版商:AIP    

年代:1948

数据来源: AIP

摘要:

A new process has been developed for making fine mesh metal screens from glass masters. The master contains grooves corresponding to the screen wires. Metal is sputtered on the master, rubbed off the surface and the remaining metal in the grooves plated to form the screen. Screens from 200 to 1500 meshes per inch have been made with better than 50 percent transmission.A method of mounting the screens on a ring and subsequent tightening by heat treatment is described.

ISSN:0034-6748    

DOI:10.1063/1.1741189

出版商:AIP    

年代:1948

数据来源: AIP