bluuebunny/crossref_metadata_2025 huggingface dataset:
An Apparatus for Determining the Transmission of Slow Electrons Through Thin Collodion Films
Authors: Ference M. , Stephenson R. J.
Published: February 2005

An apparatus is described for determining the transmission of slow electrons through thin collodion films. The range in accelerating voltages used was from 800 to 34,000 ev and the film thicknesses from 10−3 to 7×10−6 cm.
A Generating Voltmeter of Extremely High Sensitivity
Authors: Greibach E. H.
Published: February 2005

The purpose of the present paper is to describe an instrument which is capable of measuring small d.c. voltages (of the order of 10−3 volt full scale) without drawing any but an infinitesimal current, and which at the same time is as easy to use and as reliable as an ordinary d.c. instrument. When properly shunted, it can be used as an accurate, direct indicating ammeter for measuring currents of the order of 10−12 ampere full scale.
High Intensity X-Ray Monochromator
Authors: Kirkpatrick Paul
Published: February 2005

A monochromator for concentrating radiation of wave-length 0.71A has been made by disposing about a common symmetry axis a group of eight rocksalt crystals each plastically deformed and ground to the spindle surface curvature required for focusing radiation from a point source to a point image. The maximum monochromatic intensity at the focus exceeds the intensity of the total radiation from the molybdenum-target source when received directly at the same location.
A Photoelectric Star Counter
Authors: McCuskey S. W. , Scott R. M.
Published: February 2005

A new device which performs the photometry of stellar images on a photographic plate and which segregates the images according to size is described. The star images to be photometered are manually shifted into the optical focus of the device. The results of tests indicate greater accuracy in counting than is attainable by visual means. No systematic deviations of the counts so obtained from catalog compilations or from the results deduced visually were found.
A Speed Control for Sector Disks or Similar Equipment
Authors: Lee R. H. , Crisp L. R.
Published: February 2005

An apparatus is described by means of which the speed of a sector disk or other reasonably light equipment of similar nature may be accurately controlled and the speed read directly from a set of dials.
The Use of a McLeod Gauge in Measuring Small Volumes
Authors: Keevil N. B. , Errington R. F. , Newman L. T.
Published: February 2005

Some precautions necessary for accurate measurements of volume with the McLeod gauge are discussed, particularly the necessity of determining the capillary depression from each set of readings. Applications to the determination of small quantities of helium are given.
An Infra-Red Absorption Cell for Volatile Liquids
Authors: Gildart L. , Wright N.
Published: February 2005

A simply constructed absorption cell with rocksalt windows is described which is capable of sealing against a pressure of 20 lb. per square inch. The use of lead gaskets having surfaces amalgamated with mercury makes unnecessary the use of organic waxes or sealing agents.
Single Casting Magnet Cores
Authors: Jordan Edward B.
Published: February 2005

The magnets used in the new University of Illinois mass spectrograph are described. Included is a discussion of the advantages and disadvantages of single casting cores as compared to the usual built-up multiple section type of core. Core designs for mass spectrographic purposes and possible limitations as to size are suggested. Plots showing the experimental and theoretical fringing flux distributions for Armco iron, and also the general stray field distribution around the larger magnet, are included.
Operation of Electrostatic Photo-Multipliers
Authors: Winans R. C. , Pierce J. R.
Published: February 2005

This paper discusses the operation and characteristics of electrostatic photo-multipliers, using the Western Electric D-159076 photo-multiplier as an example to illustrate specific points. The following subjects are discussed: description of operation, advantages and applications, typical operating conditions, variation of sensitivity with voltage, hum due to ripple in power supply, effect of unequal voltage division, output impedance, linearity of response and fluctuation noises.
A Large Recording Spectrograph for the Infra-Red to 15μ
Authors: McAlister E. D. , Matheson G. L. , Sweeney W. J.
Published: February 2005

Heretofore the rocksalt prism spectrograph has been used mainly as a ``survey instrument'' to locate regions of spectral absorption over a wide wave-length range. When a resolving power equivalent to the theoretical limit of a large prism (varying from 1 cm−1 at 6μ to 0.3 cm−1 at 15μ) was obtained with the present instrument its scope of usefulness was found to be greatly increased. The improvements in detail necessary to achieve this practical balance between prism size, aperture and sensitivity of detection are described.
A Simple Method for Measuring Steady Currents of Brief Duration
Authors: Bennett Ralph D.
Published: February 2005

A method is described for the point-by-point measurement of volt-ampere characteristics of substantially resistive circuit elements at currents and voltages well above those which the element can tolerate continuously. Only standard indicating instruments are used. Examples are given of the application of the method to the measurement of diode and triode characteristics under overload conditions.
New Technique for Making Thin Targets
Authors: Pockman Leonard T. , Webster David L.
Published: February 2005

This paper describes a new technique for preparing thin nickel targets ranging upward in thickness from 10−6 cm. The targets are approximately 10 cm2 in area and are backed by films of cellulose acetate 5·10−6 cm thick. The periphery of the target is supported by a flexible array of fine wires.
A Spectrophotometer for Measurement of Optical Filters
Authors: Seeley Stuart Wm. , Anderson Earl I.
Published: February 2005

Some months ago the RCA License Laboratory, in connection with television development, had occasion to make measurements on the spectral characteristics of optical filters. The conventional and elaborate equipment usually used for such purposes was not immediately at hand, and a cathode-ray oscilloscope coupled to a few simple appurtenances was pressed into service and gave highly satisfactory results. The equipment is easily duplicated and possesses sufficient accuracy for many uses. Design considerations and constructional details are given.
Automatic Frequency Control for a Cyclotron
Authors: Jacques Robert B.
Published: February 2005

This paper describes a discriminator circuit which automatically compensates for the changes due to thermal effects in the capacitive and inductive reactances of a quarter-wave-length dee line of a cyclotron. The unit thereby contributes to smoother power input.
An Electronic Method of Measuring Molecular Lifetimes
Authors: Rawcliffe R. D.
Published: February 2005

An apparatus is described for following in detail changes in light intensity that occur in times of the order of one microsecond. It has been applied to measure the decay of fluorescence and to measure the decay of light from a nitrogen discharge. The light to be measured falls on an electron multiplier tube which is connected to a cathode-ray oscilloscope, on which the decay curves and a time scale are observed. In measuring fluorescence, a ``square'' pulse of exciting light is produced by a Kerr cell whose potential difference is controlled by the sweep circuit of the oscilloscope. For the fluorescence of diacetyl vapor a mean lifetime of 1.40×10−3 sec. was obtained, for diacetyl dissolved in water and in CS2 1.0×10−6 sec. and 1.9×10−6 sec., respectively. With the nitrogen discharge tube in place of the Kerr cell, photographs were taken at several pressures of the decay of the light of red and blue band systems, and of the discharge tube current which decreases more rapidly than the light. The blue system (C3Π→B3Π) decays exponentially with a mean lifetime (extrapolated to zero pressure) of 7.7×10−6 sec. The red system (B3Π→A3Σ) decay can be resolved into two exponentials with mean lifetimes of 29×10−6 sec. and about 1.5×10−6 sec., respectively.
Application of Guard Electrodes in Dielectric Measurements
Authors: Greenfield E. W.
Published: February 2005

Guard electrodes are useful devices which enable accurate dielectric measurements to be made on small samples of insulating material. They are generally applied to the electrode system of the material for the measurements of: (1) insulation resistance; (2) dielectric constant; (3) power factor. The following is a brief survey of the technique and application of guard electrodes derived from a background of considerable experience in the dielectric laboratories of the writer's company.
A New Source for Infra-Red Spectrometers
Authors: Smith Lincoln G.
Published: February 2005

A new source for infra-red spectrometers consisting of a carbon rod heated electrically in vacuum is described. Readily obtainable, such a rod may easily be machined or ground to various sizes and shapes. Ground with a V-shaped cavity one inch long in the center, a 6-mm diameter rod has been operated at a temperature of 1800°C with a power consumption of 600 watts and a lifetime of the order of 100 hours. Its emissive power is about the same from 1–10μ as that of a Globar at the same temperature while beyond 10μ it is considerably greater. The rod thus provides a source whose brightness is comparable with that of a Nernst glower but which may be made of greater width and which is much less delicate and easily burned out.
The Electrolytic Separation of Radioactive Iron from the Blood
Authors: Ross J. F. , Chapin M. A.
Published: February 2005

A technique for the electro-deposition of radioactive iron from the blood is described. This method allows accurate and reproducible estimation of radioactive iron in biological materials.
A Grid Controlled X-Ray Diffraction Tube
Authors: Eisenstein A.
Published: February 2005

A grid imposed between the filament and target of a demountable high vacuum type x-ray tube is modulated in synchronism with the full-wave rectified voltage impressed on the tube, by means of a square-wave generator. The grid potential varies in such a manner that the electron current flows only when the voltage is sufficiently high to excite the K series. For the Mo Kα radiation at 30.8 kv peak voltage an increase in efficiency of 29 percent is realized with the grid modulated. With a peak voltage of 38.2 kv a gain in efficiency of 18 percent is noted, or the x-ray intensity may be increased by this amount without altering the target heating.
A Voltage Stabilizer for a Direct-Current Generator
Authors: Schwarz W. M.
Published: February 2005

A simple stabilizer for a cyclotron magnet is described, which stabilizes the voltage across the magnet within one part in 2000. It acts as a variable resistance in parallel with the generator field, which remains shunt connected to the armature.
Emission-Regulating Circuit for an Ionization Gauge
Authors: Nelson R. B. , Wing A. K.
Published: February 2005

A description is given of the design and operation of a circuit employing gas-filled tetrodes to maintain constant electron emission in an ionization gauge by controlling the filament temperature. Performance data is given to show that variations in the electron emission due to fluctuations in line voltage or changes in the pressure in the ionization gauge have been to a large extent eliminated. Operating experience with the circuit over a considerable period has shown it to be highly satisfactory.
A Complete Proportional Counter Arrangement for Cosmic-Ray Measurements
Authors: Weisz Paul , Ramsey W. E.
Published: February 2005

An apparatus which has served successfully to study the ionizing capacity of individual particles of the cosmic radiation is described. The analyzing chamber is a carefully designed proportional counter tube filled with purified argon. Although this counter is working continuously, the amplifier has zero sensitivity unless a ray passes through a pre-determined path in the counter. This control is accomplished by a system of Geiger-Müller counters operating as a conventional telescope which ``turns on'' the amplification and recording mechanism for a period of time beginning with the passage of the ray and ending approximately 4×10−4 sec. later. During this time the amount of charge released in the proportional counter by this ray, and only this ray, is recorded. Certain general principles of proportional counter mechanism are discussed.
Attenuated Superconductors I. For Measuring Infra-Red Radiation
Authors: Andrews D. H. , Brucksch W. F. , Ziegler W. T. , Blanchard E. R.
Published: February 2005

An apparatus for measuring infra-red radiation has been constructed of fine tantalum wire, operating at a temperature of 3.22–3.23°K in the transition zone between superconduction and normal conduction. The tantalum coil is mounted on a thermostated plate with temperature electrically controlled and operates in a special self-regulating shunt circuit by which its own temperature is automatically maintained constant. The ratio of developed electrical potential to radiation flux received is 150 μv (erg cm−2 sec.−1)−1. Minimum detectable flux is ca. 10−3 erg sec.−1. Absolute measurements of intensity of radiation from sources at temperatures between 24° and 55° are consistent with the Stefan-Boltzmann law showing that instrument corrections for reflectivity, window-absorption, and changes with wave-length are very small.
A Portable Indicating X-Ray Dosimeter
Authors: Krebs Richard P. , Kersten H.
Published: February 2005

An a.c.-operated instantaneous reading x-ray dosimeter for use with both hard and soft radiation is described. The instrument requires calibration against a standard.
Some Improvements for the Analytical Ultracentrifuge
Authors: Moore Dan H.
Published: February 2005

Convection boundaries caused by small irregularities in the analytical ultracentrifuge cell are described and polishing of the sector walls is recommended. Accurate alignment of the cell in the rotor may be accomplished by a slot and pin arrangement without materially decreasing the strength of the rotor. An adaptation of Longsworth's scanning method to the analytical ultracentrifuge is described.
An Electrodynamic Slit Unit for an Infra-Red Double Monochromator
Authors: Baker Edward B. , Robb C. Dean
Published: February 2005

Electrical control of slit width by means of the unit described permits continuous adjustment as the wave-length is changed so that constant energy output of the monochromator may be achieved. As a result, percent absorption is measured directly and the slits are always set for optimum resolving power. An additional feature is curvable slits which are preset for any wave-length desired. The unit is supplied from an amplifier for automatic output control.
High Speed Automatic Infra-Red Spectrometer
Authors: Baker Edward B. , Robb C. Dean
Published: February 2005

A rocksalt, vacuum, double monochromator is described that displays the entire spectrum out to 15μ (or selected portions thereof at higher resolution) in one minute on a long-persistence oscilloscope screen. It measures percent transmission directly, automatically correcting for source-intensity distribution and spectrometer losses. Special arrangements permit rapid preparation of samples for analysis. Reflection measurements and direct comparison of two emission sources can also be made.
The Measurement of Anomalous Dispersion in Opaque Dielectrics
Authors: Lawson A. W.
Published: February 2005

An apparatus is described by means of which the index of refraction of opaque materials may be determined as a function of wave-length. The method is based essentially on the determination of Brewster's angle by reflection of polarized light from a polished surface. Typical data are given, and the precision and accuracy of the method are discussed.
A Method of Increasing the Sensitivity of Bourdon Gauges
Authors: Barnartt S. , Ferguson J. B.
Published: February 2005

A comparatively rugged optical lever system has been designed which magnified the movement of concavo-convex Bourdon gauges by a factor of 545. The system has a reproducible null point that is independent of temperature, but varies linearly, although only slightly, with pressure. The sensitivity graph is linear, and direct pressure measurements can be made to the nearest 0.005 mm of mercury.
Laboratory Liquid-Air Storage
Authors: Roebuck J. R.
Published: February 2005

To carry over interruptions in the supply of liquid air, a 120-l triple-wall, silver-plated, metal vacuum vessel was designed and built. The radiation theory for its part of the evaporative loss was worked out. The observed and calculated total loss agree at 3 kg/day. The good initial vacuum is maintained by the presence of an ample supply of activated charcoal in a small sphere reentrant into the large inner sphere. The alloy Inconel is used for situations requiring small conductivity. Alternative effective designs are given for the lower centering support for the inner spheres. The vessel is filled and emptied through an opening in the bottom, and this is controlled by a valve of ordinary design. To hasten the discharge the pressure over the liquid is raised slightly by throttling the vapor discharge. The vessel has been in use for 2.5 years without observed change in its evaporative loss.
An Apparatus for Measuring Air Flow During Inspiration
Authors: Lee Robert C. , Silverman Leslie
Published: February 2005

Measurement of the rate of flow of air during inspiration is important in respiratory physiology and for the design of protective respiratory devices. Methods that have been used previously are described and their limitations explained. A new instrument was constructed for such measurements, which offers no appreciable resistance to air flow. This instrument consists of a microscopic platinum wire suspended across the diameter of a 31.6-mm tube. One end of the wire is attached to a fixed point and the other end to a fine spring. The displacement of the wire when air flows through the instrument is recorded photographically by a moving paper camera. The deflection of the wire is linear with air flow, and its inertia, lag, and frequency of vibration do not interfere with respiratory measurements. A low resistance valve and mask system complete the apparatus.
A Mica Window Geiger Counter Tube for Measuring Soft Radiations
Authors: Copp D. Harold , Greenberg David M.
Published: February 2005

A mica window Geiger counter tube is described which combines the speed of a metal walled tube with a sensitivity to soft radiations comparable to that of the screen walled tubes. It consists of a NO2 treated metal cylinder covered at one end by a thin sheet of mica (0.02 mm) and at the other end by a glass bell with a central capillary. Through this capillary is sealed a piece of 8-mil tungsten wire with a drop of glass fused over the end. The tube is operated at a pressure of 10 cm of Hg with a mixture of 10 percent ethanol and 90 percent argon.
A Method of Cooling Hydrogen Discharge Tubes
Authors: Hsueh Chao-Wang
Published: February 2005

Experiments have been performed to cool a hydrogen discharge tube by means of rapidly evaporated liquid air. The low temperatures of liquid air resulting from such rapid evaporation were measured with a calibrated copper-constantan thermocouple. A special apparatus was constructed to determine the freezing points of the substances used for calibration. Cooling of the light source down to temperatures as low as 56°K can thus be obtained with a simple arrangement and low cost.
A Precision Optical Bench
Authors: Wallin Walter , Mazar Wm. S.
Published: February 2005

The optical laboratory at Link Aviation Devices, Inc., was in need of an optical bench capable of making precision nodal slide measurements on lenses up to five inches in diameter. The present paper describes the instrument that finally evolved from that and other requirements.
Apparatus for the Production and Measurement of Small Motions
Authors: Hull Gordon Ferrie
Published: February 2005

A cantilever bar for producing small motions of the order of 10−5 cm and greater is described together with an interferometer for measuring these motions. Two methods of using the interferometer are discussed. The first uses an uninterrupted monochromatic light source in which the interference fringes are observed to be visible and stationary for particular amplitudes of oscillation. The second method uses a stroboscopic light source synchronized with the oscillating bar. Motions of the cantilever bar measured by these two methods are compared with each other and with the theory of the cantilever bar.
Voltage-Measuring and -Control Equipment for Electrostatic Generators
Authors: Hanson A. O.
Published: February 2005

The use of the electrostatic analyzer as a voltage-measuring instrument for use with an electrostatic generator is described. This instrument is equipped with electrical detectors which are convenient for operating automatic regulating devices for keeping the high voltage source at a constant potential. With the equipment described it is possible to measure and control the average energy of the protons accelerated by the electrostatic generator with an accuracy of about 0.1 percent.
Some Phase Effects with Coincidence Proportional Counters
Authors: Meaker Charlotte L. , Roberts Arthur
Published: February 2005

With some proportional coincidence amplifiers having a short time constant input to the mixer stage it was found that the fraction of the true coincidences measured was a function of both the counter voltages and the absorber between the counters. This effect could be traced to the amplifier characteristics in conjunction with the short time constant before the mixer stage. The paper describes the counters and amplifiers, discusses the cause of the effect, and suggests possible uses.
Theory, Design, and Applications of a Short Magnetic Lens Electron Spectrometer
Authors: Deutsch M. , Elliott L. G. , Evans R. D.
Published: February 2005

A beta-ray spectrometer has been constructed utilizing the chromatic aberration of a ``thin'' magnetic lens. The lens is wound of 300 pounds of copper wire and does not utilize iron. Its focal length for transmitted electrons can be varied from 25 to 50 cm and the magnification from 0.5 to 2. Circular sources varying in diameter from 0.4 to 1.6 cm are used and the solid angle subtended at the source is varied between 0.025 and 0.1 steradian. The half-maximum width of the transmitted distribution is 0.017 to 0.06 of the momentum of the focused electrons. Larger solid angles or better resolution could probably be obtained. The focusing properties of the instrument are derived from the calculated field distribution of the lens by the method of Busch. The spectrometer has been applied to studies of radioactive disintegration schemes. Appropriate techniques are described for the measurement of discrete and continuous beta-ray spectra, of coincidences of focused electrons with other radiations, and of gamma-ray energies through secondary electron spectra. A special baffle system allows the separation of negatrons and positrons. The performance of the short lens spectrometer is compared with that of other types of beta-ray spectrometer and it is concluded that it is a particularly useful tool for the investigation of disintegration schemes because of its flexibility, the use of large circular sources, and the accessibility of source and counter which are located outside the magnetic field at a distance of 100 cm from each other.
A Vacuum Microbalance for the Study of Chemical Reactions on Metals
Authors: Gulbransen Earl A.
Published: February 2005

The construction of a vacuum microbalance having a sensitivity of 0.3×10−6 g, using a 0.6840-g sample, is described. The pressure coefficient is found to be less than 0.3×10−6 g for a 1-atmosphere change. The temperature coefficient is found to be 0.8×10−6 g/°C change. The zero point of the balance is found to be stable to better than 1×10−6 g over a period of 24 hours. The technique of measurements is briefly discussed. Several typical experiments on the formation of oxide films on iron at 25°C and 300°C are presented.
Numerical Solution of Initial Value Problems by Means of Punched-Card Machines
Authors: Kormes Jennie P. , Kormes Mark
Published: February 2005

The method of solving initial value problems by means of standard punched-card equipment is illustrated on the equation: ∂2u/∂t2—c2∂2 u/∂x2=0 with given initial conditions u(0, x) and ut(0, x) as well as boundary conditions u(t, x0)=f1(t) and u(t, xn)=f2(t). The plane continuum is replaced by a rectangular net and the differential equation by a finite difference equation. In this manner a value of the function u(t, x) in a given point of the net is expressed by its values on two lower rows of the net. The punched-card method consists of two phases: the work scheme which depends only on the equation (and can be used over and over for a given equation), and the instructions for the several operations involved. This method brings about substantial time savings for problems involving a large number of net points and can be extended to non-linear problems and to several dimensions.
The Hydrogen Gauge—An Ultra-Sensitive Device for Location of Air Leaks in Vacuum-Device Envelopes
Authors: Nelson Herbert
Published: February 2005

A new technique has been developed for locating air leaks in vacuum devices. It employs a sealed-off, highly evacuated ionization gauge having a section of its envelope made of thin palladium sheet which, when heated, is highly permeable to hydrogen. In use the gauge is connected to the manifold of a vacuum system with the palladium section isolating the vacuum of the gauge from that of the manifold. When the manifold or any vacuum device connected to it is probed with hydrogen, leaks in the system are indicated by an increase in the ion current of the gauge. This new technique, because it utilizes a sealed-off, highly evacuated gauge which responds only to hydrogen and is unaffected by other residual gases and vapors, provides a simple but sensitive test for very small leaks.
The Design of a Microdensitometer
Authors: Brentano J. C. M.
Published: February 2005

The evaluation of photographic line patterns is discussed with the object of comparing various procedures in their relation to the design of a microdensitometer. While some of the points discussed apply to the evaluation of optical spectra, the main interest of the discussion is directed towards setting out the various requirements which arise in the evaluation of x-ray patterns. The second part of the paper describes a microdensitometer designed to conform with some of these requirements.
An Oscillographic Method for the Photometry of Photographic Flash Lamps
Authors: Projector T. H. , Barbrow L. E.
Published: February 2005

A method for the photometry of photographic flash lamps with a cathode-ray oscilloscope is described. The circuits required to obtain curves of luminous flux versus time on the oscilloscope are given. Accurate timing is obtained through the use of beam modulation. Some of the precautions necessary to assure accuracy are discussed.
Infra-Red Analysis of Two Component Systems
Authors: Fuoss Raymond M. , Mead Darwin J.
Published: February 2005

Two beams from an infra-red source are focused on opposing thermocouples which are connected in series to a galvanometer. Rocksalt cells containing identical compounds A are placed in each beam, and the galvanometer is set to zero by a shunt resistance across one of the thermocouples. Then if the composition in one cell is changed by addition of another compound B, a galvanometer deflection is observed, if the integral of transmission times radiation curve is different for pure A and for mixtures of A and B. Several examples are given, showing galvanometer current as a function of composition from pure A to pure B in the second cell, while pure A is kept in the first cell. The device thus permits a simple analytical method for two component systems.
An A.C. Operated Leak Detector and Ionization Gauge
Authors: Nelson R. B.
Published: February 2005

Small leaks in vacuum systems may be found by observing the change in temperature-limited thermionic emission of a tungsten filament in the vacuum as oxygen is blown over the leak. An apparatus is described for regulating the filament heating power so that the emission is not affected by line voltage fluctuations. The apparatus also operates as an ionization gauge with emission control.
A Diffraction Specimen Holder for Electron Microscopes
Authors: Simard G. L. , Stryker C. R.
Published: February 2005

The basic elements of an electron diffraction camera—a source of high velocity monochromatic electrons, a magnetic focusing lens, and a recording photographic system—are found in the magnetic electron microscope. This has naturally led to the development of a diffraction adapter1 for electron microscopes which has proved most useful for supplementing electron micrographs with data on specimen composition. A specimen holder for an adapter lens to the Model B RCA electron microscope is here described. It is designed to accommodate a wide range of specimen sizes and shapes for diffraction investigations by both electron reflection and transmission methods. Three completely independent motions of the specimen are provided, namely: (1) translation in a direction perpendicular to the electron beam, (2) rotation about the direction of translation, and (3) rotation about an axis perpendicular to both the electron beam and the direction of translation.
Cube-Surface Coil for Producing a Uniform Magnetic Field
Authors: Rubens Sidney M.
Published: February 2005

A system of five, equally-spaced, square coils which provides a uniform magnetic field over a considerable volume is described. The region of uniformity is easily accessible from outside the coils. The method used to design the system is discussed.
A Jet Viscometer with Variable Rate of Shear
Authors: Morris William John , Schnurmann Robert
Published: February 2005

A viscometer consisting of a glass jet which is inserted in a closed system is described. With this instrument high rates of shear of the order of magnitude of 100,000 sec.−1 can be reached for hydraulic oils. Observations on straight mineral oils of sufficiently high viscosity to exclude turbulence, on refined rape oil, and on castor oil, showed that Poiseuille's law was obeyed, i.e., the rate of flow was strictly proportional to the pressure difference applied to the jet. On the other hand, for colloidal solutions temporary viscosity reductions became apparent when 1/t, the reciprocal value of the time of flow of a given volume, was plotted against p, the pressure difference, and when it was ascertained that the lowest value which the viscosity would reach was still high enough to exclude the occurrence of turbulent flow. Whenever the condition of turbulent flow applied, the curvature of the (1/t)—p curve was in the opposite direction so that in those cases in which the temporary viscosity reduction would bring the system within the range of turbulent flow a change in direction and curvature of the (1/t)—p curve would take place with the result of either indicating an asymptotic approach to a straight line or, in more pronounced cases, showing a point of inflection. For colloidal solutions the results suggest an analytical criterion for assessing the transition from laminar to turbulent flow at high rates of shear. In the laminar region log (pt) was found to decrease linearly with increasing values of the logarithm of the mean rate of shear. With the instrument described here laminar flow was found to persist when Reynolds' numbers up to about 44,000 were encountered. However, the critical Reynolds' number is not necessarily the same for the same oil and two different jets as the beginning of turbulence may depend upon the geometrical shape of the jet.
Counters for Use in Nuclear Spectroscopy
Authors: Wiedenbeck Marcellus L.
Published: February 2005

In nuclear spectroscopy conversion electrons have been counted with energies as low as 20 kv arising from an excitation process having a cross section of the order of 10−34 (cm2). The special requirements of counters for such purposes are reviewed and a description is given of several self-quenching counters which have proven useful in a study of nuclear spectra. A simple and rapid method of filling these counters is also described.
A Mass Spectrometer Type of Leak Detector
Authors: Thomas H. A. , Williams T. W. , Hipple J. A.
Published: February 2005

An instrument is described which is capable of measuring one part of helium in 400,000 parts of other gases. The instrument is built around a 180° type mass spectrometer tube which is prefocused for helium ions. Use is made of this high sensitivity tube to locate leaks in vacuum equipment. The leaky container can be connected and evacuated by the pumps in the unit. A fine stream of helium played over the surface of the container will enter the leak and register immediately on the output meter. Very small leaks can be located easily to within a quarter of an inch. The unit is completely self-contained, requiring only a line connection to a 110-volt a.c. outlet.
The Production of Film Type Bolometers with Rapid Response
Authors: Aiken C. B. , Carter W. H. , Phillips F. S.
Published: February 2005

This paper deals with the methods and equipment used in the construction of small high speed bolometers. Particular attention is given to the Type G unit which is rugged, sensitive, and capable of being used satisfactorily with radiation modulated at 30 cycles per second. Special units can be used at considerably higher frequencies. Descriptions are given of methods and equipment for making the cellulose nitrate supporting film and for evaporating thin strips of gold onto this film. Deposition of electrodes and methods of testing for noise and sensitivity during the course of production are described. The use of metal back plates, separated from the bolometer strip by a small distance, is shown to be advantageous. With this construction, and a gas pressure of 20 mm of nitrogen, very satisfactory frequency characteristics are obtained. Gold black is used to increase the absorption of radiation in the vicinity of 10μ. It is pointed out that by controlling the gas pressure either resistive or conductive layers of gold black can be made. In the latter case it is possible to omit the underlying gold strip entirely. Photographs and descriptions of the equipment used for processing bolometers in batches of ten are given, and some of the more interesting points are described in detail. Data are given on frequency characteristics, useful life, and resistance to shock and temperature effects. Finally, brief comment is made on bolometers made of metals other than gold.
Some Precision Circuit Techniques Used in Wave-Form Generation and Time Measurement
Authors: Chance Britton
Published: February 2005

This paper contains a survey of the characteristics and uses of non-linear circuit elements in the generation of wave forms particularly useful in precision timing circuits. The use of these non-linear circuit elements in detection and time measurement is also included.
Electronic Frequency Stabilization of Microwave Oscillators
Authors: Pound R. V.
Published: February 2005

Two circuits for use to control the frequency of a microwave oscillator by an external high Q cavity are described. One of the circuits uses a microwave equivalent of the frequency discriminator, in conjunction with a d.c. amplifier. The other uses the cavity in a special circuit that provides an intermediate-frequency signal that is a measure of the difference between the frequencies of the oscillator and cavity. This allows the use of an intermediate-frequency amplifier. The resulting stability of the oscillators is such that audible beat frequencies can be produced between two oscillators at 10,000 Mc/sec. The resultant signal can be frequency modulated at audiofrequencies, with stabilization acting throughout the modulation cycle. A technique by which the frequency-stabilization systems could be used to investigate, with high resolution, the structure of microwave absorption spectra is suggested.
Pneumatic Heat Detector
Authors: Zahl Harold A. , Golay Marcel J. E.
Published: February 2005

A pneumatic heat detector is described in which radiant energy is dissipated in a black absorber which is located in the center of a gas cell. The resulting heating and expansion of the gas serves to distort a collodion film located a few thousands of an inch from a nearby parallel glass window. The distortion of the film is detected by observing a shift in a system of interference fringes formed by light reflected from the film and the adjacent glass surface. The principle lends itself readily to the design of systems comprising a multiplicity of heat cells and associated detecting films. A system utilizing 61 cells is described.
A Method for Controlling Scattered Radiation in Obtaining X-Ray Absorption Data by Photographic Means
Authors: Seemann H. E. , MacGillivray L. L.
Published: February 2005

Errors caused by scattered radiation in photographic x-ray absorption measurements can be materially reduced by (1) irradiating a minimum amount of matter, (2) placing the absorbing material some distance from the film, and (3) keeping the different filter elements separated by lead partitions so that scattering cannot spread indefinitely. These conditions have been met by the use of a lead chamber made up of several parallel longitudinal compartments. Filters differing in thickness are placed over holes in the end where the x-rays enter and recording films are located at the exit end. This system has the further advantage that all filters are exposed simultaneously, thus promoting accuracy in relative absorption measurements, particularly when short exposure times only are possible. Experimental results show that, in a particular design, 97 percent of the scattering is eliminated.
Characteristics of the Pre-Corona Discharge and Its Use as a Reference Potential in Voltage Stabilizers
Authors: Brown Sanborn C.
Published: February 2005

The characteristics of a pre-corona discharge are studied. The high sensitivity of the current to changes in voltage make possible the application of such a discharge as a reference potential for electronic voltage stabilizers. The use of a stabilizing diode operating in the pre-corona region, where the discharge is maintained by ionization external to the discharge, is discussed. Characteristics of a high impedance electronic voltage stabilizer controlled by a pre-corona discharge diode appear to be very satisfactory.
A Versatile Square Wave Nerve Stimulator
Authors: Guyton Arthur C.
Published: February 2005

1. A square wave stimulator with an extreme range of voltage, duration, and frequency of stimuli is described. 2. The stimulator is coupled directly to the electrodes, thereby preventing distortion of the square wave. 3. This stimulator makes possible the rapid measurement of time and duration of stimulus necessary to cause a nerve response. For routine laboratory work, it is extremely convenient to use.
A New Magnetomotive Force Gauge and Magnetic Field Indicator
Authors: Ellwood W. B.
Published: February 2005

A new gauge and method of measurement are described, whereby the distribution of magnetic potential may be determined along the ferromagnetic core of a telephone relay, or similar electromagnetic device, while it is mounted in operating position, without disassembly, special search coils, or even change in adjustment. The gauge is portable, compact, and sensitive. A glass-enclosed, magnetically operated reed switch, which is used because of its small size, high sensitivity, and magnetic structural features, is held electrically closed by the magnetomotive force which it is desired to measure. This magnetomotive force is opposed by a countermagnetomotive force supplied by a winding on the switch. The current in the winding which opens the switch is the measure of the magnetomotive force. The necessary control circuits and the procedures for their use are described for both manual and automatic operation. The device and method are applicable to the study of permanent magnets as well as electromagnetic structures. The coercive force of the core of a relay may be determined in a nondestructive manner.
Frequency Modulated Oscillator for Leak Hunting
Authors: Brubaker W. M. , Wouk Victor
Published: February 2005

A circuit for converting a variable d.c. voltage signal into a frequency modulated audio-oscillation is described. The circuit can be used for general monitoring purposes, but this article confines the description to its use in conjunction with an ionization gauge for leak hunting in vacuum systems. The oscillator enables one operator to hunt leaks more rapidly and effectively than two men calling out meter readings. Leaks representing pressure rises of less than 4×10−8 mm of Hg have been found with an ionization gauge and this oscillator.
Design and Use of Directly Coupled Pentode Trigger Pairs
Authors: Regener Victor H.
Published: February 2005

A trigger circuit using two pentodes with direct plate-to-screen coupling is described. The mechanism of electrical stability and instability and the process of triggering are discussed. Sample diagrams for a pulse generator, an electronic switch, and a scaling circuit are given.
Decade Counting Circuits
Authors: Regener Victor H.
Published: February 2005

A direct-coupled pentode trigger pair, previously described, is made the basis of two simple ring-of-ten circuits for high speed counting. One of the circuits is especially suited for the counting of sharp pulses up to a frequency of 105 cycles per second. The other circuit is especially suited for frequency measurements on periodic currents of arbitrary wave form and of frequency from zero to above 105 cycles per second. The number of pulses or cycles counted by one ring-of-ten is indicated on the screen of a cathode-ray oscilloscope tube. Several of these ring-of-ten units, each with its cathode-ray tube, can be connected in cascade to make electronic counting with direct indication of the decimal figures possible.
Measurement of Surface Potential or Contact Potential Differences
Authors: Frost Arthur A.
Published: February 2005

The term ``surface potential'' is recommended as preferable to ``contact potential'' when surface effects are being studied. The use of a pH meter for measurement of surface potentials is described.
Design and Operation of an Improved Counting Rate Meter
Authors: Kip A. , Bousquet A. , Evans R. , Tuttle W.
Published: February 2005

The counting rate meter is an electronic amplifier and computing circuit whose output is a d.c. current or voltage proportional to the number of pulses fed into the circuit. The input pulses may be either uniformly spaced or distributed randomly in time, as in the most common use of the instrument as an amplifier and recorder for use with Geiger-Müller counters. The electronic design and operation is discussed for each of the circuit components: amplifiers, pulse equalizer, integrating circuit, degenerative vacuum-tube voltmeter, and the stabilized high voltage and low voltage supplies. The statistical interpretation of the counting rate meter output readings due to the randomly distributed pulses from radioactive sources requires a special statistical theory because an integrating and averaging circuit produces an exponential interdependence of successive observations on all preceding observations. Practical methods, with curves, are developed for determining the mean counting rate and the probable error of the mean rate directly from the output records.
Scattering of Light from Small Drops
Authors: Lander Richard L. , Nielsen Carl E.
Published: February 2005

Curves are given for the angular distribution of light scattered from drops of radius 1.4×10−3 cm and 4.8×10−4 cm for angles from 28° to 147°. The distribution is more nearly symmetrical than had been speculated and depends strongly on the drop size. The intensity of the scattered light was measured with a phototube circuit and galvanometer. The drops were produced in a downward diffusion chamber.
A Sensitive Photoelectric Method for Measuring the Faraday Effect
Authors: Ingersoll L. R. , James W. L.
Published: February 2005

A photoelectric method of measuring magneto-optic rotations as small as 1″ is described. This employs an optical system whereby light from a tungsten lamp traverses two double-image prisms and is focused by a series of concave mirrors on two 929 phototubes, after passing through a rotating polaroid chopper. The apparatus is now being used in an investigation of the Faraday effect in gases and vapors.
Magnetic Weighing and Gas-Density Balances
Authors: Simons J. H. , Scheirer C. L. , Ritter H. L.
Published: February 2005

A design is herein given for an electromagnetic device that can be employed instead of weights or springs for weighing purposes. In this particular design the balancing current is linear with the force applied to the arm of the balance so that current measurement gives a direct reading of weight. A capacity null-point indicator is also described and so also are electrical circuits that enable this null-point indicator to automatically operate the electromagnet. These auxiliaries are shown incorporated in a density balance. This balance was sensitive to a change of weight of better than 0.0000001 gram or in terms of oxygen pressure at room temperature to 0.02 mm of Hg. The designs of density balances are discussed.
Application of High Speed Flash Tube to Photographing the Fundus of the Eye in Color
Authors: Jacobs Martin , Ogle Kenneth N.
Published: February 2005

A high speed flash tube is adapted to the Nordensen retinal camera, so that the fundus of the human eye can be photographed in color. The high speed flash eliminates the usually deleterious effect of blinking and eye movements. Special electronic circuits are needed to provide a flickering light from the same flash tube to enable the operator to adjust and focus the camera. Ektachrome film is used and this is over-developed to gain equivalent exposure. For the fundus photographs this apparently results in no loss of color relationships.
Housing for Co60 Gamma-Ray Source For Experimental Work
Authors: Firestone R. F. , Willard J. E.
Published: February 2005

A relatively simple housing for experimental work with multicurie radioactive sources consists of a lead turret on a low table, the volume below the table being shielded on three sides by stationary shielding and in front by a rolling lead door. The source capsule is screwed on to the end of a rod passing through vertical holes in the turret and the table. The source can be positioned in the center of the turret when not in use and, when desired, lowered to any position adjacent to experimental equipment below the table. Using a 40-curie Co60 source and an annular glass irradiation vessel, an average gamma-ray intensity of 2×105 r/hr is obtained in a 5-ml volume of liquid.
A Minimal Noise Preamplifier for Proportional Counters and Similar Applications
Authors: Enslein K. , Brainerd B.
Published: February 2005

A minimal noise amplifier permitting the recognition of signals of 2μ volts amplitude over a frequency range at 760 kc is described. The device is linear over an input range of 74 db, and is compensated for power supply potential changes by means of negative feedback.
Measurement of the Energy of Isotropic Fast Neutrons with Li6 Loaded Plates
Authors: Roberts J. H. , Solano W. O. , Wood D. E. , Billington H. B.
Published: February 2005

100-micron E1 and C2 Ilford plates loaded with enriched Li6 were exposed to neutrons from Li7(p, n)Be7 and from H3(p, n)He3. The plates were rotated to mockup isotropic incidence. Neutron energies ranged from 200 to 1500 kev. The plates were faded and developed so as to obtain good triton-alpha discrimination. Peaks having widths from 100 to 300 kev at half-maximum were obtained, depending upon neutron energy and selection criteria.