bluuebunny/crossref_metadata_2025 huggingface dataset:
An Improved Cosmic-Ray Radio Sonde
Authors: Pickering W. H.
Published: February 2005

The technique of the radio transmission of cosmic-ray information from the stratosphere has been improved as a result of field experience. The instrument described herein is believed to be a definite improvement over the previous instrument. The scaling down of the cosmic-ray counts is now done at the ground station instead of at the transmitter. This necessitated a new means of modulating the transmitter, a new receiver, and a new recorder.
A Two-Cycle Flasher
Authors: Talbot Samuel A.
Published: February 2005

A light-valve is described for providing single flashes of 3-msec. duration of longer, operated and controlled electronically. It involves disclosure and closure of an aperture by two vanes, whose cycle is commutated automatically. Details are given for a model made mainly from commercial parts, and driven by thyratrons. A suitable control circuit is also shown.
A Synchronized Calibrator for Sweep and Gain in Cathode-Ray Recording
Authors: Talbot Samuel A.
Published: February 2005

A circuit is described comprising an RC oscillator and multivibrator which generate three timing scales suited to calibrate a wide range of sweep speeds. In addition, a square pulse with adjustable duration is provided to calibrate the gain and to record the frequency characteristics of an amplifier. Both calibrations are synchronized with the sweep.
An Automatic Frequency-Controlled Oscillator and Amplifier for Driving Mechanical Vibrators
Authors: Potter E. V.
Published: February 2005

An oscillator system has been developed for driving mechanical sound generators or other vibrating mechanical systems which require that the vibrating member be driven at its resonant frequency. The oscillator is a vacuum tube type in which an automatic frequency control, similar in principle to that employed in radio receivers, is used to keep the frequency at or very close to the resonant frequency of the vibrator. The change in phase of the vibrator motion relative to the driving force is used to supply a potential proportional to the difference between the driving frequency and the resonant frequency of the vibrating member, and having a polarity dependent on whether the driving frequency is less than or greater than the resonant frequency. This voltage is used to control a reactor tube which in turn controls the frequency of the oscillator circuit. The circuit is very effective, changes in either oscillator or vibrator frequency, or both, of approximately 500 cycles per second in 12 kilocycles, being followed automatically so that the oscillator frequency will not deviate from the resonant frequency of the vibrating member by more than 0.1 cycle per second.
A Hydrostatically Supported Cloud Chamber of New Design for Operation at High Pressures
Authors: Johnson T. H. , DeBenedetti S. , Shutt R. P.
Published: February 2005

A medium-sized cloud chamber for high pressures is described in which the pressure is sustained by the walls of an oil-filled steel container rather than by the glass parts of the chamber itself. The chamber is 30 cm in diameter and 9 cm deep, and it was designed to operate at pressures up to 200 atmospheres. When filled at this pressure with argon the gas in the chamber has a stopping power for cosmic rays traversing the diameter equivalent to 80 meters of the atmosphere, 10 cm of water or nearly 1 cm of lead. Because of its high stopping power and a long period of sensitivity this chamber, at the maximum pressure, is approximately one thousand times more effective per expansion for studying rare cosmic-ray phenomena than the largest chambers which have been operated at normal pressure. Details of the cloud chamber and its auxiliary devices are described.
Zinc Oxide Smoke as a Reference Standard in Electron Wave-Length Calibration
Authors: Lu Chia-Si , Malmberg Earl W.
Published: February 2005

Zinc oxide smoke and thinned gold foil were studied with x-rays and electrons. Our x-ray values for the lattice constants of zinc oxide and electron diffraction value for its axial ratio agree satisfactorily with Bunn's x-ray values. Our investigation also reveals no variation in these lattice constants with the age of the sample. With regard to the relative values for the lattice constants of zinc oxide and gold, both methods give consistent results. Our work indicates that the wave-length calibrations obtainable with zinc oxide smoke and with gold foil are in satisfactory agreement, contrary to the finding of Finch and Wilman.
A Cyclotron Which Allows the Accelerated Particles to Emerge in a Direction Parallel to the Dee Interface
Authors: Kruger P. Gerald , Groetzinger G. K. , Richardson J. R. , Lyman E. M. , Ogle W. E. , Nelson M. E. , Schwarz G. , Greene J. B. , Colby N. C. , Lee R. W. , McClellan C. E. , Scag D. , Smith Lloyd , Tallmadge F. K.
Published: February 2005

The construction of the dees, deflection channel, and vacuum chamber of a cyclotron is described. The design allows the accelerated ions to pass through an electrostatic deflecting field for one-quarter of a revolution and then to proceed through the magnetic fringing field for another quarter of a revolution before they leave the cyclotron vacuum chamber. This provides that the ions emerge in a direction which is parallel to the dee interface and perpendicular to the principal azimuthal plane through the long axis of the cyclotron magnet. Operation shows that the ions follow the prescribed path. The advantages of this construction are: 1. Relatively low deflection voltages are necessary. 2. Large beam currents (100 μa) mono-energetic to 2 percent can be obtained directly from the cyclotron. 3. It is easy to ``pipe'' the beam to a point many feet from the cyclotron. Therefore, many experiments can be performed outside of shielding tanks (4 feet of water) where possible errors due to background radiations from the cyclotron are small. 4. Magnetic analyzing equipment placed in the beam path provides a beam current density of approximately 0.001 μa/mm2 and mono-energetic to 0.1 percent. Several curves showing typical operational characteristics of a cyclotron are included.
The Lithium Fluoride Prism in Infra-Red Spectroscopy
Authors: Wright Norman
Published: February 2005

The performance of a lithium fluoride prism in an infra-red spectrograph is described. Coverage of the spectral range from 2 to 5.9μ with considerably higher resolving power than that obtainable with rocksalt is demonstrated. Reproductions of the spectra of several hydrocarbon compounds are included which show the high degree of resolution obtained. The methyl group band at 3.37μ is used as an illustration of the value of the apparatus in the study of molecular structure. As a specific example this group is shown to be absent in polystyrene. It is pointed out that lithium fluoride is inferior to fluorite only because it limits observations to wave-lengths shorter than 5.9μ.
Design of a Vacuum Photographic Plate Chamber
Authors: Schulz L. G.
Published: February 2005

A vacuum photographic plate chamber of large capacity is described. It is of simple mechanical design but permits complete control of plate position. A feature of the apparatus is the use of a vacuum seal developed by Wilson.
Determination of the Helium Content of Terrestrial Materials
Authors: Goodman Clark , Evans Robley D.
Published: February 2005

With only minor modifications, the direct-fusion technique, as previously developed for emanation measurements, can also be employed to liberate helium from terrestrial materials. The rock gases are purified, and the helium is measured quantitatively with a sensitive McLeod gauge. In geological age studies of igneous rocks and ``non-radioactive'' minerals, the helium contents ranged from 0.25×10−5 to 65×10−5 with modal and median values of 1.8×10−5 cc He (at 0°C and 76 cm Hg) per gram.
Cross-Prism Investigation of Fluorescence
Authors: Germann Frank E. E. , Woodriff Ray
Published: February 2005

A cross-prism method is described whereby a single photograph of a fluorescence spectrum gives directly both intensity and spectral distribution of light brought about by light of all wave-lengths used as exciting light. A vertical scanning of such a photograph gives the variation of light intensity of a given wave-length as a function of the exciting wave-length. A horizontal scanning gives the spectral energy distribution as a function of wave-length for a given frequency of exciting light. Using a continuous source of ultraviolet radiation, a single exposure thus gives all information necessary to determine the best frequencies of exciting light to produce a maximum fluorescent light of a given color or energy distribution.
A Thermopile for Microcalorimetry
Authors: Mason L. S.
Published: February 2005

In the study of the thermodynamics of solutions it is desirable to measure heat effects (of the order of 0.001 cal.) which occur during the dilution of dilute solutions. In the Lange-type calorimeter a thermopile of approximately 1000 junctions is used differentially. For this purpose a thermopile has been constructed using constantan-Chromel-P couples mounted in a sheet of Micarta, 5′′×10′′×516′′, and electrically insulated with a Vinylite resin which has an insulation resistance greater than 25 megohms. This instrument appears to offer somewhat better behavior than previously used units with respect to stability, sensitivity, and rapidity of response to temperature changes. The thermopile consists of two sections of equal numbers of junctions which are connected in parallel to a Leeds and Northrup HS galvanometer in series. At a scale distance of nine meters the sensitivity of the system is 0.25 microdegree per mm. Since one liter of diluent (water or dilute solution) is contained in each half of the calorimeter, this corresponds to a mean sensitivity of 2.5×10−4 cal./mm, with a probable error of the mean of ±0.03×10−4 cal./mm. The heat conductivity constant of the calorimeter is 0.004 min.−1 and that of the thermopile is 0.03 min.−1. Measurements with the present thermopile of the heats of dilution of sodium chloride solutions agree satisfactorily with wellestablished values.
The Fluxball A Test Coil for Point Measurements of Inhomogeneous Magnetic Fields
Authors: Brown William F. , Sweer John H.
Published: February 2005

The value of a magnetic field at a point is equal to the volume average of the field over the interior of any sphere centered at the point and not containing any sources of the field. It is therefore possible to wind a coil on the surface of a sphere in such a way that the flux through the coil is proportional to the field at a point even though the field varies over the region occupied by the coil. By combining concentric windings of this type one obtains a solid spherical winding equivalent to a series of coaxial cylindrical windings of different lengths but of equal and constant axial turn spacing, and therefore not difficult to wind. Design formulas are derived and construction procedures described.
Use of Silicones as Diffusion Pump Oils
Authors: Brown Gordon P.
Published: February 2005

Comparative performances of Litton C, Octoil, Narcoil, and two typical silicones in a non-fractionating diffusion pump are presented with a discussion of vapor pressure, stability to heat and oxidation, and the ability to operate against high forepressures. Extrapolated vapor pressure, temperature data, and test results show the high boiling silicone to produce the highest vacuum as indicated by an untrapped ionization gauge. The silicon was further found to be nearly completely resistant to oxidation when exposed to air while hot. A table showing relative merits of various oils, as applied to vacuum pumping conditions ordinarily encountered, is presented.
An Automatic Recorder for Resistance Thermometry
Authors: Stull Daniel R.
Published: February 2005

A completely automatic recording Wheatstone bridge is designed especially for use in resistance thermometry. It is built into a standard commercial recorder, contains decade coils operated by a Geneva gear mechanism, and increases the original range of the machine 100-fold. With it a continuous record of resistance versus time is made covering a range of 0 to 100 ohms that may be easily read to 0.001 ohm±0.001 ohm. Employed in connection with a standard 25-ohm platinum resistance thermometer a temperature range of −190° to 550°C can be covered with a precision of 0.01°C±0.01°.
A Direct-Reading Photoelectric Colorimeter
Authors: Barnes B. T.
Published: February 2005

A special current balance is used with photo-cell filter combinations whose spectral sensitivities are nearly proportional to the I.C.I. x̄, ȳ, and z̄ functions. Approximate color-coordinate values are indicated directly on the dials of this instrument. This makes routine colorimetry more convenient and more accurate than it was with previous equipment. The instrument also can be used as a direct-reading photometer.
A Simple Refractoscope for Liquids
Authors: Willard G. W.
Published: February 2005

Here described is a simple refractive index comparison instrument designed especially for use in mixing and testing the binary, quartz-matching, immersion liquids which are now so widely used in quartz inspection and orientation instruments. The optical system comprises only a slit and a Z-cut quartz prism immersed in the liquid, and a lens contacting the liquid surface. By observing the slit both through and to the sides of the prism it is possible to detect a ΔN=0.001 mismatch between the liquid index and the desired quartz index. Further, without additional scales or other means, the degree of mismatch may be closely estimated, by comparison with the ΔN=0.01 birefringence in the quartz prism itself.
A Modified Zisman Apparatus for Measuring Contact Potential Differences in Air
Authors: Rosenfeld S. , Hoskins W. M.
Published: February 2005

The apparatus for measuring contact potential differences between solid-solid or solid-liquid by the vibrating plate method of Zisman has been simplified in two ways. The plate is driven by a radio loudspeaker powered by the ordinary 60-cycle current and the null point is determined with an oscillograph instead of earphones. Spurious effects arising when leaves are measured are avoided by use of nonpolarizing connections through a calomel half-cell, and other stray potentials are eliminated by very careful shielding.
An Apparatus for the Measurement of Vapor Densities
Authors: Simons J. H. , Ritter H. L.
Published: February 2005

A device is described which is useful for the determination of vapor density for condensable vapors in the temperature range from the melting point to the critical temperature and in the pressure range from the vapor pressure at the melting point to the critical pressure. The method requires only a one- to two-gram sample for one entire series of measurements over the complete temperature and pressure range, and the sample is recoverable. Surface adsorption and liquid densities can be determined by parallel systems and at the same time. Precision is limited only by the measurement and control of thermostats and by the accuracy of direct weighing.
Two Simple Apparatus for Measuring the Cyclotron (Vertical) Magnetic Field with High Accuracy
Authors: Chang W. Y. , Rosenblum S.
Published: February 2005

A magnetic balance and an indicating coil for measuring a strong vertical magnetic field (the cyclotron magnetic field) are described. The magnetic balance consists of an aluminium rectangular coil, resting with agate knife-edges on agate supports, and of a pair of pulley systems. It is sensitive to about 1 gauss in 10,000 gauss. The indicating coil has such a non-linearity that, when it is working in the vertical position, it is able to indicate a field of more than 10,000 gauss and, on the top of this amount, a variation smaller than 1 in 10,000. Both of the apparatus have been tested, and actually used in conjunction with an alpha-ray magnetic spectrograph.
An Alternating Field Induction Flow Meter of High Sensitivity
Authors: Kolin Alexander
Published: February 2005

An electromotive force is induced in a fluid moving in a pipe at right angles to a magnetic field. This effect can be used to measure magnetic fields by maintaining a known flow or to measure the discharge of a fluid through a pipe by maintaining a known magnetic field. The flow of poor electrolytic conductors like tap water can be measured as well as the flow of a liquid metal like, for instance, mercury. A modification of the apparatus for the purpose of measuring the velocity distribution and fluctuations of the instantaneous velocity in large channels comprising a minute magnet with attached electrodes is described.
Steady-State Sensitivity of a Vacuum Bolometer
Authors: Amdur I. , Glick C. F.
Published: February 2005

The theory of the steady-state sensitivity of a vacuum bolometer as a function of operating temperature has been developed from exact heat flow equations which take into account losses by wire conduction as well as by radiation, and increase of bolometer resistance with temperature. Sensitivities predicted by the present theory differ by more than 50 percent from those computed from an earlier theory in which the effects of wire conduction and of increase of bolometer resistance with temperature were considered negligible. Experimental sensitivities determined with a test bolometer show good agreement with values calculated from the present theory, particularly in the region of optimum sensitivity where deviations are of the same order as experimental errors. The method of extending the theory to predict steady-state sensitivities of bolometers which are not operated in vacuum has been illustrated for the pressure region in which free molecule conduction predominates.
Durability Tester for Coated Optical Elements
Authors: Townsley M. G.
Published: February 2005

The present widespread military use of thin films of various types coated on optical elements has made it necessary to raise the abrasion resistance of these coatings to the maximum possible value. Research on improving abrasion resistance and the measurement of the abrasion resistance of finished films have been handicapped by the lack of a suitable reproducible testing method. It is the purpose of this paper to describe a reproducible and semi-quantitative testing method for measuring the abrasion resistance of thin films coated on optical elements.
The Design and Construction of Rapid-Response Thermocouples for Use as Radiation Detectors in Infra-Red Spectrographs
Authors: Roess L. C. , Dacus E. N.
Published: February 2005

The design and construction of a rapid-response vacuum thermocouple for use in an infra-red spectrograph is described. The thermocouple is made by condensing 600–1000A thick layers of Bi and Sb, which overlap slightly to form the hot junction, on a 400–500A thick film of Formvar. This film is stretched over a glass form having an opening under the hot junction. The hot junction is blackened with gold evaporated in H2 at 2–4 torr. (1 torr=1 mm Hg.) The thermocouple is intended for use with radiation interrupted at frequencies between 1 and 5 hertz. (1 hertz=1 cycle per second.) It is shown that the signal-to-noise ratio of the thermocouple, defined as the ratio of the interruption frequency component of its output to the square root of its resistance, is the only criterion of its goodness, and that in an infra-red spectrograph a single junction thermocouple has a greater signal-to-noise ratio than a multijunction thermopile. An important operation in the thermocouple construction is the use of a glow discharge before condensation of each metal to reduce the thermocouple resistance by factors of 5 to 10. Such a thermocouple has a resistance of between 20 and 50 ohms, a d.c. sensitivity of 6–7 microvolts per 10−4-watt cm−2, and an output under radiation interrupted at 7 hertz of not less than one-half the d.c. value.
Testing the Knife Edges of the Chemical Balance
Authors: Craig Archibald
Published: February 2005

Discussion of conditions necessary for accuracy in weighing, and tests available to chemists. Sharpness and straightness are tested optically and mechanically. Formulae are given for arm ratio, alignment, and parallax (the departure of the edges from parallelism with each other), from which gravimetric methods are derived. Tolerances are suggested for use in specifications to control repairs and compare bids.
An Automatic Precision Space-Indicating X-Ray Back-Reflection Instrument
Authors: Carapella Louis A. , Kaiser Herman F.
Published: February 2005

A new and simple instrument which can be employed automatically for the rapid and precise determination of x-ray back-reflection lattice spacings is described. The instrument is essentially a precision back-reflection focusing camera containing a Geiger-Müller counter, a pin-hole collimator system, and a movable x-ray disk baffle with a specially designed circular slit system. Once the instrument is calibrated, the lattice spacings are measured by the position of the slit system on disk which in itself is part of a simple micrometer measuring device. The instrument is capable of high precision and great rapidity in the measurement of lattice constants and their changes.
The Multiplier Photo-Tube in Radioactive Measurements
Authors: Blau M. , Dreyfus B.
Published: February 2005

An improved method for the measurement of alpha-ray sources, using the luminescence of fluorescent screens, is described. The improvements consist of the use of a multiplier photo-tube and long lived non-emanating alpha-standards. The chief advantage of the multiplier photo-tube is its great flexibility, allowing quite an extensive range of measurements. Alpha-ray sources, ranging from 110μC up to a few curies, can thus be measured, in a much quicker fashion than either the ionization or calorimetric method would permit. The standardization procedure of the photo-tube for measurements of absolute intensity is described in detail, the accuracy of the results being estimated at 5 percent. New applications of this method to the preparation of photometric standards and to the measurements of strong neutron sources are suggested.
An Improved Electronic Stimulator
Authors: McCombs Rollin K. , Walz Frank C.
Published: February 2005

There is described the operation and calibration of an electronic stimulator which supplies a unidirectional, rectangular current pulse of variable frequency, amplitude, and pulse length (length of the conducting portion of the cycle). Each of these three variables is independent of changes in the other two, and the amplitude is virtually independent of variations in the resistances of individual subjects. The range of frequencies extends from one cycle in several minutes to 20,000 cycles per second. With the maximum amplitude of 2 milliamperes the resistance of the subject may be as great as 200,000 ohms; smaller amplitudes or a slight modification of the circuit permits the allowable resistance to be increased. The pulse length may be varied from a minimum of 110 of the cycle to any desired value.
A Modified Kelvin Method for Measuring Contact Potential Differences
Authors: Meyerhof W. E. , Miller P. H.
Published: February 2005

A simple, rugged, and reliable apparatus for the measurement of contact potential differences (in the future abbreviated CPD) by a modified Kelvin method is described. The null circuit using a 6F5 as electrometer tube has a sensitivity of 0.5-cm scope deflection/mv of CPD/cm2 sample area, which permits the CPD to be determined to 1/100 volt for samples with surface areas as small as two square millimeters. The apparatus was developed for the study of surface characteristics of metals.
A High Speed Microtome for the Electron Microscope
Authors: Fullam Ernest F. , Gessler Albert E.
Published: February 2005

Two forms of a high speed type of microtome are described which are able to cut cross sections to the thinness required for electron microscopic study (0.1 to 0.8 micron, depending on the material). Techniques of microtome operation are suggested together with a few methods of sample preparation and subsequent section treatment, namely, collecting, selecting, and mounting. Embedding materials which sublime readily are described; these have been used successfully with this high speed microtome to support many types of materials. These volatile embedding materials have the advantage that they eliminate the difficulties that on some occasions arise with the use of solvents in the process of solvent extraction of embedding materials, such as Carbowax and paraffin, from the sections. A number of photographs are shown of the high speed microtome as well as electron micrographs of a few sections produced by the instrument. These pictures of rubber, rayon, Lucite, block Nylon, and animal tissue indicate some of the fields of application of the microtome and demonstrate the effectiveness of the necessary auxiliary techniques for it, particularly sample hardening and embedding, and section collecting and mounting.
Production of Particle Energies beyond 200 Mev
Authors: Schiff L. I.
Published: February 2005

Six proposed devices for the production of charged particles with energies greater than 200 Mev are described briefly. These are: betatron, synchrotron, microtron, linear resonator accelerator, linear wave guide accelerator, and relativistic ion cyclotron. Attractive features and possible difficulties are discussed in each case. An Appendix presents some results of the theory of radiative energy loss by fast charged particles.
A Meter for High Voltage Measurement
Authors: Alfvén Hannes , Eklund Sigvard
Published: February 2005

A high voltage meter employing a capacity divider can be used even for d.c. measurements if it is combined with a special automatic grounding device. The construction of an instrument covering the range 2–100 kv is described. Applications and further improvements are discussed.
Potentiometers
Authors: Nettleton L. A. , Dole Fred E.
Published: February 2005

The use of potentiometers in automatic electrical computing devices has necessitated a great improvement in commercial wire wound potentiometers in order to meet exacting requirements. For example, the use of ``end resistors'' has made it necessary to hold both the over-all resistance and the resistance gradient to close tolerances. The accuracy must not only be of a high order, but it must be sustained throughout a long operating life. Methods used to improve performance, including the use of noble metal alloy contact materials, are discussed in this article.
B–H Meter for Samples of Small Cross-Sectional Area
Authors: Crittenden Eugene C. , Smith Charles S. , Olsen Leonard O.
Published: February 2005

An instrument for measurement of the magnetic properties of samples of small cross-sectional area is described. The signal from two opposed pick-up coils, one of which contains the sample, is integrated, amplified, and applied to the vertical deflecting plates of a cathode-ray oscillograph. Each of the pick-up coils lies in one of a pair of identical magnetizing solenoids. The signal from a non-inductive resistance in series with the solenoids provides the horizontal deflection for the cathode-ray oscillograph so that the hysteresis loop of the sample is displayed on the fluorescent screen. The instrument is well suited for measurement of the magnetic properties of samples having cross-sectional areas of the order of magnitude of 10−5 cm2.
Reversible Decade Counting Circuit
Authors: Regener Victor H.
Published: February 2005

A ring-of-ten circuit is described, using ten pentodes, ten twin-triodes, ten resistors, and no condensers, per ring. Two pairs of input terminals are provided for clockwise and counter-clockwise feeding, respectively. This circuit can be used for electronic adding and subtracting, as well as for differential counting-rate measurements on two sources. With the addition of five resistors to a ring, the number of counted events can be indicated on the screen of a small cathode-ray tube. This circuit counts up to 5×105 evenly spaced events per second.
The Measurement of Current Transients in a Low Voltage Circuit
Authors: Barnes B. T. , Adams E. Q. , Hinman D. D.
Published: February 2005

An oscilloscope with a single-sweep circuit may be used for recording transient currents. If the current changes 1 ampere per microsecond, the oscilloscope shunt may need to have an inductance as low as .02 microhenry. An inductance tenfold lower than this can be obtained easily with a tubular resistor with a coaxial return conductor and coaxial potential leads to the oscilloscope. The resistance is provided by a layer of metal on a glass tube. Pt, Cu, and Ni have been used. Such a shunt was used to record the discharge currents of three condensers. Reasonable agreement between measured and computed currents was obtained.
Measurement of High Intensities with the Geiger-Mueller Counter
Authors: Muehlhause C. O. , Friedman H.
Published: February 2005

With sufficient amplification of the pulses from a G-M counter, it was observed that the deadtime decreased as the counting rate increased. The maximum counting rate of a tube could be advanced to 100,000 counts per second although its apparent resolving power at low rates did not exceed 10,000 per second. Above 10,000 counts per second the resolving power increased almost in proportion to the counting rate.
Design of a Proportional Counter for Gamma-Rays
Authors: Benson Bruce B.
Published: February 2005

The design and details of construction of a proportional counter for use in counting gammarays in the high proportional region are described. The circuit diagrams for the preamplifier, the main video amplifier, and the stabilized high voltage supply are included. The counter is operated with pure argon, or with argon plus a little air, at 50-cm pressure and about 1750 volts. When used with a coincidence circuit, employing blocking oscillators for sharpening the pulses, a resolving time of 4×10−8 second is obtained.
A Visual Null Indicator for Impedance Bridge Measurements at Radiofrequencies
Authors: Brine P. J. , Whitehead J. W.
Published: February 2005

With this cathode-ray null indicator, impedance measurements made with a bridge such as the General Radio Type 916A can be determined to an accuracy of 0.2 ohm in the presence of interference at levels exceeding 40 db above 1 microvolt.
A Variable Path Ultrasonic Interferometer for the Four Megacycle Region with Some Measurements on Air, CO2, and H2
Authors: Stewart James L.
Published: February 2005

A method of determining the constants of propagation for ultrasonic waves in gases, by use of the Pierce interferometer, was devised by Hubbard, and application of it extended to a limit of two megacycles by his various students. Herein is described a new interferometer which carried these investigations to the four-megacycle region. Alignment of the piston and crystal to the order of one light fringe was attained and maintained by employing Newton and Haidinger optical fringe systems. Velocities were measured to an accuracy of one-tenth of one percent, and absorption and reflection coefficients to fifty percent in air and CO2. The limit of accuracy in both cases was determined by the measurement of length, as measured to one micron with a micrometer screw. Preliminary measurements on H2 gave evidence of molecular dispersion between four and eight megacycles.
A Contact Modulated Amplifier to Replace Sensitive Suspension Galvanometers
Authors: Liston Max D. , Quinn C. E. , Sargeant W. E. , Scott G. G.
Published: February 2005

The electronic amplifier, described herein, is designed to measure extremely small d.c. and low frequency a.c. voltages in low impedance sources. Expressing the electrical noise in terms of equivalent input voltage with a 5-ohm input resistance and a 5-milliamp. Esterline-Angus recorder, the maximum departure from the mean does not exceed 1.5×10−9 volt. Under laboratory conditions the drift is less than 5×10−9 volt over a period of 8 hours. The amplifier is compact and rugged, and it is not affected by vibrations or accelerations experienced in moving vehicles. At present the amplifier is employed in the measurement of radiant energies in infra-red spectrographs. It is also used for various laboratory and field measurements.
A Sensitive Vacuum Gauge with Linear Response
Authors: Downing J. R. , Mellen Glenn
Published: February 2005

A new type of vacuum gauge is described for measuring pressures in the range between zero and 10 millimeters of mercury. The gauge response is a linear function of pressure. Three sensitivity ranges are provided by a selector switch giving pressure ranges of 0 to 0.1 millimeter, 0 to 1.0 millimeters, and 0 to 10 millimeters, the second value in each case corresponding to full-scale deflection of the output meter. The gauge is actuated by the ionization current resulting from the action of the radiation from a minute amount of radium on a small portion of the atmosphere within the vacuum system.
The Measurement of Thermal Radiation at Microwave Frequencies
Authors: Dicke R. H.
Published: February 2005

The connection between Johnson noise and blackbody radiation is discussed, using a simple thermodynamic model. A microwave radiometer is described together with its theory of operation. The experimentally measured root mean square fluctuation of the output meter of a microwave radiometer (0.4°C) compares favorably with a theoretical value of 0.46°C. With an r-f band width of 16 mc/sec., the 0.4°C corresponds to a minimum detectable power of 10−16 watt. The method of calibrating using a variable temperature resistive load is described.
Counting Rate and Frequency Meter
Authors: Lorenz Egon , Weikel Joanne , Norton Sue Gray
Published: February 2005

A counting rate and frequency meter circuit using a thyratron as pulse leveling device is described. It is characterized by its simplicity and its high resolving power of approximately 1×10−5 second for evenly spaced pulses.
A Simple Battery Operated High Voltage Supply
Authors: Williams L. E.
Published: February 2005

A simple, battery operated, portable, high voltage, power supply is described which can be assembled from easily available parts. Potentials greater than 1000 volts with load current of 100 microamperes may be obtained from a battery input of 90 volts at about 15 milliamperes.
A Simple Potentiometer Circuit for Production of the Tangent Function
Authors: Hofstadter Robert
Published: February 2005

A conventional potentiometer, wound uniformly on a cylindrical card of constant height, can be used to provide a close approximation to the tangent of an angle in terms of a voltage or current. Curves showing the degree of approximation are presented in the range (0, ±80°). By using a slight taper in the height of the card the tangent can be provided exactly, except for winding errors.
High Speed Pulse Recording Circuit
Authors: Watt B. E.
Published: February 2005

The circuits described are capable of driving a Cenco low impedance counter at rates greater than 130 counts per second. Hard tubes are used, and the circuit cannot jam.
The Liquefaction and Storage of Partially Converted Liquid Hydrogen
Authors: Grilly E. R.
Published: February 2005

Observations on the normal storage of liquid hydrogen showed the evaporation rate and ortho-para conversion rate to be consistent with those expected from a noncatalyzed reaction. A catalytic converter which gives 50 percent ortho when cooled with liquid air was installed in the feed-gas line of a 25 1/hour hydrogen liquefaction plant. The decrease in storage loss is well worth the trouble of installation and operation of the converter.
A Spiral-Scanning X-Ray Reflection Goniometer for the Rapid Determination of Preferred Orientations
Authors: Holden A. N.
Published: February 2005

A goniometer has been designed to rapidly scan polycrystalline metal samples along a spiral path in a stereographic projection, and which, when used with any recording counting-rate meter available on a modern x-ray spectrometer, enables the rapid determination of the preferred crystal orientations of the sample.
A Precision Recording Refractometer
Authors: Johnsen S. E. J. , Schnelle P. D.
Published: February 2005

An instrument is described which measures continuously and records the index of refraction of flowing liquid streams. The instrument is similar to a spectrograph employing a hollow prism through which the sample stream flows. Refractive index is inferred by measuring the position of the refracted beam of monochromatic light projected to form a slit image. Provision is made to compensate the instrument for rapid changes in temperature of the flowing stream of about ±10° Centigrade on either side of a reference temperature.
Apparatus for Measuring Internal Friction in Transversely Vibrating Metal Reeds
Authors: Jewell W. R.
Published: February 2005

This paper describes apparatus for measuring internal friction of nonferromagnetic reeds set in transverse vibration. It includes a description of a symmetrical transducer for inducing the vibrations and an optical method of observing the amplitude. Measurements can be made while the reed is temperature controlled and vibrating in a vacuum.
A Low-Frequency Oscillator
Authors: Howe R. M. , Leite R. J.
Published: February 2005

A low-frequency simple-harmonic oscillator, employing a relatively new method of approach, is described. An electronic analog computer of the differential analyzer type is used to solve the differential equation of a mass-spring system. Three dc operational amplifiers perform the computation and a sinusoidal output is obtained as the solution of the differential equation. Frequency is variable from 0.01 to 100 radians per second in steps of 0.01 radian per second. Distortion is less than 0.1 percent. Maximum output is 90 volts peak into a load of 100 000 ohms. The oscillator is particularly useful in the design and testing of servomechanisms and electronic simulators.
Nuclear Reactions Between Heavy Nuclei
Authors: Bennett Willard H.
Published: February 2005

A method is proposed for using a modified Van de Graaff machine for producing nuclear interactions between heavy nuclei. Negative ions are accelerated from ground to a stripping material in the high potential part of the machine where many electrons are stripped from the ions, and re-accelerated towards the target material in a grounded end of the machine.
An Automatic X-Ray Reflection Specimen Holder for the Quantitative Determination of Preferred Orientation
Authors: Chernock Warren P. , Mueller Melvin H. , Fish Howard R. , Beck Paul A.
Published: February 2005

A reflection specimen holder has been developed, which has several new features. A removable jig, which fits into the inner ring, is used for the rapid alignment of the specimen. Two different specimen scanning devices are described, which allow the primary beam to cover successively a large number of grains in the specimen surface while the diffracted intensity is being measured. Since many such time consuming measurements are required for an accurate pole figure, the operation of the instrument and the recording of the data have been made automatic.
A Direct-Reading Rate Meter for High-Intensity Penetrating Radiation
Authors: Morgan J. E. , Chambers F. W. , O'Connor D. T. , Istock J. T.
Published: February 2005

Inherent technical difficulties in the measurement of x-ray intensities from 100 to 5000 r/minute, at exciting potentials between 400 and 2000 KVP (kilovolts peak), have been investigated.

Extending the ranges of conventional condenser-electrometer dose meters by use of absorbing media not only increases energy dependence, but is also found to cause an apparent displacement in effective geometrical location of the ionization chamber. 250-r, 1000-r and 2500-r condenser chambers have proved susceptible to serious errors from dielectric leakage, which increase rapidly with chamber range above 100 r and with radiation energy above 200 KVP. Associated measurements of voltage saturation indicate that no error from this source need be expected for full-scale exposure times exceeding two seconds.

A direct reading circuit has been developed to combine the known wavelength characteristics of ``air wall'' thimble-type chambers with the linear current response of a portable d'Arsonval galvanometer. A 25-r Victoreen chamber, remotely read through lengths up to 70 feet of polyethylene coaxial cable, shows linear calibration from 35 to 5500 r/minute with over-all reproducibility to the order of ±1.5 percent. Ionization readings correspond, within the accuracy of chamber volume determination, to the definitive value of esu/cc second.
The Development of a Fine-Focus Flash X-Ray Tube
Authors: Criscuolo E. L. , O'Connor D. T.
Published: February 2005

Analysis of image quality indicates that a significant improvement in the technique of flash radiography might be attained through reduction of focal spot size. Existing requirements on such targets are already severe. Nevertheless it has been possible, through a novel conical design, to obtain a measured focal spot one millimeter square in a sealed-off flash tube operating at 100 kilovolts.
Pulse-Height Analyzer
Authors: Thomas J. W. , Verbinski V. V. , Stephens W. E.
Published: February 2005

A pulse-height analyzer using conversion of pulse amplitude to time is described. It has an accuracy, resolution, linearity, and stability better than one percent. It can be exposed to pulse rates of several thousand per second and records on tape up to 50 pulses per second. It is equivalent to a 250-channel discriminator of relative simplicity.
Theory of the Manometer Accelerometer
Authors: Steen Douglas , Casey Donald
Published: February 2005

The possible use of U- and O-tube manometers as extremely accurate and sensitive accelerometers is investigated. It is found that their steady-state fluid-level displacement is linearly related to the applied acceleration. Both the Navier-Stokes equation and Lagrange's equation are used to derive the equation of motion of the fluid level for a multiple cross-section tube. Nonlinear terms are derived to represent the turbulence introduced by change of cross section. Means of obtaining an overdamped, nearly linear, long time-constant accelerometer are discussed. A study of the effect of design on response reveals that almost any desired specifications can be achieved by an appropriate modification of structure and/or fluid medium. Experimental tests, conducted on a platform vibrated in a one-dimensional sinusoid by a rotating cam, confirm predictions based on the theory.
A Microbalance for the Determination of Protein Crystal Densities
Authors: Richards F. M.
Published: February 2005

A microbalance has been developed for the simultaneous measurement of the apparent weight and volume of a single protein crystal immersed in its mother liquor. The crystal density, computed from these values, is not subject to the errors, resulting from an altered environment, which are present in the usual flotation procedures. The technique, moreover, may also be used for following the volume and density changes which occur on changing the composition of the immersing liquid. The sensitivity is easily controlled by the choice of the diameter of the fiber used in the weighing mechanism. This balance may be of use in other systems where the apparent weight and/or volume of an object, immersed in a liquid of known composition, is required.
Low-Pressure Cloud Chamber
Authors: Mills Robert G.
Published: February 2005

An expansion cloud chamber has been developed which operates at a pressure before the expansion of about 45 millimeters of mercury. Since evaporation is rapid and the temperature very low during the sensitive time of the chamber, the density of the gas is higher after the expansion than before. The composition of the gas before the expansion is approximately 40 percent water vapor and 60 percent permanent gas. When the chamber is operated with oxygen or argon, the stopping power of the gas during the sensitive time is 7.6 percent that of NTP air. When it is operated with helium, the stopping power is 5.7 percent that of NTP air.
Gamma-Ray Energy Resolution with NaI-TlI Scintillation Spectrometers
Authors: Borkowski C. J. , Clark R. L.
Published: February 2005

A method for preparing and mounting NaI-TlI crystals for scintillation spectrometers which gives high optical efficiency, stability and good gamma-ray energy resolution is described. Variations in energy resolution of photomultipliers and NaI-TlI crystals is shown. Approximately 200-ev electron energy loss in a NaI-TlI crystal is required to release a single photoelectron from a photocathode whose efficiency is 60 microamperes per lumen.
A Cloud Chamber for the Study of Particles of Low Energy
Authors: Merkle T. C. , Need J. L.
Published: February 2005

A cloud chamber with a magnetic selection favoring low-energy particles is discussed. Technical aspects of shielding, expansion, mechanism, sweeping field, and poisoning troubles are included. Discussion of the present mode of operation for a study of π− capture in helium is given.
Apparatus for the Measurement of the Thermal Conductivity of Solids
Authors: Weeks James L. , Seifert Ralph L.
Published: February 2005

An apparatus has been developed with which thermal conductivities can be measured in the temperature range from 40°C to 100°C with a probable error of ±0.003 cal sec−1 cm−1 deg−1 or ±3 percent, whichever is the larger. It requires only a small sample (0.1875×0.1875×1.75 inches), does not require the attaching of thermocouples to the sample, and permits introduction and removal of the sample by remote control, if this is necessary. The apparatus is therefore especially useful to measure the thermal conductivity of large single crystals and also to observe the effect upon thermal conductivity of heat treatment, irradiation, or any other treatment that will not deform the sample yet which cannot be carried out readily with thermocouples attached to the sample.
Low-Temperature X-Ray Goniometer for Structural Studies of Crystal Transitions
Authors: Keeling R. , Frazer B. C. , Pepinsky R.
Published: February 2005

A low-temperature x-ray goniometer for use between liquid nitrogen temperature and approximately −100°C has been designed for use with a Weissenberg camera, General Electric powder camera, or a Geiger counter system. The crystal is mounted on a goniometer head inside a vertical cylindrical stainless-steel Dewar, and is irradiated through a polystyrene tip at the lower end of the Dewar. The crystal is cooled by conduction through the goniometer head, which is silver-soldered to the base of a liquid nitrogen chamber inside and concentric with the outer wall of the Dewar. The Dewar vacuum is maintained by an oil diffusion pump and a forepump, through a rotating seal and the post which supports the goniometer.

The Weissenberg camera mounts on a carriage and is driven by a 60-rpm reversing motor which also rotates the Dewar and crystal.

The carriage driving screws may be uncoupled from the motor shaft, and a Geiger counter spectrometer may be mounted on the carriage in place of the camera. The carriage is also adaptable for holding a G.E. powder camera.

A General Electric CA-7 x-ray tube mounted horizontally supplies the x-ray beam.