bluuebunny/crossref_metadata_2025 huggingface dataset:
A Broad Range Vacuum Spectrograph for the Extreme Ultraviolet
Authors: Compton K. T. , Boyce J. C.
Published: February 2005

A two meter focus, normal incidence, vacuum spectrograph is described which covers on one plate the whole range from the zero order up to the first order of λ2500. The 30,000 line per inch glass grating gives a dispersion of about 4.27A per mm and strong spectra are obtained to as short wave-lengths as λ300, with lines a little below λ200 showing on long exposures. The body of the spectrograph is exhausted by an Aristovac pump to a pressure of 2×10−5 mm, a vacuum guard ring device of double rubber gaskets being used to seal the end covers. The instrument is particularly suitable for the establishment of short wave-length standards and for the study of line and band spectra from gas discharges and the study of absorption spectra in gases. The limitations of the instrument are discussed and suggestions are given, based on several years' experience with this instrument, for a spectrograph of new design which would avoid most of the difficulties inherent in this general type of vacuum spectrograph.
An Improved Wire Grating Spectrometer for the Far Infrared
Authors: Barnes R. Bowling
Published: February 2005

A spectrometer of new design is described, which makes easier the investigation of the far infrared spectra of either solids, liquids or gases. With this instrument a very high degree of resolution has been obtained and several substances have been studied from 30μ to 180μ. From 30μ to 85μ the effective slit-width was 1.04μ; from 85μ to 122μ, 1.67μ; and from 122μ to 180μ, 2.59μ.
A Balanced Electrometer Tube and Amplifying Circuit for Small Direct Currents
Authors: Harnwell G. P. , Van Voorhis S. N.
Published: February 2005

An extension of the DuBridge circuit is described which allows tubes of a fairly wide range of characteristics to be used. The application to the old type FP-54 and to a tube obtained from the Bell Telephone Laboratories is described. A very stable direct-current amplifier is also described which may be used independently for the measurement of currents of the order of 10−12 amp. or in the output of an electrometer tube circuit.
A New Ballistic Galvanometer Operating in High Vacuum
Authors: Ellwood W. B.
Published: February 2005

A resonant ballistic galvanometer has been developed especially for precise magnetic flux measurements. The sensitivity is high, one millimeter deflection at one meter scale distance corresponding to 4 Maxwell turns as compared with 500 Maxwell turns for the same deflection in commercial galvanometers. The galvanometer is based upon the principle stated by Maxwell that, if the charge to be measured by a ballistic galvanometer can be sent repeatedly through the galvanometer in proper phase, the amplitude of the swings will increase to a steady value which is proportional to the charge and which is greater the smaller the damping. Operating the moving coil in high vacuum eliminates air damping. A flat tape suspension, thin enough to approach in its properties a simple bifilar suspension, reduces elastic hysteresis. Light from the galvanometer mirror acts on a photoelectric cell controlling the switching mechanism, to ensure the correct timing of the repeated impulses. A high accuracy of integration is attained by reducing to a minimum the eddy currents and hysteresis losses in the galvanometer itself. This is done by avoiding the use of metal in the neighborhood of the coil.
A Mechanical Rectifier for the Measurement of Small, Commercial-Frequency, Alternating Potentials
Authors: Steffens Carsten C. , Tolman Richard C.
Published: February 2005

A mechanical rectifier for use at commercial frequencies has been constructed. Accidental electromotive forces have been so far eliminated that it can be used with a sensitive direct-current galvanometer as a detecting instrument. Four galvanometers have been tried and the results are described. With the most sensitive galvanometers used, the sensitivities of the system at 50 cycles were 0.05 microvolt (without the critical damping resistance), and 40 micromicroamperes per millimeter at one meter.
Note on a Precision Variable Condenser for Direct Measurement of Extremely Small Capacity Changes
Authors: Stranathan J. D.
Published: February 2005

A precision condenser of small capacity change, and an accurate method of calibrating it, is described. In measuring very small capacity changes it has several advantages over the usual series condenser arrangement.
The Effect of Treatment of the Surfaces of Calcite Crystals Upon the Resolving Power of the Two-Crystal Spectrometer
Authors: Manning Kenneth V.
Published: February 2005

Crystals have been prepared for use on the two-crystal spectrometer by grinding and etching the cleavage faces. The widths of rocking curves in the (1, −1) position have been investigated for different conditions of the surfaces. The etched crystals have been found to give higher resolving power than the original faces. The improvement is greater at short wave-lengths than at the longer.
Portable Alternating-Current Operated Heterodyne Beat Apparatus of Unusual Frequency Stability
Authors: Stranathan J. D.
Published: February 2005

In the heterodyne beat method of measuring dielectric constants of vapors or very dilute liquid solutions, it is difficult to eliminate frequency drift in the one oscillator. Apparatus which will almost completely eliminate this drift is described; it has the further advantage of operating entirely on a.c., thus eliminating much inconvenience and appreciable battery upkeep. The apparatus is portable, and therefore useful as a laboratory piece as well as for research.
A Double Tube Vacuum Tube Voltmeter
Authors: Michels Walter C.
Published: February 2005

By the use of two type 37 vacuum tubes it has been found possible to design a high impedance voltmeter which possesses an approximate voltage squared characteristic, and is therefore suitable for the measurement of r.m.s. values of alternating potentials. The circuit of the voltmeter is such as to make the readings independent of appreciable fluctuations of the battery potential supplied to the tubes.
An Electron Microscope for Studying Thermal and Secondary Electron Emission
Authors: Meschter Emery
Published: February 2005

The construction of a magnetic electron microscope for the observation of self-emitted and secondary electrons from the same surface is described. Primary and secondary images obtained are illustrated.
The Polyelectrophysiograph: An Instrument for Teaching and Research in Biological Sciences
Authors: Huddleston O. Leonard , Whitehead Richard W.
Published: February 2005

(1) The important characteristics of three groups of luminescent materials (phosphor) used in the construction of screens for cathode-ray tubes have been described and some of the practical applications of these characteristics pointed out. (2) Some of the advantages and disadvantages of the ``slow'' screen tube, RCA 910, are discussed briefly and a description of the application of this tube to the study of heart sounds, or action currents from the heart and brain or peripheral nerves is made. (3) A method of erasing persistent phosphorescent tracings by means of exposing the tube screen to red light has been presented. (4) The general arrangement of the ``slow'' screen and ``fast'' screen cathode-ray tubes together with some of the associated control equipment of the polyelectrophysiograph has been described. This new laboratory instrument has proved extremely useful for both teaching and research.
A Recording Spectrograph for the Far Infra-Red
Authors: Randall H. M. , Firestone F. A.
Published: February 2005

This spectrograph records upon sheets of photographic paper 20×30 inches in size, spectra lying in the range between 18μ and 200μ. Of this range, 9μ may be spread over a single record, or as much as 100μ may be covered, depending upon the gratings and the adjustments used. The spectrograph is a vacuum instrument of high resolving power, being capable of separating sharp lines somewhat closer than 0.5 cm−1 apart. Detailed drawings of its construction together with several records are shown and described. The recorded galvanometer deflections are usually adjusted to lie between 100 and 300 mm.
Photoelectrically Balanced Recording Potentiometer
Authors: Fairchild C. Owen , Parsegian V. Lawrence
Published: February 2005

The problem of stopping a moving light-beam on the edge of a phototube without any tendency to oscillate or ``hunt,'' and with speed and precision has been solved by a new method and a recording potentiometer is rapidly and accurately balanced. By (1) artificially canceling the generated back e.m.f. of the moving galvanometer thus advancing its return movement from a deflected position, and (2) delaying the grid potential change of a triode amplifier in the photoelectric circuit, galvanometer lag is counteracted and the potentiometer is balanced with an accuracy of a few hundredths of a percent of the range. The total power input to the instrument is about 35 watts and the contact carriage speed is made as high as 10″ in 20 seconds.1 The fundamentals of the complete instrument are discussed and equations describing the galvanometer movement are included.
An Oscillator for Ultra-High Frequencies
Authors: Barrow W. L.
Published: February 2005

A coaxial line stabilized oscillator that is easily and rapidly adjustable over the frequency range from 70 to 700 Mc per sec. is described. Rugged mechanical construction, substantially complete shielding and coaxial line output connection are other features. With a 316A type vacuum tube, outputs of several watts are obtained over the entire range. Measurements indicate that for best stability it is necessary to tune precisely both filament leads, in addition to providing a high Q tank circuit. An optimum resonant length (λ/4, 3λ/4, ···) of line was not found. The stability decreases as the frequency increases, becoming very poor for frequencies near the limit of oscillation of the tube.
Characteristics of a Strong Ion Source
Authors: Timoshenko Gregory
Published: February 2005

Construction and operating characteristics of an ion source of the capillary arc type are described. The source yields 0.4 milliampere of singly charged argon ions through an orifice 1 mm in diameter, which allows, with pumping speeds of 14 liters per second, maintenance of a pressure of 5×10−5 mm Hg in the adjacent chamber where the ions are used. The ion beam is easily focused at ion accelerating voltages of 1000 to 6000 volts. The source has been used as part of an apparatus for study of controlled sputtering of metals bombarded by argon ions, and the accompanying secondary electron emission. The source can be used advantageously in a number of analogous researches of a fundamental character, and also has application in the field of engineering and biology.
A Vacuum Type Air-Driven Centrifuge for Biophysical Research
Authors: Beams J. W. , Linke F. W. , Sommer P.
Published: February 2005

An improved vacuum type self-balancing centrifuge which is driven by air is described. It is especially suited for spinning rotors larger than 2 inches in diameter at very constant temperatures. Either the ``quantity'' or ``analytical'' type of rotor may be used with the same driving mechanism.
The Limiting Sensitivity of an Alternating-Current Method of Measuring Small Magnetic Moments
Authors: Johnson E. A.
Published: February 2005

A method of measuring the moment of small magnetic dipoles is described. The dipole to be measured is rotated inside of a fixed coil, and the voltage induced in the coil is measured by means of an alternating-current amplifier. The limiting sensitivity is computed from the calculated signal-voltage and the thermal agitation in the input circuit. In the practical application the theoretical sensitivity is approximately obtained and moments of 3×10−7 c.g.s. unit can be detected and with a specimen 1.5 cm on a side 8×10−8 c.g.s. unit/cc can be detected. The method has been applied to the measurement of the polarization in sedimentary deposits.
Some Experiments on the Amplification of Thermocouple Electromotive Forces
Authors: Gunn Ross
Published: February 2005

Experiments employing a new type of regenerative direct-current amplifier have shown that such equipment is unsuited for use, except, perhaps, in the laboratory. A successful system of amplification employing vacuum tube amplifiers and commutators for inverting and synchronously rectifying the resulting amplified alternating potentials is described. Thermocouple electromotive forces less than 10−9 volt are readily indicated on a portable microammeter. The over-all useful amplification with portable equipment exceeds 50,000.
A Silica Gauge for Measuring Thickness by Means of Interference Colors
Authors: Blodgett Katharine B.
Published: February 2005

Details are given of the construction of a gauge for measuring the thickness of monomolecular films by means of the interference of light. The intensity of monochromatic light reflected from a thin film of a transparent material varies with the thickness of the film according to a cosine curve. When light strikes a film at an angle of incidence i=15°, the variation of the logarithm of the intensity with thickness is greatest at thicknesses 0.75λ/4n and 1.282λ/4n, where n is the refractive index of the film. In order to bring the thickness to this critical value a silica film was developed on lead glass by treating the glass with HNO3. Monolayers of various substances can be deposited on top of the silica film, and the thickness of the monolayer determined from the change in intensity of reflected light produced by the added thickness. The change of intensity can be determined very accurately by a method of measuring the ``match angle'' at which two steps of different thickness reflect light of equal intensity. When this angle can be measured with an accuracy of ±10′ the thickness of the added monolayer is known with an accuracy of ±0.76A. Equations are given for calculating thickness.
A Reflecting Mirror Optical System for the Ultracentrifuge
Authors: France Wesley G. , Lang E. Reed
Published: February 2005

(1) An inexpensive optical system suitable for use with an air-driven ultracentrifuge is described. (2) Sedimentation pictures of inorganic colloid systems indicate the quality of sedimentation pictures possible with this apparatus.
A Hard Vacuum Tube Pulse Equalizing Sharpening Circuit
Authors: Huntoon R. D. , Strohmeyer L. J.
Published: February 2005

A pulse sharpener equalizer capable of producing sharp pulses whose amplitude and width are independent of the wave form of the input signal is described. Input pulses having a width of 100 sec. to 10−4 sec. work equally well and a change of bias permits operation with either positive or negative input pulses. The circuit uses all hard tubes and gives output pulses of either sign essentially the same in form as the interstage pulses in a scaling circuit, hence the resolution of the scaling circuit is not impaired by the use of the sharpener.
Design and Performance of a Proton Accelerator for Quantitative Irradiation of Living Matter
Authors: Scott G. W. , Haskins C. P.
Published: February 2005

An apparatus is described for accelerating protons up to 400 kv with which to irradiate biological specimens in vacuum. The voltage is supplied by an air-insulated electrostatic generator used with a multiple section tube. The protons are produced by a convenient and reliable source, which is described. Details of the irradiation of spores of the fungus Aspergillus niger with protons are mentioned.
Use of Ultraviolet Source for Interferometer Measurements of Thickness of Thin Metallic Films
Authors: Clark J. C. , Fritz N. L.
Published: February 2005

A method is described for measuring the thickness of thin metallic films, using λ=3654A filtered from the mercury arc spectrum as the source of light for the Michelson interferometer. The shorter wave-length light source produces a proportionally greater fringe shift in the interference pattern and thus thinner films can be measured with a greater accuracy. This method is used satisfactorily for films of the range 150–600A.
A Calculation of the Error Due to the Absence of Guard Electrodes in X-Ray Ionization Chambers
Authors: Walbridge N. L.
Published: February 2005

An equation was derived for the fraction Q of the incident x-ray power P which escapes as kinetic energy of electrons. Q=0.140τS(1+e−μl)[r−1r(1−λλK)3+1r(1−λλL)3+1.20(1−wK)(r−1)r(λλKα−λλL)3],where τ and μ are, respectively, the linear true and total absorption coefficients for the incident wave-length λ, S is the range of an electron having an energy hν corresponding to the wave-length λ, r is the K absorption jump ratio and wK is the K fluorescent yield. λKα, λK and λL are, respectively, the wave-lengths of the K lines, the K absorption limit and the L absorption limit. This equation can be used to eliminate the necessity of guard electrodes.
A Comparison Between a Geiger-Mueller Counter, a Secondary Electron Multiplier Tube, and Photographic Film for Detecting Weak X-Rays
Authors: Eisenstein A. , Gingrich N. S.
Published: February 2005

A comparison has been made between three methods, given in the title, for the detection of weak x-rays. The secondary electron multiplier tube has a lower resolving time than the Geiger-Mueller tube, but the G-M tube is from 5 to 10 times as sensitive to x-rays of the wave-lengths here studied, 0.63A to 1.54A. A diffraction pattern of a liquid can be obtained with a G-M counter in roughly one-twentieth the time taken for a photographic exposure.
Optimum Liquid Combinations for Cloud Chambers
Authors: Beck Clifford
Published: February 2005

A search was made for liquid mixtures giving low expansion ratio, low background fog, and good electron tracks in cloud chambers filled with air at near atmospheric pressure. As was expected from theory, mixtures of any lower alcohol with water gave a minimum in the curve of expansion ratio versus concentration, while no minimum was found in the curve for mixtures of any two alcohols. The optimum mixture found for chamber use was 50 percent ethyl or normal propyl alcohol, 25 percent water, and 25 percent acetone; the presence of acetone definitely increases the contrast between tracks and background fog. A brief study of photochemical fog, with a quartz mercury arc, showed that wave-lengths below 3900A are chiefly responsible for such fog. Irradiation of pure alcohols gives no perceptible fog, but irradiation of the optimum mixture above produces dense fog. However the clean-up after irradiation is sufficiently rapid to offset the disadvantage of its sensitivity to light.
An Interferometric-Dilatometer with Photographic Recording
Authors: Nix F. C. , MacNair D.
Published: February 2005

An interferometric-dilatometer for the temperature range from +750° to −190°C with photographic recording. The method is illustrated by results obtained on quartz perpendicular to the optic axis.
Vacuum Tube Scaling Circuit
Authors: DeVault Don
Published: February 2005

A scaling circuit is described in which certain desirable characteristics are obtained by applying the tripping impulses to the cathodes of the scaling tubes. The circuit is a scale-of-sixteen type employing hard tubes with no interstage coupling.
An Integrating Photoelectric Meter
Authors: Kuper J. B. Horner , Brackett F. S. , Eicher Maynard
Published: February 2005

Integrating meters for measuring ultraviolet energy have been developed which are unaffected by weather conditions and have been operated in the field without skilled attention for over two years. They have also proved useful in the laboratory, providing radiation dosage measurement within one or two percent. These employ special photo-tubes with a condenser and cold cathode ``trigger'' tube sealed in an extension of the glass envelope, thereby eliminating moisture as a source of leakage. A suitable registering circuit for counting the pulses from the ``trigger'' tube is described. Characteristics are given of typical photo-cells useful in erythemal and bactericidal measurements.
Operation of Proportional Counters
Authors: Korff S. A.
Published: February 2005

The operation of proportional counters is described. The voltage region for proportional operation is determined, and a procedure is described for determination of the amount of ionization in the initial ionizing event.
A Ballistic Meter for Measuring Time and Speed
Authors: Reich Herbert J. , Toomim Hershel
Published: February 2005

This paper describes a speedmeter in which a ballistic galvanometer serves as the indicating and recording element. Current flow through the galvanometer is initiated and stopped by means of a thyratron controlled by two switches. The instrument was designed primarily for the measurement of automobile speeds in traffic studies, but should have other applications.
An Optical Method for the Measurement of Ultrasonic Absorption
Authors: Gregg E. C.
Published: February 2005

The absorption coefficients of various liquids were determined by measuring the voltage which must be applied to the vibrating crystal in order to bring the points of convergence of parallel light into focus in a microscope set at various distances down the sound beam. As was expected by theory, a linear relationship appeared between the logarithm of the voltage and the distance of the light beam from the radiator along the sound beam. The absorption was measured as a function of the slope of this line.
The Design of Hydrogen Liquefiers
Authors: Starr Chauncey
Published: February 2005

The general principles underlying the practical design of Joule-Thomson hydrogen liquefiers, utilizing the compressed hydrogen commercially available in cylinders, are discussed. The theory of heat interchangers is applied to these liquefiers and design formulae and data are presented. A typical design for the regenerative interchanger of a small scale liquefier is given. The liquid nitrogen requirements, expansion valve design, charcoal trap construction, and other practical aspects of these liquefiers are also discussed.
Crystal Lattice Models Based on the Close Packing of Spheres
Authors: Patterson A. L.
Published: February 2005

The problem of the close packing of spheres is investigated exhaustively for the case in which the spheres occupy the lattice points of a space lattice. This type of packing can be realized in boxes with plane walls as suggested by Langmuir and Nelson. It is shown that there are fifteen types of packing which differ from one another either in symmetry or in the number of contacts a given sphere makes with its neighbors. In these fifteen types, ten of the fourteen Bravais lattices are represented. The use of lattice close packing as a basis for models of more complex structures is discussed.
Use of the Cathode-Ray Tube for Comparison of Capacities
Authors: Cole Robert H.
Published: February 2005

A simple method is described for comparison of capacities. It consists of a circuit containing the unknown and standard capacities in series, the potential differences across them being applied directly to the vertical and horizontal deflecting plates of a cathode-ray tube. Simple methods for calibration of residual circuit capacities and of the cathode-ray tube are described. The method is capable of an accuracy of the order of 0.5 percent in the range 50 kc to 2 mc and has the advantage that determination of the unknown capacity is unaffected by parallel conductance of the unknown.
Focusing X-Ray Monochromators
Authors: Smith Charles S.
Published: February 2005

Notes on the preparation of rocksalt crystals for use as focusing x-ray monochromators are presented. Arrangements for using these monochromators in the production of powder patterns are described.
Purification of Radon
Authors: Macdonald P. A. , Margolese M. S.
Published: February 2005

A radon plant of simple design and construction is described.
Note on the D.C. Characteristics of the String Galvanometer
Authors: Rogers F. T.
Published: February 2005

A useful fifth-degree equation is derived for the d.c. behavior of the string galvanometer; it contains seven parameters, three for the (symmetric) magnetic field, three for the (elastic) suspension, and one for the length of the string. Examples and a discussion are given concerning the practical use of this equation.
Eddy Current Induction Applied to the Determination of Accelerations
Authors: Forbes J. E.
Published: February 2005

Eddy current induction effects have been utilized in the construction of a simple electrical device whose voltage output is proportional to either rotational or vibratory accelerations. The output of the device is shown to be directly proportional to harmonic linear accelerations of small amplitude and frequencies up to at least 50 cycles per second. The utility of the device in recording certain types of vibration is also presented.
Construction of a Spindle Type Svensson Diagonal Slit
Authors: Burns J. W. , Henke L. K.
Published: February 2005

The practical working part of the theory of the Svensson method for the direct photography of concentration gradients is presented, along with the design of a special diagonal slit for the accurate evaluation of diffusion constants, or the concentration of material present from the areas under Svensson diagrams. Photostats of the details of construction are available.
An Instrument for Studying the Topographies of Fine Textured Surfaces
Authors: Adams F. W. , Devol Lee , Letner H. R.
Published: February 2005

A profilograph, using a tracing point and optical lever system, makes profiles of fine textured surfaces, magnifying the elevations and depressions by as much as 6000×. With this instrument it is possible to detect surface variations as small as 0.04 micron. It is also possible to make a series of profiles along parallel paths from which topographic or relief maps can be prepared. Uses include the study of machined, lapped, and etched surfaces of importance in industry. The high accuracy is obtained with no more difficult machine work than the simultaneous lapping of two tapered bearings mounted on a single shaft. The use of torsion elements of special design for supporting the mirror makes the instrument relatively insensitive to vibration. These torsion elements are capable of supporting a mirror large enough to permit several reflections of the light beam, giving the instrument its high resolving power.
The Construction of a Mass Spectrometer for Isotope Analysis
Authors: Brown Harrison , Mitchell J. J. , Fowler Robert Dudley
Published: February 2005

The complete constructional details for a 180° Dempster type mass spectrometer are given. The ions have a radius of curvature of 15 cm, and are accelerated through a potential of 2000 volts. Circuit diagrams for the voltage stabilizers and magnet current stabilizer are included.
A Pentode Lock-In Amplifier of High Frequency Selectivity
Authors: Michels Walter C. , Curtis Norma L.
Published: February 2005

An amplifier which is based on the scheme of heterodyning the signal to be measured with a locking-in voltage of the same frequency, as proposed originally by Cosens, is described and its characteristics are discussed. The particular design used, with the locking-in voltage applied to the screen grids of two pentodes, possesses a distinct advantage over earlier instruments because the tubes operate on a linear portion of their transfer characteristics, reducing harmonic response, and also because the main power supply is direct current, so that there is little drain on the control supply. It is found that the response band can be given a width of the order of one cycle per second without undue inconvenience or expense.
An Electronic Voltage Stabilizer for 1 to 50 kv and 20 to 500 ma
Authors: Parratt L. G. , Trischka J. W.
Published: February 2005

A description is given of the design and performance of an electronic superdegenerative stabilizer in the output of a d.c. high voltage supply. This stabilizer is proposed as a satisfactory and economical solution, alternative with the usual controlled motor-generator set, of the problem of obtaining very steady high voltage at rather large powers (1 to 50 kv and 20 to 500 ma in the present design). The device reduces the residual ripple from the filter as well as stabilizes against fluctuations in the input voltage. The stabilizer, containing an 833 type tube with two stages of amplification in the grid circuit, is essentially a modification of the degenerative type of stabilizer; but, taking advantage of grid current, the stabilizer may be adjusted to have positive, negative, or infinite stabilization ratio. The device, using grid current, warrants a new name, and is termed a superdegenerative stabilizer.
An Apparatus for the Measurement of the Scattering of Low Velocity Ions in Gases at Low Pressure
Authors: Simons J. H. , Francis H. T. , Fontana C. M. , Jackson S. R.
Published: February 2005

An apparatus is described for the measurement of the scattering of low velocity ions in gases. This consists essentially of an ion source, focusing devices, a magnet for velocity and species selection, and a measuring chamber. Technique of construction and operation is described which enables scattering curves to be obtained where the effective cross-sectional area is plotted against ion velocity down to a velocity of two volts. This apparatus has been found useful for condensable gases such as water, as well as for non-condensable gases. It has been constructed in such a way that ion neutralization as well as elastic scattering can be quantitatively determined as a function of velocity.
Ultracentrifuge Cell
Authors: Pickels E. G.
Published: February 2005

Previous cells for the ultracentrifuge have proved inadequate because of leakage, distortion, breakage of quartz windows, and lack of facilities for proper alignment. These difficulties have been studied and remedies provided, particularly through the strengthening of cell parts, the use of a specially coated Duralumin centerpiece, the provision of a key for alignment, and an arrangement for always orienting the windows in the same manner to prevent reversal of stresses.
An X-Ray High Temperature Camera
Authors: de Bretteville Alexander
Published: February 2005

A powder camera is described which was designed for the purpose of taking x-ray photographs through an x-ray diffraction angle of 0°—45° in a cylindrical camera of 57.3-mm radius, to temperatures greater than 300°C. The essential features are (1) a concentric heater extending above and below the sample to minimize sharp temperature gradients; (2) easy access to the oven coils if adjustment is necessary; (3) an iron-constantan thermocouple of small dimensions which allows one to take temperatures close to the sample; (4) a water-cooled jacket surrounding the oven to avoid heating the film. Rotation of the sample at 1 r.p.m. is provided for. Calibration of the thermocouple and the type of capillaries are described for high temperatures.
Electronic Liquid Level Indicator
Authors: Coroniti S. C.
Published: February 2005

A method of continuously measuring the level of conducting and non-conducting liquids has been developed. The liquid to be measured occupies the inner space of a coaxial cylindrical condenser. As the level of liquid varies, the capacitance varies. The change in capacitance detunes a resonance resulting in a change of plate current through the oscillator tube.
Microelectrodes for Measuring Local Oxygen Tension in Animal Tissues
Authors: Davies Philip W. , Brink Frank
Published: February 2005

A description is given of two types of stationary platinum microelectrodes which electrolyze dissolved oxygen when suitable potentials are applied. With these electrodes it is possible to measure the oxygen tension in an open solution, and especially, to estimate local oxygen tensions in animal tissues. Electrodes have been constructed which can indicate oxygen tension as a function of position with a spatial resolution of 25 microns. One type of electrode, with the end of the platinum wire recessed inside the cylindrical glass tip, can be used to measure absolute oxygen tensions as often as once every five minutes. The other, an open type, with the end of the wire directly exposed to the outer medium, allows the estimation of relative oxygen tensions only, but gives continuous readings, and is useful for recording rapid changes of tension.
A Recording Echelette Grating Spectrometer for the Near Infra-Red
Authors: Smith Lincoln G.
Published: February 2005

A new prism-grating spectrometer employing replica echelette gratings and capable of resolving lines from 0.3 cm−1 to 1.0 cm−1 apart in the region 1–25μ is described. Careful shielding and construction of a stable amplifier have so reduced zero unsteadiness as to make possible the direct recording of galvanometer deflections. Atmospheric absorptions have been almost entirely eliminated by circulation of the air in the spectrometer box over chemicals contained in separate boxes.
An Infra-Red Absorption Cell for Gases at High and Low Temperatures
Authors: Smith Lincoln G.
Published: February 2005

An infra-red absorption cell for gases which may be run at any temperature from −100°C to +200°C is described. Made of monel metal, the cell is sealed with rocksalt windows fastened to thin lead end plates with Glyptal. The cell is heated by means of a coil wrapped around it and cooled by air from a reciprocating pump immersed in a low temperature bath or liquid air.
A Precision Method of Measuring Geiger Counter Resolving Times
Authors: Beers Yardley
Published: February 2005

The counting rates due to two separate constant β-ray sources and due to the two sources combined are measured. Because of the finite resolving time of the counter the sum of the counting rates due to the single source exceeds that due to the combined source. By application of formulae which are derived the resolving time and errors involved can be calculated from these quantities. Relatively high accuracy can be obtained by this method without excessive expenditure of time upon the measurements and without the use of very large counting rates which might damage the counter.
A Stabilized Ionization Gauge Circuit with Vacuum Tube Voltmeter
Authors: Rainwater James
Published: February 2005

A complete control circuit for use with the usual triode ionization gauge tube is described. A modified Ridenour Lampson type circuit is employed to stabilize grid and plate voltage, as well as emission current. A simple vacuum tube voltmeter circuit permits the use of a relatively rugged 0–1 milliameter to read plate current. Special provision is made for outgassing, and for leak hunting.
An Improved Apparatus for Supersonic Velocity and Absorption Measurements
Authors: Telfair D. , Pielemeier W. H.
Published: February 2005

The value and uses of supersonic velocity and absorption measurements are reviewed, and evidence that sound velocity measurements may still be used for heat capacity determinations is presented. An apparatus which is designed for (1) a general study of acoustical dispersion, and (2) the supersonic measurement of gaseous heat capacities. The general experimental technique to be used with such an apparatus is outlined, and results of measurements of the velocity of sound in air and of the heat capacity of propylene are briefly discussed.
An Improved Type of Electrically Driven High Speed Laboratory Centrifuge
Authors: Pickels E. G.
Published: February 2005

A description is given of a simple angle centrifuge which utilizes a direct universal motor drive that is capable of spinning an 8-inch rotor at 18,000 r.p.m. with an applied potential of 180 volts and at 12,500 r.p.m. with a potential of 115 volts. Specifications and operational data are given for rotors having diameters ranging from 7 to 10¼ inches and capacities ranging from 112 to 610 cc of fluid.
An Alternating-Current Apparatus for Measuring Dielectric Constants
Authors: Hudson Boyd E. , Hobbs Marcus E.
Published: February 2005

A heterodyne beat apparatus operating on alternating current is described. The essential features are: (1) a crystal controlled oscillator, (2) a variable capacitance oscillator, and (3) the power supply. By properly choosing plate potentials and by using a line voltage stabilizer the effects of normal voltage variations have been essentially eliminated. The frequency stability is found to be quite good, and the time of warm-up rather short. Especial care was given to rigidity of mountings, and to thermostating of both oscillators. Circuit details are shown in figures.
A Cosmic-Ray Radio Sonde
Authors: Neher H. V. , Pickering W. H.
Published: February 2005

The cosmic-ray radio sonde described in this paper was used for observations in the stratosphere near the magnetic equator. The instrument can be used for single counters or coincidences up to fourfold. It includes the necessary amplifiers and scaling circuits to operate a relay which keys the radio-transmitter. High voltage for the counters is provided by a buzzer and transformer unit. Small storage batteries are used for power to operate the unit for about three hours. Pressure and temperature signals are sent at eight-minute intervals. The complete instrument ready for flight, weighs about 3300 grams. The receiving equipment consists of a super-regenerative receiver with the signal output recorded on a paper tape.
Detection of Radon by Means of a Proportional Counter
Authors: Brown Sanborn C. , Elliott L. G. , Evans Robley D.
Published: February 2005

The detection of quantities of radon of the order of 10−12 curie by means of a proportional counter is discussed. Two methods are investigated. In one the radon is concentrated in a liquid-air trap before it is put into the counter and in the other the volume of the counter is made sufficiently large so that the radon can be swept into the counter with a few liters of inert gas. The first method has the advantage of requiring only small counters which work at conveniently low voltages but has low efficiency. The second method has the advantage of simplified filling technique and higher efficiencies, but suffers from the difficulty of obtaining stable operation unless the sweeping and filling gas is helium.
Design of the Minnesota Electrostatic Generator
Authors: Williams J. H. , Rumbaugh L. H. , Tate J. T.
Published: February 2005

A description is given of a voltage generator and ion tube which are enclosed in a vertical 100 lb./in.2 pressure enclosure 18 feet in diameter. Performance characteristics, voltage steadiness, and limitation to a present maximum of 3 Mv are discussed.
Direct Pen Recording of Galvanometer Deflections
Authors: Pompeo D. J. , Penther C. J.
Published: February 2005

An instrument is described which records directly the deflections of a light beam pointer without recourse to photographic development processes. The recording is easily accomplished at pen speeds of 12.7 cm per second across 25 cm of chart without ``hunting'' taking place. Essentially the basic idea of this recorder is that the pen follows the light beam from an external galvanometer by mounting a double cathode photo-tube on the pen carriage so that both move as a unit. By means of vacuum tube amplifiers operating a reversible motor, the pen carriage moves to the left when the light beam deflects to the left on to the left photo-tube cathode and to the right when the right photo-tube cathode is exposed. A movement of the light beam as small as 0.1 mm causes a corresponding movement of the pen. The instrument has been satisfactorily used, with considerable saving in time, for recording current-voltage curves in polarographic analysis, for obtaining infra-red absorption curves, and for recording ion currents in mass spectrographic work.
A New Apparatus for Rapid Photographic Spectrophotometry
Authors: Davis George E. , Woodrow Jay W.
Published: February 2005

A new quartz spectrograph for absorption spectrophotometry is described. The method is a modification of the usual photographic method. A very wide spectrogram is divided into transverse comparison strips by means of a grid over the photographic plate, as first proposed by Jones. The instrument offers certain important advantages, among which are high speed, predetermined spectral distribution of absorption data, certainty of obtaining values at absorption maxima and other definite wave-lengths, need for fewer photographic plates, and applicability to solids as well as to solutions and other liquids.
A Turbidity Comparator
Authors: Krebs Richard P. , Perkins Patricia , Tytell Alfred A. , Kersten H.
Published: February 2005

An a.c. operated photoelectric turbidity comparator which has been found useful in assaying physiologically active substances by measuring the growth of micro-organisms is described. A special feature is that the power supply for both the amplifier and the light source is electronically stabilized.
Sensitive Measurement of Impedance, Reactance, Frequency, and Phase Relationships with an Electronic Phase Bridge
Authors: Brown R. H.
Published: February 2005

Methods are described for making convenient and sensitive measurements of impedance, reactance, frequency, and phase relationships by means of an electronic phase bridge which is composed of a phase sensitive detector and an ``unbalanced'' bridge circuit. A general theory of the operation of Cosens' phase sensitive detector is presented. Peculiar sources of error encountered in the use of the electronic phase bridge are discussed and methods of eliminating them outlined.
War Production Board Regulations Relating to the Purchase of Scientific and Laboratory Equipment and Supplies
Authors: B. G. H.
Published: February 2005

Three general types of WPB regulations are presented: (1) Those which deal with priorities and preference ratings (P-43, P-100, P-90, and forms PD-1A and PD-25A); (2) Limitation Order L-144; and (3) Priorities Regulation No. 10. P-43 assigns a blanket preference rating of A-2 to purchases by certain research laboratories; P-100 assigns an A-10 rating to the purchase of supplies by certain ``producers'' including educational institutions; P-90 sets up the Production Requirements Plan under which certain producers must and others may operate, obtaining priorities assistance through the use of Form PD-25A; Form PD-1A may be used to apply for priorities assistance in securing required material and equipment not covered in other plans. Limitation Order L-144 limits the purchase of laboratory equipment containing critical materials to certain specified users and to users specifically approved by the WPB Supplementary rulings and unofficial interpretations have been obtained concerning L-144. Priorities Regulation No. 10 sets up an allocation classification system whereby certain symbols must be added to orders indicating the end use of the material being purchased.
An Instrument for Measuring Electrical Field Strength in Strong High Frequency Fields
Authors: Lion Kurt S.
Published: February 2005

An instrument is described which measures the intensity of the high frequency electric field, point by point, by means of the electrodeless discharge and a photoelectric device. The instrument is applicable to dosimetry and for local measurements in short wave therapy, but can also find application for investigation on insulators and other parts exposed to high voltage. The operation of the instrument and some examples of results obtained with the instrument are stated.
Simultaneous Measurement of Magnetic and Dilatometric Changes
Authors: Zmeskal Otto , Cohen Morris
Published: February 2005

This paper describes a combined magnet and dilatometer for simultaneously tracing the changes in magnetization and dilation of alloys undergoing phase transformations. Measurements may be made while the specimen is being heated to, held at, or cooled from the reaction temperature. The apparatus has been applied particularly to the study of the structural changes which occur during the tempering of hardened steel. Typical results for a plain carbon steel are included.
Ross Filter Foils by Evaporation
Authors: Clark J. C. , Esling R. H.
Published: February 2005

A method is described wherein metallic foils of those elements not available in rolled foil form may be prepared for use as absorbing foils in Ross balanced filters for x-ray analysis. Powdered antimony was evaporated in vacuum from a heated crucible to form a deposit 0.0015 cm thick on Cellophane backing, and the foil thus prepared was balanced with a rolled tin foil. A curve is given which shows the relationship between the amount of metal evaporated and the corresponding thickness of deposit. This method increases the applicability of the Ross balanced filters to x-ray measurements by adding several essentially monochromatic pass bands to those previously available.
A Non-Fouling Hydrogen Liquefier
Authors: Blanchard E. R. , Bittner H. W.
Published: February 2005

A description is given of: (a) the construction and operation of a complete throttle expansion hydrogen liquefaction cycle employing the Kapitza circuit for operation with ordinary commercial gas without fouling of the heat exchangers by low freezing impurities; (b) a simple scheme for employing ``dry ice'' as a supplementary precooling agent which effects a considerable saving in the amount of liquid nitrogen used by the liquefier; (c) a satisfactory method of soldering together a Kapitza side-by-side multiple tube interchanger; (d) an efficient and easily built combination heat exchanger and trap for freezing out water and oil vapor from large, rapid streams of compressed gas.
An Accurate High Sensitivity Apiezon Oil McLeod Gauge
Authors: Bannon J.
Published: February 2005

In the Apiezon oil McLeod gauge, the reservoir is in gas communication with the bulb, and the oil is displaced by a plunger externally controlled. The bulb has a volume of 300 cc, and the capillaries have a bore diameter of 1.44 mm. There is no evidence of sticking in the capillaries. For single measurements at pressures of 10−3, 10−4, 10−5, and 10−6 mm of mercury the gauge is considered accurate to about 1, 2, 8, and 25 percent, respectively. The equivalent compression ratio for the gauge is 3.5×10−7. To degas the oil it is necessary to raise it about five times, for half-hour periods, to the freely vaporizing state while the diffusion pumps are in operation. The whole instrument is kept continuously at a low pressure (10−2 mm of mercury or less), thus enabling it to be used, at intervals of several months, without further heat treatment, for the measurement of pressure within its range.
Reciprocal Lorentz-Polarization Factor Charts for Equi-Inclination Weissenberg Photographs
Authors: Lu Chia-Si
Published: February 2005

Two charts of reciprocal Lorentz-polarization factors for equi-inclination Weissenberg photographs are given, which will furnish simple templates of such factors to be used either directly on the Weissenberg photographs or on the reciprocal lattice nets drawn to an appropriate scale.
A Fast and Sensitive Bolometer and Galvanometer System for an Infra-Red Spectrometer
Authors: Baker Edward B. , Robb C. Dean
Published: February 2005

This bolometer and associated equipment, designed for use with a high speed recording infra-red spectrophotometer, respond in two-tenths of a second to 6×10−8 watt of radiation from a slit. Amplification of the Brownian limit of the Moll microgalvanometer in the presence of difficult vibrations is achieved by mounting the galvanometer, photo-cells, and preamplifier on a novel support employing a large compression spring. The bolometer and amplifying system described were developed for use with an f4 rocksalt infra-red spectrophotometer. In order to show the spectrum on the screen of a long-persistence (one minute) oscilloscope, unusually rapid response was desired, even at the expense of some sensitivity.
Voltage Stabilizer for Electron Diffraction Power Supply
Authors: Bauer S. H. , Hastings J. M. , MacMillan D. P.
Published: February 2005

The circuit and performance characteristics of a simple high voltage stabilizer of the degenerative type are presented. The regulator is inserted in the positive side of the high voltage line; the design given finds particular application for electron diffraction power supplies in which the positive side is generally grounded.