bluuebunny/crossref_metadata_2025 huggingface dataset:
Versatile Amplifier for Precise Radiometry
Authors: Fead P. M. G.
Published: February 2005

An amplifier is described that is suitable for the precise measurement of chopped radiation at very low intensity. It can be operated with all types of detectors used in such measurements, including thermopiles, bolometers, Golay cells, photomultipliers, photoconductive cells, and photoemissive cells, and in all cases the minimum detectable signal is determined only by the inherent noise of the detector. Comprehensive descriptions of the circuits, their principle of operation, and performance figures are given. Chopping frequencies between 5 cps and 1 kc can be used, and the amplifier gain is stabilized and defined by the application of feedback. It is shown that an electrical signal of 10−6 V rms from a 22-Ω source can be measured to a precision of 0.1%, while with very small signals such as 10−9 V rms, the precision is limited only by the amount of noise present at the detector.
Effect of Radiation Damage on the Response of Semiconductor Detectors to Fission Fragments
Authors: Britt H. C. , Benson G. C.
Published: February 2005

Measurements have been made of the pulse-height defect as a function of integrated fission-fragment and alpha-particle fluxes for a gold surface barrier and a p-n junction detector. The measurements show that the pulse-height defects increase as the detectors are damaged by radiation and that incident fission fragments are more effective in producing radiation damage than are alpha particles. It was found that, as the detectors were damaged, the pulse-height defect increased more rapidly for the high energy fission-fragment group from 252Cf than it did for the low energy group. It was also found that the rate of increase of the defect decreased as the electric field in the detector was increased.
Graphite Heater for MHD Studies
Authors: Klepeis J.
Published: February 2005

A graphite heater is described that was constructed to study magnetohydrodynamic generator performance at high values of the Hall coefficient (10 to 15). The heater can produce an intermittent, uniform flow of argon having a stagnation temperature of 2000°K and stagnation pressure of 5 psig for a time duration of approximately 30 sec. Its main component is a core of 1400 graphite rods, ⅜ in. in diameter and 24 in. long, stacked vertically within a hollow graphite cylinder 16 in. in diameter. This core is heated to 2000°K by radiation from graphite electrical resistors. Argon is passed through the spaces between the core rods and heated convectively to the core temperature. The gas flow is made electrically conductive by mixing with an easily ionizable seed material (e.g. cesium).
Metal Microscope and Dewar System for Field Emission Studies
Authors: Savage William R. , Low Frank J.
Published: February 2005

The research space of an experimental model of a metal Dewar system was adapted for field emission microscopy. The contamination time of a tungsten field emission cathode was used to estimate the residual gas pressure in the research space when the Dewar was filled with liquid helium with an upper limit for condensable gases of 10−13 Torr. Field emission patterns were obtained for niobium and niobium-zirconium (25%) alloy as examples of the application of the system to field emission microscopy.
Instrument for Determining Crushing Strength of Fuel Particles
Authors: Hallerman George , Gray R. J.
Published: February 2005

An instrument for crushing strength determinations of uncoated and pyrolytic-carbon-coated fuel particles (50–500 μ in diameter) has been developed to relate the crushing strength of the particles to their fabricability. The instrument consists of a loading mechanism, load cell, and a power supply readout unit. The information that can be obtained by statistical methods of the data analysis is illustrated by results on two batches of fuel particles.
3He–Ne–CH4 Mixtures in a Proportional Counter for Thermal Neutrons
Authors: Krohn Victor E.
Published: February 2005

Some mixtures of 3He, neon, and methane have been investigated and found to have advantages as fillings for proportional counters to detect thermal neutrons. Recipes which were satisfactory in a counter with a 3.5-in. diam include 15.7 psi of 3He+17 psi of neon+14 psi of methane and 1.0 psi of 3He+25 psi of neon+8 psi of methane.
Oscilloscope Waveform Recorder
Authors: Mackey R. C.
Published: February 2005

This paper shows how a sampling technique may be employed to record and simultaneously increase the signal-to-noise ratio of a waveform observed on an oscilloscope. The technique essentially trades bandwidth for time without sacrificing waveform fidelity. A salient feature is the minimum amount of auxiliary circuitry required in addition to readily available oscilloscope instrumentation.
Chamber for Continuous Mixing of High Pressure Combustible Gases
Authors: Oman Richard A. , Leng Jarvis
Published: February 2005

A small mixing chamber has been developed for continuous mixing of combustible gases for use in the combustion driver of a hypersonic shock tunnel. The gases are mixed while passing through the chamber and then flow directly into the shock tunnel driver tube. The system ensures immediate uniform mixing of the gases. It eliminates all waiting time needed to allow the gases to mix by diffusion (often several hours), as well as the hazard of storing combustible mixtures. It also eliminates the need for distributed injection locations and their associated hardware. The concept is applicable to many gas mixtures and has been used at Grumman to generate stoichiometric mixtures of H2 and O2, diluted with 80% He, at pressures up to 3200 psi.
EPR Spectrometer for Studying Crystals under High Hydrostatic Pressure
Authors: Clark A. F. , Wait D. F.
Published: February 2005

A spectrometer for studying the effect of hydrostatic pressure to 10 kbar on the electron paramagnetic resonance spectra of crystals is described. A two-sample comparison method is used which greatly simplifies both the experimental procedure and the analysis. The pressure is purely hydrostatic, and the cavity coupling is readily adjustable from outside the pressure vessel.
Laboratory Substandard for the Production of Small Electrostatic Charges
Authors: Gunn Ross
Published: February 2005

An apparatus for conveniently producing discrete and transportable free electrical charges of magnitude from 0.01 to 10 esu of either sign is described. A known electric field intensity E is established between two horizontal parallel plates by a battery and a voltmeter. Steel balls of radius a are suspended from the middle of the upper plate by an electromagnet, allowed to fall freely through a hole in the bottom plate, and thence into a Faraday cage or other apparatus. The free charge Q induced on and carried by each ball is estimated from Q=⅙π2Ka2E esu, where K is an apparatus constant closely approximating unity. Deviations due to contact potentials are always clearly evident, but by averaging the values for positive and negative electric fields, one may approximately determine the superposed charges due to contact potentials. These may then be applied as a correction to the above equation. The present accuracy is capable of improvement by gold- or chromium-plating the metal parts to reduce contact electromotive forces.
Wide-Range Microwave Spectroscopy of Noise Radiation from Magnetoplasmas
Authors: Lustig C. D. , McBee W. D. , Kalisky A.
Published: February 2005

A microwave spectrometer capable of measuring the noise power radiated by a plasma in a magnetic field as a continuous function of frequency from 2 to 4 Gc has been constructed. Within this bandwidth, noise resonances at the 5th to 8th harmonics of the electron cyclotron frequency have been displayed, while all discharge parameters, including the magnetic field, are kept constant.
High Current Linear Induction Accelerator for Electrons
Authors: Christofilos N. C. , Hester R. E. , Lamb W. A. S. , Reagan D. D. , Sherwood W. A. , Wright R. E.
Published: February 2005

A 150-A, 4-MeV electron accelerator has been designed and constructed for use in the ``Astron'' experiment. Design requirements include a beam quality less than 10−2 rad·cm and an energy spread of ±0.5%; the pulse length is 0.25 μsec and the repetition rate is variable to a maximum of 60/sec. The accelerating principle used is magnetic induction. Design features and the results of preliminary operation are discussed.
PLATINUM CONTAMINATION OF PALLADIUM IN PALLADIUM POINT DETERMINATIONS
Authors: Utterback C. L.
Published: February 2005

Palladium in contact with platinum, has been heated to the melting point starting with different initial temperatures. Different methods of contact and different times of heating were used. Spectrographic, photomicrographic and chemical analyses show definite contamination which increases with both temperature and time. Palladium point determinations indicate that this contamination may account for inconsistent results observed in the melting point.
GENERAL THEORY, DESIGN, AND CONSTRUCTION OF SENSITIVE VACUUM THERMOPILES (PART I)A More Complete Theory of Vacuum Thermopile Design for N Junctions for Four Types of Construction
Authors: Cartwright C. Hawley
Published: February 2005

Attention is paid to the practical construction and application of the thermopiles. The sensitivity and quickness of reaching thermal equilibrium are both calculated by considering radiation from the receivers and conduction through the wires; the other factors are proved theoretically and experimentally to be negligible for designs found practical. In designing a thermopile for sensitivity, the whole galvanometer circuit has been considered. If we assume the approximate correctness of the Wiedemann-Franz Law, simple optimum conditions are obtained. Maximum sensitivity is found to depend on the sensitivities, resistances and characteristic of the galvanometers available and the size of the area into which the radiation to be measured can be concentrated. If it is impossible to concentrate the light into as small a receiver as can be made, the number of junctions to be used in series can be calculated. While the theory given is general, it is especially adapted to high thermoelectric power bismuth alloy wires at room temperature and for a critically damped galvanometer circuit. Curves are plotted to facilitate the best choice of a galvanometer and best design of a thermopile for use in many experiments. The formulas were verified experimentally at room temperature. Greater sensitivity was gained by having thermopile at the temperature of liquid oxygen, as predicted by the theory.
A NEW FLICKER RADIOMETER
Authors: Stockbarger Donald C. , Burns Laurence
Published: February 2005

When radiation is allowed to pass alternately through one and the other of two filters having identical transmissions for all wave lengths except those lying in a narrow spectral region, a flicker is produced which is a function of the intensity of the radiation within that region. A radiometer making use of this principle is described in detail. The filters are cut in the shape of sectors and are so arranged as to form a solid wheel. The filtered radiation passes through a window into a magnesium photoelectric cell fabricated of Vitaglass. Oscillograms show that the ac component of the photoelectric current, after electrical filtering and amplification, is sinusoidal.
AUTOMATIC NEUTRALIZATION OF THE VARIABLE GRID BIAS IN A DIRECT CURRENT FEED-BACK AMPLIFIER
Authors: Carwile Preston B. , Scott F. A.
Published: February 2005

In a simple direct current feed-back amplifying circuit it is necessary to readjust the input grid bias each time the amplification is changed. A modified circuit is described whereby this difficulty of operation is eliminated.
A LABORATORY B-VOLTAGE SUPPLY
Authors: Bedell Frederick , Kuhn Jackson G.
Published: February 2005

An eliminator for full-wave rectification (600 v) or half-wave rectification (1200 v) with adjustable taps for all intermediate voltages, while introducing no new principle, gives a desirable flexibility for laboratory purposes. Ripple voltage, determined by the Bedell-Reich Stabilized Oscilloscope, is found to be unusually small.
NOTE ON A MODIFIED RANDALL UNIVERSAL CALIBRATION CURVE FOR BALLISTIC GALVANOMETERS
Authors: Frazier Richard H.
Published: February 2005

An experimental-graphical method is given for the determination of the critical damping resistance of a ballistic galvanometer. The curve used turns out to be a modification of the Randall Universal Calibration Curve which can be represented in the region of underdamping by a very readily drawn straight line with a maximum error of 1.8 percent.
A STROBOSCOPIC RIPPLE TANK
Authors: Baldwin William
Published: February 2005

A form of ripple tank is described in which the point source of waves is simply a succession of periodic air blasts directed downward onto the surface of the water. Two or more such sources can be used simultaneously and their positions are readily changed from place to place. For the production of rectilinear waves a pulsating linear vibrator is described. For the study and projection of water waves an adjustable stroboscope is used, which can either be driven in strict synchronism and in any desired phase relation with the air blasts, or slowly advanced in one direction or the other. Thus the wave images can be made to advance or retreat across the screen and to stop at any desired stage.

The series of photographs show some of the possibilities of the device in demonstrating reflection, refraction, interference, and diffraction of waves.
PRECISE MEASUREMENT OF SHORT TIME INTERVALS BY USE OF THE MICROCHRONOGRAPHIC WHEEL
Authors: Town George R.
Published: February 2005

Apparatus and methods are described by which time intervals may be measured to a precision of twenty microseconds. The duration of the time interval may be anything between twenty microseconds and ten seconds or even longer. The record obtained is continuous, making it possible to locate any event within the time interval to this same precision. The method is not limited to the measurement of electrical quantities. The application of the method to the determination of the speed of a rotating shaft is given in detail.
AN AMPLIFIER FOR MEASURING SMALL CURRENTS
Authors: Bennett Ralph D.
Published: February 2005

An amplifier is described which uses a four electrode tube of the ordinary type, and gives maximum current sensitivities of the order of 10−18 amperes. A novel feature consists in using as grid leak the positive ion emission of the filament.
DESIGN OF VACUUM PREBAKING FURNACE
Authors: Hafstad L. R. , Dahl O.
Published: February 2005

A description is given of a simple type of vacuum prebaking-furnace which has proved to be both economical and serviceable. The design embodies the experience of several laboratories with such furnaces so that most of the troublesome features and unnecessary complications have been eliminated. While this particular design is not unique and may be readily modified, the description does call attention to a number of important considerations which must be taken into account in building any furnace of this kind.
AN ELECTRICAL IMPULSE RATE INDICATOR AND RECORDER
Authors: Macalpine William W.
Published: February 2005

A circuit is described which is operated by impulses and in which the reading of a meter is a function of the rate of the impulses. In the present instance the impulses operate a Weston Model 30 Galvanometer Relay whose contacts discharge a condenser. The condenser is charged up again through a resistance after each impulse, and a microammeter reads the average voltage across the resistance. A smoothing circuit is used between the microammeter and the resistance. Variations of the device may be used according to the nature of the impulses. A Leeds and Northrup Recording Potentiometer may be attached to the device to obtain a continuous record of the rate. In another form, the average voltage may operate on the grid of a tube, the plate current of which operates a more rugged indicating meter than the microammeter. This also simplifies the filter circuit. Means for calibrating the device are discussed.
A QUANTITATIVE EXPERIMENTAL METHOD OF MAPPING EQUIPOTENTIAL LINES AND ITS APPLICATION TO ELECTRIC PRECIPITATOR PROBLEMS
Authors: Simon A. W. , Kron L. C.
Published: February 2005

A quantitative method of mapping a series of equipotential lines corresponding to definite fractions of the total voltage drop between electrodes is described. The accuracy of the method is tested by mapping several known fields, such as the field between concentric cylinders and that between parallel cylinders. The application of the method to electrostatic problems, in particular to the study of electric precipitation problems, is indicated.
A TWENTY-ONE FOOT VACUUM SPECTROGRAPH FOR THE EXTREME ULTRAVIOLET
Authors: Harrison George R.
Published: February 2005

The construction of a vacuum spectrograph containing a six inch concave speculum grating of 21 ft. radius of curvature is described. Exposures of the order of magnitude of one hour suffice to give satisfactory spectrograms having a dispersion of 2.7A per mm in the first order, the entire range 2000–1000A being recorded at one setting on a 16 inch plate. By means of a vacuum-tight screw up to thirty exposures can be taken on a single plate, and introduction of a stop-cock in the slit tube allows source and slit to be changed at will. A gate is provided which allows air to be admitted to the 40 liter camera box without destroying the vacuum in the 830 liter body of the spectrograph, to facilitate the changing of plates. By means of a Cenco Hypervac pump and three 4-stage Gaede diffusion pumps the instrument can be evacuated from atmospheric pressure to below 10−4 mm in an hour or less. High resolving power has been obtained in hot spark spectra of the elements of the first long period, which should facilitate wave-length measurements on the spectra of ionized atoms; the main purpose of the instrument, however, is to enable intensity measurements to be satisfactorily made in the Schumann region.
ACID STANDARD CELLS OF THE UNSATURATED TYPE
Authors: Ishibashi Yûichi , Ishizaki Tadashi
Published: February 2005

M. Eppley,1 studying the relation between the degree of saturation and the emf, and the temperature coefficient of emf on acid unsaturated standard cells acidified to 0.012 mol per litre of sulphuric acid, has concluded that the acid unsaturated cells with cadmium sulphate concentration of 42.93 percent have negligible temperature coefficients between 15° and 35°C, and that the solutions of these cells might have been saturated at about 4°C.

The present authors2 measured, in the first place, the solubility of cadmium sulphate into dilute sulphuric acid at different concentrations, and based on the obtained results, with electrolytes of various concentrations from dilute to nearly saturated solutions of cadmium sulphate. They attempted to find out the optimum concentration of cadmium sulphate and acidity of electrolyte, estimated from every point of view, and concluded that cells of concentration of cadmium sulphate 43.0 percent and of acidity 0.05N are most suitable.
A THERMOSTAT REGULATOR
Authors: Adams Elliot Q.
Published: February 2005

A thermostat regulator has been constructed with a tungsten-mercury contact in hydrogen permanently enclosed in glass. Adjustment is made by a mercury-tight tungsten plunger in another 2 mm capillary, one complete turn of the micrometer head advancing the plunger approximately 1 mm, equivalent to 0.08°C. The contact breaks approximately 1 milliampere which actuates relays controlling the heating circuit of one ampere, 110 volts ac. The regulator kept a 50-liter water thermostat constant to ±0.002°C, for an hour, with a 5-minute regulation cycle. With an auxilary heater close to the regulator, the temperature variation was less than ±0.001°C over a period of three hours and the regulation cycle less than 1 minute.
AN INSTRUMENT FOR MEASURING SMALL DISPLACEMENTS
Authors: Langer B. F.
Published: February 2005

An instrument is described which measures and records small displacements such as vibrations and strains from dynamic loads. The results of some recent development work on this instrument are given.
THE LATERAL CHROMATIC ABERRATION OF APOCHROMATIC MICROSCOPE SYSTEMS
Authors: Gardner I. C. , Case F. A.
Published: February 2005

Methods are described for the measurement of the lateral chromatic aberration and distortion of microscope objectives and eyepieces. Measurements have been made on 20 apochromatic microscope objectives of 4 different makes, and on 10 compensating eyepieces of 2 different makes. The results show that the compensating eyepieces in general do not entirely compensate the chromatic aberration of the objectives and that the complete microscope system is usually undercorrected. The bearing of this on the performance of the system in photomicrographic work by a three color process and in the direct visual observation of objects is considered in detail.
A METHOD OF DETERMINING THE IMPEDANCE OF HOT CATHODE DISCHARGE TUBES
Authors: Westendorp W. F.
Published: February 2005

By means of a superposed alternating current the negative resistance of hot cathode neon and mercury direct current arcs was measured and found to follow closely the slope of the static characteristic of the neon arc and to be widely different in the case of the mercury arc. At the same time the reactance for the ripple current in the arc was determined. This reactance is explained on the basis of a time lag in the concentration of metastable atoms; from the phase shift the order of magnitude of the lifetime of the metastable atoms is computed and the result is in agreement with calculations made by others.
CALIBRATION OF ABBE REFRACTOMETER WITH COMPENSATING PRISMS, TO MEASURE REFRACTIVE INDEX FOR ANY WAVE LENGTH
Authors: Dodd L. E.
Published: February 2005

The Abbe refractometer in its usual form with compensating prisms is restricted to reading index of the test liquid for but one wave length, usually λD. Although the setting of the compensating prisms for achromatization permits, by the aid of either a numerical or a graphical chart supplied with the instrument, an evaluation of the dispersion nF—nC of the liquid, the value so obtained is claimed to be no more than approximate. Data given in the present paper indicate that the degree of this approximation is variable with nD of the liquid. The agreement is better (about 5%) with a liquid of higher index such as CS2(nD=1.627), but with a liquid of lower index such as methyl alcohol (nD=1.330) the discrepancy may be as high as 30% and above. These conclusions appear to be valid for two particular instruments of quite recent manufacture, used with the charts accompanying them.

More reliable values of the dispersion were obtained by calibrating the instrument to read index for any wave length. Then from individual values of nF, nC thus obtained (which may be calculated from measurements with two other λ's if the colors C, F are not available, by use of the simpler Cauchy formula) the average deviation of the dispersion from book values for five different liquids (1.330<nD<1.627) was less than 5%. In this manner the value of the dispersion of a test sample as determined by achromatization with compensating prisms with the use of the customary chart, can be checked on the same instrument.

A method of so calibrating the refractometer to read index for any wave length and for any setting of the compensating prisms has been worked out. The derivation of the necessary equations and the procedure are given in this paper.
AN IMPROVED McLEOD GAUGE
Authors: Bryden Samuel D.
Published: February 2005

A ``short form'' of McLeod gauge has been designed and built which is believed to be an improvement over the conventional constructions. These improvements consist of a simplified and compact construction of the compression chamber and mercury cistern, and of the entrance of the tubing connecting the gauge with the vacuum system directly through the top of the compression chamber.

The actual construction is shown by a drawing and photograph.

The theory of the McLeod gauge is briefly considered and the possible advantages of combining a controlled compression or expansion chamber with several existing gauges are indicated.
A METHOD OF OBTAINING A LINEAR TIME AXIS FOR A CATHODE RAY OSCILLOGRAPH
Authors: Samuel A. L.
Published: February 2005

The usefulness of a cathode ray oscillograph tube of the type of the Western Electric No. 224-B is enhanced by any circuit that will provide a linear time axis. A number of methods of accomplishing this result have been described from time to time. One method used in the Bell Telephone Laboratories employs a hot-cathode three-element gas-filled tube in the usual ``sweep'' circuit. This method possesses advantages in reproducibility, ease of control and synchronization. A brief description of the tube is given together with a simple analysis of the behavior of the circuit. Methods of coupling the sweep circuit to the oscillograph tube, of synchronizing the sweep frequency and of improving the linearity are discussed. A complete portable laboratory oscillograph outfit is shown as an illustration of one form that the device may assume. This set is for use within the audible frequency range.
A DEVICE TO MEASURE THE AMOUNT OF PLANE POLARIZED LIGHT IN LOW INTENSITY RADIATIONS AND TO MEASURE SMALL ROTATIONS OF THE PLANE OF POLARIZATION
Authors: Morey D. R.
Published: February 2005

To investigate polarization properties of radiations too weak to be handled with the common visual devices for the purpose, a photoelectric device is used. A nicol of good quality, with end faces perpendicular to the length is mounted on a caesium vacuum cell, and this, together with the working tube of a two tube bridge amplifier, placed in a brass container free to rotate about an axis passing through the center of the nicol. Control apparatus and the dummy tube and batteries are located in a stationary container, connections being made through a flexible shielded cable. The galvanometer deflection obtained is proportional to the intensity of the component of the radiation able to pass through the nicol. The percent of polarization has been measured with illuminations down to 10−5 foot-candles. When applied to rotation measurements, a rotation of the plane of polarization of one second of arc can be detected.
A NEW PHOTO-CELL PHOTOMETER
Authors: Gleason Paul R.
Published: February 2005

The sensitive surfaces of two Weston Photronic cells have been combined into a single photometer cell such that a simple null method of photometry is available. The sensitivity of the device has been studied when a sensitive galvanometer was used as indicator and found to be about five times that of visual methods. Immediate application to the comparison of two similar sources is possible; and by incorporating windows of the filter material recently described by O'Brien, comparison of the luminosity of any two sources is possible without recourse to a flicker photometer.
A DICHROMATIC PROJECTION MICROPHOTOMETER
Authors: Harrison George R.
Published: February 2005

A new type of microphotometer is described which combines the advantages of the projection type described by Hesthal and Harrison with those of the original photoelectric type of Koch. The plate being measured is traversed by a beam of blue light supplied from a small lamp of constant intensity, which is used to make the desired density determinations. At the same time it is viewed by means of a beam of orange light furnished by a projection lamp run on the commercial a.c. This arrangement eliminates errors sometimes present in projection type microphotometers due to light scattered from the optical system (Schwarzschild-Villiger Effect). Additional advantages claimed for the instrument are: high resolving power, due to the ease of correcting lenses for only two colors; great flexibility and stability of adjustment, due to the absence of microscope lenses and microscopic slits; high reserve sensitivity; high electrical stability, due to the fact that all light sources, photoc-ells, tubes, and batteries are running at from one-tenth to one-half normal capacity; ease of handling, due to the long, open, and linear scale and the use of a rugged galvanometer. It is possible to construct the instrument so that no battery furnishing more than six volts is needed. It can be used for automatic recording, but is particularly useful for direct reading work where specific lines are to be selected from a complex spectrum. The instrument is quite simple and inexpensive to construct.
THE STROBOGLOW
Authors: Quarles L. R.
Published: February 2005

The increasing need for an extremely accurate stroboscope has been met by the Stroboglow. This instrument is a portable stroboscope, which gives excellent definition of the image at high speeds, and which may be accurately timed over a frequency range of 300 to 10,000 cycles per minute. At low frequencies, the instrument may be timed from the machine shaft, or by the electrical oscillator developed for this purpose. At high frequencies, the timing is accomplished by the oscillator, no connection to the machine being necessary.
CONSTRUCTION OF AN AIR COOLED ELECTROMAGNET
Authors: Walerstein I. , May A. I.
Published: February 2005

An air-cooled electromagnet for work in Zeeman effect has been constructed due to lack of a `soft' water supply for cooling. The pattern of the instrument follows the Boas type, but includes a number of improvements. The yoke is made of a wider cross section, thus eliminating the narrowing of the pole gap upon application of the field. The current is carried by 2000 turns of flat bare copper ribbon wound in 24 pancake coils which are cooled by a forced draft of air circulated between the coils by a fan. Temperature equilibrium is reached throughout the instrument in less than an hour, and in half an hour in the pole-gap where the temperature rise is about 5°C for an inducing current of 20 amps. Using ferro-cobalt pole caps with pole face of 8 mm diameter, fields of 39500 gauss and 43500 gauss were obtained respectively for gaps of 4 mm and 2.4 mm with a current of 25 amps. For a gap of 1 mm and a current of 33 amps, a field of 48500 gauss was reached. Zeeman patterns were produced corresponding to nearly full strength of the magnetic field with no loss in sharpness, due to thermal fluctuations even during the first hour of application of the field.
AN AUDIO OSCILLATOR OF THE DYNATRON TYPE
Authors: Hale Don
Published: February 2005

This paper describes an oscillator which makes use of the fact that the four element vacuum tube may have a negative internal resistance under certain conditions. The oscillator is capable of frequency variation over a wide range by the variation of this negative internal resistance.
ELECTROLYTIC RESISTORS OF HIGH RESISTANCE
Authors: White H. L. , Van Atta E. A.
Published: February 2005

Resistances of from 1×108 to 3×1010 ohms have been obtained by sealing capillary bridges (inside diameter 0.005 to 0.088 mm) between calomel electrodes made up with dilute KCl—saturated calomel solutions. These resistors can be used satisfactorily with an electrometer or sensitive galvanometer and condenser set-up. They do not exhibit polarization and their resistances do not change with age. The temperature coefficient is that of the KCl solution used in the preparation of a resistor.
AN IMPROVED FORM OF ELECTROCARDIOGRAPH
Authors: Caldwell S. H. , Oler C. B. , Peters J. C.
Published: February 2005

An electrocardiograph is described which has been designed to secure a more nearly uniform response characteristic, as a function of frequency, over the desired frequency range, than is obtainable with the Einthoven string galvanometer ordinarily used for this work. It is shown by harmonic analysis that relatively high frequency components are present to a large degree in the ordinary electrocardiogram, and due to their magnitudes, have a large influence on the shape of the wave.

More accurate interpretation of the electrocardiograph record is desirable, and is made possible by using an amplifier in conjunction with a standard type of oscillograph to produce a larger record, without reducing the accuracy at higher frequencies. The vacuum tube amplifier was specifically designed for the purpose. It has a high input impedance so that the effect of body resistance is negligible. A standardizing circuit is built into the amplifier so that calibrations can be obtained readily.

The tests on this apparatus were carried out both at the Massachusetts Institute of Technology and at the Evans Memorial of Boston. Illustrations from these tests are included, showing comparisons between records obtained from a standard type of string galvanometer electrocardiograph and from the new apparatus.
A NEW TYPE OF VACUUM OR CIRCULATING PUMP
Authors: Harrington E. L.
Published: February 2005

A new type of vacuum or circulating pump employing a helical tube made to rotate about the axis of the helix is described. Its action depends on a pumping liquid which fills the lower bends of the helix and crowds out the gas being pumped as the helix is rotated. There is a provision for the return of the pumping liquid to the first coil of the helix as the latter continues to rotate. The liquid may be chosen to suit the work at hand. Among the advantages claimed for the pump are the following: mercury vapour is not employed, heating and cooling elements are not required, adapted equally well to corrosive and noncorrosive gases, vapors and liquids, constant personal attention is not needed, it may be started or stopped instantly without the use of stop cocks, and its action is reversible.
A High Speed Mechanical Recorder
Authors: Neher H. Victor
Published: February 2005

A mechanical recorder is described having a resolving time of 0.8×10−3 sec. It will follow regularly spaced pulses at the rate of 1200 per sec. and should miss no more than one percent of pulses spaced random in time at an average counting rate of 10 per sec. A circuit is also described giving a pulse of short enough duration and at the same time of sufficient magnitude to satisfactorily operate the recorder.
The True Temperature Scale of an Oxide-Coated Filament
Authors: Prescott C. H. , Morrison James
Published: February 2005

Following A. G. Worthing the spectral emissive power may be obtained from measurements of the reflection coefficient. This method is applicable to the oxide-coated filament both at room temperature and at normal operating temperatures. For a particular type of filament containing dispersed nickel the reflection coefficient averaged 36 percent independent of temperature and independent of the degree of activation, i.e., the content of free alkaline earth metal.
On Electronic Voltage Stabilizers
Authors: Hunt F. V. , Hickman R. W.
Published: February 2005

Voltage stabilizing circuits employing thermionic tubes can be classified into four groups, according to their derivation from (1) the transconductance bridge, (2) the amplification factor bridge, (3) the simple degenerative amplifier, and (4) combination circuits involving two or more of the foregoing classes or utilizing amplified control voltages. It is shown that the variational performance of a stabilizer is characterized by an internal output resistance and a stabilization ratio. The effect of source resistance on these performance parameters is discussed in the general case and expressions for these parameters are evaluated for ten stabilizer circuits, seven of which are original with the authors. All but two of the circuits can be adjusted to yield perfect stabilization and four have also a very low internal resistance. Glow discharge tubes are discussed as bias battery substitutes. A simple a.c. bridge technique which is convenient for the experimental determination of stabilizer performance under normal load conditions is described in an appendix.
A Magnet Current Stabilizer
Authors: Lawson J. L. , Tyler A. W.
Published: February 2005

A precision current stabilizer is described which is suitable for controlling an electromagnet. The circuit is adaptable to a wide range of current values. Applications to a cyclotron and to a beta-ray spectrometer are discussed. Currents have been stabilized over a period of several hours to better than 1 part in 50,000.
A New Mercury Vapor Detector
Authors: Woodson Thomas T.
Published: February 2005

The history and originators of previous devices for detecting mercury are given. The features of the new detector are given along with its operation and characteristics. It is relatively small and portable; it can be used for testing the mercury content of the atmosphere or, by adding some auxiliaries, for testing the flue gas from a mercury boiler. Its direct useful range is from one part per million to one part per billion by volume.
A Variable Oscillator for Ultra-High Frequency Measurements
Authors: King Ronold
Published: February 2005

The fundamental theory of coupled circuits with distributed constants is reviewed and applied to the problem of designing an oscillator for use in parallel line measurements. An oscillator having a continuously variable frequency range from 75 to 500 megacycles, and which fulfills the theoretical requirements which permit the e.m.f. induced by it in a parallel line to be represented by point generators, is described. Its frequency characteristic is displayed, and its application to parallel line measurements is discussed briefly.
Improved Counting Rate Meter
Authors: Evans Robley D. , Alder Robert L.
Published: February 2005

We describe an improved counting rate meter circuit, whose output meter reads directly the average rate of appearance of pulses in a counter exposed to radioactive substances. Four output scales are provided on a 100-microampere meter, such that full scale corresponds to 7200, 2200, 1450, and 400 counts per minute. Even on the highest speed range, the output current is closely proportional to the counting rate over the entire scale. For very low counting rates, an optional register output is provided.
An Ultrasonic Stroboscope for Measuring Sound Wave-Length in Liquids
Authors: Fox Francis E. , Rock George D.
Published: February 2005

A stroboscopic method discussed by Bär for using a sound wave as a light shutter and viewing the same wave train with the modulated light is modified so as to permit observations to be made with a very simple optical system without lenses. This results in a method of measuring relative or absolute acoustic wave-lengths in liquids with a precision limited only by that of measuring lengths of the order of a meter and the spacing of lines on a photographic plate.
Improvement in Radio-Sounding Balloons: A Short Cycle Radiosonde
Authors: Piccard Jean , Larsen Harold
Published: February 2005

A new radiosonde has been constructed. Every four seconds it transmits information as to pressure, temperature and relative humidity. The thermometer scale, from −60°C to +40°C, is divided into 100 equal divisions of 1°C each. The barometer scale is divided into 100 divisions, corresponding to equal increments of height (850 feet each, up to 85,000 feet). The scale of the hygrometer is divided into 50 equal divisions. Provided that the thermometer and the barometer themselves follow the changes of the weather elements with sufficient accuracy, this means that the maximum error of the thermometer is ±0.5°C and the maximum error of the barometer 425 feet (the average errors being only half as great). Because of the fact that the cycle of readings is only four seconds long, each reading is repeated many times in succession. This allows one to estimate temperature and altitude within about 0.1 percent of the total range of the scale of each instrument. The carrier wave is modulated and the signals are given in ordinary Morse code. They can easily be received by ear or on a standard tape recorder without any special equipment. The radiosonde, therefore, allows amateurs to pick up the signals long after the balloon has gone out of reach of the ground station. This is important in the case of nonexpanding open neck sounding balloons which, if provided with an automatic ballast release, stay in the air for many hours. The weight of the completely equipped gondola is about 2 lb.
A Duo-Triode Bridge Voltmeter
Authors: Vollrath Richard E.
Published: February 2005

A bridge voltmeter is described in which a duo-triode is used in place of two separate triodes with a resulting gain in simplicity and compactness.
A Fixed Path Acoustic Interferometer for the Study of Matter
Authors: Hubbard J. C. , Zartman I. F.
Published: February 2005

The resources of ultrasonic interferometry have been extended by the development of an interferometer of fixed path. In this device a fixed distance is maintained between a piezoelectric resonator and a reflector. Variation of acoustic reaction of the medium between them is secured by a variation of the acoustic wave-length produced by changes of temperature, pressure or composition, or in liquids and solids by a change in frequency. It is particularly adaptable to the study of the velocity of sound in gases from the lowest temperatures attainable to approximately 500°C and over a pressure range of at least 100 atmospheres because of the elimination of moving parts and packed joints. The method is also applicable, when results are obtained with two precisely known lengths of path, to the measurement of acoustic absorption and reflection coefficients. Results obtained with air and CO2 are given.
Potentiometer Circuit for Portable Optical Pyrometer
Authors: Machler R. C.
Published: February 2005

A potentiometric circuit designed for the measurement of small currents is described, together with its application to the measurement of the filament current in a portable optical pyrometer. Its feature is the elimination of several elements from the conventional potentiometer with the advantages of increased portability and simplicity of operation.
An Improved Weigand Rubber Pendulum
Authors: Wood Lawrence A. , Bekkedahl Norman
Published: February 2005

A description is given of improvements and details of operation of a rubber heat engine of the pendulum type invented by Wiegand. The pendulum is kept in continuous operation by heat energy emitted by a radiant heater and intermittently absorbed by rubber bands. The major features of improvement in the design are essentially (1) increased mechanical stability, (2) decreased size and weight, and (3) considerable simplification of parts.
The Determination of the Internal Volume of Steel Capillaries for Measurements with Gases
Authors: Kaminsky Joseph , Blaisdell B. Edwin
Published: February 2005

Two known methods for measuring the internal volume of steel capillaries were compared. The volume obtained from the mass and density of mercury contained was from 3 to 6 percent smaller than that determined by the gas expansion method. The latter is the correct volume to be used for measurements with gases.
Electron Bombardment of Biological Materials. I. An Electron Tube for the Production of Homogeneous Beams of Cathode Rays from One to Fifteen Kilovolts
Authors: Cooper Franklin S. , Buchwald Charles E. , Haskins Caryl P. , Evans Robley D.
Published: February 2005

An apparatus for the bombardment of small samples with electrons of 1 to 15 electron kilovolts energy has been developed and used. Special features render it particularly suited to a study of those biological materials which can tolerate high vacuum. The details of the construction and operation of the tube and of auxiliary apparatus are described.
An Improved Radiobarograph
Authors: Johnson T. H. , Korff S. A.
Published: February 2005

A radiobarograph is described, which is accurate to 1 mm Hg pressure. This instrument employs a suspension giving increased sensitivity at low pressures, and rendering it free from backlash. Various tests on this barograph are described.
A Continuously Sensitive Diffusion Cloud Chamber
Authors: Langsdorf Alexander
Published: February 2005

Supersaturation necessary for condensation of a vapor upon ions is maintained continuously by the diffusion of an initially warm saturated vapor through a noncondensing gas into a refrigerated region. Convection is avoided by diffusion vertically downward between a horizontal heated roof and refrigerated floor. Calculations show what flux of vapor and what roof and floor temperatures are necessary. Experiment shows that this diffusion cloud chamber operates as expected, and with reasonable precautions it is quite stable against turbulence. Successful operation depends on avoiding production of condensation nuclei which will make a diffuse rain of condensation in the chamber. Vapor from liquid in a glass flask heated by radiation from above has been found to be practically free of aggregates. The chamber cannot produce satisfactory ion tracks in the presence of too great an average ion load. In the steady-state operation of the present apparatus the normal background ionization without shielding loads the chamber so close to its limit that most tracks are diffuse. When first applying refrigeration there is a transient condition in which many more tracks are well defined. There are several possible ways of improving the steady-state ion load capacity of the apparatus.
A High Voltage, Demountable X-Ray Tube
Authors: Kliever Waldo H.
Published: February 2005

This tube consists of a minimum number of simple parts easily made in a university shop. It is designed for steady operation up to at least 110 kv, and permits convenient interchange of targets, replacement of filaments, etc.
A Feedback Micromicroammeter
Authors: Roberts Shepard
Published: February 2005

A two-stage direct-coupled amplifier circuit with negative feedback which can be used for measuring small direct currents is described. The circuit details are given for a multi-range micromicroammeter which is compact and stable and operates from a.c. power. Through reduction of grid current in the input tube, which is a standard receiving type, it is possible to realize a high sensitivity approaching that of amplifiers using special electrometer tubes.
Concerning Thermionic Regulation of Direct-Current Generators
Authors: Danforth W. E.
Published: February 2005

In designing electronic equipment for regulation of d.c. generators it is essential to know the effect on the regulated current or voltage of all possible variables in the regulating equipment as well as those in the generator proper. This paper presents, in the static case, a method of treatment which enables one to appraise quantitatively the importance of any source of possible instability in amplifier or generator. The method is applied to two types of regulating equipment, concerning which detailed information is included.
Magnetic Operation of Chemical Balances
Authors: Blewett John P.
Published: February 2005

Two types of balance are described for measuring small weights by application of a magnetic force in place of the usual system of calibrated weights. One method is applied to an analytic balance, the other to a vacuum balance.
Note on Spark Recording of Data
Authors: Tuttle C.
Published: February 2005

An electrode for use with an instrument which records data by the firing of a spark through graph paper and a relay circuit which acts to limit the discharge to a single spark are described.
Coils for the Production of a Uniform Magnetic Field
Authors: Lyddane R. H. , Ruark Arthur E.
Published: February 2005

Extending work by F. K. Harris, we show how to produce a highly uniform magnetic field in a rectangular box long compared with its cross section, by using a pair of rectangular coils placed on opposite sides of the box. If the width of each coil is 3½ times the distance between them, the region in which the field deviates less than one percent from the value at the center is about nine times larger than that obtained with previous coils having other width-distance ratios. The use of square wire-bundlles causes the main correction terms depending on finite cross section to vanish. The homogeneity achieved compares favorably with that obtainable by Helmholtz coils.