bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Method in the Analysis of Complex Electric Waves
Authors: Rogers Walter E.
Published: February 2005

Accurate, direct measurements of the phase positions of the harmonic components of complex electric waves are now possible. The familiar laboratory technique of potential measurement by potentiometer comparison is extended to wave analysis. A known complex wave form, having a periodic relationship to the wave under analysis, becomes the standard or reference wave. A tunable, frequency-selective detector replaces the conventional galvanometer or dynamometer. The reference wave, variable in amplitude and in phase position with respect to the wave under analysis, furnishes, by comparison, the phase positions of the harmonic components as well as their amplitudes. This potentiometer method of wave analysis reduces the labor and enhances the accuracy as compared to graphical analysis.
Geometric Factors Underlying Coincidence Counting with Geiger Counters
Authors: Newell Homer E.
Published: February 2005

The coincidence rate of a perfectly efficient two-counter telescope embedded in an isotropic field of radiation is obtained in terms of the radiation intensity and the effective dimensions and separation of the counters comprising the telescope. By means of the formulas the counting rate may be located between an upper and a lower bound which in most practical cases differ by only a few percent. The information embodied in the formulas is also presented graphically in a form convenient for ready calculation of the ratio of coincidence rate to radiation intensity once the effective dimensions and separation of the two counters are known.
An Inside Geiger-Müller Counter for Soft Beta-Emitters
Authors: Labaw L. W.
Published: February 2005

A practical inside Geiger-Müller counter for the detection of soft beta-rays and alpha-particles is described in conjunction with a simplified method for the preparation of samples for assay. The method for radioactive assay used is tested for reproducibility and accuracy. Direct determination of the specific activity of samples having different chemical composition can be made simply without an initial chemical extraction of the active element.
Cathode-Ray Magnetization Curve Tracer
Authors: Scherb M. V.
Published: February 2005

An instrument developed to measure the magnetic properties of materials in a variety of forms by oscillographic techniques is described. Magnetic hysteresis loops can readily be obtained for specimens in rod, powder, tape, or wire form having cross-sectional areas as small as 10−5 cm2 or as large as 0.3 cm2 (¼ in. rod).

With slight modifications, the instrument can be adapted to magnetic measurements of materials as a function of frequency, temperature, tension, torsion, or pressure using the appropriate setup.
A Spiral Chronograph for Long Time Intervals
Authors: Warshaw H. D.
Published: February 2005

Elapsed time between two or more transient events that occur within a time interval of 12 milliseconds is measured with a maximum error of ±6 microseconds. Higher accuracies are attained when the time interval is reduced.

A spiral trace is presented on the screen of a cathode-ray tube. The trace is modulated by a crystal-controlled oscillator to provide accurate time markers. Each transient event produces a momentary radial deflection of the spiral trace. Elapsed time between any two events is determined by counting the time markers between the corresponding signals.
The Detection of Beta-Radiation by Photographic Film
Authors: Cobb Jock , Solomon A. K.
Published: February 2005

The effect of beta-radiation from C14 has been examined on nineteen different films. The method employed uses a ``radiator,'' a set of eight radiating sources of different intensities, to replace the stable light source and absorbing wedge common in spectral photometry. With this device sensitivity and contrast of the nineteen films have been measured. Based upon these results and a microscopic estimation of grain size, recommendations are made for the most desirable film for use in radioautography and detection of radioactivity. Of the films examined, Eastman No-Screen x-ray film appears best for the detection of the beta-rays, and Ansco Reprolith, and Eastman Type M x-ray stripping films appear to be most desirable for work with radioautographs.
An Improved Peak Voltmeter for Pulses
Authors: Yu Y. P.
Published: February 2005

The peak voltmeter circuit to be described was developed to minimize the error encountered in measuring pulses of short duration and low repetition frequency. Essentially the instrument contains an automatic switch connected in series with a condenser and a high d.c. source (B-supply). Closing of the automatic switch by an input voltage allows the high d.c. source to charge the condenser. As soon as the condenser voltage becomes equal to the peak amplitude of the measured voltage the automatic switch opens. The condenser voltage is coupled through a high input resistance circuit, bridge-balanced cathode follower, to an indicating meter. High accuracy is attained over wide ranges.
Dead-Time Reduction in Self-Quenching Counters
Authors: Smith Philip B.
Published: February 2005

The various methods of dead-time reduction are investigated and discussed. The application of a large negative voltage pulse to the center wire, just after the discharge starts, reduces the dead-time. This effect is due to a combination of stopping the propagation of the ion sheath, ion neutralization, and ion multiplication. In the most favorable case found, the dead-time of a Geiger tube having a normal dead-time of 160 microseconds is reduced to 80 microseconds by this means. Increasing the gain of the detecting circuit without a negative pulse does not reduce the dead-time more than a factor of two, unless the counting rate is greatly increased so that all pulses are small. Operation with high gain just below the Geiger threshold shows efficiency of the order of 50 percent for beta-particles, and no measurable dead-time.
A Method for Measuring Short Period Activities
Authors: Schelberg A. D. , Sampson M. B. , Mitchell Allan C. G.
Published: February 2005

By photographing an oscilloscope it is possible to measure short periods ranging from 0.1 second to 5 seconds. The pulses from a Geiger counter are fed into the x axis amplifier of an oscilloscope using no sweep. An oscillograph recorder is used to photograph the cathode-ray tube so that a record of all the pulses from the counter is obtained. The activated target is moved from the bombardment position to the counting position in about 0.2 second by means of a pneumatic tube. Exposure of calcium to a 23-Mev alpha-particle beam resulted in an activity with a half-life of 0.58±0.04 second. This activity may be assigned to Ti43 produced by the reaction Ca40(α,n)Ti43.
The Use of Retarding Potentials with the Mass Spectrometer
Authors: Fox R. E. , Hipple J. A.
Published: February 2005

In addition to the use of stopping potentials for the study of metastable ions in a mass spectrometer, there are several other important uses including the study of ions formed with kinetic energy. There are also several interesting phenomena associated with this method which were encountered when this arrangement was first used. A summary of the authors' experiences with this method is given for the benefit of those who might plan to use this arrangement in the future.
Multiple Geiger Counters for the Observation of Particle Tracks
Authors: Chambers William H.
Published: February 2005

An array of sixteen, self-quenching, Geiger counters is described, which employs a matrix of parallel, small diameter wires for electrodes. The gas atmosphere is common to all counters. The array and attendant recording circuit is used to observe the tracks of charged particles. A spurious count, caused by incomplete absorption of the photons by the polyatomic gas, occurs in a counter adjacent to the track for about 1.5 percent of the primary tracks.
On Cloud-Chamber Valves
Authors: Chu Fu-Hsing , Valley G. E.
Published: February 2005

An investigation of the factors which influence the opening time of Fussell-type cloud-chamber valves has been made. In particular, the action of auxiliary triggering coils has been examined. The feasibility of constructing such a valve which is held shut by a permanent magnet is demonstrated. It is shown that valves can be easily made, whose opening time is limited not by electrical but by mechanical parameters.
A New Quenching Circuit for Geiger Counters
Authors: Maier-Leibnitz H.
Published: February 2005

A quenching circuit is described that works on the multivibrator principle but uses two different grids of the input tube for the signal and for the regenerative feedback. The initial discharge in the counter excites the counter to one oscillation during which the counting voltage is kept below threshold and the counter has time to recover. At the end of the oscillation (after about 0.2 millisecond) the countervoltage and all other voltages are rapidly restored to their initial values. Thus the next count will take place under exactly the same conditions as the first; all amplifier pulses will be equal; no discharges will take place in the Geiger counter while the amplifier is unable to quench them; and corrections for dead time will be quite simple.
A Highly Sensitive Differential Manometer
Authors: Matheson Harry , Eden Murray
Published: February 2005

This paper describes the construction and performance of a differential manometer with a sensitivity of 0.001 mm of mercury over the range of absolute pressures from 1 mm of mercury to 1 atmosphere. The sensitive element employed is a pair of nesting diaphragms, displacement of which is measured by the resistive unbalance of an unbonded electrical displacement gauge to which the diaphragms are attached. Calibrations are presented for the sensitivity at 1- and 10-ma gauge current. Data are presented which indicate the operating characteristics under varying conditions of absolute pressure, temperature, gauge current, and geometric orientation.
Guide Rod for Ink Styles
Authors: Zschokke Max
Published: February 2005

For recording instruments rectangular coordinates are preferred to curved ordinates. The following article describes a method by which an arc, produced by an instrument's hand can be converted into a straight line by means of a guiding device. Simultaneously it will furnish the proof that any unavoidable aberration from the absolute straight line is of no consequence as regards the exactitude of the measuring recorded.
The Efficiency of Radiation Shields
Authors: De Barr A. E.
Published: February 2005

The effect of a number of thick radiation shields of infinite thermal conductivity and of a type realizable in practice is analyzed by matrix algebra, and a method for calculating the temperatures of the various shields is also given. For identical thin shields it is found that the ratio of the power required to maintain a radiating surface of emissivity ε0 at a given temperature with N shields to the power required to maintain the same temperature without shields is given by [1+ε0(f+f2+f3+···fN)(1εk+1εl−1)]−1,where εk, εl are the emissivities of the two sides of a shield and f is the fraction of the radiation leaving the inside of the nth shield which is incident upon the n−1th shield.
Extension of De Barr's Analysis of Radiation Shielding
Authors: Garrison J. B. , Lawson A. W.
Published: February 2005

DeBarr has derived a formula for the efficiency of n thick radiation shields with infinite thermal conductivity and diffuse surfaces surrounding a black body source. This analysis has been extended to the general case when the original source has an arbitrary emissivity. A simple procedure for calculating explicitly the temperature of any shield is given, and simple numerical examples are cited. The efficiency of shields which reflect partially diffusely and partially specularly is also discussed.
A Grating Spectrometer for Millimeter Waves
Authors: Coates Robert J.
Published: February 2005

The millimeter wave-length region appears to be the crossover region beyond which optical measuring techniques are preferable to microwave techniques. For this reason a spectrometer based upon a reflecting echelette type grating was designed for the wave-length range from 3 to 12.5 millimeters.

The operation of the spectrometer is completely automatic, and the curve of received signal intensity vs. grating angle for all orders (including the zero order) is registered by a recording output meter. From the record, the grating angles corresponding to the intensity peaks at the different orders can be read within ±1 minute of arc, giving an accuracy of about ±0.04 percent for measurements of the wave-lengths of millimeter monochromatic sources.

The factors that influenced the design of the components of the spectrometer are presented. The illumination of the grating by the antenna system is incorporated in the derivation of the theoretical equation for the grating intensity curve. It is shown that this theoretical curve agrees closely with the actual spectrometer records.
A Recording Mechanical Pressure Gauge of High Range
Authors: Higgs Paul M.
Published: February 2005

An instrument of rugged construction for recording very large and rapidly fluctuating pressures in liquids and gases is described. The pressure sensitive element is a thick, flat, circular diaphragm, rigidly mounted and fluid damped. The pressure versus time record is engraved upon the surface of a rotating polished metal disk by a stylus fastened directly to the diaphragm. The record may be read with a precision of better than one percent of full deflection. The instrument will record pressures up to 1000 pounds per square inch at frequencies from zero to five hundred cycles per second.
A Multiple-Reflection Optical Lever
Authors: Hoadley H. O.
Published: February 2005

A detailed description is given of the principles of an optical lever which secures increased sensitivity by means of multiple reflections from a single small mirror. It is of particular use where space is limited, or where the mirror must have minimum size and mass, as in a galvanometer. Its limitations are an inherent restriction of the measurable range, and a comparatively rapid loss of light with increasing number of reflections. A model system was constructed, which demonstrates that no special difficulty is met with in making an optical lever according to these principles up to seven reflections. Tests made with the fifth-order reflection proved the model to be quite satisfactory.
Apparatus for Cloud-Chamber Investigations with Free Balloons
Authors: Lofgren E. J. , Ney E. P. , Oppenheimer F.
Published: February 2005

Apparatus for taking cloud-chamber pictures in free balloon flights is described. The twelve-inch cloud chamber is photographed once per minute by stereo cameras. The complete equipment for a six-hour operation at 90,000 to 100,000 feet weighs 65 pounds and is housed in a 30-inch diameter gondola equipped with temperature control.
The Statistical Theory of the Dead Time Losses of a Counter
Authors: Clark C. E.
Published: February 2005

In the case of events at random times, the number of events must be estimated from the number of counts recorded by a counter. In this article we study the statistical distribution of the unknown number of events. We show that this distribution is approximately normal, and we approximate the standard deviation.
An Apparatus for Determining the Effect of Centrifugal Force on the Potentials of Galvanic Cells
Authors: Ray B. Roger , MacInnes D. A.
Published: February 2005

An apparatus is described with which electric potentials, developed as a result of phenomena occurring in the rotor of a centrifuge, can be measured within one microvolt, and radial temperature differences in the rotor can be determined and controlled within 0.01°. Rotation in a vacuum minimizes the rise of temperature of the rotor, which can also be measured. The speed of rotation is controlled by a friction drive within 0.01 percent and maintained at definite values, between 400 to 7200 r.p.m., corresponding to stroboscopic patterns. The instrument was designed to measure the effect of centrifugal fields on simple galvanic cells.
An Accurate Gas Metering System for Laminar Flow Studies
Authors: Andersen J. W. , Friedman R.
Published: February 2005

The design and performance of an accurate flow system utilizing critical velocity orifices is described. Results indicate that an absolute accuracy of three parts in a thousand is realized over a flow range of 0.002 to 2 cubic feet per minute. Calibration of the flow system was accomplished by means of a specially modified and carefully standardized wet test gas meter. Descriptions of the components of the flow system and of subsidiary calibrating equipment are presented.

Critical flow orifice discharge coefficients are found to be independent of the type of gas; however, because of gas impurities, prediction of relative rates of flow of various gases through an orifice by use of theoretical relationships is uncertain, and experimental data are given to illustrate this.
Sampling Devices for Determining the Bacterial Content of Air
Authors: Luckiesh Matthew , Taylor A. H. , Knowles Thomas
Published: February 2005

Appraisal of air contamination by micro-organisms which are responsible for infectious diseases or result in spoilage of products requires devices for sampling the air to determine bacterial content. The simplest technique involves the use of open petri dishes containing culture media upon which colonies of the organisms can grow. However, quantitative data require the use of devices which will sample the bacterial content of definite volumes of air.

Air samplers which yield quantitative data may be roughly divided into bubbler and impinger types. In the former type a definite quantity of air, with or without atomization, is bubbled through water, thus collecting a large part of the organisms. In the impinger types the organisms are deposited on the culture medium, either by use of high linear velocity of the air or by application of an electrostatic field.

The authors have developed two types of impinger samplers. One of these, weighing approximately 12 pounds, employs an electrostatic field of about 7000 volts. It can be used wherever 110–120-volt, 60-cycle current is available. The other sampler, called a duplex radial-jet air sampler, uses a high velocity air flow to impinge the organisms on the culture medium. Examples of the use of the latter sampler in important laboratory studies are described and typical experimental results are presented.
A Wide Range Radiation Instrument
Authors: Reiffel Leonard , Burgwald Glenn
Published: February 2005

A radiation monitoring instrument based on the scintillation counter is described which measures γ- (or β-) radioactivity levels from 1 milliroentgen/hour to 100 roentgens/hour without changing scale. The instrument may thus be entirely unattended even in the vicinity of widely varying sources. Its performance and limitations are discussed, together with means for increasing its ultimate sensitivity.
An Automatic Scanning and Recording Photometer for Night Sky Studies
Authors: Marlow Douglas , Pemberton J. C.
Published: February 2005

This paper describes a photoelectric photometer which scans the entire sky in 32 minutes, recording the light energy in a 100A band as a function of altitude and azimuth. The light is chopped by a rotating shutter and detected by a photo-multiplier tube, the output from which is amplified and synchronously rectified to produce a d.c. signal for the graphic recorder. Three different types of automatic scanning are provided, as well as a manual control of the various functions. The minimum energy which may be reliably recorded, using a 4-inch, f:1 lens, is of the order of 10−13 watt.
Stabilized High Voltage Power Supply for Electrostatic Analyzer
Authors: Henkel R. L. , Petree B.
Published: February 2005

An a.c. operated power supply has been developed which furnishes voltage for the electrostatic analyzers for the University of Wisconsin electrostatic generator. Voltage is continuously variable from about 5000 to 50,000 with stability and accuracy of measurement within ±0.01 percent. The stabilizer is of the usual degenerative type, but the error signal is amplified by a phototube galvanometer d.c. amplifier and applied to a series impedance in the high voltage transformer primary circuit. The generator beam energy automatically follows adjustments of a low voltage potentiometer used for voltage measurements in this supply.
A Low Temperature Single Crystal X-Ray Diffraction Technique
Authors: Kaufman H. S. , Fankuchen I.
Published: February 2005

A low temperature x-ray diffraction technique, especially suitable to single crystal work, is described. Crystals are grown in glass capillaries on the x-ray camera. Position and orientation are determined with the aid of a polarizing microscope on the apparatus. A special specimen holder is used which prevents moisture condensation and permits rotation and oscillation of the specimen while it is being cooled.
Fast Neutron Detector
Authors: Moulton W. G. , Sherwin C. W.
Published: February 2005

A simple fast neutron detector suitable for health physics applications has been constructed using two 931A photo-multiplier tubes in coincidence to reduce background. A ``sandwich'' made of Lucite and activated zinc sulfide is used to produce the scintillations. The efficiency of the instrument for fast neutrons from a Ra–Be source is 1.5±50 percent×10−4. It detects a fast neutron flux of 20 neutrons/cm2 sec. with a counting rate that is over ten times background.
A Simplified Emission Regulator for Mass-Spectrometer Ion Sources
Authors: Winn E. B. , Nier Alfred O.
Published: February 2005

A simplified electron emission regulator has been developed which operates by controlling the space current instead of the filament heater current. No vacuum tubes are used, but the performance is comparable with that of electronic regulators now in use.
Electromechanical Lead Networks for A.C. Servo Mechanisms
Authors: McDonald Donald
Published: February 2005

The characteristics of conventional a.c. lead networks for a.c. servo mechanisms are compared to the characteristics of d.c. lead networks. Electromechanical lead networks for a.c. servo mechanisms having superior characteristics to those of the conventional a.c. lead networks are described and analyzed. A practical design for one of these electromechanical lead networks and its application to a servo system is shown.
A High Power Attenuator for Microwaves
Authors: Alpert Daniel
Published: February 2005

A high power variable attenuator has been developed for use in 10-cm wave guide transmission lines. The attenuating material is a liquid which serves also to transfer the absorbed energy. The attenuator can handle power levels up to 100 watts, has a power standing wave ratio less than 1.1 to 1, and an attenuation which is variable from 1.5 db to 40 db.
Photo-Tube Input Impedance for a Voltage Stabilizer
Authors: Strait E. N. , Buechner W. W.
Published: February 2005

A circuit for stabilizing the voltage of an electrostatic generator is described. A photo-tube under constant illumination is used as an input impedance, eliminating the necessity for d.c. amplification of the error signal. This signal is impressed directly on the control grid of a 5693 pentode that is used to control corona-leakage current to the high voltage terminal of the generator. Convenience of operation and simplicity of construction are features of the circuit.
An Absolute Noise Thermometer for High Temperatures and High Pressures
Authors: Garrison J. B. , Lawson A. W.
Published: February 2005

A null device for determining the ratio of two absolute temperatures with an accuracy of 0.1 percent is described. This device balances the mean-square fluctuations in voltage across the terminals of two resistors arising from thermal agitation at the temperatures to be compared. The ratio of the resistances, when the noise voltages from the two resistors are equal, determines the ratio of their absolute temperatures. The limitation on the ultimate accuracy of the ratio of temperatures so determined is imposed by the relative value of the first and second moments of the voltage fluctuations observed, which in turn depends on the length of time utilized in averaging the fluctuations. With the apparatus described below, an observation time of two minutes is adequate to guarantee the accuracy claimed above for high temperatures, provided certain elementary precautions in constructing the noise thermometer are observed. Numerous tests have been conducted in the neighborhood of 1000°K which substantiate these claims. Extrapolation of the performance obtained at such temperatures indicates that material improvements in the accuracy of the absolute temperature scale above 2000°K may be obtained. The calibration of the thermometer is independent of the chemical composition and past physical history of the material from which it is constructed, in addition to being independent of the absolute pressure.
An Apparatus for Measurement of Extremely High Internal Friction
Authors: Kê T'ing-Sui , Ross Marc
Published: February 2005

A simple torsion apparatus has been developed for measurement of extremely high internal friction by determining the angle by which strain lags behind the stress in forced cyclic vibration. The results of measurement were compared with torsion pendulum measurements using free decay method. The highest internal friction measured with this apparatus was 0.55. This apparatus can be used to measure internal friction at a constant given stress amplitude and at a constant frequency of vibration. The stress amplitude and frequency of vibration can easily be varied over a wide range. There is no theoretical limit to the lowest frequency of vibration that can be used with this apparatus. The feature that measurements can be made while the zero point is changing renders this apparatus very useful in the study of internal friction of freshly cold-worked metals.
A Device for the Measurement of Rotor Temperature in the Air-Driven Ultracentrifuge
Authors: Ecker Paul Gerard , Blum Josef , Hiatt C. W.
Published: February 2005

A device is described which permits the measurement of rotor temperature in the air-driven ultracentrifuge while the machine is in operation at speeds up to 60,000 r.p.m. A Thermistor situated inside the rotor changes its resistance as the temperature changes. Measurement of the Thermistor resistance by means of a Wheatstone bridge is accomplished with the use of needle contacts on the top of the turbine shaft and at the bottom of the rotor. Rotor temperature may be measured to within ±0.02°C and is believed to represent actual temperature of the rotating solution within 0.1°C.
The Shock Tube: A Facility for Investigations in Fluid Dynamics
Authors: Bleakney Walker , Weimer D. K. , Fletcher C. H.
Published: February 2005

A qualitative description of the theory of the operation of a shock tube is given together with a discussion of its design. The construction of a particular tube 4 in.×18 in.×38 ft. is described as well as certain auxiliary equipment needed in its operation. The technique of operating the device and comparisons of its performance with expectations are discussed. This tube has been used to study certain properties of shock waves and to obtain a flow field of marked uniformity and freedom from turbulence. The Mach number of this flow may be adjusted at will from zero to the supersonic range without difficulty. An interferometer makes it possible to obtain an instantaneous picture of the density field so that the apparatus may be used as a very efficient transonic wind tunnel.
The Theoretical and Practical Sensitivity of the Pneumatic Infra-Red Detector
Authors: Golay Marcel J. E.
Published: February 2005

Following an introductory sketch of the application of the pneumatic infra-red detector to spectrometry, the absolute sensitivity of a pneumatic detector is calculated for the case of an infinitely extended flat heat cell. The calculated r.m.s.e.n.i. is seen to be in good agreement with the experimental results.
A Double Pulse Constant Current Stimulator
Authors: Schoenfeld Robert L.
Published: February 2005

A double pulse stimulator for clinical use in testing refractory time periods of peripheral nerve and muscle is described. Two rectangular stimuli of variable width, time separation, and intensity are delivered from a high impedance source to the same pair of stimulating electrodes. Provision is made for initiating the horizontal sweep of a cathode-ray oscilloscope in synchrony with the stimuli. Action potentials produced may be picked up, suitably amplified and recorded on the vertical axis of the oscilloscope. The time interval between the stimuli at which the tissue is refractory may be observed as the distance between stimulus artefacts on the cathode-ray screen.
Direct Calorimetry by Means of the Gradient Principle
Authors: Benzinger T. H. , Kitzinger C.
Published: February 2005

A rapidly responding calorimeter for continuous recording of biological heat exchange has been described. The method is based on the enclosure of the subject in a shell completely lined with a uniform heat flow metering layer (``gradient layer'') while ventilatory and respiratory heat losses are determined in heat exchange meters based on the same technic. The measurement comprises in one thermoelectric potential the sum of all components of heat loss (radiant, convective, conductive, and evaporative fractions). Partitioning measurements of respiratory and evaporative heat losses are readily obtained. Environmental conditions can be closely controlled, and widely varied.

The gradient calorimeter with its rapid response (time lag 42 seconds) is specifically designed for studies of reflex mechanisms involved in temperature control. It is, however, suggested that the characteristics described will, in general, encourage wider application of direct calorimetry in experimental and clinical studies.
Production and Measurement of Ultra-High Speed Impulses
Authors: Fletcher R. C.
Published: February 2005

The capabilities and limitations of several impulse generators and voltage dividers, and a micro-oscillograph sweep circuit for dealing with kilovolt impulses in the millimicrosecond range, are described. The most successful combination produces and measures an impulse of a rise time equal to 4×10−10 sec.
Volumetric Respirometer for Aquatic Animals
Authors: Scholander P. F.
Published: February 2005

The oxygen consumption of fish and other aquatic animals can be determined in the gas phase of a closed system provided the water is thoroughly equilibrated with the gas phase. The present respirometer employs a simpler and more efficient equilibration system than the earlier described model [Scholander, Haugaard, and Irving, Rev. Sci. Inst. 14, 48 (1943).] and permits a continuous recording of the oxygen consumption over a considerable range. The apparatus is well suited to be set up in banks and has been used extensively in temperature studies on arctic and tropical fishes and crustaceans.
Operation of the 184-In. Cyclotron
Authors: Henrich L. R. , Sewell D. C. , Vale J.
Published: February 2005

The operation of the 184-in. synchro-cyclotron is reviewed in terms of the theory as developed by Bohm and Foldy. Certain relevant data on the properties of the magnet and rotating condenser are also presented.
Circuit for Rapid Determination of Resolving Power and Other Characteristics of Coincidence-Systems
Authors: de Waard H.
Published: February 2005

A simple device is described in which pairs of pulses are produced that are moved continuously with respect to each other (wobbled) by an a.c. voltage that also sweeps an oscilloscope spot horizontally. The pulses are applied to both inputs of a coincidence system. Vertical deflection of the c.r. scope spot is caused by the output pulses of the system. Thus various characteristics can be made visible and the resolution can be read from the scope screen at a glance. With the instrument resolving powers from 3.10−6−10−9 sec. approx. can be determined. The apparatus was calibrated by feeding the wobbling pulses into a radio receiver. The output of the receiver has a sharp minimum when the pulse distance (Δt) satisfies the condition Δt=(1+2n)/2ν where n is an integer, ν is the frequency to which the receiver is tuned.
Sliding Contacts to Transmit Small Signals
Authors: Horton Billy M.
Published: February 2005

Measurements have been made of root-mean-square noise voltage in the frequency range 0.5 to 200 c.p.s. generated by contacts sliding at low speeds using four arrangements of contacting bodies and various materials. Mercury with amalgamated probes gave the lowest noise levels. Some solid contacts operating with low friction on clean metal surfaces yielded values of generated noise below 1 microvolt at a sliding speed of 35 cm/sec. when two contacts were in parallel.

The noise increases with speed and varies with normal force. The r.m.s. generated noise voltage of a large number of independently mounted contacts in parallel is inversely proportional to the square root of the number of contacts.
The Gamma-Ray Counting Efficiency for a Lead-Cathode G-M Counter
Authors: Jurney E. T. , Maienschein Fred
Published: February 2005

The dependence of gamma-ray counting efficiency on energy has been determined in the range 0.17 Mev to 2.76 Mev for a G-M counter with a lead cathode. The efficiency for six energy values was found by coincidence measurements utilizing the disintegration of In111, Au198, Co60, and Na24. The result indicates a smooth increase in counting efficiency for increasing energy over the range of energies investigated.
A Note on Analog Computer Design
Authors: Bronzo J. A. , Cohen H. G.
Published: February 2005

A method is proposed for the simplification of computers designed to solve certain types of partial differential equations. The equations are those in which the spatial derivatives may be replaced by finite difference expressions. The resulting difference—differential equations are reformulated as a system of linear simultaneous equations by making use of Laplace transforms and matrix notation is introduced. By applying a similarity transformation to the matrix a new system is obtained which lends itself more readily to the construction of an analog. As an example, the analog of the equation of the vibrating string with fixed ends is discussed.
Exposure Meter for Precision Light Dosage
Authors: Launer Herbert F.
Published: February 2005

The exposure meter is an electronic device of the type in which a photo-tube charges a capacitor to the firing voltage of a trigger tube, whose pulse is amplified by a thyratron. The device has been adapted to high intensity sources and is used for the regulation of carbon arc light dosage in the standardization of light-sensitive paper at the National Bureau of Standards. The device, including a modification for automatic extinction of the source when the desired light dosage is obtained, is described, and is shown to be capable of very high reproducibility. Two instruments simultaneously viewing a gradually aging monochromatic source gave count values whose ratios showed a coefficient of variation of 0.32 percent in two weeks of continuous measurement. One instrument, viewing a controlled tungsten lamp, showed a coefficient of variation of 0.18 percent in counts per watt hour over a period of nine days, after which the values changed—the result, presumably, of changes in the lamp.

The instrument was tested for suitability of application by comparing counts with reflectance changes of light-sensitive paper under arc exposure. The results showed that the instrument could control light dosage adequately in spite of large changes in arc voltage, glass filters, and time of exposure.

The instrument was used to test the variability of the uranyl oxalate actinometer, frequently used in photo-chemical work, by simultaneous exposure to a carbon arc. It was found that the actinometer was capable of higher precision than previous investigators had found, in that the coefficient of variation was 1.4 percent, less than ¼ as large as formerly believed.
A Capillary Collector for Measuring the Deposition of Water Drops on a Surface Moving through Clouds
Authors: Vonnegut Bernard
Published: February 2005

An instrument has been devised for the purpose of measuring the amount of water impinging on a small area moving through clouds, rain, or snow. From measurements of this sort, the liquid water content of the atmosphere can be evaluated.

The instrument uses capillary phenomena to collect and retain water drops striking a small porous surface. Its function is the same as small scoops which have been used to measure water collection in flight, but it has the advantage that its response rate is sufficiently rapid to measure collection rate over a very short interval of time. It has been successfully used in wind tunnel and flight tests. With slight modification, the instrument should find application in measurements on other liquid aerosols.
Trochotron Design Principles
Authors: Monk G. W. , Werner G. K.
Published: February 2005

A simple derivation of the perfect focusing properties of the trochoidal type mass spectrometer, which leads to convenient methods of correlating the many variables for design purposes, is given. Nomographs and general trochoids are given which apply to charged particles in crossed, uniform, electric, and magnetic fields.
A Servo Employing the Magnetic Fluid Clutch
Authors: Bettis E. S. , Mann E. R.
Published: February 2005

A simple servo unit is described. The device utilizes the electromagnetic fluid clutch developed by J. Rabinow of the National Bureau of Standards. Simplicity in design and construction, relatively high torque inertia ratio obtainable, and high power transmission capabilities appear to be the chief merits of such a servo system. Performance data on a prototype servo unit are submitted.
Counter Pulse Shape
Authors: Thomas C. D.
Published: February 2005

The shape of the decay pulse from a self-quenching counter depends on the circuit constants as well as on the motion of the positive ion sheath. This is considered mathematically and a formula developed to take account of these factors in determining pulse height and form. In order to check this relation experimentally, data obtained from photographed single pulses are presented and compared to the calculated values. These curves cover a wide range of values of circuit resistance and capacity.
Conditions for Optimum Luminosity and Energy Resolution in an Axial β-Ray Spectrometer with Homogeneous Magnetic Field
Authors: DuMond Jesse W. M.
Published: February 2005

In a β-ray spectrometer with axial homogeneous magnetic field, it is shown that optimum energy resolution and luminosity are obtained when the trajectories make an angle close to 45° with the field and that an annular resolving slit should be provided at a determined radial and axial location relative to the source. The combined effect of three independent sources of instrumental energy line width is analyzed for the optimum condition. Formulas are given for the optimum dimensions, the energy resolution and the luminosity.
A Pulse Amplitude Analyzer for Nuclear Research Using Pretreated Pulses
Authors: Westcott C. H. , Hanna G. C.
Published: February 2005

A pulse analyzer is an instrument used to record the number of pulses occurring in a given time whose amplitudes lie between certain limits. In the present equipment records are obtained from 30 ``channels'' simultaneously, the upper amplitude limit for any one channel being the lower amplitude limit of the next. Used in conjunction with an ionization chamber and linear amplifier of suitable design, the equipment gives detailed information of the frequency of occurrence of ionization pulses of various amplitudes.

The present equipment is an advance over previous designs in several respects. It is designed to deal with relatively fast counting rates and with pulses having a wide variety of shapes and durations. In order to avoid having to change the circuits of each of the 30 channel units to suit the pulse shape, the pulses are ``pretreated'' to yield signals of standard form before being passed to the channels for analysis. Further advantages of the present equipment concern the ease of calibration and of monitoring the behavior of the circuits. The whole is built into a console of convenient shape and reasonable mobility. Interchangeable plug-in channel units are employed.
A Simplified Chronotron-Type Timing Circuit
Authors: Keuffel J. Warren
Published: February 2005

A timing circuit is described similar in principle to the Neddermeyer ``chronotron,'' but with the following simplifications and modifications: parallel-wire polythene-tape line to eliminate co-ax ``plumbing,'' germanium crystal detectors, and a delay-line presentation circuit. This circuit uses a single common amplifier for all pulses, which increases stability, makes adjustment easy, and effects a tenfold saving in the number of tubes. It simultaneously records time intervals in two ranges, e.g., 0–0.1 and 0–5 μsec. The precision is 1×10−9 sec., but may be increased at the expense of the range. Problems connected with coupling the instrument to parallel-plate counters are discussed.
Parallel-Plate Counters
Authors: Keuffel J. Warren
Published: February 2005

The counter characteristics of a discharge tube using plane-parallel electrodes have been investigated, particularly with regard to the short time lags inherent in the streamer type of spark which occur with such a geometry at near-atmospheric pressure. Construction details for parallel-plate counters with good counter characteristics are given. Spurious counts were minimized by an argonxylene filling mixture and the use of a univibrator quench circuit. The uncertainty in the reaction time of the counters is ±5×10−9 sec.
Equipment and Experimental Methods for Interference Diffusion Studies
Authors: Gosting Louis J. , Hanson Edwin M. , Kegeles Gerson , Morris Margaret S.
Published: February 2005

A single lens convergent light apparatus is described with which diffusion in liquids may be studied by an interference method. Details of the optical elements and their mounting and alignment are given as well as the design of a temperature control regulating near 0°C to within 0.01°C. A modified Polson sharpening technique has been used successfully in forming diffusion boundaries in a Tiselius cell. A modification of the Rayleigh interferometer has been employed as an aid in the measurement of the refractive index increment parameter, jm, which is required for the evaluation of the diffusion coefficient. During diffusion a reference slit image obtained by the employment of special cell and plate masks permits more accurate measurements of the undeviated slit image position than have been obtained from the interference diffusion fringe picture. Results indicate that the apparatus is capable of 0.1 percent precision.
Errors in Second-Order Measuring Instruments
Authors: Benedikt Elliot T.
Published: February 2005

The various types of error which affect the result of a measurement performed by an instrument behaving as a second-order linear instrument are defined.

The theoretical systematic error is shown to be caused by the (dynamical) lag with which the instrument responds to the signal. If the damping is high, this type of error turns out to be proportional to the rate of change of the signal.

The accidental error resulting from input noise and accidental changes of the instrument constants is considered. It is shown that all these effects can be represented by an effective input noise. A formula for the mean square error in the indication of the instrument is given in terms of the correlation function of the above effective noise.

Related theoretical questions on random functions are discussed in the Appendix.
Methods for Reducing Insulator Noise and Leakage
Authors: Glass F. M.
Published: February 2005

A recent study of the insulator problem involved in radiation detection instruments disclosed the fact that insulators, in high impedance input circuits, are the predominate source of background noise when subjected to high voltages and high humidities. Methods for eliminating this trouble in some of the commonly used circuit components, and new and superior insulating materials, were found.
A Wide Range Capacitance-Conductance Bridge
Authors: Cole Robert H. , Gross Paul M.
Published: February 2005

The bridge described has been developed for reasonably accurate measurement by direct balance of capacitance and conductance in the frequency range 50 c/sec. to 5 mc/sec., and over most of this range is essentially direct reading in the two admittance components with negligible unbalance from lead effects or guard circuits of the unknown. These properties are realized by using two circuits developed from the work of others. The first employs inductively coupled ratio arms to minimize residual impedance effects and unbalance by guard circuits, the second, a conductance shifter wye network with good high frequency properties and an essentially linear conductance reading. Design considerations and limitations of these circuits are discussed, as are suitable test cells and auxiliary equipment.
Magnetic Deflector for Mesons Produced in the 184-Inch Cyclotron
Authors: Panofsky Wolfgang K. H. , Martinelli Ernest A.
Published: February 2005

A magnetic deflector has been constructed which makes the mesons artificially produced in the 184-inch cyclotron by alpha-particle bombardment available outside the cyclotron tank. The deflector consists of a magnetic shield especially designed to operate in very high external magnetic fields. The effect of the magnetic shield on the internal cyclotron beam has been compensated by pole shims. The deflector yields a total meson flux of approximately 500 mesons per minute.
Pressure Regulated Thin Window Geiger-Mueller Counter
Authors: Ter-Pogossian Michel , Robinson J. Eugene , Townsend J.
Published: February 2005

The use of very thin Zapon or Formvar windows for G-M counter tubes in beta-spectroscopy is limited by the fact that the filling mixture of the counter diffuses or leaks through the window, which forbids the use of very thin windows. A pressure regulator is described which will permit the maintenance of a constant pressure of filling mixture even if the window of the counter allows the slow escape of the gas. A thin window G-M counter presenting some improvements is also described.
Electronic Apparatus for the Determination of the Physical Properties of Freely Falling Raindrops
Authors: Gunn Ross
Published: February 2005

An apparatus is described for measuring the mass, velocity of fall, sign, and free electric charge of individual falling raindrops. Two vertically separated rings are so arranged that naturally charged raindrops fall through them and induce pulses on the grid of a vacuum tube amplifier which in turn operates a tape oscillograph. From the characteristic double pulses produced, the charges and transit times may be determined. The mass of the droplet is simultaneously determined by measuring the size of the spot produced when the drop falls on blueprint paper tape traversing the oscillograph. Short cuts for the reduction of data on drop sizes are given.
A Microwave Polarimeter
Authors: Schwaneke Alfred E. , Harvalik Zaboj V.
Published: February 2005

A microwave polarimeter is described which enables the determination of rotation of the plane of polarization of microwaves in the 3.2-cm band. The transmitter-analyzer utilizes klystron tube 723 A/B. The microwaves are fed into a horn which acts as a polarizing agent. The analyzer-receiver consists of a horn antenna, rotatable wave guide, a crystal detector, and an indicator. The microwaves are rectified by a crystal rectifier, and are either detected by a microammeter, a galvanometer, or by an amplifier of appropriate design. Changes of angles of rotation can be detected if they are not less than 2° to 3°.