bluuebunny/crossref_metadata_2025_split huggingface dataset:
Short Time Delays in Geiger Counters
Authors: Sherwin Chalmers W. 
Published: February 2005

There are at least two types of short time delays in the firing of Geiger counters. The first is due to the transit time of the secondary electrons as they migrate toward the central wire. This time can be measured when beta particles are sent parallel to the axis of the counter, creating secondaries at known distances from the axis. In a typical counter, 2.2 cm in diameter, the maximum secondary electron transit time is measured at about 11×10−8 second.
The second delay occurs between the time the electron arrives near the center wire, and the time a pulse is detected on the output of a wide band amplifier connected to the center wire. Increasing the voltage on the counter from the threshold to an over-voltage of 250 volts, decreases this delay by 10 to 20×10−8 second. It is suggested that this delay is due to the time required to form the initial part of the ion sheath.
An Inductively Coupled Series Tube D. C. High Voltage Regulator
Authors: Pepinsky R. , Jarmotz Paul 
Published: February 2005

A new d. c. high voltage stabilizer, operating in the range from +5 to +50 kilovolts and for currents up to 50 milliamperes, is described. The stabilizer is of the usual degenerative type; but the series regulator tube, which is at high voltage, is inductively coupled to the feed-back amplifier at ground-potential. The signal from the amplifier amplitude-modulates an r-f oscillator, the output voltage of which is passed through a transformer, rectified, filtered, and applied as a d. c. correcting signal to the series tube grid. Insulation between high and low voltage circuits is provided in the r-f transformer.
As an example of the short-term stabilizing action, a level of +35 kilovolts can be maintained to within 2 volts, for ±5 percent change in the input voltage, independently of load up to 50 milliamperes. The output ripple at this voltage and 20-milliamperes load is 0.05-volts r.m.s. Long-term stabilization, which depends chiefly upon constancy of the reference level, has not been measured, but means to its attainment are suggested.
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.
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.
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.
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.
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.
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.
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.
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.
Ionization Flame Detectors
Authors: Calcote Hartwell F. 
Published: February 2005

Two new ionization methods of detecting flames are described for use in the measurement of flame speeds. In one the loading characteristics of a high frequency oscillator are utilized by causing the flame to pass through an oscillator tank coil. The second method employs the flame conductivity by placing two ring electrodes around the exterior of a combustion tube, and applying a d.c. voltage across them through a large series resistance. The voltage pulse created by either method when the flame passes the detector is used to trigger an electronic chronoscope.
Both methods have the distinct advantage over previous methods of flame detection in that the direct measurement of flame speeds can be made without the introduction of electrodes or wires into the combustion tube. The oscillator detector has the additional advantage that the point at which the measurement is made can be varied at will.
Operational Features of a New Electron Diffraction Unit
Authors: Picard Robert G. , Smith Perry C. , Reisner John H. 
Published: February 2005

A new electron diffraction unit having a three-lens optical system and a maximum effective specimen-to-plate distance of 200 cm is described. The applications of such a system to the study of long interatomic spacings is discussed. Wide variations in the area of specimen irradiated are obtainable. An explanation is given of the design considerations in such an optical system, with special reference to the functioning of the post-specimen lens as both focusing and magnifying lens. The use of the unit as a shadow microscope is explained, and the advantages are given of this instrument over other shadow microscopes with respect to increased size of image, increased size of specimen field available for observation, and greater specimen protection from damage by the concentrated electron beam.
The resolution attainable with the instrument is calculated and a ``resolution index'' is defined which makes possible intercomparisons of resolution under various operating conditions. Factors which limit accuracy, as opposed to resolution, are discussed critically and the accuracy of data obtainable with the instrument is estimated.
A number of diffraction patterns are shown to illustrate the results obtained under various operating conditions as diffraction camera and shadow microscope, and also to illustrate the techniques of charge neutralization, spot diameter measurement, and internal calibration of plates using a known specimen.
Calibration of Photographic Emulsions for Low Energy Electrons
Authors: Cranberg L. , Halpern J. 
Published: February 2005

Measurements are reported for the dependence on energy of photographic darkening due to electrons of energies between 4.4 and 45 kev. For Ilford B-2 plates, in the linear density exposure region, the results can be expressed by the empirical formula D/Q/A=KEx. D is the photometric density, Q/A the exposure in electrons/mm2, E the energy in electron-volts; K and x are constants with the values (0.30±0.03)×10−12 and 1.45±0.05, respectively. The relationship for two other emulsions tested is complicated by the presence of surface coatings on the emulsions. Reproducibility of results is discussed.
Results are given on density fluctuations due to granularity of Ilford and x-ray emulsions. The limit of sensitivity, using the L. and N. recording microphotometer with scanning beam 1.0 by 1.3 mm, is estimated at 450 electrons/mm2 of 40 kev energy for the x-ray emulsion and 680 electrons/mm2 for the Ilford plates. The latter is limited by photometric sensitivity.
Precision Thermostat for High Temperatures
Authors: Eubank William R. 
Published: February 2005

A precision thermostat has been developed, based upon that of Roberts, for the control of high temperatures (1000°—1550°C). With the instrument described, temperatures are readily maintained constant within ±0.1°C for several hours, and within ±1.0°C for several days.
In this method of control a thyratron is used in conjunction with an a.c. bridge and high gain amplifier. The phase angle of the unbalanced bridge regulates the firing of the thyratron. The control is highly sensitive and independent of normal fluctuations in line voltage. The thermostat is convenient to operate, easy to adjust for any temperature, and reliable for periods of continuous operation from a few minutes to several days.
A Capacitance Bridge for High Frequencies
Authors: Mendousse J. S. , Goodman P. D. , Cady W. G. 
Published: February 2005

A type of bridge for measurements at frequencies in the megacycle range is described, containing two fixed capacitors and a variable capacitor. The unknown impedance is connected in the fourth arm as a ``load.'' The unbalanced high frequency e.m.f. is rectified by a germanium crystal rectifier and measured as a small d.c. voltage. The bridge is ``balanced'' by varying the variable capacitance until the ratio of output d.c. to input h-f voltage is at a minimum. The impedance of the variable capacitor is then numerically equal to that of the load.
In a second and perhaps more important application, the bridge is used for examining vibrational modes and measuring the Q of piezoelectric crystals or transducers. Here the variable capacitor is set at a fixed value equal to the parallel capacitance of the crystal, and the output voltage is observed, or recorded graphically, while the frequency is slowly varied over the resonance range. Some graphical records are shown, illustrating the performance of crystals at various frequencies and under different mechanical loads.
The theory of the bridge is given, and sources of error are discussed.
Construction and Performance of a Multiple Gamma-Ray Counter of High Efficiency
Authors: Gráf Tibor 
Published: February 2005

A multiple gamma-ray counter is described, composed of 24 counter tubes connected in parallel. The tubes have Bi-plated brass screen cathodes and are placed inside the same envelope. Relative and absolute values for the efficiency of the counter were determined experimentally in the range 0.28 to 2.62 Mev. Compared to a single brass counter of similar dimensions, the multiple counter shows for gamma-rays of, say, 0.7 Mev energy a tenfold increase in efficiency. Its starting voltage is 5–600 volts lower.
The ``effective resolving time'' of the multiple counter appears to be 3 to 4 μseconds.
The counting rate curve seems to follow the inverse-square law down to the shortest counter-source distances. The solid angle subtended by the multiple counter for sources, placed in its middle, is nearly 4π.
Vibration Studies: Related to Electron Microscopy
Authors: Hamm F. A. , Snowden F. C. 
Published: February 2005

This paper describes a convenient scheme for detecting and measuring vibration as related to the performance of an RCA electron microscope (Type EMU). The procedure involves the use of a Webster Model F5P2 phonograph pick-up arm in conjunction with a cathode-ray oscillograph. The cathode-ray oscillograph signal amplitude which represents the vibration of the location being investigated was calibrated by means of a Brush Development Company Type BL-301 vibration pick-up whose voltage output is proportional to the product of the vibration amplitude and the square of the frequency. An audio oscillator was used to calibrate the voltage output of the Webster (rochelle salt) pick-up as a function of frequency. After calibration, these oscillographic measurements may be used to determine absolute mechanical displacements.
Electron micrographs are included to illustrate the image displacements due to several different amplitudes of vibration. Cognizance of vibration is often necessary, especially in high resolution electron microscopy. This scheme may be used as a guide in high resolution electron microscopy.
The Theory and Properties of Low Voltage Radiation Counters
Authors: Simpson J. A. 
Published: February 2005

The behavior of permanent gas mixtures which lead to low breakdown potentials is discussed, and criteria are established for attaining minimum threshold and operating potentials for G-M counters. Curves showing the dependence of counter characteristics upon pressure and electrode parameters have been obtained for various mixtures of neon and argon. The properties of cathode surfaces have been investigated and the criteria for obtaining suitable surfaces for counter operation were found.
Two classes of counters were observed using these permanent gas mixtures. The first class possesses the lowest range of threshold potentials (approximately 115 to 135 volts) at pressures up to approximately 7 cm Hg. They require quenching circuits having relatively long time constants. The second class of counters have threshold potentials in the range of approximately 135 to 210 volts corresponding to pressures from 7 to 50 cm Hg. They operate with fast quenching circuits.
Miniature portable radiation detectors and meters have been made using these detectors.
Apparatus for Rapid Measurement of Internal Friction
Authors: Fusfeld Herbert I. 
Published: February 2005

This paper describes apparatus for measuring internal friction which satisfies the conditions (a) low induced stress amplitude to preclude any plastic flow of the specimen, (b) ability to install specimen within a few minutes after treatment, (c) rapidity of measurement, at a rate of ten to twenty per minute, (d) accuracy of at least one percent.
Longitudinal vibrations are induced by an eddy-current drive, similar to one previously described in the literature, satisfying (a) and (b). Conditions (c) and (d) are obtained by measuring the decay time of free vibrations using vacuum tube trigger circuits and a counter chronograph. Satisfactory measurements can be made with push-button rapidity and simplicity.