bluuebunny/crossref_metadata_2025 huggingface dataset:
Wilson Cloud Chambers with an Increased Time of Sensitivity
Authors: Bearden J. A.
Published: February 2005

Two types of sylphon bellows Wilson cloud chambers have been constructed which have a time of sensitivity as great as 2.0 seconds. This has been accomplished by using a slow rate of expansion and an expanding space whose floor was water. The mechanical details have been made exceedingly simple and such that once the cloud chamber is adjusted it easily remains in adjustment indefinitely. About four to five cosmic-ray tracks appear for each expansion. A test with x-rays showed that the cloud chambers were sensitive for about 2 seconds under the best conditions. Some of the principal requirements for successful operation are listed. Also motion pictures of an expansion are reproduced. Several observations concerning the high voltage condenser—capillary tube method of illumination are given.
A Van de Graaff Electrostatic Generator Operating Under High Air Pressure
Authors: Herb R. G. , Parkinson D. B. , Kerst D. W.
Published: February 2005

An electrostatic generator of the Van de Graaff type has been developed which operates in a large steel tank under an air pressure up to 45 lbs. The maximum steady voltage obtained was about 750 kv. In applying this voltage to an evacuated tube for acceleration of protons the usable voltage is limited by the dimensions of the present tube to about 400 kv. The apparatus has given satisfactory service during a year of use in nuclear disintegration work.
The Exact Measurement of Electron-Tube Coefficients
Authors: Hickman Roger W. , Hunt Frederick V.
Published: February 2005

The analysis of the conventional bridge circuits (Chaffee, Thermionic Vacuum Tubes) for the measurement of electron tube coefficients has been extended to include the effect of grid current and tube and battery capacitances. It has been found that the addition of an auxiliary capacitance bridge to the usual circuits permits annulment of the quadrature component of voltage introduced into the detector circuit by the tube capacitances. In every case in which one or more of the tube capacitances form one arm of the auxiliary bridge the conditions of balance show the expression for the tube coefficient to be independent of the capacitances of the auxiliary bridge. If all the tube capacitances are considered it appears that a single balancing condenser in the auxiliary bridge will always suffice to give an exact null balance, although the expression for the tube coefficient may contain a correction factor, usually negligible, involving the capacitances. This capacitance balancing method has been applied to circuits suitable for measuring both positive and negative values of the plate and grid coefficients and the exact expressions for the coefficients are given under the general condition that electron current flows to both grid and plate.
A Type of Geiger-Müller Counter Suitable for the Measurement of Diffracted Mo K X-Rays
Authors: LeGalley Donald P.
Published: February 2005

The design and construction of Geiger-Müller counters which will respond reliably to Mo K x-rays is described. The impulses are amplified and recorded mechanically with the aid of a thyratron circuit. The amplifying and counting circuit, and the counting mechanism, are also described. The time of recovery of the counters has been determined by the use of an oscillograph and found to be less than 0.001 sec. when the proper values are used for the resistance and capacitance of the counter circuit. It is shown that for counting rates up to 600 per minute there is less than a 1 percent correction due to the fact that the impulses are random in nature. Several fundamental tests are described, which have been applied to the counter and the circuit. These tests have shown the counter and the circuit to be a reliable method of measuring x-ray intensities. Graphs are shown of the diffraction patterns of NaCl and KCl taken by means of the counters. These graphs duplicate the well-known diffraction patterns of these materials, thus giving additional evidence of the reliability of the counters.
Electrostatic Focusing at Relativistic Speeds
Authors: Hansen W. W. , Webster D. L.
Published: February 2005

Power series are derived with which, given data on the electric field, the focal properties of some common electron lenses can be quickly computed even when the speed of the electrons approaches that of light. The expansion is in powers of the ratio of the P.D. across the lens to the sum of the P.D.'s between its electrodes and the cathode (for electrons) or anode (for positive ions), squares of this ratio being neglected in comparison with unity. As an example the focusing properties of two cylinders almost in contact are calculated.
Ion Optics of Equal Coaxial Cylinders
Authors: Kirkpatrick Paul , Beckerley James G.
Published: February 2005

The potential distribution along the axis of two long equal coaxial conducting cylinders has been found to be empirically expressible in terms of the radius and separation of the cylinders. The empirical expression checks well with the single special case (zero separation) which is known to have been solved analytically. The general empirical expression, combined with the theoretical lens equation of Hansen and Webster yields an algebraic formula for lenses of this type directly relating object and image distances to readily measurable quantities.
The Coordirectograph—A Mechanical Device for Rapid Quantitative Comparison of Curves Dissimilar in Ordinate and/or Abscissal Values
Authors: Green Harold D. , Maurer Joseph
Published: February 2005

A mechanical labor-saving device is described for converting two curves with differing ordinate and/or abscissal values to identical scales in the two axes, and for quantitatively subtracting such curves. Since the various uses of the appliance depend upon its ability to convert different ordinate values to the same scale, it is called a coordirectograph.
A Method for Measuring High Resistance
Authors: Van den Akker J. A. , Webb Glenn M.
Published: February 2005

A method is described for high resistance measurement which depends essentially on the fact that a small capacitance C, charged and discharged n times per second, is equivalent to a high resistance 1/nC ohms if the pulsating current is smoothed by a larger capacitance. Upon placing the ``equivalent high resistance 1/nC'' and unknown high resistance R, in two arms of a Maxwell bridge, it is shown that at balance, R is given by the familiar bridge equation: R=(1/nC)R1/R2. The method has been used to check the constancy of several electrolytic resistors three years old. It was found, for a resistance of the order of 108 ohms, that no change was detectable within 0.1 percent; for resistors of the order of 1010 ohms, a decrease of about 3 percent was noted.
Ion Sources for Mass Spectroscopy
Authors: Dempster A. J.
Published: February 2005

Three spectroscopic methods of exciting spectra have been examined as possible sources of positive rays. The vacuum vibrator, a mechanically interrupted low potential spark, has been found to give positive ions although the source is not constant. The discharge of a large condenser charged to 60 kilovolts between metal electrodes, has been found unsatisfactory as a source of positive ions. A high frequency alternating spark coupled inductively to a primary oscillating spark circuit, is a strong convenient source. The ions may be accelerated to form a beam, and, with the Thomson parabola method of analysis, it has been found that multiply charged ions of the electrode elements are formed in all cases tried.
Belt-Type Generator with Small Vertical Clearance
Authors: Bennett Willard H.
Published: February 2005

A high voltage electrostatic belt-type generator has been built, in which nearly horizontal ropes are used for support instead of the usual vertical supporting textolite cylinder. This new arrangement turns surfaces with maximum radius of curvature towards the shortest gaps, above and below. Evidence is presented to show that this arrangement gives the maximum voltage for a room with limited height.
An Electric Driving and Timing Apparatus for Microcinematography
Authors: Goetz A. , Romer A.
Published: February 2005

The apparatus described serves as an electric drive of a motion picture camera. It permits, in contradistinction to other devices for the same purpose, the independent adjustment of the exposure time and the interval between the exposures. The former can be adjusted between 0.2 and 5 sec., the latter continuously over a range of a factor 5000. Two applications of this apparatus in the field of microcinematography are described, one being the determination of the falling speed of suspended colloid particles in an ultramicroscope, the other being the recording of the growth of etch figures on crystal planes produced by electrolysis.
An Effective Method for Using Lead or Other Low Melting Metals for X-Ray Targets
Authors: Folsom T. R.
Published: February 2005

Experiments were conducted to develop a more economical and satisfactory target for a 650,000-volt x-ray machine. It was found that lead, electroplated onto a thin, stretched disk of copper cooled with water would withstand up to 2 ma/sq. cm electron bombardment continuously at 650 kv. This technique seems applicable for experimental tubes where lead or other low melting metal is desired for a target material.
A Continuously Active Cloud Chamber
Authors: Vollrath Richard E.
Published: February 2005

When hydrochloric acid vapor and water vapor are allowed to diffuse together the mixture obtained is supersaturated with respect to both components. An ionizing particle passing through the mixture causes a string of droplets to form by condensation of the supersaturated vapors on the ions. Utilizing this chemical method of producing supersaturated vapors a very simple type of continuously active cloud chamber without moving parts has been developed. The cloud chamber in its present stage of development is not suitable for photographic recording but is useful for demonstration purposes. Cosmic-ray tracks can be seen with ease by visual observation.
Starting Potentials of Geiger-Müller Counters
Authors: Haines C. L.
Published: February 2005

The starting potential of Geiger-Müller counters filled with various pressures of air, helium, hydrogen, oxygen, argon, and two argon-oxygen mixtures have been accurately determined for counters with oxidized copper cylinders 1.0 cm in diameter, and bare tungsten wires 0.0075 cm, 0.0125 cm, and 0.025 cm, diameter. Except at low pressures, Werner's equation fits the results fairly well, when suitable constants are chosen, for all these gases except helium. At low pressures, the starting potentials diminish as the size of the wire increases.
A New Alternating-Current Null Indicator
Authors: Gieringer C. K.
Published: February 2005

Detection of small a.c. voltages over a wide range of frequencies with sensitivity comparable with d.c. necessitates methods, equipment, and technique far in advance of that required for the equivalent d.c. measurements. The portable d.c. meter offers the ultimate in simplicity, compactness, and ruggedness for use as a d.c. null indicator. A simple method of detecting a.c. voltages is by use of a d.c. meter in conjunction with a rectifier. Perhaps the metallic thin film rectifier is the best to date for above use from the standpoint of simplicity, ruggedness and compactness. The d.c. meter and rectifier as conventionally used are unreliable for null indications because of inherent characteristics of the rectifier.
A Scale of Eight Impulse Counter
Authors: Shepherd William G. , Haxby Robert O.
Published: February 2005

A modified Wynn-Williams scale of eight counting circuit is described which employs type 885 argon filled tubes. These tubes have the advantages of a very small deionization time, characteristics independent of temperature, and low cost.
Determining Probability Curves by Photoelectric Integration of Light Impulses
Authors: Saxl Irving J.
Published: February 2005

A photoelectric device has been developed with which it is possible to measure automatically the relative times of exposure of a photo-cell placed in the path of a moving beam of light. When the photo-cell is illuminated, a relay is energized which closes contacts for an electrical stop watch. Accordingly, this clock runs only when the beam of light is projected upon the photoelectric cell. By adjusting the position of this cell upon a graduated upright or within a predetermined area, it is possible to determine by the stop watch reading the time of the photo-cell exposure to the illumination at a given location. Frequency distribution curves obtained in this manner were analyzed and have been found valuable in the analyses of filamentous materials such as textile yarns.
The Barrier-Layer Photoelectric Cell in Photoelectric Photometry
Authors: Smith Alva W. , Newhouse Herman , Drake Paul
Published: February 2005

When the barrier-layer photoelectric cell is used in measuring the intensity of polarized light, errors may arise which depend upon the direction of the electric vector with respect to the plane of incidence. Curves are given which show that these errors may amount to as much as 30 percent.
Increased Gamma-Ray Sensitivity of Tube Counters and the Measurement of the Thorium Content of Ordinary Materials
Authors: Evans Robley D. , Mugele Raymond A.
Published: February 2005

The useful sensitivity S of a tube counter exposed to feeble gamma-radiation is proportional to (N−B)/(N+B)½, where B is the background counting rate and N is the counting rate when the gamma-ray source is present. S depends upon the product of (a) the efficiency of production of secondary electrons in the counter by the incident radiation, and (b) the efficiency of the tube counter in discharging once for each such secondary electron formed within its sensitive volume. Systematic comparison of many forms of tube counters reveals that the sensitivity to gamma-radiation from a source of given strength and geometry, may be markedly increased (a) by increasing the effective area of the cathode by employing screen-wire cathodes or grooved tube cathodes in place of solid smooth cathodes, and by using cathodes of high atomic number. If the cathode is not radioactive, various cleaning treatments do not increase its sensitivity. Temperature changes between 0° and 45°C do not appreciably affect the copper cathode tube counter. The sensitivity S may be increased further (b) by careful selection of the operating voltage and the pressure of the filling gas. For every counter an optimum pressure and voltage may be found at which the counter is many times more sensitive than it would be if no care were given to the selection of these operating conditions. For a tube counter 12 cm long and 2 cm in diameter maximum sensitivity is obtained with a 100-mesh copper gauze cathode when the counter contains air at 6.5 cm Hg pressure and is operated 170 volts above threshold. The elevated sensitivity of these gamma-ray counters permits the direct measurement of the feeble gamma-radiation from the radioactive impurities in ordinary granitic rocks, and, when combined with independent measurements of the uranium content by the radon emanation method, leads to thorium measurements having a probable statistical error of about 12×10−7 g Th per g rock when only two hours of measurements are made on 1400 g of rock.
A Direct-Reading Counting Rate Meter for Random Pulses
Authors: Gingrich N. S. , Evans Robley D. , Edgerton Harold E.
Published: February 2005

Randomly distributed pulses, of any voltage shape, and of varying magnitude, actuate an amplifier whose output meter indicates only the average rate of arrival of the pulses. Counting rates of 30 per minute up to several thousand per minute are read directly from a rugged meter. The apparatus is a.c. operated, is portable, and is particularly adapted to the study of feeble gamma-radiation. The apparatus consists essentially of a preamplifier, a uniform pulse generator based on a relaxation oscillator or on an inverter circuit, an output amplifier stage, and a capacity-resistance electrical tank circuit for performing the averaging process.
Statistical Analysis of the Counting Rate Meter
Authors: Schiff L. I. , Evans Robley D.
Published: February 2005

The counting rate meter, or vacuum tube speedometer, is an integrating and averaging instrument with an electrical, exponentially decaying memory. It is designed to replace message-register equipment in all particle counting apparatus, and is ideally suited to continuous photographic recording. The average current to the output meter is proportional to the counting rate for constant sources or for decaying sources whose mean life is significantly greater than the time constant RC of the output tank circuit. This RC is analogous to a radioactive mean life and may be regarded as the mean memory time. While the output current depends only on the output resistance R, and not on the output capacitance C (except for very rapidly decaying sources), the statistical fluctuations in the output current depend upon RC, and are equivalent to the fluctuation expected in a time interval of 2RC. Expressions are derived for the condenser charge Q, or output current Q/RC, for constant and decaying sources of radiation, as well as for the expected fractional statistical fluctuations in these cases.
A Receiver for Radiometeorographs
Authors: Astin A. V. , Stockmann L. L.
Published: February 2005

A receiver for use in radiometeorography is described. It is one which has given satisfactory performance in this field for about one year. It is based on the Jones 5-meter superheterodyne receiver. Designed for the reception of pulse-type signals it has a low response to random noises.
A Universal X-Ray Photogoniometer
Authors: Hull Robert B. , Hicks Victor
Published: February 2005

A compact apparatus for making Laue, rotation, and Schiebold-Sauter photograms, without the intermediate transfer of the crystal, has been constructed. Back reflection photograms may also be made. An accurate horizontal scale and verniers, combined with a microscope which may be used as an autocollimating telescope, facilitates the adjustment of the crystal, and permits interfacial angle measurements. All essential parts are readily adjustable with respect to the goniometer axis.
Discrimination Between Partial and Total Coincidence Counts with Geiger-Müller Counters
Authors: Mouzon J. C.
Published: February 2005

A simple amplifier and recorder circuit for discriminating between partial and total coincidences of Geiger-Müller counters is described.
Wilson Cloud Machines for Portable Use
Authors: Locher Gordon L.
Published: February 2005

Two new forms of Wilson cloud apparatus, developed for stratosphere balloon flights and suitable for portable use, are described. The machines are of light weight, require only small amounts of electric power, and are arranged for optional control by Geiger-Müller counters. Both machines employ baffles for removing turbulence from the cloud chamber; one uses a metal bellows, but no diaphragm; the other uses a thin rubber diaphragm and a bellows pump. Vacuum tube circuits control the timing of events connected with the expansion cycle. Stereophotographs are taken with flash bulbs, or with a spark illuminator that uses only 10 watts of power from an a.c. supply.
The Design of Powerful Electromagnets Part I. The Use of Iron
Authors: Bitter F.
Published: February 2005

It is shown that the iron in the usual Weiss type of electromagnet is not as efficiently used as it might be whenever as intense fields as possible are desired. A design is proposed, consisting essentially of a small magnetizing coil completely surrounded by iron except for openings to the center of the coil where the magnetic field is produced.
The Design of Powerful Electromagnets Part II. The Magnetizing Coil
Authors: Bitter F.
Published: February 2005

In Part I of this article it is shown that the efficient use of iron in electromagnets is dependent on the design of efficient magnetizing coils. The characteristics of such magnetizing coils are discussed, and it is shown that the important factors are the shape of the coil, the power available, the distribution of current density, and the efficiency of cooling. Formulae applicable to coils of various types are derived, and the main features of an efficient design are determined.
Pendulum Magnetometer for Crystal Ferromagnetism. II
Authors: McKeehan L. W. , Piety R. G. , Kleis J. D.
Published: February 2005

Improvements in the method of preparing spheroidal specimens, in the suspension of the pendulum, in the method of measuring its displacement, and in correcting for the field gradient due to the magnetizing solenoid are reported. New means for protecting small specimens from atmospheric action without rigid constraint and up to the softening temperatures of Pyrex glass (or of fused silica) are described.
A Thyratron-Controlled Ionization Gauge
Authors: Hoag J. Barton , Smith Nicholas M.
Published: February 2005

A thyratron is used to maintain constant the ionizing electron current in an ionization gauge. A circuit operating entirely from the alternating current supply line is given, together with the constants found suitable in the particular apparatus used and including provision for outgassing the metal parts of the gauge. The thyratron control was found to maintain constant electron current over the usual pressure range and with line voltage fluctuations of ±6 percent.
A Coercimeter for Magnetically Weak Materials
Authors: Potter E. V. , Coleman E. F.
Published: February 2005

A form of coercimeter based on that of Davis and Hartenheim is described. By altering constructional features and using a direct-coupled thermionic amplifier and microammeter for indicating balance, the accuracy and sensitivity of measurements on the coercive force of magnetically weak materials like slags are improved. A stable two-stage amplifier makes the balance indication more sensitive by a factor of about 200. The range of application of the instrument is thus also extended to alloys of very low coercive force and to cases where the available sample is very small.
Apparatus for X-Ray Patterns of the High Pressure Modifications of Ice
Authors: McFarlan Ronald L.
Published: February 2005

The stability of the high pressure ice forms discovered by Tammann and Bridgman at very low temperatures and atmospheric pressure has made it possible to obtain x-ray diffraction photographs of these forms. A discussion is given of a low temperature powder camera designed (1) to permit continuous rotation of the crystal, (2) to permit very rapid insertion and centering of the crystal, (3) to permit evacuation of the diffraction chamber. A detailed description of the experimental technique is made including the operation of the camera, and a method for powdering the ices by grinding and repacking them while under liquid air. Two diffraction patterns of the high pressure ices are shown.
A Shielded Filament X-Ray Tube for Pure X-Ray Spectra
Authors: Dershem Elmer
Published: February 2005

An x-ray tube is described in which a shield is interposed between the tungsten filament and the target in such a manner that the latter is almost completely shaded from visible light and sputtered tungsten. The electrons emitted from the hot filament are drawn around the shield by means of an auxiliary potential of approximately 350 volts. The tube has the following advantages, particularly for work with soft x-rays which require vacuum spectrographs. (1) Fogging of photographic plates by visible light is almost entirely eliminated. (2) The intensity of characteristic x-radiation remains constant since the target is shielded from evaporated tungsten. (3) The tube current is more nearly constant since it depends mainly on the auxiliary potential rather than the filament heating current. (4) The life of the filament is increased, probably because of protection by the shield from positive ion bombardment.
Thyratron Selector for Double Trace Cathode-Ray Oscillograph
Authors: Hughes H. K.
Published: February 2005

A circuit whereby two entirely independent wave forms may be observed simultaneously on the screen of the cathode-ray oscillograph is described. The two curves to be observed are fed through separate transformers to suppressor-modulate two 57 vacuum tubes. By a special combination of a thyratron and an ordinary neon diode, a square wave is obtained which is applied to the control grids of the 57's, biasing first one, then the other to cut-off. Data are given for grid extinction of the thyratron. The uses are discussed and illustrated.
Magnetic Contamination of Galvanometer Coils
Authors: Christy Andrew
Published: February 2005

An investigation is made of the dependence of the sensitivity of a d'Arsonval galvanometer (suspension type) upon the magnetic contamination of the galvanometer coil. Graphs are drawn showing the effect upon the sensitivity of coils contaminated to various degrees. Examples are given of internal contamination, i.e., contamination of the wire from which the coils were wound, and external contamination, i.e., contamination of the surface of the finished coils. A method is given for removing external contamination.
A Simple Method for the Determination of Magnetization-Coercive Force
Authors: Davis C. W. , Hartenheim Max
Published: February 2005

Attention is directed toward the difference between induction-coercive force and magnetization-coercive force. Although the former is used more commonly the latter appears to have a more fundamental significance, so that a consideration of its meaning has led to a rapid, direct method for determining coercive force. An apparatus is described with which this method is used to determine rapidly the coercive force of solid and granular samples. Advantages of this method and apparatus are discussed.
Combinations of Circular Currents for Producing Uniform Magnetic Fields
Authors: McKeehan L. W.
Published: February 2005

The theory of magnetic field production by a limited number of circular current loops with a common axis is briefly restated. The previously known particular solutions for two, four (or three), six and eight loops are recomputed and some new solutions of special interest are given. Expansions of surface zonal harmonics and of their first derivatives, up to the twelfth order, are included.
Combinations of Circular Currents for Producing Uniform Magnetic Field Gradients
Authors: McKeehan L. W.
Published: February 2005

The theory of magnetic field gradient production by a limited number of circular current loops with a common axis is briefly restated. The best positions for combinations of two loops and four loops, carrying currents of equal magnitude, are computed. The best ratio of breadth and depth of winding for coils of rectangular section, approximating most closely to these ideal solutions are also computed.
Limitations of Tubular Ground Glass Joints
Authors: Skellett A. M.
Published: February 2005

A consideration of the stresses involved in ground glass joints when used in vacuum apparatus indicates that the weakest part of such a joint is the wall of the outer member. For dependable large joints all the dimensions should be increased proportionally. After grinding it is suggested that the surfaces be etched slightly to relieve strains.
On the General Theory of Electrometer Design
Authors: Hansen W. W.
Published: February 2005

It is shown that Brownian motion sets a lower limit on the smallest charge detectable. This limit is approximately (kTC)12 with k Boltzmann's constant, T the temperature, and C the capacity of the system in centimeters. A discussion of the difficulties of reaching this limit with a vacuum tube electrometer is given with particular emphasis on the problem of shielding in which connection several suggestions are made. The ordinary electrometer is treated in much greater detail. A general theory of all electrometers is developed and it is shown that this theory together with various practical desiderata virtually dictate the essential features of the design of an electrometer. An electrometer of the design proposed will reach the limiting useful sensitivity; the quarter period when at this sensitivity is (πδθ/2)(I/2kT)12 where δθ is the least detectable change in angle of the suspended system and I is the moment of inertia. Without resorting to extreme construction this time can be made as short as fifteen seconds and it can quite possibly be further reduced by a factor of one thousand. An electrometer of the proposed design will have a zero independent of temperature, battery voltage, and slight vibration. There are two adjustments which are noninteracting and any desired sensitivity can be obtained in a simple and straightforward manner.
Voltage Sources and Amplifiers for Geiger Counters
Authors: Gingrich N. S.
Published: February 2005

A modified pentode stabilizer is described in which a neon lamp replaces the usual battery for maintaining a constant grid bias. This circuit stabilizes the voltage as well as that with a battery, and is much more flexible. A simpler stabilizer is described in which a bank of neon lamps supplies the stabilized voltage directly. A new amplifier, using two standard radio tubes and a small neon lamp is described. A brief report is made of the use of a ``Strobotron'' in counter circuits.
Electrostatic Capacity Measurements
Authors: Kurrelmeyer Bernhard , Hayner Lucy J.
Published: February 2005

This paper describes an electrostatic method of measuring capacity and capacity changes, and its application to a precision method for measuring dielectric constants of gases.
Charge Sensitivity of Compton Electrometer
Authors: Pockman Leonard T.
Published: February 2005

The principal object of this work is to determine how to adjust a Compton electrometer for maximum charge sensitivity. First some disputed points in the theory of the charge sensitivity are treated and the solutions obtained here are confirmed experimentally. With the aid of direct measurements of the fundamental dimensions of the electrometer, its capacity, and the torsion constant of its suspension, actual values are calculated for the constants usually left arbitrary in the theoretical expressions for charge and voltage sensitivity. The resulting sensitivity formulas are confirmed experimentally. The theoretical expression for charge sensitivity is examined in order to determine the conditions for highest charge sensitivity subject to the restriction that the time required for a deflection to reduce to e−1 of its maximum value after the quadrants are grounded be not greater than some arbitrary time T0. The maximum value of the charge sensitivity thus obtained is (T0/βC)½/2 where β≅damping torque of needle per unit of angular velocity, and C=capacity of whole collecting system of electrometer to surroundings.
A Direct-Current Voltage Multiplier
Authors: Anderson Wilmer C.
Published: February 2005

A device for obtaining a higher d.c. potential from a d.c. source is described. A number of condensers are connected permanently in series and charged successively by rotating brushes. The output voltage is shown to be quite steady under normal operating conditions. Equations for the output voltage and voltage fluctuation are derived. Suitable operating conditions and modifications for very high voltages are suggested. An efficiency greater than 75 percent has been obtained. Various uses are suggested.
Light Metal Rotors for the Molecular Ultracentrifuge
Authors: Biscoe J. , Pickels E. G. , Wyckoff Ralph W. G.
Published: February 2005

Tests have been made of the range of usefulness of light metal rotors in the ultracentrifuge for molecular sedimentation. These experiments prove that duralumin 14 ST is definitely superior to the other alloys tested. They also indicate a shape of seven-inch diameter rotor which if made of 14 ST can safely be used for centrifuging at speeds up to 900 r.p.s. (field at center of cell = 215,000 times gravity). For much more intense fields special steels must be used or the rotor diameter reduced.
A Vacuum Tube Alternating-Current Bridge Detector
Authors: Breazeale William M.
Published: February 2005

An a.c. bridge balance indicator which utilizes a 6E5 (electron-ray) tube as the visual indicator is described. This bridge detector has proven as successful as one using the conventional output meter. Its low cost ($4.00 to $5.00 if a power pack is already available) together with its ability to cover a wide frequency range make it competitive with other medium sensitivity detectors now in laboratory use.
A Method of Magnetic Testing for Sheet Material
Authors: Burgwin S. L.
Published: February 2005

A method of building up a magnetic circuit from strips of sheet material has been found which permits testing for magnetic properties either by d.c. or a.c. methods just as in the case of the ring sample but without the inconvenience of the ring sample in that a permanently wound test frame similar to that of the Epstein test may be used. In testing this magnetic circuit an approximate method may be used where simplicity of testing and consistency of results are required rather than absolute accuracy. For tests where absolute accuracy is more important than simplicity of testing, a comparative test has been developed. Satisfactory results may be obtained by these methods on materials with permeabilities as high as 100,000.
The Cryogenic Laboratory of the California Institute of Technology. Part II
Authors: Goetz Alexander
Published: February 2005

In continuation of Part I the He circuit with its auxiliaries, the method of purification of He, its distribution and its storage are described. For the performance of low temperature experiments separate ``stations'' are provided, consisting each of a ventilated compartment which is connected with the necessary gas and vacuum systems. Each station contains a liquefier as an integral part of the particular apparatus designed for one type of experiment. The general design of these stations and the detail of the construction of one built especially for x-ray spectroscopy at low temperatures is described. The equipment for potentiometric measurements is centralized; its arrangements, the thermometric methods and the system of communication between stations and potentiometers is described.
The Temperature Coefficients of Shear and Longitudinal Modes of Vibration
Authors: Osterberg Harold
Published: February 2005

Expressions for the temperature coefficients of longitudinal and shear modes of vibrations are derived and discussed. The conditions for zero temperature coefficients are stated. In the case of the shear modes of vibration, the orientations which permit zero temperature coefficients are a function of the overtones and of the crystal dimensions. Hence, no unique angle of orientation independent of the dimensions of the specimen exists. The theory is applied to the grinding of quartz plates which shall regularly have temperature coefficients lower than those obtained by previous methods of orienting these plates.
Combustion Engine Temperatures by the Sodium Line-Reversal Method
Authors: Brevoort Maurice J.
Published: February 2005

The sodium line-reversal method has been used in some preliminary measurements of flame temperature. Improvements in the method involving a photographic recorder and a means of correcting for the dirtiness of the windows are described. The temperatures so obtained are compared with those calculated from pressure diagrams.
Design and Operation of Counter-Controlled Cloud Chambers
Authors: Street J. C. , Stevenson E. C.
Published: February 2005

Two cloud chambers of the pneumatic rubber diaphragm type are described, a cylindrical one 22 cm in diameter for use with a large electromagnet, and a rectangular one of wood with sensitive volume 35×30×10 cm for cosmic-ray shower studies. The expansion ratio is determined by the separation of rigid diaphragm stops. A description of auxiliary apparatus for control by G-M counters and for illuminating the chambers is given.
On the Theory of the Electrostatic Beta-Particle Energy Spectrograph
Authors: Rogers F. T.
Published: February 2005

The necessary equations for the use of the electrostatic velocity analyzer as an energy spectrograph for β-particles are derived. A table is presented in which the conversion factor for converting particle-counts as a function of the electric deflecting potential to particle-counts as a function of energy is shown for electron energies of less than 105 electron volts. At low energies the conversion factor does not cause the excessive distortion of the observed curve that the conversion factor for the magnetic spectrograph causes in the same low energy region. It is thus concluded that the electrostatic analyzer is suitable for the investigation of the lower reaches of the continuous β-particle spectrum.
A Variometer for an Oscillator of Wide Frequency Range
Authors: Pierce John Alvin
Published: February 2005

A variometer is described, of such construction that it may be used as the tank inductance in a Hartley oscillator, maintaining a constant excitation ratio over a wide frequency range. When the circuit is arranged to keep the inductance-capacitance ratio constant also, the efficiency and power output are correspondingly uniform. Although the problem, in the case illustrated, is complicated by the design of the oscillator for high plate voltages, the basic design is equally applicable to oscillators of lower power and much wider frequency range.
An Induction Pump for Liquid Mercury
Authors: Gilfillan E. S. , MacNeille S. M.
Published: February 2005

Difficulties were encountered with reciprocating pumps for the continuous circulation of mercury. An all-metal pump, without moving parts, operating on the principle of a polyphase induction motor was developed. The mercury flows in the annular region between two concentric tubes. Surrounding the tubes are coils connected to a polyphase supply. The result is a series of magnetic ripples traveling along the axis of the tubes which drag the mercury along by virtue of the currents induced in it. Lifts in excess of a meter and capacities in excess of 50 cc per second have been obtained.
A Photoelectric Method for Tracing Current Wave Forms
Authors: Huxford W. S. , Engstrom R. W.
Published: February 2005

A photoelectric timing circuit arrangement has been designed to obtain point by point plots of periodically varying currents. The circuit employs a three-electrode vacuum photo-tube in which electron emission occurs only when a sudden light flash enters the cell through a narrow slit in a disc driven by a synchronous motor. A noninductive resistance carrying the current to be measured is inserted in the grid circuit of the photo-triode. The electron emission registered by a galvanometer in the collector circuit is completely controlled by the momentary value of the potential set up in this resistance by the current at the instant of the light flash. In this manner, by changing the time at which the light flash occurs in the current cycle, a complete delineation of the current wave form is secured. The method eliminates distortion in wave form introduced by mechanical oscillographs and by amplifiers used with cathode ray oscillographs when small currents or potentials are to be measured.
A Scale-of-Eight Counting Unit
Authors: Giarratana Joseph
Published: February 2005

The factors involved in the design of a counting circuit using gas triodes are discussed. A complete circuit is given for a scale-of-eight unit together with a graph showing the performance of such a unit when used to count alpha-particle pulses from a linear amplifier.
Preparation of Large Single Crystals of Sodium Chloride
Authors: Walther H.
Published: February 2005

An apparatus and a method are described, whereby single crystals of sodium chloride are produced in the form of bars 2 cm in diameter and 30 cm long. The crystal is drawn from the melt by means of a platinum rod which is dipped into it and which is raised and rotated simultaneously by a clock mechanism. An air stream from a circular nozzle surrounding the growing crystal immediately above the surface of the molten salt provides the steep temperature gradient necessary for the continuous growth of the crystal. The orientation of the crystal with respect to the axis of the bar may be chosen at will.
A Simple Knudsen Gauge
Authors: Hughes A. L.
Published: February 2005

A simple form of Knudsen gauge has been developed in which a thin strip of aluminum leaf is suspended from its upper end in the middle of a glass tube whose axis is vertical. Alongside the aluminum leaf is mounted a platinum strip which can be heated electrically. In the presence of gas at low pressure, the aluminum leaf is pushed away from the heated strip because the molecules hitting it on the side facing the heated strip impart to it more momentum than those hitting it on the other side. The deflection of the aluminum leaf, which can be measured by a microscope with a scale in the eyepiece, is a function of the pressure of the gas, and consequently by suitable calibration, the device may be made to measure pressure. By varying the heating current through the platinum strip a wide variety of sensitivities can be readily obtained. Sensitivities ranging from 1 eyepiece scale division=3.2×10−7 mm to 1 eyepiece scale division=304×10−7 mm have been used. The upper limit at which the gauge will work satisfactorily is approximately 0.01 mm.
Two-Pulse Oscillator
Authors: Getting Ivan A.
Published: February 2005

A circuit is described which produces pairs of pulses at any frequency up to about 6000 per second. The members of the pair may be arbitrarily close and of arbitrary amplitude. The circuit is intended for testing resolving powers of pulse-recording circuits.
A Vacuum Tube Circuit for Scaling Down Counting Rates
Authors: Stevenson E. C. , Getting I. A.
Published: February 2005

A scaling circuit is described which differs from that of the Wynn-Williams type in using vacuum tubes instead of thyratrons. Its short resolving time (better than 1/50,000 second), its stability, and its durability over extended periods of operation recommend it for accurate recording of high speed Geiger counter discharges.
Radiation Thermopiles
Authors: Pfund A. H.
Published: February 2005

Thermopiles of the type to be described have been made for many years. The sole purpose of the present note is to set forth the technique which has been developed for the making of the junction. The theory of thermopiles as well as the construction of other types is covered by a fairly complete bibliography at the end of the paper. In the present procedure of forming the actual ``junction,'' no solder whatsoever is used; furthermore, the number of failures is reduced to a minimum. The mode of mounting is based on a study of those thermopiles which still survive after a long and active life.
An Improved Apparatus for Measuring Surface and Body Temperature
Authors: Hardy J. D. , Soderstrom G. F.
Published: February 2005

A radiometric device adapted to the measurement of temperatures of black surfaces is described. The precision of the instrument is such that surface temperatures may be measured to ±0.01°C. The apparatus has been used for the measuring of skin temperatures in humans. With the thermoelectric body thermometer, also described the, apparatus is ideal for studying thermal changes in the human body.
A Simplified Hydrogen Liquefier
Authors: Ahlberg J. E. , Estermann I. , Lundberg W. O.
Published: February 2005

By using a ``twisted tube'' heat interchanger, it has been possible to build a small hydrogen liquefier of great simplicity and efficiency, which can be operated from commercial hydrogen cylinders without the use of a compressor and delivers about one liter of liquid hydrogen per hour.
Simple Circuit for Generator Voltage Stabilization
Authors: Kirkpatrick Paul , Harworth Keith
Published: February 2005

The output voltage of an a.c. or d.c. generator may be rendered invariant to changes in speed by exciting the field from a storage battery bucked by an auxiliary d.c. generator which is driven at the same speed as the principal generator.
A Method for Magnetic Spectrograph Calculations
Authors: Rogers F. T.
Published: February 2005

A method is presented for calculating the kinetic energies of charged particles from magnetic spectrograph data. The method is of some generality in that it is valid for a magnetic field which may depart appreciably from perfect uniformity, provided only that the field focus the particles properly. It is suggested that, although the method is quite lengthy, it might be of use for calculations based on measurements of the highest precision and for calculations of ordinary precision based on data taken with a magnetic field which is not at all uniform.
Cloud Chamber for Nuclear Disintegration Studies
Authors: Crane H. R.
Published: February 2005

Construction of an entirely automatic cloud chamber particularly adapted to the study of the high energy electrons produced in artificial disintegration experiments is described. Air core coils which are capable of producing magnetic field strengths up to 4000 gauss at the time of expansion are used. An incandescent light source, using three 1000-watt projection bulbs furnishes sufficient light for ⅕ second camera exposure.
Axial Magnetic Suspensions
Authors: Holmes F. T.
Published: February 2005

A vertical ferromagnetic needle can be supported in macroscopic equilibrium by magnetic forces alone. One method using a variable magnetic field is described and shown to have considerable latitude in details of application. A 6 g rotor having a moment of inertia of about 0.8 g cm2 was suspended in this manner. It was spun at about 1200 rev./sec., its behavior indicating that with suitable driving arrangements much higher speeds should be attainable. At 600 rev./sec. with driving torque zero it exhibited a deceleration of about 2×10−3 rev./sec.2. A suspended element weighing about ¾ g showed torsion constants, depending on adjustments, down to 7×10−6 dy cm/rad.
An Oil-Immersed Generating Voltmeter
Authors: Thomas Harold A.
Published: February 2005

An oil-immersed generating voltmeter has been constructed and tested. Its chief advantages compared to one operated in air are compactness and increased sensitivity due to the higher dielectric constant. Dimensions of the parts of the instrument are included.
A New Focusing Method for X-Ray Powder Spectroscopy
Authors: Frevel Ludo K.
Published: February 2005

A convergent Soller type slit, adaptable to a camera of arbitrary radius, serves to select those pencils of x-rays which emanate from a broad focal spot and impinge upon any selected point on the equator of the cylindrical camera. The diffracting powder is mounted on the camera wall in the form of a thin sheet which intercepts the wedge of x-radiation. In this manner all x-rays diffracted at the same Bragg angle are brought to a focus at the equator of the camera.
Development of a Curved Quartz Crystal X-Ray Spectrograph and a Determination of the Grating Constant of Quartz
Authors: Watson Bernard B.
Published: February 2005

The construction of a small experimental spectrograph of the curved crystal type is described. The use of quartz instead of mica or gypsum which are customarily used and the improvement of the spectra obtained when quartz is used are discussed. The theory of the curved crystal x-ray spectrograph has been extended in two ways: (1) to cover the doubling of spectral lines which arises due to reflections from opposite surfaces of the crystal, and (2) to cover the vertical separation of spectral lines produced by reflections from opposite sides of atomic reflecting planes. This latter effect is traced to a nonparallelism between the reflecting planes and the axis of curvature of the crystal. By means of the curved crystal spectrograph the grating constant for the basal planes of quartz was determined. This value was found to be d=5.393±0.002A.