bluuebunny/crossref_metadata_2025 huggingface dataset:
High Temperature Verneuil Crystal Growth by Arc Melting
Authors: Bartlett R. W. , Halden F. A. , Fowler J. W.
Published: February 2005

Apparatus for fusion growth of refractory single crystals to temperatures in excess of 3500°C and pressures to one atmosphere, using an ac discharge to the boule, is described. Applications in growth of tantalum carbide and hafnium carbide crystals are discussed.
The Construction and Performance of a Large Grating Monochromator with a High Energy Output for Photochemical and Biological Investigations
Authors: French C. S. , Rabideau G. S. , Holt A. S.
Published: February 2005

A simple monochromator with a 4×6 inch replica grating f: 3.4, which covers the range 365–1000 mμ is described. The dispersion is 3.55 mμ/mm in the second order and 7.1 mμ/mm in the first order. The slits are fixed in position and the wave-length of the emergent beam is varied by rotating a mirror located between the telescope lens and the exit slit. It is useful for the production of monochromatic light with band widths of 10 mμ or more. With a 2×34-mm entrance slit it produces 4×10−2 cal./min. of red light with a band width of about 28 mμ from a 350-w tungsten lamp. The total energy output, spectral distribution and percent of stray light are given for various wave-lengths and slit settings. The transmission of the instrument is given for the wave-length range 365–800 mμ.
Measurement of Small Currents: Characteristics of Types 38, 954, and 959 as Reduced Grid Current Tubes
Authors: Nielsen Carl E.
Published: February 2005

This paper discusses the usefulness of common tube types for small current measurement and, after presenting the results of a detailed study of the three types 38, 954, and 959, offers recommendations of operating conditions for their use. The observations reported consist primarily in data showing the dependence of grid current upon applied potentials, and secondarily in information about the corresponding plate current characteristics. Grid currents less than 10−15 ampere in the 959 tube are reported, associated with stability comparable with that of special electrometer tubes.
Thin Window Counter with Special Mica-to-Glass Seal
Authors: Wu C. S. , Meaker C. L. , Glassford H. A.
Published: February 2005

A thin window counter with special mica-to-glass seal has been developed especially for the detection of low energy electrons from radioactive isotopes such as C14. It is simple to construct and has proved to be vacuum tight. It can be operated without external quenching and exhibits flat plateaus of 100 to 300 volts. The average useful life of these counters is around a year or more. The efficiency of the counters is very satisfactory.
A Paramagnetic Oxygen Analyzer
Authors: Dyer Clarence A.
Published: February 2005

An oxygen analyzer which makes use of the unique paramagnetic property of oxygen and a hot-wire bridge is described.

The instrument is designed to operate under rather extreme conditions of temperature and pressure, as specified by the Air Materiel Command of the Army Air Forces.

Percent oxygen is indicated in the range from 21 to 100 by a panel meter, and provisions are incorporated for using it in connection with a recording oscilloscope.
The Model 200 Pulse Counter
Authors: Higinbotham W. A. , Gallagher James , Sands Matthew
Published: February 2005

A complete general purpose electronic pulse counter is described which consists of an amplitude discriminator, scale-of-64, and register driver, and is suitable for use with pulse amplifiers in making nuclear measurements.
Proportioning Temperature Controller
Authors: Lazarus D. , Lawson A. W.
Published: February 2005

Unbalance voltage from a potentiometer is amplified by a simple circuit employing a 60-cycle polarized interrupter, and used to control the extent of the on-off cycle of a furnace. Automatic cold-junction compensation and a sensitive, temperature-indicating circuit are incorporated. The circuit responds to a change in input voltage of less than 4 microvolts. The long-term stability is limited by changes in 60-cycle pick-up and aging of components to about 40 microvolts.
Scintillation Counter for the Detection of α-Particles
Authors: Sherr R.
Published: February 2005

A simple battery-operated survey instrument has been developed which uses a photo-multiplier tube to detect the scintillations produced in a phosphor by α-particles. The electrical components are a 1100-volt battery pack; a 931A photo-multiplier tube; a matching transformer and headphones for registering single particles; and a crystal rectifier, choke, and meter for use with strong sources. The latter group of components are used in a novel ``charge-multiplying'' circuit which increases the meter sensitivity by a factor of 12. The instrument is insensitive to β- and γ-radiations.
A Modified Fitch Thermal Conductivity Apparatus
Authors: Harvalik Zaboj V.
Published: February 2005

A thermal conductivity apparatus based upon the increase of temperature of a receiver by heat transferred through the sample is described, and its modification to samples inclined to the horizontal. The temperature changes of the receiver are measured with thermocouples, the reference junction of which is at room temperature.
Electrostatic Analyzer for 1.5-Mev Protons
Authors: Fowler W. A. , Lauritsen C. C. , Lauritsen T.
Published: February 2005

A system for analyzing the ion beam of an electrostatic generator is described. A weak magnetic field separates protons from heavier components and a 90° electrostatic deflection gives the required energy resolution. With the analyzer controlling the generator voltage, a proton beam of one microampere with an energy spread of the order of 300 volts in one million is obtained.
A Laboratory Oscilloscope
Authors: Fitch V. L. , Titterton E. W.
Published: February 2005

The laboratory oscilloscope is designed primarily for use in the nuclear physics laboratory but is a versatile instrument well suited to general circuit research. It contains a sweep generator with writing speeds ranging from 8 inches per microsecond to 1 inch per millisecond. The sweep is initiated by a voltage amplitude discriminator which may be triggered by: (a) an internal trigger generator operating at variable repetition rates, (b) a jitter-free delayable trigger which may be generated at any time from minus 2 to plus 400 microseconds with respect to a fixed trigger from the master generator, (c) from any arbitrary signal greater than 5 volts, and (d), any input to the signal amplifier larger than 0.2 volt. A high fidelity delay line is incorporated in the amplifier circuit so that the sweep may be initiated by the input signal to the amplifier before the signal appears at the scope plates. A 1-volt input to the amplifier will give a 1½-inch screen deflection with a minimum rise time of 0.15 microsecond. The trigger generator, which starts the delay circuits, may be triggered externally by pulses of 15-volts amplitude or more. Sufficient voltage is applied to the type-5CP11 scope tube to permit photography of transients with writing speeds of 3 inches per microsecond using a camera with an f:2 lens opening and Ansco Fluorapid film or Eastman 103–0 plates.
Scale Expander for Mass-Spectrometer Recorder
Authors: Grove D. J. , Hipple J. A.
Published: February 2005

A method is described whereby a wide range recording system having good accuracy may be obtained with a 10-inch chart. The peaks to be recorded are first obtained on a highly compressed scale which is approximately logarithmic. Immediately after reaching the peak top on the non-linear scale, a system of relays selects a linear scale of the appropriate sensitivity, and the peak top is re-recorded on the linear scale. With this system all peaks between 4″ and 500″ (i.e., between 24 mv and 3000 mv) are recorded between 4″ and 10″. As a result, measurement of peak heights becomes a simple process, and wide range is obtained without loss of accuracy. Complete details are given for construction of this system.
Concave Metallic Replica Gratings
Authors: Šimon I.
Published: February 2005

A method is described of producing metallic replicas from gratings by electro-deposition of copper. It is possible to obtain concave replicas from a convex original grating—either metallic or glass. The optical figure and the grating qualities of the replicas are tested and shown in Figs. 2 to 6.
Calibration of a Ra+Be Neutron Source by the B(n, α)Li Reaction
Authors: Seidl F. G. P. , Harris S. P.
Published: February 2005

A method has been developed for determining absolute numbers of neutrons in terms of helium production in the B(n, α)Li reaction. We are able to report preliminary measurements of the number of neutrons emitted per second from a certain Ra+Be source; i.e., source called No. 38, which contains 504 millicuries of Ra, was found to emit (5.5±0.4)×106 neutrons per second.
R-F System for Frequency Modulated Cyclotron
Authors: MacKenzie K. R. , Waithman V. B.
Published: February 2005

A grounded grid oscillator and a single dee resonant system for use with a frequency modulated cyclotron are described. 7.5-Mev deuterons have been accelerated with dee voltages up to 15 kv and a frequency range from 9.5 to 12 megacycles. 15-Mev protons have been accelerated with voltages up to 11 kv and a frequency range from 19 to 24 megacycles. Coupling constants, phase correction, amplitude modulation, and discharge phenomena are discussed.
A High Speed Coincidence Circuit
Authors: Dicke R. H.
Published: February 2005

A coincidence circuit with a resolving time of from 10−9 to 10−10 second is described. It will operate satisfactorily with a 20-db variation in the pulse energy and discriminate against non-coincident pulses occurring at a rate of from 108 to 109 per second. Experimental results are given.
An Electronic Analytical Balance
Authors: Clark John W.
Published: February 2005

An electronic instrument is described which will weigh small objects with precision comparable to that of the chemical beam balance. It is a direct-reading instrument of the null-balance type, and is faster to use and requires less skill on the part of the operator than does the mechanical balance.
An Apparatus for Micro Gas Analysis
Authors: Kenty Carl , Reuter Frederic W.
Published: February 2005

Gas samples of a few micron liters can be analyzed to within a few percent accuracy with the described system. Identification of components is made from condensation points, comparison readings of Pirani and McLeod gauges, and differences in speeds of flow. Condensation points at sub-liquid nitrogen temperatures are had by evaporating liquid nitrogen at reduced pressures. Except for the removal of CO and H2 by ignition with O2, and O2 with a tungsten filament, chemical methods have been eliminated. Transfer of minute gas quantities is greatly facilitated by use of small mercury-diffusion pumps.
An Electrical Network for the Solution of Secular Equations
Authors: Hughes Richard H. , Wilson E. Bright
Published: February 2005

A method of using an electrical network to solve a determinental or secular equation has been devised (i.e., to determine the characteristic values of a real, symmetrical matrix). By plugging suitable coils and condensers into a panel board, a network is assembled which has for its description at resonance an equation identical with the secular determinant. The circuit consists of n junction points, each connected to every other through fixed reactive admittances equal to the corresponding off-diagonal terms of the matrix, and each connected to ground through a fixed admittance equal to the negative of the sum of the constant part of the diagonal term and the off-diagonal terms in the same row or column. In addition each junction is connected to ground through a variable admittance which represents the unknown in the equation; these latter admittances are equal for all of the junction points. While the network is excited with alternating current from a constant current source of constant frequency, the variable admittances are all altered simultaneously by the same amount until all the maxima of the electromotive forces of the junction points with respect to ground have been found. The values of the variable admittances at the several maxima constitute the desired roots. Usually an accuracy of better than one percent is obtained.
The Use of the Expansion of Gases in a Centrifugal Field as Cooling Process
Authors: Hilsch R.
Published: February 2005

The design of a vortex tube of good efficiency in which the expansion of a gas in a centrifugal field produces cold is described. The important variables in construction and operation are discussed and data for several tubes under various operating conditions are given. Low pressure gas, 2 to 11 atmospheres, enters the tube and two streams of air, one hot and the other cold, emerge at nearly atmospheric pressure. The cold stream may be as much as 68°C below inlet temperatures. Efficiencies and applications are discussed.
Growth of Drops Formed in a Wilson Cloud Chamber
Authors: Barrett E. O. , Germain L. S.
Published: February 2005

Water drops and water-alcohol drops formed in a Wilson cloud chamber were photographed with periodic illumination and their velocity was measured. The drop size was determined by means of Stokes' law, and the square of the radius of the drop was found to vary linearly with time as soon as the drop was large enough to register photographically. A 60-cycle neon light that moved with constant velocity during the exposure was turned on by the expansion valve. This light was photographed on the same frame, and its flashes were used to establish the zero of the time scale for the drop images. It was observed that the straight line obtained from the experimental points intersected the time axis about 0.1 sec. after the zero. This fact seems to indicate that the rate of growth of the drops is smaller during the first 0.1–0.2 sec. and then reaches a constant value. The slope of the straight part of the curve was found to be about 7.5×10−6 cm2/sec. for water and 4.4×10−6 cm2/sec. for water-alcohol.
Boron Trifluoride Neutron Detector for Low Neutron Intensities
Authors: Segrè E. , Wiegand C.
Published: February 2005

A sensitive boron trifluoride ionization chamber for the detection of weak neutron sources is described. Its efficiency for Ra-Be neutrons is about 2 percent with a background of 15 c/min.
A Pulse Analyser for Nuclear Research
Authors: Freundlich H. F. , Hincks E. P. , Ozeroff W. J.
Published: February 2005

One method of determining particle energies in nuclear research depends upon the measurement of pulses produced by the particles in an ionization chamber. The Pulse Analyser is an instrument which analyses the electrical pulses from the chamber into a number of classes according to their amplitude and hence produces an energy spectrum of the particles. It has the following features: (1) every pulse is counted ensuring the highest accuracy for a given time; (2) some indication of the final result appears while the experiment is in progress; (3) the number of pulses within a certain amplitude range is recorded by a mechanical counter, eliminating most of the labor required for obtaining results. Problems of design are discussed, and a brief survey of the ways in which they are treated in five different Pulse Analysers is given. One of these instruments, built by the authors, is described in detail. This Analyser is designed for slowly rising pulses (up to 1 millisecond in duration) and for low counting rates (up to a few hundred per minute). It has 20 identical channels, each channel recording the pulses within an amplitude range that can be varied from 0.1 to 10 volts. The performance of the Analyser is discussed and some typical results obtained with it are given.
A Helium Cryostat
Authors: Collins S. C.
Published: February 2005

A helium cryostat which is cooled by the isentropic expansion of helium without the aid of liquid air or other refrigerant provides a cold chamber for experiments at any temperature down to 2°K. Any gas can be liquefied and delivered to external receivers as desired. Three expansion devices are described. One is a diaphragm engine having a mechanically supported diaphragm and unusual valves which require no valve gear. The others are piston-cylinder-crankshaft assemblies in which leakage is controlled by extreme close fitting of piston to cylinder, and in which wear of unlubricated surfaces is avoided by constructing the piston and cylinder of nitrided alloy steel and by mounting the piston on a thin flexible piston rod which operates under tension. The piston thereby has enough freedom to permit perfect alignment within the cylinder.
A Variable Speed Rotational Viscosimeter
Authors: Buchdahl R. , Curado J. G. , Braddicks R.
Published: February 2005

The article gives a detailed description of design and construction of a variable speed rotational viscosimeter to measure the rheological properties of systems within a viscosity range of 10−1 to 104 poise. The use of a strain gauge to measure the torque is discussed briefly.
An Automatic Recording Spectrophotometer
Authors: Coor Thomas , Smith Don C.
Published: February 2005

A National Technical Laboratories Model DU Quartz Spectrophotometer has been converted into an automatic recording spectrophotometer by (a) utilizing the monochromator with unchanged optics, (b) introducing a common motor drive for the wave-length and all mechanical parts, (c) dividing the exit beam into two parts by a beam-splitter, (d) using a ``blank'' absorption cell in one beam and a ``sample'' absorption cell in the other, (e) placing an amplifier photo-tube in each exit beam to measure the transmitted light, (f) amplifying the photo-tube signals with linear cathode-follower type d.c. amplifiers, (g) recording the ratio of the amplifier outputs as percent transmission of the ``sample'' relative to the ``blank'' as a function of wave-length on a ratio potentiometer strip-chart recorder, (h) providing for automatic monitoring of the monochromator slits to maintain constant energy in the ``blank'' light beam, and (i) providing a ``correction device'' for automatic correction of all errors due to mis-matching in the relative intensities of the beams from the beam-splitter, in the transmission characteristics of the absorption cells, and in the spectral sensitivity characteristics of the photo-tubes. The instrument which has been developed has considerably greater resolution than the original spectrophotometer, has completely automatic high speed operation which permits recording of the spectrum from 4000 to 2000 angstroms in less than 15 minutes, and has an accuracy of transmission measurement very nearly equal to that obtainable with the original manual instrument.
A Simple Micromanometer
Authors: Brow Jeanne E. , Schwertz F. A.
Published: February 2005

This article contains a description of a simple micromanometer designed to measure very small pressure differences at an absolute pressure in the neighborhood of one atmosphere.
The Preparation of Pressed Ra+Be Neutron Sources
Authors: Anderson Herbert L. , Feld Bernard T.
Published: February 2005

A method for preparing pressed Ra+Be fast neutron sources is described in detail. Such sources can be made to contain as much as 5 g of Ra. They have the advantage of small volume and constancy of neutron output. The yield of fast neutrons per sec. per g of Ra can be obtained from the relationship yield=1.7×107MBeMBe+MRaBr2.
Frequency Meter for Random or Uniformly Spaced Pulses
Authors: Schultz H. L.
Published: February 2005

The instrument, designed primarily for the determination of average nuclear counting rates, incorporates the following circuit features: (1) biased diode for establishing the recording level; (2) frequency meter using a triggered blocking oscillator, the average plate current of which is proportional to the rate of arrival of pulses; (3) provisions for the operation of a mechanical impulse counter at low rates. A resolving time in the vicinity of 1 microsecond can be achieved.
A New Polarograph
Authors: Schulman James H. , Battey H. Bruce , Jelatis Demetrius G.
Published: February 2005

By use of a current recording system of negligible damping, polarograms which yield correct values of the half-wave potential may be obtained even at a high rate of voltage change. In addition, greater sensitivity is obtained due to the use of peak currents instead of average currents. The construction and performance of an instrument based on this system is described.
All-Metal Fast Geiger Counters for Cosmic-Ray Research
Authors: Regener Victor H.
Published: February 2005

A detailed description is given of the preparation of all-metal, argon-alcohol filled, Geiger counter tubes for cosmic-ray work. Two different possibilities are discussed for the construction of the feed-through insulator.
A Simplified Analysis of the Parallel-T Null Network
Authors: Givens M. P. , Saby John S.
Published: February 2005

The parallel-T resistance-capacitance null network is analyzed algebraically. General conditions for null, and expressions for network impedance and sharpness of null, are obtained in a convenient form for application to practical design problems. Vector diagrams are used to illustrate the variations of phase and amplitude of output voltage with frequency.
Some Laboratory Applications of the Low Friction Properties of the Dry Hypodermic Syringe
Authors: Brubach Howard F.
Published: February 2005

The principle of rotating either the barrel or plunger of a dry hypodermic syringe to produce a low friction gas sealed bearing is described. The application of this principle to accurate measurement of gas volume at very low pressure heads, and further applications to other instruments operating at low pressure heads is indicated. Horizontal motion of the plunger was produced in a rotating syringe barrel with pressures as low as 0.6 dynes per cm2.
Metal-Ceramic Vacuum Seals
Authors: Williams Neal T.
Published: February 2005

War time German vacuum tube research led to the development of metal-ceramic silver-soldered vacuum seals. It has been found that such seals can be made successfully with ceramic materials available in this country. The procedure is outlined, and some precautions are noted.
A Mass Spectrometer for Isotope and Gas Analysis
Authors: Nier Alfred O.
Published: February 2005

A mass spectrometer suitable for routine isotope analyses of the lighter elements is described. Complete electronic circuits are given. An all metal mass spectrometer tube is employed. A null method of determining relative abundances of the elements carbon, nitrogen, and oxygen is used. Although designed primarily for analyzing elements for which separated isotopes are available as tracers, the instrument may be modified for use over the entire atomic table or for making gas analyses.
X-Ray Diffraction Camera for Microtechniques
Authors: Chesley Frank G.
Published: February 2005

A description of an x-ray diffraction camera for recording diffraction phenomena from selected microscopic regions of solid materials is presented. Replaceable collimator systems limit beam diameters from 100 to 25 microns. The camera body may be removed from its support and replaced without readjustment.
Automatic Ratio Recorder as Applied to Infra-Red Spectroscopy
Authors: Wild R. F.
Published: February 2005

This paper describes an automatic ratio recorder as applied to infra-red spectroscopy, incorporating special control devices developed and constructed for E. I. du Pont de Nemours and Company. This instrument is designed for recording the ratio of the energies in the two channels of an infra-red spectrophotometer. It includes two preamplifiers and automatic control equipment for making readjustments periodically in the spectrometer and the preamplifiers. The instrument is provided with an electronic strip-chart recorder and has an effective span of 0.5 microvolt.
A Magnetic Airborne Detector Employing Magnetically Controlled Gyroscopic Stabilization
Authors: Vacquier Victor , Simons R. F. , Hull A. W.
Published: February 2005

An experimental type of an airborne magnetometer is described using three mutually perpendicular saturable-core magnetometers. Signals from two of these magnetometers are used to precess an air-driven gyroscope so as to align its spin axis along the earth's total magnetic intensity, thus providing stabilization for the third magnetometer which can then measure anomalies of a few gammas along the line of flight. This method of stabilization permits the use of the magnetometer in vehicles subjected to the most violent angular accelerations. It can also be made smaller than non-gyroscopically stabilized airborne magnetometers.
Carbon Dioxide Filled Geiger-Müller Counters
Authors: Brown Sanborn C. , Miller Warren W.
Published: February 2005

Efficient detection of the long period carbon isotope, C14, can be achieved when this isotope is oxidized to CO2 gas which may then be used as a Geiger-Müller counter filling. The special problems which arise in CO2 counters are discussed. Carbon dioxide ions produce undesirable effects which are eliminated by small amounts of CS2. The result of the investigation has been to develop a CO2–CS2 counter which has satisfactory properties for routine studies of C14.
The Photomultiplier X-Ray Detector
Authors: Marshall Fitz-Hugh , Coltman J. W. , Hunter L. P.
Published: February 2005

Our studies of the photomultiplier x-ray detector reveal that it is not only simple, rugged, and adaptable but that its high speed of response and high sensitivity recommend its use as a primary research tool. It can follow x-ray events as short as 10−5 second. Under optimum condition its sensitivity is limited only by the statistical noise of the incident x-ray quanta. Its chief defect is fatigue, the mechanism of which has been studied. This paper includes a general discussion of the use of this detector and of its characteristics.
A Microrespirometer
Authors: Gregg John R.
Published: February 2005

A simple constant-volume microrespirometer designed for the measurement of gas exchanges of from 0.001 to 0.5 mm3 is described. The results of some measurements of oxygen uptake by minute living organisms are presented, certain advantages of the design are pointed out, and the possibilities of application of the instrument to general microrespirometry are indicated.
A Mass Spectroscope for Analysis in the Low Mass Range
Authors: Siri William
Published: February 2005

A simplified and portable design of the 180° deflection-type mass spectroscope was developed for quantitative analyses in the mass range from 4 to 65. The principal features include an oscillating accelerating voltage, permanent magnetic field, the use of a.c. amplifiers, and an oscilloscope. Successful application has been made to fixed gas, liquid and solid samples, and continuously flowing gases with changing component concentration. Accuracy from isotope ratio determinations is of the order of 2–5 percent.
Stable Spectrophotometry of Small Density Changes
Authors: Chance Britton
Published: February 2005

Measurement and control circuits for recording small density changes by use of several photo-tube circuits are given. The minimum drift rates obtained are 1×10−6 part per minute with a differential photo-tube circuit, 3×10−5 part per minute with a single photo-tube circuit, and 4×10−4 part per minute with a photo-multiplier circuit. The differential and single photo-tube circuits have been used to measure density increments of roughly 2×10−4 and 1×10−3 with an accuracy of about 5 percent. These spectrophotometers are employed in studies of the kinetics of unstable intermediates in enzyme action. Although slow drift has been rendered negligible by suitable control circuits and stable amplifiers, the theoretical limit of performance is not achieved by this apparatus.
A Precision Method of Generating Circular Cylindrical Surfaces of Large Radius of Curvature for Use in the Curved-Crystal Spectrometer
Authors: DuMond Jesse W. M. , Lind David A. , Cohen E. Richard
Published: February 2005

A method is here described for generating circular cylindrical surfaces of large radius of curvature on blocks of steel or other material with a close approach to optical precision utilizing an ordinary machine shop surface grinder. Convex and concave surfaces about 3×5 inches in dimensions with radii of curvature of 79 inches (two meters) have been ground by this method both on cast iron and on stainless-steel blocks with a precision of about 0.0002 inches as regards surface imperfections. A very moderate amount of subsequent lapping sufficed to give surfaces of optical precision. The surfaces are used for clamping lamina of crystalline quartz for use in a curved crystal focusing gamma ray spectrometer. A companion paper describes the gamma ray spectrometer.
Decade-Ring Scaling Circuit
Authors: Seren Leo
Published: February 2005

A ring-decade counting circuit is presented, similar in design to that of Regener's. The triggering of the ring circuit has been further investigated, with reference to random pulses. A new input circuit is given so that the resulting scaler has a resolving time of 1.9 microseconds for any two consecutive pulses and 3.7 microseconds for any three consecutive pulses. A new simple method of indication is given which uses only a milliammeter and a triode instead of a cathode-ray tube.
A Photoelectric Nephelometer
Authors: Underwood N. , Doermann A. H.
Published: February 2005

A nephelometer is described that does not require a precision optical system or an electronic amplifier. It is sensitive enough to measure the growth of E. coli from a starting concentration of approximately 2×106 bacteria per ml. The readings are reliable from 107 to 109 bacteria per ml. A graph of the photo-current caused by the scattered light versus the number of E. coli per ml is given. The E. coli culture is a saturated 24-hr. nutrient broth culture in the lag phase. The bacteria were killed with 1 percent formaldehyde. In this range of bacterial concentrations the scattered light is nearly proportional to the number of scattering centers. The instrument is well adapted to the study of growth curves of bacterial cultures and the lysis phenomena that occur when the organisms are attacked by bacteriophages.

A horizontal beam of light passes through the vertical test tube containing the specimen. The light scattered downward is measured with a barrier layer photo-cell. The horizontal incident light produces a photo-current of 2.4×10−3 ampere. The light scattered by a specimen whose titer is 5×107 E. coli (growing exponentially) per ml produces a photo-current of 1.2×10−5 ampere. In this case the scattered light reaching the photo-cell is 1/200 of the incident light.
An Automatic Dewpoint Meter for the Determination of Condensable Vapors
Authors: Puck Theodore T.
Published: February 2005

A method for determination of very small concentrations of condensable vapors by measurement of the decrease in reflectivity of a cooled surface on which the vapor has been deposited is described. The method is applicable to mixtures of 2 components, one of which may be water. Use is made of the fact that a vapor will condense at a concentration below its vapor pressure in the presence of a second vapor whose liquid is soluble in that of the first. The most volatile component of the mixture is used in the pure state as a refrigerating agent whose evaporation cools the light-reflecting surface to an accurately regulated temperature which produces condensation of the two components.

An instrument embodying these principles is described which quantitatively measures triethylene glycol vapor in concentrations as low as 10−4 mm Hg. The construction is simple and the operation continuous and automatic. The calibration of the instrument is presented. By proper adjustment, automatic compensation for changing atmospheric relative humidity can be secured so as to obtain response only to the degree of saturation of the glycol vapor in air.

This device has been used to investigate condensation of vapors on atmospheric nuclei, and as a control instrument to regulate the concentration of triethylene glycol vapor employed as an aerial germicide for prevention of airborne disease transmission.
A Direct-Reading Frequency Meter for the Audio and Supersonic Ranges
Authors: Reich Herbert J. , Ungvary Robert L.
Published: February 2005

This paper describes an electronic frequency meter capable of operating in the range from 20 c.p.s. to 200 kc. The reading of the instrument is independent of wave form as long as the input wave does not cross the zero axis more than twice in its fundamental period. For sinusoidal input, the voltage required for reliable operation is less than 0.03 volt r.m.s. between the frequencies of 900 c.p.s. and 200 kc. The sensitivity in the range below 900 c.p.s. can be readily increased by minor changes in amplifier coupling networks. Over a six-month period, the experimental model has shown no change of calibration.
Coincidence Circuit of Medium Resolution
Authors: Schultz H. L. , Pollard Ernest
Published: February 2005

A reliable coincidence circuit of medium resolution with resolving time adjustable between 0.4 and 0.01 microsecond is described. The circuit uses a biased-diode pulse level selector in either channel, followed by a triggered blocking oscillator. Narrow and constant shape pulses so produced in the channels actuate a coincidence tube, output from which keys a rectangular pulse generator for turning on a power tube connected to a mechanical impulse recorder. Preliminary applications to the study of time fluctuations and delays in proportional counters and to proton time of flight measurements are described.
Electrostatic Deflection of a Betatron or Synchrotron Beam
Authors: Courant E. D. , Bethe H. A.
Published: February 2005

An electrostatic deflection scheme for removing the electron beam from a betatron or synchrotron is considered. The deflection is accomplished in two stages: The first stage is an orbit expansion achieved by a sudden decrease of the magnetic field in the orbit region. The electrons move outwards in spirals of increasing pitch; if the orbit radius is 1 meter and the rate of decrease of the magnetic field is one percent per microsecond, the pitch of the spiral is 1.26 cm at the ``neutral position'' where Hr has its maximum value. The pitch is proportional to the ⅗ power of the rate of decrease of the field.

At the neutral position the beam enters a radial electric field which deflects it outward more sharply. If this field, and the magnetic field with it, extends a distance of about a tenth of the orbit radius beyond the orbit, the electrons will be collimated into a beam whose angular divergence is approximately proportional to (H/E)¾, where H is the magnetic field at the orbit and E the electric deflecting field. With H = 10 kilogauss and E = 60 kv/cm, the angular divergence will be of the order of ten degrees. Curves showing the dependence of the angular divergence on E/H and on the distance to which the fields extend are presented.
Automatic Plotting of Electrostatic Fields
Authors: Green Paul E.
Published: February 2005

An apparatus is described by means of which plots of the equipotentials of two-dimensional fields may be made automatically from models of the electrodes. The usual electrolytic tank method has been extended by the addition of a servomechanism which causes the probe to traverse an equipotential automatically. A stepping relay operated by a limit switch effects automatic plotting of successive equipotentials and limits the plot to a desired area. A number of plots made with such an apparatus are reproduced.
An Instrument for Recording Ultra Low Frequency Ocean Waves
Authors: Munk Walter H. , Iglesias Hector V. , Folsom T. R.
Published: February 2005

An instrument has been designed to measure low amplitude waves whose frequencies fall between those of the wind-generated ocean swell and those of the astronomic tides. Its maximum sensitivity is to waves whose period is 15 minutes, and its pass band extends approximately from 2-minute periods to 2 hours. The suppression of the ocean swell and tides (whose amplitudes are much greater than those of the waves to be studied) is accomplished by means of capillaries and air chambers which give the instrument a response characteristic analogous to that of an electrical R—C circuit. Records obtained show the continual presence of waves in this previously unexplored portion of the spectrum of gravity waves in the sea.
A D.C. Voltage Regulator for Moderately High Currents
Authors: McCrea J. M. , Le Roy D. J.
Published: February 2005

The theory and design is given for a voltage stabilizer capable of supplying a current of several amperes at voltages in the region of 100 volts d.c. The main power requirements are furnished by a 220-volt d.c. line. The circuit incorporates two distinct methods of control, resulting in a large stabilization ratio and a low internal resistance.
An Apparatus and Method for the Continuous Measurement of Evaporative Water Loss from Human Subjects
Authors: Palmes Edward D.
Published: February 2005

The rate of evaporative water loss is measured by recording the difference in water vapor concentration in a stream of air before and after it passes over a man enclosed in a sealed chamber. An infra-red gas analyzer is employed for measuring the difference in water vapor concentration. Construction and application of the apparatus are discussed.
Air Proportional Counters
Authors: Simpson J. A.
Published: February 2005

Some properties of proportional counters using air at atmospheric pressure are described. It is shown that a variety of counter designs may be developed which are stable both with and without thin windows. A few counter designs which have applications in the detection of alpha-radioactive contamination are discussed in detail.
A New Form of Viscometer for Transparent Viscous Liquids
Authors: Elkarim A. A.
Published: February 2005

This method is based on the application of Stokes's law, and its aim is to measure the coefficient of viscosity of transparent viscous liquids. The method is to allow air bubbles of maximum diameter to evolve by a manometer system from the bottom to top of a liquid placed in an adjacent adjoining glass cell.
The Speeds of Diffusion Pumps for Gases of Low Molecular Weight
Authors: Blears J. , Hill R. W.
Published: February 2005

The evidence for a general relationship between the speed of a diffusion pump and the molecular weight of the gas being pumped is reviewed. Experiments are described which show that when pumps are operated at their normal ratings, the speeds for hydrogen and helium may be considerably lower than for nitrogen, and it is established that this is due to the relative ease with which the lighter molecules diffuse from the fore-vacuum to the high vacuum side of the jet. The speeds of diffusion pumps for different gases are not in fixed ratios, but in ratios which depend upon the fore-vacuum pressure and the heat input to the pump boiler. At heater wattages exceeding twice normal the inverse (M)½ law may sometimes be obeyed.
A Simon-Type Helium Liquefier with Transfer Siphon
Authors: Scott Russell B. , Cook J. Williamson
Published: February 2005

A helium liquefier utilizing the Simon expansion process is described. The liquefier is provided with a transfer siphon, so that the liquid produced is delivered into an external cryostat. By locating the expansion valve at the end of the transfer siphon, the cold gas released during the expansion is utilized in precooling the receiver, so that rather high yields are obtained. From the expansion chamber of 400-cm3 capacity, 310 cm3 of liquid are collected in the receiver.
The Production of Intense Ion Beams in a Mass Spectrometer
Authors: Bernas Rene H. , Nier Alfred O.
Published: February 2005

A simple 60° mass spectrometer has been built for the production of intense ion beams. Ions are produced by allowing an electron beam collimated by a transverse magnetic field to bombard the vapor issuing from a furnace. By adjusting conditions properly an arc may be struck and total ion currents of 1 to 2 ma could be obtained from the source when the accelerating voltage applied was 15 kev. The collected isotopes were completely resolved, and a total current of 0.3 ma for the several isotopes at the final collector was observed. Because of gas focusing at the operating pressure, space charge effects did not seriously affect the resolution and a resolving power of 1/100 could be obtained. In a 14-hr. run 6.5 mg of separated zinc isotopes were collected. Preliminary results with magnesium, as well as other solids, indicated that many other substances could be separated without modifying the apparatus. Improvements which would permit higher yields are suggested.
High Voltage Pulser for 184-Inch Cyclotron Electric Deflector
Authors: Kerns Q. A. , Baker W. R. , Edwards R. F. , Farly G. M.
Published: February 2005

This paper describes a high voltage pulse generator developed to deflect the beam of the 184-inch cyclotron at Berkeley, California. The apparatus develops a deflecting potential of 200 kilovolts that rises from 10 percent to 90 percent of peak value in 0.1 microsecond. The unit employs two similar 100 kilovolt water cooled pulse transformers connected symmetrically about ground to the electric deflector bars. Water-cooled General Electric pulse capacitors are discharged through the two turn primary windings of the pulse transformers by triggering a battery of 16 paralleled Kuthe 5C22 hydrogen thyratrons.

Output voltages are developed across the 17-turn secondary winding of the pulse transformer. The transformer is mounted in an oil-filled Lucite case that provides both insulation and compact design.
High Frequency Proton Source
Authors: Hall Robert N.
Published: February 2005

A proton source employing a 450-mc/sec. electrodeless discharge in the presence of a magnetic field is described. Ion currents of 400 μa, consisting of over 60 percent protons, are normally obtained, corresponding to a current density due to focused and analyzed protons of 0.03 amp./cm2 at the 1-mm exit hole. The source requires a hydrogen flow of 30 cc/hr., most of which is prevented from entering the accelerating column by the use of a differential pumping arrangement. The ions diffuse out through the exit hole and are accelerated without the use of a probe, resulting in a well focused, monoenergetic beam accompanied by relatively few stray ions. The experimental results were obtained on a 120-kv accelerator designed to simulate the initial sections of a typical constant voltage accelerator.
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.
A Novel Oscillator
Authors: Mouzon J. C.
Published: February 2005

An oscillator is described which employs inductive feedback between plate and cathode with the grid grounded. This arrangement results in some desirable characteristics.
A New Balanced Electrometer Circuit
Authors: Caldwell P. A.
Published: February 2005

An electrometer circuit is described in which it is possible to choose the resistances such that the plate voltage is independent of the supply voltage. When the circuit is used as the input stage of a direct-coupled amplifier, this leads to a simplification of the amplifier design. The equations determining the circuit constants in terms of the electrometer parameters are derived and applied to a G.E. Type FP-54 electrometer tube. The possibility of obtaining a higher order of balance is briefly discussed.
An Automatic Simultaneous Equation Computer and Its Use in Solving Secular Equations
Authors: Adcock Willis A.
Published: February 2005

A feed-back method is described which is suitable for an automatic computer solving linear simultaneous equations and secular equations. This method is more general than is the Gauss-Siedel method. The design for an analog computer based on this feed-back method is outlined. This design utilizes resistive voltage dividers to represent coefficients and voltages to represent the variables. The variables are automatically adjusted by the feed-back system. The performance obtained on a 4-equation model is given. Usually an accuracy of better than one percent is obtained.
A Magnetic Lens Beta- and Gamma-Ray Spectrometer
Authors: Quade E. A. , Halliday D.
Published: February 2005

A magnetic lens spectrometer has been built and tested. New features include (a) alignment with the earth's magnetic field to eliminate the deflection of the focal spot by this field, (b) use of a segmented coil to achieve a substantial reduction in spherical aberration, and (c) use of cathode rays for alignment, calibration, and for measurement of the aberration. Completely automatic operation has been achieved. Special attention is given to the effects of source backing and to focusing conditions for electrons in the very low energy region.
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.
A Magnetic Field Strength Meter Employing the Hall Effect in Germanium
Authors: Pearson G. L.
Published: February 2005

The instrument to be described measures magnetic field strengths as determined from the Hall effect in germanium. The essential parts of this instrument include a small germanium probe, and a panel type microammeter calibrated directly in gauss. Its accuracy is ±2 percent at fields between 100 and 8000 gauss. At higher fields the readings are too low, the error amounting to 9 percent at 20,000 gauss. The chief advantages of this instrument are: (a) small size and portability, (b) continuous reading rather than ballistic as in ordinary field strength meters, and (c) a small non-magnetic probe with which one can search in very narrow gaps.
A Geiger Counter Spectrometer for X-Ray Fluorescence Analysis
Authors: Friedman H. , Birks L. S.
Published: February 2005

A Geiger counter spectrometer was constructed for analysis of x-ray fluorescence spectra. The instrument is capable of measuring the K series lines of the elements beginning at about atomic number 22, up to about atomic number 50. In the middle portion of this range, spectro-chemical analyses can be performed rapidly with a sensitivity of 1 part in 10,000. Although the intensities are considerably reduced, analyses may still be carried out, using the L series spectra of the elements above atomic number 55.