bluuebunny/crossref_metadata_2025 huggingface dataset:
Starting Characteristics of a ``Trigger'' Tube with a Radioactive Cathode
Authors: Nottingham W. B.
Published: February 2005

The Westinghouse WL-759 ``trigger'' tube is designed to operate small relays and yet is controlled by currents less than 10−11 amp. in the starting anode circuit. Investigation shows that this is possible because of an ``avalanche'' effect set off by the radioactivity of the cathode after the starting anode has attained the critical potential for the efficient development of the high ion density needed to bring about the complete development of a glow discharge between the cathode and the principal anode of the tube. Other electrical characteristics of the tube are also discussed.
Resolving Power and Efficiency of Moving Coil Galvanometers. II
Authors: Cartwright C. Hawley
Published: February 2005

Formulas are derived for the change in e.m.f. and current that can be resolved with a given precision in a given time for taking readings. The resolving power of the underdamped state (κ=0.8) is about 10 percent more favorable than for critical damping. Considering a galvanometer as an engine for converting electrical energy into potential energy shows that its effective efficiency is about 40 percent that of an ideal engine.
An Apparatus for Accurate Measurements of Audiofrequencies
Authors: Ewell R. B. , Roseveare W. E. , Schaaf K.
Published: February 2005

An apparatus and procedure is described for measuring electrical frequencies from 1 to 15 kc with an accuracy of 0.001 percent. The broadcast frequency of a radio station is subdivided to give 100.000 cycles. Beats between the unknown frequency and known integral multiples of the 100 cycles are then counted.
The Design of a Magnetic Beta-Ray Spectrometer
Authors: Lawson J. L. , Tyler A. W.
Published: February 2005

A magnetic beta-ray spectrometer of high resolution has been constructed. The theory of the resolution of this instrument has been investigated in detail and applied to the design of the slit system. The effects of scattering within the vacuum chamber have been studied and reduced to a negligible value. The corrections for the efficiency of the Geiger-Müller counter and for the absorption in the counter window have been obtained as a function of the momentum of the incoming particles.
Cyclotron Radiofrequency Power Unit
Authors: Adams Norman I. , Schultz Howard L.
Published: February 2005

An oscillator-amplifier unit, suitable for supplying radiofrequency power to a cyclotron of medium size, is described. The power stage of the unit employs 4 RCA 833 air-cooled tubes operating at 80 percent efficiency with an input of 5 kw. Power is supplied to the D's through a resonant line, giving a peak radiofrequency voltage of about 45 kv. A 1-microampere beam of 3.1-Mev deuterons is obtained.
Space Potential Plotting in Thermionic Vacuum Tubes
Authors: Kenyon David E.
Published: February 2005

A method is described whereby space potentials in the interelectrode spaces of an electronic device may be mapped under operating conditions provided that approximately straight lines may be drawn through the equipotential surfaces to be determined. Results for a diode under temperature- and space-charge-limited conditions are given and compared with curves plotted from an analytical treatment of the problem.
A Square-Law Vacuum-Tube Voltmeter
Authors: Ragazzini J. R. , Boymel B. R.
Published: February 2005

A vacuum-tube voltmeter using the Type 954 acorn pentode for use in the measurement of the root-mean-square value of alternating voltages is described. A feature of the meter is the method whereby the tube response is made to fit a pre-marked square-law meter scale by the simultaneous adjustment of the screen voltage and the microammeter shunt. Operation from power lines and relative freedom from changes in calibration due to line voltage variations make the meter a useful laboratory instrument.
A High Voltage Cathode-Ray Oscillograph
Authors: Hall Albert C. , Coombs John M.
Published: February 2005

A cathode-ray oscillograph using a sealed-off Braun tube is described with which writing speeds up to twenty inches per microsecond are attainable. The circuit diagrams and description of the instrument are given in some detail in order to facilitate the construction and use of the instrument by others.
A Precision Integrating Sphere Densitometer
Authors: Frayne J. G. , Crane G. R.
Published: February 2005

An integrating sphere type of physical densitometer has been developed with a view to standardizing density measurements in the motion picture industry. The instrument accommodates films or plates up to 5″ wide. Scanning beam dimensions of 0.025″×0.100″ are used but may readily be changed. Density values corresponding to (1) the equivalent of standard visual diffuse or (2) photographic printing density may be obtained by insertion of suitable optical filters. Densities up to 3.0 are read directly on a special three-scale logarithmic meter which provides a uniform density scale. A chopper in the light path makes possible a.c. amplification using a highly stabilized amplifier with a highly selective gain-frequency characteristic. This latter feature permits operation in daylight or in a room illuminated with ordinary a.c. lamps. Calibration is based on the inverse square law.
The Generation of Square-Wave Voltages at High Frequencies
Authors: Fenn Willard H.
Published: February 2005

Three methods are described for the generation of alternating voltages having a square-wave shape and covering a wide range of frequencies. The first method is based on a previously developed system and uses an overloaded direct-coupled degenerative vacuum-tube amplifier. The second method uses a special pulse generator followed by a vacuum-tube trigger circuit. The third method is a combination of the first two and produces waves which are squarer than those produced by the individual systems. Very square waves are obtained with all systems at frequencies up to 200 kilocycles per second and with loading capacities up to 100 micromicrofarads. The applications of these waves are considered, as well as the importance of the circuits for other purposes. Of special interest are the suggested improvements in conventional ``scale-of-two'' counting circuits and the description of the high frequency pulsing circuit.
A Low Capacity Coupler for the Cathode-Ray Oscilloscope
Authors: Overbeck Wilcox P. , Löf J. L. C.
Published: February 2005

When observing voltages in high impedance circuits by means of an ordinary cathode-ray oscilloscope, one often encounters disturbance of circuit conditions by the relatively low impedance to ground of one of the oscilloscope amplifier input terminals. The authors present a coupling circuit for eliminating this difficulty in which the voltage to be observed modulates an oscillator isolated from ground. The resulting output is loosely coupled to a detector built into the oscilloscope. The paper shows that the system not only fulfills its purpose and indicates wave forms correctly, but is also economical and easily adjusted.
An Integrating Voltmeter for the Study of Nerve and Muscle Potentials
Authors: Jacobson Edmund
Published: February 2005

In the field of physiology, the measurement of action potentials is rapidly increasing in importance as time progresses. The paper describes recent progress in instruments adapted particularly for making low voltage measurements in this field. Detailed description is given of the integrating voltmeter, its characteristics and its use.
A Magnet and Cloud Chamber for Cosmic-Ray Studies
Authors: Jones Haydn , Hughes Donald
Published: February 2005

Details are given of the construction of an electromagnet, cloud chamber and accessory apparatus for use in cosmic-ray studies. The magnet has 9100 kg of steel, 1000 kg of copper, and has pole faces 30.5 cm diameter, normally used at an air-gap of 19.2 cm. The magnet is oil cooled and is usually operated at from 35 to 125 kw, the power being supplied by a motor-generator with variable field. Under these conditions the field increases from about 12,400 oersteds at the lower power to 16,000 oersteds at the higher power. The cloud chamber is of the diaphragm type, 30 cm diameter by 4.2 cm deep, and is filled with argon and ethyl alcohol vapor to 88 cm Hg pressure. The photographs are taken with the help of a 45° mirror placed against the front glass of the chamber. For illumination a Sperry carbon arc or a capillary mercury arc is used, the latter proving on the whole more satisfactory. With the lower magnetizing currents the temperature of the magnet and chamber can be maintained so close to that of the outside air that convection currents are small, and the tracks show little distortion. Errors in measuring the energy of cosmic-ray tracks are caused chiefly by distortions of the tracks. The probable error is 6 percent for a track of 109 ev, and about equal to the energy itself when this is 1.6×1010 ev.
A Rotary Shutter for X-Rays
Authors: Seemann Herman E. , Vaeth William C.
Published: February 2005

A shutter for an x-ray beam consists principally of a rotary disk with alternate open and opaque sectors, and a suitable control mechanism operated by an electromagnet. Several exposures may be made for one winding, a feature of convenience when remote control is desired. The motion of the disk is the same for opening and closing so that each part of the beam is turned on for the same length of time. The shutter will accommodate an x-ray beam directed anywhere between the vertical and the horizontal.
An Easily Constructed, Rugged, Sensitive Thermopile
Authors: Launer Herbert F.
Published: February 2005

A thermopile consisting of Chromel p-constantan junctions is described. Since the thermoelectric power of this couple is relatively high (over 60 microvolts per degree C) and since the metals have a low thermal conductivity and are easily worked, a sensitive, rugged thermopile may be constructed to meet individual needs in a short time without previous experience. A very simple technique of construction is described and the characteristics of a finished instrument are given.
A New Method for Measuring Young's Modulus
Authors: King Allen
Published: February 2005

The specimen, in the form of a circular loop of wire, is fastened at one point to a rigid support. At the diametrically opposite point a magnetic field is applied. The frequency of an alternating current in the loop is adjusted until flexural vibrations occur in the plane of the loop. Then the resonance frequency f, the radius of the loop r, the linear density m, and the radius of the wire a are related to Young's modulus by the equation E=18.395 mf2(r/a)4(1−g) in which (1−g) is a gap correction factor.
Luminous and High Resolving Universal X-Ray Spectrograph
Authors: Ingelstam E.
Published: February 2005

A universal spectrograph combining the concave-crystal methods by internal and external reflection has been constructed. The crystal employed covers the wave-length domain 0–2300 x.u. The aim was to get a convenient instrument suitable for rapid work. Direct wave-length reading is possible. Technical improvements in the crystal holder have been made.
On the Recording of Current Pulses by Slow Galvanometers
Authors: Rogers F. T.
Published: February 2005

Formulae are derived for the investigation of the lag between a current pulse through a galvanometer and the galvanometer's deflection. Examples are given, chiefly to galvanometric recording in microphotometry.
A Circuit for the Rapid Measurement of the Power Factor of Condensers
Authors: Walker Eric A.
Published: February 2005

A rugged, simple, and inexpensive circuit is described which enables one to ascertain rapidly the power factor and capacitance of condensers. With minor changes the circuit can be used to determine the magnitude and angle of any impedance.
A Precision Spectrophotometer for Use in the Range 450 to 820 mμ
Authors: Jacobsohn S. , Bent H. E. , Harrison A. J.
Published: February 2005

A precision photoelectric spectrophotometer is described which illuminates absorption cells with light which has passed through two monochromators, the half-intensity width of the spectral region isolated being from 5 to 10 mμ. Cells 20 cm long and as much as 14 cm in diameter may be used when it is necessary to work at low or high temperatures with thermostated equipment. The detector is a null instrument, giving a sensitivity of 0.0001I0 and an accuracy under favorable conditions in the optical density of 0.1 percent.
The Lining of Metal Capillaries with Glass and the Application to a Capillary Positive Ion Source
Authors: Getting I. A. , Leighton H. W.
Published: February 2005

A technique is described for the lining of metal capillaries with a thin coat of glass. The advantages of such capillaries in electrical discharges are pointed out. Use is made of such a capillary in a highly efficient positive ion source for high voltage nuclear research.
A Vacuum Interferometer for Precise Measurements
Authors: Elliott R. M.
Published: February 2005

The serious effect of pressure and temperature variations in the use of a Fabry-Perot interferometer is outlined, together with a method successfully employed to reduce these variations to a reasonable limit.
An Interval Meter and Its Application to Studies of Geiger Counter Statistics
Authors: Driscoll Raymond L. , Hodge Mary W. , Ruark Arthur
Published: February 2005

An instrument for sorting time-intervals into size-classes is described. It discriminates between intervals which differ in length by only a few tenths of one percent. This makes it possible to study the time distribution of the impulses in Geiger-Müller counters. Two argon counters, excited with gamma-rays and operated at rates between 0.9 and 3.0 counts/sec., gave results in excellent agreement with fluctuation theory; but a hydrogen counter, operating at rates between 1.9 and 4.5 counts/sec., and excited either with gamma-rays or with light, gave results so discrepant that they cannot reasonably be explained on the basis of statistical fluctuations or instrumental errors.
Constant Current Sources
Authors: Green Louis C. , Kuper J. B. Horner
Published: February 2005

A simple and inexpensive circuit for obtaining power at constant current (independent of load changes) from an a.c. supply of constant voltage has found several applications in laboratory work, particularly in operating arcs and glow discharges. The use of constant current permits the elimination of ballast resistors and chokes, with the attendant power loss, and often improves the stability so much that power inputs may be increased. Other sample applications are protection of the oscillators and rectifiers of a cyclotron against damage by short circuits or gas bursts, and operation of hydrogen arcs for proton sources. When this circuit is used on the input to a rectifier constant direct current will be obtained, and the rectifier tubes protected. In the present paper the theory of the circuit (including effects of losses) is briefly treated and the design of apparatus discussed, with descriptions of two typical outfits.
Square Root Extractor
Authors: Green Harold D.
Published: February 2005

A mechanical device is described for extracting a root or obtaining a power of successive ordinate values of curves. It is particularly useful in calculating the total volume flow in a pulsating stream from velocity (or rate of flow) records obtained from venturimeters, orifice meters or Pitot tube meters in which the deflection of the record is usually proportional to the square of the flow, and with hot wire meters and thermostromuhrs in which the deflection of the record is proportional usually to the square root of the rate of flow.
An Ultra-High Frequency Superheterodyne Receiver for Direction Finding
Authors: Yuan Luke C. L. , Miller Charles E.
Published: February 2005

An ultra-high frequency superheterodyne receiver, simple in operation, having high sensitivity and stability, was constructed primarily for direction finding on 1.67-meter waves. The 220-kilocycle intermediate frequency amplifier using resistance coupled high μ television type tubes has a constant gain of 110,000 over a 110-kilocycle band. This flat intermediate frequency response allows for any slight variation in the oscillator or signal frequency, due to temperature variations etc., without affecting the output of the receiver. A high gain and a high signal to noise ratio make the receiver well suited for direction finding observations by the null point method.
Baffles for Oil Diffusion Pumps
Authors: Morse Richard S.
Published: February 2005

Although in the use of oil diffusion pumps for the production of high vacuum, extremely cold traps in the usual sense are not required, some means must be provided to prevent both direct backstreaming and diffusion of the oil vapor. The relative advantages of (1) charcoal traps, (2) cold traps, (3) hot baffles, (4) electrical baffles, (5) mechanical baffles are discussed and specific designs for effective high speed baffles are given.
On the Construction of Very Sensitive Vacuum Thermoelectric Cells
Authors: Rogers F. T.
Published: February 2005

A new and reliable technique is described for the construction of thermocouples of high sensitivity, suited especially to astrophysical research. The technique consists essentially of a controlled-heating soldering process for very small bismuth alloy parts. The mounting of such thermocouples in permanently evacuable glass envelopes is also discussed.
A Comparative Study of Water Aspirators
Authors: Little E. P. , Pond S. E.
Published: February 2005

The relative speed of evacuation, water consumption, air pumping ability, and final vacuum produced by 14 water aspirators have been measured, making possible a more intelligent choice of aspirator for any job.
Design and Performance of an Electron Diffraction Camera
Authors: Ruedy J. E.
Published: February 2005

An electron diffraction camera has been built for use in the study of photo- and secondary electron emissive surfaces. The electron beam is produced by a modified cathode-ray tube gun having an a.c. heated tungsten wire cathode, for which the focusing voltages are supplied by rectifiers. Beam velocities up to 40 kv are available. The maximum beam current, after reduction by a screening aperture, is about 0.1 μa, which is sufficient to make visible most patterns which can be photographed. The specimen adjustment mechanism and photographic shutter control are of new design and have proved themselves very satisfactory. The pumping system consists of a Megavac fore pump and a four-inch diameter three-stage oil diffusion pump.
Measuring Average Current in a Jumpy Direct-Current Circuit
Authors: Maxstadt F. W.
Published: February 2005

An indicating instrument which gives the answer directly and in addition consumes very little voltage.
A Portable High Voltage Generator of Practical Utility
Authors: Bramhall Ervin H.
Published: February 2005

The paper discusses the design and construction of a Van de Graaff electrostatic generator capable of an output of 500 microamperes and more than a million volts. A new design is proposed embodying improvements which are based on the operation of this machine over a long period.
Determination of Voltage Wave Forms with the Rotary Voltmeter
Authors: Kirkpatrick Paul
Published: February 2005

The electrical theory of the rotary voltmeter is developed and the conclusion drawn that the instrument may be employed for analysis of the wave forms of a large class of periodically varying voltages. Two experimental methods for performing these analyses are described and experimental results are presented, pertaining to both high and low potentials.
Vacuum-Leak Hunting with Carbon Dioxide
Authors: Webster D. L.
Published: February 2005

The advantages of carbon dioxide for detecting and locating leaks in vacuum apparatus are noted here, with descriptions of methods used, especially for very small leaks.
A Seismographic Recorder
Authors: Wolfe Halley
Published: February 2005

A recorder used for making ink records of low frequency oscillations of a small rotating mirror (such as, for example, a galvanometer mirror) is described: a light beam, modulated in accordance with the mirror vibrations, excites a photoelectric cell, the output of which is sufficiently amplified by a low frequency amplifier to control a pen writer. Since the instrument has been developed for use in conjunction with photographically recording seismographs, the treatment in the article is from a seismological point of view. The frequency response of the recorder alone is calculated, and the method of obtaining it for the entire system of the recorder in combination with a given seismograph is indicated. Records are shown to demonstrate the fidelity of reproduction.
The Production of Large Single Crystals of Ice
Authors: Adams John Mead , Lewis William
Published: February 2005

A convenient method for locating the crystalline axes in ice, and therefore for determining the extent of any single crystal of ice in a block, has been developed. Single crystals of ice, satisfying this test, of dimensions limited only by the size of the apparatus, have been prepared.
Note on Life Tests of Commercial Type Standard Cells
Authors: Smith T. Townsend
Published: February 2005

Measurements of the electromotive force of standard cells made over periods of from seven to twenty years show that the electromotive force of the cells decreases at a rate which varies from cell to cell and which changes with the age of the cell. It seems further that a single cell may not be trusted unless it has been checked a short time previous to being used. These conclusions follow as the result of measurements where no attempt was made to keep the cells at a constant temperature.
The Preparation of Sputtered Metal Films
Authors: Hulburt E. O.
Published: February 2005

The technique of sputtering is described. Opaque, optically good films were sputtered in a residual atmosphere of air from cathodes of Sb, Bi, Cd, Au, Pb, Pt, Ag, Sn and Zn in about an hour; from Co, Cu, Ir, Fe, Ni, Se and Te in two hours or so; and from Mo, Ta and W in several hours. Al, Be, C, Cr, Mg and Si sputter very slowly in air. In a residual atmosphere of Hg or He or A, opaque films of Al, Cr and Si were sputtered in a few hours. Evidence is presented which indicates that a majority of the sputtered particles are of molecular or atomic dimensions. The transmission of films of Pt, Ta and Cr was nearly constant for wave-lengths from 0.5 to 2.2μ; films of Si and C were relatively transparent from 1.0 to 2.2μ.
Evaporation Technique for Highly Refractory Substances
Authors: O'Bryan H. M.
Published: February 2005

Platinum, boron, molybdenum, quartz and other substances have been evaporated in vacuum from a crucible heated by bombardment with electrons at 4000 volts from a tungsten filament. A small pure graphite crucible was heated to its melting point about 3500°C by 100 milliamperes of electron current. Most elements will alloy with a tantalum or molybdenum crucible so a graphite cup is usually preferable. Low melting point substances which would easily alloy with a tungsten filament can be readily handled by this method, which has been used in the preparation of x-ray target surfaces, small mirrors and absorbing films.
The Technique of Sputtering Sensitive Thermocouples
Authors: Harris Louis , Johnson Ellis A.
Published: February 2005

The adiabatic heat produced in a sound field up to frequencies of 5000 cycles has been measured with a thermocouple. Similar thermocouples have been used to measure small intensities of radiation. The response of these sensitive couples depends upon the use of thin films of metal and the use of a.c. amplification. The couples have been made by cathodic sputtering of bismuth, antimony and tellurium on thin cellulose. A detailed account of their construction is presented.
The Apparatus and Technique for Growing Large Specimens of Single Crystal Zinc
Authors: Cinnamon C. A.
Published: February 2005

The apparatus and technique are described for the growth of large, strain-free, single crystals of zinc of any desired orientation. It is shown that a gross mosaic structure may occur in the beginning of the growth of a crystal but may be eliminated by a steep temperature gradient. The data show the necessity of satisfying certain growth conditions, namely, that the ratio of the temperature gradient to the rate of growth must be near a certain favorable, but not necessarily the same, value for each orientation.
A Cell for Routine Electrical Measurements on Insulating Oils
Authors: Horsch William G. , Berberich Leo J.
Published: February 2005

The requirements to be met by a cell for routine determinations of the resistivity of insulating oils are given. A guard-ring cell meeting these requirements is described, and its application to power factor measurements discussed.
A Device for Showing the Direction of Motion of the Oscilloscope Spot
Authors: Mann E. R.
Published: February 2005

A circuit is described which has for its purpose the determination of the direction of rotation of the fluorescent spot obtained in current-voltage oscillograms. The figure described by the rotating spot is interrupted at a suitable point in the cycle by means of a neon lamp discharge, and examination of this interrupted figure readily leads to the correct conclusion as to the direction of rotation which prevailed in the original figure.
A Reflection Polariscope for Photoelastic Analysis
Authors: Mindlin Raymond D.
Published: February 2005

The paper embodies the description of a polariscope which offers several advantages for photoelastic investigations and is applicable to the analysis of stress distributions in parallel plates and to Mesnager's modified three-dimensional analysis. The chief characteristic of the optical arrangement is that the light, after passing through the usual arrangement of polarizing prism, retardation plate and model, is reflected directly back through the same system.
The Preparation of Specimens for the Measurement of Thermal Conductivity
Authors: Adams John Mead
Published: February 2005

The paper describes an exactly reproducible method of applying metallic coatings to the surfaces of solid specimens and of imbedding thermocouples precisely at any given depth in the coatings. The method makes possible the complete elimination of the variable discontinuity of temperature which is always present, to a greater or less degree, in measurements of thermal conductivity, between the specimen and the metallic surfaces in contact with it. A new technic for the stripping of fine silk-covered wires is described.
Grid Current Control for the Ionization Gauge
Authors: Overbeck W. P. , Meyer F. A.
Published: February 2005

The application of a saturable-core transformer to the control circuit of an ionization gauge for the purpose of maintaining constant electron current from filament to grid has proven successful.
A Stable d.c. Amplifier Using 7567A Tubes
Authors: Distad Merril , Williams John H.
Published: February 2005

Two single-tube d.c. amplifiers with 7567A tubes have been constructed which are extremely stable in operation. Following the design of DuBridge and Brown, a modified balanced bridge circuit is described wherein the drifts are not due to fluctuations in battery potentials or changes in filament emission. Data on the determination of circuit constants necessary for the elimination of drifts are given. Currents of 3×10−15 ampere give galvanometer deflections of one cm and readings can be obtained every 15 seconds.
A Differential Circuit for Blocking-Layer Photo-Cells
Authors: Wood Lawrence A.
Published: February 2005

The use of a differential photo-cell circuit employing two cells of the blocking-layer dry disk type is of advantage where a difference between two light intensities is to be measured or to serve as control, especially where fluctuations of the source prove troublesome, or where the difference to be measured is small. Experimental as well as theoretical consideration of the circuit in which terminals of opposite polarity from the two cells are connected together, with a meter or relay in parallel with the cells, shows many desirable features in respect to sensitivity, linearity of response, and stability. The advantage arises fundamentally from the fact that the effective resistance across each cell under these conditions is very low. The circuit is useful either as a null method or for obtaining, on a current-measuring instrument, scale readings proportional to light-intensity difference. Linearity is obtained over approximately the same range as for a single cell, the rate of change with light intensity being approximately the same. A comparison with the arrangement hitherto chiefly employed, which balances open-circuit voltages, indicates advantage in all respects of the circuit here described, which should consequently prove of wide utility.
A Dual Range Potential Source for Field Use with Electroscopes and G-M Counters
Authors: Bosch Walter C.
Published: February 2005

The battery powered, portable potential source described utilizes a hand cranked condenser type d.c. multiplier to keep an output condenser charged to a potential constant within 1 percent. A potentiometer and switching arrangement in the input circuit make available two output ranges of approximate values 0 to 0.43 kv and 0.65 to 1.08 kv. The unit is carefully insulated and operates efficiently under all conditions of humidity.
Important Improvements in Fused-Quartz Mercury Arcs
Authors: Johnson L. B. , Webster S. B.
Published: February 2005

Five new alternating-current mercury arcs between oxide-coated tungsten electrodes in fused-quartz are described and the spectral intensity of each lamp is tabulated. Several points of superiority over the familiar mercury-pool cathode types are discussed.
An Ultrasonic Source of Improved Design: Optical Studies of Ultrasonic Waves in Liquids
Authors: Fox Francis E. , Rock George D.
Published: February 2005

After discussing the production of sound radiation suitable for ultrasonic interferometry in liquid media, a source is described in which a piezoelectric quartz plate mounted at a nodal plane for its principal vibration mode has one vibrating face exposed directly to the liquid media so that its motion may approximate that of a piston radiating into a semi-infinite medium. A review is given of some of the optical methods using continuous illumination that can be used in the investigation of ultrasonic radiation fields in liquids. Both progressive and standing sound wave systems are used with plane and divergent light. Photographs are included and bring out in a striking manner phenomena discussed in optics and acoustics.
Design and Operation of the Oil-Turbine Ultracentrifuge
Authors: Boestad Gustav , Pedersen Kai O. , Svedberg The
Published: February 2005

The development of the oil-turbine ultracentrifuge, from the first model built in 1925 to the latest, is traced, with special attention being given to the principles of design for maximum resolving power in the analysis of mixtures as the lowest expenditure of energy. The efficiency of various types of rotors combined with centrifugal or screw-type oil pumps is reported. By proper attention to design, it has been possible to attain an efficiency at 60,000 r.p.m. of 40 percent in the oil turbines and an over-all efficiency of electric motor, oil pump, and oil turbines of 28 percent. The actual power consumption under these conditions is slightly over 1 kw, which appears to be somewhat better than has so far been attained with the air-turbine ultracentrifuge of comparable design. The frictional resistance of the rotor rotating in hydrogen at 20 mm pressure is 300 watts, 32 watts representing gas friction. The cost of electricity, cooling water and hydrogen for operating the latest rotor and assembly at 60,000 r.p.m. exclusive of the vacuum system and recording instruments, is 9¢ per hour, with electric power at 1.54¢ kw-hr., water at 6.4¢/cu.m, and hydrogen at 64¢/cu.m. The corresponding cost for an early model rotor and assembly was 28.7¢ per hour.
Van de Graaff Generator for General Laboratory Use
Authors: Trump J. G. , Merrill F. H. , Safford F. J.
Published: February 2005

An air-insulated direct-current electrostatic generator of the Van de Graaff type, characterized by simplicity and low cost and suitable for a wide variety of research applications, is described. The generator, which employs re-entrant terminals, is capable of 500 kv and produces a short-circuit current of about 200 microamperes with a single 10″ belt. The manner in which the unit can be extended to higher voltages and currents is indicated, as well as the effect of operation in the presence of CCl4 and CCl2F2 vapors. The operating principles, design considerations, theory of multiple belts, effect of humidity, problem of surge elimination, and cost are discussed.
A Tubular Vacuum-Type Centrifuge
Authors: Beams J. W.
Published: February 2005

A method of spinning tubular rotors to high speeds in a vacuum is described. The rotors are spun by air-supported, air-driven turbines situated below the vacuum chamber. The maximum rotational speed attainable is set only by the bursting strength of the tubular rotor. The material to be centrifuged enters the spinning tube at the top at a continuous rate and is collected in light and heavy fractions at the bottom. The apparatus has been used for centrifuging materials in gaseous, vapor and liquid states.
A Radiometer-Type Vacuum Gauge
Authors: Lockenvitz Arthur E.
Published: February 2005

A radiometer-type vacuum gauge is described, which is rugged and simple to construct, which can be calibrated from the dimensions of the gauge, and for which the temperature of the moving system does not enter. The gauge, when constructed entirely of metal has a range from 2 dynes per square centimeter to 0.01 dyne per square centimeter. If constructed of glass, the lower limit can be extended to 0.001 dyne per square centimeter or better.
Rapid and Accurate Measurement of Line Positions on X-Ray Diffraction Films with the Aid of a Cathode-Ray Oscillograph
Authors: Tatel Howard , Hultgren Ralph
Published: February 2005

An apparatus containing a cathode-ray oscillograph has been developed for the measurement of positions of x-ray diffraction lines. A small portion of the film is scanned by a moving slit. A trace of film transmission versus distance appears on the screen of the oscillograph. Lines are easily measured by centering their traces on the screen. Measurements are made very rapidly. Accuracy depends on the sharpness of the line measured. Ordinary back-reflection x-ray lines can be measured to better than 0.02 mm, sharper lines or points may be located much more accurately. The apparatus is compact and has no parts easily damaged. The cost is less than for a recording photo-densitometer. It can, no doubt, be used for intensity measurements and for the measurement of spectrographic and other types of lines on photographic plates or films.
A Short Ion Path High Voltage Tube
Authors: Stephens W. E. , Lauritsen C. C.
Published: February 2005

A vacuum tube for the acceleration of charged particles is described. The total acceleration of the ions takes place in a distance of 18 inches although the total height of the tube is about 14 feet. It has been used at one million volts peak a.c. with target currents of 5 ma of electrons and 0.2 ma of positive ions.
Surface Conductivity of Ceresin-Coated Quartz
Authors: Hou C. H.
Published: February 2005

The surface conductivity of clear fused quartz in a humid atmosphere is found to be greatly increased, rather than decreased, by coating the quartz with a thin layer of ceresin wax. Humidity was controlled by the addition of a measured quantity of water to a known volume of thoroughly dried air.
On a Modification of Hickman's Distillation Pump
Authors: Malter L. , Marcuvitz N.
Published: February 2005

Hickman has made a contribution to pump development which is outstanding since the original work of Gaede and Langmuir. We have checked his conclusions regarding the desirability of incorporating a distillation process in conjunction with the pumping operation. The results of our work are incorporated in a pump design based upon a design of Hickman's. This pump: (1) yields very low ultimate vacuums; (2) operates against moderately high backing pressures; and (3) is made entirely of metal. In addition, we have made ``life tests'' on Octoil which indicate its superiority over available petroleum distillates as regards vapor pressure and ability to withstand abuse.
An Automatic Dipping Mechanism for Making Built-Up Films
Authors: Mattoon Richard W. , Bernstein Seymour
Published: February 2005

A motor-driven dipping mechanism is described which has been used to make built-up Y films of 1000 molecular layers or more of barium-copper stearate, using the Langmuir-Blodgett technique. A rotating cam, the surface of which is determined by the equation ρ=aτ, imparts a reciprocating constant linear velocity to a dipping rod holding the slide on which the film is deposited. The mechanism is counterbalanced. Available adjustments are the velocity of dipping, the length of stroke and the choice of end points, the reversal of the velocity at any time, and the orientation of the slide about a vertical axis.
A Mechanical Lag-Screen Oscillograph
Authors: Hoecker Frank E. , Asher A. Graham
Published: February 2005

The article describes an apparatus which may be used for the study of low frequency or noncyclic wave forms. The instrument comprises a short period suspended magnet galvanometer from the mirror of which a beam of light is reflected to a moving phosphorescent screen in the form of a continuous belt. The wave form appears as a bright line on a nonluminous background and remains easily visible for approximately one minute when observed in a dark room. The instrument is especially suitable for the study of electrocardiac impulses.
Large Quartz Monochromator for Biophysical Research
Authors: Uber Fred M. , Jacobsohn S.
Published: February 2005

Monochromatic irradiation studies of biological objects usually require a large slit area, high intensity, comparable irradiation conditions at all wave-lengths, and frequently some provision for treating on a horizontal surface. The present instrument provides for the simultaneous irradiation of seventeen different samples, each covering 100 square millimeters of a horizontal surface with the exception of two which cover 75 mm2 each, each sample being exposed to a single wave-length of the Hg are spectrum. The seventeen wave-lengths are as follows: 3655, 3341, 3131, 3022, 2967, 2925, 2894, 2804, 2752, 2699, 2652, 2576, 2536, 2483, 2399, 2378 and 2352A. The straight spectral lines are 2×50 mm. The optical system consists of two 60° crystal quartz prisms, Cornu type, 51 mm high and 85 mm length of face; collimator and camera lenses have 70 mm aperture and 418 mm focal length. Exchangeable with the special holder for the biological materials are two other attachments: a photographic film holder and a calibrated traversing slit mechanism designed to carry a thermopile or a photo-cell. The instrument can be used in either a vertical or a horizontal position.
A Transformation Pantograph for the Reduction of Microphotometer Tracings
Authors: Hemmendinger Henry
Published: February 2005

An instrument is described for the continuous transformation to a scale of linear or logarithmic intensity of a galvanometer tracing representing the density of a photographic image. The instrument has few moving parts, and has proved capable of executing the reductions quickly and accurately.
A Magnetic Field Meter
Authors: Cole Robert H.
Published: February 2005

An instrument similar in principle to one developed by Kohaut but suitable for absolute measurements of large and inhomogeneous fields is described which consists essentially of a d.c. generator with a very small armature coil on the end of a long shaft driven by a synchronous motor, the induced voltage being a direct measure of the field. Typical results are given and the accuracy, relative and absolute, attainable discussed.
Circuits for the Control of Geiger-Mueller Counters and for Scaling and Recording Their Impulses
Authors: Johnson T. H.
Published: February 2005

An analysis is given of the controlling action of a vacuum tube in circuits similar to those proposed by Neher and Harper and Neher and Pickering. A modification of the latter's circuit eliminating some of its disadvantages is described. This circuit has been incorporated into a four tube network which controls the counter, scales down the impulse rate by any desired factor, and records the scaled counts. A new circuit is also described for recording the impulses from a single counter or from counters connected in coincidence.
A Push-Pull-Stabilized Triode Voltmeter
Authors: Williamson Charles , Nagy John
Published: February 2005

This general purpose, balanced triode voltmeter is stabilized by adjusting shunt resistors until the effective values of μ and Ip are the same for both tubes. Built-in testing equipment is provided. The electrical zero of the galvanometer is unaffected by changes of ±20 percent in power-supply voltage when the circuit has a d.c. sensitivity of 40,000 mm/volt. The tubes need not be specially selected. The balancing principle may be adapted for use in any circuit requiring matched tubes.
High Rotational Speeds in Vacuum
Authors: Smith C. Scudder
Published: February 2005

Rotors freely suspended in high vacuum were driven to high rotational speeds by electrostatic and by electromagnetic forces. The first suspension used was a modification of the photoelectrically stabilized suspension developed in this laboratory by F. T. Holmes. Another magnetic suspension was developed which was stabilized by capacity coupling. The electrostatic drive consisted of a charged bisymmetrical blade free to rotate between quadrant plates to which were applied alternating potentials generated either by interruption of a beam of light by the rotor, by capacity pick-up, or by an external oscillator. Rotors were also driven by rotating magnetic fields. Objects suspended varied in weight from 7 g to 1200 g. The highest speed attained was 3200 r.p.s. using a 14-g rotor. A deceleration of 2.2×10−4 rev./sec.2 was measured with a 47-g rotor (moment of inertia, 103 g cm2) running at 650 r.p.s. with no applied torque.
An Improved Radiation Pyrometer
Authors: Harrison Thos. R. , Wannamaker Wm. H.
Published: February 2005

In designing a new radiation pyrometer for industrial use above the lower limit of visible radiation, consideration of ambient temperature effects, which is of much importance in modern industrial practice, was carried out by aid of mathematical analysis. In one hypothetical case, with a very sensitive type of thermopile losing heat from its hot junction by radiation alone, it is shown that an increase in operating ambient temperature of 180°F (from 80°F to 260°F) results in a drop in output voltage of 38 percent for a constant furnace temperature of 1300°F. The corresponding error in reading is 315°F. At a furnace temperature of 3000°F, the decrease in voltage is 17 percent and the error in reading is 387°F. Under similar conditions, in another hypothetical case of a less sensitive thermopile constructed to lose much of its heat by thermal conduction, this 180°F increase in operating ambient temperature would result in a decrease in output voltage of from 12.2 percent to 12.5 percent for any furnace temperature between the two values mentioned. The error in reading would range from 58°F to 162°F over the stated span of furnace temperatures. The constancy of ratio of e.m.f.'s shown for the higher conduction factor makes it possible to provide ambient temperature compensation over a wide range of furnace temperatures with a nickel shunt compensator. The pyrometer here described, designed along these lines, shows ambient temperature errors of less than three degrees F in the furnace temperature being measured for ambient temperature variations from 50° to 200°F; transient errors would usually be one degree or less for most cases; the response is complete within 3.5°F in four seconds and within half a degree or less in six seconds. The calibration, with varying ratios of distance-to-target versus target diameter up to over 20 to 1, is unusually constant. A thermopile of ten units insures ample e.m.f. All of the thermopile junctions are spot-welded and the construction is arranged throughout to withstand high ambient temperatures.
A Discontinuous Oscillographic Sweep Circuit
Authors: Haworth L. J.
Published: February 2005

A vacuum tube sweep circuit is described which permits the transit of the oscilloscope beam to cover any desired interval of time during the cycle of events under observation, controllable delays being possible both before and after the transit. The circuit may also be used for single sweep work. A simple method for impressing time base markings is also described. Applications of the circuit are discussed and adaptations to multiple sweep photography are suggested.
The X-Ray Photon Efficiency of a Multiplier Tube
Authors: Allen James S.
Published: February 2005

The design and operation of a 12-stage electrostatic multiplier tube as a photon counter are discussed. The tube has a pure tantalum photoelectric surface, the multiplying electrodes being covered with oxidized beryllium. With 300 volts between successive electrodes the tube has a background counting rate of about 3 to 5 pulses per minute and records about one photon in 500 at a wave-length of 10−8 cm. The multiplication is about 18,000.
Electrostatic Generator for Nuclear Research at M.I.T.
Authors: Van Atta L. C. , Northrup D. L. , Van de Graaff R. J. , Van Atta C. M.
Published: February 2005

The electrostatic generator previously located at Round Hill has been transferred to the M.I.T. grounds in Cambridge. The present generator construction and also a high voltage accelerating tube mounted vertically in one of the columns are described. An account is given of experience with the acceleration of positive ion and electron beams and with the x-ray bombardment of indium, beryllium, and deuterium.
Cathode Phase Inversion
Authors: Schmitt Otto H.
Published: February 2005

Application of cathode phase inversion previously described is made to several practical circuits including symmetrical cathode-ray oscillograph amplification, high fidelity d.c. amplification, and differential or mixer amplifier operation. The theory of a symmetrical degenerative attenuator modification of the basic circuit is developed and practical applications are described.
Developments in Ion Accelerating Tubes
Authors: Manley J. H. , Haworth L. J. , Luebke E. A.
Published: February 2005

An artificial neutron source has been built which is very stable in operation and flexible in use. Using the D—D reaction, target currents of more than 200 microamperes at 300 kv give a neutron yield of 10 grams radium-beryllium equivalent. It has been found that voltage stability at these currents may be greatly improved by the use of special diaphragms, and that a reflux target cooling system is very satisfactory in maintaining a heavy water-ice target. Electrostatic deflection of the ion beam has produced a neutron source which may be modulated at high frequencies or otherwise time-controlled.
An Apparatus for the Direct Determination of Slow Neutron Velocity Distributions
Authors: Haworth L. J. , Manley J. H. , Luebke E. A.
Published: February 2005

Apparatus is described by means of which a modulated source of slow neutrons is produced and their intensity determined as a function of time. The deuteron beam of a high voltage tube is deflected by a modulated electrostatic field in such a way as to produce square bursts of fast neutrons of any desired length. After being slowed by hydrogenous material a selected beam of neutrons falls on a suitable detector at a measured distance from the source. Pulses from the detector are impressed on an oscilloscope screen, together with a sharply defined time scale and photographic records made. The time analysis of the neutron distribution is then made by a numerical count of the neutron pulses as a function of the time interval in which they occur.