bluuebunny/crossref_metadata_2025 huggingface dataset:
Design of Permanent Magnets for Cloud-Chamber Work
Authors: Shutt R. P. , Whittemore W. L.
Published: February 2005

For the investigation of radiations of high energies, one can place a magnetic field between two cloud chambers. For a given flux of radiation to be observed, the air gap of the magnet in this arrangement can be made much smaller than when a cloud chamber is mounted between the pole pieces of a magnet. For small gap lengths, a permanent magnet is capable of producing a strong magnetic field. In order to assure most efficient distribution of the magnetic alloy used, model experiments were performed. A calculation shows that, if the variables are chosen appropriately, a single constant can be adjusted so that all the experimental results can be fitted to a universal function within a few percent. By means of a coordinate transformation of the universal function, one can predict field intensities or determine optimum constructions of a large variety of permanent magnets. Reasonable accuracy can be expected as long as the ratio of gap length to linear dimension of the pole faces is less than 1/4. The method has been applied to the construction of a large permanent magnet to be used for a study of the anomalous scattering of cosmic-ray mesons.
A New Apparatus for the Partitioning of Expired Air
Authors: Brown Jack H. U. , Hatch Theodore F. , Cook Kenneth M.
Published: February 2005

An apparatus is described for the partitioning of exhaled air into seven separate fractions beginning with the earliest portion of upper respiratory air and continuing to the terminal fraction of deep-lung air. The same volumetric fractions from successive exhalations are collected over a test period of any practical duration. This apparatus has been employed for the study of lung retention of inhaled particulate matter with particular reference to the separate estimate of upper respiratory retention and penetration to and deposition of particulate matter in alveolar spaces. The apparatus is employed with a mechanical respirator of the Drinker type, which fixes the respiratory pattern at any desired frequency and tidal volume.
Ring Focusing in a Thin Lens Beta-Ray Spectrometer
Authors: Pratt W. W. , Boley F. I. , Nichols R. T.
Published: February 2005

The existence of a ring-shaped constriction in the electron beam of a thin lens beta-ray spectrometer is demonstrated experimentally by a photographic film method. Making use of a photographic mapping of the beam, an annular baffle is designed. Optimum relations between annular width, solid angle, and counter window diameter are investigated. A comparison of this type of baffle system with the original baffle system shows that at 2.5 percent resolution the spectrometer transmission may be increased by a factor of two by the use of an annular aperture in the region of beam constriction.
The Use of Three Long Rectangular Coils for Neutralization of the Earth's Magnetic Field in a Lens-Type Beta-Ray Spectrometer
Authors: Haynes S. K. , Wedding J. W.
Published: February 2005

Accurate neutralization of the earth's magnetic field Be over a long cylindrical region is necessary to extend the energy range of a magnetic-lens spectrometer to electrons of very low energy. Axial conductors spaced 45° apart on the surface of a circular cylinder of radius a are used to approximate a cosθ distribution. The conductors at π/2 are missing since cosθ vanishes. There are 1/√2 as many conductors at ±π/4 and ±3π/4 as at 0 and π. In the plane transverse to the length of the cylinder, the radial variation of the compensating field is given approximately by the term Be(r/a)6 cos6θ. Beta-rays of a few kilovolts energy, which reach a maximum radius a/2, experience an average residual field of about 0.1 percent of Be which produces a deflection of about 0.1 mm for a one-meter spectrometer. The construction of the coils is described.
An Analog Computer for Flame Gas Composition
Authors: McEwan William S. , Skolnik Sol
Published: February 2005

Specific impulse is an important parameter used to characterize the ballistic properties of a propellant. The calculation of this quantity has been a very tedious task, because a primary phase of this calculation involves the estimation of the composition of the products of combustion. This operation by standard techniques requires the simultaneous solution of ten equations containing ten unknown concentrations of reaction products for propellant systems composed of carbon, hydrogen, oxygen, and nitrogen. Iterative procedures have been found most efficient in solving these equations, but these are lengthy even when high speed calculating equipment is employed.

An analog computer has been developed which simulates electrically the conditions of temperature, pressure, and composition of combustion products. These conditions are imposed as resistances in a series of interlocking Wheatstone bridges which, when balanced, produce the required resistances proportional to partial pressures. Mole fractions are obtained by dividing the partial pressures by the total pressure which also is produced as a proportional resistance by the computer.
Single-Channel Analyzer
Authors: Francis J. E. , Bell P. R. , Gundlach J. C.
Published: February 2005

A single-channel analyzer has been built for measuring the pulse spectrum from proportional and scintillation counters; it counts the number of pulses whose heights lie between E and E+ΔE. The interval ΔE or ``window width'' is constant within ±1.2 percent for all values of E between zero and ninety volts. Curves are presented which show that the analyzer performs satisfactorily on the random distribution of pulse amplitudes obtained from counters.
A Radiographic Method of Dilatometry
Authors: Smith A. H. , Riley N. A. , Lawson A. W.
Published: February 2005

A method of dilatometry using x-ray illumination has been developed and applied to measurements of compressibility. Metal samples, 10 in. long and 316 in. in diameter, are subjected to pressures up to 10,000 atmospheres. Observations of the length of the compressed sample are made by causing x-rays to cast a shadow on a photographic plate. The changes in length of the shadow are then determined with a comparator. This technique, which has been used to measure the compressibilities of aluminum, iron, and copper, is easily adaptable to remote measurements of any type involving changes of length, e.g., thermal expansion.
An Automatic Magnetic Balance for the Study of Ferromagnetic Materials
Authors: Robertson R. F. S. , Selwood P. W.
Published: February 2005

An instrument is described for plotting, automatically, magnetization-temperature curves for ferromagnetic substances. The sample is placed on a torsion arm in an inhomogenous magnetic field, and the force to which it is subjected is opposed by a torque applied to a torsion wire by a reversible motor. The shaft of the motor is connected to a Beckmann Helipot, and the motion of the shaft is converted into a change in emf. which is recorded by a Leeds and Northrup Speedomax. The temperature of the sample is also controlled and recorded by the Speedomax. Data on the performance of the instrument are given and sample plots of thermomagnetic runs for Ni, Fe3O4, and Fe3C are shown.
Use of a Photo-Tube to Correlate Contact Separation with Electrical Transients
Authors: Berg O. E. , Stauss H. E.
Published: February 2005

A method is described which permits correlation between the separation of electrical contact points and the transient voltages occurring across the electrical contacts when a current is interrupted. The current from a photo-tube, energized by light passing through an aperture-slit system mounted on the same relay as the contact points, exhibits on a single-triggered oscilloscope sweep the extent of contact separation on a time axis. This trace is superimposed on the same film frame as a subsequent transient voltage trace when the current is interrupted. The double exposure gives an accurate correlation between aperture and transient characteristic, inasmuch as the same sweep speed and sweep trigger are used for both traces and the sweep origin is extremely stable.
Magnetic Electron Multipliers for Detection of Positive Ions
Authors: Smith Lincoln G.
Published: February 2005

Two designs of 15-stage electron multiplier wherein focusing from one beryllium copper dynode to the next occurs in crossed electric and magnetic fields have been developed particularly for detection of weak beams or pulses of positive ions in magnetic fields. One, with dynodes ⅜ in. wide, is usable in fields between about 250 and 460 oersteds while the other, with dynodes ⅛ in. wide, is usable in fields between about 300 and 1100 oersteds. It appears likely that, by using still narrower dynodes, such multipliers can be constructed to operate in fields of several thousand oersteds. Advantages of these designs over previously described multipliers employing crossed fields are the use of about half the number of insulated plates and less tendency, because of uniformity of the electric field, for breakdown and noise, due to ion feedback, to occur. The uniformity of the electric field also allows quite reliable calculation of the spread in transit time. From this it is concluded that, with a modified collecting system, a multiplier could be built with a rise time between 10−11 and 10−10 sec, which is very probably less than could be obtained with a static multiplier.
A Current Integrator
Authors: Bouricius G. M. B. , Shoemaker F. C.
Published: February 2005

A current integrator has been developed which is dependable to ±0.1 percent or better for ion-beam currents of a few hundredths of a microampere or greater.
An Instantaneous Peak Voltmeter
Authors: Tobin Michael W. , Grundfest Harry , Schoenfeld Robert L.
Published: February 2005

The article presents an analysis of the function and limitations of the simple diode condenser charging peak voltmeter circuit. It also describes a new circuit which makes possible instantaneous measurements of amplitudes of random pulses over a wide range of pulse width and frequency and regardless of the amplitude of the previous pulse. The circuit presented is used to measure the peak voltage of square pulses from 0.1 to 20 msec duration at frequencies as low as 0.2 sec, used for stimulation of nervous tissues.
Determination of Small Thermal Expansion Coefficients by a Micrometric Dilatometer Method
Authors: Lement B. S. , Roberts C. S. , Averbach B. L.
Published: February 2005

A method for the measurement of small thermal expansion coefficients in the vicinity of room temperature is described. The thermal expansion of Invar in the room temperature range may be reduced to zero by the elimination of impurities from the basic 36 Ni, bal. Fe composition.
A Continuous Flow, High Temperature Viscosimeter for Drilling Muds
Authors: Hoeppel R. W.
Published: February 2005

A continuous flow, tube viscosimeter is described which permits determination of viscosities and gel strengths of abrasive thixotropic fluids at temperatures up to 250°F. Provision is made for the introduction of treating chemicals into the closed system, while under pressure, without interrupting fluid flow. The new instrument employs a special rubber tube pump which maintains constant flow under various pressures and is unaffected by abrasive materials. Flow characteristics of the pump are discussed, and tube and Stormer viscosimeter data are compared.
A Phase-Sensitive Detector Circuit Having High Balance Stability
Authors: Schuster N. A.
Published: February 2005

A new phase-sensitive detector circuit has been developed having unusually high balance stability. Its inherently fixed balance should make it useful in the many types of servo circuits which utilize phase detected error signals. It has been found to be particularly useful in nuclear resonance measuring circuits.
Magnetic Field Measurements with Peaking Strips
Authors: Kelly Joseph M.
Published: February 2005

The construction of a device known as a ``peaking strip'' and its use in the measurement of static and dynamic magnetic fields to an accuracy of approximately ±0.02 gauss is described. Fields up to several hundred gauss are easily measured using air-cooled back bias coils. Using water-cooled back bias coils, the range is extended to the kilogauss region.
An Automatic Manometric Respirometer
Authors: Morrison Peter R.
Published: February 2005

An automatic manometric apparatus for the continuous determination of oxygen consumption in animals is described. A fixed manometric aliquot of oxygen ranging from 1 cc to 300 cc or larger is admitted through a solenoid valve controlled from an attached mercury manometer, and the time required to consume this aliquot is recorded on a continuous record. The apparatus is simple, compact, convenient, and very flexible, being adaptable for use with many animals under a variety of conditions.
A Hypodermic Pressure Manometer Utilizing the Bonded Wire Resistance Strain Gauge
Authors: Bierman Howard R. , Jenkins Robert
Published: February 2005

The recent development of the bonded resistance wire strain gauge has led to its use as a device for measuring physiological pressure phenomena. Further application of the strain gauge has been as an instrument for measuring intravascular blood pressures and other pressure phenomena in biology and medicine.
Instrumentation of the M.I.T. Cyclotron for the Study of Nuclear Reactions
Authors: Boyer Keith , Gove H. E. , Harvey J. A. , Deutsch Martin , Livingston M. Stanley
Published: February 2005

The emergent beam from the cyclotron has been focused to bombard targets placed in an evacuated chamber behind shielding walls. Heavy charged particle products from the targets can be counted and identified as to charge and mass by three proportional ionization chambers in time coincidence, utilizing the difference in specific ionization near the end of the particle range. Energy spectra at fixed angles are observed with an automatic foil changer which interposes aluminum absorbers between target and detector. Angular distributions can be studied by rotating the detector about the target with a remote-controlled selsyn drive. Rapid automatic recording of data is accomplished with count storage circuits, a beam current integrator, mechanisms for scanning through a preselected set of absorber foils, and a pen-recorder.

Reactions studied to date include (d,p), (d,t), (d,α), (p,d), and elastic and inelastic scattering of protons, deuterons, and α-particles. Targets throughout the periodic table have been used, with special emphasis on the elements available in thin foil form. Research papers published in the Physical Review will present some of the results obtained to date and describe certain correlations observed.
A High Intensity Source for the Molecular Beam. Part I. Theoretical
Authors: Kantrowitz Arthur , Grey Jerry
Published: February 2005

In a standard molecular beam source the maximum attainable intensity in the collimated beam is limited first by the effusion rate through the oven slit, which must be made sufficiently narrow to attain free molecule flow, and second by unfavorable geometrical factors encountered in selecting a collimated beam from random initial velocities. This paper will propose that the first slit be placed in the flow from a miniature high velocity nozzle coaxial with the final beam. The nozzle converts part (∼¾ for a Mach number of 4 in the design for air to be presented) of the random translational and internal energy of the oven gas into directed mass motion. The mass motion provides an initial rough collimation, which improves both the effusion rate and the geometrical factors, indicating a considerable possible beam intensification (by a factor of ∼75 in the sample design). The velocities of the molecules in the final beam are grouped about the initial mass velocity which provides a partial velocity selection.

In this paper a theoretical design study and estimates of performance of this type of source are given.
A High Intensity Source for the Molecular Beam. Part II. Experimental
Authors: Kistiakowsky G. B. , Slichter William P.
Published: February 2005

The ordinary effusion (``oven'') slit of a conventional molecular beam apparatus was replaced by a slit of special design facing into a supersonic jet from a miniature nozzle. Using ammonia as a test gas, it was observed that at inlet pressures above about 170 mm the molecular beam intensity began to rise far more rapidly than the pressure. The maximum observed intensity exceeded by more than a factor of twenty that obtainable from the effusion slits under optimum conditions and continued to rise rapidly at the highest inlet pressures possible with the available equipment. Certain imperfections of the present apparatus restricted observations to ammonia; their presence indicates that still greater enhancement of molecular beam intensity is possible with an apparatus of refined design.
A Millisecond Timer
Authors: Sturtevant Julian M.
Published: February 2005

A device giving a time delay up to 10-sec duration and having a precision of 1 millisec is described. A simplified form of the device can be employed as a trigger-operated stop clock for timing periods of any length.
A Medium Resolution Replica Grating Spectrophotometer
Authors: Krumholz P.
Published: February 2005

Using the simplest optical parts a monochromator with a nominal band width of about 15A was constructed, covering the range of 3600 to 9000A. This monochromator, in combination with suitable photocells and a direct reading, linear, negative feedback amplifier, permits the determination of extinctions with an error of about 1.5 percent.

The performance of the instrument was checked by measuring the absorption spectra of rare earth ions.
A Micro-Inch Micrometer of One-Tenth Inch Range
Authors: Baker Edward B.
Published: February 2005

Many instruments exist which will magnify small displacements to almost any degree desired but always at the expense of range. The micrometer screw is a notable exception, but does not given an electrical output nor will it measure distance directly and continuously without extra equipment. The present device combines a lever, a micrometer screw, a sensing element, and a servomotor to achieve this purpose.
Automatic Measurement Computation and Recording of Dielectric Constant and Loss Factor against Temperature
Authors: Baker Edward B.
Published: February 2005

An automatically computing and recording instrument for dielectric constant and dielectric loss as a function of temperature at any constant frequency from 50 cps to 600,000 cps is described. Sample curves are shown. Known magnification and zero shift are incorporated to cover the ranges of values encountered in most plastic materials. Automatic correction for and measurement of thermal expansion is incorporated.
An X-Ray Microscope Using Mirrors of Adjustable Curvature
Authors: Lucht Charlys M. , Harker David
Published: February 2005

An x-ray microscope is described in which the mirrors are thin optical flats. These flats are mechanically bent to obtain the radius of curvature necessary to focus the image. The adjustable curvature increases the flexibility of the microscope and the ease of focusing the image. The difficulties of grinding and polishing concave cylindrical surfaces are avoided.

The degree of smoothness of reflecting surfaces was studied, and the anelastic properties of various mirror materials were investigated to find a material suitable for bending. Highly polished tungsten carbide was found to be an excellent mirror material and does not require an evaporated surface coating of high density metal.

The x-ray microscope promises to be a valuable research instrument.
A New Type of High Speed Coincidence Circuit
Authors: Bay Z.
Published: February 2005

A new coincidence device using crystal diodes has been developed. The new circuit does not necessitate equalizing and can be used for pulses with an amplitude spread of two orders of magnitude. The principle of the new circuit is to compare two measurements: one made in one of the channels, and the other made between the two channels. Resolving times down to 3×10−10 sec have been obtained, which represent an improvement of one order of magnitude over former circuits. The improvement in the sensitivity also turned out to be about one order of magnitude. The new circuit should be useful in nuclear experiments in determining decay times, disintegration rates, and for the reduction of noise in scintillation counters.
Scintillation Counting with an EMI 5311 Photomultiplier Tube
Authors: Allen James S. , Engelder Theodore C.
Published: February 2005

The EMI 5311 photomultiplier tube differs from the usual tube in that the electrodes are of the Venetianblind type rather than electron optical lenses. This type of tube has been used as a scintillation counter with trans-stilbene crystals. The shape of the scintillation pulse is characterized by a rise time of 7.2×10−9 sec and a decay time of 1.8×10−8 sec. It is concluded that this type of multiplication structure results in an unusually large spread in the transit time of electrons moving through the structure.
Principle and Design of a New Type Stieltjes Integrator
Authors: Winkler Ernst H.
Published: February 2005

Principle and design of a new type of Stieltjes integrator are described. The general application of such an integrator is given. The advantages of the new design are: (a) the movement of either tracer does not cause a relative displacement of the other tracer from its curve; (b) only rectangular movements are employed; and (c) the mechanical parts are simple and very sturdy. The accuracy obtainable, as determined by sample ingrations, was found to be 0.1 percent if the curves are followed exactly.
Coincidence Methods of Measuring Disintegration Rates of Radioactive Sources
Authors: Barnothy J. , Forro M.
Published: February 2005

Errors involved in the coincidence methods of measuring disintegration rates of radioactive sources are discussed and means to avoid or to evaluate them are given. The disintegration rate of Co60 gamma-ray standard of the National Bureau of Standards is determined experimentally.
A Multiple-Anode Anticoincidence Ring Counter
Authors: Raeth C. H. , Sevold B. J. , Pederson C. N.
Published: February 2005

An annular Geiger-Müller counter with six anodes has been built as a replacement for the usual six-tube charged particle shielding ring in a cosmic-ray anticoincidence bundle. Experiments show that the multiple-anode counter has uniform pulse heights and starting voltages on all anodes, and a slightly higher shielding efficiency than the six-tube ring.
General Theory of Voltage Stabilizers
Authors: Gilvarry J. J. , Rutland D. F.
Published: February 2005

The general linear voltage stabilizer is specified by four independent performance parameters which are necessary and sufficient to determine its performance and an equivalent circuit of four elements is derived to represent it. Corresponding parameters for a stabilizer associated with a load are evaluated in terms of parameters of the stabilizer itself and the load resistance by means of this equivalent circuit. In the case of a stabilizer associated with a load and power supply, corresponding over-all parameters are defined, and the general solution of the problem of expressing the over-all performance parameters in terms of parameters of the stabilizer itself and the load and supply resistances is obtained. Prior results are based on three explicit performance parameters, and the case of the general stabilizer is tractable only by the use of a supplementary procedure to include a fourth parameter. The present results yield an analytical criterion for the case where the three-parameter analysis applies directly and permit direct evaluation of over-all performance parameters in the general case without reference to the internal configuration of the stabilizer. Confirmatory experimental results are presented.
Use of the Piezoelectric Gauge for Internal Friction Measurements
Authors: Marx J.
Published: February 2005

The addition of an auxiliary quartz crystal to the usual composite piezoelectric resonator provides a convenient strain gauge, which simplifies the measurement procedure and permits the evaluation of amplitude dependent decrements over a wide range of strain amplitudes. A unique feature of the new procedure is that virtually instantaneous values of the decrement are obtained, thus bringing transient internal friction phenomena under observation. Mechanical resonance frequencies may be precisely determined for high as well as low decrement specimens. The numerical evaluation of terms is carried out for a recommended driver-gauge construction of 18.5° X-cut quartz bars.
A High Resolution Two-Directional Focusing Beta-Ray Spectrometer
Authors: Bartlett A. A. , Bainbridge K. T.
Published: February 2005

A large beta-ray spectrometer based on the theory worked out by Siegbahn, Svartholm, and others has been constructed. The magnet design is unique in that the return path in iron for the gap flux is provided by a circumferential yoke rather than by an axial core. The mean radius of the electron orbits is r0=30 cm and the maximum acceptable solid angle with present diaphragms is 0.8 percent of a sphere. Construction is discussed and data are presented to show the resolution to be approximately 0.4 percent under these conditions.
Forced Betatron Oscillation in a Synchrotron with Straight Sections
Authors: Blachman Nelson M.
Published: February 2005

The effect of azimuthal variation in the height of the magnetic median plane on the vertical oscillations of a particle in a synchrotron having four straight sections is studied, particularly in the neighborhood of resonance between the frequency of these oscillations and the frequency of revolution. It is found that fourier analysis, which is needed in the case of a circular magnet, is replaced by analysis using modified sine and cosine functions. This investigation also applies to the effect on the radial betatron oscillations of azimuthal variation in the equilibrium radius.
Pulsed Air Core Series Disk Generator for Production of High Magnetic Fields
Authors: Strough Robert I. , Shrader Erwin F.
Published: February 2005

The possibility of the efficient storage of large amounts of energy and its subsequent rapid conversion into useful electromagnetic energy has been studied. Efficient and economical storage of energy is possible in the form of kinetic energy of rotation. Conversion of energy stored in this manner into electromagnetic energy has been accomplished by using the rotating mass as the armature of a series wound homopolar generator. A successful prototype generator has been built and its performance compared with the theoretical operation of such a device. The prototype generator was capable of storing 29,000 joules when operating at 20,000 rpm. When it is operated under short circuit conditions, a current pulse of 56,000 amperes maximum is obtained in the single-turn series field coil. Liquid mercury brushes were developed especially for this generator, since very low circuit resistance is required for self-excited operation. The starting of the flow of mercury in the brush system serves to start the generator in operation. The possible further development and uses of this generator are discussed.
Analysis of Errors in Measuring Thermal Conductivity of Insulating Materials
Authors: Somers Edward V. , Cyphers Joseph A.
Published: February 2005

Thermal conductivity measurements made by the guarded-hot-plate method are subject to error from heat loss by convection at the exposed edges of the sample. Analytical solutions are found and plotted to show the maximum errors for square and round samples in apparatus of various dimensions.
Loop-Line Windowless Flow Geiger Counter
Authors: Damon P. E.
Published: February 2005

The instrument described is of simple and rugged design. The anode is a wire loop, and the cathode includes a grounded line wire which electrically shields the sample. The line wire, when properly placed, provides greater stability and freedom from spurious effects due to the accumulation of a charge on the sample. The geometry is essentially 2π. The instrument may be used for the counting of alpha- as well as soft beta-particles. It is self-shielded.
An Apparatus for Measuring the Rates of Some Rapid Reactions
Authors: McKinney C. Dana , Kilpatrick Martin
Published: February 2005

As a means of studying the kinetics of rapid reactions in which a gas is evolved, a constant volume reactor has been designed. This reactor employs a static technique in which the reaction is followed by the increase in pressure as the gas is evolved. The apparatus is capable of contacting 1 ml of one reactant with 25 ml of a second reactant and obtaining effective mixing in less than 10 milliseconds.

The pressure-sensitive device is a strain gauge, the output of which is plotted as a function of time by a cathode-ray oscilloscope. The apparatus was tested for complete mixing and desaturation of the gas from the liquid phase by means of a reaction known to be very fast. The reaction chosen was the homogeneous reaction between the permanganate ion and hydrogen peroxide in acid solution.

The reaction between lithium borohydride and sulfuric acid was found to have a half-time of approximately one second. The half-time of the reaction between sodium-potassium alloy and ethanol was only a few milliseconds. The reactions of aluminum borohydride and ethylaluminum sesquihydride with water and with acids also were studied.
A Dee Biasing System for a Frequency Modulated Cyclotron
Authors: Davenport L. L. , Lavetelli L. , Mack R. A. , Pote A. J. , Ramsey N. F.
Published: February 2005

The requirements that must be met by a satisfactory dee biasing system are outlined. A successful and simple means of meeting these requirements is described.
Magnet Current Stabilizer
Authors: Sommers H. S. , Weiss P. R. , Halpern W.
Published: February 2005

The design and performance of a feedback amplifier for the precision control of the current through a 40-kw magnet is described. The system uses the difference between the IR drop in a standard resistor and a preset potentiometer voltage to control the current. The principal components are a high gain vibrator amplifier and a stabilized power amplifier incorporating a commercial motor-generator set. Current fluctuations are kept below one part in a million.
Rapid and Sensitive Spectrophotometry. II. A Stopped-Flow Attachment for a Stabilized Quartz Spectrophotometer
Authors: Chance Britton , Legallais Victor
Published: February 2005

The stabilization of the light sources and the photocell circuits of a quartz spectrophotometer and the design of suitable stopped flow apparatuses are described. The latter have been designed for 1.6- and 10-mm optical paths and have been shown to give rapid mixing (<0.1 sec). Errors of optical density measurement are diminished by rectangular observation tubes, and errors of extinction coefficients are minimized by a narrow spectral interval (less than 2 mμ from 230–600 mμ). The error of optical density caused by the photoelectric circuits is about 1×10−4 for a response time (10–90 percent) of 1 sec. The application of this apparatus to the measurement of rapid chemical reactions in the visible and ultraviolet regions is described.
Scintillation Detector for the Localization of Radioactive Concentrations in Vivo
Authors: Ittner William B. , Ter-Pogossian M.
Published: February 2005

A radiation detection instrument, employing a large naphthalene-anthracene crystal and a concentric conical collimator, for the localization of radioactive concentrations at a distance is described. A simplified method of obtaining the general outline of volumetric distributions of radioiodine is presented.
A Self-Tracking Bridge Detector for Audiofrequency Bridges
Authors: Upham J. L.
Published: February 2005

A tuned bridge detector with a constant band width of 5 cps for use at audiofrequencies is described. The center of this band is clamped electrically to the output frequency of the associated signal generator and deviates less than ½ cps from it. This makes manual tuning of the detector unnecessary. The narrow pass band of the amplifier reduces the noise signal to a very low value and allows detection of a ½-μv signal across a one-megohm input for a continuous range of frequencies from 100 cps to 20 kcps. The indicated noise level is of the order of ½ μv for the one megohm input; this is about the theoretical thermal noise value (0.41 μv for 5 cps, 1 megohm). The final detector signal can be easily used to activate mechanical drives for the two bridge controls in order to maintain balance of the bridge when the measured impedance changes or to reset to balance from an unbalanced condition.
Photoelectric Control Circuits for the Ion Source of a Pressure-Type Electrostatic Generator
Authors: Herwig Lloyd O.
Published: February 2005

A system for the remote control of the ion source of a pressure-type electrostatic generator is described. Control of the ion source located at the high potential is established from ground potential by means of a modulated light beam. An audio oscillator is used to modulate a light source and vibrating reed relays in the receiver are used as frequency selectors.
A Quarter-Square Multiplier Using a Segmented Parabolic Characteristic
Authors: Chance Britton , Williams Frederic C. , Yang Chia-Chih , Busser John , Higgins Joseph
Published: February 2005

A circuit for multiplying two varying voltages based on the ``quarter-square'' method has been developed. A segmented nonlinear element is used for squaring, and a time-sharing scheme permits the use of a single squaring element instead of duplicate elements as in previous designs. The circuit has a time delay of less than 40 microseconds (0–67 percent) and has an accuracy of better than ±1 percent. The original circuit was designed to operate only in the first quadrant. Various methods for including the four quadrants are discussed.
An Application of Mass Spectrometer Analysis to the Study of Respiratory Metabolism
Authors: Pratt Arnold W. , Burr Bernard E. , Eden Murray , Lorenz Egon
Published: February 2005

An application of the mass spectrometer to the study of the respiratory metabolism is described. In this application an unmodified mass spectrometer is used for high precision measurements of both the normal and abnormal components in the collected samples. From these data the oxygen consumption rate, the carbon dioxide formation rate, and the respiratory quotient are calculated for physiological interpretation.
Natural Radioactivity as a Tracer in the Sorting of Aerosols According to Mobility
Authors: Wilkening M. H.
Published: February 2005

Natural radioactivity in the atmosphere is used as a ``tracer'' in the study of aerosol particle-size distribution in the submicroscopic range. Particulate matter is collected by a device which first ionizes the particles and then separates them according to their mobilities. The results indicate that most of the natural radioactivity in the atmosphere attaches itself to particles having diameters in the range 0.001 to 0.04 micron. A predominant grouping of the activity occurs in the vicinity of two particle diameters: 0.009 and 0.018 micron. The relationship between the distribution of radioactivity and the abundance of particles in different size ranges is discussed.
On the Resolution of Short Time Intervals with Scintillation Counters
Authors: De Benedetti S. , Richings H. J.
Published: February 2005

A simple coincidence circuit of resolving time of the order of 10−9 second is described. Performance tests showed that, when the pulse-height distribution is constant during an experiment, this circuit can resolve time differences of the order of 10−10 second.
Drift Velocity of Electrons in Argon
Authors: Colli Laura , Facchini Ugo
Published: February 2005

Drift velocity of electrons in pure argon and in argon-nitrogen mixtures has been measured with a parallel plate ionization chamber. Argon was purified by a calcium-magnesium filled convection current purifier. Results for pure argon agree with those of Nielsen. Sensitivity of drift velocity against argon purity was investigated by adding to argon small amounts of nitrogen. The purifier's efficiency in regards to the most common impurities contained in tank argon was tested by absorbtion of given fractions of these impurities previously added to pure argon.
The Effect of a Low Absorption Coefficient on X-Ray Spectrometer Measurements
Authors: Keating D. T. , Warren B. E.
Published: February 2005

In x-ray spectrometer measurements with a flat sample, low absorption produces an asymmetric broadening and displacement of the measured peak. The distortion of the peak due to low absorption can be corrected by an expression involving only the measured peak shape and its derivative. The distortion can also be corrected by the Stokes method of Fourier analysis, and values of the coefficients are given for a suitable range of experimental conditions.
The Determination of Gamma-Ray Energies from Beta-Ray Spectroscopy and a Table of Critical X-Ray Absorption Energies
Authors: Hill R. D. , Church E. L. , Mihelich J. W.
Published: February 2005

The significance and limitations of the use of x-ray absorption energies in the determination of gamma-ray energies from beta-ray spectroscopy are discussed. A complete table of critical x-ray absorption energies, based primarily on the work of Siegbahn and derived using the 1950 values of the physical atomic constants, is given, with interpolation and extrapolations for elements between Z=3 and Z=100.
A Logarithmic Counting-Rate Recorder
Authors: Shaw Denman , Weltmann Ruth N.
Published: February 2005

A counting-rate recorder is described which in conjunction with a commercial scaler and associated circuits will plot directly points that are proportional to the logarithm of the time for a predetermined number of counts. The record of the logarithm of the counting rate on a linear scale is obtained from the angle of rotation of a cylinder by means of a logarithmic spiral cut helically around the cylinder, where the angle of rotation corresponds to the time interval. Instrument errors are shown to be less than one percent.
Double-Flash Microsecond Silhouette Photography
Authors: Edgerton Harold E.
Published: February 2005

Equipment is described to take double-exposure silhouette photographs of rapidly moving objects. Each exposure time is about ⅕ microsecond, and the time interval between flashes is adjustable. An eight-inch square Ektalite Fresnel lens is used as a field lens to focus the light from the illuminating spark into the camera lens; it is especially useful for subjects where the lens is frequently damaged.

Timing of the first spark is conveniently made for explosions by a photoelectric tube triggered by the light of the explosion. A double exposure photograph of a dynamite blasting cap is given as an example.
Exceptionally Stable Regulated Power Supply for Electrometer Tubes
Authors: Senett William P. , Pierce Russell W.
Published: February 2005

The possibility of producing a highly stable regulated power supply with simple circuit design is discussed. To demonstrate the theory, a supply for an FP54 amplifier was built. Performance tests show the output of 80 volts and 100 ma to be regulated to several parts per million for ac line voltage changes of ±10 percent. Drift in the output voltage is about 5 parts per million per hour.
Radiofrequency Mass Spectrometer for Upper Air Research
Authors: Townsend J. W.
Published: February 2005

Electronic circuits have been designed for the Bennett type of radiofrequency mass spectrometer so that it may be used in an experiment devised to obtain the composition of the upper atmosphere. The rocket-borne spectrometer samples the spectrum between mass numbers 48 and 5 once per second with a resolution of one part in twenty-five. Data may be obtained between pressure limits of 8×10−4 mm Hg and 2×10−6 mm Hg, corresponding to ambient pressures between 100 km and 160 km, respectively. The entire instrumentation weighs less than 50 pounds and occupies a total of 1.4 cubic feet.
The University of Pittsburgh Scattering Project
Authors: Bender R. S. , Reilley E. M. , Allen A. J. , Ely R. , Arthur J. S. , Hausman H. J.
Published: February 2005

A scattering program at the University of Pittsburgh uses charged particles from the cyclotron (8-Mev protons, 16-Mev deuterons, and 32-mev alpha-particles). An electromagnet focuses the cyclotron beam through an aperture in an 8-ft shielding wall into a scattering laboratory; a second magnet analyzes the beam in energy; a third magnet analyzes the energy of the charged particles produced in the reaction. For 116−in. analyzing slits 1.0 microamperes of 8±0.010-Mev protons are available at the target 31 ft distant from the cyclotron. The reaction particle analyzer can be rotated about the target. The energy dispersion for 5.298-Mev alpha-particles is 0.192 Mev/in. for each analyzer; the momentum resolution is 1 part in 850. The detector is a scintillation counter. The energy determinations at present stage of development are thought to be accurate to ±0.2 percent ascribed to magnet calibration uncertainties. Energies above and below this value are thought to be of the same precision but the actual calibrations have not been completed.
Particle Localization by Means of a Scintillation Detector
Authors: Yuan Luke C. L. , Poss H. L.
Published: February 2005

A cylindrical tube, 8 in. long, 2½ in. in diameter, with flat ends containing scintillation liquid, is placed between two photomultipliers. Neglecting reflection from the side walls, the intensity of light received at a photomultiplier from a scintillation is proportional to the solid angle subtended by the photocathode at the scintillation point. The ratio of two coincident pulses from the two photomultipliers will then determine the location of the scintillation along the tube independent of light intensity or particle energy.

The pulse ratio was obtained by feeding one pulse to the vertical deflection plates and the other to the horizontal ones of an oscilloscope and by measuring the inclination angle of the trace. The trace amplitude is related to the particle energy dissipated in the liquid.

Preliminary results on the localization effect were obtained using cosmic rays. The coincidence pulse from a Geiger counter telescope perpendicular to the scintillation detector was used to unblank the oscilloscope. Uncertainties resulting from statistical variations of the photomultipliers were measured by means of a light source placed at various distances between the photomultipliers to simulate scintillations. It appears that the localization can be feasibly determined within six percent of the length of the scintillator.
The Generation of High Aperture Parabolic Surfaces of Revolution
Authors: Lewis R. E. , Betz H. T. , Rodelius N. W. , Wolfson M.
Published: February 2005

A process has been developed to enable the production of high aperture parabolic surfaces of revolution with little or no hand retouching. An approximately parabolic blank is ground by stroking it with a thin blade held parallel to the axis of rotation. The blade carriage consists of a vertical-motion parallelogram using thin flexing plates as bearings. This assembly is carried on a horizontal-motion parrallelogram which swings on an arc equal to the spherical approximation of the parabolic curve. The horizontal swing reduces the vertical motion required to the difference between the sphere and parabola, thus reducing the tendency toward grooving and chattering. Polishing may be accomplished on the machine by a blade of pitch-impregnated felt.
Proportional Fission Neutron Counters
Authors: Rohr R. C. , Rohrer E. R. , Macklin R. L.
Published: February 2005

Several proportional fission neutron counters are described which use a uranium compound as the neutron sensitive material coated on the inside surface of the cathode. The counters are filled with high purity argon gas which produces very fast, clean pulses. The instruments use a discriminator circuit which eliminates the α-pulses from the uranium and also makes the instrument insensitive to γ-rays. A portable circuit has been developed consisting of two inverters, a discriminator, and a multivibrator. Subminiature tubes are used because of their small size, low current drain, and relatively high amplification factor. A laboratory model of the slow neutron instrument had an efficiency of 0.01 percent for polonium beryllium neutrons.
Squeeze-Section Phase Shifter for Microwave Measurements
Authors: Brady J. J. , Pearson M. D. , Peoples S.
Published: February 2005

The construction and calibration of a squeeze-section phase shifter for microwave measurements is described. A table from which calibration curves may be drawn is included.
Unbacked Thin Films
Authors: Sawyer George A.
Published: February 2005

Thin self-supporting films of SiO have been prepared by evaporation onto Zapon film backings which were afterwards removed by ion bombardment or solvents. The films are approximately 100 atoms thick (8 μg/cm2) and will withstand a 3-mm Hg gas pressure differential over a disk of 8-mm diameter, while passing several microamperes of deuterons in the energy range 30–100 kev. The root mean square scattering angle in the film at 30 kev is 6°.
Thermocouple Temperatures in a Diffusion Cloud Chamber
Authors: Morrison H. L. , Plain G. J.
Published: February 2005

The radial and vertical thermocouple temperatures in a cylindrical diffusion cloud chamber have been measured during operation, using copper-constantan thermocouples supported by a light Bakelite framework. Readings were taken at regular time intervals, beginning with the addition of the solid CO2, through thermal ``equilibrium,'' and until the chamber had ceased to operate upon the depletion of the refrigerant. The vertical thermocouple temperature gradient in the sensitive volume (the lower one-third of the chamber) was found to be approximately 13°C/cm. The addition of heat to the top of the chamber had negligible effect on the vertical gradient in the bottom third of the chamber and hence changed the depth of the sensitive volume only slightly. There appeared to be no appreciable horizontal gradient.
A Cantilever Microtome for Precision Sectioning in Electron and Light Microscopy
Authors: Cocks G. G. , Schwartz C. M.
Published: February 2005

A microtome has been built incorporating the principle of deflection of a cantilever to provide the highly reproducible motion necessary in cutting thin sections for electron microscopy. The prototype has been tested, and representative electron micrographs are shown. Alternative designs are discussed. Certain advantages are realized by the application of this principle. A simple construction with a minimum of precise machining readily provides an accurately reproducible motion. No sliding ways or lubricated bearings are needed. The effects of vibration, static friction, and thermal expansion are minimized. The instrument is easily adapted for cutting thin sections for light microscopy.
Proportional Counters in Corona Region
Authors: Colli Laura , Facchini Ugo , Gatti Emilio
Published: February 2005

The behavior of cylindrical counters filled with argon of various purities has been studied in the corona discharge zone. In this zone the counters act in a normal proportional manner with regard to the detection of α-particles. The amplitude of pulses obtained is found to be independent of applied voltage over an interval of about 1000 volts. The discharge mechanism is briefly discussed.
Analog Computers for Coordinate Transformation
Authors: Fritz Norman L.
Published: February 2005

Problems in multicomponent analysis frequently require repetitive solutions of a set of simultaneous equations in which the coefficient terms do not change. In these cases it is advantageous to obtain a general solution from which the specific solutions may be obtained readily with simple instruments. An instrument is described which will solve a three-equation set as rapidly as an operator can set the values on the input dials and will simultaneously present the three answers with an accuracy of better than 0.2 percent of maximum value. A method is presented for calculating the accuracy of computation for use in the design of instruments of this type.