bluuebunny/crossref_metadata_2025 huggingface dataset:
Device for Matching a Galvanometer or dc Indicator to Its Associated Circuit
Authors: Dauphinee T. M.
Published: February 2005

A simple apparatus for matching a dc galvanometer to any circuit resistance is described. Impedance matching is achieved by use of a chopper and transformer circuit which permits near optimum use of the available power. The circuit can also be used to expand the range of a microammeter or potentiometer recorder for use with thermocouples. Recorder scale expansions by factors of 10 to 30 have been achieved on low resistance thermocouples permitting readings to ±0.05 to 0.02°C with a standard 10 mv instrument.
Nonmagnetic, Vibrationless, Constant Delivery Pump for Biological Solutions
Authors: Brill Arthur S. , Den Hartog Hendrik , Legallais Victor
Published: February 2005

A pump is described which utilizes the Bellofram, a hat-shaped rubber diaphragm, as a seal between a piston and cylinder of Plexiglas. These pumps are used in a gravity-driven flow system which is completely nonmagnetic and vibrationless, and produces flow rates constant within plus or minus two percent. The pumps are also used with a synchronous motor drive which produces flow rates constant within plus or minus one percent. The motor drive makes small but observable magnetic and vibrational disturbances.
Rate of Exhaust Through a Tube or Orifice
Authors: Rothstein Jerome
Published: February 2005

A formula for the rate of exhaust through a tube or orifice given in Dushman, Scientific Foundations of Vacuum Technique, is inconvenient to apply except in two limiting cases. The differential equation from which his formula is derived is solved in another way, giving a simple hyperbolic cotangent formula easy to discuss or apply over the entire range. It is shown that the formula permits of ``ballistic'' use of a tube or orifice to measure pressure surges too rapid or too large to be monitored in the usual way. Several applications are suggested to electron tube manufacture and vacuum processing of various materials.
Some High-Pressure, High-Temperature Apparatus Design Considerations: Equipment for Use at 100 000 Atmospheres and 3000°C
Authors: Hall H. Tracy
Published: February 2005

Three items of equipment are described in detail; (1) A simple-piston and cylinder device capable of generating pressures to 50 000 atmospheres simultaneously with temperatures of 5000°C, (2) a tetrahedral-anvil device that has been successfully tested at 100 000 atmospheres and 3000°C, and (3) a stepped-piston device capable of developing pressures to 200 000 atmospheres at room temperature.

In addition consideration is given to such problems as (a) geometrical elements of design, (b) higher strength materials, (c) use of mechanical anisotropy in design, (d) electrical leads, (e) thermal and electrical insulation, (f) solid pressure transmitting media, (g) binding rings, (h) internal generation of pressure, (i) multistaging, and (j) calibration.
Captive Balloon Refractovariometer
Authors: Crozier Albert L.
Published: February 2005

A system is described for measuring and recording rapid (3 cps) fluctuations of refractive index, humidity (vapor pressure), and temperature using fast response thermistor beads. The system utilizes wet and dry thermistors whose changes are fed into a simple analog computer. The accuracy of the system is 1 part in 107 for refractive index, about 0.1 mbar for humidity and 0.1°C for temperature.

Measurements can be obtained to an altitude of 5000 ft above the measuring site, with an altitude accuracy of ±50 ft under optimum weather conditions.
Isomer Simulator and the Distortion of a Delay Analyzer
Authors: Akpinar Sait
Published: February 2005

The decay statistics of a radioactive parent-short-lived daughter mixture is simulated by means of a circuit which superposes two random series. Daughter half-life and pulse composition can be varied between wide limits. The output distribution of a differential delay analyzer for high input rates, containing disintegrations of short-lived isomeric states in the millisecond range is tested by using the simulator. A formula for such output distributions is given.
Air-Gap Test Cell for Measuring Properties of Sheet Dielectrics
Authors: Reynolds S. I. , Kollath D. A.
Published: February 2005

An air-gap capacitor has been designed to measure the dissipation factor and dielectric constant of sheet insulating materials without making contact with the dielectric. Tests indicate that the loss tangent and dielectric constant values obtained are comparable to those obtained with intimate-contact electrodes. This method provides a means of measuring, over a wide range of thickness, sheet materials which cannot have electrodes intimately fastened to their surfaces.
Liquid Hydrogen Bubble Chamber Expanded by a Piston in the Liquid
Authors: Bolze E. M. , Morris T. W. , Rahm D. C. , Rau R. R. , Shutt R. P. , Thorndike A. M. , Whittemore W. L.
Published: February 2005

A liquid hydrogen bubble chamber with useful volume 6¼×2¾×3 inches has been built which is expanded by a piston operating in the liquid hydrogen. Temperature control is provided by regulating the pressure in the hydrogen reservoir. Satisfactory tracks have been obtained with maximum expansion ratio of 3%, expansion time of about 5 msec, and chamber temperatures from 25.3 to above 27°K. Photographs have been taken with time delay between particles passing through chamber and light flash of 0.05 to 2.0 msec.
Improved NMR Spectrometer
Authors: Mays J. M. , Moore H. R. , Shulman R. G.
Published: February 2005

An improved Pound-Knight-Watkins nuclear magnetic resonance spectrometer is described. The improved spectrometer has an arrangement which reduces frequency fluctuations by a factor of 5–10 at 30 Mc. The spectrometer is capable of stable operation, with sensitive metering, down to an rf level of 0.01 v across the sample coil, an improvement of almost an order of magnitude. The instrument also allows direct measurement of the derivative of χ′, the real part of the susceptibility of the sample.
Field Homogenizing Coils for Nuclear Spin Resonance Instrumentation
Authors: Golay Marcel J. E.
Published: February 2005

The coils described in this paper are assembled in two relatively thin flat stacks which are placed on each pole piece of a nuclear spin resonance magnet. One coil of each coil pair is in each of the two stacks, and each coil pair is so designed that the current circulating in it produces, in the airgap center, a correcting magnetic field describable by one of a set of spherical harmonics. The orthogonal properties of the spherical harmonics render possible substantially independent adjustments of the currents in the several coil pairs, when some spin resonance parameter such as line width is utilized to determine that individual optima are reached.

Experimental coil stacks with 13 coil pairs, for the second, third, and zonal fourth harmonics, have been constructed, and preliminary results obtained by Rex Richards (Oxford) indicate that when a 4-mm spin sample is used, this method can serve to reduce field inhomogeneities to less than 1 part in 108 with few sets of 13 current adjustments.
Electronic Integrator with Immediate Digital Output
Authors: Hisey B. L. , Perl E. R.
Published: February 2005

A method is presented for instantaneously obtaining a numerical value proportional to the area of a recurring voltage transient. The underlying principle is the summation of pulses from a generator whose repetition rate is a linear function of the instantaneous input voltage. The technique allows accurate gating to reduce the effects of unwanted signal and noise and has a high order of stability and linearity. The particular device actually constructed and tested was designed to measure the area of the roughly triangular voltage change, about 1 msec in duration, produced by ventral root nerve fibers activated in a monosynaptic reflex.
Photoelectric Flow Birefringence Instrument of High Sensitivity
Authors: Zimm Bruno H.
Published: February 2005

We have modified a conventional concentric-cylinder flow birefringence instrument (built by the Rao Instrument Company) by adding a photocell and a rotating disk that scans the annulus with a moving spot of light. In this way the optical intensity pattern formed in the image of the annulus by the combination of polarizer, analyzer, and quarter-wave plate is converted into an electrical wave which is then analyzed by an electronic device. Full advantage can be taken of the increased sensitivity to birefringence caused by the presence of the quarter-wave plate, since the presence of a bright background, so disturbing to the eye, is not important to the photocell. In effect, the system is converted to a linear dependence on the magnitude of the birefringence, instead of the quadratic one found in the conventional method of observation. The sensitivity is in fact increased by about a factor of ten over the same instrument used in the conventional way, and at the same time the measurements are made independent of the visual judgment of the experimenter. The linearity of the system also has considerable advantages when extraneous sources of birefringence are present, as is commonly the case.
Rocking-Bomb Calorimeter for Measuring Heats of Solution
Authors: Gunn Stuart R.
Published: February 2005

A calorimeter designed for measuring the heats of rapid reactions such as dissolution and hydrolysis near room temperature is described. The instrument consists of a sealed copper bomb suspended in an evacuated submarine immersed in a thermostat; stirring is accomplished by rocking the assembly through an arc of 150°. Measurements of the heat of solution of potassium chloride in water at 25.00°C have been performed.
Easily Mounted Aluminum Oxide Foils for Windows and Backings
Authors: Hauser Ulrich , Kerler Werner
Published: February 2005

The well-known difficulties with preparation, handling, and mounting of thin foils are avoided by the use of aluminum oxide foils (25 to 250 μg/cm2, or 700 to 7000 A thickness) which are grown on a solid piece of mechanically shaped aluminum that serves also as the necessary robust frame. These foils have excellent properties for an application in the spectroscopy of particle and quantum radiation. A simple method for the mechanical and chemical preparation will be described. The foils are gas tight, smooth, and withstand a considerable pressure. A formula describes the relation between breaking pressure, diameter, and thickness for circular shaped foils.
Fast and Sensitive Magnetic Susceptometer for the Study of Rapid Biochemical Reactions
Authors: Brill Arthur S. , Den Hartog Hendrik , Legallais Victor
Published: February 2005

A Rankine balance type magnetic susceptometer of much greater sensitivity than previously obtained and combined for the first time with a flow system for the study of chemical reactions is described. The instrument can detect in one measurement a change in volume magnetic susceptibility of 5×10−12 emu. The response time is adjustable down to a fraction of a second by means of an electronic servo system. The time resolution of the flow system is presently limited by the flushing time of the cell to five seconds. A time resolution of hundredths of a second is feasible, as is the detection, in one measurement taking a second, of a change of 1.5×10−12 emu corresponding to the rms Brownian force arising from air resistance to the motion of the magnet.
Method of Measuring Sound Velocity Amplitude in Tubes over the Audio and near Ultrasonic Range
Authors: Landecker K. , Imrie K. S.
Published: February 2005

A method of measuring the velocity amplitude of sound waves propagated in hollow tubes is described. A conducting quartz fiber is stretched across a cross section of the tube where the latter is pervaded by the magnetic field of a permanent magnet. The potential difference across the oscillating fiber is recorded on an oscilloscope. Velocity amplitudes have been measured for frequencies up to about 20 000 cps. An approximate relation is derived for the velocity amplitude as a function of the generated potential. It has been found that the method is much freer from disturbances over the above frequency range than a similar method in which the cooling effect by the sound wave on a current heated wire or fiber is used. Some observations made during the production of quartz fibers sputtered with gold are reported.
Swept Frequency Eddy-Current Device to Measure Overlay Thickness
Authors: Hanysz Eugene A.
Published: February 2005

A new instrument is described which enables nondestructive measurements to be made of film and overlay thicknesses. It utilizes the change in electrical impedance of a composite sample resulting from differences in the thickness of the material being measured to cut off a swept-frequency oscillator at a frequency determined by that thickness. Operating frequencies from 200 kc to 20 Mc have been used with frequency-sweep widths, or deviations, up to 10% to measure overlay thicknesses ranging from 0.00005 to 0.007 in. on composite samples in which the conductivity-to-permeability ratio of the base and overlay differ by at least a factor of two. Equations are developed to illustrate the conditions for which a reactance-tube oscillator is employed in a unique manner to make the measurement automatic.
Furnace for the Growth of Naphthalene and Anthracene Crystals
Authors: Lipsett F. R.
Published: February 2005

A furnace for the growth of naphthalene (mp 80°C) and anthracene (mp 217°C) crystals from the melt by the Bridgman method is described. Crystals up to 15 mm diam by 3 ft may be grown. The furnace is simple in construction, and very convenient and reliable in operation.
Compact Curved-Crystal X-Ray Spectrometer
Authors: Birks L. S. , Brooks E. J. , Gourlay G. W.
Published: February 2005

A curved-crystal spectrometer has been designed with all the mechanism except the crystal and detector arms contained in a box 6×7×3½ inches. Three sets of arms are provided for focusing circles of 10-, 20-, and 40-cm radius. Either automatic drive at from ½ to 8 degrees 2θ per minute or manual scanning may be used. Precision-cut commercial gears result in accurate positioning and less than 0.01° 2θ backlash in the drive mechanism. Thus the spectrometer is satisfactory for use with rather perfect crystals such as quartz as well as with the alkali halides. Interchange of crystals and alignment of new crystals is simple and rapid.
Minnesota 10-, 40-, and 68-Mev Proton Linear Accelerator
Authors: Day E. A. , Featherstone R. P. , Johnston L. H. , Lampi E. E. , Tucker E. B. , Williams J. H.
Published: February 2005

A description is given of those features of the University of Minnesota proton linear accelerator which extend the design of the Berkeley linear accelerator. These features are: three separate resonant cavities in series which produce, respectively, beams of 10-, 40-, and 68-Mev protons, as well as appreciable currents when desired at energies between 25 and 68 Mev; a 500-kv ac injector; a 200-Mc amplifier system with three isolated output stages producing 0.6, 2.2, and 3.2 Mw of pulsed power; automatic frequency control systems; phase detectors; phase shifters; magnets; shielding and accessory equipment. The characteristics of the output proton beams are described, and a brief statement is made of the experiments being performed.
Production of Millimicrosecond Pulses by Radio-Frequency Sweeping of the Ion Beam in the Terminal of an Electrostatic Accelerator
Authors: Turner C. M. , Bloom S. D.
Published: February 2005

Apparatus has been installed in the high-voltage terminal of the Brookhaven National Laboratory research electrostatic accelerator for production of ion current pulses in the millimicrosecond range by radio-frequency sweeping of the beam across a limiting aperture between the ion source and acceleration tube. Proton and deuteron pulses with a full width at half-maximum of about 4.5 millimicroseconds are presently available, with a pulse repetition time of 134 millimicroseconds and an average current of 1–2 microamperes. A simple electrostatic refractor rejects alternate pulses to give one pulse per rf cycle. The following advantages of this method are to be noted: (1) It minimizes the production of background radiations by ions which are not used on the target, (2) The reduced duty factor makes it potentially possible to correspondingly increase the instantaneous intensity during pulses. The usefulness of the system has been demonstrated by the measurement of the delayed deexcitation by γ emission of the first excited state in B10.
Simple Digital Correlator
Authors: Collins C.
Published: February 2005

A description is given of a simple electronic correlator which employs punched-tape input and visual digital readout. Cold-cathode counting tubes are used in the arithmetic unit. Several basic design considerations are briefly discussed, and an outline is given of the recent application of the correlator to a problem in meteor physics.
Differential Calorimeter of the Tian-Calvet Type
Authors: Attree R. W. , Cushing R. L. , Ladd J. A. , Pieroni J. J.
Published: February 2005

A differential microcalorimeter of the Tian-Calvet type has been designed and constructed. The galvanometers previously employed have been replaced by a dc amplifier, which materially simplified the construction and operation of the instrument. In addition, this allows an electrical analog integrator to be used which gives directly the heat of reaction.

Sensitivity of the instrument in the range from 0.01 to 2 cal is such that measurements can be made with a precision of 1% or better. Measurements have been made, under ideal conditions, of 0.002 cal with a standard deviation of 0.1%.
Small Infrared Spectrometer
Authors: White J. U. , Alpert N. L. , Weiner S.
Published: February 2005

A small infrared spectrometer has been built for general use in the chemical laboratory. Employing a rock salt prism with a 40- ×50-mm base, it records the spectra of samples linearly in transmittance or absorbance vs wavelength on flat 8- ×23½-inch charts. Its single set of scanning conditions covers the range from 2 to 16 microns in 16 minutes with a resolution of 3 to 4 cm−1 at 10 microns and scattered light of less than 1% at 15 microns.
Effect of Suspension Position on Apparent Values of Internal Friction Determined by Forster's Method
Authors: Wachtman J. B. , Tefft W. E.
Published: February 2005

Values of internal friction determined by Forster's method may be in error by an order of magnitude if the effect of suspension damping is not eliminated. This damping may be reduced by placing the suspension near the nodes of the vibrating specimen, but the suspension must be sufficiently far from the nodes to provide adequate drive and pickup. The effect of suspension damping on measured values of internal friction as a function of suspension position was calculated. The calculated results were compared with experimental results and found to describe the variation correctly. The equation expressing this variation can be used to correct for suspension damping and to obtain the value of the internal friction of the specimen itself. Values as low as 5×10−6 have been determined by this method.
Reversible Photoelectric Fringe Counting
Authors: Eisner R. L.
Published: February 2005

Simple modifications of a Fizeau interferometer are shown which give a sense of direction to the passing fringes, enabling a suitable counting system to operate reversibly. Very fast counts can be made accurately using an electronic circuit actuated by four phototubes sighted on four points in the fringe pattern. An oscilloscope display can be used for fractional fringe interpolation.
Development of the Calorimeter Heat Transfer Gauge for Use in Shock Tubes
Authors: Rose Peter H.
Published: February 2005

A heat transfer gauge suitable for measuring extremely high heat transfer rates under the quasi-transient conditions occurring in shock tubes has been developed. The instrument is based on a calorimetric principle and is made possible by the short steady state times inherent in shock tubes. The technique developed extends, verifies, and supplements the shock tube heat transfer measurements made by thin film resistance thermometers.

The operating principles and experimental experiences with calorimeter heat transfer gauges are reported in some detail.

Much heat transfer data obtained with calorimeter gauges has been collected and published. Experimental measurements of laminar and turbulent heat transfer rates at velocities up to satellite speeds, approximately 26 000 ft/sec, have been reported. Heat transfer rates as high as 40 kw/cm2 have been encountered in these experiments.
Electron Absorption Spectrometer Using an Improved Velocity Analyzer
Authors: Marton L. , Simpson J. Arol
Published: February 2005

An electron absorption spectrometer with an improved velocity analyzer using the principle of individually designed stages for deceleration, dispersion, and reacceleration is described. The instrument is usable over an energy range of 1 to 50 kev and can obtain angular distribution data over a range of ±0.1 radian. The angular resolution is better than 10−3 radian. The demonstrated energy resolution at 20 kev is 0.6 ev. This resolution appears to be limited by the primary beam energy spread which is characteristic of a beam produced by a telefocus gun with a tungsten cathode.
Improved Electrical Differentiation of Retarding Potential Measurements
Authors: Leder Lewis B. , Simpson J. Arol
Published: February 2005

An improved system for obtaining differential spectra from retarding potential measurements by the superposition of a small ac signal on the retarding voltage has been developed. The principal improvements are the choice of the point of injection of the modulation signal, the use of a low impedance preamplifier to improve the accuracy of the energy scale, and the use of a synchronous detector to improve the stability and reduce the effect of noise. The energy profile of a 15-kev electron beam and the characteristic energy loss spectra in collodion and aluminum have been measured. The quality of these measurements illustrates the over-all performance of the present system.
Direct Quartz Crystal Control of a Low-Level Pound-Knight-Watkins Spin Magnetometer
Authors: Blume Richard J.
Published: February 2005

A quartz crystal is placed in the feedback path of the marginal oscillator, between the cathodes of the oscillator tubes. This change results both in greatly improved frequency stability (2 parts in 107 per hour at 30 Mc with the simplest unthermostatted crystal) and a useful increase of signal-to-noise ratio (although not necessarily of noise figure) owing to the rf filtering action of the crystal. Magnetometer operation at an rf level as low as 100 μv across the sample coil, equivalent to an rf field of about 5 μgauss, has been obtained. A magnet servo based on the crystal-controlled magnetometer is discussed.
Measurement of Uterine Forces in Obstetrical Labor
Authors: Marx Thomas I. , Hunter Charles A.
Published: February 2005

An electronic spherometer is described, which has been used clinically for the measurement of uterine forces during obstetrical labor. The transducer, which is taped to the surface of the abdomen, senses change in the radius of curvature of the uterus, and sends a signal from a strain gauge bridge through an amplifier-detector to a recorder. The instrument has been used to analyze muscular coordination of normal and abnormal labor.
Combination Ion Chamber-Proportional Counter Dosimeter for Measuring Gamma-Ray Contamination of Neutron Fields
Authors: Slater M. , Bunyard G. B. , Randolph M. L.
Published: February 2005

A method for measuring low gamma-ray contamination in a fast neutron field is described by which a single detector is operated sequentially as an ionization chamber and as a proportional counter. The range of collecting voltage for which the apparent gas multiplication is independent of particle type or mode of operation was determined. The method attains high accuracy in the measurement of the ratio of neutron to total dose and has been applied to several neutron sources.
Development of an Occluded-Gas Ion Source
Authors: Ehlers Kenneth W. , Gow James D. , Ruby Lawrence , Wilcox John M.
Published: February 2005

An ion source for pulsed operation has been developed which is based on producing a spark discharge between electrodes of a transition metal in which ordinary hydrogen or deuterium has been occluded. The beam consists principally of ions of hydrogen and of the electrode material. No neutral gas is evolved between pulses. High beam-current densities have been obtained, both with axial and with radial extraction. Various methods have been devised for filtering out the heavy-mass components of the beam.
Spherical Apparatus for Measuring the Thermal Conductivity of Liquids
Authors: Schrock V. E. , Starkman E. S.
Published: February 2005

A thin-film spherical conduction apparatus was designed and constructed for application to relatively viscous liquids such as hydrocarbon lubricants over a temperature range from ambient to −100°F and encompassing the solidification temperature. Freedom from the effects of convective heat transfer was demonstrated experimentally. The absolute accuracy of the measurements made with this instrument is believed to be within 2%.
Stark-Effect, Resonant Cavity Microwave Spectrograph
Authors: Verdier Peter H.
Published: February 2005

A K-band microwave spectrograph is described which employs a Stark-modulated resonant cavity as an absorption cell. The cavity is in the form of a circular cylinder of variable length, operating in the TE01p modes. The modulating field is parallel to the cylinder axis, and is sufficiently uniform to permit the resolution of Stark components. The sensitivity of the cavity spectrograph is comparable with that of a wave-guide spectrograph.
Precision Microscope for Large Nuclear Plates
Authors: Kalberg Ivar , Haskin D. M. , Schein Marcel , Zorn G. T.
Published: February 2005

A microscope, with coordinate motions of 21×15 cm which may be used in the analysis of large nuclear plates is described with particular attention given to constructional details. The design includes a magnetic clutch for fixing plate position, a rotating super-stage and dial indicators to observe both horizontal and vertical movement. A stage noise D̄noise≦0.029 μ for cell lengths up to 1 mm was obtained.
Manostat for High-Pressure Operations
Authors: Reamer H. H. , Sage B. H.
Published: February 2005

The maintenance of isobaric conditions at pressures of the order of 10 000 lb/in.2 is sometimes a difficult operation in transport studies. A manostat has been devised which will maintain isobaric conditions with a precision of about 1 part in 100 000 at pressures from 500 to 10 000 lb/in.2. The equipment functions satisfactorily as a pressure transducer for control purposes.
Measurement of Magnetization Curves in High Pulsed Magnetic Fields
Authors: Jacobs I. S. , Lawrence P. E.
Published: February 2005

An extension of familiar techniques in magnetic measurements has been made enabling the direct measurement of magnetization cuves, M vs H, in high pulsed magnetic fields (H ≳ 100 koe.). The sample is placed in the most spatially uniform region of the available field, inside one of a pair of balanced and opposing pickup coils. Their output is integrated and displayed on the vertical deflection plates of an oscilloscope as M, while the integrated output of the empty coil appears on the horizontal plates as H. As presently operated, a magnetization M of ∼30 emu or a volume susceptibility of ∼5×10−4 can be detected with reasonable but not high accuracy. The method is better suited to nonlinear magnetization curves than those methods which involve placing the sample in an inhomogeneous field, and hence may be useful in studying metamagnetics and weak antiferromagnetics.
Improved Method of Gamma-Ray Calorimetry
Authors: Myers I. T.
Published: February 2005

A method of using an isothermal calorimeter is described in which experimental errors are minimized by the proper selection of the time of measurement. The method was applied to the calorimetric measurement of the activity of a 2-curie cobalt-60 source.
Sensitive Single Channel Pulse-Height Analyzer
Authors: Simhi M. , Birk M.
Published: February 2005

A stable sensitive single channel pulse-height analyzer is described, in which 6BE6 pentagrid tubes paralleled by vacuum diodes are used as linear discriminators. The analyzer works with input pulses of 4- to 40-mv amplitude, and it can be operated directly by a scintillation detector. The dead time is approximately 6 μsec, and the stability of the instrument over a period of several days is better than 1%.
Second-Order Contamination in a Neutron Crystal Spectrometer
Authors: Haas R. , Shore F. J.
Published: February 2005

The second-order contamination in the BNL neutron crystal spectrometer is measured for the NaCl(220), NaCl(240), Be(101̄1), and Be(123̄1) reflections over the energy range 0.08 to 5 ev. Reflectivity calculations by Holm for neutrons incident on thin crystals of Be and NaCl are verified experimentally. A method is suggested for rapidly calculating the second-order fraction of the beam using a simple count rate spectrum and the calculated crystal reflectivities.
Flying-Spot Microscope Adapted for Quantitative Measurements
Authors: Box Harold C. , Freund Harold G.
Published: February 2005

Certain quantitative cytological measurements can be made by the addition of relatively simple components to a television flying-spot microscope. The flying-spot system avoids ``distributional errors'' inherent in conventional microphotometry measurements. The microscope has been used to measure the desoxypentose nucleic acid in whole nuclei.
New Electrostatic Accelerator
Authors: Michael Irving , Berners E. D. , Eppling F. J. , Knecht D. J. , Northcliffe L. C. , Herb R. G.
Published: February 2005

A new electrostatic accelerator has been constructed and tested. The entire vacuum system including the accelerating tube and ion source is of bakable construction. The accelerating tube, corona tube, and support column are constructed of thin metal disks hard-soldered to alumina ceramic rings and the insulation length of each is 5 ft. Without the accelerating tube the generator has been operated at potentials in excess of 7 Mv corresponding to gradients of over 1400 kv/ft. With flat disk molybdenum electrodes usable voltage was limited to 2.1 Mv. When these electrodes were replaced by flat disk steel electrodes having smaller beam apertures and provided with side pumpout holes, the accelerator was operated for short times at potentials in excess of 4 Mv corresponding to a tube gradient of over 800 kv/ft. There was no evidence of small discharges or electron loading in the tube. During the course of these tests three tube ceramics were cracked—probably by sparking—and it is now difficult to operate the machine at potentials much above 3.5 Mv. Voltage division is accomplished by a series of negative point-to-plane corona gaps which are enclosed in a tube. The charging belt is equipped with paper staples which are charged by induction. Accelerator voltage is very stable.
Gas Čerenkov Counters
Authors: Atkinson John H. , Perez-Mendez Victor
Published: February 2005

A gas Čerenkov counter is described which is suitable for charged-particle detection in the Bev region (β from 0.980 to 0.999). Calibrations of the counting efficiency are included along with a table of indices of refraction of suitable gases. The use of this counter as a threshold detector to discriminate between elastic and inelastic pions in the momentum range of 1 to 2 Bev/c is discussed. Use of the counter to differentiate between charged particles of different mass in a momentum-analyzed beam is also considered.
Nonmagnetic High-Pressure Vessels
Authors: Paul William , Benedek G. B. , Warschauer D. M.
Published: February 2005

The use of beryllium copper and stainless steel in the construction of pressure vessels to contain 20 000 kg/cm2 is described. Machine drawings are given for the construction of different types of pressure vessels, different types of seal, and methods of introducing electrical leads into the apparatus. Experience in the use of high-pressure vessels and plugs beyond the elastic limit of the construction material is reviewed.
New Method for Graphical Reproduction of Cathode-Ray Oscillograms
Authors: Swank Robert K. , Mroz Eugene A.
Published: February 2005

An automatic device for tracing the wave form of a repetitive oscilloscope pattern has been developed. The wave form is accurately reproduced and enlarged by a conventional X-Y recorder. Because optical and pulse techniques are used, the system is capable of reproducing signals displayed on even the fastest available oscilloscopes. When used with a high-frequency traveling-wave oscilloscope the method is applicable to phenomena in the millimicro-second region and is capable of utilizing time resolution down to 0.1 mμsec. Deflections as small as one micron may be detected. In addition to making oscilloscope measurements faster and more convenient, certain distortions normally encountered in oscilloscopes are obviated.
Small, Lightweight Ionization Gauge Control Circuit
Authors: Benton H. B.
Published: February 2005

A lightweight, compact thermionic ionization gauge control is described which is simpler and more efficient than conventional units. Emission regulation is achieved by using a transistorized feedback amplifier to maintain constant emission current in the presence of variations in supply voltage and pressure. Ion current is measured from 10−8 to 10−4 amp, in a single range, using a Zener diode as a logarithmic element in the collector circuit. Two control units were successfully flown aboard the IGY Aerobee-Hi rocket NN3.14F.
Method for Rapid Determination of Vacuum Outgassing Rates
Authors: Fish Ivory P. S.
Published: February 2005

A method for the rapid determination of vacuum outgassing rates is described. Automatic range selection and automatic recording is used to accomplish this. Outgassing rates from 10−3 to 10−7 torr liter per second can be determined.
Principle of a Semiconductor Manometer in the Pressure Range of 1 to 10−6 mm Hg
Authors: Varićak M. , Saftić B.
Published: February 2005

Experiments investigating the use of semiconductors for low-pressure measurements proved that thermistors give the best results. These experiments led to the construction of thermistor systems consisting of miniature thermistors fixed to thin metal foils. With these systems it is possible to measure pressure changes in the range of 1 to 10−6 mm Hg. The problem of temperature compensation is discussed and it is shown that in the case of thermistors this problem may be resolved by means of the voltage vs current characteristics. A detailed description of the apparatus, including the gauge head as well as the electric circuit and the calibration curves, is given.
Accurate High-Speed Voltage Comparator
Authors: Robertson D. S. , Wadsworth B. F. , Brown S. E.
Published: February 2005

A new high-speed voltage comparator using a silicon capacitor bridge is described. For an input signal with a rate of change of 300 v/sec, the resolution is better than 1 mv. The performance of the circuit is discussed and results are given.
Momentum Estimate from Magnetic Curvature in Distorted Emulsions
Authors: Bellettini G.
Published: February 2005

Kim's analysis of the precision obtainable in momentum measurements from the curvature of the tracks in an emulsion placed in a pulsed magnetic field is furthered taking into account the distortion of the plates. Calculations show that one cannot hope to reach a decisive improvement from a pulsed magnetic field, if the distortion of the plates is not reduced somewhat below present-day values. The use of thicker emulsions is suggested as a possible way of improving the situation.
Control of the Thickness of Evaporated Layers During Evaporation
Authors: Papp G.
Published: February 2005

A method is given with which the progress of evaporation can be checked at any moment simply by counting the number of interference fringes on a control plate located in the vicinity of the target.
Electronic Dodging of Electron Diffraction and Electron Microscope Pictures
Authors: Thun R. , Hass G. , Craig D. R.
Published: February 2005

In electron microscopy and electron diffraction studies, problems of image contrast are frequently encountered. In microscopy numerous objects exhibit, for instance, only low contrast insufficient for a full resolution of the potentially available detail. In diffraction, on the other hand, the sharp decrease of diffraction line and background intensities toward larger scattering angles requires, for a faithful reproduction, density ranges often not available in photographic emulsions. The detail contrast can be enhanced, however, with the aid of a recently developed electronic dodging apparatus called Logetron. The function of this device is described, and its application in electron microscopy and electron diffraction is shown on a few selected examples.
Method for the Study of Deflagration to Detonation Transition
Authors: Gibson Frank C. , Bowser Merle L. , Mason Charles M.
Published: February 2005

A method based on the variation of electrical resistance in a wire element introduced into the charge has been developed for the continuous measurement of burning and detonation rates in opaque materials. The method has been used to obtain data on nonsteady-state phenomena in high explosives, in composite propellants and in liquid fuel-solid oxidizer mixtures.

Composite propellants were found to be readily detonable when modified by the introduction of voids. Studies on liquid fuel-solid oxidizer mixtures, with bubbles of inert gas as well as voids, gave similar results.
Improved Automatic Four-Point Resistivity Probe
Authors: Dew-Hughes D. , Jones A. H. , Brock G. E.
Published: February 2005

A continuously recording automatic four-point resistivity probe is described. This instrument is the most rapid and convenient means for determining the resistivity profile, and hence the distribution of net extrinsic conduction centers along the length, of a polycrystalline bar or single crystal of semiconductor material. It is the only method available for determining the quality of such material within a very short time of its preparation, and thus is important as a quality-control tool in any semiconductor crystal growing operation. It is severely limited by three factors: (1) it is only a surface measurement, (2) it gives no information about the degree of compensation existing in the material, and (3) it cannot detect the presence of electrically inactive impurities. When combined with more complete characterization of samples cut from a few discrete points along the crystal, it is invaluable as a means of interpolation between these discrete points.
Twofold Pulsing of Van de Graaff Beams for Time-of-Flight Measurements
Authors: Lewis H. W. , Bevington P. R. , Rolland W. W. , Rummel R. L. , Wilenzick R. M.
Published: February 2005

A system has been developed which combines pre- and post-acceleration pulsing of the beam from a Van de Graaff accelerator. It has the advantages of low belt charge for a given target current, low background at the detector, and high time resolution. The internal pulser operates at a frequency of 5 Mc and produces bursts 5–10 mμsec long. The external pulser is driven sinusoidally by amplifying the pulses from a pickup loop with a tuned 5-Mc amplifier containing a phase shifter. Synchronization can be accomplished with peak beam currents at the pickup loop as small as 10 μa. The sinusoidal signal at the external pulser is used as the timing reference signal to a Los Alamos time-to-pulse height converter. The burst duration at the target is determined by the amplitude of the sweep voltage applied to the external pulser.
Magnetic Quadrupole with Rectangular Aperture
Authors: Hand L. N. , Panofsky W. K. H.
Published: February 2005

A magnetic quadrupole of rectangular aperture, employing current sheets bounded by iron rather than shaped pole faces to establish the field, is described. The performance of a rectangular quadrupole of aperture 4×23 in. is reported.
Large Crystal Total Absorption Spectrometer
Authors: Standil S. , Loveridge W. D.
Published: February 2005

A total absorption scintillation spectrometer has been built primarily for the study of the neutral component of cosmic radiation. The high energies involved necessitate a large NaI(Tl) crystal (∼70 lb) completely surrounded by an efficient anticoincidence shield. The design and performance of this instrument are discussed.
Precision High-Velocity Detonating Cord
Authors: Abrahamson G. R. , Huber G. B.
Published: February 2005

The accuracy of time delays which utilize detonating cord as the timing element is limited primarily by variations in detonation rate. A commercial detonating cord consisting of a small core of granular PETN explosive within a cylindrical lead sheath has an average detonation rate of 6275 m/sec with a range of 170 m/sec. By subjecting this material momentarily to a hydrostatic pressure of 55 000 psi, the detonation rate (after removal from the pressure chamber) is increased to 8140 m/sec and the range is decreased to 25 m/sec. Thus timing error due to detonation rate variation is reduced ninefold. These effects are attributed to increased density and decreased density variations of the explosive core.

The change in detonation rate of pressed detonating cord with temperature is found to be 0.16 to 0.19 m/sec per °F. This effect appears to be due primarily to density changes induced in the explosive core by the expansion and contraction of the lead sheath.
Use of a Diode Ring as a Four-Quadrant Multiplier
Authors: Wilcox Richard H.
Published: February 2005

At low-voltage levels a diode ring forms an extremely simple four-quadrant passive analog multiplier characterized by reliability, stability, and wide band width. Operation is analyzed theoretically, and experimental tests are described. These show that with care in selecting diodes and adjusting circuit values, 1% accuracy is obtainable at input levels up to 150 mv.
Three-Dimensional Scintillation Dosimeter
Authors: Olde Garth L. , Brannen Eric
Published: February 2005

A dosimeter for electron beams has been constructed which utilizes the luminescence of plastic phosphors under electron bombardment. A phosphor, in sheet form, was placed in a Lucite medium and the luminescence of a small volume of the phosphor was focused on a photomultiplier. By scanning the phosphor, the three-dimensional dose distribution within the medium was determined. Special attention was paid to obtaining the dose close to the surface of the medium by which the electron beam entered.
Low-Impedance Electronic Coulometer
Authors: Hudson J. B. , Dickey F. E.
Published: February 2005

An electronic coulometer is described which has 15-ohms input impedance, precision of 0.003 coulomb per minute, and long time stability of 0.1% of full scale value. Its calibration and testing are described, and means of adapting it to other operating conditions are given.
Temperature Effects in Nuclear Magnetic Resonance Spectroscopy
Authors: Slomp George
Published: February 2005

The effect of temperature on the stability of the Varian V-4300–2 NMR spectrometer has been investigated. The spectrometer was most sensitive to changes in room-air temperature. A change of 0.3°C per minute caused a spectrometer drift of about 20 cps per minute. A change of 0.1°C per minute in temperature of magnet cooling water caused a spectrometer drift of 1 cps per minute. Enclosing the magnet served to minimize effects of air temperature changes but amplified the effects of water temperature changes. Satisfactory control was attained by running the refrigeration units continuously and regulating the temperatures by controlling the suction pressure on the evaporators. Under these conditions spectra were reproducible to within ½ cps.
Grinder for Sectioning Solid Diffusion Specimens
Authors: Schamp H. W. , Oakes D. A. , Reed N. M.
Published: February 2005

A grinder which can be used for sectioning diffusion specimens in which the average diffusion distance is a very few microns is described. Three fixed steel balls are used to determine the grinding plane of the instrument, and the specimen is held with constant orientation at the center of the triangle formed by the balls. The orientation of the grinding plane with respect to the specimen surface can be changed to make the two parallel by adjusting the lengths of the legs to which the steel balls are attached. These lengths can be adjusted over several centimeters, permitting a large variation in specimen thickness and orientation. A differential screw arrangement on each leg makes it possible to orient the grinding plane and crystal surface to within 5×10−6 radian with respect to one another. The shaft on which the specimen remains mounted during the entire grinding procedure can be moved in a line perpendicular to the grinding plane so that the specimen surface protrudes beyond the grinding plane. A solid grinding plate is then used to grind the specimen away until the surface lies in the plane. Since no loose grinding compound is used, the material removed from the specimen can easily be collected for preparing a radioactive slide. It is also possible to assay the radioactivity of the specimen itself. The motion of the shaft, and, consequently, the thickness ground away, is measured directly using an electronic indicator and is checked every 10 μ against gauge blocks. It is estimated that sections parallel to within 10−5 radian and with the thickness known to the order of a few hundredths of a micron can be removed with the device, the lower limit on the thickness of the slice being about 1 μ.
High-Power Pulse Steepening by Means of Exploding Wires
Authors: Janes G. Sargent , Koritz H.
Published: February 2005

A circuit technique is described which reduces the rise times of high-power pulses by means of exploding wires. This circuit is a nonlinear lumped parameter transmission line. The magnetic energy is stored in the interstage lead inductances and rapidly transferred into (or more correctly, shared with) succeeding stages by the vaporization of exploding wire resistive fuse elements connected in shunt between the leads. In our case, each of three resistive fuse elements consisted of 20 to 50 parallel 0.001-in. diam copper wires held in place across a 2-in. gap with pressure sensitive tape. An empirically determined arrangement is described wherein we have increased the maximum rate of current rise from 300 000 amp/μsec to 800 000 amp/μsec. Using this technique, a magnetic field of 10 000 gauss is built up in 0.15 μsec throughout a volume 4 cm in length and 10 cm in diameter.

It will be shown that the best results are obtained with high conductivity fuse materials such as copper or aluminum. Similarity theorems are presented for the design of pulse steepening elements for use with circuits having similar pulse shapes but different energies and characteristic impedances.
Nonproportionality in Bayard-Alpert Ionization Gauge and the Ultimate Vacuum Determination of Diffusion Pumps
Authors: Mizushima Y. , Oda Z.
Published: February 2005

The nonproportionality between the ion current and the electron current in a Bayard-Alpert ionization gauge is systematically examined and theoretically treated. The effective pumping speed is so modified as to include the effect of back diffusion of oil vapor from the diffusion pump and the contribution of ionization pumping. The theory is experimentally verified in some respects to deduce a new criterion for the maximum attainable vacuum with the diffusion pump. Oil and mercury diffusion pumps are compared to deduce the superiority of mercury pumps for obtaining ``ultra-high'' vacuum. The best vacuum (in normal working conditions) is 10−9∼10−8 mm Hg with oil and 10−11 mm Hg with mercury.