bluuebunny/crossref_metadata_2025 huggingface dataset:
A D.C. Amplifier for Biological Application
Authors: Bishop P. O. , Harris E. J.
Published: February 2005

The limitations of direct-coupled valve amplifiers are discussed and a method is given for assessing their performance. A multichannel high gain direct-coupled amplifier is described. This was designed for use in biological applications requiring a high input impedance. The input impedance at the grid is greater than 100 MΩ at 10 kc/sec. The frequency response is flat from zero to over 10 kc/sec. Alternative condenser coupling is provided so that the large amplitude very low frequency noise elements may be eliminated. When the amplifier is direct-coupled the zero shift is of the order of 100 μv peak-to-peak over a period of 30 min. Sufficient voltage gain is available for the limit of useful amplification to be set by the noise generated in the input circuit and first amplifying valve. A parallel balanced circuit is used giving a very high discrimination against in-phase signals. Both the input and output are at earth potential.
A Differential Analyzer for the Schrödinger Equation
Authors: Garwin R. L.
Published: February 2005

A rapid differential analyzer of accuracy about 0.5 percent is discussed and its performance reviewed. Extensions to differential equations other than that of Schrödinger are mentioned.
Vibration Studies: Related to Electron Microscopy
Authors: Hamm F. A. , Snowden F. C.
Published: February 2005

This paper describes a convenient scheme for detecting and measuring vibration as related to the performance of an RCA electron microscope (Type EMU). The procedure involves the use of a Webster Model F5P2 phonograph pick-up arm in conjunction with a cathode-ray oscillograph. The cathode-ray oscillograph signal amplitude which represents the vibration of the location being investigated was calibrated by means of a Brush Development Company Type BL-301 vibration pick-up whose voltage output is proportional to the product of the vibration amplitude and the square of the frequency. An audio oscillator was used to calibrate the voltage output of the Webster (rochelle salt) pick-up as a function of frequency. After calibration, these oscillographic measurements may be used to determine absolute mechanical displacements.

Electron micrographs are included to illustrate the image displacements due to several different amplitudes of vibration. Cognizance of vibration is often necessary, especially in high resolution electron microscopy. This scheme may be used as a guide in high resolution electron microscopy.
A Rotating Specimen Mount for Use with X-Ray Spectrometer in Measuring Crystallite Orientation of Cellulosic and Other Textile Fibers
Authors: Segal Leon , Creely Joseph J. , Conrad Carl M.
Published: February 2005

The quantitative evaluation of crystallite orientation in textile fibers by x-ray methods is discussed. It is found that photographic recording and photometering of the resulting films can be replaced by automatic recording on a strip chart with the aid of an x-ray spectrometer with Geiger-Mueller counter. The design and details are given for a specimen holder capable of properly positioning and rotating a bundle of fibers in the x-ray beam so that the 002 or other selected diffraction arc passes before the window of the counter. A tentative procedure is outlined for evaluating, with the aid of this apparatus, the crystallite orientation of a bundle of cellulose fibers. Some typical recordings of the intensity curves of the 002 arcs from ramie, cotton, and high tenacity rayon are presented.
Synchrotron Radiofrequency System
Authors: Dazey Mitchell H. , Franck Jack V. , Helmholz A. C. , Nunan Craig S. , Peterson Jack M.
Published: February 2005

A description of the radiofrequency system of the Berkeley synchrotron is given.
An Electron Pair Spectrometer of Lens Type for Hard Gamma-Radiation
Authors: Siegbahn Kai , Johansson Stig
Published: February 2005

A new type of pair spectrometer is described. The rotation of the image in a short magnetic lens is used to separate negatrons and positrons by putting the pair converter a little aside from the optical axis of the lens. It is then possible to obtain coincidence ``lines.'' The apparatus has been tried on the 2.62-Mev γ-ray of ThC″ and the 2.76-Mev γ-ray of Na24.
A Focusing Device for the External 350-Mev Proton Beam of the 184-Inch Cyclotron at Berkeley
Authors: Panofsky W. K. H. , Baker W. R.
Published: February 2005

A device has been constructed to focus the external beam of the 184-in. cyclotron at Berkeley. The device consists of a cylindrical tube 4 ft. in length and 3 in. in diameter, which contains a longitudinal arc of nearly uniform current density. Such a device will focus any beam of cylindrical symmetry. Owing to the large power requirements of such a device it is applicable only to very short pulsed beams.
Relation between Apparent Shapes of Monoenergetic Conversion Lines and Continuous Beta-Spectra in a Magnetic Spectrometer. II
Authors: Owen George E. , Primakoff Henry
Published: February 2005

The method worked out previously for correcting distortions which affect the apparent shape of a continuous beta-spectrum has been further extended. A general solution of the integral equation governing the relation between the true and the observed spectra is given, and is applied to the correction of the experimental spectra from a 1-mg/cm2 source of Cu64. The kernel of the distortion integral equation is determined from a study of the internal conversion lines of I131 (47 and 330 kev) using sources of various thicknesses from 0.042 to 0.840 mg/cm2. It is found that the discrepancy between the experimental Cu64 negatron and positron spectra and those predicted by the Fermi (``allowed'') theory can be completely understood as a thick source effect.
Theory of the Capture Process in a Betatron-Injected Synchrotron
Authors: de Packh David C. , Birnbaum Milton
Published: February 2005

The investigation of electrons of all possible initial phases and phase velocities at transition between betatron and synchrotron phases of an electron synchrotron has been undertaken with a view toward determining the effect of different ways of applying the r-f. It has been found that for an average accelerator there is an advantage in a moderately slow increase of the voltage from zero to its final value, while for the extreme case where particles enter the transition region with large phase velocity, an asymptotic final radial oscillation amplitude is reached which is independent of the manner in which the voltage is applied, provided only that it is applied adiabatically.
Apparatus for Recording Fluctuations in the Refractive Index of the Atmosphere at 3.2 Centimeters Wave-Length
Authors: Crain C. M.
Published: February 2005

This article describes equipment which is being used for measuring and recording rapid fluctuations in the refractive index of the atmosphere.
Combination Two-Circle Goniometer and X-Ray Spectrometer
Authors: Baron Morton L. , deBretteville A.
Published: February 2005

A combination instrument consisting of a two-circle goniometer and x-ray spectrometer suitable for the study of crystals was designed and fabricated in Squier Signal Laboratory. A crystal can be oriented optically by using the instrument as a goniometer. X-ray techniques can then be used to study the crystal by replacing the collimator and telescope with an x-ray slit system and a Geiger counter. Absolute intensity measurements can be made by fixing the Geiger counter at twice the Bragg angle and rotating the crystal at 8° per hour from θBragg—Δθ to θBragg+Δθ. Back reflection angles of up to 160° are obtainable. The result of a test on synthetic halite (400) reflection, gave a structure factor 12.7 compared with Max Renniger's value of 12.67. No absorption corrections are required with this technique of measuring intensities.
Nuclear Emulsions and the Measurement of Low Energy Neutron Spectra
Authors: Nereson Norris , Reines Frederick
Published: February 2005

An experiment was performed with Ilford Type C2 nuclear emulsion to determine the usefulness of photographic plates for measuring neutron fluxes and spectra by proton recoils in the region of the low energy limit of the emulsion. The results show that the plates give valid data for neutron flux determinations and energy distributions down to a neutron energy of about 0.5 Mev. Below 0.5 Mev the proton recoils give low values for the number of incident neutrons but approximate results can be obtained down to 0.3 Mev by applying a correction factor in this energy region. The experimental results permit a range-energy curve for protons in C2 emulsion to be determined for the energy region from 0.2 to 1.5 Mev. Finally, recoil proton energy distributions obtained from neutron irradiations of C2 plates at various low energy values are presented and discussed.
A High Resolution Beta-Ray Spectrometer
Authors: Bruner Joseph A. , Scott F. R.
Published: February 2005

A relatively inexpensive 180° magnetic focusing beta-ray spectrometer has been constructed, having a principle orbit radius of 15 cm. A radially inhomogeneous field provides essentially perfect focusing of electrons leaving the source within a 33° angle. In operation, with a 1-mm wide source, the transmission is 0.2 percent, the full width at half-maximum of an internal conversion line is 0.4 percent, and the effects of background and scattering are generally inappreciable.
End and Wall Corrections for Absolute Beta-Counting in Gas Counters
Authors: Engelkemeir A. G. , Libby W. F.
Published: February 2005

A37 (2.8 kev Auger electrons) and Kr85 (0.74 Mev β) were used to determine end corrections for gas counters with flat ends and brass walls. The corrections were found to agree with those published previously for C14 (0.154 Mev). Argon-alcohol fillings were used with small quantities of the active gas being studied. Wall loss corrections were measured for Kr85 and calculated for A37, C14, and Kr85. It appears from the results that absolute beta-counting for energies from about 0.01 to 0.8 Mev to an accuracy of one or two percent can be accomplished by the use of flat end Geiger counters applying the corrections indicated.
Scintillation Type Alpha-Particle Detector
Authors: Goldin A. S. , Rohrer E. R. , Macklin R. L.
Published: February 2005

A portable scintillation detector for alpha-survey work is described. The instrument can detect as few as 16 alpha-counts (32 disintegrations) per minute because of the virtual elimination of spurious background. The upper limit of 50,000 counts per minute is not inherent and can be raised by appropriate circuit changes. The instrument is stable and is unaffected by most atmospheric conditions other than strong sunlight. Gamma-radiation up to 14,000 mr/hr gives no detectable response on this alpha-meter. The probe is the size of a GT type radio tube with a shield, allowing access to relatively small spaces. The sensitive area is about 1 in.×½ in. when a 931-A photo-multiplier is used.
The Theory and Properties of Low Voltage Radiation Counters
Authors: Simpson J. A.
Published: February 2005

The behavior of permanent gas mixtures which lead to low breakdown potentials is discussed, and criteria are established for attaining minimum threshold and operating potentials for G-M counters. Curves showing the dependence of counter characteristics upon pressure and electrode parameters have been obtained for various mixtures of neon and argon. The properties of cathode surfaces have been investigated and the criteria for obtaining suitable surfaces for counter operation were found.

Two classes of counters were observed using these permanent gas mixtures. The first class possesses the lowest range of threshold potentials (approximately 115 to 135 volts) at pressures up to approximately 7 cm Hg. They require quenching circuits having relatively long time constants. The second class of counters have threshold potentials in the range of approximately 135 to 210 volts corresponding to pressures from 7 to 50 cm Hg. They operate with fast quenching circuits.

Miniature portable radiation detectors and meters have been made using these detectors.
A Linear Preamplifier for Driving a Long Coaxial Cable
Authors: Lewis Lloyd G. , Robinson James G. , Toll John
Published: February 2005

A circuit for driving a long coaxial cable is described. Its response characteristics permit impedance matching of the coaxial line without sacrificing linearity of response, and make possible a relatively long line between the particle detector and the recording apparatus. The circuit was found to be reasonably stable for long periods of time, even under severe outdoor operating conditions.
A 4π-Radiometer
Authors: Benzinger T. , Kitzinger C.
Published: February 2005

Total radiated heat loss and average surface temperature of living bodies have heretofore required laborious computation from numerous local measurements. The present study introduces the blackbody principle for this objective. Shieldless surface receivers have been designed, and built from identical and symmetrical sets of thermoelectric foil junctions, which were then made different only in their power to absorb or reflect radiation. By means of thermal shunting, they have been rendered stable against air motion up to 8 m/sec. A cavity, when uniformly lined with such receivers, will integrate the measurements of radiated output into every direction of space, permitting a direct recording of the total. The receivers have been developed specifically for application to the human gradient calorimeter now under construction. However, since the laws of radiation apply to cavities of any size or shape, the proper function of blackbody radiometry could be experimentally verified with a smaller number of receivers in a body of 8×8×16 cu. in. The 4π-measurement is practically independent of location, size, or shape of the emittent source. The sensitivity is 76 μv/cal./sec. Full response is attained within 2.4 sec.
Apparatus for Rapid Measurement of Internal Friction
Authors: Fusfeld Herbert I.
Published: February 2005

This paper describes apparatus for measuring internal friction which satisfies the conditions (a) low induced stress amplitude to preclude any plastic flow of the specimen, (b) ability to install specimen within a few minutes after treatment, (c) rapidity of measurement, at a rate of ten to twenty per minute, (d) accuracy of at least one percent.

Longitudinal vibrations are induced by an eddy-current drive, similar to one previously described in the literature, satisfying (a) and (b). Conditions (c) and (d) are obtained by measuring the decay time of free vibrations using vacuum tube trigger circuits and a counter chronograph. Satisfactory measurements can be made with push-button rapidity and simplicity.
Microwave Power Stabilizer
Authors: Munson Ivan K.
Published: February 2005

An apparatus for the power stabilization of medium-level microwave power sources, intended for laboratory use, by means of a degenerative feed-back network connected in tandem with the power source is described. An analysis of the operation of the network is presented, based on obtaining optimum stabilizing action and optimum transmission efficiency for the network. Design of an electrically-operated attenuator (which is a servo device), and its effect on the stabilization characteristics of the network are discussed. A transmission efficiency of 70 percent and a stabilization factor of 21 were obtained in an experimental model.
A Recording Fluxmeter of High Accuracy and Sensitivity
Authors: Cioffi P. P.
Published: February 2005

A recording fluxmeter has been developed which employs one or two integrators and a double element L and N Speedomax recorder for tracing magnetization curves directly on standard coordinate paper. The response of the recorder pen drive mechanism is proportional to the flux density, B, and is controlled by the B integrator. The response of the paper drive mechanism is proportional to the magnetizing force, H, and is controlled either by the magnetizing current, when the specimen is in the form of a ring, or by the H integrator when the specimen is in the form of a bar. Ayrton shunt networks provide flexible B and H scale adjustments. High accuracy and sensitivity are obtained by minimizing the causes of drift. At maximum sensitivity, four interlinkages give a deflection of one mm.
Simple Variable Space Infra-Red Absorption Cell
Authors: White John U.
Published: February 2005

A variable space liquid absorption cell is described for use in the infra-red spectral region. Its range of thicknesses from 5 mm to less than 10 μ makes it suitable for the compensation of absorption by solvents in a double beam spectrophotometer; its accuracy and reproducibility are sufficient for most direct qualitative and quantitative measurements. The minimum volume is approximately one cc, and the leakage is negligible. Its windows of rocksalt may easily be removed and repolished.
Instrument for Directional Studies of Cosmic-Ray Intensity
Authors: Boehmer H. W. , Coolidge J. E.
Published: February 2005

In order to obtain a versatile instrument for directional cosmic-ray studies, and to investigate an indicated correlation of the soft component of cosmic radiation with the present cosmic-ray burst studies being carried on at the University of Colorado a dual cosmic-ray telescope was constructed. Each bank of the telescope consists of five counter trays with nine Geiger counters in each tray. The electronic circuits are connected to give three triple consecutive coincidence trains: 1, 2, and 3; 2, 3, and 4; 3, 4, and 5. By the insertion of eight centimeter-thick lead blocks covering the sensitive area of a Geiger tray between trays 3 and 4, and 4 and 5; a separation of the components of the radiation is possible.

The telescope is adjustable in zenith in 15 degree intervals from 0 to 75 degrees from the vertical. However, in azimuth, in order to investigate asymmetry characteristics, two positions 180 degrees apart are employed. The control of the telescope is entirely automatic with the recording of data being obtained by means of periodic photographs of the indicating panel, showing the counting rate, zenith and azimuthal positions, and the time and date of the measurement. The telescope changes in zenith and in azimuth every forty minutes; the changes in zenith and azimuth being displaced twenty minutes. A cycle of operation, which consists of the step change in zenith from 0 to 75 degrees with the associated alternate azimuthal changes, requires four hours.
Measurement of Secondary Electron Emission from Dielectric Surfaces
Authors: Heydt Howard L.
Published: February 2005

A technique is developed for the rapid and precise measurement of the secondary electron emission properties of certain dielectric surfaces. The dielectric surface is bombarded by primary electrons having energies which produce a secondary emission ratio greater than unity. This establishes the surface potential at a known value. With the known potential difference between the dielectric surface and primary electron source, the energies of the primary electrons are automatically determined for the first instant of surface bombardment. The net current to the dielectric surface at any moment is measured by using a cathode-ray oscillograph to observe the transient current to a metal plate which backs the dielectric. The method has been used to study metallic surfaces and has yielded results which agree very closely with those obtained using the conventional d.c. method of measurement.
A High Speed Expansion Valve for Cloud-Chamber Control
Authors: Shutt R. P. , Whittemore W. L.
Published: February 2005

In order to keep the width of cloud-chamber tracks down to less than 1 mm the time delay between passage of a ray and completion of an expansion must be 10−2 sec. or less. When Geiger counter control is employed it may be difficult to obtain a sufficiently fast acting expansion control valve, particularly for a large cloud chamber. A valve combining a number of principles not all used by others has been constructed. By balancing pressures the movable valve parts can be made very light despite a large valve opening, and the controlling electromagnet can be quite small. Calculations were made concerning all the important design features. Even a small electromagnet must be laminated to insure sufficiently fast decay of its magnetic field. Most of the remaining time delay is caused by the aerodynamic resistance at the valve opening. For a valve diameter of 5.6 cm expansions are completed in 8×10−3 sec. With a power consumption of 0.17 watt a small vacuum tube is sufficient for operation. By balancing pressures one could construct a much larger valve operating as fast as the valve described with only a slight increase in power consumption.
Single Element Verniers Reading Two or Three Dimensions
Authors: Lewis Robert E.
Published: February 2005

By superimposing concentric radial elements on rectangular coordinate rulings, vernier systems may be constructed reading in two or three dimensions without the necessity of any particular angular orientation.

A two-dimensional vernier may consist of one transparent element ruled with concentric circles. The observed tangencies of the circles, with regard to a rectangular grid placed in contact, provide the reading of the additional decimal of the coordinates of the fiducial center of the circles on the grid.

A three-dimensional vernier system may be established by means of a binocular optical system presenting images of spheres concentric with the locating point and images of coordinate boxes in the same space. The tangency of a vernier sphere and coordinate plane indicates the last decimal of the reading.

Angular orientation may be indicated by radial lines near the points of tangency.
Coincidence Circuit for a Scintillation Detector of Radiation
Authors: Elmore W. C.
Published: February 2005

This paper describes a very simple low level coincidence circuit of moderate speed, which is suitable for use with two or more multiplier photo-tubes in a scintillation detector of radiation. The operation of the circuit is analyzed, and performance data given to show its effectiveness in eliminating spurious counts due to noise pulses in the photo-tubes. Some useful modifications of the circuit are suggested.
A 100,000,000-Frame-per-Second Camera
Authors: Sultanoff M.
Published: February 2005

Shock waves close to the edge of explosive charges have been successfully photographed at rates exceeding 100,000,000 frames per second. These ultra-high framing rates are obtained with a multislit focal plane shutter which is transported optically across the film plane by a rotating mirror. Linear shutter speeds up to 3000 meters per second are easily obtained, and the resulting framing rates with the proper selection of slit widths can be varied from 105 to 109 frames per second. Each individual frame is composed of a series of lines, and the degree of ``discontinuity'' across each frame is proportional to the total number of frames.
Arithmetic Operations in a Binary Computer
Authors: Shaw Robert F.
Published: February 2005

The application of binary arithmetic in the computing circuits of a high speed digital computer is discussed in detail. The discussion covers, with numerous examples, the use of complements to represent negative numbers, the corrections necessary in the multiplication process as a result of the use of complements, and additional modifications of the process to simplify mechanization. A special division method well-adapted to automatic computer use is described, and round-off procedures are noted briefly. The article is concluded with a discussion of the storage of negative numbers as absolute values with a sign rather than in complement form.
Improvements in Mass Spectrometers for the Measurement of Small Differences in Isotope Abundance Ratios
Authors: McKinney C. R. , McCrea J. M. , Epstein S. , Allen H. A. , Urey H. C.
Published: February 2005

A Nier-type mass spectrometer and its associated electronic units have been constructed for the purpose of measuring small variations in the abundances of oxygen of mass 18 and of carbon of mass 13 in carbon dioxide, and of oxygen of mass 18 in oxygen gas, to an accuracy of ±0.01 percent of the abundance of these isotopes.

The electronic units of the necessary stability for this degree of accuracy are described. A gas feed system is described which permits fast alternate introduction of the sample of gas to be analyzed and a standard gas into the mass spectrometer. All measurements of the variation in the abundance of the oxygen and carbon isotopes are made with reference to a standard.
Boron Trifluoride Proportional Counters
Authors: Fowler I. L. , Tunnicliffe P. R.
Published: February 2005

Boron trifluoride proportional counters of calculable efficiency for neutron beam measurements are described. It has been found possible to obtain excellent pulse-size distributions with a filling of 60 cm of purified BF3 by ``soaking'' the counters for a long time (up to three months) with BF3 before putting in the final filling. These fillings are stable. Fillings of less than 5 cm BF3 made up to 50 cm with argon have also been studied. With these fillings the pulse-size distributions are very good for both beam and total irradiation conditions. A discussion of the counter efficiencies with particular reference to end correction is given.
Absolute Determination of the Emission Rate of Beta-Rays
Authors: Clark R. K.
Published: February 2005

A technique for the absolute determination of the rate of disintegration of beta-particle emitters is described. The method consists of measuring the rate at which charge is carried away from the active material by the emitted electrons. The effects of ionization are eliminated by placing the material in a high vacuum. The effects of the surroundings (excluding the parts required to support the active material) are reduced by using a tank of large dimensions, and the magnitude of these effects is determined by the use of supplementary surrounding surfaces with various potentials applied to them. Some information is obtained about the effects of the source supporting structures by placing over the active side of the source supporting foil a cover foil identical to it. It is shown that this technique makes possible the measurement of beta-ray activities with high accuracy.
An Infra-Red Microspectrometer for Biological Research
Authors: Wood Darwin L.
Published: February 2005

The apparatus herein described consists of a totally reflecting microscope of numerical aperture 0.6 coupled with a Perkin-Elmer Model 12C infra-red prism spectrometer. The combination makes possible the recording of infra-red spectra of individual cells of biological materials over the familiar range from 1 to 15μ, and has been particularly designed for the study of muscle fibers. The techniques for producing aspheric optics used in the microscope are discussed. Some preliminary performance data are given.
Modification of the Apparatus Used for the Baldes Thermoelectric Method of Measuring Osmotic Pressure
Authors: Kinsey V. Everett
Published: February 2005

The apparatus employed with the Baldes method for determining osmotic pressure has been modified by substituting a breaker-type d.c.-a.c. amplifier for a sensitive galvanometer, thereby permitting its use under conditions where galvanometers are impractical. Precise temperature control of the water bath in which the thermoelements are immersed has been shown to be unnecessary provided the bath is stirred vigorously. A switch made from one block of electrolytically pure copper provides a satisfactory current-reversing mechanism with low interfering contact potentials arising from non-thermostated portions of the circuit.
An Improved Resolving Time Measuring Device
Authors: Roberts B. W. , Perry K. E. , Fluharty R. G.
Published: February 2005

A circuit for measuring resolving times has been developed utilizing the scheme of Curran and Rae with the addition of a delayed pulse of variable width. Any random event initiates a delayed pulse which is fed into coincidence with subsequent pulses giving rise to a sharp increase in the coincidence rate at a delay time close to the resolving time. A theory is given which predicts observed curve shapes and data is given for several counters to illustrate the operation under different counting rates and overvoltages.
An Electronic A.C. Differential Voltmeter
Authors: Rosenthal L. A. , Zablocki H. S.
Published: February 2005

An electronic a.c. differential voltmeter capable of giving a direct reading of the percentage change in voltage in the region of ±10 percent for voltage levels from 1.5 to 150 volts and frequencies between 20 and 200,000 cycles, is presented. The instrument is stable in operation, and simple in design. Experimental observations and circuit details are included.
A Differential Vectorcardiograph
Authors: Briller Stanley A. , Marchand Nathan , Kossmann Charles E.
Published: February 2005

A vectorcardiograph was designed and constructed for the purpose of separating and recording the temporal components (P form, QRS form, and T form) of the spatial vectorcardiogram in two planes.

The equipment consists of a network to convert the patient voltages into an orthogonal set, a three-channel low frequency amplifier, a synchronized timing unit, a dual-beam oscilloscope, a time marker, an electronically operated camera, and a simultaneous direct-writing recorder.
The Double Super-Heterodyne Principle Applied to Dielectric Measurements
Authors: Baker Edward B.
Published: February 2005

By use of two mixers and a common variable local oscillator, a super-heterodyne receiver, such as General Radio Wave Analyzer No. 736-A, can be converted to serve simultaneously as generator and detector. Such an arrangement provides: (1) single dial tuning, (2) absolute freedom from relative frequency drift, (3) the possibility of very narrow band tuning and, thus, improved signal-to-noise ratio. Circuits to accomplish this are described for the range 0–16 kc which occupy no more space than a conventional oscillator, which they replace. Extension of the frequency range to 0–600 kc is possible by simple changes and the use of an RAK-7 commercial receiver, although in this case single dial tuning is not possible. These circuits are particularly useful for automatic balancing dielectric bridges, but should also be very useful in work with vibration and sound, and for filter and amplifier frequency response.
The Elimination of the End Effects in Counters
Authors: Cockroft A. L. , Curran S. C.
Published: February 2005

The operation of cylindrical proportional and Geiger counters near the ends of the wire is examined closely by means of thin sheets of soft homogeneous X-radiation. It is found that small field-adjusting tubes, fitted over the usual grounded guard tubes (where these are required) and maintained at the potential appropriate to their diameter, reduce the end effects to negligible proportions. The computed field distribution is thus confirmed experimentally. Both theory and practice show that the concentric field-adjusting and guard tubes need not be longer than a radius of the counter. The method can be used in designing counters of very short operating length. In practice the technique is simple and it can be applied to the construction of ionization chambers (pulse or steady current type), proportional counters with constant gas gain along the whole wire, and Geiger counters. It insures in each case a precisely defined counting volume.
On the Theory of the Electrostatic Beta-Particle Analyzer. V
Authors: Rogers F. T.
Published: February 2005

Focusing properties of the inverse-radial potential in the spherical electrostatic analyzer for charged particles having relativistic speeds are calculated by a first-order method valid for large values of β=v/c. Extending similar calculations of focusing by the logarithmic potential in the cylindrical analyzer, the treatment stresses deviations from focusing properties for low speed particles, and emphasizes analogies between the characteristics of focusing accomplished by each type of field, wherever possible. Approximate formulas are given by which the diameter of the region of least confusion may be computed for several interesting situations.
A Theory of Diffusion Cloud Chambers
Authors: Shutt R. P.
Published: February 2005

An attempt is made to understand quantitatively the effects of a given gas, gas pressure, vapor, ionization density, and temperature distribution on the operation of diffusion chambers. An integral equation is set up which takes into account diffusion of the vapor through the gas, removal of vapor by condensation, drop growth, and the motion of the drops due to gravity. Temperature distributions necessary to produce tracks through a given depth of a chamber are calculated, applying to a wide variety of different conditions. For example, the average temperature gradient for operation with methanol and air at 1 atmos or hydrogen at 10 atmos exposed to sea level cosmic radiation amounts to 3.6°C/cm while for air at 3 atmos or hydrogen at 30 atmos a gradient of 6.3°C/cm would be required. Because of the formation of uncharged drops at higher operating temperatures and because of the onset of semi-stable convection currents in the light gases operation is expected to become difficult with air at a pressure >3 atmos or hydrogen at a pressure >30 atmos, or with ionization densities >4 times sea level cosmic radiation at 1 atmos of air.
Self-Adjusting Timer for Bullet Photography
Authors: Burlock Joseph
Published: February 2005

An instrument is described which measures a time interval and them immediately generates an interval of time equal to the measured interval, for automatically timing a light source flash for photographing missiles whose velocity cannot be predicted.
Absorption, Reflection, Luminescence Emission, and Excitation Measurements with the Beckman Model DU Quartz Spectrophotometer
Authors: Klick C. C. , Schumacher J. G. , Stokes R. G.
Published: February 2005

Modifications of the Beckman Model DU Spectrophotometer are described which allow it to record continuously emission and excitation spectra of luminescent materials as well as reflection of powders and transmission of solids by point-by-point methods. All the measurements can be made over the wavelength range of 2200A to 7000A. Performance of the instrument is illustrated by measurements made on a thallium activated potassium chloride phosphor.
On Deflection at n = 1 in the Synchrocyclotron
Authors: Hamilton Donald R. , Lipkin Harry J.
Published: February 2005

This paper discusses the theory of a possible method of synchrocyclotron beam deflection in which the orbits expand until the point of maximum Hr(n=1) is reached, after which the ions escape and spiral outward. These spirals should have a uniform starting radius and a small pitch in order to give deflection efficiency of the order of 100 percent; it is shown that this requires a flat maximum of Hr at n=1, and small amplitude of radial oscillation. The radial and vertical oscillations of the beam and the couplings thereof are discussed in detail. It appears that the only field inhomogeneities which must be carefully minimized are those at n=1 and n=0. Limits on radial and vertical oscillations in the immediate vicinity of the ion source are set but the origins thereof in phenomena other than field inhomogeneity are not discussed.
Calorimetry of High Polymers. I. Automatic Temperature Recording and Control of Adiabatic Jackets
Authors: Dole Malcolm , Hettinger W. P. , Larson Norman , Wethington J. A. , Worthington A. E.
Published: February 2005

This paper describes an adiabatic aneroid calorimeter for the measurement of the specific heat of high polymers over the temperature range −20 to 300°C.

The temperature of its adiabatic jacket can be automatically recorded and, for the most part, automatically controlled, thus making possible the convenient study of temperature drifts, heat exchanges, and methods of correcting for such errors. Duplicate experiments have been carried out within an average deviation of 0.5 to 0.6 percent error, but the absolute error may be between one or two percent.
Calorimetry of High Polymers. II. Use of a Watt-Hour Meter
Authors: Dole Malcolm , Larson N. R. , Wethington J. A. , Wilhoit R. C.
Published: February 2005

A method of using an alternating current watt-hour meter for the measurement of electrical energy in calorimetry is described. Reproducibility to better than 0.1 percent is readily obtainable, but the absolute accuracy depends upon the meter calibration.
Self-Quenching Counters Containing Small Amounts of Polyatomic Constituent
Authors: Krumbein A. D.
Published: February 2005

The least amount of quenching constituent, Qm, required to produce self-quenching action in counters filled with rare gas-polyatomic gas or vapor mixtures, was measured as a function of cathode radius and total pressure for methane, butane, and ethyl acetate in helium, neon, and argon. It was found that the variation of Qm with cathode radius and with total pressure was in accord with the Korff-Present theory of quenching action for counters of this type. From these minimum amounts necessary to quench, the average least number of collisions, M12, required to affect electron transfer between the rare gas ions and polyatomic molecules, was calculated for each of the nine mixtures used. M12 was found to vary from about 1 collision/transfer for the ethyl acetate-neon mixture, to over 1000 collisions/transfer for the methane-helium mixture. The order of decreasing values of M12 in each of the three rare gases used was methane, butane, and ethyl acetate, while the order of decreasing values of M12 for any one polyatomic substance in the three rare gases was helium, argon, and neon. An attempt is made to explain these results using the theory for exchange of charge between atomic ions and molecules formulated by Kallmann and Rosen.
An Optically Recording Tambour Flowmeter and a Compensator for Large Volume Blood Flow
Authors: Brecher G. A. , Ritter E. R.
Published: February 2005

An optically recording flowmeter for measuring rate and volume of blood flow in experimental animals by the phlebotomy method is described. The advantages of the flowmeter are its great accuracy, sensitivity, linear calibration, minimal time lag, and above all its simplicity when used with optically recording manometers. In conjunction with a simple ``compensating switch'' for the outflowing blood, it permits measurement of very large volume flows without reduction of the arterial blood pressure.
A Ferromagnetic Hysteresis Potentiometer
Authors: Aspden Harold
Published: February 2005

The potentiometer embodies the principle of the normal fluxmeter method of measuring hysteresis loss but, while retaining the accuracy, enables the measurement to be made in a fraction of a minute. The potentiometer incorporates a number of tappings which are connected to individual contact studs so that by rotating a contact arm the current supplied to a magnetizing circuit can be varied in a cyclical manner between two limiting values. There are intermediate positions of the arm which correspond to intermediate values of current and these values differ by fixed amounts from one cycle of magnetization to the next. The contact arm also forms part of a stud switch so that a search coil can be disconnected from a fluxmeter over the part in each cycle over which the current changes between the intermediate and one of the limiting values. In this way a complete rotation of the arm is made to take a specimen through twelve cycles of magnetization and since the intermediate current values are evenly distributed over a complete cycle the fluxmeter registers a deflection which can be related to the hysteresis loss.
Trajectories in an Axial Focusing Double Lens Spectrometer
Authors: Snowdon S. C.
Published: February 2005

The trajectories of an electron with zero canonical angular momentum (p[open phi]−(erA[open phi]/c)=0) have been computed with third-order accuracy for a 1/(1+x2) axial field shape. By suitably matching the above solutions with a set of similar solutions obtained by shifting the origin, it is possible to obtain the complete zero canonical angular momentum trajectories corresponding to the double lens problem in which the axial field shape approximates rather closely one that is physically realizable. The numerical computations illustrate several typical trajectories. Design considerations are given to illustrate the utility and limitations of the theory.
High Pressure BF3 Proportional Counters
Authors: Tongiorgi V. Cocconi , Hayakawa S. , Widgoff M.
Published: February 2005

Construction and filling procedures are described for neutron proportional counters filled to 101-cm Hg of enriched BF3+20-cm Hg of A.

Examples are given of the plateau and bias curves obtained for different values of the gas multiplication. Characteristics taken at different times after filling are practically identical, which indicates that no deterioration occurs.

The effect of the electron affinity of the BF3 is discussed, and it is shown how the counter parameters affect the survival probability of the electrons, hence the quality of the pulse size distribution.

It has been verified experimentally that negative ions produced by electron attachment are present in the counter gas.
A Transition Nuclear Magnetic Resonance Detector
Authors: Knoebel H. W. , Hahn E. L.
Published: February 2005

A simple circuit for obtaining nuclear magnetic resonance absorption signals has been developed. Conventional modulation of the magnetic field is replaced by frequency modulation of the oscillator, a method which is technically convenient for the accurate measurement of magnetic fields in the range of 1000 to 18,000 gauss. The principles of operation and construction techniques are described in order that the user may readily duplicate results.
Scintillation Counters for Radioactive Sample Measurement
Authors: Anger H. O.
Published: February 2005

A gamma-ray counter for liquid or solid samples is described. It uses an RCA 5819 phototube at room temperature with a thallium activated sodium iodide crystal in the shape of an annular ring. The gamma-ray counting efficiencies of this counter for 2-milliliter samples of Fe59, Co60, and I131 are about equal to the beta-particle counting efficiency of a mica-window G-M counter when counting thin samples. When the counter is heavily shielded, the background is about 160 counts per minute. The phototube operating voltage is not critical since over a wide range of operating voltage the counting efficiency and background count change only slightly. A directional gamma-ray counter is also described.
A Microilluminator for the Study of the Infrared Spectra of Small Samples at Low Temperatures
Authors: Badger Richard M. , Newman Roger
Published: February 2005

An instrument is described which combines the functions of a reflecting microscope and a low temperature cell. It permits infrared absorption spectra to be obtained on single microcrystals at low temperatures, using polarized radiation.
The Design of Four-Tube Decade Scalers
Authors: Fergusson G. J. , Fraser G. H.
Published: February 2005

Design factors affecting the stability and speed of four-tube sixteen-minus-six decade scalers are discussed. A design is suggested in which the stability and speed are limited only by the basic scale-of-sixteen circuit used.
Measurement and Control of the Level of Low Boiling Liquids
Authors: Wexler Aaron , Corak William S.
Published: February 2005

An account is given of a simple, reliable, and generally applicable electrical means for accurately measuring and controlling the level of low boiling-point liquids. The sensitive elements exhibit at least a fivefold voltage difference for nitrogen and at least a five hundred-fold difference for helium depending on whether they are in the liquid or the vapor. Heat transfer characteristics for liquid nitrogen are also noted.
A Solar Furnace of 120 Inches Diameter for Studying Highly Refractory Substances
Authors: Conn Willi M.
Published: February 2005

Previous work with large solar furnaces is reviewed. New developments in the design of the 120 in. (3.05 m) solar furnace are discussed, in particular the mounting of the reflector, the parabolizing of the aluminum shell, and the production of a surface of high reflectivity. Close control of the temperature to which a sample is heated is attained by means of an aluminum cylinder which travels along the axis of the mirror and which controls the amount of radiation incident on the sample. Rotating sectors are used for separating the temperature radiation emitted by the sample and the incident radiation from the sun. Heating tests for obtaining molten materials, glasses, and products of crystallization are discussed. Methods are presented for work approximating blackbody conditions at very high temperatures. A method for the accurate determination of melting points of highly refractory samples under pure conditions is presented.
A Cloud-Ion Chamber
Authors: Cohen Martin J.
Published: February 2005

A new instrument, the cloud-ion chamber, combining the functions of an ionization chamber (utilizing free electron collection) and the Wilson cloud chamber in the same gas volume has been operated successfully for a sensitive time in excess of 1000 hours. From studies of the gas mixtures with argon as the major component, it is shown that an isoamyl alcohol and argon mixture is a satisfactory chamber filling under the operating conditions used.

The operating characteristics of the cloud-ion chamber are described.
A Convenient Micropipette
Authors: Barth L. G. , Sze L. C.
Published: February 2005

A convenient pipette is described, which has an accuracy of about 0.02 microliter. Advantages over previously described types of micropipettes are the relative ease of construction and the simple tools required, without sacrifice in accuracy of delivery.
A Count-Rate Method of Measuring Fast Neutron Tissue Dose
Authors: Hurst G. S. , Ritchie R. H. , Wilson H. N.
Published: February 2005

The problem considered is that of measuring the fast neutron tissue dose. A special proportional counter has been designed whose response to collimated neutrons is such that the number of counts produced is approximately proportional to dose, when the neutron energy is between 0.2 Mev and 10 Mev. The response has been tested experimentally with monoergic neutrons of various energies between 365 kev and 5.2 Mev and at 14 Mev and is in good agreement with the dose curve.
A New Flash Illumination Unit for Ballistic Photography
Authors: Quinn H. F. , Bourque O. J.
Published: February 2005

A description is given of a flash illumination source of very high peak intensity which has been recently developed in this laboratory for use in conjunction with Kerr cell and image converter type cameras.

The electrical circuit of the unit permits three standard commercial flash tubes of the Egerton type to be operated simultaneously using only one energy storage capacitor, one trigger circuit, and a single high voltage power supply.

A comparison is made between the circuit of the present unit and those of previous flash illumination sources particularly with regard to (a) peak flash intensity, (b) effective flash duration, (c) efficiency of conversion of the total stored electrical energy into useful light output, and (d) reliability of triggering.

Possible modifications of the present unit to enable it to be used as a flash source in the conventional ``open shutter-single flash'' photographic technique are discussed.