bluuebunny/crossref_metadata_2025 huggingface dataset:
The Production and Measurement of Surge-Ignition Sparks
Authors: Richmond J. Kenneth , Furno A. L.
Published: February 2005

In order to be able to study effectively the flammability characteristics of mixtures of hydrocarbon vapors and air, a surge generator, oscillograph, and associated equipment have been designed to deliver suitable ignition sparks and to study their characteristics. The duration, energy content, and wave shape of these sparks have been measured and studied to determine the effect that these spark parameters might have on the ignition process.
A Precision Current Integrator of Medium Sensitivity
Authors: Lewis I. A. D. , Collinge B.
Published: February 2005

A current integrator is described which will integrate currents in the range 10−10 to −5 ampere. It is shown that the circuit is inherently capable of a better performance than previous integrators. The instrument can be easily calibrated and has a stability of the order of 0.1 percent.
Factors Influencing the Life of Self-Quenching Counters
Authors: Friedland Stephen S. , Katzenstein Henry S.
Published: February 2005

Utilizing two counters connected together with a valve, thus enabling the gas from one counter to be flushed into the other, the deterioration effects of the gas could be separated from those of the wire and cylinder. It is shown that the appearance of multiple pulses may be attributed to the dissociation fragments of the gas, whereas the changes in pulse height are dependent on the condition of the wire and cylinder.
Ion Optics in Long, High Voltage Accelerator Tubes
Authors: Elkind Mortimer M.
Published: February 2005

In the past, the ion optics of long, high voltage accelerator tubes has been a problem usually dealt with experimentally. Based upon a description of a high voltage tube presented by McKibben, a first-order focusing theory is developed essentially through the combined application of geometric optics and Gans' method. The analysis indicates the need for a description of the optical properties of the ion source and its associated electrodes before focusing, magnification, and other characteristics of the over-all accelerator tube can be determined. The application of the theory to a tube and a simple source system is illustrated by an analysis of the focusing characteristics of the Rockefeller accelerator at the Massachusetts Institute of Technology. The results of this analysis yield computed focusing voltages in agreement with those used.
Neutron Measurements with the Brookhaven Crystal Spectrometer
Authors: Borst L. B. , Sailor V. L.
Published: February 2005

A new crystal spectrometer for slow neutron cross section measurements is described in detail. Beryllium has been found to be an exceptionally good neutron monochromator extending the useful range of crystal spectrometers to energies of about 50 ev with good resolution. The characteristics of crystals for use as neutron monochromators are discussed in regard to intensity of the Bragg reflection, resolution, spectral distribution, higher order contamination, and background. Evidence is presented concerning the precision of energy measurements with the BNL spectrometer. The energies of the lowest resonances in the following elements were found to be: iridium E0=0.654±0.003, rhodium E0=1.260±0.004, indium E0=1.458 ±0.005, rhenium E0=2.16±0.01, gold E0=4.93±0.03, and silver E0=5.235±0.035 ev. Comparison with similar measurements made with time-of-flight spectrometers shows that the de Broglie equation for computing neutron wavelengths is valid to within about ½ percent, the precision of present-day experimental observations.
A Bridge for Precise Comparison of AC and DC Voltages
Authors: Cunningham W. J. , Vaughan E. W.
Published: February 2005

A simple bridge circuit is described in which one arm is a high vacuum incandescent lamp. Since the resistance of this lamp varies with the voltage across it, the bridge is in balance only for a single applied voltage. The elements of the bridge can be adjusted for balance with an unknown ac voltage applied. This voltage then can be replaced with a dc voltage, which is adjusted to restore balance. Subject to a known correction, this dc voltage and the rms ac voltage are the same. Precise comparison of ac and dc voltages is possible.
Use of a Geiger Counter for the Measurement of X-Ray Intensities from Small Single Crystals
Authors: Evans Howard T.
Published: February 2005

In a recent crystal structure study, new techniques for intensity measurements utilizing a Geiger counter have been developed and are described. The present application involves the adaptation of standard Geiger-counter circuitry and equipment to a standard Weissenberg x-ray goniometer, so that diffraction intensities given by small (0.1 mm) single crystals are measured by means of a Geiger tube mounted in place of the film holder. The principle of measurement consists of the use of parallel collimated radiation and a scanning of the characteristic x-ray peak in order to obtain the integrated intensity. The measurement is made by totalizing counts on an impulse register while rocking the crystal, and correcting for background by measuring the rate-meter chart record which is made simultaneously with counting. Details of procedure and range of the method are given. The application of the method to the study of the crystal structure of tetragonal barium titanate is described.
A Method for Adjustment of the Zero Setting of an Electromagnetic Flow Meter without Interruption of Flow
Authors: Kolin Alexander
Published: February 2005

The paper describes a means of establishing the reference point of zero velocity for a flow meter scale without stopping the flow. This is accomplished by introducing two auxiliary electrodes which are disposed so that the voltage picked up by them is independent of the rate of flow. The method of adjustment minimizes artifacts caused by movement of the blood vessel in the magnetic field.
A Method of Increasing the Effective Resolution of Scintillation Counters
Authors: Standing K. G. , Peelle R. W.
Published: February 2005

A system consisting of two photomultipliers viewing one scintillating crystal is given for resolving peaks in a scintillation spectrum which otherwise would overlap because of photomultiplier statistics. A differential discriminator accepts pulses from a fixed portion of the spectrum from one of the tubes. Another differential discriminator scans the spectrum from the second tube and is coincidence gated by the first. Experimental results are presented which show that this method can separate monoenergetic lines not otherwise resolved.
A Photoconductivity Apparatus. I. General Circuitry. II. Measurement of Transient Photocurrents
Authors: Miller L. E. , Hamm F. A.
Published: February 2005

An instrument for the measurement of photocurrents is described. It has the advantage of an inherent time response of 0.1 second with an accompanying sensitivity of 2.0×10−13 ampere per inch deflection on the oscillograph screen. These characteristics are shown to be desirable for the evaluation of transient photocurrents.

A short discussion of the application of the instrument to the measurement of transient photocurrents in photographic emulsions is presented. These currents require two seconds to reach a maximum amplitude for a variety of emulsions. Thus the process giving rise to these currents may be electrolytic rather than electronic.
A Temperature-Sensitive Phosphor Used to Measure Surface Temperatures in Aerodynamics
Authors: Bradley Lee C.
Published: February 2005

A thin sheet of a temperature-sensitive phosphor has been used to show the distribution of temperature on the surface of a flat plate in supersonic flow. Calibration of the phosphor is described, and a photograph is shown. Use of a photomultiplier tube permits one to determine the temperature as a function of time, from which recovery temperatures and heat transfer coefficients may be deduced.
RC Memory Commutator for Signal-to-Noise Improvement
Authors: Beard C. I. , Skomal E. N.
Published: February 2005

An electromechanical circuit device is described capable of displaying with small time delay a low frequency, periodic signal wave form initially obscured by noise. The device chops the signal into a large number of intervals, integrates the noise and measures the average value of signal in each interval, and stores these measured values for subsequent presentation. Analysis of the fidelity of signal reproduction and the noise suppression characteristics is included. Rejection ratios of 60 cps interference of 85:1 have been realized. Salient electrical and mechanical features are mentioned to facilitate the construction of other units.
Radioactive Cobalt Laboratory for Chemical Research
Authors: Blomgren Roland A. , Hart Edwin J. , Markheim Leon S.
Published: February 2005

The essential features of two Co60 γ-ray irradiation chambers designed primarily for chemical studies are described. The ``multisource chamber'', holding up to a maximum of five separate Co60 sources in a movable shield mounted on top of the chamber, is designed basically for studies on the effect of dosage rate. Up to a total of 100 curies of cobalt activity may be housed in this chamber. The ``double cavity irradiation chamber'' is provided with a single 400 curie Co60 source which may be lowered into either of two irradiation cavities. One of these cavities is a thermostated well that may be maintained at constant temperatures in the range from −30°C to 130°C. Two intermittent γ-ray devices are also described.
An Instrument for the Direct Measurement of Intense Thermal Radiation
Authors: Gardon Robert
Published: February 2005

A new type of radiometer is described that is suitable for the measurement of the intensity of thermal radiation in the range of 1–100 cal/cm2 sec. The instrument is a simple one. It produces an emf directly proportional to intensity and can be made to have a time-constant of the order of 0.001 sec.

Equations are derived to predict the performance of the instrument, and their results are compared with experimental data obtained from three prototypes.
A Highly Stable Automatic X-Ray Diffraction Apparatus with Only One Moving Part
Authors: Jones Claude K.
Published: February 2005

Modifications are described which have been added to existing automatic x-ray diffraction apparatus. These were added in an effort to obtain accurate and reproducible data of the intensities of x-ray diffraction patterns. The modifications consisted of: (a) the addition of an ionization gauge whose purpose was to keep constant the intensity of the incident beam irradiating a sample and (b) the use of a so-called ``square wave method'' of counting. It has been shown that with these two modifications it was possible to produce records of x-ray diffraction patterns of a powdered crystal which can be duplicated time after time within the limit of errors introduced by the statistical arrival of the diffracted quanta.
The Control and Stabilization of the Magnetic Field for a Mass Spectrometer
Authors: Van Der Walt N. T.
Published: February 2005

A method is described by means of which the magnetic field for a mass spectrometer is stabilized to within one part in 25 000 over a period of 30 minutes at any value of flux density within its variable range of 580 gauss to 9.3 kilogauss.
A Portable 250-Kilovolt Accelerator
Authors: Bergstralh T. A. , Dunning K. L. , Durand E. , Ellison C. H. , Howerton H. K. , Slavin W.
Published: February 2005

A 250-kilovolt linear particle accelerator of a compact and portable design is described. The high voltage is provided by a commercial Cockcroft-Walton type voltage-multiplier supply. A magnetic type ion source is used to supply a focused beam in excess of 300 microamperes.
A Cryostat for Magnetic Susceptibility Measurements at Low Temperatures
Authors: Smith A. Lee , Johnston Herrick L.
Published: February 2005

A cryostat is described which provides excellent temperature regulation and control for magnetic susceptibility measurements in the range 78°K to room temperature. Use of the cryostat with both the Faraday test-body method and the Gouy method is described in some detail. A conveniently used thermostating arrangement is capable of maintaining sample temperatures to within ±0.1° at 115°K over periods of several hours. The method used for the temperature control is of rather general applicability.
Modification of the Scholander Plastic Semi-Microrespirometer for Use with Larger Animals
Authors: Hock Raymond J.
Published: February 2005

A modification of the volumetric plastic microrespirometer designed by Scholander is described. The purpose of this modification is to allow animals the size of small vertebrates to be studied. The principle of operation is exactly the same, but the changes in construction as described make for wider applicability of the original instrument.
An Electric Micromanipulator
Authors: Bush V. , Duryee W. R. , Hastings J. A.
Published: February 2005

A new type electric micromanipulator for experimentation with living cells, or other objects under high magnification, is described. It consists of 4 electrically operated toolholders, each suspended under spring loading by thermal expansion wires. In turn, these are controlled by variable transformers operated by two joy sticks. Selector switches determine which toolholder will be influenced by either joy stick. Ratio control transformers in the 110-volt, line-operated power unit allow an operator precise, normalized, 3-dimensional control of the microtools, viewed under any magnification of the compound microscope. In addition to joy-stick control covering the microrange of 0.5 to 400 microns, each toolholder has 3 sets of mechanical controls to allow coarser adjustments for the range of 0.1 to 10 millimeters. Magnetic chucks and other conveniences for the observer have been provided.
A Single Crystal Extensometer
Authors: Kennedy A. J.
Published: February 2005

A simple mechanical network is described which, when loaded with a constant weight, maintains constant stress on the slip planes of a single crystal extending under creep. It also automatically rotates the grips to eliminate end distortion. The problem of extending the crystal along a fixed time is examined.
Microwave Frequency Standard
Authors: Hedrick L. C.
Published: February 2005

Here described is a high stability UHF source which is used as a microwave frequency standard. Frequency measurement requires the use of a calibrated communication receiver to measure the difference between a known harmonic of the UHF source and the unknown microwave frequency. Frequencies as high as 27 kmc have been measured and the frequency stability is approximately 1 part per million.
A Fast Coincidence-Anticoincidence Analyzer
Authors: Garwin Richard L.
Published: February 2005

A modified Rossi circuit has been extended to a form in which it allows the recording of as many as six coincidence and four anticoincidence pulses with a resolving time of 3×10−9 second. All input pulses are negative and of any amplitude > 3 volts. A complete schematic is given of the circuit which has operated for six months without possibility of adjustment.
Circuit for a Radio-Frequency Spectrometer
Authors: Gindsberg Joseph , Beers Yardley
Published: February 2005

A circuit is described for amplitude stabilization of a regenerative detector for use in nuclear magnetic resonance experiments. A remotely located two-stage dc amplifier converts variations in oscillator grid leak voltage into compensating changes in plate supply potential. The stabilizer circuit adds little stray capacity and does not appreciably affect the oscillator design. The level of oscillation is adjustable from zero to approximately 0.3 volt peak rf signal at the detector grid. Once set, it remains essentially constant over the tuning range (4.8 to 6.3 Mc/sec). A noise figure of 2 or better is obtained. Circuit parameters for the regenerative detector and the stabilizer are given.
A Regulator for a 20- to 250-Kilovolt Cockcroft-Walton Accelerator
Authors: Cook C. J. , Barrett W. A.
Published: February 2005

A regulator has been built to hold the accelerating potential of a Cockcroft-Walton accelerator to within 0.015 percent of any preset potential in the range of 20–250 kilovolts. The regulator is a degenerative type where the error signal is amplified by a galvanometer-phototube dc amplifier system which controls a variable impedance transformer in series with the high-voltage power transformer primary. The regulator is very simple to put into operation. Its action is independent of the potential desired; therefore the range of operation could easily be extended.
Magnet. Part I—Design
Authors: Blewett J. P. , Blewett M. H. , Green G. K. , Moore W. H. , Smith L. W.
Published: February 2005

The magnet of the Cosmotron is designed to provide magnetic fields up to 14 000 gauss over a region roughly 9 in. by 30 in. surrounding the proton orbit of 30-ft radius. The magnet is C-shaped with the magnetic return inside the proton orbit. The magnet gap contour is shaped very precisely to accommodate and control the excursions of the proton beam from its stable orbit. The magnet is energized by current supplied to its water-cooled coil from a 26 000-kva motor-flywheel-generator set. Magnet parameters are tabulated, and the considerations which led to their choice are discussed.
Radio-Frequency System. Part IV—Accelerating Unit
Authors: Blewett J. P. , Plotkin M. , Rogers E. J.
Published: February 2005

The Cosmotron accelerating gap and its associated shield are driven by a broad-band amplifier. The impedance level at the gap is raised to the point at which it can be driven by conventional power tubes, by loading the surrounding shield with ferromagnetic material. Extensive tests on loading materials led to the choice of nickel-zinc ferrite. About 2800 pounds of ferrite are required. Techniques are described for fabrication and assembly of the ferrite structure, and for excitation of the gap by the power amplifier.
The Vacuum System. Part II—Pumping System
Authors: Kassner D. A. , Lasky C.
Published: February 2005

Twelve 20-in. oil diffusion pumps are spaced around the Cosmotron's magnet ring to evacuate the vacuum chamber. These pumps, backed by 8-in. booster pumps and mechanical forevacuum pumps, are connected to manifolds in the wall of the vacuum chamber through 16-in. valves and large rectangular transition boxes. A complete system of interlocks gives fully automatic control. Present minimum operating pressure in the Cosmotron's vacuum chamber is 5×10−6 mm Hg.
Control System. Part II—Timing System
Authors: Dexter E. W.
Published: February 2005

A gated timing system starts at the initial transient of the Cosmotron magnet cycle. Time markers in intervals from 10μsec to 1 sec are available on patch-panel outputs. In addition, outputs are available at single specific times during the accelerating cycle.
The Control System. Part IV—Pickup Electrodes
Authors: Swartz C. E.
Published: February 2005

The circulating proton beam of the Cosmotron is bunched azimuthally by the rf acceleration. The protons pass through insulated electrodes inside the vacuum chamber, and the voltage induced on these plates is used to monitor the beam and to explore its characteristics. The pickup electrodes' signal is well above noise level. It can be displayed on an oscilloscope and utilized in many operations and investigations on the beam.
Studies of Injection Phenomena in the Cosmotron
Authors: Blewett M. H. , Green G. K. , Kassner R. R. , Moore W. H. , Smith L. W. , Snyder H. S.
Published: February 2005

An intensive study of the behavior of the proton beam in the Cosmotron has been made for the period just after injection, before the application of any accelerating field. The actual orbits have been traced for small variations in energy and time of injection in order to obtain optimum injection conditions. These orbits have been used to make further refinements on the adjustments of some of the injection components. The time required for the unaccelerated beam to spiral to the inside wall of the vacuum chamber is used as a basis for the normal injection routine.
Neutron Scintillation Counting by the S(n,p)P32 Process in ZnS(Ag) Phosphors
Authors: Keepin G. R.
Published: February 2005

Evidence is presented for neutron counting by the S(n,p)P32 endothermic reaction in ZnS(AG) powdered phosphors. Preliminary studies have been made on the possible application of this reaction in sulfur-containing crystals to neutron scintillation spectrometry above ∼2 Mev.
Direct Reading of Phase Angles on an Oscilloscope
Authors: Wischmeyer Carl R. , Pfeiffer Paul E.
Published: February 2005

A simple method is described which enables the direct reading of phase-difference angle between voltages applied to horizontal and vertical deflecting plates of a cathode-ray oscilloscope equipped only with a transparent cross-section scale. Accuracies approaching plus or minus one degree are attainable.
Neutron Measurements at Great Underground Depths
Authors: Eugster J.
Published: February 2005

A preliminary report on our first extensive measurements of the cosmic-ray intensities at medium underground (5880 m water equivalent) is given. In these experiments, carried out during 1951 and 1952, two identical portions of photographic plates, one bare and one shielded with Cd, were exposed at identical temperature. For the controls, which were exposed at the surface of the earth, there was found a good agreement between our results and those obtained by Yagoda and Kaplan for slow neutrons. The Cd difference counts obtained at the underground station were much higher than the controls.
A Fast Neutron Scintillator
Authors: Emmerich W. S.
Published: February 2005

A fast neutron scintillator adapted to end-window photomultipliers is described for neutron detection above ∼0.3-Mev energy. Light pulses are produced by the action of recoil protons from paraffine on zinc sulfide phosphor, the optimum weight ratio of the paraffine-zinc sulfide mixture being 3:2. Interfering gamma-ray pulses are suppressed by a 3 microsecond time-constant in the photomultiplier output circuit, and subsequent amplitude discrimination. A detection efficiency of 3.8 percent is attained for 4.1-Mev neutrons through the incorporation of ½-inch deep Lucite light guides.
New Design of a Vacuum Jacket Precision Combustion Calorimeter
Authors: Aitken P. B. , Boxall Helen L. , Cook L. G.
Published: February 2005

A vacuum jacket precision combustion calorimeter has been designed, built, and operated. It is rugged, reliable, and easy to disassemble and assemble. The heat leakage is lower by a factor of six than in the air gap types which have been standard since 1915. The calorimeter appears to be capable of giving individual results which deviate not more than 1.5 parts in 10 000 from the mean.
Detection of Neutrons with a Large Liquid Scintillation Counter
Authors: Reines F. , Cowan C. L. , Harrison F. B. , Carter D. S.
Published: February 2005

A cylindrical liquid scintillation counter, 75 cm in diameter and 75 cm high has been used for the detection of neutrons, gamma rays, and cosmic ray μ mesons. A delayed coincidence technique has been used to detect neutrons; the first pulse corresponding to a recoil proton or other associated event, the second pulse due to neutron capture in cadmium. The capture rate of neutrons in a solution containing toluene and cadmium has been calculated as a function of the cadmium to hydrogen ration by the Monte Carlo method and an experimental check performed. Detector design considerations and some possible uses are described.
Multiple Scattering Correction for Counter Experiments
Authors: Sternheimer R. M.
Published: February 2005

The fraction of the charged particles traversing an absorber in a counter experiment which miss the last counter because of multiple Coulomb scattering in the absorber has been calculated for a general counter geometry. The results are presented in the form of graphs which give the fraction of surviving particles as a function of the counter geometry and the amount of multiple scattering in the absorber. It is shown that the effect of single scattering at large angles is very small.
A Negative Muon Beam and Its Analysis by a Radiochemical Method
Authors: Winsberg Lester
Published: February 2005

A negative muon beam effectively free of pions and secondary particles has been obtained at the 102 Mev π− channel of the Chicago synchrocyclotron by placing a graphite filter 36.0 g/cm2 thick in the beam. The emerging muons were magnetically deflected from the main beam and their energy was shown to be about 50 Mev. A radiochemical method for determining the π−/μ− ratio in the range 10 to 0.01 was used to demonstrate the purity of the negative muon beam.

Although not directly tested, his method for producing a muon beam should work equally well with positive muons.
The Design and Operation of a Magnetic Refrigerator for Maintaining Temperatures below 1°K
Authors: Heer C. V. , Barnes C. B. , Daunt J. G.
Published: February 2005

The problems involved in the construction of a magnetic refrigerator operating below 1°K, using superconducting metallic links for the thermal valves and a paramagnetic salt as the working substance, are discussed. A cycle for the operation of the refrigerator is suggested and then examined for the optimum operating conditions with readily available laboratory facilities. Design equations are obtained and compared with our more recent experimental model. The constructional details of a completely automatic experimental model of the magnetic refrigerator using lead for the thermal valves, iron ammonium alum as the working substance, a helium bath at 1°K as the high-temperature reservoir, a maximum magnetic field of 7000 gauss, a 2 minute cycle of operation, and capable of extracting 120 ergs/second from a reservoir at 0.3°K are presented in full. Temperatures as low as 0.2°K are obtained with this model. Improvements in this this design, its use either for the production of an isothermal reservoir or as a heat sink for adiabatic demagnetization work below 1°K, and the extension to a two-engine refrigerator for the production of a reservoir at temperatures as low as 0.05°K are also discussed.
The Theory of the Three-Crystal Electron Interferometer
Authors: Simpson J. Arol
Published: February 2005

An elementary theory based on light optical analogues is presented. Calculations of fringe orientation are in good agreement with experimental values. The theory leads to a value, based on experimental data, of the coherence length of an electron in excess of 5800 wavelengths.
On the Use of Nuclear Research Emulsions with Embedded Wires
Authors: Silver E. G. , Waniek R. W.
Published: February 2005

The importance of determining the nucleus involved in a specific interaction within a nuclear research emulsion is discussed, and the technique used to embed thin filaments in these emulsions is described in detail. The usefulness of this method is illustrated by an experiment in which nylon, molybdenum, and tungsten wires were embedded in Ilford G5 emulsion, and the plates subsequently used to study neutron induced interactions. The uncertainties encountered and the corrections introduced in this method are analyzed.
A Recording Vacuum Gauge
Authors: Hurd Dallas T. , Corrin M. L.
Published: February 2005

The Langmuir viscosity vacuum gauge has been modified to provide electrical recording of low-pressure data. A particular advantage of this type of gauge is that, once calibrated, it may be used with any gas, including reactive or unstable compounds, or with gases having low condensation pressures.

The gauge utilizes the changing capacitance between a stationary electrode and an oscillating fiber, the rate of damping of which is a function of the composition and pressure of the ambient gas, to modulate the frequency of an oscillator. The output from the oscillator is demodulated in a discriminator circuit, amplified, and recorded. The pressure of the gas is then determined from the recorder trace. Alternatively, the signal may be used to actuate relays or servomechanisms. The fiber is set into oscillation by means of an electromagnet, so the entire operation of the device may be made automatic if desired.
Mutual Inductance Bridge and Cryostat for Low-Temperature Magnetic Measurements
Authors: Erickson R. A. , Roberts L. D. , Dabbs J. W. T.
Published: February 2005

A mutual inductance bridge and cryostat are described which may be used to measure susceptibilities from 77°K, with liquid nitrogen, down to adiabatic demagnetization temperatures. In addition to the sensitivity necessary for measurements over such a temperature interval, the apparatus provides the following features: a usable frequency range of 5 kc, for the study of paramagnetic relaxation and paramagnetic specific heat; measurement of longitudinal susceptibilities in fields up to 3000 oersted, and transverse susceptibilities in fields up to 13 000 oersted; a simple method for changing samples with a minimum dismantling of the equipment.
Diffusion Cloud Chamber of Unusually Large Dimensions
Authors: Relf Kenneth E. , Powell Wilson M.
Published: February 2005

A diffusion cloud chamber 8 ft long, 4 ft wide, and 5 in. deep has been built and operated successfully for 540 hrs out of a continuous 720-hr run. Though the actual area is 32 sq ft, the area photographed was 21 sq ft or approximately 2 sq m. A sensitive layer of good quality extending 2½ to 3 in. above the floor was easily maintained. The coolant temperature was held near −67°C and the air above the glass sheet forming the top was held at 30°C. A clearing field of 30 v (top negative) was found desirable to keep the chamber free from general rain. The chamber contained an air and methyl-alcohol mixture operated at 1 atmos pressure. Tracks in the sensitive region were photographed through the top with the aid of several mirrors. The chamber was used to study the structure of the cores of cosmic-ray air showers. It is now being used for studies with the bevatron.
New Automatic Sharpener for Microtome Blades
Authors: Bishop Francis W.
Published: February 2005

A new compact microtome knife sharpener has been developed which, in its simplest form, provides a semi-manual method of sharpening blades for standard and ultra-thin sectioning. Fully mechanized, however, it eliminates the manual element and requires little attention except to see that the grinding powder and its vehicle are maintained. The knife is caused to move back and forth across an oscillating glass plate by means of a motor drive, and a simple mechanism periodically turns the blade over. It rapidly sharpens a blade capable of cutting ultra-thin sections for electron microscopy while such an edge is unusually fine for paraffin sections. No stropping or other treatment is required.
High Noise Cable as a Sensing Element
Authors: Meryman H. T. , Shirer H. W.
Published: February 2005

The problem of devising a sensing element of the ``burglar alarm'' type which would be highly sensitive, portable, battery operated, and adaptable to any type of terrain was solved by using a shielded cable of high noise characteristics as an extended transducer. By this means, a device of extreme simplicity was developed with sensitivity sufficient to detect almost indiscernible physical deflection.
Recording Dielectric Hygrometer for Expired Air
Authors: Webb Paul , Neugebauer M. Kenith
Published: February 2005

A method for rapid continuous measurement of water vapor in expired air was needed for studies of subjects under cold ambient conditions. The method chosen senses water vapor content by measuring the air dielectric constant. Air passes between the plates of a small capacitor so that changes in the air dielectric constant, which depend on water vapor concentration, cause capacitance changes. These small changes cause resonant frequency shifts in a 2-Mc oscillator. Design features which insure stability in the element and oscillator are presented. The frequency changes are detected by the beat frequency method, converted to proportional linear dc voltage, and used to drive the pen of a magnetic ink-writing oscillograph. The system detects changes in absolute humidity of 1.0-mgm water vapor per liter, but the sensitivity could be increased or decreased for different applications. Precautions regarding the need for simultaneous temperature measurement are pointed out, a sample tracing is shown, and the calibration procedure is mentioned. There is a brief discussion of previous developments along similar lines, followed by a listing of some of the advantages of the method.
A Versatile Projector for Assisting in Crystal Structure Determinations
Authors: Philips William Revel , McLachlan Dan
Published: February 2005

In the determination of crystal structures from x-ray data, mathematical equations are frequently used for which there are no physical analogs available. The introduction of physical analogs is advantageous because they assign a physical significance to the mathematics and, also, because they make possible the use of apparatus which either aids or replaces the long computations. In this paper a description is given of an optical device which produces as photographic records the results of the mathematical processes known as convolutions. Since there are several kinds of convolutions, and since the device is very versatile, the particular types of convolutions for which the apparatus is adaptable are the well-known Patterson projection and, also, the mixed projections. The illustrations that are furnished should aid in the understanding of some of the more recently developed methods of structure determination. The apparatus is constructed of materials readily available in any laboratory.
An AC Cathode-Follower Circuit of Very High Input Impedance
Authors: Macdonald James Ross
Published: February 2005

A cathode-follower circuit of very high-input impedance using ordinary tubes is described. At the coaxial cable input, the capacitance to ground is less than 0.3μμf from below 100 to above 5×104 cps. The magnitude of the input resistance is more than 4×109 ohms from below 100 to 4700 cps; above 3200 cps, its sign is negative and it decreases with frequency. A comparison of theoretical and experimental results is given and a stable modification of the circuit discussed with which it is possible to obtain zero or negative input capacitance.
An Ion Current Integrator
Authors: Littauer Raphael
Published: February 2005

An electronic integrator suitable for measuring ionization currents down to 10−11 ampere is described. The instrument simultaneously displays both the instantaneous value of the current and the total charge received. Automatic recycling is achieved with the aid of a contact mounted on the movement of a standard meter. Substantial lengths of coaxial cable with standard connectors may be connected to the input without producing unduly large leakage currents or changing the calibration, so that remote operation of the integrator is feasible.
A Low-Level Radon Counting System
Authors: Bate G. L. , Volchok H. L. , Kulp J. L.
Published: February 2005

A stable, convenient system for low-level counting of radon is described. The system permits a precision of ±1 percent with an efficiency of about 80 percent. The lower limit of measurement is the amount of radon in equilibrium with about 10−14 gram of radium. A vibrating reed electrometer is used to amplify slow pulses obtained from an ionization chamber operated at 300 volts. The cumulative pulse count is recorded by a mechanical register following amplification of the output of the electrometer. Special care in construction and selection of the ion chamber materials permits an alpha background as low as 15 cph for a 4-liter volume. Chemical pretreatment of the gases is unnecessary for most samples.
A Multichannel Pulse-Height and Delay Time Recorder
Authors: Ortel William C. G.
Published: February 2005

An instrument is described which records both the height of a voltage pulse from a scintillation counter and the delay time between this pulse and a pulse from a BF3 neutron counter. For each scintillation pulse, a delayed pulse is produced whose delay time is a linear function of the scintillation pulse height. This delay time and the neutron delay time are recorded in binary notation on a moving paper chart. Pulse heights are recorded in forty channels and neutron delay times in fifteen channels.
Measurement of High Vacuums at Low Temperatures
Authors: Garfunkel M. P. , Wexler Aaron
Published: February 2005

The general usefulness of the helium mass spectrometer leak detector for measuring very low pressures at liquid helium temperatures is discussed. The required relations between mass flow, pressure, pumping speed, and the dimensions of the apparatus, in which thermomolecular flow plays a major role, are derived. It is shown that the exchange gas in liquid helium calorimeters can be pumped out to pressures below 1×10−10 mm Hg.
A Wide-Range Thermistor Radiometer for the Measurement of Skin Temperature and Environmental Radiant Temperature
Authors: Stoll Alice M.
Published: February 2005

The thermistor radiometer consists of a Wheatstone bridge formed of four thermistors, two of which are exposed to incident radiation and two of which are hidden from it and act as thermal compensators. The output from the bridge is suitably amplified and fed into a microammeter on which deflections are read in microamperes and related to radiant temperatures by means of calibration charts. Calibrations are made against standard blackbody radiators and at present have been carried out for use of the instrument in ambient temperatures between −50°C and +30°C for measuring radiant temperatures between −185°C and +60°C. The instrument has been used successfully in (1) the measurement of skin temperatures indoors at normal room temperature and outdoors in ambient temperatures as low as −45°C; and (2) the measurement of the radiant temperature of the sky and ground in temperate and in arctic climates.
Millimeter Waves from Harmonic Generators
Authors: Johnson C. M. , Slager D. M. , King D. D.
Published: February 2005

The process of generating millimeter microwave energy from a crystal multiplier driven by a reflex klystron is discussed. Quantitative data are given on the intensity of the various harmonics down to a wavelength of 1.9 mm. A harmonic generator of novel construction which has proven superior to the previously used types is described, and the details of our version of a built-in crystal detector are given.
Calibration of Sensitive Differential Pressure Devices
Authors: Gross Robert A.
Published: February 2005

A new technique for the calibration of static, differential pressure sensing devices is described. The system of calibration is explained and the necessary equations are developed in detail. The basis of this technique for producing known values of very small static pressure differences is that of the air centrifuge. This method has been employed for developing pressure differences as small as 10−6 psi.
On Liquid Argon Ionization Chambers of Centimeter Size
Authors: Marshall John H.
Published: February 2005

A parallel-plate chamber with electrode separation variable from 2 mm to 2 cm has been used to measure recombination, attachment, and energy resolution for beta-ray ionization in liquid argon. A collecting voltage up to 30 kv was used without introducing spurious pulses. Amplifier noise sets the lower limit to beta-ray detection at about 150 kev and limits the energy resolution to about 100 kev (full width at half maximum at any energy).
An Instrument for Measurement of Very High Resistance
Authors: Lynch Frank J. , Wesenberg Clarence L.
Published: February 2005

An instrument for the accurate measurement of resistance in the range 109 to 1013 ohms is described. A constant current flows through the resistor under test, and the resulting potential drop is measured with an electrometer. The constant current is the displacement current flowing through a standard condenser when the potential difference across the condenser changes linearly with time. The potential drop across the resistor is measured by a recording dynamic-condenser electrometer. Provision is made for measuring resistance with potential drops from 3 mv to 10 volts across the resistor. The accuracy of the resistance measurement is dependent only upon wire-wound potential dividers, the dimensions of a parallel plate condenser, and the power-line frequency. The accuracy of the present instrument is about 0.5 percent. For this accuracy, the time of measurement is about 6R×10−11+10 seconds.
Alternating Gradient Electrostatic Focusing for Linear Accelerators
Authors: Teng Lee C.
Published: February 2005

The properties of the focusing systems using alternating convergent and divergent electrostatic lenses which were proposed by Courant et al. and Blewett are studied in detail, applied to Alvarez type of linear accelerators. It is found that the introduction and the removal of the focusing force of the system can be made approximately adiabatic by using half-length injection and extraction lenses. The appropriate choice of the parameters of the lenses in practical cases and the behavior of the ion beam going through such a system are discussed. The results can easily be reinterpreted to apply to magnetic lens systems.
An Electron-Beam Tube for Analog Multiplication
Authors: Angelo E. J.
Published: February 2005

An electron-beam tube capable of accurate, high-speed, analog multiplication has been built and tested under both static and dynamic conditions. The maximum errors in multiplication under static conditions were approximately two percent of the maximum product; the output voltage corresponding to the maximum product was approximately three volts. Dynamic measurements show that with sinusoidal input voltages the performance is independent of frequency up to at least 100 kilocycles per second at the output, except for the effects of parasitic capacitance shunting the output circuit. The capacitance effects can be made negligible by appropriate choice of impedance levels.
An Automatic Ionization Efficiency Digital Recorder
Authors: Morrison J. D.
Published: February 2005

The use of time integration to improve the signal-to-noise ratio in ionization efficiency curves obtained with the mass spectrometer requires a large amount of data. An instrument is described which performs the collection of ionization efficiency data automatically, and presents its results as binary numbers, suitable for arithmetic treatment.
An Automatic Tool for Opening Embryonated Eggs
Authors: Nadeje T. , Blum J. , Horsfall F. L.
Published: February 2005

An automatic tool for the rapid opening of embryonated eggs is described. With it, eggs can be opened at the rate of 60 or more per minute.
A Method for the Estimation of the Relative Intensities of Microwave Absorption Lines
Authors: Baird Donald H. , Bird George R.
Published: February 2005

An examination of the theoretical relationship between absorption and crystal response in a Stark-effect microwave spectrograph indicates that a direct proportionality exists between the absorption coefficient and the component of crystal current at the modulation frequency, provided that certain reasonable conditions are fulfilled.

An experimental method is described which utilizes this principle to obtain measurements of the ratio of one absorption coefficient to another. This method involves a matching of the modulation frequency component of crystal current against an adjustable reference signal. These measurements may be used to determine the energy separation of the lower states of the lines observed, thus yielding microwave data on vibrational or torsional energy levels. Line breadth and saturation can be measured equally well with minor modifications in method.

This experimental method was tested by measuring the known ratios of absorption coefficients of the carbonyl sulfide lines near 24 000 mc which are assigned to various isotopic species. The range of deviation of measured ratio from known ratio was 25 percent, and this discrepancy is attributed to reflections in the microwave transmission line, particularly at the ends of the Stark electrode. The determination of molecular vibrational or torsional energy levels is discussed.
Note on the Estimation of Absolute Absorption Intensities with a Stark-Modulated Microwave Spectrograph
Authors: Bird George R.
Published: February 2005

The method developed by Baird and Bird for the measurement of relative absorption intensities has been extended to the estimation of absolute absorption intensities. The estimation of absolute intensity is based on the measurement of the ratio of modulation-frequency component to direct component of crystal current at low microwave power levels.

A preliminary test of the method has been conducted by making measurements on the intensity of the line CH3Cl35, J=0→1, F=32→52 over a range of crystal currents. Measured intensities less than the calculated intensity by 15 percent to 25 percent were observed over a range of nine in crystal current, indicating that the method is at least feasible for the estimation of intensities. Even crude estimates can be extremely useful in the identification of spectral lines, and it seems likely that the method admits of much refinement in accuracy.
Measurements of the Effects of Moisture in Nuclear Track Emulsion
Authors: Oliver Albert J.
Published: February 2005

In order to answer a number of specific questions, thickness and density measurements were made on Ilford nuclear track emulsions before and after processing. Measurements were made as equilibrium was approached under various conditions of ambient relative humidity. Thickness measurements were made with a modified dial micrometer. Volume measurements were made by weighing plates immersed in carbon tetrachloride. A special study of plates stored in a vacuum was carried out. The washing time was found to have an important effect on the shrinkage factor. The data obtained are presented in a number of tables and graphs. The theory of water diffusion in emulsion has been appended by W. H. Barkas, and the emulsion constants evaluated from the experimental data. Attention is directed to the very long characteristic diffusion times implied for thick emulsions.
Floating Zone Recrystallization of Silicon
Authors: Keck P. H. , Van Horn W. , Soled J. , MacDonald A.
Published: February 2005

Equipment to carry out recrystallization and zone melting of silicon from a floating liquid zone is described. In the first design, silicon was melted by a tungsten ring. In an improved apparatus, no heater element inside the melting chamber is necessary, since the silicon is melted by induction heating. The system is capable of producing crystals of extreme purity. Silicon single crystals of resistivities up to several hundred ohm cm have been grown with the described equipment.
Response of the Long Counter
Authors: Nobles R. A. , Day R. B. , Henkel R. L. , Jarvis G. A. , Kutarnia R. P. , McKibben J. L. , Perry J. E. , Smith R. K.
Published: February 2005

The response of the long counter has been investigated with calibrated neutron sources having average energies up to 5 Mev and has been found to be flat down to a low energy limit that is determined by the construction of the counter. A closer examination reveals fluctuations in the sensitivity of about 5 percent which occur at resonances for neutron scattering by carbon. One can account qualitatively for these fluctuations in terms of the scattering properties of the carbon present in the paraffin moderator of the counter.