bluuebunny/crossref_metadata_2025 huggingface dataset:
Techniques of Measuring Neutron Spectra with Threshold Detectors—Tissue Dose Determination
Authors: Hurst G. S. , Harter J. A. , Hensley P. N. , Mills W. A. , Slater M. , Reinhardt P. W.
Published: February 2005

A method is described for measuring the spectrum of fast neutrons with a series of foil detectors. The detectors consist of Au and Au plus Cd for determining the thermal flux, Pu239 shielded with B10 for determining the total fast flux, Np237 for determining the total flux above 0.75 Mev, U238 for determining the total flux above 1.5 Mev, and S32 for determining the total flux above 2.5 Mev. From these data the spectrum of fast neutrons can be constructed reasonably well for spectra similar to that of fission. The amount of induced activity in the detecting elements is determined with scintillation counters, which are calibrated by irradiation of suitable foils with thermal neutrons.

Fast neutron tissue dose can be calculated from the measured spectrum. Since the foil method of measuring spectra works well for high intensity bursts of neutrons, dosimetry may be accomplished under conditions where other methods, e.g., the ionization chamber and proportional counter, would lead to questionable data.
Improved Monochromator for Diffuse X-Ray Scattering Measurements
Authors: Chipman D. R.
Published: February 2005

A close approximation to a doubly bent crystal monochromator is obtained by pressing a large number of narrow strips in a doubly concave form. Details of construction are given. For measurements of diffuse scattering from a single crystal the monochromator gives 40 times the intensity of a singly bent crystal for the same volume element in reciprocal space.
Time-to-Pulse-Height Converter for Measurement of Millimicrosecond Time Intervals
Authors: Weber W. , Johnstone C. W. , Cranberg L.
Published: February 2005

A circuit is described which is designed to measure the time elapsed between a fast-rising signal from a nuclear detector and the next pulse from a steady source of pulses which are evenly spaced in time and occur at an rf rate. This circuit has been found useful for measuring time intervals in the millimicrosecond range as part of a system of fast-neutron spectrometry which utilizes a pulsed source of neutrons. The conversion of time to pulse height is linear for time intervals from 10 mμsec to a time which is 20 mμsec shorter than the interval between the rf pulses. The resolution obtainable depends on the characteristics of the detector. The precision of time measurement is about 1 mμsec.
Automatic Beam Positioning for Mass Spectrometers
Authors: Lipkin H. J. , Porat D. I.
Published: February 2005

A system is described for the control of the position of the ion beam in a mass spectrometer. The instantaneous position of the beam with respect to the point of maximum collector current is presented on a cathoderay tube indicator. The beam can be held at this maximum point either manually using this indication, or by automatic control circuits. In automatic operation the beam first ``searches'' for the peak by sweeping slowly across the region of the collector plate. It is then ``locked in'' and hunts about the point of maximum current. The amplitude of the hunting can be made sufficiently small so that the average collector current does not differ greatly from the peak current. The beam remains locked in position during slow drifts of magnet current and acceleration voltages. After large sudden fluctuations it returns to search operation and locks in shortly thereafter. The method of control is an adaptation of principles used in automatic frequency control of radar receivers.
Area Sources of Low-Energy Electrons for Electron Optic Studies
Authors: Schneeberger Robert J.
Published: February 2005

Ordinarily, the performance of electron lenses in electron imaging devices employing photoelectric surfaces can be evaluated only after sealed-off vacuum tubes containing the processed photoelectric surfaces are made. After processing, such tubes cannot be opened to air for alterations without destroying the photoelectric surfaces. Three distinct types of structures for providing area sources of low-energy electrons simulating photoelectric sources are discussed. These structures can be inserted in demountable vacuum systems and are not destroyed by subsequent exposure to air.
Mechanic-Electric Transducer
Authors: Lion Kurt S.
Published: February 2005

Description of a transducer system which permits the conversion of mechanical displacements into electrical signals. The system is based upon a high-frequency discharge in a gas under reduced pressure. Different modifications permit the detection of either very small movements (<1 mm) or large movements (several cm), or small changes of capacitance (fraction of a micro-microfarad).
Cloud Chamber for Counting Nuclei in Aerosols
Authors: Saunders Bernard G.
Published: February 2005

A cloud chamber is described which measures either the absolute or relative concentration of nuclei in an aerosol. Water droplets are condensed on aerosol particles in a small sample, and the resulting water droplets are photographed on 16-mm film by flashtube illumination and then counted in a microprint reader. Two types of expansion cloud chambers were found to work satisfactorily: the volume-defined and the pressure-defined. The apparatus is completely automatic and will operate continuously on a one-minute cycle. It can measure aerosol concentrations that range from 200 particles/cm3 to 2×106 particles/cm3.
Electronic Wattmeter with Wide Frequency Range
Authors: Schultz T. J.
Published: February 2005

An electronic wattmeter has been constructed to give a pointer indication of the average product of two electrical signals in the audio-frequency range. The frequency response is flat (±0.17 db) between 20 cps and 20 kc/sec.
Negative Hydrogen Ion Source
Authors: Weinman J. A. , Cameron J. R.
Published: February 2005

A negative hydrogen ion source has been built which will yield from 25 to 30 μa of H− ions focused on a ¼-inch diameter spot. This is accomplished by first producing positive ions in a magnetic ion source. These ions are extracted and accelerated by at most 17.5 kv. The ions then pass through an electron pickup capillary tube into the center of which the electron donating gas is introduced. The H− ions emerging from this tube are accelerated by an additional 20 to 30 kv while the emerging secondary electrons are electrostatically repelled. The negative ions are then focused by an electrostatic ``saddle field'' lens and magnetically analyzed. An Evapor-ion pump is used to maintain the pressure in the ion source container less than 10−4 mm Hg.
Fast Timing of Scintillation Pulses
Authors: Ticho Harold K. , Gauger Joleroy
Published: February 2005

Some modifications of the conventional chronotron circuit are discussed. Using such a modified chronotron, time interval distributions due to two liquid scintillation counters have been studied under various experimental conditions. These studies suggest that even when counters with sensitive areas of ∼300 cm2 are used, a precision of ±0.25 mμsec in an individual time interval measurement can be achieved if the distance between the particle trajectory and the photosensitive surface is known.
Automatic Scanning Device
Authors: Holm Lennart W.
Published: February 2005

The driving mechanism and the control and recording circuits of an automatic device for repeated, continuous, unidimensional scanning of radioactive objects are described. The scanner can run at several different speeds from 4.10×10−3 up to 1.32 mm/sec. It is shown theoretically and illustrated with actual examples that it is possible to construct ``equilibrium curves,'' i.e., curves corresponding to an infinitely low scanning speed, from those recorded with finite scanning speeds.
New Computer Method for Obtaining Optimum Area
Authors: Tyroler J. F. , Smith C. L.
Published: February 2005

An automatic computer method for obtaining the optimum area for any fixed time interval under a transient is described and discussed. This method automatically chooses the point on the transient where integration of the area is initiated and a preset timer stops the integrator after the selected time interval has elapsed. This method is based on the use of a magnetic tape recorder with a modified playback arrangement and integrator. The initiating point is chosen with an accuracy of ±0.028 volt where the input signal range is zero to ten volts. The stability of the one-shot timing circuit is one part in a thousand with a gate time between 40 and 500 milliseconds. The system accuracy for obtaining area depends on the particular magnetic tape system and integrator used, and type of transient being examined.
Multiple Target Nuclear Magnetic Resonance Cryostat
Authors: Fuschillo N.
Published: February 2005

A cryostat is described for accurately controlling the temperatures to 0.1°K of several solid specimens during nuclear magnetic resonance experiments in the temperature range from 10 to 400°K. The specimen targets are passed through the rf coil of the spectrometer in succession. This procedure enables more certain comparisons to be made of line shapes for different samples. The method is of particular advantage when small changes are to be observed or when it is of importance to have the individual specimens undergo thermal treatments as similar as possible. Also, since several samples can be studied in succession at any desired temperature a considerable saving of time is achieved. The cryostat is designed so that solid or liquid specimens can be utilized with a minimum of disturbance to existing adjustments.
Multichannel Systems for Pulse-Height and Time-of-Flight Analysis
Authors: Schultz H. L. , Pieper G. F. , Rosler L.
Published: February 2005

Multichannel systems for pulse-height and time-of-flight analysis based on the original development of Hutchinson and Scarrott are described. The equipment can be divided into three basic categories:

(a) A time channel analyzer using serial storage and arithmetic operations. This unit provides approximately 500 2-μsec time channels each having a capacity of 10 binary digits. It is now being used for slow neutron time-of-flight spectroscopy.

(b) A pulse-height-to-time converter which when used in conjunction with the above or similar unit forms a multichannel pulse-height analyzer with 200 useful channels.

(c) Data display systems of two types, one for continuous visual monitoring and one for permanent recording in chart form.
Simplified Ionization Gauge Circuit with Logarithmic Pressure Scale
Authors: Hariharan P. , Bhalla M. S.
Published: February 2005

The control circuit described utilizes a logarithmic difference amplifier to measure the ratio of the positive ion current to the electron current drawn by the gauge. This eliminates the necessity of stabilizing the electron current within close limits and permits direct readings of pressures ranging from 10−3 to 10−7 mm of mercury on a single logarithmic scale.
Proton-Recoil Neutron Spectrometer
Authors: Johnson C. H. , Trail C. C.
Published: February 2005

A proton-recoil telescope with thin polyethylene radiator has been designed for neutron spectroscopy and for neutron detection with known efficiency in the energy region from about 2 to 20 Mev. Five radiator thicknesses may be chosen over this energy region. Protons recoiling near zero degrees from the radiator pass through two proportional counters and terminate in a NaI(Tl) crystal. Triple coincidences gate an analyzer for observing the spectrum from the crystal. A spectrum of 13.7-Mev neutrons was observed with a width at half-maximum of 5.3% and 6% background. The efficiency with this resolution at 13.7 Mev is 3.6×10−6.
Effect of Driving Pulse Shape on the Performance of a Schmitt Trigger Circuit
Authors: Fairstein Edward
Published: February 2005

It is shown that the optimum pulse shape for driving a Schmitt trigger circuit is one in which the peak of the pulse occurs near the leading edge, followed by a linear decay to the trailing edge. The magnitude of the decay should be less than the trigger hysteresis. The circuit for obtaining such a pulse shape is shown.
Three-Phase Radiofrequency System for Thomas Cyclotrons
Authors: Smith Bob H. , MacKenzie Kenneth R.
Published: February 2005

As part of the program to develop high current accelerators several model Thomas cyclotrons employing three-phase rf were built. The three phase signal was produced by a phase generator which was excited by a crystal oscillator. Each phase was amplified and applied to the corresponding dee, which was kept in tune by means of servomechanisms. Balanced dee voltages require a symmetrical resonator with equal inter-dee capacitances; stability of the servomechanism requires that the effective inter-dee capacitances be zero. This last condition was fulfilled by means of neutralizing transmission lines connected from dee stem to dee stem. Thomas cyclotrons appear to be capable of producing megawatts of beam power with an rf efficiency in excess of 70%.
Two Electron Models of a Constant-Frequency Relativistic Cyclotron
Authors: Kelly Elmer L. , Pyle Robert V. , Thornton R. L. , Richardson J. Reginald , Wright Byron T.
Published: February 2005

Two model constant-frequency cyclotrons based on the principle of L. H. Thomas, as extended by David L. Judd, are described. Both accelerated electrons to speeds of half that of light in magnetic fields of three-fold azimuthal periodicity. Three 60°-wide wedge-shaped electrodes, driven 120° out of phase, provided an energy gain per revolution of 3 eV0, where V0 is the peak electrode-to-ground voltage. Electrons were accelerated to 75 kv with V0=23 v, implying a minimum of one thousand revolutions in the cyclotron. The beam reached full energy without axial loss and it was demonstrated that essentially all of the circulating current will emerge from this type of accelerator without the use of additional deflecting systems. The success of this development program has shown the feasibility of a high-current, high-energy cyclotron based on the Thomas principle.
Small General Purpose Cycloidal-Focusing Mass Spectrometer
Authors: Robinson Charles F. , Hall Lawrence G.
Published: February 2005

A mass spectrometer employing a cycloidal-focusing mass resolving system is described. The mass analyzer proper, including the magnet and a high-speed continuous-flow inlet system, weighs approximately seventy pounds. The resolving system shows good mass resolving power, sensitivity, and analytical accuracy up to about mass 150 amu, and adequate service life. The mass resolving power can be extended substantially in cases where some loss of sensitivity and analytical accuracy is tolerable.
Space Charge in Cycloidal-Focusing Mass Spectrometers
Authors: Robinson Charles F.
Published: February 2005

In a curtate-cycloidal-focusing mass spectrometer, the first-order effect of space charge is not to impair the quality of the focus but to shift the focal point out of the plane of the resolving slit. For a given ion mass and ion current, the magnitude of the effect is about four times as large in a cycloidal-focusing instrument as in a 180° magnetic sector mass spectrometer operating in the same magnet.
Precision Measurement of Detonation Velocities in Liquid and Solid Explosives
Authors: Campbell A. W. , Malin M. E. , Boyd T. J. , Hull J. A.
Published: February 2005

A versatile chronographic technique for the measurement of detonation velocities in liquid and solid explosives is discussed. A raster-type oscilloscope is described which has a sweep linearity of 1% and a time coverage of 300 μsec. This instrument is composed of standard electronic components and requires relatively little maintenance. The basic signal mixing circuits used to generate fast-rising pulses associated with the detonation of an explosive charge are briefly described. Some electrical effects associated with the detonation of an explosive charge are briefly described to point out a possible source of spurious signals. Techniques for the preparation and assembly of explosive charges are presented together with certain precautions which must be taken against the possibility of the generation of false signals. The effect of temperature on detonation velocities of liquid and solid explosives is mentioned. Using the techniques and precautions described, it is possible to obtain detonation velocity data with a precision of 0.1% or better.
Use of Servomechanisms in the Compensation of a 70-Mv X-Ray Beam
Authors: Dye David L. , Adams Gail D.
Published: February 2005

The naturally peaked x-ray beam from the 70-Mev synchrotron has been collimated and compensated to flatness by differential absorption in a copper filter. Angulation of the synchrotron magnet produces a shift of the filter support with respect to the x-ray beam, thus altering the compensation achieved before angulation. This paper contains a description of a system of two servomechanisms which senses the change in compensation and provides correcting motions to restore proper filter position. Particular emphasis is given to items of technique which contributed to the success of this development.
Control and Measurement of an Ion Source of a Pressure Insulated Van de Graaff Generator
Authors: De Boer A. G. , Kley J. , Makkink J. H.
Published: February 2005

A very simple method has been developed for the control and measurement of an ion source in the top terminal of a high pressure insulated Van de Graaff generator. The sending and receiving of information from the outside of the tank to the high voltage (h.v.) electrode is achieved by means of light signals.
Adiabatic Specific Heat Calorimeter for the Temperature Range 4 to 15°K
Authors: Aven M. H. , Craig R. S. , Wallace W. E.
Published: February 2005

An adiabatic specific heat calorimeter bridging the interval between liquid helium and liquid hydrogen temperatures is described. The instrument uses a constant volume helium gas thermometer as the working thermometer. The sample is placed directly in the gas thermometer bulb which thus acts as a sample container. The use of the calorimeter is restricted to bulk samples with low surfaces areas.
Absolute Method for Sound Intensity Measurement
Authors: Pardue D. R. , Hedrich A. L.
Published: February 2005

Since sound propagation is an adiabatic process, a temperature fluctuation accompanies the sound wave in media for which the specific heat ratio is greater than unity. If the equation of state and the sound field are known, this temperature fluctuation may be related to the intensity of the sound wave.

A thermometer capable of measuring fast, small-amplitude temperature variations is described. Its output is calculated for the case of plane, sinusoidal sound waves in an ideal gas. Its use as a microphone and sound intensity meter is then considered.
Thyratron-Controlled Stirrer or Pump for Pressurized Systems
Authors: Brandt L. W. , Deaton W. M.
Published: February 2005

An apparatus is described which provides a simple means of obtaining stirring or pumping action in a pressurized system. Since no packing glands are employed, the device is leak-proof. The required mechanical action is provided by reciprocating motion of a soft-iron armature enclosed in the system and driven by a pair of electromagnetic coils. Input to the coils is provided by a thyratron-controlled circuit. The circuit and constructional details are given.
Bridge for Accurate Measurement of Ferroelectric Hysteresis
Authors: Diamant H. , Drenck K. , Pepinsky R.
Published: February 2005

A new instrument has been designed for the undistorted display of ferroelectric hysteresis loops even in the presence of relatively high conductivity. The electrical characteristics of a sample are determined directly from dial settings and meter readings. The basic circuit of the bridge may be described as two parallel Sawyer and Tower circuits, one containing the sample and the other containing resistors and capacitors for the compensation of conductivity and dielectric constant at saturation. The compensated hysteresis loop is displayed on an oscilloscope with the aid of a calibrated differential amplifier. The spontaneous polarization and the applied voltage, as well as the coercive field, are read on an electronic peak voltmeter. An important feature of the bridge is that measurements are independent of the frequency and wave form of the applied voltage.
Electrostatic Lens
Authors: Carleton N. P.
Published: February 2005

A possible electrostatic lens consists of a cylindrical surface along which the potential varies as the square of the distance from some original plane. If the cylinder is very long or is terminated without distorting the field within, the trajectories of charged particles inside it can be calculated analytically. These calculations show that a small diameter source of electrons inside the cylinder can be imaged, with magnification unity and slight aberration, at another point in the cylinder. A short section of the cylinder with open ends serves as a thick lens for focusing a beam of particles, the focusing effect being due to the main field inside the cylinder plus end effects. Such a lens was constructed, the boundary condition being realized by a succession of closely spaced rings maintained at the proper potentials. This lens was more efficient in focusing a highly divergent beam of ions than were several combinations of conventional lenses which were also tried.
Neutron Time-of-Flight Spectrometer for Use with the Harwell 110-Inch Cyclotron
Authors: Scanlon J. P. , Stafford G. H. , Thresher J. J. , Bowen P. H.
Published: February 2005

A description is given of a neutron time-of-flight spectrometer used for energies up to 140 Mev. A 20-mμsec neutron pulse is obtained by electrostatic deflection of the internal proton beam of the cyclotron onto a thick aluminum target. By timing the neutrons over a 26-meter flight path an energy spread of 4.2% at 15 Mev is obtained rising to 14% at 140 Mev. The advantages of the technique and possible improvements are discussed.
Liquid Tin Solution Calorimeter for Measuring Heats of Formation of Alloys
Authors: Orr Raymond L. , Goldberg Alfred , Hultgren Ralph
Published: February 2005

A liquid tin solution calorimeter has been constructed for determining the heats of formation of alloy phases from the heats of solution of the alloys and of the pure component metals in liquid tin. The design of the calorimeter is presented, and the experimental procedures and calculation methods are described and illustrated with data from representative runs. These indicate that heats of formation of alloy phases may be determined with an average uncertainty of about ±50 cal/g atom.
Second-Order Aberrations in a Modified Mattauch-Type Mass Spectrometer
Authors: Robinson Charles F.
Published: February 2005

Control of the energy-dependendent second-order aberrations in a Mattauch-type mass spectrometer is made difficult by the absence of a real image between the object slit and the focal plane in this resolving system. By curving the boundary of the magnetic field and by choosing appropriate relations between the magnetic field boundary curvature and the other parameters involved, it is possible to make both of the energy-dependent second-order aberration coefficients vanish simultaneously while retaining the advantages peculiar to this resolving system.
Spin Echo Apparatus
Authors: Schwartz J.
Published: February 2005

A spin echo apparatus is described which can measure nuclear relaxation effects for narrow resonances, convection and diffusion effects, and in some cases, chemical splittings in liquids. This apparatus is assembled mostly from commercial equipment. Commercial units used are identified, and circuit diagrams are given for specially constructed apparatus. Sufficient design information is given to make possible substitutions and improvements to suit the needs of particular projects. Necessary adjustment procedures are described and the relations of instabilities in the apparatus to instabilities in its components are treated.
Wide-Band Balun Transformer
Authors: Talkin A. I. , Cuneo J. V.
Published: February 2005

This paper describes a wide-band balun transformer which was developed for use with a 200-Mc band-width oscilloscope deflection amplifier. The balun has a band width extending from below 50 kc to above 500 Mc. Input impedance data and pulse responses are presented. One balun coil can be used alone as a passive wide-band pulse inverter.
Automatic Plotting of Probe Curves
Authors: Medicus G.
Published: February 2005

A simple circuit for automatic plotting of probe curves and diode voltage-current curves by means of commercial x-y curve plotters is described. Errors involved and corrections to be applied are discussed. The design of an electrolytic voltage divider for varying the probe voltage is given.
Criterion for Vacuum Sparking Designed to Include Both rf and dc
Authors: Kilpatrick W. D.
Published: February 2005

An empirical relation is presented that describes a boundary between no vacuum sparking and possible vacuum sparking. Metal electrodes and rf or dc voltages are used. The criterion applies to a range of surface gradient, voltage, gap, and frequency that extends over several orders of magnitude. Current due to field emission is considered necessary for sparking, but—in addition—energetic ions are required to initiate a cascade process that increases the emitted currents to the point of sparking.
Improved Ultraviolet Microbeam Apparatus
Authors: Uretz Robert B. , Perry Robert P.
Published: February 2005

An ultraviolet microbeam apparatus utilizing the principle of incident illumination has been developed for the irradiation of small parts of living cells or other microscopic objects. A reflecting microscope objective is used simultaneously in a visible light viewing-aiming system and in a bombardment system to focus a spot of ultraviolet light (as small as one micron in diameter) onto part of an experimental preparation. Provision is made in the apparatus for auxiliary phase contrast viewing and for monitoring of the energy in the microbeam. Details of construction and alignment are given and the distribution of intensities in the microbeam is discussed.
Sing-Around Ultrasonic Velocimeter for Liquids
Authors: Greenspan Martin , Tschiegg Carroll E.
Published: February 2005

A ``sing-around'' velocimeter of high stability and precision has been developed and tested. The instrument, which is of the fixed-path type, automatically measures and/or records the speed of sound in non-dispersive liquids. Stabilities of about 50 ppm over a 24-hr period can be achieved.
Fast Timing Apparatus for Measuring the Arrival Directions of Cosmic-Ray Air Showers
Authors: Clark George W.
Published: February 2005

This paper describes a millimicrosecond timing apparatus for determining the arrival directions of extensive cosmic-ray air showers. The apparatus consists of four plastic scintillation detectors in a square array and a fast oscillograph with which one can determine the relative arrival times of the first shower particles which reach the four detectors as indicated by the relative positions of pulses from the detectors on the oscillographic sweep. The uncertainty in determinations of the relative arrival times of the particles in a shower is about 3 millimicroseconds. The uncertainty in the determination of the arrival direction of a shower is about ±5°, and this uncertainty is caused primarily by the lack of coplanarity of the shower particles and not by instrumental limitations.
Resonance Mass Selector
Authors: Bierman A.
Published: February 2005

A device is proposed with which ions may be selected on account of their oscillating frequency in a static ``potential well'' whereby the ions pass several times across the same rf field tuned to the oscillation, thus gaining energy on each passage. No magnetic fields are used. As the initial velocity of the ions plays only a secondary role for the selection, the energy spread in the ion source is allowed to be much greater than with most types of mass spectrometers. Likewise, no high mechanical precision is required. The resolving power may be varied by electrical means. ``Harmonic masses'' (``ghost images'') are easily eliminated.
Sonic Gas Analyzer for Measurement of CO2 in Expired Air
Authors: Stott F. D.
Published: February 2005

A sonic gas analyzer intended primarily for estimation of CO2 in the physiological range of 0–10% is described. The instrument uses a resonant cavity maintained in oscillation by a transistor amplifier as the measuring device; the change in frequency caused by the presence of CO2 in the cavity is linearly related to the amount of CO2 present. As described the instrument is intended for continuous sampling at a rate of about 2 l/min. The time of response is about 0.5 sec for full deflection.
NaI Summing Spectrometer
Authors: Shapiro P. , Higgs R. W.
Published: February 2005

An extension of previous work on the analysis of pulse-height distributions obtained with gamma-ray sources placed inside well-type NaI(Tl) crystals is discussed. Two methods are given for the determination of the photopeak efficiency of these NaI spectrometers. It is shown that the summing property of the well-type crystal can be used to obtain the source strength and to yield information on the decay scheme of gamma-ray sources.

The photofraction, photopeak efficiency, and resolution are given for a 5-in. diameter by 3-in. long NaI crystal with a 1-in. diameter well.
On An Analog Solution of Two Point Boundary Value Problems
Authors: Greenspan Donald , Ulrick Bruno , Matsuno Shozo
Published: February 2005

The two point boundary value problem of ordinary differential equations is reduced to two initial value problems, each of which can be easily solved by analog equipment. The computer can judiciously combine these results to yield a solution of the boundary value problem. The methods involved are described analytically and an example solved on the REAC is provided. A complete diagram of the electronic mechanization is provided.
Automatic Temperature Regulation and Recording in Precision Adiabatic Calorimetry
Authors: West E. D. , Ginnings D. C.
Published: February 2005

In connection with a precision adiabatic calorimeter used for heat-capacity measurements up to 500°C, there is described apparatus for automatically controlling and recording the temperature difference between the calorimeter and its surroundings and for evaluation of the heat leak by electronic integration of the time-temperature difference function.
High Radiation-Flux, Absolute, Water-Flow Calorimeter
Authors: Glaser Peter E.
Published: February 2005

A high radiation-flux, measuring calorimeter has been designed for use in imaging furnaces. It consists of a black-body receiver provided with a cooled aperture and cylindrical housing. It can be exposed to flux densities of the order of 400 cal/cm2 sec for extended periods without deterioration. Thermopiles measure the temperatures of the inlet and outlet cooling water. The calorimeter is an absolute measuring device with a response time of one minute. The design virtually eliminates heat losses and permits the measurement of a wide range of heat fluxes. The probable error in the radiation-flux measurement is ±5%.
Absolute Determination of Monoenergetic Neutron Flux in the Energy Range 1 to 30 Mev
Authors: Bame S. J. , Haddad Eugene , Perry J. E. , Smith R. K.
Published: February 2005

Monoenergetic neutron fluxes can be measured at neutron energies above 1 Mev by observing recoil protons scattered at forward angles from a hydrogenous radiator. A counter telescope system for observing the recoil protons is described which has a relatively high efficiency for neutron detection. The major part of the paper is devoted to backgrounds and corrections, the calculation of telescope efficiency, and the accuracy of neutron flux measurements. Tables are given which make possible a simple determination of the efficiency of a counter system at neutron energies between 1 and 30 Mev. An appendix presents a semiempirical formulation of n-p scattering which is used in obtaining counter efficiencies.
Linear Gate of 200 Millimicrosecond Duration
Authors: Garwin E. L. , Penfold A. S.
Published: February 2005

An electronic gate circuit is described which has better than 1% linearity for pulses in the range 1 to 70 volts. The circuit gives an inverted output with a gain very close to unity and accepts positive inputs. The leakage of a 70-volt pulse through the closed gate is 0.6 volt and the largest negative going portion of the gating transient is 0.2 volt. The gate can be reliably opened with positive trigger pulses in the range 4 to 9 volts and the time jitter over this range is the same as the rise time of the trigger pulses. The inherent rise time of the gate output is about 50 millimicroseconds.
Continuous-Balance Photoelectric Guider
Authors: Weitbrecht Robert H.
Published: February 2005

A photoelectric guider system used in connection with a star camera on the 18½-inch refractor of the Dearborn Observatory is described. The guider uses a pyramid with four phototubes to determine the error-signals in both coordinates. Commercially available servomotors mounted on the double-slide plate-holder receive these signals and adjust the plate carriage to achieve a ``central balance-point'' upon the guide-star. The guiding action is continuous and operates on stars down to the 8th magnitude.
Crystal Mount and Techniques for Measuring High-Frequency-Induced Electroluminescence
Authors: Harman George G.
Published: February 2005

A versatile apparatus is described for use in studying electroluminescence and electrophotoluminescence. Measurements of light emission can be made with electrical excitation frequencies ranging from dc to 400 Mc and also in selected microwave bands. Oscillators that may be employed over this frequency range are discussed. The apparatus consists of a crystal mount and a simple optical system for irradiation and for the separation of excitation and luminescent spectra. Flat plate-type as well as long silver-type crystals are mounted on slides which can be easily interchanged. Tests may be run from low temperatures (−70°C or lower) up to about 300°C.
Germanium Resistance Thermometers Suitable for Low-Temperature Calorimetry
Authors: Kunzler J. E. , Geballe T. H. , Hull G. W.
Published: February 2005

Single crystal ``bridges'' of suitably doped germanium have been encased in a strain-free manner within nonmagnetic platinum-glass capsules to provide resistance thermometers with desirable low-temperature electrical properties. The stability of the resistance of these thermometers with repeated cycling between room temperature and liquid helium temperatures and their relatively constant sensitivity (percent change in resistance per percent change in temperature) between 2 and 35°K for a wide range of resistivities are improvements over existing thermometers for this temperature range. Thermometers of this type are believed to be suitable for the most precise measurements, such as calorimetry, and are being further investigated.
Argonne 7.7-Meter Bent-Crystal Gamma-Ray Spectrometer
Authors: Rose David , Ostrander Herbert , Hamermesh Bernard
Published: February 2005

A bent-crystal gamma-ray spectrometer of the transmission type having a focal length of 7.7 meters has been built for studying neutron capture radiation. The source is placed inside the reactor CP-5 in a horizontal straight-through hole. The instrument is designed to utilize a 30 cm×30 cm quartz plate cut normal to the (310) planes. Undiffracted radiation is absorbed by a baffle consisting of 108 Pb plates each 40×11×0.040 inches mounted between tapered spacers so as to focus on the virtual image of the source. The detector is an array of 16 NaI (Tl) crystals comprising a volume 10½×10½×2 in. The drive system rotates the crystal one second of arc in 20 seconds. The 2:1 motion required between the crystal and the detector is maintained by an optical lever system. The Bragg angle is measured with an interferometer. The instrument now operates with a 10×15×0.6 cm crystal.
Zenith Angle Sensitivity of a Cubical Meson Telescope
Authors: Parsons N. R.
Published: February 2005

Diagrams are presented showing the variation of relative sensitivity with zenith angle for a vertically directed cubical meson telescope of the type recommended as standard equipment for the International Geophysical Year.
Metal System for Chemical Reactions and for Studying Properties of Gases and Liquids
Authors: Neher H. V. , Prakash Satya
Published: February 2005

An all-metal system, made of copper, is herein described. It is suitable for working with those chemicals which do not attack copper. In particular it has been found very useful in the purification of BF3 and B(CH3)3. Some important features of such a system are (1) a complete absence of contaminants; (2) reactions may be carried out up to 500°C; (3) pressures up to several hundred pounds per square inch may be used; (4) flow of gases from very low to very high pressures may be easily controlled; (5) the system is very rugged. This latter point is particularly desirable where noxious or inflammable gases (such as B(CH3)3) are used. A method is also described whereby gases from sealed-off containers under either high or low pressures may be easily retrieved without introducing impurities. Other important advantages of such a system are mentioned in the text.
Method of Obtaining Derivative Spectra
Authors: Pemsler J. Paul
Published: February 2005

The first derivative with respect to wavelength of the transmission curve has been used to detect overlapping spectral bands. The commercially available Perkin-Elmer Model 13 Ratio Recording Spectrophotometer may be easily adapted to record directly the derivative spectrum throughout the ultraviolet, visible, and infrared regions.
Preparation of Silver Halide Crystals of High Purity
Authors: Nail N. R. , Moser F. , Goddard P. E. , Urbach F.
Published: February 2005

For the investigation of silver halides, crystals of very high purity are required. Methods for preparing such crystals are described. They include the procedures used for the preparation of the dry precipitates, for crystal growing in controlled atmospheres, and for the preparation of specimens for the study of optical, electrical, and photochemical properties. The crystals are optically clear and have a sharp absorption edge with no detectable impurity absorption, even in samples several centimeters thick. For the silver chloride crystals, the ionic conductance was found to show the familiar break point at an unusually low temperature, and the interior of the crystal shows extremely little darkening even upon very strong exposure. For spectrochemical determination of the purity of the crystals, a concentration series of internal standards were prepared for seventeen elements. For the more important impurities, the molar concentration does not exceed 10−7.
Some Properties of a Modified Solenoid β Spectrometer with Zero Field at the Source
Authors: Ramberg Y. , Blaugrund A. E.
Published: February 2005

The resolving power of a long magnetic lens using a field that rises linearly from a zero value at the source and becomes constant at a distance z0 has been calculated as a function of z0 for two emission angles 26.5° and 31°. For z0 smaller than the radius of the spectrometer the resolving power remains nearly equal to that of a uniform field lens and then deteriorates quickly for values of z0 greater than the radius of the spectrometer. The first-order spherical aberrations as well as the location of the ring focus and the detector are given graphically as functions of z0.
Precise Automatic Manometer Reader
Authors: Farquharson J. , Kermicle H. A.
Published: February 2005

An instrument has been developed to automatically find the level of mercury in a glass tube and indicate on a digital register the height of the mercury column. The first model has a range of 80 cm, a precision of better than ±0.05 mm and a maximum deviation of ±0.11 mm. The range and deviation depend upon the length and linear accuracy of the metric screw.
Thermistor Thermometer Bridge: Linearity and Sensitivity for a Range of Temperature
Authors: Cole Kenneth S.
Published: February 2005

The balance point of a Wheatstone bridge with a slide wire for ratio arms is a nearly linear function of the temperature of a thermistor in a third arm, the maximum errors of a linear calibration are made equal and proportional to the cube of the temperature range, and the off-balance sensitivity is nearly constant for a considerable temperature range. For a small thermistor with a 2000-ohm resistance at 25°C, the slide position of a linear potentiometer is proportional to the thermistor temperature ±0.5°C, and the deflection of a taut suspension pointer galvanometer is 20±1 mm/°C over the temperature range from 0°C to 50°C with a maximum thermistor temperature rise of 0.05°C in still air.
Gel Dosimeter for Depth-Dose Measurements
Authors: Andrews Howard L. , Murphy Raymond E. , LeBrun Edward J.
Published: February 2005

A chloral hydrate-agar gel has been used for depth-dose measurements with x-rays and electrons. HCl is formed from the chloral hydrate by the radiation and thus changes pH and electrical conductivity of the gel. Radiation beams can be visualized by adding an acid-base indicator. Quantitative measurements are made by spectrophotometry or by probing the gel with a pH electrode or a conductivity electrode pair. Spatial resolution of perhaps 0.2 mm has been obtained with conductivity electrodes. Doses of 2000 rad or more are required to obtain satisfactory records, the lower limit being set by inhomogeneities in the unexposed gel.
Theory of a New Apparatus for Determining the Thermal Conductivities of Metals
Authors: Hsu S. T.
Published: February 2005

The principle of transient temperatures inside a semi-infinite solid is applied to two identical sets of composite plates. Each of these sets consists of a standard specimen of a certain metal whose properties are known and a test speciment of a metal whose thermal diffusivity is to be determined. When these two sets, initially at different but uniform temperatures, are brought into contact with each other, the transient temperature at the contact plane between the test and standard specimens corresponding to a certain time is measured, then the coefficient of thermal diffusivity of the test specimen can be computed. It takes about 30 seconds for the measurement and will yield a result with an estimated accuracy of about 3%.
Moving-Plate Camera for Nuclear Research
Authors: Dawson W. K. , Sargent B. W.
Published: February 2005

A moving-plate camera, suitable for investigating the angular and energy distributions of photoprotons, is described. Two nuclear plates, 1×3 in., are accurately held with the emulsion surfaces vertical, parallel and facing each other on a carriage, which moves forwards and backwards at constant speed below the target and parallel to the x-ray beam in an evacuated tube. Targets are thin metal foils, 1.5×1 in. The angles and energies of tracks recorded in each plate coated with 200-micron emulsion are 20 to 160 degrees and approximately 2 to 16 Mev. The theory of the camera is developed in detail.
Autocorrelation of the Earth's Crust with Analog Computers
Authors: Diamantides N. D. , Horowitz M.
Published: February 2005

Land-form geometry of the earth's ground surface, expressed statistically, finds application in both the civil and military phases of geology and engineering. To obtain statistics about the slope of the earth's crust, autocorrelation methods have been employed. Analog computers were used to compute the autocorrelation functions of terrain profile heights. Each profile was read out by a standard curve follower, the output was sampled by a commutator, and the autocorrelation values were registered in a bank of capacitors. This process required approximately 10 min per profile. For two sample profiles considered—one near Akron, Ohio and the other near Phoenix, Arizona—the mean values of the terrain heights were 1200 and 1570 ft, respectively; and the rms relief values were 71 and 263 ft, respectively.
Apparatus for the Measurement of Vapor Pressure and Ignition or Decomposition Temperature at Pressures above Atmospheric
Authors: Whittaker A. Greenville
Published: February 2005

An apparatus is described which can be used to measure vapor pressure and ignition or decomposition temperature at pressures up to 4000 psig. The measurements can be made rapidly and under conditions simulating the combustion of liquids in an inert atmosphere. Vapor pressure data on ethyl nitrate and 2-nitropropane are presented, along with data on the decomposition temperature of triethyleneglycol dinitrate, metriol trinitrate-triacetin, and gem-dinitropropane.
Lead Glass Čerenkov Radiation Photon Spectrometer
Authors: Brabant John M. , Moyer Burton J. , Wallace Roger
Published: February 2005

A spectrometer for analyzing photons of energies extending up to several Bev has been constructed and used successfully. This instrument essentially consists of a cylinder of glass, 12-in. diam and 14-in. long containing 52% of PbO, viewed by four 5-in. diam photomultipliers. High-energy photons incident along the spectrometer axis produce electron showers in the transparent high-Z glass. The total Čerenkov radiation emitted by these electrons and detected by the phototubes is nearly proportional to the energy of the incident photon, from 50 Mev to at least 1.4 Bev. The spectrometer has been calibrated over this range of photon energies by the pulses produced by electrons of the same energies. Above 200 Mev the measured energy resolution of the spectrometer is 30% and is approximately independent of energy. For elimination of incident charged particles during the analysis of γ rays the spectrometer is operated in coincidence with a preceding photon-identifying counter system.
Remarks on Double Solute Liquid Scintillators
Authors: Avivi P. , Weinreb A.
Published: February 2005

The behavior of wavelength shifters in liquid scintillators is discussed. The properties necessary in order that a fluorescent compound act as a wavelength shifter are considered in detail and a qualitative criterion for efficient wavelength shifting is presented. Several double solute solutions have been tested; accordingly it was found that the criterion is useful.
Radioactive Uniform Extended Sources
Authors: Tait G. W. C. , Townshend R. E.
Published: February 2005

A device is described for producing a uniform distribution of a solution of radioactive material over a large area source. Droplets of controlled size are expressed from a syringe at a constant rate and systematically and uniformly placed over an area up to 50 centimeters square.
Two Resistance-Type Hot-Pressing Furnaces for Laboratory Use
Authors: Walker R. F. , Bauer S. G.
Published: February 2005

Resistance heating is employed to obtain temperatures up to 3000°C in a graphite tube furnace, and up to 2200°C in a molybdenum tube furnace, both operating from the same controls. Partial control of the atmosphere is accomplished in the former case; the latter furnace may be operated in vacuo, or selected atmospheres. Provision is made for the application of pressure to samples at high temperature. The furnaces have been found to be useful and reliable tools in refractories laboratories, and examples of their application are given.
Method of Obtaining Pressure and Temperature Insensitive Microwave Cavity Resonators
Authors: Crain C. M. , Williams C. E.
Published: February 2005

This paper describes a method of fabricating cavity resonators having very low temperature frequency dependence and also describes a means of building pressure insensitive cavity resonators. Simple schemes of compensation using invar walls with steel or brass end plates for TE011 cavity resonators are found to be unsatisfactory due to hysteresis type effects. With the arrangement described fixed frequency resonators are obtained having stable temperature-frequency coefficients less than ±0.2 ppm/°C and pressure-frequency characteristics of less than 0.003 ppm/mbar.