bluuebunny/crossref_metadata_2025 huggingface dataset:
High Voltage Measurement by ADP Crystal Plate
Authors: Namba Susumu
Published: February 2005

High voltage measurement based on the electro-optical effect of ADP crystal plate is described. When voltage is applied across a uniaxial ADP crystal, the crystal becomes biaxial. For the field EZ in the Z direction across a Z-cut crystal plate, axes of the index ellipsoid are rotated by −45° in the XY plane independent of EZ and birefringence along the Z axis becomes proportional to EZ, then the retardation of light in the Z direction becomes proportional to applied voltage across the crystal plate. Therefore, the applied voltage can be obtained by photoelectric measurement of the optical retardation.
Heavy-Ion Linear Accelerator
Authors: Hubbard E. L. , Baker W. R. , Ehlers K. W. , Gordon H. S. , Main R. M. , Norris N. J. , Peters R. , Smith L. , Van Atta C. M. , Voelker F. , Anderson C. E. , Beringer R. , Gluckstern R. L. , Knox W. J. , Malkin M. S. , Quinton A. R. , Schwarcz L. , Wheeler G. W.
Published: February 2005

Two linear accelerators have been built for the acceleration of ions in the mass region from helium to argon. The linear accelerators consist of two 70-Mc cavity resonators of the Alvarez design. Ions with a charge to mass ratio e/m≥0.15 times the e/m of a proton are injected into the first cavity of the linear accelerator with a Cockcroft-Walton accelerator. In the first cavity the ions are accelerated from the injection energy of 0.07 Mev/nucleon to 1.0 Mev/nucleon. They are then stripped to an e/m≥0.3 and accelerated to the final energy of 10 Mev/nucleon in the second linac cavity.
Multiple Cathode Sputtering System
Authors: Simmons John G. , Maissel Leon I.
Published: February 2005

The study of thin metal films, used as passive components in microelectronic circuitry, led to the development of a multiple cathode sputtering system. The major advantage of a sputtering system is that highly refractory materials can be sputtered quite readily, but they cannot be evaporated without elaborate equipment. Thus, a sputtering system permits studies of thin metal films to be extended from those with low melting points into the range of metals with high melting points. This paper describes a versatile sputtering system which incorporates several cathodes and a rotating anode, making it possible to sputter one metal after another without breaking the vacuum and to deposit films of various thicknesses under identical conditions.
Magnetically Suspended Equilibrium Ultracentrifuge
Authors: Beams J. W. , Boyle R. D. , Hexner P. E.
Published: February 2005

An improved magnetically supported equilibrium ultracentrifuge is described for the determination of molecular weights and molecular weight averages. The rotor is magnetically suspended in a vacuum. The rotor is driven to operating speed by an electric motor or by an air turbine. The rotor is allowed to ``coast'' freely during the course of the sedimentation and loses about 1 rps per day. An improved Jamin interferometer is used to measure the concentration in the ultracentrifuge cell both before and after equilibrium has been established. A precision of the order of 0.1% is obtained for monodisperse substances over a very wide molecular weight range.
Variable Coupling Reflection Cavity for Microwave Spectroscopy
Authors: Gordon J. P.
Published: February 2005

This paper describes the usefulness of a variable coupling resonant cavity for microwave spectroscopy. The variable coupling scheme achieves slightly greater sensitivity than does the usual microwave bridge circuit. It can single out either the absorption or dispersion component of a resonance signal without using bridge techniques. It is considerably less sensitive to microphonic noise than is the bridge. It is recommended for use in reflection-type cavity spectrometers.
Design and Construction of a System of Pulsed Magnets
Authors: Kuskowski R. L. , Novey T. B. , Warshaw S. D.
Published: February 2005

A system of two pulsed iron-free magnets, designed for an experiment in high energy physics is described. One of these is a small solenoid, with a working volume of about 35 cm3, pulsed at 200 kgauss; the other is a large magnet with a volume of about 6 liters, pulsed at a nominal 15 kgauss. Construction details, working lifetimes, and details of switch gear are discussed.
Gamma-Ray Attenuation Factors for Angular Correlation and Angular Distribution Measurements
Authors: Glasgow D. W. , Coleman L. W. , Schecter L.
Published: February 2005

The angular resolution and azimuthal symmetry of an unshielded NaI scintillation counter was measured for gamma rays between 0.5 and 2.8 Mev in order to estimate correction factors needed in determining angular correlation functions. The results are in agreement with the corrections calculated by Rose, and extended by Stanford and Rivers, for similar scintillation crystal geometry.
Convenient Reactor for Studying Reaction Kinetics of High Boiling Liquids in the Gas Phase
Authors: Smith Grant Gill , Bagley Frank D.
Published: February 2005

The study of the reaction kinetics of high boiling liquids in the gas phase has been limited because of the problems involved in introducing the reactant and the difficulty of monitoring pressure changes. Difficulties have arisen with these reactants because of their decomposition during their distillation into the reactor. Pressure monitoring has been hampered due to condensation of the reactant and/or products in an apparatus possessing a cold zone (such as a capillary leading to a pressure measuring device) outside the thermostat. A new reactor has been built for conveniently studying reaction kinetics of high boiling liquids in the gas phase which provides a means of rapid, easy introduction of the reactant and careful monitoring of pressure changes. Reaction rates were determined for the pyrolysis of 1,2-diarylethyl acetates.
Electromagnetic Servo-Balance Employing a Differential Transformer
Authors: Butera R. A. , Craig R. S. , Cherry L. V.
Published: February 2005

An electromagnetic servo-balance designed for use in susceptibility measurements is described. A differential transformer is used as the sensing element, and the position of the beam is indicated visually by a meter with a zero-centered scale. A switching arrangement allows the servo circuit to be disconnected from the balance and a circuit for manual control of the balancing current substituted.
High Temperature X-Ray Diffraction Techniques for Active Metals
Authors: Hanak J. J. , Daane A. H.
Published: February 2005

Techniques are described for obtaining x-ray diffraction information on active metals at high temperatures. One method has been used to 1000°C with rare-earth metals; the other method has been used to 2200°C, with tungsten, and to 1400°C with some of the higher melting rare earths. This later approach permitted measurement of resistance of the specimens vs temperature simultaneously with the diffraction pattern, which made easier the characterizing of the high temperature forms of the metals.
X-Ray Diffraction Camera for the Alignment of Large Single Crystals
Authors: Meyerhoff R. W. , Bailey D. M. , Smith J. F.
Published: February 2005

A back-reflection Laue camera incorporating three rotation axes and three orthogonal translation axes is described. This camera allows for the alignment of large single crystals with a precision of ±0.25°. The degree of single crystallinity of a specimen may be easily examined. In addition it is possible to mark accurately a crystal for subsequent utilization.
Ionization Gauge for Transient Gas Pressures
Authors: Cobine J. D. , Burger E. E.
Published: February 2005

A description and operating characteristics of a vacuum gauge circuit for the measurement of transient pressures in the range 10−4 to 10−7 mm Hg are presented. Rise times as short as 10 μsec are obtained with the experimental instrument.
Ultra-High Vacuum Seal for Space Simulation Systems
Authors: Brueschke E. E.
Published: February 2005

The operation and construction of a leak-free seal, by means of which limited translational and unlimited rotational motion in a vacuum can be obtained, is described. The seal is accomplished by using a rubber gasket in combination with a liquid which is in equilibrium with internal and external pressure. This seal can be operated from zero to several thousand rpm and can be used at 10−9 mm Hg and lower without difficulty. The seal has distinct advantages for use in space environment simulation chambers and other ultra-high vacuum apparatus.
High Voltage Square-Wave Generator
Authors: De Wijn H. W.
Published: February 2005

A description is presented of the design of a high voltage square-wave generator, intended for the modulation of the electric field in the absorption cell in a microwave Stark-spectrograph. Peak-to-peak voltages of up to 1900 v have been produced, feeding into a 1200-μμf capacitive load. The frequency may be chosen at any value between 10 and 120 kc. Rise and fall times of the square wave are less than 0.2 μsec.
Continuously Operating He3 Refrigerator for Producing Temperatures down to ¼°K
Authors: Ambler E. , Dove R. B.
Published: February 2005

A continuously acting, portable, He3 refrigerator is described. The He3 is recirculated in a system that operates without mechanical pumps. The throttling of the returning liquid is accomplished by means of a porous plug. Good regulation is obtained by using a system that allows the pressure across the porous plug to vary with the circulation rate. The lowest temperature reached while circulating is 0.26°K at zero ``external'' heat input, and 0.40°K at 2mw.
Microwave Measurement of Mobility: Analysis of Apparatus
Authors: Liu S. H. , Nishina Y. , Good R. H.
Published: February 2005

The microwave mobility in a semiconductor can be obtained by mounting a sample in a bimodal cavity with an applied static magnetic field and then measuring the power transfer which is produced by the Faraday rotation in the sample. This paper gives an analysis of the effect based on the field distributions in the cavity and the wave propagation in the sample. The dependence of the power transfer on the static applied magnetic field, on the mobility and conductivity of the sample, and on an effective sample size is obtained.
Microwave Measurement of Hall Mobility: Experimental Method
Authors: Nishina Y. , Danielson G. C.
Published: February 2005

Hall mobilities of germanium single crystals have been measured at a frequency of 9000 Mc over the temperature range 30°–300°K. A rectangular sample occupied the central part of a wall of a rectangular cavity, which was doubly degenerate in the TE101 mode and in the TE011 mode at a single resonance microwave frequency. The external magnetic field and the microwave field associated with one of the two modes gave rise to the other mode of oscillation. The theoretical analysis by Liu, Nishina, and Good was verified by measurements on an n-type sample having a room temperature resistivity of 0.40 ohm cm. The measured Hall mobility at microwave frequencies (with a size correction) was compared with the dc Hall mobility between 30°K and 300°K. The agreement was excellent.
Low Impedance Bridge for the Measurement of Level of Liquid Metals
Authors: Hyman Julius
Published: February 2005

A means is described whereby the liquid level of sodium or other conducting liquids may be determined within a sealed metal system. The measurement obtained is that of electrical resistance in an attached drain tube used as a metal ``sight tube.'' A large alternating current is induced for the measurement by using the sealed metal system itself in conjunction with the ``sight tube'' as a one turn secondary of a transformer. Techniques necessary for application and temperature compensation are discussed.
Apparatus for the Measurement of Galvanomagnetic Effects in High Resistance Semiconductors
Authors: Fischer G. , Greig D. , Mooser E.
Published: February 2005

An apparatus for the measurement of galvanomagnetic effects in high resistance semiconductors is described. The apparatus allows the resistivities of samples to be measured whose resistances fall within the range 10−1 to 1012 Ω. The Hall coefficients of these samples can also be determined with the apparatus as long as the charge carrier mobilities of the samples exceed 1 cm2/v sec. A discussion is given of the fundamental limitations of Hall coefficient measuring equipment.
Electrostatic Analyzer with Variable Focal Length
Authors: Matsuda Hisashi
Published: February 2005

A method for the electrical control of the focal length of an electrostatic analyzer is proposed. The focal length of the apparatus depends on the shape of the electric field, and the electric field in the cylindrical condenser of finite length may be modified by changing the potential near the edges of the condenser. A 90° electrostatic analyzer for such a purpose has been constructed and the focusing character of this apparatus was investigated. The electrode assembly of the analyzer consists of two cylindrical condenser electrodes of finite length and two auxiliary plates near both edges. It was possible to focus a sharp radial image and a sharp axial image on a fluorescent screen at any location by applying a suitable potential to the auxiliary plates.
Simple Apparatus for the Generation of Pressures above 100 000 Atmospheres Simultaneously with Temperatures above 3000°C
Authors: Daniels William B. , Jones M. T.
Published: February 2005

Equipment has been constructed for experimentation at very high pressures and temperatures. With the modified Bridgman anvil device described, it has proven possible to maintain pressures in excess of 100 000 atm simultaneously with temperatures above 3000°C for periods greater than one hour. [The fixed points used to infer this pressure are taken to be the pressure values established by Bridgman for discontinuities of the electrical resistance of bismuth and barium, 25 650 kg cm−2 and 80 000 kg cm−2, respectively, and called the bismuth and barium points. Recent unpublished work indicates that the barium point pressure will probably have to be revised downward materially, reducing our pressure estimates in the upper range.] The use of an extrudable plastic compressible gasket is described. Several considerations are presented concerning the support of high pressure components constructed of cemented tungsten carbide. Coesite, almandite, and diamond have been synthesized in the apparatus.
Simple Methods of Determining Water Drop Sizes by Means of Photographic Emulsions
Authors: Koenig L. Randall , Spyers-Duran Paul A.
Published: February 2005

Two simple methods of using photographic emulsions as a means of determining the size spectrum of water drops are described. The methods are sensitive to droplets 80 μ or greater in diameter; one enjoys the advantage of requiring no advanced preparation of materials, the other provides a permanent record. The procedures were developed to obtain raindrop size distributions but may be applied equally well to problems concerning drop spectrums from spray systems.
Reflex Klystron as a High Speed Microwave Switch
Authors: Whitford B. G.
Published: February 2005

Nanosecond switching of rf power is achieved using a reflex klystron in a nonoscillating state for amplitude modulation. The variation of klystron input admittance with reflector potential is used. A review of reflex klystron theory is presented explaining the technique. Experimental work at X band using a hybrid T to separate reflected power from power incident on the tube shows that flat-topped rf pulses with rise time of 1.5 nsec and decay time of 6 nsec are possible. Switch ``off'' relative to switch ``on'' attenuation of 30 db was obtained with a reflector voltage swing of 10 v. It is believed that the technique is applicable at any frequency where reflex klystrons are available.
Improved Continuously Sensitive Bubble Chamber
Authors: Kato Ryuhei
Published: February 2005

An improved type of continuously sensitive bubble chamber has been constructed. In order to increase the sensitive volume and the sensitive time, the geometrical size and the heating system of the chamber are improved. We have observed that using an organic liquid and carbon dioxide solution as a liquid in the chamber, this chamber is sensitive to fast neutron irradiation.
High Yield Generator of Pulsed 14-Mev Neutrons
Authors: Braddock J. V. , Bullen T. G. , Dunn B. J. , McDonald D. F. , Miranda H. A.
Published: February 2005

Apparatus for obtaining 14-Mev neutrons in pulses of approximately 10-μsec duration is described. It employs a gaseous discharge in deuterium at low pressure whereby deuterons of up to 180-kev energy are generated and accelerated into a tritiated zirconium target. This method provides a much greater abundance of deuterons than has been obtainable with ion guns. In its present form the device constructed has given yields approaching the theoretically expected value of 1010 neutrons per pulse.
Generation of High Power Radio-Frequency Pulses by Means of an Exploding Wire Technique
Authors: Jones Ieuan R. , Wuerker Ralph F.
Published: February 2005

A method of generating high power radio-frequency pulses is described which utilizes the ``current dwell'' period which can occur when a thin wire is exploded by means of a high current. The rf oscillation occurs in a resonant circuit placed in series with the exploding wire. A circuit is described in which is obtained a 6-μsec duration pulse of 2.74-Mc oscillations.
Technique of Shunting Pulsed, High Field Magnetic Coils
Authors: Hughes H. G.
Published: February 2005

A simple technique for shunting pulsed, high field magnetic coils after the field has reached the maximum value is described.
Guided-String Cutter for Single, Metal Crystals
Authors: Wayson Alan R.
Published: February 2005

A guided string acid saw for the strain-free planar cutting of oriented single crystals is described. A Saran monofilament used as the acid carrying element is guided completely through the cut by a grooved blade serving the three-fold purpose of guide, pressure device, and follower for a position sensing mechanism which automatically controls the feed. Guiding of the string results in a width of cut to string diameter ratio considerably lower than that of unguided acid saws. Bismuth and copper crystals have been cut with excellent results using this device.
Cavity Method Suitable for Measurement of High Electron Densities in Plasmas
Authors: Anderson J. M.
Published: February 2005

It is shown that a columnar geometry of electrical gaseous plasma may be examined by the conventional microwave cavity method, and results may be interpreted such that plasma electron densities considerably above that corresponding to ``resonance'' with the applied microwave frequency may be determined.
``Boxcar'' Integrator with Long Holding Times
Authors: Blume R. J.
Published: February 2005

The bipolar output of the rf phase detector of the receiver in a nuclear magnetic resonance pulse experiment is fed through a 4-diode sampling switch to an RC integrator, whose output is read by a recording electrometer. The switch (a ``transmission gate'') includes two type 7266 ceramic thermionic diodes, whose back resistance is extremely high (> 1012Ω at −50 v). The Mylar integrating capacitor, therefore, discharges so slowly between successive sampling gates that the typical holding time with a 0.01-μf capacitor is ∼10 min. A simple method is given for using the ``boxcar'' as a sampling oscillograph for slowly and automatically plotting the entire boxcar input signal as it is seen on a cathode ray oscilloscope, but with the noise integrated out. There is a detailed discussion of circuitry, components, and performance.
Device for Indirect Registration of the Calibrated Arterial Upstroke in Man
Authors: Rodbard Simon , Mohrherr Roderick
Published: February 2005

A device has been built which, without requiring intra-arterial puncture, automatically constructs a calibrated upstroke of the arterial pulse wave as well as the durations and intensities of the arterial sounds. The horizontal sweep of a cathode-ray oscilloscope is triggered by the electrocardiogram. The vertical axis is determined by the height of the mercury column in the sphygmomanometer. The vibration amplitude and duration of the acoustic signal are recorded as the brightness and duration of the trace during each cycle.
Anticoincidence Gamma-Ray Spectrometer for Neutron Capture Spectroscopy
Authors: Bostrom C. O. , Draper J. E.
Published: February 2005

A total absorption NaI(Tl) gamma-ray spectrometer has been assembled and has been tested over the range 0–10 Mev with thermal neutron capture gamma rays. It employs an 8-in. diam by 12-in. NaI(Tl) anticoincidence mantel. The measured width at 8.5 Mev is 3% (full width at half-maximum). Typical spectra are presented. Measurements of efficiency, line shape, and resolution are analyzed. The usefulness of this spectrometer for analysis of complex spectra at high efficiency is demonstrated.
Modification of a Cosslett-Nixon Microfocus X-Ray Tube for Use as an X-Ray Microanalyzer
Authors: Dils R. R. , Zeitz L. , Keith D. L. , Huggins R. A.
Published: February 2005

A Cosslett-Nixon type microfocus x-ray tube has been modified for use as an electron probe microanalysis unit, producing an electron beam of adequate intensity approximately one micron in diameter. The design of the unit is discussed, and a description of the electron optical design and the associated electronic power supplies is included.
Flexure Mounted Beam Balance for Long-Term Magnetic Stability Measurements
Authors: Wilcox D. E. , Scarborough W. M. , Zingery W. L.
Published: February 2005

A beam balance was designed for the long-term measurement of permanent magnet stability. The balance measures an air-gap magnetic field change with a precision of one part in 30 000. The balance is supported on crossed flexures and operates on the torque-balance servo principle. A fixed torque is applied to the balance arm. Servo action causes the permanent magnet assembly to rotate in such a way as to create an opposition torque which is equal to that applied. The magnet speed required to establish torque balance depends on the square of the magnetic field. This speed is measured with great precision by a preset counter. A large number of magnet assemblies are measured.
Design of Germanium for Thermometric Applications
Authors: Blakemore J. S.
Published: February 2005

Germanium doped with certain impurities has a strongly temperature-dependent conductivity below the liquid air range, suitable for use in secondary thermometry. Two mechanisms are responsible for this behavior: (1) Down to about 10°K, the conduction is provided by free current carriers (electrons or holes) liberated from impurity atoms. (2) Control of the conductivity below ∼10°K is exercised by the relatively feeble ``impurity conduction'' process. For both processes, conductivity depends not only on the primary doping atoms but also on the density of compensating impurities; indeed, low temperature impurity conduction can be inhibited unless some compensating centers are present. In order that germanium thermometers should have resistance-temperature characteristics which ``scale'' reasonably well from one unit to another, it is desirable to deliberately incorporate a number of compensators, sufficient to suppress any influence of uninvited impurities. Moreover, by control of both the primary and compensating impurity densities, a resistance-temperature characteristic can be controlled to emphasize a desired range. The transition between free carrier conduction and impurity conduction is relatively sharp for some impurities (e.g., gallium) but occurs over a wide range of temperature for other impurities (e.g., arsenic). This influences the suitability for thermometry in various ranges. Characteristics of wide range and narrow range thermometer materials are illustrated.
Electrical Conductance Cell Assembly for Use with Aqueous Solutions up to 800°C and 4000 Bars
Authors: Franck E. U. , Savolainen J. E. , Marshall William L.
Published: February 2005

An electrical conductance cell assembly, designed for use with aqueous solutions at extremes of temperature and pressure, is described. Its utility was demonstrated by measurements of the conductance of 0.010 molal KCl solution at 800°C and at pressures up to 4000 bars.
Thermal Diffusivity Measurements on Metals at High Temperatures
Authors: Rudkin R. L. , Jenkins R. J. , Parker W. J.
Published: February 2005

A flash method for the measurement of the thermal diffusivity of metals up to 1800°C is described. A high intensity short duration light pulse is absorbed in the front surface of a thermally insulated specimen a few millimeters thick heated in an induction furnace and the resultant temperature history of the rear surface is measured by a lead sulfide cell, displayed on an oscilloscope, and photographed by a Polaroid Land camera. The thermal diffusivity of the material is determined from this temperature versus time curve provided the theoretical boundary conditions are experimentally satisfied. Measurements of the thermal diffusivity of Armco iron, molybdenum, and titanium have been made.
Digitization and Integration of Reflecting Galvanometer Deflections
Authors: Rider N. E. , Bradley E. F.
Published: February 2005

A method of digitizing the deflections of a reflecting galvanometer and presenting the results directly on electromagnetic counters is given. The use of expensive dc amplifiers and/or multipoint recorders can often be avoided and automatic integration for time mean values of physical quantities is conveniently achieved.
Line Shape in Mössbauer Spectroscopy
Authors: Ruby Stanley L. , Hicks John M.
Published: February 2005

The line shape, amplitude as well as half-width, to be expected experimentally from a natural linewidth thin source and a natural linewidth Mössbauer absorber has been computed as a function of the thickness of the absorber. The experimental result using stainless steel source and absorber and correcting for background has double the expected width, but nearly the correct fractional change in rate. This is compatible with a blurring due to dissimilar microenvironments of about ±0.10 mm/sec.
Drift Tube-Mass Spectrometer for Studies of Low-Energy Ion-Molecule Reactions
Authors: McDaniel E. W. , Martin D. W. , Barnes W. S.
Published: February 2005

Apparatus has been developed for the mass spectrographic study of ion-molecule reactions occurring under gas-kinetic conditions. Ions are produced by electron bombardment inside a long drift tube containing gas at a pressure of up to about 0.7 torr. The ions diffuse down the drift tube under the influence of a weak electric field. A sample of the ion population at the end of the drift tube is extracted through a two-stage, field-free differential pumping section and passed into a 60° magnetic deflection mass spectrometer. The number of ion-molecule collisions in the drift tube may be varied over a wide range by changing the source position and/or the gas pressure. Information concerning the nature and probability of the reactions occurring is revealed by the resulting changes in the ionic mass spectrum.
Application of Thermistors to Measurements in Moving Fluids
Authors: Rasmussen Robert A.
Published: February 2005

Quantitative considerations of the effects of fluid motion on the cooling of self-heated thermistors are essential to their efficient application in many instruments. The investigations reported here were undertaken for the purpose of ascertaining these effects and obtaining useful expressions with which to describe them. Expressions for the time constant, sensitivity, and dissipation factor are derived, and their significance is demonstrated in qualitative considerations of practical instrumentation problems.
Piezoelectric Device for Measuring Dynamic and Static Forces
Authors: Langenecker B.
Published: February 2005

A modified piezoelectric device is described for measuring dynamic and static forces which is simpler and more sensitive than the standard devices. The standard piezoelectric interferometers, piezocapacitance devices, etc., utilize displacement of the resonant frequency of piezoelectric substances under applied loads; the present device makes use of the relation between the magnitude of a dynamic or static force applied to a piezoelectric specimen and its electromechanical coupling factor. Comparison with the standard devices shows: sensitivity of the present device is about 2 magnitudes higher in case of small forces (tenth of grams) and sensitivity is equal in case of large loads (tons).
Phase Stabilized Klystron System and Its Application to Microwave Spectroscopy and Microwave Frequency Standards
Authors: Narath A. , Gwinn William D.
Published: February 2005

A system is described for stabilizing the frequency and phase of a klystron where its frequency is to be varied continuously at any predetermined rate. This system, when applied to a microwave spectrograph and frequency standard, greatly improves the resolution, sensitivity, and accuracy of frequency measurements. The system also has application to superheterodyne detection systems in which the local oscillator is phase locked to the signal klystron.
Development of a Simple, High-Resolution Mobility Analyzer for Small, Charged Particles
Authors: Langer G. , Radnik J. , Templeton L.
Published: February 2005

The design and operation of a simple but sensitive mobility analyzer for small, charged particles is described. The unit employs a system whereby the aerosol is introduced into the parallel plate collector system surrounded by an air sheath. The latter uses clean, dry air to prevent any leakage problems with the supporting insulators. The use of this aerosol filament allows for high resolution as shown by initial tests with a fine, platinum aerosol.
Construction and Calibration of a Cylindrical Knudsen Gauge
Authors: Miller George A.
Published: February 2005

The construction and calibration of a Knudsen gauge of the Klumb-Schwarz modification is described. A practical method of correcting for nonlinearity in response is developed.
Minimum Detectable Power of a Pyroelectric Thermal Receiver
Authors: Cooper J.
Published: February 2005

For a ferroelectric crystal, the rate of change of polarization with temperature is large, especially close to the Curie point where a phase transition occurs. Thus, a change of polarization due to an incident radiation flux gives rise to a large pyroelectric voltage output. The ``minimum detectable power'' Wm is calculated. For barium titanate, the value of Wm thus obtained is found to be much better than other uncooled thermal receivers and comparable with a superconducting bolometer, if dielectric noise at the transition is small. In certain cases, Wm is limited only by temperature noise, so that the receiver may be thought of as a true thermal receiver.
Digital Transistor Circuit for Generation of Timing Pulses for Pulsed NMR
Authors: Lowe Irving J. , Howard Robert L.
Published: February 2005

A source of timing pulses for pulsed nuclear magnetic resonance experiments is described. The unit is a digital system that uses a signal from a stable oscillator as a time base. This signal is fed to a string of binary counters that act as frequency dividers. Outputs of the binary counters are fed to trigger circuits that pass only predetermined pulses to generate the pulse sequences. The unit uses transistor circuits that need only noncritical, inexpensive components.
Thermoelectric Instability of Some Noble Metal Thermocouples at High Temperatures
Authors: Walker B. E. , Ewing C. T. , Miller R. R.
Published: February 2005

Thermoelectric instabilities of noble metal thermocouples and individual thermoelements (platinum, rhodium, iridium, iridium-50% rhodium, and several platinum-rhodium alloys) have been studied in the temperature range from 1000 to 1700°C under oxidizing and neutral atmospheres. The principal source of instability was found to be contamination of the thermoelements by impurities from ceramic protection tubes. Several grades of alumina sheathing were tested, and thermocouple errors associated with each grade are reported. Criteria are discussed for the selection and application of noble metal thermocouples to attain maximum thermoelectric stability.
Air Alpha Proportional Counter Insensitive to Atmospheric Humidity
Authors: Ferrari A. M. R. , Borkowski C. J.
Published: February 2005

A conventional alpha proportional counter which uses air as the counter gas is sensitive to high relative humidity and generates spurious pulses that cannot be distinguished from actual alpha pulses. It has been found possible to operate such a counter satisfactorily at high relative humidity by passing a small current (∼15 mA) through the center wire. In this manner the center wire is heated and the relative humidity of the surrounding sheath of air is reduced sufficiently so that operation of the counter at high relative humidity is comparable to operation with dry air. Two different mechanisms are proposed for the formation of spurious pulses in such a counter at high relative humidity.
Simple Photoelectric Process-Stream Analyzer
Authors: Glasser L. G. , Kanzler R. J. , Troy D. J.
Published: February 2005

A simple photoelectric instrument for measuring spectral absorption of ultraviolet or visible radiation can be broadly applied in process-stream analysis. Measurement at two selected wavelengths, logarithmic response to radiation, and attention to spectral purity of light sources simplify use of the instrument and compensate effectively for a number of potential measurement errors.
Vacuum X-Ray Diffractometer for High Temperature Studies of Metals Sensitive to Contamination by Oxygen and Nitrogen
Authors: Willens R. H.
Published: February 2005

An x-ray diffractometer operating in vacuum has been designed and constructed to study metals sensitive to oxygen and nitrogen contamination at elevated temperature. The instrument operates in a vacuum of 2×10−6 mm Hg in which the partial pressure of oxygen and nitrogen is several orders of magnitude lower than the total pressure. The specimen is heated by radiation from a resistance-type furnace to 1200°C. With this instrument it is possible to obtain lattice parameters which are accurate to one part in forty thousand. The thermal expansion of titanium has been investigated up to 650°C. Between room temperature and 400°C the expansion coefficients in directions perpendicular and parallel to the c axis are 9.41×10−6 and 11.18×10−6/°C, respectively. For a random polycrystalline sample, the mean expansion coefficient is 10.0×10−6/°C.
High Speed Instrument for Quantitative Mapping
Authors: Green Donald R.
Published: February 2005

A new, high speed instrument for mapping the magnitude of a variable, such as temperature, vibrational amplitude, radiation, height, etc., at different positions on a surface is described. This instrument records the values of the variable as broken line segments on a two-dimensional map. The position and length of each line segment represent the position and associated average value of the variable during the recording of that particular line segment. Visible density of the map is greater within regions of greater line length so that a qualitative picture is obtained at a glance. A quantitative measurement can be obtained from the map with a ruler. The present instrument was designed for application to heat transfer testing of nuclear fuel elements. However, the method may have applications in any field where it is desirable to superimpose a quantitative record on a qualitative picture.
Origin of Apparent Negative Impedance in Three Terminal Measurements
Authors: Tallan N. M. , Graham H. C. , Vest R. W.
Published: February 2005

A brief discussion is presented of the occurrence of spurious negative dissipation factors, which appear to correspond to negative resistances, in the measurement of three terminal low loss specimens. The origin of these negative values is traced to series resistance in the guard ring lead and a technique, involving the use of a four electrode specimen, is described which obviates the need for extremely low resistance electrodes and leads.
System for Processing and Recording Excitation Function Data
Authors: John Robert M. St. , Lin Chun C. , Stanton R. L. , West H. D. , Sweeney J. P. , Rinehart E. A.
Published: February 2005

A system which automatically processes optical excitation data is described. This system is capable of producing data faster and of better quality than the old method. The apparent cross section for excitation by electron impact of a particular state is proportional to the light intensity of a radiative transition from this level divided by the product of the electron beam current times pressure. The light intensity is measured from the output current of a photomultiplier tube. When the pressure in the collision chamber is maintained constant, the apparent cross section is proportional to the ratio of photomultiplier current to electron beam current. This ratio is continuously computed by an analog divider while the electron accelerating voltage power supply is slowly swept through its range by a motor and gear reduction system so as to give a visual display of the excitation function on an oscilloscope. Permanent records of the function are made by photographing the trace. Absolute values of the excitation function can be obtained by calibration against a standard lamp. In order to suppress noise and light signals not originating in the collision chamber, the light beam from the collision chamber is square wave modulated; this then is converted into a sinusoidal wave by means of a tuned amplifier. This in turn is rectified by a phase-sensitive detector which produces a dc voltage proportional to the signal light intensity. Circuits of the phase-sensitive detector and modulation unit are presented.
Applications of Modulation Techniques to High Resolution Nuclear Magnetic Resonance Spectrometers
Authors: Anderson Weston A.
Published: February 2005

An NMR spectrometer system is described which incorporates the use of magnetic field modulation for the simultaneous purpose of baseline stabilization and stabilization of the resonance condition. Several other modulation techniques are briefly described.
Apparatus for ``Hyperbolic Glow Curves''
Authors: Halperin A. , Leibovitz M. , Schlesinger M.
Published: February 2005

A simple apparatus is described which provides a heating rate proportional to the square of the absolute temperature (T2). The apparatus is based on a Wheatstone bridge having a platinum heating coil in one arm and a variable resistor which changes linearly with time in the opposite arm. An example of a recorded glow peak is given and compared to the theoretical curve.
Preparation and Tensile Testing of Thin Metal Foils of Rolled Material
Authors: Lawley A. , Schuster S.
Published: February 2005

A photoengraving technique is described for the preparation of tensile specimens from rolled copper foil down to ∼2 μ in thickness. The tensile testing procedure gives a complete stress-strain analysis of the foils to the point of fracture. Yield stress, ultimate tensile strength, and elongation to fracture are measured.
Versatile Temperature Jump Apparatus for Following Chemical Relaxations
Authors: Czerlinski Georg
Published: February 2005

An apparatus is described with various modifications for the observation of chemical relaxation upon fast temperature rises, 2 to 4° within a few microseconds. Several types of concentric and thermostated discharge tubes are described. The smallest type holds only 50 μl, which is thus ideal for investigating biological systems with the temperature jump method. Fast temperature rises are produced by discharges of capacitances through an electrolytic solution. Changes of the chemical system are detected spectrophotometrically by means of fast photomultipliers. The signal is amplified and observed oscillographically. Special emphasis is placed on high geometric flux (use of conical lenses).
Low-Level Low-Frequency Detection System
Authors: Larsen Neil T.
Published: February 2005

An amplifier and detector having application in a null detection system or as a servo amplifier in low-frequency ac instruments is described. The design may be adapted to operate with a carrier frequency in the range from a few cps to a few kc. The unique and apparently unrecognized advantages of operating with a carrier frequency which is an even subharmonic of the principal coherent disturbing signal, such as the power line, are discussed in detail. Design considerations and performance data are presented, permitting an evaluation of the suitability of the device for a given application. For a particular input circuit configuration, it is conservatively estimated that a signal of less than 1.6×10−22 W from 100-Ω source may be detected with an observation time of less than 1 min. Experiments indicate that, with this device, the sensitivity is primarily limited by thermal noise in the input and by induced signals in the input leads.
Current Measurement and Transient Skin Effects in Exploding Wire Circuits
Authors: Bennett F. D. , Marvin J. W.
Published: February 2005

The transient response of the coaxial, current-measuring shunt commonly used in high current, high frequency applications (up to 1 Mc) is analyzed by Laplace transform methods. The exact solution is obtained as is an approximate solution which allows estimates to be made of the errors expected. The current shunt measuring a damped oscillation will always report an initial current slope of zero, and the maximum current slope is sensed shortly after switch-on. It is several percent low in typical cases. At the true current maximum, the shunt reading is a few tenths percent low and lags the impressed current by a small fraction of a cycle. A second problem concerning the transient resistance of an idealized plate condenser is analyzed using the asymptotic solution for current. A numerical calculation indicates no alteration of initial conditions on the damped oscillation to arise from this source so long as the characteristic damping time of the transient skin effect is small compared with the ringing time.
Fast Gas Valve for Plasma Research
Authors: Lowder R. S. , Hoh F. C.
Published: February 2005

A new type of fast gas valve has been developed for plasma experiments requiring a rapid injection of gas into a vacuum. The valve can be opened and closed within 70 μsec and the gas injection is highly reproducible. A fast opening and closing of the valve, which consists of a low weight aluminum disk sealing against a soft O-ring, is achieved by energizing a coil placed on the O-ring side of the disk and allowing the disk to hit a nearby piece of aluminum and bounce back onto the O-ring. The density distribution of the expanding gas in the vacuum region near the valve was mapped out at particular times shortly after the opening of the valve by using a fast gas gauge. Comparative measurements with a spring loaded valve showed the present valve to have a shorter opening time and much better reproducibility.
Triggering Mechanism of Low-Pressure Spark Gaps
Authors: Hancox R.
Published: February 2005

The triggering delay in two low-pressure spark-gap switches, operating in the pressure range 10−3 to 3×10−2 mm Hg, has been measured under a wide range of conditions. When the trigger pin is in the negative electrode, the delay is found to consist of two components. The first part depends on the construction of the trigger pin, the trigger voltage, and the impedance of the trigger circuit, while the second part depends on the nature and pressure of the gas in the gap, and the voltage and impedance of the circuit being switched. If the trigger pin is in the positive electrode a further delay is added which is approximately equal to the transit time of an ion across the gap. A mechanism for the breakdown is proposed which is consistent with the measurements and with previously reported results.
Bakeable uhv Valves with Long Life
Authors: Medicus G. , Jehn W.
Published: February 2005

Bakeable uhv valves with leak rates below about 5×106 molecules/sec ≈ 1.5×10−16 liters/sec, and one hundred or more baking and closing cycles are described. The long life and the low leak rates are achieved by plastic deformation and low-loss confinement of a thin Pt gasket diffused onto a narrow spherical zone of a tungsten carbide seat ring, with a tungsten carbide hemisphere serving as a stopper.
Technique for the Measurement of Short Carrier Lifetimes
Authors: Choo S. C. , Heasell E. L.
Published: February 2005

The phase shift method for the measurement of semiconductor carrier lifetime has been extended by the use of a light beam modulated at frequencies up to 4 Mc with a Kerr cell, to provide direct measurement of lifetimes down to at least 10−8 sec. Some typical results for the temperature variation of lifetime in indium antimonide are presented.
High Geometry Gas Cell Proportional Counter
Authors: Ludwick J. D.
Published: February 2005

A 4-chamber proportional counter was built with very thin windows to detect weak beta radiation in an external gas cell. The instrumental design permits relatively high counting efficiencies and also incorporates an anticoincidence background reduction feature inherent in the detectors' position, with respect to spurious cosmic-ray produced events. Gaseous materials containing the weak beta-emitting radioisotopes Kr85, C14, and H3 have been detected using this instrument. Over-all counting efficiencies for these isotopes were 55%, 26%, and 1%, respectively. The specific activity of the material is calculated from PVT data in the sample cell. After calibration, the counter is useful as a means of secondary standardization or where impure gas samples must be tolerated.
New Ratio Ratemeter
Authors: Hindel Robert
Published: February 2005

A new continuous ratio ratemeter is described which gives a linear indication of the single-channel rate divided by the sum rate. The effective time constant of response is derived and the first four statistical moments are calculated for random channel inputs. The predicted performance is verified by the Monte Carlo method and through experimental results. It is furthermore shown that the conventional linear ratemeter is a special case of the more general ratio ratemeter.
Vacuum Evaporation Source with Double-Wall Cylindrical Graphite Heater and Nozzle Outlet
Authors: Hemmer Ferdinand J. , Piedmont James R.
Published: February 2005

A resistance heated source is described which is capable of evaporating refractory materials in vacuo. Film thickness uniformity and deposition efficiency are improved through the use of a converging-diverging nozzle at the crucible outlet. The source also features a double-wall cylindrical graphite heater configuration which facilitates the reduction of heat losses and copper to graphite electrical connectors capable of operating over a large temperature range.
Low Temperature Double Path Absorption Cell
Authors: Smith F. J. , Smith J. K. , McGlynn S. P.
Published: February 2005

A low temperature double beam absorption cell designed specifically for the Beckman DK, DK-1, and DK-2 is described. It may be used down to at least −196°C in quantitative measurements of visible and ultraviolet absorption spectra of liquid or rigid glass solutions. A detailed listing of low temperature glasses and low temperature solvents which might be used in conjunction with the cell is given. In addition, some possible cooling systems are included.