bluuebunny/crossref_metadata_2025 huggingface dataset:
Light Extinction Photometer for Measurement of Particle Sizes in Polydispersions
Authors: Adams J. M.
Published: February 2004

By application of the Mie theory of light scattering by spherical particles and Stokes' law of settling, a measurement of the extinction of a monochromatic light beam over a known pathlength through a turbid medium allows a determination of the particle size distribution within the medium. Apparatus was fabricated and used successfully for the determination of particle size distributions of interhalogen compounds suspended in liquid nitrogen. The optical probe assemblies were constructed of a size small enough to fit into a 10 cm vessel. Optical coupling was accomplished with flexible light guides between the light source, probes, and detectors. To eliminate errors due to changes in the light source intensity or detector sensitivity over the relatively long duration of a run, a continuous reference measurement was provided by optical sampling.
Improved Electron Beam Scanning System for Electron Microprobe X-Ray Analyzers
Authors: Kniseley Richard N. , Laabs Francis C. , Van Zuuk Dean
Published: February 2004

An improved electron beam scanning system for electron microprobes has been developed which provides high quality sample current images at a frame repetition rate of ∼45 frames/sec and at sample currents as low as 1 nA. The sample current amplification system consists of an emitter follower at the output of the probe console followed by a limited bandpass video amplifier. Careful selection of the amplifier bandpass, based on the exact scanning frequency, allows high amplification of the signal information while rejecting a large portion of the noise.
Evaluation Tests of a Fixed Frequency Vibroscope
Authors: Holdaway H. W.
Published: February 2004

An evaluation test has been made of a fixed frequency, variable tension vibroscope in which the gauge length was established by passing the fiber over one pin support and under the other. Two lengths of very uniform terylene fiber of linear density ∼0.95 Tex were used in tests all of which were done at 17.8°C and 65% RH. A method was developed for accurately evaluating the total mass of long lengths of filament from a succession of readings of the vibroscope taken at intervals of half of the gauge length along the fiber. The discrepancies, approximately 3 μg in both instances, between the weighed masses of 735 and 535 μg of fiber are slightly larger than the prime source of uncertainty, that of the weighings, and are both in the direction implying an underestimation of linear density by the vibroscope. This result is consistent with an error due to underestimation of the correction for stiffness of the fiber, the latter being based on an assumption that the supports behave as ideal pinned ends. Despite the elementary nature of the principle underlying the free or forced vibrations of a tensioned filament supported at its ends, its use as an instrument requires sophisticated corrections for a number of departures of real vibroscopes from the idealized model. These corrections can be quite significant in some configurations, and, as discussed in the paper, the theoretical bases for two types of correction have yet to be fully developed. For these reasons a metrological study such as this is important in order to validate the use of the vibroscope as an absolute instrument. Since the form of vibroscope employed was such that the effect of the less theoretically certain corrections were minimized, some reserve should be exercised in accepting this study as a validation for forms of vibroscope employing a variable frequency. The results should be equally applicable, however, to vibroscopes operating at a fixed frequency but with span or gauge length varied for resonance.
New Oscilloscope Recording Camera
Authors: Burton Alexis L. , Andrews Robert V.
Published: February 2004

This paper describes a new oscilloscope or streak camera. This machine provides a means of recording events as variations of density on continuously transported motion picture film. Furthermore, it is also designed for reproduction of these records by playback. This instruments gives excellent results in terms of speed stability and linearity of film transport. The quality of the records is superior to that obtained with commercially available cameras. This was achieved by modifying and adapting several designs commonly used in optical cine film sound recorders and reproducers.
High Precision Temperature Controller Incorporating Variable Sensitivity and Proportional Control
Authors: D'Arcy R. L. , Stearn A. E.
Published: February 2004

A temperature controller utilizing continuous proportional control is described. The system uses a saturable reactor to control the heat input at a level that will continuously balance the heat losses from the system. Sensitivity of ±0.005°C coupled with drift of less than 0.05C° month has been achieved in a system using air as the heat transfer medium.
Pulsed Illuminator with Rapid Recovery
Authors: Goldie H. , Goldman M. A.
Published: February 2004

An electrodeless halogen discharge, at relatively high average power levels and low pressure, has been shown to be an effective, high repetition rate, pulsed light source. A high frequency microwave source is matched to the discharge and energy is coupled through the insulating envelope into the gas volume. Though measurements have not been made at multikilowatt power levels, the results do indicate that intense light sources usable to repetition rates of hundreds of kilohertz are feasible.
Simple Stark Modulation Absorption System for High Temperature Microwave Spectroscopy
Authors: Murty A. Narasimha , Curl R. F.
Published: February 2004

A microwave absorption cell of simple design for work up to a temperature of 1000°C is described. A novel method is employed for mounting the Stark septum avoiding the use of insulators inside the waveguide. The system has been used (up to ∼800°C) for the determination of dipole moments of some Gr IV sulphides from Stark effect measurements.
Track Density Measurement in Dielectric Track Detectors with Scattered Light
Authors: Schultz Warner W.
Published: February 2004

Fission track densities in glass and in Lexan polycarbonate resin have been measured using light scattered from the tracks as a measure of the track density. Scattered light was found to be proportional to track density up to the point at which tracks begin to overlap. For the two track detector materials tested, a scattering angle was found at which optimum signal-to-backgound ratios are obtained.
Multifoil Thermocouple Gauge for Measuring Pressures up to 1 atm
Authors: Teagan William P.
Published: February 2004

A thermocouple gauge is described which is capable of indicating pressure in the complete pressure range between 10−3 Torr and atmospheric pressure. The experimental results obtained from a test gauge are presented and found to be in good agreement with analysis. The gauge utilizes the free molecule and transition gaseous heat conduction that exists in a gas contained between the foils of multifoil thermal insulation up to pressures in the 100 Torr range. The resulting pressure variation of the thermal conductivity of multifoil insulation is used to indicate the pressure.
Temperature Determination of Copper and Iron in the Electron Microscope
Authors: Vahldiek F. W.
Published: February 2004

A technique is described which allows temperature measurements of Cu and Fe (grids and thin foils) using Cu-constantan and Fe-constantan thermocouples, respectively. Beam temperatures ranging from 20–80°C were determined for Cu grids. For Cu and Fe foils, beam temperatures ranging from 40–66°C were observed. Temperature gradients of 60–150°C were encountered in Cu and Fe foils between electron beam and hot stage. High temperature electron diffraction studies on the oxidation of Fe resulted in patterns to be indexed as γ-Fe2O3 or Fe3O4. The dislocation velocity in Fe was determined to range from 10−4–10−5 cm/sec. The ratio of immobile to mobile dislocations in Fe was estimated to be 104:1 at ``room temperature.'' At temperatures of 500–700°C an immobile-mobile dislocation ratio of 102:1 was calculated from electron microscopic observations for Fe.
Calibration of a Satellite-Borne Soft Particle Spectrometer
Authors: Wright W. H.
Published: February 2004

The calibration of an electrostatic deflection, auroral particle spectrometer, which uses bare electron multipliers for detectors, is described. The spectrometer measures the fluxes of both electrons and protons in the energy range 10 to 10 000 eV. An attempt is made to minimize the uncertainty in the measurement of the absolute particle flux to which such instruments are prone. The detection of electrons and protons by electron multipliers is investigated as a function of energy and flux of the particles, and for different values of the multiplier gain.
Automatic High Speed Particle Sizing Using a Gas Laser
Authors: Schleusener Stuart A.
Published: February 2004

Automatic high speed particle sizing is accomplished by using a visible He–Ne gas laser cavity beam as the sizing instrument and a multichannel pulse height analyzer to store and present visual size frequency distribution information in real time. Particle sizing rates as high as 10 000/sec are attainable in size ranges from about 1 to 300 μ.
Angular Correlation and Distribution Attenuation Coefficients for Planar and Coaxial Ge(Li) Detectors
Authors: Avignone F. T. , Frey G. D.
Published: February 2004

The coefficients Q2 and Q4 used to correct experimentally determined A2 and A4 angular correlation and distribution coefficients, for the finite solid angle subtended by the detectors, are tabulated for various planar and coaxial Ge(Li) detectors. The following planar detectors are considered: (1.1 cm radius ×0.4 cm thick), (1.1×.6), (1.4×0.5), (1.4×1), (1.6×0.6), (1.6×0.9), (1.8×0.8), and (2×1). The coaxial detectors considered are (1.3 cm radius ×3.5 cm long), (1.3×4), (1.3×4.5), and (1.3×5), each with a 0.6 cm bore on the axis. These represent popular, commercially available detector sizes. Tabulations of the coefficient for the case in which all absorption occurs on the surface, and for the case in which it occurs on a midplane, are included. The latter may be used for corrections when charged particle detectors are used.
Dry-Powder Aerosol Dispersing Device with Long-Time Output Stability
Authors: Crider Walter L. , Barkley Naomi P. , Strong Arthur A.
Published: February 2004

Operating parameters and performance characteristics are described for a dry-powder Fe2O3 aerosol disperser used for periods up to 23 h with minimal operator attention. Aerosol mass concentration fluctuations in a 3 m3 dynamic-flow chamber were determined over 23-h periods for the aerosol generator with and without electronic feedback circuits. From the data presented in this paper and from observations made during 2 weeks of continuous operation, this ``rust duster'' was found to be capable of continuously dispersing Fe2O3 powder into 1.5 m3 of air per minute to produce aerosols having median concentrations from about 0.7 to 3.0 mg m−3. Over most of this concentration range, with or without the feedback control circuit, the mass concentration of Fe2O3 aerosol was kept within the ±50% variability limit originally set as acceptable for chronic animal exposure conditions.
Asymptotic Theory of Beam Break-Up in Linear Accelerators
Authors: Panofsky W. K. H. , Bander M.
Published: February 2004

The phenomenon of radial beam break-up observed in terms of long, multi-section electron linear accelerators has been analyzed using a multi-cavity model. In this model the source of regeneration due to backward wave amplification is ignored. The dominant phenomenon involves build-up of radial modes in each cavity as coupled by the electron beam. The resulting differential equations are integrated by the method of steepest descent and by a numerical iteration method. Scaling laws in terms of the pulse length, beam intensity, energy gradient, and length of the structure are derived.
Thermistors as Circuit Elements in Low-Frequency Circuits
Authors: Kraus Kamil
Published: February 2004

The properties of a polarizing NTC, as well as a PTC resistor, that arise from the fact that thermistors act as a negative resistance to low frequency signals, have been investigated and the impedances were deduced both theoretically and by experiment. The properties of the thermistors as a conductor and a capacitor were investigated and the conditions for oscillating at low frequencies were given. In addition, a phase-advance network and an integrating network were proposed.
Photographic Apparatus for the Study of Fracture in Metals
Authors: Ezrol H. , Margolin H. , King R. W. , Bunshah R. , Venkatesan P.
Published: February 2004

A photographic apparatus capable of photographing metal specimens undergoing fracture has been constructed. It consists of an image converter camera, a light source, an apparatus to fracture the specimens and a synchronizing system. The image converter camera can take up to 8 pictures that have exposure times of 0.1, 0.3, 1, 3, or 10 μsec with interframe intervals of 0.5, 1.5, 5, 15, or 50 μsec. The only restriction on selection of exposure time and interframe interval occurs at an interframe time of 0.5 μsec for which the exposure time must be 0.1 μsec. Triggering of the image converter camera can be accomplished with a time delay or with a device which triggers at a preselected strain in the specimen. A photograph of a zinc crystal at −58°C with a crack travelling at 56 m/sec is presented.
Lapping Machine Attachment for Preparing Oriented Crystals
Authors: Johnson Donald E.
Published: February 2004

The description and use of a lapping attachment for the preparation of x-ray oriented reference surfaces on crystal specimens is presented. The surfaces are prepared on specimens which have been mounted and oriented on a goniometer device. The resulting prepared surface provides a reference face for machine finishing a crystal sample with all faces in a known relation to the crystalline axis or planes. Test runs of various specimens have produced finished surfaces that have retained their original orientation within 0.1° of error.
Charged Particle Transmission through Cylindrical Plate Electrostatic Analyzers
Authors: Theodoridis G. C. , Paolini F. R.
Published: February 2004

The transmission characteristics of cylindrical plate electrostatic analyzers are derived by applying the results of a previous study on the spherical plate analyzer. A transmission matrix is derived for the cylindrical analyzer; coordinates of the matrix are energy and angle of incidence, and the elements are percentage transmission for broad beams of particles. Comparison with a spherical analyzer shows that resolutions (full width half maximum angular and energy responses) are not much different, although peak transmissions are greater by almost 40% for the spherical analyzer. Angle and energy response functions are asymmetric for the cylindrical analyzer; in particular, this analyzer has a long high energy tail. Energy-angle factors are calculated from transmission matrices and are essentially identical for the two species of analyzer.
Double Beam Vacuum Spectrophotometer for Far Ultraviolet Investigations
Authors: Castex Marie-Claude , Romand Jacques , Vodar Boris
Published: February 2004

A spectrophotometer for measuring the transmission of gaseous and liquid samples in the range of 2500 to 1150 Å and having a resolution of 0.3 Å is described. Tests made show that by using the electronic ratio method a higher accuracy may be obtained than by the optical balancing method. Some spectra are discussed for demonstrating the performance of the spectrophotometer.
Theory of the Parallel Thermocouple
Authors: Wilson Alan D. , Ulsh Holmes B.
Published: February 2004

A thermocouple comprised of two elements connected in parallel and connected in series to a third element is analyzed. It is shown that the resulting thermoelectric power of the combined system is a simple function of the thermoelectric power of each and the electrical conductance of the metal conductors. Further, a thermocouple with a certain specific thermoelectric power can be constructed.
Fast Acting Diaphragm Cutter
Authors: Spurk J. H. , Gion E. J.
Published: February 2004

A diaphragm cutter with short response time, where the diaphragm is placed sandwich-like between a movable and fixed spider arrangement, is described. The principle of operation is based on Ampere's law. The experimental path of the movable spider is compared with theoretical prediction taking into consideration the actual cross section of the conductors, and good agreement is found.
Cryostat for Thermal Measurements between 2–300°K
Authors: Bigeleisen J. , Brooks F. P. , Ishida T. , Ribnikar S. V.
Published: February 2004

A modification of the Giauque-Johnston cryostat for thermal measurements in the temperature range 2–300°K has been designed and constructed. The cryostat utilizes efficient heat switches for cooling. A variable temperature regulated radiation shield between the cold wall and the inner sections of the cryostat leads to a working section which can be maintained to a millidegree at any temperature in the working range of the cryostat. The operation and performance of the cryostat are described.
Terminal Pulsing on a Low Energy Electrostatic Accelerator
Authors: Chudleigh P. W.
Published: February 2004

The modification of a low energy electrostatic accelerator for terminal pulsing is described. Beam pulse durations as low as 3.7 nsec have been obtained at the target after acceleration. Under typical operating conditions the beam pulse duration is 4–5 nsec with peak currents of 100–200 μA and a pulse repetition period of 200 nsec.
Fast Sensitive Smith Chart Plotter or Microwave Reflectometer
Authors: Kyhl Robert L.
Published: February 2004

Real and imaginary components of microwave reflection coefficient are observed simultaneously with a response time of 1 μsec for use in paramagnetic resonance experiments. At a signal strength of one μW and an i.f. bandwidth of 3 MHz a change in reflection coefficient of 5×10−4 is detectable. When the experiment permits a larger signal strength or a narrower system bandwidth, increased sensitivity is available. Adjustment procedures that use a sliding short and a matched load are described.
High-Pressure High-Temperature Visual Cell for Interfacial Tension Measurements
Authors: Schoettle Volkmar , Jennings Harley Y.
Published: February 2004

This paper describes an apparatus for measuring a wide range of interfacial tensions at greatly varied pressure and temperature (1 to 817 atm and 25 to 176°C) by the pendent drop method. A visual cell, with specially constructed seals, contains one of a selection of turret-rings. Each ring holds five needles with different sized tips, each of which can be rotated into operating position at any time. Unique details are illustrated.
Instrument for Measuring Fluid Pressures at a Solid Boundary
Authors: Boadway J. D. , Kennedy R. J.
Published: February 2004

The instrument described in this paper was developed to measure fluid pressures at a boundary surface without use of an open tap. The device consists of a metal diaphragm located in the boundary surface and capable of indicating through an electrical contact when the pressure on its inner surface exceeds that of a reference pressure on the outer side. Where static pressures are involved the precision which can be attained by use of this method is limited mainly by the means by which the reference pressure is adjusted and measured. When this device is used in a dynamic system, where pressure pulsations are present, a special form of integrating circuit is required to determine the median pressure. It is also possible to obtain statistical information concerning the pressure pulsations with the integrator.
On-Board Plasma Data Processor
Authors: Schaefer David H. , Snively James W.
Published: February 2004

A computing device that calculates quantities related to the mean, variance, and mode of the distribution of plasma as a function of the azimuthal angle of the spin stabilized satellite is aboard Explorer XXXIV. The device uses a combination of integrated circuits and discrete components including tunnel diodes. Performing computations aboard the spacecraft and telemetering the results of the calculations permits important features of the data to be sent using about one-twentieth of the number of information bits that would be required to transmit histograms of the collected data.
Precision Mask Changer for Ultrahigh Vacuum Systems
Authors: Seitchik J. A. , Stein B. F. , Goldberg N.
Published: February 2004

A precision mask changer has been fabricated which uses a novel alignment technique to obtain precise registration between successive evaporations onto heated substrates in ultrahigh vacuum. A basic feature is the manipulation of the substrate while it is under vacuum and at the desired temperature. The registration process is observed by means of a split field microscope with objectives which can be individually focused on two areas of the substrate. Patterns have been registered to better than 5μ with the substrate at temperatures up to 200°C. In all cases the chamber pressure was 2×10−10 Torr.
Continuous Averaging of X-Ray Diffraction Data Using a Multichannel Analyzer
Authors: Weymouth John W. , Costello James , Schuster Sanford , Schulze Paul
Published: February 2004

A continuously averaging system is described in which a multichannel analyzer is coupled to an x-ray diffractometer. The motion of the arm of the diffractometer is synchronized with the channel advance so that there is a 1 to 1 correspondence between 2θ increments and channels. With this system a weak x-ray diffraction signal may be scanned repeatedly and the signal built up against the random noise introduced by fluctuations in the generating and detecting system with periods long compared to the channel dwell time. Other convenient uses of the analyzer in handling the x-ray diffraction data are briefly mentioned.
Fitting Experimental Data Using the Method of Least Squares
Authors: Margulies S.
Published: February 2004

With a view toward facilitating proper use of computer curve-fitting programs, the method of least squares for fitting smooth curves to experimental data is discussed. The distinction between the problem when the functional form of the data is known, and when it is not known, is emphasized. For the latter case, the usual procedure of using an expansion having M linear coefficients to represent the functional form is considered. In making such a fit, care must be exercised in choosing M. Although the least-squares sum decreases as M is increased (tending to zero as M approaches N, the number of data points), the resulting fit is not necessarily a better representation of the data. It is shown that, in the extreme case where M=N, the least-squares fit is identical to a linear expansion which is constrained to pass through every point, and such a fit is, of course, meaningless. Tests for the statistical significance of fits are discussed.
High Speed Optical Stopped-Flow Apparatus
Authors: Berger R. L. , Balko B. , Borcherdt W. , Friauf W.
Published: February 2004

A stopped flow apparatus for the study of fast reactions in solution is described. The measured dead time was 270 μsec with an uncertainty in the measurement of 50 μsec. At 410 mμ and an optical density of about 0.09 a change of 0.0044 optical density units could be observed at a flow velocity of 30 m/sec through a 3.0 mm observation tube. Ten milliliters of each of the two reagents are required to fill the system, and less than 1.0 ml of each needs to be expended per experiment.
High Resolution Mixer for the Study of the Kinetics of Rapid Reactions in Solution
Authors: Berger Robert L. , Balko Bohdan , Chapman Howard F.
Published: February 2004

The turbulent wake of a spherical surface was utilized as part of a mixer for fast reaction studies. The mixer is capable of mixing two solutions within 100 μsec at a flow velocity of 30 m/sec. Optical and thermal methods were used to study the mixer. Highly efficient mixing was achieved for 120 cP solutions as well as aqueous solutions.
Multichannel Photoionization Chamber
Authors: Kim H. H. , Shardanand  , Caruso A. J. , Barrington A. E.
Published: February 2004

A novel multichannel photoionization chamber has been devised for use in the vacuum ultraviolet to measure absorption, photoionization yield and photoionization coefficients of gases, and consequently, the absolute intensity of light sources. The theory, design, and operational advantages of the device are discussed. In particular, it is shown that for each channel the ion-current-pressure plot passes through a maximum; and the value of the pressure at the ion current maximum is the only experimental measurement necessary to determine the absorption coefficient of the filling gas.
Magneto-Optic Measurement by Sample Exchange
Authors: Broersma S. , Hendrickson P. E.
Published: February 2004

For a precise determination of small differences in magneto-optic rotation an exchange method has great advantages. In this, the magnetic field is effectively kept constant, but it need not be known to high accuracy. Equality of temperature and optical bandwidth is ensured by the method. A cart, supporting two sample tubes, is shuttled back and forth along the light beam such that in each extreme position a different sample is magnetized. With a 15 min measurement, an accuracy of 2×10−4 has been obtained. The optical stability by itself is 3×10−5.
High Intensity Light Source
Authors: Harper J. D.
Published: February 2004

A high intensity argon flash which utilizes high explosive is described. The flash is simple to construct and offers special advantages when the interior of partially closed objects must be illuminated for photography.
Photopeak Efficiency of a Well-Type Scintillation Detector
Authors: Hanson W. G. , Sargent B. W.
Published: February 2004

The detection and photopeak efficiences of a NaI cylindrical crystal, 7.62 cm diam and 7.62 cm high, containing a 0.63 cm diam well, 4.13 cm deep, were experimentally determined for 0.51 MeV gamma radiation from 11C positron annihilation. The pulse-height distribution measured with the source on top of the crystal was used with probability theory to obtain an approximate synthetic summed spectrum for the source in the well. This in turn was used to analyze the observed pulse-height distribution for the source in the well. The detection and photopeak efficiencies are 0.70±0.02 and 0.49±0.01, respectively, from which the photofraction is 0.70±0.03. Agreement with calculated values is good.
Instrument for Microradiography of Small Specimens
Authors: Ledley Robert S. , Sing Helen C.
Published: February 2004

An instrument originally designed for contact microradiography of very thin rat bone sections is described. It is not limited to use for bone, but may be used for any biological or mineral specimens small enough for the specimen opening (0.63 cm diam). The recording material is 35 mm spectroscopic film and up to five specimens may be imaged on a single film frame.
Cylindrical Capacitor as an Analyzer. II. Relativistic Part
Authors: Sar-El H. Z.
Published: February 2004

The study of the dynamic and optical properties of the cylindrical capacitor as an analyzer for charged particles is extended to the relativistic region. The proposed analyzer is found to be absolutely unrestricted by the relativistic effect, the latter introducing some changes which do not however impair the analytical features of the device. The emission angle for which there is a second order focus is energy-dependent, shifting from θ0=42°18.5′ in the nonrelativistic case to θ0=55° in the ultrarelativistic case. It is shown that the usual derivation of the relativistic formulae from the nonrelativistic ones by replacing the nonrelativistic potential difference by an ``effective relativistic potential difference'' is incorrect for electrostatic devices, unless this quantity is given a specifically ``electrostatic'' form, distinct from the magnetic one. The figures of merit of the analyzer concerning resolution and luminosity are comparable with those of the best magnetic spectrometers. The analyzer seems to be simpler and cheaper than the magnetic type, but calls for very high deflecting voltages, which may be a disadvantage in operation.
Absolute Efficiency Measurements of NE-213 Organic Phosphors for Detecting 14.5- and 2.7-MeV Neutrons
Authors: Love T. A. , Santoro R. T. , Peelle R. W. , Hill N. W.
Published: February 2004

The absolute efficiency of two NE-213 organic phosphors for detecting 14.5- and 2.7-MeV neutrons has been determined by the associated particle technique with the recoil particles from the T(d,n)4He and D(d,n)3He reactions. The output of the neutron detector was placed in coincidence with the helium recoil pulses and the efficiency of the detector was obtained as the ratio of the coincidence counts to the helium recoil counts. The scintillators were 12 cm in diameter and had thicknesses of 2.61 and 6.10 cm, and each was preceded by a 5-mm thick NE-102 plastic scintillator and followed by a 3.3-cm (average thickness) Lucite light pipe. The detection efficiency, for neutrons striking the central 25% of the detector area, was measured as a function of the bias level on a tunnel diode driven by the current pulse from dynode 14 of a 58AVP multiplier phototube and also as a function of a bias threshold on the total light output. The bias level was calibrated in terms of the pulse-height spectra resulting from the interactions in the phosphors of gamma rays of several energies. Comparisons were made between experimental efficiencies and those obtained from Monte Carlo calculations. For a threshold of 40°±5 keV electron total light equivalent, the agreement is within 7% for the smaller detector and 1.5% for the larger.
Device for Producing Very Low Magnetic Fields
Authors: Brown Robert E.
Published: February 2004

A volume containing a reduced magnetic field may be obtained inside a lead foil sack by opening the folded sack at 4.2°K when the lead is superconducting. A multi-stage magnetic flux ``vacuum pump'' based upon this idea was used to reduce earth's field to below 10−6 Oe in a volume of several hundred cubic centimeters. The superconducting sack shields this volume against the magnetic field fluctuations of the laboratory environment. The estimated noise amplitude in the low field space is 10−8 Oe. A glass Dewar inserted into the sack permits working in the low field space at controlled temperatures near room temperature. The system has had extensive use for the study of the long term stability of flux-gate magnetometer sensors.
Noise in Hot-Wire Anemometers
Authors: Freymuth Peter
Published: February 2004

An analysis is given of the electronic noise and the signal-to-noise ratio for constant-temperature and constant-current hot-wire anemometers. The analysis shows that both anemometers are equivalent in their signal-to-noise ratio if the noise sources are equivalent and the hot-wires are operated at the same conditions. A discussion of the theoretical results and a comparison of both anemometer types based on these results are given. In addition, some noise measurements on a constant-temperature anemometer and the methods to obtain them are reported and compared with theoretical results. The agreement between measured and theoretical results is rather good.
Reliable Heterodyne-Beat Dipole Moment Apparatus
Authors: Vandenbroucke A. C. , King Roy W. , Verkade J. G.
Published: February 2004

An inexpensive heterodyne-beat solution dipole moment apparatus has been developed which employs solid state circuitry for stability. The stationary nickel cell eliminates capacitance changes in the leads due to movement, and a Thermotrimmer in the circuity reduces sensitivity of the circuits to temperature changes of the room. An inexpensive milliammeter in place of an oscilloscope eliminates the appearance of more than one null reading in the measurement of capacitances. Dielectric constant data for several compounds are presented which yield dipole moments precise to within 0.02 D with up to 12 months between measurements.
Experimental Automatic Recording Dilatometer for Thermal Expansion and Shrinkage Studies over the Temperature Range −150 to +1500°C
Authors: Sauer H. A.
Published: February 2004

A facility is described for the automatic recording of expansion and contraction over the temperature range −150 to +1500°C. It is primarily intended for broad exploration of the thermal behavior of new experimental materials with the principal objective of detecting and identifying phenomenological effects rather than of attaining the ultimate in accuracy. Particular features of this model include automatic operation, hence minimum amount of attention in performing the measurement, magnification of the temperature scale, scale range and scale zero adjustment, exploration of thermal expansion through ambient without interruption employing a gaseous heat carrier for temperature control, compensation for sample length in both expansion and sintering measurements to provide an apparent constant length of 100 mm, irrespective of sample length, within the limits of 30 to 55 mm, and time recordings on the soak phase of the sintering trace. No commercial equipment is known to the author which provides this flexibility. Based upon numerous calibrations the uncertainty in the accuracy of the expansion measurement, due to systematic and random errors in the procedure and in practicing the technique, is not greater than 7.5% up to 1000°C, over the magnification ranges. The broad usefulness of this tool is exemplified by its adaptability in the display of such information as (1) expansion of a wide variety of solids, (2) transformation ranges and softening points of glasses, (3) structural modifications in crystalline materials, (4) thermal hysteretic phenomena, (5) stress relaxation, and (6) sintering kinetics and shrinkage in controlled atmospheres.
High-Z Cylindrical Spark Chamber
Authors: Mockett P. , Frisch D. , Mannelli I. , Wahlig M.
Published: February 2004

The details of the construction of a cylindrical spark chamber made from 0.8 mm lead sheets clad with stainless steel foil and subtending a large solid angle are described. Its performance in the study of the reaction π++p→π++π0+p is discussed. In particular, the detection efficiency for this reaction, the kinematic resolution resulting from the analysis of the final state angles and the detection efficiency for low energy gamma rays are given.
Method for Measuring Small Optical Losses Using a He–Ne Laser
Authors: Brändli H. P.
Published: February 2004

The output power or threshold for oscillation, respectively, of a He–Ne gas laser are severely influenced by the presence of small losses in the resonator. Small losses between about 0.01 and 1% may be measured by substituting the unknown loss of a smaple for linearly polarized light by the known and adjustable reflection losses due to a plane parallel glass plate near the Brewster angle. A measurement apparatus based on this principle was built and the influence of various sources of error was evaluated. One source of error is the deviation from ideal linear polarization found in the output of gas lasers with Brewster angle windows. Measurements are given of the residual single pass transmission loss of doubly antireflection coated glass plates.
Three Axis Crystal Spectrometer for Neutrons
Authors: Stedman R. , Nilsson G.
Published: February 2004

The spectrometer has been in operation since 1963 at the reactor R2 in Studsvik, mainly for measurements on phonons in metals, with emphasis on precision. Shielding is considered first, with mention of conclusions drawn from experimentation with the shielding around the beam from the reactor and with that around the detector. The mechanical design aims to achieve easy exchange or replacement of parts (particularly crystals and collimators), automatic operation, and low cost. Angles are changed and measured by means of worm gears driven by further gears from stepping motors, which permits control of the spectrometer from a programming tape in a simple and reliable manner. Some examples are given of results for aluminum.
Method for Measuring Small Thermal Expansion with a Single Frequency Helium-Neon Laser
Authors: Foster Jack D. , Finnie Iain
Published: February 2004

A method for measuring extremely small coefficients of expansion (10−8 to 10−6/C°) is described. The swept frequency output characteristics of a single frequency helium-neon laser are used to attain high resolution with an easily constructed interferometer. A technique for specimen design and the advantages of using a confocal interferometer configuration are described. Experimental thermal expansion coefficient measurements for commercial Invar and special high purity, low expansion Invar are presented.
Off-Crest Optical Method of Measuring the Amplitudes of Surface Ripples
Authors: Walbridge N. L.
Published: February 2004

The optical performance of surface ripples of arbitrary profile is discussed. In particular, the light, which is transmitted through a surface with a non-zero slope, produces a better defined intersection with a screen than that from a crest or a trough. In principle, a ripple form can be found from the positions of these intersections. Using the light from off-crest surface elements, a method is developed in which the amplitude of a nearly sinusiodal ripple is given as a function of the wavelength, the index of refraction of the liquid, the width of the light source, its distance from the liquid surface, and a measured focal length. Under favorable conditions, the ratio of two amplitudes can be measured with an accuracy of 1%.
Simple System for Photoelectron Spectrum Determination
Authors: Marmet P. , Natalis P. , Dumont A.
Published: February 2004

A simple device for photoelectron spectroscopy is described using (1) a single cylindrical grid, (2) a differentiating method, and (3) a lock-in amplifier detector. This shows an improvement in resolution and sensitivity, compared with previous similar systems.
An Annular Contact Friction and Boundary Lubrication Tester
Authors: Finkin Eugene F.
Published: February 2004

A simple, inexpensive, easy to use, and very accurate annular contact friction and boundary lubrication tester is described. Data are presented to show excellent reproducibility and extremely low experimental scatter. The system allows the accurate simultaneous measurement of normal load, friction force, ambient fluid temperature, and mean surface contact temperature. Analyses are presented, which are applicable to other testers in addition to the present one, for determining the true mean surface contact temperature from a measured near surface temperature (determined with a thermocouple), and for calculating the viscous drag component of the measured friction (thereby allowing its separation). The tester is particularly well suited for simulating and studying the surface contact phenomena which arise in multiple disc brakes and clutches.
Fast Metal-to-Metal Switch with 0.1 μsec Jitter Time
Authors: Dokopoulos P.
Published: February 2004

A fast mechanical switch of plane configuration with foil insulation is described. Its closure is ensured by an exploding aluminum foil. With 0.4 mm insulation and a 500 kA current rating the switching time is 2.4±0.17 μsec. An increase of the insulation thickness and of the current rating increases the delay, but in a wide range of parameters the jitter time remains practically constant. The switch has been successfully used for series and crowbar operation on a circuit having a voltage of 18 kV, a frequency of 25 to 50 kHz, and a current of several hundred kiloamperes. When the switch components are so assembled to suppress all air gaps in the vicinity of the exploding foil, the jitter time can be brought down to 0.07 μsec.
Cell Assembly to Measure the Electrical Conductivities of Molten Salts to Their Critical Temperatures
Authors: Grantham L. F. , Harrelson E. B. , Shaw P. H. , Larsen C. M.
Published: February 2004

A cell assembly has been constructed and tested to measure electrical conductivities of fused salts up to their critical temperatures. The apparatus consisted of a quartz conductivity cell enclosed in a pressurized Hastelloy N container. Rupture of the quartz cell was prevented by application of external pressures slightly greater than the internal vapor pressure of the salt. Bismuth chloride with a critical temperature of 905°C and critical pressure of 120 bars was used as the test liquid. The determined critical conductivity of BiCl3 was 8×10−3 (Ω cm)−1. The results suggest that this technique can be used to measure conductivities at even higher temperatures and/or pressures.
New Wide Band Windowless Photon Detector
Authors: Grodski J. J. , Schumacher B. W.
Published: February 2004

A prototype of a new windowless photon detector has been built. Photoelectrons from a photocathode are accelerated to an energy level where they can be counted individually by means of the scintillation pulses which they produce in a scintillation counter. The geometry of the detector allows to collect not only photoelectrons from a single surface but from a number of thin foils placed behind one another, in order to increase the detection efficiency for hard x-rays. Any type of cathode surface can in principle be used; tests, however were made only with a gold foil cathode. The detector has been tested at two wavelengths of about 25 and 2500 Å. Its detection efficiency can be expected to be above 1% from at least 0.5 to 1300 Å, but this has not been checked out. The only noise source in this detector against which one can not discriminate is spurious counts due to corona discharge or field emission; at 20 kV acceleration voltage this noise could be kept low enough, even at pressure levels as high as 10−4 Torr, to count single photoelectrons. This detector scheme has the advantage that only one surface is exposed to a changing environment, namely the photocathode, and this is not particularly critical because the quantum yield for soft x-rays depends upon the volume photoelectric effect.
Simple Liquid Helium Pressure Transducer
Authors: Chester M. , Choudhery S. C. , Jones B. K. , Williams D.
Published: February 2004

A totally immersed capsule type pressure transducer has been developed for the study of critical velocities in liquid helium below the lambda point. The construction and operation of the pressure transducer is described. It can be made in a few hours using relatively simple laboratory construction techniques. Typically it has a sensitivity between 50 and 100 cps/mm He at a frequency of about 10 Mc/sec and at an ambient pressure of a few millimeters of mercury. Such a transducer is particularly useful in closed systems-liquid helium not at its vapor pressure- for accurate measurements of the absolute pressure and for measuring small pressure changes. The operation of the transducer spans the pressure range from a fraction of a micron to several atmospheres with increased sensitivity at the lower pressures.
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H Glass Microelectrode for in vivo Applications
Authors: Khuri Raja N.
Published: February 2004

A pH microelectrode consisting of micropipette type indicator and reference half-cells is described. The pH sensitive segment of the indicator glass microelectrode is 10 to 20 μ in length with a tip diameter of 1 μ or less. The spear shape of the microelectrodes makes them suitable for in vivo work involving tissue penetration. The electrode measures pH on 0.1 μl standard droplets in vitro with a standard deviation of ±0.03 unit. Readings of the same 0.1 μl buffer standard droplet are reproducible to ±0.01 pH unit. The in vivo intraluminal pH of 20 proximal tubules of eight nondiuretic rats yielded a mean value of 7.22±0.03 (S.E.).
Nanosecond Microscopic Kerr Magneto-Optic Apparatus and Measurement Techniques
Authors: Genovese E. R. , Chang H.
Published: February 2004

The basic design principle of a Kerr magneto-optic apparatus with nanosecond speed (3 nsec rise time) and microscopic resolution (20 μm diam) and its application to coupled film measurements have been reported before. This paper documents the details of the apparatus construction and organization, and measurement techniques. The apparatus employs only commercially available optical and electronic components. The ultimate speed is limited by the photodetector (subnanosecond risetime) and the minimum spot size by light diffraction (less than 1 μm diam). Thus there is room for futher improvement.
Fabrication of Ultrathin Films
Authors: Vouros Paul , Masters Joseph I. , Starble Richard J.
Published: February 2004

A method is described for the preparation of thin supported films of aluminum and carbon that can be several centimeters in diameter and contain as little as 1 μg/cm2 of material. The thickness of the prepared films is estimated to be well below 100 Å with a total pinhole area of less than 0.01%. Aluminum and carbon films prepared by this method were found capable of supporting pressure differentials of 10−3 to 10−9 mm Hg across their areas, at a maximum pressure of 10−3 mm Hg on one side.
Spark Erosion of Diamond
Authors: Levitt C. M.
Published: February 2004

A spark erosion method of shaping diamond is described. The problem of the diamond being non-conductive is overcome by the formation of a thin carbon layer on the diamond surface. This layer is continuously reformed as the erosion proceeded. The apparatus and methods discussed are of an elementary nature. They demonstrate that the technique is workable and can also be adapted to many unusual applications. The cutting rate was independent of orientation and imperfections in the diamond crystal. Furthermore, no diamond dust was needed to assist abrasion.
Measurement of Shock and Free Surface Velocities with Anodized Aluminum Switches
Authors: Lysne Peter C.
Published: February 2004

The utilization of an anodized aluminum surface as a shorting switch for shock time of arrival measurements was found to have several advantages over methods previously used. These pressure sensitive switches are stable up to 450°C, have breakdown times less than 10 nsec, and can be made insensitive to elastic shocks of about 4 kilobar amplitude. They can also be adapted to many experimental configurations.
Evaluation of an Imaging Furnace as a Heat Source for X-Ray Diffractometry
Authors: Stecura Stephan
Published: February 2004

The objective of this investigation was to evaluate the image furnace as a heat source for high temperature x-ray diffractometry. Thermal energy was supplied by a carbon arc whose light was focused by two 1.52 m diam paraboloidal mirrors; the light flux being controlled by an iris diaphragm. A stationary sample, located at the focal point of the second mirror, was used with an x-ray diffractometer of unique design. These studies showed that the sample temperature could be adequately controlled and programmed. The thermal gradients in the sample were significant but not prohibitive. The principal limitation was the difficulty in accurately measuring temperature above 1700°C because of the scattered light superimposed upon the emitted light.
Frequency Sweep, Field-Frequency Stabilized, Double Resonance Spectrometer
Authors: Boden N. , Capart J. , Derbyshire W. , Gutowsky H. S. , Hansen J. R.
Published: February 2004

A description is given of circuits which improve both the performance and the versatility of a high resolution nuclear magnetic resonance spectrometer. Separate channels are provided for stabilization of the field-frequency ratio, for irradiation of any resonance, and for observing the spectrum in the frequency sweep mode. To maintain the operating frequencies of the observation and irradiation channels in constant proportion to the stabilization channel, all signals are derived from a single frequency synthesizer system. Essentially modular equipment is described to stabilize the base line and to isolate the receiver from the transmitter by the time sharing technique. The design and construction of a solid state (integrated circuit), field-frequency stabilizer is discussed in detail. Finally, the design of a stable audio frequency sweep oscillator, built from a voltage-to-frequency converter, is described along with a device for periodic repetitions of the sweep.