bluuebunny/crossref_metadata_2025 huggingface dataset:
A Technique of Measuring the Transparency of Materials as a Function of Temperature
Authors: Novak T. J. , Poziomek E. J. , Mackay R. A.
Published: February 2004

A simple technique has been developed to measure the transparency of materials at any specific wavelength (ultraviolet to near infrared) vs temperature. The procedure involves heating a sample between calcium fluoride plates in a brass holder placed in a Cary 14 spectrophotometer. Changes in transmittance at a fixed wavelength are recorded continuously as the temperature is allowed to change slowly. As an illustration of the procedure the transmission properties of the nematic liquid crystal, butyl p-(p-ethoxyphenoxycarbonyl)-phenyl carbonate, in its various states are described. For comparison purposes a description of the transmittance of phenyl benzoate (which does not possess a mesophase) is also included.
Preparation of Extremely Thin Self-Supporting Metal Foils
Authors: Valenzuela A. , Eckardt J. C.
Published: February 2004

Metal foils are prepared by the technique of evaporation and deposition on a plastic backing, which is subsequently dissolved in acetone. Destruction of the foils upon traversing the air-liquid interface is avoided by letting them traverse first a layer of ether which does not dissolve the plastic. During the whole procedure of fabrication the foils are never removed from the frame upon which the plastic layer is originally mounted. Foils have been prepared of the following metals: copper, gold, nickel, silver and tin. Thicknesses as low as 8 μg/cm2 (76 Å of Ag) have been obtained.
A Digitizing Electrometer System Using an Integrating Circuit Preamplifier
Authors: Chater William T.
Published: February 2004

An electrometer system is described which makes use of a conversion from input current to frequency. The data handling section employs digital circuit techniques which allow the dynamic range of the system to be adjusted to the requirement of the experiment, and which present the output in pulse form compatible with contemporary logic systems. The conversion of the input current variable to frequency is achieved by making use of an integrating preamplifier circuit having a capacitive feedback element consisting in part of a reed relay which resets the integrator voltage. Since leakage currents can be controlled in all components of the input circuit, the calibrated current range of the system can be extended down to the order of 10−14 A. Resolution of the system as defined by the inherent noise in the integrator circuit is discussed in an appendix note.
An Inductive Water Thermostat Using On-Off Triac Control and Platinum Sensing
Authors: Diamond Joseph M.
Published: February 2004

An on-off thermostat is described using novel means for heating, sensing, and triac control. Heating is performed by sending the water through a coil of silver tubing which forms the short-circuited secondary winding of a transformer. This arrangement permits extremely good insulation, which was essential in the medical application (a dialysis water thermostat) for which it was designed; its quick response also contributes to the excellent regulation achieved with simple on-off control. Sensing is provided by a very low resistance platinum coil in direct contact with the water, thus providing quick response, stability, and, because of the transformer-coupled circuit used with this probe, the possibility of very good insulation. Because on-off control entails continual switching of a large (1.7 kW) transformer, a triac control circuit was designed which avoids the usual starting (inrush current) transients.
Method for Measurement of Surface Charge Densities on Electrets
Authors: Sessler G. M. , West J. E.
Published: February 2004

An accurate method for determining the surface charge density on foil electrets is described. The method is based on the measurement of an induction charge on a capacitive probe parallel to, and at a certain distance from, one of the charged surfaces of the electret. The method does not interfere electrically or mechanically with the electret charges. It is simple to implement and capable of measuring surface charge densities from 5×10−11 to some 10−6 C/cm2. For a surface charge density of 10−8 C/cm2, the reproducibility error is less than 1% and the systematic errors are estimated to be of the same order.
Magneto-Optical Rotation and Ellipticity Measurements with a Spinning Analyzer
Authors: Suits J. C.
Published: February 2004

An apparatus employing the spinning analyzer technique is described for measurement of Faraday and Kerr rotation in fields up to 20 kOe and at temperatures down to 3 K. Rotation angles are measurable to an accuracy better than 0.01° and are continuously recorded. The technique is extended to include measurement of Faraday and Kerr ellipticity.
Myothermic Radiometry
Authors: Fraser Allan B.
Published: February 2004

An ir radiometer utilizing a Golay cell was constructed to measure heat production in excised muscle preparations near room temperature. This radiometer resolves temperature changes of 1 mdeg on surface areas of several square millimeters with a lag time constant of a few milliseconds. It is shown that myothermic radiometry can provide an accurate measure of muscle temperature changes, with an ultimate time resolution below 0.5 msec.
The Use of a Pulsed Van de Graaff Accelerator and Time-of-Flight Techniques to Reduce Backgrounds in (α,γ) Spectroscopy Experiments
Authors: Jaszczak Ronald J. , Macklin R. L. , Dunnam F. E. , Van Rinsvelt H. A. , Bloomer R. H.
Published: February 2004

A pulsed beam of alpha particles from a 5.5 MV Van de Graaff accelerator has been used to study radiative capture reactions. Time-of-flight techniques are used to discriminate against neutrons produced when the beam interacts with collimator-target contaminants, as well as against beam independent background due to cosmic rays. With a beam pulse of less than 4 nsec (FWHM) duration and a repetition rate of 2 MHz, a portion of the 34S(α,γ)38Ar excitation function was examined near Eα=3.6 MeV and the background found to be an approximate factor of 15 below that of the effective dc excitation function. In addition it is demonstrated that an angular distribution taken on resonance by this method requires substantially less background subtraction. The method has also been successfully applied to radiative capture studies in which the incident beam energy is above the neutron threshold for the target nuclei.
Low Cost TV Display System
Authors: Brown David
Published: February 2004

The display system developed is capable of storing and displaying a computer generated display on standard TV monitors. The system is relatively inexpensive (≈ $11 000 including four monitors), has medium resolution (≈ 490×250 points), and has the capability for displaying both graphics and alphanumerics. This paper describes the operation of an interface which converts the computer output into a TV signal stored on a magnetic disk recorder. Also described is a circuit used for improving the high frequency response of the disk recorder, and thereby the resolution of the display system.
The LEED Instrument Response Function
Authors: Park Robert L. , Houston J. E. , Schreiner D. G.
Published: February 2004

The effect of the measurement system is usually ignored in the interpretation of LEED patterns. This effect can, however, be treated analytically through the use of the instrument response function, which represents the intensity function the instrument would record for a perfect surface. We have measured the response function for a particular LEED system using a double aperture Faraday collector and have identified the various experimental factors which determine its detailed functional form. The Fourier transform of the response function defines the range over which the instrument behaves as an interference detector. The effect of long range correlations on the pattern is suppressed by this finite range, with the result that fairly untidy surfaces may not be easily distinguished from those which are nearly perfect.
A New Measuring Method for Experimental Analysis of Magnetothermal Effects in Magnetic Materials
Authors: Kraus Kamil
Published: February 2004

Measurements of the reversible and total magnetothermal effects together with relevant magnetic quantities of annealed nickel using a new measuring equipment have been made. It is shown that the reversible magnetothermal components measured by the direct and indirect method are in reasonable agreement in the field range applied. The numerical value of the constant b″ is evaluated and it is concluded that in moderate fields, reversible changes in intrinsic magnetization and rotation of the magnetization vectors predominate.
Feedthrough Induced Distortions in Sampling Oscilloscopes and Their Compensation
Authors: Bosshard R.
Published: February 2004

When signals in the duration range from some tens of nanoseconds to some tens of microseconds are measured in detail with a sampling oscilloscope coupled to a fast time averaging system, severe shape distortions are usually observed one to two decades below the maximum amplitude. It is shown that these distortions are mainly due to capacitive feedthrough over the nonoperating sampling gate. The analysis of this phenomenon shows that the observed response is the sum of the input signal and of its weighted convolution by a slow response of microsecond duration. Feedthrough was decreased by up to two orders of magnitude by a minor change in the input circuit of the sampling gate, without affecting the intrinsic high speed of the oscilloscope response. The methods to optimize this compensation are described. Applications to the correct measurement of exponentially decreasing signals over more than three decades are shown.
Low Temperature Thermometry in High Magnetic Fields. II. Germanium and Platinum Resistors
Authors: Neuringer L. J. , Perlman A. J. , Rubin L. G. , Shapira Y.
Published: February 2004

The effect of static magnetic fields up to 210 kG on the characteristics of commercial germanium and platinum resistance thermometers was measured at various temperatures in the range 3.5–78 K. Measurements of the transverse (sample current I normal to magnetic field H) and longitudinal (I∥H) magnetoresistance were carried out on both types of thermometers. A description is given of the dc resistance measuring technique used in these experiments. This method is a semiautomatic potentiometric scheme which increases the speed of measurement while maintaining high resolution and reasonable accuracy. The magnetoresistance of the germanium sensors was found to be large and orientation dependent over the temperature range investigated. These effects preclude the use of germanium elements, as presently fabricated, for temperature sensors in a high magnetic field environment. In the case of platinum resistance thermometers, the magnetoresistance at temperatures above 30 K is small enough so that it becomes practical to correct for it. In fact, these thermometers have been recently used in studies of the magnetic phase transitions in antiferromagnets in fields up to 200 kG.
Methods for Preparing Replicas of Slip Bands Preshadowed with Uranium Oxide
Authors: Ahearn J. S. , Mitchell J. W.
Published: February 2004

Three reliable methods are described for preparing uranium oxide preshadowed replicas of the surfaces of deformed single crystals of copper alloys. Difficulties experienced in detaching direct carbon replicas from the surfaces of these alloys have been overcome by the use of a parting layer for low resolution and of a chemical treatment for high resolution work. The fine linear source of uranium oxide produces a sharply defined shadowing deposit of high density and low granularity. This deposit is backed by a film of silver or silicon monoxide for high resolution work with the optical microscope and by a carbon film for work with the electron microscope. The advantages of pre-compared with postshadowing with uranium oxide for quantitative work on slip bands have been established. The methods are simple and convenient and allow high resolution to be achieved in replica microscopy.
Astronomical Infrared Spectroscopy with a Connes-Type Interferometer. I. Instrumental
Authors: Beer Reinhard , Norton Robert H. , Seaman Clay H.
Published: February 2004

The construction and operation of a Connes-type Fourier spectrometer are discussed in an astronomical context with a sample of the type of spectra obtained with the system.
A Sealed Crucible for the Growth of Metal Crystals in a Controlled Atmosphere
Authors: Jensen H. J. , Murtha M. J. , Burnet G.
Published: February 2004

A vacuum tight crucible has been constructed for use in growing metal single crystals. This crucible design can be used for growing metal single crystals of reactive, volatile, or toxic materials by a Bridgeman technique.
Determination of Zero Phase Position of Far Infrared Interferometers
Authors: Clayman B. P.
Published: February 2004

A mechanical ``symmetrizer'' has been built for use with far infrared interferometers driven by stepping motors. It allows convenient and consistent setting of the position of zero phase difference and thereby permits straightforward Fourier analysis of the measured one-sided (even) interferogram.
Oscilloscope Display for Signal Averaging and X-Y Data Plotting
Authors: Lashinsky H. , Monblatt R. E.
Published: February 2004

An oscilloscope display is described that can be used for signal-to-noise enhancement, presentation of spectral data in compact form, and X-Y data plotting. The display also functions as an optical signal averager and is useful in the detection of signals whose frequencies are not known a priori and signals whose frequencies drift in time. Results obtained in simulation tests and in experimental research on plasma waves and instabilities are described.
A Reflectometer for Studying Liquids in the Vacuum Ultraviolet
Authors: Kerr G. D. , Cox J. T. , Painter L. R. , Birkhoff R. D.
Published: February 2004

A reflectometer has been built for measuring the reflectance of liquids in the vacuum ultraviolet. A monochromator is rotated about a liquid sample in equilibrium with its vapor in a windowless dish. A continuous range of angles of incidence is provided between 15 and 70°. The light traverses a path of approximately 1 cm in length in the vapor adjacent to the sample. The reflected beam is collected by a light pipe. A description of the mechanisms for positioning the light pipe, adjusting the sample dish, and rotating the monochromator with respect to the reflecting surface is given, as well as the system used to maintain a pressure differential between the monochromator and chamber containing the liquid sample.
A Plane Electrostatic Analyzer for Laser Produced Plasma Studies
Authors: Allen F. J.
Published: February 2004

The use of an electrostatic analyzer as a time-of-flight spectrometer for studying laser produced plasmas is discussed. It is shown that a plane electrostatic analyzer, accommodating several detectors simultaneously, can be used to determine several points on the velocity distribution curve for the ions produced upon irradiation of a target with a single Q-switched laser pulse. This minimizes the problem of shot-to-shot reproducibility of the laser. It is shown also that with a 30° plane analyzer good energy and time resolution are obtainable in determining the time dependent ion velocity distribution for a laser produced plasma.
Compensation of Earth's Field Variations by Field Controlled Rubidium Oscillator
Authors: Driscoll R. L. , Olsen P. T.
Published: February 2004

The east-west variations of the earth's magnetic field over the working volume of the NBS precision solenoid are being canceled out by a closed loop system featuring a field controlled rubidium oscillator. The rubidium oscillator and solenoid are sufficiently separated in distance and do not affect each other's operation. Each system is enclosed in three-dimensional Helmholtz coils. Vertical and north-south components of earth's field are canceled. An east-west bias field is provided for rubidium oscillator operation at 10 kHz. The output of a phase sensitive detector locked to the 10 kHz frequency standard provides current for the electrically series connected east-west Helmholtz coils at both locations. The magnitude of this current is proportional to the phase difference of oscillator and reference. The full range of compensation is 100 nT. The rate of compensation is limited by a time constant of 0.002 sec, an adequate rate for most disturbances. To the extent that the two separated components of the closed loop system can be oriented directionally the same at any given time, the earth's field east-west variation is compensated exactly.
Capacitance Microphones for Measurement of Ultrasonic Properties of Solids
Authors: Meeks E. L. , Peters R. D. , Arnold R. T.
Published: February 2004

Two capacitive transducer designs have been used in this laboratory for amplitude measurements of longitudinal ultrasonic waves in solids. The designs are simple, can be fabricated easily, are rugged, and should prove to be a useful ultrasonic laboratory item. Each of the microphones can be conveniently altered to be used with a variety of specimen sizes, and displacement amplitudes as small as 10−14 m have been measured for 30 MHz frequency longitudinal waves. As an example application of the transducer, measurement of phase shift upon reflection from an X-cut quartz transducer bonded to an SrTiO3 crystal is given.
Flow Gas Lasers at 6328 Å, 4416 Å, and 95 μ
Authors: Schearer L. D. , Riseberg L. A. , Sinclair F. D.
Published: February 2004

To avoid the time consuming process of high vacuum bakeout of laser tubes, we have constructed a variety of lasers which utilize a small mechanical forepump and a slow flow of the gas medium through the laser tube. No stringent requirements are placed on the vacuum integrity of the system; the gas flow rate (2–20 scm3/min) is sufficiently low that the use of commercially available tank gas is economically justifiable. The chief advantage offered by the flowing system is that laser operation can be obtained within minutes after exposure to the atmosphere; thus, the operator has access to a wide variety of operating pressures, gas mixtures, etc. A helium-neon laser at 6328 Å and 1.15 μ, helium-cadmium at 4416 Å, and helium at 95 μ have been successfully operated in this manner. The ease of operation in these three cases suggests that a wide variety of gas lasers can be constructed in this manner.
A Comparison of Results from Phase Plate and Knife Edge Diaphragms in Conjunction with the Schlieren Optical System in an MSE Analytical Ultracentrifuge
Authors: Rowe Arthur J. , Khan Ghulam Mustafa
Published: February 2004

It is common practice in schlieren optical systems to use a phase plate diaphragm incorporating a fine wire. The optical theory of such diaphragms is, however, complex, and their behavior over a range of refraction gradients has never been critically evaluated. It is shown that the older knife edge diaphragm, the optics of which are relatively simple, can be used in conjunction with modern double-sector ultracentrifuge cells, thus providing a reference standard against which the behavior of a phase plate diaphragm can be checked over a range of conditions. Results are presented showing near ideal behavior for an MSE phase plate.
Ultralow Temperature Rotating Nuclear Polarization System
Authors: Krane K. S. , Sites James R. , Steyert W. A.
Published: February 2004

A system has been constructed to study very small asymmetries in the directional distribution of γ radiation from polarized nuclei. The system combines the ultralow temperatures of a 3He–4He dilution refrigerator (down to 14 mK) and the large hyperfine field of a ferromagnetic host lattice. The hyperfine field direction is smoothly and continuously rotated by means of an external field to compare the γ-ray intensity in different directions. Many experimental tests have been performed, and upper limits are placed on various sources of spurious asymmetry.
A New Photoelectron Spectrometer: Combination of Cylindrical Mirror Analyzer with Soft X-Ray Source
Authors: Maeda Kogoro , Ihara Takashi
Published: February 2004

A photoelectron spectrometer composed of a cylindrical mirror type of electron energy analyzer and an Al Kα x-ray source is described. Performance tests with a tungsten filament and with gold samples have proved that the analyzer performs well. The doublet peaks of N6 and N7 of gold were completely resolved, and half-widths of the two peaks were both found to be about 1.5 eV, which is comparable with the value of 1.3–1.4 eV given by Siegbahn et al. with Mg Kα x rays.
Continuous Wave Chemical Laser for Laser-Induced Fluorescence Studies
Authors: Stephens Ronald R. , Cool Terrill A.
Published: February 2004

Laser-induced vibrational fluorescence experiments have been accomplished with a newly developed cw chemical laser. The design and operating characteristics of this small-scale transverse flow chemical laser source are presented. The fluorescence measurement technique and apparatus provide several advantages over the use of pulsed chemical lasers for similar measurements. The present laser is also useful as a selectively tunable probe for single pass gain measurements in chemical lasers.
A New Scanning Low Energy Electron Probe (SLEEP)
Authors: Flemming J. P. , Ahmed H.
Published: February 2004

Practical details of a scanning low energy electron probe (SLEEP) are described. The SLEEP incorporates a demountable electron optical system (EOS) with a triode type gun, an electrostatic and a magnetic lens, and a magnetic scanning system. The cathode is at approximately ground potential. The EOS can be operated satisfactorily at anode voltages between 500 V and at least 10 kV and produces an electron beam of between 5 and 25 μ in diameter which can be scanned over a mesh electrode of 5 cm in diameter. The specimen is placed beyond the mesh electrode but close to it and the electron beam decelerates in the region between mesh and specimen and is partially reflected from the specimen. Electronic circuits for measurements and the control of the EOS are described, and the practical limitations to be expected are discussed briefly. Instruments of this type can be used to make quantitative measurements of electrical parameters. Applications of the SLEEP are discussed briefly.
The Matched Filter for Resonance Type Signals
Authors: Bryson Charles E.
Published: February 2004

The limitations of the RC filter for making measurements on resonance type signals are examined by comparing it with the matched filter. An approximate matched filter for measuring amplitudes that require no previous knowledge of the signal is presented and compared with both the matched filter and the RC filter.
Application of the Faraday Method to Magnetic Measurements under Pressure
Authors: Wohlleben D. , Maple M. B.
Published: February 2004

Weak static magnetic moments have been measured under hydrostatic pressure up to 20 kilobars with the full sensitivity of the Faraday method over a wide temperature range. Only minor modifications of the magnetometer and cryogenic equipment are needed to accommodate a miniature pressure clamp. The method is simple, at least two orders of magnitude more sensitive than previous techniques, and makes Pauli paramagnets and dilute magnetic alloys accessible to magnetic measurements under high pressure.
A Chemical Ionization Mass Spectrometer Source
Authors: Beggs D. , Vestal M. L. , Fales H. M. , Milne G. W. A.
Published: February 2004

The design and construction of an ion source designed for the MS-9 mass spectrometer are described. The source is designed to operate at ion chamber pressures up to 2 Torr while the pressure in the remainder of the source housing does not exceed 2×10−4 Torr. It is possible with this source to study ion-molecule reactions, i.e., chemical ionization mass spectrometry. Alternatively, if operated at lower ion chamber pressures, the source provides normal electron impact mass spectra and is thus a dual-purpose source. Modifications necessary to the MS-9 are described, as are performance characteristics of the new source.
Measurement of Laser Energy of Linear Components of Polarization at 1.060 μ
Authors: Rasmussen A. L.
Published: February 2004

A double reflecting plate calorimeter [Rev. Sci. Instrum. 41, 1479 (1970)] was used to evaluate the energy components of a pulsed 1.060 μ neodymium laser light beam entering the calorimeter polarized parallel (EH) and perpendicular (EV) to a horizontal plane. The relationship between these components varied from EH = 0.94 EV to EH = 1.25 EV. Estimated error of EH and EV is 2.3%. As a check on the accuracy of polarization component measurements at 1.060 μ, an intercomparison of data was made between this calorimeter and an NBS liquid cell calorimeter. The agreement was about 0.2%.
A Sensitive Calorimetric Method for Scanning Measurements of the Optical Absorption of Metals and Alloys
Authors: Hunderi Ola
Published: February 2004

We have developed a sensitive calorimetric method for measuring the absorptivity of metals in the visible and infrared. The short thermal time constant of the system, typically 25 msec, has allowed us to use phase sensitive detection and continuous wavelength scanning. The absolute accuracy of this method was five times better than the best accuracy obtained in reflectivity measurements. The system has also been used to measure the difference between the absorptivities of pure and dilute alloy samples.
A Versatile Pulse Generator System for Pulsed NMR Applications
Authors: Ramadan B. , Tward E.
Published: February 2004

A modular analog pulse generation system for use in pulsed NMR applications is described. All commonly used pulse sequences can be produced. The system offers the complete control of pulse width in the range of 0.5–500 μsec, pulse delays in the range 0 μsec–1000 sec, and repetition rates in the range 10−3 Hz-100 kHz. Pulse delays can be swept between any two delay times over the complete delay range and with a sweeping time in the range 10 μsec–1000 sec. The output pulses from the system can be synchronized and thus made coherent with the rf sinusoidal waveform of the rf transmitter.
A Technique for the Direct Observation of Filaments in Electron Microscopes
Authors: Passoja D. E.
Published: February 2004

A technique was developed by which filaments could be observed during their operation in a transmission electron microscope. The methods of specimen preparation and microscope operation were simple; filament images of fair quality could be obtained without making any modifications to the microscope. Calibration of magnification and interpretations of the filament images were facilitated by observations performed on a scanning electron microscope.
Determination of Ion Transit Times in an Ion Cyclotron Resonance Spectrometer
Authors: McMahon T. B. , Beauchamp J. L.
Published: February 2004

A method for directly determining ion transit times in an ion cyclotron resonance spectrometer has been developed which employs a simple combination of pulsed ion formation and time dependent trapping conditions. The variation of transit times with the adjustable parameters associated with the experiment (magnetic field strength, drift voltage, trapping voltage, pressure, and ion kinetic energy) is examined and found to be in quantitative agreement with the predictions of electrodynamic theory. The accurate determination of ion transit times facilitates the calculation of ion-molecule reaction rate constants of increased credibility. In addition, a technique for recording single resonance spectra by trapping voltage modulation is presented.
High Stability Electrodeless Discharge Lamps
Authors: Gleason William S. , Pertel Richard
Published: February 2004

A detailed procedure is described for the laboratory construction of electrodeless discharge lamps. Although this work pertains to Hg in Ar discharges, the same general experimental techniques are also applicable for other substances. The lamps made were without any getters and had an intensity variation of less than one part in 1000 over a period of 50 h of continuous operation. The described procedure allows for continuous monitoring of critical cleaning procedures in the evacuated lamp blank before it is filled and sealed off.
A Nanosecond Temperature-Jump Apparatus
Authors: Hoffman Geoffrey W.
Published: February 2004

A simple apparatus that extends the applicability of the temperature-jump method for the investigation of fast chemical kinetics in solution from the microsecond to the nanosecond time range is described. A sample solution can be resistively heated a maximum of 10°C within 50 nsec using the discharge of a coaxial cable capacitor. Relaxation of the reaction to a new equilibrium is followed spectrophotometrically. The design of the sample microcell (minimum volume 40 μl) is of particular interest for biochemists working with relaxation kinetics, because the volume of solution required is an order of magnitude less than for previous Joule heated temperature-jump cells.
Nanosecond High Resolution Framing Camera
Authors: Lieber Albert J. , Sutphin H. Dean
Published: February 2004

A framing camera employing proximity focused image intensifiers with an effective frame rate of 108 frames/sec and a spatial resolution of greater than 10 line pairs/mm on the 25 mm diam photocathode has been constructed and tested. The camera consists of six proximity focused image intensifiers coupled in a hexagonal array. This array may be viewed by either a standard film camera or an image orthicon television camera for remote monitoring. Interframe duration is adjustable from overlapping to several times the frame duration. Frame duration is adjusted by changing the pulse width from the main pulse generator. The shuttering circuit demonstrates zero interframe jitter and accurately known interframe and frame durations. Tests indicate there is no physical reason this technique cannot be extended to equivalent frame rates of greater than 109 frames/sec using low resistance photocathodes.
Apparatus for Measuring the Normal Hall Coefficient in Magnetic Conductors
Authors: Bierstedt P. E. , Hanlon J. E.
Published: February 2004

An ac Hall apparatus of high sensitivity and resolution is described for measuring the normal Hall constant in magnetic materials.
Selected Microarea Electron Diffraction Technique in High Voltage Electron Microscopy and Some Metallurgical Applications
Authors: Koreeda A. , Okamoto H. , Shimizu K. , Katsuta T.
Published: February 2004

In view of the practical uses of the selected microarea electron diffraction technique in high voltage electron microscopy, errors in correspondence between the selected and contributed areas for diffraction have been observed with a 650 kV electron microscope provided with a five-stage imaging lens system. Under optimum conditions, the observed errors were the same order as the theoretical ones due to the spherical aberration of the objective lens. That is, the contributed areas for diffraction were displaced relative to the selected ones by about 300 Å for diffraction angles the order of 2×10−2 rad which correspond to reflections from the planes of ∼0.6 Å spacing. Thus, it was concluded that a specimen area about 300 Å in diameter can be selected significantly so far as the diffractions of angles larger than 2×10−2 rad are ignored. The technique of selected microarea electron diffraction has been applied to the study of crystallography of small precipitates in 18% Ni maraging steel and the diffraction effects due to a dislocation line in a pure iron.
Compensation of Source Fluctuations in Raman Spectroscopy by Quick Analog Dividing
Authors: Topp J. A. , Schmid W. J.
Published: February 2004

A new ratio recording system is described which was especially developed for photon counters. The advantages of this system over previous ones for rapidly fluctuating sources are shown. The mean error which is introduced into the spectra by the new device was computed. The effectivity of the compensation is demonstrated with three examples.
A New Device for the Maximum Electrochemical Thinning of Metal Disks
Authors: Bulckaen V. , Paganini L.
Published: February 2004

The following paper deals with a device for the maximum thinning of metallic disk-shaped specimens. The apparatus described in the present work is an improved version of an earlier device described in a previous paper [V. Bulckaen, Electrochim. Met. 4, 262 (1969)], which was designed for the sole purpose of testing the validity of the technique used. This new device, like the former, is equipped with circular electrodes placed in a horizontal position. The anode, that is to say the specimen, floats and rotates on the cathode. An electrolyte film, fed to the cell through a hole in the center of the cathode, fills the space between the electrodes. The present improvements, of essentially mechanical nature, permit a much more effective geometrical control of the thinning process. The parallelism error between the two surfaces of the thin foil (minimal along the circumferences) is kept, at an appropriate distance from the center, below 2%, even in a radial direction, on areas extensive enough to allow us to obtain very low magnification electron micrographs working by transmission. This is true for specimens of even a few millimeters of thickness provided that they are disk shaped and of a certain diameter. The most appropriate running conditions for the preparation of thin foils of steel are described.
A Single-Coil Probe Damper for Pulsed Nuclear Magnetic Resonance
Authors: Roeder Stephen B. W. , Rhodes Norman L. , Schmidt Gregory W.
Published: February 2004

A circuit design is presented for a probe damper suitable for single coil NMR probes which improves the time for ringdown following an rf pulse by a factor of 2.5. The damping is provided for a precisely controlled time and removed positively to enable the use of high-Q single-coil NMR probes for samples with very short T2's. The damper can be adapted for use with negative or positive transmitter gating pulses.
Shift Register Readout for Wire Spark Chambers
Authors: Nunamaker Thomas A.
Published: February 2004

Spark information is read out by means of integrated circuit shift registers placed directly on the spark chamber. This information is held on individual wire capacitors until the electrical pulsing noise has subsided, at which time it is parallel loaded into the shift register. Subsequently this information is serially transferred out at the user's convenience. The advantage of this system over other capacity readout systems is fewer components and interconnections, simplified cabling and readout, and lower cost. A 1024-wire system has been tested at the Chicago Cyclotron; these tests (2×106 individual sparks) indicate that the circuits hold up very well. Spatial resolution at 1 mm wire spacing is 1 mm FWHM, and the efficiency is 99%. The average number of adjacent wires read out at full efficiency is 4.5.
Electromechanical Feedback Control for Lang Topography
Authors: Angilello Joseph , Wood Clinton
Published: February 2004

Described is a simple attachment to a Lang camera to keep large bent crystals in the Bragg condition.
Simplified Adjustable SQUID
Authors: King C. A.
Published: February 2004

The construction of a point contact superconducting quantum interference device (SQUID) is described. The construction technique is simplified and results in a very stable rugged device.
Theoretical Performance of Arc Driven Shock Tubes
Authors: Besse Arthur L.
Published: February 2004

Arc driven shock tubes customarily have small diameter driver sections and their performance is generally limited by the available electrical energy. A theory of shock tube operation based on these considerations is presented and compared to observed performance.
Quantitative Spectroscopy—Reproducible Production of Thin Layers on Supports from Solutions
Authors: Hofmann K. P. , Zundel G.
Published: February 2004

An equipment is described, which allows the preparation of films on supports from soluble substances with exactly definite thickness.
Precise Laser Initiated Closure of Multimegavolt Spark Gaps
Authors: Moriarty J. J. , Milde H. I. , Bettis J. R. , Guenther A. H.
Published: February 2004

Single- and double-channel laser triggered switches in high pressure gas have been designed and operated in the voltage range from 1 to more than 3 MV. Jitter times of <1 to 3 nsec were observed in most cases. Gas pressures of 10.5 and 21 kg·cm−2 were used. The gases were either 100% nitrogen or various mixtures of N2, SF6, and Ar. Significant accomplishments were (1) the simultaneous firing of four stages of a Marx generator by an optically divided laser beam, (2) up to 40% reduction in the risetime observed in the output pulse from a multimegavolt dc generator when switched into a load through two simultaneously laser triggered channels, and (3) the design and operation of a laser triggered, dc charged switch at more than 3 MV with subnanosecond jitter.
Heat Pipe Oven Applications. I. Isothermal Heater of Well Defined Temperature. II. Production of Metal Vapor-Gas Mixtures
Authors: Vidal C. R. , Haller F. B.
Published: February 2004

A concentric heat pipe oven is described, which serves as an oven with a highly homogeneous temperature distribution as required by such applications as crystal growing, thermal treatment of materials, and radiation standards. The design is simpler than conventional ovens with similar temperature stability and homogeneity. The temperature control is replaced by a pressure control. This device is used in a modification of the heat pipe oven that generates homogeneous mixtures of a vapor (such as a metal vapor) and an inert gas at well defined total pressure, partial pressure, temperature, and optical path length. All the features of the previously described heat pipe oven are maintained with the additional option that allows quantitative total and partial pressure measurements without relying on vapor pressure curves.
Calibration of a Laboratory Spectrophotometer for Specular Light by Means of Stacked Glass Plates
Authors: Allen William A. , Richardson Arthur J.
Published: February 2004

Stacked glass plates have been used to calibrate a laboratory spectrophotometer, over the spectral range 0.5–2.5 μ, for specular light. The uncalibrated instrument was characterized by systematic errors when used to measure the reflectance and transmittance of stacked glass plates. Calibration included first, a determination of the reflectance of a standard composed of barium sulfate paint deposited on an aluminum plate; second, the approximation of the reflectance and transmittance residuals between observed and computed values by means of cubic equations; and, finally, the removal of the systematic errors by a computer. The instrument, after calibration, was accurate to 1% when used to measure the reflectance and transmittance of stacked glass plates.
Transparent Conducting Films of Antimony Doped Tin Oxide on Glass
Authors: Peaker A. R. , Horsley B.
Published: February 2004

A simple laboratory technique for the routine preparation of transparent conducting films on soda and borosilicate glasses is described. The process uses the surface hydrolysis of stannic chloride at a temperature approaching the softening point of the glass. High electrical conductivity (50 Ω/sq) and good optical transmission (80%) have been obtained by the addition of small quantities of antimony and the optimization of deposition conditions. The technique has been found to give uniform and consistent results.
A Method for the Precision Comparison of the Densities of Small Specimens
Authors: Franklin A. D. , Spal R.
Published: February 2004

The density of an unknown is compared to that of a set of several standard specimens (weighing about 40 mg each) with a standard deviation in the ratio of densities from a single determination of 3×10−4 or better. The apparatus consists of two immiscible liquids and a float in the upper, supporting the specimen in the lower by a wire that passes through the interface. The wire provides a buoyant force gradient. From the change in position of the float when the unknown is substituted for the standards, the density of the unknown relative to that of the standards can be calculated. Other contributions to the buoyant force gradient are also present; their variation during the course of the measurement established the precision of the measurement.
A Rocket Borne Mass Spectrometer with Helium Cooled Ion Source
Authors: Offermann D. , Trinks H.
Published: February 2004

A new electron bombardment ion source was developed to reduce the influence of gas-wall interactions on the measurement of the neutral gas in the upper atmosphere. The ion source is cooled to low temperatures by means of supercritical helium. Ion source, mass spectrometer, cryogen supply system, and their arrangement in a rocket payload are described. The instrument was first successfully launched on 13 October 1970.
A Low Temperature Specimen Stage with Airlock for the Siemens Elmiskop I
Authors: Tischer P. , Bahr H.-J.
Published: February 2004

A low temperature stage is described which consists of a 1200 cm3 helium vessel and two thermal shields, one cooled by gaseous helium and the other by liquid nitrogen. The evaporation rate of the liquid helium is 230 cm3/h. The lowest temperature of the specimen is about 8–10 K. It is possible to apply a magnetic field parallel to the plane of the sample. The direction of the field can be rotated around the optical axis. The specimen can be exchanged through an airlock while the cryostat is cold. The low temperature specimen stage is used for Lorentz microscopy of low temperature ferromagnets, e.g., europium sulfide, which has a Curie point of 16.5 K.
Generation of High Pressure Oxygen and Synthesis of CoCrO4 with CrVO4 Type Structure
Authors: Kume S. , Kanamaru F. , Shibasaki Y. , Koizumi M. , Yasunami K. , Fukuda T.
Published: February 2004

A gas compressor was built for oxygen. For safety, water was chosen as a pressure transmitting medium. Oxygen gas compressed by high pressure water was led into a reactor. In the reactor, syntheses of oxides of transition metals were conducted in the range of temperature and pressure up to 600°C and 2000 bars. One of the successful results was the production of CoCrO4 with CrVO4 type structure.
A Method for Fatigue Testing of Ceramic Materials
Authors: Acquaviva Samuel J.
Published: February 2004

Equipment and a technique are described for obtaining the fatigue characteristics of ceramic materials. Data obtained by this method are comparable with previously published measurements.
Microwave Exposure System for Biological Specimens
Authors: McRee D. , Walsh P.
Published: February 2004

A microwave exposure system for use in the study of the bioeffects of cw microwave radiation has been designed, built, and calibrated. The specifications to which the system was designed are as follows: single frequency of 2450 MHz; power density range at the biological sample holder of 0.01–200 mW/cm2; uniform field at the sample holder as defined by a 10% variation in power density over a 15 cm diameter and half-power variation over a 30 cm diameter; minimum cost consistent with safety, reasonable convenience of operation, and meeting technical criteria; and total space requirement not to exceed a floor space of 4.1×4.9 m. The assembled system costs approximately $13 000 and provides better field characteristics than those specified above.
Measurement of Differential Atomic Collision Cross Sections
Authors: Fitzwilson R. L. , Thomas E. W.
Published: February 2004

An apparatus for the study of differential angular scattering of atomic projectiles by gas targets is described. The design facilitates system alignment and provides for accurate reproducible location of components. The performance of the instrument is studied for scattering of H+ at 5–25 keV energies by helium and argon targets. Differential cross sections for elastic scattering and charge transfer are presented as well as total charge transfer cross sections. The coefficients for secondary electron ejection by impact of H0 and H+ on a metal surface are compared.
Threshold Photoelectron Detector for Use in the Vacuum Ultraviolet
Authors: Spohr R. , Guyon P. M. , Chupka W. A. , Berkowitz J.
Published: February 2004

The device described responds selectively to those photoelectrons that are formed practically at rest in a gaseous target. The energy discrimination is achieved by accelerating the charged particles to reject those formed with appreciable transverse velocity. When this is used in connection with a light source of continuously variable wavelength over the range 10–20 eV, the resulting threshold photoelectron spectra allow the direct spectroscopic determination of ionization energies within a few millielectron volts. The potential of the method for detection of direct ionization and suppression of autoionization is illustrated by measurements of argon, krypton, and xenon. Simultaneously, ions can also be detected by use of a mass spectrometer. Thus the threshold photoelectron spectrum can be correlated with the photoion spectrum; and it is suggested that the method is applicable to coincidence measurements between electrons and ions.
LEED Optics as Electron Mirror Microscope
Authors: Chang Chuan C.
Published: February 2004

The LEED electron optics can be used as an electrostatic mirror microscope with resolution better than 5 μ and magnification over 1000×. Defects in silicon picture tube-diode arrays and scratches on sapphire substrates at which deposited aluminum had preferentially nucleated have been successfully imaged using LEED optics with no modifications. This method can be used to investigate surface topography and electric and magnetic field variations.
Equipment for Measurement of Elasticity Modulus for Hot Cell Applications
Authors: Sorrentino François
Published: February 2004

An equipment has been developed for in-cell determination of Young's modulus of irradiated materials in a continuous manner in the 20–1000°C temperature range. Longitudinal vibrations are electrostatically induced and maintained in the sample at its resonance frequency. The equipment has been used to check U-C nuclear fuel samples and alloy specimens.
Automatic System for Determining the Spin Wave Instability Threshold in Ferromagnetic Materials at Microwave Frequencies
Authors: Patton Carl E. , Green Jerome J.
Published: February 2004

A system has been developed which allows spin wave thresholds in ferromagnetic materials to be determined extremely rapidly. Curves of the change in cavity reflection coefficient as a function of the microwave field amplitude are generated on an X-Y recorder. The thresholds are read directly off the calibrated recorder plot.
Double Crystal X-Ray Dilatometer Using Continuous Radiation
Authors: Bottom Virgil E. , Carvalho Renê Ayres
Published: February 2004

A new type of dilatometer has been built to measure the strain induced in crystals, for example, by irradiation. The instrument uses high angle diffraction to obtain large lattice dispersion, and the parallel crystal configuration to achieve low wavelength dispersion. It is not necessary to know the wavelength of the x rays nor the order of diffraction and the measurement of strain is reduced to the measurement of an angle. Strains of 1×10−5 may be measured with error less than 5%. The paper discussed the theory, design, and accuracy of the instrument and presents typical experimental results.