bluuebunny/crossref_metadata_2025 huggingface dataset:
Low Cost Beam Current Integrator
Authors: Carra W. M. , Ehret J. E. , Meese J. M.
Published: February 2004

An inexpensive beam current integration system is described which measures the total integrated charge in a direct current accelerator beam during electron damage or ion implantation experiments over a wide range of positive or negative beam currents used in these experiments.
An Inexpensive Technique for the Fabrication of Two-Dimensional Wind Tunnel Models
Authors: Collins Donald J.
Published: February 2004

Details of a new and inexpensive technique are described for the production of thin airfoil models for aerodynamic testing. Using this technique, spanwise uniform models of arbitrary cross-section may be fabricated with a high density of instrumentation.
Statistical Error in Molecular Cross Section Measurements
Authors: Baldwin George C. , Miller Kenneth J.
Published: February 2004

The probability that a set of counts of particles transmitted over a measured path through a gas at a sequence of pressures can correspond to a particular value of the total cross section is calculated. From this, recipes are given for determining the best value of the cross section and of its mean square deviation, for evaluating the random and systematic errors in the cross section caused by random fluctuations in gas pressure and errors in the reading of gas pressure, and for prescribing the parameters of an experiment to achieve maximum precision in a given time of measurement.
A Thermionic Point Source of Low Energy Electrons
Authors: Porter J. H. , Franzen W.
Published: February 2004

A novel type of electron gun is described in which a spherically symmetric field is simulated. The structure is hemispherical: The inner hemisphere is a space-charge-limited emitter, and the outer concentric hemisphere is the anode. The hemispheres are terminated by a plane electrode with a radial potential variation designed to match the field between concentric spheres. This field is known from a new numerical solution to Poisson's equation. The energy distribution produced by the gun is measured and compared with the calculated distribution.
A Reliable, Repetitively Pulsed, High-Power Nitrogen Laser
Authors: Woodward Benjamin W. , Ehlers Vernon J. , Lineberger W. C.
Published: February 2004

The design and construction of high-power nitrogen 3371 Å laser is described in detail. The laser produces 13 mJ at 3371 Å in a 12 nsec FWHM pulse at a repetition rate of 5 pulses per second. Various models of the laser have yielded 108 pulses with very infrequent component failure. When a second mirror is added, strong laser action is observed in the N2 first positive system; the total resultant ir output energy is about 3 mJ in a 50 nsec FWHM pulse.
Reliable Single-Mode Operation of a Flashlamp Pumped Dye Laser
Authors: Marowsky Gerd
Published: February 2004

After efficient spectral narrowing with an interference filter and two succesive Fabry-Perot etalons single-mode operation of a flashlamp pumped dye laser has been achieved using a Michelson-type mode selector as proposed by Fox and Smith. Typical output powers of 1 kW with a linewidth of 0.05 pm have been obtained.
A Nondispersive Electron Energy Analyzer for ESCA
Authors: Lee J. D.
Published: February 2004

The energy analyzer described is of the spherical mirror-spherical grid retarding potential type. It obtains high resolution through a small energy overlap between low energy pass and high energy pass filter functions. The first filter is a spherical electron mirror operating slightly off-axis in a reflection mode. The second filter is a conventional spherical grid retarding field operating in transmission. Unlike other narrow bandpass monochromators, acceptance angle does not affect resolution and can be made to yield high luminosity. In addition, the resolution varies as the square of the entrance aperture dimension; hence larger entrance aperture areas can be used than for dispersive electron energy analyzers of similar size. This analyzer is examined theoretically, and experimental results as applied to ESCA (electron spectroscopy for chemical analysis) are presented.
A New Approach to Burnett Cell Design
Authors: Ruska W. E. A. , Pope G. A. , Kobayashi Riki
Published: February 2004

A method of fabrication of Burnett cells is presented which significantly reduces the error in Burnett data due to the volume change with pressure of the Burnett cell. The Burnett method can be used to generate extremely high precision P-V-T data because no volume or mass measurements are required. The new design uses similar, homogeneous, hollow spheres for the Burnett cell in order to eliminate almost completely the usual contribution to the error from volume distortion corrections.
A Closed System for High Temperature-Pressure Chemical Reactions
Authors: Penninger J. M. L. , Alberigs M.
Published: February 2004

For the study of homogeneous chemical reactions of fluids at high temperature and high pressure, a closed system is described consisting of a metal bellows sample container inserted in a bomb. Operating conditions ranged up to 500°C and 5000 bars.
Field Annealing Apparatus for Ferroelectric Crystals
Authors: Pandey R. K.
Published: February 2004

An inexpensive, simple laboratory apparatus is described which can be used for field annealing of ferroelectric crystals and ceramics. It can also be used as a reliable thermal chamber for determining accurately the temperature dependence of the spontaneous polarization and dielectric constant up to about 800°C.
The Perfect Direction and Velocity Focus at 254 °34′ in a Cylindrical Electrostatic Field
Authors: Dromey R. G. , Morrison J. D. , Peel J. B.
Published: February 2004

It is shown that for a cylindrical electrostatic analyzer particles entering the field on the central orbit are perfectly focused on the central orbit at an angle of 254°34′ independent of their velocity or incidence angle. An application of this result is suggested.
A Reflectance Analog Computer for the Determination of Thin Film Optical Properties
Authors: Reche J. J. H. , Pulfrey D. L.
Published: February 2004

Apparatus is described which allows the continuous automatic recording of the intensity of linearly polarized light reflected from a growing thin film. From these data the optical properties of the thin film can be determined.
A Bandpass Filter System for Far-Infrared Radiation Measurements
Authors: Nee S. F. , Trivelpiece A. W.
Published: February 2004

A simple bandpass filter system that is suitable to resolve the radiation emitted by far-infrared (4–0.1 mm wavelength) source that has a relatively flat emission spectrum is described. This system, which has a resolving power of 2, an insertion loss of 3 dB, and an acceptance angle of 7°, was used in conjunction with a cooled InSb detector to measure the temperature vs wavelength characteristics of a mercury arc lamp from 4 to 0.3 mm.
Precise and Rapid Measurements of Small Currents from High Impedance Sources
Authors: Samuelson G. , Bengtsson L. G.
Published: February 2004

A control unit has been designed which together with standard electronic equipment enables the repeated and precise measurement of average current through the measurement of the time required to accumulate a given charge on a capacitor. Charges of 10 nC are measured with a precision considerably better than 0.01% and an accuracy better than 0.1%. Measurement times longer than 5 sec are used and a typical application is the measurement of ionization currents between 10 and 1000 pA.
Analysis and Improvement of the Kelvin Method for Measuring Differences in Work Function
Authors: de Boer J. S. W. , Krusemeyer H. J. , Jaspers N. C. Burhoven
Published: February 2004

An analysis is given of the Kelvin method employing a variable shield potential, which takes nonuniformity of the surfaces into account. The influence of stray capacitance can be determined and eliminated by measuring as a function of spacing between the Kelvin electrodes for different values of the shield potential. These extended Kelvin measurements make it also possible to detect nonuniformity of the sample electrode and to eliminate its influence in certain cases, as is demonstrated by measurements on a vacuum cleaved TiO2 (rutile) (110) surface.
A Low Temperature Bolometer Heterodyne Receiver for Millimeter Wave Astronomy
Authors: Phillips T. G. , Jefferts K. B.
Published: February 2004

Liquid helium cooled InSb hot electron bolometers are used in a balanced mixer configuration as detectors for an imageless microwave receiver. The system is designed for mounting at the prime focus of the National Radio Astronomy Observatory (NRAO) 11 m antenna at Kitt Peak, Arizona, and is suitable for the study of rotational line spectra of interstellar gas molecules. Currently the operating frequency is in the 90–140 GHz band where the double sideband system noise temperature is 250 K.
A Tilted Plate Interferometer for Heat Transfer Studies
Authors: Marsters G. F. , Advani A.
Published: February 2004

This paper describes a tilted plate interferometer suitable for studies in natural convection. The basic element consists of a pair of highly reflecting plates; these plates are separated by about 15 cm. Collimated light from a He–Ne laser is normally incident on the first plate; Fizeau fringes appear at the second plate. The plates are highly reflecting, resulting in sharp fringes. Despite the complicated nature of fringe formation, due to multiple reflection, fringe displacement is simply proportional to the change in index of refraction of the medium between the plates if terms of order (Δμ/gm∞)2 are neglected. Thus the form of the fringe shift vs temperature relationship is the same as for the Mach-Zehnder interferometer. An experimental program of calibration has been conducted, and the fringe shift vs temperature relationship is confirmed.
Application of X-Ray Emission Spectrometry to the Determination of Mercury in Biological Samples
Authors: Walsh P. , Hamrick P. , Underwood N.
Published: February 2004

This paper describes the application of x-ray emission spectrometry to quantitative determination of mercury in biological samples. Measurement of mercury in blood, water, kidney, and urine has been accomplished. Matrix effects were detectable but not critical.
Comparison of Langmuir Double Probe and Laser Scattering Measurements of Plasma Parameters
Authors: Irisawa J. , John P. K.
Published: February 2004

Langmuir double probe and Thomson scattering measurements of density and temperature were made on a plasma with a view to estimating the reliability of probe measurements. The plasma used was the afterglow of a small θ-pinch plasma for which density and temperature were of the order of 1015 cm−3 and 1 eV, respectively. There was close agreement between probe measurement and scattering measurement of the electron temperature while the density as measured by the probe was lower by a factor of about 4 as compared to the scattering measurement.
A Retarding Field Electron Impact Spectrometer for Qualitative Analysis
Authors: Ridgway Stuart L.
Published: February 2004

A description is given of an electron impact spectrometer developed particularly for characterizing different gaseous molecules on the basis of the differences in the term scheme of the excited molecular electronic states over the energy range from 3.0 to 20 eV. A beam of monoenergetic (100 mV FWHM) electrons is incident upon a gas target within a constant potential region defined by an extremely electron-transparent tungsten wire grid wound over the six faces of an insulating cubical frame. Electrons emerging from this region are analyzed in energy by observing the variation in current to an enclosing collector electrode as a function of its electrical potential. A spectrum over the energy range 3–11 eV with a signal-to-noise ratio of better than 500, and an over-all resolution of 180 mV, of sufficient quality to discriminate between closely similar molecules, such as the isomers of chlorotoluene, is obtained in 20 sec at 100 nA exciting beam current and a sample pressure of 10−4 Torr.
A High Resolution Pulse Transmission Technique for Determining Ultrasonic Velocities
Authors: Junck Rodger N. , Benson David A.
Published: February 2004

Measurements and interpretation of ultrasonic velocities in complex media place requirements upon the measurements techniques which cannot be met by conventional ultrasonic equipment. The widely used high resolution echo and pulse overlap techniques are not generally applicable to such materials, especially in composites where the pulse is often severely distorted. A new high time resolution method based upon the pulse transmission technique is described to meet these applications. This approach is well suited to the measurement of ultrasonic velocities and velocity changes in media which are highly dispersive and/or highly attenuating. By using a crossover-point detecting circuit, time measurements may be made at a single reference point in the received acoustic pulse with a resolution of better than 1 nsec. If the pulse is distorted, such measurements at more than one crossover-point are useful in performing a mathematical analysis upon the rf pulse. In single crystal aluminum, where echo measurements can be used for comparison, a timing accuracy of 2 nsec is demonstrated for the technique. Also, the unusually wide frequency capability of the method is demonstrated with measurements of the dispersion curve for high purity polymethylmethacrylate (PMMA).
Slow Scan Display System for a Scanning Electron Microscope
Authors: Beck Vernon
Published: February 2004

This paper describes a new type of system for displaying slow scan video signals from a scanning electron microscope. The system uses digital buffering so that an image can be viewed on a TV monitor while it is being accumulated in a storage tube. The display system can simultaneously record two images and hold up to four images in storage. These images may be overlaid on one another in different colors. [A. V. Crewe and V. Beck, Proceedings of the 29th Annual Meeting of the Electron Microscopy Society of America (1971) p. 40]. The display system is also well suited for interfacing the microscope to a computer. A Nova 800 computer and a Kennedy 8000 series tape system are used with the display system to simultaneously record and analyze two channels of digitized data.
A Q-Meter Method for Measuring the Grain Size and the Resistivity Temperature Dependence of Metallic Powders
Authors: El-Hanany U.
Published: February 2004

A method for determining the average grain size and the specific resistivity temperature dependence of a metallic powder sample is presented. The method utilizes the change in the rf Q value of a coil, caused by placing the sample in it.
Design of Fast-Decay Pulsed rf Power Amplifier
Authors: El-Hanany U.
Published: February 2004

This paper describes an optimal design of a transformer-coupled matching stage for use in a high-power pulsed rf amplifier and the practical considerations for obtaining a rapid fall of the rf pulse. It also describes a high-power stage for use in pulsed NMR experiments, and presents a passive quenching technique for achieving rapid termination of the rf pulse.
A Pulsed NMR System for Nuclear Thermometry Below 2 K
Authors: Aalto M. I. , Collan H. K. , Gylling R. G. , Nores K. O.
Published: February 2004

A pulsed NMR system for platinum nuclear spin thermometry and for measurements of the nuclear spin-lattice relaxation time τ1 has been developed. The nuclear free precession signal is detected with a fast linear detector and an RC integrator. The τ1 measurements were performed by the transient recovery method with the aid of automated circuitry multiplexing of the linear detector output into four separate integrators. The thermometer was tested between 10 mK and 2 K using a powdered platinum sample. Within the experimental accuracy of about 2% the amplitude of the nuclear free precession signal was found to be proportional to 1/T. The thermometer could be calibrated with the aid of the Korringa relation τ1T=κ, with κ=29.6 msec K. Thermal equilibrium problems of the τ1 measurements are discussed in detail.
Theoretical Analysis of Bimodal Cavity Spin Inductors
Authors: Conciauro Giuseppe , Randazzo Edoardo
Published: February 2004

A field theory of bimodal cavity spin inductors for ERP spectrometry is developed. All the leakage effects are taken into account in order to attain results which are useful for an optimum design of such devices. Furthermore, perturbations of the cavity shape are considered in order to study the behavior of external decoupling devices. A general equivalent network is derived and formulas are given to evaluate all its parameters for any particular case. All the requirements to be fulfilled in order to minimize leakage and its frequency dependence are discussed. The general results obtained can be useful for the designer, who will be able to quantitatively evaluate the characteristic of a particular resonator, to compare different solutions, and to optimize all the parameters involved in a particular design.
Computerized Crystal Orientation
Authors: Lisbôa J. , Edwards David F.
Published: February 2004

A computer program has been developed for accurately and rapidly determining the Miller indices for any number of Laue diffraction spots for a crystal of any symmetry and with arbitrary orientation relative to the x-ray beam. Using the xy coordinates of each Laue spot the program goes directly to the assignment and verification of the Miller indices without the necessity of using nets and measuring angles.
Improved FEM for Precise Evaluation of Rapid Changes in Work Function
Authors: Maly Rudolf
Published: February 2004

An improved FEM for probe hole measurements and a convenient method for the evaluation of probe hole data have been developed during studies of coadsorption of oxygen on tungsten and oxygen and/or cesium on molybdenum. The entire emission pattern is accessible thereby for the investigation of adsorption parameters. An arbitrary plane can be chosen for examination by means of a manipulator. The changes in the field emission current during adsorption processes are recorded as a function of time. From these plots the corresponding changes in work function are derived by a special evaluation method. Time required for measuring and evaluating FEM data is considerably reduced and an improvement in accuracy is achieved as compared to the conventional method of drawing FN plots. The FEM, the method of evaluation, and some characteristic data obtained by this technique are presented.
On the Stabilization and Modulation of Microwave-Excited Sources for Spectroscopy
Authors: Smith K. L.
Published: February 2004

An improved microwave power source for electrodeless discharge lamps is described. Stabilization of the integrated visible light output is achieved, rather than mere regulation of the magnetron current. A new controllable modulator system is given, which allows all modes from cw to variable level pulse modulation to be applied to the microwave power fed to the discharge lamp. Some observations on the characteristics of certain electrodeless lamps are discussed briefly.
Crystal Alignment Holder for Electro-Optic Studies at High Temperatures
Authors: Vella G. J. , Harris L. B.
Published: February 2004

An experimental arrangement able to support crystal specimens for longitudinal electro-optic measurements at temperatures up to 180°C is described. It allows for rapid and accurate alignment of crystallographic axes with respect to a polarized light beam, while also providing for some adjustment of the crystal at experimental temperature.
Two and Four Quadrant Gating Circuits for Crossed Atomic Beam Experiments
Authors: Williams J. F. , Willis B. A. , Devlin C. R.
Published: February 2004

Descriptions are given of two circuits which generate scaler gating pulses and beam modulating pulses as required for crossed atomic beam experiments. For the case when only one of the crossed beams is modulated, a circuit is described in which a sinusoidal-type signal is filtered by a tuned amplifier whose gain is 2000 and Q value is 260, and then passes through a level crossing detector, a frequency doubler, and several variable delays to produce two complementary square wave pulses. When both atomic beams are modulated, a second circuit produces a scaler gating pulse from each of the quadrants of the modulating period. Several combinations of variable delays permit variable phase differences between each of the four gating pulses. Circuit stability is better than 0.01%.
Low Power Laser-Triggered Switching at Voltages > 500 kV
Authors: Strickland Daniel M. , Bettis Jerry R. , Guenther Arthur H.
Published: February 2004

The laser-triggered switching of a 575 kV, Van de Graaff charged, high-pressure, gas-filled spark gap is described. Subnanosecond switch jitter could be maintained with laser powers of only 10 MW. The application of this technique to repetitive switching of high-voltage, pulse-power systems with nanosecond delay and subnanosecond jitter is considered.
Regulated Low-Voltage Power Supply with Controllable Temperature Coefficient
Authors: Verster T. C.
Published: February 2004

It is shown how a low-voltage regulated power supply, which can operate from a limited supply voltage of 6 V or less, can be designed making use of a silicon-germanium transistor pair as voltage reference element in a novel circuit configuration. Pair selection efforts are not required, and the temperature coefficient can be assigned beforehand through design calculations and a single output voltage adjustment. The circuit example shown is able to function with an input-output voltage differential of only a few tenths of a volt and its temperature compensation is effective between − 30° and + 85°C.
High Resolution Electron Microscopy of Magnetic Specimens in the Philips EM 200
Authors: Sprague J. A.
Published: February 2004

A simple procedure is described that allows high-resolution transmission electron microscopy of strongly ferromagnetic specimens in the Philips EM 200. The electromagnetic beam tilt device of the microscope is used to compensate for the interaction of the electron beam with the magnetization of the specimen. Using this method, even relatively massive magnetic samples can be examined.
Simple Floating Preamplifier for Electron Multipliers
Authors: Christman S. B.
Published: February 2004

A simple preamplifier is described which allows one to simultaneously measure ac and dc signals from electron multipliers operating several thousand volts above ground potential.
Simple Modification to Commercial Michelson Transform Spectrometer for Increased Resolution
Authors: Korn Donald M.
Published: February 2004

A description is given of a method of modifying the mirror-drive mechanism in a commercial Fourier transform spectrometer in order to double the resolution. Comparative spectra are given which were taken before (resolution ≈ 0.050 cm−1) and after the modification (resolution ≈ 0.026 cm−1).
Device for Stabilizing Electrodeless Discharge Lamps
Authors: Ball Joseph J.
Published: February 2004

Increased stability for electrodeless discharge lamps used in atomic spectroscopy is attained by mounting a heater coil below the lamp. Heating by convection maintains the lamp at a constant temperature resulting in stable output within 2%.
A Method for Observing Lichtenberg Figures Using High-Speed Image-Converter Cameras
Authors: Kawashima Akihiro , Fukuda Setsuo
Published: February 2004

Lichtenberg figures have been studied, using high-speed image-converter photography, current and voltage measurements, and measurements of radiated light intensity.
Technique for Gain Determinations in Pulsed CO2 TEA Lasers
Authors: Jacobs Ralph R.
Published: February 2004

A gain measuring apparatus is described which yields information on the temporal and spatial gain properties of pulsed CO2 TEA lasers. The technique permits the observation of a probe beam amplitude prior to, during, and after amplification though a gain medium under investigation.
A Low Interaction Tension (or Compression) Torsion Load Cell
Authors: Michno M. J. , Findley W. N. , Reed R. M.
Published: February 2004

A load cell for combined axial load and torque with good sensitivity and repeatability and low cross talk is described. The instrument consists of a maraging steel tube with gimbal mounted dc differential transformers to sense the axial deflection and twist of the tube. Free-Flex pivots were used in the gimbals to minimize friction.
High Accuracy Potentiometers for Use with Ten Millivolt Josephson Devices. I. Double Series-Parallel Exchange Comparator
Authors: Finnegan T. F. , Denenstein A.
Published: February 2004

High accuracy determinations of 2 e/h using the ac Josephson effect require correspondingly accurate measurements of small dc voltages. In the preliminary stages of a determination of 2 e/h with substantially improved accuracy, two different potentiometric instruments based on two independent principles of operation were designed and built. Both instruments were used in an extended series of 2 e/h measurements at the University of Pennsylvania and subsequently at the National Bureau of Standards where they have been used to realize the U. S. legal volt as recently redefined via the ac Josephson effect. One of these instruments is based on a modified series-parallel technique and is described in detail in this paper. After treating the general theory of the low resistance case, the design and construction of a portable self-checking instrument based on the double series-parallel exchange method is described. This series-parallel comparator (SPC), built to compare a Josephson device (10 mV) and a standard cell (1 V), was evaluated and tested in the course of determinations of 2 e/h with one standard deviation (1 σ) uncertainties of about 0.1 ppm. The sources of systematic uncertainty are discussed. The uncertainty attributable to the comparator alone is about 3 parts in 108(1 σ).
Measurement of Ion Ratios in Capillary Discharges
Authors: Fitzwilson R. L. , Chanin L. M.
Published: February 2004

An apparatus for the study of relative ion concentrations in the positive column of noble gas capillary discharges is described. The technique employs ion sampling through a small orifice in the wall of the discharge tube. Consideration is given to identification and removal of possible systematic errors. The performance of the instrument is studied for discharges in helium and neon for pressures varying from 0.10 to 30 Torr and for discharge currents between 10 and 40 mA.
Ultrasonic Measurements with Milliliter Liquid Samples in the 0.5–100 MHz Range
Authors: Eggers F. , Funck Th.
Published: February 2004

A resonator and a pulse method for relative ultrasonic absorption measurements in liquids from about 0.5 to 100 MHz are described and discussed. Due to the small sample volumes needed (around 1 ml) both techniques are suitable for relaxational studies on fast biochemical reactions. Cells are described, which have been operated with aqueous and organic media in a temperature range from − 10 to 80 °C.
A Versatile, Linear, Interface Amplifier for Signal Averaging
Authors: Torgeson D. R.
Published: February 2004

A direct coupled linear amplifier is described which has been used as an interface between time mode operated multichannel analyzers or instrument computers and electromagnet control amplifiers or voltage controlled oscillators for magnetic resonance signal averaging. The amplifier accepts the analog memory channel address voltage from the analyzer or instrument computer and attenuates, biases, amplifies, and inverts the signal as required. Operating techniques and circuit stability are discussed.
An Improved Hydraulic Heat Flow Simulator
Authors: Harmathy T. Z.
Published: February 2004

A hydraulic network analog device is described that offers great versatility in simulating one-dimensional heat flow problems. The simulation procedure is illustrated by examples.
Experimental Study of a Sintered-Copper Heat Exchanger
Authors: Pundak N. , Winograd Y. , Rosenbaum Ralph L.
Published: February 2004

The inlet and outlet temperatures and the block temperature of a discrete heat exchanger in a dilution refrigerator have been measured. Temperatures measured on the outgoing 3He–4He stream were higher than temperatures predicted theoretically; this discrepancy has been attributed to viscous effects within the dilute 3He–4He channel which degrade the performance of the heat exchanger significantly below 80 mK.
``Boxcar'' Attachment for Oscilloscopes Useful for Low Level Signals
Authors: Collins Frank G. , Katchinoski Ronald
Published: February 2004

The design of an inexpensive ``boxcar'' integrator for improving the signal-to-noise (S/N) ratio of low level repetitive signals is described. The design is simplified by using the timing circuits of an oscilloscope to generate the gate and delay for the boxcar. The S/N ratio can be improved up to 60 dB. It is useful for signals from 500 μV to 30 mV rms containing frequencies up to 50 kHz, at repetition rates to several kHz. Examples of its use for sine and square waves are included.
Measurement of Complex Permittivity of Liquids at Frequencies from 5 to 40 GHz
Authors: Van Loon R. , Finsy R.
Published: February 2004

Computer analysis of reflected power profiles allows accurate determination of complex dielectric permittivity of low, medium, and high permittivity liquids by one single method if nonideal plunger properties are taken into account. For low loss measurements account is taken of the losses in the waveguide walls. For medium and high permittivity liquids, dumbell plunger design leads to important errors due to higher mode excitation and propagation.
A Method for Correcting Curved-Pipe Flow Effects Occurring in Coiled Capillary Viscometers
Authors: Dawe R. A.
Published: February 2004

The error in viscosity measurements caused when using coiled tubes has been experimentally assessed. Previous methods for obtaining a correction factor are shown to be unreliable. A method for calculating the Dean number for an unsteady state viscometer is proposed with which the flow data obtained in a curved-pipe can be satisfactorily correlated. Experimental results obtained using a new coiled viscometer are used to illustrate how such a correction can be applied.
An Improved Adiabatic Titration Calorimeter
Authors: Amdur S. , Marinsky J. A.
Published: February 2004

The complexity and cost of instrumentation that has been necessary to provide the ability to measure the complete temperature profile of a chemical reaction without heat loss has been sizeably reduced in the improved adiabatic titration calorimeter that is described. Its design is such that even large changes in temperature during reaction can be accommodated without transfer of heat into or out of the calorimeter. This is accomplished simply by matching such changes in the calorimeter temperature by simultaneous and equivalent changes in the temperature of a surrounding water bath. This capability of the calorimeter eliminates the special instrumentation that is required in other calorimeters to measure the small temperature change that can be tolerated without significant loss of heat. The titrant is stored in a glass coil in thermal contact with the solution in the calorimeter prior to its controlled transfer into the solution by displacement with air. By this approach the heat capacity of the calorimeter is essentially unchanged during calorimetric study of a reaction. This simplification removes the need for repetitive calibration inherent in the operation of other calorimeters.
Absolute Length Measurement at High Pressure
Authors: Lincoln R. C. , Ruoff Arthur L.
Published: February 2004

A length measurement system is described which can make absolute length change measurements of a meter long specimen within a pressure vessel (to pressures of 8 kilobar) with a fractional 3σ random error of ± 6 × 10−8 and a possible systematic error of less than 4 × 10−7 for changes in length of 1 cm. Possible uses of such a system for measuring the volume thermal expansivity (at pressure) and the isothermal bulk modulus (at pressure) are described. Moreover it is noted that when this system is combined with an ultrasonic velocity measurement system, the adiabatic bulk modulus (at pressure) and Grüneisen parameter as a function of pressure can be directly determined and the absolute pressure itself can be measured.
Digital Microstress Gauge for Magneto-Thermal Gas Transport Studies
Authors: Taboada J. , Adair T. W.
Published: February 2004

A description is given of an extremely sensitive stress gauge system designed for studying rarefied gas transport in magnetic fields. A novel approach employing a vertical quartz cantilever with an associated optical electronic readout is used to detect changes in the Maxwell stress on a thin aluminum disk in the magnetic-thermal field. Forces acting on the detecting disk as small as 10−5 dyn can be resolved.
A New Ion and Electron Detector for Ion Cyclotron Resonance Spectroscopy
Authors: Huntress W. T. , Simms W. T.
Published: February 2004

A new detector using an externally driven tuned circuit has been developed for use in ion cyclotron resonance spectroscopy experiments. Based on the ``Q-meter'' circuit, this detector will operate at frequencies greater than 1 MHz at rf levels less than 1 mV. Operation in the frequency range 1–15 MHz allows the use of higher magnetic fields for more efficient storage of low mass ions in the trapping mode of operation. In the frequency range 2–6 MHz electrons can be detected in the ion cyclotron resonance cell by their resonant motion in the trapping plane.
A Multiple Sweep, Floating Langmuir Probe System for Pulsed Discharge Diagnostics
Authors: Lacoste J. , Dimoff K.
Published: February 2004

A multiple sweep probe and recording system is described which operates at floating potential. It is adaptable to measuring plasma characteristics generated by a high voltage discharge. Shielding problems are avoided by allowing the system to trigger with the initial transient and then recover automatically to predischarge settings. Duration, frequency, and number of sweeps are easily controllable to fit requirements of the postdischarge regime under study.
A Simple Flying Spot Scanner Design for Electron Lithography
Authors: Melliar-Smith C. M. , Storm A. R.
Published: February 2004

A simple, inexpensive flying spot scanner system is described which enables a conventional scanning electron microscope (SEM) to be used for research projects in electron beam lithography. The unit, built almost entirely from readily purchased parts, bolts onto the SEM without any modification of the microscope itself. The ultimate resolution of the system exceeds 45 line pairs/cm over a 9 cm square frame, giving over 900 beam on, beam off operations per frame. The system has been used with electron lithography to etch thin films into patterns of considerable complexity with linewidths of less than 5000 Å.
An Automated Facility for Microsecond Kinetic Spectrophotometry
Authors: Michaels H. B. , Basser T. E. , Taylor W. B. , Hunt J. W.
Published: February 2004

A method is described for the calculation and recording of spectra of transient absorbing species observed in pulse radiolysis and flash photolysis experiments. The level of the absorption signal is sampled using fast linear gates, and an analog computation of the optical density is carried out by logarithmic amplifiers and subtractor. The output is displayed on an X-Y recorder as a spectrum of OD plotted against wavelength and is calculated on-line as the experiment proceeds. Linearity of the plotter facility is discussed, and the over-all performance of the system is demonstrated by sample spectra of the (CNS)2− radical anion and of the transient product produced by the attack of hydroxyl radicals on polyadenylic acid.
Ionospheric Electric Field Measurements with a Spin Stabilized Detector
Authors: Robar J. D. , Koehler J. A. , Kavadas A.
Published: February 2004

A spin stabilized probe was constructed to make three component vector measurements of dc electric fields in the auroral ionosphere. The resolution of an electric field component was found to be as high as ≃ 0.5 mV/m in magnitude and ≃ 20 msec in time, while the total vector was resolved in ≃ 0.5 sec. This miniaturized instrument was mounted on the exterior skin of sounding rockets and, containing its own telemetry and magnetometer system, was ejected into the ionosphere. The floating double Langmuir probe detector was designed to have a high input impedance of ≃ 8 × 103 Ω at 60 Hz. Spin rates from 10 to 100 Hz allowed the dc offset errors, normally measured by other techniques, to be removed by ac coupling of the electronics. A simplified data reduction procedure is obtained by an envelope analysis of the amplitude modulated electric and magnetic field signals.
A New Multiparameter Separator for Microscopic Particles and Biological Cells
Authors: Steinkamp J. A. , Fulwyler M. J. , Coulter J. R. , Hiebert R. D. , Horney J. L. , Mullaney P. F.
Published: February 2004

A new flow-system instrument for quantitative analysis and sorting of microscopic particles, particularly biological cells, based on multiple measurements of physical and biochemical properties has been developed. Cells stained with fluorescent dyes in liquid suspension enter a unique flow chamber where electrical and optical sensors measure cell volume, single- or two-color fluorescence, and light scatter, and emerge in a liquid jet that is broken into uniform droplets. Sensor signals are electronically processed several ways for optimum cell discrimination and are displayed as pulse-amplitude distributions using a pulse-height analyzer. Processed signals trigger cell sorting according to preselected parametric criteria. Sorting is accomplished by electrically charging droplets containing the cells and electrostatically deflecting them into collection vessels. This instrument is described in detail with illustrative examples of experiments using polystyrene fluorescent microspheres, cultured human cells, and human leukocytes.
A Computer-Controlled Digital Frequency Synthesizer for NMR Spectroscopy
Authors: Wilkins Charles L. , Thoennes David J.
Published: February 2004

A hardware/software computer interface for control of a digital frequency synthesizer is described. This synthesizer is controlled by selection of a suitable oscillator between 2.5 and 60.2 MHz, which in turn is controlled by two 8-bit modulo N counters. The ratio of the two integers (Q /P) selected as the moduli of the counters determines the ratio of synthesized to reference frequency. The interface described directly selects these functions and thus permits computer calculation and setting of the required ratio. Addition of a manually controlled offset frequency completes the synthesis. In this way, frequencies can be synthesized with a maximum error of approximately 10 Hz or less. The interface therefore allows rapid and accurate synthesis of any desired frequency within the 2.5–60.2 MHz range. This method is of utility in both spin-spin decoupling experiments in NMR spectroscopy and as a central element of a variable frequency NMR spectrometer system. The algorithm for computing the necessary values of Q and P is described. Such an interface is easily adaptable to any minimal laboratory computer system. In the present case an 8K word Varian 620/i computer was used.
Apparatus for In Situ Measurements of Optical Properties of Evaporated Thin Films
Authors: Bluzer N. , Bahl S. K.
Published: February 2004

A single beam device which measures continuously as a function of wavelength reflectance and transmittance is described. The unit is attached to a McPherson 218 monochromator, but it can be adapted for any monochromator. A notable feature of the device is that with a specially constructed vacuum evaporator this system enables the study of the optical properties of thin films without exposing them to air. Described also is a feedback light control system designed to compensate for signal intensity variations with wavelength caused by various optical components.
A Furnace System with Versatile Time-Temperature Programming and Electrical Measurement Capability
Authors: Fuller G. L. , Vest R. W.
Published: February 2004

A furnace and electrical measurement system is described that is capable of a wide range of time-temperature relationships while allowing for the simultaneous measurement of sample temperature and resistance over any 3–4 decades in the range 10−2–107 Ω. The furnace system consists of a servo-controlled push rod moving a sample fixture in a gradient furnace. The servo system is controlled by a cam wheel driven by a stepping motor whose speed can easily be changed during rotation to provide for increased profile versatility. Two- or four-terminal resistance measurements and temperature measurements are possible with four lead wires; each is monitored with a chart recorder. Possible applications and examples of performance are discussed.
Analysis of the Sensitivity of Low Energy Electron Transmission Experiments
Authors: Golden D. E.
Published: February 2004

Approximate expressions are given for the fraction of scattering events which contribute to the attenuation of the transmitted electron current in cylindrically symmetric electron spectrometers, with and without an imposed axial magnetic field. The sensitivity to scattering is shown to decrease strongly with increasing magnetic field strength owing to the trapping of scattered electrons by the magnetic field and multiple scattering effects due to the path length being a function of the magnetic field strength. The effect of applying a retarding electric field to electrons leaving the interaction region is shown to leave the conclusions substantially the same.
The Flux Leak Compensating Current Belt
Authors: Mendel C. W.
Published: February 2004

This paper describes a simple current measuring device which has better response than the Rogowski belt for very high currents and fast rise times and better response than the Rogowski belt and transformer under all conditions. The device consists entirely of passive components, does not require calibration, and is easily adjusted so that there is no linear (in time) component to the droop.
Improvements of the Properties of the Relativistic Parallel Plate Particle Analyzer
Authors: Proca Georges A.
Published: February 2004

Using a three dimensional formalism previously established, the freedom to choose the coupling function g (θ, φ) between the polar angles defining the mean trajectory in the field-free region of the analyzer is exploited to improve the properties of the instrument. It is shown that a partial correction to the z variation of the image when θ and φ vary can be achieved yielding a maximum excursion Δz /z of 6% for a total θ excursion of Δθ = 18° at φ = const with a corresponding increase of resolving power by a factor of 2. Indications are also given on the possibility of cylindrization of the focal surface.
A High Pressure Temperature-Jump Apparatus
Authors: Yu Andrew D. , Waissbluth Mario D. , Grieger Richard A.
Published: February 2004

A technique is described for carrying out temperature-jump experiments at pressures up to 1000 atm, thus allowing the measurement of activation volumes for reactions in the μsec-sec range. The main features of the new technique are an electrical lead which has been tested to 2000 atm and 10 000 V ungrounded electrodes, and a flexible cell to transmit pressure from the external fluid to the solution.
Errors in Luminescence Decay Time Measurements Caused by Photomultiplier Saturation
Authors: Jones P. F. , Calloway A. R.
Published: February 2004

A possible source of error in measuring luminescent decay times as a result of photomultiplier saturation is discussed. Photomultiplier saturation can occur by exceeding the maximum linear output current, which decreases with increased light pulse duration. For this reason it is necessary to calibrate the instrument response appropriate to the lifetime and light intensity being measured.
A Simple Casting Device for Use with an Argon Arc Furnace
Authors: Crow J. E. , Sweedler A. R.
Published: February 2004

A simple vacuum casting device for use with a conventional arc furnace is described. It has been possible to cast refractory metals and intermetallic compounds into rods of 1.6 mm diam and up to 50 mm long without modifying the arc furnace.
Fast and Slow Afterpulsing in a Magnetic Electron Multiplier
Authors: Erskine M. E. , Delaney C. F. G.
Published: February 2004

Two types of afterpulses with quite distinct delay times with respect to the primary pulse can be observed in a magnetic electron multiplier. This Note gives details of their characteristics and the effect on them of altering various multiplier parameters. Some mechanisms for their generation are also discussed.
A Simple, Versatile Swenson Cryostat
Authors: Cheng V. M. , Crawford R. K. , Daniels W. B.
Published: February 2004

Employing Swenson's method of temperature control [Rev. Sci. Instrum. 25, 608 (1954)], we have designed and built a simple cryostat capable of controlling temperature over a very wide range (it has been used successfully between 80 and 309 K, with the potential of being used at even lower temperatures when suitable coolant is employed). The features of this particular construction allow the low temperature chamber to be exposed to the atmosphere outside. Various advantages and disadvantages of this apparatus are presented.
Beam Scanner for a 1 MeV Van de Graaff
Authors: Carra W. M. , Ehret J. E. , Locker D. R. , Meese J. M.
Published: February 2004

An electron beam scanner is described which is used to produce uniform scans and steering of the electron beam from a 1 MeV Van de Graaff accelerator during electron radiation damage experiments.
A Method of Construction of Protein Backbone Models
Authors: Keefe William E. , Howe Donna-Beth
Published: February 2004

A method is described by which a backbone model of a protein can be constructed making use of the two angles of rotation at the alpha carbon of each amino acid in a peptide chain. A model of the protein myoglobin constructed using this method is shown.
High-Temperature Thermal Gravimetric Apparatus
Authors: Gardner Richard A. , Swiss William R.
Published: February 2004

A thermal gravimetric apparatus is described that permits accurate weight determinations in a wide variety of atmospheres at temperatures from 50 to 1700 °C. The unique features of the apparatus are its versatility, ease of operation, high accuracy, durability, and low cost. The design can be used with either programmed heating rates or for high-temperature isothermal kinetic studies.
Magnetic susceptibility measurements using a superconducting magnetometer
Authors: Cukauskas Edward J. , Vincent Daniel A. , Deaver Bascom S.
Published: February 2004

The design and performance of an apparatus for measuring magnetic susceptibility using a superconducting magnetometer and superconducting magnet and shields are described. Measurements of static susceptibility and of nuclear magnetic resonance have been made with this system. Volume susceptibility changes of 10−10 cgs can be measured with a 1 sec response time, a 100 Oe applied field, and a 1 cm3 sample. Noise limitations and potential for improvement of sensitivity by several orders of magnitude are discussed.
Low capacitance electrical feedthrough and simple, reuseable closure seal for hydrostatic pressures to 7 kilobar and temperatures to 200 °C: application to NMR
Authors: VanderHart D. L.
Published: February 2004

An electrical feedthrough having a capacitance of 7 pF is described. It consists of a stack of two right circular cylinders, one an insulator, and one a metal with polyimide gaskets appropriately placed. A very simple, reuseable, polymeric closure seal is also described. The seal is patterned after the ``C'' seal and features easy extraction and sealing on the small bore of the pressure vessel. The closure seal and feedthrough have been tested to 7 kilobar at room temperature and 5 kilobar at 200 °C without failure.
An optical delay line
Authors: Meckley J. R.
Published: February 2004

An optical system is presented that can produce long time delays without long path lengths. This system can also produce pulses of variable length, be used to create various sequences of pulses, and can shape pulses.