bluuebunny/crossref_metadata_2025 huggingface dataset:
Reaction Rate Analysis by Gas Evolution: A Constant Volume Variable Pressure Kinetic Apparatus
Authors: Timberlake J. W. , Martin J. C.
Published: February 2004

An automatically recording constant volume variable pressure apparatus for measurement of reaction kinetics is described. This instrument has been found to be useful for following rates of reactions in solution that proceed with an increase in pressure of the gas phase over the reaction solution.
A Fringe Counting Laser Interferometer Manometer
Authors: Tilford Charles R.
Published: February 2004

A prototype standard mercury manometer using a fringe counting laser interferometer to measure the differential height of the mercury columns has been built and successfully operated. The 10.6 μ wavelength radiation from a CO2 laser and specially treated manometer tubes have been used to reduce the effect of disturbances on the mercury surface so that reliable operation of the manometer is possible.
Spectrometer for Measuring Secondary Electron Yields Induced by Ion Impacts on Thin Film Oxide Surfaces
Authors: Dietz L. A. , Sheffield J. C.
Published: February 2004

We have developed a spectrometer for studying secondary-electron yields from ion-to-electron converter dynodes. Ions, formed by surface ionization, are mass-analyzed in a small double-focusing mass spectrometer which is followed by a post-accelerating lens to increase the kinetic energy of the ions to ∼30 keV before they strike an ion-converter dynode. The ion-converter dynode is a flat, narrow strip positioned along the the axis of rotational symmetry of a cylindrical lens and is rotatable about this axis. Secondary electrons are emitted from the thin-film oxide surface of the converter dynode. They are accelerated to ∼30 keV in the cylindrical lens and are focused onto a silicon solid state detector for pulse-height analysis of the secondary-electron spectrum. Idividual secondary-electron groups containing 1,2,3,…, etc., electrons are resolved and recorded in a 400-channel pulse-height analyzer. Deconvolution of the resulting energy spectrum gives precise estimates of secondary electron yields for monatomic or polyatomic ions of different mass, atomic number, energy, and angle of entry. Experimental results are given for thin films of oxidized aluminum, plasma-anodized aluminum, and for an activated beryllium-copper surface. Our results support the hypothesis that the Poisson distribution represents the minimum statistical variance (most sharply peaked distribution) that is physically attainable for secondary electron emission from an ion-converter dynode.
Using the Quasistatic Method for MOS Measurements
Authors: Lopez A. D.
Published: February 2004

The quasistatic technique used to obtain MOS capacitance voltage characteristics and interface-state density is finding increased use. While the basic technique has been described, it is felt that a detailed description of the apparatus setup and measurement technique will prove useful. This technique allows the rapid evaluation of MOS properties with accuracy of about 1 × 1010 states/cm2 eV near midgap. Experimental considerations such as MOS geometry, sweep rate, stray light, and series resistance, and their influence on the resulting C-V characteristic, are discussed.
Absolute Velocity-Sense Determination in Mössbauer Spectrometry
Authors: Yeboah-Amankwah D.
Published: February 2004

A method for determining absolutely the velocity sense of a Mössbauer spectrum taken in the multiscaler mode is described. It is shown that relative motion of the Mössbauer source with respect to the absorber naturally leads to a parabolic profile of the absorption spectrum. This parabola is used to determine the sense of the different sections of the spectrum uniquely without reference to a standard asymmetric Mössbauer spectrum.
Differential Thermal Analysis Furnace Using Dynamic Flow of Water Vapor
Authors: Garn Paul D.
Published: February 2004

A modification of the Lodding-Hammell furnace is described in which steam can be generated and passed through the sample and reference to supply a dynamic water vapor atmosphere at any easily controlled pressure.
Moisture Absorption by Some Instrument Materials
Authors: Shepherd W.
Published: February 2004

Absorption of moisture by various instrument materials during 24-h storage, under high humidity is considered. Glass, copper, stainless steel, and nickel absorbed <0.5 mg dm−2, chromium and clean brass <4 mg dm−2, and tarnished brass and polytetrafluoroethylene approximately 10 mg dm−2. Silicone rubber, natural rubber, and neoprene absorbed 30, 123, and 217 mg dm−2, respectively.
A Continuous Liquid Chemical Injector
Authors: Roberts T. G. , Pratt H. L.
Published: February 2004

A continuous liquid chemical injector for use with arc-driven gas dynamic lasers or cw chemical lasers is described. The injector can be easily constructed in the laboratory and the mass flow rate may be programed as functions of time. Mass flow rates as small as 1 g/sec into environments at pressures of several tens of atmospheres and temperatures of the order of 1300°C have been achieved.
Vacuum Cleavage Device for Mica
Authors: Reichelt K.
Published: February 2004

A vacuum cleavage device for mica is described, which works reliably up to the decomposition temperature of mica.
A Method for Producing Long, Cylindrical, Superconducting Flux Shields
Authors: Newton A. C. , Martin F. , Lorant S. J. St. , Toner W. T.
Published: February 2004

A technique is described for making long, cylindrical, magnetic flux shields from Nb3Sn superconducting tape.
A New Retarding Field Electron Spectrometer with Differential Output
Authors: Lindau I. , Helmer J. C. , Uebbing J.
Published: February 2004

We describe the construction and performance of a new electron spectrometer for analysis of low kinetic energy electrons, 0–2000 eV. The design of the analyzer is based on computer calculations and combines many favorable properties of both the retarding and the deflection energy analyzer. The energy analyzer consists of a set of electrodes with cylindrical symmetry and a planar retarding field grid followed by an electrode system with postmonochromatic action. Therefore a differential spectrum is obtained directly. The performance of the analyzer is discussed in terms of resolution, sensitivity, luminosity, and signal-to-background. The resolution achieved is 0.5%, with a resolution of 30 meV, making it possible to resolve and study electronic vibrational levels in atoms and molecules. A few spectra of nitrogen and argon are shown as representative of the performance of the new analyzer.
A Servo-Controlled Axial Fatigue Machine with Strain Rate Feedback for Testing Polymers and Composites
Authors: Dharan C. K. H. , Colvin A. D.
Published: February 2004

An inexpensive servo-controlled electrohydraulic fatigue machine, capable of a maximum load of 22.2 kN (5000 lbf) and a maximum servo-controlled strain rate of 0.2 sec−1, is described. Its primary capability is to perform load and strain-range controlled fatigue tests conducted at constant strain rate feedback. In addition, the machine is capable of performing constant strain rate tensile tests and closed loop stress relaxation tests. The results of some initial fatigue tests are presented.
Magnetic and Electrostatic Deflectors for Charged-Particle Beams
Authors: Haeberli W.
Published: February 2004

It is often assumed that uniform electrostatic or magnetic fields are required if all particles in a parallel beam of ions of finite diameter are to be deflected through the same angle. It is shown that the nonuniform field caused even by very short electrodes or pole pieces produces uniform deflection under certain conditions.
Apparatus and Techniques for Electron Beam Fluorescence Probe Measurements
Authors: Ocheltree S. L. , Storey R. W.
Published: February 2004

A laboratory apparatus and experimental techniques have been developed to investigate the properties of a 5–30 keV electron beam fluorescence probe system in air, nitrogen, and helium test gases over a pressure range from 10−3 to 10 Torr at 302 K. The design and performance characteristics of the electron beam generating system and optical detector system are described. The electron beam system used in this work was especially designed for wind tunnel remote measurements of local gas density in low density high velocity flow fields. A 1 mm diam collimated beam of 5–30 keV electrons was used to irradiate each of the test gases and excite fluorescence radiation, specifically the 391.44 nm (0,0) First negative band of N2+ in air and nitrogen, and the 501.57 nm (21S–31P) He line in helium. A precision optical detector system has been designed and used to observe the spatial distribution and pressure dependence of this fluorescence radiation excited by the electron beam. Calibration and test procedures have been implemented to reduce significantly experimental errors and provide relative fluorescence intensity measurements with a precision better than ±2%. Typical results are presented and discussed which illustrate data obtained using the developed apparatus and test procedures.
Analysis of High-Charge State Output from a Penning Ion Source
Authors: Darling R. L. , Davis R. H.
Published: February 2004

Charge state yield data for the production of Ar ion beams from a Penning ion source have been previously analyzed by Fuchs. These data have been reanalyzed in calculations which take into account the Auger process at any level of ionization, electron recombination, and charge state dependent and independent losses. For a wide range of simple two-energy electron distributions, and for a discrete approximation to a distribution of thermalized electrons plus a Gaussian distribution of primary electrons, fits can be obtained which are as much as two orders of magnitude better for Ar9+ and even more improved for 10+. The fitting parameters all lie near α [inverted lazy s] 10−8 for the recombination rate coefficient and τ [inverted lazy s] 1 μsec for ion lifetime for an electron density of 3×1014/cm3 The contribution to the rate of change of charge state population qi due to electron recombination is assumed to be (ρe qi i2 α), where ρe is the electron density. The Auger effect is included as a 2-electron process for most of the calculations. The estimated cross sections for Auger effects are derived similarly to those used in a feasibility study of electron beam sources of very heavy, highly ionized beams.
A Sampling Linear Detector for Accurate rf Pulse Amplitude Measurement
Authors: Bloyet D. , Piejus P. , Varoquaux E. , Avenel O.
Published: February 2004

A sampling linear detector is described which has been developed for measuring one-shot free precession amplitudes at 1.5 MHz in a pulsed NMR experiment. A 10−3 accuracy is achieved over a 30 dB dynamic range with a 60 μsec gate aperture time. The rectifying circuit is made up of two low threshold hot carrier diodes placed in the feedback loop of a fast operational amplifier. A bias voltage technique is employed for further linearization. Commercial integrated circuits and operational amplifiers are used throughout and make layout and wiring noncritical. Checking and calibration prodedures, as well as circuit operation, are carefully analyzed.
Coaxial Anode for Background Suppression in X-Ray Proportional Counters
Authors: Bunner A. N. , Kraushaar W. L. , McCammon D. , Vanderhill M. , Williamson F.
Published: February 2004

We have devised, constructed, and tested in flight a scheme which permits the ends (near the anode seals) as well as the bottom and sides of an x-ray astronomy proportional counter to be protected by anticoincidence guard counters. A rocket-borne test has shown that the non-x-ray background is reduced by an additional factor of about 30 when the end guard counter feature is added.
Bi2Se3 Hall Effect Magnetometer for Reliable Low Temperature Use
Authors: Woollam John A. , Beale Harry A. , Spain Ian L.
Published: February 2004

Single crystals of n-type Bi2Se3 grown by the Bridgman technique are found to make excellent Hall effect magnetometers capable of repeated cycling to liquid helium temperatures. Plots of Hall resistivity, ρyx, versus magnetic field B to 11 tesla deviate from linearity by less than ±0.8% for all temperatures between 1.1 and 300 K. Furthermore, the slope of the ρyx versus B curve varies by less than 2% in the region 1.1 to 78 K.
A Simple Method for Estimating H1 in ESR Experiments—The Microwave Power Saturation of γ-Irradiation Induced Glycylglycine Radicals
Authors: Copeland Edmund S.
Published: February 2004

A technique is described whereby the shape of the first derivative electron spin resonance (ESR) spectra observed for γ-irradiated glycylglycine can be used in ESR experiments to estimate the microwave magnetic field H1 in the 40–1000 mG range. The ratio of the minor to major derivative peak heights of the glycylglycine doublet is found to vary with H1. Slow passage progressive saturation studies are included in an attempt to explain the phenomenon. The technique provides a means of measuring H1, without knowing effective cavity Q, incident power, or the field concentrating effects of quartz inserts and is proposed as an interlaboratory ESR microwave power comparison standard.
Poly(halo)styrene Thin-Film Dosimeters for High Doses
Authors: Bishop William P. , Humpherys Kent C. , Randtke Peter T.
Published: February 2004

A useful thin-film passive dosimeter system has been developed through use of a poly(halo)styrene matrix doped with malachite green methoxide as an indicator. Extensive characterization studies of the chlorostyrene dosimeters have been completed and the range of conditions under which they are useful has been defined. Exposure to radiation causes development of a blue color (absorption at 630 and 430 nm) which has an optical density proportional to dose over the range 104−107 rad and may be calibrated to above 3×107 rad. No effects of dose rate have been observed between 102 and 1015 rad/sec, and no effects of photon energy between 2 keV x-rays and 1 MeV gamma rays. Of the environmental parameters studied, only extraneous uv light, temperature, and a few noxious gases have a significant effect on the performance of the dosimeters. Oxygen has only a small effect (a few percent) at low dose rates, but acidic gases such as NO2, SO2, and HCl will first color, then bleach the films. The rate and ultimate amount of coloration are dependent on temperature, but this effect is negligible from 0 to 35°C. These films have an indefinite shelf life at room temperature in the absence of light and corrosive gases, and the small effects of oxygen and temperature can be compensated for in the calibration for a particular application.
A Precision Goniometer Polishing Jig
Authors: Butz R. , Krahl-Urban B. , Mench K.
Published: February 2004

The description and use of a precision goniometer polishing jig are presented. Specimens pre-oriented within 6° can be exactly oriented and prepared on the jig. Samples of single crystals of refractory metals have been prepared with a surface polished within 1/20 of a wavelength of sodium light and with an orientation to within 15′ of the desired plane. This jig can operate on any horizontal running polishing machine.
A Simple, Inexpensive SIMS Apparatus
Authors: Schubert R. , Tracy J. C.
Published: February 2004

A simple secondary ion mass spectrometry (SIMS) apparatus has been constructed. A Superior Electronics, 3K/5U, electron gun has been converted to an ion gun capable of producing a 1 mm diam, 2 keV, 1 μA beam. To achieve wide dynamic range at high resolution in the mass analysis of the secondary ions using a quadrupole mass spectrometer (QMS), the ion injection energy must be ≲4 eV. Ions sputtered from the target with these low energies are selected with a simple cylindrical mirror analyzer placed in front of the QMS. Single monolayers are easily analyzed using a beam density of 10−7 A/cm2; bulk profile analysis is performed while sputtering with higher beam densities. Signal-to-background ratios in excess of 106 are acheved. Positive SIMS of clean and cesiated GaAs single crystals have been obtained and are discussed. A composition versus depth profile of a GaAs–AlxGa1−x As sandwich structure is also presented.
A Simple Automatic Conductance Bridge for Measuring the Rates of Chemical Reactions in Solution
Authors: Queen A. , Shabaga R.
Published: February 2004

An apparatus is described which automatically records the times at which the resistance of a system undergoing change becomes equal to a series of fixed resistors of known values. The apparatus consists of an ac conductance bridge coupled to a null detector which triggers a stepping switch and a digital clock. This arrangement is particularly suitable for measuring the rates of chemical reactions in solution.
A Multichannel, Variable-Threshold, Time-Sequence Recorder
Authors: McKinstry Mark L.
Published: February 2004

The analysis and design of a ten-channel, variable-threshold, time-sequence recorder that uses TTL is presented. Channel-to-channel time resolution is ∼ 250 nsec, and risetime is ∼ 6 usec, for a 2-V p-p signal. Although the recorder is designed to examine the flux-jump phenomenon in large, superconducting magnets, it has application wherever variable-threshold time-sequencing is required.
Fluxless Large-Area Solder Connection to Al
Authors: Zair E. , Greenfield A. J.
Published: February 2004

A procedure is described for making a solder connection to Al at large area interfaces. By avoiding the use of flux, defect-free joints may be achieved.
Wide Band Reversing Transformer as Automatic Backing-off Device in Nanosecond Absorption Spectrophotometry
Authors: Luthjens L. H. , Schmidt A. M.
Published: February 2004

Presented in detail are the construction and relevant properties of a high-pass wide band filter with a low frequency cutoff of several kilohertz and a high frequency cutoff of about 1 GHz to be used with 50 Ω characteristic impedance systems. The application to absorption spectrophotometry makes it possible to bring small transient signals on very high levels of analyzing light automatically on the screen of a fast oscilloscope with negligible offset at high gain settings.
Applications of IMPATT Diodes as rf Sources for Microwave EPR Spectroscopy
Authors: Hogg R. D.
Published: February 2004

IMPATT diodes are presented as an alternate rf source for EPR. Their noise-performance is shown to be comparable to klystrons while having the advantages of low cost, long life, and simple power supply requirements. The stability of the IMPATT diode is such that frequency locking is not usually necessary. Where needed, locking may be done with existing klystron lock boxes through the addition of a varactor. An IMPATT marginal oscillator with a sensitivity of about 2 × 1012 spins/G is also described. The oscillator's sensitivity is essentially independent of power and it can be used with an external detector or in the self-detection mode.
Thermal Expansion Coefficient Measurement of Diffusely Reflecting Samples by Holographic Interferometry
Authors: Heflinger Lee O. , Wuerker Ralph F. , Spetzler Hartmut
Published: February 2004

Double exposure holographic interferometry is used to measure thermal expansion coefficients of diffusely reflecting small samples of arbitrary shape. A particular arrangement is used to obtain insensitivity to rigid body motions, simplifying the support and heating of the specimen. The expansion coefficient is easily determined from the readout photograph by a simple formula.
High Stability, High Resolution Dialable Constant Current Supplies
Authors: Dye D. , Lowndes D. H.
Published: February 2004

Selected components, construction techniques, and a simple circuit are described for use in building constant current supplies which are dialable throughout the 100 μA—100 mA range, with 0.01% resolution and long term stability approaching 0.001%.
Linearity and Fatigue in Photomultipliers
Authors: Fenster A. , LeBlanc J. C. , Taylor W. B. , Johns H. E.
Published: February 2004

In this paper a tester is described which can be used to determine the linearity and fatigue in photomultipliers. Using this device, we have shown how to find the optimum arrangement of voltages to be applied to the dynodes of the photomultipliers to give linearity over the greatest possible range. When perfect linearity cannot be achieved, we have described a method which may be used to correct measured results for the lack of linearity. Detailed results are given for the 1P28 photomultiplier, but most of the ideas can similarly be applied to the other types.
Measurement of High Resistivity Semiconductors Using the van der Pauw Method
Authors: Hemenger Patrick M.
Published: February 2004

Apparatus is described that permits measurement of the electrical transport properties of semiconductors with resistance values over 1012 Ω. The system utilizes a guarded approach to the van der Pauw method which simplifies sample geometry and contacting and permits evaluation of thin layers. The equipment is easy to operate, reliable, and constructed of readily available commercially purchased components.
A Linear Accelerator for Simulated Micrometeors
Authors: Slattery J. C. , Becker D. G. , Hamermesh B. , Roy N. L.
Published: February 2004

Theory, design parameters, and construction details are presented for a linac which accelerates charged microparticles in the 1–10 μ diam range to meteoric velocities. The linac is of the Sloan-Lawrence (low-frequency, ac driven) type and contains 92 accelerating gaps with 100 kV accelerating potential applied at each gap. Particles are injected into the linac after preacceleration by a 1.6 MV modified Van de Graaff, giving a total accelerating potential of 10.8 MV for the system. In a significant departure from conventional accelerator practice, the linac is adapted to single particle operation by employing a square wave driving voltage with the frequency automatically adjusted from 12.5 to 125 kHz according to the variable velocity of each injected particle. Radial focusing is entirely second-order and is adequate to contain the particle ``beam'' within 1.8 cm diam. Compared to the Van de Graaff alone, the linac provides a particle mass increase of about 300 times for a given velocity, or a velocity increase of about 2.5 times for a given mass.
Thermal Conductivity Cell as a Pressure Gauge
Authors: Freud P. J. , Rothberg G. M.
Published: February 2004

A thermal conductivity measurement cell is utilized as a high pressure gauge for hydrostatic media. It is based upon the pressure dependence of the thermal conductivity of the media. The gauge offers electrical readout and high sensitivity compared to a typical manganin resistance cell.
New Methods for Studying Gas Solid Reaction Kinetics Using Automated Resistance Monitoring
Authors: Nordine P. C. , Rosner D. E. , Kindlmann P. J.
Published: February 2004

A new analog-to-digital method of monitoring and recording transient electrical resistance vs time data is described, together with its application to kinetic studies of gas/metal reactions at filament temperatures above 1000 K. Resistance measurements with a precision of 0.02% are recorded at up to 40/sec on paper tape to facilitate digital computer data processing. Owing to its speed and accuracy, the method is shown to permit reaction rate determinations during transient temperature operation; allowing a portion of the Arrhenius diagram to be obtained in a single experiment, and experiments through or up to phase transformation temperatures (e.g., filament melting). Illustrative results are presented and discussed for the F-atom/platinum reaction, which exhibits a reaction rate maximum at a temperature well below the Pt melting point.
A Reliable Teflon Cell with Many Electrical Leads for Pressures up to 40 Kilobars
Authors: Brouha M. , Rijnbeek A. G.
Published: February 2004

A description is given of a reliable Teflon cell with up to about ten electrical leads and a Thermocoax thermocouple for pressures up to 40 kilobars in a piston-cylinder device. The temperature can be varied from 100 to 600 K. The cell is 12 mm i.d. and 27 mm high.
Electrochemical Thinning of a Metal Disk Rotating on a Floating Self-Moulded Cathode
Authors: Bulckaen V. , Paganini L.
Published: February 2004

In this paper we discuss some improvements in a new technique and inherent apparatus for preparation of thin foils. In the present version of the special electrolyzer used there is a more convenient separation of the rotary and floating motion between the cathode and the anode, motion which previously was confined only to the anode. With the rotating anode and the floating cathode it is possible to obtain maximum ease of operation and maximum control of the surface parallelism of the specimen being thinned. The measuring of residual thickness against time is also facilitated. The possibility of regulating the balancing force of the floating motion over a wide range starting from zero gives rise to another important variable in choosing the best thinning conditions and, in particular, permits the thinning of disks of smaller diameter. The most important technical improvement concerns the employment of electrochemically moulded cathodes with profiles rigorously conjugated with a perfectly flat anodic surface.
A New Epoxy Putty for Low Temperature Applications
Authors: Trefny J. U. , Fox J. N.
Published: February 2004

A commercial epoxy putty having properties suited to low temperature applications is described. In particular, we have measured the thermal conductivity and vacuum characteristics below 4 K.
Electrode Heat Dissipation Limits on Multiaperture Ion Source Performance
Authors: Cole H. C. , Hammond D. P. , Jones E. M. , Riviere A. C. , Sheffield J.
Published: February 2004

The dissipation of heat in the electrodes of multiaperture ion sources is a major factor in limiting the power output and beam pulse duration. The results of a series of tests on multiaperture and single aperture arrays are used as the basis for the derivation of formulas which define the limits of the practical operating regime for a single edge cooled electrode element.
Semiautomated Data-Recording and Control System for an Electron Energy Analyzer
Authors: Powell C. J.
Published: February 2004

A description is given of a digital data-recording and control system that has been used with a high resolution low energy electron scattering apparatus for the measurement of characteristic electron energy-loss spectra and Auger-electron spectra of solids (at room and elevated temperatures) and liquids. This system is based on a multichannel analyzer and has the following features: (a) Specimens can be prepared many times with data accumulated in arbitrarily short times after preparation (prior to specimen contamination), and final spectra of high precision can be obtained by summation of individual runs; (b) the voltage sweep applied to the electron energy analyzer can be calibrated dynamically; and (c) data can be accumulated and the target heated by electron bombardment in a cyclic manner with variable accumulation and heating periods. Characteristic loss spectra of tungsten at 800 °C and of liquid aluminum are presented as examples of operation of the system.
Low-Level Average Power Measurements: Noise Figure Improvements Through Parallel or Series Connection of Noisy Amplifiers
Authors: Poussart Denis J-M.
Published: February 2004

Four basic configurations suitable for recording low frequency noise from two-terminal devices-single voltage and single current amplifiers, dual voltage and dual current amplifiers with cross-correlation-are reviewed. Simple signal-to-noise ratio comparisons form the basis for the practical selection of the configuration which achieves the best match between the characteristics of the source (including its electrical access) and those of available amplifiers.
X-Ray Determination of Stresses in Thin Films and Substrates by Automatic Bragg Angle Control
Authors: Rozgonyi G. A. , Ciesielka T. J.
Published: February 2004

A modification of a scanning x-ray topographic camera is described which automatically plots the lattice curvature of single crystal substrates strained by thin films or surface treatments such as diffusion and ion implantation. Film and substrate stresses are calculated from the radius of curvature. The unit operates as an electromechanical feedback system which maintains the orientation of a wafer such that the diffracted x-ray intensity remains within preset limits while a finely collimated x-ray beam traverses the wafer. An x-y recorder continuously plots the changes in orientation as a function of position yielding a trace whose slope is proportional to the radius of curvature of the substrate lattice. The sensitivity of the apparatus is such that radii of curvature of 2000 m can be measured. In addition, the lateral spatial resolution is such that the local substrate lattice curvature can be determined under alternating and overlapping 2.5 mm wide stripes of metal and oxide films. It is also shown that both the curvature and uniformly exposed x-ray topographs can be obtained simultaneously even though the wafers are severely warped due to the processing steps.
A Solid-State Marginal Oscillator for Pulsed Ion Cyclotron Resonance Spectroscopy
Authors: McIver Robert T.
Published: February 2004

A pulsed marginal oscillator has been developed for use in pulsed ion cyclotron resonance experiments. The circuit performs quite well as a means of detecting gaseous ions in a magnetic field when the cyclotron frequency of the ions is equal to the resonant frequency of the oscillator. A pulsed marginal oscillator is different from previous marginal oscillator designs in that a gated amplifier is incorporated in the feedback loop for pulsing the oscillator on and off. This feature is important for delayed detection of ions which are formed as a result of chemical reactions in the gas phase. Oscillation levels from 2 to 500 mV (p-p) are obtained over a frequency range fram 50 kHz to 2 MHz.
Electrical Birefringence Apparatus for Conducting Solutions
Authors: Bernengo J. C. , Roux B. , Hanss M.
Published: February 2004

Birefringence studies on conducting solutions are not easily performed for several experimental reasons; these difficulties are discussed. An apparatus which allows Kerr effect experiments on high ionic strength solutions is described. It is built around a fast high-power switching device, which generates the electric pulse. Rectangular pulses of 30 kV can be applied to weakly conducting solutions (<10−2M NaCl). For a 0.1 M NaCl solution, the amplitude still reaches 15 kV. In any case, the 10%–90% rise and decay time is about 50 nsec. The pulse amplitude and duration are adjustable in large limits. This pulse generator can also be used to apply reversing pulses or sinusoïdal wave bursts. It is possible with this apparatus to measure the electric birefringence of urea, for instance, in high ionic strength solvents (NaCl 0.1 M).
Studies on Deflection Mapping with a Babinet Compensator
Authors: Saxena A. K. , Srivastava B. C.
Published: February 2004

Following a recent communication, deflection mapping studies have been made on a heated wire grid, the wake of a reacting drop, and a bat's wing flame. The compensator fringes have been used either as virtual inclined slits or for tracing back the deflected rays. The sensitiveness of the device has been discussed in either case and the corresponding utilities have been pointed out.
Simple Phase Adjustment for ``Difference'' Holography
Authors: Bergmann Ernest E.
Published: February 2004

A simple, readily implemented method of changing the optical phase of the reference beam is described. A thin glass microscope coverslip is obliquely introduced into the beam. Slight tilting, which can be effected in complete darkness, produces the controlled phase change.
Thermal Expansion Coefficient of KAP Crystals
Authors: Blake R. L. , Wick W. D.
Published: February 2004

We have measured the coefficient of thermal expansion of potassium acid phthalate crystals in the direction perpendicular to the cleavage planes. This is the direction applicable to x-ray diffraction with interplanar spacings of 13.3 Å. The measured value is 40.5 × 10−6 °C−1 with an estimated uncertainty of about ± 5%.
The Use of Resonance for the Dynamic Stabilization of the Rayleigh-Taylor Instability and for the Excitation of the Related Parametric Instabilities
Authors: Holitzner H. , Wolf G. H.
Published: February 2004

The dynamic stabilization of the hydrostatic Rayleigh-Taylor instability and the excitation of the related short wavelength parametric instabilities (resonances) require the application of enforced oscillations vertically to the unstable interface. The use of the resonance between the frequency of these oscillations and the appropriately chosen eigenfrequency of the over-all system allows operation in regions of the stability regime which are difficult to reach otherwise. An air cushion between the body of liquid and the vibrator which delivers the enforced oscillations can be used as the spring determining this eigenfrequency instead of the familiar mechanical elements.
The Geometrical Factor of Large Aperture Hemispherical Electrostatic Analyzers
Authors: Chase L. M.
Published: February 2004

A method for calculating the angular response, energy resolution, and geometrical factor of hemispherical electrostatic analyzers with large plate separations is presented. The method is applicable to analyzers with inside to outside plate radii ratios as small as 0.5. The effects of fringing fields near the analyzer apertures are considered in detail.
Size Spectrometry of Aerosols Using Light Scattering from the Cavity of a Gas Laser
Authors: Schehl R. , Ergun S. , Headrick A.
Published: February 2004

A gas laser cavity beam is used as monochromatic radiation source for detecting and sizing aerosol particles. The aerosol is forced through the cavity of a (1/2) mW open cavity He–Ne laser having one plane mirror and one spherical mirror. Light scattered from individual particles is collected by a hemispherical mirror and is focused onto a detector. The system has good resolution and sensitivity and has the capability of measuring high aerosol concentrations without dilution.
Ohmic Contacts to Photoconducting CdS Single Crystal Samples Using Pure Indium
Authors: Zold T.
Published: February 2004

We have prepared ohmic contacts to photoconducting CdS samples by either soldering or diffusing high purity indium into the samples. The electric field distribution was measured along the samples with an electric field measuring equipment of 40 μ resolution. From these measurements we found that spikes or contact fields appear at the ends of the sample when the contacts were made by soldering indium to the sample. These contact fields can be large enough to nucleate high electric field domains at the contacts which strongly influence the development of the electric field in the rest of the sample. Such contact fields were absent when high purity indium was diffused into the sample for times longer than 30 min, at 600 °C in He atmosphere. On the other hand, for diffusion times shorter than 30 min, same as in the case of the soldered indium contacts, contact fields were observed at the ends of the sample. Furthermore, for diffusion times longer than 30 min, the electric field distribution indicated the existence of heavily doped layers at the ends of the sample; the thickness of these layers being typically of the order of 100 μ. These layers changed distinctly with time since after three months the thickness of these layers has been reduced by about 50 μ. The reduction of the thickness of these layers is probably caused by the recapture of some of the electrons by the donors, since atomic diffusion in solids at room temperatures is known to be extremely slow.
The Slip Correction in Accurate Viscometry
Authors: Dawe R. A.
Published: February 2004

The slip correction in capillary viscometers can cause significant errors. Some of the factors which affect slip are described and suggestions are made so that inaccuracies may be avoided in future accurate viscosity determinations.
Minimization of Fringing Field Effects in the Parallel Plate Electrostatic Spectrograph
Authors: Proca Georges A. , Rüdinger Christian
Published: February 2004

The effects of fringing fields at the entrance and exit windows of the parallel plate electrostatic particle analyzer on the trajectory of particles is studied taking into account the finite thickness of the condenser plate bearing the windows. The influence of the physical dimensions of the spectrograph on the field variation is assessed together with that of a grounded plate parallel to the condenser and located in the entrance-exit region. A set of inequalities expressed in terms of the physical dimensions of the instrument is deduced to define a reference model spectrograph of known characteristics and minimal electric field distortion with the help of which any actual instrument may be studied using the electrostatic scaling laws.
Cavity Type Permanent Magnet Suspension
Authors: Fremerey J. K.
Published: February 2004

A new type of permanent magnet bearing with short axial gaps and intrinsic radial stability for ferromagnetic suspension of small and heavy rotors at almost negligible power is presented.
X-Ray Filtering to Improve Signal-to-Noise in Soft X-Ray Appearance Potential Spectroscopy
Authors: Baun W. L. , Chamberlain M. B. , Solomon J. S.
Published: February 2004

A method is described which improves the signal-to-noise ratio in soft x-ray appearance potential spectroscopy (SXAPS). The incoming photon beam is filtered ahead of the detector by means of thin metallic foils or organic films, resulting in reduction of very low energy photons which produce unwanted noise in the detector. A specific example is given of the use of a 6.3 μ aluminum foil filter in the study of samarium M spectra.
A phase-coherent, extended-frequency-range, high-power rf transmitter system for pulsed nuclear magnetic resonance
Authors: Narath A. , Barham D. C.
Published: February 2004

A high-power transmitter for pulsed nuclear magnetic resonance experiments in the frequency range 2–200 MHz is described. Frequencies below 40 MHz are provided by a multistage, 15 kW (peak rms power), variable-tuned, rf amplifier; the power output can be increased to 100 kW by means of a single-stage booster. Frequencies between 40 and 200 MHz are provided by a three-stage 20 kW frequency multiplier which can be tuned to either triple or quintuple the output of the low-frequency amplifier. Extension of the high-power multiplication scheme to higher frequencies is discussed. Finally, a versatile spectrometer system is described which illustrates the practical utilization of the transmitter.
Protein coated electrodes
Authors: Uzgiris E. E. , Kaplan J. H.
Published: February 2004

We describe a simple method for coating platinized Pt electrodes with bovine serum albumin. The coating does not alter the electrical properties of the electrodes in dilute salt solutions, seems to be durable enough for extended use, and, most importantly, prevents a specific type of surface reaction from occurring between the Pt surface and a sucrose buffer. These electrodes are then used for studies of cellular electrokinetic phenomena by the technique of laser Doppler spectroscopy.
A large, inexpensive, reliable rotary vacuum seal
Authors: Anderson Roger W.
Published: February 2004

A 57 cm i. d. rotating seal utilizing conventional ethylene propylene O-rings and rollers as a thrust bearing is described. The seal is hand rotatable and shows no pressure bursts at 3 × 10−7 Torr.
An integral square cell-flat cell system for an ion cyclotron resonance spectrometer
Authors: Dymerski Paul P. , Dunbar Robert C.
Published: February 2004

The ion cyclotron resonance spectrometer square cell and flat cell configurations have been redesigned into an integral system. This new square cell with flat cell insert increases operating efficiency by greatly reducing change-over time.
Inexpensive cryogenic reservoirs
Authors: Kaufmann Kenneth J. , Bullitt Marion K.
Published: February 2004

A simple inexpensive method for manufacturing a cryogenic reservoir is presented.
Use of a microchannel plate for ion beam tuning of analytical mass spectrometers
Authors: Aberth William H. , Sperry Russell R.
Published: February 2004

The application of a microchannel plate image intensifier to ion beam monitoring is described.
Miniature shielded cable for use in low temperature experiments
Authors: Rutledge J. E. , Washburn T. E. , Mochel J. M.
Published: February 2004

Miniature shielded cables for use in cryostats can be built by running Teflon-insulated niobium wires through 0.397 mm o.d. cupronickel tubes. The cables are designed to minimize their thermal conduction and are flexible and solderable.
Thickness measurements of films on transparent substrates by photoelectric detection of interference fringes
Authors: Pierce R. D. , Venard W. B.
Published: February 2004

Apparatus for epitaxial film thickness measurement by photoelectric detection of interference fringes is described. The apparatus features high speed, immunity to noise from ambient light and the ability to distinguish between films grown on opposite sides of a transparent substrate, and is implemented with a minimum of components.
A modified ionization gauge for measurement of relatively high pressures
Authors: Suchannek Rudolf G. , Sheridan J. Roger
Published: February 2004

Distortions of pressure measurements with a Bayard-Alpert gauge in the range 10−4−10−3 Torr were investigated, and changes in gauge sensitivity were found to be correlated with the observation of different electric charges on the glass envelope. A modified Bayard-Alpert gauge was designed. The gauge incorporated a screen grid between the gauge elements and the glass envelope. The screen grid was connected to the gauge filament and was intended to reduce the impact energy of electrons on the glass surface and the interaction of electric charges on the envelope with charged particles in the gauge. Four modified gauges were built and tested, and the comparison of the gauges with a McLeod gauge showed that the ion-collector current was a linear function of gas pressure over the range from 5 × 10−5 to 7.2 × 10−4 Torr. For further improvements, a beam type ionization gauge is proposed.
Precision micropositioning using acoustic surface wave variable delay lines
Authors: Baker J. P. , Epstein M. , van den Heuvel A. P.
Published: February 2004

Phase comparison in an acoustic surface wave variable delay line is utilized to indicate precise micropositioning over distances of several centimeters. A special phase-locked loop design provides thermal compensation to render a device capable of repeatable measurements with accuracies of better than 0.5 μ.
A sun glint heliostat for atmospheric spectroscopy
Authors: Green A. E. S. , Sutherland R. A. , Ganguli G.
Published: February 2004

A simple arrangement based upon sun glint, the brilliant image of the sun behind a convex reflecting surface, is used to produce a nearly stationary image of the sun. Using a telescope mirror, this image is directed into a spectrometer and is spectrally analyzed for the purpose of remote sensing of trace species in our atmosphere. Typical data using a reflecting sphere are reported and discussed qualitatively in relation to the atmospheric absorbers between the sun and detector. The over-all uses of the system are described, and some cautions concerning its limitations are discussed. Alternate geometries and possible variations of the system are described.
Frequency shifts of Zeeman transitions in a Teflon-coated storage bulb
Authors: Larson D. J.
Published: February 2004

Frequency shifts of Zeeman lines have been observed in a Teflon-coated storage bulb. The data suggests that the origin is a contamination dependent wall interaction. A simple model of unpaired electrons on the surface of the wall provides a possible explanation if the relaxation times for such wall spin sites is long enough.
Laser doppler spectrometer for study of electrokinetic phenomena
Authors: Uzgiris E. E.
Published: February 2004

The laser Doppler spectrometer consists of a laser source, a scattering cell, a photomultiplier, a spectrum analyzer, and electrodes for applying an electric field. In a suitably applied field, bioparticles or macromolecules in the scattering cell will be forced to move along the electric field lines with a velocity given by the product of the electrophoretic mobility and the field amplitude. This induced motion causes a Doppler shift of the scattered laser light which is detected and measured by the spectrometer. Both the electrophoretic mobility and the diffusion constant can be measured simultaneously by measuring the scattered light spectrum in this way. Several procedures are used to obtain high resolution Doppler spectra. Convective instabilities due to Joule heating are minimized by use of rectangular electrodes with a very narrow gap (200 μ to 1 mm). Gas bubbling is minimized by a platinization of the Pt electrodes and by use of a square wave electric field. Examples of high resolution Doppler spectra from suspensions of polystyrene spheres are given and the various resolution limiting factors are described.
An improved ultrasonic nebulizer system for the generation of high density aerosol dispersions
Authors: Denton M. B. , Swartz D. B.
Published: February 2004

An ultrasonic nebulizer system capable of converting solution into an aerosol of various controlled droplet sizes with conversion rates in excess of 1 ml/min is described. This design allows generation of various sizes of droplets through overtone operation and simplified transducer substitution. The described irradiation cell is constructed from glass and fluorocarbon materials providing a high degree of chemical inertness.
A flow reactor for use with an unmodified high resolution NMR spectrometer. Application to CIDNP
Authors: Lawler R. G. , Halfon M.
Published: February 2004

A continuous flow system for use with an unmodified Varian A-69A NMR spectrometer is described. Normal sample spinning is preserved, and high resolution is maintained. The transfer time of the sample stream between a reaction cell placed in a variable external magnet and the spectrometer may be made as short as 1 sec. The apparatus has been used to obtain chemically induced dynamic nuclear polarization (CIDNP) spectra during the photolysis of di-t-butyl ketone in low magnetic fields.
A digital tracer scanner for studies of longitudinal self-diffusion in thin films
Authors: Tai K. L. , Ohring M.
Published: February 2004

A digital tracer scanner, which was constructed to measure the distribution of radio tracers along the surface of thin films in a nondestructive manner, is described. The radiation is measured through a stationary slit as the tracer source is scanned back and forth utilizing a stepping motor; simultaneously, the sweep of a multichannel analyzer operating in the multiscaling mode is synchronized to this motion, such that a given channel corresponds exactly to a given position on the film (to better than 3 μ after many days of scanning). The tracer distribution can then be viewed on an oscilloscope or read out on a teletypewriter. An analysis is presented indicating the distortion of a profile when observed through a slit of finite width, and a method of unfolding the value of the diffusion coefficient, D, from the measured tracer distribution is given. During a typical measurement on a polycrystalline Au film, the value of D was determined to be 3.14±0.3 × 10−11 cm2/sec at 500 °C and the ultimate resolution attainable for a 50 μ slit and a 40 h anneal corresponds to ∼ 6 × 10−12 cm2/sec.
A broadband NMR spectrometer for field stabilization in the range 4–23 kG
Authors: Hawk Roger M. , Sharp Robert R. , Tolan John W.
Published: February 2004

A broadband ``time-shared'' NMR spectrometer has been constructed for the purpose of magnetic field stabilization. An error signal for field correction is derived from the 7Li or 1H resonance of a saturated LiCl solution in formamide. The unit has been tested only under low resolution conditions using a 24 cm magnet, but operates well in pulsed and wide-line experiments at fields in the range 4–21 kG. Integrated circuitry is used throughout, and the design is relatively simple and inexpensive to construct.