bluuebunny/crossref_metadata_2025 huggingface dataset:
A Lecher Wire Microwave Interferometer for Measurements of Electron Density and Electron Temperature in a Flowing Transient Plasma
Authors: Cheung A. Y. , Koopman David W.
Published: February 2004

A microwave diagnostic system for measurement of electron density and temperature in a transient plasma flow, generated by a laser pulse focused on a solid target, has been constructed using a twin conductor (Lecher wire) probing element coupled to X-band waveguide components by tapered parallel planes. The analysis of the operation of the probing section has required the solution of a symmetric seven layer dielectric problem, which models the transmission, reflection, and attenuation of the microwave signal by plasma located around Lecher wires. Simultaneous measurements of the phase and amplitude of the transmitted signal, together with an experimental configuration which accurately defines the interaction of the plasma with the Lecher wire section, have made possible the reliable determination of plasma properties with a spatial resolution of ∼0.5 cm and a temporal resolution of ∼5×10−8 sec.
A New Technique to Photograph Small Particles in Motion
Authors: Temkin S. , Reichman J. M.
Published: February 2004

A new method to photograph small particles in motion is presented and shown to be feasible. The method combines the advantages of the two methods presently in use. It provides several consecutive photographs of a particle on a single negative, so that particle trajectories are easily obtained and analyzed. Further, the method uses backlight illumination, so that the shape of the particle is recorded on each exposure. The technique requires no special equipment other than that commonly used to photograph small particles. However, the method requires better synchronization than other methods, and cannot be used for all particle sizes. In the case of liquid droplets falling in air, the method is suitable for droplets 100 μ in diameter or larger. The feasibility of the method is demonstrated by recording the trajectories of a droplet falling with and without the effects of a horizontal electric field.
An Apparatus for Electron Energy Analysis in Glow Discharge Plasmas
Authors: Neiswender D. D. , Kohout F. C.
Published: February 2004

An apparatus has been designed and built for the analysis of electron energies in low temperature glow discharge plasmas. The technique involves sampling the plasma via a molecular leak and energy analyzing the electrons by a retarding potential field. Integral retarding potential curves can be plotted directly on an X-Y recorder, or the integral signal can be differentiated electronically to yield a curve which is proportional to the electron energy distribution. The characteristics of the apparatus, including its resolving power, are discussed, and some preliminary results are described.
Printed Circuit Board Evaluation by Holographic Interferometry
Authors: Lo D. S.
Published: February 2004

Application of real time holographic interferometry for the examination of a printed circuit board is described. The procedures and the resulting holographic interferograms of two specific studies are presented: (1) The heat conduction of a spacer used for mounting transistors on a heat sink, and (2) the detection of inner layer short circuits on a multilayer printed circuit board.
A Portable Self-Contained Gas Chromatograph
Authors: Stevens M. R. , Giffin C. E. , Shoemake G. R. , Simmonds P. G.
Published: February 2004

The design and fabrication of a completely portable, self-contained gas chromatograph is described. This instrument utilizes a closed-loop hydrogen carrier gas flow as maintained by a hydrogen generator-separator. It employs an auxiliary hydrogen generator to keep a positive flow of hydrogen through the detector. The detector is an ionization cross section detector. The only maintenance required is the addition of water (5–15 cc/day) to the auxiliary hydrogen generator. Lower limit of detection for the present system is of the order of 1–10 ppm ethane.
Versatile Wide Range Electron Current Regulator
Authors: Chapman R.
Published: February 2004

An electron current regulator that may be applied to almost any electron tube is described. Stability is defined as over-all system performance over a set time period, rather than line or load regulation. Under typical laboratory conditions system stability was maintained at 0.005% of 8 mA, over a 3½ h period.
A Reliable Heat Sink for Low Temperature Applications
Authors: Schlosser W. F. , Munnings R. H.
Published: February 2004

The thermal conductance of metallized ceramic heat sinks obtained from ``off-the-shelf'' electronic components at 4.2 and 77.3 K is reported. These metallized ceramics are good low temperature heat sinks, rugged and repeatedly soft-solderable, with a low electrical capacitance and very high electrical resistivity.
Superconducting Transition of a Silver Solder Alloy at Very Low Temperatures
Authors: Landau Judah , Rosenbaum Ralph
Published: February 2004

The superconducting transition of a silver solder alloy has been detected at 64.4 mK. This will make the alloy unsuitable as a medium for thermal contact at ultralow temperatures and may interfere with magnetic thermometry.
IR Laser Radiation Eye Protector
Authors: Spencer Donald J. , Bixler Henry A.
Published: February 2004

Eye protection equipment has been developed that makes possible safe, unobstructed viewing in environments of potential eye damage due to ir laser radiation. The viewing window consists of a 3 mm water sheet contained within Lucite panes. The water absorbs virtually all the radiation at all wavelengths in the ir>1.9 μ. A 3μ laser beam from a continuous HF laser at a power level of 15 W and a heat flux of 400 W/cm2 for 20 sec produced a depression in the beamward Lucite window pane but did not penetrate to the water.
High Intensity Proton Source with Low Energy Spread
Authors: Layton J. K. , Magnuson G. D.
Published: February 2004

A high intensity proton source with a low energy spread is described. The source produces beams of about 60% protons with an energy spread of 0.4 eV or less.
A Combined Magnetic Circular Dichroism and Electron Paramagnetic Resonance Spectrometer
Authors: Izen E. H. , Modine F. A.
Published: February 2004

A combined magnetic circular dichroism and electron paramagnetic resonance spectrometer is described. This two-channel spectrometer enables the detection of an optical microwave double resonance, which gives a direct correlation of optical and paramagnetic resonance spectra.
Rocket-Borne Instrumentation to Measure Ionospheric Electron Temperature with Good Spatial Resolution
Authors: Wrenn G. L. , Blades J.
Published: February 2004

An ac Langmuir probe technique has been developed in order to make measurements of electron temperature in the lower ionosphere with good temporal and spatial resolution. The requirement to counter changes in rocket potential led to the incorporation of a servo system on the collector bias voltage and a novel method of sweeping this bias to analyze the electron retardation current characteristic. Sweep rates of 45 Np/sec have proved feasible and almost continuous monitoring of electron temperature appears possible. The provision of a real plasma reference should also be valuable for other ionospheric instruments, e.g., ion mass spectrometers, low energy particle detectors, and electric field sensors.
A Compact Low Cost Collective Effect Linac
Authors: Heese Norbert R. , Raudorf W. R.
Published: February 2004

An inexpensive linear accelerator for electrons was built and is now in operation. The acceleration is accomplished by an electrodynamical space-charge effect in a cylindrical electron beam. The 2.5 m long instrument, operated with a 20 keV, 350 mA beam, produces electrons of energies up to 14 MeV. Design and operational characteristics are presented along with the results of performance tests.
A Position Sensitive Proportional Detector for X-Ray Crystallography
Authors: Gabriel A. , Dupont Y.
Published: February 2004

A position sensitive proportional detector applied to x-ray low angle scattering is described with emphasis on its performance in the biological field, where the time element is of great importance. Spatial resolutions of 160 μ have been obtained for counting rates up to 3×105 counts per second. Owing to this performance and to a quantum efficiency that can reach 100%, this detector can replace with advantage the x-ray film used so far for a great number of experiments.
Integrating Debye-Scherrer and Guinier-de Wolff Powder Diffraction Cameras
Authors: Heyding R. D. , Brown R. J. C.
Published: February 2004

Attachments for commercial Debye-Scherrer and Guinier-de Wolff cameras have been designed and constructed which permit integration of powder diffraction lines during exposure.
A Slope Reversal Video Processor Having Amplitude and Pulse Width Discrimination
Authors: Hoge F. E. , Nelson B. E. , Hines D. E.
Published: February 2004

A timing discriminator whose output is relatively insensitive to input pulse width and amplitude is described. The video-handling technique is known as slope reversal processing and is based on tapped delay line estimation methods. The concept, design, breadboard construction, and preliminary laboratory test results are reviewed. The processor system features (a) a peak input voltage dynamic range of 80× starting at 100 μV; (b) a four stage preamplifier/line-driver having a voltage gain of 2400×; (c) a tapped delay-line estimator implemented for slope reversal triggering by differential comparison; (d) a nominal ±2.5 nsec shift of the output trigger leading edge over the entire input voltage range, (e) up to 7 dB discrimination against pulse widths less than 35 nsec; and (f) up to one order of magnitude reduction in the false alarm rate compared to a constant fraction system. Deviations in specific portions of the ``walk'' curve are attributed to differential comparator response and preamplifier saturation effects. Design criteria, circuit schematics, and construction details are given. The system is intended for use with pulses having a width of 35 nsec; however, the processor is easily adapted and improved for other pulse widths. The expression for relative pulse width sensitivity is given and experimentally verified.
Automated Multiple-Specimen Holder for an X-Ray Powder Diffractometer
Authors: Walker G. A. , Goldsmith C. C.
Published: February 2004

To better take advantage of automated x-ray diffractometer systems, a multiple-specimen holder has been designed for an x-ray powder diffractometer. This holder is also automated allowing four samples to be run at a time. The sample holding and aligning procedures used are versatile, allowing a wide range of sample type and size to be accommodated. The inherent accuracy of the diffractometer is maintained and individual alignment of each specimen is permitted.
Technique for the Preparation of Ge and Si Field-Emission Cathodes
Authors: McNeil W. D. , Shepherd W. B.
Published: February 2004

Methods are described for the fabrication of Ge and Si field-emission cathodes by grinding of single crystal, oriented blanks of the semiconductor followed by electrolytic etching. Highly symmetrical, well formed emitters result. A glow discharge cleaning and shaping technique is presented that leads to atomically clean, well developed surfaces in the field-emission microscope.
Crossed-Coil Nuclear Magnetic Resonance Probe for High Sensitivity Low Temperature Measurements
Authors: Drain L. E.
Published: February 2004

A crossed-coil probe suitable for nuclear magnetic measurements at low temperatures is described. The probe may be used with commercial continuous wave spectrometers and enables improved sensitivity to be obtained, particularly at liquid helium temperatures. The electrical balance of the probe is controlled by an external circuit, and because the probe is compact and contains no moving parts, it may be cooled conveniently. Thermal insulation of the sample from the probe is, therefore, unnecessary and high filling factors may be obtained. High performance Dewar vessels may be used giving economy of refrigerant, freedom from microphonic interference, and the possibility of long uninterrupted runs at liquid helium temperatures. Factors that influence the design and performance of probes of this type are discussed.
An ENDOR Spectrometer Using a Slow Wave Resonance System
Authors: Schmalbein Dieter , Witte Alexander , Röder Rainer , Laukien Günter
Published: February 2004

An ENDOR spectrometer is described that uses a microwave helix instead of a resonant cavity. With this arrangement, the sample can be irradiated simultaneously with large rf fields (15 G; 10–40 MHz) using a low power rf amplifier (10 W) and a microwave field (X band). Measurements have been performed on organic radicals at room temperature.
High Pressure ENDOR Cavity
Authors: Doyle W. T. , Dutton T. F. , Wolbarst A. B.
Published: February 2004

The apparatus employed in a room temperature examination of the effects of intense hydrostatic compression (to 11½ kilobars) upon F center hyperfine interactions is described.
A Simple Method for Making Fine Mesh Hemispherical Grids
Authors: Shaw D. A. , Bennett D. A.
Published: February 2004

A simple method of cold forming fine mesh hemispherical grids is described. The grids are formed over a simple male mold, support is provided by a soft aluminium ring which is pressed into the edges of the mesh. Accurate grids can be repeatably produced by this method.
Filters with Continuously Adjustable Hole Size
Authors: Fleischer R. L. , Viertl J. R. M. , Price P. B.
Published: February 2004

A filter with adjustable hole size can be made by etching charged particle tracks in a stretchy polymer. Consequently, biological cells having only slight differences in sizes can be separated from one another.
Measurement of the Emissivity with Variation of Temperature at 35 GHz, Application to the Determination of the Dielectric Constant
Authors: Picherti F. , Easthope J. P.
Published: February 2004

The emissivity is measured at 35 GHz with a receiver provided with an very directive antenna specially made for the experiment. The permittivity of samples having various sizes may be also determined in free space.
Angular Displacement Detector
Authors: Buchalter Daniel N. , Hargreaves John H.
Published: February 2004

This Note describes a detector for small angular deflections (0.1 μrad resolution). It uses a modulated infrared beam focused on a mirror whose angular deflection is to be measured. The beam is then reflected onto two photo-transistors. The difference of the output voltages from these transistors is a measure of the angular displacement.
A Multiple-Crystal Holder for Ultrasonic Measurement
Authors: Chen Y. C. , Martinson R. H. , Ruoff Arthur L.
Published: February 2004

A multiple-crystal holder for simultaneous ultrasonic measurement on several crystals is presented. Figures are included to show clearly how it is assembled and how each component works.
A High Frequency Heterodyne Lock-In Amplifier
Authors: Miller John R. , Pierce John M.
Published: February 2004

A two-phase (quadrature) lock-in amplifier system is described in which the rf signal is heterodyned down to audio frequency to allow all phase splitting, control, and detection as well as amplitude detection to be done in a commercial af lock-in. At 60 MHz, the system exhibits a 2 dB noise figure. Phase drifts and quadrature accuracy are held to 0.1° for ∼1 h in a laboratory environment. Design considerations are discussed in some detail.
Resolution of the Ambiguity of Measurement between Rotation and Ellipticity in the Microwave Polarimetry of Nonstationary Plasmas
Authors: Sardos R.
Published: February 2004

Given the growing importance of careful and precise measurements with microwaves in the study and analysis of plasmas (Faraday effect, Cotton-Mouton-Voigt effect, etc.) the author proposes the use of an interference polarimeter-ellipsometer of great sensitivity capable of recording at the same time both rotation and ellipticity. This instrument may also be used as a reflector-polarimeter (in the study of Kerr effects).
A Field Mill for Tethered Balloons
Authors: Gathman Stuart G.
Published: February 2004

An instrument is described for obtaining time averages of the resultant of the vertical and one horizontal component of electric field in the lower atmosphere. This instrument is designed to be suspended from a tethered balloon and to telemeter the desired data to an operator by means of an audio pulse width modulation technique which requires the operator to be equipped only with a hand-held AM receiver and a stopwatch. The net self-charge on the field mill is maintained at or near zero by means of a 210Po alpha source. If we assume that the horizontal component of the electric field is small compared with the vertical, the field mill system can be used to observe the average vertical atmospheric electric field profile produced by the electrode effect near the ocean surface.
A Versatile 60 kV Switching System for Pulsed Excitation of Lasers
Authors: Lidholt L. R.
Published: February 2004

A fast switching high voltage system capable of handling 60 kV is described. The system utilizes a sealed-off pressurized hydrogen spark gap as a switching device. A versatile silicone rubber coupling module makes different high voltage components easily interchangeable without the need of draining off any insulation liquid. The system was used to build a laser, which emits radiation pulses of a few nanoseconds duration at a wavelength ranging from 337 nm in the ultraviolet region of the spectrum to 9.0 μ in the infrared. The uv pulses contain enough energy to permit pumping of a tunable rhodamine 6 G dye laser.
Thruster Characterization Using a Thrust Balance
Authors: Bailey Adrian G.
Published: February 2004

A procedure is described which enables thrusters to be characterized in a continuous manner in a relatively short time. The method should be particularly suitable for electric thrusters with variable thrust.
A Simplified Graphical Evaluation of High-Frequency and Quasistatic Capacitance-Voltage Curves
Authors: Wagner Sigurd , Berglund C. N.
Published: February 2004

High-frequency and quasistatic capacitance-voltage curves of metal silicon-dioxide silicon capacitors can be evaluated quickly by the use of only two graphs to give doping density, flat band voltage, and density of interface states at selected points in the band gap.
Beam Current and Position Monitor for the Astron Accelerator
Authors: Fessenden T. J. , Stallard B. W. , Berg G. G.
Published: February 2004

A beam current and position monitoring system very similar to one developed for the Berkeley ERA accelerator has been developed for use on the Astron accelerator. Beam current measurements are accurate to less than 2%. At beam currents above 500 A beam displacements less than 1 mm off-axis can be observed. The beam current and position at any two of 30 locations in the accelerator and transport section can be simultaneously monitored on either of two oscillograph systems. The current sensors do not interfere with the beam propagation and are outside the vacuum system for easy maintenance and calibration.
Instrumentation for In Situ Electron Microscope Studies of Sputtered Thin Film Growth
Authors: Sherman Dudley M. , Hutchinson Thos. E.
Published: February 2004

An assembly has been constructed for the investigation of the nucleation and growth of ion beam-sputtered thin films inside the transmission electron microscope. A commercial microscope has been modified to allow a dynamic investigation of the formation of films on electron-transparent substrates. The resolution of the microscope is not significantly impaired by the apparatus; the resolution during deposition is generally 15–25 Å. To date silver, gold, niobium, and silicon have been successfully deposited.
A Programmable Digital Pulser for NMR
Authors: Lind A. C.
Published: February 2004

A programmable digital pulser for pulsed NMR applications employing inexpensive integrated circuits is described. This pulser employs two types of modules, one master clock and several counters. The required pulse sequence determines the number of counters to be front-panel interconnected. The master clock module simultaneously provides crystal-controlled clock pulses with periods from 10−7 to 1 sec in decade steps. These pulses are used by the counter modules to generate either time delays or pulses with a maximum resolution of five digits.
A Method for Performing High Precision Lattice Parameter Change Measurements on Quenched Aluminum
Authors: Eubig C. , Tomizuka C. T.
Published: February 2004

Experimental techniques to measure x-ray lattice parameter changes to 1 ppm in quenched aluminum single crystal foils are described. Included in the description is a cryostat designed to allow the mounting of a sample cooled to liquid nitrogen temperature after quenching. X-ray diffraction measurements are performed on the sample at liquid nitrogen temperature. In between successive measurements, the sample is annealed at temperatures up to 260°C. The measurement of simultaneous lattice parameter and Bragg line shape changes is shown to be possible for quenched samples.
Frequency Sweep Adiabatic Fast Passage on the Varian HA-100
Authors: Chien Mingjien , Samulski E. T. , Wade Chas. G.
Published: February 2004

A modification of the Varian HA-100 NMR spectrometer to permit frequency sweep adiabatic fast passage measurements of T1 is described. The spectrometer can be operated in the lock mode making signal averaging possible.
A Technique for Reactant Introduction in Measurement of Rapid Reaction Rates
Authors: Nordlander J. Eric , Gruetzmacher Robert R. , Stuehr John E.
Published: February 2004

A simple technique is reported for rapid introduction of solid or liquid reactants into solution for continuous observation of ensuing reactions during ≥1 sec. The accuracy of the method is attested by congruent temperature dependence of the derived rate constants together with those from an independent procedure. The new technique allows measurement of solvolysis reactions considerably faster than those heretofore accessible.
A Simple Camera Attachment for a Vacuum Ultraviolet Monochromator
Authors: Clough G. A. , Koehler H. A.
Published: February 2004

An inexpensive camera attachment for a vacuum uv monochromator is described.
Thickness Measurements of Nematic Liquid Crystal Layers
Authors: Kashnow R. A.
Published: February 2004

The thickness of homeotropic nematic liquid crystal layers, as used in electro-optic display devices, can be conveniently determined by relative intensity measurements in polarized light. An expression is given for the thickness as a function of the incident angle at which the first intensity minimum occurs. The expression is evaluated numerically for MBBA.
Measurement of 60 Hz Voltages Using the Kerr Effect
Authors: Hebner Robert E. , Cassidy Esther Christmas
Published: February 2004

The Kerr effect has been used to measure 60 Hz alternating voltage up to 30 kV peak. The system behaves much as it does under the influence of a short high-voltage pulse except that in this case the frequency of the applied voltage is sufficiently low that the space charge effects in the liquid are not negligible.
A Mechanical Thermal Switch for Using a Cryostat between 4 and 650 K
Authors: Bluzer N. , Bahl S. K.
Published: February 2004

Design of a mechanical thermal switch used in a low temperature cryostat is described. In the thermal switch on position, the sample can be cooled to 4 K. In the thermal switch off position, the sample can be maintained at any temperature in the range from 4 to 650 K with cryogenic liquid (liquid helium at low temperatures and liquid nitrogen at higher temperatures) in the cryostat.
Variable Temperature (1.6–300 K) X-Band EPR System with a Variable Cavity Coupler
Authors: MacKinnon J. A.
Published: February 2004

A variable temperature (1.6–300 K) electron paramagnetic resonance (EPR) X-band spectrometer is described. The spectrometer is a Varian V-4502 EPR spectrometer using a V-4500–42 X-band microwave bridge and a V-K3525 superheterodyne accessory. The Dewar system is an Andonian Associates Cryostat with a 4.43 cm i.d. sample area. The sample cavity resonates in the TE102 rectangular mode. The coupling of the cavity can be adjusted from outside the helium Dewar.
Removal of a Glowing Spot from an Image Tube Using Laser Radiation
Authors: Gurski T. R.
Published: February 2004

The use of a ruby laser to remove a glowing spot from a Kron electronograph image tube is described. The intense laser radiation eliminated the glowing spot and did not damage the image tube.
Thermometer Clamps for Low Temperature Thermal Conductivity
Authors: Giedd Ronald E.
Published: February 2004

A thermometer clamping method for use in thermal conductivity apparatus is discussed. Copper alligator clips are employed on both soft and brittle samples to avoid sample damage and still achieve good thermal contact.
Reliable Starting Technique for an Ion Laser Tube with Internal Gas Return Bores
Authors: Wexler Bernard L.
Published: February 2004

A technique for reproducibly starting an arc discharge down either the larger or smaller of two bore sizes in a BeO laser tube is given. The V-I curves of the two discharge paths are plotted and an explanation of the starting characteristics of the tube using a simple load line analysis is given.
The Design of Optimum Heat Exchangers for Dilution Refrigerators
Authors: Siegwarth J. D. , Radebaugh Ray
Published: February 2004

The behavior of discrete heat exchangers as a function of temperature, heat transfer area, and 3He flow rate is shown for a general case by means of some machine calculated curves. From these curves, the appropriate heat exchanger size can be determined for the various steps of a discrete heat exchanger. Also, curves for the mixing chamber temperature Tm as a function of total surface area divided by flow rate for various amounts of external heat to the mixer are shown for the continuous exchanger. From these curves the optimum 3He flow rate for a given heat input and exchanger size can be determined. Viscous heating has been included in the calculation of one typical coaxial tube exchanger. It is found that heating in the dilute stream has negligible effect on Tm, whereas the viscous heating in the concentrated side, though several times smaller than that in the dilute side, has considerably more effect on Tm. Based on this behavior, an improved method of ``heat sinking'' heat leak paths to the mixer is suggested.
Heat Capacity Measurements on Small Samples at Low Temperatures
Authors: Bachmann R. , DiSalvo F. J. , Geballe T. H. , Greene R. L. , Howard R. E. , King C. N. , Kirsch H. C. , Lee K. N. , Schwall R. E. , Thomas H.-U. , Zubeck R. B.
Published: February 2004

We describe a new calorimeter for measuring heat capacity in the range 1–35 K, using a silicon chip bolometer as sample holder, temperature sensor, and sample heater. The apparatus is capable of measuring very small samples (1–500 mg), and may be used with a number of different experimental methods.
System for Data Acquisition from High Voltage Terminals
Authors: York George W. , Park John T. , Miskinis James J. , Crandall David H. , Pol Victor
Published: February 2004

An inexpensive data acquisition system has been designed to provide high voltage isolation for data acquisition in analog, digital, and pulse modes. The telemetry system uses GaAs light sources, fiber optics, and phototransistors to accomplish the data transmission. Prewired logic boards have been adapted to accomplish the timing and logic functions. Seven decades of digital data are transmitted error free, pulse data can be transmitted at rates up to 1 MHz, and analog data are transmitted with 0.05% full scale accuracy.
A Closed Wet Cell for the Electron Microscope
Authors: Fullam Ernest F.
Published: February 2004

Based on early experiments, a simple closed wet cell has been designed to retain volatile material in the vacuum of the transmission electron microscope. A description is given of the procedure for making the triple film windows for retaining liquid in the cell yet permitting good electron beam penetration and the clamping arrangement of the windows to seal the edge. The assembly and use of the cell are described. Electron micrographs are shown of chromium hydroxide spheres suspended in water that indicate a mechanism of formation of the spheres.
Pseudodiamagnetic Suspension
Authors: Wilk Leonard S.
Published: February 2004

A device is described that develops stable levitating forces in a magnetic field of the same vector form that a diamagnet would (thus called pseudodiamagnetic suspension) but of substantially larger magnitude. Although requiring an energy source, it can be completely self-contained. A laboratory experiment is described where stable suspension was provided at the rate of 232 kg/W. The analysis is extended to the electric field case (which is shown to be analogous and is called pseudodiadielectric suspension) and to an orthogonal set of superconducting rings. The superconducting rings can also be levitated in stable equilibrium and they do not need an energy supply.
Optical Switch for Transient Plasma Diagnostics
Authors: McIntosh R. E.
Published: February 2004

A photometric technique is described which facilitates the determination of the electron number density profile of a plasma generated by transient microwave pulses.
Study of He–Se Laser Performance
Authors: Hernqvist K. G. , Pultorak D. C.
Published: February 2004

The construction and performance of He–Se lasers are described. A comparison is made of the performance of He–Se, He–Ne, He–Cd, and He–Zn lasers.
Real Time Measurement of Induced Variation of Birefringence in Transparent Media
Authors: Micheron F. , Bismuth G.
Published: February 2004

An apparatus permitting high accuracy measurements of fast variation of birefringence in various media has been built using the following principle. A feedback loop cancels automatically the corresponding rotation of the light polarization vector by a calibrated voltage change applied to a KDP crystal. It has been used to measure the optical damage effect in electro-optic crystals such as LiNbO3.
Heating Rate Controller for Thermally Stimulated Conductivity and Thermoluminescence Measurements
Authors: Manning E. G. , Littlejohn M. A. , Hutchby J. A. , Oakley E. M.
Published: February 2004

A temperature controller is described which enables the temperature of a sample mounted on a cold finger to be varied linearly with time. Heating rates between 0.5 and 10 K/min can be achieved for temperatures between 90 and 300 K. Provision for terminating the sample heating at any temperature between these extremes is available. The temperature can be held at the terminating temperature or be reduced to the starting temperature in a matter of minutes. The controller has been used for thermally stimulated conductivity measurements and should be useful for thermoluminescence measurements as well.
Mirror Mount for Long Wavelength Lasers
Authors: Gundersen Martin , Lloyd Herbert B. , Poarch Bernard W.
Published: February 2004

A mirror mount is described which features independent rotational and translational motion and satisfies high vacuum requirements.
A Simple Continuously Weighed, Rotating Disk Reactor
Authors: Knapp Malcolm , Li Kun , Philbrook W. O.
Published: February 2004

A disk is rotated by a drive consisting of an electric motor, batteries, and variable resistor speed control. The entire drive is suspended from an analytical balance which weighs both the disk and the drive. This apparatus is used in fluid-solid kinetics to achieve uniform mass transfer to a weighed solid.
Backward Diodes as Sensitive Detectors for Microwave Spectroscopy
Authors: Christen P. , Bauder A. , Günthard Hs. H.
Published: February 2004

Signal-to-noise ratios for a backward and a point contact diode were investigated as a function of incident amplitude modulated microwave power. Measurements were made for a 30 kHz modulated carrier at 10 GHz. Comparison of the results reveals a gain of at least 10 dB in ultimate sensitivity for the backward diode over the point contact diode. In addition, the beneficial effect of an external dc bias could be substantiated.
A Tandem Isothermal Calorimetric Probe Technique for Measuring Atomic Flow Rates
Authors: Poirier Robert V. , Carr Robert W.
Published: February 2004

An isothermal calorimetric probe apparatus for measuring atom concentrations in flowing gases is described. It uses two inefficient probes, one immediately behind the other, permitting measurements of absolute atom concentrations under experimental conditions where complete removal of atoms by one efficient probe is not feasible. This arrangement also minimizes probe perturbation of the atomic concentration gradient in the apparatus. Measurements of atomic hydrogen flow rates, made in a conventional discharge-flow system, are presented.
Electrostatic Bridge Circuit for Simultaneous Measurement of Charges Captured by the Plates of an Electrostatic Precipitator
Authors: Iribarne J. V. , Klemes M.
Published: February 2004

The problem of measuring simultaneously the positive and the negative charges arriving at the two plates of an electrostatic precipitator, as well as their net difference, has been considered. An electrostatic bridge is described that can be applied to determine the net charge using one electrometer, or both charges simultaneously, using two electrometers. It is based on distributing the charges acquired by both plates of an insulated precipitator with two capacitors in opposition. An electrometer measures the unbalance produced in these capacitors, and a second electrometer may provide a simultaneous measurement on another capacitance. The bridge is particularly suitable to determine small net differences between larger positive and negative charges.
Sensitive Instrument for the Study of Circular Polarization of Luminescence
Authors: Steinberg Izchak Z. , Gafni Ari
Published: February 2004

A sensitive instrument is described for the measurement of the extent of circular polarization of light emitted by chiral molecules. In this instrument the intensity of the circularly polarized component of the luminescence light is selectively modulated by an electro-optic or photoelastic light modulator, while the unpolarized component of the luminescence is unaffected. The modulated light beam is detected by a photomultiplier and the ac component of the electric signal produced is amplified by a phase-sensitive amplifier tuned to the modulation frequency. The light used for the excitation of the sample and the luminescence light are monochromated. An accessory is described which produces controlled mixtures of unpolarized and circularly polarized light and thus permits calibration of the output of the instrument in terms of the degree of circular polarization of the light under examination. Signal to noise ratios of 20 have been readily obtained with luminescence which is circularly polarized to an extent of 10−3 to 10−4.
Electric Control of Fluid Jets and Its Application to Recording Devices
Authors: Hertz C. H. , Månsson Å.
Published: February 2004

A new method for the intensity modulation of ink jets used for recording of electrical signals is described. It uses the fact that a liquid jet ejected from a fine nozzle towards a recording paper is dispersed into a spray if an electric field is established near the nozzle. This allows the intensity modulation of the recording trace with frequencies exceeding 100 kHz. The use of this method in facsimile recording, graphic data displays, and alphanumeric printing devices is described briefly as well as results showing the capacity of the method.
A Solid Electrolyte Oxygen Gauge for Monitoring Trace Quantities of Water Vapor in Hydrogen Gas
Authors: Klinedinst K. A. , Stevenson D. A.
Published: February 2004

An oxygen gauge, capable of measuring water content in hydrogen gas as low as a few parts per billion, is described. The gauge consists of a solid state electrochemical concentration cell employing yttria doped thoria as an electrolyte. The performance of the gauge at four operating temperatures between 600 and 900°C is evaluated.
Compact Inexpensive High Resolution Retarding Field Energy Analyzer
Authors: Goto Keisuke , Ishikawa Kazuo
Published: February 2004

A compact energy analyzer which has the four-grid construction as is widely used in LEED—Auger systems was developed to analyze secondary electrons. It is about 4.0 cm diam ×3.5 cm in length, with an entrance aperture of 5.6 mm diam and an angular aperture of about 10°. To get a uniform retarding field, a pair of fringing rings were added at the edge of the first and the second grids. The first and the second grids (gold coated tungsten, 100 mesh) were shaped into a portion of a sphere. The distance between the source of secondary electrons and the first or the second grid was made somewhat longer than their radius of curvature. The energy resolution was studied by adjusting the distance between the grids, and a value of ΔE/E of about 0.09% was attained.
A Grazing Incidence Vacuum Ultraviolet Monochromator with Fixed Exit Slit
Authors: Dietrich H. , Kunz C.
Published: February 2004

A new monochromator with parallel incident light, a fixed exit aperture, and higher order rejection properties has been built and tested with the 7.5 GeV electron accelerator DESY which was used as a synchrotron light source. The parameters of the instrument are chosen to match the source characteristics at DESY. The exit beam is focused on a spot of 50×300 μ at the exit slit yielding about 107 monochromatic photons/sec at the intensity maximum (100 Å). The resolution attained is about 500 over the whole range 40–350 Å. Virtually no higher order admixing occurs in this range. The instrument can be used up to 1000 Å in a different mode of operation with less ideal performance.
Analog Simulation of a Josephson Junction
Authors: Hamilton C. A.
Published: February 2004

The paper describes an analog model which uses inexpensive integrated circuits to simulate the properties of a Josephson junction. The circuit automatically eliminates cumulative error and thus can operate in a continuous mode. The model is useful as a demonstrator and in analyzing the behavior of a Josephson junction in a complex circuit.
Picoampere Charged Particle Beam Monitor
Authors: Smathers James B. , Routt Kenneth R. , Hightower Dan
Published: February 2004

A transmission ion chamber for charged particles was designed to give a continuous indication of beam symmetry and magnitude. Consisting of four separate ion chambers, the signals from opposing chambers were compared to determine beam symmetry and summed to obtain a beam intensity signal. The system is quite simple and offers good linearity at low cost for proton beam currents in the range of 1–100 pA.
How to Keep the Temperature of a Hot Wire Constant
Authors: Ouwens C. Daey , Koken J.
Published: February 2004

A method is described of stabilizing the temperature of a heated wire under changing conditions of cooling and evaporation. It depends on controlling the resistance of the wire by the use of a power supply having a special current-voltage characteristic. The characteristic has been obtained by a slight change in a normal commercial apparatus. The great advantage of the control is its simplicity. Application of a thermocouple or optical measurement of the temperature of the heated wire is not necessary. Measurements on a tungsten wire at 1100°C showed the temperature to change less than 10°C in spite of a 800% variation in the energy input. Working at constant voltage causes the temperature to change more than 200°C by this input variation. The method can be applied to electrical furnaces, degassing of metals, electromotors, hot filament ionization of gases, etc. Variations in cooling rate require a different voltage-current characteristic of the power source than does evaporation or aging of the wire.
Radio Frequency Heating Apparatus Using a Cylindrical Cavity Resonator
Authors: Guinet P.
Published: February 2004

A new type of rf furnace is described. It has been studied to heat, to very high temperatures, materials in the intermediate resistivity range (106−10 Ω·cm) and thus to obtain fusion without contamination. The furnace is a half-wave resonator of the shielded helix type. Power is generated by a commercial HF triode directly coupled to the resonator. Calculations concerning the resonant conditions are proposed, and results obtained with a furnace 20 kW HF power are given. Hot refractory oxides are replaced by tap water for reliable measurements. Ti2O3, Al2O3, and Y2O3 melting points have been reached. However, it has not been possible to obtain the conditions required for a self-crucible type of fusion to be obtained.
Instrumentation for Measuring Bioelectrical Signals in Plants
Authors: Karlsson L.
Published: February 2004

An electronic instrumentation for the measurement of bioelectrical signals in plants is presented. The problems of common mode signal rejection and amplifier bias current are considered. With the instrumentation presented recordings have been made of bioelectrical signals generated in the India rubber tree (Ficus elastica).
Constant Stress Continuous Load Compression Creep Machine for Small Single Crystals
Authors: Coghlan W. A.
Published: February 2004

In order to learn more about the fundamental aspects of high temperature deformation, a machine was designed and built which can be used to study compression creep of small samples at constant stress and temperature. Constant stress is maintained in the deforming sample through the use of a specially curved arm which increases the applied load to compensate for the increasing cross section area. The temperature is maintained by enclosing the sample region in a tube furnace. A sample of polycrystalline aluminum is tested in the machine and the resulting creep rate and activation energy agree very well with previously published data.
A Surface Viscosimeter Based on Oscillations of Large Amplitude
Authors: Bragadin Eugenio
Published: February 2004

This paper describes a very large amplitude torsional device for measuring surface viscosity. Its main feature is the possibility of submitting the floating ring to angles of oscillation as great as 270°, thus allowing study of the same film for the entire range of the elastic and the Newtonian viscous state. The design and performance of the viscosimeter is described, and certain possibilities for future investigations are briefly outlined.
Fringing Field of Electrostatic Analyzers
Authors: Bosi G.
Published: February 2004

Several models of electrostatic mirrors are investigated; field distortions due to the entrance and exit slits are taken into account by carrying out exact solutions of the Laplace equation. The Dirichlet problems solved may be regarded as samples of a class of boundary value problems in a plane. The iterative method used throughout this paper enables contiguous solutions to be connected through a ``broken'' equipotential line. The results are presented in the form of recursion formulas allowing coefficients of a given order to be calculated as functions of lower order coefficients.
Detection of Nonuniform Thermal Gradients in Galvanothermomagnetic Measurements Using Liquid Crystals
Authors: Ziernicki R. S. , Leonard W. F.
Published: February 2004

Anomalous electrical measurements encountered during galvanothermomagnetic measurements of Hg1−xCdxTe were found to be caused by spurious temperature gradients in the sample mounting substrate. The magnitude and spatial orientation of these gradients were investigated to an accuracy of 0.25 K using cholesteric liquid crystal mixtures.
An Amplifier for Electron Multiplier Pulse Counting Applications
Authors: Smith J. B.
Published: February 2004

This paper describes an amplifier designed for use in a soft particle spectrometer on the ISIS series of scientific satellites. The amplifier design reflects the satellite constraints of low power (∼90 mW), low weight (120 g), and small size (∼10×3×2.5 cm). It uses a voltage sensitive front end which accepts multiplier pulses ranging from about 0.5 to 50 mV and produces output pulses of uniform amplitude and duration suitable for driving a counter. Dynamic limiting is used to produce a variable gain depending on the amplitude of the input pulse. This allows maximum gain for small pulses, avoids heavy saturation by large pulses, and minimizes recovery time. The amplifier has full sensitivity for input pulse rates up to 20 MHz for a uniform test signal.
A Comparison of the Funk and Idso Techniques for Measuring Hemispherical All-Wave Radiation
Authors: Idso Sherwood B.
Published: February 2004

A comparison of four Fritschen net radiometers and two Funk net radiometers converted to hemispherical operation by the procedures of Idso and Funk, respectively, was made in a large, open, bare field over a period of 17 consecutive days. Data were collected every half-hour during this period. Under both clear and cloudy conditions, the mean 24 h energy totals received by each instrument type differed by only 2.3%. The Idso technique generally gave the higher results throughout the entire 24 h period, and agreed almost exactly with the combination of measured solar and calculated clear sky atmospheric thermal radiation utilizing the Idso-Jackson formula. If the Swinbank formula had been used, however, the theoretical results would have been about 2% lower and thus closer to the Funk results. Since there is no basis for choosing between these two formulas in the air temperature range of this study, both instrument transformation techniques were concluded to be equally valid.
A Versatile Trapped Ion Cell for Ion Cyclotron Resonance Spectroscopy
Authors: McMahon T. B. , Beauchamp J. L.
Published: February 2004

Experimental methods have been developed which permit operation of the standard ICR cell in a trapped ion mode. Appropriate configurations of applied electrostatic fields permit trapping of ions in the source region of the ICR cell. Detection is effected after a suitable delay by drifting the ions from the source through the analyzer region where their power absorption is monitored with the usual marginal oscillator-detector. The minor modifications required do not inhibit normal operation of the cell, thus allowing for the full range of conventional ICR experiments with the additional capability of examining variation of ion abundance with time. The latter mode of operation greatly simplifies elucidation of reaction kinetics. The ion molecule reactions of methyl chloride have been investigated using this new technique. Accepted values of reaction rate constants are reproduced, demonstrating the accuracy of the method.