bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical method for determination of thermal conductivity of gases
Authors: Jaiswal V. K. , Pandya T. P.
Published: March 2003

An optical method, utilizing interferometry and particle track photography, for determination of thermal conductivity of gases and their non-reacting mixtures at elevated temperatures is described. Values are presented for oxygen and compared with earlier data. The accuracy of results, the sources of error, and limitations of the technique have been discussed. Its application to
Novel smoothing algorithm
Authors: Wertheim G. K.
Published: March 2003

A new interrelationship between smoothing and deconvolutions is derived. It provides an insight which leads to a one-parameter smoothing function containing the Fourier transform of the instrumental resolution functions. The parameter is determined by the signal-to-noise ratio of the data being smoothed. This approach removes some of the arbitrary aspects of data smoothing.
Inexpensive dc sputtering system for scanning electron microscopy
Authors: Bolon R. B.
Published: March 2003

A simple, easy to construct dc gold sputtering system suitable for coating nonconducting scanning electron microscope (SEM) samples is described. Gold foil is used for the target cathode and air for the ionizing gas. Components are readily available and can be assembled in less than a day.
Photon-blind, high collection efficiency ion detector for a quadrupole mass spectrometer
Authors: Nakao Fusafumi
Published: March 2003

A low noise ion detector for microimpurity analysis with a quadrupole mass spectrometer has been developed using the off-axis technique with an electrostatic deflector plate and a channel electron multiplier. This arrangement of ion detector can greatly reduce the noise and baseline shifts caused by photons and excited neutrals, which are dependent on the emission current and pressure in the ion source. The ion collection efficiency of 100% in this arrangement is obtained at a multiplier voltage of −3 kV and a deflector voltage of 10 V. The noise count rate was on the order of 1–2 Hz. The off-axis ion collector gives a factor of 140 increase in effective sensitivity of the mass spectrometer. The minimum detection limit of the mass spectrometer with the off-axis detector is also determined.
Simple high-stability potentiometric ac bridge circuits for high-resolution low-temperature resistance thermometry
Authors: Gearhart C. A. , McLinn J. A. , Zimmermann W.
Published: March 2003

Three designs of ac bridge circuits for use in carbon or germanium resistance thermometry at low temperature are presented. These circuits combine simplicity of design with high sensitivity and stability of calibration during a low-temperature run and enable the performance of the bridge to be checked accurately. The designs are intended for use in applications in which the thermometer can be calibrated during each low-temperature run. The combination of these designs as alternate modes of operation of a single, versatile, practical bridge circuit is described. The operation of this bridge with regard to sensitivity and noise is discussed.
Sensitive pressure monitoring device
Authors: Wright P. W. , Franck J. P.
Published: March 2003

The use of tunnel junctions as pressure monitoring devices in both solid and fluid pressure transmitting media is described. While very sensitive to pressure changes, these devices have been found to have a negligible dependence on temperature over the range 0–77 K. Their pressure response has been found to be reversible and if maintained at temperatures less than 77 K, they can be used for prolonged periods. An actual example of their use at low temperature is given.
Thickness measurement in liquid film flow by laser scattering
Authors: Salazar Ronald P. , Marschall Ekkehard
Published: March 2003

A method is described for measuring the thickness of a flowing liquid film by the use of laser scattering from suspended latex particles. The apparatus described has a linear voltage to film thickness relationship, unlike capacitance and resistance methods.
200 kA circuit breaker with 10 μsec current transfer time
Authors: Bleys C. A. , Lebely D. , Rioux C. , Rioux-Damidau F.
Published: March 2003

A circuit breaker capable of transferring a current of 200 kA to a fuse placed in parallel in 10 μsec is described. The conducting element is a bar with a cross section in the shape of a T which is burst open at the joint of the arms and leg by pressurized insulating oil. The command, which uses magnetic pressure, is very efficient. The circuit breaker–fuse combination can be used to transfer energy stored in a coil driven by a homopolar generator rapidly to a load.
Simple swept double probe for streaming plasma diagnostics
Authors: Lee J. J.
Published: March 2003

A simple double probe for energetic plasma beam experiments (1016/cm3, 10 cm/μsec) is reported. By capacitive discharge, the probe can be used to obtain the entire I–V curve in a single shot, so that the electron temperature and the ion density can be easily estimated. For supersonic conditions, the ion saturation current is limited by the incident ion flux instead of the factor (kTe/M)1/2, as in the case of a stationary plasma.
Voltage focusing of a telefocus electron gun
Authors: Rasmussen V. K.
Published: March 2003

An electron gun based on Steigerwald’s design is described. It is of particular interest in that large changes in the cathode to focus distance can be effected by changing the voltage on one electrode, which operates at moderate voltages with respect to the cathode.
Laser-triggered spark gap and Kerr cell shutter using a low impedance transmission line
Authors: Diels J.-C.
Published: March 2003

Kerr cells driven by 50 Ω impedance circuits are generally risetime limited due to the capacitance of the cell. Faster risetimes may be achieved with lower impedance circuits. However, the lower the impedance, the more reflections occur at the localized elements and the higher the electric fields in the insulation. These two technical difficulties have been overcome here for Z0=1.5 Ω and Z0=2.5 Ω characteristic impedance parallel plate transmission lines. An impedance matched distributed resistance provided a reflection-free termination for the circuit.
Thin polymer films for transmission infrared spectroscopy
Authors: Koberstein Jeffrey T. , Cooper Stuart L. , Shen Mitchel C.
Published: March 2003

A temperature controlled centrifugal casting technique is used to quickly and reproducibly prepare thin polymer films which are suitable for transmission infrared spectroscopy. Films prepared by this method are shown to be without preferential orientation.
Operating injection lasers by fast square current pulses of variable amplitude
Authors: Armstrong D. R. , Katzir A. , Yariv A.
Published: March 2003

A simple solid state circuit was used to drive GaAs injection lasers by fast (∼100 nsec) square pulses of variable amplitude (0–25 A). The amplitudes of the current pulses and the corresponding emitted light pulses were measured by a dual peak detector circuit. Using these circuits we were able to plot automatically the current vs light curve and determine the threshold current of the laser diodes.
Variable width rectangular slit jet impactor
Authors: Delany A. C. , Dolan G. J.
Published: March 2003

A rectangular slit jet impactor has been designed and fabricated for use as an airborne collector of supergiant aerosol particles. The width of the slit is variable, allowing the impactor size cutoff to be set so that only particles greater than a determined size are collected. The jet convergence angle was made to be 53° 13′ to ensure that the width of the slit is always the same as the distance from jet mouth to the impaction substrate. Experimental calibration of the impactor indicates that this configuration gives excellent impaction characteristics.
Rhenium bonded LaB6 electron source
Authors: Ramachandran K. N.
Published: March 2003

A new technique has been developed to bond LaB6 to rhenium under a high temperature arc. Such a bond exhibits remarkable stability even when reheated to the emission temperatures above 1500°C, and thus presents a convenient method for making compact, high intensity electron sources for SEM and other applications.
Simple setup for Raman difference spectroscopy
Authors: van den Boom H. , Breemer R. E.
Published: March 2003

A system is described which is entirely composed of commercially available instruments. The construction of a rotating cell with two compartments is described in detail. It is furthermore shown that a differential amplifier, although applicable in most cases, cannot be used in the case of small signals on a large background because of its small dynamic range. This difficulty can be overcome by incorporating a lock-in amplifier in the system.
Bulk gas temperature measurement during vessel discharge using transient PVT
Authors: Johnston S. C. , Dwyer H. A.
Published: March 2003

A transient pressure–volume–temperature (PVT) experimental technique for determining true bulk gas temperature during gas discharge from a vessel to the atmosphere is described. The bulk temperature obtained is valid no matter how nonuniform gas temperature is inside the vessel and accounts for all modes of heat transfer during discharge.
Versatile cells for optical studies in fluids
Authors: Hocken R. , Moldover M. R. , Muth E. , Gerner S.
Published: March 2003

A sample cell for optical studies of fluids is described.
Two-tank sequencer for control of liquid nitrogen withdrawal
Authors: Shepherd John R. , Corbin Robert L.
Published: March 2003

The described device permits continuous, prolonged cooling by sequencially switching LN2 demand from an empty tank to a full one after complete depletion of the first tank.
Low temperature application of metal film resistors
Authors: Chu T. K.
Published: March 2003

Because of their small mass (and heat capacity), metal film resistors are found to be suitable for low temperature applications. A technical improvement in thermal conductivity measurements was made possible by their use as sample heaters.
Flyer plate adhesion tests for copper and nickel plated A286 stainless steel
Authors: Dini J. W. , Johnson H. R.
Published: March 2003

Flyer plate shock wave tests were used to evaluate the influence of using an intermediate copper electrodeposited coating on A286 stainless steel prior to plating to final thickness with nickel. Neither varying the copper plating solution (cyanide or pyrophosphate) nor the deposit thickness from 0.008 to 0.084 mm affected the adhesion as measured by this work.
Variable energy neutral molecular beam source for large molecules
Authors: Greene D. B. , Halprin E. A. , Skofronick J. G.
Published: March 2003

A variable energy neutral beam source is presented which utilizes a class of large molecules having the property of forming long−lived temporary negative ions. Negative ions are produced, accelerated, and focused, after which autodetachment of the electrons occur, leaving a beam of neutral molecules. The source has been used in total cross section experiments, where SF6 was the beam gas and various target gases were used in a scattering cell. Some results of the collision process SF6 + CO2 are presented. At 1200 eV lab energy (27 eV c.m. energy) the total collision cross section for CO2 is 54.2±15.9 Å2. Advantages and disadvantages of this type of source are discussed, and extensions to other types of experiments are explored.
Growth of large single crystals of Ce2Zn3(NO3)12⋅24H2O(CZN)
Authors: Fisher R. A.
Published: March 2003

A large (50 mm long by 50 mm diam), clear, visually flawless, oriented single crystal of cerous zinc nitrate 24−hydrate (CZN) has been grown in a Teflon coated cylindrical Pyrex container at 30°C by evaporation of H2O from a saturated solution. The growth rate along the c crystal axis was 0.7 mm/day. The growth in the ab plane was limited by the cylinder diameter. Initial pH of the solution was 0.8 (excess HNO3 present). Two crystals similarly grown at pH 1.5 and 1.2 mm/day were translucent, while a crystal grown at pH 1.5, 0.5 mm/day and 0°C had small cracks as well as being translucent. It is suggested that the translucence is caused by light scattering from microscopic regions due to occluded water and/or hydrolysis products, which can be suppressed by a sufficient excess of H3O+. Crystals grown in a solution with excess acid, however, have a water deficiency. The translucent crystals have a Ce3+ deficiency.
A high rate Ṫ−T controller for thermally stimulated currents
Authors: Paterson William L.
Published: March 2003

A hot stage temperature controller with automatic transition between linear sweep and constant temperature modes, using only two operational amplifiers, is described. The derivative of temperature is nulled against a fixed reference signal instead of the usual approach in which temperature is compared with a time−dependent reference. This allows an increased loop gain at high speeds, while allowing the Ṫ−T crossover to be achieved without additional amplifiers. Ramp speeds of 0.1−10 K/sec in the range 300−820 K are obtained with accuracy of 1%−3%. Noise− and transient−free dc heater power simplifies shielding requirements in the 10−15 A range. A new approximation of the type K thermocouple characteristic is used to estimate its influence on linearity.
A simple x−ray microscope for photographing laser produced plasmas
Authors: Seward F. D. , Palmieri T. M.
Published: March 2003

We have built two simple x−ray microscopes and have used these instruments to take x−ray pictures of laser produced plasmas. The sensitive range is 0.2 −8 keV with greatest sensitivity from approximately 0.5−2 keV. For low energy x rays the resolution is better than that which can be obtained with a pinhole camera.
Apparatus for thermopower measurements on organic conductors
Authors: Chaikin P. M. , Kwak J. F.
Published: March 2003

An apparatus is described for making transport measurements, especially thermopower, on single crystals of highly conducting organic solids. It is designed specifically for small fragile anisotropic samples such as TCNQ salts. The temperature range is 400−1.2 k. A slow ac technique is used so that stray thermal emfs are eliminated and measurements can be taken with a small (0.5 K) temperature gradient for good temperature resolution in regions where the transport properties are changing quickly.
Secondary high pressure standard for the far−infrared spectral region
Authors: Smith B. T. , Sievers A. J.
Published: March 2003

The infrared−active defect lattice mode in NaCl:Cu+ provides a convenient secondary pressure standard for far−infrared measurements of solids at low temperatures.
Application of multilayer dielectric coatings to cylindrical substrates
Authors: Firester A. H. , Hoffman D. M. , Heller M. E.
Published: March 2003

Occasionally the need arises for a multilayer dielectric coating applied to a cylindrical surface. We describe a technique and device for making and simultaneously monitoring multi−layer dielectric coatings on cylindrical substrates, and some typical results which demonstrate the degree of filter uniformity attainable.
Ion beam profile monitor
Authors: EerNisse E. P. , Peterson G. D. , Schueler D. G.
Published: March 2003

An ion beam profile monitor, which consists of a two−dimensional array of sample points placed in the beam, is described. The monitor provides an accurate and unambiguous display of the beam profile on a laboratory oscilloscope. Performance of the monitor under various ion beam conditions is presented.
Simple schemes for measuring autocorrelation functions
Authors: Kam Z. , Shore H. B. , Feher G.
Published: March 2003

Several methods for obtaining the autocorrelation function of fluctuating signals are discussed. The efficiency of data processing and the signal−to−noise ratio obtained for a given time of data acquisition using each method is compared to that obtainable with a full (ideal) autocorrelator. Two simple methods utilizing a signal averager (CAT) were tested experimentally with a variety of noise sources and the results compared with the theoretically predicted correlation functions.
A simple, reliable waveguide dye laser for ophthalmological applications
Authors: Burlamacchi P. , Pratesi R. , Vanni U.
Published: March 2003

The principle of operation, construction, and performance of a compact waveguide dye laser, especially designed as a source of retinal photocoagulators, are described, The guiding effects produced by the thermal gradients induced by the pumping pulse and the use of closed resonator make the laser very reliable, simple, and with good pulse repeatibility. The construction is very simple and inexpensive. Except for flashlamps, which are commercial, no part of the laser requires sophisticated technology to be built or assembled; neither optical components have critical flatness and need careful alignment. The system does not need cooling, and slow recirculation of the solution, necessary to replace the degraded dye in the waveguide, is provided by a magnetically coupled 0.1 W electric motor. The dye cell, pump, and dye reservoir form a single component of the laser which can be easily extracted for inspection and replacement of the dye solution. The single, regular pulse emitted by the laser, its time duration (a few microseconds), the possibility to operate the laser at the absorption peaks of the ocular tissues make the laser better than the random spiking ’’passive’’ ruby laser or than the ’’explosive’’ Q−switched ruby laser for ophthalmological applications. If connected with a slit lamp, the laser should compete with the much more expensive ion gas lasers. Good retinal photocoagulations have been made in rabbits using a solution of Rhodamine 6G in ethanol. Retinal spots of rectangular shape of variable dimension but of constant energy density have veen produced by simply masking the exit window of the laser.
A 1024−channel digital correlator
Authors: Ables J. G. , Cooper B. F. C. , Hunt A. J. , Moorey G. G. , Brooks J. W.
Published: March 2003

A 1024−channel digital correlator designed for spectral analysis of radio astronomy signals is described. The correlator has a maximum sampling rate of 20 MHz, allowing it to analyze noise signals with bandwidths up to 10 MHz. Other bandwidths of 5, 2, 1, 0.5, 0.2, 0.1, and 0.05 MHz are provided. Quantization mode can be either one−bit or two−bit. Either autocorrelation or cross−correlation functions can be generated. These are Fourier transformed on−line by a PDP−9 computer to generate high resolution power spectra. Subdivision of the correlator into four independent 256−channel units is also possible. Software used with the correlator is briefly described, and some observational results presented.
Analytical approximations for the focal properties of the plane−grid and cylinder electrostatic lens system
Authors: Young C. E.
Published: March 2003

Analytical expressions are derived for the paraxial focal properties of the unsymmetrical lens system formed by adjacent planar−grid and cylindrical conductors. Resulting focal lengths and principal plane positions are shown to be in good agreement with existing ray−tracing calculations, especially in the converging lens region of voltage ratios 0.1 ? V2/V1 ? 1. Modifications applicable in the strongly diverging lens region (V2/V1≳ 2) are indicated.
Real−time harmonic analysis by minicomputer
Authors: Templeton I. M.
Published: March 2003

A technique is described in which a minicomputer (PDP8−E) is used to perform signal averaging and Fourier analysis of harmonic content on a stationary or slowly varying repetitive audio frequency waveform. Examples are given of the averaging and analysis process, and the performance of the system in rejecting spurious random or non−synchronized signals is discussed.
Simple single and tandem microchannelplate mountings for x−uv or low energy particle windowless image converters
Authors: Bettinali L. , Pecorella F. , Rager J. P.
Published: March 2003

Full details are given for the realization of a windowless image converter for low energy particle or soft x−ray spectroscopy, based on the use of new microchannelplate mountings in which the electrical contacts are secured by small spring load pin−contacts. Among other improvements, this kind of mounting can match any microchannelplate thicknesses and can easily be extrapolated to the case of tandem microchannelplate mounting.
Experiments on a new surface ionization ion source with lithium
Authors: Rasser B. , Remy M.
Published: March 2003

We have constructed a surface ionization ion source able to ionize many elements. Currents of 3 mA for Li+ ions with a current density of 1.7 mA/cm2 can be obtained.
Technique for preparing homogeneous bulk samples of concentrated alloys
Authors: Ekin J. W. , Deason V. A.
Published: March 2003

A technique has been developed for casting relatively large samples (∼100 g) of concentrated alloys. It was used to prepare Al−Mg castings having Mg concentrations near the maximum limit of solid solubility. Concentration gradients and nonequilibrium eutectic solidification were minimized by the rapid cooling and directional solidification that are characteristic of the technique.
Modification of a liquid buffer technique for measuring ultrasonic attenuation
Authors: Kittinger Erwin , Walder Josef
Published: March 2003

A modified liquid buffer technique has been devised and used for the measurement of ultrasonic attenuation in polystyrene samples. The use of a small area probe makes the requirements on sample parallelism less stringent than with the usual single transducer pulse echo method. For this immersion technique rather large samples have to be used; while sample preparation is greatly facilitated.
Multidimensional gamma−ray spectrometer with a liquid−scintillation−counter anticoincidence ring
Authors: Grismore R. , Barbee A. W. , Berry M. L. , Taboas A. L. , Emmons D. R.
Published: March 2003

Details are given of a NaI(Tl) multidimensional gamma−ray spectrometer employing a low−cost liquid−scintillation−counter anticoincidence ring which has been constructed at Indiana State University. Data are presented on the background counting rates of this spectrometer both with and without the anticoincidence ring operating, and comparisons are made with the background of a very similar spectrometer employing a NaI(Tl) anticoincidence ring. The liquid−scintillator anticoincidence ring is shown to be effective, and capable of improvement so as to bring the background of the spectrometer down to nearly the same level as with a NaI(Tl) ring.
New two−photon absorption spectrometer and its application to diphenylbutadiene
Authors: Swofford Robert L. , McClain W. M.
Published: March 2003

We describe a new spectrometer which promises to increase by several orders of magnitude the sensitivity for measurement of aboslute two−photon absorptivities. The spectrometer employs two TEM00 laser beams propagating in opposite directions through the sample. A tunable pulsed laser generates the powerful beam and a continuous krypton ion laser provides a constant frequency probe beam for the two−photon spectrometer. We report the two−photon absorptivity of 1−chloronaphthalene at 35 400 cm−1 to be 1.3×10−50 cm4 sec photon−1 molecule−1, in good agreement with previously reported values. We also report the two−photon absorptivity of 1,4−diphenyl−1,3−butadiene at 28 259 cm−1 to be 1.0×10−50 cm4 sec photon−1 molecule−1. This relatively high value indicates the presence of a previously undetected 1Ag excited state as the lowest excited singlet state of this molecule.
Variable frequency exposure system for small biological specimens
Authors: McRee D. , Walsh P. , Mathew R.
Published: March 2003

A variable frequency microwave exposure system for use in the study of the bioeffects of cw and frequency modulated radiation has been designed, built, and calibrated. The frequency range of the system is 1−10 GHz. The power density range at the specimen location for all the specified frequencies is from 0 to 20 mW/cm2. The field uniformity at the specimen location is ±10% over a distance of 6 cm and ±20% over a distance of 9 cm at a frequency of 10 GHz. The field uniformity increases with decreasing frequency. At a frequency of 1 GHz, the field uniformity is within ±8% over a distance of 16 cm.
Simple, adjustable lens holder
Authors: Jennings Donald A.
Published: March 2003

The construction of a simple, adjustable lens holder is described. This lens holder is unique in that it will firmly hold small lenses without taking up space at the edge of the lens or stopping them down.
Simple system for producing an atomic beam of alkaline earth metastables
Authors: Heider Stephen M. , Brink Gilbert O.
Published: March 2003

A simple system is described which produces an intense atomic beam of alkaline earth atoms in metastable states. This system, which used an arc discharge in the effusion orifice of the atomic beam oven, has been used in hyperfine structure investigations of these states, as well as in the study of their scattering properties.
Novel electrical insulator for an ultrahigh vacuum line
Authors: Jones J. C.
Published: March 2003

A simple and inexpensive electrical standoff insulator is described for use in ultrahigh vacuum lines. A metal gasket–polyimide sandwich, used as the metal seal between standard flanges and bolts, is insulated from the flanges by polyimide sleeves and washers.
Simple modifications to increase intensity of xenon light source and allow use of mercury lamp
Authors: Benkiki Moshe , Penchina Claude M.
Published: March 2003

We present two independent modifications made on the Bausch and Lomb 150-W xenon light source. One, the addition of a mirror to the lamp housing increases light output by 42%. The other, addition of a resistor and a switch to the power supply, allows for easy interchange of the standard 150-W xenon lamp with a 100-W mercury lamp.
Design of a water-activated switch for a diffusion pump
Authors: Chopra D. , Babb H.
Published: March 2003

We describe the design of a simple and inexpensive switch to safeguard against the overheating of oil in a water-cooled diffusion pump, caused by water supply failure.
Viewing port window for crystal pullers
Authors: Weinberg Erwin
Published: March 2003

A viewing port window that prevents volatile material from being deposited on it during crystal growth has been developed. It has been used successfully for the Liquid Encapsulated Czochralski (LEC) growth of gallium arsenide.
Pulsed image converter for use under ambient light conditions
Authors: Aslam M. , Habel R.
Published: March 2003

A single stage magnetically focused image converter, having a nickel mesh at its first accelerating electrode, was constructed. An S-11 post-oxidized photocathode was processed in this image tube. The imaging properties of this type of image converter have been studied under static and pulsed conditions. The output image resolution was studied as a function of the pulse duration or the switching on time. The effect of the application of a pulse to the photocathode or the control grid on the output image resolution is also mentioned. The ’S’ distortion and pincushion distortion under pulsed conditions is also briefly described. Applications of this image converter in spark gap photography, plasma diagnostics, and beam cross-section photography of the 1.3 GeV synchrotron at Frascati are briefly mentioned.
Improvements of a magnetic monopole detector
Authors: Eberhard P. H. , Ross R. R. , Taylor J. D.
Published: March 2003

Modifications to our previously described detector of magnetic monopoles resulting in substantial improvements in performance have been made. The sensitivity has been increased a factor of 35 by using a sensitive magnetometer (SQUID) to measure changes in current. The modifications, new measurement techniques, and implications for past and future experiments are described.
Merged beams at Minnesota
Authors: Gentry W. Ronald , McClure Donald J. , Douglass Charles H.
Published: March 2003

A new merged-beam apparatus is described, which permits the measurement of the energy dependence of the absolute cross sections for ion–neutral and neutral–neutral reactions yielding ionic products over the energy range <0.010 to ∼10 eV. The apparatus has a somewhat different geometry than that of any previous merged-beam instrument and incorporates several innovations which facilitate the rapid measurement of relative cross sections, the accurate determination of the beam overlap integral, and the high-resolution measurement of the product energy distribution. The performance of the instrument is illustrated with data on the reaction H+2 + H2 → H+3 + H.
Scanning Fabry–Perot interferometer for precision measurement
Authors: Bruce C. F. , Duffy R. M.
Published: March 2003

A description is given of an electromechanical scanning Fabry–Perot interferometer, designed primarily for rapid and precise wavelength comparisons and spectral line profile studies under vacuum conditions. It has a continuously variable path difference range of up to 1 m. Wavelengths may be compared with the present primary krypton-86 standard to the uncertainty of this standard (± 4 parts in 109). Provision is also made for automatic control of plate parallelism and plate separation.
An inexpensive method to stabilize the frequency of a CO2 laser
Authors: Thomason William H. , Elbers Don C.
Published: March 2003

An inexpensive method to stabilize the frequency of a CO2 laser is described. The method is completely electronic and utilizes variations in the impedance of the laser plasma tube to produce a frequency correction.
Protection technique for Channeltrons in space research
Authors: Cerulli-Irelli P. , Egidi A. , Marangoni G.
Published: March 2003

In the development of the design of a space experiment a device has been built and tested which allows the blanking of a Channeltron detector after a given number of pulses have been counted. With this device the average counting rate can be controlled without limiting the instantaneous counting rate. The tests performed indicate that a satisfactory blanking factor is achieved and that the fatigue effect depends on the average frequency, with no appreciable effect of the instantaneous frequency in the bursts.
Magnetic field control by time-shared minicomputer with milligauss precision
Authors: Cook Thomas J. , Zegarski Bernard R. , Miller Terry A.
Published: March 2003

Swept magnetic fields can be stabilized about a center field to a precision of ∼0.3 ppm. The stabilization apparatus consists of a time-shared minicomputer, a voltage-tunable, locking NMR fluxmeter, a frequency counter, and various interfaces. The software and operation of the computer are described as well as the hardware interfaces, which are mainly solid-state logic devices incorporating mostly integrated circuits.
Ultraviolet spectrograph using microchannel plates
Authors: Lawrence G. M. , Stone E. J.
Published: March 2003

An ultraviolet spectropgraph was constructed using double microchannel plates as detectors at the focal plane. The photoelectron pulses were located one at a time by measuring the charge division to the ends of a resistor strip behind the microchannel plates. The system worked to 20 000 counts/sec and gave resolution exceeding 100 elements.
Apparatus for local sensing of nitric oxide as a pollutant
Authors: Bonczyk P. A.
Published: March 2003

An apparatus is described which is capable of detecting 1/4 ppm of NO in a NO–N2 mixture. The apparatus consists of a CO laser, which emits radiation that is absorbed by the NO in the mixture, the amount of absorption being proportional to the concentration of NO present. Optimum detection sensitivity is achieved when the mixture is situated in a magnetic field. The field shifts the absorption wavelength of the NO into coincidence with the fixed laser wavelength.
Improved electron microprobe scanning images
Authors: McCoy D. D. , Gutmacher R. G.
Published: March 2003

The count-rate discriminator, CoRaD, was developed for use with the x-ray microprobe and scanning electron microscope. It is a digital device that facilitates the production of background-free x-ray scanning images. It has been used to great advantage in analyzing multiphase specimens containing the same elements in different proportions. CoRaD permits the selective display of any one phase exclusive of the others. When CoRaD is interfaced to three scalers, the volume fraction and mean particle size of selected phases can be determined.
Monochromatized x-ray source for high resolution electron spectroscopy
Authors: Baer Y. , Busch G. , Cohn P.
Published: March 2003

An x-ray monochromator system for the Al Kα emission line has been developed specifically for x-ray photoelectron spectroscopy. It is composed of a fine focus, high power x-ray tube with a water-cooled rotating anode and a spherically bent quartz crystal. The parameters have been chosen to achieve very high resolution with acceptable intensity and to fulfill the geometrical conditions imposed by the electron spectrometer. A description is given of the adjustments and tests of the different components of this equipment. It is demonstrated, on the basis of spectra particularly suitable for this purpose, that a total instrumental line width of 0.3 eV or better is achieved.
Simple persistent switch for superconducting solenoids
Authors: Isaac R. D. , Schwarz R. B.
Published: March 2003

The construction of a compact persistent switch for operating a superconducting solenoid in the persistent mode is described. It is easily built using only common laboratory materials.
Microscope stage sample holder capable of temperature variation between 30 and 800 K
Authors: Tynan E. E. , von Gutfeld R. J.
Published: March 2003

A novel vacuum sample holder is described for use with an optical microscope. The sample stage temperature can be made to vary from ∼ 30 to 800 K. Electrical feedthroughs together with an optical window provide convenient features for use in a wide variety of experiments. Data for optically induced transverse thermoelectric voltages of a Pd film as a function of temperature are presented.
Machine for rapidly counting and measuring the size of small nematodes
Authors: Byerly L. , Cassada R. C. , Russell R. L.
Published: March 2003

A machine has been developed to accurately count and size large populations of the small nematode Caenorhabditis elegans with minimal effort. Like the related Coulter counter, this machine detects the change in electrical current which a particle (nematode) produces as it passes between two electrodes in a small transducer. Despite the use of alternating current, detailed analysis shows that detection is based primarily on resistance changes. The machine also employs a sheathed-flow system to orient the long thin animals reproducibly in the transducer, so that resistance changes correspond directly to animal size. Accurate, non-destructive measurement of live nematodes which have a 20-fold length-to-width ratio and vary over a 103 range in volume can be achieved at a counting rate of 103 per min with 1% coincidence. Sources of measurement errors have been identified and controlled or eliminated. The machine has been calibrated against the optically measured lengths of nematodes in all stages of the life cycle.
Effect of temperature on magnetic shielding with Co-netic
Authors: Martin Douglas L. , Snowdon Robert L.
Published: March 2003

For frequencies in the range 1–400 Hz and fields of ∼1 G, the signal transmitted through shields made of 0.01 cm thick Co-netic foil increased by ∼50% on cooling from 293 to 4.2 K. Annealing reduced the transmitted signal by an order of magnitude at all temperatures, provided the shield was not strained. Application to shielding the N.B.S. Superconductive Fixed Point Device is discussed.
Tracking, pulsed ultrasonic interferometer
Authors: Angel William T. , Bean Vern E.
Published: March 2003

A pulsed ultrasonic interferometer was designed and constructed that has the ability to track changes in transit time as the ambient pressure and temperature of the sample are changed. The stability over 17 h approached one part in 107. This instrumentation will be incorporated into an automated high pressure transfer standard calibration system.
Evaluation of photomultiplier tubes for use in photon counting correlation spectroscopy
Authors: Gethner Jon S. , Flynn George W.
Published: March 2003

A simple experimental technique is described for qualitatively determining the afterpulse spectrum of a photomultiplier tube for use in a photon counting mode. Results for several common photon counting tubes are evaluated with particular interest in the use of the tube for photon correlation spectroscopy (PCS) applications. A discussion of the problems which arise due to afterpulsing is included.
Versatile plasma probe
Authors: Holmes J. C. , Szuszczewicz E. P.
Published: March 2003

We have developed a plasma probe circuit which couples standard Langmuir probe diagnostic procedures with pulse mode operation. Circuit versatility provides the means for studying time-dependent phenomena and establishes an improved capability for measuring plasma density and temperature. As an application of our circuit, we show that pulse mode operation substantially reduces the time variance of electrode surface conditions which often causes hysteresis in the Langmuir probe current–voltage characteristic.
Tunnel diode oscillator for 0.001 ppm measurements at low temperatures
Authors: Van Degrift Craig T.
Published: March 2003

The results of a systematic study of the design considerations of a low-temperature tunnel diode oscillator are presented. The calculated circuit performance satisfactorily describes the measured frequency noise and dependence on bias voltage, magnetic field, and temperature. The overall performance allows measurement of changes in the resonant frequency of an LC circuit with a precision of 0.001 ppm. One can thereby detect extremely small changes in a number of material properties such as thermal expansion, surface impedance, and electric and magnetic susceptibilities.
Field/frequency lock monitor for signal averaging with high resolution NMR spectrometers
Authors: Bangerter Benedict W.
Published: March 2003

A method for monitoring the field/frequency lock condition of a high resolution NMR spectrometer and suspending signal averaging in the event of loss or degradation of the lock is described. This procedure involves amplification and conditioning of the absorption mode lock signal, followed by analog-to-digital conversion under control of the data acquisition computer, or by a binary comparison of the lock signal amplitude with a chosen threshold value with analog circuitry.
Manufacture of DT-filled, hollow glass microsphere, laser targets
Authors: Souers P. C. , Tsugawa R. T. , Stone R. R.
Published: March 2003

The fabrication of highly characterized DT-filled, hollow glass microsphere targets is described. The DT is loaded by gas permeation through the glass walls at 420 °C. The DT fill is nondestructively measured by counting the emitted x rays with a proportional counter. The counter system is empirically calibrated by individually crushing microspheres in an ionization chamber. Outer diameters are measured optically with a split-image eyepiece. Wall thicknesses and sphericities are measured by light interference. For a 40-μ diam microsphere and 1-μ walls, we estimate our best absolute accuracies of measurement to be, o.d., ±1.6%; wall thickness at any point, ±10%; overall microsphere sphericity, ±7%.
Germanium thermometer calibration
Authors: Martin Douglas L.
Published: March 2003

The advisability of calibrating only carefully selected thermometers is emphasized. The relation between calibration point spacing and the weighting method used in curve fitting the calibration is discussed and then illustrated by various fits to different data sets for a particular germanium thermometer. Apart from different end effects, which could be minimized by a higher density of points at each end of the range, there is little significant difference between the results of the various methods tried.
Simple optical absorption spectrometer suitable for measurements at low temperatures
Authors: Mollenauer L. F. , Olson D. H.
Published: March 2003

A spectrometer for making absolute absorption measurements is described. The system is especially suitable for work with solid state samples at low temperatures. Both sample and reference beams pass through the same set of Dewar windows, making compensation for the losses in these unnecessary. Simplicity and low cost are achieved by using a chopper wheel of special configuration rather than the usual rotating mirror. Direct measurement of optical densities as high as 4.0 is possible.
X-band spectrometer with a rectangular resonant Stark cell
Authors: Reesor G. E. , Dagg I. R. , Wong A. M. C.
Published: March 2003

The design of a Stark resonant cell and the microwave spectrometer used with it are described. The features of the cell are its simplicity, ease of construction, and convenient size. The method of maintaining the cell on tune is discussed. Performance is expressed in terms of results obtained for two lines in the spectrum of D2O.
Fast air gap crowbar switch decoupled by a low pressure gap
Authors: Kitagawa Shiro , Hirano Kei-ichi
Published: March 2003

A high pressure air gap is used as a fast ’’crowbar’’ switch with the aid of a low pressure gap decoupler. In order to trigger the switch, a special trigger circuit is designed, in which a single pulse breaks down the high and low pressure gaps successively. The jitter of breakdown time of this switch is less than 20 nsec over a wide range of operating conditions, pressures in both gaps, and working voltage. The switch is designed for 40 kV operation. Its inductance is 22 nH, and the resistance at a current of 40 kA is 4 mΩ. Seventy switches are installed in a 40 kV, 210 kJ fast bank. Up to now they have been running for about 20 000 shots with little maintenance.
Schottky diode fabrication for electroreflectance measurements
Authors: Studna A. A.
Published: March 2003

A method is described for fabricating and evaluating metal–semiconductor (Schottky diode) samples for electroreflectance measurements over a wide spectral range. This technique has been used successfully on a variety of semiconductors. The completed samples have been cycled from 300 to 6 K maintaining very stable characteristics and allowing excellent reproducibility in electroreflectance data.
Nonresonant ion trap
Authors: Brink Gilbert O.
Published: March 2003

A nonresonant ion trap, which allows the creation and containment of variously charged positive ions, has been designed and constructed. The ions are trapped in a potential depression produced by a high current electron flow. A preliminary model of the trap has been constructed and tested, and data showing its operational characteristics are presented. Possible applications of the trap for research in atomic physics are discussed.
Eddy-current method for measuring the electrical conductivity of metals
Authors: Rajotte R. J.
Published: March 2003

A simple method for measuring the conductivity of metals is described. The conductivity is derived from the measurement of the voltage induced in a magnetic probe at the surface of a metallic specimen, subjected to an alternating magnetic field produced by a spiral magnet coil. This method will permit a rapid and accurate determination of the electrical conductivity of a metal sample, provided that the frequency of the current in the spiral coil is high enough to ensure that the skin depth is not more than one-fifth the thickness of the metal sample. The specimen being tested must also be at least 1.5 times larger than the outside diameter of the spiral coil to avoid edge effects.
Simple, special purpose, real-time Hadamard-transform computer
Authors: Slingerland J.
Published: March 2003

This paper describes a simple, versatile Hadamard-transform computer. By using fast CMOS dynamic shift registers as memory elements, computation speed is high, and transformation takes place during the measurement. The apparatus can also be used as a signal averaging computer.
The rotating-bubble apparatus
Authors: Torza S.
Published: March 2003

An improved rotating-bubble device for measuring surface and interfacial tension of liquids has been built and its accuracy checked and found comparable with published data. It is based on the phenomenon by which a fluid phase, when placed in a denser liquid contained in a horizontal tube rotating about its long axis, deforms into a long cylindrical thread until centrifugal and interfacial forces balance. The present device permits higher angular rotational velocities and its quasi-frictionless motion reduces vibrations and overheating. The theory and the procedure of the method are summarized briefly and several experimental results to corroborate the theory are presented.
Simple method of generating and coupling rf energy to a reactive collisionless plasma
Authors: Schumacher R. W. , Holt J. L. , MacKenzie K. R.
Published: March 2003

A grounded grid oscillator is placed at the end of an electrical half-wave line and the plasma generating electrode at the other. This simple one-mode circuit enables the oscillator to efficiently deliver power in spite of frequency changes caused by the plasma reactance.
Set of coils for measuring differential magnetization perpendicular to the magnetic field of a superconducting solenoid
Authors: Filho A. Paduan , Becerra C. C. , de Oliveira N. F.
Published: March 2003

A set of coils for measuring differential magnetization perpendicular to an external dc magnetic field, provided by a superconducting solenoid of axial access, is described. Test measurements with the external field parallel to the easy axis of the antiferromagnetic MnCl24H2O are shown.
Plastic optical fiber displacement sensor for study of the dynamic response of a solid exposed to an intense pulsed electron beam
Authors: Bailly-Salins R.
Published: March 2003

The principle of the branched fiber bundle sensor has been known for many years. The apparatus which is described in this paper is distinguished by simple fabrication, low cost, high sensitivity, and a fast response time. It is used for measuring the velocity of the back surface of an irradiated aluminum target. In spite of intense consecutive bremsstrahlung, the plastic fiber probe gives good results, whereas with glass fiber a large scintillation impulse appears which covers the signal.
Contained SEM for examining radioactive materials
Authors: Makohon P. A. , Sisson R. D. , Sheehan J. E.
Published: March 2003

A contained scanning electron microscope (CSEM) was designed and constructed at the Savannah River Laboratory. The facility consists of two stainless-steel glove boxes with separate compartments for specimen mounting and coating, specimen decontamination, SEM column and sample chamber, and containment of the vacuum pumping systems.
Device for automatic compensation of zero drift for use with torsion pendulum apparatus for internal friction measurements
Authors: Bergamasco G. , Zini G.
Published: March 2003

An electronic device is described by which the rest position of a mechanical oscillating system can be locked onto a given point or angle. This is obtained by generating a square wave that develops a dc component every time the rest position of the system does not coincide with the required one, and by making a motor automatically displace the oscillation center until the dc component of the square wave is zero. The device has been tested in connection with a torsion pendulum for internal friction measurements: it can correct large displacements of the rest position of the oscillating pendulum within few a periods, provided the angular velocity of the compensation motor is suitably chosen in relation to pendulum oscillation amplitude and period.
CO2 oscillator–pulse shaper–amplifier system producing 0.1 J in a 500 psec laser pulse
Authors: Kwok Hoi-Sing , Yablonovitch Eli
Published: March 2003

The output of an optical free induction decay pulse generator was amplified up to the 0.1 J level. A pulse width of 500 psec was resolved on a Tektronix 519 oscilloscope using a pyroelectric detector. This agreed well with a linear computer model of the system response.