bluuebunny/crossref_metadata_2025 huggingface dataset:
A Laser Power Meter for Large Beams
Authors: Jennings D. A. , West E. D.
Published: February 2004

A power meter is described in detail for large or divergent laser beams, either cw or repetitively pulsed. The meter measures the flow of heat generated by the beam and is calibrated with an electrical heater wound just behind the absorbing surface. The meter is capable of power measurements of 1 to 30 W accurate to ±2.5%.
Techniques and Apparatus for the Fast and Accurate Measurement of Fluid Temperature and Flow Speed Fields
Authors: Fowlis William W.
Published: February 2004

Techniques and apparatus for the accurate and fast measurement of temperature and speed at many ``points'' within a fluid are described. Using bead thermistors in liquids and a digital data acquisition system, up to 150 measurements/sec can be made for (1) temperatures within and beyond the range from 10 to 40°C to an accuracy of ±0.01°C and (2) speeds in the range from 0 to 5 cm/sec to an accuracy of ±0.1 cm/sec. The very small size of bead thermistors now available with bead diameters less than 0.25 mm and with lead diameters less than 0.025 mm, means that many of these transducers may be mounted with small or negligible disturbance to the flow. A mounting configuration where the beads are supported only by their leads is described.
Magnetic Susceptibility Measurements with a Tunnel Diode Oscillator
Authors: Clover R. B. , Wolf W. P.
Published: February 2004

A tunnel diode oscillator is described which has been successfully used for paramagnetic susceptibility measurements at frequencies from 3 to 55 MHz, at temperatures from 1.2 to 77 K, and at magnetic fields up to 18 kG. In appropriate cases, such measurements may be used to infer magnetic specific heats and spin-lattice relaxation times.
Thermal Anchoring of Wires in Cryogenic Apparatus
Authors: Hust J. G.
Published: February 2004

Thermal anchoring of wires to heat sinks in cryogenic equipment is discussed. An analysis is presented to relate the length of tempered wire required and measurable parameters of the system. The solution of the problem is included along with tabular values for typical situations.
Design of a Permittivity Cell for Liquids Subjected to High Pressures
Authors: Scaife W. G. , Lyons C. G. R.
Published: February 2004

The evolution of a design for a permittivity cell and encapsulation suitable for liquids subjected to pressures up to 6 kilobars in the range of temperatures from −25 to +100°C is described. Summarized data obtained with this design are compared with material published elsewhere.
A Flexible Mounting for Making Silver Chloride Seals
Authors: Chiu Ying-Chech
Published: February 2004

A flexible mounting device for making silver chloride seals is described. With this device, special surface treatments are not required prior to the sealing process. The mounting is especially effective for making seals of irregularly shaped objects and may be applied to sealing problems which involve physical changes of materials during oven baking.
Operation and Control of a High Pressure Ionization Gauge
Authors: Wadsack R. L.
Published: February 2004

This paper reviews the characteristics of a high pressure ionization gauge originally reported by Schulz and Phelps [Rev. Sci. Instrum. 28, 1051 (1957)]. The gauge is available commercially as the Westinghouse WL-7903. A brief theoretical treatment is given for the linear regime, p≲1 Torr. The gauge sensitivity is derived from known ionization cross sections for a number of atomic and molecular gases, including argon, krypton, and xenon. Also, an improved gauge controller circuit is described. For a given gas the controller normalizes the gauge sensitivity to unity and provides a direct reading of gas pressure on a linear scale. The controller has proved very useful in the operation of a cw flowing-gas laser in which 0.1 to 300 mTorr pressures occur. In addition, new experimental data are presented for argon, krypton, nitrogen, and air in the ``nonlinear'' range 2–500 Torr.
A New Apparatus for the Production of Uniform Liquid Drops
Authors: Raghupathy B. , Sample S. B.
Published: February 2004

An inexpensive device is described for producing uniform liquid drops which are colinear in trajectory. The device uses both an electrically induced dripping mode and a harmonic electrical spraying mode to achieve continuously variable drop diameters over a 20 to 1 range. Because the drops are uniformly charged (∼10−10 C), their velocity and trajectory can be readily varied using inexpensive electrical means.
Vibrating Sample Magnetic Image Effects in an Nb3Sn Solenoid
Authors: Richards D. B. , Edwards L. R. , Cornforth C. M. , Legvold S.
Published: February 2004

Serious difficulties encountered with a vibrating sample magnetometer in an Nb3Sn ribbon wound superconducting solenoid are described. A useful sensitivity of 10−4 emu was achieved, but absolute accuracy was severely limited by unstable magnetic image effects which precluded proper calibration. It is suggested that use of large bore solenoids will overcome the basic difficulties.
A Phase Locked rf Magnetometer
Authors: Maartense I.
Published: February 2004

Attention is drawn to the use of phase locking of two oscillators for the measurement of transient magnetic or dielectric changes of samples placed in a resonator. Improvements in speed and sensitivity are possible over other methods. A specific design for operation at 10 MHz is given for the measurement of magnetic susceptibility changes at low temperatures. As an example of the results obtained, the magnetic canting transition of KMnF3 near 82 K is shown.
Crystal Etch Monitoring by Internal Reflection Interferometry
Authors: Rode D. L. , Johnson W. A.
Published: February 2004

Precision etching of semiconductor wafers without continuous monitoring is not possible due to the variability of etch rate with time during etching, and due to the dependence of etch rate upon temperature, age, and rate of stirring of the etchant. Therefore, a method has been developed whereby the thickness of semiconductor wafers can be continuously measured to submicron precision during etching. Accurate in situ monitoring of wafer thickness is accomplished through the use of internal reflection interferometry. Experimental results indicate that a precision of 0.1 μ is routinely achieved in gallium arsenide and silicon wafers with the interferometer source a 3.39 μ wavelength helium-neon laser. Infrared absorption data show that most semiconductors of current interest are sufficiently transparent at this wavelength to allow a wide variety of application of the technique.
A Polarized 59Co Target Using a 3He–4He Dilution Refrigerator
Authors: Fisher T. R. , Healey D. C. , Parks D. , Lazarus S. , McCarthy J. S. , Whitney R.
Published: February 2004

A 3He–4He dilution refrigerator has been used to cool a 32 g polycrystalline cobalt rod to 0.034 K. The rod is held in a longitudinal magnetic field of 6.5 kOe and has a nuclear polarization of 0.38. The cobalt piece will be used to study the scattering of polarized and unpolarized fast neutrons from polarized 59Co.
Low Temperature Specific Heat of Copper: Comparison of Two Samples of High Purity
Authors: Bloom D. W. , Lowndes Douglas H. , Finegold Leonard
Published: February 2004

We have compared with good precision between 1.5 and 20 K the specific heat of two well characterized copper samples with residual resistivity ratio R(293 K)/R(4 K) of approximately 2000 (Calorimetry Conference, Argonne National Laboratories) and 30 000 (National Bureau of Standards, Boulder), and find that the electronic specific heat of the former is about 1% higher in the range 1.5–5 K, although the Debye temperatures are the same. The total specific heat of the former is up to 0.8% higher throughout the 1.5–20 K range. This discrepancy indicates that the specific heat may depend on the residual resistivity ratio. The germanium thermometer used in the measurements was calibrated against the National Bureau of Standards acoustic temperature scale T65, and so a test has been made of the smoothness of that scale.
Simplified Construction and Processing of a Helium-Cadmium Laser
Authors: Hernqvist K. G. , Pultorak D. C.
Published: February 2004

Simplified construction of an He–Cd laser is described where the quartz tube containing the cadmium vapor is made separately. The quartz tube is dosed with cadmium before sealing into the Pyrex envelope. Tube processing using a flow-through technique is described.
Utilization of a Rotating Sample Magnetometer
Authors: Flanders P. J.
Published: February 2004

The RSM can be used to detect magnetic moment (vM≥5×10−6 emu), rotational hysteresis (vWR/H≥10−2 emu), spin flop (vM≥5×10−5 emu), and properties related to anisotropy energy [vK/H, v(χ⊥−χ∥)H and vMx≥5×10−6 emu], i.e., anisotropy constants, anisotropic susceptibility, and anisotropic spontaneous magnetization. Samples are either symmetric about, or offset from, an axis of rotation which is set parallel or perpendicular to an applied dc field. Coils are oriented to sense magnetization along or normal to the field axis. For measuring specific parameters, a phase sensitive detector, an electronic integrator, or an oscilloscope is employed. Detailed expressions relating magnetic properties and signal output are presented, along with illustrative experimental results.
A Method for the Measurement of Scattering Angle in an Electron Beam Spectrometer
Authors: Cole R. S. , Jennings J. C. E.
Published: February 2004

The design procedure and the experimental details are given for the construction of a magnetic deflection system which has been used in an electron beam spectrometer to measure the angular distribution of the energy loss spectra of thin solid films. A collimated electron beam is deflected in such a way that it is incident on the specimen at the angle of scatter at which measurements are required. Electrons which emerge normally from the far side of the specimen are then momentum analyzed. The deflection was found to be proportional to current up to an angle of at least 0.04 rad.
Square Wave Source for Producing High Intensity Fields in the Bulk of Semiconductors and Insulators
Authors: Jonas Malkiel , Alon Yosef
Published: February 2004

A 5–100 kHz square wave voltage of amplitude variable between 100–2000 V p-p is generated by the described instrument. Capacitive loads of up to 300 pF can be driven at the highest voltage and frequency of operation. Modulation is provided to enable subsequent synchronous detection. A fast response shutoff circuit protects against overloads and accidental shorts.
In Situ Vapor Pressure Measurement for Low Temperature Thermometry
Authors: Gonano Roland , Adams E. D.
Published: February 2004

By use of a capacitance diaphragm manometer operated at low temperatures, it is possible to measure the vapor pressure of cryogenic liquids without the uncertainties introduced by thermomolecular pressure gradients (thermal transpiration). Since the zero of this manometer is more stable at low temperature than at room temperature, useful sensitivity is increased. Because of the increased sensitivity at low pressure as well as great convenience and simplicity, this technique appears to have wide application in precise vapor pressure thermometry and similar work.
Precompressed Pyrophyllite for Ultrahigh Pressure Research
Authors: Chao C. C. , Ruoff A. L.
Published: February 2004

Pyrophyllite, a mineral used for high pressure gasketing, exhibits wide sample-to-sample variations in density and in mechanical properties. Samples of varied initial densities, after compressions to uniform density, are found to have uniform mechanical properties in subsequent use. Large improvements in work hardening response of tungsten carbide anvils are obtained through use of precompressed pyrophyllite gaskets.
The Preamplified Spiraltron Electron Multiplier
Authors: Wolber W. G. , Klettke B. D. , Graves P. W.
Published: February 2004

A new channel electron multiplier having a simple straight line geometry that preserves the desirable pulse characteristics of the curved channel is described. The channel consists of a Spiraltron element (a length of glass tubing twisted about its central axis) preceded by a preamplifier element to increase the geometrical open area ratio of the device. Experimental results have indicated that the new multiplier, which has a maximum operating voltage of 5.5 kV, an input aperture 1 cm in diameter, and a dark pulse count rate of <0.5 count/sec, is comparable to or better than the best curved channels in all properties except FWHM.
Minimum Aperture Aberrations of Quadrupole Lens Systems
Authors: Moses Ronald W.
Published: February 2004

A focusing system for monochromatic beams of charged particles, with magnetic quadrupole fields having common planes of optical symmetry, is treated theoretically. After specifying certain linear focusing properties for such systems, the calculus of variations is applied to obtain systems with minimum aperture aberrations. First order variational theory is applied to obtain the Euler equations that define extremal systems. This derivation gives four second order, coupled, ordinary differential equations. An iterative technique is presented for solving these Euler equations. Second order variational theory shows that the extrema of the aperture aberrations are local minima with respect to other systems having the same specified linear focusing properties. A digital computer was used to calculate a variety of systems with minimum aperture aberrations. Sample calculations are given for systems with magnifications of −1 and −2. General studies are presented for high magnification systems where the lenses are confined to a region near the object. The best orthomorphic systems have four lenses while the best anamorphotic systems have three. Several methods for regulating the quadrupole gradient strength are studied. It is found that optimum systems have aberration coefficients about one fifth as large as the best systems previously studied. It appears that quadrupoles alone are not as good as round lenses unless the quadrupole bore radius is less than 1/14 of the length of the shortest quadrupole.
Device for Determination of the Change in Calibration of a Torsion Load Cell when under Hydrostatic Pressure
Authors: Abey A. E. , Wagner L. M.
Published: February 2004

A device has been developed to find the change in calibration of a torsion load cell when the cell is under hydrostatic pressure. The change in calibration was found to depend upon load as well as pressure. The correction was found to vary between 10 and 20% at 10 kilobars, being higher for the lower stresses.
Microwave Measurement of the Electron Density Profile in a Supersonic Arc Jet
Authors: Carlile R. N. , Baker F. A. , Somes A. H.
Published: February 2004

A microwave probe is described which allows the electron density profile in a supersonic constricted arc jet plasma to be measured. Peak electron densities of 6×1013/cm3 have been measured near the edge of the jet stream, with the electron density decreasing toward the center.
Method for Observing and Controlling Microcracks in Ceramics
Authors: Leipold Martin H.
Published: February 2004

A technique has been developed by which a microcrack may be propagated in a controlled manner through a small slab, with simultaneous microscopic observation of the path of the crack and the force changes occurring during propagation. For studies of grain boundaries effects, specimens require grain sizes at least as large as specimen thickness (∼50 μ) in order to define the effect of a single boundary on the crack path. Crack behavior may be observed by means of optical microscopy and would be suitable for scanning or transmission electron microscopy. Application of the technique to ceramic bicrystals indicates strong crack pinning points within the individual crystals as well as at the grain boundaries. In polycrystalline materials, these pinning points result in a start-stop process which is repeated numerous times.
Microwave Measurements of the Loss in Low Loss Dielectrics
Authors: Jaeger R. E. , Gyorgy E. M.
Published: February 2004

A technique has been developed which offers a significant improvement in the measurement of the loss in low loss materials having dielectric constants ≥4. The device consists of a cutoff section of circular waveguide concentrically loaded with a rod of the dielectric to be measured. The principal advantage of the technique is that by proper choice of sample and waveguide dimensions one can minimize the effect of resistive losses due to the metal walls. This is achieved by using the sample rod essentially as a section of dielectric waveguide in which the major fraction of the energy is confined to the rod. Both the reduction in wall losses and the simplicity of the design make the use of the waveguides fabricated from lower conductivity, high melting point metals much more attractive for measurement of low loss ceramic dielectrics at high temperatures. Results are reported for single crystal sapphire.
The Measurement of Thin Film Thicknesses in Normally Inaccessible Locations with the Scanning Electron Microscope
Authors: Floyd S. R. , Anstead R. J.
Published: February 2004

A method of using the scanning electron microscope (SEM) to measure the thickness of thin films in inaccessible locations is described. Emphasis is placed on the calibrations of the SEM necessary to obtain good reproducible data and comparisons are made between thickness measurements made using the SEM and interferometric techniques. Actual measurements in the 10 000–15 000 Å range have been made with errors of 2–5%.
High Speed Optical Pyrometer
Authors: Foley G. M.
Published: February 2004

Incandescent solids at temperatures above 1500 K radiate sufficient energy to allow optical pyrometry with a precision of 2 K or less in 1 msec. An instrument system has been built which achieves accuracy of a few kelvins. The sensitivity is 0.4 K when making 1200 measurements/sec near 2000 K or it can be increased as required to 0.01 K with a measurement rate of 1/sec. The system permits dynamic measurement of high temperature thermal properties of refractory metals with better accuracy than has been obtained by methods using slow heating.
Measurement of the Velocity of Gas Bubbles in Water by a Correlation Method
Authors: Matthes W. , Riebold W. , De Cooman E.
Published: February 2004

The application of a correlation method for the measurement of gas (vapor) bubble velocity in liquid flow is described. Contrary to previous similar procedures an optical method (laser light) is used for the bubble (or void) detection. First experimental results are reported.
A Complementary Driven Quinary Ring Scaler
Authors: Reedy E. K. , Pierce J. F.
Published: February 2004

A modified version of the quinary ring scaler was developed incorporating speed-up techniques which had previously been applied only to individual current-mode switches. Computer evaluation of this circuit, using the generalized circuit analysis program NET I, indicated that a minimum theoretical triple pulse resolution time of 1.2 nsec was possible in an idealized environment. An experimental version of this circuit had a minimum double pulse resolving time of 1.7 nsec. This value is equivalent to a periodic repetition rate of approximately 600 MHz.
Balanced Filters for Silver Kα X Rays
Authors: Berman Martin , Ergun Sabri
Published: February 2004

The use of rhodium, ruthenium, and technetium is proposed for balanced filters for silver Kα x rays. Rhodium and ruthenium are used to isolate the Kα1, ruthenium and technetium for the Kα2, and rhodium and technetium are used for the Kα doublet. General criteria are given for optimizing the intensity in terms of the transmission of one of the filters at the line of interest. The transmission of filter A (lowest atomic number) for any of the filter pairs should be about 12% for silver Kα x rays.
X-Ray Spectrometric Characteristics of Potassium Acid Phthalate Crystals
Authors: Chopra D.
Published: February 2004

The x-ray diffraction characteristics of potassium acid phthalate (KAP) crystals have been measured with a vacuum two-crystal x-ray spectrometer using a flowing-gas proportional counter as a detector. The values of resolving power, percent reflection, and coefficient of reflection as determined from the (1, −1) position rocking curves are reported for the wavelengths between 1.54 Å (Cu Kα) and 23.7 Å (O Kα). These crystals offer spectral resolving powers from 2000 to 4000 and from 3 to 40% reflection in the soft x-ray wavelength region. On the basis of these measurements, the crystals will serve as suitable diffracting elements in that range.
A Low Energy Ion Accelerator for Hot Atom Chemical Research
Authors: Pohlit H. M. , Erwin W. R. , Reynolds F. L. , Lemmon R. M. , Calvin M.
Published: February 2004

An ion accelerator is described that delivers magnetically separated ion currents of 0.1–20 μA at 5 eV–10 keV energy into targets of 5 mm2. An electrostatic decelerator in front of the target permits continuous lowering of the ion energy to ca. 5 eV. The accelerator has been used mainly for the production of 14C+ ion beams from 14CO2 for the study of the hot atom chemistry of carbon in solid benzene. The ion source is of all metal construction and is a straight capillary arc type. It delivers C+ currents of approximately 2 μA, obtained at 0.2–0.5% efficiency from the 14CO2 source gas.
A Compact High Temperature Dilatometer
Authors: Etter D. E.
Published: February 2004

A program controlled, inductively heated, compact high temperature dilatometer was designed and built. The dilatometer is capable of measuring the thermal expansion of arc-melted hemispherical metal samples as small as 1.5 mm high by 3.2 mm diam up to 1600°C. The design of the instrument incorporates a linear variable differential transformer (LVDT) transducer with a sensitivity of 1.02×10−3 mm/mV.
Skin Simulants for Studies of Protection against Intense Thermal Radiation
Authors: Davies John M.
Published: February 2004

A simulant with a suitable surface and the correct thermal inertia, β=kρc, meets the primary requirement of accepting heat at the same rate as the skin. For protected skin, a simulant with a blackened opaque surface, β½=0.035 cal·cm−2·sec−½·°C−1, and equivalent depth x/2√α=0.12 sec12 (α=k/ρc) is suitable. Such simulants have been made of fused silica and of an epoxy resin filled with aluminum powder. The detector was a butt welded copper-constantan thermocouple, flattened to a thickness of 0.0015 cm, or a thermocouple of evaporated gold and bismuth films, ∼6000 Å thick. Results with water flow simulating blood flow in the skin indicate that an inert system simulates the response of skin rather well; if some adjustment must be made for varying blood flow it can be done experimentally or by calculation.
A Microwave Saturation Spectrometer for the Measurement of Linewidth and Absolute Intensity
Authors: Gilbert Jacques
Published: February 2004

This paper analyzes and describes a K-band saturation effect spectrometer designed for the detection of resonance absorption in gas phase microwave spectroscopy. As a means of obtaining molecular information, this spectrometer exploits the nonlinear response of a balanced bridge to the amplitude modulation of a saturating microwave field. To enhance saturation the sample cell terminating the signal arm of the bridge is in the form of a high-Q cavity consisting of a half-symmetric confocal resonator excited in the fundamental TEM00q (q≃50) mode. Microwave detection is accomplished with a sensitive superheterodyne technique using phase coherent 30 MHz intermediate frequency (i.f.) conversion. By combining the double feature of in-phase and quadrature-phase i.f. demodulation, this system provides means for a fully automatic bridge balance giving rise to a detected molecular signal which depends on absorption only. The theory implied in the interpretation of this signal as a function of the unsaturated absorption coefficient of the gas is worked out and the techniques relevant to the construction and operation of the instrument are presented in detail. New and potentially useful methods of using the spectrometer for the precise determination of linewidth and absolute intensity of spectral lines are outlined. The capabilities of the methods have been tested on selected lines of the molecules OCS, C2H4O, and CH3OH and the resulting data have shown that a measurement accuracy on the order of a few percent can be achieved for both linewidth and intensity.
Movable and Fixed Modular Vacuum Devices with Confined Fluorocarbon Plastic Seals
Authors: Anderson R. L. , Guildner L. A. , Edsinger R. E.
Published: February 2004

Sealing techniques have been perfected which utilize the properties of fluorocarbon plastics to make high vacuum seals. Several designs are described in which confined gaskets are used instead of O-rings, with consequent reduction of contamination from outgassing and permeation. These sealing techniques have been incorporated into a series of modular components which may be used for assembly of high vacuum systems. Some of these components are movable joints which allow leak-free motion between parts of a system. While not suited for high temperature bakeout, systems constructed from these modular components are capable of being pumped below 10−7 Torr. Dependable systems can easily be assembled or modified using these components, with no detectable helium leaks at a level of 2×10−10 std cm3/sec.
Counting and Sizing of Submicron Particles by the Resistive Pulse Technique
Authors: DeBlois R. W. , Bean C. P.
Published: February 2004

The resistive (Coulter) method of counting and sizing particles in a conducting fluid has been extended to polystyrene spheres 900 Å in diameter, with a present detection limit near 600 Å, through the use of individual submicron pores etched in irradiated plastic sheet. The use of a nonionic surfactant and ultrasonic cleaning effectively relieves the problem of plugging. The particles may be driven through the pore by the electric field, without the use of pressure, to yield the vector sum of the electrophoretic and electro-osmotic velocities. A new theory, yielding an upper limit to the resistive pulse on passage of a sphere, agrees well with data for spheres with diameters d<0.4D, where D is the pore diameter, and complements a previous theory that gives a lower limit, valid for d>0.9D. We estimate that a detection limit near 250 Å will be attainable with the further development of current techniques.
Apparatus for the Study of Electron Ejection from Controlled Metal Surfaces by the Impact of Low Energy Atmospheric Ions
Authors: Prince R. H. , French J. B.
Published: February 2004

A detailed description is given of an ion beam system and instrumentation used in studies of the ejection of electrons associated with the Auger neutralization of N2+, H2+, and N+ ions in the energy range 10–30 eV under controlled surface conditions. Ions are generated in a low pressure discharge, electrostatically focused and mass analyzed by a refocusing magnetic spectrometer to remove undesired ion, neutral, and metastable species. The ion kinetic energy spread is low (approximately 0.4 eV at half-maximum) and the beam intensity is as high as 10−8 A. The combination of ultrahigh vacuum techniques to lengthen the time required to reach adsorption equilibrium after flashing, and special guarding and analog data reduction techniques to reduce instrumentation time response, permitted the study of transient adsorption effects as well as the more usual equilibrium studies.
An Analog Shift Register
Authors: Orsten George S. F.
Published: February 2004

We describe a shift register which is operated by a digital clock as usual, but shifts analog rather than binary signals. This system can be used, among other purposes, as a delay line, in which mode it overcomes many of the limitations of LC delay lines with extremely long delays. The circuit will operate as a digital filter when the delay is immaterial, and the clock rate is chosen to provide the proper folding frequency. Some applications to radio astronomy are discussed.
The Image Instability in High Current Linear Accelerators
Authors: Woods C. H.
Published: February 2004

In high current linear accelerators there may be instability in the coherent lateral motion of the particles caused by the electrostatic image of the beam. Appropriate placement of focusing magnetic lenses (the type normally employed to prevent symmetric radial expansion of the beam) can be used to control the lateral motion. Criteria for stability are derived.
Automatic Mass Spectrometric Analysis of the Deuterium to Hydrogen Ratio in Natural Water
Authors: Thurston W. M.
Published: February 2004

A new sampling concept to convert liquid water to vapor without changes in the deuterium to hydrogen ratio has made possible the construction of an automated mass spectrometer system for determining the deuterium to hydrogen ratio of water samples. The automatic cycle uses an increasing pressure approach to mass spectrometer dosing with excellent suppression of memory effects. Mass-2 ion abundance is used as the pressure sensor to actuate the single control valve in the automatic cycle, coupled with digital readout of the mass-3 ion abundance. A precision of ±0.1 ppm at the natural concentration level is achieved with a cycle time of 2 min. The automatic cycle has also been applied to on-stream gaseous hydrogen analysis with a resulting precision of ±0.1 ppm and a 50 sec cycle time.
Geometrically Exact Monochromator Alignment
Authors: Aspnes D. E. , Studna A. A.
Published: February 2004

We describe a geometrically exact procedure for aligning the grating and collimating mirrors of a monochromator with respect to its primary reference, the grating rotation axis. A laser and a spectral lamp are required.
A Portable Counter and Size Analyzer for Airborne Dust
Authors: Moroz W. J. , Withstandley V. D. , Anderson G. W.
Published: February 2004

A portable dust particle counting and size analyzing instrument with immediate readout would enable number-vs-size distributions of airborne particulate matter to be made known quickly in locations difficult of access, such as underground mines. This device operates on the principle of light scattering by individual particles. Battery operation, solid state circuitry, and miniaturized optical design allow the entire instrument to be housed in a briefcase. Total weight is less than 7 kg and over-all dimensions are 43×33×20 cm. The shaping of the hole edges and conduits and the location of critical flow channels within the photometer head permit stable flow of aerosol past the light field volume where light scattering takes place. A photomultiplier tube receives the pulses of scattered light. The resulting current pulses, height discriminated and continuously integrated, activate milliammeters representing particular (adjustable) size ranges and calibrated in numbers of particles per cubic centimeter.
Gas Gun for Impact Studies
Authors: Fowles G. R. , Duvall G. E. , Asay J. , Bellamy P. , Feistmann F. , Grady D. , Michaels T. , Mitchell R.
Published: February 2004

A detailed description of a 10.16 cm gas gun that has been designed and installed at Washington State University is presented. The design velocity is 1.5 mm/μsec; the maximum velocity achieved to date is 0.9 mm/μsec with an 1100 g projectile. Angular misorientation of the projectile with respect to the target surface is consistently below 0.5 mrad. Brief descriptions of ancillary instrumentation and equipment are also given.
Convex Curved Crystal X-Ray Spectrograph
Authors: Birks L. S.
Published: February 2004

The convex side of a curved crystal will diffract a continuous range of x-ray wavelengths simultaneously. Thus, it is useful for spectral analysis of flash x-ray tubes or plasmas where there is not sufficient time to scan through the spectrum with a spectrometer. It is also convenient for detecting impurities in x-ray targets and could be used for x-ray spectrochemical analysis. The choice of analyzing crystal, the particular diffracting planes, and the orientation of the bending axis allows a considerable versatility in intensity and dispersion including the recording of two or three separate spectra in a single exposure.
The Measurement of Circular Dichroism in the Vacuum Ultraviolet
Authors: Schnepp O. , Allen Susan , Pearson Earl F.
Published: February 2004

An instrument is described for the measurement of circular dichroism in the vacuum ultraviolet. A magnesium fluoride Rochon prism serves as polarizer and a stress plate modulator is the ¼-wave retardation element. CD spectra have been recorded to 165 nm, but substitution of two elements in the optical system by available parts is expected to allow further extension of the wavelength region accessible. A previously used less successful system is also described which used a rotating Rochon prism and a Fresnel rhomb.
An ac System for Measuring Thermopower
Authors: Freeman Ross H. , Bass Jack
Published: February 2004

Using available, or easily borrowed, equipment we have constructed an ac system for measuring thermopower. With this system we have measured the thermopower of a gold-aluminum thermocouple from 30 to 150°C with accuracy of a few percent, using a temperature difference of 0.03 K. With care, and the proper equipment, measurements accurate to about 1% appear possible, using a temperature difference smaller than 0.01 K.
A Technique for Determining p-n Junction Doping Profiles and Its Application to GaP
Authors: McGahan T. E. , Hackett W. H.
Published: February 2004

A technique for determining p-n junction doping profiles is presented. The doping level distribution is determined from a series of surface-barrier capacitance (SBC) measurements, using the recently developed continuous impurity plotter (CIP) [J. A. Copeland, IEEE Trans. Electron Devices ED-16, 445 (1969)]. The SBC measurements are made on an array of Schottky barrier diodes deposited on a 3° angle-lapped junction. The effective spatial resolution normal to the junction is 5 μ. This method yields a higher resolution than the four-point probe method, requires less time than the step layer capacitance technique, and is more accurate than either method. In general, it is the most efficient approach to determining accurate junction impurity profiles presented to date. To illustrate the utility of the technique, an impurity doping profile is determined for an n-on-p liquid-phase epitaxy GaP diode.
Suppression of Nutation Angle Variation in Pulsed Nuclear Magnetic Resonance
Authors: MacLaughlin D. E.
Published: February 2004

In pulsed nuclear magnetic resonance a random variation of the nutation angle is produced if the rf pulse initiation occurs at a random phase with respect to the rf carrier. The effect is most important at low resonance frequencies and large rf pulse amplitudes. An approximate calculation of the rms variation is presented, and a circuit is described which minimizes the variation by synchronizing the rf pulse with the rf phase.
Fluorine Compatible Apparatus for Accurate PVT Measurements
Authors: Straty G. C. , Prydz Rolf
Published: February 2004

A fluorine compatible apparatus, incorporating numerous safety features, is described. This apparatus has been used to make accurate determinations of the PVT properties of gaseous and liquid fluorine from 53.5 K (the triple point) to 300 K and to pressures of 20 MN/m2 (3000 psi). The experimental method is similar to the isochoric one used previously in this laboratory for oxygen and hydrogen. A limited testing program, to determine the suitability of various materials for use with high pressure fluorine, is described and the test results tabulated. Some general fabrication techniques, suitable for construction of fluorine handling apparatus, are discussed.
Extreme Ultraviolet Spectroscopy with the Use of a Storage Ring Light Source
Authors: Gähwiller Christian , Brown Frederick C. , Fujita Hiizu
Published: February 2004

The 240 MeV storage ring at the Physical Science Laboratory of the University of Wisconsin has been used as a source of radiation for extreme uv spectroscopy in the 40–400 Å wavelength range. The characteristics of the synchrotron radiation emitted by this machine are summarized. The experimental setup with a 2 m grazing spectrometer and the data acquisition system is described along with some of the procedures used for thin film photoabsorption measurements.
Apparatus for Direct Recording of Magneto-Optic Rotation and Magnetic Hysteresis
Authors: Sawatzky E. , Horne D. H.
Published: February 2004

The design and construction of an apparatus for domain observation and for the measurement of magneto-optic rotation and coercivity of thin magnetic films, by means of the Faraday effect, are described. A spatial resolution of 5 μ is achieved, allowing scanning of magneto-optic properties across the film. Gas flow cooling and heating of the samples result in a temperature range of −120 to +200°C. A special sampling detector allows continuous recording of magneto-optic rotation and coercivity as a function of temperature and wavelength.
Hydrogen Maser With Deformable Storage Bulb
Authors: Debely Pierre E.
Published: February 2004

The value which most affects the accuracy of the hydrogen maser is the experimental determination of the frequency shift produced by the collision of the atoms with the surface of the storage bulb. In the current method of using different bulbs with various sizes in order to determine the frequency shift, a large amount of uncertainty is due to the unreproducibility of the FEP Teflon coatings from one bulb to another. A way to get rid of this error is to use a single deformable bulb whose volume can be changed while the same surface is retained. Such a bulb has been developed which can be adapted to any regular maser.
Technique for the Study of Highly Attenuated Ultrasonic Waves in Gases
Authors: Miller J. G. , Bolef D. I.
Published: February 2004

The sampled-cw ultrasonic technique is applied to the study of highly attenuated waves in gases. Phase velocity and attenuation are obtained from a measurement of the reflection coefficient at the solid-gas interface of a gas-immersed crystal resonator.
Anemometer Linearizer with Reverse Curvature Capability
Authors: Skinner G. T. , Hiemenz R. J.
Published: February 2004

A biased silicon transistor chain is used as the heart of a temperature stable circuit which will linearize the usual range of power law characteristics of hot wire and thin film constant temperature anemometers. In addition, this device can be used for characteristics which include segments with reverse curvature, a feature which has been found in some probes used to measure blood flow velocities in the aorta.
A Simply Constructed Proton NMR Probe for High Field Super-conducting Solenoid Calibration
Authors: Sari Seppo O. , Carver Thomas R.
Published: February 2004

A proton nuclear resonance probe for high field calibration of room temperature access superconducting solenoid fields is described. The probe may be made in a simple fixed-tuned version, or a tunable version to cover the range from about 40 to 70 kG. Such a probe has the advantage that it may be used on the end of a long probe stem, may be made quite small if necessary, has a high Q, may be used to calibrate homogeneity and persistence easily, may be tested prior to use with DPPH, and may be constructed in just a few hours. The probe can be adapted to use at liquid helium temperatures utilizing 3He samples.
Electronic Correction of Digitizer Errors
Authors: LeVine M. J. , Chase R. L.
Published: February 2004

An electronic system that provides for the unambiguous reading of simple mechanical shaft angle digitizers is described. The system is virtually insensitive to contact bounce, to bridging between adjacent contacts, and to the errors that can occur when several contacts change state at the same time. The system is based upon repetitive comparisons between the last valid reading and the current digitizer state. The output is updated only when the input is found to be unambiguous.
A Microstrip Line Stretcher
Authors: Hoffswell Robert A.
Published: February 2004

A simple and inexpensive microstrip transmission line of adjustable length is described. The device, although physically considerably smaller, is electrically similar to the usual coaxial line stretcher and can be fabricated easily from standard printed circuit or microstrip boards.
Arc Welding Generators Used as Air Core Magnet Power Supplies
Authors: Cato J. E. , Hipp J. E. , Kristiansen M. , Hagler M. O.
Published: February 2004

An experimental study has shown that dc arc welding generators can be used satisfactorily as an inexpensive power source for large magnet systems. A 120 Hz load current ripple of only 0.05% rms was measured at one-half load and decreased for heavier loads. Random low frequency current fluctuations of ⪞3% peak-to-peak were detected but were reduced to ⪝0.5% peak-to-peak with a feedback technique.
Production and Focusing of a High Power Relativistic Annular Electron Beam
Authors: Friedman M. , Ury M.
Published: February 2004

A new electron beam injection gun has been developed to produce pulsed relativistic electron beams with a power of 1010 W. The annular shaped beam propagates in a magnetic field with efficiencies approaching 100% and its radius may be controlled by the magnetic field configuration.
Sampling and Synchronous Detection for Studying Fast Low Intensity Light Signals
Authors: Benci S. , Benedetti P. A. , Manfredi M.
Published: February 2004

Superimposed modulation and lock-in techniques have been successfully applied in order to minimize statistical fluctuations and to eliminate the low frequency internally generated noise in a sampling apparatus for fast, repetitive light signals detection. Some improvements are suggested here for applying the described technique to the study of ir fast light pulses, by means of electro-optical sampling.
Free Vibrating Reed Apparatus for the Measurement of Internal Friction and Young's Modulus down to 4 K
Authors: Buchdahl R. , Morgan R. J. , Nielsen L. E.
Published: February 2004

This paper describes in detail a freely vibrating reed apparatus which we have developed to study these low temperature dynamic mechanical properties of polymers (at approximately 5 cps). The apparatus is capable of measuring these properties from 4 up to 340 K. This method has the advantage over other methods of being relatively easy to set up and may be modified so more than one specimen can be investigated in a given temperature run. In addition measurements on the logarithmic decrement and Young's modulus of polystyrene are presented and compared with previous data.
Ultrahigh Vacuum Twist Compression Apparatus
Authors: Bradford J. M. , Wear K. B. , Sikorski M. E.
Published: February 2004

A new apparatus is described which is used for bonding of metals in ultrahigh vacuum by the twist compression technique. It is shown that adhesion between hard metal specimens can be readily measured in ultrahigh vacuum after some initial mechanical abrasion of the surfaces, while adhesion tests in air at atmospheric pressure do not yield measurable adhesion coefficients. Experimental results are reported on the coefficients of adhesion and friction obtained for an atomically ordered platinum-cobalt alloy.
A Multichannel Monitor for Repetitive Auger Electron Spectroscopy with Application to Surface Composition Changes
Authors: Sickafus E. N. , Colvin A. D.
Published: February 2004

A multichannel monitor has been designed to shorten the effective scanning time of Auger electron spectroscopy. The circuitry of the multichannel monitor is described with specific reference to its application to the second derivative curve of a retarding potential analyzer. By adopting the monitor to a retarding potential analyzer of a LEED system, sufficiently fast response time has been obtained to permit various kinds of surface kinetics to be monitored. By way of illustrating the use of the monitor, results are given of surface composition changes on the Ni(110) surface that accompany heating subsequent to adsorption at room temperature. It was found, for example, that surface carbon may cover surface sulfur and, consequently, on heating the latter suddenly appears as a result of the removal of carbon. In this manner the nature of surface sites occupied by various surface species can be characterized. And by monitoring the kinetics specific activation energies may be determined.
Fractional Fringe HCN Laser-Interferometer
Authors: Olsen J. N.
Published: February 2004

An HCN laser-interferometer is reported with better than 1/100 of a fringe phase shift sensitivity at a wave-length of 337 μ. Applied to plasma density measurement this corresponds to electron density line integrals of 3.3×1012 cm−2 or lower. The fractional fringe technique involves sinusoidally driving the reference path mirror in a focused Michelson interferometer; changes in the effective path length alter the relative magnitude of even and odd harmonics in the resultant interferometer signal. Results are shown from application of this diagnostic to the Burnout V plasma.
A Convenient Laboratory Method for Measuring Energy Transfer in Electrical Devices
Authors: Wuchinich David
Published: February 2004

A simple oscilloscope display is described for making power measurements in the laboratory. The method is easily applied and particularly useful to those needing a power measuring tool for a wide variety of electrical waveforms. Tests indicate that such displays are capable of measuring power with an accuracy of 1%.
A Torsion Balance for Magnetic Susceptibility Measurements on Fluids
Authors: Splittgerber A. G. , Gill S. J.
Published: February 2004

A magnetic balance has been developed which utilizes a torsion principle and is particularly adapted to the measurement of magnetic susceptibilities of fluids. Equations are developed for the torque on a disk quadrant suspended in a fluid contained in an inhomogeneous magnetic field, and experimental determination of fluid magnetic susceptibilities from torque measurements is described.
A Cold Electron Source Suitable for Mass Spectrometry
Authors: Sprouse J. F. , Jackson K. M. , Raju T. A. , Testerman M. K.
Published: February 2004

An electron emitting source, which operates at ambient temperature, has been developed for instrumental applications including its use for electron emission in an ion source of a mass spectrometer. By the proper generation of a high resistance micron size gap in an electrically conducting tin oxide film, electrons will be emitted at the region of the gap. When the tin oxide film gap is located at the edge of the inner diameter of a very short length of capillary tubing, electron emission of 100 to 200 μA can be typically achieved with 300 V potential placed across the gap. Power consumption for the operation of this device usually remains below 300 mW. If the capillary tubing is made longer and the electrons are made to traverse the length of the capillary bore, a collimated electron beam will emerge at currents appreciably less than above with a diameter equal to the bore of the capillary. If the gap in the tin oxide film is located down in the bore of the capillary, the application of the operating potential will cause the electrons to emerge at one end while an ion current proportional to the pressure in the system comes out the other end.
Feedback Control of Proportional Counter Gain
Authors: Lampton Michael
Published: February 2004

A technique is described for stabilizing the gain of a gas proportional counter system. A feedback signal is derived from an auxiliary calibration counter, which controls the high voltage applied to the detectors. Theoretical speed and accuracy limitations are discussed. Performance of an actual system is described.