bluuebunny/crossref_metadata_2025 huggingface dataset:
Modification to enhance the beam current of a simple ion gun
Authors: Dove D. B. , Molzen W. , Johnson G.
Published: March 2003

An ion gun has been modified to operate in a continuously pumped mode, in which gas is leaked directly into the ionization region, and the vacuum system is pumped to ∼10−7 Torr Ar by a helium cryopump. A milling rate of 3.8 Å/sec was obtained for SiO2 using 2 keV Ar ions. Sample to gun distance was 5 cm. This may be compared with the rate 0.8 Å/sec, obtained when operating in a static vacuum of 5×10−5 Torr Ar.
Simple optical detector for measuring production rate and local velocity of drops
Authors: Dunn W. E. , Chao B. T. , Clausing A. M.
Published: March 2003

An optical detector is described that has been used in measurements of the production rate and equivalent-spherical diameter of water drops produced at the tips of glass capillaries and their local velocity during free fall. Velocity measurements agree well with published data.
High-temperature thermodynamical studies by a mass spectrometry device for measurements using multiple effusion cells
Authors: Chatillon C. , Senillou C. , Allibert M. , Pattoret A.
Published: March 2003

A device is described to facilitate direct comparative measurements of vapor pressures with multiple effusion cells attached to a mass spectrometer, particularly for the reproducibility of mechanical repositioning of the cells and the ionization conditions of the molecular beam in the ion source. Measurements show that with this device this method can be applied satisfactorily to the determination of thermodynamic activities in high-temperature systems.
Novel technique for MOS pulse capacitance measurements in C(V) and C(t) mode
Authors: Bräunig D. , Richter G.
Published: March 2003

For the purpose of MOS doping profile evaluation and generation time constant analysis a pulse capacitance measurement setup has been developed. The principle of operation consists in the capacitance of MOS varactors tuning the resonant frequency of a parallel resonant circuit. The range of capacitance measurement is 0–1000 pF, corresponding to the MHz range. First the pulse voltage ranges from 0 to ±100 V, and second the resolution of time ranges from 1 msec to 100 sec. So MOS-doping profiles as well as transients of capacitance are available. The accuracy of capacitance measurements is better than 0.1%. Output of data is done by punched tape for subsequent evaluation on a desk calculator.
Background current subtractor for the detection of transient signals in kinetic spectrophotometry
Authors: Whyte D. Andrew
Published: March 2003

In real-time kinetic spectrophotometry the background current signal due to the analyzing light beam must be backed off to enable the sensitive detection of the superimposed transient signal. Methods employing filters or amplifiers in the signal path have restrictions in their frequency response so that not all signals of practical duration from a few nanoseconds to a millisecond can be measured with one system. This note describes a current subtraction technique which isolates the subtraction circuit from a direct, low-impedance path between the photomultiplier and a wide-band oscilloscope, thereby imposing no significant frequence limitation on the measurement of transient signals.
Gas absorption cell photometer for rocket observations of local interstellar helium
Authors: Freeman Jay , Bowyer Stuart , Paresce Francesco , Lampton Michael
Published: March 2003

A photometer sensitive at the 584-Å line of HeI, incorporating a helium-gas absorption cell, has been developed. The helium is confined at a pressure of 0.2 Torr between thin metal foil broad-band ultraviolet filters. The cell contains sufficient helium to absorb 584-Å radiation scattered from atmospheric helium. The ratio of fluxes seen with cell full and cell empty provides a valuable datum for fitting models of the local interstellar medium, which is independent of solar 584-Å flux, interstellar helium density, and photometer sensitivity.
High-resolution imaging x-ray detector
Authors: Kellogg E. , Henry P. , Murray S. , Van Speybroeck L. , Bjorkholm P.
Published: March 2003

We describe an x-ray detector using microchannel plates as a photocathode surface and imaging photoelectron multiplier, and a crossed wire grid as a two-dimensional position-sensitive detector. The position resolution is σ=10 μ. The crossed wire grid consists of 100-μ-diam wires on 200-μ centers. Position sensing is accomplished by electronic interpolation to 1/20 of the wire spacing. The quantum efficiency of the microchannel plates varies from 29% at 0.28 keV to 5% at 3 keV. This detector will provide second-of-arc x-ray imaging in the focal plane of the 342.9-cm focal length grazing incidence telescope now being prepared for the HEAO-B observatory. By addition of suitable photocathodes, it can be used for single-photon imaging light detection in uv, visible, and near ir as well. In all cases, it gives a very low dark counting rate, allows timing of individual events to 1 μsec or less, and can handle counting rates up to 104 sec−1.
Precise wavelength calibration of a pressure scanned flat Fabry–Perot interferometer
Authors: Woerner R. L. , Greytak T. J.
Published: March 2003

A precise method for calibrating the wavelength scan of a pressure swept flat Fabry–Perot interferometer is presented. A second Fabry–Perot is used to measure changes in the refractive index of the gas which sweeps the interferometers.
New cell for Raman spectroscopy of molten alkali nitrates containing superoxide or peroxide ions
Authors: Kawamura Kazutaka , Okada Isao
Published: March 2003

A new cell for Raman spectroscopy of molten alkali nitrates containing superoxide or peroxide ions is described. The melt is hung from a spiral cone of platinum wire taking advantage of the high wettability of the alkali nitrate melt. This design is tested in practice and found to perform well.
Swept-amplitude square-wave generator for liquid crystal measurements
Authors: Hottinger W. , Kmetz A. R.
Published: March 2003

Measurement of liquid crystal electrooptic characteristics with improved accuracy and greatly reduced setup time is facilitated by a simple circuit, comprising a CMOS bilateral switch and calibrated high voltage operational amplifier. This circuit generates a swept-amplitude square wave having no damaging dc component by chopping a ramp used to drive the recorder x axis.
Gain-switching amplifier for compression of optical radar return signals
Authors: Spinhirne J. D. , Reagan J. A.
Published: March 2003

A circuit for a gain-switching amplifier that has been used for accurate compressional amplification of lidar return signals is presented. Gains of the amplifier vary from unity to over three decades, and bandwidths is over 2.5 MHz. Gain stages switch and settle to 1% in less than 1 μs with small transients. The design utilizes monolithic LSI circuits rather than discrete componnets and may be readily modified to suit varying applications.
Transient analyzer with logarithmic time base
Authors: Austin R. H. , Beeson K. W. , Chan S. S. , Debrunner P. G. , Downing R. , Eisenstein L. , Frauenfelder H. , Nordlund T. M.
Published: March 2003

Many transient phenomena extend over more than two orders of magnitude in time. Such processes are most efficiently observed with systems that possess logarithmic time bases. A digital analyzer is described that records smoothly and in one sweep transient processes over more than eight orders of magnitude in time. A typical sweep covers the time range from 2 μsec to 5 min.
Pulsed microsecond high-energy electron beam accelerator
Authors: Martin T. H. , Clark R. S.
Published: March 2003

Electron beams delivering up to 60 kA at 1.5 MV with pulse durations of 0.5–1.5 μsec were obtained by connecting a low-inductance Marx generator directly across a vacuum diode. Beams with up to 44 kJ and conversion efficiencies up to 51% from Marx energy into electron beam energy were obtained.
Use of varistors to produce single high-current pulses
Authors: DeSilva A. W. , Pechacek R. E.
Published: March 2003

A current pulse closely resembling a half-sine wave may be produced by an LRC circuit in which the resistance is a voltage-dependent resistor (varistor). A simple analysis of this circuit is given, and curves are presented to aid in the design of such circuits. A comparison is given between predictions of the analysis and a circuit used to produce the 350-kA pulse that drives the magnetic field coils of a plasma cusp containment experiment.
Calibrated ’’four-color’’ x-ray microscope for laser plasma diagnostics
Authors: Seward F. , Dent J. , Boyle M. , Koppel L. , Harper T. , Stoering P. , Toor A.
Published: March 2003

Four quartz, orthogonal, cylindrical mirror pairs, two of which are coated with nickel, image the x-ray emission from laser fusion targets on hard film with a magnification of 3. K-edge filters used in conjunction with the mirror pairs permit us to take simultaneous pictures in four energy bands between 0.7 and 3.5 keV. We have measured microscope resolution, mirror reflection efficiency, and film sensitivity and used them to deduce the absolute emissivity and spectral characteristics of various laser fusion targets. This instrument is now used routinely for studying laser-generated plasmas at Lawrence Livermore Laboratory.
Improved apparatus for thermophysical measurements on liquid metals up to 8000 K
Authors: Gathers G. R. , Shaner J. W. , Brier R. L.
Published: March 2003

An apparatus is described for making thermophysical measurements on liquid metals up to 0.4 GPa and 8000 K. Metal samples are resistively heated on a submillisecond time scale along an isobar. Techniques for measuring enthalpy, specific volume, electrical resistivity, and temperature are discussed with a critical evaluation of the accuracy and limitations of each measurement.
High-resolution stepping motor drive
Authors: Layer Howard P.
Published: March 2003

A digital sine–cosine stepping motor drive has been constructed which decreases the rotational step size by a factor of 31. This system improves the smoothness and resettability of the motor and retains the conventional slew speed and accuracy.
Quantum-limited near-infrared vidicon camera system
Authors: Sandford M. T. , Gow C. E. , Jekowski J. P.
Published: March 2003

A television camera system utilizing an RCA C33020H, S-1 photocathode, electrostatic intensifier tube fiber optically coupled to an RCA C21145 SIT vidicon has been constructed and laboratory tested. The 40-mm-diam I-SIT tube assembly is cooled with dry ice to −40 °C, and the commercial Cohu video preamplifier is maintained at +15 °C with a dc heater. The camera integration unit incorporates a target preparation cycle to linearize the SIT tube target response at low light levels. The camera head operates with a four-position filter wheel controlled by an integration logic unit. Hughes model 639 scan converters or an Ampex disk unit allow real-time comparison of data frames taken with different filters. Data frames are recorded on video tape for later analysis. The camera obtains ∼300 TV-line resolution frames in 1 min integration with highlight irradiance 1.4×10−13 W/cm2 at λ=10 830 Å. Signal-to-noise ratio is limited by the shot noise from the S-1 intensifier photocathode in laboratory tests and by the sky background in astronomical or geophysical application. Astronomical observations show that the camera successfully detects the CIT infrared sources and easily images the Orion nebula in He I λ=10 830 Å light.
Comment on resistance thermometry bridges
Authors: Tausch Peter J. , Newrock R. S.
Published: March 2003

An improvement in the accuracy and sensitivity of the ac Kelvin bridge of Zair and Greenfield is reported. In their bridge a ratio transformer is inserted in the bridge arms to allow direct measurement of the ratio of two germanium resistance thermometers. The resistance of the transformer windings adds to the resistance of the bridge arms, degrading the accuracy of the bridge. We have isolated the transformer from the bridge arms using voltage followers, which allows the use of lower valued resistors in the bridge arms, thus improving the sensitivity of the bridge.
Plastic ENDOR cavity for studies of biological compounds at 2 K
Authors: Van Camp H. L. , Scholes C. P. , Isaacson R. A.
Published: March 2003

We report the design and fabrication of a plastic helium temperature EPR–ENDOR cavity with provision for easy insertion and removal of large frozen biological samples. Representative ENDOR and 100-kHz field modulation amplitudes, attenuations, and helium boil-off rates have been measured with the cavity immersed in liquid helium.
Modification of a Van de Graaff ion source to accelerate metal elements
Authors: Oona H. , Bickel W. S.
Published: March 2003

Large currents of metallic ions can be extracted from a radio-frequency ion source by fabricating a section of the exit channel from the desired metal.
Simple atomic or molecular beam intensity modulator
Authors: Hahn Stefan , Radecki Karol
Published: March 2003

A simple mechanical atomic or molecular beam modulator in the form of a pendulum excited by an electromagnet external to the vacuum chamber is described. A short analysis of the beam waveform with the chosen geometry of the pendulum slit is given. Experimental results are briefly described.
Fast-acting high vacuum valve for atmospheric sampling
Authors: White Franklin E.
Published: March 2003

A valve is described which, when opened, will provide an unobstructed sample flow by moving away from the gas volume being sampled. The valve is electrically operated, bakeable, and provides a helium-tight seal.
Quantitative schlieren densitometer employing a neutral density wedge
Authors: Ahlborn Boye , Humphries Christopher A. M.
Published: March 2003

In this schlieren system the probing laser beam is attenuated by a neutral density wedge (instead of the usual knife edge) so that the intensity is proportional to the deflection angle, which in turn is proportional to the density gradient. Time integration of the attenuated probe beam intensity yields the absolute refractive index variation across moving objects. The device is tested by measuring the density jump across a Mach 9 shock wave.
Operation of a 1P28 photomultiplier with subnanosecond response time
Authors: Beck G.
Published: March 2003

The parameters governing the time response of an RCA 1P28 photomultiplier are investigated, and special circuitry for optimum time response is described. Photomultiplier performance is extensively evaluated with respect to application in flash photolysis and pulse radiolysis. The output signal rise time achieved is 360 psec for a light impulse and 540 psec for a step function over a linear range extending to an anode current of 8 mA.
Automatic digital microwave hygrometer, model II
Authors: Stokesberry Daniel P. , Hasegawa Saburo
Published: March 2003

A ’’ruggedized’’ microwave hygrometer which requires no moving parts in the basic measurement method is described. It is designed to measure atmospheric humidity over the vapor pressure range 3–7400 pascals (Pa) (0.03–74 millibar).
Microwave resonator probe for localized density measurements in weakly magnetized plasmas
Authors: Stenzel R. L.
Published: March 2003

A simple diagnostic tool for performing spatially resolved density measurements in a large, weakly magnetized, low-temperature plasma is described. The principle is based on a microwave technique to determine the cold plasma dielectric property ε=1−ωp2/ω2, where ωp is the electron plasma frequency. A parallel-wire quarter-wavelength resonator is immersed into the plasma, the resonance frequency (ωres≳ωp) is measured and the density derived from the simple relation ωp2=ω2res−ω2res(ε=1). In contrast to the familiar cavity resonance shift method, the present method is suited for localized density measurements. The spatial resolution is comparable to the size of the resonator (2-mm width×8 mm length, fres=7.45 GHz). The microwave technique is largely independent of sheath and thermal effects and is thus more reliable than probe measurements in nonuniformly rf-heated magnetoplasmas. A comparison with independent density diagnostic tools is presented and additional applications are pointed out.
New method of gripping hard, thin, flat tensile specimens
Authors: van der Kuur J. H. , Parr W. E.
Published: March 2003

A new method for gripping hard sheet tensile specimens suitable for use in laboratory or ’’hot-cell’’ facilities is described.
Counting statistics for nonnegligible dead time corrections
Authors: Lucke Robert L.
Published: March 2003

If a detecting system records N counts in T seconds, with each recorded count followed by a dead time τ, the statistical variation in N is ±N1/2/(1+Rτ) (not just ±N1/2), where R is the true rate of occurrence of events. The value of R inferred from this experiment is subject to a statistical error of ΔR/R=±N1/2. This equation is accurate as long as N1/2/Rτ≫1.
Fast, high-current pulse generator with variable amplitude and width
Authors: Armstrong D. R. , Katzir A. , Yariv A.
Published: March 2003

A simple pulse generator, providing continuous variation of current amplitude (0.1–35 A) and pulse width (100–700 nsec) is described. This pulser has been used for operating injection lasers at repetition rates up to 5 kHz.
All quartz optical cell of constant diameter for use in high pressure studies
Authors: le Noble W. J. , Schlott R.
Published: March 2003

A simple optical cell is described for photochemical or spectrophotometric experiments under pressure. The cell, basically a syringe with optical windows at each end, is made entirely of quartz; the sample is not in contact with plastic or metal parts. Since the cylindrical sample space has a variable, self-adjusting length and a constant diameter, no compressibility corrections are required.
Method to detect volume flows in the nanoliter range
Authors: Wiedner Günther
Published: March 2003

A method has been developed to detect small volume changes using capacitance measurements between a probe and a liquid surface. The change in capacitance is a measure of the change in distance and hence the volume.
Simple electron beam evaporator for aluminum
Authors: Benndorf C. , Seidel H. , Thieme F.
Published: March 2003

Aluminum surfaces evaporated from Ta or W baskets are partially oxidized. The contamination of the aluminum surfaces could be reduced by electron beam evaporation. The assembly used by us is described in this paper.
Piezoelectric driven Kelvin probe for contact potential difference studies
Authors: Besocke K. , Berger S.
Published: March 2003

A convenient piezoelectric driven Kelvin probe for the measurement of work function changes is described. The probe has a simple construction, is small, bakeable, and can be mounted on any 35-mm-i.d. UHV flange. As the piezoelectric device is inside the vacuum chamber, only one electrical feedthrough is needed for operating the probe. The distance between reference electrode and sample can be varied within ±0.5 mm simply by applying a dc voltage to the piezoelectric device in addition to the ac oscillator-driving voltage, not requiring any mechanical driving and feedthrough provisions. The probe was tested studying the adsorption of O2 on Pt(111). The sensitivity for contact potential measurements is better than 0.1 mV at a response time of 10 sec.
Use of SrTiO3 prisms as dispersive elements in a dye ring laser
Authors: Marowsky G.
Published: March 2003

The dependence of pump threshold and spectral bandwidth on the dispersion and the resonator length of a cw dye ring laser have been experimentally studied. Using strontium titanate prisms of extremely high dispersion (74×10−5 nm−1) a spectral bandwidth of 2 pm was obtained.
Hydrostatic optical cell with glass windows for 25 kilobar
Authors: Whalley E. , Lavergne A. , Wong P. T. T.
Published: March 2003

An optical cell with three glass windows for hydrostatic pressures up to 25 kilobar has been made. Its collecting angle is 13°, and it has been used mainly for Raman spectroscopy. The fundamental Raman spectrum of diamond has been recorded.
Contactless measurement of semiconductor conductivity by radio frequency-free-carrier power absorption
Authors: Miller G. L. , Robinson D. A. H. , Wiley J. D.
Published: March 2003

It is shown that, under suitable conditions, the power absorbed by a thin semiconductor slice in an oscillating magnetic field is accurately proportional to the material conductivity. The magnitude of this power absorption can be used to determine the conductivity by coupling the semiconductor to an amplitude-stabilized marginal oscillator and noting the power needed to maintain the demanded level of oscillation. Instruments of this type have been constructed exhibiting ∼1% linearity over a 100:1 range of sample conductivity, a resolution of ∼1 in 104 and a limiting sensitivity of ∼10−5 mho/⧠. The method may be applied to the measurement of essentially any conducting material from semiconductors to metals.
Computer-based photoelectron counting system
Authors: Matsumoto Gen , Shimizu Hideaki , Shimada Junichi
Published: March 2003

A photoelectron counting system has been constructed for the statistical studies of fluctuating light intensities of a limited duration, where a maximal exploitation of the data on the pulse sequence in a photoelectron pulse train is required to maximize the statistical accuracy of the desired information on the light. The idea that has been adopted here is to store the collected data in the computer memory and to use them repeatedly until complete information is extracted. The performance of the system is demonstrated for He–Ne laser light scattered from a suspension of polystyrene spheres in water.
Technique for measuring the natural angular divergence of ions exiting low-intensity ionization sources
Authors: Brown H. L. , Cross R. H.
Published: March 2003

A technique is presented for measuring the natural angular divergence of ions exiting an ionization source by using a microchannel plate-image intensifier. The technique is applied to low-intensity beams from field ionization sources, although with appropriate modifications the same method could be applied as a general technique.
Digital enhancement of torque magnetometer signals
Authors: Grodski J. J. , Dixon A. E.
Published: March 2003

Torque signals from a metal single crystal in a rotating magnetic field and the corresponding angular position of the rotating magnet, for both directions of rotation, were digitally recorded on magnetic tape at equal time intervals, with a maximum recording frequency of 18.8 data pairs per degree of rotation. The signals included induced, background, and de Haas–van Alphen effect torques. Only the induced torque is an odd function of rotation direction, and enhancement of the induced torque signals is achieved by subtracting the data obtained for one rotation direction from that for the other rotation direction. Computer analysis of recorded data yielded enhancement only if prior correction of each angular reading was performed to take into account the finite compliance of the torque magnetometer. The resulting enhanced rotation diagrams were plotted on a Calcomp plotter. The technique is also useful for continuous recording of anisotropy torque data from weakly magnetic samples, since the induced-torque signals can be cancelled by adding the data from one rotation direction to those obtained from the other direction.
Helium cooling units for X- and Q-band ESR spectrometers
Authors: Cambell S. J. , Herbert I. R. , Warwick C. B. , Woodgate J. M.
Published: March 2003

Two cooling units which have been designed for use with ESR spectrometers are described. A main aim of the designs has been to achieve good cryogenic performance consistent with a relatively simple mode of operation. Both units rely on the continuous flow of helium for their cooling with one unit operating in the range 1.8–300 K at X band and the other covering 4.8–300 K at Q band. The X-band unit has easy top loading access and incorporates a helium reservoir of 0.13-l capacity close to the sample region. This unit relies on two helium flow paths—one to supply the reservoir and the other to draw helium from the reservoir through the sample region. This feature allows sample temperatures of 1.8 K to be obtained and the base temperature to be achieved with a total liquid helium consumption of 1.6 l/h. The temperature stability was ±0.02 K in the liquid phase and ±0.08 K in the gas phase. In the Q-band unit the sample is positioned on the end of the rotatable sample mount and conduction cooled through this mount. The sample is vacuum loaded, and for convenience of sample changing the sample vacuum is separate from the main vacuum. This unit has a helium consumption of 1.5 l/h at 10 K with an overall temperature stability of ±0.1 K.
Velocity spectrometer for particles in the 10-meV to 10-keV range
Authors: Hammer D. , Benes E. , Blum P. , Husinsky W.
Published: March 2003

We have measured the velocity spectrum of a Na beam emerging from a charge exchange source from the thermal up to the 2-keV region. The spectrometer is based on the Doppler-shifted resonance absorption of photons, produced by a tunable single-mode cw dye laser. A sensitivity of less than 100 atoms/cm3 at velocity resolutions of about 70 m/sec in the thermal region and 0.5% at higher energies is achieved. The performance of the spectrometer is discussed. 361
Single peak distortions due to electronic time constants
Authors: Edwards D.
Published: March 2003

A method is described in which various types of distortions of a single peak input into an electronic amplifier with time constant τ are evaluated. Expressions are given for the delay in the peak maximum, peak amplitude reduction, and peak width increase in terms of τ, β—the rate of change of the independent variable, and ΔW—the peak width, and are applicable whenever the distortions are not large (i.e., βτ/ΔW<0.15). It is found that the delay of the peak maximum is, in lowest order of βτ/ΔW, τ sec independent of the input peak parameters. It is further shown that both the peak amplitude reduction and peak width increase are proportional to τ2. The general expressions for the various distortions are evaluated for several specific types of input functions. In particular it is found that a necessary condition for the peak amplitude reduction and peak width increase to be less than 4% is that βτ/ΔW⩽0.1.
Bakeable hollow cathode duoplasmatron ion source
Authors: Schnitzer Rafael , Engesser Ferdinand C.
Published: March 2003

The construction of a relatively simple and inexpensive hollow cathode duoplasmatron ion source is described. This ion source is suitable for prolonged operation and can be readily pumped and baked. 362
Large range digital micromanometer
Authors: Gupta A. K. , Kumar S.
Published: March 2003

A simple large range digital readout micromanometer has been designed and fabricated. The innovative feature is a suitable gear train which transmits the rotational motion of the lead screw to a 5-digit reversible mechanical counter. The digital readout makes the data collection easier, convenient, and less liable to reading errors.
Combined ion implantation–analysis sample chamber
Authors: Peterson G. D. , EerNisse E. P.
Published: March 2003

An ultrahigh vacuum sample chamber for ion implantation and energetic ion beam analysis is described. The apparatus allows any combination of ion implantation, Rutherford backscattering, and ion-induced nuclear reaction analysis on three separate spots on each of 18 different samples without breaking the ultrahigh vacuum. A technique for making sputtering measurements is described which utilizes the versatility of the apparatus.
Low-angle light-scattering apparatus
Authors: Kim Boris F.
Published: March 2003

An apparatus is described which was designed to measure light scattering from the cornea at small scattering angles. This apparatus will measure light scattering at angles from 6° to 15°, while resolving the scattering depth to 200 μm or less.
Broad spectral electromagnetic radiation calorimeter: Centimeters to microns
Authors: Efthimion P. , Smith P. R. , Schlesinger S. P.
Published: March 2003

A specially designed calorimeter is presented capable of measuring total electromagnetic radiated power, in a single pulse mode over the complete spectral range, microwaves to far infrared. The device is assembled in the shape of a pyramid made from thin sheets of graphite absorber, giving it an operating range from centimeter wavelengths to the infrared region with an absorption coefficient of 0.99 at 1.25 cm wavelength. The calorimeter is capable of yielding a linear voltage response from less than 8 mJ up to at least 35 J with an overall sensitivity of 0.05 V/J. The device has the added feature of yielding information on waveguide modes. An example of the calorimeter use is presented.
Viscometer for slurries and suspensions
Authors: Underwood W. M.
Published: March 2003

A viscometer for use with a slurry or suspension was made using a special spindle in a Brookfield viscometer. The design of the sample holder is such that the particles are maintained in uniform suspension by vigorous agitation, but the fluid motion does not affect the viscometer reading. The reading can be converted to absolute units by means of conversion factors derived from the geometry of the spindle and sample holder.
Gridless retarding potential analyzer for use in very-low-energy charged particle detection
Authors: Shyn T. W. , Sharp W. E. , Hays P. B.
Published: March 2003

The theory of the hyperbolic retarding potential analyzer in the electrostatic mode is developed in detail and verified in the laboratory. A monoenergetic electron beam is used for the laboratory investigation. The analyzer (acronym HARP) has advantages over other conventional electrostatic analyzers; among them are less contact potential influence and high throughput because of the symmetry shape of the analyzer. The most useful application of the HARP is in detecting low-energy charged particles. A sample of low-energy particle data obtained in the earth’s ionosphere is given. 360
Electronic system for optical shutter control
Authors: Viljoen H. C. , Gaylord T. K.
Published: March 2003

A versatile electronic system for accurate shutter control in optical experiments is described in detail. Digital and analog circuitry is used to provide automatic timing, exposure control, manual operation, and remote programmability.
Apparatus for measuring the force of gravity on freely falling electrons
Authors: Witteborn F. C. , Fairbank W. M.
Published: March 2003

An apparatus and data analysis technique for measuring the gravitational force on freely falling electrons are described. The measurement required that all forces acting on the electrons be uniform and measurable to about 10−11 eV/m. The electrical force along the axis of the 5-cm-diam, vertical copper tube used in the experiment was found to be about 6×10−11 eV/m±9% when the tube was cooled to 4.2 K. Forces on electrons due to magnetic field gradients were reduced well below the electrical ones by selecting only ground state electrons for measurement. Other forces were reduced sufficiently by careful attention to the vacuum and thermal environment. The absence, at 4.2 K, of much stronger electric fields, which were expected to arise from the patch effect and from differential lattice components, contrasts strongly with measurements of electric fields near metal surfaces made at room temperature.
50-kilobar gasketed diamond anvil cell for single-crystal x-ray diffractometer use with the crystal structure of Sb up to 26 kilobars as a test problem
Authors: Schiferl David
Published: March 2003

A single-crystal gasketed diamond anvil cell of a new design for use on a diffractometer is described. It has achieved hydrostatic pressures of 50 kilobars as determined from the ruby fluorescence shift. The design combines several advantages. Nearly half the area of the Ewald sphere is available without having to remount the crystal. For reflecting planes nearly parallel to the diamond anvil faces, all reflections in the angular range ∼4°⩽ϑ⩽85° can be observed. Alignment of the diamonds, as well as loading and alignment of the sample crystals, is very simple and quick. The diffractometer geometry allows accurate measurements of weak reflections as well as accurate determinations of the x-ray absorption corrections for the cell. The materials of construction are nontoxic except for one diamond mount, a small beryllium cylinder situated so that it is never touched, scraped, or rubbed. As a test problem, the z parameter of antimony has been found to increase linearly from z=0.23357 at 1 bar to z =0.2380±0.0005 at 26 kilobars.
Uncertainty in the sensitivity of thermistor ebullioscopes
Authors: de Oliveira Walace A.
Published: March 2003

Boiling-temperature elevations may be estimated from the ebullioscope sensitivity. Equations to calculate the sensitivity of twin-thermistor ebullioscopes are given. Thermistor calibrations were performed and the data fitted to several equations. The standard errors in the parameters of these equations were calculated and the resulting uncertainty in the sensitivity derived. It is shown that data of moderate accuracy are sufficient to yield sensitivity values with a reliability of 0.3%. Differences in boiling temperatures obtained by this method are capable of a precision which is among the highest reported for ebulliometry.
Single-frequency, atmospheric pressure CO2 laser
Authors: Ernst G. J.
Published: March 2003

In the paper we describe a TEA CO2 laser operating on only one axial mode. The laser resonator is only 15 cm in length. In order to achieve reliable operation for such a small system a special excitation technique has been developed. This technique is described in detail. The main advantages of the system are the absence of a separate uv source and very reliable operation. In order to obtain single axial mode operation the frequency of the mode has to lie close to the central frequency of the transition. A cavity with tunable length was necessary to achieve this. The total output power of the laser is 35 mJ and the time duration of the pulse is 25 ns.
Position sensitive x-ray detector
Authors: Gabriel A.
Published: March 2003

A position sensitive proportional counter is described which shows some novel features in the method of position encoding compared with previous systems. The encoding is done by an inductance-capacity (L-C) line connected to cathode strips, rather than by resistance-capacity encoding (high resistance) using the anode wire. The spatial resolution for a counter length of 8 cm is 0.2 mm (which corresponds to 0.01° for the geometry used here). Counting can be at high rates for indefinite periods.
Dust cloud concentration probe
Authors: Liebman I. , Conti R. S. , Cashdollar K. L.
Published: March 2003

An optical probe was developed to measure dust cloud concentration during the propagation of dust flames or explosions. Principal features of the probe are a miniature light-emitting diode and photosensor in a U-shaped configuration and air jets to keep the windows of the device dustfree.
Apparatus for the measurement of internal friction as a function of frequency between 10−5 and 10 Hz
Authors: Woirgard J. , Sarrazin Y. , Chaumet H.
Published: March 2003

A new torsional pendulum allowing the measurement of internal friction as a function of frequency on a wide frequency range is described. It is shown that both high and low values of Q−1 may be simply obtained by phase lag measurements, at any frequency between 10−5 and 10 Hz. Some experimental spectra, obtained at different temperatures, are shown to illustrate the accuracy of the method.
Driver design for a laser cavity dumper
Authors: Spears Kenneth G. , Larsen James
Published: March 2003

We present detailed schematic diagrams for a cavity dumper circuit suitable for use with a cw dye laser that is mode locked. The dumper frequency is an integral harmonic of the mode-locked frequency and the average output power is monitored to protect the dumper transducer. A fast logic countdown circuit is used to provide synchronization of the 400-MHz dumper pulse with the mode-locked pulse at rates slower than the 100-MHz mode-locked frequency.
Magnetostriction measurements with a recording rotating field magnetostrictometer
Authors: Hoekstra B. , Gyorgy E. M. , Zydzik G. , Flanders P. J.
Published: March 2003

A compact magnetostrictometer has been constructed utilizing a rotating SmCo5 permanent magnet. The signal is detected with a lock-in amplifier at a frequency variable between 2 and 60 Hz. Magnetostriction constants can be recorded at a fixed field as a function of temperature between very low temperature and +250 °C with a sensitivity better than λ≈3×10−8.
Use of a new type of plasma-ion analyzer to determine the hydrogen content of metals
Authors: Daly N. R. , Powell R. E.
Published: March 2003

A pulsed laser has been used to vaporize and ionize very small areas on the surface of materials that contain hydrogen. A thin foil scintillation detector has been used to examine the plasma that expands away from the interaction region. This device has high sensitivity for detecting hydrogen ions and very low sensitivity for heavy mass ions. Its use to determine hydrogen concentrations in materials at low level has been examined. It can also be used to determine energy distributions for hydrogen ions from mixed ion plasmas by the time-of-flight method.
High-pressure optical cell for Raman scattering studies in solid hydrogen
Authors: Stryland J. C. , Till S. M.
Published: March 2003

An optical cell suitable for Raman studies and absorption studies of gases, liquids, and molecular solids is described. The cell, which has been used at temperatures down to 2 K and pressures up to 2 kilobar, was designed with self-sealing sapphire windows whose conical seats were machined directly into the cell wall, thus minimizing the size of the cell and simplifying its construction.
Sealed metal-freezing-point cell for thermometer calibration
Authors: Sostman Henry E.
Published: March 2003

Cells for realizing the pure metal freezing points which are defining or reference temperatures of the International Practical Temperature Scale must be kept from degradation. We describe the design and construction of a sealed cell in which the danger of contamination is virtually eliminated.
High-vacuum sample heater using a Zener diode
Authors: Kyser D. S. , Jones V. O.
Published: March 2003

A commerical 10-W Zener diode has been evaluated as a moderate-temperature sample heater. It is found to be compatible with high vacuum and eliminates the thermal contact problem common to other types. A temperature control system using the diode is described.
Diagnostic probe for intense electron beams
Authors: Nassisi V. , Luches A.
Published: March 2003

A diagnostic probe is described for rise time and current of intense electron beams. The probe rise time is lower than 1 ns and currents of hundreds of kA can be recorded. A coaxial calibration fixture was made with a square-wave pulser to calibrate the probe. Results on its use in an electron beam machine are also given.
Double-pendulum vibration isolator or seismograph
Authors: Lorrain Paul
Published: March 2003

The device consists of a platform suspended by three chains and supporting a short light pendulum whose bob is submerged in an oil bath resting on the floor. The transmissibility curve for the platform is comparable to those of much more elaborate isolators. The transmissibility decreases as the inverse of the frequency squared. One isolator of this type has been in constant use for the past three years.
Rotatable sample holder with voltage readout for low-temperature experiments
Authors: Ashton G. R. , Hsu D. K. , Leisure R. G. , Seiber B. A.
Published: March 2003

A rotatable sample holder suitable for use at low temperatures is described. This holder was designed for continuous wave ultrasonic experiments. The rotation mechanism and the angle sensing mechanism are discussed.
New arrangement for high-intensity 313-nm light
Authors: Ahmed Farid E. , Robb David C. , Hart Ronald W.
Published: March 2003

We describe a new arrangement high-intensity 313-nm light for studies on photolysis of bromodeoxyuridine-substituted DNA. This device was mainly made of aluminum, except for lamp mounts which were of stainless steel. Water, used for cooling and ventilation depending on convection currents, was essential for optimal operating conditions of the lamps. Two high-pressure mercury quartz lamps and two bandpass filters were used for selective passage of 313-nm light. Physical calibration was achieved by using a gas photodiode. Calibration filter sets reduced the intensity of the 313-nm light below the photodiode saturation level. Manufacturers, suppliers, and specifications are given in the text. This device has the advantages of being comparatively inexpensive, easily constructed and used, and producing 313-nm light of high intensity.
Data smoothing using low-pass digital filters
Authors: Kaiser J. F. , Reed W. A.
Published: March 2003

With the increasing use of computer-controlled data acquisition systems which record data in digital form, there has developed a need for techniques which perform a general smoothing process on digitized experimental data. This processing enables the experimentalist to eliminate or greatly reduce the amount of high-frequency noise in order to obtain as accurate and clean representation of the true phenomenon as is consistent with his measurement accuracies. This filtering or smoothing process should be as simple and efficient (least amount of arithmetic per data sample) as is consistent with the experimental situation. The basic concepts of low-pass filters are discussed and four different low-pass filter design procedures are described, each with its own particular smoothing properties. These design procedures give directly the coefficients of a symmetrical weighting sequence having the desired passband width and the desired high-frequency noise rejection. The uses of the filters are illustrated with examples and the fortran code for implementing each of the design procedures is given in an Appendix.
Evaluation of a hydrogen chloride detector for enviornmental monitoring
Authors: Gregory Gerald L. , Moyer Rudolph H.
Published: March 2003

The paper describes a hydrogen chloride detector designed to monitor concentrations of hydrogen chloride gas in the ambient environment. The detector was developed for NASA for use in launch vehicle effluent monitoring. The detector operates on chemiluminescence principles with a lower detection limit of less than 5×10−3 ppm (by volume). The hydrogen chloride in the air sample reacts with a bromide–bromate coating in the inlet tube of the instrument producing bromine. Bromine is then quantitated by chemiluminescent oxidation of luminol. The visible light generated in the chemiluminescent reaction is proportional to the hydrogen chloride concentration of the sampled airstream. The detector’s response to 90% of signal ranges from less than 1 s at 50 ppm to 10 s at 1 ppm. Below about 5×10−2 ppm the response is somewhat slower, of the order of several minutes. Due to the lack of specificity, the detector is most suited to laboratory or field studies where hydrogen chloride is the dominant pollutant, as compared to the interfering species. Interferences include strong acids, acid-forming gases, and halogen gases. Of the interferences investigated the most serious in these groups are hydrochloric and sulfuric acid, sulfur dioxide, and chlorine, respectively. The detector has been in use since 1974 and has been found to be highly portable, rugged, and stable under extreme environmental conditions ranging from aircraft and seacraft operations to desert operations at temperatures above 35 °C.
Ion cycloton resonance spectroscopy: A sensitivity calibration of marginal oscillators as a function of frequency
Authors: Kemper Paul R. , Bowers Michael T.
Published: March 2003

The design and operating characteristics of a circuit suitable for accurate calibration of the frequency dependence of marginal oscillator detectors used in ion cyclotron resonance spectroscopy is discussed. The results of calibration curves determined from this ’’Q-spoiler’’ circuit are compared with an empirical ’’chemical’’ calibration of the marginal oscillator. The excellent agreement between these two methods indicates the Q-spoiler circuit can give accurate relative frequency calibration of the marginal oscillator over the frequency range 100–1000 kHz.
Laser-monitored electrothinner for preparation of ultrathin metal foils
Authors: Spitznagel J. A. , Choyke W. J.
Published: March 2003

Apparatus and techniques are described which allow the preparation of metal foils several square centimeters in area with thickness as small as 2 μm. The foils retain the microstructure of the 25–50-μm-thick starting material and are especially useful in experiments utilizing charged particle bombardment to simulate the effects of fast neutron damage on mechanical, electrical, thermal, and mass transport properties. The thinning rate is controlled by monitoring the transmittance of 6328-Å light passed through the electrolyte. Intermittent specimen rotation, dc voltage pulsing, and periodic adjustments in electrolyte composition permit reproducible thinning rates with point-to-point variations in foil thickness smaller than 20%.
On interfacial tension measurement with a spinning drop in gyrostatic equilibrium
Authors: Manning C. D. , Scriven L. E.
Published: March 2003

Depending on operating speed, gyrostatic equilibrium is not approached closely enough for reliable tension measurement. Flow visualization experiments show that virtually rigid rotation gives way to secondary flows around the drop as spin velocity is decreased. Flows are attributable to a gravity-induced, internal, hydrodynamic shear layer, to a misalignment-induced Taylor column, to externally excited inertial oscillations, and to mass transfer effects. Bizarre shapes of ultralow tension drops are probably caused by these effects, which should be avoided by design or operation of the instrument. Relevant criteria are given.
Measurements of noise on an electron beam
Authors: Dixon R. D.
Published: March 2003

A technique for observing the noise on an electron beam is presented. The technique involves calculating the Fourier line spectrum from data in the form of x-ray intensity as a function of time. The results show that noise on the beam is observable in this manner and that the noise associated with the beam parameters (voltage and current) changes as the parameters change.
Low-temperature magnetoresistance of a Speer carbon resistance thermometer
Authors: Thompson J. R. , Thomson J. O.
Published: March 2003

The influence of an applied magnetic field on the resistance of a frequently used low-temperature sensor is described. The fractional change in resistance is negative and follows a simple ’’universal curve’’ up to ∼10 kOe, above which it saturates. The temperature range studied is 0.05–0.012 K, for fields of 0–19 kOe.
High-sensitivity magnetic susceptometer employing superconducting technology
Authors: Philo J. S. , Fairbank W. M.
Published: March 2003

A magnetic susceptometer of very high sensitivity and precision has been developed using superconducting technology. Measurements show this instrument has a volume susceptibility sensitivity (in SI units) of Δκ=±9×10−12, and a precision of 0.0001% of the diamagnetism of a typical substance such as water. The capability of measuring magnetic changes during fast reactions in solution has also been demonstrated. System design and measurement techniques are described. The magnitudes and frequency spectra of the noise sources in this type of instrument are analyzed and compared with measured performance.