bluuebunny/crossref_metadata_2025 huggingface dataset:
Calibration of a Continuously Scanning Bridge Circuit Using On-Line Data
Authors: White John J.
Published: February 2004

Several related methods for determining the calibration formula of a continuously scanning bridge circuit using on-line data are analyzed and discussed. High-resolution resistance thermometry requires a sensitive, accurate conversion of off-balance voltage measurements to resistance measurements. The objective is to properly determine the relation R = f(V,RB,Ci), where V is the bridge output-voltage, RB is a balance resistance, and the Ci are unknown coefficients that depend on RB and other fixed circuit parameters. Linearization to the form R = RB + C1(RB)V can yield a fairly accurate conversion from V(t) to R(t). If Ṙ (t) or higher derivatives are required, linearization leads to systematic errors and a more sophisticated method is needed. From the analysis of three techniques for determining corrective terms, we conclude that parameterization of a model for the bridge circuit is the most satisfactory procedure. An empirical, self-consistent method is useful if the circuit model is unknown or extremely complicated. Calibration data from a high-resolution specific-heat experiment were used to test the various methods.
A Desorption Cryostat for Experiments from 1.5–120 K
Authors: Naugle D. G. , Adair T. W. , Maddox J. E.
Published: February 2004

A large desorption cryostat particularly suited for measurement of the properties of cryogenic materials between 1.5 and 60K is described. In the difficult range above 20K temperature control and uniformity remains excellent. For measurements above 20K either hydrogen or helium may be used as the adsorptive. The temperature range of the cryostat may be extended to 120K with the use of nitrogen as the adsorptive.
Simple Methods For High-Resolution Scanning of Laser Beams And Alignment of Small Spatial Filtered Beams
Authors: Ems Stephen C. , Marshall Thomas R. , Gucker Frank T.
Published: February 2004

A 50-μ glass filament from a fiber-optics bundle, bent at 90° near the lower end and fastened to an adjustable support, proves to be a better light pickup than the usual pinhole aperture for high-resolution scanning of a laser beam. Scans of a 50-mW laser beam were used to develop a spatial filter combined with a short-focus collimating lens which yields a uniform, Gaussian-shaped beam with no increase in size.
Design of an Ideal Digital Correlation Computer
Authors: Asch R. , Ford N. C.
Published: February 2004

We describe the design of an ideal digital correlator we have built. An essential feature of this design is a three-bit real time multiplication scheme.
A High-Angle Tilting Stage for the 650 kV Hitachi Electron Microscope
Authors: Bouchard M. , Worthington W. L. , Jurica D. J. , Swann P. R.
Published: February 2004

A new tilting stage has been developed for the Hitachi 650 kV electron microscope. The design allows specimen tilting of ± 30° in any direction and can be inserted with no modifications to the microscope.
Mirror with Adjustable Radius of Curvature
Authors: Bin-Nun E. , Dothan-Deutsch F.
Published: February 2004

The surface of a uniformly loaded, simply supported plate is used as a mirror in an unstable laser resonator. The design of mirrors of this kind is discussed.
Detection of Large Water Clusters by a Low rf Quadrupole Mass Filter
Authors: Lin Sin-Shong
Published: February 2004

A quadrupole mass filter with a radio frequency of 650 kc was used to detect large clusters in supersonic water jets. Numerous water cluster ions in the form of H(H2O)n+, where n = 1 to 180 corresponding to mass 19 to 3241 amu, are observed.
Micropowered Water Activated Switch Using Capacitive Sensing
Authors: Rikoski Richard A. , Newfeld Stewart
Published: February 2004

A water activated switch using a capacitance transducer as one element of an RC phase shift oscillator is described. When water enters a sensing chamber, its electrical capacitance increases, driving the circuit into oscillation. The oscillations are detected and used to trigger an external circuit. Designed around a micropowered integrated circuit, the special advantages of this system are low standby current and freedom from false triggering caused by water spray or mist. The device works equally well for salt or fresh water.
Target Bonding (For Sputtering)
Authors: Terhune Charles
Published: February 2004

This Note describes a bonding method for the joining of targets used for rf sputtering to target holders. The use of a low vapor pressure, low melting point bonding medium results in a strong, reliable bond applicable to a wide range of materials.
Large Area Focusing Collector for the Observation of Cosmic X Rays
Authors: Gorenstein P. , DeCaprio A. , Chase R. , Harris B.
Published: February 2004

A large area focusing x-ray collector constructed for a sounding rocket is described. The instrument consists of nested reflecting plates that are curved slightly in one dimension to form a set of parabolas with a common focus. An array of plates such as the one in the sounding rocket focuses a parallel beam of x-rays to a line. The reflecting surfaces are commercial float glass with an evaporated metallic coating such as gold or nickel. With a gold coating the effective area of the rocket collector is about 250 cm2 for 0.3 keV x rays and about 150 cm2 at 1.2 keV. Its angular resolution is a few arc minutes and field of view is about ±0.75° (full width at half maximum). The collector performed successfully during a sounding rocket flight.
Electron Spin Echo Envelope Spectrometry
Authors: Blumberg W. E. , Mims W. B. , Zuckerman D.
Published: February 2004

A system is described for recording the envelope of electron spin echoes and for obtaining the superhyperfine splitting of the electron resonance interval from the form of the envelope. The envelope modulation property on which this system depends is summarized briefly, the microwave system and logic systems used to record the envelope are described, and the problems encountered in making a Fourier transform of the envelope in order to derive the superhyperfine frequencies are discussed. The system was set up in order to make measurements on unoriented glass-like samples. Some results obtained with samples of this type are shown.
A Capacitor for Use at High Pressure and Low Temperature
Authors: Costantino M. S. , Silverman H. L. , Daniels W. B.
Published: February 2004

A system that is capable of dielectric permittivity measurements in liquids and solids in the temperature range 10–300 K and at pressures to 11 kilobar is described. A brief discussion of some experimental data and sources of error is included.
The Rotating Heat-Pipe Oven; A Universal Device for the Containment of Atomic and Molecular Vapors
Authors: Hessel Merrill M. , Lucatorto Thomas B.
Published: February 2004

A new type of heat-pipe oven has been developed that uses centrifugal force as a return mechanism for the condensed vapors in contrast to capillary return forces for the conventional heat-pipe oven. Since this new oven is no longer limited to materials that wet wicks, it can be used to contain any material that does not react with the walls of the containing vessel. We describe the operation of this oven with sodium and InI even when the InI is solid. Spectroscopic and laser applications of the ``rotating'' heat-pipe oven are discussed.
Construction and Operation of a Heatable Substrate
Authors: Hines William A.
Published: February 2004

The physical characteristics of a substrate are very important in determining the structure of any thin film of an evaporated material which is deposited upon it. In particular, the substrate temperature is very influential in determining whether the material condenses in the form of a continuous film or distinct, isolated particles. For this purpose, a heatable substrate which is simple, inexpensive, reusable, and capable of temperatures up to 350°C is described here.
Rotating Sample Magnetometer for Diamagnetic Susceptibility Measurements
Authors: Hudgens Stephen J.
Published: February 2004

A rotating sample magnetometer capable of measuring the relative room temperature magnetic susceptibilities of two 1 g samples with a reproducibility of Δχ/χ=0.02 is described. The sensitivity of the instrument is Δχ=± 3 × 10−9, or ∼ 1% of the volume susceptibility of a typical diamagnetic solid. The magnetometer signal waveform is electronically processed by either a commercial signal correlator or by a gated double integrator of our own design.
Dynamic Pressure Transducer System for Pulsed Plasma Flow Diagnosis
Authors: York Thomas M. , McKenna Kenneth F. , Michels Charles J.
Published: February 2004

The response characteristics of high sensitivity piezoelectric pressure transducers suitable for use in the plasma flow induced by megawatt-level electric discharges in low density (<1 Torr) gases are described. The uniquely designed probe records the initial impingement of a large magnitude total pressure pulse (104N/m2 with 30μsec duration), followed by the flow of primary interest with order-of-magnitude smaller signals (103N/m2 for 400 μsec). Effects relating to probe and support accelerations, blast shielding and probe heating are evaluated and accounted for in a probe system with a sensitivity of 40 V/atm.
Deposition of Sulfur Films for X-Ray Filters
Authors: Leighton W. H.
Published: February 2004

Sulfur films up to 20 μ in thickness have been vacuum deposited on 0.025 mm beryllium foil for use as x-ray filters. The films are more adherent and uniform than chemically deposited films, and much simpler to prepare than the sulfur-polystyrene sandwiches described previously. Substrate cooling is required to obtain uniform, reproducible fine-grained films. An apparatus is described that provides a simple means of cooling substrates and also minimizing sulfur contamination of the vacuum pump.
A Film System for Flash X-Ray Diffraction Studies of Shock-Compressed Materials
Authors: Mitchell A. C. , Johnson Quintin , Evans L.
Published: February 2004

A film system for flash x-ray diffraction studies of shock-compressed samples is described. This system consists of three elements: A blast cassette; a film assembly; and a small shock-wave generator. The blast cassette contains baffles, slits, and plastic x-ray windows to prevent shrapnel penetration of the film holder and destruction of the film. High-speed film is used in conjunction with a ZnS fluorescent screen. Shock pressures of 85–340 kilobars can be generated in typical samples by a miniature explosive lens and booster weighing about 100 g. Tailoring of the sample pressure is achieved through the selection of the base plate and explosive material. We have used this system to obtain diffraction data in the two-theta range of 15°−50° using Cu and Mo x-radiation.
A Spectroradiometer for Field Use
Authors: Leamer R. W. , Myers V. I. , Silva L. F.
Published: February 2004

The configurations and operation of a field spectroradiometer (Exotech model 20-B spectroradiometer) that measures the intensity of incident and reflected radiation from 0.37 to 2.52 μ and emitted radiation from 2.76 to 13.88 μ are described. The instrument was built by Exotech Inc. from specifications and plans developed by the USDA. Exotech contributed many engineering concepts based upon knowledge of the theory involved. The instrument consists of two systems, each made up of an optical unit and a control unit. One system covers the spectral range 0.37–2.52 μ; the other system covers the spectral range 2.76–13.88 μ. The optical units of the two systems mount side-by-side on a tiltable base mounted on an aerial lift truck. Separation between the objective lenses is about 30 cm to minimize parallax. The systems may be operated separately or in the tandem, boresighted mode. The control units are mounted in a camper-type equipment van and are connected to the optical units by 60 m of armored cable. Preamplifiers and auxiliary electronics in the optical units are designed to operate without picking up interferences over this length of cable. The entire system is designed to operate in an outdoor environment. Provision has also been made for photographic annotation of field data setups.
Energetic Ion Beam Source and Free-Stream Beam Diagnostic Techniques
Authors: Stenzel R. L. , Ripin B. H.
Published: February 2004

A steady state, dc discharge, electrostatically focused ion beam source with permanent magnet multipole confinement is described. The ion beam is low density, nb [inverted lazy s] 108 cm−3, low divergence, θ [inverted lazy s] 1°, energetic, Vb≤5 kV, and is suitable for investigating ion beam-plasma interactions. Ion beam speed and species are determined either by modulating the beam and analyzing the resulting free-streaming perturbations or by a pulse and time-of-flight technique. The amplitude of the free-streaming signal is enhanced in the electron cyclotron harmonic passbands due to the decreased dielectric function of the background plasma. Two beam-plasma instabilities, the electron cyclotron drift instability, and an instability at the lower hybrid frequency are observed using this ion source.
Image Pickup Tube for Coherent Optics
Authors: Kanazawa Y. , Eto Y.
Published: February 2004

When the image reconstructed from a Fourier transform hologram is picked up with a conventional image pickup tube, such as a vidicon, interference fringes which turn out to be an obstructing component are generated in the face plate of the image pickup tube. In this article, the causes of these fringes are discussed and three methods for removing them are described. These experiments include: (1) use of a fiber optics face plate, (2) use of a ground surface face plate, and (3) attaching of a special-shaped glass block. These three methods are equally effective, but the first two methods require the manufacture of a special image pickup tube and therefore the last method is deemed most useful. The reduction of the effects of the interference fringes by means of a multiple object beam hologram is also discussed.
Thermal Expansion Coefficient Measurements of Specularly Reflecting Samples
Authors: Spetzler Hartmut , Heflinger Lee O. , Wuerker Ralph F.
Published: February 2004

A simple method is described for obtaining the expansion coefficient of specularly reflecting objects. The method photographically records the interference pattern of laser light reflected from the object. The moire beat between interference patterns recorded at two temperatures gives the expansion coefficient. When limited to smooth round objects, the technique is insensitive to rigid body motions of the specimens.
A Precision Sampling Circuit
Authors: Yamashita Mikio
Published: February 2004

A sampling circuit is described, which provides clean output pulses free from transients with excellent linearity and stability in the dynamic range of 0.2–10.0 V. The circuit has been incorporated in a threshold detecting device, allowing the performance of the device to be improved.
Mechanically Operated Air Admittance Valve with Timing Facilities
Authors: Eilander J.
Published: February 2004

A description is given of a simple and cheap air admittance valve for automatic air inlet into turbomolecular pumped UHV system upon (controlled or uncontrolled) power cutoff. The valve is operated by a mechanical timer switch which can be adjusted such that dry air admittance starts just before the turbo pump has finished its pumping action completely. Thus, contamination of the UHV compartment by oil vapor from the turbo pump and other active gases from the force vacuum is prevented and quick reobtainment of vacuum in the 10−9 Torr region after system restart becomes an easy matter.
Cavity for High Temperature Experiments in Electron Paramagnetic Resonance
Authors: Grosmaitre C. S. , Roy J. C.
Published: February 2004

A vacuum oven inside a microwave cavity for high temperature experiments is described. Temperatures up to 800°C can be easily obtained while the cavity stays at room temperature.
A New Conductive Coating for Channel Electron Multipliers
Authors: Gerhardt U.
Published: February 2004

A high resistivity coating develops at the surface of a special glass when heated in a hydrogen atmosphere at about 470°C. The glass contains 85% heavy lead oxide glass and 15% Bi2O3, and is ideally suited to prepare channel electron multipliers.
Automatic Calorimetry in the 3–30 K Range. The Specific Heat of Copper
Authors: Martin Douglas L. , Bradley L. L. T. , Cazemier W. J. , Snowdon Robert L.
Published: February 2004

Automatic data acquisition is by means of a slightly modified version of a hard-wired system described previously (Martin and Snowdon, 1970) combined with an on-line minicomputer which controls the calorimeter heating rate and computes temperature and specific heat. The new cryostat, calorimeter assembly, and adiabatic shield control are briefly described. Experiments to verify the accuracy of germanium thermometry with the automatic ac bridge are detailed. Operation of the system is illustrated by results on pure copper which show a standard deviation of 0.3% (mostly due to temperature scale defects rather than inherent lack of precision) and agree well with the Copper Reference Equation below 20 K but above this temperature agree more closely with the results of Cetas, Tilford, and Swenson [Phys. Rev. 174, 835 (1968)].
A Rocket-Borne Instrument for the Measurement of Nighttime Atmospheric Densitites
Authors: Quessette Jacques-Alain , Ajello Joseph M.
Published: February 2004

A rocket instrument has been designed for the determination of nighttime atmospheric densities by means of resonant scattering. By illuminating the atmosphere with an intense parallel beam of light at the resonant wavelength of an atmospheric gas and observing the back scattering, it is possible to determine either relative or absolute atmospheric densities. In particular, the measurement of atomic hydrogen densities from 70 to 110 km will be considered.
A Simple Method for Electronic Division in Modulation Spectroscopy
Authors: Sasaki Yoshiro , Hamaguchi Chihiro , Yamada Masayoshi , Nakai Junkichi
Published: February 2004

An electronic servo system has been developed to perform the I 0ΔR / I 0R division in modulation spectroscopy measurements, which is operable under variable extraneous incident light intensity. Response faster than that of the mechanical servo system is easily achieved in the electronic servo system.
A Rugged Silver-Silver Chloride Electrode for Field Use
Authors: Corwin Robert F. , Conti Ugo
Published: February 2004

A rugged silver-silver chloride electrode has been developed and used successfully in a variety of field applications. The electrode housing is made of 2.54 cm o.d. clear acrylic plastic rod. The filling solution is 2.7M potassium chloride saturated with silver chloride, and contact with the external medium is made through a porous ceramic rod. Results of laboratory and field tests measuring the response of the electrode to chemical, thermal, mechanical, and electrical disturbances are presented.
High Speed Single Event Sampler
Authors: Baldis Hector A. , Aazam-Zanganeh Jamshid
Published: February 2004

In this paper is described a circuit that has been developed for recording fast single electronic events. The single event signal is sampled with a time resolution of 2 nsec and stored in a memory bank after all the samples have been digitized.
Improved Space Focusing of Polar Diatomic Molecules in a System of Quadrupole and Hexapole Fields
Authors: Everdij J. J. , Huijser A. , Verster N. F.
Published: February 2004

This paper describes a method for the compensation of the spherical aberration of a polar diatomic molecule in an electrostatic quadrupole field. This perturbation, caused by the higher order terms in the Stark effect, limits the opening angle of the lens and is compensated by an electrostatic hexapole field placed in the middle of the quadrupole field where the influence is the strongest. A detailed mathematical treatment of the motion of a molecule in a composite lens is given and the calculations show that the transmission of the lens increases by a factor 5. Preliminary experiments confirm the theoretical predictions.
A Digital Microwave Frequency Lock System
Authors: Woo Lecon , Levy Donald H.
Published: February 2004

The design and performance of a digital microwave frequency lock system is described. The system locks a microwave source to a fixed intermediate frequency oscillator by digitally comparing the down-converted microwave frequency to the IF. The microwave source may be frequency swept at a variable rate whose precision is the same as the reference oscillator, and the microwave source retains the long term stability of the fixed frequency reference oscillator even when the microwave frequency is being swept. The digital frequency lock system is compared with an analog phase lock system, and it is concluded that the digital frequency lock is superior with respect to capture range and reliability, identical with respect to long term stability, and inferior with respect to spectral purity.
A Low Noise, Very Low Power Charge Sensitive Amplifier for Space Applications
Authors: Evangelisti F. , Orsi G. , Ventura G.
Published: February 2004

A charge sensitive preamplifier (CSP) followed by an amplifier with pulse shaping networks (PSA) of single differentiation-single integration type (SDSI), designed to be used with uncooled silicon nuclear particle detectors aboard space vehicles, is described. Noise performance at 5 μsec SDSI time constant was measured to be 0.91 keV FWHMSi with a slope of 43 eV/pF. The total power drain is 42 mW at + 12 V supply. The amplifier is stabilized against supply voltage and temperature variations.
An External Voltage Sweep for Field-Regulated Magnets
Authors: Glarum S. H.
Published: February 2004

Modifications which permit control and sweeping of Hall-effect magnetic-field regulators by an external voltage source are presented. A four-quadrant multiplier is used as a modulator. Cost is nominal, installation and alignment straightforward, and no loss in performance with respect to stability, linearity, and accuracy is introduced for most applications.
Dual Beam Flash Photolysis System for Studying Transients
Authors: LeBlanc J. C. , Fenster A. , Whillans D. W. , Herbert M. A. , Johns H. E.
Published: February 2004

A dual beam flash photolysis system for studying the kinetics of transient species is described. The system has high sensitivity and is capable of detecting species absorbing 0.1% of the analyzing light with a noise level equivalent to 0.02% of the analyzing light. This high sensitivity has been achieved by producing an intense (6.2×1018 photons in the uv) flash of short duration (0.9 μsec to decay to half height and 3 μsec to decay to 1%). We have also used an analyzing lamp which is intensified to 30 times its normal brightness and a long path (27 cm) through the solution. The photomultipliers have been adjusted to be linear up to 10 mA so that the potentialities of the intensified analyzing beam may be exploited. Spurious transients produced in the water have been reduced by careful distillation of the water followed by further purification through the photolysis reaction of the flash itself. The configuration of the apparatus and components is described in detail.
An Efficient Continuously Operated Cold Trap
Authors: Timsit R. S. , Kiang A. K. C.
Published: February 2004

A liquid nitrogen cold trap 140 cc in volume, constructed from glass and suitable for continuous operation is described. When the trap is operated automatically the liquid nitrogen consumption remains low at about 2 liters per day.
An Apparatus for Measuring Fluid Stirring Temperatures
Authors: Miguel A. San
Published: February 2004

An apparatus utilizing quartz thermometer probe as a fluid stirring agitator is described.
A Matching Circuit and Bucking Current Stabilizer for a Detector in an ESR Spectrometer
Authors: den Boef J. H.
Published: February 2004

In this Note an active electronic matching circuit is described enabling one to make a proper ac and dc adjustment for a point-contact diode. It is also possible to stabilize the bucking current to ensure constant detector sensistivity.
An Improved Apparatus for Interfacial Tension Measurement by the Ring Method
Authors: Bond W. D. , Bischoff K. , Sprunger E.
Published: February 2004

An apparatus for measuring both the interfacial tension by the DuNouy ring method and the film elongation is described which uses a stepmotor to raise or lower the interface past the ring.
A Dynamic Bridge Measurement for Lossy Systems
Authors: Tick P. A. , Johnson D.
Published: February 2004

A new dynamic bridge for measuring the capacitance of lossy loads has been designed and constructed. Initial testing has demonstrated 10% accuracy over a range of frequencies from 1 to 105 Hz in loads having loss tangents which can exceed 104.
A New Differential Calorimetry Technique
Authors: Jones R. W. , Knapp G. S. , Veal B. W.
Published: February 2004

A new differential technique to measure the ratio of specific heats of two samples (and their addenda) to 0.25% or better is described. The technique has been used in the temperature range 1.5–400 K to give specific heats to an accuracy of 0.50%. The unique feature of the technique is a heat link placed between the samples as an aid in maintaining them in a near-equilibrium state.
Calorimetry of Small Samples with Low Thermal Diffusivity
Authors: Novotny V. , Meincke P. P. M.
Published: February 2004

A system for measuring small specific heats of samples with low thermal diffusivity is described. A simple method for treating data obtained using discontinuous heating when temperature drifts and thermal nonequilibrium are large is introduced. The measurements on a copper sample deliberately in poor thermal contact with a calorimeter provided a test of the system and data handling.
Cold Trap Fractionation as an Organic Analysis Technique
Authors: Crosmer W. E. , Thomas N. C. , Tsang P. H. S. , Duckett R. J.
Published: February 2004

A highly simplified, alternate approach to the gas chromatograph-mass spectrometer has been developed. In this approach, a low temperature trap replaces the entire GC portion of the combined GC-MS instrument and no carrier gas is necessary. Using the cold trap technique, the sample is first passed into a chilled trap. Depending on the trap temperature, many compounds are condensed or trapped out (most at − 196°C). Those which are not, such as helium, neon, and nitrogen, pass through the trap directly into the spectrometer for analysis. Then the trap is programmed to increase in temperature at an appropriate rate. This allows evaporation (or sublimation) of the trapped materials according to the specific vapor pressure characteristics of the compound, providing some temporal separation between constituents. These partially resolved components are directed to the MS as they evolve from the trap. The total efflux pressure changes in the ion source are analogous to the GC output, and positive identification can be performed within the limits of detection of the spectrometer. The technique has been demonstrated to have a broad application in the field of organic analysis.
Single Coil Series Resonant Circuit for Pulsed Nuclear Resonance
Authors: Clark W. Gilbert , McNeil John A.
Published: February 2004

This paper presents a description of and design optimization criteria for a series resonant single coil system suitable for use in pulsed nuclear magnetic or quadrupolar resonance. The design is adaptable to the frequency range 1–100 MHz, and permits both efficient use of transmitter power and signal reception with a high signal-to-noise ratio. An example of the design of a system to operate at 10 MHz is worked out and compared against the ideal case. An active damping circuit to speed the recovery following an rf pulse is also discussed.
Flexural Frequencies of Cylindrical Gravitational Wave Detectors
Authors: Gram R. Q. , Douglass D. H. , Tyson J. A.
Published: February 2004

Calculated flexural frequencies of right circular cylinders are presented as a function of diameter-to-length ratio for a Poisson's ratio of 0.333. The uniform spacing between modes observed for large length/diameter vanishes for wavelengths comparable to the diameter, with some adjacent modes changing order. Experimental verification of the results is presented.
A Soft X-Ray Source for Photoelectron Spectroscopy
Authors: McLachlan A. D. , Leckey R. C. , Jenkin J. G. , Liesegang J.
Published: February 2004

The physical design of a cylindrical x-ray source, producing Al Ka radiation (1486.6 eV) for use with a spherical photoelectron spectrometer, is presented. Design requirements, such as maximum efficiency and maximum intensity of characteristic radiation for minimum bremsstrahlung, are included in the presentation. The electron trajectories from filament to anode are calculated for various geometries. A brief description of the calculations, involving a numerical solution of Laplace's equation in cylindrical coordinates is given. Experimental evidence is presented to confirm the adaptation of these calculations in the design of the source.
An Instrument for Real-Time Determination of Polar Electrojet Position and Current Parameters
Authors: Sellers Bach , Hanser Frederick A. , Vancour Roger P.
Published: February 2004

A portable instrument for on-site determination of polar electrojet position and intensity has been assembled and used during auroral magnetic disturbances at Ft. Churchill, Canada. The instrument provided data for determination of optimum launch time for rockets used to study auroral phenomena associated with the disturbances.
Susceptibility Measurements at High Frequency: A Versatile and Sensitive Apparatus
Authors: Boschi A. , Bucci C. , Vignali C.
Published: February 2004

Susceptibility measurements, χ′, can be precisely and simply performed in terms of the relative frequency shift (Δν/ν) of a rf self-oscillator, occurring when the permeability of the space is changed by the introduction of the sample. The essential feature is the transfer of the sensitive volume from the inductor to a narrow gap of a ferrite toroid. When Δν is a periodic function, standard frequency modulation detection is employed. The calibration of the apparatus against known diamagnetic and paramagnetic substances indicates a sensitivity Δν/ν0 = 1.6 × 10−8 (which corresponds to a minimum detectable value of the susceptibility per unit volume of 3 × 10−9 emu, accessible with a sample volume as small as 0.1 cm3). It is also shown that the minimum Δν/ν can be further decreased with respect to the experimental condition of the present measurements.
Automatic Data Acquisition and Control of Experiments in a Powder X-Ray Diffractometer
Authors: Gangulee A. , Tomko C. J.
Published: February 2004

The instrumentation of a powder x-ray diffractometer for automatic data acquisition and control of experiments is described. The present system configuration is set up to step-scan preselected intervals in the 2θ range, in preset stepping increments, while operating either in the fixed time or in the fixed count mode. The data can either be stored in punched paper tape and cards, or be transmitted to a computer. At the end of a complete 2θ-scan, one or more experimental parameters can automatically be changed, after which the whole scan is started again.
On the Protection of Solid State Detectors from Mercury
Authors: Hils D. , McGregor I.
Published: February 2004

A method is described to protect encapsulated solid state detectors from mercury vapor. This method is compared with an older procedure which was found to apply to nonencapsulated detectors only.
Improved Transistorization of Varian V-2100B Magnet Power Supply
Authors: Au K. S. , Farmer J. B. , Marshall Alan G. , Sallos J.
Published: February 2004

The eight 304 TL pass tubes in the Varian V-2100B magnet power supply have been replaced with high voltage power transistors. The inadequate protection against high voltage surges in a previous circuit has been corrected, using a fast acting SCR clamp. In addition, further circuit modifications have reduced ripple and thus extended the useful regulating range of the power supply.
A Regulated Filament Temperature Power Supply for Electron Guns
Authors: Wellenstein H. F. , Ensman R. E.
Published: February 2004

Placing the hot filament of an electron gun into one arm of a Wheatstone bridge the resistance and hence the temperature of the filament is kept constant, consequently reducing the electron beam current fluctuations. A complete circuit description is given and the performance of the gun with and without filament temperature regulation is discussed.
Apparatus to Measure Hydrogen Evolution from Corroding Metals
Authors: Thompson C. D. , Hackerman Norman
Published: February 2004

Construction details of an apparatus to measure hydrogen evolution from corroding metals automatically is described. The device has a motor driven rack and piston controlled by a mercury U-tube switch. Sensitivity of 0.2 ml and accuracy of 2% is claimed.
The 10 cm Atom Probe
Authors: Panitz J. A.
Published: February 2004

A novel atom probe is described which can determine the mass-to-charge ratios of all ion species produced during a single desorption event or of individual species at several preselected crystallographic locations during each desorption event. This is accomplished without tip movement in an instrument no larger than a conventional field ion microscope by using a new channel plate photomultiplier detector. Alignment, aiming, and pulse stability problems common to all previous designs have been eliminated. Although the present mass resolution is 4 amu at m/n = 184/3, single isotope resolution, if desired, seems possible.
A Comparison of Two Transient Methods of Measuring Thermal Conductivity of Particulate Samples
Authors: Scott Ronald W. , Fountain James A. , West Edward A.
Published: February 2004

A comparison is made of the line source (LS) method and the differential line source (DLS) method of measuring thermal conductivity of particulate materials in vacuum. The DLS method requires more instrumentation in the measuring circuitry (an additional amplifier and a differentiating circuit), but since it does not require a stable temperature to initiate a test, it does not need a sample temperature control system. DLS tests can be taken as the temperature in the samples is rising from liquid nitrogen temperature to room temperature. This eliminates the practice of extrapolating thermal conductivity over this large temperature range. Also, the advantages of reduced test time, data reduction time, and small sample temperature rise enable the experimenter to take about 7–12 DLS tests in the time of 2 LS tests. Test data from the two methods agree very well. The DLS method gives slightly lower conductivity values for the small particles tested. The difference between the two methods is smaller at low temperatures than at high temperatures. The agreement in the large particle tests at room temperature is good. An error analysis shows that the LS and the DLS have total relative errors of 18 and 20%, respectively.
Absolute Determination of Change in Magnetic Susceptibility Due to Electron Spin Resonance
Authors: Zuckermann B.
Published: February 2004

An automatic compensation method is applied to ESR measurements, and the corresponding addition to a standard spectrometer permits the measurement of the resonant magnetic susceptibility independently of microwave power level, magnetic field modulation amplitude, amplifier gain, etc. A calibration of the instrument is described. Using this, one obtains an accuracy in the measurement of the susceptibility of approximately 0.1%.
A Cell for Optical Studies of Low Temperature Fluids
Authors: Verbeke O. B. , Gielen H. L. , Bruneel M. T.
Published: February 2004

An optical cell, which has been used for studies of liquefied gases at temperatures from 78 to 350 K and at pressures up to 10 MN/m2, is described. The cell features a reusable, metal, C-type sealing ring.
Effect of Longitudinal Magnetic Field on the Performance of a Channel Electron Multiplier
Authors: Hashimoto Masashi , Hayashi Tomonao
Published: February 2004

The effects of a longitudinal magnetic field on the performance of a channel electron multiplier are studied and the gain variation due to the magnetic field is explained by considering hopping and gyrating motion of electrons.
A Spatial Fourier Analyzer for Plasma Studies
Authors: Ogata Atsushi , Adati Keizo
Published: February 2004

A device is constructed for plasma studies which calculates the Fourier coefficients and power spectral densities of spatially periodic signals and displays their time variations on oscilloscopes with large signal bandwidth of dc to 10 MHz.
A Superfluid-Tight Coaxial Coupling
Authors: Flint Ephraim B. , Hallock Robert B.
Published: February 2004

A coupling which facilitates the union of RG-174 to microcoaxial cable is described. Features of the coupling involve a superfluid seal to the microcoax and electrical connections which do not require special handling.
Modification of a Quadrupole Mass Filter to Accept a Channel Electron Multiplier
Authors: McMillan M. R. , Coplan M. A.
Published: February 2004

A commercial quadrupole mass filter has been modified to accept a channel electron multiplier. The modification is relatively simple and inexpensive. The resulting mass filter is very sensitive (gain > 107) and compact.
Constant Logarithmic-Decrement Controller for Maintaining a Constant Temperature Differential
Authors: Kitchens T. A.
Published: February 2004

A potentiometric circuit is described which can be used to control the temperature or other physical variables affecting two matched resistors in the circuit. The control is such as to hold the ratio of the difference of the resistances to one of the resistances constant.
Positive Displacement Gas Circulating Pump
Authors: Stewart Thomas B.
Published: February 2004

The design and operation of a simple gas circulating pump is described. This pump incorporates a piston with an O-ring seal and hollow glass check valve and is capable of circulating gases over a large pressure range, 769–1 Torr. The pump could conceivably operate at lower pressure by changing the check valves. During pumping operations the leak rate was less than 1 μ (for 400–500 cycles). The maximum pumping speed is about 110 cm3/sec although greater pumping rates can be obtained from larger pumps. The pump is designed so that it can be easily disassembled for cleaning.
An Adiabatic Twin Calorimeter Using Electron Beam Heating
Authors: Steffen H. , Wollenberger H.
Published: February 2004

An adiabatic twin calorimeter is described in which sample and dummy are heated by bombarding them with 5 keV electrons. The electron beam coming from outside the adiabatic jacket is directed alternatingly to sample and dummy. The heating power generated in the sample is varied by changing the hold-up time of the beam at the sample with respect to that at the dummy. The required measurement of the ratio of heating powers in sample and dummy is replaced by a time measurement. The calorimeter is capable of measuring the ratio of the heat capacities of sample and dummy with a resolution better than 10−3. By measuring the specific heat of nickel and comparing the result with literature data the systematic error of the calorimeter was found to be less than 1%.
Stabilized and Calibrated Michelson Interferometer
Authors: Küpper F. P. , Mastop W. J.
Published: February 2004

The integral value of the refractive index of a plasma in a toroidal device is measured by a stabilized Michelson interferometer with a HeNe gas laser (λ = 0.63 μ) as light source. A calibrated phase modulator enhances the accuracy with which small phase shifts are measured, and automatically indicates phase shifts exceeding π/2.
Further Improvements in the Berg-Barrett X-Ray Camera
Authors: Liang S. J. , Pope D. P.
Published: February 2004

The Berg-Barrett technique has been used extensively for the observation of imperfections in crystals. A further developement of the Berg-Barrett camera has been achieved which has two significant advantages over previous designs. First, this design provides a totally enclosed camera which completely prevents the operator's exposure to X-ray radiation without decreasing the diffracting area of the crystal. In certain cases a large area of the crystal surface gives no Bragg reflection due to large tilt angles in the substructure or because an off-zero layer reflection is being used. A scanning attachment has been built which helps overcome these difficulties.
A Differential System for Magnetic Probe Measurements
Authors: Ignat D. W. , Heym A.
Published: February 2004

Use of an integrated circuit differential amplifier and passive RC integration provides magnetic probe signals of large bandwidth untroubled by electric pickup.
Peak Height Measurement System for Pulsed Laser Experiments
Authors: Swofford Robert L. , McClain W. M.
Published: February 2004

A peak height measurement system (PHMS) is described which detects and measures the peak height of several simultaneous pulses with peaks as narrow as 1 nsec. Jitter in the input pulses produces no error in the measured heights. A detailed description of the peak detector circuit is given, and an experimental setup is presented for determining two-photon absorption cross-sections with PHMS. It is expected that this system will see application to numerous experiments which use pulsed lasers.
A High Precision Scanning Ratio Calormimeter for use Near Phase Transitions
Authors: Buckingham M. J. , Edwards C. , Lipa J. A.
Published: February 2004

Near a phase transition the rate of change with temperature of the specific heat and the thermal relaxation time can both become very large with resulting difficulties in the measurement of specific heat by conventional methods. This paper describes a calorimetry method specially adapted to overcome these difficulties, which has proved successful for measurements near the critical point of fluids.
Modified Poppet Valve for Quasisteady Gas Injection into Vacuum
Authors: Morimoto Sinji , Kuriki Kyoichi
Published: February 2004

A fast acting valve has been developed for quasisteady gas injection with a short rise time. The valve has a structure which is a combination of the conventional poppet and piston valves. From gas density measurements by a fast ionization gauge, the rise time was found to be limited by the expansion of the gas front. The minimum rise time is 70 μsec for a specific geometry of gas exit. The design criteria are also discussed.
A Sensitive Magnetometer and its Application to Nuclear Magnetic Thermometry in the Compound AuIn2 at Ultralow Temperatures
Authors: Andres K. , Wernick J. H.
Published: February 2004

A method is described with which small magnetic moments of samples can be measured using a superconducting transformer and a commercial flux gate magnetometer. It is applied to nuclear magnetic thermometry in the temperature range from 1.7 mK to 0.5 K using the intermetallic compound AuIn2, which is particularly suitable for this purpose.
Computer Controlled NMR Spectrometer for Two-Pulse Experiments
Authors: Wright David A. , Rogers Max T.
Published: February 2004

A general method has been developed by which two-pulse experiments may be largely automated by interfacing a minicomputer to an NMR pulse spectrometer. The necessary pulses and time delays are supplied by the computer and the interface converts these to the levels necessary for the rf oscillator and power amplifier of the spectrometer. Values of the relaxation times (T1, T2, T1ρ) are extracted from the collected data by data analysis subroutines which perform a least-squares fit of the data to an exponential decay. Deviations of the data points from the least-squares slope are displayed to permit an immediate visual check for experimental errors. The advantages of the simple pulse sequences are retained while their disadvantages, particularly inefficient data collection for very long or very short relaxation times, are greatly reduced. The lower limit of relaxation times which may be measured by this method is about 100 μ sec.
An Analysis of the Transmission Properties of Spherical Electrostatic Electron Spectrometers
Authors: Kemeny P. C. , McLachlan A. D. , Battye F. L. , Poole R. T. , Leckey R. C. G. , Liesegang J. , Jenkin J. G.
Published: February 2004

A detailed analysis of the transmission properties of low-energy spherical electrostatic electron spectrometers employing preacceleration or preretardation is presented, which shows that the transmission efficiency of such instruments is not necessarily related inversely to electron energy nor directly to analyzer pass energy. A prescription, which enables observed spectra to be corrected over a wide energy range for intensity variations resulting from instrumental effects, is provided, and a detectable shift (≤ 0.1 eV) in the apparent position of electron lines under certain conditions is predicted. The theory is applied to the design and performance of two spherical photoelectron spectrometers employing ultraviolet and soft x-ray sources. The analysis may readily be extended to other forms of electrostatic spectrometers employing preacceleration or preretardation.
Time-of-Flight Measurements of Metastable State Lifetimes
Authors: Kaslow David E. , Zorn Jens C.
Published: February 2004

A time-of-flight method for measurement of the lifetime of metastable molecules is described. The method is applicable to a molecules in several different metastable excited states. As compared to methods used previously, the method has the advantages that it does not require selective excitation or quenching of the different states; moreover, it does not require a determination of the relative populations or velocity distributions of molecules in the excited states. The feasibility of the method is demonstrated with a measurement of the lifetime of the a 1πg state of N2.
Method for Plotting Work Function Distribution of a Thermionic Emitter
Authors: Haug R. , Lebas J.
Published: February 2004

A plotter of the work function distribution of a thermionic emitter has been designed with analog circuits connected to a plane diode. In the best conditions, a full width at half-maximum (FWHM) of 160 meV has been measured. The apparatus has been tested with a plane tantalum emitter.
A High Speed Microprogrammed System for Generation and Acquisition of Signals
Authors: Zornig J. G. , McDonald J. F.
Published: February 2004

A high speed microprogrammed system has been constructed to perform the synthesis and recording of high frequency nonrepeating pulse signals. The system can drive an analog device with arbitrarily designed waveforms and record individual pulses from several sensors in return. The present design operates at frequencies up to 1.5 MHz and can accept pulse durations of up to 16 000 samples. Accuracy is limited by the availabe ADC and computer word size and is presently 8 bits (0.3%). A primary advantage of the design is the reliance to the maximum extent on the hardware of a small general purpose computer. Very little more external hardware is required than the ADC, DAC, and multiplexer. Waveforms are read directly from and stored directly in the host computer core memory. This enables the maximum flexibility in the design of service programs for particular experiments. At present the system is used for an experiment in which a fast pulse input is to be adjusted adaptively in real time based on the measured outputs of a system.
Direct Reading Mobility Indicator
Authors: Howes M. J.
Published: February 2004

Performance evaluation studies of a simple instrument which indicates directly the carrier mobility in extrinsic semiconductor samples of small aspect ratio is presented. Experimental results on Ge, Si, GaAs, and InP samples and encapsulated microwave devices (transferred electron oscillator structures) indicate a maximum variation of ±5% as compared with measurements using the Hall effect.