bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase Transients in Pulsed NMR Spectrometers
Authors: Mehring M. , Waugh J. S.
Published: February 2004

When a square wave modulated rf voltage is applied to a tuned probe in an NMR spectrometer, the effective transverse magnetic field in the rotating reference frame changes direction as it grows and decays. The resulting deviations in the nutational behavior of the spins from naive expectations are typically small, but may lead to important cumulative errors in experiments employing long pulse trains. These errors can be made to vanish by very accurate tuning of the probe circuit to its free ringing frequency ωr [not to ω0=(1/LC)½] and by providing suitable coherence between the rf carriers and the timing of pulses.
A Simple Circuit for Continuous On-Line Evaluation of Noise
Authors: Steinitz R. , Grinberg J. , Bar V. , Seidman A.
Published: February 2004

Measurements of noise and application of these measurements are discussed. A simple circuit has been developed, giving a continuous evaluation of noise at a moment as close as possible to its occurrence, rendering it suitable for feedback purposes.
Construction and Operation of a Double-Discharge TEA CO2 Laser
Authors: Pan Yu-Li , Bernhardt Anthony F. , Simpson Joe R.
Published: February 2004

We have operated a double-discharge transversely excited atmospheric pressure (TEA) CO2 laser with a Marx bank system at high output energies and efficiencies over a large discharge volume. The typical laser energy output is approximately 17 J/liter at an efficiency of 24% and a pulse-to-pulse variation of less than 10%. The parameters that govern the operation of the system are discussed.
Effects of Temperature Scale Differences on the Analysis of Heat Capacity Data: The Specific Heat of Copper from 1 to 30 K
Authors: Holste J. C. , Cetas T. C. , Swenson C. A.
Published: February 2004

Specific heat data for copper from 1 to 30 K which were published previously have been reanalyzed using five different experimental temperature scales which could be associated with the germanium resistance thermometer used in these experiments. Three of the scales which were derived from a common set of paramagnetic salt thermometer data give comparable results with maximum differences of 0.3% that vary slowly with temperature. The other two scales, one of which was derived from gas thermometer measurements and the other from the NBS-Acoustic scale, show systematic oscillatory differences from this smooth behavior. These differences can be understood analytically in terms of the absolute temperature differences and the differing sizes of the degrees for the scales. Smooth copper specific heat values which are based on the magnetic thermometer smoothed scales are given for the 1–30 K interval. A comparison of these results as analyzed in terms of T58 and other published data suggests that the major differences which exist in the 1–4 K region cannot be ascribed to thermometry but probably are due to differences in samples or techniques.
A Tunable NMR Spectrometer for the vhf-uhf Range
Authors: Gottlieb Albert M. , Srivastava Vishnu C. , Heller Peter , Rubin Lawrence G.
Published: February 2004

A nuclear magnetic resonance detection system for the vhf-uhf frequency range is described in detail. It consists of a radio frequency bridge built around a coaxial hybrid T. The sample is contained in a tunable L-C resonator coupled with an adjustable impedance transformer to a 50 Ω airline. The system is thus fully tunable over wide ranges of frequency from a remote location. For example, using a two-turn copper ribbon coil, the range 270–710 MHz is covered: The system may be set to any desired point in this range within a few minutes. The system was used with standard lock-in detection to obtain the absorption derivative ∂χ″/∂H. An absolute noise measurement was made at a radio frequency of 300 MHz and an audio detection frequency of 200 Hz. This showed that the root mean square noise at the lock-in output was between four and seven times the value corresponding to the rf Johnson noise at the bridge. The system was used to observe a proton resonance in a Bitter type solenoid at 125 kG.
A Method to Increase the Sensitivity of a Microbalance by Electric Fields
Authors: Bracher J.
Published: February 2004

By superimposition of an unstable system, realized by electric fields, the stable system of a torsion microbalance can be continuously brought near to the state of labile equilibrium without the need to touch the delicate balance. The increase of the sensitivity could be demonstrated by a detection of light pressure. Detection limit: 4×10−11 N/cm2.
A Simple Goniometer for the Berg-Barrett X-Ray Technique
Authors: Arnstein G. M. , Shapiro M. I. , Raghuram A. C.
Published: February 2004

The design of an integrated goniometer with a camera assembly for obtaining Berg-Barrett x-ray micrographs is described. A simple procedure for taking a Berg-Barrett micrograph using this instrument is also described. A Berg-Barrett micrograph taken in an annealed zinc single crystal is presented to illustrate the quality of the micrographs that can be obtained with this instrument.
Molecular Beams of Short Lived Radioactive Nuclides. II. Preparation of Beams by Wall Reactions
Authors: Grover J. Robb , Lilenfeld Harvey V.
Published: February 2004

To prepare beams of atomic astatine-217 (T½=0.032 sec), gaseous H217At is conducted into a specially shaped platinum tube held at 1000°C. Experiments for identification of the beam are described, and intensity data are given.
A Simple Mass Spectrometer of High Scanning Range
Authors: Bracher J. , von Rohden H. J.
Published: February 2004

A mass spectrometer is described using two sets of deflection plates and the ac voltage of a voltage controlled generator. The frequency of the generator could automatically be changed over a range of 1–100 by the voltage of the time base of an oscilloscope, on which the collector current was displayed. This frequency change allows a scan of mass numbers from 10 to 105.
Improvement of a Homodyne Electron Spin Resonance Spectrometer
Authors: Mehlkopf A. F. , Smidt J. , Tiggelman T. A.
Published: February 2004

By means of a filter in the leakage branch of a homodyne ESR spectrometer, stabilization of the klystron on the resonance frequency of the cavity is still possible at a cavity power level of about 10−10 W.
MTS Modification for Acoustic Emission Testing
Authors: James Darrell R. , Benson David A. , Belland Robert E.
Published: February 2004

A simple, inexpensive modification to a closed loop servo hydraulic testing machine was made which eliminated virtually all machine noise with respect to acoustic emission monitoring.
Channeltron Gain in Magnetic Fields
Authors: Hahn Yu Bong , Hebner Robert E. , Kastelein Daniel R. , Nygaard Kaare J.
Published: February 2004

The gain and total count rate of electron channel multipliers depend strongly on applied magnetic fields. We report experimental results for Channeltrons operated in magnetic fields of up to 300 G, and find that the applied voltage must be increased to about 4000 V to maintain a sufficiently high gain. Slightly higher count rates are observed if the magnetic field is parallel to the plane of the Channeltron, as compared to perpendicular to that plane.
A Vacuum Atmosphere Actuated Linear Motion Device for the Preparation of Samples Free of Surface Contamination
Authors: Koehler Conrad F.
Published: February 2004

A simple small bore air cylinder has been used effectively in vacuum to provide automatic linear motion for an air-tight enclosure as an aid in the preparation of samples free of surface contamination.
A Bright Continuum Source for the Vacuum Ultraviolet
Authors: Hildum J. S. , Cooper J.
Published: February 2004

A versatile source of a bright continuum extending from the visible down at least to 1100 Å with effective temperature greater than 35 000 K is described.
An Economical High Vacuum Water Cooled Sputtering Cathode Assembly and Feedthrough
Authors: Guttensohn A. E.
Published: February 2004

A very economical high vacuum feedthrough and water cooled cathode pedestal and dark space shield assembly were designed and built in our laboratories without requiring any model shop time and without purchasing any expensive material from the outside. The effectiveness of this design to sputter alloys was verified by x-ray spectrographic techniques. During a typical supttering run 5000 V dc at 150 mA could be handled by this cathode assembly and feedthrough without difficulty. This particular feedthrough design was tested successfully in the 10−7 Torr range.
A Cathode-Anode Configuration for an Abnormal Glow Discharge with Long Term Stability
Authors: Geissler K. H. , Nichols P. A. , Greenwald R. A.
Published: February 2004

Depositions of sputtered cathode material often have a degrading influence on the performance of discharge tubes. A properly designed guard ring system near the cathode can alleviate this problem and permit long term stable operation.
A Frequency Swept Injection Locked Nuclear Induction Spectrometer with Signal Averaging
Authors: Linzer Melvin
Published: February 2004

A frequency sweep injection locking technique, suitable for signal averaging and fast passage studies, has been developed for use with a nuclear induction spectrometer.
Refinements to a Standard LEED-Auger System for the Analysis of Electron Emission at Low Primary Beam Energies
Authors: Skinner D. K. , Willis R. F.
Published: February 2004

Refinements to a basic three-grid LEED-Auger system are described which permit a more detailed analysis to be made of the electron emission from solids at low primary beam energies. This is accomplished by (i) cross modulation of electron gun and analyzer grids for suppression of unwanted signal, (ii) improving the collector efficiency for low energy electrons, and (iii) recording the second derivative of the energy distribution curve.
A High Pressure Optical Cell for Study of Biochemical Solutions
Authors: Papanek Thomas , Fabry Thomas L.
Published: February 2004

This paper will describe the construction and use of an optical cell for spectrographic studies of biochemical solutions under pressures up to 4080 atm. Data from such studies of myoglobin will also be presented. The optical cell described incorporates the following design features: It is a monoblock configuration comprising both a pressure intensifier and an optical portion; the sample contacts only glass and paraffin; the cell interfaces easily with spectrophotometric equipment commonly used in biochemistry; it is relatively easy to operate and survives repeated use; it is constructed of a material not previously used for this application.
A Method for Precise Measurement of the Dielectric Constant of Liquids in a Wide Frequency Range
Authors: Kakimoto Akira
Published: February 2004

A rapid precise method for measurement of the dielectric constant of liquids in a wide frequency range is described. Using a micrometer-controlled electrode in a cell filled with the specimen liquid, the dielectric constant is precisely determined from the micrometer scale to within ±0.2%. Even though the cell is two-terminal, this method is nearly free of the influence of the stray capacitances and the residual inductances of the electrodes or of the leads. It makes possible an accurate measurement at high frequency. Once the micrometer scale calibration has been done, it takes only a few minutes for the measurement. The measured frequency responses of the dielectric constants of several compounds are also shown in this paper.
Rapid Response Flow Microcalorimeter
Authors: Gill Stanley J. , Chen Yeong-jgi (Norman)
Published: February 2004

A flow microcalorimeter with rapid response (20 sec) and high sensitivity (10−8 μcal/sec detectability) is described. The design of the instrument permits easy construction. The operating temperature is determined by a liquid thermostat bath that can be set as desired. Typical test results are described.
A Versatile Method for Digitizing the Information on Oscilloscope Photographs
Authors: Busch G. E. , Jones R. P. , Topp M. R. , Rentzepis P. M.
Published: February 2004

A simple and inexpensive technique is presented whereby the analog data on a photograph obtained in standard oscilloscope experiments may be digitized. The automatic system is much faster than manual digitizing when a large number of data points must be analyzed. It is also versatile enough to allow several levels of sophistication, depending on individual requirements of speed, accuracy, and expense.
A Laser Flash Technique for Determining Thermal Diffusivity of Liquid Metals at Elevated Temperatures
Authors: Schriempf J. T.
Published: February 2004

The laser flash technique has been frequently employed in many laboratories as a relatively fast and easy technique of modest accuracy for measuring the thermal diffusivity of solids at ordinary and elevated temperatures. We have refined this technique and extended it to measurements of the thermal diffusivities of liquid metals. In both solid and liquid metallic specimens we have found, on both experimental and theoretical grounds, that the accuracy of the results is very sensitive to the degree of uniformity of the laser pulse. By introducing appropriate optics between the laser and the specimen we have been able to obtain a very uniform laser pulse and thus considerably enhance the accuracy of our measurements. In particular in measuring the thermal diffusivity of liquid mercury at temperatures from 13 to 300°C the difference between our values and values derived from published results of steady state measurements was never more than 5%. A cinematographic study of the impact of the laser beam on the surface of the liquid mercury was also carried out.
Method for Shock Wave Investigation of Magnetic Material
Authors: Grady D. E.
Published: February 2004

An experimental method developed for investigation of shock induced demagnetization in yttrium iron garnet is reported. The method was found reliable and quite easy to implement. It has the potential of being a useful experimental tool for further investigation of magnetic properties in shock wave studies.
In-Line High Vacuum Conductance Valve for Shock Tubes
Authors: Hickman R. S. , Suitor Jerry W.
Published: February 2004

A simple but highly efficient valve for shock tube evacuation is described. It is constructed as part of the shock tube with a diffusion pump attached beneath. When closed, the valve becomes part of the shock tube. When opened, the shock tube is evacuated to the attached pump. Results are presented to show improved pump-down time and ultimate pressure.
Noise Figure Rating for Marginal Oscillators
Authors: Brooks Rodney A.
Published: February 2004

The concept of noise figure is extended to marginal oscillators, devices which are commonly used in nuclear resonance experiments for detecting small changes in coil Q. This permits the absolute sensitivity of the circuit to be evaluated, without regard to extraneous factors, such as coil Q and sample material. The method is illustrated by applying it to a new FET oscillator built for use in a low temperature nuclear resonance thermometer.
A Measurement of the Fast Luminescent Decays of the MV-50 LED
Authors: Sutton John F.
Published: February 2004

The fast luminescent decay of the MV-50 GaAs doped Si light emitting diode has been studied. The MV-50 provides a fast, inexpensive, bright, and convenient light source for calibration of fast optical timing systems. A simple passive electronic module is described which allows driving the light source directly by a laboratory pulse generator.
Some Comments on Xenon Arc Lamp Stability
Authors: Breeze R. H. , Ke B.
Published: February 2004

The results of stability tests of five different xenon arc lamps are presented. Some comments on arc wander and forced air cooling are given, and such currently established stabilization procedures as current regulation, overfilling of the slit, ``burning-in'' of lamps, and feedback techniques are considered.
A Method for the Control and Measurement of Wire Temperature in Preparatory Anneals on Standard Pt/Pt-10Rh Thermocouples
Authors: McLaren E. H. , Murdock E. G. , Kirby C. G. M.
Published: February 2004

An electric wire annealing arrangement for standard thermocouples is described that incorporates 60 Hz electric current heating with simultaneous measurement and control of the wire temperature to ±10°C in the range 0–1450°C derived from the dc thermal emf (with ice reference) generated in the thermocouple.
An Improved High Pressure Conductivity Cell
Authors: Oliver B. G. , Adams W. A.
Published: February 2004

An improved high pressure conductivity cell which eliminates cracking at the glass-to-electrode seal and which transmits pressure to the liquid in the cell in a unique manner is described in detail. Conductivity measurements on a 0.01 demal aqueous KCl solution show that the cell is reliable up to at least 3000 bar.
An Apparatus for Measuring Quantum Efficiency in Electroluminescent Devices over a Wide Current Range
Authors: Ralston J. M.
Published: February 2004

An apparatus is described which measures quantum efficiency (or power or luminescent efficiency) in electro-luminescent devices. The device test current is pulsed and may be varied over a 100–1 dynamic range. Efficiency measurements are self-normalizing and direct-reading at any test current. Heating effects are minimized by maintaining a low (1 mA) time-averaged LED current. Luminescence is detected using a highly efficient, small volume optical cavity which permits measurements of quantum efficiencies as low as 0.0001% (10−6).
Pulsed Laser Kerr System Polarimeter for Electro-Optical Fringe Pattern Measurement of Transient Electrical Parameters
Authors: Cassidy Esther Christmas
Published: February 2004

Novel electro-optical fringe pattern methods are developed for measurement of transient high voltages and electric fields. Several techniques employing the Kerr effect, a pulsed laser source, and high speed photographic recording equipment are described. Typical fringe pattern results are compared with conventional resistive divider measurements.
A Modification of the Varian HR-60 NMR Spectrometer Probe for Operation at Very Low Temperatures
Authors: Jensen F. R. , Smith L. A. , Bushweller C. H. , Beck B. H.
Published: February 2004

An insert design and probe modification is given which makes it possible to obtain spectra with good spinning and resolution as conveniently at −170°, or below, as can be obtained at 0°. Because of the placement of the pickup coil, the resolution and sensitivity are superior to commercial inserts. At −170° the temperature variation through the sample region is no more than ±0.01°.
Hydraulically Actuated Valve for Very Low Temperatures
Authors: Roach Pat R. , Ketterson J. B. , Kuchnir M.
Published: February 2004

In order to seal off an experimental cell containing liquid He at temperatures down to 20 mK and at pressures up to 25 atm we have developed a valve that is actuated hydraulically by liquid He and which seals repeatedly with a leak rate of less than 10−10 cm3/sec of liquid He II.
A Simple Multiple Spark System
Authors: Wiebelt J. A. , Williamson R. D.
Published: February 2004

A simple multiple spark system is described. This spark system was used to provide two spark discharge light sources for use with Schlieren photography. The spark durations were such that shock waves with velocities up to 520 m/sec could be satisfactorily photographed.
Neutral Pressure Measurements in the Vicinity of a Magnetized Plasma
Authors: Jacquinot J. , Deck C. , Godaert J.
Published: February 2004

We describe a fast pressure gauge which is protected against the parasitic effects induced by a magnetized plasma. The protection techniques include a modulated electron beam, a secondary electron repeller, and a geometrical shielding of the collector against radiation and fast atoms emitted by the plasma. The apparatus has a rise time of 200 μsec and gives a good signal-to-noise ratio for pressures greater than 10−7 Torr when it is located near a dense, hot plasma (n=1013cm−3,T≃100 eV).
A dc X-Ray Fiducial Pulse Generator for Light-Gas Gun Work
Authors: Long J. R. , Mitchell A. C.
Published: February 2004

Interruption of a dc x-ray beam by a projectile has been used to produce a timing pulse for light-gas gun work. A finely collimated x-ray beam from a conventional dc x-ray generator intersects the projectile path at the muzzle. This beam is detected by a detector consisting of a thin NaI(Tl) scintillator, a beam splitter, and two photomultiplier tubes. The projectile, as it leaves the gun barrel, interrupts the x-ray beam; this results in a current drop from the photomultiplier tubes. Associated electronics convert this drop into a single electrical pulse. Response time of the electronics is approximately 3 μsec.
A Time-of-Flight Chemical Accelerator for Low Center-of-Mass Energy Spreads
Authors: Leffert Charles B. , Jackson William M. , Rothe Erhard W. , Fenstermaker Roger W.
Published: February 2004

An apparatus to obtain high resolution of relative kinetic energy for collision experiments in the electron volt range is described. Because it is the center-of-mass system that is important in the interpretation of experiments, energy spreads in both the projectiles and the targets are considered. We achieve high resolution in a primary beam with a time-of-flight technique. The target particles are in the form of a crossed beam. Basically, the scheme consists of observing only those reaction products that are formed in a short range of primary-beam flight times. This means that good resolution may be obtained in spite of any inherent energy spread in the beam. The measured quantity is modeled mathematically to show the effect of the energy spreads that remain. These calculations may be used to arrive at the true velocity dependence of the center-of-mass cross sections.
A One-Dimensional Focusing Critical Angle Refractometer for Mass Transfer Studies
Authors: Beach K. W. , Muller R. H. , Tobias C. W.
Published: February 2004

A focusing critical angle refractometer has been constructed to measure the one-dimensional refractive index profile immediately adjacent to the glass wall of a liquid container. The instrument displays a graphic image of the entire refractive index profile. It is capable of resolving concentration differences of 10−4 M (10−5 refractive index units) and distances of 0.02 mm.
Magnetically Stirred, High Pressure Microreactor
Authors: Cerveny W. J. , Weitkamp A. W.
Published: February 2004

A magnetically stirred, 14 cm3, stainless steel reactor has been developed for studies up to 138 bar and 343°C. It is contaminant-free and it can be easily assembled, disassembled, and cleaned. Construction details are given.
A Low Temperature Baffle for Single Crystal X-Ray Diffraction
Authors: Dernier P. D.
Published: February 2004

A low temperature helium gas baffle has been designed for collecting single crystal x-ray diffraction data below 40 K. The device is easily installed on a General Electric XRD-5 diffractometer with little reduction in freedom of sample rotation. Sample temperatures as low as 10 K have been attained and maintained for several hours using a suitably insulated transfer extension tube.
Laboratory Apparatus for High Temperature Forging under Vacuum or Inert Atmospheres
Authors: Blickensderfer Robert
Published: February 2004

An apparatus was designed, constructed, and used to forge refractory metal specimens at temperatures up to 1900°C under a vacuum or an inert atmosphere. The electrical resistance heater with radiation shielding located inside the vacuum chamber allowed good temperature control. Simultaneously with the forging stroke, the specimen was automatically moved onto the anvil below the heating element, where it was immediately forged. The apparatus has the potential for operation at considerably higher temperatures and for multiple forging blows if required.
Bypass Valve for Liquid Helium Transfers
Authors: Anderson Robert A. , Ginsberg D. M.
Published: February 2004

A simple bypass valve has been designed and used to conserve liquid helium during refill transfers into a cryostat.
Precision Drive Mechanism for Vacuum Use
Authors: Pritchard David E. , Burnham David C.
Published: February 2004

We suggest using small electric motors located inside the vacuum envelope to provide mechanical motion for experimental apparatus in the vacuum system. Potentiometers may be used to sense the position of the apparatus. We describe the construction and performance of a simple servo system using these components that can be set to a precision of one part in 104.
An Improved CW Technique for Measurement of Ultrasonic Attenuation
Authors: Leisure R. G.
Published: February 2004

A technique is described for measuring ultrasonic attenuation by determining the inflectional points of ultrasonic standing wave resonance lines. Results obtained by this technique are compared to those obtained by the pulse echo technique. A suggestion is given for automating the system to make simultaneous measurements of velocity and attenuation
A Technique for Measuring Spectral Emittance
Authors: Birkebak Richard C.
Published: February 2004

A radiometer system is described which allows one to measure directly the spectral emittance of both solid and powdered surfaces. The data logging is automated by interfacing a spectrophotometer with a minicomputer system.
Improved Gearing for Rotary-Vane Attenuators
Authors: Foote William J. , Hunter Ronald D.
Published: February 2004

A WR15 rotary-vane attenuator is modified and driven by a 180:1 precision gear set. This one step drive provides an accurate, repeatable readout resolution 20 times better than that used on commercial attenuators.
A Versatile Substrate Design for LEED and AES Studies in uhv
Authors: Holloway P. H. , Hudson J. B.
Published: February 2004

A substrate design is described that incorporates a single crystal disk into an electrically isolated, electron bombardment heated mount. Electron and photon leakage from the bombarding filament are prevented, and LEED and AES may be used at elevated temperatures. A cold finger, thermally coupled to the mount, decreases the time lost between cleaning the crystal and cooling it to the desired observation temperature. The cold finger also allows observation at temperatures below ambient.
Variable Output Coupling Device for Far Infrared Laser
Authors: Swain David W. , Mix L. Paul
Published: February 2004

A simple output coupler for far infrared lasers is described. The degree of coupling is continuously variable. The device is easily constructed, requires little precision machining, and is easily adjusted.
Hardening of Quartz Optical Contact by Thermal Treatment
Authors: Ghiţă C. , Ghiţă L.
Published: February 2004

A method is presented which provides a good stability of quartz optical contact for the use in the construction of very precise optical cells for differential refractometry and dye lasers.
Spherical Electrical Feedthroughs for High Pressure Vessels
Authors: Benzing W. M. , Jamieson J. C. , Halleck P. M.
Published: February 2004

A new scheme for bringing electrical leads into high pressure gas systems has been developed. The seal is formed by forcing a spherical ball into a hemispherical seat with a layer of plastic film as insulation and sealing material. These seats are trivial to make. Gas pressures as high as 24 kilobars have been held.
The Effect of an Axial Magnetic Field on Boltzmann Temperature
Authors: Corson Bayard R.
Published: February 2004

Measurements of indicated electron temperatures of oxide cathodes at various values of axial magnetic fields show that as the field is increased from zero to a few hundred G there may be a large drop in the indicated temperature. Above this range of axial field the indicated temperature may continue to drop to ≈2430 G. The probable error in repeatability of the measurements is shown to be less than 0.3°.
Mechanical Properties of Very Thin Polymer Films
Authors: Spivack M. A.
Published: February 2004

The uniaxial and biaxial mechanical properties of five thin film polymers have been measured. Parylenes N, C, and M exhibit uniform properties to thicknesses as low as 0.12 μ; the 4.3 μ polyester (Mylar) and the 2.3 μ polycarbonate (Kimfol) show tensile and elongation properties inferior to those measured on thicker sections. Biaxial rupture strengths were found to vary directly with film thickness and inversely with the half-power of the unsupported area. The measured rupture constant is shown to be a function of the tensile strength and ultimate elongation of the material.
A General Technique for the Spectroscopy of Transient Absorbing Species
Authors: Aldrich John E. , Foldvary Peter , Hunt John W. , Taylor William B. , Wolff Ronald K.
Published: February 2004

A convenient routine method for the study of spectra of transient absorbing species produced by radiation is described. The specific example discussed in detail is an addition to the stroboscopic pulse radiolysis system to allow determination of the spectra of transient species after 30 psec or after several nanoseconds. New electronic circuits have been designed to increase the sensitivity and linearity of the detection system. The electronic systems have been carefully evaluated, and the over-all performance of the system is shown by a sample spectrum of the hydrated electron.
The Topografiner: An Instrument for Measuring Surface Microtopography
Authors: Young Russell , Ward John , Scire Fredric
Published: February 2004

A noncontacting instrument for measuring the microtopography of metallic surfaces has been developed to the point where the feasibility of constructing a prototype instrument has been demonstrated. The resolution of the preprototype unit is 30 Å perpendicular to the surface and 4000 Å in the plane of the surface. Inherent noise in the perpendicular direction corresponds to 3 Å or one atomic layer. By using a typical field emitter with radius of 100 Å, an ultimate limit of 200 Å would be expected for the horizontal resolution. Topographic maps of an infrared diffraction grating have been measured in order to demonstrate the performance of the instrument in measuring a well characterized surface. The instrument has been shown to conform to the Fowler-Nordheim description of field emission while spaced at the usual operating distances from the surface. When moved to within 30 Å of the surface, its performance is compatible with Simmons' theory of MVM tunneling. In the MVM mode, the instrument is capable of performing a noncontacting measurement of the position of a surface to within about 3 Å. The instrument can be used in surface science experiments to study the density of single and multiple atom steps on single crystal surfaces, adsorption of gases, and processes involving electronic excitations at surfaces.
Thermoprobe: An Instrument for Determining the Temperature of Opaque, Translucent, and Transparent Surfaces in the Incandescent Temperature Range
Authors: Madjid A. H. , Martinez J. M.
Published: February 2004

An instrument has been developed that is a temperature counterpart of an electrical potentiometer. The apparatus consists of a tantalum vacuum blackbody furnace or an electrically heated tantalum ribbon of accurately known spectral emissivity, as the standard temperature surface, an ``unknown'' surface, the surface temperature of which is to be determined, and a balancing probe with which the surface temperatures of standard and unknown may be compared. The probe, in essence, consists of either a needle or a U-shaped body that can be electrically heated to the desired temperature. The probe carries a thermocouple connected to a null detector near its tip. The thermoprobe is balanced by repeatedly contacting the unknown and by varying its heating current until the null detector reading is unchanged upon contacting the surface. The probe is then switched to the standard surface and the procedure is repeated varying the temperature of the standard this time. Null balance now indicates that standard and unknown have the same surface temperature. The temperature of the standard is determined by using an optical pyrometer. This method of temperature measurement is useful when determining temperatures of transparent and translucent surfaces which cannot be pyrometrically measured, and also in cases where emissivities tend to vary rapidly. The probe was tested on a metallic (Mo, Ta), a sintered oxide (ThO2), and translucent single crystal (NiO) surface. The sensitivity of the probe approached that of a high quality optical pyrometer and it was ±1, ±2, ±1.5 K for the three surfaces in the temperature range between 1100 and 1600 K, respectively.
Levitation and Stabilization of a Single Particle by Use of Negative Feedback
Authors: Harries W. L. , Dimock D.
Published: February 2004

An optical sensing and electrical feedback system is described which will damp out the orbital motion of a particle levitated in a three-phase electric field. This eliminates the necessity of introducing a background gas for this purpose.
Design and Performance of the Lovelace Aerosol Particle Separator
Authors: Kotrappa P. , Light M. E.
Published: February 2004

The Lovelace aerosol particle separator (LAPS) provides a continuous separation of aerosol particles in the micron and submicron size ranges according to their aerodynamic equivalent diameters. This new device uses the principle of centrifugal separation of particles in a spinning spiral duct. The LAPS is essentially a spinning rotor driven by a motor at a desired constant speed. An aerosol sample is drawn into an expanding spiral duct through an inlet at the axis of the rotor and is entrained in a laminar stream of clean air and drawn by negative pressure through the channel. The particles are deposited according to their aerodynamic diameters along a 46.2 cm long collection foil lining the outer wall of the spiral duct and the very small particles on a filter at the exit end of the spiral, thereby providing a continuous separation of aerosol particles in the entire size range of interest. The device is relatively inexpensive, rugged, easy to operate, and can be driven either by an induction-type household motor or by a more elaborate centrifuge drive. It is suitable for separating aerosol particles for a variety of purposes including analysis of aerodynamic particle size distribution, preparation of monodisperse particles, measurement of densities of spherical aerosol particles, and measurement of particle shape factors. Because the centrifugal forces are directed toward the collection foil and cause the collected particles to be held firmly in place, the instrument can be used to collect large samples without significant change in calibration or resolution characteristics.
ThO2 on Ir Cathodes for Electron Bombarded Semiconductor Devices
Authors: Gray H. F. , Harris F. H. , Pankey T. , Haas G. A.
Published: February 2004

Thorium oxide on iridium substrates has been investigated as an electron emitter for electron bombarded semiconductor (EBS) devices, a new type of vacuum tube-solid state hybrid. Thermionic emission measurements and evaporation rate studies using quadrupole and Auger techniques show the low evaporation rate/temperature properties of the emitter to be particularly suited to this application. Improvements in semiconductor diode reverse breakdown as well as semiconductor current gain characteristics of the EBS device have been demonstrated when compared to use with standard oxide cathode emitters. Resistance to air exposure and poisoning the ThO2 on Ir is also useful in demountable applications of EBS device development.
High Speed Thermal Analysis with Thin-Foil Calorimeter
Authors: Hager N. E.
Published: February 2004

A method is described for performing adiabatic scanning calorimetry on thin samples heated at high speeds. A heater is fabricated by soldering copper bus bars to opposite ends of a 45×2.54 cm strip of 0.001065 cm Advance foil. The heater is folded at 1.77 cm intervals to form an accordionlike array. Two 2.54×3.80 cm sheets of sample film are inserted between each fold in the heater, so there are twice as many sample sheets as heater sections. A 0.001 cm thick copper-constantan foil thermocouple is inserted between two sample sheets near the median plane of the array. The experiment consists of bringing the sample array to equilibrium, turning on the heater current, and recording the temperature of the median plane as a function of time. During an initial period, when heating at the thermocouple location is adiabatic, the sample specific heat is calculated on an absolute basis from the slope of the recorded curve. Scanning rates of the order of 500 K/sec are obtained with 0.005 cm thick polymer samples when the heater is run at 40 A or 1.6 kW. With a 2 mm thick array, the adiabatic period lasts about 1 sec; thus, the recording contains continuous data on specific heat vs. temperature over a 500 K temperature range. Polytetrafluoroethylene and polyethylene terephthalate, heated at rates of about 75 and 500 K/sec, respectively, yield apparent specific heat results which agree with values shown in the literature. When heated at about 15 K/sec, polyvinyl chloride exhibits an unusually sharp peak in apparent specific heat at the glass transition temperature; during a 0.2 sec period the temperature of the sample actually falls even though being heated by the foil heater at a rate of about 30 W/cm3.
A Simple Modification for Observing A Variety of Nuclei in NMR Spectroscopy
Authors: Traficante Daniel D. , Simms James A.
Published: February 2004

A method is described for observing a variety of nuclei in NMR spectroscopy, either in the cw or FT mode. The method basically involves raising or lowering the magnetic field. A simple modification of the lock channel is described that can maintain a field-frequency lock at the new field strength. Thus, at the new field, other nuclei can be resonated with one of the spectrometer transmitters and receivers used for another nucleus. The equipment required is a frequency synthesizer and two rf mixers. The method can be extended to include additional nuclei observed in the FT mode if another rf mixer and a wide-band power amplifier are used.
Analysis of the Optical Properties of an Electrostatic Parallel Plate Spectrograph for Relativistic Particles
Authors: Bitter M. , Proca G.
Published: February 2004

The analysis of the optical properties of the electrostatic parallel plate spectrograph is extended to relativistic particles. The conditions for first and second order focusing are derived and a comparison of both types of focusing is given. The second order focusing is found to be superior with respect to intensity and resolution and to offer some other experimental advantages. The analyzer dimensions can be kept small even for high energies.
A Simple System for Real-Time Digital Acquisition of Fast Kinetic Data
Authors: Gorman Donald S. , Connolly John S.
Published: February 2004

We have assembled a data acquisition system (DAS) for the study of fast kinetics, specifically transient light absorption by molecular species formed by single pulses from a Q-switched laser. The DAS consists of a sample-and-hold amplifier, 10-bit analog-to-digital converter, solid state (MOS) memory, and associated timing and control circuitry. The analog signal (e.g., from a photomultiplier-preamplifier circuit) is sampled at preset times, converted to binary digital form, and stored in the memory. The nominal accuracy of A-to-D conversion is ±0.05%, and the time between sampled points can be as short as 1.25 μsec. Following each laser flash, the data points are read sequentially from the memory, translated from binary to decimal numbers, and delivered to a digital panel display and a paper tape punch. The punched tape is then used to enter the data into a time shared computer for detailed analysis. The system can be readily adapted for on line use and can be used in conjunction with any of the various techniques available for studying fast chemical and biological processes [see, e.g., Methods in Enzymology, edited by K. Kustin (Academic, New York, 1969), Vol. 16].
Deflection Mapping with a Babinet Compensator
Authors: Pandya T. P. , Saxena A. K. , Srivastava B. C.
Published: February 2004

The potentialities of a Babinet compensator for use in deflection mapping studies have been examined. Its suitability for use with small ray deflections has been demonstrated by examining the wake of small glycerine drops moving through castor oil.
A Compact Efficient Liquid Nitrogen System for Cooling Solid State Lasers: Application to YAG:Nd3+ and ABC-YAG
Authors: Doehler J. , Solin S. A.
Published: February 2004

A recirculating liquid nitrogen cooling system for optically pumped solid state lasers is described. It has been used to obtain cw emission from YAG:Nd3+ and ABC-YAG at 1.06 and 2.09 μ, respectively. The system is versatile and can easily accommodate intercavity components such as an acoustic Q-switch or a Brewster window. With 3 kW electrical input to a pair of tungsten iodine pump lamps coupled to either YAG:Nd3+ or ABC-YAG by a double elliptical cavity, the measured liquid nitrogen consumption was ∼3.3 cm3/sec at a flow rate of 37 cm3/sec.
Production of Large Area High Current Ion Beams
Authors: Okamoto Yukio , Tamagawa Hajime
Published: February 2004

A newly designed microwave ion source has produced with a hydrogen ion beam up to 0.5 A steady state operation with ion energy of 1 keV. The 4 cm diam extraction electrodes are multiple apertures and are arranged in an accel-decel arrangement. Maximum divergence is 2° from the beam axis. The beam is 85% molecular ions, of which either the diatomic or triatomic component can be maximized by an adjustment of the gas fed to a discharge region. The source is technologically simple, inexpensive, and long lived. The basic concepts underlying the production of ion beams are described.
35 Volt, 180 Ampere Pulse Generator with Droop Control for Pulsing Xenon Arcs
Authors: Hviid Thorkild , Nielsen Sigurd O.
Published: February 2004

The pulse generator described works as a combined switch and series current regulator and allows the shape of the current pulse to be adjusted at each optical wavelength to produce a flat pulse of monochromatic light.
A Simple Method of Obtaining Visible Emission from Ultraviolet Discharge Lamps
Authors: Bruce R. , Elings V.
Published: February 2004

Ultraviolet light sources with emission lines (260–370 nm) can easily be made visible with the use of fluorescing plastics such as those used in nuclear particle detection.
Development of a Hot-Wire Anemometer for Hypersonic Turbulent Flows
Authors: Doughman E. L.
Published: February 2004

A technique is described for constructing hot-wire anemometer probes suitable for measuring turbulence in hypersonic wind tunnels. The main element of the technique is the use of liquid gold resinate for attaching extremely fine hot wires to the probe prongs. Probes mounting wires as small as ¼ μ diam have been built and tested successfully in flows of Mach numbers as high as 10, dynamic pressures of 370 mm Hg, and temperatures exceeding 540°C. The resistivity coefficients of these wires are normal, and their time constant has been measured to be as low as 5 μsec. At Reynolds numbers prevailing in typical flows the heat transfer and temperature recovery characteristics of these wires do not conform to the available theoretical predictions.
A Circulating Pump for Ultrapure or Toxic Gases
Authors: Leiby C. C. , Dunton E. C.
Published: February 2004

A small, stainless steel, Roots-type pump for gases is described. The pump employs helium leak tight rotary seals which render it suitable for use in ultrahigh vacuum gas handling systems. A throughput (at atmospheric pressure) of 100 liters/min has been measured at 1800 rpm. At higher rpm's, the throughput is correspondingly larger.
A Fast High Current Pulser Suitable for Low Temperatures
Authors: Singer I. L. , Ems S.
Published: February 2004

An avalanche pulsing circuit, constructed with off the shelf components operates reliably at 4.2 K. Nanosecond pulses with amperes of peak current are delivered to low impedance loads. Physical proximity of generator and load eliminate cross talk and transmission line distortion.
Chemically Induced Dynamic Nuclear Polarization in Unmodified NMR Spectrometers
Authors: Tomkiewicz M. , Klein M. P.
Published: February 2004

Photochemical reactions leading to chemically induced dynamic nuclear polarization (CIDNP) can be studied conveniently in conventional NMR spectrometers. Light is conveyed into the sample tube by a light guide. A description of a simple setup and results illustrating the sensitivity of the technique using an A-60 spectrometer are given.
Projectile Loader for Research Gas Gun
Authors: Holt W. H. , Mock W.
Published: February 2004

A projectile loader of simple design for use with a research gas gun is presented and its operation described.
Composite Dilatometer for Measuring Density of Liquids and Solids
Authors: McKinney John E. , Penn Robert W.
Published: February 2004

A composite dilatometer for measuring densities of liquids and solids over wide ranges of temperature and pressure is described. The dilatometer has a glass capillary and a mechanically removable seal at the base to facilitate loading. The seal is leakproof, and constant volume is maintained with successive loadings.
A Simple and Versatile Frequency Marker Generator
Authors: Muenter J. S.
Published: February 2004

A one transistor circuit that takes BCD data output from frequency counters and generates decade markers in the form of relay contact closures is given. This circuit will operate with either Hewlett-Packard 5245 series counters or counters with DTL data output.
A Metal Tube Plasma Container for Argon Ion Lasers
Authors: Ferrario A. , Sironi A.
Published: February 2004

A new kind of plasma discharge tube is described which allows cw laser emission up to 8 W in argon. The major advantages are exceptional mechanical ruggedness and simple construction technique.
Studies of a Glass-Ceramic Capacitance Thermometer between 0.007 and 0.040 K
Authors: Bakalyar Donovan , Swinehart Robert , Weyhmann Walter , Lawless W. N.
Published: February 2004

We find that the capacitance of a Corning type 1100 capacitance thermometer depends linearly on temperature from 7 to 25 mK with an apparent sensitivity dC/CdT≃−10−4/mK.
Automated Analysis of Cloud Chamber Tracks
Authors: Smith D. E. , Finn H. F. , Baltz D. W.
Published: February 2004

Automated methods have been developed for counting individual droplets along diffuse cloud chamber tracks. A programmable film reader measures film density in two dimensions. Computer programs analyze this density map to obtain droplet counts. Droplets with diameters of 15 μ and density contrast of 0.5 have been successfully identified, measured, and counted. Real space track dimensions are obtained by making track measurements on both views of a stereo camera pair. Reproducibility of droplet counts is ± 3% and accuracy is ∼8%.
A Simple Nanosecond Gate for Side Window Photomultipliers and Echoes in Such Photomultipliers
Authors: Rossetto M. , Mauzerall D.
Published: February 2004

A simple pulsing unit which gates on an inexpensive side window photomultiplier for 10–300 nsec with a rise time of 9 nsec is described. Following a strong pulse of light, a signal change of 1 part in 104 relative to the main pulse can be detected. Under low light conditions, the noise level is such that single photoelectrons can be detected. The performance of the system is shown in a measurement of light induced echoes in the photomultiplier which are 1000-fold weaker than the main signal.
Proposed Ultraviolet Bandpass Filters
Authors: Olson D. L. , Rigney D. A.
Published: February 2004

The ultraviolet transmission characteristics of selected alkali alloys are presented, and a scheme for constructing simple ultraviolet bandpass filters is described.