bluuebunny/crossref_metadata_2025 huggingface dataset:
Electronic Speed Control for the Beckman Model E Analytical Centrifuge
Authors: Smiriga Stephen R. , Hearst John E.
Published: February 2004

A speed control has been designed for the Beckman model E analytical centrifuge which employs as the velocity transducer a photoelectric pickoff and a digital counter. The controller regularly gives a short term stability of one part in 20 000 and a long term stability (24 h) of one part in 10 000 at rotor speeds greater than 15 000 rpm. The speed controller can be used for any motor which can be controlled by changing the current in the field winding. Even further, the method of control can be used to control any quantity that can be measured by digital means if the relatively low sampling can be tolerated.
Mobile Telescope for Examining Vertical Intensity of Cosmic Ray Fluxes
Authors: MacGregor G. Allen , D'Arcy Raymond G.
Published: February 2004

This report describes the mechanical and electrical features of a mobile fluorescer-photomultiplier cosmic ray telescope. The telescope has been used on frequent occasions to obtain cosmic ray equator points and to examine the vertical cosmic ray intensity at atmospheric depths of 200 to 250 g/cm2. Statistical errors in the total counting rates were less than 1% and over-all experimental errors totaled less than 2%.
A Simple Scanning Electron Microscope
Authors: Crewe A. V. , Isaacson M. , Johnson D.
Published: February 2004

A simple scanning microscope has been built which uses a field emission electron gun alone, without the aid of auxiliary lenses. The design and operation of the microscope are described and the calculated performance is compared with experiment. Resolution of 100 Å has been obtained and is shown in transmission electron micrographs. The probe current is of the order of 10−10 to 10−11 A, a value which is high enough to allow micrographs to be taken with scan times of 10 sec.
Automatic Measurement of Equilibrium Orbits at the Brookhaven AGS
Authors: Frankel R.
Published: February 2004

A method of equilibrium orbit measurement in a synchrotron which utilizes a small computer for on-line data acquisition and analysis is presented. It includes a discussion of a low cost transducer circuit which is capable of processing the high frequency, phase sensitive pulse train signals obtained from pickup electrodes located along the circumference of an alternating gradient accelerator. The analog signal thus obtained is directly suitable for use by a computer's analog/digital converter. The speed with which orbits may be measured combined with the inherent flexibility of a programmable device enables accelerator physicists and machine operators to more readily probe into the behavior of the Brookhaven AGS.
Low Temperature Optical-EPR Sample Probe Using Tunable Coaxial Coupling
Authors: Ensign T. C. , Chang Te-Tse
Published: February 2004

An optical-EPR sample probe using tunable coaxial coupling, for use at fixed temperatures in the range 1–300 K, has been designed and constructed. It allows both critical coupling of the resonant cavity to the microwave system and good sample illumination, while minimizing thermal agitation.
Pyroelectric Thermometer for Use at Low Temperatures
Authors: Lang Sidney B. , Shaw Steven A. , Rice Lynn H. , Timmerhaus K. D.
Published: February 2004

The applicability of pyroelectric thermometry to temperature change or temperature rate measurement at low temperatures was studied, with particular emphasis on calorimetry. The pyroelectric coefficients, dc dielectric constants, and volume resistivities of three ferroelectric ceramic materials, Clevite Ceramic B, PZT-4, and PZT-5A, were measured over the temperature range 4.2 to 300K. The pyroelectric coefficients were found to be reproducible, but large electric fields, thermal shock, and aging affected them. Expressions are derived for the temperature responsivity (voltage output per unit temperature change), noise equivalent temperature change (temperature change equivalent to the electrical noise in a pyroelectric thermometer), and figure of merit (a parameter characterizing the physical properties of a pyroelectric material). Typical temperature responsivities of 8.0 and 165 V/K, and values of noise equivalent temperature change of 2.5 and 0.12 μK, at 5 and 300K, respectively, are calculated. Recommendations are given for the use of a pyroelectric thermometer in a low temperature calorimeter.
A Programmable Magnetic Field Mass Spectrometer with On-Line Data Processing
Authors: Wasserburg G. J. , Papanastassiou D. A. , Nenow E. V. , Bauman C. A.
Published: February 2004

A single focusing, 30.48 cm radius, 60° sector magnet mass spectrometer was constructed with symmetric conjugate foci calculated from fringe field data and corresponding to a beam deflection of 68°. Experimental and calculated optical characteristics agree well. A rotating coil probe and a rate coil are employed as field sensors for a nulling device and for field scanning. The magnetic field can be set to 27 values corresponding to the center of spectral lines and zero lines on both sides of each peak. The automatic scanning consists of: (1) rapid field change between adjacent field values (∼500 G/sec); (2) locking in at the preset field values (∼0.3 sec); (3) remaining in a channel for a preset time during which the ion beam current is integrated and the data digitized. Repeated arbitrary excursions between channels do not cause effective field variations of more than |ΔB/B| = 2×10−5. For 0.2 mm source and 0.64 mm collector slit settings, a typical peak at mass 88 is flat for 2.7 G to 0.01% at a 14 kV accelerating potential. Data consist of channel intensity, scale factors, and internally provided clock time; data signals drive a typewriter and tape punch. A cyclic scan of five isotopes including background requires 35 sec. A segment of data (∼10 cycles) is processed by the computer and the results returned to the operator.
Stability of a Current Ring Supported in a Magnetic Field
Authors: Neil V. Kelvin , Cooper Richard K.
Published: February 2004

The stability of a superconducting, current-carrying ring levitated in a static magnetic field is investigated theoretically. The azimuthally symmetric supporting field has components Br, Bθ, and Bz. A first-order perturbation calculation is performed to determine the oscillation frequencies of the stable modes and the stability criteria for the potentially unstable modes. In the absence of external feedback and/or image currents in the surrounding walls, the ring is unstable. The stability criteria involve the ring current and mass as well as the configuration of the external field and the surrounding walls. It is found that the ring may be stabilized by proper choice of the wall configuration, and if a given configuration is not such as to satisfy the stability criteria, the magnitude of external feedback necessary may be determined from the results.
A Secondary Standard Vacuum Ultraviolet Detector
Authors: Johnson M. C.
Published: February 2004

Uniformity of response, stability, and absolute quantum efficiency of channel electron multipliers was measured in the vacuum ultraviolet. The results indicate that these devices may be used as sensitive secondary standards in this region. A cesium iodide photocathode tube containing one of these multipliers is described.
Versatile Cathodoluminescence Attachment for Electron Microprobe Analysis
Authors: Reid Lee R. , Smith James P.
Published: February 2004

A versatile cathodoluminescence attachment has been developed which can be adapted to any electron microprobe analyzer equipped with a microscope which views the sample during electron bombardment. Fiber optics directs the cathodoluminescence radiation from the microscope to a scanning monochromator equipped with a fused-quartz prism. A cooled S-20 response photomultiplier detects the diffracted radiation. The intensity of radiation in the wavelength range 0.35 to 1.4 μ can be measured. This information can be used in conjunction with electron beam scanning, x-ray measurements, and selected electron accelerating voltage to yield a variety of useful data. Several examples of the use of this instrument are discussed.
Apparatus for the Study of Proton Sputtering
Authors: Finfgeld C. R. , Furr A. Keith
Published: February 2004

An apparatus for the study of proton sputtering, consisting of a differentially pumped ultrahigh vacuum system, rf ion source, electrostatic lenses, and double focusing magnetic spectrometer has been designed and built. The system was capable of delivering a proton beam of energy from 500 eV to 8 keV, and average current density of 1.0 mA/cm2, to a target at 5×10−8 Torr.
Analysis of Cockcroft-Walton Voltage Multipliers with an Arbitrary Number of Stages
Authors: Weiner Melvin M.
Published: February 2004

Expressions for the direct and alternating output voltages of Cockcroft-Walton voltage multipliers with an arbitrary number of stages are determined for the joint effects of charge dissipation in the load resistance and charge storage in the diode shunt capacitances.
Magnetic Densimeter Utilizing Optical Sensing
Authors: Senter James P.
Published: February 2004

An improved magnetic densimeter utilizing optical sensing and solid state components is described. The system has been calibrated with sucrose solutions at 20°C demonstrating a sensitivity of 1 ppm and a precision of 5 ppm. A density measurement can be made on 0.3 ml of solution in 10 min. The operation is simple and convenient for the routine determination of partial specific volumes of minor components in a solution. The accuracy of the densimeter has been verified by measuring the partial specific volume of ribonuclease at 20°C. Excellent agreement with previous measurements was obtained.
Low Temperature Electrical Resistivity Measurements on Reactive Samples
Authors: Pack J. G. , Libowitz G. G.
Published: February 2004

An apparatus and a technique for measuring electrical resistivities on reactive samples are described. Measurements were made in an inert atmosphere vacuum glove box containing a high purity helium environment. A precision micromanipulator was used to position a four point probe while observation was made through a microscope to guide the positioning of the probe. A cold stage permitted measurements to be made from room to liquid nitrogen temperature. This method was used to measure the electrical resistivities of cerium hydride single crystals.
An Electrodiffusion Apparatus for Solid Semiconductors
Authors: Laananen David H. , Nowak Welville B.
Published: February 2004

An apparatus has been developed for the study of the influence of applied electric fields and currents on solid state diffusion of impurities in semiconductors. Special features of the apparatus are simple procedures, versatility, and allowance for determination of impurity profiles.
Apparatus for High-Pressure High-Temperature X-Ray Powder Diffraction Studies
Authors: Freud P. J. , Sclar C. B.
Published: February 2004

A high-pressure high-temperature x-ray powder diffraction apparatus has been developed based on a modification of the belt apparatus, which is an internally heated compressible gasket device. The unique feature of this device is that the die-support ring assembly is fabricated in two parts which mate along a plane normal to the piston axis. The split-die design permits entry of the x-ray beam into the high-pressure volume and egress of both the diffracted rays and the undeviated beam through suitable grooves and fan-shaped slots ground in the mating surfaces. The high-pressure x-ray windows are either a beryllium ring with a wedge-shaped cross section or epoxy resin stops at the bore of the die. The high-pressure medium is ``amorphous'' boron, and the sample is in the form of a thin cylinder which is coaxial with the pistons and normal to the x-ray beam. The compressible gaskets between the pistons and the die are made of pyrophyllite, as they are in conventional devices, inasmuch as they are not part of the x-ray path. High sample temperatures are attained by resistance heating of carbon rods adjacent to the sample. Present limitations on pressure and temperature are 100 kilobars and 1000°C. High-intensity Mo Kα radiation is employed. The apparatus is portable and may be positioned on a conventional x-ray source.
Molecular-Beam Time-of-Flight Spectroscopy
Authors: Alcalay Jack A. , Knuth Eldon L.
Published: February 2004

A method for determining the speed distribution and density of a molecular beam from time-domain measurements of propagated beam perturbations is examined. Algebraic relations between the moments of the measured time-of-flight signal, of the speed-distribution function, of the modulator gate function, and of the dynamic function of the detector and its electronics are derived. By extracting a sufficient number of moments, one can characterize any speed-distribution function to any desired accuracy. For use in applications, moments and recursion relations of a general class of speed-distribution functions and moments of some typical gate functions are developed. Sufficient conditions for approximating a rectangular gate function by an impulsive gate function are presented. An application to time-of-flight measurements in an arc-heated supersonic molecular beam illustrates the use of the general method and emphasizes the need to consider the characteristic time of the gate function and the dynamic response functions of the detector and its electronics when interpreting time-of-flight signals.
A 200 ml Solution Calorimeter with Semiautomatic Adiabatic Control
Authors: Stubblefield C. T.
Published: February 2004

This adiabatic solution calorimeter was designed specifically for thermochemical studies of the less familiar oxidation states of the rare earths. It has been used in the determination of the heats of solution of Pr, Eu, EuCl2, and Pr(NO3)3 in acids. Currently, it is being employed in the determination of the heats of formation of the various stable, nonstoichiometric oxides of Pr. Close control of adiabatic conditions is maintained automatically throughout a run; manual manipulations are held to a minimum. The calorimeter holds about 200 ml of acid or water into which a solid sample is dissolved at the appropriate time. The temperature of the adiabatic shield which surrounds the calorimeter automatically increases at nearly the same rate as that of the calorimeter itself, and the increment of temperature is measured with a platinum resistance thermometer. The heat generated by a chemical reaction is calculated from a comparison of this rise in temperature to that caused by a calibrated quantity of electrical heat. Included in this paper are (1) a complete description of the apparatus, including figures; (2) a table giving results of some calorimetric experiments; and (3) a summary of the characteristics of the calorimeter.
Pulse Width Modulated Optical Data Link
Authors: Witkover R. L.
Published: February 2004

A compact data transmission system for crossing a high voltage interface has been built and tested. The system employs an infrared, incoherent light emitting diode and a silicon photodiode detector to telemeter the pulse width modulated signals. Departure from linearity was observed to be 2.7% rms. The frequency response was 3 dB down at 10 kHz.
Lumped Element Line Generators to Produce Pulsed Sinusoidal Oscillations of Very Large Power
Authors: Lietti A.
Published: February 2004

After reviewing the present state of knowledge concerning the technique of making high power sinusoidal pulses, an improved kind of line generator is proposed. An analysis of wave propagation in a periodic structure together with the numerical solution of the network differential equations shows that it is possible to utilize the recurrent triggering system (hitherto applied only to homogeneous lines) with lumped element lines. A method for designing such lines is presented. Numerical tables are included and some selected examples are discussed. The theory agrees with an experiment made with a prototype line. The construction of a 720 MW, 3 MHz installation for use in plasma physics experiments is already underway. This large power is achieved by paralleling a number of lumped element line generators.
Analytic Stop Motion Stereo Photogrammetry
Authors: Ingels Neil B. , Rush Stephen K. , Thompson Noël P.
Published: February 2004

A photogrammetric system is described which was developed to measure the three-dimensional coordinates of a matrix of 100 μ diam markers identifying a surface whose topography changes with time. The distance between any two markers whose centers are more than 300 μ apart can be determined with a standard error of 34 μ. An application of this system to the determination of cardiac muscle dynamics is demonstrated.
An Apparatus for the Production of Uniform Sized Water Drops, at Desired Time Intervals
Authors: Reil K. , Hallett J.
Published: February 2004

A drop, whose size may lie between 0.4 and 2.0 mm, is blown from a capillary tube tip as it reaches a given size. Drop size and frequency may be varied independently by controlling liquid flow rate and pulse rate.
A Crossed-Beam Apparatus for Investigation of Ion-Molecule Reactions
Authors: Herman Z. , Kerstetter J. D. , Rose T. L. , Wolfgang Richard
Published: February 2004

A crossed-beam apparatus for the study of ion-molecule reactions is described. The device can provide information on the velocity and angular spectra of reaction products as well as on the angular displacement between reactant and product ions. It can thus yield data sufficient to provide a detailed characterization of the dynamics of the system studied. Furthermore, the mass selected ion beam is variable in energy from 100 eV down to the critical low energy region of about 1 eV or less. Although the apparatus thus seems to have broader capabilities than previously described beam devices, it is quite small and comparatively inexpensive.
70 Kilobar Shear Apparatus
Authors: Abey A. E. , Stromberg H. D.
Published: February 2004

An apparatus is described which has been developed to shear bulk samples under nearly hydrostatic pressure. This apparatus gives complete stress-strain curves in the plastic region at pressures from about 10 to approximately 70 kilobars.
Comparison of Exact and Measured Open Circuit Photoconductor Voltages
Authors: Mattauch R. J.
Published: February 2004

It is necessary to determine the open circuit voltage of a photoconductor in order to find its responsivity and detectivity. The ideal case of a photodetector in series with an ideal current source is analyzed and an expression for the open circuit device voltage is given. Since this case is almost impossible to obtain in the laboratory with devices of 10x Ω internal impedance where x>7 and a bias of several hundred volts across the device is needed, the realistic nonideal current source case is treated. It is shown that what is believed to be the actual open circuit device voltage can be incorrect by as much as 10% in certain cases. The conditions necessary for accuracy are given along with curves enabling one to determine accurately the device open circuit voltage if these conditions are not met.
Some Low Temperature Thermometry Observations
Authors: Rosenbaum Ralph L.
Published: February 2004

The temperature calibration on annealed Chromel-P/Au–Fe thermocouples has been extended from 1.3 to 0.55 K. Temperature calibration tables on annealed copper/Au–Fe thermocouples are presented. Electromotive force constants representing the potentials from annealed Au–Fe thermocouples between liquid helium and liquid nitrogen temperature references and between liquid helium and ice temperature references have been measured. Through the use of these emf constants, the calibration tables have been shifted and may be used either with an ice bath or liquid nitrogen temperature reference bath. Temperature calibrations on small platinum sensors manufactured by Minco Products, Inc. are given.
Tunnel Diode-Transistor Twisted Ring Counter
Authors: Tan Z. C.
Published: February 2004

A new tunnel diode-transistor twisted ring counter is described. Each stage of the counter consists of a tunnel diode controlling a long tailed pair which switches current into the following stage. Rectangular input pulses are ``differentiated'' by a shorted delay cable and the tunnel diodes are progressively switched to high voltage states by the positive pulses and then progressively reverse switched to low voltage states by the negative pulses. The scaling capacity of the counter for rectangular input pulses is (2n−1) where n is the number of stages. A maximum scaling rate of 450 MHz was observed for a practical three stage quinary counter.
Pole Figure Integrator
Authors: Wilchinsky Zigmond W.
Published: February 2004

A device, applicable to samples with fiber texture, is used on a diffractometer to average the diffracted x-ray intensities representing values on a pole figure. In the process, the fiber axis is rotated end-over-end continuously at a constant rate through an angle φ which is also the colatitude coordinate of the pole figure. To convert the time average of the intensity to a space average over the pole figure, the instantaneous intensity is multiplied by a factor |sin φ|; this factor is generated by a rotating variable attenuating filter located in the path of the incident beam. When the diffraction angle is varied at a uniform rate during this process, the resulting scan is equivalent to a diffractometer pattern of the sample material with random orientation. By using, in addition, a similar scan made with an attenuating filter generating the function cos2φ|sinφ|, an orientation parameter 〈cos2φ〉 can be easily evaluated for plane normals, crystal axes, and molecular axes.
Application of Color Photography to Electron Microbeam Probe Samples
Authors: Ingersoll R. M. , Derouin D. H.
Published: February 2004

A technique is presented for taking color photographs on the electron microbeam probe analyzer. The procedure involves the multiple exposure photography of a white beam CRT tube using various color filters to create artificially any desired color.
Peltier Measurements below 4 K
Authors: Trodahl H. J.
Published: February 2004

Accurate low temperature Seebeck measurements are difficult since they require the detection of very small emf's. An alternative Peltier measurement, which provides equivalent information, is described, and satisfactory experimental results are presented on materials with Seebeck coefficients as low as 2×10−8 V/K. The technique has the capability of measuring a Seebeck coefficient of 10−9 V/K with 2% precision and should be particularly useful for use on high resistivity alloys and for measurements in the presence of a magnetic field.
A Technique for Measurement of the Heat Capacity of Metals under Pressure
Authors: Jura G. , Stark W. A.
Published: February 2004

A method is described that can be used for the determination of the heat capacity of a metal (or a semiconductor) as a function of pressure and temperature. The method involves use of a dc electric pulse. If a constant current I is passed through a wire sample of resistance R, the heat capacity Cp is related to the increase in temperature by the expression Cp=I3RR′/(dE/dt)t=0,where R′ is the temperature derivative of the resistance, and (dE/dt)t=0 is the limiting value of the time rate of change of the emf across the sample. Data are given for iron to 100 kilobars in the temperature interval from 77 to 300 K. The results obtained are in accord with earlier theoretical estimates. The Curie temperature Tc of gadolinium has also been determined from heat capacity measurements; its rate of change with pressure was found to be dTc/dP=−1.3 K/kilobar. With the equipment that is available at the present time, the measurements can be made as long as the specific resistance is 5 μΩ·cm or greater.
A High Energy Electron Beam Monitor
Authors: Crannell Carol Jo , Crannell Hall , Zeman H. D.
Published: February 2004

A high energy electron beam monitor which detects the Čerenkov light emitted in nitrogen gas at atmospheric pressure is described. The monitor is designed to have a constant sensitivity to electrons of energies above 200 MeV, to have a response time of less than 10−7 sec, and to have a current output which is linearly proportional to the beam intensity over a range of five decades. The results of tests made on the monitor are presented. The tests show that the monitor has a sensitivity, speed, range, and lack of dependence on beam position and background radiation which make it ideal for many monitoring applications.
Apparatus for PVT Measurements of Gases to 10 Kilobars
Authors: Babb S. E. , Scott G. J. , Epp C. D. , Robertson S. L.
Published: February 2004

Apparatus has been developed for the measurement of PVT properties of gases to pressures of 10 000 bars and to temperatures of 400°C. The apparatus is described, the corrections which must be applied to the raw data discussed, and some illustrative results presented.
Degradation of Continuous-Channel Electron Multipliers in a Laboratory Operating Environment
Authors: Frank L. A. , Henderson N. K. , Swisher R. L.
Published: February 2004

Measurements of the counting rates (∼103 to 104 counts/sec) of continuous-channel electron multipliers mounted in an electrostatic analyzer responding to a monoenergetic beam of electrons, while operating in a vacuum chamber at a pressure ∼3×10−6 Torr attained with an oil diffusion pump, display a degradation of their gain (fatigue) which is proportional to the accumulated counts. The useful lifetime of these devices when employed with fixed-threshold pulse amplifiers is defined here as the accumulated counts until gain degradation has produced a reduction of the counting rates to 15% of the initial responses at an operating bias voltage of 4000 V and constant stimuli. The lifetimes of these particle detectors in this laboratory environment are ∼1010 counts or, for example, an average counting rate of 300 counts/sec for one year. Comparison of this laboratory lifetime with the responses of similar instrumentation which has been flown on the earth satellites OGO's 3, 4, and 5 and IMP 4 demonstrates that the expected lifetimes for these electron multipliers in a spaceflight environment are several years. Efficiencies of an electron multiplier for counting monoenergetic electrons over an energy range ∼60 to 50 000 eV are also presented.
Low Pressure Sputtering System of the Magnetron Type
Authors: Wasa Kiyotaka , Hayakawa Shigeru
Published: February 2004

A new design of a low pressure sputtering system of magnetron type is described. The optimum sputtering conditions are discussed in relation to the system. It is shown that this system is able to produce uniform thin films with good reproducibility, and especially to produce a metal oxide film by reactive sputtering. Some typical configurations are presented for use in the laboratory and on a production scale.
Temperature Control of Metallic Targets in vacuo by Electron Beam and Infrared Radiometry Techniques
Authors: Lewis Robert N. , Van Loon L. S. , Holt Ben D.
Published: February 2004

A system is described that employs infrared radiometry and electron beam techniques to raise sequentially the temperatures of small metal targets from a level near liquid nitrogen to the 100 to 600°C range. The system is automatic and achieves the selected temperature with an over-all error less than 0.5°C.
A Rocket Borne Scintillation Spectrometer for Observing Cosmic X Rays
Authors: Harri J. , McGee M. , Toor A.
Published: February 2004

A rocket borne spectrometer system sensitive to 6–80 keV photons is described. The system includes a shutter-collimator that makes it possible to measure the contribution to the background due to charged particle interactions in the mass of the rocket payload. Also described is a detector rotation mechanism that allows the look angle of the detector with respect to the rocket axis to be changed during flight.
Calibration Heater for a Liquid-Vapor Deformation Calorimeter
Authors: Wolfenden A.
Published: February 2004

A technique for calibrating a liquid-vapor deformation calorimeter has been developed which involves the use of an electrical heater coil to simulate a deforming tensile specimen. The known Joule heat generated in a submerged coil vaporizes a measured amount of calorimetric fluid. The calibration heater thus permits evaluation of the relationship between integrated evaporation rate-time quantities and dissipated energy.
A 77–1300 K Single Crystal X-Ray Specimen Chamber
Authors: Gehlen P. C.
Published: February 2004

An x-ray specimen chamber suited for single crystal diffraction work (particularly for studies of the state of order in alloys) is described. The evacuated chamber can be used between 77 and 1300 K. Temperatures can be controlled to ±1°. The chamber has its own degrees of freedom and no auxiliary equipment is needed to bring any crystallographic plane into diffracting position. The two degrees of freedom provided (the so called φ and χ rotations) permit investigation of large parts of reciprocal space, using only one face of a large flat crystal. As an example of the versatility of the camera, the lattice parameter of copper was measured between 100 and 1200 K.
A Plasma Scanner and Data Processing System for Current-Voltage Curves
Authors: Gritzmacher Thomas J. , Boyer Ellsworth L. , Holt James F.
Published: February 2004

A new plasma diagnostic tool, called a plasma scanner, has been developed for use in obtaining current cross sections and current-voltage characteristics of a hollow cathode magnetically confined arc plasma in argon. The scanner assembly consists of an annular copper arc anode, a boron nitride baffle, a boron nitride scanning wheel, and a plane copper current collector. To obtain current cross sections the wheel was rotated at 1 rpm. To obtain current-voltage characteristics, the wheel was stopped with the collector exposed to the plasma through a chosen scanner hole. Most of the data were produced in an arc of 20 A and 45 V. A cylindrical Langmuir probe provided data for comparison. The scanner showed a sharp increase in electron current in the center of the arc, whereas the probe did not. Typical temperatures derived from the scanner were 4 eV while temperatures obtained using the probe were 3.2 eV. Electronic equipment gave a direct readout of the inverse of the electron temperature.
An Improved Method for High Reflectivity Ellipsometry Based on a New Polarization Modulation Technique
Authors: Jasperson S. N. , Schnatterly S. E.
Published: February 2004

We report the development of a new ellipsometry technique which is especially well suited to the measurement of the dielectric constants of high reflectivity metals. Modulation methods are used to permit the measurement of a differential reflectance parameter which does not decrease in sensitivity in the high reflectivity limit as do the usual reflectance parameters measured with standard techniques. In addition the ellipsometer is faster than previous methods, being capable of recording the relevant data in a few minutes as the wavelength is swept continuously over a range of several thousand angstroms. The precision of the dielectric constants so measured is 1% in most cases. The polarization modulation technique, upon which the ellipsometer is based, is presented in detail, with emphasis on its wider applicability to any problem involving the study of dichroic phenomena.
Broad Band Correlation Measurements with an x-y 'Scope
Authors: Jensen T. H. , Moore R. W.
Published: February 2004

A broad band correlation technique using an x-y oscilloscope has been developed. When two noise signals are applied to the inputs of the oscilloscope, a characteristic pattern is formed on the oscilloscope face. It is shown that an equal intensity contour of the pattern, which may be obtained by photographing, is an ellipse and that the correlation depends only on the eccentricity and the angle of inclination of the ellipse. The bandwidth of this correlator is only limited by the oscilloscope. The instrument has been used to measure the correlation between fluctuations measured by two spatially separated probes in a plasma.
Low Temperature Specific Heat (1.6 to 4 K) of Six Commercial Aluminum Alloys
Authors: Zoller Paul , Dillinger J. R.
Published: February 2004

We have measured the low temperature specific heat (1.6 to 4 K) of six commercial aluminum alloys (ASM types 7075, 7079, 2219, 2014, 2618, and 2024). The results are given in the form of fits to the relation C=γT+BT3. Some alloys show deviations from this relation at the lowest temperatures. This may be due to the presence of 3d transition elements in these alloys.
Pulse Radiolysis Apparatus for Monitoring at 2000 Å
Authors: Christensen H. C. , Nilsson G. , Pagsberg P. , Nielsen S. O.
Published: February 2004

A pulse radiolysis apparatus with photometric monitoring has been built around an 11 MeV, 250 mA peak current, linac that delivers single 0.25 to 4 μsec pulses. The novel features of the apparatus include (1) a 450 W xenon lamp as the analyzing light source which in pulsed operation had a 25 times increased luminance; (2) a fast electronic switch that cut out the signal due to the Čerenkov radiation; (3) a secondary emission chamber that allowed the simultaneous measurement of the current and the direction of the pulsed electron beam; and (4) a system for remote controlled change of liquid samples stored in glass syringes. Reliable measurements of optical transmission could be made starting 0.2 μsec after the electron pulse at wavelengths down to 2000 Å on transient species having products of yield and absorptivity G×ε>500 mole (100 eV)−1·liter−1·cm−1.
Resolution and Sensitivity Considerations of an Auger Electron Spectrometer Based on Display LEED Optics
Authors: Taylor N. J.
Published: February 2004

Some of the important considerations in the design of a retarding field analyzer suitable for Auger electron spectroscopy based on display LEED optics are described. From such considerations an instrument has been built with an instrumental linewidth of less than 0.3% (resolution greater than 360). Analysis is made of the limitations insensitivity of the device due to shot noise, and on this basis a comparison is made with a 127° cylindrical electrostatic analyzer. The analysis can be readily extended to other forms of retarding field and deflection analyzers.
Low Frequency Bridge for Guarded Three-Terminal and Four-Terminal Measurements of Admittance
Authors: Berberian John G. , Cole Robert H.
Published: February 2004

The null method described permits either guarded three-terminal or four-terminal potential probe measurements of conductance from 1 kHz to dc and of capacitance to frequencies as low as 0.01 Hz. Sample currents to a null detector are balanced by adjustable currents derived from dc voltage inverter and follower circuits which drive fixed standards of conductance and capacitance. Procedures for minimizing errors from circuit residuals and results of representative measurements are described.
An Improved Apparatus for Measuring Anelasticity in Metal Specimens
Authors: Mosher D. R.
Published: February 2004

A low frequency torsion pendulum, employing Joule heating of metal wire specimens, is described. End losses are compensated by a strip heater attached to the fixed grip and by an induction heating coil surrounding the oscillating grip. Regulation of the three heat inputs by precision current adjusting type temperature controllers provides exceptional temperature uniformity and long term stability. Rapid response to changes in temperature set-point results from the low thermal inertia of the system. Examples of experiments utilizing these features are given.
Switch Arrangement and Power Averaging in Constant Current Calorimetric Heating
Authors: Chang S. S.
Published: February 2004

In order to minimize the transient effect associated with switching a constant current power supply to different loads, a break-before-make type of switch contact arrangement is shown to be preferable to a make-before-break type of arrangement. Series resistance in the load circuit may be required for low current applications. With a constant heater current, the average heater power for the entire heating period can be precisely determined as the product of the current and the mean value of two particular potential readings. These two readings, symmetrical about the midpoint of the heating period, should be taken at specified intervals as determined by the exponential heat conduction characteristics of the calorimeter assembly.
A Technique for Determining the Dielectric Behavior of High Conductivity Materials
Authors: Seitz M. A. , McSweeney R. T. , Hirthe W. M.
Published: February 2004

A transformer ratio bridge is usually capable of measuring the capacitance of specimens with a maximum dissipation factor of about 101. The technique described herein allows this type of bridge to measure the capacitance, with a reasonable degree of accuracy, of specimens with a dissipation factor as high as 104. This is accomplished by correcting for and minimizing effects due to stray inductance and capacitance in the measurement system. The technique uses standard laboratory instrumentation, is simple in nature, and provides for the determination of dielectric behavior over a wide range of electrical conductivity.
Design and Operation of an Atomic Hydrogen Target for Precision Scattering Cross Section Measurements
Authors: Bayfield James E.
Published: February 2004

A new design for a hydrogen atom target is described. An H2 dissociation of 96±4% is obtained for pressures near 3×10-5 Torr and temperatures of about 2400 K. The scattering cell proper is uniformly heated by radiation from a separate resistance heater element. Magnetic field effects are eliminated by gating the 700 A heater current out of phase with the incident particle beam. A method for absolute measurement of the dissociation fraction is described. Target impurities other than H2 are estimated to be less than 0.2%.
A Pulsed Gas Valve for Fast Timeable High Pressure Operation
Authors: Henins Ivars , Marshall John
Published: February 2004

A fast opening, high pressure gas valve has been developed. It is electrically timeable and can admit several hundred cubic centimeters · atm gas from a plenum of 1 to 10 cm3 volume, initially filled at pressures up to 100 atm. The opening rate of the valve stopper is about 7 m/sec and is derived from the sudden release of the stored energy in an axially compressed nylon rod. Emptying time depends on plenum volume and is of the order of a few hundred microseconds.
A Bubble Chamber Film Measuring System Employing High Accuracy Image Plane Digitizers
Authors: Hill D. G. , Palmer R. B.
Published: February 2004

A bubble chamber film measuring system is described. Measurement is performed manually on the projected image employing an essentially bipolar coordinate system. The lengths of wires between the measured point and the two drums are determined from the rotation of the two drums which are mounted on optical angle encoders. The accuracy of the system when measuring test grids is ±4 μ on film. The measuring device and the procedure, speed, and accuracy of measuring bubble chamber events are discussed.
An Automated Retarding Potential Difference Technique Using a Multichannel Scaler
Authors: Chantry P. J.
Published: February 2004

A commercially available multichannel analyzer, used in the multiscaling mode, has been adapted so as to accumulate automatically data from electron beam experiments employing the retarding potential difference (RPD) technique for improving the electron energy resolution. The electron accelerating voltage is generated by digital-to-analog conversion of the ``live'' channel address, the lower and upper limits of the sweep being adjustable over a wide range. The analyzer is swept alternately in the add and subtract modes with a period which is short compared to possible drifts in electron current, collision chamber pressure, multiplier sensitivity, etc. The tedious labor involved in obtaining RPD data by conventional means, and its subsequent arithmetic reduction, is all performed automatically by the analyzer. Examples of data obtained by the technique are presented, showing the improvement in signal to noise obtainable by operating for a suitably large number of sweeps.
An Improved Collimator for Extreme Ultraviolet and X Rays
Authors: Underwood J. H.
Published: February 2004

The mechanical collimator for x rays and extreme ultraviolet described by McGrath may be improved by replacing the plates pierced with apertures arranged in a regular array with plates pierced with apertures arranged at random. With this scheme, fewer plates are required to suppress off-axis radiation.
Pulsed High Field Microphotographic Apparatus for Measuring Electrophoretic Mobility in Insulating Liquids
Authors: Harris Lee B.
Published: February 2004

A new technique has been developed for the measurement of electrophoretic mobility of colloidal suspensions in liquids of very low dielectric constant (D≃2) at electric field strengths as high as a few times 104 V/cm. The technique is based on a pulsed electric field. It provides a photographic record of the particle motion and is capable of studying relatively fast transient effects (a few milliseconds or more in duration). Some preliminary data are presented as an application of this method.
Dielectric Permittivity Measurements at Centimeter Wavelengths
Authors: Cutnell J. D. , Kranbuehl D. E. , Turner E. M. , Vaughan W. E.
Published: February 2004

Improved apparatus for dielectric permittivity measurements at centimeter wavelengths is described. A method of data reduction which minimizes the effect of systematic errors, helps to average out random errors, and is free from significant mathematical approximations is presented. This method is compared to data reduction techniques common in the literature.
A ``Sampled-Continuous Wave'' Ultrasonic Technique and Spectrometer
Authors: Miller J. G. , Bolef D. I.
Published: February 2004

A continuous wave ultrasonic measurement technique, which is particularly well suited to the study of inherently single-ended acoustic systems, is presented. In this method the cw signal which establishes acoustic resonance is interrupted for the period during which sampling of particle motion amplitude is accomplished. The ``sampled-cw'' technique incorporates the freedom from crosstalk associated with pulse—echo methods while retaining the monochromaticity of cw schemes. Analyses of the relative sensitivities of pulse—echo, ``sampled-cw,'' and cw ultrasonic techniques are presented. A detailed description is given of a sampled-cw spectrometer which includes a frequency locking scheme.
Ionization Measurements in a Helium Streamer Chamber
Authors: Kanofsky A. , Schoen N.
Published: February 2004

A measurement of the density of ionization produced in a helium streamer chamber by singly charged particles as a function of momentum, helium pressure, and high voltage delay time is described. The results are compared with expected theoretical values based on the Bethe formula.
Quadrupole Field in Circular Concave Electrodes with Finite Thickness
Authors: Hayashi Tomonao , Sakudo Noriyuki
Published: February 2004

The influence of the finite thickness of circular concave quadrupole electrodes on the spatial higher harmonics is investigated. A design curve for obtaining the proper electrode angle to best approximate the quadrupole field is given by analyzing the results of field plotting. The residual higher harmonics which are mainly due to the 20-pole field component are confirmed to be negligibly small in the vicinity of the axis. The effect of the finite size of the conducting paper used in the field plotting on the measured amplitude of the spatial higher harmonics is also estimated.
An Improved Microwave Spectrometer for Linewidth Measurements
Authors: Roberts James A.
Published: February 2004

A microwave spectrometer capable of determining linewidth data with repeatability better than 2% for spectral lines of intensities of 10-6 and 10-7 cm-1 has been developed. The technique of source modulation has been utilized effectively to produce molecular transition without resorting to the conventional technique of Stark modulation. This scheme of source modulation has enabled the use of an absorption cell of any reasonable length to be used. The cells employed in this investigation were 6.1, 15.2, and 30.5 m in length. Data on signal-to-noise ratios for spectral lines of 10-4, 10-5, and 10-6 cm-1 intensity are given to demonstrate the merit of an increased cell length. A circular waveguide rather than the conventional rectangular waveguide is utilized as the absorption cell.
A Versatile Toroid Hysteresis Loop Tracer with Direct Readout of Loop Parameters
Authors: Patton Carl E.
Published: February 2004

A versatile hysteresis loop tracer for toroidal samples has been constructed which allows loop parameters to be determined extremely rapidly. (1) The winding operation is eliminated for toroids with inside diameters greater than 1.5 cm. (2) The loop axes are calibrated directly in oersteds (horizontal) and gauss (vertical) by setting three Helipots to the toroid dimensions. (3) Direct Helipot dial readout of coercive force and remanent induction is possible.
Apparatus for Measuring Optical Properties of Photochromic Spiropyrans
Authors: Carlson Carl O. , Flavin Michael A. , Stone Eliot , Pearson Irving M.
Published: February 2004

An apparatus for measuring the optical properties of photochromic spiropyrans, which are of importance in display and microimaging applications, is described. Step wedges are formed on the photochromic materials by means of rotating disk choppers. Step height readouts enable determinations of optical densities. Examples are given of the use of the apparatus in testing the writing sensitivity and erasability, at controlled temperatures, of solid dispersions of specific spiropyrans in polymeric binders.
A Low Energy Electron Accelerator Producing Measurably Small Fluxes through Utilization of the Photoelectric Effect
Authors: McCullough Edwin C.
Published: February 2004

Described is an accelerator which utilizes the photoelectrons from an ultraviolet irradiation of a gold cathode to provide measurably small fluxes of low energy electrons. Operation of the accelerator is based upon the well established proportionality of photoelectric emissivity with intensity of irradiation such that accurately known small electronic fluxes are established through the use of filters of known transmissivities. With a stable light source and vacuum environment extraordinary flux stability is obtained with this accelerator.
A Continuous Wave Technique for the Automatic Measurement of Ultrasonic Velocity Changes
Authors: Leisure R. G. , Moss R. W.
Published: February 2004

A technique is described for the automatic measurement of ultrasonic velocity changes in continuous wave experiments. An oscillator is locked to a mechanical resonance of the sample. Velocity changes appear as frequency changes of the oscillator and are easily recorded. Some typical results are given.
Use of a Two Channeltron Coincidence in a New Line of Research in Atomic Physics
Authors: Amaldi U. , Egidi A. , Marconero R. , Pizzella G.
Published: February 2004

Quasifree scattering of electrons on bound electrons gives direct information on the electronic wave functions in atoms and molecules, if the incoming energy is definitely higher than the electron binding energy. To tackle this new line of research the two outcoming electrons, whose energies are typically in the 0.1–10 keV range, have to be detected with good energy resolution and short resolving time. These technical problems have been solved by using two hemispherical electrostatic analyzers (ΔE/E≃±0.4%) and two Channeltrons as detectors; the measured FWHM resolving time is 4.3 nsec. Energy spectra are presented, in which the peak due to K electrons in carbon is well resolved.