bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Modulated Retarding Potential Difference and Retarded Energy Modulated Electron Spectrometers
Authors: Golden D. E. , Koepnick N. G. , Fornari L.
Published: February 2004

The similarities and differences between the operation of a modulated retarding potential difference and a retarded energy modulated electron spectrometer are described. The energy modulation technique automatically eliminates to a large degree slow variations of the scattering cross section with electron energy as well as the relatively slower variations in electron transmission with electron energy due to electron optical effects. Furthermore, the retarded energy modulation technique gives a response characteristic of a monoenergetic electron beam as does the retarding potential difference technique. In this connection, the electron spectrum of He near 19.3 eV is discussed.
A Corbino Disk Apparatus to Measure Hall Mobilities in Amorphous Semiconductors
Authors: Carver G. P.
Published: February 2004

The Corbino disk technique finds a modern application in the measurement of the Hall mobility in amorphous semiconductors. Unlike conventional Hall effect experiments, the technique yields a direct measurement of the mobility and does not depend on a separate measurement of the conductivity. In addition, no voltage contacts are required. The apparatus described here is optimized for the regime of low mobility and high resistivity amorphous semiconductors but also works well on higher conductivity samples. The sensitivity of the apparatus is adequate to routinely measure mobilities to as low as 0.1 cm2/V·sec with a sample current of less than 1 mA at a frequency of 105 Hz and a magnetic field of up to 2 T. Under these conditions, reproducibility errors are less than 5%. Improvement in performance through the use of higher magnetic fields and digital signal averaging is discussed.
A Laboratory Photomask Production Facility
Authors: Gaylord T. K.
Published: February 2004

A simple, rapid procedure is described for making photomasks consisting of reduced and repeated microelectronic patterns. This process utilizes two compact and economically constructed cameras. The first camera, using a pinhole array, produces the initial reduction and repeat of the circuit pattern, while the second camera, using a conventional camera lens, accomplishes the final reduction.
An Automatic Optical Bias Control for Laser Modulators
Authors: Waksberg A. , Wood J.
Published: February 2004

A technique is presented whereby the temperature variation of the natural birefringence of electro-optic modulators can be compensated automatically in an optical modulation system. A description is given of a 80 M bits He–Ne PCM communication system that uses this concept.
A Preset Timer for Control of Mass Spectrometer Scan Functions
Authors: Laurendeau N. M. , Shaw A. D.
Published: February 2004

A timer for controlled regulation of the sequential operation of existing mass spectrometer scan circuits has been constructed. The instrument allows for automatic acquisition of mass spectra at preset time intervals. Mass range and scanning frequency can be controlled. With proper recording instrumentation, a complete mass spectrum can be obtained every 10—1–104 sec.
An Apparatus for Polishing Water Soluble Crystals
Authors: Ramaswamy V. , Divino M. D.
Published: February 2004

A simple, semiautomatic single lap apparatus for polishing soft crystalline materials, especially water soluble crystals such as KDP and ADP, has been constructed. Starting with string sawed surfaces, use of this equipment with KDP has produced finished surfaces which are scratch free under at least 1000 × magnification with bright field illumination and 500 × dark field. Total lapping time was about 2 h for removal of a 12–15 μ layer of material. The design and use of the polishing machine and lap are described.
The Preparation and Calibration of a Convenient EPR Field Marker and Intensity Reference
Authors: Miner G. K. , Graham T. P. , Johnston G. T.
Published: February 2004

The preparation, calibration, and use of forsterite as an EPR field marker and intensity reference are described. Measurements of field separations and relative line heights at room temperature for the manganese hyperfine lines in forsterite are reported.
Gas Flame Heating Equipment Providing up to 2300°C for an X-Ray Diffractometer
Authors: Nukui Akihiko , Iwai Shin'ichi , Tagai Hideo
Published: February 2004

Gas-flame heating equipment for a single crystal x-ray diffractometer has been designed and constructed for the study of materials in the molten state up to 2300°C. An application of this equipment to structural investigation of molten platinum is discussed. Radial distribution functions were computed and analyzed employing the diffracted intensities.
A Two-Film Cassette for a High Pressure X-Ray Camera
Authors: Singh A. K.
Published: February 2004

The paper describes a film cassette for high pressure x-ray cameras which permits recording in a single exposure of the diffraction pattern on two films separated from each other by an accurately known distance. This arrangement eliminates the errors in the d spacings, arising from sample shift, absorption, and uncertainty of sample-to-film distance.
A Droplet Generator with Electronic Control of Size, Production Rate, and Charge
Authors: Abbott Charles E. , Cannon Theodore W.
Published: February 2004

A droplet generator has been developed which can produce small droplets one at a time, in groups with adjustable time intervals between droplets or in a continuous stream with controllable production rates of up to 100 per second for the smallest size. Size, charge, and time of production as well as horizontal position at the time the droplet is made may be changed electronically from droplet to droplet. Droplets are produced with nine adjustable and overlapping size ranges covering radii from 4 to 130μ. An application is described where one droplet generator is used in a cloud physics study of collisions between pairs of droplets of unequal size and charge.
Simple X-Ray Bandpass Filters for Nanosecond Resolution of Plasma Spectra
Authors: Bernstein Melvin J.
Published: February 2004

A novel type of bandpass filter for x rays has been developed for use in studies of hot transient plasmas. Suitable bandpass intervals are defined by transmission through thin K-edge filters and absorption in matched thicknesses of scintillator material. The scintillator light signals are detected by either a set of photomultipliers or an image-converter camera, operated in the streak mode. Filters of Mg, Al, Cl, and Ti cover the 1–5 keV photon energy range and are useful with plasmas having temperatures of 0.2–2.0 keV.
Micropump-An Apparatus for Steady State Synthesis of Gas Mixtures at Very Dilute Concentrations
Authors: Ruska W. E. A. , Carruth G. F. , Kobayashi Riki
Published: February 2004

An 8 cm3 positive displacement plunger pump and its associated control systems are described. A choice of 224 precise flow rates from 0.36 cm3/min to 8×10−8 cm3/min is possible. Calibration flow mixtures of paraffin hydrocarbons in helium were prepared in the range 10−7–10−11 mole/sec.
Angular Correction to Absolute Photometric Calibration by Photon Coincidence
Authors: Hanley S. T. , Blair J. S.
Published: February 2004

A correction for photon-photon coincidence calibrations due to angular correlation in two cascaded photons is discussed. An angular correction is made for a particular example to demonstrate the method of estimating this correction and to treat some complicating features often encountered in atomic applications.
An Apparatus to Investigate Plasmas at Very High Pressure
Authors: Bauder Uwe H. , Stephens Everett D.
Published: February 2004

Steady state electrical arc discharges are operated in argon at pressures up to 950 atm and arc currents up to 200 A. The high pressure system consisting of various arc configurations, pressure vessels, gas and water pumps with heat exchanger and pressure equalization chamber is described. Also the electrical and spectroscopic measurements performed at the discharges are discussed. Voltage-current dependences of arcs with different currents are presented as functions of the gas pressure and are compared with predictions based on the energy equation of the arc columns.
An Ungrounded Electronic Field Meter
Authors: Cudney R. A. , Phelps C. T. , Barreto E.
Published: February 2004

An induced charge type of instrument for measuring the horizontal electric field in an enclosed, charged fog or mist is described. The instrument is electrically isolated and insensitive to its own net charge, permitting unambiguous measurement of the ambient field anywhere within the charged volume.
Simple Lapping and Grinding Machine for Use in the Surface Preparation of Organic and Biological Crystals
Authors: Vaala A. R. , Sauers T. E. , Henry H. P. , Osgood R. L. , Madjid A. H.
Published: February 2004

The construction of a simple grinding, polishing, and lapping machine, which is specifically designed for the surface preparation of organic and biological crystals, is described. The machine may be used with abrasives and also in a solvent etching mode. The principal feature of the apparatus is an accurately counterbalanced lapping platen. This permits the processing of fragile and easily deformable specimens without damaging them.
Simple Photolithic Masks of Mathematical Curves
Authors: Krall A. D. , DeSavage B. F.
Published: February 2004

A method for cutting photolithic masks using a desk calculator coupled with an X-Y recorder is outlined. The method is especially adaptable for cutting mathematical curves where frequent changes in parameters are desired.
Superconducting Solenoid Field Monitoring with 133Cs NMR
Authors: Dickson Edward M.
Published: February 2004

Magnetic field monitoring in superconducting solenoids using 133Cs NMR is suggested and fabrication of samples that withstand repeated thermal cycling is described.
Sensitive Optical Heterodyne Method for Light Scattering Studies
Authors: Uzgiris E. E.
Published: February 2004

A two beam optical heterodyne method is described which yields high heterodyne mixing efficiency without critical angular alignment. The reference beam is obtained by scattering part of the primary beam from a thin layer of fixed scatterers. The sensitivity to low light levels is shown to increase by a factor of 4 over the homodyne method when the heterodyning process is nearly ideal.
A Technique for Preparing Wall Coated Cesium Vapor Cells
Authors: Singh Gurbax , Dilavore Philip , Alley Carroll O.
Published: February 2004

A convenient technique for the preparation of reproducible cesium vapor cells, coated with a thin transparent layer of Paraflint, is described. Cells of 7.5 cm diam showed relaxation times of about 250 msec.
FEP Teflon Seals for Low Temperature
Authors: Vesel J. E.
Published: February 2004

A design is presented for an inert, demountable, cylindrical, glass-walled Raman cell which utilizes FEP Teflon seals and can be used for helium II.
Q-Switched CO2 Lasers with Variable Pulse Delay
Authors: Burak I. , Gamss L. A. , Ronn A. M. , Szöke A.
Published: February 2004

By tilting a single mirror, variable pulse delays may be obtained between the output of two wavelength-tunable CO2 lasers with a common active Q-switch.
A Near-Infrared Circular Dichroism and Magnetic Circular Dichroism Instrument
Authors: Osborne G. A. , Cheng J. C. , Stephens P. J.
Published: February 2004

We report a high sensitivity, near-infrared circular dichroism (CD) instrument. CD is measured by the standard modulation method; phase modulation is provided by an Infrasil quartz photoelastic modulator. The spectral range 0.8–3.0 μ is spanned. Incorporation of a superconducting magnet allows magnetic circular dichroism (MCD) measurements to be made. The natural CD of nickel and samarium tartrate complexes and the MCD of a single crystal of Co/MgO at 12 K and 40.6 kG are reported. Performance of the instrument is comparable to visible-ultraviolet CD instruments.
A Versatile Low Temperature Calorimeter
Authors: Johnson D. L. , Cluxton D. H. , Young R. A.
Published: February 2004

An apparatus and techniques are described which have been found adequate for making nominally 1% accurate specific heat measurements on relatively low thermal conductivity alloys in the range of temperature from 0.5 to 10 K and in magnetic fields of 0 to 1.5 T (15 kG). Emphasis is given to thermometry and to experimental methods of establishing the accuracy of the measurements. Several competing effects which must be quite delicatelybalanced in the design of the calorimeter are discussed and the necessary experimental compromises are described in detail. Some consideration is given to techniques for extending the useful range of temperature and magnetic field.
An Improved Thin-Film Gauge for Shock-Tube Thermal Studies
Authors: Willeke Klaus , Bershader Daniel
Published: February 2004

An improved type of thin-film heat gauge has been developed and used to measure heat-transfer rates from a shock-heated plasma to the end wall of a shock tube. The gauge is a resistance thermometer consisting of a triplelayered sensor coated by a moderately thick film of SiO2. It was used to measure heat transfer from nonionized argon at temperatures of up to 16 000 K. A marked increase in heat transfer at the onset of ionization near the wall indicates that the gauge can be used to obtain the contribution of free electrons to the thermal transport.
Simple Optical System for Measurement of Dihedral Angles on Small Specimens
Authors: Brown B. R. , Henry G. R.
Published: February 2004

An extremely simple, easily used system has been devised for the measurement of the dihedral angle between two plane faces on small specimens. The faces must be specular (rather than diffuse) reflectors, but may be quite lossy. Alignment criteria are extremely loose, but measurement precision is diffraction limited. The system will probably be of most use on objects of submillimeter dimensions
Turning Angles of Charged Particle Tracks in Large Bubble Chambers
Authors: Knop Robert E.
Published: February 2004

Low energy separated beams into very large bubble chambers, such as the Argonne National Laboratory 12 ft chamber, will have the consequence that many of the secondary particles will be magnetically trapped within the chamber volume. We show that for a highly uniform magnetic field, the turning angle of the tangent to a track of known mass, taken from production to stopping, provides visual estimates of the range to stopping, the total momentum, and the in-flight decay probability. We also show that these estimates are independent of depth in the chamber and orientation in the magnetic field, and can be obtained for any view projection in the presence of optical distortions.
A Differential Counter for the Determination of Small Differences in Decay Rates
Authors: Harbottle G. , Koehler C. , Withnell R.
Published: February 2004

An instrument for the determination of small changes in the rate of decay of a radioisotope has been constructed. It operates on the principle of differential comparison of the unkown decay rate with that of a known, usually practically nondecaying (e.g., 36Cl) reference. The apparatus can be used both for the determination of long half-lives, and for studying the effect of chemical state upon the half-life of a radioisotope.
A Voltage Limiting Circuit for Superconducting Magnets
Authors: Martin P. M. , Garland J. C.
Published: February 2004

A simple circuit is described for safeguarding superconducting magnets from the large induced voltages which can occur upon quenching or power supply failure.
Double Focusing Uniform Field Magnet with Circular Poles
Authors: Livingood J. J.
Published: February 2004

Double focusing of charged particles by a magnet with uniform field and circular poles can be obtained for any single deflection angle by directing the beam at an appropriate point away from the axis of the poles. For a bend of 119.25° the aberration arising from radially divergent ions is eliminated.
Measurement of the Neutral H2O Density in Low-Pressure Plasmas
Authors: Lindinger W. , Howorka F.
Published: February 2004

An experimental arrangement is described which allows the exact determination of the density of neutral water traces in a cylindrical hollow cathode during operation of the discharge.
A Stabilization Circuit for Optical Derivative Measurements
Authors: Veal B. W. , Dexter R. N.
Published: February 2004

We describe a feedback stabilization circuit useful for measuring optical reflectivity (or absorptivity) derivatives. The circuit is designed to suppress signal amplitude variations from the measured ΔR/R without involving the light source, spectrometer, or detector in the feedback stabilization loop. The use of this circuit for normal incidence reflectance measurements is also discussed.
Electrostatic Wafer Chuck for Electron Beam Microfabrication
Authors: Wardly George A.
Published: February 2004

Vacuum wafer chucks are useless for electron beam microfabrication. An analysis of the required electrostatic forces and frequency response of a specimen wafer on a field plate is made. An experimental electrostatic chuck and its high voltage square wave power supply have been fabricated. Full clamping action has been provided by electrostatic pressures of 1/6 atm, and 1 atm pressures are feasible. In-vacuum operation is excellent down to supply frequencies of 0.01Hz.
Energy Loss of Low Energy Nuclei in Silicon Surface Barrier Detectors
Authors: Campbell R. Dean , Lin R. P.
Published: February 2004

We present measurements of window energy loss and pulse height defect in a silicon surface barrier detector for nuclei of hydrogen, helium, nitrogen, neon, and argon at incident energies of ≲ 15 to ≳ 200 keV. The values of dE/dx in the gold window were low by [inverted lazy s] 20% for neon and [inverted lazy s] 40% for argon, and high by [inverted lazy s] 30% for nitrogen and [inverted lazy s] 50% for helium, compared to previously calculated energy loss curves extrapolated to these low energies. The pulse height defect energy losses were within [inverted lazy s] 10% for neon, low by [inverted lazy s] 15% for argon and low by [inverted lazy s] 30% for nitrogen compared to theoretical calculations.
Power Stabilization of a Helium-Neon Laser Using the Zeeman Effect
Authors: Franke Earnest A.
Published: February 2004

The helium-neon laser is utilized in many applications today by scientists and engineers. These applications frequently require a visible amplitude-stable optical source. Helium-neon lasers have been shown to have amplitude fluctuations of typically ± 1%. Amplitude stabilization techniques have been previously concerned with mechanical improvements, discharge current regulation, and variable loss modulation. The Zeeman effect of a magnetic field will be shown to control the output power of a helium-neon laser. A servo feedback system was constructed to demonstrate the ability to stabilize the visible power by reducing power fluctuations from ± 1.0% to ± 0.05%. The Zeeman effect stabilizer overcomes the necessary insertion loss of the current regulation stabilizer. It is also independent of the negative impedance high voltage discharge system.
A Plasma Calorimetric Probe
Authors: Katta S. , Lewis J. A. , Gauvin W. H.
Published: February 2004

A high-temperature calorimetric probe was shown to be a reliable method of measuring temperatures in argon and helium plasma jets in the range 2000 to 10 000 K. A number of simple corrections were found to be necessary to account for the heat transfer interactions between the calorimeter, its insulating jacket, and its water-cooled support, as well as for the flow of heat to the nose section of the calorimeter. At the high temperature level (12 000 K), the probe measurements agreed with the spectroscopic data reported in the literature, while the values in the lower temperature range were confirmed by thermocouple measurements. The probe could also be used to measure gas composition and gas velocity, and results of typical applications are given.
Molecular Beam Techniques Applied to Mass Spectrometric Thermospheric Density Measurements
Authors: Melfi Leonard T. , Brock F. J.
Published: February 2004

The kinetic theory of a drifting Maxwellian gas has been applied to the gas sampling problem in atmospheric density measurements aboard satellites and high velocity probes; and a molecular beam mass spectrometer has been developed for gas density measurements in the upper atmosphere which substantially eliminates gas-surface scattering and gas-surface reactions in the sample, and preserves the integrity of the gas sample during the analysis process. An ion source lens system has been developed and experimentally evaluated over the pressure range 10−7−10−4 Torr. The extracted ion beam was analyzed for energy distribution and angular distribution. For ion energy sufficiently high that the thermal energy of the gas can be neglected, the ion energy spread is less than 4 eV on-axis and 90% of the ions are within 2.5° of the beam axis. It is concluded that the application of this technique to atmospheric composition studies will substantially improve our knowledge of the upper atmosphere of the earth and other planets.
Internal Investigation of Microchannel Plates by Scanning Electron Microscopy
Authors: Polaert R. , Rodière J.
Published: February 2004

A new method for investigating microchannel plate quality is described. The microchannel plate is operated with an applied voltage, either with normal or reverse polarization. Without any polarization, the scanning electron microscope takes a picture only of the external flat face. With a reverse voltage, the secondary electrons may be collected from the full depth of the channel and give a clear and bright picture of the internal surface of the channel. With normal polarization, the secondary electrons are multiplied through the plate and give the image of the electron gain of each individual channel. This use of the SEM is therefore very helpful for studying the quality of the microchannel array.
Utilization of a Buffer Rod with the Ultrasonic Pulse-Echo-Overlap Technique
Authors: Trivisonno J. , Felice R.
Published: February 2004

The ultrasonic pulse-echo-overlap technique has been adapted for use with the buffer rod technique to measure sound velocities in solids. The proper cycle for cycle identification of the overlapped echoes is straightforward and unambiguous and the high sensitivity of the overlap technique is maintained.
Hydrophilic Support Films of Controlled Thickness and Composition
Authors: Taylor Kenneth A. , Glaeser Robert M.
Published: February 2004

A method is described for producing thin, hydrophilic support films for electron microscopy. These films have a well defined composition and can be made as thin as 10–15 Å. An application is described in which these hydrophilic films are used as ultrathin ``windows'' for frozen, aqueous specimens.
An apparatus for measuring adiabatic and isothermal Joule-Thomson coefficients at low temperatures
Authors: Alkasab K. A. , Budenholzer R. A.
Published: February 2004

An apparatus has been designed and constructed which is capable of measuring the adiabatic Joule-Thomson coefficient μ and the isothermal Joule-Thomson coefficient φ for gases at low temperatures and high pressures. The apparatus was calibrated with nitrogen gas using pressures as high as 73.82 atm, and temperatures as low as 155.5 K. Furthermore, measurements on three methane-ethane mixtures were carried out for a temperature range from 206.35 to 274.86 K and a pressure range from 3.37 to 42.24 atm for the adiabatic mode; and a temperature range from 222.22 to 274.70 K, and a pressure range from 3.77 to 62.93 atm for the isothermal mode.
A four probe cell for rapid resistivity measurements
Authors: Cahen David , Hahn J. R. , Anderson James R.
Published: February 2004

A device is described that enables rapid measurements of the specific resistivity of powdered semiconductors and metals. The apparatus is especially useful for the screening of a large number of materials as the only sample preparation involved is the pressing of a pellet of the material. The 4-probe van der Pauw method with pressure contacts is used. Circuits for both ac and dc measurements are given and their relative merits discussed. The cell can be used between 77 and 400 K. A controlled atmosphere can be maintained around the sample.
A time-of-flight trigger system for use with the SLAC 40 inch hydrogen bubble chamber
Authors: Smart W. M. , Moriyasu K. , Leith D. W. G. S. , Johnson W. B. , Friday R. G.
Published: February 2004

A data acquisition system consisting of time-of-flight scintillation counters, associated electronics, and a PDP-9 computer was developed and installed for use with the SLAC 40 in. hydrogen bubble chamber (HBC). The system was designed for optimum timing resolution subject to the limitations imposed by the HBC design and was used primarily to determine the momentum of a neutral beam of KL0 and neutrons, by measuring time-of-flight from a production target to the chamber. The system was also used to trigger the HBC flash only when a low momentum beam particle was recorded. This paper gives the details of the design and operation of the hardware and of the procedures necessary to incorporate the time-of-flight information into the more conventional bubble chamber picture analysis.
A precise refractometer for thermal neutrons
Authors: Schneider C. S.
Published: February 2004

A double crystal spectrometer control has been built to precisely measure semiautomatically both the small angles (20″) of refraction suffered by a thermal neutron beam in passing through a prism and, by substitution of a compatible second goniometer element, the large angles due to Bragg reflection of the monochromatic neutron beam. The construction, calibration, and sensitivity are described. With it a value of 4.147(2) fm was found for the neutron scattering amplitude of the silicon nuclear potential.
An ultrasonic attenuation recorder
Authors: Aker David , Kraft David W.
Published: February 2004

Circuitry for a simple and accurate ultrasonic attenuation recording system, for use with the pulse echo technique is described. Direct processing of low level signals and the use of generally available laboratory equipment reduce cost. Sensitivity is enhanced by the use of sufficient zero offset.
The determination of electron energy distributions at low energy
Authors: Fedak D. G.
Published: February 2004

Secondary electron energy distributions from most materials contain a great deal of fine structure, including Auger transitions, in the range 0–200 eV. Especially in the case of retarding field energy analyzers, these relatively small peaks are superimposed on a large smoothly varying background signal with the result that quantitative measurement of peak heights is especially difficult. A method for minimizing the undesirable background signal is described; it utilizes appropriate programing of the ac modulation of the retarding potential, VacαEm sinωt. This technique results in improved energy resolution of retarding field analyzers at low electron energies where, in general, resolution is more critical than sensitivity. The detection of fine structure which would normally be lost if a constant modulation signal were employed as in the conventional procedure is demonstrated.
Microscopic circuit fabrication on refractory superconducting films
Authors: Palmer D. W. , Decker S. K.
Published: February 2004

Fabrication of thin film refractory metal superconducting weak links by photoresist and selective anodization techniques is described. Structures as small as 0.3 μ have been fabricated with registry of subsequent structures to a precision of better than 0.5 μ.
A photoemission electron microscope using an electron multiplier array
Authors: Baxter W. J. , Rouze S. R.
Published: February 2004

A Philips thermionic emission electron microscope has been converted into a photoemission electron microscope by the addition of a simple ultraviolet illumination system and an electron multiplier array for image intensification. Photoemission images are formed without heating or activation of the surface. One example includes the first electron optical image of exoelectron emission from an abraded metal surface.
Air spark fiducial for ultra-high-speed photography
Authors: Graham H. M. , Leavitt G. A.
Published: February 2004

A triggered air gap has been developed for inserting timing marks on the film of streaking cameras used in ultra-high-speed photography. The gap has a rise time ten times faster than existing xenon flashlamps. The peak output of 7 × 106 cd/cm2 (7Mcd/cm2) achieves the same film density as the lamps. This paper describes both the design used to achieve low inductance in the gap and the driving circuitry.
Difference Auger spectroscopy for studying small quantities of elements on metallic surfaces
Authors: Varma M. N. , Joshi A. , Strongin Myron , Radeka V.
Published: February 2004

Increased sensitivity in the detection of small amounts of impurities has been demonstrated by using a difference technique in Auger electron spectroscopy. The primary electron beam is switched at a frequency of 30 Hz between two points or two samples of interest. The signals from the two samples are subtracted electronically so that the final output is the difference of the Auger spectra from the two samples and is therefore sensitive to small differences in composition between the samples.
Software emulated multichannel lock-in detector
Authors: Alles H. G. , Higgins R. J.
Published: February 2004

A computer program and simple hardware are described for performing multiple channel phase sensitive detection (and synchronous signal averaging) in the low audio frequency range using a laboratory minicomputer. Additional techniques are described to provide a real-time display of the harmonic content of a signal and a method of calibrating the frequency dependent phase shift of a filter network. The application of these techniques to precise measurements of the wave form of the de Haas-van Alphen oscillations are discussed.
A multiple substrate-mask-source thin film deposition system
Authors: Kazmerski L. L. , Morgan G. K. , Pedersen A. P.
Published: February 2004

A versatile and relatively inexpensive thin film deposition system which provides the selection of a number of substrate-mask-source arrangements is presented. The system, designed for use in a 36 cm ultrahigh vacuum chamber, uses one linear and one rotary feedthrough to accomplish all mechanical motion.
High intensity pulsed analyzing light sources for nano- and micro-second absorption spectrophotometry
Authors: Luthjens L. H.
Published: February 2004

This paper describes in detail the construction, circuitry, and performance of high intensity pulsed analyzing light sources with 500 W xenon short arc lamps, used in nano- and micro-second absorption spectrophotometry. Operation is based on discharge of a rectangular current capacitor bank with sag correction, and initiated by firing a single high current thyristor. Light pulses of about 1 msec duration with a flat top, where the intensity is constant within 0.2% during 100 μsec, are produced. Data on the ratio of the light intensity as a function of wavelength in the pulsed mode as compared to continuous operation are presented as measured in the actual absorption spectrophotometer used in pulse radiolysis experiments. At a wavelength of 600 nm the pulsed intensity is found to be linear with capacitor bank voltage. Routine operation of an Osram XBO 450 W lamp in an Oriel C-60–50 housing with the capacitor bank charged to 110 V gives typically a pulsed to continuous intensity ratio of 16 at 600 nm and 40 at 300 nm. Approximately 20 times higher light intensities have been obtained by using a Varian Eimac xenon illuminator 500 × 10 R.
Single photon detection and sub-nanosecond timing resolution with the RCA C31034 photomultiplier
Authors: Reisse R. , Creecy R. , Poultney S. K.
Published: February 2004

The very high quantum efficiencies and low dark count rates achieved with selected RCA C31034 photomultipliers make them attractive candidates for single photoelectron fast timing experiments. Single photoelectron plateau counting and a timing resolution of 0.60 nsec (FWHM) were obtained using fast amplifiers, constant fraction timing discriminators, and a pulsed light emitting diode. A redesign of the C31034 incorporating features of the very fast C31024 is suggested to yield even better timing resolution.
Simple windowless lamp for ultrahigh vacuum photoemission spectroscopy
Authors: Rowe J. E. , Christman S. B. , Chaban E. E.
Published: February 2004

A windowless resonance discharge lamp with differential pumping is described. The lamp can be isolated from an ultrahigh vacuum sample chamber by a bakable valve. The differential pumping arrangement is very simple and uses only one mechanical forepump and one oil diffusion pump.
Static ultrahigh pressures above 500 kilobars
Authors: Lorent R. E.
Published: February 2004

A two-stage apparatus for ultrahigh pressures has been developed. It consists of a pair of Bridgman anvils in a Bundy-type high compression belt. A normal working pressure for this arrangement is 160 kilobars in the outside belt, which gives around 700 kilobars between both Bridgman anvils or only 500 kilobars if we consider Drickamer's new calibration values. A new calibration point is proposed: ZnS maximum of resistance at 640 or 480 kilobars. The apparatus is capable of reaching pressures far above the last known calibration point of ZnS at 550 or 415 kilobars in a new scale. Attempts to convert graphite to metallic carbon without heating have not been successful.
A large volume quiescent plasma in a uniform magnetic field
Authors: Ault Earl R. , MacKenzie K. R.
Published: February 2004

A reasonably uniform cylindrical plasma, 15–20 cm diam, and collisionless for many wave experiments, is generated in fields up to 500 G by applying 200 V of rf at 80 Mc to a fine wire grid stretched across a diameter. Axial containment is provided by opposing sets of μ-metal strips that gather lines of force and create multimirror fields. Drift waves are inhibited by a short range peripheral alternating shear field, produced by an azimuthal ring of bar magnets. Densities are 108−109 ions/cm3 in argon with electron temperatures up to 12 eV, with a noise level, δn / n ≈ 3 × 10−3, over the ion acoustic frequency range.
A capacitance method for measurement of film thickness in two-phase flow
Authors: Özgü Mustafa R. , Chen John C. , Eberhardt Nikolai
Published: February 2004

A new capacitance method is described for the measurement of local, time-varying or steady-state film thickness in two-phase flow studies. The method is suitable for use in simple and complex geometries, and works for either electrically nonconducting or slightly conducting fluids. Test data were obtained on bubbles of different lengths rising in a circular tube filled with water. Results for film thicknesses and bubble residence times showed good self-consistency and agreement with other available data.
A gas circulation system, using a Toepler pump, for the construction of a polarized 3He target
Authors: Timsit R. S. , Hilger W. , Daniels J. M.
Published: February 2004

A flow system capable of circulating polarized 3He gas between a target chamber and an optical pumping volume has been constructed. The two vessels hold the gas at pressures of approximately 760 and 1 Torr, respectively. The circulation unit consists of a reliable Toepler pump and a gas retrieval device made from a heated length of glass capillary tubing with a copper wire insert. Under the conditions of our experiment, the 3He gas circulation rate may be varied between 0.50 and 0.15 cc STP min−1.
Microtool fabrication by etch pit replication
Authors: Kiewit D. A.
Published: February 2004

Small tools can be made by etching one of a variety of crystallographically limited pits into a single crystal mandrel, filling the pit with tool material and removing the mandrel. Fabrication of arrays of chisels and pyramidal points using a silicon mandrel and process technology common in the semiconductor electronics industry is discussed.
A new polarization-modulated light scattering instrument
Authors: Hunt Arlon J. , Huffman Donald R.
Published: February 2004

A new light scattering instrument is described for measuring, as a function of scattering angle, the elements of the matrix describing light scattered from small particle systems. The instrument uses a piezo-optical birefringence modulator to modulate the polarization state of the incident light beam, and uses lock-in amplifier detection of the scattered light. The first and second harmonics of the modulation frequency are used with various combinations of filters and orientations to give the separate matrix elements. A treatment of a simple scattering experiment by means of Mueller calculus is carried through to illustrate the interactions of the light with the scattering system and with the various components of the measuring instrument. Evaluation of the instrumental performance is shown through measurements on two systems of monodisperse polystyrene spheres of average radius 550 and 3940 Å, compared with Mie calculations. Further measurements on sulfur colloids are presented, and suggestions of the value of this type of instrument in future work are given.
A simple, electrical calibration technique for bolometer detection systems
Authors: Alphin H. B. , Fisk G. A.
Published: February 2004

A simple, purely electrical technique for determining the responsivity of a bolometer detection system is presented. This technique is easy to use and allows the system to be calibrated under actual operating conditions.
The cleaning of magnetic ion pumps by chemical etching
Authors: Schmidt Paul H. , Shen L. Y. L.
Published: February 2004

A chemical etching method is described to improve the speed and ultimate vacuum of sputter ion pumps. The entire pump is immersed in strong acid solution in order to avoid the difficult and unnecessary task of disassembly recommended by the manufacturers.
Photoelectric scanning device for spectrographs
Authors: Fabeni P. , Fontani P. , Pazzi G. P. , Ranfagni A. , Tirelli D.
Published: February 2004

A device is described which permits the transformation of a plate prism spectrograph into a photoelectric scanning monochromator. A movable slit followed by a photomultiplier tube, which drives an x-y plotter, makes possible the direct recording of the spectrum.
Fluidropper—A Device for Forming Highly Uniform Drops
Authors: Samuels W. Ed , Sparks Robert E.
Published: February 2004

A technique is discussed for forming liquid drops of uniform size from a syringe needle. The method is unique in that it employs fluidic technology to produce drops with diameter independent of rate of formation over a wide range of rates. The velocity and placement of the drop after formation are controlled. Drops from 100 to 3000μ in diameter may be produced at rates between 0 and 15 drops per second. Standard deviations of diameter below 1% can be obtained.
Method for Determining the Time of Flow in a Capillary Viscometer with an Absolute Accuracy of 3×10−6
Authors: Priel Z. , Sasson M. , Silberberg A.
Published: February 2004

A method was developed for measuring the time of flow in an Ubellohde viscometer to an accuracy of 3 ppm. For this purpose the following points were shown to be crucial: (a) use of a thermostat with a long time thermal stability of ±2×10−4°C; (b) closing the viscometer off to the outside during all stages of the experiment; (c) adoption of a standard procedure for cleaning and preparing the glass surface; (d) maintenance of the viscometer bulb and capillary always in contact with the fluid by raising level immediately after each experiment; (e) adjustment of the position of the viscometer reproducibly; (f) measurement of the time of flow to within 1 msec. A full description of all parts of the system except the thermostat is given. The thermostat has been described separately. Examples are given illustrating both the accuracy of the technique and the importance of each and all of the above points.
Apparatus for the Measurement of Magneto-Optical Rotation and Ellipticity
Authors: Scholtens D. J. , Kleibeuker J. F. , Kommandeur J.
Published: February 2004

An apparatus based on the spinning analyzer technique is described for the measurement of MORD and MCD as a function of wavelength in the region of 6500–3200 Å. Rotation angles can be measured to an accuracy of 0.002°, while the spectrum can be recorded continuously. A discussion of the signal-to-noise ratio is given. It is shown that the performance is very close to the theoretical limit.
The Design, Analysis, and Performance of Resonant and Nonresonant Microwave Transmission Devices with Theoretically Infinite Rejection
Authors: Moore W. S.
Published: February 2004

There have been several designs proposed for bimodal transmission resonators for use in EPR, Hall effect, and Faraday rotation measurements. Some of these are based on attempts to spatially define the field patterns of the normal modes of cylindrically symmetric resonators. Others try to separate the modes so that in some parts of the resonator, the radio frequency fields of predominantly one mode will be found. In this way, independent adjustment of the mode characteristics is attempted so that an adjustable null transmission resonator results. The property to be measured for a sample placed inside the resonator causes an imbalance and the resulting output appears in place of the null. This paper describes a different approach to the practical realization of such a resonator and gives the appropriate theory for its operation. In the resonator to be described the spatial position of the normal modes can be altered by a simple rotation control, and the input radio frequency field polarization direction can be rotated by another such control. There is a direct analogy between microwave propagation through this device and optical propagation through an anisotropic medium situated before an analyzer. The complete cavity resonator shows a minimum rejection in transmission which can be made arbitrarily large, and a tunable rejection notch whose attenuation has been observed to be greater than 100 dB, and which is theoretically infinite. A practical nonresonant device based on the same approach is also described.
A TE01n Cavity Resonator Method to Determine the Complex Permittivity of Low Loss Liquids at Millimeter Wavelengths
Authors: Stumper U.
Published: February 2004

Two oversized TE01n cavity resonator systems have been constructed that are suitable for measuring the complex permittivity ε=ε′ (1 − j tanδ) of low loss liquids at millimeter wavelengths. One of them operates at frequencies from 26 to 70 GHz, while the second, which is described in detail, was tested at frequencies around 136 GHz where a quality factor of about 60 000 was obtained. ε′ is determined from the wavelengths measured in the filled and unfilled resonator. The loss factor tanδ is obtained from the half-widths of the resonance curves in both resonator states. For that purpose, the frequency of the oscillator is swept, and the resonance curves vs frequency are displayed on an oscilloscope. Frequency calibration marks are generated by the absorption resonances of a second long open resonator operating in the HE11m dipole mode which is guided by a thin dielectric thread. To restrict the influence of traces of water in the liquids to be measured, the resonator is permanently connected to an apparatus that permits drying the liquids and filling and emptying the resonator without contact with atmospheric moisture. By this method, the complex permittivity at 136 GHz of seven nonpolar liquids (tanδ=3×10−4−30×10−4) has been determined. Insofar as possible the data are compared with published values.
The Calibration of Electrostatic Analyzers and Channel Electron Multipliers Using Laboratory Simulated Omnidirectional Electron Beams
Authors: Arnoldy R. L. , Isaacson P. O. , Gats D. F. , Choy L. W.
Published: February 2004

The difficulty of obtaining accurate calibrations of electrostatic analyzers employing large aperture channel electron multipliers is discussed. This is due primarily to the varying efficiency of large aperture multipliers depending on point and angle of impact on the aperture. This varying response makes the assignment of an over-all detector efficiency uncertain by at least a factor of 2. A laboratory calibration scheme is discussed by which the combined efficiency and geometry factor is obtained for flight detectors using a simulated omnidirectional source of particles.
A Rapid Scan Apparatus for Flash Photolysis Electron Spin Resonance
Authors: Hsi Edward S. P. , Fabes Leonard , Bolton James R.
Published: February 2004

A rapid field scan apparatus for use with ESR detection of transients produced by flash photolysis is described. Design data and test results are presented.
An Electromagnetic Technique for Measuring Material Velocity
Authors: Fritz J. N. , Morgan J. A.
Published: February 2004

An electromagnetic technique for measurement of particle or material velocity inside an insulator or the free surface velocity of a conductor subjected to plane shock waves is described. The theory of the technique is described and two illustrative experiments are presented and discussed. The relative merits of the technique are discussed.
A Modified Technique for Cutting Metallic Crystals
Authors: Bansal S. K. , Duggal V. P.
Published: February 2004

A modified spark cutter for cutting metallic crystals is described. A weakly conducting electrolyte is employed instead of a pure dielectric. The cutting rate is faster and the damage caused to the cut surface is considerably reduced.
A Simple High-Vacuum Valve Which Can be Built into a Container Wall
Authors: Wellenstein H. F. , Bonham R. A.
Published: February 2004

A high-vacuum valve is described which consists of a wedge driven inside a rectangular cavity. The wedge fitted with an O-ring is moved over the opening to close the valve. The bore of the valve can be up to two times the valve thickness.
A Paint-On Vacuum System Heater
Authors: Winsemius P. , Lengkeek H. P.
Published: February 2004

A painted layer of a colloidal dispersion of graphite provides a versatile vacuum system heater.
Detection of Atomic Beams Using a Commercial Residual Gas Analyzer
Authors: English Thomas C. , Pernicka John C.
Published: February 2004

The detection efficiency of a high sensitivity, commercial, residual gas analyzer, when used as an atomic beam detector, has been experimentally determined to be 5.5×10−6 for a thermal beam of argon atoms.
High Pressure Optical Cell for the Study of Biochemical Reactions
Authors: Williams R. K.
Published: February 2004

An inner fused quartz cuvette with flexible inert seal is described which allows the examination of biochemical solutions at high pressures without contact with metal surfaces. The cuvette is used in a commercially available high pressure optical cell without further engineering.
A Simple Automatic Single Crystal Goniometer for Electron Spin Resonance Spectroscopy
Authors: Weymann D. , Flossmann W. , Hüttermann J.
Published: February 2004

A goniometer is described which permits automatic aquisition of electron spin resonance spectra of single crystals upon rotation about one axis in the magnetic field by means of an interface between the magnetic field sweep unit of the spectrometer and a stepper motor as rotating device.
Helium Recovery Using Weather Balloons
Authors: Linz R.J. , Chu T.K. , Lipschultz F.P.
Published: February 2004

Ordinary weather balloons are inexpensive, temporary storage vessels used to collect and transport small amounts of liquid helium vapors.