bluuebunny/crossref_metadata_2025 huggingface dataset:
An electron spectrometer for measuring both angular and energy distributions of photoemitted electrons
Authors: Pauty F. , Matula G. , Vernier P. J.
Published: February 2004

A velocity spectrum is obtained by dispersing the photoelectrons with a uniform electrostatic field; it is recorded on an electronographic film with the help of an electronic camera. To each point of the plate correspond definite values of the tangential and normal velocities of photoelectrons. The angular and energetic distribution N(W, φ) is calculated from the density of the electronographic plate. We hereby show the first structures obtained from thin films of gold.
A combined electron impact, chemical ionization, field ionization and field desorption mass spectrometer source
Authors: Gierlich H. H. , Heindrichs A. , Beckey H. D.
Published: February 2004

Detailed information about the construction and design of a combined ion source is given. By the use of an exchangeable ion exit slit for the ionization chamber the source is constructed to operate either at a source pressure of about 1 Torr for chemical ionization or at lower source pressures for electron impact ionization, field ionization or field desorption. The potentialities of this source are demonstrated by the mass spectra of a peptide as obtained with the different ionization modes.
Static electricity events detector
Authors: Rosenthal L. A. , Davis D. A.
Published: February 2004

A neon lamp is employed as a static electricity sensor. Each discharge event corresponds to a discrete energy. Instruments described for detecting single or multiple events are useful for static electricity evaluations and surveys.
Doubly resonant current-to-voltage converter preamp for surface spectroscopy
Authors: Pocker D. J.
Published: February 2004

The need for, and approaches to, frequency domain enhancement of signals from noisy, limited current experiments are reviewed. A doubly resonant current-to-voltage converter circuit for such applications, having low intrinsic time constant, noncritical tuning and yielding 90–110 dB rejection of frequencies a factor of 2 from that desired, is presented and analyzed in detail. Examples of its superb rejection of power line noise, transients and signals harmonically related to the frequency desired are demonstrated and general comments about its use are given.
A high precision volumetric gas adsorption apparatus for surface studies
Authors: Drzal Lawrence T. , Putnam Frederick A. , Fort Tomlinson
Published: February 2004

This paper describes a volumetric adsorption system and measurement procedure which takes advantage of current vacuum technology and computational techniques, to determine adsorption isotherms and adsorption thermodynamics under ultraclean conditions with high accuracy, over a wide range of temperatures and pressures.
Technique for a contour display of photoemission uniformity
Authors: Hollish C. D. , Hertel R. J.
Published: February 2004

A contour plotter has been designed to display the sensitivity uniformity of photocathodes in quantized format on the Z axis of an oscilloscope. An optical scanner, synchronously driven by the oscilloscope X-Y deflection signals is used to raster scan the photocathode with a focused light beam. Sensitivity, resolution, and scanning time are sufficient to use the plotter to monitor sequential processing steps for photocathodes in demountable, ultrahigh vacuum systems. A general description of the contour plotter system and a detailed circuit description are given. An example relating to cesium uniformity on a III-V photocathode is presented to illustrate the use of the contour plotter.
Optical surface roughness and slopes measurements with a double beam spectrophotometer
Authors: Abdulkadir A. , Birkebak R. C.
Published: February 2004

Double beam spectrophotometers are commonly used in chemical analysis and transmittance measurements. With some modifications, the function of such instruments can be enlarged to measure the optical surface roughness and surface slopes of any roughened material. Results obtained using a modified Perkin-Elmer 621 double beam spectrophotometer are presented for stainless steel 304.
Contact optical cell for studying strong absorption bands in gases at high pressures
Authors: Laporte Pierre
Published: February 2004

An original thin optical cell for high pressure studies is described. The system of back pressure employed prevents the two windows from moving. In this way the only limitation in the control of thickness is due to elastic deformation of the two windows under pressure. The cell is particularly convenient for measurement of shifts of intense absorption bands. An example is given in the case of atomic lines of xenon in the region 1150–1500 Å, where thicknesses of less than 1 μ are necessary.
The measurement of transient circular dichroism: A new kinetic technique
Authors: Ferrone F. A. , Hopfield J. J. , Schnatterly S. E.
Published: February 2004

We report the construction of a system to measure the circular dichroism of transient phenomena. The technique employs rapid modulation of the polarization of an analyzing beam, and consequently significant information can be obtained in a single run. The system is sensitive to changes in polarization strength of 2×10−5 occurring in 1 msec. The particular system described has been constructed to follow transient structure changes in hemoglobin following laser photolysis of CO hemoglobin. The technique is quite general, however, and design details are presented which would be useful in any attempt to apply modulation spectroscopy to transient measurements.
A spark gap switching system for gasdynamic facilities
Authors: Leibowitz Lewis P.
Published: February 2004

A spark gap switching system has been developed to coordinate the discharge of a 300 kJ capacitor bank with the high speed flow of helium in a shock tube driver. The trigger system includes a flow transducer, a pulse forming circuit, a high voltage spark generator, and four heavy duty spark gaps that can carry total peak currents greater than 1.5×106 A. A glow gauge flow transducer sensitive to small gas density changes was used whose input power and signal output can withstand high voltage fluctuations. This switching system is of use with gasdynamic discharge devices requiring a minimum number of switches.
A method for the accurate measurement of lattice compressions of low-Z materials at pressures up to 12 GPa by x-ray diffraction
Authors: Halleck P. M. , Olinger Bart
Published: February 2004

The technique developed by Jamieson and Lawson for x-ray diffraction at high pressure has been modified so that low-Z materials can be studied under high pressure conditions to 12 GPa. A beryllium annulus replaces the commonly used boron annulus, allowing the use of Cu Kα or Fe Kα radiation, thus improving the accuracy of d-space determinations. The inclusion of a 4:1 methanol-chanol mixture developed by Piermarini, et al. relieves pressure gradients and anisotropy, improving both the quality and range of compression data. Excellent compression results are obtained in the 0–1 GPa region where x-ray techniques have formerly been inaccurate.
An ultrastable Mössbauer spectrometer using integrated circuits
Authors: Gupta A. K. , Sarma K. R. , Huntzicker J. J. , Rao G. N.
Published: February 2004

An ultrastable Mössbauer spectrometer using integrated circuits has been designed and tested. The system is designed to operate at velocities up to 100 cm/sec. Frequency stabilization of the order of 1 in 105 is obtained using a crystal-controlled oscillator. With the help of an automatic gain control circuit very good amplitude stability of the drive signal is obtained. The electronic system is designed to produce a sinusoidal velocity. The drive is capable of taking reasonably heavy loads so that the drive system can be kept at room temperature and the source is mounted at one end of a long stainless steel tube which goes into a helium Dewar.
Magnetosedimentation in macromolecular solutions
Authors: Simonsen W. John , Gill S. J.
Published: February 2004

The redistribution of macromolecules dissolved in a paramagnetic solvent upon application of an inhomogeneous magnetic field has been observed. Using a special apparatus, this effect termed ``magnetosedimentation'' can be measured and used to determine the molecular weights of macromolecules.
A microprogrammed computer interface with error detection and correction capability
Authors: Lewis J. W.
Published: February 2004

A computer interface for a clinical chemistry analyzer has been implemented using an MOS microprocessor. The interface uses ANSCII serial data transmission, incorporates error detection and correction, and may additionally serve as a teleprinter driver. Several benefits resulted from the use of a microprogrammable processor. Design changes during the development cycle were easily accommodated, and different instruments or communications protocols may be accommodated by changing only the microprogram stored in an erasable, reprogrammable read-only memory.
Economical mass spectrometer ion current measurement with a commercial parametric amplifier
Authors: Russell R. D. , Ahern T. K.
Published: February 2004

A Philbrick model 1702 parametric amplifier has been used as an input device for the measurement of mass spectrometer ion currents. The results obtained have been comparable with those obtained by other methods, although the cost is very modest. Combined with an Analogic AN-2544 ratio meter, it has been used to make an economical ratio recording system for oxygen isotopic analysis.
A multi-exposure x-ray powder camera for high pressure work
Authors: Singh Joginder
Published: February 2004

A multi-exposure powder camera for high pressure x-ray diffraction studies up to 150 kilobars is described.
A differential pressure sensor for use in high ambient pressures
Authors: Boyle W. P.
Published: February 2004

A differential pressure sensor is described. This instrument is capable of resolving pressure changes of about 3.0 kN/m2 in ambient pressures of up to 1.0 GN/m2. The instrument is of the deflecting diaphragm type with the movement being measured by an inductive transducer.
Ultrahigh-vacuum, high pressure and temperature infrared-ultraviolet-visible spectrophotometer cell
Authors: Gallei E. , Schadow E.
Published: February 2004

An ir-uv-visible spectrophotometer cell for examining gas-solid interactions at elevated temperatures up to 600°C and high pressures or ultrahigh vacuum has been designed and fabricated. The cell is employed for characterization of reactive catalyst species and reaction intermediates which exist only at conditions above ambient. The pressure maxima are limited by the window material which in turn is determined by the spectral range to be investigated. A compact design out of one piece and large windows permit the use of the cell interchangeably among a variety of commercially available ir and uv-visible spectrophotometers. The design of the cell has been reported. In addition two specific applications of the cell to high vacuum and high pressures at elevated temperature (200°C) are described.
A digital autocorrelator for quasi-elastic light scattering using a minicomputer
Authors: van Resandt R. W. Wijnaendts
Published: February 2004

A fast averaging, multibit digital autocorrelator for use in quasi-elastic light scattering is described. An essential feature is the on-line data processing. Its performance is tested by measuring the quasi-elastic light scattering of Ludox particles suspended in water.
Seeded supersonic alkali atom beams
Authors: Larsen R. A. , Neoh S. K. , Herschbach D. R.
Published: February 2004

A seeded supersonic beam source for alkali atoms is described which provides velocities up to ∼ 5 km/sec. Potassium or rubidium vapor at ∼ 0.02 to 0.2 Torr is mixed with a diluent gas of H2, He, or Ar at ∼ 800 Torr and expanded through a pinhole nozzle. The beam properties are found to compare well with the simple theory of isentropic expansions. Typically, the alkali flux is ∼ 1016 atoms sr−1 sec−1 and the velocity spread is ∼ 8% (FWHM).
300 kV rectangular pulse generator with nanosecond risetime
Authors: Genuario R. D. , Blackburn J. C.
Published: February 2004

A system is described for producing rectangular pulses up to 300 kV in amplitude with rise times of about 1 nsec and pulse widths adjustable between 5 and 20 nsec. A coaxial line is pulse charged from a Martin-type autotransformer and then discharged by a fast-rise high pressure switch into a matched CuSO4 load resistor. A low inductance, capacitive voltage divider allows monitoring of the pulse. The pulse reproducibility is excellent and the low jitter (250 nsec) in the discharge switch allows synchronization with other events. The system has been in use for two years with satisfactory results.
A high accuracy, high resolution, remote control uniaxial stress apparatus
Authors: Gorman M. , Doehler J. , Solin S. A.
Published: February 2004

A uniaxial stress apparatus designed for low-temperature light-scattering experiments is described. It is more compact and potentially more accurate than previous designs. The apparatus can be used to produce a compressive uniaxial force of up to 8.92×108 dynes with an estimated accuracy of 1.5% and can operate in a temperature range of 1.2 to 300 K. The design does not restrict this apparatus to light-scattering measurements and it could be easily modified for application to tensile uniaxial stress. This apparatus has been used to observe the splitting of the valley-orbit Raman line in Ge(As) as a function of uniaxial stress along the [110] axis and to successfully apply the highest reported uniaxial stress along the [110] axis in germanium, 23 kilobar.
Self-contained continuously variable attenuator for pulsed CO2 laser radiation
Authors: Robinson A. M. , Nohr M.
Published: February 2004

A continuously variable attenuator for pulsed CO2 laser radiation is described. The attenuator uses an absorbing gas and a variable absorption length.
Constant speed drive for the magnetically supported equilibrium ultracentrifuge
Authors: McGee J. H. , Beams J. W. , Kupke D. W.
Published: February 2004

A constant speed drive (10−3%) is described for the magnetically supported equilibrium ultracentrifuge
Ultrahigh-vacuum manipulator for LEED studies
Authors: O'Neill M. R. , Dunning F. B.
Published: February 2004

A simple manipulator is described which allows rotation of a target crystal about two mutually perpendicular axes in addition to the normal up-down, tilt, and translational motions.
An x-ray spectral measurement system for nanosecond plasmas
Authors: Johnson David J.
Published: February 2004

A 15-channel Ross filter/silicon diode detection system has been developed for measuring nanosecond pulsed x-ray spectra in the energy range from 4.5 to 116 keV. The theory and practical aspects of Ross filters and silicon diode detectors are discussed as applied to this system. The data read-out system consists of a current integrator array, a simultaneous multichannel digital voltmeter, and oscilloscopes. The system is designed for compatibility with a small computer to allow real time spectral measurements. The x-ray spectrum of a 24 kJ dense plasma focus has been obtained with this system and a theoretical thick target electron beam x-ray spectrum fit to the experimental data. The best fit is obtained with an E−2 power law electron beam spectrum extending from 5 to 125 keV.
A cloud chamber control system
Authors: Hagen Donald E. , Tebelak Andrew C. , Kassner James L.
Published: February 2004

We describe an analog control system for the temperature control of an expansion cloud chamber. During the expansion, the sample gas and the chamber walls are cooled at the same rate so as to maintain adiabaticity. The control system measures the wall temperature with transistor temperature sensors, calculates the gas temperature from the gas pressure using the adiabatic gas law, and generates a control signal proportional to their difference. The control precision is sufficient to allow the chamber to be used in the study of atmospheric phenomena.
Interferometric measurement of fully turbulent free convective heat transfer coefficients
Authors: Black W. Z. , Norris Jack K.
Published: February 2004

A Mach-Zehnder interferometer provides information about the local temperature surrounding a heated body. When using this type of interferometer, the measurement of turbulent heat transfer coefficients is often difficult to achieve, and as a result most interferometric studies of heat transfer rates have been limited to laminar flow. A differential interferometer, on the other hand, provides a measure of the temperature gradient and this type of interferometer produces fringe patterns that are an excellent means of observing the flow structure within a turbulent free convection boundary layer. Parallel fringe patterns can easily be converted to local heat transfer coefficients. Heat transfer coefficients measured in air above an isothermal inclined flat plate are presented. These are in excellent agreement with previously published results.
An experimental technique for monitoring dynamic cracks
Authors: Lavengood R. E. , Peretz D. , Brissey F. L. , Wu E. M.
Published: February 2004

A technique is presented which, by means of plating and etching processes, permits the creation of a wide variety of crack propagation gauges. High precision gauges of arbitrary size and shape are easily prepared. Specific gauge configurations are shown for center notch, edge notch, and cleavage type specimens. Optimum-gauge design is discussed and typical readout circuits are shown.
Circular plotter and kinoform lens
Authors: Ichioka Yoshiki
Published: February 2004

A kinoform is an optical device that shapes the phase of a wavefront in any arbitrary manner. For making a kinoform, one first has to plot a black-grey-white pattern that is then photographed and bleached. Bleaching is a process that converts a photographic amplitude distribution into a corresponding phase distribution. Often a kinoform has circular symmetry, then called a ``kinoform lens.'' We describe a plotter that can provide a circular pattern suitable for kinoform lenses. Our circular plotter is easy to assemble from simple commercial components. We show two results: a Fresnel lens, and an aspherical corrector plate.
The direct evaluation of a first-order rate constant from spectrophotometric data using (i) a logarithmic-logarithmic circuit, and (ii) a logarithmic-differentiator-logarithmic circuit
Authors: O'Donnell D. , Phillips E. G. , Rees N. H.
Published: February 2004

These methods enable the rate constant of a first-order reaction to be determined directly, and eliminate the need to perform a conventional kinetic analysis. The logarithmic-logarithmic technique is more versatile since it is suitable for determining the rate constant of fast reactions studied by both stopped-flow and temperature-jump techniques. The disadvantage of this method is that two kinetic runs are required in order to determine the rate constant. The second method, using the logarithmic-differentiator-logarithmic circuit is most suitable for reactions studied by the stopped-flow technique but the rate constant is determined from only one kinetic run.
An alternate to hot film flow sensors
Authors: Sorrell F. Y. , Sturm G. V.
Published: February 2004

A sensing element different than the usual hot film is used with a conventional constant-temperature anemometer. The sensing element is flat and quite thin, so it can be coated with a protective film which permits it to be used in liquids which would normally react with a hot wire. The probe is very much cheaper and easier to construct than a hot film probe, yet sensitivity is similar. In addition this probe is considerably more rugged than the usual hot film. Velocity measurements using a typical probe in water are given.
A simple two-fiber optical displacement sensor
Authors: Powell J. Anthony
Published: February 2004

An optical displacement sensor is described in which only a pair of large-diameter fibers is used rather than a branched bundle of many small-diameter fibers. The basic idea of the two-fiber sensor is that the axes of the fibers are at an angle to one another at the sensor face, rather than parallel as is the case for the many-fiber configuration. The sensitivity of this two-fiber sensor is approximately the same as the most sensitive configuration of the many-fiber sensor.
A 4.2–300 K cryostat for neutron diffraction under high pressure
Authors: Claudet G. , Disdier F. , Senet L. , Buevoz J. L. , Roult G.
Published: February 2004

We describe a cryostat for neutron diffraction experiments under pressure of 40 kilobar at 4.2–300 K. In this device liquid nitrogen is not used to cool the thermal screens. The pressure is transmitted by columns cooled only by helium boil-off vapor. One of them can move freely over a range of several centimeters. The liquid helium consumption at 4.2 K is 0.7 liter/h.
A circuit for the detection of turbulence
Authors: Paizis S. T. , Schwarz W. H.
Published: February 2004

Circuitry is described for the detection of turbulence. Also the criteria on which the detection is based are discussed. The device was used to study the features of the interface that exists on unbounded turbulent flows.
The measurement of energy in acoustic emission
Authors: Beattie A. G. , Jaramillo R. A.
Published: February 2004

A circuit for measuring the energy in randomly occurring bursts of rf energy is described. The circuit is linear to within 10% (over a 15 dB dynamic range) for frequencies up to 1.5 MHz. Examples are given of its use with acoustic emission data from a martensitic phase transition in the indium thallium system and from a nondestructive test on a filament wound vessel.
A medium scale minicomputer system for laboratory measurements
Authors: Higgins R. J. , Nosler J. C.
Published: February 2004

A flexible, powerful, and interactive computer-assisted measurement system is described, based on a 16-bit minicomputer and an extensive set of peripherals. A general purpose hardware-software configuration is described which enables different users to computerize measurements in completely unrelated experiments, with minimal changes in interfacing. General purpose subroutines to control the digitizing of measurements are FORTRAN -callable from user programs. The result is a system for computer-assisted measurements which may be used as a general purpose laboratory instrument, requiring only a knowledge of FORTRAN. Illustrative applications are described in several fields of physics. A comparative evaluation of other computerization schemes is given.
A novel and highly accurate technique for polarized light spectroscopy (the PNP method)
Authors: Yogev Amnon , Margulies Leon , Sagiv Jacob , Mazur Yehuda
Published: February 2004

A new, highly accurate technique for the measurement of linear dichroic spectra is described. This technique, named PNP method, is based on the measurement of absorption spectra with two successive scans, one with polarized light and the other with nonpolarized light. The main advantages of this method are as follows: (1) The use of a simple device including two identical units consisting each of a polarizer and two depolarizers; (2) recording of continuous spectra without rotating either the polarizer or the measured sample; (3) the possibility of accurate recording of polarization spectra of highly dichroic samples and of samples showing very sharp bands; (4) the possibility of using wider slits and the whole range of the spectrophotometer, without requiring additional resolving power.
Charge sampling method for low current measurement
Authors: Yair R.
Published: February 2004

A simple method of measuring low currents from current sources (transducers) is described. This method has a noise equivalent to an input current of 5 fA (5 × 10−15 A). A possible modification for 1 fA noise input is given. In this method of measurement, a charge generated by a current source is collected on a capacitor during a fixed time interval. In discharging the capacitor, an ac pulse is produced which is then amplified, and the required information extracted.
Microcalorimeter for measuring heat of straining or destraining of sheetlike materials
Authors: Ebeling Kari , Swanson John W. , Van den Akker J. A.
Published: February 2004

A gas-filled microcalorimeter is described. This instrument can be used to measure the simultaneous work and heat phenomena during uniaxial straining or destraining of thin sheetlike materials. The average accuracy of the heat-flow measurements of 0.1 mW or higher is about ± 10%. The same accuracy applies for heat measurements of 2 mJ or greater in the case of 1–2 min deformation experiments.
Apparatus for producing laser targets of 50 μ deuterium pellets
Authors: Jarboe Thomas R. , Baker William R.
Published: February 2004

Apparatus is described which produces 50 μ deuterium pellets that are being used in a laser produced plasma facility. The pellets are sliced from a continuously spun solid deuterium thread at a rate of up to 10 pellets/sec. The methods of thread production and slicing, and pellet collimation are discussed. A unique feature of the apparatus is that it uses no liquid helium.
Xenon arc lamp intensity stabilizer
Authors: Katzir A. , Rosmann M.
Published: February 2004

A simple method for stabilizing the light intensity of a xenon arc lamp, used in conjunction with a monochromator, is described. With this setup the stability of the emerging monochromatic light was better than 5%, throughout the spectrum.
A simple ``camera'' for high energy beams
Authors: Longo Michael J. , Haas Orman E.
Published: February 2004

By incorporating an x-ray intensifying screen into a standard 10×12.7 cm Polaroid film back, we have been able to reduce the exposure time required to obtain a beam profile drastically. The modified film backs have been used very successfully in high-energy neutron and charged particle beams.
An improved window seal for high temperature-pressure spectroscopic flow cells
Authors: Alberigs J. M. , Penninger J. M. L.
Published: February 2004

A window seal which enables spectroscopic flow cells with minimum dead space to be constructed is described. For windows with a diameter of 20 mm and an unsupported area of 10 mm diam the maximum operating conditions obtained were 450°C and 300 bars nitrogen pressure.
Calorimeter for measuring heats of wetting of solids in organic media
Authors: Topić M. , Micale F. J. , Leidheiser H. , Zettlemoyer A. C.
Published: February 2004

A thermistor type adiabatic calorimeter has been designed with the capability of measuring the heat of wetting of high surface area solids in organic liquids. Since the primary source of error in this type of experiment is trace water in the organic liquid, a method has been devised for introducing freshly distilled liquids directly into the calorimeter vessel and for maintaining dry conditions while introducing additional sample bulbs for measurements. The main feature in the design of the calorimeter vessel is the arrangement for removing the sample and readmitting a new sample under a positive pressure of dry nitrogen. This design allows this single-bulb calorimeter to achieve the advantages of a multibulb calorimeter for detecting the presence and effects of trace water in the organic wetting liquid. The sensitivity of the calorimeter, which contains a volume of 50–100 ml, was found to have an experimental uncertainty of ±0.03 cal. A series of heat of immersion experiments of NiO in organic liquids, where consecutive immersions were determined in the same liquid, yielded reproducibility results which were within experimental error and indicated that water was not present in measurable amounts in the wetting liquid.
A time-of-flight detection system for near threshold photoelectron spectroscopy
Authors: Tsai Bilin , Baer Tomas , Horovitz Michael L.
Published: February 2004

A time-of-flight detection system and apparatus have been developed to obtain photoelectron spectra for electron energies between 0 and 1 eV. This method has the advantage of collecting and analyzing photoelectrons of all energies simultaneously and therefore compensating for low signal levels due to low light intensities or small ionization cross sections. The collection efficiency and energy resolution are highest for electrons with near zero kinetic energy (≤100 meV). This technique has made it possible to obtain photoelectron spectra with a continuum light source dispersed by a monochromator. It is thus particularly useful for the study of autoionization events. Also presented are calculated potentials in 3-dimensional rectangular acceleration regions and the effect of initial kinetic energy on space focusing in nonconstant electric fields.
Adapting small dc motors for precise speed control
Authors: Wilcox S. D. , Eide S. A. , Caldwell D. R.
Published: February 2004

Utilizing a light-reflective transducer as sensor and an integrated circuit phase comparator for error detection, the rotation rate of an ordinary permanent-magnet dc motor can be controlled throughout wide ranges of both speed and load with the same precision as can the frequency of an oscillator. Both motor adaptations and circuitry are simple and relatively inexpensive.
Low temperature direct current comparators
Authors: Sullivan D. B. , Dziuba R. F.
Published: February 2004

This paper presents an improved version of the low temperature direct current comparator described originally by Harvey. The comparator described herein exhibits a resolution of 1.5 nA ·turn and provides ratios which have uncertainties of less than 4 parts in 1010. An alternate approach to the shielding of the windings is discussed and a preliminary comparator based on this concept is shown to have equally good performance. The latter comparator is probably better suited to the attainment of large current ratios.
Measurement of complex permittivity of liquids at frequencies from 60 to 150 GHz
Authors: Van Loon R. , Finsy R.
Published: February 2004

A method using standard waveguide components is described for accurate measurements of complex dielectric permittivity of low, medium, and high loss liquids up to 150 GHz. Measurements on cyclohexane, carbon tetrachloride, chloroform, and 1,1,1-trichloroethane are reported. The data of chloroform are compared with results from different authors, confirming an additional absorption above 40 GHz. The method is also suitable for determining the level of the continuous spectra obtainable by far infrared Fourier transform spectroscopy.
Focal properties of the two-tube electrostatic lens for large and near-unity voltage ratios
Authors: DiChio D. , Natali S. V. , Kuyatt C. E.
Published: February 2004

Accurate calculations of focal properties of the two-tube electrostatic lens are extended to cover a range of voltage ratios from 1.1 to 10000. The accuracy of the calculations is discussed in detail. For voltage ratios near 6400 the lens is found to be telescopic. Results are given in tabular form and as P-Q (object-image) curves. A simple analytical form for the focal properties of lenses with near-unity voltage ratios is given.
An instrument for recording the motions of microorganisms in chemical gradients
Authors: Lovely Peter , Dahlquist F. W. , Macnab Robert , Koshland D. E.
Published: February 2004

A relatively simple instrument is described which records the three-dimensional trajectories of swimming microorganisms. An important feature is the large sample chamber; this permits prolonged tracking in stable, defined gradients of chemotactic stimulants. Data concerning the motility and chemotaxis of the bacterium Salmonella typhimurium are presented.
Apparatus for fatigue tests in vacuum at low temperatures
Authors: Bachmann V. , Böhmer M. , Munz D.
Published: February 2004

Experimental apparatus is described for push-pull fatigue tests between room temperature and 77 K and in a pressure range between 760 and 5 × 10−8 Torr. The specimen grips are cooled with liquid nitrogen. The variation of the temperature is less than ±2°C in the whole temperature range. To ensure good heat insulation, the loading rod is divided by a system of steel rings interspaced with glass balls. First results with an aluminium alloy are presented.
A gated electron beam technique for Auger electron spectroscopy
Authors: Byrum B. W.
Published: February 2004

The necessary circuitry to implement recording of useful Auger electron spectra in the minimum practical time is described. The technique minimizes electron beam exposure of the sample, thus minimizing changes of the sample surface which can result from extended exposure to the electron beam.
A simple resistance probe for measurements from 4.2 to 300 K
Authors: Mitchell Michael
Published: February 2004

A simple apparatus for making resistance measurements from 4.2 to 300 K in liquefied gas storage Dewars is described.
A useful 350 MHz scaler
Authors: Baldwin Alan R. , Madey Richard
Published: February 2004

A single decade 350 MHz scaler has been designed and used to extend the pulse rate capability of present scaling instruments. The scaler counts fast negative pulses and has a pulse pair resolution of less than 3 nsec. The complete circuit and operating characteristics are described.
An instrument for nitric oxide measurements in the stratosphere
Authors: Ridley B. A. , Howlett L. C.
Published: February 2004

A completely automatic chemiluminescent instrument has been developed for in situ measurements of NO in the stratosphere. Signal intensity is linear in NO. Typical responsivity at 21.3 km is 1860 counts/sec ppbv. With a 1 sec measuring time constant, the detection limit as determined by noise is 0.03 ppbv. The instrument has been flown from balloon platforms to 30.8 km and from aircraft platforms between 12.2. and 18.3 km.
A continuous wave photofragment spectrometer
Authors: Dzvonik Michael J. , Yang Sze-cheng
Published: February 2004

A continuous wave photofragment spectrometer is described which can investigate photodissociative reactions by measuring angular dependent mass spectra of the recoiling photofragments. The three-state differentially pumped vacuum system consists of three mutually orthogonal axes: a polarized light axis (high pressure Hg–Xe), a molecular beam axis, and a quadrupole mass filter axis. The electric vector of the polarized light is rotated by a stepper motor (1-rpm). The photofragment signal from the tuned amplifier is lock-in detected and displayed on a strip chart recorder. Various inorganic filter solutions are employed in order to suitably excite the desired transitions of molecules with favorable absorption coefficients (∼100 1 mole−1 cm−1) in the spectral range of the excitation source. Signal averaging is accomplished using long lock-in amplifier time constants as well as multichannel scaling. The relative merits of cw photofragment spectroscopy are also discussed with particular reference to the photodissociation of large aromatic molecules. From the angular data, the polarization of the transition dipole relative to the detector axis, the lifetime of the excited molecular state, and the relative ease of fragmentation into different channels can be determined.
Metal vapor confinement in vacuum
Authors: Bacal Martha , Reichelt Walter
Published: February 2004

A new method for confining a metal vapor at a pressure of about 10−3 Torr, with extremely low loss of metal into the vacuum chamber surrounding the metal cell, has been demonstrated; it consists in recycling the metal, condensed in the liquid state; its return to the high pressure region is ensured by capillarity. Two versions of the new cell, built for different applications, are described: a heat pipe heated lithium cell, characterized by a high uniformity of temperature, and a cesium cell, equipped with a surface ionization gauge for cesium pressure measurement, and a LiF window. Measurements carried out with the surface ionization gauge in the cesium cell led to a ratio 103 between the cesium atom flux at the center of the canal and at its port. The contribution of direct metal loss from the hot central region of the canal and that due to desorption from the canal ports is discussed.
A magnetic spectrometer system for on-line studies of β rays and internal conversion electrons of short-lived mass-separated activities
Authors: Halbig J. K. , Wohn F. K. , Talbert W. L.
Published: February 2004

A π√2 high-resolution magnetic spectrometer has recently become operational at the TRISTAN on-line isotope separator facility. The design and operational modes of the spectrometer have been developed especially for on-line studies of short-lived mass-separated fission product activities. The spectrometer configuration is described, with particular emphasis on the magnetic field control and stabilization, the data collection modes and techniques developed to study nonequilibrium source activities, and the stabilization of the ion-beam deposit position by use of a split-tape ion-beam collector.
An ultra-low-noise preamplifier using superconducting quantum devices
Authors: Davidson A. , Newbower R. S. , Beasley M. R.
Published: February 2004

The application of superconducting (SQUID) galvanometers as low-noise preamplifiers with considerable bandwidth is explored. The important role of negative feedback in maximizing the bandwidth of these preamplifiers is carefully analyzed. Also discussed is the design and construction of superconducting impedance matching transformers suitable for making the unexcelled noise characteristics of these amplifiers available over a wide range of source impedances. A working preamplifier is described which has exhibited a maximum bandwidth of 10 kHz and noise temperatures in the liquid helium temperature range or below for all source impedances up to a few ohms. The operating characteristics of this preamplifier are compared to the best conventional room temperature amplifiers and are found to be superior for source impedances less than ∼10 Ω.
Use of cylindrical Auger spectrometers for retarding-potential secondary-electron yield measurements
Authors: Henrich Victor E.
Published: February 2004

The retarding-potential method of secondary-electron yield measurement described previously for use with hemispherical retarding-grid LEED optics has been extended to use with cylindrical mirror Auger spectrometers. The basic operation of the system was found to be comparable in the two cases, but a serious problem with the design of some electron guns was encountered. This problem could occur with either LEED or Auger spectrometers.
An autoranging scanning system and compatible methods of noise reduction
Authors: Saufley Duane C. , Andrew Kenneth L.
Published: February 2004

We have designed and constructed an autoranging scanning system to digitize the output of an infrared spectrometer and record it on magnetic tape. This system automatically scales the input signal, whose amplitude may range over ratios of 2000 to 1, to give a signal between 0.25 and 0.90 multiplied by an appropriate factor. Four noise reduction techniques compatible with the autoranging feature have been implemented. Two are a part of the electronic system itself and two utilize the computer in data processing. In particular, smoothing of data by least squares convoluting numbers and co-addition (addition of corresponding points) of spectral scans over the same region give definite advantages when compared to narrow band amplifier methods in distinguishing and measuring real features with intensities of the order of the noise background of the system. The methods described have general applicability to scanning systems in which the profile of the curve generated is the important measurement.
Fast digital correlator for weak optical signals
Authors: Corti M. , De Agostini A. , Degiorgio V.
Published: February 2004

A double-clipped digital correlator is described which works in real time up to a sampling frequency of 16 MHz and can perform auto-, cross-, and triple-correlation functions over 108 delays. The instrument is specifically designed to measure intensity correlations of weak light beams. A discussion of the statistical and systematic errors is given, with particular emphasis on the distortion introduced by the double-clipping procedure. As an example of the possible applications of the correlator a measurement of the intensity autocorrelation of the light scattered by a pure fluid is reported.
Dynamic background subtraction and the retrieval of threshold signals
Authors: Houston J. E.
Published: February 2004

An approach is outlined for handling the general experimental problem of retrieving characteristic signals from the presence of large backgrounds. The method consists of n th-order differentiation followed by multiple integration of the same order. It is shown that this procedure results in a function which has the form of the remainder of the (n - 1)th-order Taylor series for the background plus characteristic signals. If the function is one with a very large radius of convergence, then an order can be found such that the remainder is arbitrarily close to zero over the region of interest. Threshold functions, which are characterized by having very small convergence radii and which asymptotically approach zero on one or both sides of the point corresponding to the minimum radius of convergence, are shown to be accurately retrieved if the minimum convergence radius is contained in the region of integration. The particular advantages of the technique are demonstrated by its application to soft x-ray appearance potential spectroscopy.
Precise length measurement technique under hydrostatic pressure: Isothermal bulk modulus of PMMA
Authors: Spetzler H. A. , Meyer M. D.
Published: February 2004

An ultrasonic technique for precise measurement of sample length changes under pressure has been developed. The sample is immersed in mercury, and the length of the mercury column below the sample is measured by an ultrasonic interferometric method to give the length change of the sample relative to the steel container. The length change has been measured and the bulk modulus obtained for PMMA (polymethylmethacrylate) up to a pressure of 10 kilobars. An error analysis indicated that the principal sources of error are temperature changes during the experiment, and nonreproducible acoustic coupling effects at the mercury boundaries.
A marginal oscillator detector for ion cyclotron resonance spectrometers
Authors: Warnick A. , Anders L. R. , Sharp T. E.
Published: February 2004

Design, construction, and performance of a solid state marginal oscillator for detection of ions in ion cyclotron resonance experiments are described. Special design features include noise matching a high Q tank to an FET preamplifier which sacrifices voltage level for improved S/N ratio, amplitude limiting to remove noise from the feedback signal, and impedance matching the feedback resistor to the tank to minimize phase shift, parasitic capacitive coupling, and tank loading. A simple electrical circuit which simulates power absorption by ions for performance testing and comparison among marginal oscillators for icr applications is also described.
Production of a monochromatic, low energy positron beam using the 11B(p,n)11C reaction
Authors: Stein T. S. , Kauppila W. E. , Roellig L. O.
Published: February 2004

A new technique has been developed to produce an intense positron source by making use of the 11B(p,n)11C reaction. Positrons with well-defined low energies have been observed emerging from the irradiated boron target itself without any additional moderating materials. A description of the apparatus used to produce the 11C and to detect the low energy positrons is given.
A high voltage pulse generator for acoustoelectric studies
Authors: Griffing Bruce
Published: February 2004

A simple high voltage pulse generator, suitable for acoustoelectric studies, is described. Pulse outputs of variable width and amplitudes up to 1 kV are achieved. A technique to increase the maximum output to 3 kV is mentioned.
Lyman-alpha detector with MgF2 window
Authors: Masuoka Toshio , Oshio Takanori
Published: February 2004

Ion chambers having a polished MgF2 window and filled with nitric oxide gas have been developed for the measurements of absolute intensities of solar and geocoronal hydrogen Lyman-α radiation. The area sensitivities of the detectors and the effects of moisture on the transmittances of MgF2 single crystals were measured and compared with those in the cleaved LiF cases. The results indicate that an ion chamber with a polished MgF2 window has a superior suitability for the reliable measurement in rocket and satellite experiments as well as in laboratory work.
A simple, high current gold ion source
Authors: Mattes H. G.
Published: February 2004

A simple, compact ion source has been developed capable of producing a continuous, uncontaminated beam of singly ionized gold with intensities up to 0.75 mA. Electron-impact ionization is used in a gold plasma; no support gas is used.
A sensitive two-frequency radiometer for remote sensing of temperature profiles
Authors: Snider J. B.
Published: February 2004

The design and operating characteristics of a two-frequency radiometer operating in the 50–60 GHz band are described. The system was developed as a remote sensor of the vertical temperature profile in the lower atmosphere. Recent applications of the system as a temperature probe are summarized.
The absolute thermopower of some low temperature thermocouple wires in high transverse magnetic fields
Authors: Chiang C. K.
Published: February 2004

The thermopowers of some low temperature thermocouple wires have been measured from 4.2 to 100 K in magnetic fields up to 100 kG. Our technique is designed to circumvent the usual problems of temperature measurement in high magnetic fields. Some representative curves which display the absolute thermopowers of Au–0.07 at.%Fe, Chromel P, and ``Silver Normal'' in a transverse magnetic field are presented. A complete set of calibration tables for thermocouples of type Chromel P vs Au–0.07 at.%Fe and type ``Silver Normal'' vs Au–0.07 at.%Fe have been prepared and are available upon request.
Premature field evaporation in the atom probe
Authors: Krishnaswamy S. V. , Müller E. W.
Published: February 2004

The motion of ions evaporating in the subnanosecond period before a pulse has matured is invoked in the interpretation of resolution limiting energy deficits in the TOF atom-probe. The second order, nonlinear differential equation of motion in the time and space dependent field is numerically solved by computer. Two shapes of the pulse front, in which the final voltage level is approached either from below or from an overshoot are considered. The latter case accounts for the actual observations by giving the proper magnitude and mass dependence of the energy deficits.
The Shallow-water Octopuses (Cephalopoda: Octopodidae) of the Philippines
Authors: Norman M. D. , Sweeney M. J.
Published: February 2004

The shallow-water octopuses of the Philippines are diagnosed on the basis of material collected in a series of expeditions by the Smithsonian Institution to the region between 1978 and 1990. Twenty species of shallow-water octopuses are recognised, 18 in the genus Octopus, and one species each in the genera Hapalochlaena and Cistopus. Three new species are described from Philippine waters: Octopus abaculus, O. nocturnus and O. pumilus. Octopuses reported in the earlier work of G. L. Voss on the cephalopod fauna of the Philippines are reviewed and identifications updated. A diagnostic key and illustrations are provided along with information on taxonomy, distribution, aspects of life history and importance in fisheries.