bluuebunny/crossref_metadata_2025 huggingface dataset:
System for reflection electron microscopy and electron diffraction at intermediate energies
Authors: Cowley J. M. , Albain J. L. , Hembree G. G. , Ho/jlund-Nielsen P. E. , Koch F. A. , Landry J. D. , Shuman H.
Published: March 2003

A system employing medium energy electrons (1–15 keV) for scanning microscopy and diffraction intensity measurements has been constructed. The specimen is situated in an UHV environment and can be cleaned by argon ion sputtering and heated up to 1000 °C. The resolution is currently about 300 Å for scanning images formed when secondary electrons are detected. The use of diffracted beams to form images is shown to provide new types of information regarding the structure and defects of crystal surfaces. Intensities and intensity profiles of diffracted beams can be measured for comparison with theoretical data and structure analysis.
High-power, ultrasonic fatigue testing machine
Authors: Tien J. K. , Purushothaman S. , Arons R. M. , Wallace J. P. , Buck O. , Marcus H. L. , Inman R. V. , Crandall G. J.
Published: March 2003

A machine capable of fatigue testing high strength alloys at an ultrasonic frequency (20 kHz), and a range of temperatures likely to be encountered by such materials in aerospace and power generation applications and in basic research, is described. The machine is assembled entirely from commercially available components used in ultrasonic joining processes. Basically, it consists of a power supply module and heavy duty transducer capable of delivering up to 1.2 kW of acoustic energy at peak-to-peak amplitudes ranging from 10 to 20 μ, which is further amplified by tuned acoustic horns. The machine sets up a 20 kHz standing wave in the resonant test specimen. Peak-to-peak displacement amplitudes in the specimen of up to 300 μ (typical stress levels up to 1400 MN/m2) can be achieved. Provisions have also been made to accurately monitor the frequency of testing and the displacement amplitude during the test. As an example of the capabilities of the machine, results of high-frequency fatigue tests performed over a range of temperatures are presented. Lastly, it is indicated that ultrasonic fatigue testing, by virtue of its extremely high rate of testing, can be conveniently used for the study of very slow fatigue crack propagation in engineering alloys.
Calibration of large area scintillation counters on cosmic rays
Authors: Saterlie Steven F. , Tompkins Donald R.
Published: March 2003

We report on the construction and calibration of a 6 m2 scintillation counter. The counter consisted of two 1.22×2.44×0.051 m pieces of clear Lucite which were optically joined along a common edge. Optically coupled on top of these were sixteen 0.61×0.61×0.019 m squares of NE 110 plastic scintillator. Light collection was achieved with eight photomultiplier tubes. This counter had an operational attenuation length of 4.8±0.9 m. Calibration of this counter with an anticoincidence counter to discriminate against multiple particle events is described. This anticoincidence counter permitted particles that passed through a small calibration area to be counted only if no other particles were passing through the remainder of the detector at the same time. Large area counters will often receive more than a single particle per event. Theoretical calculations for purely electromagnetic extensive air showers indicate that the 6 m2 counter tested receives an average of 2.5 particles per event. The calibration data yield 1.79±0.08 particles per event. These results imply that if calibration on the response from a single particle of an extensive air shower is desired, it is necessary to use the anticoincidence counter method described for counters of more than a few square meters area.
Simple moiré calibrator for velocity transducers used in Mössbauer effect measurements
Authors: Wit H. P.
Published: March 2003

A simple instrument to make absolute velocity calibrations of velocity transducers used in Mössbauer effect measurements is described. A short comparison with other calibration techniques is made.
Resistance alloy for low temperatures
Authors: Warnecke P. , Kose V.
Published: March 2003

A ductile copper–germanium alloy shows a negative relative temperature coefficient of resistivity of a few parts in 106/K in the temperature range of 1.5–4.2 K. Resistors based on this material are studied for stability under thermal cycling.
Lead-resistance-free resistance bridge for thermal conductivity measurements at low temperatures
Authors: Hsu Yingchieh
Published: March 2003

A bridge circuit is described. It eliminates the influence of sample temperature fluctuations as well as of lead resistance.
Current-regulated, high-voltage power supply for cw gas lasers
Authors: Maxson Dwight , Seiler D. G. , Tipton Larry
Published: March 2003

An economical, high-voltage, highly stable, current-regulated power supply with less than 0.1% rms ripple is described. The dynamic capabilities of 0–30 kV and 0–30 mA provide a versatile instrument for use with many cw gas lasers.
Contact shock-wave detector
Authors: Mulac A. J. , Guzman J. A.
Published: March 2003

A simple shock-wave detector for use in shock tube experiments is presented. The detector consists of a thin metal diaphragm and an electrode which contact upon arrival of the shock-wave pressure step.
Simple and inexpensive linear resistivity meter for applications in pure water measurements
Authors: Russ Tomás
Published: March 2003

A linear, liquid-resistivity meter circuit is described that operates by charging and discharging a capacitor through a cell in which the liquid is included, rendering no dc component across it. The resulting oscillating waveform is shown to have a period proportional to the cell resistance. A period–voltage converter is added in order to indicate the resistance on a moving coil instrument. The system’s dc supply and low consumption permit easy battery operation.
Inexpensive tungsten boat evaporation source
Authors: Silverman P. J. , Baker J. W.
Published: March 2003

A description is given of an inexpensive tungsten boat evaporation source which is easily made in the laboratory.
How to make high critical current joints in Ni–Ti wire
Authors: Blair David G. , Paik HoJung , Taber Robert C.
Published: March 2003

Methods are presented for making high critical joints in various thicknesses of niobium–titanium superconducting wire.
New signal-processing instrument for dual-wavelength/split-beam spectrophotometers
Authors: Wade Charles W.
Published: March 2003

Several new techniques for processing signals from dual-wavelength/split-beam spectrophotometers are discussed and contrasted with earlier methods. Based on these techniques, a signal-processing instrument has been built which achieves significant improvements in speed, range, accuracy, and noise reduction. Since this instrument does not use dynode feedback, any light detector (photodiode or photomultiplier) can be used. Additionally, the instrument can be interfaced to virtually all spectrophotometers by simply connecting it to the detector output and a signal of the same frequency as the light chopper. Older spectrophotometers can, therefore, be upgraded easily. At the heart of this instrument is a new type of phase sensitive detector (PSD) which can demodulate the detector output (which has been modulated by the light chopper) in such a way as to provide two simultaneous signal outputs: one corresponds to the ’’reference’’ beam or sample, while the other is the ’’measure’’ beam/sample. Any function of these two signals (e.g., difference, ratio, or log ratio) can easily be computed directly. Because the PSD is gated in such a way as to ignore switching transients from the light chopper, these transients do not appear as an error in the demodulated output. The full theoretical signal bandwidth of one-half the chopper frequency is available at the output since sample and hold amplifiers are used instead of low pass filters. Not only is speed improved, but chopper ripple in the output is reduced considerably.
Simplified method for the calibration of an atom-probe field-ion microscope
Authors: Wagner Alfred , Hall Thomas M. , Seidman David N.
Published: March 2003

A simplified method for determining the mass-to-charge ratio of single pulse-field evaporated atoms in a time-of-flight (TOF), atom-probe, field-ion microscpoe (FIM) is described. The method is rather insensitive to the value of the pulse factor (α). This is achieved physically by making the pulse voltage a constant small fraction (f) of the steady-state imaging voltage, where f is much less than unity and is as small as possible to maximize the mass resolution. Examples of the W+3 and W+4 spectra of specimens pulse-field evaporated at ∼25 K in a background vacuum of 6×10−10 Torr are presented. The W+3 spectrum exhibited very clearly the five naturally occurring isotopes (180W, 182W, 183W, 184W, and 186W) with isotopic abundances that are in good agreement with the handbook values. The value of α chosen has only a very minor effect on the exact shape of the W+3 and W+4 spectra. The ratio of W+4 events to the total number of events (W+3 and W+4) is 0.17 for the (551) plane.
On-line treatment chamber for surface studies
Authors: Bouwman R. , Toneman L. H. , Moers M.
Published: March 2003

A simple, on-line treatment chamber for surface studies using a knife-edge sealing construction is described. In it samples can be treated with gases up to a pressure of 1 bar and up to a temperature of 600 °C at a leak conductance of about 10−8 liter/sec to the ultrahigh vacuum analyzing chamber.
Automated, photon-counting Raman spectrometer
Authors: Harney R. C. , Milanovich F. P.
Published: March 2003

Current research directed towards establishing the use of laser Raman spectroscopy as an effective means of making rapid determinations of isotope abundance ratios in at least nitrogen, carbon, oxygen, and hydrogen has necessitated the construction of a spectrometer of unique capabilities. The instrument, an automated, photon-counting Raman spectrometer contains as many state-of-the-art components as is feasible. The spectrometer is described along with the automatic data retrieval system, which offers the unique capability of unlimited integration time while running unattended. A concrete example of its performance, the resolution of the Q branch of 16O16O, is presented.
Device for rapid manipulation of frequencies in NMR
Authors: Ackerman J. L. , Hester R. K. , Waugh J. S.
Published: March 2003

A direct digital synthesis technique has been used to accomplish rapid changes in transmitter frequency in NMR without loss of phase coherence.
High-vacuum Raman cell for the study of finite particle effects
Authors: Böckelmann H. K. , Schlecht R. G. , McKay R.
Published: March 2003

A high-vacuum Raman cell using the backscattering geometry for use in studies of microcrystals, surface effects, and physical and chemical adsorption is described. The circuit and description for a temperature controller are also included.
Simple flow microphotometer for rapid cell population analysis
Authors: Eisert W. G. , Ostertag R. , Niemann E.-G.
Published: March 2003

A simple particle analyzer has been developed using a modified high speed flow-through technique and absorption measurements of a continuous He–Ne laser beam. From pulse-shape analysis and the integration of absorption pulses, size distributions of stained or unstained cells can be derived. The range of 5–300 μ is covered without changing the flow system and a rate up to 200 000/sec can be achieved. Typical applications in cell analyses are shown.
Microwave Hall measurement techniques on low mobility semiconductors and insulators. II. Experimental procedures
Authors: Sayed Mohamed M. , Westgate Charles R.
Published: March 2003

An experimental technique for the measurement of Hall mobilities at microwave frequencies is described. The design of a dual mode TE111 cavity is described, and a comparison among receivers for the detection system is given. A procedure for tuning the cavity for orthogonality, degeneracy, and equal quality factors is presented. With a superheterodyne receiver and a well designed gold plated, probe-coupled cavity, the minimum detectable mobility is 0.07 cm2/V⋅sec for a high conductivity sample.
Counting rate dependent gain shifts in flow proportional counters
Authors: Spielberg N. , Tsarnas D. I.
Published: March 2003

The counting rate dependent shift of pulse height distributions in cylindrical (flow) proportional counters has been studied. The effects of various counter tube constructional and operational parameters on this shift were investigated. Certain of these parameters also introduce time dependent features into the shift phenomenon. Space charge effects are not major causes of the shifts except under extreme operating conditions. Direct intervention of adsorbed molecules or molecular ions in the multiplication process may also be eliminated as major factors. It is hypothesized that the primary mechanism for the shift is the buildup on the anode wire of a loosely adherent sheath of polarizable molecules or molecular fragments of quench gas, which effectively increases the diameter of the anode wire, thereby decreasing the gas gain for a fixed applied voltage. The equilibrium thickness of the sheath is a function of counting rate, photon energy, gas gain, gas pressure, and wire diameter and surface condition. Calculation of the thickness of this sheath gives a reasonable result. By proper choice of anode wire diameter, material, and heat treatment, the shift can be made negligible. There is also some hope that a proper choice of quench gas can also reduce or eliminate the effect.
Three-transducer differential phase-shift method for the measurement of ultrasonic velocity in liquids
Authors: Chen Chuan , Vanderborgh Nicholas E.
Published: March 2003

A new method for determining ultrasonic velocity (500 kHz) is described. Differential phase shift measurements are made with a three-transducer cell to a precision of ± 0.2%. Calibration data are given for aqueous solutions of NaCl and with mixtures of water and tertiary butyl alcohol.
Simple and reliable subsonic HF chemical laser with 40 W power output (16 W DF)
Authors: Proch D. , Pummer H. , Kompa K. L. , Wanner J.
Published: March 2003

The design and performance of a transverse flow subsonic chemical laser with a total power output of 40 W for HF and 16 W for DF are presented. Laser operation has been observed in the wavelength range 2.6–3.0 μ for HF and 3.6–4.0 μ for DF resulting from v=2−1 and 1−0 transitions of the HF molecule and from v=3−2, 2−1, and 1−0 transitions of DF. The range of the participating rotational states in the emission spectra can be controlled to some extent by a variation of the gas temperature in the optical cavity region. The observed total power levels correspond to an electrical efficiency of 1.3% for HF and 0.9% for DF.
Water-jacketed electric field birefringence cell
Authors: Baily E. D.
Published: March 2003

A simple water-jacketed electric birefringence cell is described which is suitable for use with a laser light source. The electrodes in the cell form an integral part of the cell walls, thus permitting a low internal volume (∼ 0.4 ml) to be achieved. This makes the cell particularly suitable for use in studying macromolecular materials, such as biopolymers, which may be available only in small quantities.
Low energy ion backscattering spectroscopy (ISS) with a commercial Auger cylindrical mirror analyzer (CMA)
Authors: Niehus H. , Bauer E.
Published: March 2003

A commercial Auger CMA is used alternately for AES and ISS experiments by simple changes of the deflection and secondary electron multiplier voltages. A retractable movable aperture between CMA and target defines the scattering angle. ISS measurements on W(110) surfaces show that in the chosen experimental arrangement less than 6% of all ions entering the CMA are scattered out of the plane of incidence of the ion beam. Thus no aperture is necessary for routine investigations which allows rapid switchover from AES to ISS.
Emulsions for exo-electron photography
Authors: Baun W. L.
Published: March 2003

Suitable films and plates for exo-electron photography are shown. Emulsion criteria and techniques of exo-electron photography are enumerated. Examples are shown of exo-electron photography of deformed surfaces.
Q-switching of laser cavity with an open-air spark gap
Authors: Ishii S. , Ahlborn B.
Published: March 2003

A laser cavity has been Q-switched using a spark plasma as the optically active element.
Atmospheric sampling: Description of a small flow-control valve unit
Authors: Stone J. P. , Eaton H. G. , Williams F. W.
Published: March 2003

A midget valve package incorporating filters and a critical orifice controls time-integrated sampling of whole air for intervals exceeding 8 h. The valve, in conjunction with a container, comprises a shirt-pocket-size sampler.
Tri-coil electromagnet
Authors: Johnson C. B.
Published: March 2003

The second derivative of the axial magnetic flux density is found to vanish for an electromagnet composed of three circular coaxial coils if the spacing between adjacent coils is a, if each coil contains equal ampere turns, if the radii of the end coils are a, and if the radius of the center coil is ∼5a/4. Consequently, this tri-coil electromagnet produces a relatively constant axial magnetic flux density within its length of 2a. Comparisons are made to the Helmholtz coil.
Spin induction by bimodal cavities with non-perpendicular magnetic fields
Authors: Conciauro G.
Published: March 2003

It is shown both theoretically and experimentally that bimodal cavities can be satisfactorily operated as spin inductors for ESR spectrometers, even if the sample is placed in a volume where the bias field and the inducing and induced magnetic fields are not mutually perpendicular. Removing the constraint of the mutual perpendicularity among these fields allows a greater flexibility in the cavity design.
System for rapid injection of metal atoms into plasmas
Authors: Marmar E. S. , Cecchi J. L. , Cohen S. A.
Published: March 2003

A system for producing 300-μsec bursts of 1017 metal atoms with 3-eV average energy is described. It is shown that this system can be successfully used to introduce impurities into CTR-oriented tokamaks for transport and confinement studies.
Transient response of circular foil heat-flux gauges to radiative fluxes
Authors: Keltner N. R. , Wildin M. W.
Published: March 2003

An approximate analytical model of the transient response of a circular foil heat-flux gauge to a step change in incident radiant heat flux is described. This model demonstrates that the sensitivity and the transient response of the gauge are significantly affected by heat flow from the foil to the center lead wire. Results obtained for the transient response to a step change in incident radiant flux from the model agree closely with experimental results from several gauges with different sensitivities. Convolution of the present model and previous exponential models of the unit step response, with a transient incident flux represented by a terminal ramp, shows that the response predicted by a previous exponential model differs significantly from that predicted by the present model.
New interferometric method for piezoelectric measurements
Authors: Bruins Douglas E. , Garland Carl W. , Greytak Thomas J.
Published: March 2003

A new interferometric technique has been developed for measuring the amplitude of very small ac displacements. The technique, utilizing a spherical Fabry–Perot interferometer, is more sensitive and less susceptible to acoustic vibrations than previous methods. We have used this technique to measure displacements as small as 4×10−4 Å, and the theoretical sensitivity in a well-isolated environment is about 10−5 Å.
Magnetoresistance of carbon-glass thermometers at liquid helium temperatures
Authors: Swartz John M. , Gaines James R. , Rubin Lawrence G.
Published: March 2003

The low-temperature behavior of carbon-glass thermometers in intense magnetic fields is described. At 15 T, the field-induced error is 0.3 K at 4.2 K and 0.08 K at 2.1 K. An empirical equation is presented which fits the positive magnetoresistance data to better than 0.1% in the liquid-helium range. No significant (<0.1%) orientation dependence was found at either 4.2 or 77 K.
Evaluation of plasma-wave spectral density from cross-power spectra
Authors: Ilić D. B. , Harker K. J.
Published: March 2003

The plasma-wave spectral density is evaluated by performing a spatial Fourier transform on experimental cross-power spectra of ion acoustic waves. The cross-power spectra are recorded on analog magnetic tape, converted to digital form, transferred to digital magnetic tape, and Fourier transformed on a digital computer. The important effects of sampling, finite data strings, and data smoothing on the end results are discussed and illustrated. The results indicate the usefulness of the spectral density method for the study of nonlinear wave phenomena.
Facility for high-speed particle impact testing
Authors: Graham Marlyn E. , Carlyle John D. , Menna Thomas L.
Published: March 2003

This article describes an erosion test facility which is based on exploding-foil and exploding-wire technology. The large controllable energy released by exploding foils and exploding wires is utilized to launch 100–8000 μ particles to velocities ranging from 250 to 7000 m/sec. Specific features which are unique to the facility are the high degree of aiming accuracy, high-speed framing photography of the particle in flight, and the use of simple, expendable launch assemblies to provide a low cost, flexible, and reliable method for obtaining small-particle impact data.
Matsushita carbon resistors as thermometers for use at low temperatures and in high fields
Authors: Saito Sinhachiro , Sato Takashi
Published: March 2003

A survey has been made of the properties of 1/8 W composite resistors made by the Matsushita Electric Ind. Co. Ltd. to determine whether they might be suitable as secondary thermometers in the low-temperature region. From the measurements of resistance vs temperature, between 105 °C and 40 mK, it is confirmed that the grade ERC-18SGJ resistors in various nominal room-temperature resistance values from 20 to 510 Ω are suitable in very low -temperature work, and that resistors in the nominal resistance range 20–100 Ω are the most suitable for work down to several tens of mK. An advantage of Matsushita resistors as thermometers in the low-temperature region is that they are available in 1/8 W size, and we can choose their nominal resistances from 10 Ω to several hundreds of ohms in steps of a few ohms. The magnetoresistance of Matsushita resistors having nominal resistances of 30 to 510 Ω has been measured in fields up to about 80 kG at temperatures between ∼4.2 and ∼1.5 K. It is shown that the percentage change in resistance due to the application of magnetic field as a function of temperature and field can be described approximately by the equation 100 ΔR/R= (C1H2+C2H)/(1+C3H2) T1.5, where R is the resistance in zero field, ΔR the change in resistance when a field H is applied, and T the temperature. C1–3 are adjustable temperature-dependent parameters determined from the experimental data.
Two-channel laboratory scattering meter
Authors: McCluney W. R.
Published: March 2003

An instrument was designed and built that measures the light scattered at 2° and at 90° simultaneously. The instrument employs a laser source, solid-state detectors, and a flow-through scattering cell for laboratory use. A Mie theory computer program was used to calculate the theoretical volume-scattering function for suspensions of latex spheres. The ratios of the theoretical to measured scattering functions for these suspensions are not greatly different from unity, thereby providing acceptable verification of the calibration technique employed.
Aiming performance of the atom probe
Authors: Krishnaswamy S. V. , McLane S. B. , Müller E. W.
Published: March 2003

We evaluate the aiming performance of our artifact-free energy focused atom-probe FIM employing bright contrast rhenium atoms in tungsten alloys as target atoms. The aiming efficiency averaged over the entire surface is 42% with the maximum of 60% on the (011) plane limited by the efficiency of the dual channel plate detector. We conclude that aiming through a 4.7×10−4 sr angular aperture is nearly perfect, and that aiming errors due to ion trajectory deviation as seen by multilayer field desorption patterns are minimal. Aiming capability is further established by the identification of bright impurity atoms in rhodium specimens as due to 0.1% platinum. Depth profiling of dilute constituents which do not provide visibility contrast is facilitated when the base metals such as V, Fe, Ni, W, or Pt have one or more low-abundance natural isotopes which may be employed for counting and evaluating the statistical errors. This is demonstrated with the 192Pt isotope for the case of Pt–0.1% Mo.
One nanosecond CO2 laser chain for laser–target interaction studies
Authors: Rheault F. , Lachambre J.-L. , Lavigne P. , Pépin H. , Baldis H. A.
Published: March 2003

A CO2 oscillator–amplifier laser system generating short pulses of radiation in the gigawatt range is described. Emphasis is laid upon self-oscillation problems associated with a high-gain amplifier chain. The insertion of SF6, Freon, and C2H5OH cells between the amplifier modules is found efficient in suppressing any oscillation in the presence of a polyethylene target. The characteristics of the output radiation are given together with the reflection measurements of the target during the interaction with the laser pulse.
Microwave resonators for EPR studies at high hydrostatic pressure
Authors: Stankowski J. , Gal/ȩzewski A. , Krupski M. , Waplak S. , Gierszal H.
Published: March 2003

The sapphire cylindrical resonator with H112 wave directly coupled to the waveguide is the most advantageous of those hitherto investigated operating in the X band. It has a Q factor of 2500 and a very weak, linear pressure dependence of the resonance frequency with a coefficient of 6.5×10−4 kilobar−1.
Modification of the diamond cell for measuring strain and the strength of materials at pressures up to 300 kilobar
Authors: Kinsland Gary L. , Bassett William A.
Published: March 2003

A diamond anvil cell has been adapted for determination of the strain ellipsoid in a polycrystalline sample. An x-ray beam (Mo Kα) is directed through the sample perpendicular to the loading axis. Since the diamond anvils are transparent to Mo Kα radiation, a complete cone of diffraction is available from each set of crystallographic planes (hkl). These cones produce rings on a flat film placed in front reflection geometry. From the ellipticity of these rings it is possible to calculate directly the strain ellipsoid. Material strengths as a function of pressure can then be calculated.
Modified unsupported-area hydraulic seal for pressures of 50 kilobar
Authors: Whalley E. , Lavergne A.
Published: March 2003

An unsupported-area static or dynamic seal for sealing hydraulic pressures up to 50 kilobar in cylindrical pressure vessels is described.
Push-rod ac susceptibility apparatus
Authors: Hauser J. J. , Antosh C. M.
Published: March 2003

A push-rod ac susceptibility apparatus which permits the measurement of ultrathin films of superconductors and ferromagnets as a function of temperature and magnetic field is described. Films prepared at 77 K can be mounted under liquid nitrogen and measured without warmup.
Velocity-tracking circuit for a laser Doppler velocimeter using real-time spectrum analysis
Authors: Mustacich R. V. , Ware B. R.
Published: March 2003

A circuit is described which will adapt a laser Doppler velocimeter using real-time spectrum analysis for automatic velocity tracking. The circuit provides an analog voltage which is proportional to velocity by tracking the position of crossing of a selected intensity level on the spectrum analyzer output. Examples of applications to the study of protoplasmic streaming and simulated hemodynamics are presented.
Low temperature sample holders that provide rotation about two orthogonal axes
Authors: Gates John V. , Potter W. H.
Published: March 2003

Two sample holders for operation at liquid helium temperatures are described that provide rotation through large angles about two orthogonal axes, in addition to a possible rotation about the long axis of the cryostat. The basic motion is derived from a thread or wire rather than from gears.
Simple dc technique for precise electron beam current regulation
Authors: Debe Mark K. , Johnson D. C.
Published: March 2003

A straightforward dc circuit has been built for the precise regulation and accurate measurement of the total incident beam current in an elastic low-energy electron diffraction (ELEED) apparatus. It functions simply by comparing the returning ground current to a reference current and optically coupling the result to control the filament-to-Wehnelt cylinder potential difference. Beam currents down to 0.1 μA are regulated to within 1% at sweep rates up to 8 v/sec and energy ranges up to 200 eV wide. An additional useful feature is the ability to monitor and null out any leakage or displacement currents without confusion with the true beam current.
Precision, combined crystal–Faraday cup manipulator for LEED
Authors: Debe Mark K.
Published: March 2003

A manipulator is described which supplies two independent, orthogonal rotational motions to both a crystal and a Faraday cup (FC) integrally mounted on the same ultrahigh vacuum flange. Three translational and two tilting motions are also applied to the combined crystal–Faraday cup assembly. Following a description of the motions and their derivation, the results of tests for any interactions between the motions are briefly presented. Lastly, the additional features incorporated for retrieval of the FC signal and the self-consistent stray magnetic field trimming and crystal-incident beam alignment are discussed.
Areal detection efficiency of channel electron multiplier arrays
Authors: Panitz J. A. , Foesch J. A.
Published: March 2003

The areal detection efficiency of a channel electron multiplier array (CEMA) and the nature of its secondary emission surface were investigated with the ion microprobe mass analyzer (IMMA). Previous speculations of detection efficiency based on simple geometric arguments of channel-to-interchannel area ratios are shown to be in error. With a positive bias applied to a front electrode surface of high secondary yield, areal detection efficiency of a CEMA may approach 100% even for single-ion impacts. The secondary emission properties of a CEMA are shown to be determined by an alkali-rich surface layer on each channel wall, and not a concentration of Pb or PbO as previously thought. Both reversible and irreversible gain degradation observed when heating a CEMA in vacuum are interpreted as a change in the composition of this layer.
Quasioptical band-rejection filter at 100 GHz
Authors: Wannier P. G. , Arnaud J. A. , Pelow F. A. , Saleh A. A. M.
Published: March 2003

We describe a tunable Fabry–Perot type filter which has application to radio astronomy in the frequency band 80–110 GHz. The filter causes image sideband suppression when used with a heterodyne spectral line receiver having an intermediate frequency of 4.75 GHz. The transmission loss in the signal sideband is about 0.4 dB, while the image sideband rejection is more than 15 dB; there appears to be little if any problem with scattering or distortion of the antenna radiation pattern.
Cryostat for generating pressures to 100 kilobar and temperatures to 0.03 K
Authors: Webb A. W. , Gubser D. U. , Towle L. C.
Published: March 2003

An apparatus is described which allows studies to pressures of 100 kilobar and to temperatures of 0.03 K. A low temperature hydraulic press is incorporated with a dilution refrigerator to permit the continuous variation in pressure while at low temperature; thus, the entire pressure study of a material can be accomplished in one low temperature run. The sample is sensed magnetically using a SQUID magnetometer to detect changes in its magnetic moment. Operation of the system is described for measurements of the transition temperature of aluminum as a function of temperature and pressure.
Modification of a mass spectrometer for the measurement of the translational energy of ionic fragments
Authors: Weiner E. R. , Ossinger A. I.
Published: March 2003

A modification of the ion source of a time-of-flight mass spectrometer is described which permits measurement of the angular spread of the ion beam leaving the ionization region. From these measurements, it is possible to obtain kinetic energy information for a specific, selected ionic species in a mass spectrum. In the modified ion source, ions leave the ionization region through a small, circular aperture, and then enter a region with a uniform accelerating electric field. Before they enter the drift tube for mass analysis, the ions must pass through a second small aperture, which is movable in a direction perpendicular to the flight tube of the mass spectrometer. The instrument has had all magnets removed. Analysis of the ion beam cross-section profile yields values for excess kinetic energy and the relative abundances of ions which are formed from molecular states excited by electron impact. Typical results are presented.
Simple fast-discharge device for high-power pulsed lasers
Authors: Wang C. P.
Published: March 2003

A fast-discharge device that is volume scalable, capable of a high pulse-repetition rate, and simple in construction is described. The device has two novel features: (1) it is assembled within a vacuum chamber so that atmospheric pressure is used to compress a parallel-plate transmission line, and (2) it utilizes multiple transmission lines to provide increased lasing volume. This device is useful for generating laser action in N2, H2, and Ne, and for pumping many other self-terminating lasers, such as metal vapor lasers and dimer lasers. Its discharge characteristics and its performance as a N2 laser are discussed.
Interference position monitoring system employing Ronchi gratings
Authors: Jablonowski D. P.
Published: March 2003

A technique for obtaining positional information using a Ronchi grating is described. By employing the grating as a diffraction element, modulation of the phase of a coherent light beam is accomplished. The phase contains information as to the position of the beam on the grating surface. The use of an interference technique allows one to monitor the light phase, and therefore the beam’s position. Using a single grating, directional as well as positional information is obtained in two dimensions. Advantages and other system characteristics are described.
Preactivated highly efficient linear field ionization source
Authors: Cross R. H. , Brown H. L. , Anbar M.
Published: March 2003

A new type of field ionization source is described. The emitter comprises carbonaceous dendrites grown along the edge of a 20-μm-thick tungsten foil by field ionization of pyridine at 1200 °C. The flow of the material to be ionized is directed to the ionization region by a second foil which defines a slit along the ionizing edge. This field ionization source, which provides a line-shaped image, has an ionization efficiency comparable to that of a well-activated multipoint source, and it does not undergo significant deactivation by negative ion bombardment.
High dispersion rutile prism for tuning dye lasers
Authors: Krasiński J. , Majewski W.
Published: March 2003

A high dispersion rutile prism was constructed to tune dye lasers. With the help of this prism, a laser line was produced with smaller spectral width and greater strength than that obtained with the use of a 1800 grooves/mm diffraction grating. This prism is as durable as a glass prism.
Simple method for determining molar flow rates in dilution refrigerators
Authors: Fagaly R. L. , Bohn R. G.
Published: March 2003

A single thermocouple pressure gauge has been successfully used to measure molar flow rates in a dilution refrigerator. It is shown that over an appreciable pressure range the measured flow rates for not only helium but nitrogen can be predicted to within 10% by knowing the pressure, the speed of the vacuum pump, and using the equation of state for an ideal gas.
Determination of nanosecond high-voltage pulse shapes at the surface of needle emitters
Authors: Panitz J. A. , Walko R. J.
Published: March 2003

A method is described for determining, in situ, the shapes of nanosecond, positive high-voltage desorption pulses at the surface of a field-ion specimen, without the use of waveform-distorting probes or voltage dividers. In practice, a negative pulse known to be identical in shape to the positive desorption pulse is used to initiate field electron emission from the specimen surface. The resulting time-varying field emission current is recorded by a detector, and the Fowler–Nordheim equation is iterated to obtain the actual time-varying specimen potential. The pulse shape obtained can be used to predict accurately the arrival time of unknown surface species in time-of-flight atom-probe instruments, or to monitor the effect of changes in the pulse transmission line to the specimen. When applied to pulsed e-beam devices and flash x-ray machines, time-varying potentials at field-emission cathodes can be determined with nanosecond resolution.
Proton and hydrogen atom detection efficiency of resistance strip magnetic electron multiplier particle-counting system
Authors: Wehrenberg P. J. , Clark K. C.
Published: March 2003

The absolute detection efficiency for protons and for hydrogen atoms in the energy range 5–60 keV is determined for a resistance strip magnetic electron multiplier particle-counting system. Significant history-dependent gain variations are discussed. The detector system is suitable for use in coincidence experiments requiring particle-counting rates to 1.0 MHz and timing accuracies of 3.0 nsec.
Apparatus for optical characterization of displays
Authors: Barna Gabriel G.
Published: March 2003

An apparatus has been designed and constructed for the measurement of the optical characteristics of passive displays. It provides isotropic illumination to the top surface of the display and generates data on the contrast ratio of individual segments as they are viewed from any direction above the display. Typical results on the brightness, contrast ratio, and the angle dependence of this contrast ratio are shown for a commercially available LCD.
Mesh-initiated large area detonators
Authors: Butler R. I. , Cowan M. , Duggin B. W. , Mathews F. H.
Published: March 2003

Inexpensive large area detonators are described which utilize a mesh of etched copper brigewires to detonate PETN. Breakout simultaneity within 100 nsec is achieved on the surface of a PBX-9407 booster at discrete initiation points originating from the individual bridgewires. Initiation point densities as high as 3.1×105 m−2 are achieved by printed circuit manufacturing techniques. Electrical requirements are established from threshold burst current experiments. Two initiators are described; a general purpose 200-mm diam detonator, employing 750 or 10 000 bridgewires (depending on the mesh pattern used), and a 150×600 mm detonator employing 2300 that was developed for a fast explosive generator. These detonators achieve simultaneous detonation of large surface areas at lower cost and with much less explosive than conventional lens systems. They can also be applied to singly curved surfaces.
Quadrant anode image sensor
Authors: Lampton M. , Malina R. F.
Published: March 2003

A position-sensitive event-counting electronic readout system for microchannel plates (MCPs) is described that offers the advantages of high spatial resolution and fast time resolution. The technique relies upon a four-quadrant electron-collecting anode located behind the output face of the microchannel plate, so that the electron cloud from each detected event is partly intercepted by each of the four quadrants. The relative amounts of charge collected by each quadrant depend on event position, permitting each event to be localized with two ratio circuits. A prototype quadrant anode system for ion, electron, and extreme ultraviolet imaging is described. The spatial resolution achieved, ?10 μ, allows individual MCP channels to be distinguished.
Cable temperature jump apparatus with improved sensitivity and time resolution
Authors: Pörschke Dietmar
Published: March 2003

The cable temperature jump apparatus developed by Hoffman is modified in order to suppress artifacts like electrodichroism and electroluminescence. Construction of a polarization optics with strain-free quartz windows in the temperature jump cell as well as application of interference–reflection filters allows the elimination of these artifacts. The reconstruction leads to an increase in sensitivity and also to an extension of the time resolution to 10 nsec.
Ear-borne sound level dosimeter
Authors: Erlandsson B. , Håkansson H. , Ivarsson A. , Nilsson P. , Salén B.
Published: March 2003

An apparatus has been constructed which measures the time during which a certain preset noise level is exceeded. The information is recorded on a photographic film and the blackness of the film is a function of the time during which the noise has exceeded the preset value.
Electric method for measurements of enzymatic activity
Authors: Arwin Hans , Lundström Ingemar
Published: March 2003

In collaboration with the Peptide Research Group, AB KABI, we have developed a simple electric method for the measurement of the activity of serine proteases. The method is based on a synthetic polypeptide, which in solution adsorbs on metal surfaces. The desorption rate of the polypeptide on the introduction of serine proteases is a measure of their enzymatic activity. The desorption rate is measured as a capacitance change between two metal electrodes.
Array of large high-purity Ge planar detectors
Authors: Quayle P. , Raudorf T.
Published: March 2003

The performance of an array of four high-purity germanium detectors of 10 cm2 active area and 10 mm depth is described.
Semiautomated torsion pendulum for high-temperature damping studies
Authors: Cooper P. , Corti C. W.
Published: March 2003

A torsion pendulum device is described for measuring the amplitude-dependent damping properties of high-temperature alloys both at room temperature and at elevated temperatures. Its features include the use of data processing techniques for rapid access to damping information and the use of a simple specimen geometry to allow specimens to be cut from bulk engineering samples. Some typical results obtained with the system are given to illustrate its capabilities and the extraneous background losses in the machine are discussed.
Determination of strains in optical windows of a high-pressure chamber by holographic interferometry and finite element analysis
Authors: Soga N. , Holcomb D. , Spetzler H.
Published: March 2003

Holographic interferometry and finite element analysis have been applied to determine the strain in a large optical window installed in a high-pressure chamber. Two different shapes of windows were chosen, and the outside and inside surface strains of the windows were followed as a function of internal pressure by taking double exposed holograms at 69-bar intervals up to 483 bars. The results were compared with the values calculated by a standard finite element code with an assumption of no displacement at the load-bearing edge. The agreement between two results was found to be good for both cases.
Simple far uv transmission grating monochromator for use with resonance radiation lamps
Authors: Flodstrom S. A. , Bachrach R. Z.
Published: March 2003

A freestanding transmission grating has been used as a dispersive element in a simple monochromator. The monochromator, to be used with the collimated light beam from a resonance lamp radiation source, has been tested in the far uv with the helium and neon emission spectra. The results show that the simple monochromator will resolve all major lines in the emission spectra. A high efficiency into first-order diffracted beams is obtained, and the efficiency is independent of photon energy. The results show that the resonance lamp–transmission grating combination is a unique source of monochromatic light for photoemission and optical work in the far uv region. More advanced monochromator designs and the possibility of extension of the monochromator for use at x-ray energies are discussed.
Time-of-flight energy spectrometer for positive ions
Authors: Wood R. M. , Edwards A. K. , Steuer M. F.
Published: March 2003

A technique is described for the simultaneous measurement of the time-of-flight and energy of positive ions produced in the decay of excited molecules. The technique permits the separation and determination of the energy spectra of ion species with different mass to charge ratios. Data from the bombardment of CO by 1-MeV He+ are presented.
Single coil probe with transmission-line tuning for nuclear magnetic double resonance
Authors: Cross V. R. , Hester R. K. , Waugh J. S.
Published: March 2003

First we discuss a method of tuning NMR probe circuits and matching impedances which employs a variable length transmission line as one of the tuning elements. This method is useful for high voltage circuits where, due to space considerations, suitable tuning elements may not be placed adjacent to the rf field-producing coil. Second, we describe the design of a single coil double resonance probe which uses λ/4 transmission lines as filters as well as tuning elements. This double resonance probe is useful when the two frequencies of interest are widely separated.
Extremely fast recovery time receiver for pulsed NMR
Authors: Adduci D. J. , Hornung P. A. , Torgeson D. R.
Published: March 2003

A radio-frequency receiver–amplifier for pulsed nuclear magnetic resonance applications is described. This amplifier has a voltage gain of 2000 and a bandwidth of 5–115 MHz and consists of three identical stages having nonsaturating overload characteristics. Each individual stage recovers within a time of 1 nsec following a 20 dBm overload. The blocking effect of capacitive interstage coupling following rf pulses has been essentially eliminated using series-tuned broad bandwidth resonant circuits between stages. Measured receiver recovery times range from 250 nsec for short (400 nsec) transmitter pulses to 2.0 μsec for long (75 μsec) pulses. The effective receiver input noise voltage measured following phase-sensitive detection and at the output of a video amplifier having a bandwidth of 320 kHz was 1.2 μV.
Atomic beam spectrometer for surface investigations
Authors: Scherb P. , Hörl E. M.
Published: March 2003

An atomic beam spectrometer for the study of the interactions of neutral rare gas atoms with solid surfaces is described. These atoms, preferably neon atoms, have a very low kinetic energy, in the order of only a few meV, so that energy gains or energy losses by surface phonon processes can be detected. The change of the momentum of these particles is given by the preset scattering angle.
Apparatus for measuring internal friction Q factors in brittle materials
Authors: Tittmann B. R. , Curnow J. M.
Published: March 2003

This report describes a flexural analog of the torsion pendulum for measuring Young’s modulus and the internal friction Q factor on brittle materials. The design provides features to minimize fracture or chipping of the sample and reduces apparatus background damping so that a sample Q of ≳103 can be reliably measured. Other features include strain amplitudes as low as 10−7, small size for use in an environmental chamber, and zero static stress.
Marginal oscillator optimized for radiofrequency size effect measurements
Authors: Probst P. A. , Collet B. , MacInnes W. M.
Published: March 2003

A marginal oscillator (1–50 MHz) operating at relatively high, stable oscillation levels, with very low noise, is described. Phase-sensitive detection of the real and imaginary parts of the surface impedance of metals or the nuclear susceptibility can be carried out from 0.5 Hz as a result of the low 1/f noise. The noise is dominated by this 1/f noise below 200 Hz, while at higher frequencies it is white and the oscillator has a noise factor of 1.15 or 0.6 dB.