bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical detection system for the evaluation of laser welds
Authors: Duncan Hibbert A.
Published: March 2003

The laser, because of its high energy output and speed, has become a most viable welding tool. Quality control is a fundamental concern in most welding operations. An optical technique in conjunction with signal processing and a microcomputer is used to obtain data from which the weld quality can be determined. The technique is one in which the plume that is generated on each impingement of the laser on the material is detected by a photodiode and processed. The processed data are related to the spectral content and temporal response of the plume.
Radio frequency excited CO2 waveguide lasers
Authors: Sinclair R. L. , Tulip J.
Published: March 2003

This paper reports on the operation of radio frequency (rf) excited carbon dioxide waveguide lasers. An efficiency of greater than 10% has been achieved with a maximum power of 21 W. The effects of bore size, waveguide fabrication techniques, and gas mixture are discussed.
Electromechanical tuning element (EMT) with extended range for dither stabilization of lasers
Authors: Sielmann H. , Bajsarowicz A.
Published: March 2003

A device has been developed which offers improved performance in many applications where tubular piezoelectric elements are currently being employed. The device, called an EMT (electromechanical translator) can displace optical and small mechanical components over a range of more than 60 μm with a resolution of a few nanometers. The motion is smooth, continuous, almost tilt free (better than 50 μrad), and can be controlled in speed over a range from zero to several hundred μm per second. A self-contained driver unit for dither stabilization schemes for laser systems has also been developed. The article describes the principle of operation of the EMT and reports various test results.
Particle discrimination and background suppression in photon-correlation laser velocimetry
Authors: Fansler Todd D.
Published: March 2003

Selective data acquisition controlled by a particle-identification circuit is demonstrated here to improve the performance of photon-correlation laser-Doppler velocimetry (LDV) under unfavorable background-light conditions (e.g., near a window surface). A gated cross-correlation technique is used to accumulate data only when a photon-counting particle discriminator indicates the presence of a light-scattering particle in the LDV measurement volume. Background-light contributions between particle transits are suppressed. The particle discriminator is also shown to facilitate measurements of temporal statistics of turbulence (e.g., time scale, energy spectrum) using particle recurrence-rate correlation. Further applications of the particle discriminator to Rayleigh and Raman scattering are suggested, an adaptation of the circuit for higher-velocity flows is outlined, and the relation of particle-discriminated photon correlation to clipped correlation is discussed.
Gating circuit for single photon-counting fluorescence lifetime instruments using high repetition pulsed light sources
Authors: Laws William R. , Potter David W. , Sutherland John Clark
Published: March 2003

We have constructed a circuit that permits conventional timing electronics to be used in single photon-counting fluorimeters with high repetition rate excitation sources (synchrotrons and mode-locked lasers). Most commercial time-to-amplitude and time-to-digital converters introduce errors when processing very short time intervals and when subjected to high-frequency signals. This circuit reduces the frequency of signals representing the pulsed light source (stops) to the rate of detected fluorescence events (starts). Precise timing between the start/stop pair is accomplished by using the second stop pulse after a start pulse. Important features of our design are that the circuit is insensitive to the simultaneous occurrence of start and stop signals and that the reduction in the stop frequency allows the start/stop time interval to be placed in linear regions of the response functions of commercial timing electronics.
Real-time data acquisition for gas electron diffraction
Authors: Ewbank John D. , Schäfer Lothar , Paul David W. , Benston O. Joel , Lennox John C.
Published: March 2003

An instrument for gas electron diffraction (GED) studies is described which eliminates the photographic intermediary and sector device which are currently used almost universally in molecular structure determinations using GED. Specifically, the scattered electrons are detected by a fluorescent screen which is optically coupled to a custom multichannel analyzer (EG&G model 1412 photodiode array detector and model 1218 controller, combined with a MINC-DEC LSI 11/23 computer). Rapid operation not only eliminates photographic film development and densitometry, but also allows for repeated measurements to be easily made. Dynamic data acquisition provides for virtually steady-state conditions in the experimental environment, minimizing systematic errors and providing a means for instrument control. The design has been completed to the extent that small angle scattering data are now readily recorded in this novel way. The data range accessible in the current configuration (maximum s values of approximately 20–25 Å−1) is smaller than that normally used in structural GED work (maximum s values of typically 30–40 Å−1), but useful structural information can be derived from it. To demonstrate the currently achieved resolution, several test molecules have been modeled based on this novel data recording technique, and results are compared to those found in the literature. The success of the current scheme brings to mind other configurations to be tested, including direct exposure of the photodiode array detector to the scattered electrons. Powder diffraction data are also readily recorded on the new instrument. It is expected that the instrument will be particulary useful in time-resolved studies of dynamical processes, in the investigation of transient species, and in practical applications, for example, for analytical purposes.
Development of dispersion compensation for use in high-resolution electron-energy-loss spectroscopy
Authors: Kevan S. D. , Dubois L. H.
Published: March 2003

A new high-resolution electron-energy-loss spectrometer (EELS) based on dispersion compensation has been designed, built, and tested. A detailed analysis indicates that this system should yield two to three orders of magnitude more signal than conventional spectrometers operating at comparable energy resolution. Second-order imaging aberrations have been calculated and shown to be consistent with this expectation. A specific design is presented which will allow studies of the vibrations of transient species on a surface. Initial tests on the chemisorption of CO on Cu (100) indicate the applicability of this new technique.
Evaluation of LiF lenses as monochromators for inverse photoemission spectroscopy
Authors: Childs T. T. , Royer W. A. , Smith N. V.
Published: March 2003

A LiF lens followed by a pinhole can function as an efficient vacuum ultraviolet monochromator. The principles of such an instrument are described, and its limitations are determined using ray-tracing calculations. Two practical instruments for ultraviolet inverse photoemission with tunability in the 8–11.7-eV range are proposed: a biconvex singlet with good resolution (0.23 eV at 10.2 eV) but moderate collection angle ( f/5); and a planoconvex doublet with large collection angle ( f/1.5) but moderate resolution (0.38 eV at 10.2 eV). The main principles have been demonstrated using a prototype instrument.
Tapered tungsten filament for a long life cathode
Authors: Tanaka Shigeru , Ohara Yoshihiro
Published: March 2003

Directly heated tapered tungsten filament was proposed as a long life cathode of the ion source for a neutral beam injector. The shape of this filament is such that the cross section gradually increases from the positive leg to the negative leg. Numerical calculations of the time-dependent temperature distribution along the filament showed that overheating at the negative leg due to superposition of the arc discharge current on the filament current could be prevented in long pulse or dc discharges. As a result, the tapered filament may live 20 to 30 times longer than the conventional constant cross-section filament, provided the filament life were determined by evaporation only.
New application for multipolar plasmas: High-temperature treatment of materials
Authors: Pelletier J. , Arnal Y. , Debrie R. , Pomathiod L. , Rifflet J. C.
Published: March 2003

In a multipole plasma reactor, large volumes of homogeneous steady-state plasma of satisfactory density can be obtained. This type of plasma appears to be well adapted to high-temperature treatment of materials. The mechanisms involved, advantages, and limitations of the process are analyzed in the light of some preliminary results.
Melting and triple point temperatures of gallium as fixed points of the International Practical Temperature Scale
Authors: Borovička Milan , Sostman Henry E.
Published: March 2003

The liquid–solid (melting) and liquid–solid–vapor (triple point) phase equilibrium temperatures of pure gallium have been realized and studied as proposed secondary reference points of the International Practical Temperature Scale. The melt temperature is found to be 29.771 94 °C (302.921 94 K) and the triple point temperature 29.773 88 °C (302.923 88 K) for gallium 99.999 99% pure. The technique and apparatus for these realizations, suitable for the calibration of high-precision thermometers, are described. These calibration points are finding important uses in medical, biological, ecological, and energy-source thermometry.
Experimental method to determine the heat production rate, thermal diffusivity, and conductivity of solids
Authors: Iida Y. , Ohtani S. , Stephan K.
Published: March 2003

A new method for measuring, simultaneously or individually, the heat production rate, thermal diffusivity, and conductivity of solids accompanying internal heat production or consumption is presented. The method utilizes the principle of the Laplace transform and has the advantage of measuring the above variables under arbitrary heating or cooling conditions imposed on the samples as far as a unidirectional heat flow is concerned. The theory is developed for some practical measuring systems and verified by a numerical test and simple experiments.
Comparison of two methods for flash thermal diffusivity on drawn low-density polyethylenes
Authors: Jonza James M. , Porter Roger S.
Published: March 2003

The flash technique has been used on a systematic series of drawn low-density polyethylenes. Results from two different temperature monitoring modes are compared. Both the temperature rise of the rear face and the difference between front- and rear-face temperatures was measured on each sample using the same instrumentation. A positive difference of <10% in the thermal diffusivity by the rear-face analysis was observed over the differential method. Radiation loss corrections were applied to both analyses and estimated by a heat balance for the differential case. Instrument pressures below which losses to the air become negligible were calculated and experimentally confirmed. The thermal conductivity calculated from diffusivity for the low-density polyethylenes is shown to be proportional to the extent of deformation in the draw direction.
Low thermal conductivity superconducting metallized Mylar leads
Authors: Hays K. M. , Rutledge J. E. , Sellers G. J.
Published: March 2003

We describe the fabrication of PbSn-coated, 2.5-μm-thick, Mylar ribbons that can be used as electrical leads in low-temperature experiments. We present measurements of the thermal conductivity of the leads and of uncoated Mylar ribbons between 0.08 and 2.0 K. At 0.1 K, a conveniently sized coated Mylar lead has the same thermal conductance as an ∼6-μm-diam manganin wire of the same length.
Miniature Penning ionization gauge for pulsed gas measurements
Authors: Humphries S. , Hwang Chang-Sing
Published: March 2003

A miniature Penning ionization vacuum gauge was developed for measurement of pulsed gas distributions. The gauge is sensitive to pressure in the range 0.3 to 50 mTorr. It has spatial resolution of 1–2 cm and temporal resolution better than 25 μs. The gauge is inexpensive and easy to construct. It requires only one vacuum lead for bias and signal. Signal levels are high, so the gauge can function in a noisy environment. When applied to steady-state measurements, it can detect pressure differences as small as 0.1 mTorr at 10 mTorr.
Ion beam profile monitor
Authors: Galvin James E. , Brown Ian G.
Published: March 2003

We describe a simple and inexpensive diagnostic for rapid measurement and display of the radial profile of the ion beam generated by an experimental ion source. The technique may be useful for other kinds of beams also.
Low-cost data-acquisition system for pulsed laser experiments
Authors: de O. Nunes Luiz A. , Matinaga Franklim M. , Castro Jarbas C.
Published: March 2003

A system based on a single-board microcomputer (M/A-COM OSI) provides flexibility in recording data in pulsed dye laser applications.
Portable data-acquisition and analysis system for thermal conductivity measurements
Authors: Drotning William D. , Tormey Thomas V.
Published: March 2003

A data-acquisition and analysis system based on the Hewlett–Packard HP85 Personal Computer and the HP 3497A Data-Acquisition and Control Unit was developed to provide a portable, stand-alone device for the measurement of the thermal conductivity of materials.
Low-cost CO2 laser beam profile monitor
Authors: Wildmann D. , Brönnimann R. , Schürch G.
Published: March 2003

Construction and performance of a low-cost easy-to-build CO2 laser beam profile monitor are described. Its specifications correspond to those of commercial devices. In this monitor a small slit covered by a temperature dependent fluorescent surface is imaged on a photodiode. A rotating mirror scans the spatial intensity distribution over the slit. This allows one to avoid an expensive photodiode array. The signal-to-noise ratio is improved by repetitive sampling with a low-cost digital processing unit. The dynamic range of measurement is 7 to 1 and the linearity is 10% within this range.
Numerical calculation of the temperature evolution and profile of the field ion emitter in the pulsed-laser time-of-flight atom probe
Authors: Liu H. F. , Tsong T. T.
Published: March 2003

The temperature evolution and profile of metal field ion emitters under pulsed laser irradiation are solved numerically using an implicit alternating direction method. The temperature profile along the emitter axis at selected times and the temperature evolution curve at the emitter apex during and after the pulsed-laser irradiation have been obtained. This numerical result shows that the emitter can cool down from the peak temperature by ∼20 K in less than 5 ns, and the heated region is very much localized to the irradiated part of the emitter. The cooling rate is higher for specimens of larger thermal diffusivity, and also if the laser pulse width is narrower and the laser heating is better localized. The peak temperature of the tip apex reached depends almost linearly on the incident flux of the laser beam.
Dynamic observation of surfaces by scanning Auger electron microscopy: A motion picture technique
Authors: Goto K. , Ohwaki T. , Taga Y.
Published: March 2003

The dynamic observation of surfaces has been developed by using a scanning Auger electron microscope (SAM). The images of Auger and secondary electrons are photographed continuously with a 16-mm movie camera. Each frame is photographed for very short time exposures of 24 to 48 s for the Auger and 3 s for the secondary electrons. Particular logic circuits to control the system were made providing for the rejection of the secondary electrons ejected by the ions and for the photons from the filament of the ion gun which greatly degrade the images.
Laser-heated miniature pedestal growth apparatus for single-crystal optical fibers
Authors: Fejer M. M. , Nightingale J. L. , Magel G. A. , Byer R. L.
Published: March 2003

We have designed and built a single-crystal fiber growth apparatus. The apparatus employs novel optical, mechanical, and electronic control systems that enable the growth of high optical quality single-crystal fibers. We have grown oriented single-crystal fibers of four refractory oxide materials, Al2O3, Cr:Al2O3, Nd:YAG, and LiNbO3. These materials exhibit similar growth characteristics and yield fibers of comparable quality. Fibers as small as 20 μm in diameter and as long as 20 cm have been grown. Measured optical losses at 1.06 μm for a 10-cm-long, 170-μm-diam Cr:Al2O3 fiber were 0.074 dB/cm.
Manual/automated I–V system for analyzing solar cells
Authors: Turner R. D. , Moore C. J. L. , Brodie D. E.
Published: March 2003

A measurement system for the current–voltage characterization of solar cells has been developed. The instrument is based on an Intel 8088 microprocessor, which allows for enhanced data collection and storage, as well as automated measurement control. A high-power analog supply makes measurements in the range of −10 to +10 V and −0.75 to 0.75 A possible, and provides the capability for sinking currents up to 1 A at +10-V output. Measured data may be transferred to an IBM personal computer for immediate display, and for consequent analysis (to obtain the characteristic parameters). The system provides a rapid, effective I–V curve measurement and analysis method for many devices, and experimental solar cells in particular.
Simple carrier modulation system for minimizing low-frequency noise modulation of synchrotron orbital radiation
Authors: Chance B. , Kumar C. , Korszun R. , Khalid S. , Graham N.
Published: March 2003

An analysis of the frequency distribution of noise of two synchrotrons (CHESS and SSRL) indicates significant increases of noise at frequencies below 10 Hz. Noise energy distributions above 10 Hz and extending through 200 Hz indicate significant regions of noise distributions relatively independent of frequency, presumably ‘‘white noise.’’ We report tests of two carrier modulation systems in which the ratio (or difference) of a reference signal and measure signal is computed. In one case, the reference and measure sample are alternated at equal intervals, for example, where difference spectroscopy is required. In another version, the measure signal is periodically interrupted by the reference signal at a duty ratio of 10%–15%, thereby maintaining high efficiency of measure signal detection. When using a 10-Hz oscillator for reference and measure samples, the improvement as observed on beam line A-3 at CHESS over the ‘‘single-ended’’ signal is 10- to 20-fold in the nonscanning mode. In the case of a vibrating reed modulator, the signal-to-noise ratio at a count rate of 6×105 per s is equal to the statistical limit to within the error of calculation. The improvement over a conventional fluorescence signal to ionization chamber output ratio F/I0 is over tenfold. Application of these modulation techniques to a variety of detectors is included.
A simple high-performance high-resolution electron energy-loss spectroscopy system
Authors: Unwin R. , Stenzel W. , Garbout A. , Conrad H. , Hoffmann F. M.
Published: March 2003

A simple spherical analyzer combination suitable for use in high-resolution electron energy-loss spectroscopy (HREELS) is described. The system is designed to be intrinsically insensitive to extraneous magnetic fields. The problems presented by the control of the spectrometer are also discussed and the advantages of Fourier filtering demonstrated.
Continuous gaseous ammonia analyzer by gas titration method
Authors: Kato Akira , Uno Shigeo , Kamo Tomoichi , Matsuda Shimpei
Published: March 2003

A new instrument for simply and rapidly determining an ammonia concentration in a gaseous mixture has been developed. The principle is based on the fact that ammonia reacts with NO exactly at 1:1 mole ratio in the presence of an appropriate catalyst: NH3+NO+ 1/4 O2=N2+ (3)/(2) H2O. A sample gas containing NH3 is mixed with NO and made to contact with a catalyst capable of promoting reaction of NH3 and NO to form N2 and H2O in an oxidative atmosphere at an elevated temperature, preferably, 300°–400 °C. The catalyst capable of conducting the reaction is composed of TiO2 and at least one of the oxides of V, Fe, Cu, W, Mo. The concentration of NH3 is determined by measuring concentrations of NO before and after the reaction and calculating the consumption of NO. For the analysis of NO in the gas, a chemiluminescence-type analyzer can be preferably used. According to the present method, ammonia in a sample gas can be analyzed within a few minutes without any influence of various coexisting gas components.
Fast scanning heterodyne receiver for the measurement of the time evolution of the electron temperature profile on the Tokamak Fusion Test Reactor
Authors: Taylor G. , Efthimion P. , McCarthy M. , Arunasalam V. , Bitzer R. , Bryer J. , Cutler R. , Fredd E. , Goldman M. A. , Kaufman D.
Published: March 2003

Two fast scanning heterodyne receivers, swept between 75–110 and 110–170 GHz in 2 ms every 4 ms, were developed to measure the electron cyclotron emission on the horizontal midplane of the Tokamak Fusion Test Reactor (TFTR) plasma. An absolute, in situ calibration technique enables the determination of the profile of the plasma electron temperature from the cyclotron emission intensity. The 4-ms repetition rate of the receiver allowed the resolution of ‘‘sawtooth’’ fluctuations of temperature, whose period was 10–100 ms, in profiles with central temperatures of 1–2.5 keV.
Absolute and angular efficiencies of a microchannel-plate position-sensitive detector
Authors: Gao R. S. , Gibner P. S. , Newman J. H. , Smith K. A. , Stebbings R. F.
Published: March 2003

This paper presents a characterization of a commercially available position-sensitive detector of energetic ions and neutrals. The detector consists of two microchannel plates followed by a resistive position-encoding anode. The work includes measurement of absolute efficiencies of H+, He+, and O+ ions in the energy range between 250 and 5000 eV, measurement of relative detection efficiencies as a function of particle impact angle, and a simple method for accurate measurement of the time at which a particle strikes the detector.
High-power electron-beam controlled switches
Authors: Commisso R. J. , Fernsler R. F. , Scherrer V. E. , Vitkovitsky I. M.
Published: March 2003

The application of an electron-beam controlled diffuse discharge to high-power (>109 W), repetitive opening switches is analytically formulated under a set of assumptions. Basic physics considerations are combined with energy transfer requirements to obtain analytical estimates of the e-beam controlled switch parameters for given circuit requirements. The switch design is optimized by minimizing the switch pressure subject to the constraint of system efficiency. The result of this optimization is that each of the major energy losses—conduction, opening, and electron-beam production—are roughly equal to each other. This formulation is used to relate the switch parameters to the desired operating characteristics for an arbitrary number of pulses. As an example, the formalism is utilized in outlining the design of a single pulse, high-power (≂1010 W) inductive storage system. A judicious choice of gas or gas mixture results in desirable changes in the system design or efficiency.
Microcomputer-based system for control of applied uniaxial stress and magnetic field
Authors: Jiles D. C. , Atherton D. L. , Lassen H. E. , Noble D. , deVette J. , Astle T.
Published: March 2003

A system is described which allows on-line control of uniaxial stress and magnetic field for the investigation of the magnetic properties of materials under stress. This has been of considerable importance in studies of the properties of samples of steel, in particular the investigation of ferromagnetic hysteresis and the magnetomechanical effect. As a result, exact algorithms for the demagnetization of samples and for obtaining the anhysteretic or ideal magnetization curve have been devised.
Technique for the efficient and reproducible fabrication of electromagnetic levitation coils
Authors: Ethridge E. C. , Curreri P. A. , Theiss J. , Abbaschian G. J.
Published: March 2003

A technique has been developed for fabricating electromagnetic induction coils in a reproducible manner. The process utilizes a split mandrel that can be disassembled to remove the mandrel from the coil. The technique has increased coil production rates by a factor of 8 over the freehand winding method. The success rate for producing a functional levitation coil has been increased from 50% to 95%. The levitation coil designed during this work has successfully levitated and melted a variety of alloys including Cu, Ag, Ag–Ni, Cu–Fe, Fe–C, and Nb–Ge. W was also levitated but not melted at temperatures as high as 2700 °C. The highest sample melt temperature achieved was 2400 °C for the Nb–Ge samples.
Excimer-pumped dye laser with high beam quality
Authors: Brink D. J. , van der Hoeven C. J.
Published: March 2003

A novel design for a dye cuvette used in an excimer-pumped dye laser is described. The cuvette consists of a thin-walled quartz tube illuminated equally from four sides. This, combined with the focusing action of the dye-filled tube, results in a homogeneous excitation of the central core of the dye volume and a near TEM (00) output beam is obtained at moderate repetition frequencies. Sufficient data are provided to allow interfacing of the cuvette with standard oscillator-amplifier arrangements.
Frequency-agile electro-optically Q-switched CO2 laser for DIAL measurements
Authors: Marcus S.
Published: March 2003

An intracavity piezoelectrically tuned étalon was used to permit rapid wavelength tuning of an electro-optically Q-switched CO2 laser. The laser wavelength could be swept sequentially through the entire 10-μm P branch. Alternatively, as required for operation in a single laser DIAL system, the output could be switched rapidly between two or more prescribed transitions. The observed settling times were typically a few milliseconds.
Dither-free stabilization scheme for submillimeter wave pumping sources
Authors: Lachambre J.-L. , Gagné M.
Published: March 2003

A new method is described for the stabilization of a CO2 laser source used to pump a CH2F2 SMM laser. The discriminator is an absorbing cell with an optical transmission which varies monotonically throughout the spectral width of the pump. The technique allows autonomous, reliable, and modulation-free operation of the infrared source at the optimum pumping frequency.
Temperature measurement system for optical-fiber preform fabrication
Authors: Bodeep G. E.
Published: March 2003

A system has been developed to measure the temperature profile across the growing surface of a soot preform in an axial vapor deposition process for optical-fiber preform fabrication. The system assembled at a fraction of the cost of commercially available instrumentation, makes use of an infrared pyrometer driven by a computer-controlled stepping motor. The pyrometer used has a temperature range of 300 °–1300 °C. The system has a spot size resolution of 1.5 mm and completes a scan in 30 s. Many combinations of sensing head detectors and controllers can be used for various temperature ranges and applications. The computer digitizes, stores, and displays the temperature information, and acts as a controller to generate appropriate feedback signals for process control.
Nodal point supported gravitational-wave antennas
Authors: Coccia Eugenio
Published: March 2003

We present here a nodal point suspension system for cylindrical gravitational-wave antennas, designed to get optimum seismic and acoustic isolation. The mechanical Q factor at room temperature of a test Al 6061 cylindrical bar with this support was 5.1×105.
Microcomputer-based system for on-line EPR data accumulation
Authors: Trousson Patrick , Rinne Michel
Published: March 2003

A simple and low-cost microcomputer-based data accumulation system was developed for use with the Varian E-line series of EPR spectrometers. The hardware is based on the Apple II europlus microcomputer with 12K of read-only memory, 48K of random access memory, and an 8-bit A/D and D/A converter. The software has been written in MOTOROLA assembler language and is used to collect data from spectral scans in single-scan and multiscan modes, store and recall those data on or from floppy disks, scale data, display data on a high-resolution graphic VDU, and output data to the spectrometer X–Y recorder. The microcomputer controls part of the spectrometer functions during the scans. The software described is the first part of a whole spectral analysis programs set.
Further modification of a commercial NOx detector for high sensitivity
Authors: Dickerson R. R. , Delany A. C. , Wartburg A. F.
Published: March 2003

We describe modifications of a commercial NOx detector for very high sensitivity and ease of computer assisted data acquisition. These changes include a larger gold-coated reaction chamber, increased ozone flow, a faster vacuum pump, analog outputs to define mode and range status, and enhanced cooling for the PMT. The detection limit, defined as a signal-to-noise ratio of 1:1 at the ±2 σ level is about 10 ppt with a 1/e response time of about 20 s or about 45 ppt for 1 s. Detection of other reactive nitrogen compounds is also discussed.
Stable high-temperature (500 °C) thermistors
Authors: Carlson R. O.
Published: March 2003

Thermistors which are stable in their resistance-temperature characteristic after extended high-temperature exposure have been formed by attaching platinum wires or Fernico (Kovar) ribbons with Birox thick film paste to thermistor spinel material (from two vendors) with a resistivity of 2000 Ω cm. Other resistivity compositions were not stable at elevated temperatures. Shifts in the original calibration curve were less than 2 °C at room temperature after 10 000 h at 240 °C, even with periodic jumps to 500 °C. Held and measured at 500 °C, resistance shifts were less than 2 °C for periods up to 750 h. These thermistor structures should provide low-cost, stable, reliable, and interchangeable temperature sensors for oven and furnace measurement and control.
Pressure and temperature measurements in the annulus between the piston and cylinder of a simple dead-weight piston gauge
Authors: Welch B. E. , Bean Vern E.
Published: March 2003

Precise and accurate pressure measurements are obtained using appropriately designed and operated piston gauges. Elastic distortion of the piston and cylinder is the leading cause of inaccuracy in measurement of higher pressures. The distortion depends upon the ratio of the pressure in the annulus between the piston and the cylinder to the pressure under the piston. Heretofore, as the proper value of this ratio or a method to determine it was unknown, the practice has been to assume a value of 0.5 when calculating distortion effects. In this work, the pressure and temperature of the fluid in the annulus have been measured along the working length of the piston and the cylinder. The model for the pressure ratio proposed by Bass on the basis of the clearance between the piston and cylinder is in excellent agreement with the pressure measurements. The appropriate value of the pressure ratio for the calculation of the distortion is marked by a sharp decrease in the slope of the pressure ratio curve. The corresponding value on the length axis is the appropriate location to calculate the area of the gauge from the dimensional measurements. The temperature measurements indicate that the temperature gradient along the cylinder is due solely to the flow of fluid up through the annulus and, for the most extreme case, was less than 60 mK.
Time-of-flight spectroscopy of sub-MeV cluster ions in the mass range of 1–106 atoms per charge
Authors: Moser H. O.
Published: March 2003

A time-of-flight spectrometer has been developed for ions in the mass and energy range of 1–106 atoms per charge and 100 keV–1 MeV, respectively. The ion beam is chopped by electrostatic deflection plates, the gate function being step-like. The instrument has been used to measure velocity spectra of intense energetic cluster-ion beams made of hydrogen.
Experimental observation of the ambipolar potential in a tandem mirror by use of negative ion beam
Authors: Ishii K. , Inami H. , Kawabe T. , Miyoshi S.
Published: March 2003

A negative ion beam probe is described. Advantages of this method for the potential measurement of the plasma in a minimum-B magnetic field are discussed and the method is applied to measure the potential difference between the plug and the central cell in a GAMMA-6 tandem mirror.
Production of negative ions by bombarding a cesiated metal surface with cluster ions and post-acceleration
Authors: Be S. H. , Yano K.
Published: March 2003

A new method of producing H− ions by bombarding cluster ions with a small glancing angle on a cesiated metal surface is proposed. On the basis of available experimental results, we conclude: (1) disintegration of clusters and conversion of their constituent atoms into H− ions can be simultaneously carried out on the surface; (2) an incident cluster ion beam is expected to produce the same equilibrium fraction of H− ion beams, as H+ ion beams of the same speed. Acceleration of the H− ions is investigated by computer simulation and it is found that a useful beam is obtained.
High-precision multicomponent borehole deformation monitoring
Authors: Gladwin Michael T.
Published: March 2003

An instrument capable of deep borehole measurement of vector plane strain to 0.3 nstrain and tilt to 1.0 nrad has been developed for deployment in crustal deformation and earthquake prediction studies. The instrument has been deployed in California where shear strains dominate the deformation. The 125-mm-diam package is grouted in 175-mm boreholes at depths of approximately 200 m. The wall thickness and the grout thickness are chosen to match instrument strength to expected rock parameters. The instrument is capable of flat response from dc to 10 Hz on any single channel. The electronics package is stable to three parts in 108 over the temperature range 10 to 45° C. Reliable shear strain data is available immediately on installation when simple volume strain meters show only bond curing effects or thermal recovery signals.
Relative electron detection efficiency of microchannel plates from 0–3 keV
Authors: Goruganthu R. R. , Wilson W. G.
Published: March 2003

The relative electron detection efficiency of a detector consisting of two microchannel plates (MCP) in a chevron arrangement with a carbon coated high transmission (94%) copper grid 6 mm in front of the first MCP was experimentally determined. The energy of the electrons hitting the detector was varied by accelerating a pulsed electron beam of known energy. By modeling the secondary electron emission from the grid and averaging for possible variations in the electron flux, the relative efficiency was determined to within 2% in the range ∼0 to 3 keV. Fits of the relative efficiency to an analytic expression as a function of incident energy and grid bias energy are reported.
Pulsed microchannel-plate mounting for subnanosecond x-ray image intensifiers
Authors: Luppi R. , Pecorella F. , Cerioni I.
Published: March 2003

The electrical and mechanical setup for the pulsed gating of a microchannel plate (MCP) operating in the subnanosecond range is presented. Shaping of the plate electrodes as conductors of a strip transmission line allows voltage pulses of duration down to 400 ps to be propagated with negligible attenuation and distortion. This MCP mounting will be used as an x-ray image intensifier with very high temporal and spatial resolutions.
Data reduction of x-ray diffraction signals using an Apple II computer
Authors: Wolf J. Douglas , Aulds J. Michael
Published: March 2003

A system based on an Apple IIe microcomputer is used to acquire and manipulate x-ray diffraction data.
New high-performance electron energy loss spectrometer for valence and inner-shell excitation studies
Authors: Daviel S. , Brion C. E. , Hitchcock A. P.
Published: March 2003

A new high-resolution, differentially pumped, electron energy-loss spectrometer with the capability of measuring both valence and inner-shell spectra (at impact energies of 1–10 keV) has been constructed. Advanced electron optics have been incorporated, and the design and operation of the electron optics is discussed. Spectra of N2 are presented, demonstrating the significant improvements obtained in signal to noise and collection time in the inner-shell region compared with previous instrumentation. In addition, both valence and inner-shell spectra of HCl are presented, demonstrating the efficiency of the differential pumping, and the ability of the instrument to study highly reactive target species.
Intelligent multichannel data-acquisition system for pulsed laser applications
Authors: Jones L. M. , Leroi G. E. , Myerholtz C. A. , Enke C. G.
Published: March 2003

A microcomputer-controlled data-acquisition system which is readily adapted to a wide variety of pulsed laser applications is described. Signals are sampled by commercially available gated integrators. Multichannel operation allows data to be normalized to a reference beam intensity, a necessity due to the pulse-to-pulse fluctuations of many pulsed lasers. Data are acquired and stored independently for each pulse. The advantages of postacquisition processing versus pulse-to-pulse averaging are demonstrated by an example of measurements on a nonlinear system.
Improved polar display technique of the phase angle of optical interference
Authors: Umeda N. , Shirai H. , Takasaki H.
Published: March 2003

A technique which displays the fractional order of optical interference by the azimuthal angle of radial arm has been improved by using a digital electronic circuit such as phase-locked loop and D flip–flop. The phase quadrature reference signals of this system are derived by reforming a reference signal and shifting it by a quarter wavelength referring to its waveform. As the result the orthogonal phase relation of the two signals is not affected by the frequency of the signal. This system has been proven to operate properly over the frequency range of 200–600 kHz without readjusting the electric system.
Fiber-optic interferometer for remote subangstrom vibration measurement
Authors: Drake Allen Dean , Leiner Dennis C.
Published: March 2003

A single-mode fiber-optic interferometer for measuring subangstrom vibrations has been designed and constructed. The interferometer is based on the Fizeau configuration and employs peak detection schemes in the signal processing. The instrument has been used to measure the displacement of a cricket’s tympanic membrane.
Simple, highly stable nitrogen laser with preionization
Authors: Bojara A. , Gawlik W. , Grabski R. , Zachorowski J.
Published: March 2003

The design and performance of a discharge-excited N2 laser which emits 7-ns-long pulses of 337.1-nm wavelength at a 300-Hz repetition rate is described. The peak power is 150 kW at 50 pps and the shot-to-shot amplitude stability is ±1.5%. The construction compromises between requirements of high power, high repetition rate, and good stability.
Quantitative real-time schlieren system for ultrasound visualization
Authors: Porter B.
Published: March 2003

A real-time schlieren system is described that incorporates a video imaging system to permit quantitative data to be obtained as to relative sound pressure distribution and wave front shape of ultrasonic waves. For 2.5-MHz sound, system jitter is less than a tenth of a wavelength, field of view is 125 mm, and position can be measured to 25 μm. To illustrate the capabilities of this system, a study of 1-μs-duration sound pulses in water reflecting off a metal surface at different angles of incidence was performed on the system. Rayleigh waves 3° removed from the Rayleigh angle were observed. At the Rayleigh angle, a null is observed in the reflected beam.
Field effect transistor tracking surface field sensor
Authors: Horenstein Mark N.
Published: March 2003

A closed-loop tracking circuit incorporating high-impedance metal–oxide–semiconductor (MOSFET) transistors has been developed for measuring high-voltage electrostatic fields on the surfaces of conducting electrodes. One MOSFET is used as a field sensor, and the other as a tracking ‘‘dummy.’’ The feedback circuit yields a signal voltage output that is at the same time linearly dependent on the external surface field being measured, and virtually independent of the gain and the offset parameters of the specific MOSFET device used as a sensor.
Gunn source for electron-spin-resonance spectroscopy
Authors: Giordano M. , Momo F. , Sotgiu A.
Published: March 2003

A Gunn diode oscillator stabilized by a transmission cavity is described; it has a center frequency of 9.4 GHz and a tuning range of about 1.2 GHz. The cavity provides a stabilizing factor of the order of 600 relative to the unstabilized oscillator. It was tested as the microwave source in an ESR spectrometer and gives the same performances as a commercially available klystron.
Simple real-time monitor of subpicosecond pulses
Authors: Watanabe Akira , Hirose Masanori , Terane Hideyuki , Tanaka Shosaku , Kobayashi Hiroshi , Hara Minoru
Published: March 2003

A real-time subpicosecond-pulse monitor with a simple new circuit is described. The autocorrelator consists of an usual audio speaker and the electronic circuit, which can detect the displacement of the interferometer.
Digital pulse programmer for an electron-spin-resonance computer-controlled pulsed spectrometer
Authors: Thomann Hans , Dalton Larry R. , Pancake Charles
Published: March 2003

A computer-controlled pulsed electron-spin-resonance spectrometer (EPR) based on a 100-MHz pulse programmer directly interfaced to a DEC LSI-11/23 minicomputer has been constructed. The pulse programmer is a programmable digital signal generator capable of generating parallel binary data patterns and complex digital timing waveforms to directly form the time base for pulsed EPR experiments. It utilizes an emitter coupled logic (ECL) design and provides eight channels of simultaneous ECL and TTL outputs; 16 state periods programmable between 20 ns and 655.36 μs per period with a resolution of 10 ns; an internal hardware autoincrement counter for one state period duration; two internal loop counters; and 2-byte TTL parallel interface to the LSI-11/23. All timed intervals are derived from and are synchronous to the 100-MHz master clock. The spectrometer configuration, analogous to modern commercial FT-NMR spectrometers, permit direct programming of pulsed EPR experiments using software developed on the host computer to operate the pulse programmer.
Fabrication of 80 Å metal wires
Authors: Williams W. D. , Giordano N.
Published: March 2003

Some years ago Possin reported the fabrication of wires as small as 400 Å in diameter with a method involving electroplating into etched particle tracks in mica. We have refined this technique, and can now use it to routinely produce wires as small as 80 Å. These refinements are described, and the possibility of making even smaller wires with this method is discussed.
Feedback control of a Darrieus wind turbine and optimization of the produced energy
Authors: Maurin T. , Henry B. , Devos F. , de Saint Louvent B. , Gosselin J.
Published: March 2003

This paper presents a microprocessor-driven control system, applied to the feedback control of a Darrieus wind turbine. The use of a dc machine as a generator to recover the energy and as a motor to start the engine, allows simplified power electronics. The architecture of the control unit is built to ensure four different functions: starting, optimization of the recoverable energy, regulation of the speed, and braking. An experimental study of the system in a wind tunnel allowed us to optimize the coefficients of the proportional and integral (pi) control algorithm. We found that the electrical energy recovery was much more efficient using our feedback system than without the control unit. This system allows a better characterization of the wind turbine and a regulation adapted to the wind statistics observed in one given geographical location.
Passive dosimeters for rf and microwave fields
Authors: Doss James D.
Published: March 2003

A tuned, passive dosimeter is described which measures the time integral of the H component of rf and microwave fields. A method for calculating the average power-density exposure is presented.
Inexpensive high-pressure mixing dilatometer
Authors: Bozdag O. , Chaudhry M. S. , Lamb J. A.
Published: March 2003

A mixing dilatometer constructred of standard, commercially available tubing and connectors and capable of working at pressures up to 4 kbar is described. Volume changes can be measured to an estimated accuracy better than ± 0.0001 cm3.
Ion source operation with different magnetic confinement geometries
Authors: Leung K. N. , Ehlers K. W.
Published: March 2003

A comparison has been made between the longitudinal line cusp and the ‘‘continuous’’ checkerboard magnet geometries. We find that the checkerboard arrangement can provide a larger uniform density profile with approximately 20% less plasma density than the longitudinal line cusp. Results seem to indicate that the reduction in plasma density is closely related to the containment of primary ionizing electrons by the permanent magnets. A new magneto-electrostatic containment scheme was generated by using an internal magnetic cage system. The overall efficiency of this ion source was increased when it was operated with a xenon or argon plasma.
Circuit design for transient measurements of electrical properties of thin metal films and thermal properties of insulating solids or liquids
Authors: Gustafsson Silas E. , Karawacki Ernest , Chohan Mohammad Aslam
Published: March 2003

A general circuit design is described for the transient hot-strip method which is presently used for studies of electrical properties of thin metal films and for measurements of thermal properties of insulating solids and liquids. It is demonstrated that a low driving voltage can be used for thin films having comparably high resistance, and that the output of power in the strip source (being the nonlinear component of the circuit) can be kept constant throughout the transient recording. The experimental arrangement for constant power conforms with the assumptions of the theory for the method and extends its validity to substantially larger temperature increases of the nonlinear resistance.
Accurate measurement of hydrogen diffusivity in metals
Authors: Pine David J. , Cotts R. M.
Published: March 2003

An accurate resistiometric technique for measuring fast diffusion of hydrogen in metals is described. The sample is in the form of a foil having uniform cross section and a length much greater than its width. Samples are electrolytically loaded with hydrogen to about 0.5 atomic percent. Initially the hydrogen is held at uniform concentration in essentially half the length of the foil by the effect of a dc electrotransport current of 2500 A/cm2 in the other half. After this current is removed, the diffusion of hydrogen into the second half is monitored by its effect on the resistance of a small section of the foil. With this technique a single sample may be reused to make many measurements of D. The measurement of D is absolute, and use of a sensitive differential ac measurement yields results for low hydrogen concentrations.