bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct current servo motor controlled four-jaw slits for synchrotron radiation
Authors: Garrett R. F. , Cookson D. J. , Davey P. , Janky S. , Wilkins S. W.
Published: July 2002

A four-jaw slit assembly and eight-axis dc servo motor controller have been constructed and are in use at the Australian National Beamline Facility (ANBF) at the Photon Factory. Because of the vacuum operation of the beamline diffractometer, dc servo motors were preferred to stepper motors. Due to the large number of motors to be controlled, commercial dc servo controllers were unsuitable, and an eight-axis controller was designed to be used in conjunction with the E500 CAMAC stepper motor controller. The system has been in use at the ANBF for about one year, and has allowed the integration of approximately 30 dc servo and stepper motors into a standard control system.
New beamline (BL-28B) for circularly polarized x rays at the Photon Factory
Authors: Iwazumi Toshiaki , Koyama Atsushi , Sakurai Yoshiharu
Published: July 2002

Design and experience of the initial operation of a new beamline (BL-28B) for an elliptical-multipole wiggler constructed at the Photon Factory are described. An indirect-water-cooled premirror has been installed for horizontal focusing and vertical collimating. The fixed-exit double-crystal monochromator also has an indirect-water-cooled system. The post-mirror has been commissioned in order to refocus the x-ray beam vertically and cut the higher harmonics of the monochromatized x rays. All the elements of this beam line are high-vacuum compatible.
Multilayer transmission phase shifters for the carbon K edge and the water window
Authors: Di Fonzo S. , Müller B. R. , Jark W. , Gaupp A. , Schäfers F. , Underwood J. H.
Published: July 2002

A multilayer transmission filter with 100 periods Cr/C has been produced in order to achieve a significant phase retardation for photon energies just below the carbon K edge. The phase retardation of this device was characterized and despite being smaller than expected the filter was suitable for the polarization characterization of a soft x-ray beamline with a primary standard. Neither the filter nor the beamline were found to change their characteristics in the course of seven months. Considering the state of the art of multilayer coatings additional model calculations show that these transmission filters can be applied also at 400 eV photon energy with an upper limit at 500 eV.
Time-resolved x-ray scattering program at the Advanced Photon Source
Authors: Rodricks Brian
Published: July 2002

The time-resolved scattering program’s goal is the development of instruments and techniques for time-resolved studies. This entails the development of wide bandpass and focusing optics, high-speed detectors, mechanical choppers, and components for the measurement and creation of changes in samples. Techniques being developed are pump-probe experiments, single-bunch scattering experiments, high-speed white- and pink-beam Laue scattering, and nanosecond to microsecond synchronization of instruments. This program will be carried out primarily from a white-beam, bend-magnet source, experimental station, 1-BM-B, that immediately follows the first optics enclosure (1-BM-A). This paper will describe the experimental station and instruments under development to carry out the program.
Raman imaging with near-field scanning optical microscopy
Authors: Jahncke C. L. , Paesler M. A. , Hallen H. D.
Published: July 2002

Raman spectroscopy in conjunction with near-field scanning optical microscopy is used to image Rb-doped KTiOPO4 within a spectral feature with high spatial resolution. We present Raman spectra as well as the first Raman images obtained in the near field. Differences between near-field and far-field Raman measurements are discovered and discussed.
A review of spaceborne infrared Fourier transform spectrometers for remote sensing
Authors: Persky M. J.
Published: July 2002

Infrared spectroscopy has many applications, and the Fourier transform spectrometer (FTS) has become an important analytical tool for these purposes. In addition to its use in benign laboratory environments, the FTS has found great acceptance for the difficult tasks of remote sensing of the Earth from satellites, and for space exploration by probes to other planets. This paper provides an overview of the characteristics and applications of many of the spaceborne FTS systems used in the past as well as those on the drawing boards for future use. A discussion of critical design issues is included in addition. A review of Fourier transform spectroscopy principles; a brief history of FTS instrument development; and a discussion of a possible future direction are also provided. An extensive list of references is contained as well.
Development of a neutron spectrometer, counter telescope with thick radiator, for TFTR D-T experiments
Authors: Osakabe M. , Fujita J. , Kodaira J. , Sasao M. , Yamanishi H. , Itoh S. , Diesso M. D. , Johnson L. C. , Roquemore A. L.
Published: July 2002

A ΔE-E type proton recoil telescope, called COTETRA, was developed and is presently being applied to TFTR D-T fusion experiments. Two types of COTETRA were prepared for this experiment. One set is used primarily for high-resolution measurements of the neutron energy and uses Si diode as an E detector (set A), while another set (set B) uses a plastic scintillator to attain high count-rate capability. Both sets of COTETRA have small physical dimensions and use fast NIM electronic modules for high neutron flux rate measurements. A data acquisition system has been developed for the TFTR CAMAC system. A calibration experiment has been performed using a D-T neutron generator. Energy resolution of 4.0% is obtained for set A. Set B is expected to work at a count rate of up to 104 cps, which corresponds to a neutron flux rate of ∼109 (n/cm2)/s at the detector position. Currently, both of them are installed under the multichannel neutron collimator of TFTR.
Dynamic measurements of the spreading of liquid metals in controlled atmospheres with in situ surface preparation and analysis
Authors: Peebles D. E. , Peebles H. C. , Ohlhausen J. A. , Hurst M. J.
Published: July 2002

A specially designed ultrahigh vacuum in situ surface analysis and wetting system has been constructed to study the spreading of liquid metal solders on carefully prepared and well-characterized solid substrates. The system consists of a standard ultrahigh vacuum surface analysis chamber linked to a reaction chamber for wetting or other experiments at pressures up to atmospheric. A sophisticated video system allows real-time monitoring of the spreading of the liquid metal through both side and top views. An infrared imaging system allows accurate remote temperature measurements. Sample surfaces are prepared and spreading experiments performed without intermediate exposure of the surfaces to the contaminating atmospheres. Solder spreading is performed under 50 Torr of highly purified helium gas to allow for adequate thermal coupling between the solder and the substrate. Initial studies have been completed for the spreading of pure tin solder on copper substrates in the absence of any fluxing agent. Three types of copper substrate surfaces were investigated in these experiments: the sputter-cleaned, air-exposed, and the as-received surface. Surface chemical analysis by x-ray photoelectron spectroscopy showed the air-exposed surface to consist of about 3 nm of Cu2O, while the as-received surface consisted of about 8 nm of Cu2O. The sputter-cleaned surface contained less than one monolayer (0.3 nm) of Cu2O. Spreading experiments utilizing a linear temperature ramp show that pure tin solder spreads readily on oxidized copper surfaces at elevated temperatures. The initiation temperature for rapid tin spreading on the as-received copper surface was 325 °C. Decreasing the thickness of the oxide on the surface lowered the observed temperature for the initiation of spreading and increased the rate of spreading. On the sputter-cleaned copper surface, rapid solder spreading was observed immediately upon melting of the solder.
Interferometer for the measurement of defects on ball bearings
Authors: Bartl J.
Published: July 2002

This paper describes an interference instrument for the control of the quality of spherical surfaces. The instrument was developed for contactless control of ball bearings. The interference image in numerical form is electronically processed using special interference techniques.
High-intensity source of polarized negative hydrogen ions with a resonant charge-exchange plasma ionizer
Authors: Belov A. S. , Esin S. K. , Netchaeva L. P. , Plokhinski Yu. V. , Vasil’ev G. A. , Klenov V. S. , Turbabin A. V. , Yakushev V. P. , Dudnikov V. G.
Published: July 2002

The Moscow Institute for Nuclear Research atomic-beam type source of polarized negative hydrogen ions is described. The production of H− ions is based on the resonant charge exchange of polarized thermal hydrogen atoms and D− ions in deuterium plasma. Improvements in the D− plasma source are outlined. The polarized source produces a pulsed H− beam with a peak current up to 1 mA and a pulse duration of 180 μs at a repetition rate of 10 Hz. The normalized emittance for 90% of the beam particles is 1.8 π mm mrad. The polarimeter of low energy H− ions is also described. The polarization of the H− ions was measured to be 0.87±0.02.
Characteristics of AuSi liquid metal alloy ion source with coupling extractor electrodes
Authors: Higuchi-Rusli Ronnie H.
Published: July 2002

Characteristics of AuSi liquid metal alloy ion source with single and coupling (double) extractor electrodes have been investigated both in the focused ion beam machine, and in the vacuum test bed system equipped with quadrupole mass spectrometer. Liquid metal ion source with coupling extractor electrode produce a stable total ion current which increases almost linearly when compared with a single extractor electrode. The isotope current of 197Au+ observed with quadrupole mass spectrometer is higher in the ion source with coupling extractor electrode than in a single extractor electrode, nonetheless, the pattern of its current–voltage characteristics remain the same for both single and coupling extractor electrodes. However, for lighter isotopes such as 28Si+ and 28Si++, the result is reversed (higher in ion source with single extractor electrode). The secondary electron image of copper grid pictures obtained from focused ion beam systems installed with an AuSi liquid metal alloy ion source with single and coupling extractor electrodes remain the same.
A 4.5 kV 6H silicon carbide rectifier
Authors: Kordina O. , Bergman J. P. , Henry A. , Janzén E. , Savage S. , André J. , Ramberg L. P. , Lindefelt U. , Hermansson W. , Bergman K.
Published: July 2002

Reactive ion etched silicon carbide mesa pin diodes with voltage blocking capabilities as high as 4.5 kV have been fabricated from 6H–SiC epitaxial layers. The epitaxial structure was grown by chemical vapor deposition on an n+ substrate giving a low-doped 45 μm thick n− active base layer and a 1.5 μm thick high-doped p+ emitter layer on top. A high minority carrier lifetime of 0.43 μs in the n− active base layer provides good on-state properties with a typical forward voltage drop of 6 V at 100 A/cm2.
Longitudinal beam emittance monitor for 433 MHz proton linac
Authors: Dewa H. , Ao H. , Kihara T. , Tonguu H. , Shirai T. , Okamoto H. , Iwashita Y. , Fujita H. , Kakigi S. , Noda A. , Inoue M.
Published: July 2002

We have developed a longitudinal emittance monitor for a 7 MeV proton beam provided by the 433 MHz linac at the Institute for Chemical Research, Kyoto University. In the present system, the beam first hits a thin gold target on the beam line, and a fraction of the scattered protons comes into a small cavity. After deflected by a rf electric field in the cavity, the protons finally reach a position sensitive detector (PSD). The PSD gives the information of the energy and position of the individual scattered proton, which enables us to reconstruct the longitudinal distribution of the beam before colliding with the target. The phase and energy resolution of the system are estimated to be 13° and 23 keV full width at half-maximum, respectively. The longitudinal rms emittance measured was 0.39±0.07 π deg MeV under the nominal operating condition of the linac.
A soft x-ray standing wave measurement system for analyzing compound semiconductor surfaces prepared by molecular beam epitaxy
Authors: Sugiyama M. , Maeyama S. , Oshima M.
Published: July 2002

A soft x-ray standing wave (soft-XSW) measurement system has been developed for analyzing III–V compound semiconductor surfaces prepared by molecular beam epitaxy (MBE). It consists of a fast entry chamber ( a load-lock chamber), a transfer chamber, a MBE growth chamber, and an analysis chamber. It is connected to NTT’s synchrotron radiation beam line at the Photon Factory. Samples prepared by MBE can be transferred to the analysis chamber through ultrahigh vacuum. The goniometer in this analysis system was shown to be suitable for soft-XSW triangulation studies. Both backreflection and angle-scan soft-XSW experiments for adsorbate/GaAs(001) systems prepared by MBE were demonstrated.
An automated system for current–voltage characterization of ceramic superconductors
Authors: List F. A. , Martin P. M. , Kroeger D. M.
Published: July 2002

An automated system for determinations of transport current–voltage (I–V) characteristics as a function of temperature (25–125 K), magnetic field (0–1.6 T), and magnetic field orientation (−125 to +145°) is described. Currents of up to 100 A are applied either as a continuous ramp or as pulses of 2–100 ms duration. A closed-cycle helium refrigerator provides a rapid (∼45 min), convenient, cost effective, cooldown from 300 to 25 K. Control of current, temperature, magnetic field, and field orientation is fully automated and requires no user interaction. The characterization of performance of a ceramic superconductor typically involves several temperatures, fields, and orientations and requires 8–30 h to complete.
Depth profile of implanted species with a detector telescope
Authors: Avasthi D. K. , Kabiraj D. , Jain A. , Mehta G. K.
Published: July 2002

Conventional elastic recoil detection analysis (ERDA) is considered to be an ideal nondestructive technique for depth profiling of implanted species of light mass elements in a material. The present work shows that it can lead to inaccurate misleading results in the cases where the implanted sample has surface impurity of nearby light mass element. It is also shown that the detector telescope behind the stopper foil in ERDA allows accurate profiling of implanted specimen as well as surface impurities simultaneously.
Use of hydrogen negative ions in particle accelerators
Authors: Dimov G. I.
Published: July 2002

The use of negative hydrogen ions in different accelerators, especially in charge-exchange injection of protons into orbits of high energy accelerators, is reviewed. The principles of charge exchange for particle acceleration and control and the benefits are discussed after which the performance and characteristics of selected accelerators are summarized. Recent trends in negative ion sources for charge-exchange accelerators also are reviewed.
Optimization of an ion-optics system with “thick” electrodes for the diagnostic neutral beam injector of the TEXTOR tokamak
Authors: Davydenko V. I. , Ivanov A. A. , Rogozin A. I. , Uhlemann R.
Published: July 2002

The optimization results of the ion-optics system in a neutral beam injector are considered which is developed for application of beam emission spectroscopy in the TEXTOR tokamak. The injector is capable to deliver a neutral beam of at least 1 A in hydrogen and deuterium at 50 keV for a pulse length of 5 s into the plasma. The simulation results with the AXCEL code for grids of 4 mm thickness are discussed. The ion current of 2 A extracted by a multihole grid system at a current density of 120 mA/cm2 is generated by a rf driven ion source. The beamlet half angular divergence is below 0.6° for the optimized four-electrode ion optics system. The estimated temperature rise of the inertially cooled molybdenum grids with 150 holes and 58% transparency is max. 270 K and the related degradation in beam quality by thermal grid expansion is acceptable.
Time-resolved two-dimensional monochromatic imaging of laser-imploded plasma
Authors: Miyanaga N. , Aoki Y. , Shiraga H. , Shimada K. , Fujimoto K. , Heya M. , Nakasuji M.
Published: July 2002

To prepare a new diagnostic tool for the laser-imploded plasma, we have developed a time-resolved, two-dimensional monochromatic imaging system that consists of a pinhole array, a flat diffraction crystal, and an x-ray streak camera without cathode slit. We have successfully reconstructed time-resolved two-dimensional images of an Ar resonance line emitted from an imploded plastic shell filled with D2/Ar mixture gas. The current system provides the temporal resolution of ∼24 ps and the spatial resolution of ∼16 μm for the direction perpendicular to the spectral dispersion. The spatial resolution parallel to the spectral dispersion is ⩽27 μm, that depends on the crystal broadening and the spectral linewidth.
Spatial resolution of gated x-ray pinhole cameras
Authors: Robey H. F. , Budil K. S. , Remington B. A.
Published: July 2002

We have conducted an investigation of the spatial resolution of a new gated x-ray pinhole camera (FXI). The spatial resolution, or its Fourier transform the modulation transfer function (MTF), is critical for quantitative interpretation of recent hydrodynamic instability data taken on the Nova laser. We have taken data corresponding to backlit straight edges, pinholes, and grids, both on the bench and in situ on Nova. For both the pinhole and edge data, the MTF at all wavelengths of interest can be deduced from a single image. Grids are of more limited usefulness, giving the value of the MTF only at the spatial period of the grid. These different techniques for characterizing the MTF of gated x-ray pinhole cameras will be discussed, with results specific to the FXI presented.
A low cost remotely operable cutting machine for segmenting metal clad ceramic fuel pellets
Authors: Ravi sankar G. , Manivannan R. , Anandkumar A. , Subramanian S. , Antony M. P. , Vasudeva Rao P. R.
Published: July 2002

Cutting of irradiated zircaloy metal clad ceramic fuel pellets requires a special cutting saw that can be remotely operated. The remote operation is essential because of the pyrophoric nature of zircaloy metal and high radiation field associated with the irradiated fuel elements. Conventional saws cannot meet the operational requirements because these are not readily amenable for remote operation and maintenance. Hence we have developed a new laboratory scale cutting saw for cutting radioactive samples remotely.
Development of the next generation H− ion source for the LANSCE facility
Authors: Wengrow A. B. , Leitner M. A. , Leung K. N. , Williams M. D. , Wutte D. C.
Published: July 2002

The upgrade of the Los Alamos Neutron Science Center (LANSCE) will require an ion source producing high intensity H− beams. The new LANSCE source in particular will need to generate 40 mA of H− beam current at a duty factor of 12% (1 ms pulse at 120 Hz). To achieve this, the present Los Alamos results were first reproduced employing a prototype surface conversion source similar to the existing LANSCE source. Using these results as a benchmark for further testing, it was discovered that by moving the filament cathode into the chamber’s cusp-field, the H− ion yield was enhanced. Considering this result, two extension chambers were added with movable magnetic filters at each end of the source to further improve the H− beam current. In addition, construction has been started on a new prototype axial source which will enable more plasma ions to funnel across the filter field into the central region where the converter is located. Results of the magnetic filter operation as well as the new axial source design will be presented.
Design and performance of an electrospray ion source for magnetic-sector mass spectrometers
Authors: Belov Mikhail E. , Colburn Alex W. , Derrick Peter J.
Published: July 2002

An electrospray ion (ESI) source capable of operating at accelerating potentials of up to 11 kV has been designed and fabricated. The ESI source has been shown to deliver ion beams with a total current up to 20 pA and an emittance of 2–3 mm mrad in analysis of the peptide gramicidin S (molecular mass 1140.7 Da) and the protein bovine insulin B chain (molecular mass 3495.9 Da). Coupled to a two-sector tandem mass spectrometer, the ESI source produced efficiently the multiply charged ions of proteins, such as bovine ubiquitin (molecular mass 8564.8 Da) and cytochrome c (molecular mass 12327 Da). The high ion currents and high kinetic energies of the electrospray ions (up to 200 keV) characterize this ESI source as a powerful tool to be used in structural analysis of macromolecules by collision-induced dissociation.
An instrument for electron beam and light transmission imaging of mass distribution in paper and fibrous webs
Authors: Keller D. Steven , Luner Philip
Published: July 2002

An instrument was developed for the rapid measurement of local mass density (formation) in fibrous networks and films using electron beam transmission (EBT) imaging. A transmission electron microscope (80 keV) was modified for use as a beam source for irradiating 5 cm×5 cm samples of paper or other fibrous webs. Local transmission of electrons through paper (directly proportional to the mass) was measured indirectly by video imaging of the pattern emitted by a Ca(Eu)F2 cathodoluminescing window supporting the specimen. The local optical density was also determined using a diffused electroluminescent lamp. A single CCD imaging system, with a spatial resolution of 0.1 mm, was used for both the electron and light transmission methods. EBT results were calibrated using mylar samples of known grammage. The irradiation sources and the detection system were characterized to establish the limits of operation and measurement capabilities. Electron beam flux was measured directly, and the attenuation curve for mylar correlated well with Monte Carlo estimation with an upper limit of ∼85 g/m2. For EBT imaging, procedures were established to prevent disruption of images by electrostatic discharging. Correction also was made for the back-reflected light that was a function of the reflectivity, R0, of the sample. A group of samples prepared from different pulps was imaged, and the actual grammages were compared with those determined from the instrument. The results demonstrated that, with few exceptions, good correlation existed.
A low noise synchronous detector
Authors: Sutton John F.
Published: July 2002

A high performance analog switching-type synchronous detector is described. The magnitude of the detected output signal is double that of previous designs, and the signal-to-noise ratio is improved. The square wave caused by dc offsets and 1/f noise components, and the ripple voltage normally produced by synchronous sinusoidal input signals have been eliminated, thus minimizing low pass filter requirements.
Ultrasensitive excitation/relaxation calorimeter for simultaneous measurement of thermal conductivity and heat capacity in fluids
Authors: Jin Albert J. , Mudd C. P. , Gershfeld N. L. , Fukada K.
Published: July 2002

An ultrasensitive heat conduction microcalorimeter for fluids with a novel method of data analysis is described. The instrument measures the thermal conductivity (λ) and heat capacity (Cp) simultaneously on the same sample with a resolution of 1 part in 105 for each of these properties. Baseline and sample filling errors are below the instrument resolution. The accuracies for λ and Cp are approximately 1 part in 104, limited primarily by the uncertainty in the properties of the standards used for calibration. The instrument operates essentially isothermally, and is capable of automated temperature stepping between 5 and 55 °C.
Imaging x-ray crystal spectrometers for the National Spherical Torus Experiment
Authors: Bitter M. , Hill K. W. , Roquemore A. L. , Beiersdorfer P. , Kahn S. M. , Elliott S. R. , Fraenkel B.
Published: July 2002

A new type of high-resolution x-ray imaging crystal spectrometers is described for implementation on the National Spherical Torus Experiment (NSTX) to provide spatially and temporally resolved data on the ion temperature, toroidal and poloidal plasma rotation, electron temperature, impurity ion-charge state distributions, and impurity transport. These data are derived from observations of the satellite spectra of heliumlike argon, Ar XVII, which is the dominant charge state for electron temperatures in the range from 0.4 to 3.0 keV and which is accessible to NSTX. Experiments at the Torus Experiment for Technology Oriented Research (TEXTOR) demonstrate that a throughput of 2×105 photons/s (corresponding to the count-rate limit of the present detectors) can easily be obtained with small, nonperturbing argon gas puffs of less than 1×10−3 Torr l/s, so that it is possible to record spectra with a small statistical error and a good time resolution (typically 50 and 1 ms in some cases). Employing a novel design, which is based on the imaging properties of spherically bent crystals, the spectrometers will provide spectrally and spatially resolved images of the plasma for all experimental conditions, which include ohmically heated discharges as well as plasmas with rf and neutral-beam heating. The conceptual design, experimental results on the focusing properties, and relevant spectral data from TEXTOR are presented.
Automated constant voltage anemometer with in situ measurements of overheat and time constant of the hot wire
Authors: Sarma Garimella R. , Lankes Robert W.
Published: July 2002

The operational features of an automated constant voltage anemometer (ACVA) designed for flight applications have been presented. Diagnostic voltage outputs are provided in ACVA, which will enable the calculation of in situ hot wire time constant and overheat for postprocessing of the turbulence data from the measured output voltage. TTL outputs provide identification of the output state. Using this automated system in a wind tunnel, time constant values obtained as a function of the hot wire Reynolds numbers and hot wire currents (overheats) are presented for 5 and 10 μm hot wires showing agreement with prior analysis and results
A new detector for measuring three-dimensional momenta of charged particles in coincidence
Authors: Lavollée M.
Published: July 2002

A detector system for the study of the dissociation dynamics of molecular ions is described. The measurements of the time of flight and of the hit coordinates of the charged fragments on the detector are transformed into the three momentum components along Cartesian coordinates. The detector uses 2×32 independent channels which makes possible the simultaneous detection of several particles and a spatial resolution of 0.65 mm on a 40 mm diameter channel plate. The low dead time of this detector (≃1 ns) enables us to study the dissociation of homonuclear molecules and also the angular correlation and energy distribution between two electrons of very low kinetic energies. As an illustration of its possibilities, results obtained in the dissociation of charged molecular ions will be considered to illustrate the capacity of this detector for the identification of dissociation channels, the accurate kinetic-energy distribution, and the investigation of the dissociation kinematics.
Transient dielectric study of bistable reflective cholesteric displays and design of rapid drive scheme
Authors: Huang Xiao-Yang , Yang Deng-Ke , Doane J. William
Published: July 2002

Transient dielectric measurement is used to study the transitions among the planar, focal conic, and homeotropic states of cholesteric liquid crystals. If the initial state is the field-induced homeotropic state, at low bias fields, the liquid crystal transforms to the planar state in a sequence of homeotropic-transient planar–planar; at high bias fields, the liquid crystal transforms to the focal conic state. The homeotropic-transient planar transition is on the order of 1 ms while the homeotropic-focal conic transition is on the order of 100 ms. Large hysteresis is observed in the transitions between the homeotropic and the focal conic state. Based on the rapid homeotropic-transient planar transition and the hysteresis effect in the focal conic-homeotropic transition, we have designed a drive scheme which can address bistable reflective cholesteric displays at the speed of one line per millisecond.
Design and development of a highly sensitive, field portable plasma source instrument for on-line liquid stream monitoring and real-time sample analysis
Authors: Duan Yixiang , Su Yongxuan , Jin Zhe , Abeln Stephen P.
Published: July 2002

The development of a highly sensitive, field portable, low-powered instrument for on-site, real-time liquid waste stream monitoring is described in this article. A series of factors such as system sensitivity and portability, plasma source, sample introduction, desolvation system, power supply, and the instrument configuration, were carefully considered in the design of the portable instrument. A newly designed, miniature, modified microwave plasma source was selected as the emission source for spectroscopy measurement, and an integrated small spectrometer with a charge-coupled device detector was installed for signal processing and detection. An innovative beam collection system with optical fibers was designed and used for emission signal collection. Microwave plasma can be sustained with various gases at relatively low power, and it possesses high detection capabilities for both metal and nonmetal pollutants, making it desirable to use for on-site, real-time, liquid waste stream monitoring. An effective in situ sampling system was coupled with a high efficiency desolvation device for direct-sampling liquid samples into the plasma. A portable computer control system is used for data processing. The new, integrated instrument can be easily used for on-site, real-time monitoring in the field. The system possesses a series of advantages, including high sensitivity for metal and nonmetal elements; in situ sampling; compact structure; low cost; and ease of operation and handling. These advantages will significantly overcome the limitations of previous monitoring techniques and make great contributions to environmental restoration and monitoring.
Dependence of the direct piezoelectric effect in coarse and fine grain barium titanate ceramics on dynamic and static pressure
Authors: Demartin Marlyse , Damjanovic Dragan
Published: July 2002

The direct piezoelectric effect in fine and coarse grain barium titanate ceramics is examined as a function of the external alternating and static pressure. It is found that domain wall vibrations contribute to the piezoelectric effect in both types of ceramics, but this contribution is smaller in the fine grain material. The external static pressure reduces domain wall contributions in the coarse grain samples and has little effect on the properties of the fine grain material. The results are consistent with the presence of a strong internal pressure in the fine grain ceramics.
A pulse-driven programmable Josephson voltage standard
Authors: Benz S. P. , Hamilton C. A.
Published: July 2002

A voltage standard based on a series array of pulse-biased, nonhysteretic Josephson junctions is proposed. The output voltage can be rapidly and continuously programmed over a wide range by changing the pulse repetition frequency. Simulations relate the circuit margins to pulse height, width, and frequency. Experimental results on a prototype circuit confirm the expected behavior.
Cu precipitation in Cr ribbon of Cu-15 wt % Cr in situ composite
Authors: Jin Y. , Adachi K. , Takeuchi T. , Suzuki H. G.
Published: July 2002

Although the solubility of Cu in Cr is negligible in the equilibrium state, Cu precipitates were discovered in extensively cold-rolled Cr ribbons of Cu-15 wt % Cr in situ composite by means of analytical transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM). The precipitation sequence was found to be a Cu-rich cluster ⇒ Cu GP zone ⇒ Cu equilibrium phase.
Interface structure of selectively oxidized AlAs/GaAs
Authors: Takamori T. , Takemasa K. , Kamijoh T.
Published: July 2002

We present studies of the interface abruptness of selectively oxidized AlAs/GaAs multilayer structures using transmission electron microscopy (TEM). High-resolution cross-sectional TEM images reveal that the interfaces between oxidized AlAs and unoxidized regions (GaAs and AlAs) are extremely abrupt on atomic scale. The widths of the transitional region are found to be within 4 monolayers for the interface between oxidized AlAs and unoxidized GaAs and 6.5 nm for the one between oxidized and unoxidized AlAs. The oxide layer thickness is found to decrease gradually from the oxidation front over a length of 200 nm.
A field effect transistor based on the Mott transition in a molecular layer
Authors: Zhou C. , Newns D. M. , Misewich J. A. , Pattnaik P. C.
Published: July 2002

Here we propose and analyze the behavior of a field effect transistor (FET)-like switching device, the Mott transition field effect transistor, operating on a novel principle, the Mott metal-insulator transition. The device has FET-like characteristics with a low “ON” impedance and high “OFF” impedance. Function of the device is feasible down to nanoscale dimensions. Implementation with a class of organic charge transfer complexes is proposed.
Correlation of cathodoluminescence inhomogeneity with microstructural defects in epitaxial GaN grown by metalorganic chemical-vapor deposition
Authors: Rosner S. J. , Carr E. C. , Ludowise M. J. , Girolami G. , Erikson H. I.
Published: July 2002

We discuss the relationship between microstructure and luminescence efficiency for heteroepitaxial films of GaN grown on c-axis sapphire substrates by metalorganic chemical-vapor deposition. We directly characterize the correlation between threading dislocations as observed by transmission electron microscopy, surface morphology as observed by atomic force microscopy, and wavelength-resolved cathodoluminescence imaging. We show that the inhomogeneity in the luminescence intensity of these films near band edge can be accounted for by a simple model where nonradiative recombination at threading dislocations causes a deficiency of minority carriers and results in dark regions of the epilayer. An upper bound for average diffusion length is estimated to be 250 nm.
Activation energy for diamond growth from the carbon–hydrogen gas system at low substrate temperatures
Authors: Stiegler J. , Lang T. , von Kaenel Y. , Michler J. , Blank E.
Published: July 2002

The growth kinetics of diamond films deposited at low substrate temperatures (600–400 °C) from the carbon–hydrogen gas system have been studied. When the substrate temperature alone was varied, independently of all other process parameters in the microwave plasma reactor, an activation energy in the order of 7 kcal/mol was observed. This value did not change with different carbon concentrations in hydrogen. It is supposed that growth kinetics in this temperature range are controlled by a single chemical reaction, probably the abstraction of surface bonded hydrogen by gas phase atomic hydrogen.
Electrical effects generated by experimental volcanic explosions
Authors: Büttner R. , Röder H. , Zimanowski B.
Published: July 2002

We report on the experimental study of electrical phenomena during explosive volcanic eruptions, which provides qualitative and quantitative insight into different fragmentation and eruption mechanisms of magmatic melt. The experiments show that air friction and surface enlargement by hydro- and/or aerodynamic magma fragmentation are only minor contributors to electrical charging of erupted particle clouds in comparison to thermo-hydraulic fracturing of magma by explosive magma/water interaction. This process has the potency to explain the frequently observed occurrence of lightning in eruption clouds of explosive volcanic events.
On the dynamics of the oxidation-induced stacking-fault ring in as-grown Czochralski silicon crystals
Authors: Sinno Talid , Brown Robert A. , von Ammon Wilfried , Dornberger Erich
Published: July 2002

The behavior of the oxidation-induced stacking-fault ring (OSF ring) in Czochralski (CZ)-grown silicon crystals is predicted based on the dynamics of point defects during growth. Preexponential constants for the equilibrium point defect concentrations and diffusivities are determined by fitting the predictions of the model to a single set of experimental data for OSF-ring dynamics. Other experimental data is well fit by this model. Moreover, point defect properties used are consistent with other estimates. Asymptotic analysis of the point defect model leads to a closed-form expression for the dependence of the OSF-ring location on processing conditions and thermophysical properties of point defects at the melting temperature. These results indicate that differentiation between defect types in CZ-grown material can be done entirely on the basis of point defect dynamics.
Stop-bands for periodic metallic rods: Sculptures that can filter the noise
Authors: Kushwaha Manvir S.
Published: July 2002

We perform extensive band structure computation for two-dimensional (2D) periodic arrays of rigid stainless steel cylinders in air, with Bloch vector being perpendicular to the cylinders. For cylinders 2.9 cm in diameter and period of 10 cm (i.e., filling fraction f=0.066) there is no acoustic gap for frequencies below 6.4 kHz. However, the density of states reveals prominent minima at 1.7 and 2.4 kHz. These frequencies do agree with those of the first two attenuation maxima observed in the experiment [Nature 378, 241 (1995)] and are indeed related to diffraction from the [100] and [110] planes. Thus, even with idealization, Sempere’s sculpture exhibits pseudogaps—not full gaps. We stress that, for any value of the period, there is no acoustic gap for f⩽30%; magnitude of the gap, for f>30%, is inversely proportional to the period of the system. Moreover, if the filling fraction exceeds 40%, a second gap, higher in frequency, opens up. In addition, we propose the fabrication of a multiperiodic system in tandem that could create a huge hole in sound within the human audible range of frequencies.
Optical properties of wurtzite structure GaN on sapphire around fundamental absorption edge (0.78–4.77 eV) by spectroscopic ellipsometry and the optical transmission method
Authors: Yu G. , Wang G. , Ishikawa H. , Umeno M. , Soga T. , Egawa T. , Watanabe J. , Jimbo T.
Published: July 2002

Spectroscopic ellipsometry (SE) together with the optical transmission method is successfully used to determine the refractive index n and absorption coefficient α of undoped gallium nitride film over the spectral range of 0.78–4.77 eV of photon energy. The SE measurement is carried out at angle of incidence of 60° over the 1.5–4.77 eV energy range and optical transmission measurement over the 0.78–3.55 eV energy range. The refractive index n and absorption coefficient α obtained by both methods show unique results in the overlap wavelength region. Refractive index n is found to follow the Sellmeir dispersion relationship n2(λ)=2.272+304.72/(λ2−294.02) below the fundamental band edge. A free excitonic structure at the band is clearly observed at room temperature, with the transmission energy of free exciton at 3.44 eV, which is in reasonable agreement with the reported results.
The role of strain in magnetic anisotropy of manganite thin films
Authors: Suzuki Y. , Hwang H. Y. , Cheong S-W. , van Dover R. B.
Published: July 2002

We show the importance of the role of strain in La0.7Sr0.3MnO3 films by revealing the dominance of stress anisotropy effects over magnetocrystalline anisotropy effects in the magnetic anisotropy of these films. Magnetic anisotropy measurements of (001) and (110) La0.7Sr0.3MnO3 thin films on SrTiO3 and LaGaO3 substrates, with excellent structural quality, reveal twofold symmetry on (110) La0.7Sr0.3MnO3 films and fourfold symmetry on (001) films. Such symmetries can only be explained by stress anisotropy contributions in the plane of the film. In conjunction with the thickness dependence of the magnetic properties, the results indicate the dominant role of strain in the magnetic properties of these doped manganites.
Luminescence of pulsed laser deposited Eu doped yttrium oxide films
Authors: Jones S. L. , Kumar D. , Singh Rajiv K. , Holloway P. H.
Published: July 2002

Europium doped yttrium oxide (Eu:Y2O3) phosphor thin films were grown using a pulsed laser deposition (PLD) technique at varying growth conditions. The structural characterization carried out on a series of Eu:Y2O3 films grown on (100) silicon at substrate temperatures in the range of 250–600 °C and oxygen pressure in the range of 10−5 Torr to 200 mTorr indicated that films were preferentially (111) oriented. Measurements of photoluminescence and cathodoluminescence properties of laser deposited Eu:Y2O3 thin films and powder used for laser target showed that the best in situ grown films were ∼10%–22% as bright as Eu:Y2O3 powder. A postdeposition annealing treatment of Eu:Y2O3 films led to further improvements in their brightness (up to ∼70% with respect to Eu:Y2O3 powder), with cluster sizes of <400 nm.
Nanoscale field emission structures for ultra-low voltage operation at atmospheric pressure
Authors: Driskill-Smith A. A. G. , Hasko D. G. , Ahmed H.
Published: July 2002

Novel field emission devices with electron path lengths an order of magnitude less than the elastic mean free path of electrons in air have been fabricated and tested at atmospheric pressure. The nanoscale-tip field emission system consisted of multiple emitter tips of radii about 1 nm within an extractor aperture of diameter 50 nm. The extractor turn-on voltage was approximately 7.5 V; field-emitted currents of up to 10 nA were collected at extractor voltages of less than 10 V. Maximum current densities of over 1011 A m−2 have been observed, and the emission stability in air at atmospheric pressure is better than 3%.
Ink-jet printing of doped polymers for organic light emitting devices
Authors: Hebner T. R. , Wu C. C. , Marcy D. , Lu M. H. , Sturm J. C.
Published: July 2002

Ink-jet printing was used to directly deposit patterned luminescent doped-polymer films. The luminescence of polyvinylcarbazol (PVK) films, with dyes of coumarin 6 (C6), coumarin 47 (C47), and nile red was similar to that of films of the same composition deposited by spin coating. Light emitting diodes with low turn-on voltages were also fabricated in PVK doped with C6 deposited by ink-jet printing.
Self-forming InAs/GaP quantum dots by direct island growth
Authors: Leon R. , Lobo C. , Chin T. P. , Woodall J. M. , Fafard S. , Ruvimov S. , Liliental-Weber Z. , Stevens Kalceff M. A.
Published: July 2002

InAs/GaP semiconductor quantum dots (QDs) were spontaneously formed using direct island growth (Volmer–Weber) rather than Stranski–Krastanow (S-K) growth. Structural investigations of InAs/GaP QDs suggest kinetically limited growth and show a broad size distribution. Photoluminescence and cathodoluminescence spectroscopy reveal large inhomogeneous broadening with the emission peak centering at 1.7 eV. Device applications exploiting broad optical emission in QDs are discussed.
Planar thin film YBa2Cu3O7−δ Josephson junctions via nanolithography and ion damage
Authors: Katz A. S. , Sun A. G. , Woods S. I. , Dynes R. C.
Published: July 2002

We have developed a process to fabricate planar high-Tc Josephson junctions using nanolithography and a 200 keV ion implanter. Conduction occurs in the ab plane and is interface free. We can systematically tune devices to operate at temperatures between 1 K and the Tc of the undamaged superconducting material by varying the length of the weak link and by changing the amount of ion damage. All of the devices showed clear dc and ac Josephson effects. Measurement of R(T) and Ic(T) of the weak links revealed trends which were consistent with a proximity effect.
Terahertz NbN/AlN/NbN mixers with Al/SiO/NbN microstrip tuning circuits
Authors: Uzawa Yoshinori , Wang Zhen , Kawakami Akira
Published: July 2002

We have developed a low-noise quasioptical NbN/AlN/NbN superconductor-insulator-superconductor (SIS) mixer that operates at terahertz frequencies. The mixer uses a MgO hyperhemispherical lens with an antireflection cap, a single-crystal NbN log-periodic antenna, and two-junction tuning circuits which employ Al/SiO/NbN microstriplines. The NbN/AlN/NbN junction size was about 0.9 μm in diameter, and the current density was about 45 kA/cm2. The frequency dependence of the receiver noise temperature was investigated by using an optically pumped far-infrared laser and a backward-wave oscillator as a local oscillator at several frequencies from 670 to 1082 GHz. The experimental results showed that the center frequency was around 800 GHz, and the receiver noise temperature measured by the standard Y-factor method was 457 K (DSB) at 783 GHz including a 9-μm-thick Mylar beam splitter loss and other optical losses at the physical bath temperature of 4.2 K. This is the first SIS mixer based on NbN with low-noise performance (12hν/kB) above the gap frequency of Nb.
Enhancement of the quantum efficiency and stability of electroluminescence from porous silicon by anodic passivation
Authors: Gelloz B. , Nakagawa T. , Koshida N.
Published: July 2002

The use of anodic oxidation as a post-treatment of porous silicon has been investigated to enhance the external quantum efficiency of electroluminescence from a device based on a thin transparent indium tin oxide contact on porosified n+-type silicon. Enhancement in external quantum efficiency of three orders of magnitude has been obtained. We report here an external quantum efficiency of 0.21%. The treatment also greatly improves the stability of the device. Results can be explained by the fact that anodic oxidation considerably reduces leakage current flowing via nonconfined silicon.
Direct detection and imaging of low-energy electrons with delta-doped charge-coupled devices
Authors: Nikzad Shouleh , Yu Qiuming , Smith Aimée L. , Jones Todd J. , Tombrello T. A. , Elliott S. Tom
Published: July 2002

We report the use of delta-doped charge-coupled devices (CCDs) for direct detection of electrons in the 50–1500 eV energy range. We show that modification of the CCD back surface by molecular beam epitaxy can greatly improve sensitivity to low-energy electrons by introducing an atomically abrupt dopant profile to eliminate the dead layer. Using delta-doped CCDs, we have extended the energy threshold for detection of electrons by over an order of magnitude. We have also measured high gain in response to low-energy electrons using delta-doped CCDs. The effect of multiple electron hole pair production on the observed signals is discussed. Electrons have been directly imaged with a delta-doped CCD in the 250–750 eV range.
Graphitization of nanodiamond powder annealed in argon ambient
Authors: Chen Jian , Deng S. Z. , Chen Jun , Yu Z. X. , Xu N. S.
Published: July 2002

Nanodiamond powder was annealed at each of the following temperatures: 300, 600, 800, 1000, and 1150 °C, for an hour in flowing argon ambient. The variations of x-ray diffraction patterns and Raman spectra of the powder with different annealing temperatures were studied. While being annealed at temperatures higher than 800 °C, the powder can undergo a phase-transition process from cubic diamond to graphite. In addition, the size of nanodiamond crystallites decreased from ∼50 to ∼25 Å. The physical mechanism responsible for the variation in Raman spectra is discussed using a phonon-confinement model.