bluuebunny/crossref_metadata_2025 huggingface dataset:
Transmission electron microscopic study of the ordered structure in GaInP/GaAs epitaxially grown by metalorganic chemical vapor deposition
Authors: Morita E. , Ikeda M. , Kumagai O. , Kaneko K.
Published: July 2002

GaInP epitaxial crystals grown on (001) GaAs at 660–700 °C by metalorganic chemical vapor deposition are examined by transmission electron microscopy. The computer-processed image of the high-resolution electron micrograph clearly reveals a lamellate-ordered domain structure of two variants of {111} superlattices, which is also investigated using cross-section and plan-view dark field electron micrographs. The spikes of well-defined superspots in the diffraction pattern were found to originate from the shape of the domains. The investigation of GaInP grown with different Zn concentrations showed that the disordering occurs as a result of a decrease in the density rather than the size of the domain.
Electromigration behavior of aluminum films deposited on silicon by ionized cluster beam and other techniques
Authors: Hummel R. E. , Yamada I.
Published: July 2002

Electromigration experiments have been carried out on aluminum thin films which have been deposited on oxide-free (111) silicon by employing the ‘‘ionized cluster beam’’ technique as well as other related deposition methods. It has been found that the same high electromigration resistance and film structure is obtained with or without utilizing a nozzled crucible and with or without applying ionization and acceleration voltages during deposition. The conclusions are supported by electromigration lifetime measurements, scanning electron micrographs, optical micrographs, reflective high-energy electron diffraction, and x-ray diffraction.
Gallium desorption from GaAs and (Al,Ga)As during molecular beam epitaxy growth at high temperatures
Authors: Gibson E. M. , Foxon C. T. , Zhang J. , Joyce B. A.
Published: July 2002

Direct measurements of the desorption rate of gallium from GaAs and (Al,Ga)As during growth by molecular beam epitaxy at high temperatures have been made by modulated beam mass spectrometry. The activation energy for desorption is dependent upon the nature of the site from which the gallium is lost. From free gallium atoms not incorporated into the lattice, behavior similar to that encountered under equilibrium conditions for gallium over gallium or gallium over GaAs is observed. For gallium lost from the GaAs lattice the apparent activation energy is higher and is influenced by the arsenic flux reaching the surface.
Band offset transitivity at the InGaAs/InAlAs/InP(001) heterointerfaces
Authors: Hybertsen Mark S.
Published: July 2002

First principles calculations of the valence-band offsets at the lattice-matched In0.53Ga0.47As/ In0.52Al0.48As/InP(001) heterointerfaces, including interface strain, exhibit transitivity to within 0.01 eV. The theory is in good agreement with the experimental data and together they suggest the values ΔEv=0.35–0.41 eV for In0.53Ga0.47As/InP and 0.15–0.20 eV for In0.53Ga0.47As/In0.52Al0.48As. The theory gives ΔEv=0.25 eV for In0.52Al0.48As/InP, in general agreement with experiment for this less studied interface.
Quantum size microcrystals grown using organometallic vapor phase epitaxy
Authors: Hiruma K. , Katsuyama T. , Ogawa K. , Koguchi M. , Kakibayashi H. , Morgan G. P.
Published: July 2002

Needle-shaped quantum size microcrystals as thin as 10 nm have been selectively grown by employing reduced pressure organometallic vapor phase epitaxy using trimethylgallium and arsine as source materials. The microcrystals grown within a SiO2 window area have their growth axes along the [111] direction. Transmission electron diffraction analysis shows that the crystal structure of microcrystals is consistent with the zinc-blende structure of GaAs. The mechanism for growing the needle-shaped crystals is similar to a vapor-liquid-solid (VLS) equilibrium phase growth model. From photoluminescence measurements at 4.2 K, it is found that the microcrystals show a very distinct spectra for free exciton and neutral acceptor-bound exciton recombinations, meaning good crystal quality.
Method for the local incorporation of Er into LiNbO3 guided wave optic devices by Ti co-diffusion
Authors: Gill D. M. , Judy Aaron , McCaughan L. , Wright J. C.
Published: July 2002

Co-diffusion of Er with Ti into LiNbO3 produces more than an order of magnitude enhancement in Er diffusivity over that achieved by ion implanting and thermal diffusion. The enhancement is dependent on the amount of Ti present. Er doped channel waveguide fabrication is completely compatible with standard Ti:LiNbO3 technology. Fluorescence measurements from co-diffused and bulk grown Er doped LiNbO3 show that the co-diffused Er3+ is in the LiNbO3 phase.
Interfacial reactions and Schottky barriers of Pt and Pd on epitaxial Si1−xGex alloys
Authors: Liou H. K. , Wu X. , Gennser U. , Kesan V. P. , Iyer S. S. , Tu K. N. , Yang E. S.
Published: July 2002

The evolution of interfacial reactions during the deposition of Pt and Pd on epitaxial Si1−xGex alloys was studied using x-ray photoelectron spectroscopy (XPS) for metal coverage up to 10 Å. Auger electron depth profiling was performed on a thicker metal overlayer before and after in vacuo annealing to study the redistribution of composition in the reactions. We have found that Pt and Pd react mainly with Si to form silicides at 350 °C, leaving some Ge to segregate at the surface. These results were correlated with Schottky barrier height measurements. We found that the Schottky barrier heights of Pt/n-Si0.8Ge0.2 and Pd/n-Si0.8Ge0.2 are about the same, pinned at 0.68 eV, which is much smaller than those of n-Si. These barrier heights are quite stable up to 550 °C.
Doping profiles studied by scanning tunneling spectroscopy
Authors: Chiu Yi , Reed M. L. , Schlesinger T. E.
Published: July 2002

Tunneling spectra have been measured at various locations on uniformly doped, ion-implanted, and epitaxial silicon samples. We find that the I-V characteristics consistently vary with the variation of doping concentrations. Significant differences in the I-V curves are observed between n- and p-type samples. Combined with the high resolution of scanning tunneling microscopes (STM), this principle can be used to obtain two-dimensional doping profiles in submicron VLSI circuits.
Monte Carlo hydrodynamic simulation of neutral radical transport in low pressure remote plasma activated chemical vapor deposition
Authors: Hartig Michael J. , Kushner Mark J.
Published: July 2002

In electron cyclotron resonance plasma sources for semiconductor processing (1–10 s mTorr), the mean free paths of neutral radical species are commensurate with the dimensions of the reactor. To address these conditions, a hybrid hydrodynamic Monte Carlo simulation has been developed to model the transport of neutral excited state and radical species. The continuity and momentum equations are solved to obtain an average advective flow field. Monte Carlo techniques are then employed to model the trajectories of the neutral particles, while allowing for momentum transfer collisions with the background gas, and chemical reactions. Results are presented for Ar/SiH4 plasmas where the uniformity of the radical flux and hot atom effects are investigated.
Metalorganic chemical vapor deposition of TiN films for advanced metallization
Authors: Sandhu Gurtej S. , Meikle Scott G. , Doan Trung T.
Published: July 2002

Titanium nitride (TiN) films are used extensively in advanced metallization schemes for ultralarge scale integrated applications. In the present experiments, physical properties of thin TiN films deposited using low pressure chemical vapor deposition from tetrakis-dimethyl-amino titanium and ammonia have been investigated. Deposited films were characterized by resistivity, stoichiometry and etch rates. It was found that bulk resistivity correlated to wet etch rates with high resistivity films having higher wet etch rates. High bulk resistivity films were unstable in atmosphere and Auger analysis showed higher relative oxygen content. It is concluded that high resistivity films are low density and thereby susceptible to ex situ contamination. Optimized films had bulk resistivity of 250 μΩ cm and wet etch rates comparable to reactively sputtered TiN.
Noncontacting measurement of opaque thin films using a dual beam thermal wave probe
Authors: Suddendorf M. B. , Liu M. , Somekh M. G.
Published: July 2002

A dual beam thermal wave probe has been used to measure the thickness of opaque thin films in a noncontact, nondestructive manner. The method relies on the measurement of the differential phase of two interferometrically determined photodisplacement signals. The technique does not require calibration against standard samples and can be used to determine film thicknesses from a few tens of nanometers up to several micrometers. Alternatively, if the film thickness is known, thermal material properties like diffusivity or conductivity can be determined. The conditions under which the system is expected to give the most accurate results are analyzed.
Etching technique for transmission electron microscopy observation of nanostructure of visible luminescent porous silicon
Authors: Teschke O. , Goncalves M. C. , Galembeck F.
Published: July 2002

We present a special configuration for the electrochemical etching of silicon, in which thin samples suitable for direct transmission electron microscopy observation are produced. This technique allows the observation of images of an irregular matrix of pores and individual columnlike structures with a ∼15 Å cross-sectional diameter. These images show that the preferential etching directions are the projections of the {100} planes on the (111) plane for the etched <111≳-oriented silicon. The large pore (≳50 nm diam) axis orientation is independent of the preferential etching direction and is parallel to the etching current direction.
Scanning tunneling microscopy investigations of the Si(111) topography produced by etching in 40% NH4F: Observation of an optimum etch duration
Authors: Hsiao Gregor S. , Virtanen Jorma A. , Penner Reginald M.
Published: July 2002

The time evolution of the topography of an oxidized Si(111) surface immersed in an aqueous 40% NH4F etching solution is investigated ex situ by STM. The topography of a rough oxide layer of thickness ≊24 Å becomes smoother as this layer is thinned. An exposure of 75 s completely removes the surface oxide and a minimum obtainable roughness of ≊1.4 Å rms is observed ≊15 s, hence. With continued etching, two processes—etching of the silicon surface and gas evolution—operate in conjunction to produce pillars of silicon at locations on the Si(111) surface which are shielded from etching by adsorbed gas bubbles. Gas evolution and roughening are suppressed by the addition of the reductant NaCNBH3 (0.50%) to the etching solution.
Positron trap sites in the native oxide film grown on a hydrogen-terminated silicon surface
Authors: Fujinami M. , Chilton N. B.
Published: July 2002

Positron behavior in thin native oxide layers grown on an initially hydrogen-terminated Si(100) surface was investigated and correlated with the chemical structure of the layers determined using Fourier-transform infrared absorption attenuated total reflection spectroscopy, and x-ray photoelectron spectroscopy. Hydrogen termination of the Si surface by 4 vol % HF treatment gave rise to a narrower Doppler-broadened positron-electron annihilation line than that of bulk Si. By a process of oxidation in pure water very thin (up to 7.8 Å) layers were grown on the H-terminated Si. The Doppler broadening of annihilations from the Si surface was seen to increase monotonically with thickness away from the value seen for amorphous bulk SiO2. The positronium fraction was monitored throughout but was found to be independent of the oxidation duration. It was found that the chemical structure of the surface, in particular the oxidized Si-OH bond, was correlated with the positron annihilation mode and to the level of observed Doppler broadening.
Characterization of a tunable thin film microwave YBa2Cu3O7−x/SrTiO3 coplanar capacitor
Authors: Galt David , Price John C. , Beall James A. , Ono Ronald H.
Published: July 2002

We have fabricated and characterized electrically tunable high temperature superconductor coplanar microstrip resonators incorporating tunable SrTiO3 ferroelectric thin films. The low frequency capacitance of the SrTiO3 capacitor is measured directly. High frequency capacitance and loss information are extracted from the observed resonances and compared with the low frequency data. Hysteresis loops display an onset of ferroelectricity at 160 K. The spontaneous charge and coercive voltage (at 10 kHz) as a function of temperature are extracted from these loops.
Mo0.5Si0.5/Si multilayer soft x-ray mirrors, high thermal stability, and normal incidence reflectivity
Authors: Stock H.-J. , Kleineberg U. , Kloidt A. , Schmiedeskamp B. , Heinzmann Ü. , Krumrey M. , Müller P. , Scholze F.
Published: July 2002

Multilayer soft x-ray mirrors with an absorber consisting of the mixture Mo0.5Si0.5 have been fabricated by electron-beam evaporation in UHV. This has been done to get soft x-ray normal incidence mirrors for 80–100 eV photon energy with enhanced thermal stability and still high reflectivity. The thermal stability is studied by baking them at temperatures between 600 and 950 °C. The results were compared with multilayers of pure Mo and Si, which were also fabricated by electron-beam evaporation. After each baking step the x-ray mirrors are characterized by small angle CuKα x-ray diffraction. The reflectivity of the first-order Bragg peak is nearly constant up to 20 min baking at 900 °C. Further we present the normal incidence soft x-ray reflectivity for wavelengths between 12 and 18 nm of a Mo0.5Si0.5/Si mirror with 12 double layers (N=12) and of a Mo0.5Si0.5/Si mirror as deposited with 33 double layers (N=33). With the latter a reflectivity of 46% is achieved.
Ferroelectric/superconductor PbZr0.52Ti0.48O3/Y1Ba2Cu3O7−x/LaAlO3 heterostructure prepared by Nd:YAG pulsed laser deposition
Authors: Björmander C. , Grishin A. M. , Moon B. M. , Lee J. , Rao K. V.
Published: July 2002

Ferroelectric/superconductor PbZr0.52Ti0.48O3/Y1Ba2 Cu3O7−x heterostructures have been grown on single-crystal LaAlO3 in a Nd:YAG pulsed laser deposition system. The cuprate superconductor is used as the metallic electrode for polarizing the lead zirconate titanate (PZT) layer. X-ray diffraction and rocking curve data evidence almost epitaxial growth of both the PZT (≊4500 Å) and the (YBCO) (≊2500 Å) layers on LaAlO3 substrates. Ferroelectric measurements yield remnant polarization values (at 177 kV/cm) of 29 μC/cm2, and coercive fields in the range of 70–85 kV/cm. The electrical resistivity of the PZT layer is determined to be 5×108 Ω cm. The electrical resistivity data for the YBCO underlayer even in the presence of the PZT overlayer yields Tc=89.5 K with a transition width of δT=1 K. In summary, excellent characteristics of coexisting superconducting and ferroelectric properties have been achieved in laser deposited PZT/YBCO/LaAlO3 heterostructures. As far as we know this is the first time such a result has been obtained by using a Nd:YAG pulsed laser deposition technique.
Study and analysis of submicron-period grating formation on polymers ablated using a KrF laser irradiated phase mask
Authors: Dyer P. E. , Farley R. J. , Giedl R. , Ragdale C. , Reid D.
Published: July 2002

Submicron-period gratings have been formed in polyethylene terephthalate and polyimide films using a KrF laser irradiated, zero suppressed, phase mask with a period d=533 nm. The imprinted grating has a dominant period of d rather than d/2, a result which is shown to be due to recording the pattern by a threshold surface ablation process.
Formation of interfacial phases between silica and undoped or antimony-doped silicon melts
Authors: Huang Xinming , Terashima Kazutaka , Anzai Yutaka , Tokizaki Eiji , Sasaki Hitoshi , Kimura Shigeyuki
Published: July 2002

Interfacial phase formation during dissolution of silica in undoped or Sb-doped Si melts were studied using electron probe microanalysis. Results showed that reaction between silica and the Si melt depended on the Sb concentration in the Si melt. A foil-shaped interfacial phase with a composition about SiO1.8 appeared between the Si melt and the wall of the silica ampoule when the Sb concentration was less than 0.5 at. %. However, the interfacial phase changed both in shape and composition when the Sb concentration was higher. The shape of the interfacial phase became dendritic and the composition was SiO2 when the Sb concentration was in the range from 0.5 to 2.0 at. %. The interfacial phase disappeared when the Sb concentration was higher than 2.0 at. %.
Strong Tb3+ emission of TbAlO3 at room temperature
Authors: Sekita Masami , Miyazawa Yasuto , Morita Shoji , Sekiwa Hideyuki , Sato Yoichiro
Published: July 2002

Optical spectra are measured for transparent and colorless TbAlO3 single crystals grown by the Czochralski method in a reducing atmosphere, although those grown in an inert atmosphere show blackbody color due to broadband absorption of Tb4+ ions. This is a report on strong Tb3+ emission spectrum at room temperature of aluminates and relevant crystals which contain the Tb ion as a stoichiometric agent. All fine structures in absorption and emission spectra can be assigned to the intra-4f transitions of Tb3+ ions. Similar concentration quenching is observed in TbxGd1−xAlO3 system to that in the Nd:YAG crystals; however, the quenching is found to be very small compared with that of the Nd:YAG. An order estimate of the induced emission cross section for the strongest emission line is calculated to be about 6×10−21 cm2.
Empirical relationship between the low-frequency noise spectral density and the transconductance of silicon-on-insulator n-channel metal-oxide-semiconductor transistors
Authors: Simoen E. , Claeys C.
Published: July 2002

In this letter, the relationship between the input-referred low-frequency noise spectral density SVG and the transconductance gm of a large number of similar silicon-on-insulator n-channel metal-oxide-semiconductor transistors is investigated. As will be shown, a large, two orders of magnitude dispersion is observed in the noise, which corresponds with a factor two variation in gm. It is demonstrated that the average SVG depends exponentially on the corresponding transconductance. This holds both for linear operation—in strong and weak inversion—and for saturation. The practical implications of these findings are discussed.
Improved corrosion resistance of cation substituted YBa2Cu3O7−δ
Authors: Zhou Ji-Ping , Savoy Steven M. , Lo Rung-Kuang , Zhao Jianai , Arendt Mark , Zhu Y. T. , Manthiram A. , McDevitt John T.
Published: July 2002

A cosubstitution of Ca2+ for Y3+and La3+ for Ba2+ in YBa2Cu3O7−δ is found to improve the corrosion resistance of this high- Tc superconductor. The reactivity characteristics of bulk and thin film samples of Y1−zCazBa2−yLayCu3O7−δ indicate that the corrosion resistance in water environments increases with increasing degree of cation substitution up to z=y=0.4. The composition of Y0.6Ca0.4Ba1.6La0.4Cu3O6.96 with a Tc of 80 K is found to be at least 100 times more stable than YBa2Cu3O6.94. Possible contributing factors that could be responsible for the marked improvement in the corrosion resistance of this high-Tc phase are discussed.
Observation by scanning tunneling microscopy of a hexagonal Au(111) surface reconstruction induced by oxygen
Authors: Huang L. , Chevrier J. , Zeppenfeld P. , Cosma G.
Published: July 2002

In this letter the observation by scanning tunneling microscopy of a Au(111) surface reconstruction induced by prolonged annealing of gold films in oxygen (pO2=1 bar) at high temperature (T=800 °C) is reported. At the atomic scale, the surface is characterized by a (√3×√3)R30° surface structure. In addition, the surface exhibits a long-range ordered hexagonal superstructure with a periodicity of 80 Å and a corrugation of about 0.5 Å. Convincing evidence is presented that this surface morphology is induced by chemisorption of atomic oxgyen at the Au(111) surface.
Improved timing resolution using small side-on photomultipliers in single photon counting
Authors: Canonica Silvio , Forrer Jörg , Wild Urs P.
Published: July 2002

The time-resolution capabilities of two 28-mm-diam side-on photomultiplier tubes, Hamamatsu R928 and RCA 931-A, were studied by point illumination of the photocathode surface with the attenuated beam of a synchronously pumped dye laser (10-ps pulse width). Using the time-correlated single photon counting technique, an apparatus response of 112 ps FWHM was obtained. Contour maps giving the time shift and the width of the response were constructed as a function of the point of illumination of the photocathode surface. These data permit selection of the optimized photocathode region to be illuminated during fluorescence decay measurements.
X-ray and radioactive measurements in ICF research at ILE Osaka (invited)
Authors: Nishimura H. , Niki H. , Miyanaga N. , Okada K. , Azechi H. , Yabe T. , Tsuji R. , Ido S. , Yamanaka M. , Mochizuki T. , Nishihara K. , Yamanaka T. , Yamanaka C.
Published: July 2002

The experimental basis and instrumentation for the Gekko XII laser fusion program developed at the Institute of Laser Engineering (ILE), Osaka University are presented. Many diagnostics are in use to evaluate the key parameters of target implosion in an extremely dense, short period region. In this paper, we describe the present status and future planning of these diagnostics, such as x-ray, radioactive, and reaction particle measurement, because of their importance for fuel ρR determination.
Directional sensitivity of unplated normal-wire probes
Authors: Samet M. , Einav S.
Published: July 2002

This paper describes an experimental study of the response to yaw of normal-wire probes oriented at various roll angles with respect to the yaw plane. The results obtained show that unplated normal wires are most sensitive to yaw when the plane formed by the wire element and the prongs is aligned with the yaw plane. When the wire-prongs plane is normal to the yaw plane, the sensitivity of these probes is reduced by 30 to 33%. When the wire-prongs plane is inclined at 45° to the yaw plane, the probe response is almost insensitive to yaw within a large range of flow angles. The current experimental results are compared qualitatively with the ‘‘effective cooling velocity’’ model. It is shown that this model is too oversimplified to be correct; the tangential and the binormal cooling parameters are Re number and yaw dependent and, under certain flow conditions, the tangential cooling parameter k2 may even attain negative values. It is concluded, therefore, that much better signal-interpretation expressions should be sought.
Tokamak Fusion Test Reactor prototype x-ray pulse-height analyzer diagnostic
Authors: Hill K. W. , Bitter M. , Diesso M. , Dudek L. , von Goeler S. , Hayes S. , Johnson L. C. , Kiraly J. , Moshey E. , Renda G. , Sesnic S. , Sauthoff N. R. , Tenney F. , Young K. M.
Published: July 2002

The x-ray pulse-height analysis (PHA) diagnostic uses a liquid-nitrogen cooled array of 5 Si(Li) and one HpGe detectors to do time-resolved (5–100 ms) x-ray spectroscopy of the central horizontal chord of the Tokamak Fusion Test Reactor (TFTR) plasmas in the 1–50-keV range. Central electron temperature Te and concentration of medium and low-Z impurities are derived from the spectra. Remotely selectable absorber-foil arrays provide selection of the energy range. Fixed and movable aperture arrays allow approximate equalization of count rates in different energy bands and extend dynamic range. Amplifier pulse shapes are approximately triangular. Main amplifier peaking time is 4 μs yielding 230-eV FWHM at 5.9 keV. Pileup inspection times are selectable at 0.13, 0.4, or 0.9 μs. Throughput is up to 42 kHz. The PHA has been used to study temperature and impurities over a wide range of TFTR operational parameters. Dramatic variations in metal impurities with density, plasma current, and major radius have been observed.
Fast beams apparatus for the study of photodissociation processes
Authors: Gardner L. D. , Graff M. M. , Kohl J. L.
Published: July 2002

An apparatus is described for studying the photodissociation of neutral free radicals and positive molecular ions with a fast beam technique. Particular attention is given to studies of diatomics whose constituent atoms have very different masses and to photodissociation of polyatomic systems. Novel features of this design include fast neutral beam generation by photodetachment of negative ions, beam energies sufficiently high to detect neutral products, and a beam filter for reducing noise from background processes. A position-sensitive detector provides the data required to determine separation energies and angular distributions for dissociation studies where only one fragment is detectable.
Solid deuterium fiber extruder
Authors: Sethian J. D. , Gerber K. A. , Sy M. O.
Published: July 2002

A simple fiber extruder has been developed to produce small diameter filaments of frozen deuterium. The extruder is based on a commercially available liquid-helium-cooled cryostat, and only the actual deuterium extruder mechanism must be fabricated. The extruder features interchangeable nozzles and fibers ranging in diameter from 40 to 300 μ have been made. All fibers are over 10 cm in length and their physical dimensions remain unchanged for at least 4 min. The neutral gas density outside the fiber is on the order of 1013 and drops off with the inverse of the radius. These fibers are used to provide the plasma for the NRL dense z-pinch experiment whose objective is to study the fusion application of small, dense plasmas.
Precision of lock-in amplifiers as a function of signal-to-noise ratio
Authors: Gualtieri D. M.
Published: July 2002

The increase in output measurement error of lock-in amplifiers with decreasing input signal-to-noise ratio, which has been shown to be linear over several orders of magnitude [G. T. Gillies and S. W. Allison, Rev. Sci. Instrum. 57, 268 (1986)], is a consequence of the function of a lock-in amplifier as a bandwidth reduction filter.
Molecular luminescence cryothermometer
Authors: Petrin Michael , Maki August H.
Published: July 2002

A thermometer is described which employs luminescence emitting molecular sensors to measure temperatures in the cryogenic range below 20 K. Upon photoexcitation, the molecular sensor emits luminescence from an excited spin state having two optically resolved sublevels. The sublevels are in thermal equilibrium due to rapid spin-lattice relaxation and thus act as a two-level radiator whose relative luminescence intensities vary with temperature according to the Boltzmann population equation. A device is described which employs photon-counting techniques to measure the intensity ratio of the luminescence originating from these two levels and then uses this ratio to calculate the temperature of the sensor and thereby of its surroundings. The device employs remote fiber-optic sensing and is independent of fluctuations in the excitation source or in the detection system efficiency since it monitors the intensity ratio of two emission bands. Since this temperature measurement technique is based on photophysical and thermodynamic properties of a well-defined system, the molecular sensors employed need not be individually calibrated, only the response curve of the device needs to be determined.
New thick-film strain gauge
Authors: Abe Osamu , Taketa Yoshiaki , Haradome Miyoshi , Inokuma Toshio
Published: July 2002

Thick-film strain gauges having strain characteristics with small temperature dependency have been developed. Their gauge factor is more than ten times higher than that of a thin-film strain gauge and nearly half the value of a semiconductor gauge. This strain gauge is a thick film composed of 15 wt. % WO3⋅15 wt. % RuO2⋅70 wt. % glass (weight percent ratio). Its gauge factor is 40 to 55, its temperature coefficient of resistance is 0 to −200 ppm/°C, and its temperature coefficient of gauge factor is about −400 ppm/°C. The change of gauge factor in a repeat test after a strain had been applied to the gauge was smaller than 1%. The gauge was also very stable.
New ultrahigh-vacuum cleaver for brittle materials
Authors: Carr Roger
Published: July 2002

In materials research it is often necessary to cleave brittle materials, such as semiconductors, in order to perform experiments on clean surfaces. This note presents the design of an ultrahigh-vacuum cleaving tool which can yield crystal surfaces of very high quality.
Resolution of time-of-flight mass spectrometers evaluated for secondary neutral mass spectrometry
Authors: Kato Makoto , Mogami Akinori , Naito Motohiro , Ichimura Shingo , Shimizu Hazime
Published: July 2002

Mass resolution of a time-of-flight mass spectrometer with a two-stage electrostatic reflector is calculated for secondary neutral mass spectrometry. The instrument parameters are optimized for energy and space focusing: correcting the flight time difference due to the energy width ΔE of sputtered particles and the spatial width Δs of an ionizing laser beam. The effect of Δs can be compensated by applying an acceleration field to the ionizing region, and the maximum resolution becomes about 1000 for ΔE=10 eV and Δs=1.0 mm.
MINGL database system for TFTR
Authors: Wieland R. M. , Murphy J. A. , Goldston R. J. , Zarnstorff M. C.
Published: July 2002

The MINGL database system is an integrated set of tools which provides a means of collecting and managing diagnostic data and transport code results from TFTR. An interactive menu-driven format allows users to collect scalar and profile data from various data sources into shareable INGRES databases. LOCUS and INGRES/QUEL/SQL interfaces make it easy to browse, select, compare, and display the data in one of several formats. Utilities exist for managing the individual data sets and restricting their accessibility, for indexing the tables by author, and for maintaining a table of contents for an entire database. The modularity of the system allows automated database-server applications for between-shot analysis and display.
The phase contrast method as an imaging diagnostic for plasma density fluctuations (invited)
Authors: Weisen H.
Published: July 2002

An imaging diagnostic for the observation of plasma density fluctuations is presented. It is based on the phase contrast method, and is used on the TCA tokamak to investigate fluctuations associated with plasma turbulence and driven waves in radio frequency heating experiments. The diagnostic uses a 23-cm-wide CO2 laser beam transmitted through the plasma, and produces an image of the plasma where the small phase shifts (‖φ‖∼10−5 to 10−3) due to refractive perturbations are revealed as corresponding intensity variations. A wide range of fluctuation wavelengths between 0.2 and about 20 cm is accessible to observation, with a sensitivity better than 10−5 rad for a 1-MHz bandwidth.
Density profile reconstructions from 2-D interferometric data on Microtor using novel tomographic analysis techniques
Authors: Howard J. , Doyle E. J. , Reibeiz G. , Savage R. L. , Peebles W. A. , Luhmann N. C.
Published: July 2002

Plasma tomographic reconstructions are subject to aliasing ambiguity as a result of the limited angular and radial sampling rates for the line-integrated data. The two-view interferometer installed on the Microtor tokamak yields unambiguous information, specifically, a collection of six low-order alias-free moments of the 2-D electron density distribution. The unspoiled coefficients can be related to physically intuitive quantities and so yield information pertinent to the equilibrium and dynamical behavior of the plasma column. Alternatively, they can be used as constraints for a maximum entropy reconstruction of the source to produce an image free of aliasing artifacts.
Fluorescence referencing for fiber-optic thermometers using visible wavelengths
Authors: Grattan K. T. V. , Selli R. K. , Palmer A. W.
Published: July 2002

A fiber-optic temperature sensor, operating on the principle of differential absorption effects with temperature, has been constructed using visible wavelength sensing and a ruby fluorescence-based internally generated reference scheme. Results of an investigation of the system and a comparison with previous work by the authors on a related system are reported.
Measurement of the absolute spectral response of an inverse photoemission detector
Authors: Avci Recep , Cai Qing , Lapeyre Gerald J.
Published: July 2002

The absolute quantum yield of an inverse photoemission detector is reported. The detector consists of a 650-Å KBr photoemission film on the mouth of a channeltron with either a CaF2 or a SrF2 window for a low-pass cutoff filter. The spectral response for the CaF2 window peaks at 9.8 eV with a FWHM of 1.6 eV and a maximum yield of 0.18 pulse/photon, while for the SrF2 window the peak is at 9.3 eV with a FWHM of 1.4 eV and a maximal yield of 0.06 pulse/photon. Performance of the detector was tested by measuring the inverse photoemission spectra from a W(001)-(1×1) surface.
Small-signal recovery and analysis with a novel, phase-locked digital filter
Authors: Gillies G. T. , Scudiere M. B. , Allison S. W.
Published: July 2002

A new technique for recovering small signals from large background disturbances is described. The technique combines the narrow-band sensitivity of synchronous detection via lock-in amplifier with the waveform-recovery capabilities of boxcar averaging. However, unlike a boxcar averager, this technique operates in real time. A digital filter-based realization of this technique phase-locks to a reference signal at frequencies up to 500 Hz. It samples input at a rate of 256 kHz with 12-bit precision, recovers the complete synchronous and asynchronous components of the input signal, and reconstructs them with a precision of 12 bits. This allows for either the extraction of or deletion from the original signal of phase-lockable waveforms. We describe here the design and performance of this instrument and present the results of its use in a signal-recovery problem made difficult by the presence of power-line noise.
Thermal barrier potential and two-dimensional space-potential measurements with gold neutral-beam probes in GAMMA 10
Authors: Ishii K. , Kotoku M. , Segawa T. , Katanuma I. , Mase A. , Miyoshi S.
Published: July 2002

Gold neutral-beam probes are used for the space-potential measurements in the barrier and in the central cells of the GAMMA 10 tandem mirror. The thermal barrier potential depth is directly observed by simultaneous measurements of the on-axis space potentials at both locations. Two-dimensional space potentials in the barrier region are measured by sweeping the probing beams with different beam energies.
Characterization of reconstructed SiC(100) surfaces using soft-x-ray photoemission spectroscopy
Authors: Bermudez V. M. , Long J. P.
Published: July 2002

The surface quality of βSiC films grown on Si(100) by chemical vapor deposition has been assessed through synchrotron photoemission measurements of the valence band and of the linewidths and surface-induced structure in Si 2p core-level spectra. For these n-type samples, band bending is small on the c(2×2) and (3×2) surfaces but larger on the (2×1), which also exhibits an increased Si 2p linewidth and evidence of elemental Si patches. All three reconstructions show emission from gap states extending from the valence band maximum to the Fermi level.
Design and construction of beamline-NE1 for circularly polarized synchrotron radiation from the 6-GeV TRISTAN Accumulation Ring
Authors: Kawata H. , Miyahara T. , Yamamoto S. , Shioya T. , Kitamura H. , Sato S. , Asaoka S. , Kanaya N. , Iida A. , Mikuni A. , Sato M. , Iwazumi T. , Kitajima Y. , Ando M.
Published: July 2002

The beamline for the circularly polarized synchrotron radiation at the 6-GeV Accumulation Ring for the TRISTAN project is now under construction. The insertion device of this beamline was designed to produce circularly polarized x rays at the photon energy range of 200 eV∼100 keV. The beamline is divided into the following three branches: (1) High resolution Compton scattering and magnetic Compton scattering experiments; (2) multipurpose experiments such as magnetic x-ray scattering and magnetic x-ray absorption; and (3) completely circularly polarized soft x rays.
Synchrotron resource of the Howard Hughes Medical Institute
Authors: Staudenmann J.-L. , Hendrickson W. A. , Abramowitz R.
Published: July 2002

The Synchrotron Resource of the Howard Hughes Medical Institute will be dedicated to structural analyses of biological macromolecules, primarily through crystallography. This facility is under construction at the X4 port of the National Synchrotron Light Source at Brookhaven National Laboratory, and it will comprise three beamlines. The first line to be built has been devised to apply the multiwavelength anomalous diffraction method which provides direct estimates for the phases of reflections. The second line will be devoted to rapid and essentially routine diffraction measurements, mainly through the rotation method. These two experimental stations are contained within refrigerated radiation enclosures that will maintain clean environments, narrowly defined constant temperatures, and protection against biohazard at biosafety level BL-2. At the same time as the second line will be developed, the swath center is planned to first serve as a monitor of the white x-ray beam vertical stability. This project will be done in collaboration with accelerator physicists of the National Synchrotron Light Source. Later, this third line will be equipped for Laue experiments to study, for instance, dynamical processes in proteins.
Inspection of plasma-sprayed coatings using fast infrared scanning technique
Authors: Hartikainen J.
Published: July 2002

Fast infrared scanning technique (FIRST), in which a laser beam focused to a line is used for heating and the temperature rise is detected with an IR scanner, is applied to the nondestructive inspection of plasma-sprayed coatings. The surface temperature profiles are computed numerically for faultless and defective coatings, and the functionality of the technique is demonstrated using a sample with artificial defects.
High-resolution pulsed dye laser calibration in the 500–350 nm region using iodine atlas reference lines
Authors: Clouthier Dennis J. , Karolczak Jerry
Published: July 2002

A simple, inexpensive method for precisely calibrating high resolution, pulsed dye lasers in the 500–340-nm wavelength region has been devised. The residual portion of the laser beam exiting from an experiment is Raman shifted to longer wavelnegths in a high-pressure hydrogen cell. The Stokes shifted output is used to excite laser induced fluorescence (LIF) signals in I2 vapor, which, in turn, are used to accurately calibrate the wavelength of the Raman shifted beam. The constant Raman shift, which can be precisely calculated, is then added to give the original laser wavelength. The method is readily adapted to computerized data acquisition and gives results of comparable accuracy to those of I2 LIF calibrations in the conventional 850–500 nm region.
Cavity design for a cosmic axion detector
Authors: Hagmann C. , Sikivie P. , Sullivan N. , Tanner D. B. , Cho S.-I.
Published: July 2002

We discuss cavity tuning schemes for cosmic axion searches and strategies to extend such searches to high frequency without sacrifice in volume and hence signal-to-noise. Particular regard is given to the difficulties that arise from the tendency of the cavity mode to localize in a small region of the cavity and from the fact that the modes may become relatively dense in frequency space. Computer simulations of cavity performance have been carried out in order to optimize the cosmic axion search rate for a given magnet size and field.
Novel scanning interferometer for two-dimensional plasma density measurements
Authors: Howard John
Published: July 2002

A novel multichannel scanning interferometer designed for tomographically inferring contours of electron density in magnetically confined plasmas is described. The scanning element is a multisectored blazed rotating grating. The diffracted beam emerges at a different angle from each sector, giving rise to a fan array of discrete beams for each rotation of the grating. Signals from the probing chords are multiplexed in time enabling the use of a single detecting element for the extraction of many channels of line-integrated density information. An air-turbine-driven grating wheel assembly has been fabricated and initial tests performed. The proposed interferometer is to operate at 337 μm and will be installed on the H-1 helical axis stellarator currently under construction at the Australian National University.
Electron-suppression experiments in a small multicusp H− source
Authors: Leung K. N. , Hauck C. A. , Kunkel W. B. , Walther S. R.
Published: July 2002

Several techniques for suppressing the electrons before they form part of the extracted beam have been studied in a small multicusp H− source. It is found that some schemes reduce both the electron and the H− output currents. Other approaches, such as the installation of a collar at the extraction aperture, the addition of xenon or cesium to the hydrogen discharge, or the reduction of the source plasma potential, not only can reduce the electron current substantially, but bring about an enhancement in the extracted H− current.
A sealess pump to circulate supercritical fluids in high pressure systems
Authors: Pleass W. , Prescott E. H. A. , Steer D. , Steytler D.
Published: July 2002

Electro-magnetically operated devices have proved useful in providing remote operation in sealed systems. A pump has been developed to assist the development of supercritical CO2 as a solvent for the extraction of food materials. This can circulate supercritical fluids within a 316 stainless-steel tube capable of withstanding pressures up to 100 MPa.
Method for fast sine-wave calibration of hot-wire frequency response
Authors: Walker D. A. , Walker M. D.
Published: July 2002

Direct measurement of the transfer function of hot-wire anemometers is needed whenever any turbulence frequencies approach the hot-wire frequency response. In particular, in high-speed applications it is not possible to obtain hot-wire frequency response sufficient to capture all of the turbulent kinetic energy. With knowledge of the hot-wire response, either an estimate of the turbulent integral scale or an approximation of the high-frequency part of the turbulent spectrum may be sufficient to correct measurements by post-detection frequency compensation. Described in this article are simple electronic circuits and a technique for obtaining sine-wave test frequency response of a hot-wire anemometer in a very short time without prohibitively high sampling rates.
Optical power monitor using a thin-film pyroelectric bimorph
Authors: Peralta S. B. , Ghandi K. , Mandelis A.
Published: July 2002

A novel pyroelectric detector, based on a bilayer laminate of pyroelectric thin films, is described. A theoretical analysis shows that this detector element, which is called a pyroelectric bimorph, has the potential of having a higher sensitivity than an equivalent single-element detector. Verification of this result was found by characterizing three bimorph detectors based on polyvinylidene fluoride (PVDF). The specific detectivity for one particular bimorph was measured to be 6.6×108 cm Hz1/2/W, at a modulation frequency of 1 Hz, approximately twice the reported value for a single-element pyroelectric polymer film. We discuss operating characteristics for the three pyroelectric bimorph elements and evaluate their use in optical power monitoring.
Magnetic resonance spectrometer with a dc SQUID detector
Authors: Connor C. , Chang J. , Pines A.
Published: July 2002

We describe a dc superconducting quantum interference device (SQUID) based magnetic resonance spectrometer particularly suited to measurements in the frequency range of 100 kHz to several megahertz. Results are presented for nuclear quadrupole resonance (NQR) of boron-11 in boron nitride at 4.2 K, yielding ωQ =1467±2 kHz. We also present a direct measurement of the methyl group tunneling frequency, ωt =210±10 kHz, of propionic acid in low field, at 4.2 K.
A method for measuring the specific heat of small samples
Authors: Xu Jing-chun , Watson C. H. , Goodrich R. G.
Published: July 2002

A technique for measuring the specific heat of small samples over a wide temperature range is described. The method uses a sequence of increasing and decreasing power levels applied to a heater thermally attached to a sample and thermometer with the entire assembly connected to a heat reservoir through a weak thermal link. By recording the temperature both on the heating and cooling portions of the sequence, the heat loss to the surroundings automatically can be eliminated from the calculation of the specific heat. The measuring system and data analysis technique are described. Example data of the specific heat change at the superconducting transition of 34 mg of In are given.
Proposal for measuring magnetic fluctuations in tokamaks by Thomson scattering
Authors: Haas F. A. , Evans D. E.
Published: July 2002

Thomson scattering is proposed for the direct measurement of magnetic field fluctuations in a tokamak. The analysis is based on the electron fluid equations. The ordering λ≪λturb≪a, where λ and λturb are the incident and turbulence wavelengths, respectively, and a is the torus minor radius, is suggested by spectral information from observations on the TEXT tokamak, as well as general theoretical arguments. With this ordering, temperature effects are unimportant and an expression is derived for probe radiation-induced plasma polarization that depends upon density and magnetic fluctuations only. By choosing the incident probe beam to have its plane of polarization parallel to the local mean magnetic field B0, and observing the scattered power in the plane of polarization perpendicular to B0, it is shown that contributions from density fluctuations are automatically excluded. Faraday rotation is shown to have negligible influence on the scattered signal, which is accordingly determined by magnetic field fluctuations alone.
An experimental technique for measurement of emission cross sections of excited state species in ion–molecule reactions
Authors: Mahmood Mohammad F.
Published: July 2002

A novel technique has been described in the present studies for the measurement of emission cross sections of excited state species formed in ion–molecule reactions and has been applied to the case of collisions of N+/Ar+ ions with HgI2 molecules. Emission spectra of HgI radical due to (B–X) transition from highly excited levels to lower levels have been observed and identified. Using the integrated intensity of the most intense band of the HgI (B2Σ+, v′=0−X 2Σ+, v″=22) transition at 445 nm, emission cross sections were measured in the kinetic energy range of 100–1000 eV (laboratory frame).
Spatial resolution of FIR scattering measurements on TEXT
Authors: Brower D. L. , Yu C. X. , Zhao S. J. , Peebles W. A. , Luhmann N. C. , Yang X. Z. , Schoch P. M. , Hickok R. L.
Published: July 2002

A multichannel, heterodyne, far-infrared laser scattering system is employed on TEXT to determine the spectral and spatial properties of electron density fluctuations. The spatial resolution of this system is demonstrated by utilizing a perturbation to the plasma potential profile induced by an applied resonant field. The perturbation changes the sign of the radial electric field over a certain region of the plasma. Shifts in the density fluctuation frequency spectra can be associated with changes in the radial electric field allowing one to unambiguously resolve fluctuations in the plasma interior and edge.