bluuebunny/crossref_metadata_2025 huggingface dataset:
The experimental research of EBIS ‘‘KRION-C’’ for LHE accelerating facility in Dubna
Authors: Ovsyannikov V. P. , Alfeev V. S. , Drobin V. M. , Kovalenko A. D. , Romanov Yu. I.
Published: July 2002

The design of ‘‘KRION-C’’ with an energy of up to 80 keV and preliminary results on the ionization of sulfur and argon ions are presented. The cryogenic electron beam ionizer ‘‘KRION-C’’ was used as an ion source for the first run with sulfur relativistic nuclei at the accelerating facility of the Laboratory of High Energies (LHE) in Dubna.
Impact of supplemental implantation of oxygen on defect centers in the separation by implantation of oxygen structure
Authors: Vanheusden K. , Stesmans A.
Published: July 2002

The influence of supplemental O+ implantation on standard separation-by-implantation of oxygen (SIMOX) structures in terms of inherent defects has been analyzed by electron spin resonance. The monitored defects include the Eγ′ and Eδ′ variants of the oxygen-deficiency centers in the buried oxide layer (BOX), and the likely O-related, shallow donor (UL1) centers in buried interfacial Si layers. E′ generation sensitivity depth profiles were mapped using etch back in combination with E′ generation by exposure to a dc Ar glow discharge. A major finding is that supplemental O implantation significantly reduces the E′ generation sensitivity (precursor sites) quite uniformly all over the BOX layer. The reduction, though, is about two times greater for Eδ′ as compared to Eγ′. The UL1 centers, by contrast, are seen to increase by up to a factor 6. Apparently these defects, inherent to the SIMOX formation process, are insufficiently removed by the postsupplemental O+ implantation anneal performed at 1100 °C.
Enhanced Zn diffusion in GaAs pnpn structures: Growth versus annealing
Authors: Chen C. Y. , Cohen R. M. , Simons D. S. , Chi P. H.
Published: July 2002

Zn diffusivity, DZn in heavily doped pnpn GaAs structures has been measured after growth and annealing. During growth at 650 °C, DZn∼10−12 cm2/s in the buried p-type layer is found to be ≳104×DZn in the top p-type layer. During annealing at 800 °C, DZn≊5×10−14 cm2/s in the buried layer remains orders of magnitude larger than DZn in the top layer. The measurements provide clear experimental evidence that (1) a large flux of Ga interstitials, IGa, is injected from the surface during the growth of n-type layers, (2) the IGa are trapped in the buried p-type layer by the electric field of the pn junctions, and are thus positively charged, (3) the resulting large concentration of IGa in the buried layer accounts for the enhanced DZn via a kick-out mechanism, and (4) the mobile Zn interstitial is positively charged.
Construction of a high-resolution electron energy loss spectrometer
Authors: Nagao Tadaaki , Iizuka Yoshitaka , Umeuchi Makoto , Shimazaki Teruhiko , Nakajima Michio , Oshima Chuhei
Published: July 2002

A new version of a high-resolution electron energy loss spectrometer has been constructed. Major modifications are the enlargement of the analyzer, gold coating of all the electrode surfaces facing the electron beam, and the reduction of magnetic fields. A high detector current of 4 pA has been obtained together with the narrow energy half width of 1.2 meV (FWHM) in the straight-through mode.
A sensitive low-power homodyne reflectometer for impedance measurements at 0.25–1.0 GHz
Authors: Pieper John B. , Price John C.
Published: July 2002

We describe a single-sideband homodyne reflectometer for sensitive impedance measurements in the 1 GHz range on electronic devices at liquid-helium temperatures and below. At 50 pW measurement power, the instrument is capable of resolving a fractional change of 10−5 in the impedance of a nominally 50 Ω resistive device with a measurement time of one minute. We include details of an application to ac magnetoconductance measurements on mesoscopic devices, and an in situ calibration method for this application.
Thermal sensors for investigation of heat transfer in scanning probe microscopy
Authors: Xu J. B. , Läuger K. , Dransfeld K. , Wilson I. H.
Published: July 2002

Planar thermocouples designed for investigation of heat transfer in scanning tunneling microscopy and scanning thermal microscopy are described. The limit of sensitivity to local thermal power can be as small as 10 nW. The devices are based on two different thin films formed as a cross on a thin glass substrate. Heat fluxes in the cross point can be detected by measuring the thermoelectric signal from two ends of the cross. As described elsewhere planar thermocouples of this type have been successfully used to detect the energy which is deposited by tunneling electrons and to measure the heat which is coupled across a submicron vacuum gap between two metals by the fluctuating fields of electromagnetic surface modes.
Forming of high-voltage nanosecond and subnanosecond pulses using standard power rectifying diodes
Authors: Belkin V. S. , Shulzchenko G. I.
Published: July 2002

A new simple circuit for producing high-voltage nano- and subnanosecond pulses at high repetition rates is presented. Output peak voltages and rise times are 6 kV, 2 ns or 8 kV, 0.1 ns. Only standard commercial components are employed. Diode parameters that limit achievable voltage levels have been studied.
High-electron-mobility-transistor gain stability and its design implications for wide band millimeter wave receivers
Authors: Wollack E. J.
Published: July 2002

Advances in the noise performance and frequency range of high-electron-mobility-transistor devices have led to an increase in their usage in systems below ∼100 GHz. In light of these developments, the effects of low frequency noise upconversion on the performance of the current GaAs device generation are investigated. A spectrum of gain fluctuations characterized by δg2(f)=δg21/(f/1 Hz)α, with α≂0.9 and a spectral density at 1 Hz of δg21≂12 GHz−1 is observed in 45 GHz low noise cryogenic amplifiers. The measured level of fluctuations is in agreement with theoretical device scaling stability predictions. The presence of these fluctuations will limit continuum receiver performance with bandwidths greater than ∼1 GHz under typical operating conditions. The implications of these measurements on the design of wide band receivers and means of reducing sensitivity to gain fluctuations are discussed.
An optical remote controlled high voltage dome for electron microscopes
Authors: Ruan Shengyang , Kapp Oscar H.
Published: July 2002

A low cost high voltage dome has been completed for an electron microscope with a thermal emission tip as electron source. Two fibers are used to provide communication across the high electrical field zone between the computer and the dome. This system provides a reliable method to operate the dome circuitry (floating at high voltage) and ensures the safety of both the computer system and the operator. Because of the application of ‘‘dummy’’ serial data transfer, the least number of fibers and associated components are used, providing a relatively low-cost solution to this problem.
A hydrostatic optical cell with synthetic diamond windows for quantitative infrared measurements of fluids
Authors: Kato Minoru , Taniguchii Yoshihiro
Published: July 2002

An optical cell with synthetic diamond windows that achieves hydrostatic pressures up to 600 MPa has been constructed. It is capable of being used for various quantitative optical measurements of fluids because of its accuracy in controlling the pressure generated and constant optical pathlength. Designing features and its performance are described. A particular application in the determination of the infrared absorption coefficient of symmetric stretching mode of liquid CS2 under pressure is presented.
1.7 μm excited state absorption measurement in erbium-doped glasses
Authors: Román José E. , Hempstead Martin , Ye Chenchun , Nouh Salim , Camy Patrice , Laborde Pascale , Lerminiaux Christian
Published: July 2002

We have measured the complete 1.7 μm excited state absorption (ESA) spectrum in erbium-doped glasses. The spectrum is obtained by measuring the gain of an erbium-doped waveguide in the 1400–1800 nm region. Using the measured spectra, we estimate the 1.5 μm uniform upconversion rate by calculating the spectral overlap between the 1.5 μm emission and 1.7 μm ESA cross sections. The technique is applied to erbium-doped, ion-exchangeable silicate glasses yielding upconversion constants in the range of 1–10×10−18 cm3/s.
A simple high-power 10 ps KrF discharge laser system
Authors: Leng Y. , Yun V. E. , Goldhar J. , Griem H. R.
Published: July 2002

A simple and rugged KrF laser system which generates 10 ps 100 mJ pulses is described. A holographic distributed feedback dye laser generates a transform-limited 10 ps seed pulse, which is amplified in two discharge modules. High electron density and temperature plasmas were produced by focusing this laser pulse to a spot with a <30 μm diameter.
Workshop summary on thermal management of x-ray optical components for synchrotron radiation
Authors: Mills Dennis M. , Freund Andreas , Ishikawa Tetsuya
Published: July 2002

The Workshop on Thermal Management of X-ray Optical Components for Synchrotron Radiation, held July 14 and 15, 1994, at Argonne National Laboratory, is summarized. This workshop, a satellite meeting of the Fifth International Conference on Synchrotron Radiation Instrumentation, is the latest in a series of workshops that have been held to explore solutions to mitigate thermally induced distortion in optical components exposed to high-heat-flux x-ray beams generated by insertion devices. Presentations were made on a variety of approaches to address this problem including techniques to expand the footprint of the beam on the optic, ways to reduce the deposited power, use of cryogenically cooled optics, diamond optics, and various combinations of the aforementioned methods.
High-repetition-rate electro-optic cavity dumping
Authors: Krüger E.
Published: July 2002

A method for obtaining very high electro-optic switching rates is demonstrated and employed for cavity dumping of a synchronously pumped mode-locked dye laser. The intracavity light switch consists of a Pockels cell and a thin-film polarizer. A synchronous, field-effect transistor-switch based generator delivers, at 10 MHz repetition rate, 15-ns pulses with an amplitude of 300 V required for operating the Pockels cell. High electrical efficiency is obtained by connecting the Pockels cell via a resonant line. Dispersion of the high-voltage pulse shuttling on the line is minimized by using phase compensation networks at its ends. From the optical pulse circulating in the laser cavity at 80 MHz, an adjustable fraction is dumped out on every eighth round trip. Intermediate pulses are suppressed by about 1:100.
Beijing Synchrotron Radiation Facility
Authors: Jiang Xiaoming , Tang Esheng , Xian Dingchang
Published: July 2002

The storage ring for the Beijing Synchrotron Radiation Facility (BSRF) is the 1.6–2.8 GeV Beijing Electron-Positron Collider, which was constructed for China’s first project on high-energy physics research. The storage ring was designed to be operating either in the colliding mode or in the dedicated synchrotron-radiation mode. The project was approved by the Chinese government at the end of 1983, and was completed in 1989. The Beijing Synchrotron Radiation Laboratory was founded in July of 1985, and the construction of the first beam line was completed in 1989. The first phase construction of BSRF was finished in 1991; three beam ports, seven beam lines, and nine experimental stations were constructed. Since 1991, BSRF has been opened to users from all over the country. The description of the beam lines and experimental stations and present research activities is given in this paper. The second phase construction of BSRF as well as the plan of constructing a third-generation new synchrotron-radiation source, the Beijing Light Source, adjacent to BSRF, are described.
Biomagnetic measurements using low-noise integrated SQUID magnetometers operating in liquid nitrogen
Authors: DiIorio M. S. , Yang K-Y. , Yoshizumi S.
Published: July 2002

We have fabricated high-Tc SQUID magnetometers with a pickup coil and a multiturn input coil integrated onto the same substrate. A four-channel system operating in liquid nitrogen has been developed and used to measure biomagnetic signals emanating from both the heart and the brain. The magnetic field sensitivity of the integrated SQUID magnetometer reaches 70 fT/√Hz at 1 kHz and 280 fT/√Hz at 1 Hz. The use of superconductor-normal metal-superconductor (SNS) step-edge junctions with YBa2Cu3O7−δ as the superconductor and Ag–Au alloy as the normal metal allows the measurements to be performed with standard dc bias electronics.
Ion-implantation system for near surface studies
Authors: Virdi G. S. , Nath N.
Published: July 2002

An ion-implantation system designed and fabricated indigenously is described. It consists of a versatile ion source, Einzel lens system, EXH velocity filter, dose measuring equipment, and target chamber. The ion-implantation system fabricated has been used to prepare ion-implanted luminescent phosphors by implanting Sb+ ions into CaS.
Thermionic aluminosilicate sources of Tl+ ions
Authors: Zhou Z. L. , Tan T. L. , Ong P. P.
Published: July 2002

Thermionic filament sources of Tl+ ions were made using tungsten wire coated with synthetic thallium aluminosilicates in the β-eucryptite (Tl2OAl2O32SiO2) and two other compositions (2Tl2OAl2O32SiO2 and 2Tl2OAl2O34SiO2). Three different methods for the production of aluminosilicate melts were used. The performance characteristics as thermionic emission sources of Tl+ ions based on total emission current and purity of ion emission as functions of time and filament surface temperature were studied and compared. Our results indicated that the sample of composition ratio of 2Tl2OAl2O32SiO2, which was produced by resistance heating under atmospheric pressure in air, is an optimum Tl+ ion source at temperatures between 1150 and 1350 °C after 150 h of continuous heating.
A linear array position sensitive detector based on amorphous silicon
Authors: Martins Rodrigo , Lavareda Guilherme , Fortunato Elvira , Soares Fernando , Fernandes Luís , Ferreira Luís
Published: July 2002

A linear array thin film position sensitive detector (LTFPSD) based on hydrogenated amorphous silicon (a-Si:H) is proposed for the first time. Taking advantage of the optical properties presented by a-Si:H devices, we have developed a LTFPSD with 128 integrated elements able to be used in 3D inspections/measurements. Each element consists of a one-dimensional LTFPSD, based on a p-i-n diode produced in a conventional PECVD system, where the doped layers are coated with thin resistive layers to establish the required device equipotentials. By proper incorporation of the LTFPSD into an optical inspection camera it will be possible to acquire information about an object/surface, through the optical cross-section method. The main advantages of this system, when compared with the conventional CCDs, are the low complexity of hardware and software used and that the information can be continuously processed (analog detection).
Fine particulate contaminant control by the UV/photoelectron method under a low pressure condition
Authors: Seto Takafumi , Okuyama Kikuo , Inoue Yuuki , Yokoyama Shin , Kurose Shin-ichi , Hirose Masataka , Fujii Toshiaki
Published: July 2002

A new method for removing fine airborne particles using an UV/photoelectron method is investigated for low pressure conditions. In the UV/photoelectron method, particles are unipolarly charged by collision with ions, which are produced by photoelectrons emitted from an UV-irradiated Au film. The particles are collected on electrodes under a strong electric field. To investigate the particle collection efficiency, a test chamber of 53ℓ in volume is used in the experiment. More than 95% of the particles are removed by the method where the chamber pressure is above 10 Torr and the particle diameter ranges from 200 to 400 nm. The results can be explained by the current charging theory of fine particles. This method can be used to design superclean spaces for the storage and handling of wafers, such as wafer stockers, wafer delivering systems, and vacuum load-lock chambers under conventional operating conditions.
A high speed, medium voltage pulse amplifier for diode reverse transient measurements
Authors: Chudobiak Michael J.
Published: July 2002

A dc-coupled nonlinear pulse amplifier circuit is presented. The circuit presented can produce 40 V peak-to-peak pulses with 3 ns rise and fall times. This speed is obtained by using class D transistor amplifier stages. This circuit is shown to be useful for measuring the reverse recovery transients of fast switching diodes such as the 1N4148, and fast recovery power rectifiers.
Matching the resistivity of Si:Nb thin film thermometers to the experimental temperature range
Authors: De Vecchio Derik , Taborek P. , Rutledge J. E.
Published: July 2002

The useful temperature range of semiconducting resistive thermometers is limited by declining sensitivity at high temperature and inconveniently high resistivity at low temperatures. The useful temperature range of sputtered thin film Si:Nb resistance thermometers is controlled by the Nb concentration. We have developed a simple technique for controlling the Nb concentration during the fabrication process. We describe an extremely sensitive family of thermometers with useful temperature ranges that overlap and span temperatures from below 1 K to above 450 K.
High frequency electron nuclear double resonance at 239 GHz using a far-infrared laser source
Authors: Paschedag L. , van Tol J. , Wyder P.
Published: July 2002

We report on the application of 14N electron nuclear double resonance (ENDOR) at 8.5 T and 239 GHz (λ=1.2 mm) in a γ-irradiated betaine arsenate single crystal. A laser was used as a far-infrared radiation source in a transmission-type electron paramagnetic resonance (EPR) setup without a cavity. The four expected nitrogen ENDOR lines were observed, but due to insufficient saturation of the EPR transitions the signal/noise ratio was not larger than 10 and the signals vanished at temperatures above 20 K.
Present status of the Pohang Light Source
Authors: Kim Y. S. , Han K. S. , Namkung W. , Lee T. N. , Kim Hogil
Published: July 2002

The Pohang Light Source (PLS) Project is now in its final year of the construction phase. The machine consists of a full energy (2 GeV) linear accelerator injector, a storage ring with a 12-period TBA structure, and 32 eventual beamlines from insertion devices and bending magnets. The commissioning of the injector linac was completed in June 1994. The overall commissioning of the PLS is expected to be completed by the end of 1994. The facility will provide high brightness, tunable radiation in a wide spectral range up to 30 keV of photon energy, and will serve national and international users starting in mid-1995.
A simple double-focusing sector mass spectrometer with permanent magnets
Authors: Samano E. C. , Carr W. E.
Published: July 2002

Most commercial mass spectrometers are intended to select ions by focusing them in one direction by means of electromagnets. However, double focusing is demanded in applications where the pole-pieces gap is too tight. A mass spectrometer has been planned and built to focus an ion beam in the radial and axial directions using permanent magnets in a circuit with nonparallel pole pieces. Consequently, the magnetic circuit in the spectrometer does not require any ex vacuo connection for its functioning, and the size can be controlled by just choosing the appropriate magnets. The measurements of the magnetic field configuration show good agreement with the theoretical prediction in the gap radial region where the H− species from a H− surface production experiment are deflected. The description of the criteria followed in the design and construction of the mass spectrometer is the main object of this report.
In situ measurement of zinc oxide film thickness and optical losses
Authors: Wacogne B. , Pannell C. N. , Roe M. P. , Pattinson T. J.
Published: July 2002

We report a simple interferometric method for simultaneous, in situ measurement of both the thickness and the depth resolved optical losses of thin transparent films. The experimental arrangement is simple requiring only a laser and a detector regardless of the substrate. The originality of our method is based on the evaluation of the optical losses from the envelopes of the laser signal, while the thickness is measured conventionally by counting the number of signal periods. The technique has been tested while growing ZnO films in a planar rf magnetron sputtering system. Using the above method, the evolution of optical losses is easily observed during deposition, leading to the possibility of a real time control of the film quality. Both theoretical calculations and experimental results are presented in this letter.
A magnetizing system for dichroism measurements in soft x-ray emission excited by synchrotron radiation
Authors: Dallera C. , Ghiringhelli G. , Braicovich L.
Published: July 2002

We present the design and performance of a magnetic circuit suitable for magnetizing solid samples in the measurements of soft x-ray emission dichroism excited by synchrotron radiation. The system allows a variety of samples to be magnetized and satisfies the rather stringent geometrical constraints due to the need for minimizing the effect of photon self-absorption by the sample. The magnetic circuit is ultrahigh vacuum compatible, can reach about 2800 G, and allows fine adjustment of sample position.
Magnetic field measurements using the transient internal probe (TIP)
Authors: Galambos J. P. , Bohnet M. A. , Jarboe T. R. , Mattick A. T.
Published: July 2002

The transient internal probe (TIP) is a novel diagnostic technique for measuring magnetic fields in hot plasmas. The concept involves shooting a diamond clad magneto-optic probe through the plasma at high velocity allowing measurement of the local magnetic field before ablation occurs. Magnetic field measurements are obtained by illuminating the probe with an argon laser and measuring the amount of Faraday rotation in the reflected light. The diagnostic was tested by measuring a permanent magnetic field inside a vacuum chamber with a probe traveling at 2 km/s using an unclad probe. The purpose of this experiment was to demonstrate the capability of the TIP diagnostic and to verify compatibility with plasma vacuum requirements. Magnetic field resolutions of 20 G and 1 cm spatial resolution were achieved. The response time of the detection system is 10 MHz. Introduction of a helium muzzle gas into the plasma chamber was limited to less than 0.4 Torr ℓ.
Increased deposition rate of chemically vapor deposited diamond in a direct-current arcjet with a secondary discharge
Authors: Baldwin S. K. , Owano T. G. , Kruger C. H.
Published: July 2002

A secondary discharge was used to enhance chemical nonequilibrium in the boundary layer of a stagnation point flow reactor during the atmospheric pressure deposition of chemically vapor deposited (CVD) diamond with a direct-current (dc) arcjet. The secondary discharge was induced by means of a positive potential on the deposition surface to drive a current through the boundary layer and produce energetic electrons. These electrons can promote superequilibrium concentrations of radicals at the growth surface. It was found that with 3.5 A/cm2 at 115 V in the secondary discharge, the growth rate of diamond in this reactor increased by a factor of 6 as compared with the floating or grounded substrate case.
Amorphous layer formation on a Ni65Cr15P16B4 alloy by irradiation of an intense pulsed ion beam
Authors: Yatsuzuka M. , Yamasaki T. , Uchida H. , Hashimoto Y.
Published: July 2002

Amorphous layer formation by irradiation of an intense pulsed ion beam (PIB) has been studied experimentally. A mixed carbon and fluorine PIB with energy of 180 keV, current density of 180 A/cm2, and pulse duration of 25 ns is exposed to a Ni65Cr15P16B4 alloy, resulting in an amorphous layer on the substrate surface within 0.66 μm in depth. The cooling rate for a nickel substrate from the melting point to the glass transition temperature is estimated to be ∼3.8×105 K/s.
A simple kinetic model for the optimization of electron cyclotron resonance/reactive ion beam etching performance for GaAs
Authors: Sugiyama Masakazu , Yamaizumi Takayuki , Nezuka Masahiro , Shimogaki Yukihiro , Nanako Yoshiaki , Tada Kunio , Komiyama Hiroshi
Published: July 2002

In order to obtain the optimum performance for the electron cyclotron resonance/reactive ion beam etching (ECR-RIBE) reactor, we have examined the effect of Cl2 flow rate on Cl concentration by utilizing the optical emission peak intensity from Cl as the index of its concentration. The peak intensity observed in the reactor not containing GaAs substrate decreases monotonically as the flow rate increases. However, when the GaAs substrate is introduced into the reactor, we observe the intensity decrease drastically at lower Cl2 flow rates. At the same time, strong emission peaks from Ga are observed, and their intensity also shows flow rate dependency. These results can be explained using a simple model that divides the ECR-RIBE reactor into two continuous stirred tank reactors (CSTRs). We believe that this model and the kinetic constants obtained here can contribute to the efficient optimization of the ECR-RIBE process.
Dynamic compression-shear loading with in-material interferometric measurements
Authors: Espinosa H. D.
Published: July 2002

The present article introduces a new technique for window interferometry in the case of combined normal and shear wave motion. The method can, in principle, be used for micromechanical studies of damage and inelasticity in a variety of materials. Preliminary tests conducted on brittle materials indicate the feasibility of the technique and its advantages over other in-material measurements using embedded manganin gauges or electromagnetic particle velocity gauges. An analysis of the interferometric signals, incorporating variations in the index of refraction of the window material, is used in the interpretation of the velocity histories. The suitability of the technique in the study of dynamic failure and material instabilities is presented. Furthermore, the use of the in-material measurement technique in the design of pressure-shear recovery experiments is described.
Suppression of transient enhanced diffusion following in situ photoexcitation during boron ion implantation
Authors: Ravi J. , Erokhin Yu. , Rozgonyi G. A. , White C. W.
Published: July 2002

The effect of in situ photoexcitation during boron ion implantation on subsequent transient enhanced B diffusion in Si has been investigated. Photoexcitation using a mercury arc lamp was performed during B+ implantation at 35 keV for a dose of 5×1014 cm−2 at 177 K. A reduction in the electrical activation dip, i.e., reverse annealing effect, in the temperature range 550–700 °C was observed. Also, the transient enhanced diffusion of B, measured using SIMS following 800 °C, 30 min annealing, was suppressed. Both effects demonstrate that the creation of self-interstitials during the implantation process is significantly reduced.
Anomalous temperature character of phase conjugation in doped-LiNbO3 crystal
Authors: Liu Jinsong , Liang Changhong , An Yuying , Li Minghua , Xu Yuheng , Wu Zhongkang
Published: July 2002

We report here an anomaly that the photorefractive phase conjugate reflectivity increases sharply near 55, 70, and 110 °C in three different doped-LiNbO3 crystals. The anomalous phenomenon is possibly concerned with the structural phase transformation of the crystal, which induces an extra internal electric field and enhances the reflectivity.
High-current superconducting Tl1Ba2Ca2Cu3Oy thick films on polycrystalline Ag by spin coating
Authors: He Qing , Christen D. K. , Klabunde C. E. , Tkaczyk J. E. , Lay K. W. , Paranthaman M. , Thompson J. R. , Goyal A. , Pedraza A. J. , Kroeger D. M.
Published: July 2002

Thick films of the high-temperature superconductor Tl1Ba2Ca2Cu3Oy with high current density Jc have been deposited on polycrystalline Ag substrates by a spin-coating method. The spin-coated precursor films were annealed in a two-zone Tl reaction furnace. Film thicknesses ranged from 10 to 30 μm, leading to good total current capabilities. The films have highly-textured c-orientation as evidenced by rocking curves with FWHM of 4° for the (006) peak. Scanning electron micrographs revealed a dense, plate-like layered structure and almost no reaction between the film and the Ag substrate. Values of Jc (77 K) up to 2.5×104 A/cm2 in zero field and more than 1000 A/cm2 in a 1 tesla field (H∥c axis).
Pressure influence on the decay of the photoluminescence in Si nanopowder grown by plasma-enhanced chemical vapor deposition
Authors: Roura P. , Costa J. , Sulimov N. A. , Morante J. R. , Bertran E.
Published: July 2002

The quenching of the photoluminescence (PL) intensity of Si powder grown by plasma-enhanced chemical vapor deposition due to the residual gas pressure is reported. For He as well as for Ar, the dependence is exponential (IPL∝e−P/P0) with P0 depending on the gas. This behavior is further analyzed through the pressure influence on the PL decay transients. Conclusions are drawn concerning the way the presence of the gas influences the emitting centers.
Imaging spectrometer for ultraviolet–near-infrared microspectroscopy
Authors: Johansson Thomas , Pettersson Anders
Published: July 2002

We describe the design and performance of a new high-speed imaging spectrometer system developed for the spectral analysis of micrometer-sized features in transmitted light. The instrument utilizes the wavelength range from ultraviolet (UV) to near infrared (NIR) (250–975 nm). The extension into the ultraviolet range is to our knowledge unique. The system comprises two white light sources (xenon and halogen lamps), a motorized sample stage, microscope optics with slit-determined field of view, and three (UV, visible and NIR) parallel optical recording channels. The dispersive optical recording system is based on holographic gratings and uses charge-coupled-device (CCD) cameras as imaging detectors. The instrument has been fully integrated with data acquisition and control systems. Subsequent data analysis is performed by dedicated software. The instrument provides spectral images from narrow wavelength bands (5 nm). In such an image the spectral information from a selected wavelength band is depicted with its corresponding geometric location, i.e., a single pixel on the CCD chip. Hence, objects can be visualized in different wavelength bands and a spectrum can easily be produced for each location of the object. The instrument can measure objects up to 900 μm×27 mm with a spectral resolution better than 5 nm and a spatial resolution better than 5 μm. The imaging spectrometer system provides a powerful combination of spectroscopy and image processing for use in many applications in research, control and quality assessment, where spectral information and its location are of interest. Although the system has been primarily developed for applications in the pulp and paper industry, it has a vast potential for spectroscopic analysis with a micrometer spatial resolution in general and for measurements of impurities and their locations in products in particular. As an example of a measurement, spectral image data from a wood fiber are presented.
Multiturn split-conductor transmission-line resonator
Authors: Haziza Nathalie , Bittoun Jacques , Kan Siew
Published: July 2002

A split-conductor parallel-plate transmission line resonator is a simple structure made from bending a strip of double-face copper-clad printed-circuit board into a loop with alternate electrical discontinuities (gaps) on opposite sides. Its natural resonant frequency (Fn) is determined by the transmission line characteristic impedance, the loop diameter or strip length, and the number (Ng) of gaps. It is easy to design high frequency resonators simply by increasing Ng. We propose here a single-gap multiturn resonator for low frequency operation as well as a simplified expression for the determination of Fn. A design procedure of this type of resonator is outlined and illustrative examples with parallel-plate as well as ordinary 50 Ω coaxial transmission lines are given. Also, for a given cable length, numerical calculation shows that the minimum resonator frequency can be attained with a form factor of the order of 2.
Photoacoustic study of the effect of degassing temperature on thermal diffusivity of hydroxyl loaded alumina
Authors: Sankara Raman S. , Nampoori V. P. N. , Vallabhan C. P. G. , Ambadas G. , Sugunan S.
Published: July 2002

The thermal diffusivity of γ-alumina is determined by the photoacoustic method. The method is calibrated by determining the thermal diffusivity of copper and aluminum. The effect of the chemisorbed hydroxyl groups on thermal diffusivity is studied by degassing the sample at different temperatures.
A very precisely regulated compact thermostat for small-angle neutron scattering
Authors: Bonetti M. , Calmettes P.
Published: July 2002

We have built a simple two-stage thermostat for measuring small-angle neutron scattering from liquids or solids in the vicinity of a phase transition. The thermostat was tested between 20 and 75 °C. The long-term temperature stability varies within ±0.2 and ±0.5 mK, depending on the set-point temperature. Positive and negative temperature steps of 0.5 mK and more can be obtained without overshoot. Small-angle neutron spectra from a binary ionic mixture in the critical domain are also reported.
On chirp control in two section distributed feedback semiconductor lasers
Authors: Feng J. , Chen T. R. , Yariv A.
Published: July 2002

The characteristics of frequency chirp of a two section distributed feedback (DFB) laser, which is under large signal modulation, is studied while the optical intensity and optical modulation depth are fixed. It is found that the measured time-averaged power spectrum of the laser changes from one of a predominantly negative frequency chirp (red shift) to positive chirp (blue shift) as the injection current distribution between the two sections is changed. Our theoretical calculation of frequency chirp in DFB lasers based on the Green’s function method explains the shift of the frequency chirp in the two section DFB laser.
Transverse magnetotransport anisotropy in a semiconductor superlattice
Authors: Aristone F. , Palmier J. F. , Gassot P. , Portal J. C. , Mollot F.
Published: July 2002

The vertical magnetotransport properties of GaAs–AlAs superlattices have been investigated as a function of the in-plane magnetic field orientation. Two main effects were observed: (i) the influence of the roughness anisotropy with respect to the crystallographic orientation, and (ii) the nonparabolicity of the energy in the plane of the layers. The interface fluctuations induced a modulation of the miniband transport with a period of 180°. The nonparabolic energy of the deflected electronic orbits also induced a modulation of the vertical transport but with a period of 90°. Both observed effects are in qualitative agreement with a semiclassical description of the Boltzmann transport equation.
Mechanism of grain refinement in undercooled Cu30Ni70
Authors: Xiao J. Z. , Leung K. K. , Kui H. W.
Published: July 2002

It was found that remelting is the origin of grain refinement in undercooled Cu30Ni70 specimens. It was also demonstrated that composition difference across a dendrite is the cause of remelting. The critical undercooling, ΔT* for grain refinement is 145 K for undercooledCu30Ni70.
Critical mechanical behavior in the fluid/solid transition of suspensions
Authors: Esquivel-Sirvent R. , Green D. H. , Yun S. S.
Published: July 2002

Velocity and attenuation measurements of compressional waves at 3 and 5 MHz, as a function of solid volume concentration, are reported for different suspensions. The suspensions were made of 1 μm size particles of kaolinite or glass beads in water or light oil. At a volume concentration of 40%, a sharp peak in attenuation accompanied by a change in velocity is observed. The volume concentration at which this peak occurs is independent of frequency and particle geometry. The observed critical change in attenuation around 40% is consistent with an excess attenuation induced by the fluid-shearing processes between neighboring particles, and corresponds to the jamming point concentration predicted by particle packing simulations.
Measurement of forces and spring constants of microinstruments
Authors: Saif M. T. A. , MacDonald N. C.
Published: July 2002

Micromachines, including micro scanning tunneling microscope and high force (≈0.1 mN and higher) actuators, are examples of a new class of silicon-based microinstruments for atomic scale surface imaging and modification, as well as submicrometer scale material investigations. A large class of such microinstruments and sensors consist of actuators, such as interdigitated comb drives, that generate force, F, in the form F=βV2, where β is a constant and V is the applied voltage. Such actuators often move a large distance during actuation so that the restoring force, R, of the springs varies nonlinearly with x, i.e., the springs behave as hard springs, and R=K1x+K3x3+… (restoring force is similar for +ve and −ve x due to symmetry). β and Ki, i=1,3,…, of the micro-actuators usually differ from their design values due to processing nonuniformities. Hence, evaluation of these constants becomes necessary for each actuator, and is essential for the instruments that are employed to study materials’ behavior on a small scale. In this article, a methodology is developed to calibrate microinstruments, i.e., to evaluate the values of β and Ki, i=1,3,… . The method is based on buckling of a long slender beam of known dimensions, and made of a material with known property (elastic modulus). Buckling is achieved by an axial compressive force on the beam applied by the actuator of the microinstrument. β and Ki are derived from the relation between the applied voltage on the actuator, and the post buckling deformation of the beam. The beam is designed and cofabricated with the actuator, and hence the calibration mechanism is integrable with each microinstrument. An analysis is provided to estimate the possible errors in calibration due to errors in the measured dimensions of the calibrating beam. It is shown that the calibration error increases linearly with the error in the measured linear dimensions. The applicability of the method is demonstrated by fabricating microinstruments, which, prior to their calibration, are employed to apply torque on single crystal silicon bars (in the form of pillars), until the bars fracture. The instruments are then calibrated, and the calibrated values of β and Ki are used to evaluate the torques applied on the bars at different voltages. Stresses to fracture of the bars are also estimated. The torsion experiment is an example of the application of integrated microinstruments for small scale material studies.
A sensitive ultrasonic method for measuring transient motions of a surface
Authors: Royer D. , Casula O.
Published: July 2002

A method for measuring surface displacements is described. The principle is based on the detection of the phase shift of a high frequency continuous ultrasonic wave reflected from the moving surface. The analysis shows that the long time delay undergone by the ultrasonic wave produces a significant enhancement of the Doppler phase shift signal. Experiments were carried out in water with a 30-MHz focused transducer probe and transient mechanical displacements smaller than 1 Å (surface velocities smaller than 1 mm/s) were detected in a 10 MHz bandwidth.
Novel hybrid interferometer stabilization scheme used in wavelength shift measurement for Bragg grating sensors
Authors: Shi W. J. , Ning Y. N. , Grattan K. T. V. , Palmer A. W.
Published: July 2002

A novel hybrid interferometer stabilization scheme used for wavelength shift measurement, such as for in-fiber Bragg grating-based sensors, is described. This scheme combines the advantages of the long term optical imbalance stability offered by the locking system used and a comparative insensitivity to vibration-induced noise at frequencies up to 200 Hz, achieved with the use of a so-called “detection-and-compensation” scheme. By including an additional reference beam and the hybrid interferometer stabilization scheme, the vibration-induced fluctuation in the signal can be reduced by about 20 dB, and the value of the phase variation can be reduced by a factor of 20.
Kingdon trap apparatus and technique for precise measurement of the lifetimes of metastable levels of ions
Authors: Moehs D. P. , Church D. A. , Phaneuf R. A.
Published: July 2002

A portable system consisting of a Kingdon electrostatic ion trap and associated vacuum system and electronics has been especially designed to capture multiply charged ions from a beam produced by an electron cyclotron resonance ion source and to measure the lifetimes of the decays of metastable levels of these ions, which are excited in the source. Measurements on ion charge states as high as 14+ have been completed, with precisions exceeding 1% achieved with a few hours of data collection time in favorable cases. Gaseous and metallic ions of astrophysical interest have been studied. The measured lifetime of the 3s23p2 D21 level of Mn11+, τ=11.16±0.10 ms, is discussed as an example of the apparatus capabilities.
A simple calibration method for potassium halide thermoluminescence dosimeters
Authors: Pashchenko L. P. , Pérez Salas R. , Aceves R. , Barboza-Flores M.
Published: July 2002

We present a simple calibration method for europium-doped potassium halide dosimeters. The procedure is based on the self-irradiation absorbed dose of potassium halide thermoluminescence dosimeters due to the natural content of the radionuclide 40K in potassium halide crystals. In the small dose range of the order of 0.5 mGy, the precision of the proposed method is highly competitive with traditional calibration methods, without the need of artificial radiation sources and rather expensive and sophisticated measurement equipment.
Laser-induced dark traces in doped LiNbO3 crystals
Authors: Li Jiang , Chen Xiaojun , Wu Bin , Li Bing , Pan Shihong
Published: July 2002

Laser-induced dark traces in doped LiNbO3 crystals are studied with the 1064 nm fundamental radiation and the 532 nm second harmonic radiation of the Nd:YAG laser operating in a pulse mode. The results show that the dark traces are induced only by the 532 nm radiation. The linear relationship between the transmission loss and the 532 nm power density indicates that dark traces are not due to two-photon absorption. The recovery rates of the absorption in LiNbO3 with different wavelength probe laser are measured and show that laser-induced dark traces accompany more than one defect appearing in LiNbO3, and disappear quicker at higher temperature.
Optical bistability in two-dimensional nonlinear optical superlattice with two incident waves
Authors: Chen Xiang-fei , Lu Ya-lin , Wang Zhen-lin , Ming Nai-ben
Published: July 2002

With two coherent waves incident to a two-dimensional (2D) nonlinear optical superlattice containing Kerr form dielectric nonlinearity, the optical bistability related to transition between a forbidden transmission state and an allowed transmission state can occur through the index-modulation mechanism. This kind of bistability is difficult to obtain in the case of only one incident wave. The power cost for the bistability might be very low.
Surface acoustic wave on the (112) cut [11̄0] direction of gallium arsenide
Authors: Miškinis Rimantas , Urba Emilis
Published: July 2002

The properties of an acoustoelectrically active surface acoustic wave (SAW) propagated on the (112) cut [11̄0] direction of gallium arsenide are studied theoretically. The leaky nature of this SAW (LSAW) which has three displacement components of comparable magnitude is demonstrated. The low attenuation (4.94×10−5 dB per wavelength) of the LSAW is obtained. The values of the velocity and the electromechanical coupling coefficient of the LSAW, equal to 3047.4 m/s and 9.3×10−4, respectively, are acquired and agree with the results of experiments carried out previously.
Simple device for monitoring secondary electron emission of materials in the pulse mode
Authors: Krainsky Isay L. , Lesny Gary G.
Published: July 2002

A simple device for simultaneously measuring the secondary electron emission coefficient σ and the primary current in the pulse mode has been built. It allows convenient monitoring of these parameters for either conductive or insulating materials.
Degradation of the second order optical nonlinearity in cubic media by straight dislocations
Authors: Bottomley D. J.
Published: July 2002

The influence of straight dislocations on the second order nonlinear optical susceptibility χ(2) of cubic noncentrosymmetric media has been modeled. The resulting degradation of χ(2) has been evaluated for screw and edge dislocations in GaAs. It is found that single screw and edge dislocations reduce the χ(2) of GaAs by a third and ∼60%, respectively. This implies that second order nonlinear optical effects are very sensitive to misfit dislocation generation in epitaxially grown noncentrosymmetric media and that dislocation-free epilayers are required to realize the optimum χ(2).
Effects of axial tensile and bending strains on critical currents of monoand
Authors: Suenaga M. , Fukumoto Y. , Haldar P. , Thurston T. R. , Wildgrüber U.
Published: July 2002

Improved strain sensitivity of critical currents Ic of the multicored over the monocored (Bi,Pb)2Sr2Ca2Cu3O10–Ag tapes is shown for bending strains, but not for axial tensile strains. The improved mechanical tolerance is due, in part, to a better alignment of the Bi-cuprate platelets achieved in the multicored tapes. Furthermore, the difference in the response to these tapes to axial tensile and bending strains is due to the difference in the precise manner in which the strains are applied to the tapes.
MoI density measurements by laser induced fluorescence spectroscopy
Authors: Orsitto F. , Borra M. , Coppotelli F. , Gatti G. , Neri E.
Published: July 2002

The density of molybdenum atoms produced by sputtering of a TZM (molybdenum) target by Ar+ ions is measured by laser induced fluorescence (LIF) using tunable dye laser. The excitation transition involved is a7S3−z5P30 at 345.64 nm, while the fluorescence signal is from the decay z5P30−a5S2 at 550.6 nm. The LIF measurements are carried out by varying the laser power incident on Mo atoms by means of neutral density filters. An absolute calibration of the detection system together with the realization of a well defined optical probe volume allows for the determination of the density of the emitting atoms. An evaluation of LIF diagnostic performance on Frascati Tokamak upgrade put a lower limit of 2.5×1014 atoms/m3 on the detectable local density of MoI close to the toroidal limiter.
A method for measuring the 2 3S population in a fast He4 beam by means of laser atomic absorption spectroscopy
Authors: Christmann A. , Seidel S. , Kunze H. J.
Published: July 2002

We test the laser atomic absorption spectroscopy as a method to measure the population density of the 2 3S level in an energetic He4 beam. The 2 3S projectiles are produced by quasiresonant charge transfer collisions of He+ in lithium vapor. The population density is measured with a tunable distributed Bragg reflector diode laser operating at 1083 nm. The absorption of the 2 3 S →2 3Pj transitions yields an absolute value for the line-integrated density, and from the knowledge of the radial beam particle density profile the density of the 2 3S state itself is obtained.