bluuebunny/crossref_metadata_2025 huggingface dataset:
Calibration and standards beamline 6.3.2 at the Advanced Light Source
Authors: Underwood J. H. , Gullikson E. M. , Koike M. , Batson P. J. , Denham P. E. , Franck K. D. , Tackaberry R. E. , Steele W. F.
Published: July 2002

This bending magnet beamline has been in operation since February 1995 for the characterization of optical elements (mirrors, gratings, multilayers, detectors, etc.) in the energy range 50–1000 eV. Although it was designed primarily for precision reflectometry of multilayer reflecting optics for EUV projection lithography, it has capabilities for a wide range of measurements. The optics consist of a monochromator, a reflectometer, and refocusing mirrors to provide a small spot on the sample. The monochromator is a very compact, entrance-slitless, varied-line-spacing plane-grating design in which the mechanically ruled grating operates in the converging light from a spherical mirror working at high demagnification. Aberrations of the mirror are corrected by the line spacing variation, so that the spectral resolving power λ/Δλ is limited by the ALS source size to about 7000. Wavelength is scanned by simple rotation of the grating with a fixed exit slit. The reflectometer has the capability of positioning the sample to within 10 μm and setting its angular position to 0.002°. LABVIEWTM based software provides a convenient interface to the user. The reflectometer is separated from the beamline by a differential pump and can be pumped down in 1/2 hour. Auxiliary experimental stations can be mounted behind the reflectometer. Results are shown that demonstrate the performance and operational convenience of the beamline
Use of a semiconductor detector for measurement of high energy end loss ions from a tandem mirror
Authors: Saito T. , Sakakibara M. , Kiwamoto Y. , Tatematsu Y. , Yoshimura Y. , Ichimura M. , Tamano T.
Published: July 2002

A semiconductor detector is applied for measurement of high energy end loss ions (E⩾15 keV) from a tandem mirror. Its energy sensitivity to protons calibrated by using a monochromatic ion source is found to be the same as that to electrons. The semiconductor detector is installed on an end wall of the GAMMA 10 tandem mirror and high energy end loss ions are observed with the detector when ions in the confinement region are strongly heated by ion cyclotron waves. Counts of high energy end loss ions are closely related with a diamagnetic signal representing ion heating. The energy of the end loss ions spreads with time and attains to 50–60 keV. Time behavior of the ion count suggests that unknown loss processes other than classical Coulomb scattering are relevant to ion end loss.
Control of a multidegree of freedom standing wave ultrasonic motor driven precise positioning system
Authors: Ferreira Antoine , Minotti Patrice
Published: July 2002

A newly developed positioning system incorporating a multidegree of freedom standing wave ultrasonic motor (SWUM) is presented and its advantageous features, operating principles, and some experimental results are described. The principle of motorization is based on the conversion, through frictional contact, of a stationary bending vibration sustained in a slotted metallic resonator, into rigid body displacements. A small autonomous multidegree of freedom nanopositioner using a SWUM motor is presented for fine positioning in scanning tunneling microscopy. The positioning system is achieved via the simultaneous operation of two identical pulse width modulation servo-control systems, each having a laser vibrometer position feedback loop. The closed loop position schemes are theoretically considered and their results are demonstrated and evaluated in practice. Evaluations of experimental tests indicate that a positioning resolution less than 100 nm are successfully achieved for an unlimited X−Y travel range with linear speeds between 1 mm s−1 and few cm s−1.
Detector for spatial and temporal imaging of single photons
Authors: Sinclair A. G. , Kasevich M. A.
Published: July 2002

A photon detector with spatial and temporal resolution capabilities is described. The detector consists of an image intensifier and a position-sensitive photomultiplier tube. It has 2.5×103 resolvable pixels, a dark count rate of 5×10−2 pixel−1 s−1, and a quantum efficiency of 12% at 670 nm. The maximum data rate for a pixel is 500 kHz, which is also the limit of the entire detector aperture. The absolute time of a single event can be determined to within 100 ns. The single pixel response was found to be linear with incident intensity for short pulses of light containing up to several thousand photons.
Computer stabilized spin polarized electron source
Authors: Hayes P. A. , Yu D. H. , Williams J. F.
Published: July 2002

A systematic optimization of the components of our polarized electron source has markedly improved its long term stability over earlier versions. The major factors shortening the lifetime of the source have been identified. The essential parts of the spin polarized electron source, such as the vacuum system, crystal holder, cleaving mechanism, caesium dispenser, oxygen admittance tube, and computer control activation features are discussed. The lifetime of the source now exceeds 500 h with a constant polarization of 28.5%.
A possible device for selective detection of magnetic field sources using superconducting and ferromagnetic cylinders
Authors: Sakasai K. , Ara K.
Published: July 2002

The authors have studied a system, consisting of superconducting and ferromagnetic cylinders, and a magnetic field sensor for selectively detecting a magnetic dipole parallel to the extension of the axis of the cylinders. The superconducting cylinder has an open slit in its side so that the magnetic field from the dipole can be measured selectively according to its diamagnetic characteristics. The magnetic fields detected by the sensor are estimated with the aid of magnetic field analysis. It may be possible to use the system for positioning of one or two parallel dipoles. The system will be useful for nondestructive testing of metallic materials.
Development of heating holders for the field-emission scanning electron microscope
Authors: Yamamoto Youiti , Higuchi Kouji
Published: July 2002

We have developed a practical heating holder for the field-emission scanning electron microscope (FESEM, JSM-6000F) to study and apply the specimen heated and electron beam induced conductivity. The design is described in detail. A surface temperature up to 943 K is achieved. The temperature fluctuation is less than 0.5%/h at about 20 min after the heating up to 943 K, and the thermal drift is suppressed to less than 5 nm/min up to 873 K. The temperature of the observation area is proportional to the input power of the heater up to about 700 K. The charging on a nonconducting surface such as porous pipe glass can be prevented at a surface temperature above about 673 K. It is demonstrated that this is useful to the high resolution observations of the nonconducting surfaces.
Increasing the accuracy of liquid analysis and pH-value control using a liquid-core waveguide
Authors: Dress P. , Franke H.
Published: July 2002

A liquid-core waveguide (LCW) with pure water as core material has been fabricated by coating the inner core of a glass tube with Teflon AF® 2400. Its guiding properties are proven and the guiding losses are determined to be 0.016 dB/cm. A first theoretical model is proposed and its validity is shown by comparing theoretical and experimental results. As an example for application the LCW system is used for optical pH-value control. The proposed LCW system exhibits the same accuracy for pH-value determination as commercial electrochemical pH meters.
A versatile substrate heater for thermal and plasma-enhanced chemical-vapor deposition
Authors: Bottin Jeffrey R. , McCurdy Patrick R. , Fisher Ellen R.
Published: July 2002

A simple and inexpensive substrate heater that can be used in both thermal- and plasma-enhanced chemical-vapor deposition (PECVD) systems has been constructed. This heater design can be used to achieve and sustain substrate temperatures as high as 650 °C with a minimal amount of outgassing under both CVD and PECVD conditions. Substrates are heated very quickly with all but the highest temperatures achieved within 30 min. The heater is also very robust, with a lifetime of more than 30 h of continuous use under vacuum with several heating and cooling cycles. We have used this heater design to thermally deposit TiS2 from 1-methyl-1-propanethiol and TiCl4 in the temperature range of 200–500 °C. In addition, amorphous hydrogenated silicon carbide (a-Si1−xCx:H) was deposited in the temperature range of 30–570 °C using a 13.56 MHz rf plasma reactor and a modified version of the same heater.
A miniature total-electron-yield detector for the measurement of x-ray absorption spectra
Authors: Harris V. G. , Elam W. T.
Published: July 2002

We have designed, built, and tested a total-electron-yield detector for the collection of x-ray absorption spectra. The virtues of this detector are its compact size and simplicity of design, fabrication, assembly, and use. Sample exchange and realignment with respect to the incident beam are easily performed. The design and performance of this detector are presented and discussed in comparison with other detection schemes.
Hot gas temperature controller for a cryostat insert having high stability
Authors: Bonaldi Michele , Jung Grzegorz , Vecchione Antonio , Vitale Stefano
Published: July 2002

A very low-noise, variable temperature insert for a standard liquid-helium cryostat has been developed. The design provides a 10–100 K operating range, with temperature stability better than 20 mK in the range 25–100 K, improving to 2 mK below 25 K. This temperature stability figure is obtained by balancing the cooling power due to the thermal coupling of the sample to liquid helium, with the heating power of a stream of room-temperature He gas flowing through a heat exchanger. The heating power is continuously regulated within a feedback loop by throttling the gas flow with a proportional valve, using the error signal from the temperature controller. The system provides good temperature stability without the need for low-resistance leads in the vicinity of the sample holder as those needed to feed an electrical heater. This is relevant to experiments where electromagnetic interference must be minimized.
Differential isothermal capacitance transient spectroscopy for the studies of deep levels in semiconductors
Authors: Suno K. , Yoshino J. , Okamoto Y. , Morimoto J. , Miyakawa T.
Published: July 2002

Differential isothermal capacitance transient spectroscopy (DICTS) and normalized isothermal capacitance transient spectroscopy (NICTS) were proposed to improve the resolution of the conventional isothermal capacitance transient spectroscopy (ICTS) which could characterize the deep levels in semiconductors isothermally. The resolution of the methods was studied for the closely spaced energy levels by the numerical simulation. Though the resolvable emission rate ratio R (R=λ2/λ1, where λ1 and λ2 are each thermal emission rate for two levels) of ICTS was around 5, R of DICTS was around 4. Moreover, R of NICTS reached 3.5 which is less than that of any other conventional methods. The error ratio of the estimation is almost the same as ICTS. The new method was applied to study the deep levels in a Si:Au system as an example and found two closely spaced energy levels explicitly.
Versatile 4 K nuclear magnetic resonance probe and cryogenic system for small-bore high-field Bitter magnets
Authors: Reyes A. P. , Bachman H. N. , Halperin W. P.
Published: July 2002

A complete design for a versatile nuclear magnetic resonance cryostat/probe system specifically adapted for small 32 mm bore bitter magnets is described. The probe solves two main problems associated with constrained environments (1) high voltage arcing across cold tuned circuits in helium atmosphere and (2) loss of temperature control due to helium bubbles in a long Dewar tail at high fields. The probe implements a variable cold-tuned system with an evacuated space for tuning capacitors to avoid high voltage breakdown. The cryostat makes use of a unique counterflow design. The simple construction and disassembly ensures reliability and allows quick repair and replacement of parts.
A frequency doubling electro-optic modulation system for Pockels effect measurements: Application in LiNbO3
Authors: Theofanous N. G. , Aillerie M. , Fontana M. D. , Alexakis G. E.
Published: July 2002

A novel system is presented which is capable of measuring with high accuracy the linear (Pockels) electro-optic effect by means of a new dynamic (ac) method. This method is based on the observation of the photodetected output obtained from a Senarmont-type ellipsometric system with an ac (modulating) voltage being applied onto the electro-optic sample under test. This observation is made on a high sensitivity oscilloscope and allows us to determine accurately the null point of the system by locating the position of the analyzer that produces in the output a characteristic and abrupt doubling of the (modulation) frequency. By locating this frequency doubling position without and with electric field one can finally determine the corresponding electro-optic coefficients. Theoretical analysis and considerations of practical interest are presented in the article and show that the system in question can ensure reduced errors and increased sensitivity. Also, experimental evidence in support of the expected performance is obtained by implementing and applying the system for the measurement of the composite electro-optic coefficient rc of LiNbO3 for various temperatures in the range of 17–20 °C.
X-ray welding of metal-matrix composites
Authors: Rosenberg Richard A. , Ma Qing , Farrell William , Keefe Mark , Mancini Derrick C.
Published: July 2002

We present the first results of use of the high power x-rays from an insertion device beamline at the Advanced Photon Source for welding. X-rays with energies between 3 and 200 keV and power densities greater than 10 000 W/cm2 can penetrate deeply into most materials and thus can be used as volumetric heating sources. In this article we show results of bead-on-plate welds of a 3.3-mm-thick Al/Al2O3 metal-matrix composite and discuss results obtained for other materials. The potential of x-rays for welding is also discussed.
Easy axis distribution in two-dimensional recording media
Authors: Iglesias R. , Merayo J. M. G. , Rubio H.
Published: July 2002

In contrast to preceding methods valid only for noninteracting many-particle assemblies, we describe a theory applicable to two-dimensional recording media, which includes interactions between particles through a mean-field model. Expressions are obtained for the angular dependence of magnetic remanences parallel and perpendicular to the applied field. We define a quantity independent of interaction, the remanent magnetization direction, which provides a realistic distribution of easy axes. From this distribution, plus saturation squareness measurements, the interaction strength may be estimated.
An improved inductive coupler for suppressing a shift in the resonance frequency of electron paramagnetic resonance resonators
Authors: Hirata Hiroshi , Walczak Tadeusz , Swartz Harold M.
Published: July 2002

The development of in vivo electron paramagnetic resonance spectrometers has generated a need for a better method of inductive coupling between a microwave resonator and a transmission line. We describe here an approach, based on introducing an additional impedance transformer between a coupling loop and the transmission line. This additional transformer decreases (by a factor of 20) the resonance frequency shift that occurs during adjustment of the coupling. The calculated optimal length is slightly greater than a quarter of the wavelength of the electromagnetic waves. Experimental measurements of the return loss for the matching circuit has shown the validity of the calculations and the usefulness of the proposed theoretical model.
Effect of atomic hydrogen on the acetylene adsorbed Si(100)(2×1) surface
Authors: Chen Yan , Liu Zhaohui , Zhang Qingzhe , Feng Kean , Lin Zhangda
Published: July 2002

High-resolution electron energy loss spectroscopy, low-energy electron diffraction, and quadrupole mass spectrometer have been employed to study the effect of atomic hydrogen on the acetylene saturated preadsorbed Si(100)(2×1) surface at room temperature. It is evident that the atomic hydrogen has a strong effect on the adsorbed C2H2 and the change of the underlying surface structure of Si. The experimental results show that CH and CH2 radicals coexist on the Si surface after the dosing of atomic hydrogen; meanwhile, the surface structure changes from Si(2×1) to a dominant of (1×1). These results indicate that the atomic hydrogen can open C=C double bonds and change them into C–C single bonds, transfer the adsorbed C2H2 to C2Hx(x=3,4) and break the underlying Si–Si dimer, but it cannot break the C–C bond intensively. Some C4 species have been formed during the dosing with atomic hydrogen. It may be the result of atomic hydrogen abstraction from C2Hx which leads to carbon catenation between two adjacent CC dimers. The formed C4 is stable on Si(100) surfaces up to 1100 K and can be expected to host diamond nucleation.
New grating fabrication technology for optoelectronic devices: Cascaded self-induced holography
Authors: Lin C. H. , Zhu Z. H. , Lo Y. H.
Published: July 2002

A method of fabricating submicron gratings for optoelectronic devices from a glass mask was proposed and demonstrated. The glass mask has gratings on both sides with a period of at least four times of the final feature size. By modifying the grating periods on the mask, one can achieve multiple-period gratings with a very fine period spacing for advanced wavelength division multiplexing (WDM) devices. In this letter, we demonstrated 0.5 μm second-order gratings for 1.55 μm distributed-feedback lasers and gratings with a 6 Å period difference for WDM laser arrays using only optical sources.
Nonlinear response of type II superconductors: A new method of measuring the pressure dependence of the transition temperature Tc(P)
Authors: Raphael M. P. , Reeves M. E. , Skelton E. F.
Published: July 2002

A technique of measuring Tc(P) in the diamond anvil cell by the third harmonic of the ac susceptibility (V3f) is described. It requires no background subtraction and allows the use of gasket materials made from hardened steels. In addition, the observed peak structure in the V3f vs T data allows regions with different critical temperatures to be distinguished. Results for single crystals (with typical size, 0.25 mm×0.25 mm×0.1 mm) of the Tl2Ba2CuO6+δ and YBa2Cu3O7−δ systems are presented. The effects of sample inhomogeneities and nonhydrostatic conditions are discussed.
Time and frequency-resolved photoluminescence up conversion using broadly tuneable picosecond infrared pulses
Authors: Poole P. J. , Hong J. , Stolow Albert , Charbonneau S.
Published: July 2002

A simultaneous time and frequency-resolved photoluminescence setup based upon the concept of sum-frequency generation has been developed using the parallel collection capabilities of a liquid nitrogen cooled, high quantum efficiency charge coupled device (CCD) detector. This up conversion system can provide excellent time resolution (down to ∼100 fs), when the detector is used in the single channel mode, with large dynamic range. When the CCD detector is used in its full capacity (1024 channels), wide spectral range as well as temporal information are obtained simultaneously from the up-converted signal, thus providing important information on the dynamics of various emission peaks which can occur simultaneously. Together with this, an efficient method for generation of high repetition rate, low energy infrared light between 1.44 and 1.62 μm is described. The technique uses difference frequency mixing of the fundamental wavelength of a mode-locked Nd:yttrium aluminum garnet laser and the output of a synchronously pumped Rhodamine 640 dye laser in a 10 mm long lithium triborate crystal. This source was then used to performed cw and time-resolved up-conversion photoluminescence measurements on a 1.54 μm emitting InGaAsP epitaxial layer.
A resonance shear force rheometer modeled as simple oscillating circuit
Authors: Dushkin Ceco D. , Kurihara Kazue
Published: July 2002

A novel resonance method for studying the viscoelasticity of very thin liquid films and elastic materials is developed using a shear force apparatus. The shear stress created by an oscillating piezo unit attached to leaf springs is recorded as the lateral displacement by capacitance probe. The oscillation frequency is varied around the resonance frequency of the mechanical system in order to trace the amplitude and the phase of the resonance peak. Two reference states are obtained: the resonance of free oscillations in air and one under constrain introduced by the cantilever spring in contact with the shear mechanical unit. The presence of a liquid film changes these resonance states depending on the film thickness and the cantilever load. A simple mechanical model is proposed entrapping the contribution of different parts in effective spring, mass, and damping constants. The model separates the effect of the liquid film from the background oscillation of the mechanical parts. The method is applied here to investigate the elastic contact between two solid surfaces.
Electrically induced thermal transient experiments for thermal diffusivity measurements on chemical vapor deposited diamond films
Authors: Wörner E. , Wild C. , Müller-Sebert W. , Füner M. , Jehle M. , Koidl P.
Published: July 2002

To investigate the in plane thermal diffusivity of chemical vapor deposited diamond layers, two new techniques were developed based on electrically induced converging and linear thermal waves. With these methods, free-standing, laser-cut diamond samples, 100 μm or larger in thickness can be analyzed. Laser cutting leaves a graphitic surface layer along the cutting edge. Therefore, a short high voltage pulse, applied at the graphitic rim resistor, is used to generate a thermal transient. The propagation of the wave is measured optically either in the center of the circular disk or at one side of a bar shaped sample. Both techniques require only very little sample preparation. They are shown to be simple, accurate, and independent of sample thickness and induced energy. In order to analyze the experimental data we present both an analytical model and a numerical simulation.
Calorimetric method for adjusting the mass of culture fluid in a bioreactor
Authors: Kotelnikov G. V. , Moiseyeva S. P. , Krayev V. P.
Published: July 2002

A new calorimetric method for adjusting the mass of culture fluid in a bioreactor and the results of its experimental testing are described. The method is based on constant heat capacity of liquids in the presence of disturbing factors accompanying biotechnology processes. A new measuring parameter independent of thermal noise induced by the stirrer, the flow of fluids, chemical and physical interactions of substances in the bioreactor was used for adjusting the mass of culture fluid. This parameter is Ph, the power increment in the heater under steady-state conditions of heating the bioreactor. The scanning calorimetry principle was used to make the measurements. It was shown that it is necessary to provide a constant heating rate V for the bioreactor and a high-speed response of the automated control system (ACS) for bioreactor temperature. The ACS developed on the base of the dynamic error and transient response h(t) calculated by the inverse Laplace transform with the use of the closed-loop transfer function gives V=const and the control time of about several seconds. The experimental data reported show the adjustment of the mass of culture fluid in a 3 l bioreactor with an error of no more than 10 g. This enables an accurate evaluation of the biomass amount in the bioreactor, specific growth rate, and other growth parameters determined using specific growth rate.
Quasioptical antennas for fundamental and second harmonic gyrotrons
Authors: Timms G. P. , Brand G. F.
Published: July 2002

Gyrotron V, the latest University of Sydney gyrotron, is a source of millimeter waves tunable from 150 to 300 GHz when operating at the fundamental of the electron cyclotron frequency and from 300 to 600 GHz when operating at the second harmonic. Quasioptical antennas are used to direct this radiation into an oversized waveguide leading to the experiment area. In this article, the performance of these antennas and coupling of radiation into the oversized waveguide are analyzed. Of special interest is a variety of quasioptical antenna employing a parabolic blazed grating which proves to be very effective in separating second harmonic radiation from fundamental.
Precise and accurate measurement of ac signals by high precision-type digital multimeter HP3458A
Authors: Ueda R. , Kazihara K. , Takajo H.
Published: July 2002

The HP3458A has been well known as a high precision-type digital multimeter (DMM). However, when trying to identify any infinitesimally small ac signals as effective values, the existence of large residual noise appearing at the output reading when input signals to be measured are zero impedes the achievement of high precision to its full capability. This article shows that the greater part of the residual noise is produced as electronic noise from within the DMM and presents a trial of achieving high precision measurement by introducing a concept of noise decoupling. An equivalent zero noise state is searched for on one of the decoupled components by attaching an additional circuit in parallel and/or antiparallel to the input terminals and is found to be attainable with respect to the attached circuit. Consequently, possibilities of providing the full resolution to its capability and serving high precision measurement are discussed.
A two-dimensional Couette viscometer for Langmuir monolayers
Authors: Ghaskadvi R. S. , Dennin Michael
Published: July 2002

We have developed an apparatus that is capable of simultaneously measuring the viscosity of Langmuir monolayers and visualizing their flow. It consists of a circular trough with a nearly circular elastic barrier that can be rotated to generate two-dimensional Couette flow. The “inner cylinder” is a Teflon knife-edge disk that is hung by a thin wire. The torque on the inner cylinder is determined by measuring the angular displacement of the disk. A stepper motor controls the barrier rotation. Viscosity can be measured in two different ways: by oscillating the torsion pendulum and by generating Couette flow. The dynamic viscosity range of the apparatus is 10−4<η<103 g/s. Typical shear rates range from 10−4 to 101 s−1. A Brewster angle microscope is mounted on the apparatus. This is used to study various properties of the monolayer such as: velocity profiles, domain shape during shear, domain relaxation after shear, and size distribution of domains.
Neutron monitor using microfission chambers for the International Thermonuclear Experimental Reactor
Authors: Nishitani T. , Kasai S. , Johnson L. C. , Ebisawa K. , Walker C. , Ando T.
Published: July 2002

We are designing microfission chambers, which are pencil size gas counters with fissile material inside, to be installed in the vacuum vessel as neutron flux monitors for the International Thermonuclear Experimental Reactor (ITER). We computed the neutron and gamma flux around the shielding blanket by a two-dimensional neutron calculation, in order to find suitable locations for microfission chambers. We found that the U238 microfission chambers are not suitable because the detection efficiency will increase up to 50% during the ITER lifetime by breeding U239. We propose to install U235 microfission chambers on the front side of the back plate in the gap between adjacent blanket modules and behind the blankets at ten poloidal locations. One chamber will be installed in the divertor cassette, just under the dome. Employing both the pulse counting mode and Campbelling mode in the electronics, we can accomplish the ITER requirement of 107 dynamic range, with 1 ms temporal resolution, and eliminate the effect of gamma rays. An in-vessel neutron monitor will be affected by changes of the detection efficiency due to the change in the plasma position and neutron source profile. Here we demonstrate by neutron Monte Carlo calculation with three-dimensional modeling that we avoid those detection efficiency changes by installing microfission chambers at several poloidal locations inside the vacuum vessel.
On the mechanism of contamination of diagnostic windows in fusion devices
Authors: Voitsenya V. S.
Published: July 2002

The sputtering by charge exchange (CX) atoms off the diagnostic duct wall was suggested as the mechanism of deposit growth on diagnostic windows of fusion devices, or on the “first mirrors” in ITER. The rate of deposit growth was estimated as a balance between the deposition rate of wall material, D, and sputtering of the deposit already existing, S. For estimation, the dependencies of the sputtering yield on the projectile energy and incidence angle were used. It was found that the duct length to its diameter ratio, L/d, is an important parameter for deposit growth. The D value exceeds several times S value if L/d>2, but D/S is less than one in the case of a short duct, L/d≪1, and also in the case of the very long duct, L/d⩾10. Based on such a mechanism, a duct structure with diaphragms made of refractory metal was proposed to decrease significantly the rate of deposit growth.
Measurement of the deuterium/tritium fuel mixture in magnetic confinement fusion plasmas by Doppler-free two-photon spectroscopy
Authors: Voslamber D. , Seidel J.
Published: July 2002

Doppler-free two-photon excitation of fluorescence may be used to measure the deuterium/tritium fuel mix in magnetic confinement fusion plasmas. Two atomic transition schemes of the hydrogen isotopes come into question for this purpose: (I) excitation of the first excited energy level (n=2) and observation of Lyman-α, (II) excitation of the second excited energy level (n=3) and observation of Balmer-α. Comparison of the two schemes indicates that both may have their merits in particular situations. Due to lack of information about the future laser characteristics achievable for scheme II, the detailed performance of this scheme cannot yet be definitely assessed.
Evanescent microwave probes on high-resistivity silicon and its application in characterization of semiconductors
Authors: Tabib-Azar M. , Akinwande D. , Ponchak G. E. , LeClair S. R.
Published: July 2002

In this article we report the design, fabrication, and characterization of very high quality factor 10 GHz microstrip resonators on high-resistivity (high-ρ) silicon substrates. Our experiments show that an external quality factor of over 13 000 can be achieved on microstripline resonators on high-ρ silicon substrates. Such a high Q factor enables integration of arrays of previously reported evanescent microwave probe (EMP) on silicon cantilever beams. We also demonstrate that electron–hole pair recombination and generation lifetimes of silicon can be conveniently measured by illuminating the resonator using a pulsed light. Alternatively, the EMP was also used to nondestructively monitor excess carrier generation and recombination process in a semiconductor placed near the two-dimensional resonator.
Compensation electronics for larger dynamic range of a SQUID based nondestructive evaluation system
Authors: Kreutzbruck M. v. , Theiss A. , Mück M. , Heiden C.
Published: July 2002

We have developed a compensation system for any given SQUID sensor which allows sensitive eddy current measurements above 100 Hz in the presence of strong and slowly varying background fields. High Tc SQUIDs have been used successfully in nondestructive evaluation (NDE) systems based on eddy current excitation when searching for defects in conductive samples such as aircraft parts. Due to their high and frequency independent field resolution and their excellent spatial resolution, SQUIDs provide in the case of deep lying defects—compared to other conventional electromagnetic NDE systems—a more reliable crack detection. Fast readout electronics having an unsurpassed dynamic range of up to eight orders of magnitude enabled us to perform measurements in an environment polluted with electromagnetic noise, e.g., an aircraft hangar. Nevertheless, test objects containing ferromagnetic structures with a high remanent magnetization, such as aircraft wheels or steel bolts in an aircraft wing, very often cause instabilities of the flux-locked loop operation of the SQUID. To prevent unlocking, we have developed a new background field compensation scheme. Special compensation electronics take care of slowly varying magnetic fields of up to 1 mT/s and allow us to perform eddy current measurements in the presence of slow (<30 Hz) background field variations of up to 5 mT.
Characterization of electrochemically etched tungsten tips for scanning tunneling microscopy
Authors: Müller A.-D. , Müller F. , Hietschold M. , Demming F. , Jersch J. , Dickmann K.
Published: July 2002

Shape and composition of electrochemically etched tungsten tips for use in scanning tunneling microscopy (STM) were investigated in a transmission electron microscope (TEM) with a Gathan imaging filter (GIP). The tips are prepared by a lamella drop-off technique. We observe typical tip radii of less than 10 nm. After a storage of some days under ambient conditions, an amorphous oxide film is detectable. The electron energy-loss spectroscopy confirms that the surface is contaminated by compounds that contain carbon, too.
Pulsed field ionization-photoion spectroscopy using two-bunch synchrotron radiation: Time-of-flight selection scheme
Authors: Jarvis G. K. , Shiell R. C. , Hepburn J. W. , Song Y. , Ng C. Y.
Published: July 2002

We have demonstrated that the time-of-flight (TOF) selection method for pulsed field ionization (PFI) photoelectron detection [Jarvis et al., Rev. Sci. Instrum. 70, 2615 (1999)] can also be applied for the detection of PFI-photoions (PFI-PIs) using the two-bunch synchrotron radiation at the Advanced Light Source. By employing the supersonic beam technique to lower the translational temperature of the sample gas, we show that background prompt ions formed in direct and spontaneous autoionization processes arrive at the ion detector in a pattern similar to that of the vacuum ultraviolet light bunches. The PFI-PIs formed at dark gaps can be designed to arrive at the detector in between adjacent prompt ion peaks, enabling the gating of the PFI-PI signal with only minor contamination from background prompt ions. This experiment has revealed important considerations for the design of a general TOF selection scheme for PFI-PI detection using synchrotron radiation.
Development of a high precision quadrupole mass filter using the zero-method control circuit
Authors: Tsukakoshi O. , Hayashi T. , Yamamuro K. , Nakamura M.
Published: July 2002

A high precision quadrupole mass filter has been developed using the zero-method control circuit. With this method, peak values of a control voltage are compared with a high-precision reference voltage and detected by a diode and signal-producing resistance connected in series. The dc component of the signal is selectively amplified and fed back to a module in the amplifying system of the rf voltage so as to minimize the voltage in excess of the reference voltage. An instrument has been constructed and the doublet of He+4–D2+ has been successfully separated.
Characterization of SrS evaporated materials grown from a new high temperature source with a carbon heater
Authors: Isai Masaaki , Fukui Kousuke , Higo Kazunaga , Fujiyasu Hiroshi
Published: July 2002

Strontium sulfide (SrS) was used as the evaporant material to prepare the phosphor layer for a blue electroluminescent (EL) element. SrS evaporation was performed by using a resistively heated carbon heater. No heat treatment of the phosphor layer after deposition was made. A crucible temperature of more than 1400 °C was obtained in this evaporation system which makes this system equally applicable for the evaporation of other materials with high melting temperature. Cerium (Ce) luminescent centers were doped in SrS films and a Ce concentration of 0.3 mol % was determined to be optimum for EL. For SrS:Ce films deposited onto a quartz substrate, x-ray diffraction and photoluminescent measurements indicated an optimum substrate temperature (Tsub) of 500 °C. In the EL fabrication process, Tsub was restricted to ≦410 °C by the softening temperature of the alumino-silicate substrate used in the EL device.
Development of a compact, handheld Raman instrument with no moving parts for use in field analysis
Authors: Cullum Brian M. , Mobley Joel , Chi Zhenhuan , Stokes David L. , Miller Gordon H. , Vo-Dinh Tuan
Published: July 2002

This article describes a lightweight, self-contained, field portable Raman instrument that has been developed for rapid on-site determination of primary mixture components. The instrument consists of a helium neon (HeNe) laser for excitation, an acousto-optic tunable filter (AOTF) for wavelength discrimination, and an avalanche photodiode for detection. The AOTF is the primary component of this system and has been selected based on its spectral range (600–900 nm) along with its high resolution, ∼7.5 cm−1. Labview™ based software for controlling the AOTF frequency and the signal acquisition has also been developed. Several different samples were analyzed (both solids and liquids) using this instrument for the evaluation of parameters such as spectral resolution, sensitivity, and data acquisition speed for certain environmentally important compounds. The results from these measurements are compared with those using a conventional laboratory Raman system consisting of a grating-based spectrograph and a charge-coupled device.
A new method to measure the oscillation of a cylindrical cantilever: “The laser reflection detection system”
Authors: Antognozzi M. , Haschke H. , Miles M. J.
Published: July 2002

A new optical detection system for measuring the oscillation of cylindrical cantilevers has been designed. A laser beam is directed perpendicularly to the oscillating plane and is focused on the curved surface of the vibrating probe. The surface reflects the light and a second lens refocuses it onto a two-segment photodiode. The sensitivity of this method lies in the fact that a small displacement of the probe produces a large angular deflection of the reflected laser. Applications of this new system are presented in order to demonstrate its reliability, accuracy, sensitivity, and the possible use in a shear force microscope. All the results are finally analyzed by modeling the motion of the cantilevers using harmonic oscillator theory and the continuous model for oscillating bars. The agreement between experimental data and models is well inside the experimental errors confirming the possibility of using this system to accurately study the dynamics of cylindrical cantilevers.
A picoampere current generator for membrane electroporation
Authors: Pescio E. , Ridi A. , Gliozzi A.
Published: July 2002

Electroporation is the electric-field induced formation of a voltage-dependent population of hydrophilic pores within a bilayer lipid membrane (BLM). This phenomenon can be observed as a transient increase in membrane conductance after the application of a voltage jump above a certain threshold. A very low current source is required to measure voltage fluctuations of a BLM due to voltage induced creation of dynamical pores during the electroporation. A current source able to drive a high-resistive load (on the order of 1012 Ω) by a constant current of 10 pA has been designed and realized. The current is maintained constant, with an uncertainty of 1.2% even when the resistive load fluctuates to 109 Ω over a very brief interval (10−3 s). These peculiar features have been obtained by designing a very simple circuit configuration, that gives an excellent match between the planned and the experimental behavior. The circuit bandwidth and the current precision are not the result of the circuit configuration, but are only limited by active components.
Design and development of a phase sensitive detector for a microwave receiver
Authors: Raina M. K. , Raina Sushil
Published: July 2002

A phase sensitive detector employed in microwave/mm wave radiometric systems measures an output as a pure dc, proportional to the difference between the phase of the input modulated signal and a reference signal. This difference signal takes the form of a square wave, one level corresponding to a constant blackbody temperature and the other to the incoming radiation, cancelling the inherent noise of the receiver, thereby achieving a high degree of stability of the radiometer. A phase sensitive (or a synchronous) detector was designed and fabricated to be used in the microwave receiver. The phase sensitive detector was fabricated for a minimum reference signal of 3 V square wave and a minimum signal input of 75 mV with an integration time of 6 s.
Sampling of the path difference in asymmetric white-light interferometry by means of ultraviolet HeCd-laser radiation
Authors: Hohm Uwe , Loose Achim
Published: July 2002

HeCd-laser radiation at a vacuum wavelength of 325.13 nm is used for sampling the path difference between the two arms of a Michelson interferometer. This allows for a simpler and more effective determination of the wavelength dependence of the refractive index n(λ) of gases in the visible and near ultraviolet by means of asymmetric white-light interferometry. Examples of n(λ) are given for gaseous P4 and I2 in the visible wavelength range.
Photoacoustic imaging of voids in direct wafer bonding
Authors: Gracias A. C. , Kuranaga C. , Senna J. R. , Silva M. D.
Published: July 2002

We demonstrate photoacoustic thermal imaging of the voids occurring at the interface of directly bonded silicon wafers. The wafers are not touched by probes, minimizing wafer contamination, and the technique does not require the outer surfaces of the bonded wafers to be polished. The method is effective for infrared-opaque materials, as demonstrated by coating a silicon bonded pair with bismuth and obtaining an improvement in the contrast.
A capacitive transducer for monitoring tridimensional submicrometric displacements
Authors: Cabiati Franco , Giaretto Valter , Miraldi Elio
Published: July 2002

A new three-in-one capacitive transducer that operates with three transformer bridges at separate frequencies is here described. Three plane capacitors result from the placing of a triangular right pyramid (the moveable element, being fixed to the point to be monitored) to face a reentrant right triangular pyramid which was carved into one of the bases of a triangular prism (the fixed element). Three out-of-balance signals result when the moveable element moves from the zero position, where each variable capacitance equals the corresponding reference one. The three differences between the currents that flow through each series of capacitances are summed up in one shielded output cable. One transconductance preamplifier converts the current signals into three superimposed voltage signals. By selecting the reference frequency to be sent to a lock-in amplifier, one can monitor the movement of the selected face of the moveable element, that is, by choosing one of the three bridge frequencies in sequence one obtains the three Cartesian components of the vectorial displacement that the moveable element has undergone. The use of glass–ceramic material with a negligible thermal expansion coefficient and the integration of reference capacitors in the body of the transducer, allow this transducer to operate within fairly large ranges of temperature and humidity. The use of a current detector with low input impedance allows this transducer to be connected to the bridges and to the preamplifier with some meters of coaxial cables, without any appreciable effects on the sensitivity. The various noise and uncertainty sources are also here discussed. A ≈40 nm uncertainty with displacements in the ±12 μm range has been obtained in a thermal test that was carried out using four transducers applied to a cylindrical aluminum sample.
Optical heterodyne detection of 60 GHz electro-optic modulation from polymer waveguide modulators
Authors: Wang Wenshen , Chen Datong , Fetterman Harold R. , Shi Yongqiang , Steier William H. , Dalton Larry R. , Chow Pei-Ming D.
Published: July 2002

An optical heterodyne technique has been used to demonstrate electro-optic modulation up to 60 GHz, the highest reported to date, in polymer waveguide modulators. The frequency response of the device from 40 to 60 GHz was obtained by measuring the frequency down converted modulation signal with a low frequency photodetector. No rolling-off was identifiable from the measured device response, indicating no fundamental material limitations in this frequency range for the polymer material which we used. Such an optical heterdyne system can be a powerful tool for modulator characterization at millimeter wave frequencies because of its high sensitivity and low frequency demands on photoreceivers.
Efficient multichannel Thomson scattering measurement system for diagnostics of low-temperature plasmas
Authors: Kono A. , Nakatani K.
Published: July 2002

An efficient multichannel Thomson scattering measurement system for measuring the electron energy distribution function in low-temperature processing plasmas was constructed. It consists of a specially designed triple-grating spectrometer, equipped with a spatial filter for eliminating the interference due to Rayleigh scattering, and an image-intensified charge-coupled-device (ICCD) camera working in the photon counting mode. The spectrometer produces a dispersed Thomson spectrum with the Rayleigh interference highly suppressed, thereby enabling us to operate the ICCD camera in the photon-counting mode giving a high signal-to-noise ratio; the measured Rayleigh light suppression ratio was ∼10−6 at the center wavelength. Proper operation of the system was demonstrated in the measurements for a low-pressure (20–100 mTorr) inductively coupled Ar plasma.
Thin films of CoAs from low-temperature metalorganic chemical vapor deposition of a novel single-source precursor compound
Authors: Klingan Franz-Robert , Miehr Alexander , Fischer Roland A. , Herrmann Wolfgang A.
Published: July 2002

A new structurally defined precursor compound for the low-temperature metalorganic chemical vapor deposition (MOCVD) of CoAs thin films is reported. The easily accessible 1,3-bis(tert-butyl)-2-[tetracarbonyl-cobalt(-l)]-1,3,2-diazarsolidine was decomposed by hot-wall low pressure CVD. Thin films of cobalt arsenide with retention of the stoichiometry of the precursor (Co:As=1/1) were formed at temperatures as low as 210 °C. Electron micrographs show uniform films, energy dispersive x-ray spectroscopy, and Auger electron spectroscopy confirm their bulk composition, and powder diffraction patterns and conductivity measurements prove their crystallinity and electrical properties.
Electronic density of state at metal/polyimide Langmuir-Blodgett film interface
Authors: Itoh Eiji , Iwamoto Mitsumasa
Published: July 2002

Surface potentials of heat-treated polyimide Langmuir-Blodgett (PI LB) films deposited on Au, Cr and Al electrodes were measured in a dark vacuum vessel at room temperature as a function of the number of deposited layers. The potential depended on the thickness of PI LB films and the work function of base electrode. The spatial charge distribution in PI LB films on various electrodes was determined from the relationship between the surface potential and the number of deposited layers. Based on this result, distribution of the density of electronic state in PI LB films was determined. It was experimentally shown that the electrostatic phenomena in PI LB films at the metal/film interface were explained with taking into consideration of surface states which exist within the range of ∼1 nm from the interface and molecular-ion states which exist in the entire range.