bluuebunny/crossref_metadata_2025 huggingface dataset:
An integrated scanning tunneling, atomic force and lateral force microscope
Authors: Wenzler L. A. , Han T. , Bryner R. S. , Beebe T. P.
Published: July 2002

We describe the design and operation of a combined scanning tunneling–atomic force–lateral force microscope [(STM), (AFM), (LFM)]. Including these capabilities in a single instrument reduces construction costs and increases flexibility. AFM and LFM may be performed simultaneously; a simple reconfiguration (requiring removing the AFM/LFM cantilever holder and replacing with a STM tip) changes the instrument into a STM. We present atomic forces depicted in force-to-distance curves and experimental imaging applications with all three techniques.
Metal vapor vacuum arc ion source research at Ansto
Authors: Evans P. J. , Watt G. C. , Noorman J. T.
Published: July 2002

Following the pioneering work on metal vapor vacuum arc (MEVVA) ion sources at Lawrence Berkeley Laboratory by Brown and co-workers, the Australian Nuclear Science and Technology Organization (Ansto) commenced a program of research aimed at constructing a MEVVA based ion implanter. This phase of the program has been completed and the system is now in routine use for surface modification studies. The purpose of the present article is to give an overview of the Ansto implanter with particular reference to those features, such as triggering reliability, which entailed some developmental work. Finally, current ion implantation research activities on this system are briefly described.
Development of TAMEK and other vacuum arc ion sources
Authors: Tolopa Alexander M.
Published: July 2002

This article briefly summarizes the work of the author in the field of vacuum arc ion sources from the first version made in 1984, which generated metal ion beams of 20 cm diam with ion current up to 1 A at an accelerating voltage up to 130 kV, pulse duration of 300 μs, and repetition rate up to 50 Hz, for doing high dose implantation, to the creation in 1987 of the Technological Accelerator of Metal ions and Electron Kit (TAMEK) source which can produce, without switching off the source, the regimes of high-dose implantation, ion deposition, ion-beam mixing, and ion-beam-assisted deposition of the same metal ions, as well as the generation of electron beams with the same time and energy parameters and current up to 10 A. Sources with a vacuum arc current of several amperes (Iarc≳2 A, Ii≳0.1 A for a copper cathode) and milliseconds duration, and with a vacuum arc current up to 100 kA (Ii=1–10 kA) and microseconds duration, are described. Application of TAMEK sources for improving the properties of surface layers of metal and dielectric materials are also discussed.
A digital device for measuring high-order structure functions
Authors: Herweijer J. A. , Nijmweegen F. C. van , Kopinga K. , Voskamp J. H. , Water W. van de
Published: July 2002

We describe a prototype digital device for measuring high-order structure functions in turbulence. Because the structure function is a special case of the correlation function, the device may find usage outside the study of turbulence. The device operates at 20 kHz on 12-bits data and updates probability distribution functions of signal differences for 64 arbitrarily chosen time delays in real time.
Shape of the cantilever deflection for the atomic force microscope in force curve measurements
Authors: Sasaki Minoru , Hane Kazuhiro , Okuma Shigeru , Bessho Yoshinori
Published: July 2002

The lateral force induces a torsional motion in the cantilever for an atomic force microscope. This phenomenon affects not only the surface image but also the force curve. The two-dimensional deflections of the cantilever under several force curve measurement conditions are investigated using the heterodyne interferometer. In most cases, the deflection agrees well with that obtained theoretically from linear static analysis. At some points on a rough sample surface, undesirable behaviors are seen in both force curve and two-dimensional deflection of the cantilever. The relation between the force curve and the deflection of the cantilever is investigated in detail experimentally and theoretically.
Nuclear quadrupole resonance gaussometry of low magnetic fields
Authors: Jung Jae Kap , Han Kee Tae , Choh Sung Ho , Kim Chang Suk
Published: July 2002

A new method of measuring low magnetic fields accurately by employing a nuclear quadrupole resonance (NQR) technique in which a hexamethylene–tetramine [(CH2)6N4] crystal is used as the detector is proposed here. By applying the magnetic field (B0) along the Z axis of the electric field gradient tensor at 14N in this crystal (η=0), one 14N NQR line (ν0) splits into two lines (ν+ and ν−). The difference of these two lines (δν=ν+−ν−) is proportional to the applied low magnetic field. Consequently, the magnetic field can be measured with this frequency difference in terms of the nuclear magnetic moment of the 14N nucleus. The accuracy, advantages, and limitations of this technique are discussed.
Increased ion intensity and reliability of the Stockholm electron beam ion sourcea)
Authors: Beebe E. , Liljeby L. , Pikin A. , Björkhage M. , Engström Å. , Paal A.
Published: July 2002

The electron beam ion source, CRYSIS, produces highly charged ions for injection into the heavy ion storage ring—CRYRING at MSL, as well as low energy atomic physics experiments and the Stockholm–Mainz Penning trap recently installed at MSL. CRYSIS has produced ions up to Ar18+ and 136Xe52+. Pulsed beams of Ar13+ ions 60 μs in duration have been injected into CRYRING via an RFQ and ions of charge up to 136Xe44+ have been used in atomic physics experiments with pulse duration 10–250 ms. A vacuum separation of the cryostat and ionization volumes has been made. Temperature control and measurement of internal electrodes have increased the gas injection efficiency and reduced the memory effect associated with a cryogenic EBIS. External ion injection has been added as an alternative to neutral gas injection for introducing the species to be ionized to high charge states. Monitoring of the radio frequency noise signal with a spectrum analyzer has aided in the propagation of quiet, high current (450 mA) dc electron beams. These quiet electron beams have been used to produce extracted ion pulses of higher intensities than in previous operation.
Ion sources for induction linac driven heavy ion fusiona)
Authors: Rutkowski H. L. , Eylon S. , Chupp W. W.
Published: July 2002

The use of ion sources in induction linacs for heavy ion fusion is fundamentally different from their use in the rf linac-storage rings approach. Induction linacs require very high current, short pulse extraction usually with large apertures which are dictated by the injector design. One is faced with the problem of extracting beams in a pulsed fashion while maintaining high beam quality during the pulse (low emittance). Four types of sources have been studied for this application. The vacuum arc and the rf cusp field source are the plasma-types and the porous plug and hot alumino–silicate surface source are the thermal types. The hot alumino–silicate potassium source has proved to be the best candidate for the next generation of scaled experiments. The porous plug for potassium is somewhat more difficult to use. The vacuum arc suffers from noise and lifetime problems and the rf cusp field source is difficult to use with very short pulses. Operational experience with all of these types of sources is presented.
H− beam based projection microlithography: A conceptual study of the beam parametersa)
Authors: Guharay S. K. , Reiser M. , Dudnikov V. G.
Published: July 2002

The current trends of research and development work in ion-beam microlithography are examined with particular emphasis on the choice of ion sources and the beam parameters. The common approach with duoplasmatron-type ion sources for projection ion-beam lithography is revisited, and the suitability of H− beams is examined. The beam brightness and energy spread, which constitute the figure of merit of a beam, appear to be better in the case of H− beams. From a surface plasma source type discharge operating under stable condition, H− beams with an emission current density of ∼1–5 A/cm2 and a normalized brightness of ∼7×1012 A/(m rad)2 can be extracted. Several key issues of an ion-projection lithography device, such as the ion source parameters, beam optics, and thermal load are discussed.
Modeling the electromagnetic excitation of a compact ECR ion/free radical sourcea)
Authors: Grotjohn T. A. , Tan W. , Gopinath V. , Srivastava A. K. , Asmussen J.
Published: July 2002

The electromagnetic excitation of a discharge inside a microwave plasma source has been numerically modeled in the time domain. The source is a cylindrical, single-mode microwave-excited cavity. The time-varying electromagnetic fields inside the resonant cavity, both inside and outside the discharge region, are obtained by applying a finite-difference time-domain method to solve Maxwell’s equations. The electromagnetic properties of the discharge load are described using a conductivity model. The spatial electric field patterns, natural frequencies, stored energy, and quality factor of a plasma-loaded, microwave-resonant cavity are simulated. Additionally, the simulated results for a simplified plasma source structure are compared to a known analytical solution to verify the simulation technique.
Investigations of polarization profiles in multilayer systems by using the laser intensity modulation method
Authors: Bloß Peter , Schäfer Hartmut
Published: July 2002

The laser intensity modulation method (LIMM), developed by Lang in the early eighties, is a useful technique for determining the spatial polarization and/or space charge distributions in pyroelectric and/or piezoelectric materials, for instance in thin polymer electret films. The advantage of the LIMM is the high spatial resolution near the irradiated side. Therefore, we introduced the logarithmic spatial grid distribution into the deconvolution process. For the first time the self-consistency method developed by Honerkamp and Weese is applied to the deconvolution program with respect to LIMM. Using multilayer systems with known spatial distributions our new equipment is tested with regard to providing reasonable results as well as the deconvolution program to represent the known spatial distributions.
Design parameters of dual-stage ion reflectrons
Authors: Wang Tzyy-Ing , Chu Chun-Wen , Hung Hui-Ming , Kuo Gen-Sen , Han Chau-Chung
Published: July 2002

Exact solutions of the second-order differential equation describing the energy dependence of ion flight time in a reflectron time-of-flight mass spectrometer are derived, from which numerical evaluation of the construction and operation parameters of a dual-stage reflectron can easily be performed. Considerations in choosing the design parameters are discussed.
Band diagram of the polycrystalline CdS/Cu(In,Ga)Se2 heterojunction
Authors: Kronik L. , Burstein L. , Leibovitch M. , Shapira Yoram , Gal D. , Moons E. , Beier J. , Hodes G. , Cahen David , Hariskos D. , Klenk R. , Schock H.-W.
Published: July 2002

Contact potential difference measurements in the dark and under illumination are used to derive the conduction band offset (ΔEc) in a solar cell quality junction formed by chemical bath deposition of CdS on a polycrystalline thin film of Cu(In,Ga)Se2. Our experimental measurements and the estimates made for dipole contributions show that the junction is of type II, i.e., without a spike in the conduction band ( ΔEc=80 meV±100 meV). This is consistent with the high performance of the actual solar cell. However, it differs from most previous results on junctions based on single crystals and/or vacuum deposited CdS, which indicated the existence of a conduction band spike.
Discharge mechanism of the Kyoto University-type microwave plasma cathode or microwave ion source
Authors: Rao Yusheng , Wu Jiannan , Yan Yuhong , Zhang Yong , Qi Lei
Published: July 2002

In this paper the discharge mechanism of the Kyoto University-type microwave plasma cathode is studied. The relationship between the electron-absorbed power pe and electron impact frequency γc is obtained. When B=875 G, pe decreases with the increment of γc. At the same time when γc→0 or γc≪ω, electron cyclotron resonance (ECR) discharge will be set up. When B≳875 G and γc =107–108 s−1, the off-resonance discharge exists. With γc increased up to a certain limit, it follows that when ωz‖γ=ω=(2×3−1/2)1/2ω, a new type of discharge, the so-called double resonance (DR) discharge, occurs. For the Kyoto University-type MPC or MIS, the off-resonance discharge and DR discharge can be satisfied and it is verified by experiment.
A new device for expansivity measurements of liquids at high temperature and pressure and expansivity data for liquid tin to 1450 °C
Authors: Fiske Peter S. , Stebbins Jonathan F.
Published: July 2002

We have developed a new technique for measuring thermal expansion of liquids at high temperature. Our device, the volumeter, is a volumetric dilatometer which uses liquid tin to transmit volume changes to a series of electrical contacts. Measurements can be carried out from 250 °C to at least 1450 °C irrespective of the viscosity of the sample. In addition, our technique allows for the direct determination of volume changes due to melting and crystallization, as well as the volumetric properties of heterogeneous mixtures of materials. Furthermore, the device is designed to operate inside an internally heated gas-pressured vessel, allowing for the determination of compressibility. We have measured the thermal expansivity of tin from 435 to 1445 °C. Our data match previous measurements using the Archimedean technique to within 4% and shows the volumetric expansivity of tin to have a temperature dependence of −4×10−9 °C−2. Preliminary measurements of the thermal expansivity of a high-viscosity silicate liquid show a wide degree of scatter but fall within previous estimates based on density data. Improved performance of the device may require its operation under pressure.
Response of radio frequency superconducting quantum interference devices to electromagnetic interferencea)
Authors: Mück M. , Dechert J. , Gail J. , Kreutzbruck M. , Schöne S. , Weidl R.
Published: July 2002

A number of applications of high-temperature superconductor radio frequency superconducting quantum interference devices (rf SQUIDs) require a certain immunity of these sensors against electromagnetic interference (EMI). We have investigated effects of electromagnetic radiation in the high-frequency and ultrahigh-frequency range on various types of rf SQUIDs. It has been found that EMI of sufficient field strength reduces the voltage versus flux transfer function, and thus increases the flux noise of the SQUIDs. SQUIDs with a wire wound tank circuit coil have been found to be more sensitive to EMI than SQUIDs integrated into a superconducting microstrip resonator.
Correction of intensity-dependent phase delay in avalanche photodiodes for high-frequency modulation light
Authors: Yokoyama Shuko , Suzuki Norihito , Araki Tsutomu
Published: July 2002

The output characteristics of an avalanche photodiode show an unwanted dependence on incident light intensity. For intensity modulated inputs, the corresponding signal delay in the diode output increases with decrease in the incident intensity. This characteristic leads to errors in distance measurements where the optical modulation method is employed. Such phase delay errors can be corrected by applying an optical dc bias into the modulated optical input. When the bias intensity is adjusted to make the mean diode output current constant at all times, the resultant phase value becomes independent of the intensity of modulated input.
A revised control system for a semi-continuous flowing-solvent liquefaction reactor
Authors: Xu Bin , Dix Malcolm , Kandiyoti Rafael
Published: July 2002

An integrated control and measurement system based on a single host computer (PC) has been constructed for running a semi-continuous flowing-solvent coal liquefaction reactor. The system, composed of a mix of special circuits and commercially available units, provides accurate temperature and flow control, data acquisition, real time display, and safety interlock. The real-time job-conflict problems are solved by using the interrupt concept: the background basic feedback control loop working in external interrupt mode took priority, with a foreground service routine executing more time-consuming tasks, including data recording to disk, and real-time result display on screen. Improved computer reliability, ease of maintenance, increased flexibility in the design of individual experiments, suppression of temperature overshoots and closer control of the solvent flow rate, have all served to improve the quality of data required for evaluating kinetic parameters. The design is readily adaptable to experiments requiring temperature and flow (or other variable) control, data acquisition, real-time results display, and safety interlock (fail-safe) functions.
A closed loop scheme for phase-sensitive fluorometry
Authors: Vadde Venkatesh , Srinivas Vivek
Published: July 2002

A phase-sensitive detection technique for measuring fluorescence lifetime has the advantage that the measurement is independent of the intensity of the detected fluorescence signal which is usually a function of several properties of the sample and the environment. However, lifetime measurements require bulky and expensive instrumentation and are more suited to the laboratory. In this paper we report on a low cost, closed loop scheme applied to a fiber optic oxygen sensor. The sensor has all the advantages of lifetime-based sensors as well as the virtue of being small, compact, robust, and economical.
An inexpensive STM conversion to a BEEM
Authors: Zhang Rong , Stefaniuk Robert , Ivey Douglas G.
Published: July 2002

Ballistic electron emission microscopy (BEEM) is a relatively new technique enabling spectroscopic investigation of subsurface interface structures and electronic properties. BEEM is a direct, nondamaging method with nanometer spatial resolution. In this paper, an inexpensive modification to a conventional scanning tunneling microscope, converting it to a BEEM, is presented. BEEM performance is significantly affected by the preamplifier and the low-pass filter, which is used to improve the signal-to-noise ratio. The system is tested on a thin Au metallization to (100) Si.
Effects of ambient gas in beam drift space on performance of high brightness and low energy ion beam
Authors: Yoshikawa Takafumi , Nakamura Shin , Ueda Yoshio , Nishikawa Masahiro , Goto Seiichi
Published: July 2002

Effects of the ambient gas in the ion drift space on the transport property of the low energy (155 eV) and high brightness beam are studied experimentally. A bucket ion source with single-aperture triode extraction is used. Beam characteristics such as the divergence angle and the current density are improved by the increase in the ambient gas pressure in the high brightness beam (high deceleration voltage, −2000 V), but not in the low brightness beam (low deceleration voltage, −600 V). The beam spreading due to the space charge of the ion beam is seen at the low ambient gas pressure when the central current density, which is measured at 35 cm downstream side from the electrode system, exceeds 5 μA/cm2. The electron density in the ion-beam plasma increases with the ambient gas pressure, but the space charge is not sufficiently neutralized by the electrons produced by the ambient gas atom ionization.
Microsecond time scale thermocouple temperature measurements in solid penetrated by a shaped charge jet
Authors: Gao Juxian , Bai Rongshang
Published: July 2002

The development of microsecond time scale temperature measurements in shock-loaded solids is briefly reviewed. The feasibility of making thermocouple temperature measurements near a cavity created by a shaped charge jet in medium carbon steel and glass fiber reinforced epoxy composite solid targets has been studied. Thermal diffusion calculations demonstrated that these measurements were feasible if the foil thermocouple was on the order of 600 Å thick. Chromel–alumel thermocouples were used because of the anticipated temperature measurement range and also because they have a small pressure correction. The thermocouple fabrication method is discussed in this article. By embedding the thermocouples in the target plates at different distances from the shaped charge generated cavity, temperature distributions were obtained in the steel and composite materials. These temperature distributions were shown to be consistent with temperatures for melting at the cavity in the steel and for epoxy degradation in the composite material.
Fluorescence yield x-ray absorption fine structure measurements in the soft x-ray region
Authors: Kitajima Yoshinori
Published: July 2002

In the soft x-ray region below 3 keV, various electron yield (EY) techniques have been employed in x-ray absorption fine structure (XAFS) measurements of bulk materials. The fluorescent x-ray yield (FY) is also utilized for samples of low concentration. Although FY becomes much smaller for lighter elements, it has several advantages compared with EY to measure XAFS spectra; for example, a higher signal-to-background ratio and applicability to insulating materials. However, it has been thought to be unsuitable for concentrated samples due to a self-absorption effect. In this report, the sampling depth and self-absorption effect for bulk concentrated samples are discussed concerning XAFS measurements in a few keV energy region. Some typical FY XAFS spectra of concentrated materials, including insulators, are presented.
Biological imaging with a new type of soft x-ray microscope
Authors: Hirsch Gregory
Published: July 2002

Imaging of biological specimens using a new type of soft x-ray microscope is described. The instrument is significantly simpler in design than existing x-ray microscopes. The technique used is a variation of the photoelectron-conversion contact method. The instrument is very similar to the field emission microscope in geometry but uses special cone-like hollow emitters instead of solid emitters. Specimens to be examined are placed inside the hollow emitter tips. Soft x rays are beamed down the axis of the hollow cone from the open end, through the specimen, and onto the hemispherical emitter tip membrane. An x-ray contact image is thereby produced on the emitter tip, corresponding to the x-ray absorption of the specimen. Photoelectrons are liberated into the vacuum, outside the emitter tip, in a pattern corresponding to the contact image of the specimen. A high voltage placed on the emitter accelerates the photoelectrons radially to a detector. The result is a magnified, high-resolution, real-time image. Experiments produced images of various dried fungi, bacterial, and mammalian cells with a resolution down to ≊1000 Å.
Apparatus and method for sideband suppression by variable low speed magic-angle-spinning nuclear magnetic resonance experiments
Authors: Bonagamba T. J. , Panepucci H. , Vidoto E. A.
Published: July 2002

We describe a simple method and apparatus to suppress spinning sidebands in low speed magic-angle-spinning nuclear magnetic resonance experiments. The method uses a continuous varying rotor speed and works well even when the highest available spinning speeds cannot clearly resolve the spinning sidebands.
An evaluation of errors in determining the refractive index and thickness of thin SiO2 films using a rotating analyzer ellipsometer
Authors: Kim S. Y. , Irene E. A.
Published: July 2002

Errors are examined in determining the refractive index and thickness of very thin SiO2 films on c-Si substrates as measured with the commonly used rotating analyzer ellipsometer. Systematic errors in the ellipsometric parameters Δ, ψ, δΔ, and δψ are calculated from the experimental hardware errors. Random errors are measured. The propagation of errors from δΔ and δψ to errors in refractive index (n) and film thickness (d), δn and δd, are calculated for oxide thicknesses from 30 to 200 Å. It is verified that the thinner the oxide is and the lower the photon energy where c-Si becomes less absorbing, the larger the errors become. A minimum error of δn and δd is observed at the spectral region of 3.6–4.0 eV and around 5.2 eV. From the reported results for a high precision ellipsometer, judgments are made about the value of the extracted parameters for thin films, and recommendations are offered to minimize the errors.
Electrostatic ion guide using double cylindrical electrode for atmospheric pressure ionization mass spectrometry
Authors: Takada Yasuaki , Sakairi Minoru , Ose Yoichi
Published: July 2002

A novel electrostatic ion focusing lens that consists of two cylindrical electrodes positioned coaxially with each other is described. Square openings are formed in the inner electrode and their angular positions alternate by 90° with respect to the neighboring openings in the axial direction. When a potential difference is applied between the inner and outer electrodes, an electric field penetrates into the interior of the inner electrode through the openings. In the capillary electrophoresis/mass spectrometry analysis of peptides, use of the lens makes it possible to apply a higher voltage to the postacceleration dynode and the signal to background ratio is improved by a factor of 7.
A fully automated precise electrical resistance measurement system
Authors: Marhas Manmeet Kaur , Balakrishnan K. , Ganesan V. , Srinivasan R.
Published: July 2002

A fully automated precise electrical resistance measurement system for more than one sample has been constructed. Conventional four-probe measurements with van der Pauw and Montgomery configurations are possible with this system. Resistance measurements in the range of a few μΩ to a few GΩ are possible for six samples at a time from room temperature down to liquid-helium or liquid-nitrogen temperatures with a temperature control accuracy of better than 10 mK. The design features of the system with special reference to the low-noise switching methods of currents and voltages are described in detail. Precision of the results thus obtained using this system are highlighted for a few superconducting and semiconducting samples.
Limitations of the axial recoil approximation in measurements of molecular dissociation
Authors: Wood R. M. , Zheng Q. , Edwards A. K. , Mangan M. A.
Published: July 2002

The axial recoil approximation holds that when a diatomic molecular ion is formed in a dissociative state, the atoms produced in the dissociation process will move outward along the straight line defined by the internuclear axis of the molecule. Analysis of experiments measuring the angular distribution of Auger electrons emitted by N2 following K-shell ionization of N2 molecules shows that the axial recoil approximation is not strictly true. Significant corrections must be made for the rotation of the molecule during the time of dissociation. Smaller corrections must be made for the thermal distribution of the translational velocities of the target molecules, and for instrumental effects. In the analysis of the N2 data, the corrections have the effect of smoothing the predicted angular distribution functions. The amount of the smoothing depends primarily on the temperature of the target gas and the shape of the potential-energy curve for the N22+ final state involved in the Auger transition.
Transient enhanced diffusion without {311} defects in low energy B+-implanted silicon
Authors: Zhang L. H. , Jones K. S. , Chi P. H. , Simons D. S.
Published: July 2002

Low energy and low dose B+-implanted Si has been studied using transmission electron microscopy (TEM) and secondary ion mass spectrometry (SIMS). Czochralski-grown (100) Si wafers were implanted with 4 keV B+ to a dose of 1×1014/cm2. Subsequently, anneals were performed between 700 and 800 °C for times between 15 s and 8 h in an ambient atmosphere of N2. SIMS results show transient enhanced diffusion (TED) of the boron that saturates in less than 15 min for all annealing temperatures studied. TED results in an increase in the junction depth by at least 60 nm at a 1×1016/cm3 concentration. TEM studies show that, even for the shortest times before TED is observed, {311} defects are not detected. These results imply that there may be more than one source of interstitials for TED.
Multichannel electron cyclotron emission radiometry for magnetohydrodynamic mode studies in TEXTOR
Authors: Waidmann G. , de Vries P. C. , Krämer-Flecken A. , Eulenberg H. P. , Huxhagen K.
Published: July 2002

Localized magnetohydrodynamic modes occur frequently as precursors to dangerous plasma disruptions in tokamaks. Fast electron cyclotron emission (ECE) radiometry permits a space-resolved study of the dynamic behavior of these instabilities. Two types of multichannel, heterodyne ECE systems working on TEXTOR are briefly described. Temperature profile perturbations caused by tearing modes are shown. Typical Te fluctuations generated by rotating magnetic islands are presented. An early disruption warning system was built and tested on TEXTOR discharges. A real-time cross correlation calculation of two ECE signals is used to identify an m=2 mode. An analog alarm signal is generated then early during the instability evolution. An experimental test result is presented from a beam-heated tokamak plasma.
Ultrahigh speed imaging system for the measurement of solidification velocity via direct observation of rapid solidification
Authors: Bassler B. Timothy , Brunner Russell S. , Hofmeister William H. , Bayuzick Robert J.
Published: July 2002

An ultrahigh speed imaging system has been developed and built to image rapid solidification of materials. The system collects data from a 10 by 10 array of parallel tapped photodiodes. Up to 8192, frames of data are digitized with 8-bit flash converters at frame rates ranging from 500 to 1 000 000 frames per second. The system has been used to image solidification of a gamma titanium aluminum (γ-TiAl) alloy, with composition Ti-60a/o Al, over a range of undercoolings. The data collected includes the first images of solidification from multiple solidification fronts, images of solidification of a disordered phase followed by the alloy ordering, and quantitative measurement of solidification velocity as a function of undercooling in a γ-TiAl alloy.
On derivation of a thermal transfer model of a thermostat housing a heat source with several watts
Authors: Kazihara K. , Yoshihiro A. , Sonoda T. , Ueda R.
Published: July 2002

This article presents a trial for deriving a thermal transfer model of a thermostat housing a heat source generating several watts and achieving high temperature stabilization. It is intended for investigating the open-loop linearity of operational amplifiers labeled as high precision or low noise and their noise characteristics. This thermostat is built up with a double-jacket constructed with a copper plate of 10 mm thickness and an approach of deriving a lumped parameter model to each jacket on the temperature control is presented. The temperature stability of the order of 3×10−5°C per 1°C temperature change in the air outside in 1 h is realized in the inner jacket. The linearity is measurable and it is clarified that amplifiers are classified into three groups.
A low-temperature ultrahigh-vacuum scanning tunneling microscope with rotatable magnetic field
Authors: Wittneven Chr. , Dombrowski R. , Pan S. H. , Wiesendanger R.
Published: July 2002

We present a new design of a low-temperature ultrahigh-vacuum (UHV) scanning tunneling microscope setup with a combination of a solenoid and a split-pair magnet. The scanning tunneling microscope can be operated at temperatures down to 8 K and in a rotatable magnetic field of up to 1 T. Magnetic fields of up to 7 T perpendicular and 2 T parallel to the sample surface can be applied. The UHV part of the system allows in situ preparation and low energy electron diffraction/Auger analysis of samples. First topographic and spectroscopic measurements on p-InAs(110) are presented.
In situ pulsed laser deposition of large-area ceramic and multilayer films for applications in industry
Authors: Auyeung R. C. Y. , Horwitz J. S. , Knauss L. A. , Chrisey D. B.
Published: July 2002

High-quality superconducting films have been deposited onto 2 in. diameter substrates in a large-area pulsed laser deposition (PLD) system incorporating a novel pseudoblackbody radiation heater. A KrF laser (λ=248 nm) was rastered across the radius of a rotating target and a slot in the blackbody heater collected the ablation plume onto a rotating substrate holder. Critical temperatures of >90 Kwith critical current densities of 2–4 MA/cm2 were measured across a 2 in. diam YBa2Cu3O7−δ(YBCO) film deposited on an LaAlO3(LAO) substrate. Metal atom concentrations were measured by Rutherford backscattering spectrometry to be nearly stoichiometric and the film thickness uniformity was ±7% about the mean. Purely c-axis orientation was observed in the x-ray diffraction patterns. A multilayer LAO/YBCO film was deposited in situ on an MgO substrate using a large-area target load-lock chamber and exhibited good crystalline quality. YBCO films deposited onto both sides of a 1 in. square by 0.010-in.-thick MgO substrate were patterned and fabricated into a four-channel microwave receiver operating near 10 GHz. The receiver exhibited low loss and good frequency selectivity at 77 K.
Rapid-scanning interferometer for ultrafast pump–probe spectroscopy with phase-sensitive detection
Authors: Diffey William M. , Beck Warren F.
Published: July 2002

We describe a rapid-scanning modified Mach–Zehnder interferometer suitable for use in femtosecond pump–probe or dichroism spectroscopy with self-mode-locked titanium–sapphire oscillators. A galvanometer-type rapid-scanning translation stage is employed in the pump arm of the interferometer. The intensity or polarization of the pump beam is modulated by a fused-silica photoelastic modulator employed as a half-wave retarder. The detection system exploits the rapid-scanning stage and photoelastic modulator by combining phase-sensitive detection with transient digitization. The system we describe permits pump–probe or dichroism spectroscopy to be conducted without temporal distortion of the laser pulses used in the experiment, with high scan-to-scan reproducibility, and with all of the previously noted advantages of rapid-scanning methods in terms of sensitivity. The approach is especially well suited for use with pulse-picked or cavity-dumped sources, which are often required to be operated at moderate pulse-repetition rates in order to avoid artifacts from sample heating or from long-lived intermediates.
Spectroscopic imaging system for quantitative analysis of the divertor plasma of the Tokamak de Varennes
Authors: Meo F. , Stansfield B. L. , Chartré M. , de Villers P. , Marchand R. , Ratel G.
Published: July 2002

A toroidally viewing spectroscopic imaging system has been developed for the Tokamak de Varennes providing measurements of the poloidal distribution of the absolute radiated power of deuterium and impurity species in the upper divertor region. Real time digitization is achieved using a low cost PC based digital imaging system. This system is used to obtain measurements of the divertor strike point as well as the shape of the flux surfaces in the divertor. The diagnostic’s excellent spatial resolution and toroidal view provides an opportunity to quantitatively compare the measured two dimensional (2D) radiated power distribution to that calculated from 2D Monte Carlo transport codes. These 2D images provide unique and valuable information on the physics of local plasma interactions with divertor components and particle transport in a closed divertor. Additionally, by using two cameras simultaneously, the line ratio technique can be applied to the images to estimate plasma parameters in the divertor.
A fully automated precise measurement system for sound velocity and internal friction in solids down to liquid helium temperatures using the vibrating reed technique
Authors: Balakrishnan K. , Marhas Manmeet Kaur , Ghodke Nandkishor L. , Ganesan V. , Srinivasan R.
Published: July 2002

The design and fabrication of a fully automated, computer controlled, precise measurement system for sound velocity and internal friction using the vibrating reed technique is described in detail. Relative variation of sound velocity and internal friction has been measured using automatic frequency locking. A detailed description of the apparatus is given. The associated electronics that took care of quite a few problems in getting a good lock-in condition have been highlighted. With a bath cryostat and sample insert, measurements were made down to liquid helium temperatures with a temperature control accuracy better than 10 mK. The resonance frequency and the peak amplitude were recorded as a function of temperature which in turn provided temperature variation of sound velocity and internal friction with a relative accuracy better than 1 part in 104 and 1.5%, respectively. Precise nature of the results obtained using this setup is highlighted for a specimen of an amorphous alloy near it’s Curie temperature.
Estimation of thermal noise in the mirrors of laser interferometric gravitational wave detectors: Two point correlation function
Authors: Nakagawa N. , Auld B. A. , Gustafson Eric , Fejer M. M.
Published: July 2002

A general formula and a computational scheme for estimating the power spectrum of the displacement correlation function of suspended test masses such as those used in interferometric gravitational wave detectors are presented. Unlike previous mode-summation approaches, the fluctuation-dissipation theorem has been applied directly to the displacement correlation. The resulting formula expresses the correlation in terms of material damping parameters and mechanical Green’s functions, and provides an efficient and flexible method to compute thermally induced surface displacements of arbitrarily shaped anisotropic elastic bodies. The formula can be used for optimizing the shape and size of test masses in gravitational wave receivers. A simple one-dimensional example is included to clarify the relationship with the modal expansion approach and to illustrate the advantage of the Green’s function method. This paper presents the theoretical formulation; numerical evaluations of the formula will be presented elsewhere.
Contact dynamics recording and analysis system using an optical fiber sensor approach
Authors: Anghel F. , Pavelescu D. , Grattan K. T. V. , Palmer A. W.
Published: July 2002

A contact dynamics recording and analysis system configured using an optical fiber sensor has been developed having been designed with a particular application to the accurate and time-varying description of moving contact operating during electrical arc breaking, in an experimental platform simulating the operation of a vacuum circuit breaker. The system utilizes dynamic displacement measurement and data recording and a post-process data analysis to reveal the dynamic speed and acceleration data of the equipment.
Q
-switched CO 2 laser with pulsed longitudinal discharge for nonlinear optical applications
Authors: Geist F. , Guyenot M. , Herbst W. , Pascher H. , Verkerk R. , Prettl W.
Published: July 2002

Easy to realize recipes are given to modify a conventional low pressure longitudinally excited Q-switched CO 2 laser by pulsing the electrical discharge. An increase of the peak power of strong laser lines up to a factor of 6 is obtained, as well as laser emission on a considerably larger number of vib–rot transitions.
Spectroscopic determination of cold electrons in electron cyclotron resonance discharges with highly charged ions
Authors: Bibinov N. K. , Bolshukhin D. O. , Bratsev V. F. , Kokh D. B. , Ochkur V. I. , Vinogradov I. P. , Wiesemann K.
Published: July 2002

A spectroscopic method based on the analysis of molecular and atomic spectra of nitrogen was used for the determination of electron distribution functions (EDFs) in electron cyclotron resonance (ECR) discharges run in nitrogen. EDFs were determined for the plasma region seen by the VUV-monochromator. This region includes the hot core plasma surrounded by a less dense and not so hot halo plasma. The EDF between 1.5 and 4.5 eV was determined from the vibrational distribution of excited molecular states of nitrogen, and that in the energy range above 8.5 eV was evaluated from the intensities of different emission lines and bands of NI and N2. The shape of the EDF in the energy range between 4.5 and 8.5 eV was interpolated by using the electron density measured with Langmuir probes and normalizing the EDF to the same density. Due to the low gas pressure of 2×10−5 Torr vibrational relaxation processes on the discharge chamber wall had to be taken into account. In the wavelengths range 30–400 nm the emission spectra of the ECR discharge were measured for the input microwave power range Pin=100–1500 W. This wavelength range includes the emission bands of the molecular transitions N2(C3Πu→B3Πg), N2(a1Πg→X1Σg−), and N2+(B2Σu−→X2Σg+) and emission lines of the atoms and ions e.g., transitions N(4P→4S, 120.0 nm), N(2P→2P, 124.3 nm), and N+(3P→3P, 91.6 nm), N+(3D→2P, 108.4 nm). For these transitions the experimental emission cross sections for the excitation from N2(X) and the some intermediate stable states [e.g., from the atomic ground state N(4S)] are known from the literature. The other cross sections used in our EDF calculations especially N and N+ excitation cross sections were calculated in this work.
Quartz antenna for radio frequency ion source operation
Authors: Lee Y. , Gough R. A. , Leung K. N. , Perkins L. T. , Pickard D. S. , Vujic J. , Wu L. K. , Olivo M. , Einenkel H.
Published: July 2002

Radio-frequency (rf) driven multicusp ion sources developed at the Lawrence Berkeley National Laboratory use an internal induction coil (antenna) for plasma generation. The copper rf-antenna with a thin layer of porcelain coating, which is presently used, cannot fully satisfy the increasing demands on source cleanliness and antenna lifetime under high power cw or pulsed operation in applications where water cooling is not possible. A quartz antenna has been designed and operated in the multicusp ion source. It has been demonstrated that the overall performance of the new antenna exceeds that of the regular porcelain-coated antenna. It can be operated with a long lifetime in different discharge plasmas. The quartz antenna has also been tested at the Paul Scherrer Institute for cw source operation at rf power higher than 5 kW. Results demonstrated that the antenna can survive under dense plasma discharge operations.
Aspects of the suspension system for GEO 600
Authors: Plissi M. V. , Strain K. A. , Torrie C. I. , Robertson N. A. , Killbourn S. , Rowan S. , Twyford S. M. , Ward H. , Skeldon K. D. , Hough J.
Published: July 2002

The GEO 600 gravitational wave detector is currently under construction in Germany. To ensure that the detector sensitivity is not limited by seismic noise above 50 Hz a significant degree of seismic isolation has to be provided for each test mass. To achieve this level of isolation each test mass, which will be made from fused silica (mass ∼14 kg), will be suspended as the final stage of a triple pendulum from an isolation stack consisting of layers of stainless steel masses and graphite loaded silicone rubber. Extending from the stack will be three cantilever springs supporting an upper mass from which a double pendulum stage will be suspended. This double pendulum will incorporate cantilever springs in the upper stage in order to enhance the vertical isolation, and will use fused silica fibers in the lower pendulum stage in order to minimize thermal noise from the pendulum modes. The expected performance from this arrangement of stacks, vertical spring stages, and double pendulums should achieve our goals for seismic isolation.
Summary of the performances of the superconducting electron cyclotron resonance ion source at 14 GHz
Authors: Ludwig P. , Bourg F. , Briand P. , Girard A. , Melin G. , Guillaume D. , Seyfert P. , La Grassa A. , Ciavola G. , Gammino S. , Castro M. , Chines F. , Marletta S.
Published: July 2002

This article deals with the most recent performance of the superconducting electron cyclotron resonance ion source (SERSE) working at 14 GHz with high magnetic fields after the required conditioning and optimization of several operating parameters. SERSE has now achieved an outstanding level of performance in delivering highly charged ion beams in argon and oxygen gases: the results obtained while operating in a stainless steel chamber and with an aluminum liner are shown and discussed.
Characterization of high charge electron beams induced by excimer laser irradiation
Authors: Nassisi V. , Giannico E.
Published: July 2002

This work reports on electron beam characteristics obtained from a Cu photocathode utilizing an UV excimer laser of 222 nm for the first time. The values of the current, emittance, and brightness of the electron beams generated are reported. A suitable slit–slit emittance meter was developed to assess the electron beam emittance. This instrument allowed us to determine the electron beam phase-space areas by slicing the beam in small beamlets and measuring the beamlet direction distributions. Small Faraday cups placed after the slits were utilized to this reason. The laser beam was focused in a 4 mm2 spot and the maximum energy laser was established to 0.5 mJ. The highest current was 410 mA and the corresponding normalized emittance value was 10 π mm mrad corresponding to 80% of the total points. From these data the beam quality, expressed as normalized beam brightness, resulted in 4.1×109 A[π m rad]−2 and the quantum efficiency was 4.6×10−5. By increasing the KrCl laser spot and its energy a very charge electron beam was extracted of 16.4 A.
Ion beam mass spectrometer for compositional analysis of plasma assisted surface processes in the pressure range of 1–50 mbar
Authors: Kátai Sz. , Tass Z. , Bori L. , Hárs Gy. , Deák P. , Geelhaar L.
Published: July 2002

Ion beam mass spectrometry (IBMS) has been developed for in situ, real-time monitoring of the ion composition of a plasma in the vicinity of the substrate surface up to a pressure of 50 mbar. Our system was designed for the specific case of diamond deposition in a microwave plasma enhanced chemical vapor deposition chamber, however, it can be adapted to other applications as well, without significant change in the process chamber. Ion beam mass spectrometer is a quadrupole mass spectrometer (QMS) based plasma sampling system installed into a separately pumped small analysis chamber. The interface between the two chambers is the top part of the IBMS, specially designed to serve as the sample holder of the reactor chamber (sample heating and biasing is possible). A technique containing wet etching and laser treatment has been developed to form a sufficiently small orifice in various substrates. This orifice samples the particles arriving onto the surface from the plasma but is small enough to maintain the flow effusive into, and an appropriate pressure in the analysis chamber. Directly behind the orifice specially designed ion-optics direct the ions coming from the process chamber into the QMS for mass and energy separation. Since the total flow from the reactor chamber is low, the mean free path in the analysis chamber is sufficiently longer than the distance from the orifice to the QMS, therefore, ions do not collide, thus they do not react after sampling. As a consequence, nonstable species are also detected. The carefully designed ion-optics ensure that a high ion current reaches the QMS. In this article, it is shown that the intensity ratios in the spectra correspond to the concentration ratios of the ions arriving to the substrate surface. The QMS is also equipped with a conventional cross electron beam ion source allowing measurements of neutral species by conventional ionization.