bluuebunny/crossref_metadata_2025 huggingface dataset:
Comment on ‘‘High-spatial and high-mass-resolution SIMS instrument for the surface analysis of chemically complex materials’’ [Rev. Sci. Instrum. 6
, 53 (1989)]
Authors: Conty C.
Published: July 2002

The article on which we comment contains inaccurate and misleading information regarding the current status of the SIMS technique. We present a comparison with the CAMECA IMS 4F.
High current negative ion sources (invited)
Authors: Ehlers K. W.
Published: July 2002

A brief historical survey is presented of the origin of negative ion sources and their application for tandem accelerators and for fusion. Present-day volume-production sources and surface-production negative ion sources are described.
Construction and performance of a temperature-jump NMR apparatus
Authors: Akasaka Kazuyuki , Naito Akira , Nakatani Hiroshi , Imanari Mamoru
Published: July 2002

A first, versatile, computer-controlled temperature-jump NMR apparatus was constructed. The system uses compressed air or nitrogen gas for changing the temperature of the sample solution and maintaining it during data acquisition. The sample is placed in a pyrex capillary tube of 3 mm o.d. on a conventional high-resolution NMR probe. The temperature of the sample is changed by controlling gas flows with three different temperatures, T1, T2, and T3. First, a gas of temperature T1 maintains the sample at its initial temperature. Then a gas of T2 is sent to the probe for 1–2 s for momentary over-cooling or over-heating. And finally a gas of T3 is sent to maintain the final temperature. In this way, either temperature-jump up or down by as much as 20 °C is attained in about 6 s. After the final temperature is reached in the sample, free induction decay signals are acquired at constant time intervals. For a reversible reaction, the entire heat cycle can be repeated under full control by the NMR pulse programmer. Finally, the accumulated free induction decay signals are Fourier transformed to give time-dependent spectral changes (‘‘NMR snap shots’’) occurring in the time range of seconds or longer.
High-temperature NMR using inductive heating
Authors: Maresch G. G. , Kendrick R. D. , Yannoni C. S.
Published: July 2002

We report a simple, efficient method for carrying out nuclear magnetic resonance (NMR) experiments at high temperature in any NMR probe without modification. The sample tube is coated with a thin film of metal and the rf coil used for the NMR experiment is used to inductively heat the film, thus heating the sample inside the tube. Using this approach, we have obtained both proton and high-resolution carbon-13 NMR spectra at temperatures as high as 730 K.
Amplitude and phase modulation (AM-PM) wide-band photothermal spectrometry. I. Theory
Authors: Power J. F.
Published: July 2002

Amplitude and phase modulation (AM-PM) wide-band photothermal spectrometry is a new technique of excitation and signal recovery with extensive applications in thermal-wave imaging using linear photoacoustic and photothermal techniques. The excitation waveform consists of the superposition of two orthogonal amplitude-modulated frequency sweeps, and exhibits an optimally flat input autospectrum over an arbitrary bandwidth. Signal quality is greatly superior to earlier wide-band photothermal methods based on linear frequency sweep excitation. The new methodology also permits ‘‘multiband acquisition’’ in which several arbitrary narrow-band segments or ‘‘slices’’ of the photothermal frequency response are acquired, a capability that is missing in conventional linear FM measurements. This multiband acquisition capability has many potential applications for information recovery in thermal-wave imaging.
Some novel design features of the LBL metal vapor vacuum arc ion sources
Authors: MacGill Robert A. , Brown Ian G. , Galvin James E.
Published: July 2002

The family of MEVVA (metal vapor vacuum arc) high current metal ion sources developed at LBL over the past several years has grown to include a number of different source versions with a wide range of some of the design and operational parameters. The MicroMEVVA source is a particularly compact version, about 2 cm diam and 10 cm long, while the MEVVA IV weighs some 30 kG. MEVVAs IV and V incorporate multiple cathode assemblies (16 and 18 separate cathodes, respectively), and the operating cathode can be switched rapidly and without downtime. The new MEVVA V embodiment is quite compact considering its broad beam (10 cm), high voltage (100 kV), and multiple cathode features. The large-area extractor grids used in MEVVA V were fabricated using a particularly simple technique, and they are clamped into position and can thus be changed simply and quickly. The electrical system used to drive the arc is particularly simple and incorporates several attractive features. In this article we review and describe a number of the mechanical and electrical design features that have been developed for these sources.
VUV spectroscopy for plasma diagnostics of an ECR ion source
Authors: Pöffel W. , Schartner K.-H. , Mank G. , Salzborn E.
Published: July 2002

Spectroscopic measurements of relative line intensities in the vacuum ultraviolet spectral range (VUV) were performed using a Giessen 5 GHz ECR ion source in order to obtain direct information about the plasma parameters. The ratio of intensities of the 2s2p 3P–2p2 3P to 2s2 1S–2s2p 1P transitions in the Be-like isoelectronic sequence for C iii, O v, and Ne vii were measured at different gas pressures and ion source conditions. This ratio varied with changing plasma parameters. The measurement of this ratio may make possible estimation of the electron density of the ECR ion source plasma.
H− source and low energy transport for an RFQ preinjector
Authors: Alessi J. G. , Brennan J. M. , Kponou A.
Published: July 2002

A radio-frequency quadrupole (RFQ) accelerator has replaced a 750-keV Cockcroft-Walton as the H− preinjector for the Brookhaven alternating gradient synchrotron. A magnetron surface-plasma source with a circular aperture is used to produce 65–100 mA of H− at 35 keV with a discharge current of less than 20 A. The symmetry of the beam is maintained in the 2-m transport to the RFQ via the use of magnetic solenoids for focusing. Currents up to 60 mA have been obtained out of the RFQ. A traveling-wave electrostatic chopper in the 35-keV transport line leads to a distortion of the emittance due to space-charge effects.
External ion sources at the Uppsala cyclotron
Authors: Ekström C. , Bäcklin A. , Holm S. , Ärje J. , Nieminen V.
Published: July 2002

Two external ion sources, an electron cyclotron resonance (ECR) source for heavy ions and an atomic-beam source for polarized protons and deuterons, are currently under construction for the cyclotron at the Svedberg Laboratory (TSL), Uppsala. The sources will be placed in partly newly built localities outside the cyclotron hall, which will also contain an area for atomic-physics experiments with heavy ions from the ECR source. The beam-transport system, which will be common for the two ion sources, is based on magnetic elements.
The nonlaminar flow characteristics of Cs+ in an intense Cs+ gun
Authors: Rao Yusheng , Xi Youhao , Xi Boling
Published: July 2002

The nonlaminar flow characteristics of Cs+ have been studied in an intense Cs+ gun. In the physical model established here, the effects of space charge and thermal initial velocity are taken into account, and a Maxwellian distribution of the thermal initial velocity and its cosine angular distribution of current density with respect to the normal line of the ion-emitting surface are assumed. Poisson’s equations are solved in terms of iteration to find a self-consistent solution, and the nonlaminar trajectories are traced; hence the phase diagram at the exit of the gun is obtained. The calculated results are compared with experimental data, and they are in good agreement.
Extruded sodium wires for Z-pinch implosions
Authors: Deeney C. , Prasad R. R. , Nash T. , Knobel N.
Published: July 2002

Presently, investigation of the sodium-neon photopump x-ray laser scheme on Z pinches is hindered by the lack of a well-defined sodium source. Metal vapor sources have been pursued; however, they have tended to be less characterized than the traditional wire arrays and gas puffs. In this note, the development of a sodium wire extruder which produces an array of 6 or 12, greater than 50 μm diameter, wires is described and successful implosions of the said array on the DNA/Double-EAGLE generator are reported.
Induction-coupled ion-beam source
Authors: Pai J. R. , Venkatramani N. , Rohatgi V. K.
Published: July 2002

A prototype rf ion source for extracting a hydrogen-ion beam has been developed. The system consists of a rf source and a water-cooled quartz tube, which contains the plasma. The rf power is coupled through a four-turn coil located outside the tube. A perforated metal grid and an aperture located about 8 mm from the grid has an opening of 5 mm in diameter. The axially extracted beam is transported through a column of about 1 m maintained at a pressure of 10−4 Torr, while the pressure in the plasma region is about 10−2 Torr. The rf source is a class-C, variable-power oscillator of fixed frequency 7 MHz. Operating the system with about 300 W in the discharged plasma, a continuous proton beam of 55 μA has been observed at a distance of 10 cm from the extracter at a voltage of 2.5 kV. Under similar operating conditions an argon-ion beam of 14 μA has been extracted. Experiments are in progress to optimize the extraction of ions at 10 kV, increase the rf power, and provide a suitable focusing system to transport the beam at a distance of 1 m with maximum efficiency.
Specific heat of speer carbon resistor thermometers at low temperatures and in magnetic fields
Authors: Andraka B. , Stewart G. R.
Published: July 2002

We have measured the specific heat of a Speer carbon resistor in the temperature range 0.32 to 4 K and in 0, 1.2, 6, and 12 T magnetic fields. Our zero field data disagree by an order of magnitude with previously reported results; the specific heat is also field sensitive. Where a piece of Speer resistor forms part of the addenda of a small-mass specific heat platform, lack of proper accounting for its addenda contribution can lead to large errors in the specific heat measurements, particularly in field.
Design and experimental results of a new electron gun using a magnetic multipole plasma generator
Authors: Tanaka S. , Yokoyama K. , Akiba M. , Araki M. , Dairaku M. , Inoue T. , Mizuno M. , Okumura Y. , Ohara Y. , Seki M. , Watanabe K.
Published: July 2002

A new electron gun utilizing a magnetic multipole plasma generator was designed and fabricated as the heat source of the high heat flux test facility, called JEBIS (JAERI electron beam irradiation stand). By changing the acceleration grids, this electron gun is able to produce a pencil to a sheetlike electron beams up to 4 A at 100 keV for 1 ms to continuous mode. In this electron gun, magnetic lens system is not adopted to focus the electron beam, but the space charge neutralization effect by the beam plasma produced downstream of the electron gun is utilized to prevent the blow-up of the electron beam. In addition, high permeability metal is embedded in the first and the second grids to magnetically shield the earth field and the stray field from the beam bending magnet. It was experimentally demonstrated that wide range of heat flux from 0.2 MW/m2 to over 2000 MW/m2 can be realized at the test sample position about 1.7 m downstream of the electron gun.
Hardware and software corrections of the spatial distortions of position-sensitive detectors
Authors: Leclerc G. , Ozenne J.-B. , Corbeil J.-P. , Sanche L.
Published: July 2002

Possible causes of the spatial distortion encountered when using pierced resistive anodes for position-sensitive detection are discussed. An accurate map of the spatial distortion around a circular hole in a resistive anode is presented, which shows that the hole’s effect is felt at distances up to three times its radius. The effect of load conditions on the detector’s spatial linearity, as well as the distortions induced near the center of the detector due to penetrating electrostatic fields, are also discussed. In response to these points, alternative methods are described−in hardware and software−for the correction of distorted images. The hardware approach, which makes use of electrically programmable read-only memories, has the advantage of allowing real-time operation albeit with some loss in the precision of the intensities of the features within an image. One benefit of the software approach, beside the fact that it provides the best possible correction of the intensities, lies in the fact that all the information contained in the raw data is kept intact, which gives some latitude for future recalibration of the detector, or for emulation of a detector of another shape.
Measurements of spatial distribution of a primary electron and its effects on the performance of a magnetic multicusp ion source
Authors: Ueda Yoshio , Doi Makoto , Nishikawa Masahiro , Goto Seiichi
Published: July 2002

The measurements of spatial profiles of primary electron (high-energy tail electron) density in a magnetic multicusp ion source have been made in the cases of different current directions of ‘‘T’’-shaped filaments, and its effects on the beam extraction have been studied. The axial profiles of arc plasma parameters in the ion source were measured by use of a movable Langmuir probe. A high-energy tail electron density ntail is calculated from the electron energy distribution function derived from probe current-voltage characteristics using Druyvesteyn’s method. It is confirmed that the axial profiles of tail electron density ntail relates to the location of primary electron emission. The results indicate that higher ion-beam current is observed in the case that ntail and equivalent electron temperature Tequ are higher near the plasma electrode.
Automated apparatus for the determination of the specific heat and the thermal diffusivity of nonconducting solids using ac techniques
Authors: Yang G. , Migone A. D. , Johnson K. W.
Published: July 2002

A fully automated experimental setup is described that allows the determination of the heat capacity and thermal diffusivity on the same piece of a nonconducting thin solid sample. Both properties are measured using ac techniques. Measurements have been made on microscope glass cover slides for temperatures between 25 and 300 K. The values obtained for the specific heat are within 5% of those reported in the literature and the values of the thermal diffusivity are within 10% of reported values.
Optimization and redesign of an electron spectrometer for high-resolution gas phase UV photoelectron, Auger electron, and ion fragment spectroscopy
Authors: Baltzer Peter , Wannberg Björn , Carlsson Göthe Mats
Published: July 2002

Extensive modifications of an electrostatic electron spectrometer of the hemispherical type are described. The purpose of the modifications is to make the instrument more suitable for high-resolution gas phase spectroscopy. The changes concern substitution of electrical adjustments for mechanical precision, improved flexibility in focusing, and a new system of computer-controlled power supplies and detector interface. The instrument is also used for energy analysis of positive ions. Conversion between positive and negative particle analysis is achieved simply by reversing the polarities of all relevant voltages by a number of switches. A gas cell with internal heating is described. The influence of gas cell conditions on resolution is briefly discussed. The computer programs used for spectrometer control, data acquisition, spectrometer optimization, and calibration are described.
Hot electron studies in the Minimafios ECR ion source
Authors: Barué C. , Briand P. , Girard A. , Melin G. , Briffod G.
Published: July 2002

The experimental data obtained by three different measurements related to the hot electron population involved in ion stripping in an electron cyclotron resonance ion source (ECRIS), i.e., electron cyclotron emission, bremsstrahlung x-ray radiation, and diamagnetism are presented and shortly discussed. The volume-averaged electron energy essentially depends upon the working pressure, and does not vary much with the rf power, at least above 200 W. The main effect of increasing the rf power is to raise the electron density.
Y–Ba–Cu–O multilayer structures with amorphous dielectric layers for multichip modules using ion-assisted pulsed-laser deposition
Authors: Reade R. P. , Berdahl P. , Russo R. E. , Schaper L. W.
Published: July 2002

Existing technology to construct high-temperature superconductor (HTSC) multichip modules (MCM’s) incorporating several YBa2Cu3O7−δ (YBCO) thin films and thick dielectric layers are based on epitaxial growth of all layers from the template of a single-crystal substrate. This work demonstrates an alternate method to fabricate these structures: the use of a biaxially aligned yttria-stabilized zirconia (YSZ) intermediate layer deposited by ion-assisted pulsed-laser deposition. Using this technique, a YBCO thin film with Tc∼87 K and Jc∼3×105 A/cm2 was grown on a 5 μm amorphous SiO2 layer. In addition, YBCO/YSZ/SiO2/YSZ/YBCO/CeO2/YSZ and YBCO/YSZ/amorphous-YSZ/YBCO/CeO2/YBCO multilayer structures were constructed.
X-ray fluorescence detection of low-Z elements using a microchannel plate detector
Authors: Rosenberg R. A. , Simons J. K. , Frigo S. P. , Tan K. , Chen J. M.
Published: July 2002

We demonstrate the utility of a simple, inexpensive, microchannel plate (MCP) detector for monitoring the x-ray fluorescence (XRF) yield in the soft x-ray region. The detector consists of a dual MCP array, and appropriately biased grids. We compare the Al 2p XRF yield to the total-electron yield (TEY) (obtained with the same detector) of single-crystal sapphire. These measurements show that the XRF yield has the following advantages over TEY for monitoring absorption spectra in the soft x-ray region: (1) a greater bulk sensitivity, (2) an insensitivity to charging.
Determination of the areas of a square sample suitable to the resistance measurement by Van der Pauw’s method
Authors: Sun Yicai , Ehrmann Oswin , Wolf Jürgen , Reichl Herbert
Published: July 2002

By using conformal transformation to take account of the boundary effect, it has been confirmed that there are some areas of a square sample near the corners besides the boundary suitable to the resistance measurement of Van der Pauw’s method. The theoretical criterion of the suitability is whether Van der Pauw’s formula for calculation of the sheet resistance is still valid provided the voltage values in the formula for two times the measurement are substituted with those obtained by using the theory of conformal transformation. The experimental criterion is whether the experimental values of sheet resistance for probes in some areas are equal to that for them at the boundary for the same sample. The experimentally confirmed areas are larger than what the theory predicts. Our repeated experiments show that the areas out of the circle tangent to the boundary are suitable to Van der Pauw’s method.
Performance characteristics of a microwave plasma source using an axial mirror and multipole magnetic fields
Authors: Nihei H. , Morikawa J. , Nagahara D. , Enomoto H. , Inoue N.
Published: July 2002

The performance characteristics of a microwave plasma source are presented. The plasma source consists of two chambers: chamber 1 generates a high-density plasma over which a magnetic field is applied at electron cyclotron resonance condition or greater, and chamber 2 makes the plasma uniform in its lower region by surrounding the peripheral region with magnetic multipole line-cusp fields. Plasma parameters were measured with a movable Langmuir probe located 1 cm above a plasma grid which is attached at the bottom of chamber 2. The dependence of plasma parameters on the magnetic field configuration, gas pressure and microwave power were examined, and radial distributions were measured. Uniform high-density plasmas over a 9-cm-diam area were produced on the plasma grid in a suitable magnetic field configuration, and uniformity was maintained over a wide pressure range. The uniform density region was determined by the magnetic multipole fields existing in chamber 2’s peripheral region. The ion beam current density evaluated from the extracted ion beam correlated well with the ion saturation current density estimated from the plasma parameters.
Subnanometer behavior of a capacitive feedback, piezoelectric displacement actuator
Authors: Harb S. , Smith S. T. , Chetwynd D. G.
Published: July 2002

This paper presents the calibration of piezoelectrically actuated capacitance micrometers for use as a transfer standard of nanometer level precision using x-ray interferometry. Because of the interferometer’s extreme sensitivity to twisting moments, there is a pressing need for high-quality transfer systems to widen its range of applicability. Two promising candidates for this are piezoelectric actuators controlled by internal capacitive sensors and parallel-plate capacitive micrometry. Both are investigated to determine useful precision for the discrimination and traceability over the range 1–20 nm. It is shown that systems of high mechanical stability can readily be produced. They offer at the very worst traceable accuracy of a few tenths of a nanometer, with, in the case of the gauge, a wide bandwidth of greater than 1 kHz. It is argued that existing technologies can provide calibrators working at relatively rapid speeds with uncertainties better than around 20 pm over usefully large ranges, presently 15 μm.
Absolute phasing of segmented mirrors using the polarization phase sensor
Authors: Klumpe Herbert W. , Lajza-Rooks Barbara A. , Blum James D.
Published: July 2002

The polarization phase sensor (PPS) is an optical sensor capable of measuring absolute displacements between two segments of a spherical mirror. The sensing apparatus consists of a white light polarization interferometer which forms a set of interference fringes representative of the displacement between the two segments. A detector array senses these fringes and computer software performs an analysis. The result of these calculations is a measurement of the absolute misalignment between the two segments. The sensor, in its current configuration, is capable of measuring ±30 μrad of tilt between the two segments with an accuracy of 3.29 μrad and a precision of 2.27 μrad and ±2 μm of piston between the two segments with an accuracy of 0.00516 μm, and a precision of 0.031 μm. This paper will address the optical design and operating characteristics of this sensor. A conclusion will discuss alternate modes of operation and upgrades to the instrument which will increase piston capture range.
An automated flow calorimeter for the determination of liquid and vapor isobaric heat capacities: Test results for water and n-pentane
Authors: Sandarusi Jamal A. , Mulia Kamarza , Yesavage Victor F.
Published: July 2002

An automated flow calorimeter has been developed for the measurement of highly accurate isobaric heat capacities and enthalpies of fluids at elevated temperatures and pressures. The instrument was successfully tested over the range 300–600 K and 0–12 MPa and is readily extensible to 700 K and 30 MPa. The flow calorimeter relied on an adiabatic design with a two-chambered cell design incorporating several concentric shells of active and passive shields designed to minimize heat losses, facilitate easy component replacement, and eliminate any external temperature regulation baths. A pair of miniature standard platinum resistance thermometers were built to determine the differential calorimeter temperatures. A precision metering pump eliminated the need for direct mass flow-rate determinations while a complete automation system supplied all of the required data acquisition, monitoring, and control (except for pressure) resources necessary to operate the calorimeter and make measurements from a single personal computer. Measurements of isobaric heat capacities were performed on water (liq.) and n-pentane (liq. and vap.) to test the new calorimeter. These experiments compared well with the published values, indicating an overall measurement precision of 0.1% and uncertainty in the range of 0.2%–0.3%. The total calorimeter heat leak was small affecting the experimental uncertainty as much as the combined mass flow-rate and calorimeter temperature difference errors.
A measurement method for the determination of the anisotropy ratio of thermal conductivity of plastic foils
Authors: Rantala J.
Published: July 2002

An experimental system to determine the anisotropy ratio of thermal conductivity of polymer foils parallel to the sample surface is presented. This kind of measurement is important because the drawing of the foil orients the molecular chains making thermal conductivity parallel to the orientation higher than perpendicular to it. The measurement method is based on heating the foil with a dc-supplied resistor and detecting the temperature by an infrared detector. The temperature of the foil is measured as a function of distance from the heat source in two separate measurements perpendicular to each other, i.e., rotating the sample 90° between the measurements, and the anisotropy ratio of thermal conductivities in these directions is obtained by using curve fitting. In this article the method has been applied on several plastic foils showing anisotropies ranging from 1 to 2.
Ion sources for ion beam assisted thin-film depositiona)
Authors: Ensinger W.
Published: July 2002

Ion beam assisted deposition (IBAD) is a coating technique which combines a thin-film deposition method such as evaporation with irradiation by highly energetic ions from an ion source. Application of an ion source and a vapor source which are operated independently of each other render the IBAD technique highly controllable, reproducible, and flexible. Ion flux, atom flux, ion energy, ion impact angle, and other parameters can be controlled independently over a wide range. In order to take advantage of the beneficial features of this technique and obtain optimum process conditions ion sources with special properties are required. In this article different ion source types and equipment which has been used for IBAD to-date are presented and their special features discussed. Ion sources which should be applicable for IBAD are described. Finally, general requirements of IBAD ion sources are discussed.
z calibration of the atomic force microscope by means of a pyramidal tip
Authors: Jensen F.
Published: July 2002

A new method for imaging the probe tip of an atomic force microscope cantilever by the atomic force microscope itself (self-imaging) is presented. The self-imaging is accomplished by scanning the probe tip across a sharper tip on the surface. By using a pyramidal probe tip with a very well-defined aspect ratio, this technique provides an excellent z-calibration standard for the atomic force microscope.
A computer simulation study on electron multiplication of parallel-plate electron multipliers
Authors: Suzuki S. , Konno T.
Published: July 2002

Electron multiplication of parallel-plate electron multipliers with a parallel electric field (PPEM-parallel) and with a tilted electric field (PPEM-tilt) have been studied by a Monte Carlo simulation method. The optimum geometrical condition is represented with a ratio of the dynode length Ld to the dynode spacing Ds, Ld/Ds=0.040Vd, for the PPEM-parallel, and with a ratio of the dynode displacement Xd to the dynode spacing Ds, Xd/Ds=0.40, for the PPEM-tilt, where Vd is an applied voltage. For optimum geometrical conditions, the PPEM-parallel and the PPEM-tilt have almost equal characteristic properties of operation such as mean gain, pulse height distribution, and transit time distribution of secondary electrons. These are inherent results of the almost equivalent electron multiplication processes such as collision energy of secondaries and number of electron multiplication steps. A simplified analytical method is used to explain the computer simulation results.
Metal vapor vacuum arc ion sources ‘‘Raduga’’
Authors: Ryabchikov A. I. , Dektjarev S. V. , Stepanov I. B.
Published: July 2002

A brief review is presented of the ‘‘Raduga’’ 1–4 repetitively pulsed metal vapor vacuum arc ion sources. Their operation principles and functional ranges are described. The Raduga ion sources provide single- and multi-element implantation. These advantages are achieved by using not only pure single-element or mixed ion fluxes, but also pulsed beam sequences with controllable composition and energy of each ion species. Another feature of the ion sources is their ability to generate a sequence of ion beam and plasma stream pulses. Switching between ion irradiation and plasma deposition can be done from pulse to pulse, within each pulse, or after accumulation of a required dose. Some specific features of the emission properties of broad beam metal vapor vacuum arc ion sources are described.
Laser system for high accuracy alignment and positioning
Authors: Bursanescu L. , Vasiliu V.
Published: July 2002

A laser system for high accuracy positioning, either on-axis or off-axis, over distances up to 50 m along the beam path is described. A beam delivery system with four degrees of freedom is used for initial alignment to an accuracy of 1 μm. Proper processing of the signals from a semiconductor quadrant detector reduces the measurement uncertainties and provides real-time response. Theoretical consideration of the beam propagation characteristics is included. Laboratory and field test results show the system gives uncertainties of less than 1% for off-axis positions up to 1 mm.
Prototype fiber-optic-based ultrahigh pressure remote sensor with built-in temperature compensation
Authors: Rao Y. J. , Jackson D. A.
Published: July 2002

A prototype single-mode fiber-based ultrahigh pressure remote sensor based upon a Fizeau cavity using a dual-wavelength coherence reading technique with built-in temperature compensation has been constructed capable of remote operation at distances up to 10 km. A separate fiber-based temperature sensor with similar cavity length was incorporated into the pressure probe to allow the pressure measurement to be corrected for the temperature dependence of the pressure sensor. A range to resolution of ∼1.67×104:1 and an overall measurement accuracy of ∼±0.69% over a pressure range of ∼1000 bar have been achieved. This system represents a practical approach for industrial applications, such as measuring the pressure of an oil well.
Control of multipolar electron cyclotron resonance discharges using internal cavity impedance matchinga)
Authors: Asmussen J. , Mak P.
Published: July 2002

Recently, electron cyclotron resonance (ECR) discharges have been successfully applied to numerous ion source applications. These range from accelerator to etching and thin film deposition applications, and have strong potential for application in several commercial/industrial processes. Thus, new design requirements related to process automation and control are now imposed on plasma source design. Internal cavity tuning methods for excitation and impedance matching and ECR discharge control are presented. These impedance matching methods utilize a variable cavity end plate and an adjustable coupling probe to provide the two independent adjustments required to match the discharge loaded cavity applicator. Both end feed and side feed coupling create a well matched plasma source but the end feed excitation produces the most efficient (∼220–230 eV/ion) and most uniform (1σ=2.5%) discharge. Control of internal tuning can serve not only to match discharge impedance, but with the proper control can also avoid hysteresis and multiple steady states and jumps in plasma source outputs. Adjusting the internal cavity tuning to always produce a slight mismatch helps insure a stable and repeatable discharge operation.
Production of electron cyclotron resonance plasma for uniform deposition using a TE01 mode microwave
Authors: Hidaka Ryota , Yamaguchi Toru , Tsuruta Akihisa , Tanaka Masayoshi , Kawai Yoshinobu
Published: July 2002

An electron cyclotron resonance (ECR) plasma is produced at pressures up to 10 mTorr with a circular TE01 mode microwave. The plasma density is almost radially uniform even at 10 mTorr. SiC films are formed on silicon wafers by introducing methane gas into the ECR plasma. It is shown that a circular TE01 mode microwave is useful for the ECR plasma chemical vapor deposition (CVD).
Mesh effect in a parallel-plate analyzer
Authors: Hamada Y. , Kawasumi Y. , Iguchi H. , Fujisawa A. , Abe Y. , Takahashi M.
Published: July 2002

The effect of field irregularity due to the use of conducting meshes to cover holes of a lower electrode in a parallel-plate electrostatic analyzer, is experimentally and numerically investigated. Displacement of a focal point and degradation of analyzer characteristics are found in the experiment. Dependence of analyzer characteristics on wire spacing is obtained. Primary results are also confirmed by numerical analysis. Criteria for error estimation are theoretically derived and found to be consistent with the experiment.
A channel plate detector for electron backscatter diffraction
Authors: Barr D. L. , Brown W. L.
Published: July 2002

Electron backscatter diffraction (EBSD) using a scanning electron microscope has proven to be a valuable means for determining the crystal orientation of crystallites as small as ∼0.25 μm. However, it is still not widely used. One deterrent is the high cost of the image intensified video camera system that is commonly used to record the weak EBSD images produced on a phosphor screen. A much less expensive detector system has been devised using a microchannel plate (MCP) electron multiplier to provide the necessary gain in image intensity and a standard video camera to record the image. Excitation of the MCP by secondary electrons and low energy backscattered electron is prevented by a thin aluminum foil on the MCP front surface. The benefits and disadvantages of this approach to EBSD are presented, together with typical EBSD images obtained from it.
A high hydrostatic pressure cell for optical experiments at low temperatures
Authors: Johnson M. R. , Burgmair M. , Trommsdorff H. P.
Published: July 2002

A pressure cell for high resolution spectroscopic experiments at low temperatures is described. The use of helium as pressure medium allows convenient and precise pressure adjustment and assures that minimal strain is experienced by the sample, while the optical access by quartz fibers makes it possible to keep the dimensions of the cell minimal. Hole burning experiments on methyl group tunneling in organic molecular crystals are used to demonstrate potential applications of this cell.
Advances in the design of a thermomechanical analyzer for fibers. II. Computer facilities and software
Authors: Noui L. , Hearle J. W. S.
Published: July 2002

PC-based software for the full control of the flexible thermomechanical analyzer (FTMA) for yarns and fibers is described. The software permits a flexible procedure to control three essential parameters of the FTMA, namely tension, twist, and temperature. The computer program allows data acquisition at a programmable rate of up to 62.5 ksamples/s, on-line data display, and on-line data storage. Up to eight channels can be monitored. A circular buffer was used to store unlimited amount of data. For FTMA applications, data were calibrated in terms of Newtons for the tension, degree Celsius for the temperature, and Newton-meter for the torque and can be saved in three different formats, ASCII, LOTUS, or binary. The software is user friendly as it makes use of graphical user interface for motor control and data display. The software is also capable of controlling thermomechanical tests at constant force.
Application of a grating polarizer to the 106.4 GHz ECH system on Heliotron-E
Authors: Nagasaki K. , Isayama A. , Ejiri A.
Published: July 2002

A grating polarizer with rectangular grooves is designed for the 106.4 GHz electron cyclotron heating (ECH) system on the Heliotron-E helical device. The polarizer is installed on mirrors of waveguide miter bends. In oversized waveguides, the HE11 mode can be treated by the plane wave theory. The polarization of the reflected wave is calculated as a function of the groove parameters and the mirror rotation angle. When launching the ECH power to fusion devices with moderate or strong magnetic shear such as heliotron/torsatron configurations, we should take into account the change of the wave polarization through the plasma. The effect of the magnetic shear can be investigated by using the polarizer. The dependence of the absorbed power on the mirror rotation angle is presented.
Energy spread of boron palladium liquid metal ion source and characterization with focused ion beam system
Authors: Higuchi-Rusli Ronnie
Published: July 2002

The characteristics of a PdB liquid metal ion source have been investigated in terms of its energy spread, current voltage, and total energy distribution. The beam energy spread increases with ion source applied voltage and species mass. The total energy distribution curve exhibits full width at half maximum increase from 20 to 26 eV as the total current increases from 6 to 25 μA. The energy spread of the heavy isotope, 106Pd+, is 44 eV at an extractor applied voltage of 8.5 keV. The energy spread of 11B+ is observed to saturate at high total current (or high extractor applied voltage). This implies that beyond 8.5 keV, the energy spread of 11B+ is independent of applied voltage. Throughout the measurement, the energy spread remained a Gaussian distribution which is an inherent characteristic of sources with Taylor cone formation.
Goniometer for magnetic light scattering studies
Authors: Riddolls T. , Dutcher J. R. , Gigault C.
Published: July 2002

A two-axis goniometer for magnetic light scattering studies that can be constructed easily and cheaply is described.
Large tokamak diagnostics (invited) (abstract)
Authors: Costley A. E.
Published: July 2002

In order to meet the objectives of safely operating, controlling, and optimizing a long-pulse ignited plasma in next-step devices (e.g., ITER), it will be necessary to measure accurately and reliably a wide range of plasma parameters. The choice of measurement techniques and design of the corresponding diagnostic systems will be strongly influenced by the specific measurement requirements and by the practical constraints arising from the harsh radiation environment, limited access, and the need for very high levels of reliability and availability. The experience gained on existing large tokamaks such as JET is a good starting point for the diagnostic design but the extrapolation to next step conditions is substantial and it is already obvious that it will not be possible to apply some of the established techniques. For some measurements new approaches are required and specific R&D is necessary. In this paper, the likely measurement requirements will be outlined and the practical constraints summarized. Potentially suitable measurement techniques will be identified and the problems of implementation briefly discussed. Attention will be concentrated on those areas where the most difficult problems are foreseen and where new approaches are required.
A new high pressure sapphire nuclear magnetic resonance cell
Authors: Bai Shi , Taylor Craig M. , Mayne Charles L. , Pugmire Ronald J. , Grant David M.
Published: July 2002

A new version of a single-crystal sapphire high pressure nuclear magnetic resonance (NMR) cell is described that is capable of controlling the sample pressure independent of the temperature. A movable piston inside the cell adjusts and controls the sample pressure from ambient conditions to 200 atm within ±0.3 atm. The linewidth at half-height for a 13C spectrum of carbon dioxide at 15 °C and 57.8 atm is found to be 0.5 Hz. The carbon dioxide gas/liquid phase transition is clearly observed by measuring 13C chemical shifts as the sample pressure approaches equilibrium. The time required for this NMR cell to reach equilibrium with its surroundings is relatively short, usually 15–30 min. The cell body has the same outer dimensions of a standard spinning turbine and fits into a standard 10 mm commercial probehead capable of controlling the sample temperature using the spectrometer’s variable temperature unit. The flexibility of the device and the increased speed in making the measurement is demonstrated. Such control of important thermodynamic variables facilitates the NMR study of important biochemical and chemical reactions in gas, liquid, and supercritical fluid environments.
Brilliance and flux reduction in imperfect inclined crystals
Authors: Lee W.K. , Blasdell R.C. , Fernandez P.B. , Macrander A.T. , Mills D.M.
Published: July 2002

The inclined crystal geometry has been suggested as a method of reducing the surface absorbed power density of high-heat-load monochromators for third-generation synchrotron radiation sources. Computer simulations have shown that if the crystals are perfectly aligned and have no strains then the diffraction properties of a pair of inclined crystals are very similar to a pair of conventional flat crystals with only subtle effects differentiating the two configurations. However, if the crystals are strained, these subtle differences in the behavior of inclined crystals can result in large beam divergences causing brilliance and flux losses. In this manuscript, we elaborate on these issues and estimate potential brilliance and flux density losses from strained inclined crystals at the APS.
Normal incidence photoresponse in GaAs/AlGaAs quantum well infrared photodetector
Authors: Yuan Zhenyu , Chen Zhenghao , Cui Dafu , Ma Jianwei , Hu Qiang , Zhou Junming , Zhou Yueliang
Published: July 2002

A normal incidence quantum well infrared photodetector consisting of asymmetric GaAs/AlGaAs quantum wells has been demonstrated. The detector uses electron intersubband transitions between bound to extended states in the step quantum well. The infrared photocurrent spectrum characterized using a glowbar monochromator source shows a photovoltaic response in the configuration of normal incidence. The peak wavelength is 10.3 μm and a detectivity Dλ*=3.7×108 cm √Hz/W was achieved at T=80 K.
Compensation method based on formularizing hysteresis of piezoelectric tube scanners
Authors: Wei Cao , Zhang Honghai , Tao Lu , Li Wenju , Shi Hanmin
Published: July 2002

Based on a circular arc scanning model and the formularizing of hysteresis curves of piezoelectric tubes, a three-dimensional scanning model of piezoelectric tubes is presented and used to compensate distortions of measured images scanned by a piezoelectric tube. This model-based compensation method can correct three-dimensional distortions simultaneously with two key parameters which are obtained just by measuring vertical deformation-voltage characteristics of the piezoelectric tube. Experiments showing the effectiveness of this method are also discussed in this article.
An electrical impedance tomography measurement system for experimental use
Authors: Savolainen T. , Kaipio J. P. , Karjalainen P. A. , Vauhkonen M.
Published: July 2002

In electrical impedance tomography (EIT) currents are applied into a volume through electrodes and the resulting voltages at the electrodes are measured. The impedance distribution inside the volume can then be calculated by solving the associated inverse problem. Usually the equipment that is needed for the generation of the current patterns and the measurements are large, expensive and tailored to specific situations. In such cases many of the measurement parameters are fixed and the user cannot change these to adapt the equipment to another measurement situation. In this article we present a simple and affordable EIT measurement device that is based on a PC computer, commercial data acquisition board and software and an external current generation and switching board. We also verify the performance and applicability of the system with a phantom measurement and an unusual measurement object for which there is no specific equipment, that is, the measurement of internal impedance distribution of spruce logs.
A high sensitivity time-resolved microfluorimeter for real-time cell biology
Authors: Martin-Fernandez M. L. , Tobin M. J. , Clarke D. T. , Gregory C. M. , Jones G. R.
Published: July 2002

We describe an instrument based on the novel combination of synchrotron radiation, a high sensitivity time-resolved microfluorimeter, and a multiframe single photon counting data acquisition system. This instrument has been designed specifically to measure kinetic events in live cells using fluorescence resonance energy transfer, and is capable of rapidly collecting multiple consecutive decay profiles from a small number of fluorophores. The low irradiance on the samples (<10 mW/cm2) greatly reduces probe photobleaching and specimen photodamage during prolonged exposures. The Daresbury Synchrotron Radiation Source provides fully wavelength tunable light pulses that have a full width half-maximum of 160 ps at a repetition rate of 3.125 MHz, with the high temporal stability required for continuous measurements over periods of hours. A very low limit of detection (<104 molecules/mW/cm2) is accomplished by combining a high-gain single photon counting detection system with a low fluorescence background optical layout. The latter is achieved by the inclusion of collimating optics, a reflecting objective, and a specially designed beam stop situated in the epi-fluorescence light-path. A typical irradiance of 8 mW/cm2 on a sample of ∼105 fluorescein molecules gives, in under 20 s, a fluorescence decay profile with a peak height of 104 counts, over 400 channels, and a signal to background ratio better than 40. The data acquisition system has been developed to have a real-time time-resolved fluorescence collection capability (denoted as TR2) so that fluorescence lifetime data can be continually collected throughout a changing process. To illustrate the potential of this instrument, we present the results of a TR2 experiment in which lifetime measurements of fluorescence resonance energy transfer are used to monitor the degree of clustering of epidermal growth factor receptors during endocytosis, over a period of about 1 h, with a 5 s resolution.
Reply to ‘‘Comment on ‘Modular digital boxcar for applications in pulsed laser spectroscopy’ ’’ [Rev. Sci. Instrum. 66, 3507 (1995)]
Authors: Dygdala R. S. , Zieliński M.
Published: July 2002

The modular system was designed to be effective, simple, and cheap, given the performance and cost factors of the Logic available at that time, but prepared to work with new modules as needed. Some of these factors have changed with time.
Picosecond transient grating spectroscopy: The nature of the diffracted spectrum
Authors: Högemann Claudia , Pauchard Marc , Vauthey Eric
Published: July 2002

A ps transient grating setup using white light continuum for probing is presented. Measurements on an aromatic molecule in solution have been carried out with this system. The diffracted spectrum is analyzed using Kogelnik’s coupled wave theory. At short time delay after excitation, the diffracted spectrum is strongly dominated by absorption and in this case transient grating spectroscopy is equivalent but more sensitive to transient absorption spectroscopy. If some of the excitation energy is dissipated as heat, the diffracted spectrum is essentially the same as the dispersion spectrum of the transient species at time delays approaching half the acoustic period. The performances of this technique and of transient absorption spectroscopy are compared.