bluuebunny/crossref_metadata_2025 huggingface dataset:
He–Ne interferometer for density measurements in plasma opening switch experiments
Authors: Weber B. V. , Hinshelwood D. D.
Published: July 2002

A He–Ne interferometer is used to measure the line-integrated electron density in the plasma of an operating plasma opening switch (POS). A heterodyne technique is used, where an acousto-optic modulator generates a 40-MHz frequency shift between the reference and scene beams. The phase shift is calculated numerically from the zero-crossing times of the beat signal. The precision of the phase measurement is ±0.5°, however, several nonplasma sources of phase shift are present just after the current through the POS is interrupted. In particular, charged particle flow into the vacuum window results in a negative phase shift. This anomalous phase shift is effectively eliminated by using magnets to deflect the particles away from the window. Measurements during POS shots show a localized decrease in line density prior to current interruption.
Design changes in the sample mount and temperature sensors of the Janis Supervaritemp Dewar: Liquid-nitrogen operation
Authors: Bouchalkha A. , Wicksted J. P. , Shields P.
Published: July 2002

A new sample holder for the Janis Supervaritemp Dewar has been designed which allows very accurate temperature readings at the sample and avoids sample breakage by reducing thermally induced stress. In addition, the successful operation of this helium dewar using liquid nitrogen has been achieved allowing temperatures above 80 K, stable to within ±0.04 K, to be obtained.
A low-profile molecular beam source isolation valve for ultrahigh vacuum applications
Authors: Chaban E. E. , Reutt-Robey J. E.
Published: July 2002

We describe the design of a novel low-profile valve to isolate a molecular beam source from an ultrahigh vacuum system. The valve thickness is simply the thickness of a standard double-sided Conflat flange, on which the valve gate and actuation mechanism are assembled in a fully recessed configuration. The valve gate can accommodate a skimmer and/or several source collimating apertures. The manual actuator is mounted radial to the Conflat flange.
rf SQUID magnetometer with simplified circuitry
Authors: Simacek I. , Zrubec V. , Skakala M.
Published: July 2002

This note contains a brief description of a portable type of magnetometer which uses an rf SQUID. In the simplified electronic circuit no low-frequency modulation is used.
Comment on ‘‘A thermal phase-locked loop for frequency stabilization of internal mirror HeNe lasers (λ=0.633 μm)’’ [Rev. Sci. Instrum. 62, 933 (1991)]
Authors: Holzapfel Wolfgang , Luxem Wolfgang , Settgast Walter
Published: July 2002

In the cited article the frequency stability of a HeNe laser stabilized with the two-mode difference method is directly concluded from the measured intensity difference variation of the two orthogonally polarized laser modes. We point out that this derivation of frequency stability from intensity difference variations may show considerable systematic errors.
Properties of fixed-position Bragg diffractors for parallel detection of x-ray spectra
Authors: Wittry D. B. , Li R. Y.
Published: July 2002

Advantages of wavelength-dispersive spectrometers over energy-dispersive spectrometers for parallel detection of x rays are discussed and factors involved in the design of wavelength-dispersive spectrometers are reviewed. The dispersion and collection solid angle of fixed-position Bragg diffractors used for parallel detection of x rays are calculated and the properties of four such spectrometers based on singly and doubly curved diffractors are compared with the properties of scanning monochromators. It is concluded that the previously studied parallel-detection spectrometers based on Bragg diffractors are less advantageous than scanning monochromators but they may be preferred when it is necessary to detect many characteristic x-ray lines simultaneously or to avoid the use of moving parts.
A laser diode as a light source for calibrating the time base of a streak camera
Authors: Schunke B. , Gowers C. W. , Hirsch K. , Nielsen P.
Published: July 2002

The dc operation of some laser diodes produces high-frequency amplitude modulation of the laser output in the GHz frequency range. This phenomenon provides a simple and inexpensive method for checking the sweep linearity of a fast-gated streak camera.
Simultaneous angle-resolved measurement of the band structure of single-crystal graphite by an improved two-dimensional display analyzer
Authors: Nishimoto Hiroyuki , Daimon Hiroshi , Suga Shigemasa , Tezuka Yoshihiro , Ino Shozo , Kato Isao , Zenitani Fukuo , Soezima Hiroyoshi
Published: July 2002

We have embodied a new version of two-dimensional display-type spherical mirror analyzer [H. Daimon and S. Ino, Rev. Sci. Instrum. 61, 57(1990)]. A couple of concentric hemispherical small grids and 12 pairs of obstacle rings have been attached to the original type of analyzer in order to operate with a constant pass-energy mode and improve the uniformity of the energy resolution of the analyzer all over the detection area, respectively. We performed a test on the resolution of the analyzer, and applied it to the simultaneous angle-resolved photoelectron spectroscopy on the band structures of single-crystal graphite (Kish graphite) within the acceptance cone of ±50°. The observed band structure is in good agreement with those reported by other investigators. We observed a ring-like pattern which enlarged as the binding energy approached the Fermi level. This ring is ascribed to the cross section of the π band. Although the designed energy resolution is 1% of the pass energy, the minimum value realized reached in this study was 0.2 eV for the pass energy of 10 eV [H. Daimon, Rev. Sci. Instrum. 59, 545 (1988); 61, 205 (1990)].
Instrument for research on interfaces and surfaces
Authors: Bonnelle C. , Vergand F. , Jonnard P. , André J.-M. , Staub P. F. , Avila P. , Chargelègue P. , Fontaine M.-F. , Laporte D. , Paquier P. , Ringuenet A. , Rodriguez B.
Published: July 2002

We describe an instrument designed for studying the electronic structure of bulk, surface, and deep solid–solid interface. The analysis is made by soft-x-ray emission spectroscopy induced by electron bombardment. The target is placed under ultrahigh vacuum and can be prepared and treated in situ. High resolution is achieved both as concerns the photon energy and the electron-beam energy. Tests have been made in the dispersive mode and in the characteristic isochromat mode. In both cases experimental resolution is in good agreement with the expected one.
Analyses for a charged microparticle from an ion pump to trap at low electric field with high enhancement factor
Authors: Saeki Hiroshi , Momose Takashi , Ishimaru Hajime
Published: July 2002

An experiment using a wire simulating an electron beam was carried out in atmosphere to find organic particles (5-μm thickness collected from an ion pump) trapped in a low electric field. It was found that these needlelike charged flakes stood upright at the bottom surface of the beam chamber without applied electric field. In spite of large adhesive action between the particle and the inner chamber surface in air, it was also found that the sample microparticles were trapped at the low electric field of 2525 V/m. Furthermore, the measured charge on the samples ranged from 1×10−13 C to 3×10−13 C. Our new theoretical analyses for the samples show that the electric field acting on the needlelike microparticles is enhanced approximately 104 times from the results of the atmospheric experiment, and that the charged particles in vacuum can be trapped at a lower electric field of 70 V/m in the TRISTAN accumulation ring (time average electric field at the beam current of 30 mA) because of weak adhesion between the particles and an inner chamber surface rather than that in atmosphere. Therefore, microparticle trapping phenomena can be caused by such a charged particle coming from an ion pump or a distributed ion pump used in an electron accelerator.
Ultradry oxidation system equipped with a newly designed gas preheating unit for growing ultrathin silicon oxide films
Authors: Yamada Hiroshi
Published: July 2002

A practical thermal oxidation system used in ultradry, ultrathin silicon oxide film growth is described. It comprises a double-wall-type fused-quartz reactor, a newly designed material-gas preheating unit, and three vacuum chambers for dehydrating and exchanging wafers. The preheating unit, used to eliminate temperature disturbances in the reactor, is assembled with a SiC composite shrouded by fused quartz and an infrared lamp heater. The temperature of material gases is quickly elevated to about 600 °C by passing them through this unit just before reaching the reactor’s gas inlet. Consequently, the temperature of Si wafers in the reactor can be precisely controlled within ±0.15° at 800 °C. Moreover, the moisture concentration (humidity) in the reactor is always kept below 1 ppb. By rigorously controlling the growth temperature and ambience, high-reliability 5.0±0.05-nm-thick oxide films are obtained.
An atomic-resolution cryogenic scanning tunneling microscope
Authors: Chen X. , Frank E. R. , Hamers R. J.
Published: July 2002

A design is presented for a cryogenic scanning tunneling microscope which has demonstrated atomic resolution at temperatures between 300 and 120 K in ultrahigh vacuum. The design features simple in situ exchange of samples and tips, active cooling of the sample, excellent visibility of the sample-tip region, and the use of a thermally isolated inchworm translator for coarse approach. It has demonstrated atomic resolution on SI(111)-(7×7) and Si(001) surfaces at 120 K.
A new image processing method for extracting integrated intensities from low-energy electron diffraction spots
Authors: Toofan Jahansooz , Watson Philip R.
Published: July 2002

We have devised and programmed a new scheme based on image processing techniques for extracting the intensity of fluorescent display low-energy electron diffraction spots. The method make no assumptions about spot shape, does not use thresholding, and can deal with badly behaved backgrounds, noise spikes, and dead pixels. All decisions about whether a particular pixel belongs to a spot or to the background are made on purely logical grounds with generally binary operator masks. Once the spot edge has been defined, a local background is subtracted to generate an integrated spot intensity. Extensive tests with diffraction features ranging from very strong to indistinguishable from background by eye show this method to be stable, fast, and reproducible.
Measurement of dynamic polarization modulation depth utilizing the J1–J4 method of spectrum analysis
Authors: Sudarshanam V. S. , Desu S. B.
Published: July 2002

A spectrum analysis method for the linear, direct, and self-consistent measurement of dynamic modulation depth of polarization modulators is presented. This method utilizes the Bessel recurrence relation to determine the modulation depth from the photodetector voltage amplitudes at the fundamental frequency and its next three harmonics. Based on the existing J1–J4 method of dynamic phase-shift measurement in homodyne interferometry, this method is useful for calibration of polarization modulated ellipsometers. The method is demonstrated through the use of a highly birefringent transparent thin film of piezoelectric polyvinylidene fluoride with indium tin oxide electrodes. The theoretical analysis of the measured noise factor for the particular system configuration predicted a minimum detectable polarization modulation depth of 0.2 rad, and was experimentally verified.
Comment on ‘‘High intensity low tube-voltage x-ray source for laboratory extended x-ray absorbed fine structure measurements’’ [Rev. Sci. Instrum. 64, 2702 (1993)]
Authors: Sakurai Kenji , Sakurai Hitoshi
Published: July 2002

In the cited article, an x-ray source developed for extended x-ray absorption fine structure measurements is described. After the publication, the authors have further improved the performance by employing a compact rotating anode and by optimizing an electron gun. This new x-ray generator provides high tube current of 1100 mA at 18 kV with the narrow focal spot of about 0.1 mm in width. Extremely intense monochromatic x rays, which are completely free from higher order reflections, are now available in a laboratory, and the measurement time required for a practical sample has been shortened to less than 2 h.
Determination of the crystallographic orientation of a single crystal using resonant ultrasound spectroscopy
Authors: Sarrao J. L. , Chen S. R. , Visscher W. M. , Lei Ming , Kocks U. F. , Migliori A.
Published: July 2002

Using resonant ultrasound spectroscopy (RUS) we have determined the crystallographic orientation of a tantalum single crystal from a measurement of its mechanical resonance spectrum. This accomplishment is significant not only because it reduces the sample requirements for RUS but also because it is the simplest method for simultaneous determination of a crystal’s elastic constants and microscopic crystallographic orientation.
Noninvasive measurement of temperature distributions with high spatial resolution using quantitative imaging of NMR relaxation times
Authors: Doran Simon J. , Carpenter T. Adrian , Hall Laurance D.
Published: July 2002

The steady-state temperature distribution within a block of cis-polybutadiene has been mapped using quantitative magnetic resonance imaging. The experiment described makes use of the temperature dependence of the nuclear magnetic longitudinal relaxation time (T1) of the polymer protons. Hot and cold water flowed through two axially mounted pipes in a cylindrical sample, creating a dipolar temperature distribution. A fast inversion recovery imaging sequence was used to map T1 values in the sample with a spatial resolution of 0.3 mm and random error of ±5% for individual pixels in the 128×128 image. The T1 values thus obtained were converted into temperatures using an empirical calibration curve, leading to a temperature resolution of ±2 K for each pixel. Using a median filter (which reduces the image resolution by a variable factor of up to 3), the data are rendered smooth enough to obtain a clear contour plot. This is compared with a finite element solution of Laplace’s equation over the same domain, demonstrating that the MRI technique is reliable. A number of experimental problems limiting both the exact comparison between theory and experiment and the long-term utility of the technique are discussed.
Computer models of wall–sensor interactions in measurements using zero-balance heat-flux meters
Authors: Poloniecki José Gabriel , Grignon Michel , Saïdi Azouaou
Published: July 2002

The principles of the zero-balance heat-flux meter (HFM) technique are studied with two steady-state finite difference computer models developed to simulate the responses of a sensor mounted either on the cold face or on the warm face of a wall. Computations show that a particular Biot number (defined by the authors), the dimensionless wall width, and the dimensionless wall thickness are the parameters affecting the HFM accuracy. The authors present outputs of their models that show the influence of these parameters, and propose three empirical expressions that allow corrections of the operational errors. It can be affirmed that the flux meter should be mounted on the cold face in the case of a small Biot number (it assures an accuracy of at least 5% if the Biot number value is smaller than 0.2). And it should be mounted on the warm face when the Biot number is large (in the case of building insulators in normal environment conditions it assures an accuracy of at least 10%). In other cases, the flux meter should be used as a gradient flux meter switching off the internal heater.
Laser-excited confocal-fluorescence gel scanner
Authors: Mathies Richard A. , Scherer James R. , Quesada Mark A. , Rye Hays S. , Glazer Alexander N.
Published: July 2002

A high-sensitivity, laser-excited, confocal-fluorescence scanner has been developed for the detection of fluorescently labeled nucleic acids separated on slab gels. The gel is placed on a motor-driven, two-dimensional scan stage and raster scanned past the optical detection system. The 488-nm argon ion laser beam is introduced into the confocal optical system at a long-pass dichroic beam splitter and focused within the gel to an ∼2 μm diameter spot by a high-numerical aperture microscope objective. The resulting fluorescence is gathered by the objective, passed back through the first long-pass beam splitter, and relayed to a second dichroic beam splitter that separates the red and green emissions. The fluorescence is then focused on confocal spatial filters to reduce stray and scattered light, passed through spectral filters, and detected with photomultipliers. The resulting signals are amplified, filtered, and digitized for display on a computer. This system can detect as little as 5×10−12 M fluorescein, the resolution as operated is 160 μm, and it can scan a 6 cm×6 cm gel using a scan rate of 4 cm/s in 12 min. The detection of DNA on slab gels, two-color DNA fragment sizing, and microtiter plate scanning are presented to illustrate some of the possible applications of this apparatus.
A laboratory EXAFS spectrometer in transmission dispersive mode
Authors: Lecante P. , Jaud J. , Mosset A. , Galy J. , Burian A.
Published: July 2002

A laboratory spectrometer designed for routine extended x-ray absorption fine structure (EXAFS) measurements in dispersive mode is described. Factors determining energy range and resolution are detailed. An empirical energy calibration procedure is proposed. EXAFS spectra obtained for copper and zirconium metal foil and molecular complex ZrOCl2 compare favorably with data obtained using a conventional synchrotron facility.
A metrological constant force stylus profiler
Authors: Howard L. P. , Smith S. T.
Published: July 2002

A second-generation constant force profiler is described combining a capacitance based stylus force probe with interferometric optical metrology to monitor position of the specimen carriage. The probe has a vertical range of 15 μm with a resolution of 0.23 nm and a flat bandwidth response with a −3 dB cutoff at 228 Hz. Passing the output signal through a single pole 200 Hz low-pass filter, an overall system peak-to-peak broadband noise of less than 5 nm is observed. Manufactured primarily from inexpensive materials, the instrument demonstrates a stability of around 1 nm min−1 under controlled laboratory conditions. Using an inexpensive motor/gearbox/micrometer open-loop drive with velocity variations of up to 20%, profiles showing nanometer repeatability over 15 mm traces are demonstrated. Also shown is a profile of a soft contact lens in the hydrated state. The effect of the contact stiffness on the stylus probe/specimen interaction is illustrated by examining the dynamics of the force probe system while operating in the repulsive mode.
A low-energy and low-emittance ion beam source for use with the super-microbeam production system (abstract)
Authors: Isoya Akira
Published: July 2002

We are developing a new type of microbeam system, intentionally utilizing the process of acceleration, accompanied with the beam contraction effect (conservation of normalized emittance). This device will enable one to produce microbeams for any ion species, less than 0.1 μm in diameter. A tentative design of lens system (ion energy=100 kV), composed of an entrance aperture lens and an einzel lens, will be described, and it will be discussed why the spherical aberration can be depressed much lower than the usual nonaccelerating lenses. The chromatic aberration due to the fluctuation of the acceleration voltage can be avoided in principle. Hence the only source of this type of aberration is the energy spread of the ion beam from the ion source. The maximum performance of this microbeam system may be obtained when the energy increasing ratio is large enough so that the incident beam energy is kept as low as possible. For investigating these points a hydrogen ion source of special design has been tested. It was found that the intrinsic energy spread can be made considerably low (∼0.5 eV) and a narrow parallel ion beam of several tens eV, which is nearly perfectly neutralized in space charge, can be obtained.
Measurements of discharge parameters of the ion source at high potential
Authors: Li H. J. , Shi Y. X. , Li M.
Published: July 2002

The present measurement system is composed of signal preprocessors, an A/D conversion card, optical fibers, a microcomputer, and an interface. After discharge parameters of an ion source at high potential, i.e., analog signals, are preprocessed by means of LPF, amplitude limit, and normalization, they are changed into digital signals by A/D conversion. The digital signals are transferred through optical fibers to low potential, then they are gathered, processed, or stored by the microcomputer. The system can measure eight analog signals at high potential through scanning. Each measurement will take about 160 μs with a precision of ±1 LSB, i.e., ±0.4% maximum relative error at full range. Measurements of discharge parameters of the ion source at high potential were made for a steady state ion source and a high current pulse ion source successively, whose results are in good agreement with practical cases. The formation and propagation of interference and approaches of anti-interference under high current and high pulse voltage conditions are briefly described in the present article.
Experimental characterization of a hydrogen/argon cascaded arc plasma source
Authors: Qing Zhou , de Graaf M. J. , van de Sanden M. C. M. , Otorbaev D. K. , Schram D. C.
Published: July 2002

A H2 /Ar cascaded arc plasma source has been experimentally characterized by determination of the efficiency, the electric field, and the pressure gradient of the arc. The results show that the efficiency of a H2/Ar cascaded arc drops when the hydrogen flow rate is increased. The electron temperature in the argon cascaded arc has been derived to be in the range 9000–12 500 K. For a hydrogen arc, the mass dissociation degree of hydrogen molecules has been derived to be above 60%.
Gallium liquid metal ion source (abstract)
Authors: Tang J. T.
Published: July 2002

Considerable interest has been shown in the electrohydrodynamic liquid field emission ion source, from which positive ions emitted under the action of high electric fields, and high brightness sources are being developed with a variety of applications in mind. The basic principles of such sources are discussed. The threshold voltage Vth, the ion current (I) versus extraction voltage (V) relationships under various operating temperatures To, I versus To relationship, the angular current intensity and brightness, energy spread, as well as the current changes slowly with time under a definite voltage, are presented and discussed. The experiments show that the present performance of the ion source is as follows: The threshold voltage is about 5.4 kV, the brightness equal to 1×108A/cm2 sr, and energy spread of 26 eV.
Some characteristics of a cylindrical mesh hollow-cathode magnetron ion source (abstract)
Authors: Miljević V. I.
Published: July 2002

A hollow-cathode magnetron ion source, based on a new type of hollow-cathode discharge [V. Miljević, Phys. Lett. A 92, 439 (1982); V. Miljević, VI ESCAMPIG, Oxford (1982), p. 123; V. Miljević, VII ESCAMPIG, Lisbon (1984), p. 166], is presented. This ion source has all the good characteristics of a conventional magnetron ion source [B. Cobić et al., Nucl. Instrum. Methods 24, 358 (1963)], but in addition, it provides very effective axial ion extraction from a cylindrical mesh hollow cathode [V. Miljević, Rev. Sci. Instrum. 55, 121 (1964)]. In this study a special type of ion extraction is used.
Optimization and control of a small angle ion source using an adaptive neural network controller (invited)
Authors: Brown S. K. , Mead W. C. , Bowling P. S. , Jones R. D. , Barnes C. W.
Published: July 2002

This project developed an automated controller based on an artificial neural network and evaluated its applicability in a real-time environment. This capability was developed within the context of a small angle negative ion source on the Discharge Test Stand at Los Alamos. The controller processes information obtained from the beam current wave form, developing a figure of merit (fom) to determine the ion source operating conditions. The fom is composed of the magnitude of the beam current, the stability of operation, and the quietness of the beam. Using no knowledge of operating conditions, the controller begins by making of rough scan of the four-dimensional operating surface. This surface uses as independent variables the anode and cathode temperatures, the hydrogen flow rate, and the arc voltage. The dependent variable is the fom described above. Once the rough approximation of the surface has been determined, the network formulates a model from which it determines the best operating point. The controller takes the ion source to that operating point for a reality check. As real data is fed in, the model of the operating surface is updated until the neural network’s model agrees with reality. The controller then uses a gradient ascent method to optimize the operation of the ion source. Initial tests of the controller indicate that it is remarkably capable. It has optimized the operation of the ion source on six different occasions bringing the beam to excellent quality and stability.
Simulation of ion beam extraction (invited)
Authors: Spädtke P.
Published: July 2002

A description of methods is given which are used in computer programs for the simulation of extraction systems for ion sources. Specific equations which are important for ion beam extraction will be given. The need of specialized programs will be pointed out with the help of examples.
Particle simulation of ion optics and grid erosion for two-grid and three-grid systems (abstract)a)
Authors: Peng Xiaohang , Ruyten Wilhelmus M. , Friedly Verlin J. , Keefer Dennis , Zhang Quan
Published: July 2002

A particle simulation code has been developed to study ion optics and the effect of charge-exchange-induced grid erosion in electron bombardment ion thrusters. The code is based on the particle-in-cell method to simulate the beam extraction and ion optics and a Monte Carlo method to calculate the charge exchange collisions between fast beam ions and neutral particles. The space charge effects for both fast beam ions and slow charge exchange ions are included. Both two- and three-dimensional versions of this code have been developed for both two-grid and three-grid systems. The two-dimensional model provides a qualitative description of the details of the ion flow and the charge exchange collisions. The three-dimensional version has successfully predicted the experimentally observed erosion pattern in which the maximum erosion occurs at the geometric centers of accelerator grid apertures.
Negative-ion production probability in rf plasma sputter-type heavy negative-ion source (abstract)a)
Authors: Tsuji Hiroshi , Ishikawa Junzo , Kawabata Yasuyuki , Gotoh Yasuhito
Published: July 2002

We have constructed a rf plasma sputter-type heavy negative ion source, which can deliver high current negative ion beams such as Cu− of 12.1 mA, Si− of 3.8 mA, and B−2 of 1 mA in dc operation mode. In our source, the estimated negative ion production probability of Cu was much more than the value obtained by the conventional negative ionization probability equation with an exponential dependence on velocity. We measured heavy negative ion production probabilities by Xe+ sputtering on various cesiated metals. The probabilities were strongly affected by the cesiated surface condition which was determined by a flux of neutral cesium supply to the surface and a target surface temperature. The measured maximum probabilities at the optimal conditions were considerably high, and they were about 10% or more for Cu, C, Si, Ge, and W targets and about 1% for Ta and Mo targets. The probability for very low velocity particles such as sputtered heavy metal atoms might be affected by a surface ionization process with a high local surface temperature.
A neutral lithium beam source
Authors: Zhang XiaoDong , Wang ZhengMin , Hu LiQun
Published: July 2002

A low energy neutral lithium beam source with energy about 6 keV and a neutral beam equivalent current of 20 μA/cm2 has been developed in ASIPP in order to measure the density gradient and the fluctuations in the edge plasma of the HT-6M tokamak. In the source, lithium ions are extracted from a solid emitter (β-eucryptite), focused in a two-tube immersion lens, and neutralized in a charge-exchange cell with sodium. This source operates in pulsed mode. The pulse length is adjustable from 10 to 100 ms.
Scanning tunneling microscope for cluster studies
Authors: Poothackanal Thomas , Ouseph P. J. , Mathur R. G.
Published: July 2002

Details of the construction of a scanning tunneling microscope (STM) are given in this article. This STM enables one to change the atmosphere around the sample easily from air to inert gases or to vacuum. The STM is compatible with a chamber in which metallic clusters are prepared.
Prevention of electron emission from negative electrode in a beam direct energy converter using localized magnetic field
Authors: Hashimoto Kiyoshi , Kawauchi Koji
Published: July 2002

The present article describes prevention of electron emission by means of localized magnetic field covering a negative electrode to reduce power loss in an ion beam direct energy converter. An experiment was carried out to recover a 10-cm-diam helium ion beam with energy of 50 keV, where the prevention of electron emission was attempted by using a solenoid coil surrounding the electrode and with permanent magnets set on the electrode surface. When the solenoid coil was used, the negative electrode current hardly decreased due to increase in slow ion inflow from gas cell plasma generated by beam-gas collision. On the other hand, the scheme with permanent magnets reduced the current loss successfully.
Versatile model position monitoring system
Authors: Grauer-Carstensen Helmut
Published: July 2002

A nonintrusive optical model displacement monitoring system is presented, which was primarily developed for wind tunnel model monitoring purposes but proved to be extremely versatile, reliable, and easy to handle, mainly due to its design principles of operating with a variable number of independent optical sensing units and needing no special preparation of the object to be monitored except for a sufficiently high lighting contrast between object and background.
A nonleak trough for monolayers at the air/water interface
Authors: Qiu Ruozi , MacDonald Robert C.
Published: July 2002

The problem of barrier leakage in surface pressure-surface area measurements has been overcome with a trough wherein the sample is compressed inside a band of teflon-covered spring steel strip. A computer-controlled stepping motor drive applies force to one side of the band, deforming it from a rounded triangle to a ‘‘v’’ shape. The compression range extends up to 4:1 and is repeatable to ±2%. Calibration is conveniently and accurately done with a computer-interfaced video imaging and analysis system. The design greatly simplifies the construction of surface troughs and completely obviates the possibility of leakage at high surface pressures. The trough is useful for investigations involving high surface pressures and/or requiring long times.
Cryogenic bolometric radiometer and telescope
Authors: Tucker G. S. , Peterson J. B. , Netterfield C. B. , Griffith E. L. , Griffin G. S.
Published: July 2002

The design and performance of an instrument to measure cosmic microwave background (CMB) anisotropy on angular scales from 10′ to 30′ is reported. The instrument utilizes a single-mode waveguide bolometer cooled by an adiabatic demagnetization refrigerator. This is the first time a 100 mK bolometer has been used in a CMB experiment. Observations of the CMB were made using this radiometer from the South Pole during the 1991–1992 season and, with minor modifications, during the 1992–1993 season. The radiometer is used with a fully steerable altitude-azimuth Cassegrain telescope built for this observation, also described here.
An automatic apparatus for measuring interfacial and film tension under static and dynamic conditions
Authors: Soos Janos M. , Koczo Kalman , Erdos Elemer , Wasan Darsh T.
Published: July 2002

A fully automated and computer controlled apparatus is described that measures the interfacial tension (IFT) of fluid interfaces and the film tension of liquid films. The fluid interface is formed as a nearly spherical drop at the tip of a capillary which is immersed into another immiscible fluid. The size of the interface is controlled and measured by controlling the size of the drop and the capillary pressure is monitored by a sensitive pressure transducer. The interfacial tension is calculated by the Young–Laplace equation. The drop at the capillary tip can also be covered with a cap shaped liquid film and then the film area can be controlled and the film tension measured. This apparatus is useful for measuring equilibrium interfacial tension or film tension, the adsorption kinetics by stress relaxation experiment and the dynamic interfacial tension or dynamic film tension under both interface expansion or contraction conditions. The capabilities of this versatile, automatic instrument are illustrated with typical experimental results.
A Freeman ion source for oxygen ions in an implanter
Authors: Song Zhizhong , Yu Jinxiang
Published: July 2002

A Freeman ion source for the LC-2F implanter was improved. In this source the filament is a 2-mm-diam tungsten wire covered with a LaB6 cylinder. The discharge chamber is made of antioxidation and high temperature resistant stainless steel. The source lifetime is more than 10 h in pure oxygen discharges, and no oxidation phenomenon occurs on the discharge chamber during long time operation. The source discharge and extraction characteristics are similar to those used before for BF3 and P discharge. So the source can be used in a wide range of microelectronics and material science.
A thermosensitive quartz resonator with a built-in microheater as a multipurpose sensor
Authors: Spassov Lozan , Yankov Dimitar Y. , Georgiev Vesselin , Yossifov Eduard , Vergov Lazar
Published: July 2002

A design of a thermosensitive quartz resonator with a built-in microheater is suggested. The resonator uses a piezoelement of a special crystal cut and has a very high-temperature sensitivity. Because of the linear temperature-frequency characteristic of the resonator, it can be used as a temperature sensor in a wide temperature range—from −20 to 100 °C. The change of the heater’s input power at a constant ambient temperature leads to a corresponding resonator’s frequency change. Because of the linearity of the resonator’s temperature-frequency characteristic the power-frequency dependence is also linear. In such a way the resonator can be utilized as an electrical power meter in the range of 0–400 mW with a sensitivity of about 136 Hz/mW. Using the heater, the resonator can be heated to temperatures higher than the ambient temperature. If the resonator is placed in a path of a flowing liquid, the liquid flow cools the resonator and causes a frequency change, related to the flow rate. The dependence of the resonator’s temperature change on the water flow rate at different input powers has been studied in the range of 0.1–1.2 m/s.
Current ratio controller CRC2 for electrodeposition
Authors: Fiedler D. A. , Scheer U. , Fritz H. P.
Published: July 2002

For the quasicontinuous potentiostatic electrodeposition of compound semiconductors, up to four injection anodes of different and differently changing resistances were used simultaneously. The design of an automatic current control unit to keep the relative anodic currents constant is shown. To allow for dynamic adjustment of the working potential, a ramp generator is added. The all-in-one design facilitates completely oscillation-free operation.
An image acquisition system built with a modular frame grabber for scanning electron microscopes
Authors: Ruan Shengyang , Kapp Oscar H.
Published: July 2002

We have built an image acquisition and processing system based on a modular frame grabber board (MFG) for use with scanning (or scanning transmission) electron microscopes. The variable-scan acquisition module of the grabber board provides compatibility with electron microscopes processing various scan speeds, e.g., the very slow scan rate of our mirror-type electron microscope. In addition to the acquisition function, the board provides many image processing capabilities. A special time-base unit was built to synchronize the acquisition system with the scanning system on the electron microscope. A Windows application has been built to operate the MFG as well as manage all functions of the electron microscope. Using this approach we have been able to greatly simplify the task of digital image acquisition as well as creating a powerful and seamless interface to our Windows-based environment.
Annular-type solid state detector for a scanning x-ray analytical microscope
Authors: Shimomura S. , Nakazawa H.
Published: July 2002

An annular-type solid state detector (SSD) was attached to a scanning x-ray analytical microscope to accomplish certain superior analytical features. The major advantages of this kind of attachment are a large solid angle for detection of scattered x rays from a small point covering the entire Debye–Sherrer ring diffracted from a polycrystalline sample. To demonstrate the above features, the crystallite distribution of an agate sample was depicted as a micrograph using the diffraction intensities of 101̄1 reflection of quartz. For comparison and to emphasize the special features of the present setup, a similar observation was also carried out by a conventional SSD.
A real-time, nonintrusive trace gas detector based on laser photothermal deflection
Authors: de Vries H. S. M. , Dam N. , van Lieshout M. R. , Sikkens C. , Harren F. J. M. , Reuss J.
Published: July 2002

We present the layout and technical details of a trace gas monitor based on photothermal deflection. The operating principle of this instrument, i.e., the deflection of a (weak) probe laser beam by the thermal refractive index gradient induced by trace gas absorption of an intense pump laser beam, allows nonintrusive measurements with good space and time resolution. An intra-cavity CO2 laser is used as the pump beam and a red HeNe laser as the probe. The latter runs perpendicular to the pump beam to optimize spatial resolution. To increase sensitivity, the probe laser is incorporated in a multipass setup. The instrument is demonstrated by the localization of ethylene emission sites on a cherry tomato and by monitoring ammonia production due to nitrogen fixation by cyanobacteria. Both C2H4 and NH3 can be detected at the 1–3 ppb level, at a spatial resolution of 2 mm (along the pump laser)×0.6 mm (perpendicular to it), and a response time of 0.1 s (without background correction) or 15 s (including background correction). Sensitivity can be increased at the expense of spatial resolution, and vice versa. In principle, this instrument is applicable to all those gases possessing a characteristic (‘‘fingerprint’’) spectrum in the CO2 laser range. The great advantage of the photothermal deflection technique with respect to other trace gas detection schemes lies in the nonintrusive character of the measurements. There is no need to enclose the sample in a vessel or to suck large volumes of air into the detector; measurements can be performed in open air and in real time. This should prove especially useful where sticky (polar) gases, like H2O, NH3, CH3OH, etc., are to be detected quantitatively. Main applications include air quality monitoring, especially concerning dry deposition rate measurements using the eddy correlation technique, and the study of volatile metabolite emission of biological samples.
Measurement of the electrical properties of electromigration specimens
Authors: Jones B. K. , Xu Y. Z.
Published: July 2002

A description is given of the design, implementation, and performance of a circuit to measure the electrical properties of resistive specimens of about 10 Ω such as are used in electromigration studies. The ac bridge can measure the changes in resistance, second-harmonic amplitude, second-harmonic phase shift, thermal noise, and excess (1/f) electrical noise. All the parameters can be monitored simultaneously and continuously. The performance is comparable with that of systems designed to measure each of the quantities only. The special features are that it is an autobalance bridge so that changes in the measured quantities are recorded by the feedback signal, the spectrum analyzer is not overloaded, and the recovery of the noise signal is performed by software.
A method for measuring large changes in the payload voltage of rockets and satellites
Authors: Siefring Carl L. , Rodriguez Paul , Baumback Mark M. , Antoniades John A. , Walker David N.
Published: July 2002

We present a method for measuring large changes in the electrical potential of a spacecraft. It is known that a spacecraft in the ionosphere can obtain voltages as large as a few kilovolts. Spacecraft charging can occur naturally in the auroral regions due to high-energy streaming electrons or during the operation of active experiments, such as ion/electron beams or electromagnetic tethers. Charging and discharging events are often impulsive in nature and a method fast enough to track these potential changes could be extremely useful. For this purpose we have designed the Naval Research Laboratory Floating Probe (FP). The FP consists of a metallic sphere containing a high-impedance amplifier and a capacitive divider network for scaling large voltages to the range that typical solid state circuits can handle. Operation is similar to other floating probes; when placed in the surrounding ionosphere via a long deployable boom, the sphere quickly attains a voltage that approximates its local plasma potential. By measuring the difference between the sphere potential and the spacecraft-body potential it is possible, under certain circumstances, to determine the payload potential relative to the surrounding region. The probe can be used for either positive or negative polarity measurements, however, the ‘‘worst case’’ time response is associated with negative charging since the probe must collect ions to reach the local plasma potential. We tested the FP in a large vacuum chamber and followed this with a successful flight on a sounding rocket (SPEAR III). We will discuss the FP design, construction, theory of operation, and some problems and limitations encountered during the testing of the instrument.
Low-noise optical heterodyne spectrum analyzer
Authors: Krüger E.
Published: July 2002

A prototype setup for a low-noise, high-resolution, multi-Gigahertz-span optical heterodyne spectrum analyzer is presented. The frequencies of the unknown optical spectrum are converted to zero intermediate frequency by heterodyning with the output from a tunable single-mode local oscillator laser in an optical mixer. The low-frequency beats are rectified, and their strength is recorded while the spectrum is scanned by tuning the local oscillator. Low-noise heterodyning requires double balance (or at least single balance) of the optical mixer. Further optimization of the noise performance can be achieved by adjusting the power levels of the light beams. Successful operation of the analyzer has been demonstrated by recording the output spectrum of a mode-locked dye laser.
Spectroscopy beamline at the Advanced Photon Source for the photon energy region from 0.5 to 3 keVa)
Authors: Randall K. J. , Gluskin E. , Xu Z.
Published: July 2002

Interest in the 0.5 to 3 keV, intermediate x-ray, energy region has recently intensified as this spectral region covers, among others, the important L and M edges of transition-metal and rare-earth magnetic materials, respectively. Third-generation synchrotron facilities with their inherent high brightness have the unique potential to cover this energy region with high-resolution, high-flux x-ray beams ideal for spectroscopic studies. A 5.5-cm-period, planar undulator to be installed on the 7-GeV Advanced Photon Source will produce a high brightness source of intermediate-energy x rays. The 0.5- to 3-keV spectroscopy beamline is based on the spherical grating monochromator design that has already been shown to yield high resolution and throughput in the soft-x-ray region, below 1 keV. The beamline has been designed to cover the entire region with a peak resolving power of 6000–10 000. Photon flux at the sample is calculated to be in the range from 1011 to 1013 photons/s into a spot size of 1 mm2. A refocusing mirror will be used to further demagnify the image size at a second experimental station. As a second phase to the spectroscopy program, an elliptically polarized insertion device will be used. The polarization preserving nature of the grazing incidence optical elements in the SGM is crucial to obtain x rays of well-defined polarization. The beamline layout, together with calculations of resolution, throughput, power loading, and high harmonic suppression, will be presented. The photoemission experimental end stations for the spectroscopy station will also be briefly described.
A fiber-optic sensor for microwave field measurements
Authors: Schmauß B. , März M. , Ernst J.
Published: July 2002

A fiber-optic sensor for weak interaction measuring of the electric field intensity in microwave fields is presented. The most remarkable features of the sensor are a low isotropy error, a good selectivity between the electric and magnetic field component, a high sensitivity, low field distortions, and inexpensive fabrication. A tiny microwave absorber mounted at the end of an optical fiber changes its temperature according to the electric field intensity. The absorber temperature is measured by making use of the optical transmittivity variation of a semiconductor element. A simple evaluation of the optical attenuation leads to a readout which is proportional to the square of the electric field strength. In order to overcome the problems due to fiber bend losses a mode acceptance filter is described.
Report on x-ray science with polarized radiation
Authors: Shen Qun , Finkelstein Kenneth D.
Published: July 2002

In this report, the highlights of the satellite meeting on ‘‘X-ray Science with Polarized Radiation,’’ which was held on July 24–25, 1994, at Cornell University in Ithaca, New York, are summarized.
Workshop on techniques and experimental methods for x-ray absorption fine structure spectroscopy
Authors: Lamble G. M.
Published: July 2002

The topics discussed at the Workshop included the following: 1) X-ray Absorption Fine Structure Spectroscopy (XAFS) experiments which will be made possible by the 3rd generation high brilliance machines; 2) experiments on the L-edges of the transition metals in proteins; 3) the instrumentation for the x-ray standing-wave beamline. (AIP)