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Review of Scientific Instruments

Issue 5 • Date May 1999

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Displaying Results 1 - 25 of 58
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Review of black surfaces for space-borne infrared systems

    Page(s): 2193 - 2217
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    Low reflectivity (“black”) surface treatments for space-borne infrared systems are reviewed. The uses of black surfaces in general, as well as for specific space-borne applications are discussed. Compositions of a wide variety of surface treatments with examples of experimental data to characterize performances are provided. Specific treatments included are: Ames 24E paint; AZKO 463 (Sikkens, Cat-A-Lac) paint; Ball IR black paint; Chemglaze (Aeroglaze) Z306 and Z302 paints; Eccosorb 268E paint; Parsons Black paint; black anodize; black Hardlub; black Hardcoat; Martin Black; InfraBlack; Enhanced Martin Black; Ebonal C; Teflon; ion beam textured; appliqués; black chrome; black etched beryllium on beryllium; plasma sprayed boron on beryllium; plasma sprayed beryllium on beryllium; boron carbide on POCO graphite; and Kapton. Data presented for some but not all of the surfaces include: spectrally integrated, 5–25 μm hemispherical-directional reflectance; spectral reflectance at wavelengths between 2 and 500 μm for a variety of incident angles from 5° to 80°; and bidirectional reflectance at a number of wavelengths between 5 and 300 μm for a variety of incident angles from 0° to 80°. The instrumentation employed to obtain these data is briefly described. Long term stability of optical performance, as well as manufacturing reproducibility is demonstrated for several of the surfaces. Outgassing and atomic oxygen interaction information is also included. Methodology for calorimetric measurement of hemispherical emittance as an alternative to optical measurements is given. © 1999 American Institute of Physics. View full abstract»

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  • Subpicosecond optical sampling spectrometer using asynchronous tunable mode-locked lasers

    Page(s): 2218 - 2224
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    We have developed a subpicosecond nondegenerate pump-probe spectrometer based on the optical sampling technique using a combination of asynchronous tunable femtosecond lasers. Owing to its simple instrumentation, time evolution of subpicosecond to nanosecond excited molecular processes in solution and of exciton relaxation processes in semiconductor multiple quantum wells has been detected on an oscilloscope by an effective time base magnification of 760 000 times. Fast acquisition of the temporal profiles and ease of wavelength scanning allowed compilation of time-resolved absorption and excitation spectra. A possible extention of the spectrometer with one of the light sources being a synchrotron radiation instead of the femtosecond laser is discussed. © 1999 American Institute of Physics. View full abstract»

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  • Noncontact measurement of étalon spacing using a retroreflection technique

    Page(s): 2225 - 2229
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    A novel technique is described for the noncontact determination of the spacings of solid and air-gap étalons of low reflectivity by the retroreflection of a He–Ne laser beam. Gaps as small as 50 μm were measured with a precision of better than ±1 μm. Typical measurement accuracy is better than 2%. © 1999 American Institute of Physics. View full abstract»

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  • Acoustically adjustable LiNbO3 double-crystal monochromator for synchrotron radiation

    Page(s): 2230 - 2234
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    First experiments with the acoustically controlled LiNbO3 double-crystal monochromator for synchrotron radiation have been performed on the diffraction beamline of the Brazilian National Synchrotron Light Laboratory. In order to modify x-ray optical properties of LiNbO3 crystals, 290 MHz surface acoustic waves were generated with the aid of interdigital transducers, fabricated on the polished crystal surfaces by using microelectronics technology. It was shown that by the appropriate choice of diffraction planes, the LiNbO3 double-crystal monochromator can be used for both high-flux and high-resolution applications. Surface acoustic waves allow adjustment of an angular width of diffraction profile to a divergence of the incident synchrotron radiation, optimizing matching conditions for x rays of different wavelengths. Diffraction measurements under surface acoustic wave excitation demonstrated that the parameters of the x-ray beam issuing from the monochromatization system are indeed acoustically controlled, providing a 2–2.5-fold broadening of the diffraction profile and a 1.5-fold gain in the maximum diffraction intensity. © 1999 American Institute of Physics. View full abstract»

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  • Large area and high sensitivity a-Si:H/a-SiC:H based detectors for visible and ultraviolet light

    Page(s): 2235 - 2237
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    In this article we discuss the fabrication and performance of a-Si:H/a-SiC:H based ultraviolet sensitive devices. They were deposited over a large area (10 cm×10 cm) in p-i-n configuration using a new, multichamber, ultrahigh vacuum plasma enhanced chemical vapor deposition facility. The intrinsic layer thickness was 10–100 nm. The devices were characterized in the spectral range 365–660 nm and showed good sensitivity in the UV (365 nm). A good rejection of visible light was also measured. Responsivity as high as 0.30 A/W was measured at 365 nm for samples where the p layer and i layer were 5 and 10 nm thick, respectively. The linearity of the photogenerated current as a function of photon flux was measured. It was found that over an area of 25 cm2 the uniformity was within 15%. Using a laser (200 mW at 351 and 363 nm) the aging characteristics were measured and showed a 25% decrease in responsivity after the absorption of 105J cm-2 under operating conditions. © 1999 American Institute of Physics. View full abstract»

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  • Nanometer focusing of hard x rays by phase zone plates

    Page(s): 2238 - 2241
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    Focusing of 8 keV x rays to a spot size of 150 and 90 nm full width at half maximum have been demonstrated at the first- and third-order foci, respectively, of a phase zone plate (PZP). The PZP has a numerical aperture of 1.5 mrad and focusing efficiency of 13% for 8 keV x rays. A flux density gain of 121 000 was obtained at the first-order focus. In this article, the fabrication of the PZP and its experimental characterization are presented and some special applications are discussed. © 1999 American Institute of Physics. View full abstract»

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  • Hermetic sample enclosure for simultaneous differential scanning calorimetry/synchrotron powder x-ray diffraction

    Page(s): 2242 - 2245
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    A hermetic sample enclosure for performing simultaneous differential scanning calorimetry/synchrotron powder x-ray diffraction was designed, and a prototype was fabricated. The enclosure design is based upon a Perkin–Elmer DSC-2C measuring head with modifications allowing an unobstructed x-ray beam access to the sample in a controlled-atmosphere environment. The modifications to the measuring head base are limited to exposing the sample and reference platinum cups and providing a mating surface for the head cover. A completely new head cover, featuring semicylindrical beryllium x-ray windows, is hermetically attached to the base. A new graphite sample pan, addressing the conflicting requirements of differential scanning calorimetry and powder x-ray diffraction, was designed, and multiple pans were fabricated. An alternative temperature measurement and control system was developed and assembled. The complete system was tested in three experiments. No problems were encountered with diffraction data acquisition and temperature control, however, calorimetric resolution was mediocre. The alternative temperature measurement and control system will have to be optimized. © 1999 American Institute of Physics. View full abstract»

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  • A segmented ion chamber to measure the intensities and energies of synchrotron radiation x rays

    Page(s): 2246 - 2247
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    A segmented cascade ion chamber was built to measure the intensities and energies of synchrotron radiation x rays at the same time. The ion chamber consists of 20 cathode cells. By measuring the ionized current collected in each cell and fitting the result, the energies and intensities of fundamental and high harmonic x-ray photons can be extracted. © 1999 American Institute of Physics. View full abstract»

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  • A high temperature furnace for in situ and time-resolved x-ray diffraction studies

    Page(s): 2248 - 2252
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    A high temperature furnace has been built and mounted on a six-circle goniometer for in situ diffraction studies of polycrystalline and powder samples. Temperatures up to 1400 K are controlled with a stability better than ±0.05 K in a vacuum better than 10-7atm. The furnace is also able to work in oxidizing or reducing atmosphere and is mounted on a χ circle table using the Φ circle as a driver for precise translation of the sample in the z direction. The sample can be rotated continuously via a mechanical feedthrough. The temperature is measured by means of a thermocouple placed at the sample holder (0.5 mm from the sample position). The temperature has been calibrated up to 1073 K by following the known thermal expansion of an AlCuFe quasicrystal. © 1999 American Institute of Physics. View full abstract»

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  • Evaluation of laser-irradiated Ar clusters as a source for time-resolved x-ray studies

    Page(s): 2253 - 2256
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    We have measured the absolute average photon flux, the spectral characteristics, and the time structure of x rays emitted from Ar clusters which were irradiated by a 100 fs laser with an intensity of 1017W/cm2. The measured photon flux was 107 photons per shot in the Kα (at 3 keV) line in a 4π sr solid angle. The temporal structure was measured using a streak camera with a 10 ps time resolution. It was found that less than 1% of the photons were emitted within the 10 ps time-response function of the streak camera. The emission profile is roughly exponential with a time constant of 3 ns. © 1999 American Institute of Physics. View full abstract»

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  • Design and construction of a nanoelectrospray ion source for a triple quadrupole mass spectrometer

    Page(s): 2257 - 2261
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    The design and construction of a nanoelectrospray ion source for a triple quadrupole mass spectrometer that is used for identification and analysis of minimum peptide amounts is described. This interface exhibits several improvements over commercially available devices: a new capillary holder that allows very simple loading and placement of the spray capillary, and a rotary stage that enables reproducible adjustment of the capillary’s angle at the orifice of the mass spectrometer. We also introduced a pressure-regulating system for fast and reproducible adjustment of the static backing air pressure onto the sample solution in the spray capillary. Furthermore, an electric safety circuit increases handling and operation safety of the nanoelectrospray interface. © 1999 American Institute of Physics. View full abstract»

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  • Experimental adaptive optimization of mass spectrometer ion optic voltages using a genetic algorithm

    Page(s): 2262 - 2267
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    We use a genetic algorithm (GA) to optimize the mass resolution and detection efficiency of a multi-photon ionization, time-of-flight mass spectrometer. The algorithm uses experimental fitness functions to optimize eight voltages supplied to a set of ion optics. The GA optimized the ion detection efficiency by a factor of 10 and the mass resolution by a factor of 11 over previous settings obtained from computer simulations of the instrument. This experiment highlights the usefulness of adaptive algorithms to the experimental optimization of multidimensional search problems commonly found in modern laboratories. © 1999 American Institute of Physics. View full abstract»

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  • Photoelectron–multiple-photofragment coincidence spectrometer

    Page(s): 2268 - 2276
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    A new photoelectron–photofragment-coincidence spectrometer is described. Using a multiparticle time- and position-sensitive detector, this apparatus allows the study of dissociation processes of negative ions yielding three photofragments in coincidence with a photoelectron. The photoelectron spectrometer uses two detectors and works in time of flight mode, detecting 10% of the photoelectrons with an energy resolution of 5% at 1.3 eV as shown in studies of the photodetachment of O2-. A third detector is used for collection of multiple photofragments (up to 8) in coincidence. This multiparticle detector uses a crossed-delay-line anode and fast timing signals to encode the time- and position-of-arrival of multiple photofragments. The detector was demonstrated to record all three particles produced in a single three-body dissociation event, yielding an energy resolution of ≈15% ΔE/E at 0.7 eV in experiments on the three-body dissociative photodetachment of O6-. © 1999 American Institute of Physics. View full abstract»

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  • Efficient and robust anion source, based on a microchannel plate electron source

    Page(s): 2277 - 2281
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    In this work, an efficient, cheap, and robust anion source is described, which is based on a high-pressure supersonic expansion crossed with a pulsed high-energy electron beam. The special property of this anion source is “soft” electron attachment and efficient stabilization and cooling, which results predominantly in molecular and cluster anions of intact molecules. As electron source, a stack of microchannel plates is used, which is seeded by photoelectrons generated by a weak ultraviolet light pulse. By this special electron source 109–1010 electrons of 1 keV energy are provided at a pulse width of 150 ns. These operational conditions can be maintained up to a repetition rate of 4 kHz. Further advantages of this device are its long lifetime even at relatively high vacuum pressures and its stability against reactive samples, such as oxygen and organic molecules. © 1999 American Institute of Physics. View full abstract»

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  • A fast, parallel acquisition, electron energy analyzer: The hyperbolic field analyzer

    Page(s): 2282 - 2287
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    This article describes a new kind of electrostatic charged particle analyzer capable of the parallel detection of a large kinetic energy range. The main purpose envisaged is for the simultaneous detection of electrons scattered from surfaces and having energies between a few tens of eV to greater than 2000 eV. A prototype has been constructed that approximates a hyperbolic deflection field for the electrons entering an entrance slit. It exhibits an energy resolution of a few eV and a collection efficiency of 0.05% of 2π sr. Useful Auger spectra can be acquired in a time of less than 2 s. The significant improvement in spectrum acquisition time that this represents offers many possibilities to further Auger and photoelectron spectroscopy. © 1999 American Institute of Physics. View full abstract»

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  • A new method for nondestructively monitoring the position of a charged particle beam in real time

    Page(s): 2288 - 2292
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    The design and construction of a simple new device for nondestructively monitoring the position of an electron beam is described. By modulating a small portion of the electron-beam current, changes in the amounts of charge induced on the monitor electrodes are detected as currents. These currents are related to the location of the “center of charge” of the electron beam. Calculations and experimental results which illustrate the performance of the device are reported. This device is primarily intended for use in electron-beam ion sources and traps, although it could be applied to other situations where the beam current can be modulated. © 1999 American Institute of Physics. View full abstract»

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  • Trim coil system design of a superconducting ring cyclotron

    Page(s): 2293 - 2299
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    The trim coil system of a superconducting ring cyclotron currently under design at RIKEN is composed of five sets of superconducting and twenty sets of normal-conducting coils. A major correction for isochronization of the magnetic field is accomplished by the superconducting coils, and a fine correction by the normal-conducting coils. For an optimal design of the system, a numerical procedure was developed to generate isochronous fields for design nuclei and consequently current settings on the main and trim coils, employing an iteration of a least-squares fitting to minimize orbital frequency errors. The main and normal-conducting coils can also be used to correct unwanted harmonic fields with sector dependent and/or radially localized excitations. The correction schemes were conceived for presumed error fields, alignment tolerances being estimated based upon beam optics requirements. On the other hand, a new trim coil design was envisaged, which comprises only superconducting trim coils. The subcoils in the present five-set design can be independently excited to replace the normal-conducting coils. This option may be more economical, but complications on the superconducting coil system raise a reliability concern. © 1999 American Institute of Physics. View full abstract»

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  • Analysis of an asymmetric resonant cavity as a beam monitor

    Page(s): 2300 - 2313
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    We analyze the excitation of an arbitrary, externally coupled resonant structure by a charged particle beam, providing a rigorous formulation of the effect of spurious modes and intrinsic mode nonlinearity on inferred beam coordinates. Results are illustrated for a two-cavity system employed for beam-position monitoring with an idealized front-end signal processor. © 1999 American Institute of Physics. View full abstract»

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  • Measurements of thick target neutron yields and shielding studies using beams of 4He, 12C and 16O at 155 MeV/nucleon from the K1200 cyclotron at the National Superconducting Cyclotron Laboratory

    Page(s): 2314 - 2324
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    Measurements of neutrons from a thick target of Hevimet were made, using beams of 4He, 12C, and 16O ions at 155 MeV per nucleon. These measurements were made both inside and outside of thick concrete shielding, using Bonner-sphere techniques. Yields, spectra, and spectral integral quantities were obtained. The neutron yields were parameterized, and a Moyer-model approach was taken to estimate the dose-equivalent outside of the thick concrete shielding. The effect of local iron shielding, and the dose equivalent outside of iron roof shielding were also investigated. Finally, two methods to obtain neutron field integral values, the “reconstructed spectra” and “six-spheres” methods, were compared. The measurements and analyses should prove useful to other present or planned medium-energy heavy-ion accelerator facilities.© 1999 American Institute of Physics. View full abstract»

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  • On apparatus for studying catalysts and catalytic processes using neutron scattering

    Page(s): 2325 - 2330
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    The design of a cell, built to investigate catalysis and catalytic processes, is reported. The cell is for use at ISIS spallation neutron source at the Rutherford Appleton Laboratory. It is required to operate in a dual manner either under gas flows of controlled composition at low pressure (ambient -5 bar) and at high vacuum (10-6mbar working pressure). The temperature range of this cell is 4–1273 K. It will be used on a variety of instrument beam lines on ISIS. In use the cell is attached either to a furnace or cryofurnace center-stick assembly and gas is supplied from a gas circuit assembly. © 1999 American Institute of Physics. View full abstract»

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  • A large-area plasma source excited by a tunable surface wave cavity

    Page(s): 2331 - 2337
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    A large-area high-density microwave plasma is successfully generated at low pressure by a tunable surface wave cavity which consists of a 12 period vane-type slow wave structure. This cavity is operated in the π mode and resonant at 2.45 GHz. The plasma area is in excess of 50 cm×25 cm with a uniformity of ±10% at pressures less than 30 mTorr. A plasma surface wave has been excited so that a plasma density as high as 1.0×1012cm-3 can be achieved at 30 mTorr for a microwave power of 2.0 kW. The plasma temperature is ∼1.5 eV and the plasma potential is ∼12 V. Above all, the number of the periods of the π-mode cavity can be increased without changing the resonance frequency and the distribution of the microwave fields such that this plasma source is easy to up-scaled. © 1999 American Institute of Physics. View full abstract»

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  • Effects of filament positions on the arc discharge characteristics of a negative hydrogen ion source for neutral beam injector

    Page(s): 2338 - 2344
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    The influence of filament positions on the arc discharge characteristics of a negative hydrogen ion source for a neutral beam injector were studied by simulations and experiments. We have made a simulation code named PRIMELOC2,” which calculates the orbits of primary electrons emitted from cathode filaments, including collisions with H2 gas molecules filled in the source, to obtain the spatial distribution of ionization points. We applied this code to a large negative hydrogen ion source having an external magnetic filter for LHD-NBI No. 1 (neutral beam injector 1 for a large helical device). As a result of the calculations, we have found that the moving area of emitted primary electrons differs markedly according to the filament positions. Calculation results agreed well with the experimental results of high-power arc discharge and the spatial distribution of plasma parameters obtained by Langmuir probe measurements. By applying PRIMELOC2 to filament–arc ion sources, we can choose appropriate areas in arc chambers for filament positioning. © 1999 American Institute of Physics. View full abstract»

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  • A dusty double plasma device

    Page(s): 2345 - 2348
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    A novel dusty plasma device to create spatially and temporally uniform steady state dusty plasma is described. An ultrasonic vibrator is used to vibrate a dust dispenser which disperses the dust uniformly through a fine mesh. A dusty plasma of large dimension with controllable dust density is produced. Measured dusty plasma parameters are compared with existing theories. Some experimental results related to propagation characteristics of dust-ion-acoustic waves in a dusty plasma column are presented. © 1999 American Institute of Physics. View full abstract»

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  • Characterization of a high-density large scale pulsed gas jet for laser–gas interaction experiments

    Page(s): 2349 - 2354
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    We present the characteristics of a high-density pulsed gas jet developed to study the interaction of a short-pulse, high-intensity laser with a large scale underdense plasma. The jet was characterized by laser interferometry. Measurements of density profile were performed for a 5 mm diam cylindrical nozzle and for a 20×1 mm slit. In this latter case, a systematic study of the output density as a function of the backing pressure and of the valve opening duration is presented. At 1 mm from its outlet, the cylindrical nozzle provides densities up to 6.9×1019cm-3 for an 8 bar backing pressure with a 3 mm full width at half maximum Gaussian-shaped profile. Under the same conditions, the slit produces a 20 mm long flat-top profile with a maximum density of 2.1×1019cm-3. © 1999 American Institute of Physics. View full abstract»

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Review of Scientific Instruments, published by the American Institute of Physics, is devoted to scientific instruments, apparatus, and techniques.

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Editor
Albert T. Macrander
Argonne National Laboratory