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BROWSE VOLUME

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December 2004

Volume 75, Issue 12,  pp. 5079-5369

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ARTICLES

GRAVITY; GEOPHYSICS; ASTRONOMY AND ASTROPHYSICS

Design and calibration of a cryogenic blackbody calibrator at centimeter wavelengths

A. Kogut, E. Wollack, D. J. Fixsen, M. Limon, P. Mirel, S. Levin, M. Seiffert, and P. M. Lubin

Rev. Sci. Instrum. 75, 5079 (2004) (5 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (270 kB)

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We describe the design and calibration of an external cryogenic blackbody calibrator used for the first two flights of the Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE) instrument. The calibrator consists of a microwave absorber weakly coupled to a superfluid liquid helium bath. Half-wave corrugations viewed 30° off axis reduce the return loss below –35  dB within a compact footprint. Ruthenium oxide resistive thermometers embedded within the absorber monitor the temperature across the face of the calibrator. The thermal calibration transfers the calibration of a reference thermometer to the flight thermometers using the flight thermometer readout system. The calibrator thermometry is stable in time over four years, with statistical uncertainty in the temperature calibration of order 2  mK near 2.7  K, limited primarily by thermal fluctuations in the liquid helium bath. Observations of the superfluid transition demonstrate that the absolute temperature scale is accurate within 0.3  mK.
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95.55.Ym, 07.20.Dt, 07.20.Mc

GENERAL INSTRUMENTS

A simple noise subtraction technique

F. Douarche, L. Buisson, S. Ciliberto, and A. Petrosyan

Rev. Sci. Instrum. 75, 5084 (2004) (6 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (226 kB)

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Measuring very low level signals at low frequency is a tedious task, because environmental noise increases in this frequency domain and it is very difficult to filter it efficiently. In order to counteract these major problems, we propose a simple and generic noise subtraction technique, which mixes several features of traditional feedback techniques and those of noise estimators. As an example of application, large band measurements of the thermal fluctuations of a mechanical oscillator are presented. Our results show that the proposed noise subtraction technique is easy to implement and gives good results.
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84.40.Ua

NUCLEAR PHYSICS, FUSION AND PLASMAS

Vessel eddy current measurement for the National Spherical Torus Experiment

D. A. Gates, J. E. Menard, and R. J. Marsala

Rev. Sci. Instrum. 75, 5090 (2004) (4 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (947 kB)

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A simple analog circuit that measures the National Spherical Torus Experiment (NSTX) axisymmetric eddy current distribution has been designed and constructed. It is based on simple circuit model of the NSTX vacuum vessel that was calibrated using a special axisymmetric eddy current code which was written so that accuracy was maintained in the vicinity of the current filaments [J. Menard, J. Fusion Tech. (to be published)]. The measurement and the model have been benchmarked against data from numerous vacuum shots and they are in excellent agreement. This is an important measurement that helps give more accurate equilibrium reconstructions.
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52.70.Ds, 28.52.Lf, 52.55.Hc, 52.25.Fi

OPTICS; ATOMS AND MOLECULES; SPECTROSCOPY; PHOTON DETECTORS

A setup for probing collisions of highly charged ions with liquid droplets

G. K. Padmashree, A. Roy, D. Kanjilal, G. Rodrigues, R. Ahuja, R. Somashekar, and C. P. Safvan

Rev. Sci. Instrum. 75, 5094 (2004) (6 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (318 kB)

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We describe the design and implementation of an experimental setup for investigating the collisions of highly charged ions (HCI) with liquid droplets. To the best of our knowledge, this is the first report on the feasibility of such experiments, since studies on HCI–droplet interactions were hitherto precluded following design constraints. Visible, UV, and x-ray emissions from the collisional interaction of liquid droplets with HCI is reported here. The preliminary results from our experiment strongly suggest that charge-exchange appears to be a dominant process. In light of the recent investigations and reports on x-ray and extreme ultraviolet emissions from comets due to solar–wind interaction with cometary coma, our experiment suggests that liquid droplet–HCI interaction might mimic the astrophysical processes, and are promising candidates for laboratory simulations of such processes.
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07.77.Ka, 29.25.-t, 96.50.Gn, 96.50.Ek

ELECTRONICS; ELECTROMAGNETIC TECHNOLOGY; MICROWAVES

A low-power timing discriminator for space instrumentation

P. Devoto, J.-L. Médale, C. Aoustin, and J.-A. Sauvaud

Rev. Sci. Instrum. 75, 5100 (2004) (6 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (143 kB)

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A front-end electronics for three-dimensional time-of-flight space plasma analyzers has been developed. These mass spectrometers, allowing the determination of the distribution functions of the main ion species, are based on the selection of the ion energy per charge and arrival direction using an electrostatic analyzer, and on the determination of their velocity from the time separating a start and a stop pulse. The start pulse is provided by the collection on a microchannel plate (MCP) of secondary electrons emitted when each ion crosses a thin carbon foil. The stop pulse is provided by the ion hitting a second MCP. The aim of the electronics presented in this article is to process the signals provided by MCPs to generate logic pulses, allowing the measurement of precise time differences. The design consists of an amplifier and a timing discriminator which performs a timing compensation to eliminate the time walk. A first version of the circuit has been developed and achieves a time walk of ~400  ps for an input amplitude dynamic range of 25  dB. The total power dissipation per channel is ~14  mW at an event rate of 100  KHz and ~19  mW at a rate of 1  MHz. The influence of the temperature on the circuit behavior has been investigated. The performances of the circuit in a complete detector were also evaluated. This circuit is designed to be used in various designs for future missions.
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95.55.-n, 95.30.Qd, 07.50.Ek, 07.75.+h, 82.80.Rt, 79.20.Hx, 84.30.Sk

GENERAL INSTRUMENTS

Optimal two-point static calibration of measurement systems with quadratic response

Ramon Pallàs-Areny, Josep Jordana, and Óscar Casas

Rev. Sci. Instrum. 75, 5106 (2004) (6 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (122 kB)

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Measurement devices and instruments must be calibrated after manufacture to correct for component and assembly tolerances, and periodically to correct for drift and aging effects. The number of reference inputs needed for calibration depends on the actual transfer characteristic and the desired accuracy. Often, a linear characteristic is assumed for simplicity, either for the overall input range (global linearization) or for successive input subranges (piecewise linearization). Thus, only two reference inputs are needed for each straight line. This two-point static calibration can be easily implemented in any system having some basic computation capability and allows for the correction of zero and gain errors, and of their drifts if the system is periodically calibrated. Often, the reference inputs for that calibration are the end values of the measurement range (or subrange). However, this is not always the optimal selection because the calibration error is minimal for those reference inputs only, which are not necessarily the most relevant inputs for the system being considered. This article proposes three optimization criteria for the selection of calibration points: limiting the maximal error (LME), minimizing the integral square error (ISE), and minimizing the integral absolute error (IAE). Each of these criteria needs reference inputs whose values are symmetrical with respect to the midrange input (xc), have the form xc±Deltax/(2[square root of]n) when the measurand has a uniform probability distribution function, Deltax being the measurement span, and do not depend on the nonlinearity of the actual response, provided this is quadratic. The factor n depends on the particular criterion selected: n = 2 for LME, n = 3 for ISE, and n = 4 for IAE. These three criteria give parallel calibration lines and can also be applied to other nonlinear responses by dividing the measurement span into convenient intervals. The application of those criteria to the linearization of a type-J thermocouple illustrate their performance and advantages with respect to the customary end-point linearization (n = 1) even for nonquadratic responses. For quadratic responses, n = 1 yields the maximal error at the center of the input measurement range.
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06.20.Dk, 06.20.Fn, 02.50.-r

A device to investigate the axial strain dependence of the critical current density in superconductors

A. Godeke, M. Dhalle, A. Morelli, L. Stobbelaar, H. van Weeren, H. J. N. van Eck, W. Abbas, A. Nijhuis, A. den Ouden, and B. ten Haken

Rev. Sci. Instrum. 75, 5112 (2004) (7 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (565 kB)

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We have developed an instrument to study the behavior of the critical current density (Jc) in superconducting wires and tapes as a function of field (µ0H), temperature (T), and axial applied strain (epsilona). The apparatus is an improvement of similar devices that have been successfully used in our institute for over a decade. It encompasses specific advantages such as a simple sample layout, a well defined and homogeneous strain application, the possibility of investigating large compressive strains and the option of simple temperature variation, while improving the main drawback in our previous systems by increasing the investigated sample length by approximately a factor of 10. The increase in length is achieved via a design change from a straight beam section to an initially curved beam, placed perpendicular to the applied field axis in the limited diameter of a high field magnet bore. This article describes in detail the mechanical design of the device and its calibrations. Additionally initial Jc(epsilona) data, measured at liquid helium temperature, are presented for a bronze processed and for a powder-in-tube Nb3Sn superconducting wire. Comparisons are made with earlier characterizations, indicating consistent behavior of the instrument. The improved voltage resolution, resulting from the increased sample length, enables Jc determinations at an electric field criterion Ec = 10  µV/m, which is substantially lower than a criterion of Ec = 100  µV/m which was possible in our previous systems.
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84.71.Mn, 74.25.Sv, 07.10.Pz, 74.25.Ld, 02.70.Dh

THERMOMETRY; THERMAL DIFFUSIVITY; ACOUSTIC; PHOTOTHERMAL AND PHOTOACOUSTIC

Analysis of heat flow in layered structures for time-domain thermoreflectance

David G. Cahill

Rev. Sci. Instrum. 75, 5119 (2004) (4 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (63 kB)

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The iterative algorithm of Feldman for heat flow in layered structures is solved in cylindrical coordinates for surface heating and temperature measurement by Gaussian-shaped laser beams. This solution for the frequency-domain temperature response is then used to model the lock-in amplifier signals acquired in time-domain thermoreflectance measurements of thermal properties.
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44.20.+b, 42.62.Eh, 07.20.Dt, 78.20.Nv

GENERAL INSTRUMENTS

Heat power source controller circuit

F. Madrid, X. Jordà, M. Vellvehi, X. Perpiñà, and P. Godignon

Rev. Sci. Instrum. 75, 5123 (2004) (3 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (50 kB)

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Experimental works on thermal management of electronic systems, such as thermal resistance or thermal conductivity measurement, often require a controlled heat power source. This article proposes a circuit based on an integral automatic controller that sets a heat power dissipation level of a power metal-oxide-semiconductor field effect transistor used as a heating device. It can operate in dc mode, setting a steady power generation, and in pulsed mode, controlling a transient power wave form. The controller operation principle is established together with all details for its implementation and use.
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85.30.Tv

OPTICS; ATOMS AND MOLECULES; SPECTROSCOPY; PHOTON DETECTORS

Design of a transversely pumped, high repetition rate, narrow bandwidth dye laser with high wavelength stability

R. Bhatnagar, Nageshwar Singh, R. Chaube, and H. S. Vora

Rev. Sci. Instrum. 75, 5126 (2004) (5 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (1015 kB)

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The paper presents the design and performance of a transversely pumped, narrow bandwidth, high wavelength stability tunable dye laser that neither uses low expansion coefficient materials for construction nor incorporates any active control on the wavelength or the dye solution and environmental temperature as generally used in such lasers. The scheme essentially involves designing the mechanical assembly in such a way that, when bolted together it forms a massive monoblock, enclosing all the optical components and the dye laser axis within itself. This ensures the environmental temperature changes can only affect the output characteristics over long time scale. Short term (pulse to pulse) fluctuations in wavelengths and bandwidths, generally associated with the dye flow instabilities, were minimized by using a specially designed a dye cell made of a near 360°-curved rectangular duct, in which the turbulent flow is transformed itself into laminar flow as it reaches the dye laser axis. The laser was operated with Rhodamine 6G-ethanol-ethylene glycol solution, pumped by a copper vapor laser operating at 5.6  kHz. The dye laser output, consisting of three axial modes, separated by about 990  MHz, was stable over the observation period of about 90  min. Maximum long term (> 1  h) fluctuation in Deltanu/nu was about ±3.6×10–6. The bandwidth of the individual mode varied between 245  MHz  to  315  MHz.
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42.55.Mv, 42.60.By, 42.60.Lh, 42.65.Re

Generation of a doughnut-shaped beam using a spiral phase plate

Takeshi Watanabe, Masaaki Fujii, Yoshi Watanabe, Nobuhito Toyama, and Yoshinori Iketaki

Rev. Sci. Instrum. 75, 5131 (2004) (5 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (481 kB)

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To generate a doughnut-shaped beam, i.e., the first order of a Bessel beam, a spiral phase plate with 8 divided etching areas is fabricated with an etching accuracy of better than 6 nm. The etching depth of each area is designed so that the phase distribution of the laser beam passing through has a phase difference of pi at a symmetric position with respect to the optical axis. Using a laser beam with a wavefront aberration of 1/10lambda, the phase distribution of the beam passing through the plate is measured by a Shack Hartman wavefront sensor. It has been found that the beam has a spiral phase change of 2pi along the optical axis. The focused beam has a circular doughnut pattern, as predicted by a theoretical calculation, and we succeeded to generate the ideal first-order of a Bessel beam.
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42.79.-e, 42.60.Jf

Optimum design and construction of a Zeeman slower for use with a magneto-optic trap

C. J. Dedman, J. Nes, T. M. Hanna, R. G. Dall, K. G. H. Baldwin, and A. G. Truscott

Rev. Sci. Instrum. 75, 5136 (2004) (7 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (431 kB)

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A method for optimizing the design and construction of a Zeeman slower coil is presented. Unlike traditional designs, the measured magnetic field profile very accurately matches the desired field profile, enabling significant advantages for loading a magneto-optic trap.
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07.55.Ge

CHEMISTRY

High-pressure cell for fluorescence fluctuation spectroscopy

Mohac Tekmen and Joachim D. Müller

Rev. Sci. Instrum. 75, 5143 (2004) (6 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (169 kB)

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We introduce a high-pressure cell for fluorescence fluctuation spectroscopy. The pressure cell consists of a cylindrical, fused silica microcapillary and a modified pressure plug, which connects the cell to a pressure generating apparatus. The capillary serves both as the body and the optical window of the cell. The pressure cell is mounted onto the stage of an optical microscope. The small diameter of the capillary allows the use of high numerical aperture objectives, which are required for fluorescence fluctuation experiments. The pressure stability of the cell has been tested up to 4  kbar. We performed two-photon excitation experiments on simple dyes as a function of pressure. The diffusion coefficient was determined by fluorescence correlation spectroscopy. We also used the same cell to measure the pressure dependence of fluorescence lifetimes.
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07.35.+k, 07.60.-j, 42.79.Ci, 78.55.Kz

CONDENSED MATTER; MATERIALS

Highly efficient gaseous sample loading technique for diamond anvil cells

Jiyong Zhao, Guoyin Shen, Wolfgang Sturhahn, and E. Ercan Alp

Rev. Sci. Instrum. 75, 5149 (2004) (3 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (90 kB)

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A clean and highly efficient technique has been developed to load diamond anvil cells (DACs) using a small amount of gaseous samples. The loading process consists of two steps. First, gas is condensed on a designated cold surface in a pre-evacuated system; second, the solidified sample is loaded into a DAC at liquid-nitrogen temperature. A hundred milliliters of gas at ambient condition is typically required to produce a solidified sample. The use of solid sample material for DAC loading is beneficial to a clean loading process. We demonstrated this technique by loading isotopically enriched (99.925%-83Kr) krypton into a DAC. 200  ml of this rare and expensive gas were solidified with 99.6% efficiency and almost completely recovered.
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07.35.+k, 06.60.Ei, 81.30.Fb, 07.20.Mc, 64.70.Dv, 64.70.Fx

PARTICLE SOURCES, OPTICS AND ACCELERATION; PARTICLE DETECTORS

Hot-cathode-ionization-gauge system with a self-compensating circuit for errors caused by an external-electron source

Hiroshi Saeki, Tamotsu Magome, Tsuyoshi Aoki, Nobuaki Gotoh, and Takashi Momose

Rev. Sci. Instrum. 75, 5152 (2004) (8 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (733 kB)

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A hot-cathode-ionization-gauge system, consisting of a gauge head with a correcting electrode, an automated-pressure-compensating circuit, and a shield tube, succeeded in overcoming two kinds of erroneous pressure indications with hot-cathode-ionization gauges. Several tens of hot-cathode-ionization gauges in the SPring-8 storage ring have indicated abnormally low pressures (of the order from 10–8 to 10–9  Pa) at stored-electron-beam conditions due to an influx of photoelectrons. Some of these gauges, located near photon absorbers, have indicated negative pressures (from –2×10–9 to –2×10–7  Pa). To investigate these pressure-measurement errors, simulated experiments to reproduce the phenomena were carried out using an external-electron source which was located near a hot-cathode-ionization-gauge head. The kinetic energy of incident electrons to the gauge head from the external-electron source was varied from 10 to 90 eV. The maximum total-electron-beam current from the external-electron source at the position of the gauge head was about 0.12 mA (90 eV), which was 3% of the normal emission current from the gauge filament. In the pressure range of 10–7  Pa, the pressure-measurement errors which occur in the ring were reproduced. During the experiment, the variation of the indicated emission current was less than 1% of the normal emission current. With no emission from the gauge filament, negative currents were detected at the grid and the collector of the gauge from the external-electron source at the same pressures as in the simulated experiment. It was found that detected negative current at the grid of the gauge was 50%–60% of the total-electron-beam current from the external-electron source and it was confirmed that the detected negative current at the collector depends on the kinetic energy of the incident electrons. From these results and calculations, it was also found that the variation of the emission of the gauge filament did not cause the negative-pressure indications at all. Furthermore, it was also confirmed that the hot-cathode-ionization gauge indicated abnormally low pressures or negative pressures when the net current detected at the collector in operation of the gauge was extremely small or negative, respectively, due to the influx of many electrons from the external environment. These experiments were done to simulate operation conditions at the SPring-8 storage ring. In the simulated experiments for abnormally low-pressure indications, pressure measurements using a hot-cathode-ionization-gauge head with a correcting electrode and an automated-pressure-compensating circuit were carried out in the pressure range from 10–6 to 10–8  Pa. It was found that the compensated pressure indicated the actual pressure within an error range of ±15% for incident electrons with 20 eV, although the indicated pressure of the ionization-gauge controller was in a different order than that of the actual pressure and the error current was less than the order of 10–10  A. In the simulated experiment for negative-pressure indications, it was found that the shield tube could reduce incident electrons from the external-electron source by a factor of about 1/10.
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07.30.Dz, 07.77.Ka, 29.25.Bx, 07.07.Mp, 29.20.Dh

NUCLEAR PHYSICS, FUSION AND PLASMAS

Design and initial operation of the Auburn Linear Experiment for Instability Studies: A new plasma experiment for studying shear driven flows

Edwynn Wallace, Edward Thomas, Jr., Ashley Eadon, and Jon David Jackson

Rev. Sci. Instrum. 75, 5160 (2004) (6 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (547 kB)

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The Auburn Linear Experiment for Instability Studies (ALEXIS) is a new plasma physics experiment that is designed to investigate the role of spatially nonuniform E×B drifts using a cylindrical plasma column. This article discusses the design and construction of the ALEXIS device and preliminary measurements of the electric and magnetic field configuration of the device.
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52.55.Hc, 52.75.-d, 52.70.Ds, 52.35.Qz, 52.30.Cv, 52.55.Pi

OPTICS; ATOMS AND MOLECULES; SPECTROSCOPY; PHOTON DETECTORS

Heat and temperature distribution in a cladding-pumped, Er: Yb co-doped phosphate fiber

Andrey Kosterin, J. Kevin Erwin, Mahmoud Fallahi, and Masud Mansuripur

Rev. Sci. Instrum. 75, 5166 (2004) (7 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (255 kB)

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High-gain-per-unit-length, Er: Yb co-doped, phosphate glass fibers are a new class of active photonic materials. Due to their high concentration of active ions (typically 2–6×1020  cm–3), the generation of heat in these materials is rather severe. To facilitate the design of cladding-pumped, high-power lasers and amplifiers using these materials, we introduce two diagnostic techniques for measuring the total heat and the profile of temperature distribution along the length of an active fiber. Thermal experiments on a 6.0-cm-long piece of cladding-pumped phosphate fiber with Er: Yb doping (3:16  wt  %) are conducted, and the results are compared with indirect estimates of total heat by scattered light measurements using a power-balance argument. The difference between the two methods is about 8.0%. Even at low pump powers, the temperature of the core (without heat-sinking) is found to be a large fraction of the glass transition temperature. The temperature distribution along the length of the fiber is found to be relatively flat compared with the absorption profile. Our thermal diagnostic tools yield valuable information that can be used to optimize the design of fiber lasers and amplifiers.
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42.81.Cn, 07.20.Fw, 07.20.Dt

MICROSCOPY AND IMAGING

Temporally resolved Schwarzschild microscope for the characterization of extreme ultraviolet emission in laser-produced plasmas

Y. Tao, M. Nakai, H. Nishimura, S. Fujioka, T. Okuno, T. Fujiwara, N. Ueda, N. Miyanaga, and Y. Izawa

Rev. Sci. Instrum. 75, 5173 (2004) (4 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (191 kB)

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A temporally resolved monochromatic extreme ultraviolet (EUV) imager has been developed for use in EUV radiation source research. The imager consists of a Schwarzschild microscope, with near-normal-incident Mo/Si multilayer mirrors adjusted for 13.5  nm and 4% bandwidth, and an x-ray streak camera (XSC). The spatial resolution of the microscope was limited by the image detector's resolution to 3.5  µm for the CCD camera and 15  µm for the XSC, respectively, for a field of view of 1.2  mm. With the high photon collection efficiency, clear streak images could be obtained on a single-shot basis with laser pulse energy as low as 50  mJ at an intensity of 1×1010  W/cm2. Expansion behavior of the EUV emission region was successfully observed for laser-produced Sn plasmas.
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52.70.Kz, 07.57.Kp, 07.60.-j, 06.60.Jn, 52.25.Os, 42.79.Bh, 42.79.Pw

CONDENSED MATTER; MATERIALS

Experimental technique for studying high-temperature phases in reactive molten metal based systems

A. Ermoline, M. Schoenitz, V. K. Hoffmann, and E. L. Dreizin

Rev. Sci. Instrum. 75, 5177 (2004) (9 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (363 kB)

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Containerless, microgravity experiments for studying equilibria in molten metal–gas systems have been designed and conducted onboard of a NASA KC-135 aircraft flying parabolic trajectories. An experimental apparatus enabling one to acoustically levitate, laser heat, and splat quench 1–3  mm metal and ceramic samples has been developed and equipped with computer-based controller and optical diagnostics. Normal-gravity testing determined the levitator operation parameters providing stable and adjustable sample positioning. A methodology for optimizing the levitator performance using direct observation of levitated samples was developed and found to be more useful than traditional pressure mapping of the acoustic field. In microgravity experiments, spherical specimens prepared of pressed, premixed powders of ZrO2, ZrN, and Zr, were acoustically levitated inside an argon-filled chamber at one atmosphere and heated by a CO2 laser up to 2800  K. Using a uniaxial acoustic levitator in microgravity, the location of the laser-heated samples could be maintained for about 1  s, so that local sample melting was achieved. Oscillations of the levitating samples in horizontal direction became pronounced in microgravity. These oscillations increased during the sample heating and eventually resulted in moving the sample out of the stable position and away from the laser beam.
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07.20.Ka, 64.70.Dv, 07.20.Hy, 43.25.Uv, 81.70.Ha, 06.60.Ei, 64.60.Fr

OPTICS; ATOMS AND MOLECULES; SPECTROSCOPY; PHOTON DETECTORS

High-power short-pulse laser repetition rate improvement by adaptive wave front correction

B. Wattellier, J. Fuchs, J. P. Zou, K. Abdeli, C. Haefner, and H. Pépin

Rev. Sci. Instrum. 75, 5186 (2004) (7 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (480 kB)

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Dynamic wave front correction is applied before each shot on a 100  TW, 30  J/300  fs high power laser facility using an adaptive optics system. This system allows one to increase the repetition rate of high-energy lasers while maintaining excellent and constant beam focusability with a Strehl ratio > 0.75 despite the amplifiers not being in thermal equilibrium. Best results in terms of highest Strehl ratio and intensities are obtained when locking the system on wave front sensing after pulse recompression.
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42.65.Hw, 42.60.Fc, 07.60.Ly, 42.65.Re

Precision short-pulse damage test station utilizing optical parametric chirped-pulse amplification

Igor Jovanovic, Curtis Brown, Benoit Wattellier, Norman Nielsen, William Molander, Brent Stuart, Deanna Pennington, and C. P. J. Barty

Rev. Sci. Instrum. 75, 5193 (2004) (10 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (607 kB)

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The next generation of high-energy petawatt (HEPW)-class lasers will utilize multilayer dielectric diffraction gratings for pulse compression, due to their high efficiency and high damage threshold for picosecond pulses. The peak power of HEPW lasers will be determined by the aperture and damage threshold of the final dielectric grating in the pulse compressor and final focusing optics. We have developed a short-pulse damage test station for accurate determination of the damage threshold of the optics used on future HEPW lasers. Our damage test station is based on a highly stable, high-beam-quality optical parametric chirped-pulse amplifier (OPCPA) operating at 1053  nm at a repetition rate of 10  Hz. We present the design of our OPCPA system pumped by a commercial Q-switched pump laser and the results of the full system characterization. Initial short-pulse damage experiments in the far field using our system have been performed.
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42.65.Yj, 42.79.Dj, 42.60.Fc, 42.65.Re

Improved efficiency of a hybrid CO2 laser as a result of increased TEM00 mode filling factor

Aniruddha Kumar, J. Padma Nilaya, and Dhruba J. Biswas

Rev. Sci. Instrum. 75, 5203 (2004) (2 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (31 kB)

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Considerable improvement in the operating efficiency of a hybrid CO2 laser has been achieved by increasing the TEM00 mode filling factor in the TEA section. The usage of helium-free gas mixture in the TEA section restricted the width of the glow discharge to the central zone in the interelectrode region allowing the oscillating TEM00 mode to experience a higher gain in the TEA section resulting in an improved performance of the laser.
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42.60.Lh, 42.55.Lt, 42.60.Jf, 42.60.Rn

Multichannel optical diagnostic system for field-reversed configuration plasmas

Tsutomu Takahashi, Hiroshi Gota, Toshiyuki Fujino, Masanori Okada, Tomohiko Asai, Kayoko Fujimoto, Yasunori Ohkuma, and Yasuyuki Nogi

Rev. Sci. Instrum. 75, 5205 (2004) (8 pages)

Online Publication Date: 30 November 2004

Full Text: PDF (202 kB)

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A constructed diagnostic system consisting of a 60-channel set of optical detectors with flexible viewing configurations is realized to investigate three-dimensional magnetohydrodynamic (MHD) motions and the internal structure of a field-reversed configuration (FRC) plasma. The system can detect radiation from the plasma in the wavelength range of 420–820  nm. Optical filters are used to select the wavelength ranges required in the experiment. The sensitivities of all the optical detectors are calibrated using radiation from the FRC plasma at a quiescent phase. Radiation profiles measured by orthogonal viewing configuration of the detectors are shown at three toroidal cross sections. From these profiles, the time evolution of the three-dimensional MHD motion of the plasma is depicted. The radiation profile measured by a one-dimensional viewing configuration yields not only an electron density profile inside the separatrix but also the width of an edge-layer plasma. A bright halo around the edge-layer plasma is observed using a Balmer-alpha line filter. The orthogonal viewing configuration can also be used to analyze the internal structure of the FRC. The deviated position of the major axis is estimated from the comparison between the measured radiation profiles and the nonconcentric density profile based on the rigid rotor profile model.
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52.58.Lq, 52.70.Kz, 52.30.Cv, 07.07.Df

THERMOMETRY; THERMAL DIFFUSIVITY; ACOUSTIC; PHOTOTHERMAL AND PHOTOACOUSTIC

PVDF sensor in laser ablation experiments

M. A. P. Gião, N. A. S. Rodrigues, R. Riva, and C. Schwab

Rev. Sci. Instrum. 75, 5213 (2004) (3 pages)

Online Publication Date: 10 November 2004

Full Text: PDF (120 kB)

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This article presents the use of piezoelectric PVDF films as a sensor for the vapor stream in laser ablation experiments. The analysis of the PVDF electric signal gives the translational temperature and the vapor drift velocity of the ablated plume. A PVDF sensor was used in a tungsten ablation experiment, using HyBrID copper laser, and it was obtained a translational temperature of 9×104  K and a drift velocity of 4×105  cm/s.
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07.07.Df, 85.50.-n

CONDENSED MATTER; MATERIALS

A magnetoelasticity instrument for testing the mechanical properties of ferromagnetic materials

Qi Xin, Hou Zhi Ling, and Tian Jian Long

Rev. Sci. Instrum. 75, 5216 (2004) (5 pages)

Online Publication Date: 11 November 2004

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Magnetoelasticity noise is the electromagnetic energy and sound energy released at the surface of ferromagnetic materials due to the movement of the magnetic domain walls inside the material when the material is magnetized by an alternating magnetic field. The electromagnetic energy and sound energy are released simultaneously and interact with each other. These energies carry many characteristics of the material, such as the electromagnetic character, the mechanical character, the material character, etc., and thus can be used to test these characteristics of the material. Based on this theory, an instrument for testing the stresses in ferromagnetic materials is developed in this article. The theory and the structure of the instrument are introduced. The experiment for testing the one-dimensional and two-dimensional stresses in ferromagnetic materials and the analysis of the fatigue damages are carried out. It is a portable instrument and can be used on the field. The outcomes of the test fit quite well with those obtained by the x-ray method.
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07.55.-w, 07.10.Lw, 75.80.+q, 81.70.Bt

OPTICS; ATOMS AND MOLECULES; SPECTROSCOPY; PHOTON DETECTORS

Position sensitive detection coupled to high-resolution time-of-flight mass spectrometry: Imaging for molecular beam deflection experiments

M. Abd El Rahim, R. Antoine, L. Arnaud, M. Barbaire, M. Broyer, Ch. Clavier, I. Compagnon, Ph. Dugourd, J. Maurelli, and D. Rayane

Rev. Sci. Instrum. 75, 5221 (2004) (7 pages)

Online Publication Date: 11 November 2004

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We have developed and tested a high-resolution time-of-flight mass spectrometer coupled to a position sensitive detector for molecular beam deflection experiments. The major achievement of this new spectrometer is to provide a three-dimensional imaging (X and Y positions and time-of-flight) of the ion packet on the detector, with a high acquisition rate and a high resolution on both the mass and the position. The calibration of the experimental setup and its application to molecular beam deflection experiments are discussed.
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07.75.+h, 06.20.Fn, 39.10.+j

CHEMISTRY

High-pressure, high-temperature x-ray absorption fine structure transmission cell for the study of aqueous ions with low absorption-edge energies

John L. Fulton, Yongsheng Chen, Steve M. Heald, and Mahalingam Balasubramanian

Rev. Sci. Instrum. 75, 5228 (2004) (4 pages)

Online Publication Date: 11 November 2004

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We describe a method to acquire x-ray absorption fine structure (XAFS) spectra of low-Z atoms dissolved in high-pressure liquids and supercritical fluids. The method is applicable to energies at and below the Ca K edge (4038.5  eV). The cell design incorporates 25-µm-thick×700  µm diameter diamond x-ray windows in a Poulter-type seal geometry. X-ray focusing mirrors were used to reduce both the horizontal and vertical beam size to about 200  µm so that the incident beam would pass cleanly through the 300  µm aperture of the cell. Pathlengths in the range from 50  to  1000  µm can be selected with appropriate spacers. The maximum operating conditions of the flow-through cell design are 500  °C and 1  kbar. We show that only a relatively small number of XAFS scans are required to generate high signal-to-noise ratio spectra for a supercritical water solution (400  °C) containing 1  m CaCl2 using a bending-magnet beamline (20-BM, PNC-CAT, Advanced Photon Source, Argonne National Laboratory).
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07.85.-m, 07.35.+k, 07.20.Ka, 78.70.Dm

CONDENSED MATTER; MATERIALS

High-resolution solid-state nuclear magnetic resonance experiments on highly radioactive ceramics

Ian Farnan, Herman Cho, William J. Weber, Randall D. Scheele, Nigel R. Johnson, and Anne E. Kozelisky

Rev. Sci. Instrum. 75, 5232 (2004) (5 pages)

Online Publication Date: 11 November 2004

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A triple-containment magic-angle spinning rotor insert system has been developed and a sample handling procedure formulated for safely analyzing highly radioactive solids by high-resolution solid-state NMR. The protocol and containment system have been demonstrated for magic-angle spinning (MAS) experiments on ceramic samples containing 5–10  wt  % 239Pu and 238Pu at rotation speeds of 3500  Hz. The technique has been used to demonstrate that MAS NMR experiments can be used to measure amorphous atomic number fractions produced by accelerated internal radiation damage. This will allow incorporated alpha-emitters with short half-lives to be used to model the long-term radiation tolerance of potential ceramic radioactive waste forms. This is an example of MAS NMR spectroscopy on samples containing fissionable isotopes.
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07.57.Pt, 76.60.Es

BIOLOGY AND MEDICINE

Radial 32P ion implantation using a coaxial plasma reactor: Activity imaging and numerical integration

M. A. Fortin, V. Dufresne, R. Paynter, A. Sarkissian, and B. Stansfield

Rev. Sci. Instrum. 75, 5237 (2004) (7 pages)

Online Publication Date: 15 November 2004

Full Text: PDF (462 kB)

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Beta-emitting biomedical implants are currently employed in angioplasty, in the treatment of certain types of cancers, and in the embolization of aneurysms with platinum coils. Radioisotopes such as 32P can be implanted using plasma-based ion implantation (PBII). In this article, we describe a reactor that was developed to implant radioisotopes into cylindrical metallic objects. The plasma first ionizes radioisotopes sputtered from a target, and then acts as the source of particles to be implanted into the biased biomedical device. The plasma therefore plays a major role in the ionization/implantation process. Following a sequence of implantation tests, the liners protecting the interior walls of the reactor were changed and the radioactivity on them measured. This study demonstrates that the radioactive deposits on these protective liners, adequately imaged by radiography, can indicate the distribution of the radioisotopes that are not implanted. The resulting maps give unique information about the activity distribution, which is influenced by the sputtering of the 32P-containing fragments, their ionization in the plasma, and also by the subsequent ion transport mechanisms. Such information can be interpreted and used to significantly improve the efficiency of the implantation procedure. Using a surface barrier detector, a comparative study established a relationship between the gray scale of radiographs of the liners, and activity measurements. An integration process allows the quantification of the activities on the walls and components of the reactor. Finally, the resulting integral of the 32P activity is correlated to the sum of the radioactivity amounts that were sputtered from radioactive targets inside the implanter before the dismantling procedure. This balance addresses the issue of security regarding PBII technology and confirms the confinement of the radioactivity inside the chamber.
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87.80.-y, 87.56.-v, 52.77.Dq, 87.50.Gi

ELECTRONICS; ELECTROMAGNETIC TECHNOLOGY; MICROWAVES

Miniaturized impression creep testing of ball grid array solder balls attached to microelectronic packaging substrates

D. Pan, R. A. Marks, I. Dutta, R. Mahajan, and S. G. Jadhav

Rev. Sci. Instrum. 75, 5244 (2004) (9 pages)

Online Publication Date: 15 November 2004

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This article reports on the design and implementation of a miniaturized impression creep apparatus for characterizing the creep behavior of tiny solder balls attached to a ball grid array (BGA) microelectronic packaging substrate. The technique requires no special sample preparation, can probe individual solder balls, and proffers high data throughput by allowing numerous creep curves to be obtained from one substrate, as well as by minimizing the time required to achieve steady state creep. The apparatus reported here uses a 100-µm-diameter cylindrical WC punch to characterize the creep behavior of 750-µm-diameter BGA solder balls from ambient temperature to 423  K. A video imaging system facilitates precise alignment and placement of the indenter on the specimen at the test temperature. The possible effect of substrate curvature on the experimental solder creep curves was evaluated and was deemed to be insignificant. Example creep curves and data based on 90Pb-10Sn BGA solder balls are presented. The test is further scalable for testing of smaller flip-chip joints, using a smaller punch. The present work reports on the implementation of impression creep for testing nonbulk specimens.
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07.07.-a, 81.70.Bt, 81.40.Lm, 85.40.-e, 62.20.Hg

A broadband waveguide for protein crystallography under intense microwave fields

R. Weissenborn, T. Reinhardt, V. Hansen, G. Maret, and T. Gisler

Rev. Sci. Instrum. 75, 5253 (2004) (4 pages)

Online Publication Date: 15 November 2004

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We present a slab-line waveguide whose geometry is optimized for wide-angle x-ray diffraction (XRD) experiments on protein crystals during irradiation with intense microwave fields. Characterization of the waveguide transmission and reflectivity (using time-domain reflectometry) and of the electric field distribution inside the waveguide (using finite-difference time-domain calculations) shows that the present device has a broad bandwidth from below 0.5  to  18  GHz, allowing one to perform frequency-dependent XRD studies with a well-defined transverse mode structure and negligible reflection losses. As shown with a specific example, our device provides a simple way to couple microwave irradiation experiments with high-resolution x-ray diffraction measurements from millimeter-size crystalline samples. The present design might prove useful for systematic studies of microwave effects on protein structure and dynamics.
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61.82.Pv, 87.14.Ee, 61.10.Nz, 02.70.Bf

GENERAL INSTRUMENTS

Threshold-crossing counting technique for damping factor determination of resonator sensors

Kefeng Zeng and Craig A. Grimes

Rev. Sci. Instrum. 75, 5257 (2004) (5 pages)

Online Publication Date: 15 November 2004

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The behavior of resonator-type sensors at resonance is characterized by two fundamental parameters: resonance frequency and damping factor (or Q-factor). Practical applications require accurate and efficient measurements of these two parameters. Using magnetoelastic resonant sensors as a test case earlier work [K. Zeng, K. G. Ong, C. Mungle, and C. A. Grimes, Rev. Sci. Instrum. 73, 4375 (2002)] demonstrated the ability to determine resonance frequency by counting the number of cycles in the transient response of a pulsewise excited sensor. Presented in this paper is a novel technique for measuring the damping factor of a resonant magnetoelastic sensor, or any resonator type sensor, using threshold-crossing counting of the transient response. The damping factor determination technique eliminates the need for a lock-in amplifier or FFT analysis as in the conventional method of quality factor estimation from spectrum analysis, significantly simplifying the electronic implementation as well as improving measurement speed and accuracy.
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07.55.-w, 85.70.Ec

BIOLOGY AND MEDICINE

Magnetic resonance-guided near-infrared tomography of the breast

Ben Brooksby, Shudong Jiang, Hamid Dehghani, Brian W. Pogue, Keith D. Paulsen, Christine Kogel, Marvin Doyley, John B. Weaver, and Steven P. Poplack

Rev. Sci. Instrum. 75, 5262 (2004) (9 pages)

Online Publication Date: 15 November 2004

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The design and implementation of a multispectral, frequency-domain near infrared tomography system is outlined, which operates in a MRI magnet for utilization of MR-guided image reconstruction of tissue optical properties. Using long silica optical fiber bundles, measurements of light transmission through up to 12 cm of female breast tissue can be acquired simultaneously with MRI scans. The NIR system utilizes six optical wavelengths from 660 to 850 nm using intensity modulated diode lasers nominally working at 100 MHz. Photomultiplier tube detector gain levels are electronically controlled on a time scale of 200 ms, thereby allowing rapid switching of the source to locations around the tissue. There are no moving parts in the detection channels and for each source position, 15 PMTs operating in parallel allow sensitivity down to 0.5  pW/cm2 at the tissue surface. Images of breast tissue optical absorption and reduced scattering coefficients are obtained using a Newton-type reconstruction algorithm to solve for an optimal solution using the measurement data. In medical imaging, it is beneficial to compare the same tissue volume as seen by a variety of modalities, and perhaps more importantly, there is the hypothesis that one imaging system which has high spatial resolution can be used to enhance the reconstruction of another system which has good contrast resolution. In this study we explore the synergistic benefits of a combined NIR-MRI data set, specifically the ways in which MRI (i.e., high spatial resolution) enhances NIR (i.e., high contrast resolution) image reconstruction. The design, calibration, and performance of the imaging system are described in the context of preliminary phantom tests and initial in vivo patient imaging. Co-registered MRI validates and improves optical property estimation in 2D tomographic image reconstructions when specialized algorithms are used.
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87.61.Ff, 87.80.Tq, 87.57.Gg, 87.57.Ce, 87.66.Xa, 87.64.Ni

MICROSCOPY AND IMAGING

Phase contrast radiography: Image modeling and optimization

Benedicta D. Arhatari, Adrian P. Mancuso, Andrew G. Peele, and Keith A. Nugent

Rev. Sci. Instrum. 75, 5271 (2004) (6 pages)

Online Publication Date: 15 November 2004

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We consider image formation for the phase-contrast radiography technique where the radiation source is extended and spatially incoherent. A model is developed for this imaging process which allows us to define an objective filtering criterion that can be applied to the recovery of quantitative phase images from data obtained at different propagation distances. We test our image model with experimental x-ray data. We then apply our filter to experimental neutron phase radiography data and demonstrate improved image quality.
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07.85.-m

CHEMISTRY

Microwave-induced plasma reactor based on a domestic microwave oven for bulk solid state chemistry

David J. Brooks and Richard E. Douthwaite

Rev. Sci. Instrum. 75, 5277 (2004) (3 pages)

Online Publication Date: 17 November 2004

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A microwave-induced plasma (MIP) reactor has been constructed from a domestic microwave oven (DMO) and applied to the bulk synthesis of solid state compounds. Low pressure MIP can be initiated and maintained using a range of gases including Ar, N2, NH3, O2, Cl2, and H2S. In order to obtain reproducible synthesis conditions the apparatus is designed to allow control of gas flow rate, gas composition, and pressure. The use of the reactor is demonstrated by the synthesis of three binary metal nitrides formed in a NH3 MIP. The reactions are rapid and the products show good crystallinity and phase purity as judged by powder x-ray diffraction.
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52.75.-d, 07.20.Hy, 52.50.Sw, 52.77.-j, 52.25.-b, 52.30.Ex

MICROSCOPY AND IMAGING

Cryogenic variable temperature ultrahigh vacuum scanning tunneling microscope for single molecule studies on silicon surfaces

E. T. Foley, N. L. Yoder, N. P. Guisinger, and M. C. Hersam

Rev. Sci. Instrum. 75, 5280 (2004) (8 pages)

Online Publication Date: 17 November 2004

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The design and performance of a variable temperature ultrahigh vacuum (UHV) scanning tunneling microscope (STM) is presented. This STM operates from 8.2  to  300  K in a UHV environment with a base pressure of less than 6×10–11  Torr. Cooling is achieved from 300  to  80  K within 3.5  h and from 80  to  8.2  K within 4.5  h. The base temperature of 8.2  K is maintained at a liquid helium consumption rate of 0.9  l/h. This design allows for direct optical access to the tip-sample interface and direct line-of-sight dosing while the sample is mounted in the STM. The STM tip may be coarse translated laterally in two dimensions through a 6-mm-diam area at all temperatures. With the feedback loop off, the drift in the tip-sample spacing is approximately 0.008  Å/min at 8.2  K. Atomic resolution feedback controlled lithography is performed on hydrogen passivated Si(100) and differential tunneling conductance maps are gathered for isolated cyclopentene molecules on unpassivated Si(100), thus demonstrating that this system is well suited for studying single molecules on silicon surfaces from 8.2  to  300  K.
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07.79.Cz, 07.20.Mc, 81.16.Ta, 07.30.-t

CONDENSED MATTER; MATERIALS

Flexible microprocessor-based evaporation controller

F.-J. Meyer zu Heringdorf and A. C. Belton

Rev. Sci. Instrum. 75, 5288 (2004) (5 pages)

Online Publication Date: 17 November 2004

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Electron beam evaporation sources require two power supplies, one each for the filament current and the electron acceleration. To obtain a stable deposition rate, the emission current between filament and target must remain constant. During film deposition, slight geometry changes in the evaporator cause significant rate variations, making constant readjustment of the emission current necessary. While in commercial solutions, analog feedback regulators are often used to perform this task, these controllers cannot easily be adapted to home-built evaporation sources. The microcontrolled feedback controller presented here is more flexible and versatile than the commercial solutions. The controller can be easily modified to work with different external power supplies and allows the easy upgrade of most existing electron beam evaporation setups. A serial-port computer interface completely integrates the controller into the automated laboratory environment.
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07.05.Dz, 07.05.Bx

MICROSCOPY AND IMAGING

Simplified Besocke scanning tunneling microscope with linear approach geometry

S. J. Ball, G. E. Contant, and A. B. McLean

Rev. Sci. Instrum. 75, 5293 (2004) (9 pages)

Online Publication Date: 17 November 2004

Full Text: PDF (821 kB)

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Besocke-style scanning tunneling microscopes are used in low and variable temperature applications because they are compact and the tip-sample spacing is insensitive to thermal drift. It is demonstrated that the economical Besocke design can be simplified even further if a linear approach geometry is used. In this geometry, the sample has only to be moved along two orthogonal axes and just 11 wires are required to control both tip-sample approach and image acquisition. This simplifies the control electronics, increases the reliability of the microscope and, if the microscope is operated in a cryostat, it weakens the thermal link between low and room temperature. Nevertheless, all of the advantages of the Besocke design are retained including thermal compensation of the tip-sample spacing. A self-aligning mechanism is also described that automatically locates the sample relative to the scanner before tip-sample approach. This feature is particularly useful because the microscope is designed for remote operation in a cryostat where there is restricted visual access. Graphite was used as a test surface and images are presented of beta-site corrugation and moiré supermeshes.
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07.79.Cz, 68.37.Ef

GENERAL INSTRUMENTS

Dedicated Max-Planck beamline for the in situ investigation of interfaces and thin films

A. Stierle, A. Steinhäuser, A. Rühm, F. U. Renner, R. Weigel, N. Kasper, and H. Dosch

Rev. Sci. Instrum. 75, 5302 (2004) (6 pages)

Online Publication Date: 17 November 2004

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A dedicated beamline for the Max-Planck-Institut für Metallforschung was recently taken into operation at the Ångstrømquelle Karlsruhe (ANKA). Here we describe the layout of the beamline optics and the experimental end-station, consisting of a heavy duty multiple circle diffractometer. For both a new design was realized, combining a maximum flexibility in the beam properties [white, pink, (focused) monochromatic, energy range 6–20 keV] with a special diffractometer for heavy sample environments up to 500 kg, that can be run in different geometrical modes. In addition the angular-reciprocal space transformations for the diffractometer in use are derived, which allows an operation of the instrument in the convenient six circle mode. As an example, results from surface x-ray diffraction on a Cu3Au(111) single crystal are presented.
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07.78.+s, 42.25.Fx

Multi-mode combustion facility for thermal treatment studies of wastes and biomass

Fadi Eldabbagh, Janusz A. Kozinski, Michael Bourassa, Jean-Pierre Farant, Peter Gangli, Michael Groves, Eric Rosen, Vic Uloth, Jalal Hawari, and Wes Hutny

Rev. Sci. Instrum. 75, 5308 (2004) (7 pages)

Online Publication Date: 30 November 2004

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This article describes newly built Multi-Mode Combustion Facility (MCF) used for investigating thermal destruction of industrial wastes and combustion of biomass. A flexible, refractory-lined combustion chamber consists of individual sections of various heights and diameter of 0.5  m. The MCF can be used either as a fluidized bed combustor (FBC) to study the combustion of solid residues or as a single-burner furnace (SBF) to study cofiring of biomass and natural gas. The facility is designed such that the outer wall temperature should not exceed 327  K with the use of water-cooling system and refractory materials. The inner temperature of each section is independent of the rest of the sections and controlled individually. This arrangement allows for the combustion process to be carried out in a multizone manner called low–high–low (LHL) temperature approach. The LHL approach means that the waste/biomass is initially fed into a low temperature zone (<1060  K) and then subjected to the high temperature treatment (~1500  K) that is followed by another low temperature zone (<1160  K). The LHL setup allows for heavy metals encapsulation and immobilization within the fly ash particles. The facility has 25 openings for sampling of solids and gases at different stages of the combustion process, as well as in situ observation. Experiments reported in this article were performed in the bubbling FBC mode with the purpose of testing the leachability of heavy metals (Cd, Cr, and Pb) from fly ash generated during two different combustion approaches: (1) multi-zone LHL treatment, and (2) no-LHL. Baseline fluidization properties of different bed materials were tested. Axial profiles of temperature and gas concentration (CO2, NO, and NOx) were compared. The results show that the leachability of the heavy metals (Cd, Cr, and Pb) contained in the LHL-generated ash particles was negligible (0.14, 0.061, and 1.55  ppm, respectively), while the leachability data from the no-LHL technique were 30.7, 14.3, and 0.647  ppm, respectively. It was concluded that the MCF facility is easy to operate, flexible, and useful for studies of various waste-to-energy options. Our results also show an improvement in heavy metals leachability when using the LHL combustion technique.
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82.33.Vx, 81.40.Gh

BIOLOGY AND MEDICINE

Design and performance of a wide-bandwidth and sensitive instrument for near-infrared spectroscopic measurements on human tissue

Luigi Rovati, Andrea Bandera, Maurizio Donini, Giorgia Salvatori, and Luca Pollonini

Rev. Sci. Instrum. 75, 5315 (2004) (11 pages)

Online Publication Date: 30 November 2004

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The article describes an instrument designed to perform in vivo near-infrared spectroscopic measurements on human tissues. The system integrates five continuous-wave laser diode sources emitting in the near-infrared spectral region and a low-noise detection system based on an avalanche photodiode. The optical probe is based on a compact, reliable, and low-cost fiber based system with four quantitative measuring points. The excellent sensitivity of the instrument allows one to perform quantitative assessments of the hemoglobin concentration exploiting precise absorption measurements close to the absorption peak of the water: 975  nm. Moreover, a good signal to noise ratio is obtained also at a high acquisition rate, allowing us to follow rapid changes in oxidative metabolism. The system bandwidth is selectable within the range 2.3–27  Hz, i.e., 20 channels (five chromatic and four spatial channels) can be acquired 27 times for each measuring second, whereas the system amplification can be set to measure optical density ranging from 3.5 to 8.5. A prototype version of the instrument has been realized and characterized.
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87.80.-y, 07.57.Ty, 87.14.Ee, 87.64.Je, 87.15.Aa

THERMOMETRY; THERMAL DIFFUSIVITY; ACOUSTIC; PHOTOTHERMAL AND PHOTOACOUSTIC

Some considerations for a method that simultaneously measures the temperature and emissivity of a metal in a high temperature furnace

Tohru Iuchi and Tohru Furukawa

Rev. Sci. Instrum. 75, 5326 (2004) (7 pages)

Online Publication Date: 30 November 2004

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This article describes some considerations for designing a practical radiation thermometry system for a glossy metal moving through a high temperature furnace, such as a continuous annealing furnace. In order to accomplish this task, two problems must be solved. The emissivity compensation of an object must be calculated and the furnace's background radiation noise must be eliminated. The authors have proposed a method that uses the radiance's polarized directional properties to simultaneously measure the emissivity and temperature to solve the first problem and a technique using a pseudo-blackbody installed in the furnace to solve the second problem. During heating, there is a one-to-one correspondence between the emissivity and the ratio of p- and s-polarized radiances for metals. This characteristic has successfully led to the development of a method for simultaneously measuring the emissivity and temperature of metals regardless of a potential large change in emissivity. Introducing a pseudo-blackbody radiator into a furnace removes the background radiation noise. Moreover, the blackbody radiator supplies a constant reference radiance. This reference plays an important role in maintaining the principle of emissivity-compensated radiation thermometry inside the furnace. Experimental results have simultaneously measured the emissivity and temperature of stainless steel at 1300  K with errors of 12% and 0.96%, respectively. These values were attained even though the s-polarized emissivities change from 0.25 to 0.75 at a wavelength of 0.9  µm. These errors can be achieved by designing the apparatus to have a solid angle, the aperture of the pseudo-blackbody subtended by a measuring point of the specimen, of more than 0.02pi steradians. The accuracy of this method is heavily dependent upon the specimen's surface roughness. The maximum surface roughness that allows for the successful utilization of this method is Ra = 0.12  µm.
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07.20.Dt, 07.20.Hy, 07.20.Ka, 68.35.Bs

OPTICS; ATOMS AND MOLECULES; SPECTROSCOPY; PHOTON DETECTORS

Room temperature, THz photomixing sweep oscillator and its application to spectroscopic transmission through organic materials

E. R. Brown, J. Bjarnason, T. L. J. Chan, D. C. Driscoll, M. Hanson, and A. C. Gossard

Rev. Sci. Instrum. 75, 5333 (2004) (10 pages)

Online Publication Date: 30 November 2004

Full Text: PDF (1027 kB)

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An all-solid-state continuous-wave sweep oscillator has been developed that provides high-resolution, transmission measurements between ~30  GHz and 3  THz. It is based on difference-frequency generation between two cw frequency-offset lasers driving an ultrafast photoconductive mixer (photomixer). The output power around 100  GHz is approximately 10  µW, falling to about 1  µW around 1  THz and 0.1  µW around 3  THz. The sweep oscillator is used with two types of detectors: a hot electron bolometer for high-sensitivity measurements of weak absorption features below 1  THz, and a room temperature Golay cell for coarse measurements anywhere between 30  GHz and 3  THz. The sweep oscillator facilitates the rapid characterization of a broad variety of materials including inorganic solids, biological materials, liquids, and gases with far greater resolution (~10  MHz), frequency accuracy (~0.1  GHz), and spectral density (~1  µW/MHz) than competitive wideband instruments such as Fourier-transform or time-domain spectrometers. To demonstrate the versatility of the sweep oscillator, results are presented for two diverse cases of interest: (1) fast scan, broadband (> 1  THz) absorption profiles from biomaterials such as polysaccharides, and (2) slow scan, narrow-band (~1  GHz) atmospheric lines from water vapor.
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84.30.Ng, 07.57.Pt, 06.60.Jn, 42.65.Ky, 07.57.Kp

NUCLEAR PHYSICS, FUSION AND PLASMAS

emiT: An apparatus to test time reversal invariance in polarized neutron decay

H. P. Mumm, A. Garcia, L. Grout, M. Howe, L. P. Parazzoli, R. G. H. Robertson, K. M. Sundqvist, J. F. Wilkerson, S. J. Freedman, B. K. Fujikawa, L. J. Lising, M. S. Dewey, J. S. Nico, A. K. Thompson, T. E. Chupp et al.

Rev. Sci. Instrum. 75, 5343 (2004) (13 pages)

Online Publication Date: 2 December 2004

Full Text: PDF (714 kB)

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We describe an apparatus used to measure the triple-correlation term (D sigma-hatn·pe×pnu) in the beta decay of polarized neutrons. The D coefficient is sensitive to possible violations of time reversal invariance. The detector has an octagonal symmetry that optimizes electron–proton coincidence rates and reduces systematic effects. A beam of longitudinally polarized cold neutrons passes through the detector chamber, where a small fraction undergo beta decay. The final-state protons are accelerated and focused onto arrays of cooled semiconductor diodes, while the coincident electrons are detected using panels of plastic scintillator. Details regarding the design and performance of the proton detectors, beta detectors, and the electronics used in the data collection system are presented. The neutron beam characteristics, the spin-transport magnetic fields, and polarization measurements are also described.
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24.80.+y, 14.20.Dh

BIOLOGY AND MEDICINE

Ranque–Hilsch vortex tube thermocycler for fast DNA amplification and real-time optical detection

Ryan J. Ebmeier, Scott E. Whitney, Amitabha Sarkar, Michael Nelson, Nisha V. Padhye, George Gogos, and Hendrik J. Viljoen

Rev. Sci. Instrum. 75, 5356 (2004) (4 pages)

Online Publication Date: 2 December 2004

Full Text: PDF (294 kB)

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An innovative polymerase chain reaction (PCR) thermocycler capable of performing real-time optical detection is described below. This device utilizes the Ranque–Hilsch vortex tube in a system to efficiently and rapidly cycle three 20  µL samples between the denaturation, annealing, and elongation temperatures. The reaction progress is displayed real-time by measuring the size of a fluorescent signal emitted by SYBR green/double-stranded DNA complexes. This device can produce significant reaction yields with very small amounts of initial DNA, for example, it can amplify 0.25  fg (~5 copies) of a 96  bp bacteriophage lambda-DNA fragment 2.7×1011-fold by performing 45  cycles in less than 12  min. The optical threshold (150% of the baseline intensity) was passed 8  min into the reaction at cycle 34. Besides direct applications, the speed and sensitivity of this device enables it to be used as a scientific instrument for basic studies such as PCR assembly and polymerase kinetics.
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87.80.-y, 87.14.Gg, 06.60.Ei, 87.15.Rn
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NOTES

Novel method to preserve freshly cleaved surfaces

M. Fink and V. R. Smith

Rev. Sci. Instrum. 75, 5360 (2004) (2 pages)

Online Publication Date: 2 December 2004

Full Text: PDF (199 kB)

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A novel method is presented by which one can ensure that a freshly cleaved surface is protected from contamination. The surface, cleaved in a protective atmosphere like argon, is dipped into molten camphor while still in the inert environment. The surface can then be transported out of the hood and exposed to regular air. The camphor coating has the advantage of ease of removal and can protect the surface for a time scale as long as hours. The camphor can be removed including the last monolayer without exposing the surface to any stressful treatment as shown by computer controlled thermal desorption measurements.
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81.65.-b, 68.43.Vx

A differential mechanical profilometer for thickness measurement

J. Maia Alves, M. C. Brito, J. M. Serra, and A. M. Vallêra

Rev. Sci. Instrum. 75, 5362 (2004) (2 pages)

Online Publication Date: 2 December 2004

Full Text: PDF (64 kB)

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A low cost differential profilometer based on standard commercial displacement transducers is fully described. Unlike most common profilometers this device can be used to measure the thickness profile of samples having both surfaces irregular. A sensitivity of about 0.2  µm, independent of the sample thickness is achieved.
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06.30.Bp, 07.07.Mp

High sensitivity bulk electro-optic modulator field sensor for high voltage environments

Mao-Sheng Huang, Mao-Hong Lu, and Jow-Tsong Shy

Rev. Sci. Instrum. 75, 5364 (2004) (3 pages)

Online Publication Date: 2 December 2004

Full Text: PDF (59 kB)

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An optical electric field sensor is an effective instrument for surveying the electric or magnetic field around a high voltage electrical system. A Mach–Zender interferometer type modulator is generally used in this kind of sensor. The sensor has good sensitivity to electric or magnetic fields, but an unexpected high field could easily destroy the modulator owing to its short electrode separation. A bulk modulator usually has long separation between the two electrodes, which can prevent modulator breakdown, but its sensitivity is usually worse than the Mach–Zender interferometer type sensor. To solve this problem, a Fabry–Perot cavity is used to improve the sensitivity of the bulk modulator type sensor. This work also discusses the optimization of the sensor sensitivity. When the sensor works on the point where a cavity resonance has maximal slope, the proposed sensor has approximately the same sensitivity for sensing a field as the Mach–Zender interferometer type sensor.
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07.07.Df, 07.60.Ly, 42.79.Hp, 84.37.+q

Noise selection in multielectrode devices by using a correlation spectrum analyzer

Giorgio Ferrari, Laura Fumagalli, and Marco Sampietro

Rev. Sci. Instrum. 75, 5367 (2004) (3 pages)

Online Publication Date: 2 December 2004

Full Text: PDF (49 kB)

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In this article, we present a technique to sort out in a multielectrode device a vanishing small noise component between two electrodes affected by a much larger overall noise. The technique is based on the use of a correlation spectrum analyzer and has proven to detect a current noise of interest as low as 1  fA/sqrt(Hz) in the presence of undesirable noise of 50  fA/sqrt(Hz). The possibility offered by this technique is useful in a number of applications, ranging from gate current investigation in metal-oxide-semiconductor field effect transistors to the study of leakage currents in nanodevices.
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07.50.Hp

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