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Dec 2004

Volume 75, Issue 12, pp. 5079-5369

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back to top 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); http://dx.doi.org/10.1063/1.1821622 (5 pages) | Cited 4 times

Online Publication Date: 10 November 2004

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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.
Show PACS
95.55.Ym Gravitational radiation detectors; mass spectrometers; and other instrumentation and techniques
07.20.Dt Thermometers
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
back to top GENERAL INSTRUMENTS

A simple noise subtraction technique

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

Rev. Sci. Instrum. 75, 5084 (2004); http://dx.doi.org/10.1063/1.1821625 (6 pages) | Cited 6 times

Online Publication Date: 10 November 2004

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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 Telecommunications: signal transmission and processing; communication satellites
back to top 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); http://dx.doi.org/10.1063/1.1813091 (4 pages) | Cited 7 times

Online Publication Date: 10 November 2004

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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 Electric and magnetic measurements
28.52.Lf Components and instrumentation
52.55.Jd Magnetic mirrors, gas dynamic traps
52.25.Fi Transport properties
back to top 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); http://dx.doi.org/10.1063/1.1813971 (6 pages)

Online Publication Date: 10 November 2004

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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 Charged-particle beam sources and detectors
29.25.-t Particle sources and targets
96.30.Cw Comets
96.50.Ek Heliopause and solar wind termination
back to top 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); http://dx.doi.org/10.1063/1.1818511 (6 pages)

Online Publication Date: 10 November 2004

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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 Astronomical and space-research instrumentation
95.30.Qd Magnetohydrodynamics and plasmas
07.68.+m Photography, photographic instruments; xerography
07.75.+h Mass spectrometers
82.80.Rt Time of flight mass spectrometry
79.20.Hx Electron impact: secondary emission
84.30.Sk Pulse and digital circuits
back to top 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); http://dx.doi.org/10.1063/1.1818531 (6 pages)

Online Publication Date: 10 November 2004

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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±Δx/(2√n) when the measurand has a uniform probability distribution function, Δx 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 Measurement and error theory
06.20.F- Units and standards
02.50.-r Probability theory, stochastic processes, and statistics

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); http://dx.doi.org/10.1063/1.1819384 (7 pages) | Cited 28 times

Online Publication Date: 10 November 2004

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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 (εa). 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(εa) 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 Superconducting wires, fibers, and tapes
74.25.Sv Critical currents
07.10.Pz Instruments for strain, force, and torque
74.25.Ld Mechanical and acoustical properties, elasticity, and ultrasonic attenuation
02.70.Dh Finite-element and Galerkin methods
back to top 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); http://dx.doi.org/10.1063/1.1819431 (4 pages) | Cited 149 times

Online Publication Date: 10 November 2004

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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.
Show PACS
44.20.+b Boundary layer heat flow
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
07.20.Dt Thermometers
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
back to top GENERAL INSTRUMENTS

Heat power source controller circuit

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

Rev. Sci. Instrum. 75, 5123 (2004); http://dx.doi.org/10.1063/1.1819451 (3 pages)

Online Publication Date: 10 November 2004

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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 Field effect devices
back to top 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); http://dx.doi.org/10.1063/1.1819535 (5 pages) | Cited 10 times

Online Publication Date: 10 November 2004

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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 Δν/ν 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 Dye lasers
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

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); http://dx.doi.org/10.1063/1.1819555 (5 pages) | Cited 17 times

Online Publication Date: 10 November 2004

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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 π at a symmetric position with respect to the optical axis. Using a laser beam with a wavefront aberration of 1/10λ, 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 2π 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 Optical elements, devices, and systems
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

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); http://dx.doi.org/10.1063/1.1820524 (7 pages) | Cited 9 times

Online Publication Date: 10 November 2004

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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 Magnetometers for magnetic field measurements
back to top CHEMISTRY

High-pressure cell for fluorescence fluctuation spectroscopy

Mohac Tekmen and Joachim D. Müller

Rev. Sci. Instrum. 75, 5143 (2004); http://dx.doi.org/10.1063/1.1821624 (6 pages) | Cited 5 times

Online Publication Date: 10 November 2004

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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 High-pressure apparatus; shock tubes; diamond anvil cells
07.60.-j Optical instruments and equipment
42.79.Ci Filters, zone plates, and polarizers
78.55.Kz Solid organic materials
back to top 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); http://dx.doi.org/10.1063/1.1813111 (3 pages) | Cited 1 time

Online Publication Date: 10 November 2004

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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 High-pressure apparatus; shock tubes; diamond anvil cells
06.60.Ei Sample preparation (including design of sample holders)
81.30.Fb Solidification
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
64.70.D- Solid-liquid transitions
64.70.F- Liquid-vapor transitions
back to top 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); http://dx.doi.org/10.1063/1.1818471 (8 pages) | Cited 4 times

Online Publication Date: 10 November 2004

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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 Vacuum gauges
07.77.Ka Charged-particle beam sources and detectors
29.25.Bx Electron sources
07.07.Mp Transducers
29.20.db Storage rings and colliders
back to top 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, Ashley Eadon, and Jon David Jackson

Rev. Sci. Instrum. 75, 5160 (2004); http://dx.doi.org/10.1063/1.1818491 (6 pages) | Cited 9 times

Online Publication Date: 10 November 2004

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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.Jd Magnetic mirrors, gas dynamic traps
52.75.-d Plasma devices
52.70.Ds Electric and magnetic measurements
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.55.Pi Fusion products effects (e.g., alpha-particles, etc.), fast particle effects
back to top 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); http://dx.doi.org/10.1063/1.1818591 (7 pages)

Online Publication Date: 10 November 2004

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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 Fiber testing and measurement of fiber parameters
07.20.Fw Calorimeters
07.20.Dt Thermometers
back to top 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); http://dx.doi.org/10.1063/1.1818891 (4 pages) | Cited 8 times

Online Publication Date: 10 November 2004

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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 Optical (ultraviolet, visible, infrared) measurements
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
07.60.-j Optical instruments and equipment
06.60.Jn High-speed techniques (microsecond to femtosecond)
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
42.79.Bh Lenses, prisms and mirrors
42.79.Pw Imaging detectors and sensors
back to top 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); http://dx.doi.org/10.1063/1.1819011 (9 pages) | Cited 5 times

Online Publication Date: 10 November 2004

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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 High-temperature instrumentation; pyrometers
64.70.D- Solid-liquid transitions
07.20.Hy Furnaces; heaters
43.25.Uv Acoustic levitation
81.70.Ha Testing in microgravity environments
06.60.Ei Sample preparation (including design of sample holders)
64.60.F- Equilibrium properties near critical points, critical exponents
back to top 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); http://dx.doi.org/10.1063/1.1819379 (7 pages) | Cited 6 times

Online Publication Date: 10 November 2004

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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.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.60.Fc Modulation, tuning, and mode locking
07.60.Ly Interferometers
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

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); http://dx.doi.org/10.1063/1.1819382 (10 pages) | Cited 5 times

Online Publication Date: 10 November 2004

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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 Optical parametric oscillators and amplifiers
42.79.Dj Gratings
42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

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); http://dx.doi.org/10.1063/1.1819531 (2 pages) | Cited 2 times

Online Publication Date: 10 November 2004

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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.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.60.Rn Relaxation oscillations and long pulse operation

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); http://dx.doi.org/10.1063/1.1823791 (8 pages) | Cited 14 times

Online Publication Date: 30 November 2004

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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-α 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 Z-pinches, plasma focus, and other pinch devices
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
back to top 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); http://dx.doi.org/10.1063/1.1819556 (3 pages) | Cited 2 times

Online Publication Date: 10 November 2004

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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 Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
back to top 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); http://dx.doi.org/10.1063/1.1821646 (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 Magnetic instruments and components
07.10.Lw Balance systems, tensile machines, etc.
75.80.+q Magnetomechanical effects, magnetostriction
81.70.Bt Mechanical testing, impact tests, static and dynamic loads
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