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May 2012

Volume 83, Issue 5, Articles (05xxxx)

Issue Cover Spotlight Figure

Rev. Sci. Instrum. 83, 051101 (2012); http://dx.doi.org/10.1063/1.4709621 (18 pages)

Igor Lubomirsky and Oscar Stafsudd

The periodic pulsed heating technique for measuring pyroelectricity (the Chynoweth method) is one of several measurement techniques that have been significantly enhanced through advances in instrumentation such as fast digital averaging oscilloscopes and modulated light sources.

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back to top General Instruments

A wall-free climate unit for acoustic levitators

M. C. Schlegel, K.-J. Wenzel, A. Sarfraz, U. Panne, and F. Emmerling

Rev. Sci. Instrum. 83, 055101 (2012); http://dx.doi.org/10.1063/1.4705968 (3 pages) | Cited 3 times

Online Publication Date: 1 May 2012

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Acoustic levitation represents the physical background of trapping a sample in a standing acoustic wave with no contact to the wave generating device. For the last three decades, sample holders based on this effect have been commonly used for contact free handling of samples coupled with a number of analytical techniques. In this study, a wall-free climate unit is presented, which allows the control of the environmental conditions of suspended samples. The insulation is based on a continuous cold/hot gas flow around the sample and thus does not require any additional isolation material. This provides a direct access to the levitated sample and circumvents any influence of the climate unit material to the running analyses.
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43.38.-p Transduction; acoustical devices for the generation and reproduction of sound
06.60.Ei Sample preparation (including design of sample holders)
43.35.Yb Ultrasonic instrumentation and measurement techniques

An atomic beam source for fast loading of a magneto-optical trap under high vacuum

Peter D. McDowall, Tzahi Grünzweig, Andrew Hilliard, and Mikkel F. Andersen

Rev. Sci. Instrum. 83, 055102 (2012); http://dx.doi.org/10.1063/1.4708617 (4 pages)

Online Publication Date: 2 May 2012

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We report on a directional atomic beam created using an alkali metal dispenser and a nozzle. By applying a high current (15 A) pulse to the dispenser at room temperature we can rapidly heat it to a temperature at which it starts dispensing, avoiding the need for preheating. The atomic beam produced is capable of loading 90% of a magneto-optical trap (MOT) in less than 7 s while maintaining a low vacuum pressure of <10−11 Torr. The transverse velocity components of the atomic beam are measured to be within typical capture velocities of a rubidium MOT. Finally, we show that the atomic beam can be turned off within 1.8 s.
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37.20.+j Atomic and molecular beam sources and techniques
37.10.Gh Atom traps and guides
03.75.Be Atom and neutron optics

Influence of the number of detectors by laser scattering method for estimation of particle size

Tatsuo Igushi and Hideto Yoshida

Rev. Sci. Instrum. 83, 055103 (2012); http://dx.doi.org/10.1063/1.4709493 (7 pages)

Online Publication Date: 2 May 2012

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Effect of the number of detectors on an inversion problem of a scattering pattern by laser scattering method based on Mie scattering model has been investigated. The influence of the number of detectors is obtained by comparing a given size distribution and a calculated size distribution by computer simulation and experimental method. An observing range of scattering angles is from 0.0007 to 2.5 rad. A non-linear iteration method is used for calculating particle size distribution. The number of detectors is changed from 6 to 81 elements by the computer simulation. The algorithm of the inversion problem is applied with mean diameters of log-normal distribution in a range from 0.546 to 214 μm at standard deviation of 0.27 and 0.68. Experimental results of certified mono-disperse polystyrene latex standards and a poly-disperse aluminum sample are obtained with 21, 41, and 81 elements detector, respectively. All tests are performed under conditions at diluted aqueous suspensions. Narrow size distribution is influenced by the number of detectors compared with wide size distribution. Not the number of physical detectors but the number of useful detectors affects the algorithm of the inversion problem. When the detector elements are over 20, the influence of the number of detectors is decreased.
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06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
82.70.-y Disperse systems; complex fluids
85.60.Gz Photodetectors (including infrared and CCD detectors)
02.60.-x Numerical approximation and analysis

Micro-reactors for characterization of nanostructure-based sensors

R. Savu, J. V. Silveira, A. Flacker, A. R. Vaz, E. Joanni, A. C. Pinto, A. L. Gobbi, T. E. A. Santos, A. L. P. Rotondaro, and S. A. Moshkalev

Rev. Sci. Instrum. 83, 055104 (2012); http://dx.doi.org/10.1063/1.4709495 (6 pages)

Online Publication Date: 2 May 2012

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Fabrication and testing of micro-reactors for the characterization of nanosensors is presented in this work. The reactors have a small volume (100 μl) and are equipped with gas input/output channels. They were machined from a single piece of kovar in order to avoid leaks in the system due to additional welding. The contact pins were electrically insulated from the body of the reactor using a borosilicate sealing glass and the reactor was hermetically sealed using a lid and an elastomeric o-ring. One of the advantages of the reactor lies in its simple assembly and ease of use with any vacuum/gas system, allowing the connection of more than one device. Moreover, the lid can be modified in order to fit a window for in situ optical characterization. In order to prove its versatility, carbon nanotube-based sensors were tested using this micro-reactor. The devices were fabricated by depositing carbon nanotubes over 1 μm thick gold electrodes patterned onto Si/SiO2 substrates. The sensors were tested using oxygen and nitrogen atmospheres, in the pressure range between 10−5 and 10−1 mbar. The small chamber volume allowed the measurement of fast sensor characteristic times, with the sensors showing good sensitivity towards gas and pressure as well as high reproducibility.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
85.35.Kt Nanotube devices

Large-scale generic test stand for testing of multiple configurations of air filters utilizing a range of particle size distributions

Paxton K. Giffin, Michael S. Parsons, Ronald J. Unz, and Charles A. Waggoner

Rev. Sci. Instrum. 83, 055105 (2012); http://dx.doi.org/10.1063/1.4717671 (12 pages) | Cited 1 time

Online Publication Date: 14 May 2012

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The Institute for Clean Energy Technology (ICET) at Mississippi State University has developed a test stand capable of lifecycle testing of high efficiency particulate air filters and other filters specified in American Society of Mechanical Engineers Code on Nuclear Air and Gas Treatment (AG-1) filters. The test stand is currently equipped to test AG-1 Section FK radial flow filters, and expansion is currently underway to increase testing capabilities for other types of AG-1 filters. The test stand is capable of producing differential pressures of 12.45 kPa (50 in. w.c.) at volumetric air flow rates up to 113.3 m3/min (4000 CFM). Testing is performed at elevated and ambient conditions for temperature and relative humidity. Current testing utilizes three challenge aerosols: carbon black, alumina, and Arizona road dust (A1-Ultrafine). Each aerosol has a different mass median diameter to test loading over a wide range of particles sizes. The test stand is designed to monitor and maintain relative humidity and temperature to required specifications. Instrumentation is implemented on the upstream and downstream sections of the test stand as well as on the filter housing itself. Representative data are presented herein illustrating the test stand's capabilities. Digital images of the filter pack collected during and after testing is displayed after the representative data are discussed. In conclusion, the ICET test stand with AG-1 filter testing capabilities has been developed and hurdles such as test parameter stability and design flexibility overcome.
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89.20.Kk Engineering
06.60.Mr Testing and inspecting procedures
89.20.Bb Industrial and technological research and development

Effect of multiplicative noise on least-squares parameter estimation with applications to the atomic force microscope

John E. Sader, Barry D. Hughes, Julian A. Sanelli, and Evan J. Bieske

Rev. Sci. Instrum. 83, 055106 (2012); http://dx.doi.org/10.1063/1.4709496 (6 pages) | Cited 1 time

Online Publication Date: 16 May 2012

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Measurement of the power spectral density of (stochastic) Brownian fluctuations of micro- and nano-devices is used frequently to gain insight into their mechanistic properties. Noise is always present in these measurements and can directly influence any parameter estimation obtained through a least-squares analysis. Importantly, measurements of the spectral density of stationary random signals, such as Brownian motion, inherently contain multiplicative noise. In this article, we theoretically analyze the impact of multiplicative noise on fit parameters extracted using a least-squares analysis. A general analysis is presented that is valid for any fit function with any number of fit parameters. This yields closed-form expressions for the expected value and variance in the fit parameters and provides a rigorous theoretical framework for a priori determination of the effect of measurement uncertainty. The theory is demonstrated and validated through Monte Carlo simulation of synthetic data and by comparison to power spectral density measurements of the Brownian fluctuations of an atomic force microscope cantilever – analytical formulas for the uncertainty in the fitted resonant frequency and quality factor are presented. The results of this study demonstrate that precise measurements of fit parameters in the presence of noise are inherently problematic – individual measurements of the power spectral density are capable of yielding fit parameters that are many standard deviations away from the mean, with finite probability. This is of direct relevance to a host of applications in measurement science, including those connected with the atomic force microscope.
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07.79.Lh Atomic force microscopes
02.50.Cw Probability theory

Differential membrane-based nanocalorimeter for high-resolution measurements of low-temperature specific heat

S. Tagliati, V. M. Krasnov, and A. Rydh

Rev. Sci. Instrum. 83, 055107 (2012); http://dx.doi.org/10.1063/1.4717676 (11 pages)

Online Publication Date: 16 May 2012

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A differential, membrane-based nanocalorimeter for general specific heat studies of very small samples, ranging from 0.5 mg to sub-μg in mass, is described. The calorimeter operates over the temperature range from above room temperature down to 0.5 K. It consists of a pair of cells, each of which is a stack of heaters and thermometer in the center of a silicon nitride membrane, in total giving a background heat capacity less than 100 nJ/K at 300 K, decreasing to 10 pJ/K at 1 K. The device has several distinctive features: (i) The resistive thermometer, made of a Ge1 − xAux alloy, displays a high dimensionless sensitivity |dlnR/dlnT| ≳ 1 over the entire temperature range. (ii) The sample is placed in direct contact with the thermometer, which is allowed to self-heat. The thermometer can thus be operated at high dc current to increase the resolution. (iii) Data are acquired with a set of eight synchronized lock-in amplifiers measuring dc, 1st and 2nd harmonic signals of heaters and thermometer. This gives high resolution and allows continuous output adjustments without additional noise. (iv) Absolute accuracy is achieved via a variable-frequency-fixed-phase technique in which the measurement frequency is automatically adjusted during the measurements to account for the temperature variation of the sample heat capacity and the device thermal conductance. The performance of the calorimeter is illustrated by studying the heat capacity of a small Au sample and the specific heat of a 2.6 μg piece of superconducting Pb in various magnetic fields.
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07.20.Fw Calorimeters
65.40.Ba Heat capacity
74.25.Bt Thermodynamic properties
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.10.Cm Micromechanical devices and systems

A ultra-high-vacuum wafer-fusion-bonding system

Kyle McKay, Scott Wolter, and Jungsang Kim

Rev. Sci. Instrum. 83, 055108 (2012); http://dx.doi.org/10.1063/1.4718357 (7 pages)

Online Publication Date: 17 May 2012

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The design of heterojunction devices is typically limited by material integration constraints and the energy band alignment. Wafer bonding can be used to integrate material pairs that cannot be epitaxially grown together due to large lattice mismatch. Control of the energy band alignment can be provided by formation of interface dipoles through control of the surface chemistry. We have developed an ultra-high-vacuum system for wafer-fusion-bonding semiconductors with in situ control and measurement of surface properties relevant to interface dipoles. A wafer-fusion-bonding chamber with annealing capabilities was integrated into an ultra-high-vacuum system with a sputtering chamber and an x-ray photoelectron spectroscopy system for preparing and measuring the surface chemistry of wafers prior to bonding. The design of the system along with initial results for the fusion-bonded InGaAs/Si heterojunction is presented.
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85.30.De Semiconductor-device characterization, design, and modeling

Testing the performance of a cryogenic visualization system on thermal counterflow by using hydrogen and deuterium solid tracers

M. La Mantia, T. V. Chagovets, M. Rotter, and L. Skrbek

Rev. Sci. Instrum. 83, 055109 (2012); http://dx.doi.org/10.1063/1.4719917 (8 pages) | Cited 2 times

Online Publication Date: 21 May 2012

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An experimental apparatus has been designed to analyze by visualization cryogenic flows of liquid 4He and consequently address unresolved problems of quantum turbulence. The newly implemented flow visualization setup is described and its specific features discussed. Thermal counterflow experiments have been performed and the motion of solid hydrogen and deuterium tracers studied by using the particle tracking velocimetry technique in order to probe the system capabilities. It is shown that the obtained results are consistent with the two-fluid model describing the behavior of superfluid 4He. A number of technical and fundamental issues, such as particles’ aggregation, role of rotating particles in counterflow and evidence of non-Gaussian distribution of tracers’ velocities, are also discussed. The apparatus appears to be well-suited to the task of analyzing cryogenic flows and potentially capable of obtaining new results stimulating further understanding of the underlying physics.
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47.80.Jk Flow visualization and imaging
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
47.27.te Turbulent convective heat transfer
47.32.Ef Rotating and swirling flows

Versatile system for the temperature-controlled preparation of oxide crystal surfaces

H. H. Pieper, C. Lammers, L. Tröger, S. Bahr, and M. Reichling

Rev. Sci. Instrum. 83, 055110 (2012); http://dx.doi.org/10.1063/1.4717674 (5 pages) | Cited 2 times

Online Publication Date: 21 May 2012

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We present a versatile system for the preparation of oxide crystal surfaces in the ultra-high vacuum (UHV) at temperatures up to 1300 K. Thermal treatment is accomplished by direct current heating of a tantalum foil in contact with the oxide sample. The sample temperature is measured by a thermocouple at a position close to the crystal and its reading is calibrated against the surface temperature determined by a second thermocouple temporarily attached to the surface. The design of the sample holder is based on a transferable plate originally developed for a commercial UHV scanning probe microscope. The system is, however, also suitable for the use with electron spectroscopy or electron diffraction based surface analytical techniques. We present results for the high-temperature preparation of CeO2(111) surfaces with atomically flat terraces exhibiting perfect atomic order and cleanliness as revealed by non-contact atomic force microscopy (NC-AFM) imaging. NC-AFM imaging is, furthermore, used to demonstrate the temperature-controlled aggregation of gold atoms on the CeO2(111) surface and their evaporation at high temperatures.
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81.20.-n Methods of materials synthesis and materials processing
81.40.Gh Other heat and thermomechanical treatments
68.35.bt Other materials
68.37.Ps Atomic force microscopy (AFM)

Modeling technique of capacitive discharge pumping of metal vapor lasers for electrode capacitance optimization

F. A. Gubarev, G. S. Evtushenko, N. K. Vuchkov, V. B. Sukhanov, and D. V. Shiyanov

Rev. Sci. Instrum. 83, 055111 (2012); http://dx.doi.org/10.1063/1.4719920 (5 pages)

Online Publication Date: 22 May 2012

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To estimate optimum gas discharge tube (GDT) electrode capacitance of metal vapor lasers (MVLs) pumped by a longitudinal capacitive discharge, we offer to use series connection of capacitors to the electrodes of a conventionally pumped GDT with inner electrodes. It has been demonstrated that the maximum output power in CuBr lasers is obtained when the capacitances of high-voltage and ground electrodes are equal. When using a model circuit an average output power reaches 12 W that suggests the possibility of generating high average output power (>10 W) in MVLs pumped using a capacitive discharge.
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52.80.-s Electric discharges
52.25.Fi Transport properties

Characterization of solid and liquid sorbent materials for biogas purification by using a new volumetric screening instrument

J. Rother, T. Fieback, R. Seif, and F. Dreisbach

Rev. Sci. Instrum. 83, 055112 (2012); http://dx.doi.org/10.1063/1.4717681 (7 pages) | Cited 1 time

Online Publication Date: 22 May 2012

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With the increasing utilization of biogas as an energy source the need for new materials and methods to purify and clean the corresponding gas mixtures is rising. In this regard, the application of ad- or absorptive gas purification methods has increased significantly over the last years. For fast and economic evaluation of the potential of different sorbent materials, a new volumetric screening instrument has been developed. First the measuring method and the new instrument design will be described. This instrument allows ad- and absorption, as well as desorption measurements in a technically relevant, wide pressure, and temperature range. It was used for the characterization of common sorbent materials such as activated carbons and zeolite molecular sieves. Additionally, new substances like metal-organic frameworks and ionic liquids were analyzed. Thereby the sorption of CO2, CH4, N2, and H2 was measured. The obtained data allow the direct comparison of the sorption properties of the different materials, the results of which will be presented in the second part of the paper.
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88.20.F- Renewable alternative fuels from biomass energy
68.43.Mn Adsorption kinetics
81.20.Ym Purification
82.80.-d Chemical analysis and related physical methods of analysis
68.43.Nr Desorption kinetics

Means to remove electrode contamination effect of Langmuir probe measurement in space

K.-I. Oyama, C. H. Lee, H. K. Fang, and C. Z. Cheng

Rev. Sci. Instrum. 83, 055113 (2012); http://dx.doi.org/10.1063/1.4722167 (12 pages) | Cited 2 times

Online Publication Date: 24 May 2012

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Precaution to remove the serious effect of electrode contamination in Langmuir probe experiments has not been taken in many space measurements because the effect is either not understood or ignored. We stress here that one should pay extra attention to the electrode contamination effect to get accurate and reliable plasma measurements so that the long time effort for sounding rocket/satellite missions does not end in vain or becomes less fruitful. In this paper, we describe two main features of voltage–current characteristic curves associated with the contaminated Langmuir probe, which are predicted from the equivalent circuit model, which we proposed in 1970's. We then show that fast sweeping dc Langmuir probes can give reliable results in the steady state regime. The fast sweeping probe can also give reliable results in transient situations such as satellite moves through plasma bubble in the ionosphere where the electron density drastically changes. This fact was first confirmed in our laboratory experiment.
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52.70.Ds Electric and magnetic measurements
06.20.Dk Measurement and error theory

Development of a novel 3-degrees of freedom flexure based positioning system

Hyo-Young Kim, Da-Hoon Ahn, and Dae-Gab Gweon

Rev. Sci. Instrum. 83, 055114 (2012); http://dx.doi.org/10.1063/1.4720410 (11 pages)

Online Publication Date: 29 May 2012

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Flexure mechanisms have been widely used for nanometer positioning systems. This article presents a novel conceptual design of an ultra-precision 3-degrees of freedom (XYθZ) positioning system with nanometer precision. The main purpose of this novel stage design is for the application of measurement equipment, in particular biological specimens. The stage was designed as a hollow type and with a compact size for the inverted microscope. This stage includes piezoelectric transducer actuators, double compound amplification mechanisms, moving plate, and capacitor sensors. The double compound amplification mechanism was designed using a mathematical model and analyzed by the finite element method. Since the relationship between the variables of the hinge parameters and system performances are complicated, an optimization procedure was used to obtain the optimal design parameters, which maximized the system bandwidth. Based on the solution of the optimization problem, the design of the stage and FEM simulation results are presented. Finally, the stage was manufactured and tested.
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89.20.Kk Engineering
46.70.De Beams, plates, and shells
46.35.+z Viscoelasticity, plasticity, viscoplasticity
02.70.Dh Finite-element and Galerkin methods
02.60.Pn Numerical optimization
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