Rev. Sci. Instrum. - Review of Scientific Instruments

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Registration of Alfvén resonances in TCABR tokamak by the scanning reflectometer at sideband frequencies

L. F. Ruchko, A. G. Elfimov, C. M. Teixeira, J. I. Elizondo, E. Sanada, R. M. O. Galvão, M. E. Manso, and A. Silva

Rev. Sci. Instrum. 82, 023504 (2011); http://dx.doi.org/10.1063/1.3541756 (4 pages)

Online Publication Date: 22 February 2011

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A frequency scanning O-mode reflectometer was used for studies of plasma density oscillations during local Alfvén wave (LAW) excitation in the Tokamak Chauffage Alfvén Brésilien (TCABR) at the frequency f_A = 5 MHz. It was found that the spectrum of the reflectometer output signal, which consists mainly of the “beat” frequency f_B, is modified by the LAW excitation, and two additional frequency peaks appear, which are symmetrical in relation to the LAW excitation frequency f = f_A ± f_B. This result opens the possibility to improve the efficiency of studying the LAW induced density oscillations. The symmetry of these frequency peaks yields the possibility of finding the microwave frequency at which the reflectometer cutoff layer coincides with radial position of the LAW resonance zone in the TCABR tokamak.

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52.35.Bj	Magnetohydrodynamic waves (e.g., Alfven waves)
52.55.Fa	Tokamaks, spherical tokamaks
52.25.-b	Plasma properties
52.35.Fp	Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.70.Gw	Radio-frequency and microwave measurements

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Design and performance of a punch mechanism based pellet injector for alternative injection in the large helical device

J. S. Mishra, R. Sakamoto, G. Motojima, A. Matsuyama, and H. Yamada

Rev. Sci. Instrum. 82, 023505 (2011); http://dx.doi.org/10.1063/1.3541807 (7 pages) | Cited 1 time

Online Publication Date: 22 February 2011

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A low speed single barrel pellet injector, using a mechanical punch device has been developed for alternative injection in the large helical device. A pellet is injected by the combined operation of a mechanical punch and a pneumatic propellant system. The pellet shape is cylindrical, 3 mm in diameter and 3 mm in length. Using this technique the speed of the pellet can be controlled flexibly in the range of 100–450 m/s, and a higher speed can be feasible for a higher gas pressure. The injector is equipped with a guide tube selector to direct the pellet to different injection locations. Pellets are exposed to several curved parts with the curvature radii R_c = 0.8 and 0.3 m when they are transferred in guided tubes to the respective injection locations. Pellet speed variation with pressure at different pellet formation temperatures has been observed. Pellet intactness tests through these guide tubes show a variation in the intact speed limit over a range of pellet formation temperatures from 6.5 to 9.8 K. Pellet speed reduction of less than 6% has been observed after the pellet moves through the curved guide tubes.

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28.52.Cx	Fueling, heating and ignition
28.52.Av	Theory, design, and computerized simulation
52.55.Jd	Magnetic mirrors, gas dynamic traps
52.25.-b	Plasma properties

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Work function measurements during plasma exposition at conditions relevant in negative ion sources for the ITER neutral beam injection

R. Gutser, C. Wimmer, and U. Fantz

Rev. Sci. Instrum. 82, 023506 (2011); http://dx.doi.org/10.1063/1.3541790 (7 pages) | Cited 7 times

Online Publication Date: 23 February 2011

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Cesium seeded sources for surface generated negative hydrogen ions are major components of neutral beam injection systems in future large-scale fusion experiments such as ITER. The stability and delivered current density depend highly on the work function during vacuum and plasma phases of the ion source. One of the most important quantities that affect the source performance is the work function. A modified photocurrent method was developed to measure the temporal behavior of the work function during and after cesium evaporation. The investigation of cesium exposed Mo and MoLa samples under ITER negative hydrogen ion based neutral beam injection relevant surface and plasma conditions showed the influence of impurities which result in a fast degradation when the plasma exposure or the cesium flux onto the sample is stopped. A minimum work function close to that of bulk cesium was obtained under the influence of the plasma exposition, while a significantly higher work function was observed under ITER-like vacuum conditions.

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52.55.Fa	Tokamaks, spherical tokamaks
52.50.Gj	Plasma heating by particle beams
52.50.Dg	Plasma sources
52.25.Vy	Impurities in plasmas
28.52.Fa	Materials
52.70.Kz	Optical (ultraviolet, visible, infrared) measurements

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Simultaneous four-color imaging of single molecule fluorophores using dichroic mirrors and four charge-coupled devices

Takanobu Haga, Tsuyoshi Sonehara, Tomoyuki Sakai, Takashi Anazawa, Takeshi Fujita, and Satoshi Takahashi

Rev. Sci. Instrum. 82, 023701 (2011); http://dx.doi.org/10.1063/1.3524570 (6 pages) | Cited 2 times

Online Publication Date: 4 February 2011

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We developed a total-internal-reflection (TIR) fluorescence microscopy using three dichroic mirrors and four charge-coupled devices (CCDs) to detect simultaneously four colors of single-molecule (SM) fluorophores. Four spectrally distinct species of fluorophores (Alexa 488, Cy3, Cy5, or Cy5.5) were each immobilized on a different fused silica slide. A species of fluorophores on the slide was irradiated simultaneously, by two excitation beams from an Ar ion laser (488 and 514.5 nm) and a diode laser (642 nm) through TIR on the slide surface. Fluorescence emitted from the fluorophores was spectrally resolved into four components by the dichroic mirrors, and four images were generated from them simultaneously and continuously, with the four CCDs at a rate of 10 Hz. A series of images was thus obtained with each CCD. Fluorescence spots for a species were observed mainly in the series of images recorded by its respective-color CCD. In the first image in the series, we picked out the spots as continuous pixel regions that had the values greater than a threshold. Then we selected only those spots that exhibited single-step photobleaching and regarded them as SM fluorescence spots. Pixel values of SM fluorescence spots widely differed. Some SM fluorophores had pixel values smaller than the threshold, and were left unpicked. Assuming the pixel values of SM fluorescence spots differed with a Gaussian profile, we estimated the ratios of unpicked fluorophores to be less than 20% for all the species. Because of the spectral overlaps between species, we also observed cross-talk spots into CCDs other than the respective-color CCDs. These cross-talk SM fluorescence spots can be mistaken for correct species. We thus introduced the classification method and classified SM fluorescence spots into correct species in accordance with two kinds of four-dimensional signal vectors. The error rates of fluorophore classification were estimated to be less than 3.2% for all the species. Our system is suitable for the biological studies that desire to simultaneously monitor the four colors of SM fluorophores.

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33.50.Dq	Fluorescence and phosphorescence spectra
42.79.Pw	Imaging detectors and sensors
42.79.-e	Optical elements, devices, and systems
42.50.Gy	Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption
42.79.Bh	Lenses, prisms and mirrors

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Experimental facility for two- and three-dimensional ultrafast electron beam x-ray computed tomography

T. Stürzel, M. Bieberle, E. Laurien, U. Hampel, F. Barthel, H.-J. Menz, and H.-G. Mayer

Rev. Sci. Instrum. 82, 023702 (2011); http://dx.doi.org/10.1063/1.3529435 (7 pages) | Cited 1 time

Online Publication Date: 9 February 2011

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An experimental facility is described, which has been designed to perform ultrafast two-dimensional (2D) and three-dimensional (3D) electron beam computed tomographies. As a novelty, a specially designed transparent target enables tomography with no axial offset for 2D imaging and high axial resolution 3D imaging employing the cone-beam tomography principles. The imaging speed is 10 000 frames per second for planar scanning and more than 1000 frames per second for 3D imaging. The facility serves a broad spectrum of potential applications; primarily, the study of multiphase flows, but also in principle nondestructive testing or small animal imaging. In order to demonstrate the aptitude for these applications, static phantom experiments at a frame rate of 2000 frames per second were performed. Resulting spatial resolution was found to be 1.2 mm and better for a reduced temporal resolution.

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47.80.Jk	Flow visualization and imaging
47.55.-t	Multiphase and stratified flows
06.60.Jn	High-speed techniques (microsecond to femtosecond)

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Atomic force microscope imaging and force measurements at electrified and actively corroding interfaces: Challenges and novel cell design

Markus Valtiner, Genesis Ngwa Ankah, Asif Bashir, and Frank Uwe Renner

Rev. Sci. Instrum. 82, 023703 (2011); http://dx.doi.org/10.1063/1.3541650 (8 pages) | Cited 1 time

Online Publication Date: 11 February 2011

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We report the design of an improved electrochemical cell for atomic force microscope measurements in corrosive electrochemical environments. Our design improvements are guided by experimental requirements for studying corrosive reactions such as selective dissolution, dealloying, pitting corrosion, and/or surface and interface forces at electrified interfaces. Our aim is to examine some of the limitations of typical electrochemical scanning probe microscopy (SPM) experiments and in particular to outline precautions and cell-design elements, which must necessarily be taken into account in order to obtain reliable experimental results. In particular, we discuss electrochemical requirements for typical electrochemical SPM experiments and introduce novel design features to avoid common issues such as crevice formations; we discuss the choice of electrodes and contaminations from ions of reference electrodes. We optimize the cell geometry and introduce standard samples for electrochemical AFM experiments. We have tested the novel design by performing force–distance spectroscopy as a function of the applied electrochemical potential between a bare gold electrode surface and a SAM-coated AFM tip. Topography imaging was tested by studying the well-known dealloying process of a Cu₃Au(111) surface up to the critical potential. Our design improvements should be equally applicable to in situ electrochemical scanning tunneling microscope cells.

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07.79.Lh	Atomic force microscopes
68.37.Ps	Atomic force microscopy (AFM)
07.10.Pz	Instruments for strain, force, and torque
82.45.Fk	Electrodes

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High precision particle mass sensing using microchannel resonators in the second vibration mode

Jungchul Lee, Andrea K. Bryan, and Scott R. Manalis

Rev. Sci. Instrum. 82, 023704 (2011); http://dx.doi.org/10.1063/1.3534825 (4 pages) | Cited 3 times

Online Publication Date: 17 February 2011

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An intrinsic uncertainty in particle mass sensing with the suspended microchannel resonator results from variation in a particle's position near the free end of the resonator. To circumvent this error we employ the second flexural bending mode. This mode exhibits additional frequency peaks while particles pass over the antinode, a point where the frequency shift is insensitive to the lateral position of the particle. We measure polystyrene beads with the first and second modes and confirm that the second mode sensing provides a narrower mass histogram. For 3 μm diameter beads, second mode sensing at the antinode improves the coefficient of variation in buoyant mass from 1.76% to 1.05% for population measurements and from 1.40% to 0.53% for a single trapped particle.

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06.30.Dr	Mass and density
47.57.E-	Suspensions
07.10.Cm	Micromechanical devices and systems
47.60.Dx	Flows in ducts and channels

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Low temperature ultrahigh vacuum noncontact atomic force microscope in the pendulum geometry

U. Gysin, S. Rast, M. Kisiel, C. Werle, and E. Meyer

Rev. Sci. Instrum. 82, 023705 (2011); http://dx.doi.org/10.1063/1.3551603 (6 pages) | Cited 2 times

Online Publication Date: 18 February 2011

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A noncontact atomic force microscope (nc-AFM) operating in magnetic fields up to ±7 T and liquid helium temperatures is presented in this article. In many common AFM experiments the cantilever is mounted parallel to the sample surface, while in our system the cantilever is assembled perpendicular to it; the so called pendulum mode of AFM operation. In this mode measurements employing very soft and, therefore, ultrasensitive cantilevers can be performed. The ultrahigh vacuum conditions allow to prepare and transfer cantilevers and samples in a requested manner avoiding surface contamination. We demonstrate the possibility of nc-AFM and Kelvin force probe microscopy imaging in the pendulum mode. Ultrasensitive experiments on small spin ensembles are presented as well.

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07.79.Lh	Atomic force microscopes
68.37.Ps	Atomic force microscopy (AFM)

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Spectral-domain phase microscopy with improved sensitivity using two-dimensional detector arrays

K. Singh, C. Dion, M. R. Lesk, T. Ozaki, and S. Costantino

Rev. Sci. Instrum. 82, 023706 (2011); http://dx.doi.org/10.1063/1.3556787 (4 pages) | Cited 4 times

Online Publication Date: 22 February 2011

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In this work we demonstrate the use of two-dimensional detectors to improve the signal-to-noise ratio (SNR) and sensitivity in spectral-domain phase microscopy for subnanometer accuracy measurements. We show that an increase in SNR can be obtained, from 82 dB to 105 dB, using 150 pixel lines of a low-cost CCD camera as compared to a single line, to compute an averaged axial scan. In optimal mechanical conditions, phase stability as small as 92 μrad, corresponding to 6 pm displacement accuracy, could be obtained. We also experimentally demonstrate the benefit of spatial-averaging in terms of the reduction of signal fading due to an axially moving sample. The applications of the improved system are illustrated by imaging live cells in culture.

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42.79.Pw	Imaging detectors and sensors
06.30.Bp	Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)

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Three-dimensional imaging of undercut and sidewall structures by atomic force microscopy

Sang-Joon Cho, Byung-Woon Ahn, Joonhui Kim, Jung-Min Lee, Yueming Hua, Young K. Yoo, and Sang-il Park

Rev. Sci. Instrum. 82, 023707 (2011); http://dx.doi.org/10.1063/1.3553199 (5 pages) | Cited 3 times

Online Publication Date: 24 February 2011

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Sidewall surface roughness is an important parameter in electronic device manufacture. At present, no high resolution technique exists to quantitatively characterize this property for undercut structures created by semiconductor processing techniques. We developed a three-dimensional atomic force microscope (3D-AFM) to measure the surface roughness of undercut sidewalls with nanometer precision. Decoupled from the positional scanner, the 3D-AFM probe had a variable tilt up to 40° off the normal. Nonorthogonal scans resolved the sidewall surface roughness, base width, and acute critical angle for undercut structures, including a metal overhang and the transmission line of a photonic device. Compatible with standard cantilevers, the 3D-AFM demonstrates great potential for characterizing the sidewalls of soft materials such as photoresist.

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68.37.Ps

Atomic force microscopy (AFM)

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Adhesive-free colloidal probes for nanoscale force measurements: Production and characterization

M. Indrieri, A. Podestà, G. Bongiorno, D. Marchesi, and P. Milani

Rev. Sci. Instrum. 82, 023708 (2011); http://dx.doi.org/10.1063/1.3553499 (11 pages) | Cited 1 time

Online Publication Date: 24 February 2011

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We describe novel approaches for the production and characterization of epoxy- and adhesive-free colloidal probes for atomic force microscopy (AFM). Borosilicate glass microspheres are strongly attached to commercial AFM cantilevers exploiting the capillary adhesion force due to the formation of a water meniscus, and then a thermal annealing of the sphere-cantilever system at a temperature slightly below the softening point of borosilicate glass. Controlling the wettability of the surfaces involved turned out to be a crucial element for the control of surface adhesion and for the implementation of a completely adhesive-free production method of colloidal probes. Moreover, we present a statistical characterization protocol of the probe dimensions and roughness based on the AFM inverse imaging of colloidal probes on spiked gratings. We have assessed the influence of defects of the grating on the characterization of the probe, and discussed the accuracy of our characterization technique in comparison to the methods based on scanning electron or optical microscopy, or on the manual analysis of AFM inverse images.

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07.79.Lh	Atomic force microscopes
07.10.Pz	Instruments for strain, force, and torque
68.08.Bc	Wetting
68.03.Cd	Surface tension and related phenomena
68.35.Np	Adhesion
82.70.Dd	Colloids

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Apparatus for vectorial Kerr confocal microscopy

M. Savoini, F. Ciccacci, L. Duò, and M. Finazzi

Rev. Sci. Instrum. 82, 023709 (2011); http://dx.doi.org/10.1063/1.3555757 (4 pages) | Cited 2 times

Online Publication Date: 28 February 2011

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We present a confocal microscopy setup that is able to record magneto-optical hysteresis cycles separating the in-plane and out-of-plane magnetization components. This apparatus is based on a modified commercial microscope, where the light beam has been deviated from the cylindrical symmetry axis of the objective lenses by inserting a translating plate in the optical path. The instrument allows for the magneto-optical imaging with a lateral resolution of 600 nm at λ = 635 nm light wavelength.

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42.65.Jx

Beam trapping, self-focusing and defocusing; self-phase modulation

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Aspect-ratio and lateral-resolution enhancement in force microscopy by attaching nanoclusters generated by an ion cluster source at the end of a silicon tip

L. Martínez, M. Tello, M. Díaz, E. Román, R. Garcia, and Y. Huttel

Rev. Sci. Instrum. 82, 023710 (2011); http://dx.doi.org/10.1063/1.3556788 (7 pages) | Cited 3 times

Online Publication Date: 28 February 2011

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One of the factors that limit the spatial resolution in atomic force microscopy (AFM) is the physical size of the probe. This limitation is particularly severe when the imaged structures are comparable in size to the tip's apex. The resolution in the AFM is usually enhanced by using sharp tips with high aspect ratios. In the present paper we propose an approach to modify AFM tips that consists of depositing nanoclusters on standard silicon tips. We show that the use of those tips leads to atomic force microscopy images of higher aspect ratios and spatial resolution. The present approach has two major properties. It provides higher aspect-ratio images of nanoscale objects and, at the same time, enables to functionalize the AFM tips by depositing nanoparticles with well-controlled chemical composition.

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73.63.Bd	Nanocrystalline materials
68.37.Ps	Atomic force microscopy (AFM)

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A novel method for on-orbit measurement of space materials degradation

Ronen Verker, Eitan Grossman, and Irina Gouzman

Rev. Sci. Instrum. 82, 023901 (2011); http://dx.doi.org/10.1063/1.3529878 (7 pages) | Cited 1 time

Online Publication Date: 1 February 2011

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The low Earth orbit (LEO) environment is considered hazardous to spacecraft, resulting in materials degradation. Currently, in order to evaluate the degradation of materials in LEO, a retrieval of space exposed samples is required. In this study, a novel approach is proposed to evaluate degradation of materials in LEO without the need of retrieval. The method is utilizing photovoltaic cells (PVCs), an existing component onboard of any satellite. The PVCs are coated by various materials which are sensitive to different LEO constituents, such as atomic oxygen (AO) or ultra-violet (UV) radiation. The method's acronym is ORMADD (on-ORbit MAterials Degradation Detector). The ORMADD's principle of operation is based on measuring the PVC output power which depends on the cell coating material's optical transmission. Erosion of the coating by AO or coloring due to UV radiation affects its optical transmission and, accordingly, the PVC output. The ORMADD performance was tested using different coatings, such as polyimide and amorphous carbon (sensitive to AO), and siloxane based coating which is sensitive to UV radiation. The proposed ORMADD reveals sensitivity to different LEO components and can be used either as material degradation detector or as an AO monitor.

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89.40.Dd	Air transporation
85.60.Gz	Photodetectors (including infrared and CCD detectors)
61.80.Ba	Ultraviolet, visible, and infrared radiation effects (including laser radiation)

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Pressure cell for investigations of solid–liquid interfaces by neutron reflectivity

Martin Kreuzer, Thomas Kaltofen, Roland Steitz, Beat H. Zehnder, and Reiner Dahint

Rev. Sci. Instrum. 82, 023902 (2011); http://dx.doi.org/10.1063/1.3505797 (7 pages) | Cited 4 times

Online Publication Date: 9 February 2011

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We describe an apparatus for measuring scattering length density and structure of molecular layers at planar solid–liquid interfaces under high hydrostatic pressure conditions. The device is designed for in situ characterizations utilizing neutron reflectometry in the pressure range 0.1–100 MPa at temperatures between 5 and 60 °C. The pressure cell is constructed such that stratified molecular layers on crystalline substrates of silicon, quartz, or sapphire with a surface area of 28 cm² can be investigated against noncorrosive liquid phases. The large substrate surface area enables reflectivity to be measured down to 10⁻⁵ (without background correction) and thus facilitates determination of the scattering length density profile across the interface as a function of applied load. Our current interest is on the stability of oligolamellar lipid coatings on silicon surfaces against aqueous phases as a function of applied hydrostatic pressure and temperature but the device can also be employed to probe the structure of any other solid–liquid interface.

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68.08.De	Liquid-solid interface structure: measurements and simulations
87.16.D-	Membranes, bilayers, and vesicles

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Photopyroelectric response of PTCa/PEEK composite

Giuliano Pierre Estevam, Washington Luiz Barros de Melo, and Walter Katsumi Sakamoto

Rev. Sci. Instrum. 82, 023903 (2011); http://dx.doi.org/10.1063/1.3552193 (6 pages) | Cited 1 time

Online Publication Date: 17 February 2011

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A pyroelectric composite made of calcium modified lead titanate ceramic and polyether–ether–ketone high performance polymer was obtained in the film form by hot pressing the ceramic/polymer mixture into the desired composition. After polarization with a suitable electric field, a ceramic composite film (60% vol.) exhibited a pyroelectric figure of merit three times higher than that of a lead zirconate titanate ceramic. The material was used as infrared radiation sensor. The voltage responsivity decreases with the inverse of the frequency showing the same behavior of the thermally thick sensor. The reproducibility of the sensor responses was observed.

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85.60.Gz	Photodetectors (including infrared and CCD detectors)
78.20.nc	Photopyroelectric effects

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High efficiency multichannel collimator for structural studies of liquids and low-Z materials at high pressures and temperatures

G. Morard, M. Mezouar, S. Bauchau, M. Álvarez-Murga, J.-L. Hodeau, and G. Garbarino

Rev. Sci. Instrum. 82, 023904 (2011); http://dx.doi.org/10.1063/1.3551988 (6 pages) | Cited 1 time

Online Publication Date: 18 February 2011

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A high efficiency multichannel collimator (MCC) device has been developed at the high pressure beamline ID27 of the European Synchrotron Radiation Facility to drastically reduce the x-ray background from the sample environment in the Paris-Edinburgh press. The main technical difficulty, which resides in the minimum slits size achievable using the classical mono-bloc design, has been resolved using an original concept based on a set of independent slits. Then, a very small slit size of 50 μm was manufactured resulting in a great improvement of the signal to background ratio. In addition, the transfer function of the MCC has been measured using the x-ray diffusion signal of a metal doped glass and efficiently applied to correct the raw data. The potential of this new device is illustrated in two challenging examples: iron–sulfur liquid structures and C₆₀ polymerization process at high pressure and high temperature.

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07.85.-m

X- and γ-ray instruments

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A broadband and high throughput single-monochromator Raman spectrometer: Application for single-wall carbon nanotubes

Gábor Fábián, Christian Kramberger, Alexander Friedrich, Ferenc Simon, and Thomas Pichler

Rev. Sci. Instrum. 82, 023905 (2011); http://dx.doi.org/10.1063/1.3544023 (5 pages) | Cited 3 times

Online Publication Date: 18 February 2011

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We present a high sensitivity single-monochromator Raman spectrometer which allows operation with a tunable laser source. The instrument is based on the modification of a commercial Raman spectrometer; such instruments operate with interference Rayleigh filters which also act as laser mirrors and are usually considered as inherently narrow band. In our design, the two tasks are separated and the filter can be freely rotated without much effect on the light alignment. Since rotation shifts the filter passband, this modification allows tunable operation with efficient stray light filtering down to 150 cm⁻¹. The design is optimized for single-wall carbon nanotubes, for which the performance is demonstrated using a tunable dye laser source. The spectrometer thus combines the high sensitivity with the broadband characteristics of usual triple monochromator systems.

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81.07.De	Nanotubes
78.67.Ch	Nanotubes
78.30.Na	Fullerenes and related materials
78.20.Ek	Optical activity
42.79.Ci	Filters, zone plates, and polarizers
42.79.Bh	Lenses, prisms and mirrors

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Combined ultrasonic elastic wave velocity and microtomography measurements at high pressures

Yoshio Kono, Akihiro Yamada, Yanbin Wang, Tony Yu, and Toru Inoue

Rev. Sci. Instrum. 82, 023906 (2011); http://dx.doi.org/10.1063/1.3552185 (7 pages) | Cited 2 times

Online Publication Date: 23 February 2011

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Combined ultrasonic and microtomographic measurements were conducted for simultaneous determination of elastic property and density of noncrystalline materials at high pressures. A Paris–Edinburgh anvil cell was placed in a rotation apparatus, which enabled us to take a series of x-ray radiography images under pressure over a 180° angle range and construct accurately the three-dimensional sample volume using microtomography. In addition, ultrasonic elastic wave velocity measurements were carried out simultaneously using the pulse reflection method with a 10° Y-cut LiNbO₃ transducer attached to the end of the lower anvil. Combined ultrasonic and microtomographic measurements were carried out for SiO₂ glass up to 2.6 GPa and room temperature. A decrease in elastic wave velocities of the SiO₂ glass was observed with increasing pressure, in agreement with previous studies. The simultaneous measurements on elastic wave velocities and density allowed us to derive bulk (K_s) and shear (G) moduli as a function of pressure. K_s and G of the SiO₂ glass also decreased with increasing pressure. The negative pressure dependence of K_s is stronger than that of G, and as a result the value of K_s became similar to G at 2.0–2.6 GPa. There is no reason why we cannot apply this new technique to high temperatures as well. Hence the results demonstrate that the combined ultrasonic and microtomography technique is a powerful tool to derive advanced (accurate) P–V–K_s–G–(T) equations of state for noncrystalline materials.

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43.35.Yb	Ultrasonic instrumentation and measurement techniques
07.85.-m	X- and γ-ray instruments

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Effect of window reflections on photonic Doppler velocimetry measurements

T. Ao and D. H. Dolan

Rev. Sci. Instrum. 82, 023907 (2011); http://dx.doi.org/10.1063/1.3551954 (8 pages) | Cited 3 times

Online Publication Date: 24 February 2011

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Photonic Doppler velocimetry (PDV) has rapidly become a standard diagnostic for measuring velocities in dynamic compression research. While free surface velocity measurements are fairly straightforward, complications occur when PDV is used to measure a dynamically loaded sample through a window. Fresnel reflections can severely affect the velocity and time resolution of PDV measurements, especially for low-velocity transients. Shock experiments of quartz compressed between two sapphire plates demonstrate how optical window reflections cause ringing in the extracted PDV velocity profile. Velocity ringing is significantly reduced by using either a wedge window or an antireflective coating.

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06.30.Gv

Velocity, acceleration, and rotation

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Calorimetry of epitaxial thin films

David W. Cooke, F. Hellman, J. R. Groves, B. M. Clemens, S. Moyerman, and E. E. Fullerton

Rev. Sci. Instrum. 82, 023908 (2011); http://dx.doi.org/10.1063/1.3554440 (4 pages) | Cited 4 times

Online Publication Date: 24 February 2011

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Thin film growth allows for the manipulation of material on the nanoscale, making possible the creation of metastable phases not seen in the bulk. Heat capacity provides a direct way of measuring thermodynamic properties of these new materials, but traditional bulk calorimetric techniques are inappropriate for such a small amount of material. Microcalorimetry and nanocalorimetry techniques exist for the measurements of thin films but rely on an amorphous membrane platform, limiting the types of films which can be measured. In the current work, ion-beam-assisted deposition is used to provide a biaxially oriented MgO template on a suspended membrane microcalorimeter in order to measure the specific heat of epitaxial thin films. Synchrotron x-ray diffraction showed the biaxial order of the MgO template. X-ray diffraction was also used to prove the high quality of epitaxy of a film grown onto this MgO template. The contribution of the MgO layer to the total heat capacity was measured to be just 6.5% of the total addenda contribution. The heat capacity of a Fe_.49Rh_.51 film grown epitaxially onto the device was measured, comparing favorably to literature data on bulk crystals. This shows the viability of the MgO/SiN_x-membrane-based microcalorimeter as a way of measuring the thermodynamic properties of epitaxial thin films.

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07.20.Fw	Calorimeters
81.15.Jj	Ion and electron beam-assisted deposition; ion plating
68.55.aj	Insulators
65.40.Ba	Heat capacity

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Viscometer using drag force measurements

M. H. Noël, B. Semin, J. P. Hulin, and H. Auradou

Rev. Sci. Instrum. 82, 023909 (2011); http://dx.doi.org/10.1063/1.3556445 (7 pages) | Cited 2 times

Online Publication Date: 28 February 2011

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A robust and precise viscometer using the forces exerted by a laminar flow inside a small duct is presented: the force is measured on a long cylindrical sensor dipped into the flow. Two devices of respective volumes 1.4 and 0.031 ml have been realized, demonstrating that the technique is usable with small fluid volumes. Several Newtonian and non-Newtonian fluids have been tested at shear rates ranging from 0.3 to 10 s⁻¹ for the first device and from 85 to 2550 s⁻¹ for the second one. For Newtonian fluids, of viscosities ranging from 10⁻³ to 0.1 Pa s, the linear response of the device has been verified and a 90% agreement with the values provided by commercial rheometers is obtained. For non-Newtonian polymer solutions, the variation of the force with the flow velocity allows one to determine the dependence of the viscosity on the shear rate. Two shear thinning polymer solutions with a power law behavior at intermediate shear rates have been investigated and their rheological parameters have been determined.

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47.80.-v

Instrumentation and measurement methods in fluid dynamics

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Measuring the relative concentration of H₂ and D₂ in HD gas with gas chromatography

C. Steven Whisnant, Patrick A. Hansen, and Travis D. Kelley

Rev. Sci. Instrum. 82, 024101 (2011); http://dx.doi.org/10.1063/1.3531974 (11 pages) | Cited 2 times

Online Publication Date: 8 February 2011

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Frozen-spin polarized hydrogen deuteride (HD) targets are being prepared for photonuclear experiments at Jefferson Lab. The targets are frozen HD gas. To polarize and achieve the required spin–lattice relaxation times, the targets are made from high purity HD gas in which the residual H₂ and D₂ concentrations are known. To determine these residual concentrations, a gas chromatograph is used. The separation of the gas components is done in a column cooled to ≈120 K by immersing it in a mixture of liquid nitrogen and isopentane and using neon as the carrier gas. The different hydrogen isotopes have different transit times through the column and their arrival is registered by a thermal conductivity detector. The peaks in the chromatograms are fit using an exponentially modified Gaussian line shape to extract the areas of these peaks. The ratios of areas are corrected for differences in thermal conductivity to give the relative concentrations. Here, H₂ and D₂ concentrations on the order of a few percent have been measured with uncertainties of less than ± 5%. The linear response of the system is confirmed to within about ± 6.3%.

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82.80.Bg	Chromatography
51.20.+d	Viscosity, diffusion, and thermal conductivity

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An improved single crystal adsorption calorimeter for determining gas adsorption and reaction energies on complex model catalysts

Jan-Henrik Fischer-Wolfarth, Jens Hartmann, Jason A. Farmer, J. Manuel Flores-Camacho, Charles T. Campbell, Swetlana Schauermann, and Hans-Joachim Freund

Rev. Sci. Instrum. 82, 024102 (2011); http://dx.doi.org/10.1063/1.3544020 (15 pages) | Cited 4 times

Online Publication Date: 17 February 2011

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A new ultrahigh vacuum microcalorimeter for measuring heats of adsorption and adsorption-induced surface reactions on complex single crystal-based model surfaces is described. It has been specifically designed to study the interaction of gaseous molecules with well-defined model catalysts consisting of metal nanoparticles supported on single crystal surfaces or epitaxial thin oxide films grown on single crystals. The detection principle is based on the previously described measurement of the temperature rise upon adsorption of gaseous molecules by use of a pyroelectric polymer ribbon, which is brought into mechanical/thermal contact with the back side of the thin single crystal. The instrument includes (i) a preparation chamber providing the required equipment to prepare supported model catalysts involving well-defined nanoparticles on clean single crystal surfaces and to characterize them using surface analysis techniques and in situ reflectivity measurements and (ii) the adsorption/reaction chamber containing a molecular beam, a pyroelectric heat detector, and calibration tools for determining the absolute reactant fluxes and adsorption heats. The molecular beam is produced by a differentially pumped source based on a multichannel array capable of providing variable fluxes of both high and low vapor pressure gaseous molecules in the range of 0.005–1.5 × 10¹⁵ molecules cm⁻² s⁻¹ and is modulated by means of the computer-controlled chopper with the shortest pulse length of 150 ms. The calorimetric measurements of adsorption and reaction heats can be performed in a broad temperature range from 100 to 300 K. A novel vibrational isolation method for the pyroelectric detector is introduced for the reduction of acoustic noise. The detector shows a pulse-to-pulse standard deviation ≤15 nJ when heat pulses in the range of 190–3600 nJ are applied to the sample surface with a chopped laser. Particularly for CO adsorption on Pt(111), the energy input of 15 nJ (or 120 nJ cm⁻²) corresponds to the detection limit for adsorption of less than 1.5 × 10¹² CO molecules cm⁻² or less than 0.1% of the monolayer coverage (with respect to the 1.5 × 10¹⁵ surface Pt atoms cm⁻²). The absolute accuracy in energy is within ∼7%–9%. As a test of the new calorimeter, the adsorption heats of CO on Pt(111) at different temperatures were measured and compared to previously obtained calorimetric data at 300 K.

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07.20.Fw	Calorimeters
07.07.Df	Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
82.65.+r	Surface and interface chemistry; heterogeneous catalysis at surfaces
68.43.Mn	Adsorption kinetics

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A novel target-type low pressure drop bidirectional optoelectronic air flow sensor for infant artificial ventilation: Measurement principle and static calibration

Paola Saccomandi, Emiliano Schena, and Sergio Silvestri

Rev. Sci. Instrum. 82, 024301 (2011); http://dx.doi.org/10.1063/1.3549624 (9 pages) | Cited 2 times

Online Publication Date: 15 February 2011

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An optoelectronic target-type volumetric air flow-rate transducer for bidirectional measurements is presented. The sensor is composed of a T-shaped target and two nominally identical LED-photodiode couples which are operated in differential mode. The sensitive surfaces of the photodiodes are differentially shadowed by the deflection of the target, which in turn depends on the gas flow-rate. The principle of operation is described in mathematical terms and the design parameters have been optimized in order to obtain the highest sensitivity along with minimal pressure drop and reduced dimensions. The sensor is placed in a 20 mm diameter hose and was tested with air flow-rate in the typical temperature range of mechanical ventilation between 20 and 40 °C. The theoretical model was validated through experiments carried out in the volumetric flow range from −7.0 to +7.0 l min⁻¹. The nonlinear behavior allows sensitivities equal to 0.6 V l⁻¹ min for flow rates ranging from −2.0 to +2.0 l min⁻¹, equal to 2.0 V l⁻¹ min for flow rates ranging from −3.0 to −2.0 l min⁻¹ and from +2.0 to +3.0 l min⁻¹, up to 5.7 V l⁻¹ min at higher flow rates ranging from −7.0 to −3.0 l min⁻¹ and from +3.0 to +7.0 l min⁻¹. The linear range extends from 3.0 to 7.0 l min⁻¹ with constant sensitivity equal to 5.7 V l⁻¹ min. The sensor is able to detect a flow-rate equal to 1.0 l min⁻¹ with a sensitivity of about 400 mV l⁻¹ min. The differential nature of the output minimizes the influence of the LEDs’ power supply variations and allows to obtain a repeatability in the order of 3% of full scale output. The small pressure drop produced by the sensor placed in-line the fluid stream, of about 2.4 Pa at 7 l min⁻¹, corresponds to a negligible fluid dynamic resistance lower than 0.34 Pa l⁻¹ min.

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87.85.Ox	Biomedical instrumentation and transducers, including micro-electro-mechanical systems (MEMS)
85.60.Dw	Photodiodes; phototransistors; photoresistors
06.20.fb	Standards and calibration
47.80.-v	Instrumentation and measurement methods in fluid dynamics
85.60.Jb	Light-emitting devices

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