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Aug 2010

Volume 81, Issue 8, Articles (08xxxx)

Issue Cover Spotlight Figure

Rev. Sci. Instrum. 81, 081101 (2010); http://dx.doi.org/10.1063/1.3480478 (24 pages)

Francis Halzen and Spencer R. Klein

Aerial view of the geographic South Pole with the NSF's research station (left side of the picture) and the IceCube project separated by the runway for ski-equipped aircraft. The inset shows a kilometer-long track of light radiated by a 100 TeV neutrino-induced muon in the ice instrumented at depths of 1.5 to 2.5 km.  (Forest Banks, photo credit)

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Invited Review Article: IceCube: An instrument for neutrino astronomy

Francis Halzen and Spencer R. Klein

Rev. Sci. Instrum. 81, 081101 (2010); http://dx.doi.org/10.1063/1.3480478 (24 pages) | Cited 27 times

Online Publication Date: 30 August 2010

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Neutrino astronomy beyond the Sun was first imagined in the late 1950s; by the 1970s, it was realized that kilometer-scale neutrino detectors were required. The first such instrument, IceCube, is near completion and taking data. The IceCube project transforms 1 km3 of deep and ultratransparent Antarctic ice into a particle detector. A total of 5160 optical sensors is embedded into a gigaton of Antarctic ice to detect the Cherenkov light emitted by secondary particles produced when neutrinos interact with nuclei in the ice. Each optical sensor is a complete data acquisition system including a phototube, digitization electronics, control and trigger systems, and light-emitting diodes for calibration. The light patterns reveal the type (flavor) of neutrino interaction and the energy and direction of the neutrino, making neutrino astronomy possible. The scientific missions of IceCube include such varied tasks as the search for sources of cosmic rays, the observation of galactic supernova explosions, the search for dark matter, and the study of the neutrinos themselves. These reach energies well beyond those produced with accelerator beams. The outline of this review is as follows: neutrino astronomy and kilometer-scale detectors, high-energy neutrino telescopes: methodologies of neutrino detection, IceCube hardware, high-energy neutrino telescopes: beyond astronomy, and future projects.
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96.50.sb Composition, energy spectra and interactions
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back to top Optics; Atoms and Molecules; Spectroscopy; Photon Detectors

Optical coherence tomography monitoring of angioplasty balloon inflation in a deployment tester

Hamed Azarnoush, Sébastien Vergnole, Rafik Bourezak, Benoit Boulet, and Guy Lamouche

Rev. Sci. Instrum. 81, 083101 (2010); http://dx.doi.org/10.1063/1.3465556 (8 pages) | Cited 3 times

Online Publication Date: 2 August 2010

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multimedia

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We present an innovative integration of an intravascular optical coherence tomography probe into a computerized balloon deployment system to monitor the balloon inflation process. The high-resolution intraluminal imaging of the balloon provides a detailed assessment of the balloon quality and, consequently, a technique to improve the balloon manufacturing process. A custom-built swept-source optical coherence tomography system is used for real-time imaging. A semicompliant balloon with a nominal diameter of 4 mm is fabricated for the experiments. Imaging results correspond to balloon deployment in air and inside an artery phantom. A characterization of the balloon diameter, wall thickness, compliance, and elastic modulus is provided, based on image segmentation. Using the images obtained from the probe pullback, a three-dimensional visualization of the inflated balloon is presented.
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87.85.-d Biomedical engineering
87.63.L- Visual imaging
87.57.nm Segmentation
87.19.X- Diseases

A lightweight near-infrared spectrometer for the detection of trace atmospheric species

T. Gardiner, M. I. Mead, S. Garcelon, R. Robinson, N. Swann, G. M. Hansford, P. T. Woods, and R. L. Jones

Rev. Sci. Instrum. 81, 083102 (2010); http://dx.doi.org/10.1063/1.3455827 (11 pages) | Cited 2 times

Online Publication Date: 3 August 2010

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This paper describes the development and deployment of a lightweight in situ near-infrared tunable diode laser absorption spectrometer (TDLAS) for balloon-borne measurements of trace species such as methane in the upper troposphere and stratosphere. The key feature of the instrument design is its ability to provide high sensitivity measurements with better than 1 part in 106 Hz−1/2 optical sensitivity in a lightweight package weighing as little as 6 kg, and maintaining this level of performance over the wide range of conditions experienced during field measurements. The absolute accuracy for methane measurements is approximately 10% limited by uncertainties in determining the gas temperature in the measurement volume. The high sensitivity and high temporal resolution (2.3 s measurement period) enables details of the fine-scale structure in the atmosphere to be measured. The TDLAS instrument has been used on a number of major international measurement campaigns. Intercomparison with other instruments during these campaigns have confirmed the comparability of the results from this instrument with measurements made by a range of other techniques, and demonstrated the instruments suitability for studies of atmospheric dynamics, transport, and mixing processes.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

System for time resolved spectral studies of pulsed atmospheric discharges in the visible to vacuum ultraviolet range

G. Laity, A. Neuber, G. Rogers, and K. Frank

Rev. Sci. Instrum. 81, 083103 (2010); http://dx.doi.org/10.1063/1.3478016 (6 pages) | Cited 2 times

Online Publication Date: 31 August 2010

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Vacuum ultraviolet (VUV) emission is believed to play a major role in the development of plasma streamers in pulsed atmospheric discharges, but detection of VUV light is difficult in pulsed experiments at atmospheric pressures. Since VUV light is absorbed in most standard optical materials as well, careful attention must be given to the selection of the lens and mirror optics used in these studies. Of highest interest is the VUV emission during the initial stage of pulsed atmospheric discharges, which has a typical duration in the nanosecond regime. An experiment was designed to study this fast initial stage of VUV emission coupled with fast optical imaging of streamer propagation, both with temporal resolution on the order of nanoseconds. A repetitive solid-state high voltage pulser was constructed which produces triggered flashover discharges with low jitter and consistent pulse amplitude. VUV emission is captured utilizing both photomultiplier and intensified charge-coupled device detectors during the fast stage of streamer propagation. These results are discussed in context with the streamer formation photographed in the visible wavelength regime with 3 ns exposure time.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.80.-s Electric discharges
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
back to top Particle Sources, Optics and Acceleration; Particle Detectors

Design and characterization of 2.45 GHz electron cyclotron resonance plasma source with magnetron magnetic field configuration for high flux of hyperthermal neutral beam

Seong Bong Kim, Dae Chul Kim, Won Namkung, Moohyun Cho, and Suk Jae Yoo

Rev. Sci. Instrum. 81, 083301 (2010); http://dx.doi.org/10.1063/1.3477998 (6 pages) | Cited 1 time

Online Publication Date: 26 August 2010

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A 2.45 GHz electron cyclotron resonance (ECR) source with a magnetron magnetic field configuration was developed to meet the demand of a hyperthermal neutral beam (HNB) flux on a substrate of more than 1×1015 cm−2 s−1 for industrial applications. The parameters of the operating pressure, ion density, electron temperature, and distance between the neutralization plate and the substrate for the HNB source are specified in a theoretical analysis. The electron temperature and the ion density are measured to characterize the ECR HNB source using a Langmuir probe and optical emission spectroscopy. The parameters of the ECR HNB source are in good agreement with the theoretically specified parameters.
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52.50.Dg Plasma sources
52.25.Fi Transport properties
52.50.Qt Plasma heating by radio-frequency fields; ICR, ICP, helicons
52.70.Ds Electric and magnetic measurements
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

High homogeneity 25 cm low-energy rf ion source with inherent electron compensation

S. V. Dudin, D. V. Rafalskyi, and A. V. Zykov

Rev. Sci. Instrum. 81, 083302 (2010); http://dx.doi.org/10.1063/1.3477999 (6 pages) | Cited 4 times

Online Publication Date: 31 August 2010

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A 25 cm single-grid low-energy rf ion source with inherent electron compensation is described and characterized. Measurements were carried out using Ar and CF4 filling gas. The dependence of the ion beam current to the target as well as the current partition between the beam fast and slow ions on the rf discharge pressure for both filling gases is discussed. The unique ability of generation of coinciding ion and electron flows is demonstrated and the measured ion and electron energy distribution functions are presented as well. The developed broad ion beam source is able of providing 0.5–5 mA/cm2 current density in the low ion energy range of 50–250 eV, with possibility of independent current density and energy control. It is shown that complementing the rf plasma source with a profiling electrode allows for CF4 ion source operation attaining ±5% ion beam uniformity over 250 mm in diameter. The presented CF4 etching test results exhibit the possibility of highly directional anisotropic Si and SiO2 etching utilizing the developed single grid rf ion source.
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07.77.Ka Charged-particle beam sources and detectors
52.50.Dg Plasma sources
52.80.Pi High-frequency and RF discharges
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
back to top Nuclear Physics, Fusion and Plasmas

Low voltage operation of plasma focus

Rohit Shukla, S. K. Sharma, P. Banerjee, R. Das, P. Deb, T. Prabahar, B. K. Das, B. Adhikary, and A. Shyam

Rev. Sci. Instrum. 81, 083501 (2010); http://dx.doi.org/10.1063/1.3470917 (4 pages) | Cited 6 times

Online Publication Date: 2 August 2010

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Plasma foci of compact sizes and operating with low energies (from tens of joules to few hundred joules) have found application in recent years and have attracted plasma-physics scientists and engineers for research in this direction. We are presenting a low energy and miniature plasma focus which operates from a capacitor bank of 8.4 μF capacity, charged at 4.2–4.3 kV and delivering approximately 52 kA peak current at approximately 60 nH calculated circuit inductance. The total circuit inductance includes the plasma focus inductance. The reported plasma focus operates at the lowest voltage among all reported plasma foci so far. Moreover the cost of capacitor bank used for plasma focus is nearly 20 U.S. dollars making it very cheap. At low voltage operation of plasma focus, the initial breakdown mechanism becomes important for operation of plasma focus. The quartz glass tube is used as insulator and breakdown initiation is done on its surface. The total energy of the plasma focus is approximately 75 J. The plasma focus system is made compact and the switching of capacitor bank energy is done by manual operating switch. The focus is operated with hydrogen and deuterium filled at 1–2 mbar.
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52.75.Kq Plasma switches (e.g., spark gaps)
52.80.-s Electric discharges
52.50.Dg Plasma sources

Polycrystalline diamond based detector for Z-pinch plasma diagnosis

Linyue Liu, Xiaoping Ouyang, Jizhen Zhao, Liang Chen, and Lan Wang

Rev. Sci. Instrum. 81, 083502 (2010); http://dx.doi.org/10.1063/1.3465559 (4 pages) | Cited 1 time

Online Publication Date: 10 August 2010

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A detector setup based on polycrystalline chemical-vapor-deposition diamond film is developed with great characteristics: low dark current (lower than 60 pA within 3 V/μm), fast pulsed response time (rise time: 2–3 ns), flat spectral response (3–5 keV), easy acquisition, low cost, and relative large sensitive area. The characterizing data on Qiangguang-I accelerator show that this detector can satisfy the practical requirements in Z-pinch plasma diagnosis very well, which offers a promising prototype for the x-ray detection in Z-pinch diagnosis.
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52.70.-m Plasma diagnostic techniques and instrumentation
52.58.Lq Z-pinches, plasma focus, and other pinch devices
52.59.Qy Wire array Z-pinches

A new large area lanthanum hexaboride plasma source

C. M. Cooper, W. Gekelman, P. Pribyl, and Z. Lucky

Rev. Sci. Instrum. 81, 083503 (2010); http://dx.doi.org/10.1063/1.3471917 (8 pages) | Cited 5 times

Online Publication Date: 16 August 2010

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A new 18×18 cm2 active area lanthanum hexaboride (LaB6) plasma source for use in a dc discharge has been developed at UCLA. The cathode consists of four tiled LaB6 pieces indirectly heated to electron emission (1750 °C) by a graphite heater. A molybdenum mesh anode 33 cm in front of the LaB6 accelerates the electrons, ionizing a fill gas to create a 20×20 cm2 nearly square plasma. The source is run in pulsed operation with the anode biased up to +400 V dc with respect to the cathode for up to 100 ms at a 1 Hz repetition rate. Both the cathode and anode “float” electrically with respect to the chamber walls. The source is placed in a toroidal chamber 2 m wide and 3 m tall with a major radius of 5 m. Toroidal and vertical magnetic fields confine the current-free plasma which follows the field in a helix. The plasma starts on the bottom of the machine and spirals around it up to four times (120 m) and can be configured to terminate either on the top wall or on the neutral gas itself. The source typically operates with a discharge current up to 250 A in helium making plasmas with Te<30 eV, Ti<16 eV, and ne<3×1013 cm−3 in a background field of 100 G<Bo<320 G, giving a magnetized plasma with 0.1<β<1.
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52.50.Dg Plasma sources
52.55.Fa Tokamaks, spherical tokamaks
52.80.-s Electric discharges

Compact lanthanum hexaboride hollow cathode

Dan M. Goebel and Ronald M. Watkins

Rev. Sci. Instrum. 81, 083504 (2010); http://dx.doi.org/10.1063/1.3474921 (6 pages) | Cited 2 times

Online Publication Date: 26 August 2010

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A compact lanthanum hexaboride hollow cathode has been developed for space applications where size and mass are important and research and industrial applications where access for implementation might be limited. The cathode design features a refractory metal cathode tube that is easily manufactured, mechanically captured orifice and end plates to eliminate expensive e-beam welding, graphite sleeves to provide a diffusion boundary to protect the LaB6 insert from chemical reactions with the refractory metal tube, and several heater designs to provide long life. The compact LaB6 hollow cathode assembly including emitter, support tube, heater, and keeper electrode is less than 2 cm in diameter and has been fabricated in lengths of 6–15 cm for different applications. The cathode has been operated continuously at discharge currents of 5–60 A in xenon. Slightly larger diameter versions of this design have operated at up to 100 A of discharge current.
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82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
52.80.Hc Glow; corona
81.20.Vj Joining; welding
81.05.uf Graphite
66.30.-h Diffusion in solids
82.30.-b Specific chemical reactions; reaction mechanisms

Image processing with cellular nonlinear networks implemented on field-programmable gate arrays for real-time applications in nuclear fusion

S. Palazzo, A. Murari, G. Vagliasindi, P. Arena, D. Mazon, and A. De Maack

Rev. Sci. Instrum. 81, 083505 (2010); http://dx.doi.org/10.1063/1.3477994 (10 pages) | Cited 1 time

Online Publication Date: 31 August 2010

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In the past years cameras have become increasingly common tools in scientific applications. They are now quite systematically used in magnetic confinement fusion, to the point that infrared imaging is starting to be used systematically for real-time machine protection in major devices. However, in order to guarantee that the control system can always react rapidly in case of critical situations, the time required for the processing of the images must be as predictable as possible. The approach described in this paper combines the new computational paradigm of cellular nonlinear networks (CNNs) with field-programmable gate arrays and has been tested in an application for the detection of hot spots on the plasma facing components in JET. The developed system is able to perform real-time hot spot recognition, by processing the image stream captured by JET wide angle infrared camera, with the guarantee that computational time is constant and deterministic. The statistical results obtained from a quite extensive set of examples show that this solution approximates very well an ad hoc serial software algorithm, with no false or missed alarms and an almost perfect overlapping of alarm intervals. The computational time can be reduced to a millisecond time scale for 8 bit 496×560-sized images. Moreover, in our implementation, the computational time, besides being deterministic, is practically independent of the number of iterations performed by the CNN—unlike software CNN implementations.
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52.55.-s Magnetic confinement and equilibrium
07.68.+m Photography, photographic instruments; xerography
25.60.Pj Fusion reactions
84.30.Sk Pulse and digital circuits

Absolute measurements of fast neutrons using yttrium

M. V. Roshan, S. V. Springham, R. S. Rawat, P. Lee, and M. Krishnan

Rev. Sci. Instrum. 81, 083506 (2010); http://dx.doi.org/10.1063/1.3478020 (6 pages) | Cited 1 time

Online Publication Date: 31 August 2010

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Yttrium is presented as an absolute neutron detector for pulsed neutron sources. It has high sensitivity for detecting fast neutrons. Yttrium has the property of generating a monoenergetic secondary radiation in the form of a 909 keV gamma-ray caused by inelastic neutron interaction. It was calibrated numerically using MCNPX and does not need periodic recalibration. The total yttrium efficiency for detecting 2.45 MeV neutrons was determined to be fn ∼ 4.1×10−4 with an uncertainty of about 0.27%. The yttrium detector was employed in the NX2 plasma focus experiments and showed the neutron yield of the order of 108 neutrons per discharge.
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29.40.-n Radiation detectors
29.25.Dz Neutron sources
52.70.-m Plasma diagnostic techniques and instrumentation
52.77.-j Plasma applications
52.58.Lq Z-pinches, plasma focus, and other pinch devices
back to top Microscopy and Imaging

High-resolution friction force microscopy under electrochemical control

Aleksander Labuda, William Paul, Brendan Pietrobon, R. Bruce Lennox, Peter H. Grütter, and Roland Bennewitz

Rev. Sci. Instrum. 81, 083701 (2010); http://dx.doi.org/10.1063/1.3470107 (11 pages) | Cited 10 times

Online Publication Date: 2 August 2010

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We report the design and development of a friction force microscope for high-resolution studies in electrochemical environments. The design choices are motivated by the experimental requirements of atomic-scale friction measurements in liquids. The noise of the system is analyzed based on a methodology for the quantification of all the noise sources. The quantitative contribution of each noise source is analyzed in a series of lateral force measurements. Normal force detection is demonstrated in a study of the solvation potential in a confined liquid, octamethylcyclotetrasiloxane. The limitations of the timing resolution of the instrument are discussed in the context of an atomic stick-slip measurement. The instrument is capable of studying the atomic friction contrast between a bare Au(111) surface and a copper monolayer deposited at underpotential conditions in perchloric acid.
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07.10.Pz Instruments for strain, force, and torque

Electrostatic actuator probe with curved electrodes for time-of-flight scanning force microscopy

Chuan-Yu Shao, Yusuke Kawai, Masayoshi Esashi, and Takahito Ono

Rev. Sci. Instrum. 81, 083702 (2010); http://dx.doi.org/10.1063/1.3469796 (6 pages)

Online Publication Date: 11 August 2010

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In this study, we fabricated an electrostatic actuator probe having curved electrodes and evaluated its applicability for use in time-of-flight scanning force microscopy. In this probe, the end position of a cantilever with a tip is switched through electrostatic pull-in effect; the measurement modes can be changed between mass analysis and scanning force microscopy (SFM) modes. We achieved a large displacement of 400 μm for changing working modes. To prevent electrical shortage of the probe and curved electrodes, stoppers were formed along the curved electrodes. Because of the pull-in effect, the spring constant and resonance frequency increased through stiction of the cantilever to the stoppers. Using the fabricated probe, the SFM imaging of a sample featuring a 2-μm-pitch Au grid was demonstrated.
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07.10.Cm Micromechanical devices and systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

An experimental methodology to relate local strain to microstructural texture

J. Carroll, W. Abuzaid, J. Lambros, and H. Sehitoglu

Rev. Sci. Instrum. 81, 083703 (2010); http://dx.doi.org/10.1063/1.3474902 (9 pages) | Cited 14 times

Online Publication Date: 23 August 2010

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This paper introduces an experimental methodology for obtaining high resolution full-field strain measurements in polycrystalline metals. The (sub)grain level resolution of these measurements was indispensable for relating measured strain fields to observed microstructure in the material. Microstructural information was obtained through electron backscatter diffraction and the optical technique of digital image correlation (DIC) was used to acquire full-field deformation measurements. By spatially overlaying both sets of results, the effects of different microstructural features such as orientation, grain boundary character, misorientation between grains, and twin boundaries on material response can be quantitatively studied. To obtain the necessary resolution for such measurements, the images used in DIC had to be captured at high magnifications. This necessity reduces the field of view and constrains the area of interest that can be monitored. To address this issue, results from adjacent measurement areas are combined together to create a data set with high spatial strain resolution over a larger region than can otherwise be observed. The procedure for performing this technique is outlined here, along with benefits, drawbacks, possible modifications, and example applications of the technique to cyclic plasticity and fatigue crack growth.
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81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
61.72.Mm Grain and twin boundaries
62.20.fq Plasticity and superplasticity
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.me Fatigue

A versatile high resolution scanning tunneling potentiometry implementation

T. Druga, M. Wenderoth, J. Homoth, M. A. Schneider, and R. G. Ulbrich

Rev. Sci. Instrum. 81, 083704 (2010); http://dx.doi.org/10.1063/1.3469809 (7 pages) | Cited 2 times

Online Publication Date: 26 August 2010

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We have developed a new scanning tunneling potentiometry technique which can—with only minor changes of the electronic setup—be easily added to any standard scanning tunneling microscope (STM). This extension can be combined with common STM techniques such as constant current imaging or scanning tunneling spectroscopy. It is capable of performing measurements of the electrochemical potential with microvolt resolution. Two examples demonstrate the versatile application. First of all, we have determined local variations of the electrochemical potential due to charge transport of biased samples down to angstrom length scales. Second, with tip and sample at different temperatures we investigated the locally varying thermovoltage occurring at the tunneling junction. Aside from its use in determining the chemical identity of substances at the sample surface our method provides a controlled way to eliminate the influence of laterally varying thermovoltages on low-bias constant current topographies.
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07.79.Cz Scanning tunneling microscopes
Author Select

Single-molecule binding experiments on long time scales

Mark P. Elenko, Jack W. Szostak, and Antoine M. van Oijen

Rev. Sci. Instrum. 81, 083705 (2010); http://dx.doi.org/10.1063/1.3473936 (9 pages) | Cited 2 times

Online Publication Date: 27 August 2010

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We describe an approach for performing single-molecule binding experiments on time scales from hours to days, allowing for the observation of slower kinetics than have been previously investigated by single-molecule techniques. Total internal reflection fluorescence microscopy is used to image the binding of labeled ligand to molecules specifically coupled to the surface of an optically transparent flow cell. Long-duration experiments are enabled by ensuring sufficient positional, chemical, thermal, and image stability. Principal components of this experimental stability include illumination timing, solution replacement, and chemical treatment of solution to reduce photodamage and photobleaching; and autofocusing to correct for spatial drift.
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33.50.Dq Fluorescence and phosphorescence spectra
33.15.Bh General molecular conformation and symmetry; stereochemistry
07.60.Pb Conventional optical microscopes
back to top Condensed Matter; Materials

Fiber optic based system for polarization sensitive spectroscopy of semiconductor quantum structures

Ashish Arora, Biswajit Karmakar, Sayantan Sharma, Michael Schardt, Stefan Malzer, Bhavtosh Bansal, Gottfried Döhler, and Brij M. Arora

Rev. Sci. Instrum. 81, 083901 (2010); http://dx.doi.org/10.1063/1.3462977 (5 pages)

Online Publication Date: 19 August 2010

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We describe an optical fiber based setup for performing polarization resolved magneto-optical spectroscopy measurements under low temperatures ( ∼ 4 K) and high magnetic fields ( ∼ 8 T). The measurements are performed in a windowless helium Dewar. Circularly polarized light is produced inside the Dewar by inserting the polarizing elements between the fiber end and the sample. Photoconductivity spectra of a GaAs/AlGaAs multiquantum-well sample have been measured over the photon energy range of 1.5–1.7 eV in left and right circularly polarized light under crossed magnetic and electric fields. It is shown that reversing the direction of magnetic field produces the same spectral changes as caused by changing the direction of circular polarization with the optical components.
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07.60.Vg Fiber-optic instruments
72.40.+w Photoconduction and photovoltaic effects
78.20.Ls Magneto-optical effects
78.66.Fd III-V semiconductors

Nanosecond x-ray Laue diffraction apparatus suitable for laser shock compression experiments

Matthew Suggit, Giles Kimminau, James Hawreliak, Bruce Remington, Nigel Park, and Justin Wark

Rev. Sci. Instrum. 81, 083902 (2010); http://dx.doi.org/10.1063/1.3455211 (4 pages) | Cited 2 times

Online Publication Date: 26 August 2010

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We have used nanosecond bursts of x-rays emitted from a laser-produced plasma, comprised of a mixture of mid-Z elements, to produce a quasiwhite-light spectrum suitable for performing Laue diffraction from single crystals. The laser-produced plasma emits x-rays ranging in energy from 3 to in excess of 10 keV, and is sufficiently bright for single shot nanosecond diffraction patterns to be recorded. The geometry is suitable for the study of laser-shocked crystals, and single-shot diffraction patterns from both unshocked and shocked silicon crystals are presented.
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42.62.-b Laser applications
61.05.C- X-ray diffraction and scattering

Simultaneous measurement of circular dichroism and Faraday rotation at terahertz frequencies utilizing electric field sensitive detection via polarization modulation

G. S. Jenkins, D. C. Schmadel, and H. D. Drew

Rev. Sci. Instrum. 81, 083903 (2010); http://dx.doi.org/10.1063/1.3480554 (10 pages) | Cited 5 times

Online Publication Date: 30 August 2010

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A far-infrared system measures the full complex Faraday angle, the rotation as well as the ellipticity, with an unprecedented accuracy of 10 μrad/T. The system operates on several far-infrared laser lines in the spectral range from 0.3 to 6 THz and produces results as a continuous function of temperature from 10 to 310 K and applied fields between ±8 T. Performance of the instrument is demonstrated by measurements on a GaAs two-dimensional electron gas heterostructure and Bi2Sr2CaCu2O8+x single crystal.
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78.20.Fm Birefringence
78.20.Ls Magneto-optical effects
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.30.Fs III-V and II-VI semiconductors
81.05.Ea III-V semiconductors
back to top Chemistry

Identification of a deuterated alkanethiol inserted in a hydrogenated alkanethiol self-assembled monolayer by mapping of an inelastic tunneling signal

Norio Okabayashi and Tadahiro Komeda

Rev. Sci. Instrum. 81, 084101 (2010); http://dx.doi.org/10.1063/1.3469777 (4 pages) | Cited 4 times

Online Publication Date: 9 August 2010

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We show an experimental technique for visualizing distributions of vibrational modes of molecules through mapping of an inelastic tunneling signal with a scanning tunneling microscope. A topographic information and d2I/dV2 signal processed by a lock-in amplifier were simultaneously imaged, where the feedback loop for the tunneling gap was engaged and a modulation voltage was superimposed to the gap voltage. The current signal used for the tunneling gap control was tuned by the filtering in order to minimize the response of the feedback loop caused by the modulation voltage. The effectiveness of this technique was demonstrated for a self-assembled monolayer composed of a mixture of normal and deuterated hexanethiol molecules, where both molecules have the same molecular length and the former was embedded in the matrix of the latter. Two types of molecules were successfully discriminated by chemical properties.
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07.79.Cz Scanning tunneling microscopes

A pair of concentric capillaries as an interface for gas chromatography and supersonic jet/multiphoton ionization/mass spectrometry

H. Okudaira, T. Uchimura, and T. Imasaka

Rev. Sci. Instrum. 81, 084102 (2010); http://dx.doi.org/10.1063/1.3462982 (5 pages)

Online Publication Date: 10 August 2010

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A pair of concentric capillaries was developed to mix helium, which was used as the carrier gas for gas chromatography, with argon for efficient molecular cooling by supersonic jet expansion. A simple instrument was constructed for the evaluation of nozzle diameter using the Hagen–Poiseuille equation. The effects of nozzle diameter, type of expansion gas, flow rate, and the distance from the nozzle to the observation region were investigated. Mixing argon gas with the carrier gas helium resulted in efficient molecular cooling from 30 to 10 K and the complete disappearance of the background signal from the multiphoton ionization spectrum. Consequently, the spectral selectivity was significantly improved and the nozzle was successfully applied to isomer-selective analysis of dichlorotoluenes. Since the dead volume in the nozzle was negligible, it was suitable as an interface for gas chromatography and supersonic jet/multiphoton ionization/mass spectrometry.
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47.40.Ki Supersonic and hypersonic flows
82.80.Bg Chromatography
47.15.Rq Laminar flows in cavities, channels, ducts, and conduits
47.60.Dx Flows in ducts and channels
47.27.nf Flows in pipes and nozzles
47.60.Kz Flows and jets through nozzles
back to top Biology and Medicine
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Microbial population dynamics by digital in-line holographic microscopy

Zak Frentz, Seppe Kuehn, Doeke Hekstra, and Stanislas Leibler

Rev. Sci. Instrum. 81, 084301 (2010); http://dx.doi.org/10.1063/1.3473937 (6 pages) | Cited 2 times

Online Publication Date: 24 August 2010

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Measurements of population dynamics are ubiquitous in experiments with microorganisms. Studies with microbes elucidating adaptation, selection, and competition rely on measurements of changing populations in time. Despite this importance, quantitative methods for measuring population dynamics microscopically, with high time resolution, across many replicates remain limited. Here we present a new noninvasive method to precisely measure microbial spatiotemporal population dynamics based on digital in-line holographic (DIH) microscopy. Our inexpensive, replicate DIH microscopes imaged hundreds of swimming algae in three dimensions within a volume of several microliters on a time scale of minutes over periods of weeks.
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87.64.M- Optical microscopy
42.40.My Applications
87.18.-h Biological complexity

Design of a standalone-type beryllium vessel for high-pressure protein crystallography

Yoshihisa Suzuki, Masayuki Tsukamoto, Haruhiko Sakuraba, Masamitsu Matsumoto, Makoto Nagasawa, and Katsuhiro Tamura

Rev. Sci. Instrum. 81, 084302 (2010); http://dx.doi.org/10.1063/1.3478000 (3 pages)

Online Publication Date: 30 August 2010

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A standalone-type beryllium (Be) high-pressure crystallography vessel has been developed. Using a coupler-joint unit and a pressure valve, we could keep the pressure in the vessel constant at 100±1 MPa for more than 24 h without connecting to a pressure-generating apparatus. Diffraction spots of a glucose isomerase (GI) crystal under 100 MPa were collected using the vessel and a rotating copper-anode in-house x-ray generator (0.8 kW). We successfully collected a 2.0 Å resolution data set of a 0.5 mm size GI crystal in an aqueous solution at 100 MPa.
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87.80.-y Biophysical techniques (research methods)
87.15.B- Structure of biomolecules
87.14.ej Enzymes
87.15.R- Reactions and kinetics
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
back to top Gravity; Geophysics; Astronomy and Astrophysics

New portable sensor system for rotational seismic motion measurements

Johana Brokešová and Jiří Málek

Rev. Sci. Instrum. 81, 084501 (2010); http://dx.doi.org/10.1063/1.3463271 (8 pages) | Cited 4 times

Online Publication Date: 19 August 2010

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A new mechanical sensor system for recording the rotation of ground velocity has been constructed. It is based on measurements of differential motions between paired sensors mounted along the perimeter of a rigid (undeformable) disk. The elementary sensors creating the pairs are sensitive low-frequency geophones currently used in seismic exploration to record translational motions. The main features of the new rotational seismic sensor system are flat characteristics in the wide frequency range from 1 to 200 Hz and sensitivity limit of the order of 10−8 rad/s. Notable advantages are small dimensions, portability, easy installation and operation in the field, and the possibility of calibrating the geophones in situ simultaneously with the measurement. An important feature of the instrument is that it provides records of translational seismic motions together with rotations, which allows many important seismological applications. We have used the new sensor system to record the vertical rotation velocity due to a small earthquake of ML = 2.2, which occurred within the earthquake swarm in Western Bohemia in autumn 2008. We found good agreement of the rotation record with the transverse acceleration as predicted by theory. This measurement demonstrates that this device has a much wider application than just to prospecting measurements, for which it was originally designed.
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93.85.Rt Seismic methods
91.30.Mv Strong motions and shock waves
91.30.Px Earthquakes
93.30.Ge Europe
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