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Aug 2011

Volume 82, Issue 8, Articles (08xxxx)

Issue Cover Spotlight Figure

Rev. Sci. Instrum. 82, 081301 (2011); http://dx.doi.org/10.1063/1.3624752 (22 pages)

Daniel B. Turner, Katherine W. Stone, Kenan Gundogdu, and Keith A. Nelson

Artist's illustration of the coherent optical laser beam recombination technique (COLBERT) spectrometer. Using two spatial light modulators, the device generates and controls multiple phase-related laser fields for use in coherent multidimensional spectroscopy measurements. The coherent signals yield 2D and 3D spectra. Illustration by Heidi Bone, Boston.

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Invited Article: The coherent optical laser beam recombination technique (COLBERT) spectrometer: Coherent multidimensional spectroscopy made easier

Daniel B. Turner, Katherine W. Stone, Kenan Gundogdu, and Keith A. Nelson

Rev. Sci. Instrum. 82, 081301 (2011); http://dx.doi.org/10.1063/1.3624752 (22 pages)

Online Publication Date: 23 August 2011

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We have developed an efficient spectrometer capable of performing a wide variety of coherent multidimensional measurements at optical wavelengths. The two major components of the largely automated device are a spatial beam shaper which controls the beam geometry and a spatiotemporal pulse shaper which controls the temporal waveform of the femtosecond pulse in each beam. We describe how to construct, calibrate, and operate the device, and we discuss its limitations. We use the exciton states of a semiconductor nanostructure as a working example. A series of complex multidimensional spectra—displayed in amplitude and real parts—reveals increasingly intricate correlations among the excitons.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
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back to top Optics; Atoms and Molecules; Spectroscopy; Photon Detectors

Fabrication of silver tips for scanning tunneling microscope induced luminescence

C. Zhang, B. Gao, L. G. Chen, Q. S. Meng, H. Yang, R. Zhang, X. Tao, H. Y. Gao, Y. Liao, and Z. C. Dong

Rev. Sci. Instrum. 82, 083101 (2011); http://dx.doi.org/10.1063/1.3617456 (4 pages) | Cited 2 times

Online Publication Date: 1 August 2011

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We describe a reliable fabrication procedure of silver tips for scanning tunneling microscope (STM) induced luminescence experiments. The tip was first etched electrochemically to yield a sharp cone shape using selected electrolyte solutions and then sputter cleaned in ultrahigh vacuum to remove surface oxidation. The tip status, in particular the tip induced plasmon mode and its emission intensity, can be further tuned through field emission and voltage pulse. The quality of silver tips thus fabricated not only offers atomically resolved STM imaging, but more importantly, also allows us to perform challenging “color” photon mapping with emission spectra taken at each pixel simultaneously during the STM scan under relatively small tunnel currents and relatively short exposure time.
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07.79.Cz Scanning tunneling microscopes

Dual-trap optical tweezers with real-time force clamp control

Anders E. Wallin, Heikki Ojala, Gabija Ziedaite, and Edward Hæggström

Rev. Sci. Instrum. 82, 083102 (2011); http://dx.doi.org/10.1063/1.3615309 (7 pages)

Online Publication Date: 3 August 2011

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multimedia

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Single molecule force clamp experiments are widely used to investigate how enzymes, molecular motors, and other molecular mechanisms work. We developed a dual-trap optical tweezers instrument with real-time (200 kHz update rate) force clamp control that can exert 0–100 pN forces on trapped beads. A model for force clamp experiments in the dumbbell-geometry is presented. We observe good agreement between predicted and observed power spectra of bead position and force fluctuations. The model can be used to predict and optimize the dynamics of real-time force clamp optical tweezers instruments. The results from a proof-of-principle experiment in which lambda exonuclease converts a double-stranded DNA tether, held at constant tension, into its single-stranded form, show that the developed instrument is suitable for experiments in single molecule biology.
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87.80.Cc Optical trapping
87.14.ej Enzymes
87.14.gk DNA
87.15.R- Reactions and kinetics
87.50.wf Biophysical mechanisms of interaction
87.15.Cc Folding: thermodynamics, statistical mechanics, models, and pathways

High resolution extreme ultraviolet spectrometer for an electron beam ion trap

Hayato Ohashi, Junji Yatsurugi, Hiroyuki A. Sakaue, and Nobuyuki Nakamura

Rev. Sci. Instrum. 82, 083103 (2011); http://dx.doi.org/10.1063/1.3618686 (4 pages)

Online Publication Date: 4 August 2011

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An extreme ultraviolet spectrometer has been developed for spectroscopic studies of highly charged ions with an electron beam ion trap. It has a slit-less configuration with a spherical varied-line-spacing grating that provides a flat focal plane for grazing incidence light. Alternative use of two different gratings enables us to cover the wavelength range 1–25 nm. Test observations with the Tokyo electron beam ion trap demonstrate the high performance of the present spectrometer such as a resolving power of above 1000.
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29.25.-t Particle sources and targets
07.60.Rd Visible and ultraviolet spectrometers

A combined small- and wide-angle x-ray scattering detector for measurements on reactive systems

Linda Vallenhag, Sophie E. Canton, Peter Sondhauss, Dörthe Haase, and Frederik Ossler

Rev. Sci. Instrum. 82, 083104 (2011); http://dx.doi.org/10.1063/1.3613958 (8 pages)

Online Publication Date: 10 August 2011

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A detector with high dynamic range designed for combined small- and wide-angle x-ray scattering experiments has been developed. It allows measurements on single events and reactive systems, such as particle formation in flames and evaporation of levitating drops. The detector consists of 26 channels covering a region from 0.5° to 60° and it provides continuous monitoring of the sampled signal without readout dead time. The time resolution for fast single events is about 40 μs and for substances undergoing slower dynamics, the time resolution is set to 0.1 or 1 s with hours of continuous sampling. The detector has been used to measure soot particle formation in a flame, burning magnesium and evaporation of a toluene drop in a levitator. The results show that the detector can be used for many different applications with good outcomes and large potential.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
61.05.cf X-ray scattering (including small-angle scattering)

Interface for time-resolved electrochemical infrared microspectroscopy using synchrotron infrared radiation

Scott M. Rosendahl, Ferenc Borondics, Tim E. May, Tor M. Pedersen, and Ian J. Burgess

Rev. Sci. Instrum. 82, 083105 (2011); http://dx.doi.org/10.1063/1.3624693 (5 pages)

Online Publication Date: 16 August 2011

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A description of a coupled electrochemical and spectrometer interface using synchrotron infrared radiation is provided. The interface described allows for the precise and accurate timing needed for time-resolved IR spectroscopic studies of electrochemical systems. The overall interface uses a series of transistor-transistor logic trigger signals generated from the commercial FTIR spectrometer to regulate the recording of control, electrochemical, and IR signals with reproducible and adjustable timing. The instrument has been tested using a thin-layer electrochemical cell with synchrotron light focused through microscope optics. The time-resolved response of the benzoquinone/dihydroxybenzoquinone redox couple is illustrated as an example of the instrument's capability.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
07.60.Pb Conventional optical microscopes

High resolution 3D gas-jet characterization

Björn Landgraf, Michael Schnell, Alexander Sävert, Malte C. Kaluza, and Christian Spielmann

Rev. Sci. Instrum. 82, 083106 (2011); http://dx.doi.org/10.1063/1.3624694 (6 pages)

Online Publication Date: 17 August 2011

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We present a tomographic characterization of gas jets employed for high-intensity laser-plasma interaction experiments where the shape can be non-symmetrically. With a Mach-Zehnder interferometer we measured the phase shift for different directions through the neutral density distribution of the gas jet. From the recorded interferograms it is possible to retrieve 3-dimensional neutral density distributions by tomographic reconstruction based on the filtered back projections. We report on criteria for the smallest number of recorded interferograms as well as a comparison with the widely used phase retrieval based on an Abel inversion. As an example for the performance of our approach, we present the characterization of nozzles with rectangular openings or gas jets with shock waves. With our setup we obtained a spatial resolution of less than 60 μm for an Argon density as low as 2 × 1017 cm−3.
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52.38.Kd Laser-plasma acceleration of electrons and ions
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.75.-d Plasma devices
52.25.Fi Transport properties
52.35.Tc Shock waves and discontinuities

An LIF characterization of supersonic BO (X2Σ+) and CN (X2Σ+) radical sources for crossed beam studies

Pavlo Maksyutenko, Dorian S. N. Parker, Fangtong Zhang, and Ralf I. Kaiser

Rev. Sci. Instrum. 82, 083107 (2011); http://dx.doi.org/10.1063/1.3624695 (7 pages)

Online Publication Date: 18 August 2011

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Various ablation sources generating supersonic boron monoxide (BO; X2Σ+) radical beams utilizing oxygen (O2), carbon dioxide (CO2), methanol (CH3OH), and water (H2O) as seeding gases were characterized in a crossed molecular beams setup by mass resolved time-of-flight spectroscopy and spectroscopically via laser induced fluorescence. Intensities of the sources as well as rovibrational energy distributions were analyzed. The molecular oxygen source was found to produce excessive amount of an unwanted BO2 byproduct. Internal vibrational energy of boron monoxide generated in the water and methanol sources was too high to be considered for the study of dynamics of ground state radicals. The best combination of intensity, purity, and low internal energy was found in the carbon dioxide source to generate boron monoxide. We successfully tested the boron monoxide (BO; X2Σ+) radical beam source in crossed beams reactions with acetylene (C2H2) and ethylene (C2H4). The source was also compared with supersonic beams of the isoelectronic cyano (CN; X2Σ+) radical.
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82.80.Rt Time of flight mass spectrometry
37.20.+j Atomic and molecular beam sources and techniques

Creation of arbitrary spectra with an acousto-optic modulator and an injection-locked diode laser

Pei-Ying Lin, Bor-Wen Shiau, Ya-Fen Hsiao, and Ying-Cheng Chen

Rev. Sci. Instrum. 82, 083108 (2011); http://dx.doi.org/10.1063/1.3626903 (6 pages) | Cited 1 time

Online Publication Date: 23 August 2011

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We use a double-passed acousto-optic modulator (AOM), driven by an arbitrary waveform generator to produce multiple frequency components for a laser with arbitrary frequency spacings. A programmed sequence containing various sections of radio-frequency sinusoidal signal at different frequency is applied to drive the AOM. The diffracted light is used to injection-lock a diode laser. The combined techniques allow us to generate the multi-line spectra for the diode laser with arbitrary frequency spacings in the range of 100 MHz at a relatively high output power of 80 mW and a small power variation of 2%. Such a light source can be used in the application for laser cooling of molecules.
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42.79.Jq Acousto-optical devices
42.79.Hp Optical processors, correlators, and modulators
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
84.30.Ng Oscillators, pulse generators, and function generators
42.50.Wk Mechanical effects of light on material media, microstructures and particles

High spectral resolution, real-time, Raman spectroscopy in shock compression experiments

N. Hemmi, K. A. Zimmerman, Z. A. Dreger, and Y. M. Gupta

Rev. Sci. Instrum. 82, 083109 (2011); http://dx.doi.org/10.1063/1.3627444 (5 pages)

Online Publication Date: 25 August 2011

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The use of Raman measurements to examine molecular changes associated with shock-induced structural and chemical changes in condensed materials often poses two challenging requirements: high spectral resolution and significantly reduced background light. Here, we describe an experimental method that addresses these requirements and provides better quality data than the time resolved approach used previously. Representative measurements are presented for shock compression of two energetic crystals: pentaerythritol tetranitrate and cyclotrimethylene trinitramine. The high spectral resolution data have provided insight into molecular changes that could not be obtained from lower-resolution, time-resolved methods.
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78.30.Jw Organic compounds, polymers
78.47.da Excited states

Offset phase locking of noisy diode lasers aided by frequency division

E. N. Ivanov, F.-X. Esnault, and E. A. Donley

Rev. Sci. Instrum. 82, 083110 (2011); http://dx.doi.org/10.1063/1.3627535 (8 pages)

Online Publication Date: 31 August 2011

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For heterodyne phase locking, frequency division of the beat note between two oscillators can improve the reliability of the phase lock and the quality of the phase synchronization. Frequency division can also reduce the size, weight, power, and cost of the instrument by excluding the microwave synthesizer from the control loop when the heterodyne offset frequency is large (5 to 10 GHz). We have experimentally tested the use of a frequency divider in an optical phase-lock loop and compared the achieved level of residual phase fluctuations between two diode lasers with that achieved without the use of a frequency divider. The two methods achieve comparable phase stability provided that sufficient loop gain is maintained after frequency division to preserve the required bandwidth. We have also numerically analyzed the noise properties and internal dynamics of phase-locked loops subjected to a high level of phase fluctuations, and our modeling confirms the expected benefits of having an in-loop frequency divider.
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42.60.Fc Modulation, tuning, and mode locking
42.55.Px Semiconductor lasers; laser diodes
back to top Particle Sources, Optics and Acceleration; Particle Detectors

Increasing the energy dynamic range of solid-state nuclear track detectors using multiple surfaces

A. B. Zylstra, H. G. Rinderknecht, N. Sinenian, M. J. Rosenberg, M. Manuel, F. H. Séguin, D. T. Casey, J. A. Frenje, C. K. Li, and R. D. Petrasso

Rev. Sci. Instrum. 82, 083301 (2011); http://dx.doi.org/10.1063/1.3617475 (7 pages) | Cited 1 time

Online Publication Date: 10 August 2011

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Solid-state nuclear track detectors, such as CR-39, are widely used in physics and in many inertial confinement fusion (ICF) experiments. In the ICF experiments, the particles of interest, such as D3He-protons, have ranges of order of the detector thickness. In this case, the dynamic range of the detector can be extended by recording data on both the front and back sides of the detector. Higher energy particles which are undetectable on the front surface can then be measured on the back of the detector. Studies of track formation under the conditions on the front and back of the detector reveal significant differences. Distinct front and back energy calibrations of CR-39 are therefore necessary and are presented for protons. Utilizing multiple surfaces with additional calibrations can extend the range of detectable energies on a single piece of CR-39 by up to 7-8 MeV. The track formation process is explored with a Monte Carlo code, which shows that the track formation difference between front and back is due to the non-uniform ion energy deposition in matter.
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29.40.Gx Tracking and position-sensitive detectors
02.70.Uu Applications of Monte Carlo methods
06.20.fb Standards and calibration

An ultra-low energy (30–200 eV) ion-atomic beam source for ion-beam-assisted deposition in ultrahigh vacuum

Jindřich Mach, Tomáš Šamořil, Stanislav Voborný, Miroslav Kolíbal, Jakub Zlámal, Jiří Spousta, Libuše Dittrichová, and Tomáš Šikola

Rev. Sci. Instrum. 82, 083302 (2011); http://dx.doi.org/10.1063/1.3622749 (7 pages)

Online Publication Date: 15 August 2011

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The paper describes the design and construction of an ion-atomic beam source with an optimized generation of ions for ion-beam-assisted deposition under ultrahigh vacuum (UHV) conditions. The source combines an effusion cell and an electron impact ion source and produces ion beams with ultra-low energies in the range from 30 eV to 200 eV. Decreasing ion beam energy to hyperthermal values (≈101 eV) without loosing optimum ionization conditions has been mainly achieved by the incorporation of an ionization chamber with a grid transparent enough for electron and ion beams. In this way the energy and current density of nitrogen ion beams in the order of 101 eV and 101 nA/cm2, respectively, have been achieved. The source is capable of growing ultrathin layers or nanostructures at ultra-low energies with a growth rate of several MLs/h. The ion-atomic beam source will be preferentially applied for the synthesis of GaN under UHV conditions.
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29.25.Lg Ion sources: polarized
41.85.-p Beam optics

A Thomson parabola ion imaging spectrometer designed to probe relativistic intensity ionization dynamics of nanoclusters

R. Rajeev, K. P. M. Rishad, T. Madhu Trivikram, V. Narayanan, and M. Krishnamurthy

Rev. Sci. Instrum. 82, 083303 (2011); http://dx.doi.org/10.1063/1.3624698 (12 pages)

Online Publication Date: 22 August 2011

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Conventional techniques of probing ionization dynamics at relativistic intensities for extended target systems such as clusters are difficult both due to problems of achieving good charge resolution and signal integration over the focal volume. Simultaneous measurement of arrival time, necessary for these systems, has normally involved complicated methods. We designed and developed a Thomson parabola imaging spectrometer that overcomes these problems. Intensity sampling method evolved in this report is proved to be mandatory for probing ionization dynamics of clusters at relativistic intensities. We use this method to measure charge resolved kinetic energy spectra of argon nanoclusters at intensities of 4 × 1018 W cm−2.
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29.30.Ep Charged-particle spectroscopy
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.70.Nc Particle measurements

Profiling of barrier capacitance and spreading resistance using a transient linearly increasing voltage technique

E. Gaubas, T. Čeponis, and J. Kusakovskij

Rev. Sci. Instrum. 82, 083304 (2011); http://dx.doi.org/10.1063/1.3626796 (4 pages)

Online Publication Date: 24 August 2011

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A technique for the combined measurement of barrier capacitance and spreading resistance profiles using a linearly increasing voltage pulse is presented. The technique is based on the measurement and analysis of current transients, due to the barrier and diffusion capacitance, and the spreading resistance, between a needle probe and sample. To control the impact of deep traps in the barrier capacitance, a steady state bias illumination with infrared light was employed. Measurements of the spreading resistance and barrier capacitance profiles using a stepwise positioned probe on cross sectioned silicon pin diodes and pnp structures are presented.
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85.30.Kk Junction diodes

A solid-state Marx generator driven Einzel lens chopper

T. Adachi, T. Arai, K. W. Leo, K. Takayama, and A. Tokuchi

Rev. Sci. Instrum. 82, 083305 (2011); http://dx.doi.org/10.1063/1.3626932 (7 pages)

Online Publication Date: 31 August 2011

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A new type of pulse chopper called an Einzel lens chopper is described. An Einzel lens placed immediately after an electron cyclotron resonance ion source is driven by high-voltage pulses generated by a newly developed solid-state Marx generator. A rectangular negative barrier pulse-voltage is controlled in time, and the barrier pulse is turned on only when a beam pulse is required. The results of successful experiments are reported herein.
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84.30.Ng Oscillators, pulse generators, and function generators
07.77.Ka Charged-particle beam sources and detectors
29.25.Lg Ion sources: polarized
29.25.Ni Ion sources: positive and negative
back to top Nuclear Physics, Fusion and Plasmas

Development of a real time monitor and multivariate method for long term diagnostics of atmospheric pressure dielectric barrier discharges: Application to He, He/N2, and He/O2 discharges

N. O’Connor, V. Milosavljević, and S. Daniels

Rev. Sci. Instrum. 82, 083501 (2011); http://dx.doi.org/10.1063/1.3624743 (10 pages)

Online Publication Date: 18 August 2011

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In this paper we present the development and application of a real time atmospheric pressure discharge monitoring diagnostic. The software based diagnostic is designed to extract latent electrical and optical information associated with the operation of an atmospheric pressure dielectric barrier discharge (APDBD) over long time scales. Given that little is known about long term temporal effects in such discharges, the diagnostic methodology is applied to the monitoring of an APDBD in helium and helium with both 0.1% nitrogen and 0.1% oxygen gas admixtures over periods of tens of minutes. Given the large datasets associated with the experiments, it is shown that this process is much expedited through the novel application of multivariate correlations between the electrical and optical parameters of the corresponding chemistries which, in turn, facilitates comparisons between each individual chemistry also. The results of these studies show that the electrical and optical parameters of the discharge in helium and upon the addition of gas admixtures evolve over time scales far longer than the gas residence time and have been compared to current modelling works. It is envisaged that the diagnostic together with the application of multivariate correlations will be applied to rapid system identification and prototyping in both experimental and industrial APDBD systems in the future.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.70.Ds Electric and magnetic measurements
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.80.Vp Discharge in vacuum
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)

New signal processing technique for density profile reconstruction using reflectometry

F. Clairet, B. Ricaud, F. Briolle, S. Heuraux, and C. Bottereau

Rev. Sci. Instrum. 82, 083502 (2011); http://dx.doi.org/10.1063/1.3622747 (9 pages)

Online Publication Date: 25 August 2011

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Reflectometry profile measurement requires an accurate determination of the plasma reflected signal. Along with a good resolution and a high signal to noise ratio of the phase measurement, adequate data analysis is required. A new data processing based on time-frequency tomographic representation is used. It provides a clearer separation between multiple components and improves isolation of the relevant signals. In this paper, this data processing technique is applied to two sets of signals coming from two different reflectometer devices used on the Tore Supra tokamak. For the standard density profile reflectometry, it improves the initialization process and its reliability, providing a more accurate profile determination in the far scrape-off layer with density measurements as low as 1016 m−1. For a second reflectometer, which provides measurements in front of a lower hybrid launcher, this method improves the separation of the relevant plasma signal from multi-reflection processes due to the proximity of the plasma.
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07.60.Hv Refractometers and reflectometers
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
84.40.Ua Telecommunications: signal transmission and processing; communication satellites
06.30.Dr Mass and density

Tritium plasma experiment: Parameters and potentials for fusion plasma-wall interaction studies

Masashi Shimada, Robert D. Kolasinski, J. Phillip Sharpe, and Rion A. Causey

Rev. Sci. Instrum. 82, 083503 (2011); http://dx.doi.org/10.1063/1.3627609 (9 pages)

Online Publication Date: 31 August 2011

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The tritium plasma experiment (TPE) is a unique facility devoted to experiments on the behavior of deuterium/tritium in toxic (e.g., beryllium) and radioactive materials for fusion plasma-wall interaction studies. A Langmuir probe was added to the system to characterize the plasma conditions in TPE. With this new diagnostic, we found the achievable electron temperature ranged from 5.0 to 10.0 eV, the electron density varied from 5.0 × 1016 to 2.5 × 1018 m−3, and the ion flux density varied between 5.0 × 1020 to 2.5 × 1022 m−2 s−1 along the centerline of the plasma. A comparison of these plasma parameters with the conditions expected for the plasma facing components (PFCs) in ITER shows that TPE is capable of achieving most (∼800 m2 of 850 m2 total PFCs area) of the expected ion flux density and electron density conditions.
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52.40.Hf Plasma-material interactions; boundary layer effects
52.55.Fa Tokamaks, spherical tokamaks
52.70.Ds Electric and magnetic measurements
52.25.Fi Transport properties
28.52.Fa Materials
back to top Microscopy and Imaging

Compact device for cleaning scanner-mounted scanning tunneling microscope tips using electron bombardment

D. Hellmann, L. Worbes, and A. Kittel

Rev. Sci. Instrum. 82, 083701 (2011); http://dx.doi.org/10.1063/1.3622519 (3 pages)

Online Publication Date: 8 August 2011

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Most scanning probe techniques rely on the assumption that both sample and tip are free from adsorbates, residues, and oxide not deposited intentionally. Getting a clean sample surface can be readily accomplished by applying ion sputtering and subsequent annealing, whereas finding an adequate treatment for tips is much more complicated. The method of choice would effectively desorb undesired compounds without reducing the sharpness or the general geometry of the tip. Several devices which employ accelerated electrons to achieve this are described in the literature. To minimize both the effort to implement this technique in a UHV chamber and the overall duration of the cleaning procedure, we constructed a compact electron source fitted into a sample holder, which can be operated in a standard Omicron variable-temperature (VT)-STM while the tip stays in place. This way a maximum of compatibility with existing systems is achieved and short turnaround times are possible for tip cleaning.
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07.79.Cz Scanning tunneling microscopes

Systematic analyses of vibration noise of a vibration isolation system for high-resolution scanning tunneling microscopes

Katsuya Iwaya, Ryota Shimizu, Tomihiro Hashizume, and Taro Hitosugi

Rev. Sci. Instrum. 82, 083702 (2011); http://dx.doi.org/10.1063/1.3622507 (6 pages) | Cited 1 time

Online Publication Date: 10 August 2011

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We designed and constructed an effective vibration isolation system for stable scanning tunneling microscopy measurements using a separate foundation and two vibration isolation stages (i.e., a combination of passive and active vibration isolation dampers). Systematic analyses of vibration data along the horizontal and vertical directions are present, including the vibration transfer functions of each stage and the overall vibration isolation system. To demonstrate the performance of the system, tunneling current noise measurements are conducted with and without the vibration isolation. Combining passive and active vibration isolation dampers successfully removes most of the vibration noise in the tunneling current up to 100 Hz. These comprehensive vibration noise data, along with details of the entire system, can be used to establish a clear guideline for building an effective vibration isolation system for various scanning probe microscopes and electron microscopes.
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07.10.Fq Vibration isolation

Dynamic timber cell recognition using two-dimensional image measurement machine

Peng Zhao

Rev. Sci. Instrum. 82, 083703 (2011); http://dx.doi.org/10.1063/1.3623500 (8 pages)

Online Publication Date: 10 August 2011

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Image motion blur and defocus blur often occur when there is a relative motion between the imaging camera and the detected object. In this paper, we propose a robust timber cell recognition scheme using the low quality color timber cell images with the above-mentioned image blurs. First, a novel two-dimensional image measurement machine is devised, to obtain the object images sequentially by using a color camera. Second, the image-moment-based blur invariant features are calculated. Third, timber cell recognition is performed by using the computed Euclidean distance based on the moment invariants. We have experimentally proved that the effective use of image blur information improves the recognition accuracy of camera-captured timber cells. Moreover, the allowed maximum translation speed of the moving gallery is also discussed theoretically and experimentally. This scheme can identify the timber species by means of the cell recognition so as to judge the physical property and economic value of different timber species correctly.
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89.20.Kk Engineering
89.60.-k Environmental studies
42.30.Sy Pattern recognition
42.30.Va Image forming and processing

Angle dependence of the interaction distance in the shear force technique

J. M. Merlo, J. F. Aguilar, E. Martí-Panameño, R. Cortés, and V. Coello

Rev. Sci. Instrum. 82, 083704 (2011); http://dx.doi.org/10.1063/1.3624691 (3 pages)

Online Publication Date: 16 August 2011

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We study the interaction distance in the lateral force detection, using a standard quartz tuning fork as a force transducer. That is the distance at which the interaction sample-probe starts to be detected. We study in particular the dependence on the approaching angle. For angles smaller than 0.366 radians, we found an exponential behavior of the interaction distance as a function of the approaching angle. We show an equation that adjusts well with the experimental data, and discuss the possible phenomena.
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07.07.Mp Transducers
07.10.Pz Instruments for strain, force, and torque

Cranz-Schardin camera with a large working distance for the observation of small scale high-speed flows

C. Skupsch, H. Chaves, and C. Brücker

Rev. Sci. Instrum. 82, 083705 (2011); http://dx.doi.org/10.1063/1.3624692 (6 pages) | Cited 1 time

Online Publication Date: 17 August 2011

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The Cranz-Schardin camera utilizes a Q-switched Nd:YAG laser and four single CCD cameras. Light pulse energy in the range of 25 mJ and pulse duration of about 5 ns is provided by the laser. The laser light is converted to incoherent light by Rhodamine-B fluorescence dye in a cuvette. The laser beam coherence is intentionally broken in order to avoid speckle. Four light fibers collect the fluorescence light and are used for illumination. Different light fiber lengths enable a delay of illumination between consecutive images. The chosen interframe time is 25 ns, corresponding to 40 × 106 frames per second. Exemplarily, the camera is applied to observe the bow shock in front of a water jet, propagating in air at supersonic speed. The initial phase of the formation of a jet structure is recorded.
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47.80.Jk Flow visualization and imaging
47.40.Ki Supersonic and hypersonic flows
47.40.Nm Shock wave interactions and shock effects

Scanning magneto-optical Kerr microscope with auto-balanced detection scheme

Y. Halahovets, P. Siffalovic, M. Jergel, R. Senderak, E. Majkova, S. Luby, I. Kostic, B. Szymanski, and F. Stobiecki

Rev. Sci. Instrum. 82, 083706 (2011); http://dx.doi.org/10.1063/1.3625687 (6 pages)

Online Publication Date: 19 August 2011

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We have developed a scanning magneto-optical Kerr microscope dedicated to localization and measurement of the in-plane magnetization of ultra-thin layered magnetic nanostructures with high sensitivity and signal-to-noise ratio. The novel light detection scheme is based on a differential photodetector with automatic common mode noise rejection system with a high noise suppression up to 50 dB. The sensitivity of the developed detection scheme was tested by measurement of a single Co layer and a giant magnetoresistance (GMR) multilayer stack. The spatial resolution of the Kerr microscope was demonstrated by mapping an isolated 5×5 μm spin-valve pillar.
Show PACS
07.79.-v Scanning probe microscopes and components
85.60.Gz Photodetectors (including infrared and CCD detectors)
85.70.Sq Magnetooptical devices
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
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