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Apr 2012

Volume 83, Issue 4, Articles (04xxxx)

Issue Cover Spotlight Figure

Rev. Sci. Instrum. 83, 041101 (2012); http://dx.doi.org/10.1063/1.3697599 (19 pages)

Michael A. Duncan

The laser vaporization cluster source in the "cutaway" configuration. The sample rod is mounted from above with a flexible nylon screw in a holding block. The pulsed gas valve is mounted in the stainless steel can (left) and the skimmer is mounted on the opposite wall.

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Note: Multiplexed multiple-tau auto- and cross-correlators on a single field programmable gate array

G. Mocsár, B. Kreith, J. Buchholz, J. W. Krieger, J. Langowski, and G. Vámosi

Rev. Sci. Instrum. 83, 046101 (2012); http://dx.doi.org/10.1063/1.3700810 (3 pages) | Cited 3 times

Online Publication Date: 4 April 2012

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We introduce a new multiple-tau hardware correlator design for computing fluorescence correlation functions (CFs) in real time. Use of hardware resources is minimized by scheduling the computation of different segments of the CFs on a single correlator block. Simultaneous calculation of two multiple-tau autocorrelation (ACFs) and two cross-correlation functions (CCFs) is implemented in LabVIEW on a National Instruments field programmable gate array (FPGA) card with a minimal sampling time of 400 ns. Raw data are stored with a time resolution of 50 ns. The design can be easily adapted to other FPGA cards and extended to more inputs.
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84.30.Sk Pulse and digital circuits

Note: Development of a compact x-ray particle image velocimetry for measuring opaque flows. II. Three-dimensional velocity field reconstruction

Sung Yong Jung and Sang Joon Lee

Rev. Sci. Instrum. 83, 046102 (2012); http://dx.doi.org/10.1063/1.3700811 (3 pages)

Online Publication Date: 4 April 2012

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An x-ray particle image velocimetry (PIV) system using a cone-beam type x-ray was developed. The field of view and the spatial resolution are 36 × 24.05 mm2 and 20 μm, respectively. The three-dimensional velocity field was reconstructed by adopting the least squares minimum residue and simultaneous multiplicative algebraic reconstruction techniques. According to a simulation study with synthetic images, the reconstructions were acceptable with 7 projections and 50 iterations. The reconstructed and supplied flow rates differed by only about 6.49% in experimental verification. The x-ray tomographic PIV system would be useful for 3D velocity field information of opaque flows.
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47.80.Jk Flow visualization and imaging
07.85.-m X- and γ-ray instruments
47.80.Cb Velocity measurements

Note: Three-dimensional stereolithography for millimeter wave and terahertz applications

A. Macor, E. de Rijk, S. Alberti, T. Goodman, and J-Ph. Ansermet

Rev. Sci. Instrum. 83, 046103 (2012); http://dx.doi.org/10.1063/1.3701738 (3 pages)

Online Publication Date: 6 April 2012

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Metal-coated polymers shaped by 3D stereolithography are introduced as a new manufacturing method for passive components for millimeter to terahertz electromagnetic waves. This concept offers increased design capabilities and flexibilities while shortening the manufacturing process of complex shapes, e.g., corrugated horns, mirrors, etc. Tests at 92.5, 140, and 170 GHz are reported.
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85.40.Hp Lithography, masks and pattern transfer
84.40.Ba Antennas: theory, components and accessories

Note: Reliable and reusable ultrahigh vacuum optical viewports

P. Arora and A. Sen Gupta

Rev. Sci. Instrum. 83, 046104 (2012); http://dx.doi.org/10.1063/1.4704082 (3 pages)

Online Publication Date: 12 April 2012

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We report a simple technique for the realization of ultrahigh vacuum optical viewports. The technique relies on using specially designed thin copper knife-edges and using a thin layer of Vacseal® on tip of the knife-edges between the optical flat and the ConFlat® (CF) flange. The design of the windows is such that it gives uniform pressure on the flat without breaking it. The assembled window is a complete unit, which can be mounted directly onto a CF flange of the vacuum chamber. It can be removed and reused without breaking the window seal. The design is reliable as more than a dozen such windows have survived several bake out and cooling cycles and have been leak tested up to 10−11 Torr l/s level with a commercial Helium leak detector. The advantages of this technique are ease of assembly and leak proof sealing that survives multiple temperature cycling making the windows reliable and reusable.
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07.30.Hd Vacuum testing methods; leak detectors

Note: Improved sensitivity of photoreflectance measurements with a combination of dual detection and electronic compensation

Amlan Mukherjee, Sandip Ghosh, and Vasam Sugunakar

Rev. Sci. Instrum. 83, 046105 (2012); http://dx.doi.org/10.1063/1.4704087 (3 pages) | Cited 1 time

Online Publication Date: 12 April 2012

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A setup is described for performing photoreflectance (PR) measurements using two photodetectors, wherein the photodetectors need not be identical. The second detector monitors the photoluminescence and scattered pump laser background signal in real time. It is then eliminated from the measured PR signal using electronic circuits that compensate for amplitude and phase differences between the background signals from the two detectors. The technique overcomes the adverse effect of short-term fluctuations in the pump laser intensity. The signal-to-noise ratio is shown to improve significantly, enabling measurement of weak PR signals.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy

Note: Adhesive stamp electrodes using spider silk masks for electronic transport measurements of supra-micron sized samples

E. Steven, E. Jobiliong, P. M. Eugenio, and J. S. Brooks

Rev. Sci. Instrum. 83, 046106 (2012); http://dx.doi.org/10.1063/1.4704838 (3 pages)

Online Publication Date: 17 April 2012

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A procedure for fabricating adhesive stamp electrodes based on gold coated adhesive tape used to measure electronic transport properties of supra-micron samples in the lateral range 10–100 μm and thickness >1 μm is described. The electrodes can be patterned with a ∼4 μm separation by metal deposition through a mask using Nephila clavipes spider dragline silk fibers. Ohmic contact is made by adhesive lamination of a sample onto the patterned electrodes. The performance of the electrodes with temperature and magnetic field is demonstrated for the quasi-one-dimensional organic conductor (TMTSF)2PF6 and single crystal graphite, respectively.
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07.68.+m Photography, photographic instruments; xerography
07.10.Cm Micromechanical devices and systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)

Note: Characterization of CaF2/acetone bandpass photon detector with Kr filter gas

M. Maniraj, B. N. Raja Sekhar, and S. R. Barman

Rev. Sci. Instrum. 83, 046107 (2012); http://dx.doi.org/10.1063/1.4704374 (3 pages)

Online Publication Date: 17 April 2012

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A modified design of a CaF2/acetone bandpass photon detector that uses Kr as a filter gas to tune the energy resolution is presented. Our design combines two standard single window detector tubes to build the Kr filter gas chamber. Synchrotron radiation has been used to determine the energy resolution of the detector, as a function of Kr pressure. The improvement in the detector energy resolution by 250 meV compared to the CaF2/acetone detector is better than that reported earlier. Substantial variation in the shape of the CaF2/acetone detector response functions is observed for different acetone pressure (≤3 mbar), and anode voltage (≤800 V). Our analysis reveals that the changes in the shape of the detector response function are associated to different regions of the detector operation.
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85.60.Gz Photodetectors (including infrared and CCD detectors)

Note: Real time control of a tunable vibration absorber based on magnetorheological elastomer for suppressing tonal vibrations

Young-Keun Kim, Hyo-In Bae, Jeong-Hoi Koo, Kyung-Soo Kim, and Soohyun Kim

Rev. Sci. Instrum. 83, 046108 (2012); http://dx.doi.org/10.1063/1.4704455 (3 pages)

Online Publication Date: 17 April 2012

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An adaptive tunable vibration absober based on magnetorheological elastomer (MRE) is designed as an intelligent device for auto-tuning itself to the time-varying harmonic disturbance force to reduce the unwanted vibration of the primary system in the steady state. The objectives of this note are to develop and implement a continuous control method for a MRE tunable vibration absorber (TVA) and to evaluate its performance in suppressing time-varying tonal vibrations. In the proposed control, the stiffness of MREs is continuously varied based on a nonlinear tuning function that relates the response of the system to the input magnetic field density. Through experiments, it will be shown that the proposed MRE TVA reduces in real time the transmission of a time-varying excited vibration of 48–55 Hz, which shows the potential applicability of the MRE in reducing unwanted vibration to precision devices.
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07.10.Fq Vibration isolation

Note: Development of fast heating inert gas annealing apparatus operated at atmospheric pressure

S. C. Das, A. Majumdar, T. Shripathi, and R. Hippler

Rev. Sci. Instrum. 83, 046109 (2012); http://dx.doi.org/10.1063/1.4704836 (3 pages) | Cited 2 times

Online Publication Date: 18 April 2012

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Here, we report the development of a simple, small, fast heating, and portable, homemade, inert gas (Ar) atmospheric annealing setup. Instead of using a conventional heating element, a commercial soldering rod having an encapsulated fast heating heater is used here. The sample holder is made of a block of stainless steel. It takes 200 s to reach 700 °C, and 10 min to cool down. The probability of oxidation or surface contamination has been examined by means of x ray photoelectron spectroscopy of virgin Cu sample after annealing at 600 °C. In addition, we compare the annealing of a hydrogenated carbon nitride film (HCNx) in both a conventional vacuum and our newly developed ambient Ar atmosphere setup.
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07.20.-n Thermal instruments and apparatus

Note: Self Q-switched Nd:YVO4 laser at 914 nm

Pradeep K. Gupta, Amarjeet Singh, Sunil K. Sharma, Pranab K. Mukhopadhyay, Kushvinder S. Bindra, and Shrikant M. Oak

Rev. Sci. Instrum. 83, 046110 (2012); http://dx.doi.org/10.1063/1.4705996 (3 pages)

Online Publication Date: 19 April 2012

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By exploiting the saturable nature of re-absorption loss under the quasi-three-level laser transition self Q-switching operation in Nd:YVO4 laser at 914 nm is demonstrated. The stable self-pulsing operation was observed with Nd:YVO4 crystal with doping concentration of 0.3 at.%. At an incident pump power of 30 W around 600 mW of average power was obtained. Individual pulse energy and FWHM pulse duration were experimentally measured to be 10 μJ and 460 ns, respectively. The performance of the laser was analyzed with the help of a rate equation model. The simulation results show good agreement with the experiment.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Note: Self-characterizing ultrafast pulse shaper for rapid pulse switching

Brett J. Pearson and Thomas C. Weinacht

Rev. Sci. Instrum. 83, 046111 (2012); http://dx.doi.org/10.1063/1.4708618 (3 pages)

Online Publication Date: 26 April 2012

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We use a high-efficiency acousto-optic modulator at the input to a two-dimensional Fourier-domain pulse shaper to achieve built-in characterization of the shaped output pulses. The acousto-optic modulator directs the beam to different vertical positions on a two-dimensional spatial light modulator, each of which can contain a different pulse shape. The undiffracted portion of the light serves as a reference beam for characterizing the shaped pulse via spectral interferometry. Pulse switching rates of 100 kHz can be achieved, making the device especially useful for quantum-control spectroscopy.
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42.60.-v Laser optical systems: design and operation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.79.Hp Optical processors, correlators, and modulators
42.79.Jq Acousto-optical devices
07.60.Ly Interferometers

Note: Unique characterization possibilities in the ultra high vacuum scanning transmission x-ray microscope (UHV-STXM) “MAXYMUS” using a rotatable permanent magnetic field up to 0.22 T

D. Nolle, M. Weigand, P. Audehm, E. Goering, U. Wiesemann, C. Wolter, E. Nolle, and G. Schütz

Rev. Sci. Instrum. 83, 046112 (2012); http://dx.doi.org/10.1063/1.4707747 (3 pages) | Cited 1 time

Online Publication Date: 27 April 2012

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Using the x-ray magnetic circular dichroism effect, the soft x-ray range provides powerful detection capabilities concerning element specific structural, chemical, and magnetic properties. We present the implementation of a variable 0.22 T magnet system based on permanent magnets into the new UHV scanning microscope “MAXYMUS” at HZB/BESSY II, allowing surface sensitive and simultaneous standard transmission microscopic investigations in a variable external magnetic field. The outstanding potential of these new investigation possibilities will be demonstrated showing the development of the magnetic domain structure concurrently at the surface and in the bulk, providing a profound understanding of fundamental mechanisms in coupled magnetic systems.
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07.85.Tt X-ray microscopes
75.50.Ww Permanent magnets
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