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Jun 2012

Volume 83, Issue 6, Articles (06xxxx)

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Rev. Sci. Instrum. 83, 061101 (2012); http://dx.doi.org/10.1063/1.4720102 (35 pages)

Marcel Lucas and Elisa Riedo

Versatility from combining scanning probe microscopy with optical spectroscopy. Scanning probe microscopy can characterize (top, left to right) mechanical properties, topography, transport properties and chemical composition of the sample. Optical spectroscopy (bottom, left to right) can probe chemical composition, crystal structure, and deformation, and map them in hyperspectral images.

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back to top General Instruments

Apparatus for the high temperature measurement of the Seebeck coefficient in thermoelectric materials

Joshua Martin

Rev. Sci. Instrum. 83, 065101 (2012); http://dx.doi.org/10.1063/1.4723872 (9 pages) | Cited 3 times

Online Publication Date: 1 June 2012

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The Seebeck coefficient is a physical parameter routinely measured to identify the potential thermoelectric performance of a material. However, researchers employ a variety of techniques, conditions, and probe arrangements to measure the Seebeck coefficient, resulting in conflicting materials data. To compare and evaluate these methodologies, and to identify optimal Seebeck coefficient measurement protocols, we have developed an improved experimental apparatus to measure the Seebeck coefficient under multiple conditions and probe arrangements (300 K–1200 K). This paper will describe in detail the apparatus design and instrumentation, including a discussion of its capabilities and accuracy as measured through representative diagnostics. In addition, this paper will emphasize the techniques required to effectively manage uncertainty in high temperature Seebeck coefficient measurements.
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07.20.Dt Thermometers

A novel alignment mechanism employing orthogonal connected multi-layered flexible hinges for both leveling and centering

Jian Zhao, Hongxi Wang, Renjing Gao, Ping Hu, and Yintang Yang

Rev. Sci. Instrum. 83, 065102 (2012); http://dx.doi.org/10.1063/1.4722946 (7 pages)

Online Publication Date: 6 June 2012

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To eliminate the effects of motion coupling for measuring cylindrical work pieces, a novel alignment mechanism integrating functions of both leveling and centering is designed and fabricated by introducing multi-layered orthogonal connected flexible hinges as the key supporting and joining elements. Different from traditional leveling mechanisms with many separate parts fabricated together, all of the flexible hinges were integrated in one three-dimensioned machining part without assembling process, and thus synchronously simplifying the structure and reducing assembly errors. Based on the screw theory, the mathematic model of the proposed alignment mechanism is established for any resolution requirements depending on screw characteristics. A millimeter-sized device is fabricated with the alignment precision of 1.0 μm for centering within the range of ±1 mm and 1 in. for leveling within ±1°. The experiment results are in very close agreement to those obtained by simulation, which validate the feasibility of introducing multi-layered orthogonal flexible hinges in the centering and leveling mechanisms.
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89.20.Kk Engineering
81.20.Wk Machining, milling

A novel approach for x-ray scattering experiments in magnetic fields utilizing trapped flux in type-II superconductors

R. K. Das, Z. Islam, J. P. C. Ruff, R. P. Sawh, R. Weinstein, P. C. Canfield, J.-W. Kim, and J. C. Lang

Rev. Sci. Instrum. 83, 065103 (2012); http://dx.doi.org/10.1063/1.4725523 (7 pages) | Cited 2 times

Online Publication Date: 8 June 2012

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We introduce a novel approach to x-ray scattering studies in applied magnetic fields by exploiting vortices in superconductors. This method is based on trapping magnetic flux in a small disk-shaped superconductor (known as a trapped field magnet, TFM) with a single-crystal sample mounted on or at close proximity to its surface. This opens an unrestricted optical access to the sample and allows magnetic fields to be applied precisely along the x-ray momentum transfer, facilitating polarization-sensitive experiments that have been impractical or impossible to perform to date. The TFMs used in our study remain stable and provide practically uniform magnetic fields for days, which are sufficient for comprehensive x-ray diffraction experiments, specifically x-ray resonance exchange scattering (XRES) to study field-induced phenomena at a modern synchrotron source. The TFM instrument has been used in a “proof-of-principle” XRES study of a meta-magnetic phase in a rare-earth compound, TbNi2Ge2, in order to demonstrate its potential.
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78.70.Ck X-ray scattering

Synchronization of high speed framing camera and intense electron-beam accelerator

Xin-Bing Cheng, Jin-Liang Liu, Zhi-Qiang Hong, and Bao-Liang Qian

Rev. Sci. Instrum. 83, 065104 (2012); http://dx.doi.org/10.1063/1.4727881 (5 pages) | Cited 1 time

Online Publication Date: 8 June 2012

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A new trigger program is proposed to realize the synchronization of high speed framing camera (HSFC) and intense electron-beam accelerator (IEBA). The trigger program which include light signal acquisition radiated from main switch of IEBA and signal processing circuit could provide a trigger signal with rise time of 17 ns and amplitude of about 5 V. First, the light signal was collected by an avalanche photodiode (APD) module, and the delay time between the output voltage of APD and load voltage of IEBA was tested, it was about 35 ns. Subsequently, the output voltage of APD was processed further by the signal processing circuit to obtain the trigger signal. At last, by combining the trigger program with an IEBA, the trigger program operated stably, and a delay time of 30 ns between the trigger signal of HSFC and output voltage of IEBA was obtained. Meanwhile, when surface flashover occurred at the high density polyethylene sample, the delay time between the trigger signal of HSFC and flashover current was up to 150 ns, which satisfied the need of synchronization of HSFC and IEBA. So the experiment results proved that the trigger program could compensate the time (called compensated time) of the trigger signal processing time and the inherent delay time of the HSFC.
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29.20.Ba Electrostatic accelerators
85.60.Dw Photodiodes; phototransistors; photoresistors
84.30.Sk Pulse and digital circuits

Design and performance of a new induction furnace for heat treatment of superconducting radiofrequency niobium cavities

Pashupati Dhakal, Gianluigi Ciovati, Wayne Rigby, John Wallace, and Ganapati Rao Myneni

Rev. Sci. Instrum. 83, 065105 (2012); http://dx.doi.org/10.1063/1.4725589 (5 pages) | Cited 1 time

Online Publication Date: 11 June 2012

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Superconducting radio frequency (SRF) cavities made of high purity niobium (Nb) are the building blocks of many modern particle accelerators. The fabrication process includes several cycles of chemical and heat treatment at low (∼120 °C) and high (∼800 °C) temperatures. In this contribution, we describe the design and performance of an ultra-high-vacuum furnace which uses an induction heating system to heat treat SRF cavities. Cavities are heated by radiation from the Nb susceptor. By using an all-niobium hot zone, contamination of the Nb cavity by foreign elements during heat treatment is minimized and allows avoiding subsequent chemical etching. The furnace was operated up to 1400 °C with a maximum pressure of ∼1 × 10−5 Torr and the maximum achievable temperature is estimated to be higher than 2000 °C. Initial results on the performance of a single cell 1.5 GHz cavity made of ingot Nb heat treated at 1200 °C using this new induction furnace and without subsequent chemical etching showed a reduction of the RF losses by a factor of ∼2 compared to cavities made of fine-grain Nb which underwent standard chemical and heat treatments.
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29.20.-c Accelerators
29.27.-a Beams in particle accelerators
81.40.Gh Other heat and thermomechanical treatments
81.65.Cf Surface cleaning, etching, patterning

Real-time inverse hysteresis compensation of piezoelectric actuators with a modified Prandtl-Ishlinskii model

Guo-Ying Gu, Mei-Ju Yang, and Li-Min Zhu

Rev. Sci. Instrum. 83, 065106 (2012); http://dx.doi.org/10.1063/1.4728575 (8 pages) | Cited 3 times

Online Publication Date: 11 June 2012

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This paper presents a novel real-time inverse hysteresis compensation method for piezoelectric actuators exhibiting asymmetric hysteresis effect. The proposed method directly utilizes a modified Prandtl-Ishlinskii hysteresis model to characterize the inverse hysteresis effect of piezoelectric actuators. The hysteresis model is then cascaded in the feedforward path for hysteresis cancellation. It avoids the complex and difficult mathematical procedure for constructing an inversion of the hysteresis model. For the purpose of validation, an experimental platform is established. To identify the model parameters, an adaptive particle swarm optimization algorithm is adopted. Based on the identified model parameters, a real-time feedforward controller is implemented for fast hysteresis compensation. Finally, tests are conducted with various kinds of trajectories. The experimental results show that the tracking errors caused by the hysteresis effect are reduced by about 90%, which clearly demonstrates the effectiveness of the proposed inverse compensation method with the modified Prandtl-Ishlinskii model.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Supersonic helium beam diagnostic for fluctuation measurements of electron temperature and density at the Tokamak TEXTOR

U. Kruezi, H. Stoschus, B. Schweer, G. Sergienko, and U. Samm

Rev. Sci. Instrum. 83, 065107 (2012); http://dx.doi.org/10.1063/1.4707150 (13 pages) | Cited 3 times

Online Publication Date: 14 June 2012

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A supersonic helium beam diagnostic, based on the line-ratio technique for high resolution electron density and temperature measurements in the plasma edge (r/a > 0.9) was designed, built, and optimised at TEXTOR (Torus Experiment for Technology Oriented Research). The supersonic injection system, based on the Campargue skimmer-nozzle concept, was developed and optimised in order to provide both a high neutral helium beam density of n0 = 1.5 × 1018 m−3 and a low beam divergence of ±1° simultaneously, achieving a poloidal resolution of Δpoloidal = 9 mm. The setup utilises a newly developed dead volume free piezo valve for operation in a high magnetic field environment of up to 2 T with a maximum repetition rate of 80 Hz. Gas injections are realised for a duration of 120 ms at a repetition rate of 2 Hz (duty cycle 1/3). In combination with a high sensitivity detection system, consisting of three 32 multi-channel photomultipliers (PMTs), measurements of edge electron temperature and density with a radial resolution of Δradial = 2 mm and a maximum temporal resolution of Δt ≃ 2 μs (470 kHz) are possible for the first time. The diagnostic setup at TEXTOR is presented. The newly developed injection system and its theoretical bases are discussed. The applicability of the stationary collisional-radiative model as basis of the line-ratio technique is shown. Finally, an example of a fluctuation analysis demonstrating the unique high temporal and spatial resolution capabilities of this new diagnostic is presented.
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52.25.Gj Fluctuation and chaos phenomena
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.40.Hf Plasma-material interactions; boundary layer effects
52.55.Fa Tokamaks, spherical tokamaks
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.20.Fs Electron collisions

A high-performance magnetic shield with large length-to-diameter ratio

Susannah Dickerson, Jason M. Hogan, David M. S. Johnson, Tim Kovachy, Alex Sugarbaker, Sheng-wey Chiow, and Mark A. Kasevich

Rev. Sci. Instrum. 83, 065108 (2012); http://dx.doi.org/10.1063/1.4720943 (9 pages)

Online Publication Date: 15 June 2012

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We have demonstrated a 100-fold improvement in the magnetic field uniformity on the axis of a large aspect ratio, cylindrical, mumetal magnetic shield by reducing discontinuities in the material of the shield through the welding and re-annealing of a segmented shield. The three-layer shield reduces Earth's magnetic field along an 8 m region to 420 μG (rms) in the axial direction, and 460 and 730 μG (rms) in the two transverse directions. Each cylindrical shield is a continuous welded tube which has been annealed after manufacture and degaussed in the apparatus. We present both experiments and finite element analysis that show the importance of uniform shield material for large aspect ratio shields, favoring a welded design over a segmented design. In addition, we present finite element results demonstrating the smoothing of spatial variations in the applied magnetic field by cylindrical magnetic shields. Such homogenization is a potentially useful feature for precision atom interferometric measurements.
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41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems
02.70.Dh Finite-element and Galerkin methods

Parametric noise squeezing and parametric resonance of microcantilevers in air and liquid environments

Gyan Prakash, Arvind Raman, Jeffrey Rhoads, and Ronald G. Reifenberger

Rev. Sci. Instrum. 83, 065109 (2012); http://dx.doi.org/10.1063/1.4721282 (12 pages)

Online Publication Date: 20 June 2012

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In this work, parametric noise squeezing and parametric resonance are realized through the use of an electronic feedback circuit to excite a microcantilever with a signal proportional to the product of the microcantilever's displacement and a harmonic signal. The cantilever's displacement is monitored using an optical lever technique. By adjusting the gain of an amplifier in the feedback circuit, regimes of parametric noise squeezing/amplification and the principal and secondary parametric resonances of fundamental and higher order eigenmodes can be easily accessed. The exceptionally symmetric amplitude response of the microcantilever in the narrow frequency bandwidth is traced to a nonlinear parametric excitation term that arises due to the cubic nonlinearity in the output of the position-sensitive photodiode. The feedback circuit, working in both the regimes of parametric resonance and noise squeezing, allows an enhancement of the microcantilever's effective quality-factor (Q-factor) by two orders of magnitude under ambient conditions, extending the mass sensing capabilities of a conventional microcantilever into the sub-picogram regime. Likewise, experiments designed to parametrically oscillate a microcantilever in water using electronic feedback also show an increase in the microcantilever's effective Q-factor by two orders of magnitude, opening the field to high-sensitivity mass sensing in liquid environments.
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42.82.-m Integrated optics
42.50.Dv Quantum state engineering and measurements

Multifunctional magnetic rotator for micro and nanorheological studies

Alexander Tokarev, Alexey Aprelev, Mikhail N. Zakharov, Guzeliya Korneva, Yury Gogotsi, and Konstantin G. Kornev

Rev. Sci. Instrum. 83, 065110 (2012); http://dx.doi.org/10.1063/1.4729795 (8 pages) | Cited 1 time

Online Publication Date: 21 June 2012

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We report on the development of a multifunctional magnetic rotator that has been built and used during the last five years by two groups from Clemson and Drexel Universities studying the rheological properties of microdroplets. This magnetic rotator allows one to generate rotating magnetic fields in a broad frequency band, from hertz to tens kilohertz. We illustrate its flexibility and robustness by conducting the rheological studies of simple and polymeric fluids at the nano and microscale. First we reproduce a temperature-dependent viscosity of a synthetic oil used as a viscosity standard. Magnetic rotational spectroscopy with suspended nickel nanorods was used in these studies. As a second example, we converted the magnetic rotator into a pump with precise controlled flow modulation. Using multiwalled carbon nanotubes, we were able to estimate the shear modulus of sickle hemoglobin polymer. We believe that this multifunctional magnetic system will be useful not only for micro and nanorheological studies, but it will find much broader applications requiring remote controlled manipulation of micro and nanoobjects.
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47.57.Qk Rheological aspects
47.61.-k Micro- and nano- scale flow phenomena

An accurate system for onsite calibration of electronic transformers with digital output

Zhang Zhi and Hong-Bin Li

Rev. Sci. Instrum. 83, 065111 (2012); http://dx.doi.org/10.1063/1.4729475 (7 pages)

Online Publication Date: 29 June 2012

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Calibration systems with digital output are used to replace conventional calibration systems because of principle diversity and characteristics of digital output of electronic transformers. But precision and unpredictable stability limit their onsite application even development. So fully considering the factors influencing accuracy of calibration system and employing simple but reliable structure, an all-digital calibration system with digital output is proposed in this paper. In complicated calibration environments, precision and dynamic range are guaranteed by A/D converter with 24-bit resolution, synchronization error limit is nanosecond by using the novelty synchronization method. In addition, an error correction algorithm based on the differential method by using two-order Hanning convolution window has good inhibition of frequency fluctuation and inter-harmonics interference. To verify the effectiveness, error calibration was carried out in the State Grid Electric Power Research Institute of China and results show that the proposed system can reach the precision class up to 0.05. Actual onsite calibration shows that the system has high accuracy, and is easy to operate with satisfactory stability.
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84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
84.30.-r Electronic circuits
06.20.fb Standards and calibration
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