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Feb 2012

Volume 83, Issue 2 (partial)

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back to top Optics; Atoms and Molecules; Spectroscopy; Photon Detectors

A capillary absorption spectrometer for stable carbon isotope ratio (13C/12C) analysis in very small samples

J. F. Kelly, R. L. Sams, T. A. Blake, M. Newburn, J. Moran, M. L. Alexander, and H. Kreuzer

Rev. Sci. Instrum. 83, 023101 (2012); doi:10.1063/1.3680593 (14 pages)

Online Publication Date: 6 February 2012

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A capillary absorption spectrometer (CAS) suitable for IR laser isotope analysis of small CO2 samples is presented. The system employs a continuous-wave (cw) quantum cascade laser to study nearly adjacent rovibrational transitions of different isotopologues of CO2 near 2307 cm−1 (4.34 μm). This initial CAS system can achieve relative isotopic precision of about 10 ppm 13C, or ∼1‰ (per mil in delta notation relative to Vienna Pee Dee Belemnite) with 20–100 picomoles of entrained sample within the hollow waveguide for CO2 concentrations ∼400–750 ppm. Isotopic analyses of such gas fills in a 1-mm ID hollow waveguide of 0.8 m overall physical path length can be carried out down to ∼2 Torr. Overall 13C/12C ratios can be calibrated to ∼2‰ accuracy with diluted CO2 standards. A novel, low-cost method to reduce cw-fringing noise resulting from multipath distortions in the hollow waveguide is presented, which allows weak absorbance features to be studied at the few ppm level (peak-to-rms) after 1000 scans are co-added in ∼10 s. The CAS is meant to work directly with converted CO2 samples from a laser ablation-catalytic combustion micro-sampler to provide 13C/12C ratios of small biological isolates currently operating with spatial resolutions ∼50 μm.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
42.55.Px Semiconductor lasers; laser diodes

The electron spectro-microscopy beamline at National Synchrotron Light Source II: A wide photon energy range, micro-focusing beamline for photoelectron spectro-microscopies

R. Reininger, S. L. Hulbert, P. D. Johnson, J. T. Sadowski, D. E. Starr, O. Chubar, T. Valla, and E. Vescovo

Rev. Sci. Instrum. 83, 023102 (2012); doi:10.1063/1.3681440 (8 pages)

Online Publication Date: 13 February 2012

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A comprehensive optical design for a high-resolution, high-flux, wide-energy range, micro-focused beamline working in the vacuum ultraviolet and soft x-ray photon energy range is proposed. The beamline is to provide monochromatic radiation to three photoelectron microscopes: a full-field x-ray photoelectron emission microscope and two scanning instruments, one dedicated to angle resolved photoemission spectroscopy (μ-ARPES) and one for ambient pressure x-ray photoelectron spectroscopy and scanning photoelectron microscopy (AP-XPS/SPEM). Microfocusing is achieved with state of the art elliptical cylinders, obtaining a spot size of 1 μm for ARPES and 0.5 μm for AP-XPS/SPEM. A detailed ray tracing analysis quantitatively evaluates the overall beamline performances.
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07.85.-m X- and γ-ray instruments
07.85.Tt X-ray microscopes
29.30.Kv X- and γ-ray spectroscopy
42.15.Dp Wave fronts and ray tracing
back to top Particle Sources, Optics and Acceleration; Particle Detectors

Characteristics of low-energy ion beams extracted from a wire electrode geometry

M. Vasquez, Jr., S. Tokumura, T. Kasuya, S. Maeno, and M. Wada

Rev. Sci. Instrum. 83, 023301 (2012); doi:10.1063/1.3680105 (6 pages)

Online Publication Date: 2 February 2012

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Beams of argon ions with energies less than 50 eV were extracted from an ion source through a wire electrode extractor geometry. A retarding potential energy analyzer (RPEA) was constructed in order to characterize the extracted ion beams. The single aperture RPEA was used to determine the ion energy distribution function, the mean ion energy and the ion beam energy spread. The multi-cusp hot cathode ion source was capable of producing a low electron temperature gas discharge to form quiescent plasmas from which ion beam energy as low as 5 eV was realized. At 50 V extraction potential and 0.1 A discharge current, the ion beam current density was around 0.37 mA/cm2 with an energy spread of 3.6 V or 6.5% of the mean ion energy. The maximum ion beam current density extracted from the source was 0.57 mA/cm2 for a 50 eV ion beam and 1.78 mA/cm2 for a 100 eV ion beam.
Show PACS
29.27.Ac Beam injection and extraction
52.25.Fi Transport properties
52.50.Dg Plasma sources
52.80.-s Electric discharges
29.25.Ni Ion sources: positive and negative

The dependence of extracted current on discharge gas pressure in neutral beam ion sources on HL-2A tokamak

H. L. Wei, J. Y. Cao, J. Rao, G. J. Lei, S. F. Jiang, H. Liu, L. M. Yu, W. M. Xie, M. Li, X. F. Yang, G. Q. Zou, D. L. Lu, and X. R. Duan

Rev. Sci. Instrum. 83, 023302 (2012); doi:10.1063/1.3681446 (4 pages)

Online Publication Date: 7 February 2012

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The discharge gas pressure is a key factor to influence the extracted current of ion source. In this paper, the dependence of extracted current on discharge gas pressure was investigated in detail at different arc discharge currents. The discharge gas pressure with a very broad range (0.1 Pa–2.7 Pa) was scanned for the first time. It is turned out that, with the increasing of discharge gas pressure, the extracted current increases and the arc voltage decreases at different arc currents; however, when the discharge gas pressure exceeds a certain value, the extracted current decreases. For the same discharge gas pressure, the higher the arc current, the higher the arc voltage and the extracted current are. The arc efficiency was also calculated, and its dependence on gas pressure was almost the same with the dependence of extracted current on gas pressure, but at the same discharge gas pressure, the lower the arc current, the higher the arc efficiency is and the lower the extracted current is.
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52.55.Fa Tokamaks, spherical tokamaks
52.50.Gj Plasma heating by particle beams
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.50.Dg Plasma sources
52.25.Fi Transport properties
back to top Nuclear Physics, Fusion and Plasmas

Improved chopping of a lithium beam for plasma edge diagnostic at ASDEX Upgrade

M. Willensdorfer, E. Wolfrum, R. Fischer, J. Schweinzer, M. Sertoli, B. Sieglin, G. Veres, F. Aumayr, and the ASDEX Upgrade Team

Rev. Sci. Instrum. 83, 023501 (2012); doi:10.1063/1.3682003 (7 pages)

Online Publication Date: 6 February 2012

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The lithium beam diagnostic at ASDEX Upgrade routinely delivers electron density profiles in the plasma edge by lithium beam impact excitation spectroscopy. An accurate background subtraction requires a periodically chopped lithium beam. A new, improved chopping system was developed and installed. It involves a voltage modulation for the extractor electrode and the beam deflection plates. The modulation of the extractor electrode reduces the unused portion of lithium ions and improves the stability of the beam with respect to its position. Furthermore, the data indicate an extended emitter lifetime. The extractor chopping was also found to be insensitive to sparks. The deflection chopping experiments demonstrated beam chopping in the kilohertz range. The significantly higher modulation frequency of the deflection chopping improves background subtraction of fast transient events. It allows a more accurate density measurements in the scrape off layer during impurity injections and edge localized modes.
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52.70.Nc Particle measurements
52.40.Hf Plasma-material interactions; boundary layer effects
52.25.Vy Impurities in plasmas
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.80.Mg Arcs; sparks; lightning; atmospheric electricity

Measurement of ion and electron temperatures in plasma blobs by using an improved ion sensitive probe system and statistical analysis methods

K. Okazaki, H. Tanaka, N. Ohno, N. Ezumi, Y. Tsuji, and S. Kajita

Rev. Sci. Instrum. 83, 023502 (2012); doi:10.1063/1.3681778 (5 pages)

Online Publication Date: 7 February 2012

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We have measured ion temperature as well as electron temperature in plasma blobs observed in a linear plasma device by using an improved ion sensitive probe. Current–voltage characteristics of the ion sensitive probe inside and outside plasma blobs were re-constructed with a conditional sampling method. It is clearly found that both ion and electron temperatures in plasma blobs decrease more slowly in a cross-field direction than those in a bulk plasma without plasma blobs.
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52.70.Ds Electric and magnetic measurements
52.75.-d Plasma devices
52.25.Fi Transport properties
02.50.-r Probability theory, stochastic processes, and statistics

Tracer-encapsulated solid pellet injection system

Shigeru Sudo and Naoki Tamura

Rev. Sci. Instrum. 83, 023503 (2012); doi:10.1063/1.3681447 (6 pages)

Online Publication Date: 10 February 2012

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The method of tracer-encapsulated solid pellet (TESPEL) is now flourishing in various fields. The original purpose to study impurity transport without giving substantial perturbation on the plasma is implemented successfully for years. In addition to this, TESPEL is being intensively applied to study thermal (especially non-local) transport, high energy particles with the use of TESPEL ablation cloud, and spectroscopy from the viewpoint of atomic data. It is now further growing up to the utilization of multiple tracer methods which was not planned at the initial phase of the project. The proof-of-principle experiment using triple tracers has been successfully implemented. This opens a way to compare the Z dependence or mass dependence of impurity transport. In this article, as TESPEL is used in a variety of fields, the TESPEL injection system is summarized together with the method of TESPEL production, TESPEL storage disk, TESPEL guide system, and the differential pumping system. Also, the observation system for TESPEL flight and TESPEL ablation is explained.
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82.80.-d Chemical analysis and related physical methods of analysis

Electric field-perturbation measurement of the interaction between two laser-induced plasmas

C. Sánchez-Aké, F. Bredice, and M. Villagrán-Muniz

Rev. Sci. Instrum. 83, 023504 (2012); doi:10.1063/1.3683453 (6 pages)

Online Publication Date: 13 February 2012

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The interaction between two ns-laser-induced plasmas in air at the early-stage of expansion has been analyzed by using a method based on the direct measurement of the perturbation of an externally applied electric field. In this experimental method, the plasmas were produced by focusing two laser beams between the plates of a parallel-plane-charged capacitor. These plasmas produce a perturbation in the electric field of the capacitor which can be measured as a voltage change across a resistor connected to the ground plate. It was found that for delays shorter than 5 ns, the interaction between plasmas is mainly due to the interaction of the dipole-charge distribution of each plasma. For longer time delays, the shielding effect was dominant.
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52.20.-j Elementary processes in plasmas
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
back to top Microscopy and Imaging

A new TriBeam system for three-dimensional multimodal materials analysis

McLean P. Echlin, Alessandro Mottura, Christopher J. Torbet, and Tresa M. Pollock

Rev. Sci. Instrum. 83, 023701 (2012); doi:10.1063/1.3680111 (6 pages)

Online Publication Date: 3 February 2012

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The unique capabilities of ultrashort pulse femtosecond lasers have been integrated with a focused ion beam (FIB) platform to create a new system for rapid 3D materials analysis. The femtosecond laser allows for in situ layer-by-layer material ablation with high material removal rates. The high pulse frequency (1 kHz) of ultrashort (150 fs) laser pulses can induce material ablation with virtually no thermal damage to the surrounding area, permitting high resolution imaging, as well as crystallographic and elemental analysis, without intermediate surface preparation or removal of the sample from the chamber. The TriBeam system combines the high resolution and broad detector capabilities of the DualBeamTM microscope with the high material removal rates of the femtosecond laser, allowing 3D datasets to be acquired at rates 4–6 orders of magnitude faster than 3D FIB datasets. Design features that permit coupling of laser and electron optics systems and positioning of a stage in the multiple analysis positions are discussed. Initial in situ multilayer data are presented.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Effectiveness of frequency mapping on 28 nm device broken scan chain failures

S. H. Goh, Yan Pan, G. F. You, Y. H. Chan, He ran, Thomas Herrman, Thomas Heller, Victor S. K. Lim, Z. H. Mai, Jeffrey Lam, C. M. Chua, W. P. Chua, and S. H. Tan

Rev. Sci. Instrum. 83, 023702 (2012); doi:10.1063/1.3680584 (8 pages)

Online Publication Date: 6 February 2012

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Frequency mapping methodology is an effective diagnostic tool for detection of manufacturing defects in scan chains. It analyses reflected laser modulations from toggling scan cells to localize defective scan path or scan cell. In this paper, we demonstrate experimentally that the use of solid immersion lens technology to enhance signal and spatial resolution is not a prerequisite for this technique up till 28 nm technology node. We present case studies to show the effectiveness of frequency mapping for detecting systematic and random broken scan chain failures on a 28 nm technology node test chip. We achieved 81% success rate in this methodology.
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42.60.Fc Modulation, tuning, and mode locking
42.60.By Design of specific laser systems
Author Select

A nanopositioner for scanning probe microscopy: The KoalaDrive

Vasily Cherepanov, Peter Coenen, and Bert Voigtländer

Rev. Sci. Instrum. 83, 023703 (2012); doi:10.1063/1.3681444 (4 pages)

Online Publication Date: 7 February 2012

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We present a new type of piezoelectric nanopositioner called KoalaDrive which can have a diameter less than 2.5 mm and a length smaller than 10 mm. The new operating principle provides a smooth travel sequence and avoids shaking which is intrinsic to nanopositioners based on inertial motion with sawtooth driving signals. In scanning probe microscopy, the KoalaDrive can be used for the coarse approach of the tip or sensor towards the sample. Inserting the KoalaDrive in a piezo tube for xyz-scanning integrates a complete scanning tunneling microscope (STM) inside a 4 mm outer diameter piezo tube of <10 mm length. The use of the KoalaDrive makes the scanning probe microscopy design ultracompact and accordingly leads to a high mechanical stability. The drive is UHV, low temperature, and magnetic field compatible. The compactness of the KoalaDrive allows building a multi-tip STM as small as a single tip STM.
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07.79.Cz Scanning tunneling microscopes
06.60.Sx Positioning and alignment; manipulating, remote handling
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)

3D mechanical measurements with an atomic force microscope on 1D structures

Christian Kallesøe, Martin B. Larsen, Peter Bøggild, and Kristian Mølhave

Rev. Sci. Instrum. 83, 023704 (2012); doi:10.1063/1.3681784 (7 pages)

Online Publication Date: 9 February 2012

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We have developed a simple method to characterize the mechanical properties of three dimensional nanostructures, such as nanorods standing up from a substrate. With an atomic force microscope the cantilever probe is used to deflect a horizontally aligned nanorod at different positions along the nanorod, using the apex of the cantilever itself rather than the tip normally used for probing surfaces. This enables accurate determination of nanostructures’ spring constant. From these measurements, Young's modulus is found on many individual nanorods with different geometrical and material structures in a short time. Based on this method Young's modulus of carbon nanofibers and epitaxial grown III-V nanowires has been determined.
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07.10.-h Mechanical instruments and equipment
07.79.Lh Atomic force microscopes

The long range voice coil atomic force microscope

H. Barnard, C. Randall, D. Bridges, and P. K. Hansma

Rev. Sci. Instrum. 83, 023705 (2012); doi:10.1063/1.3683235 (4 pages)

Online Publication Date: 9 February 2012

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Most current atomic force microscopes (AFMs) use piezoelectric ceramics for scan actuation. Piezoelectric ceramics provide precision motion with fast response to applied voltage potential. A drawback to piezoelectric ceramics is their inherently limited ranges. For many samples this is a nonissue, as imaging the nanoscale details is the goal. However, a key advantage of AFM over other microscopy techniques is its ability to image biological samples in aqueous buffer. Many biological specimens have topography for which the range of piezoactuated stages is limiting, a notable example of which is bone. In this article, we present the use of voice coils in scan actuation for an actuation range in the Z-axis an order of magnitude larger than any AFM commercially available today. The increased scan size will allow for imaging an important new variety of samples, including bone fractures.
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68.37.Ps Atomic force microscopy (AFM)
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Constant tip-surface distance with atomic force microscopy via quality factor feedback

Lin Fan, Daniel Potter, and Todd Sulchek

Rev. Sci. Instrum. 83, 023706 (2012); doi:10.1063/1.3683236 (4 pages)

Online Publication Date: 10 February 2012

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The atomic force microscope (AFM) is a powerful and widely used instrument to image topography and measure forces at the micrometer and nanometer length scale. Because of the high degree of operating accuracy required of the instrument, small thermal and mechanical drifts of the cantilever and piezoactuator systems hamper measurements as the AFM tip drifts spatially relative to the sample surface. To compensate for the drift, we control the tip-surface distance by monitoring the cantilever quality factor (Q) in a closed loop. Brownian thermal fluctuations provide sufficient actuation to accurately determine cantilever Q by fitting the thermal noise spectrum to a Lorentzian function. We show that the cantilever damping is sufficiently affected by the tip-surface distance so that the tip position of soft cantilevers can be maintained within 40 nm of a setpoint in air and within 3 nm in water with 95% reliability. Utilizing this method to hover the tip above a sample surface, we have the capability to study sensitive interactions at the nanometer length scale over long periods of time.
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07.79.Lh Atomic force microscopes
07.05.Dz Control systems
07.07.Tw Servo and control equipment; robots
back to top Condensed Matter; Materials

A plastic miniature x-ray emission spectrometer based on the cylindrical von Hamos geometry

B. A. Mattern, G. T. Seidler, M. Haave, J. I. Pacold, R. A. Gordon, J. Planillo, J. Quintana, and B. Rusthoven

Rev. Sci. Instrum. 83, 023901 (2012); doi:10.1063/1.3680598 (9 pages)

Online Publication Date: 8 February 2012

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We present a short working distance miniature x-ray emission spectrometer (miniXES) based on the cylindrical von Hamos geometry. We describe the general design principles for the spectrometer and detail a specific implementation that covers Kβ and valence level emission from Fe. Large spatial and angular access to the sample region provides compatibility with environmental chambers, microprobe, and pump/probe measurements. The primary spectrometer structure and optic is plastic, printed using a 3-dimensional rapid-prototype machine. The spectrometer is inexpensive to construct and is portable; it can be quickly set up at any focused beamline with a tunable narrow bandwidth monochromator. The sample clearance is over 27 mm, providing compatibility with a variety of environment chambers. An overview is also given of the calibration and data processing procedures, which are implemented by a multiplatform user-friendly software package. Finally, representative measurements are presented. Background levels are below the level of the Kβ2, 5 valence emission, the weakest diagram line in the system, and photometric analysis of count rates finds that the instrument is performing at the theoretical limit.
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07.85.Nc X-ray and γ-ray spectrometers
29.30.Kv X- and γ-ray spectroscopy
07.60.Dq Photometers, radiometers, and colorimeters

Cryogenic high-frequency readout and control platform for spin qubits

J. I. Colless and D. J. Reilly

Rev. Sci. Instrum. 83, 023902 (2012); doi:10.1063/1.3681195 (7 pages)

Online Publication Date: 13 February 2012

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We have developed a cryogenic platform for the control and readout of spin qubits that comprises a high density of dc and radio frequency sample interconnects based on a set of coupled printed circuit boards. The modular setup incorporates 24 filtered dc lines, 14 control and readout lines with bandwidth from dc to above 6 GHz, and 2 microwave connections for excitation to 40 GHz. We report the performance of this platform, including signal integrity and crosstalk measurements and discuss design criteria for constructing sample interconnect technology needed for multi-qubit devices.
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84.40.Ua Telecommunications: signal transmission and processing; communication satellites
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

Solid-state source of atomic oxygen for low-temperature oxidation processes: Application to pulsed laser deposition of TiO2:N films

Daiki Ojima, Tetsuya Chiba, Kazunari Shima, Hidenori Hiramatsu, Hideo Hosono, and Katsuro Hayashi

Rev. Sci. Instrum. 83, 023903 (2012); doi:10.1063/1.3683571 (5 pages)

Online Publication Date: 13 February 2012

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An atomic oxygen (AO) source has been redesigned to coordinate with a pulsed laser deposition system and used to grow nitrogen-doped TiO2 films by deposition of TiN and simultaneous irradiation of the substrate with AO. The AO source uses an incandescently heated thin tube of zirconia as an oxygen permeation media to generate pure AO of low kinetic energy. The emission flux is calibrated using a silver-coated quartz crystal microbalance. The thin shape of the probe and transverse emission geometry of this emission device allow the emission area to be positioned close to the substrate surface, enhancing the irradiation flux at the substrate. AO irradiation is crucial for formation of TiO2 phases via oxidation of the deposited TiN laser plume, and is effective for decrease of the substrate temperature for crystallization of anatase phase to as low as around 200 °C.
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81.15.Fg Pulsed laser ablation deposition
68.55.ag Semiconductors
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
81.65.Mq Oxidation
81.40.Gh Other heat and thermomechanical treatments
back to top Chemistry

Pilot-scale cooling tower to evaluate corrosion, scaling, and biofouling control strategies for cooling system makeup water

S. H. Chien, M. K. Hsieh, H. Li, J. Monnell, D. Dzombak, and R. Vidic

Rev. Sci. Instrum. 83, 024101 (2012); doi:10.1063/1.3680563 (10 pages)

Online Publication Date: 6 February 2012

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Pilot-scale cooling towers can be used to evaluate corrosion, scaling, and biofouling control strategies when using particular cooling system makeup water and particular operating conditions. To study the potential for using a number of different impaired waters as makeup water, a pilot-scale system capable of generating 27 000 kJ/h heat load and maintaining recirculating water flow with a Reynolds number of 1.92 × 104 was designed to study these critical processes under conditions that are similar to full-scale systems. The pilot-scale cooling tower was equipped with an automatic makeup water control system, automatic blowdown control system, semi-automatic biocide feeding system, and corrosion, scaling, and biofouling monitoring systems. Observed operational data revealed that the major operating parameters, including temperature change (6.6 °C), cycles of concentration (N = 4.6), water flow velocity (0.66 m/s), and air mass velocity (3660 kg/h m2), were controlled quite well for an extended period of time (up to 2 months). Overall, the performance of the pilot-scale cooling towers using treated municipal wastewater was shown to be suitable to study critical processes (corrosion, scaling, biofouling) and evaluate cooling water management strategies for makeup waters of complex quality.
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07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
82.45.Bb Corrosion and passivation
back to top Gravity; Geophysics; Astronomy and Astrophysics

Active noise cancellation in a suspended interferometer

Jennifer C. Driggers, Matthew Evans, Keenan Pepper, and Rana Adhikari

Rev. Sci. Instrum. 83, 024501 (2012); doi:10.1063/1.3675891 (6 pages)

Online Publication Date: 2 February 2012

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We demonstrate feed-forward vibration isolation on a suspended Fabry-Perot interferometer using Wiener filtering and a variant of the common least mean square adaptive filter algorithm. We compare the experimental results with theoretical estimates of the cancellation efficiency. Using data from the recent Laser Interferometer Gravitational Wave Observatory (LIGO) Science Run, we also estimate the impact of this technique on full scale gravitational wave interferometers. In the future, we expect to use this technique also to remove acoustic, magnetic, and gravitational noise perturbations from the LIGO interferometers. This noise cancellation technique is simple enough to implement in standard laboratory environments and can be used to improve signal-to-noise ratio for a variety of high precision experiments.
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04.30.-w Gravitational waves
07.60.Ly Interferometers
95.55.Ym Gravitational radiation detectors; mass spectrometers; and other instrumentation and techniques
02.70.Rr General statistical methods
back to top Electronics; Electromagnetic Technology; Microwaves

Thermal-structural analysis of electron gun with control grid

Lieming Yao, Kai Zhang, Hailong Yu, Tao Huang, and Bin Li

Rev. Sci. Instrum. 83, 024701 (2012); doi:10.1063/1.3680555 (4 pages)

Online Publication Date: 1 February 2012

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Steady state thermal-structural analysis of electron guns is essential due to the requirement of high reliability in beam performance. Temperatures and displacements for all the components of an electron gun with a control grid are computed. Steady-state thermal analysis has been carried out for various cathode temperatures and various intercepted powers on the control grid to determine the temperature of the control grid. These results are verified experimentally based on measured results from an assembled electron gun. Structural analysis of the electron gun is used to evaluate the deformation of the inner electrodes under the hot condition. The results show that the thermal stress slightly changes the characteristics of the gun. The obtained thermal deformation data can be helpful to modify the design dimensions and assembly of an electron gun.
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84.47.+w Vacuum tubes
81.70.Pg Thermal analysis, differential thermal analysis (DTA), differential thermogravimetric analysis

Performance of a fast digital integrator in on-field magnetic measurements for particle accelerators

P. Arpaia, L. Bottura, L. Fiscarelli, and L. Walckiers

Rev. Sci. Instrum. 83, 024702 (2012); doi:10.1063/1.3673000 (7 pages)

Online Publication Date: 2 February 2012

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The fast digital integrator has been conceived to face most demanding magnet test requirements with a resolution of 10 ppm, a signal-to-noise ratio of 105 dB at 20 kHz, a time resolution of 50 ns, an offset of 10 ppm, and on-line processing. In this paper, the on-field achievements of the fast digital integrator are assessed by a specific measurement campaign at the European Organization for Nuclear Research (CERN). At first, the architecture and the metrological specifications of the instrument are reported. Then, the recent on-field achievements of (i) ±10 ppm of uncertainty in the measurement of the main field for superconducting magnets characterization, (ii) ±0.02 % of field uncertainty in quality assessment of small-aperture permanent magnets, and (iii) ±0.15 % of drift, in an excitation current measurement of 600 s under cryogenic conditions, are presented and discussed.
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29.20.-c Accelerators
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
84.71.Ba Superconducting magnets; magnetic levitation devices
07.55.Ge Magnetometers for magnetic field measurements

Generalized four-point characterization method using capacitive and ohmic contacts

Brian S. Kim, Wang Zhou, Yash D. Shah, Chuanle Zhou, N. Işık, and M. Grayson

Rev. Sci. Instrum. 83, 024703 (2012); doi:10.1063/1.3677331 (11 pages)

Online Publication Date: 2 February 2012

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In this paper, a four-point characterization method is developed for samples that have either capacitive or ohmic contacts. When capacitive contacts are used, capacitive current- and voltage-dividers result in a capacitive scaling factor not present in four-point measurements with only ohmic contacts. From a circuit equivalent of the complete measurement system, one can determine both the measurement frequency band and capacitive scaling factor for various four-point characterization configurations. This technique is first demonstrated with a discrete element four-point test device and then with a capacitively and ohmically contacted Hall bar sample over a wide frequency range (1 Hz–100 kHz) using lock-in measurement techniques. In all the cases, data fit well to a circuit simulation of the entire measurement system, and best results are achieved with large area capacitive contacts and a high input-impedance preamplifier stage. An undesirable asymmetry offset in the measurement signal is described which can arise due to asymmetric voltage contacts.
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84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
84.30.Le Amplifiers

Broadband microwave spectroscopy in Corbino geometry at 3He temperatures

Katrin Steinberg, Marc Scheffler, and Martin Dressel

Rev. Sci. Instrum. 83, 024704 (2012); doi:10.1063/1.3680576 (5 pages)

Online Publication Date: 3 February 2012

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A broadband microwave spectrometer has been constructed to determine the complex conductivity of thin metal films at frequencies from 45 MHz to 20 GHz working in the temperature range from 0.45 K to 2 K (in a 3He cryostat). The setup follows the Corbino approach: a vector network analyzer measures the complex reflection coefficient of a microwave signal hitting the sample as termination of a coaxial transmission line. As the calibration of the setup limits the achievable resolution, we discuss the sources of error hampering different types of calibration. Test measurements of the complex conductivity of a heavy-fermion material demonstrate the applicability of the calibration procedures.
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73.61.At Metal and metallic alloys
78.70.Gq Microwave and radio-frequency interactions
06.20.fb Standards and calibration
06.30.Ka Basic electromagnetic quantities
07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques

An explosively driven high-power microwave pulsed power system

M. A. Elsayed, A. A. Neuber, J. C. Dickens, J. W. Walter, M. Kristiansen, and L. L. Altgilbers

Rev. Sci. Instrum. 83, 024705 (2012); doi:10.1063/1.3681443 (11 pages)

Online Publication Date: 6 February 2012

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The increased popularity of high power microwave systems and the various sources to drive them is the motivation behind the work to be presented. A stand-alone, self-contained explosively driven high power microwave pulsed power system has been designed, built, and tested at Texas Tech University's Center for Pulsed Power and Power Electronics. The system integrates four different sub-units that are composed of a battery driven prime power source utilizing capacitive energy storage, a dual stage helical flux compression generator as the main energy amplification device, an integrated power conditioning system with inductive energy storage including a fast opening electro-explosive switch, and a triode reflex geometry virtual cathode oscillator as the microwave radiating source. This system has displayed a measured electrical source power level of over 5 GW and peak radiated microwaves of about 200 MW. It is contained within a 15 cm diameter housing and measures 2 m in length, giving a housing volume of slightly less than 39 l. The system and its sub-components have been extensively studied, both as integrated and individual units, to further expand on components behavior and operation physics. This report will serve as a detailed design overview of each of the four subcomponents and provide detailed analysis of the overall system performance and benchmarks.
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84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables
84.30.Jc Power electronics; power supply circuits
84.60.Ve Energy storage systems, including capacitor banks
84.32.Dd Connectors, relays, and switches
84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)

Application of length vernier in phase coincidence detection and precision frequency measurement

Miao Miao, Zhou Wei, and Wang Bin

Rev. Sci. Instrum. 83, 024706 (2012); doi:10.1063/1.3678343 (4 pages)

Online Publication Date: 6 February 2012

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For comparison of arbitrary frequency signals, the paper proposed two levels of length vernier based on the time-space relationship are used in three levels of phase coincidence detecting circuits to extract the phase coincidence information by proper logic calculation. The length/phase of each vernier is respectively corresponding to the accuracy and the resolution of detecting circuit. The time-space relationship is based on high-stability, high-accuracy, and high-speed of signal transmission. The method is effective to reduce the fuzzy region in the phase coincidence information and reach a higher measuring precision.
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06.30.Ft Time and frequency
84.30.Qi Modulators and demodulators; discriminators, comparators, mixers, limiters, and compressors
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
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