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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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back to top General Instruments

Quantitative calcium resistivity based method for accurate and scalable water vapor transmission rate measurement

Matthew O. Reese, Arrelaine A. Dameron, and Michael D. Kempe

Rev. Sci. Instrum. 82, 085101 (2011); http://dx.doi.org/10.1063/1.3606644 (10 pages) | Cited 8 times

Online Publication Date: 8 August 2011

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The development of flexible organic light emitting diode displays and flexible thin film photovoltaic devices is dependent on the use of flexible, low-cost, optically transparent and durable barriers to moisture and/or oxygen. It is estimated that this will require high moisture barriers with water vapor transmission rates (WVTR) between 10−4 and 10−6 g/m2/day. Thus there is a need to develop a relatively fast, low-cost, and quantitative method to evaluate such low permeation rates. Here, we demonstrate a method where the resistance changes of patterned Ca films, upon reaction with moisture, enable one to calculate a WVTR between 10 and 10−6 g/m2/day or better. Samples are configured with variable aperture size such that the sensitivity and/or measurement time of the experiment can be controlled. The samples are connected to a data acquisition system by means of individual signal cables permitting samples to be tested under a variety of conditions in multiple environmental chambers. An edge card connector is used to connect samples to the measurement wires enabling easy switching of samples in and out of test. This measurement method can be conducted with as little as 1 h of labor time per sample. Furthermore, multiple samples can be measured in parallel, making this an inexpensive and high volume method for measuring high moisture barriers.
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07.07.Vx Hygrometers; hygrometry

Self-integrating inductive loop for measuring high frequency pulses

Mónica V. Rojas-Moreno, Guillermo Robles, Juan M. Martínez-Tarifa, and Javier Sanz-Feito

Rev. Sci. Instrum. 82, 085102 (2011); http://dx.doi.org/10.1063/1.3622521 (5 pages) | Cited 1 time

Online Publication Date: 10 August 2011

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High frequency pulses can be measured by means of inductive sensors. The main advantage of these sensors consists of non-contact measurements that isolate and protect measuring equipment. The objective of this paper is to present the implementation of an inductive sensor for measuring rapidly varying currents. It consists of a rectangular loop with a resistor at its terminals. The inductive loop gives the derivative of the current according to Faraday's law and the resistor connected to the loop modifies the sensor's frequency response to obtain an output proportional to the current pulse. The self-integrating inductive sensor was validated with two sensors, a non-inductive resistor and a commercial high frequency current transformer. The results were compared to determine the advantages and drawbacks of the probe as an adequate inductive transducer.
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84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
84.30.-r Electronic circuits
84.32.Ff Conductors, resistors (including thermistors, varistors, and photoresistors)

A range-based method to calibrate a magnetic spectrometer measuring the energy spectrum of the backward electron beam of a plasma focus

E. Ceccolini, F. Rocchi, D. Mostacci, M. Sumini, and A. Tartari

Rev. Sci. Instrum. 82, 085103 (2011); http://dx.doi.org/10.1063/1.3622523 (7 pages) | Cited 2 times

Online Publication Date: 12 August 2011

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The electron beam emitted from the back of plasma focus devices is being studied as a radiation source for intraoperative radiation therapy applications. A plasma focus device is being developed for this purpose, and there is a need for characterizing its electron beam, particularly, insofar as the energy spectrum is concerned. The instrument used is a magnetic spectrometer. To calibrate this spectrometer, a procedure relying on the energy-range relation in Mylar® has been devised and applied. By measuring the transmission through increasing thicknesses of the material, electron energies could be assessed and compared to the spectrometer readings. Thus, the original calibration of the instrument has been extended to higher energies and also to better accuracy. Methods and results are presented.
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87.55.-x Treatment strategy
06.20.fb Standards and calibration
52.59.Hq Dense plasma focus

High-speed analog fiber-optic link for electromagnetic interference suppression in infrared power measurement

Fei Liu, Stefanie Strauch, Robert Horton, Russell Evans, and David Hwang

Rev. Sci. Instrum. 82, 085104 (2011); http://dx.doi.org/10.1063/1.3624628 (6 pages)

Online Publication Date: 16 August 2011

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Electromagnetic interference (EMI) is a common problem in a high-power pulsed infrared laser measurement. In order to eliminate susceptibility to radiated EMI, we developed, tested and implemented an infrared power measurement system using a high-speed analog fiber-optic link. Key components are commercially available parts designed for high-speed digital data transmission, but can be operated in analog mode. We successfully utilized the system for time-resolved measurements of high-power transversely-excited atmospheric-pressure CO2 lasers in amplifier and oscillator configurations. This paper presents experimental setup, testing results, and the details of the laser power measurements results.
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42.79.Sz Optical communication systems, multiplexers, and demultiplexers
07.50.Hp Electrical noise and shielding equipment

A novel smooth impact drive mechanism actuation method with dual-slider for a compact zoom lens system

Jonghyun Lee, Won Sik Kwon, Kyung-Soo Kim, and Soohyun Kim

Rev. Sci. Instrum. 82, 085105 (2011); http://dx.doi.org/10.1063/1.3624701 (8 pages) | Cited 2 times

Online Publication Date: 17 August 2011

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multimedia

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In this paper, a novel actuation method for a smooth impact drive mechanism that positions dual-slider by a single piezo-element is introduced and applied to a compact zoom lens system. A mode chart that determines the state of the slider at the expansion or shrinkage periods of the piezo-element is presented, and the design guide of a driving input profile is proposed. The motion of dual-slider holding lenses is analyzed at each mode, and proper modes for zoom functions are selected for the purpose of positioning two lenses. Because the proposed actuation method allows independent movement of two lenses by a single piezo-element, the zoom lens system can be designed to be compact. For a feasibility test, a lens system composed of an afocal zoom system and a focusing lens was developed, and the passive auto-focus method was implemented.
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07.68.+m Photography, photographic instruments; xerography
42.15.Eq Optical system design
42.79.Bh Lenses, prisms and mirrors
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

One hundred anode microchannel plate ion detector

Yi He, John F. Poehlman, Andrew W. Alexander, Kirk Boraas, and James P. Reilly

Rev. Sci. Instrum. 82, 085106 (2011); http://dx.doi.org/10.1063/1.3622506 (6 pages) | Cited 1 time

Online Publication Date: 22 August 2011

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A one-hundred-anode microchannel plate detector is constructed on a 10 cm × 15 cm printed circuit board and attached to a homebuilt matrix assisted laser desorption ionization (MALDI) time-of-flight mass spectrometer. Ringing and cross talk between anodes have been successfully eliminated and preliminary mass spectra of peptide ions recorded. With one hundred anodes on the printed circuit board, spatial information about the ion beam can also be readily determined with this detector. During operation, the detector anode assembly loses sensitivity after ions strike it for a considerable period of time due to charging of the non-conductive regions between anodes. However, this effect can be minimized by deflecting matrix ions away from the detector.
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87.80.Dj Spectroscopies
42.79.Ls Scanners, image intensifiers, and image converters
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
85.60.Ha Photomultipliers; phototubes and photocathodes
87.64.-t Spectroscopic and microscopic techniques in biophysics and medical physics

Experimental study of a semi-passive ventilation grille with a feedback control system

A. D’Orazio, L. Fontana, and F. Salata

Rev. Sci. Instrum. 82, 085107 (2011); http://dx.doi.org/10.1063/1.3626793 (7 pages)

Online Publication Date: 23 August 2011

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The diffusion of window frames with low air permeability, due to the energy saving regulations, has implied in several cases the worsening of the indoor microclimate and air quality. On the other hand, air-tight window frames imply uncontrolled and too high air change rates. The mechanical ventilation not always is a practicable solution because of economic reasons and because it implies energy waste. Various Italian and European environmental and energetic laws take into consideration and promote the use of controlled natural ventilation, though this definition is not associated to well defined and tested technical solutions. An adequate solution can be achieved by using semi-passive self adjustable ventilation devices, able to ensure controlled changes of indoor air. In this paper, a semi-passive damper with a feedback control system is proposed and its behavior is investigated by means of experimental study. The presented semi-passive grille allows to control the air flow rate, injected into the room by natural or artificial pressure gradient, more effectively than the usual passive ventilation grilles made available by the present industrial production. However, since the semi-passive grille has a one-way flow, in the natural ventilation of a flat the proper functioning of the system could be ensured with a more complex configuration, with respect to the passive self-regulating grilles, able to limit the flow of fresh air in the presence of high levels of Δp; conversely, it could have widespread use in applications requiring a more accurate control of airflow in case of mechanical ventilation plants.
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88.05.Sv Energy use in heating and cooling of residential and commercial buildings
88.10.cn Heating and cooling of buildings; space heating

The new cold neutron chopper spectrometer at the Spallation Neutron Source: Design and performance

G. Ehlers, A. A. Podlesnyak, J. L. Niedziela, E. B. Iverson, and P. E. Sokol

Rev. Sci. Instrum. 82, 085108 (2011); http://dx.doi.org/10.1063/1.3626935 (6 pages) | Cited 17 times

Online Publication Date: 23 August 2011

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The design and performance of the new cold neutron chopper spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge are described. CNCS is a direct-geometry inelastic time-of-flight spectrometer, designed essentially to cover the same energy and momentum transfer ranges as IN5 at ILL, LET at ISIS, DCS at NIST, TOFTOF at FRM-II, AMATERAS at J-PARC, PHAROS at LANSCE, and NEAT at HZB, at similar energy resolution. Measured values of key figures such as neutron flux at sample position and energy resolution are compared between measurements and ray tracing Monte Carlo simulations, and good agreement (better than 20% of absolute numbers) has been achieved. The instrument performs very well in the cold and thermal neutron energy ranges, and promises to become a workhorse for the neutron scattering community for quasielastic and inelastic scattering experiments.
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29.30.Hs Neutron spectroscopy
29.25.Dz Neutron sources

A time-of-flight backscattering spectrometer at the Spallation Neutron Source, BASIS

E. Mamontov and K. W. Herwig

Rev. Sci. Instrum. 82, 085109 (2011); http://dx.doi.org/10.1063/1.3626214 (10 pages) | Cited 28 times

Online Publication Date: 25 August 2011

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We describe the design and current performance of the backscattering silicon spectrometer (BASIS), a time-of-flight backscattering spectrometer built at the spallation neutron source (SNS) of the Oak Ridge National Laboratory (ORNL). BASIS is the first silicon-based backscattering spectrometer installed at a spallation neutron source. In addition to high intensity, it offers a high-energy resolution of about 3.5 μeV and a large and variable energy transfer range. These ensure an excellent overlap with the dynamic ranges accessible at other inelastic spectrometers at the SNS.
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07.75.+h Mass spectrometers
29.25.Dz Neutron sources

Thermoelectric temperature control device for vapor pressure measurements

Robert F. Berg

Rev. Sci. Instrum. 82, 085110 (2011); http://dx.doi.org/10.1063/1.3628668 (6 pages) | Cited 2 times

Online Publication Date: 31 August 2011

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The static method of measuring equilibrium vapor pressure requires locating the sample at the coldest part of the apparatus to avoid errors due to evaporation and recondensation elsewhere. This paper describes a device that can hold the sample 1 K below the temperature of the surrounding air without a liquid bath. It comprises a pair of thermoelectric elements and two thermometers attached to an insulated aluminum block. The device can operate as high as 200 °C while controlling the sample with a precision of 0.02 K; below 110 °C, the precision is 2 mK. Also described is a method to measure the small temperature offset due to heat flow between the sample and the surrounding aluminum block. The uncertainty due to the offset is small compared to the 6 mK uncertainty due to the thermometer.
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85.80.Fi Thermoelectric devices
07.20.Dt Thermometers
06.30.-k Measurements common to several branches of physics and astronomy
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