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Jun 2000

Volume 71, Issue 6, pp. 2263-2611

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back to top MICROSCOPY and IMAGING

Infrared imaging of defects heated by a sonic pulse

L. D. Favro, Xiaoyan Han, Zhong Ouyang, Gang Sun, Hua Sui, and R. L. Thomas

Rev. Sci. Instrum. 71, 2418 (2000); http://dx.doi.org/10.1063/1.1150630 (4 pages) | Cited 40 times

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High-frequency pulsed sonic excitation is combined with an infrared camera to image surface and subsurface defects. Irreversible temperature increases on the surface of the object, resulting from localized heating in the vicinity of cracks, disbonds, or delaminations, are imaged as a function of time prior to, during, and following the application of a short pulse of sound. Pulse durations of 50 ms are sufficient to image such defects, and result in surface temperatures variations of ∼2 °C above the defect. As an example, sonic infrared images are presented for two fatigue cracks in Al and of interply delamination impact damage in a graphite–fiber-reinforced polymer composite. The shorter of the two fatigue cracks is ∼0.7 mm in length, and is tightly closed. Thus, this new technique is sensitive, and capable of rapid imaging of defects under wide surface areas of an object. © 2000 American Institute of Physics.
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81.70.Fy Nondestructive testing: optical methods
42.79.Pw Imaging detectors and sensors
43.35.Ty Other physical effects of sound
back to top CONDENSED MATTER; MATERIALS

An experimental station for advanced research on condensed matter under extreme conditions at the European Synchrotron Radiation Facility - BM29 beamline

Adriano Filipponi, Michael Borowski, Daniel T. Bowron, Stuart Ansell, Andrea Di Cicco, Simone De Panfilis, and Jean-Paul Itiè

Rev. Sci. Instrum. 71, 2422 (2000); http://dx.doi.org/10.1063/1.1150631 (11 pages) | Cited 82 times

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We describe state-of-the-art experimental techniques using the beamline BM29 of the European Synchrotron Radiation Facility (ESRF). This station exploits the unique characteristics of an ESRF bending magnet source to provide a tunable, collimated, x-ray beam to perform high quality x-ray absorption spectroscopy within the energy range of E = 5–75 keV using Si(111), Si(311), and Si(511) crystal pairs. Energy scans can be performed over this wide energy range with excellent reproducibility, stability and resolution, usually better than ΔE/E ≃ 5×10−5. The experimental setup has been exploited to study condensed matter under extreme conditions. We describe here two sample environment devices; the L’ Aquila–Camerino oven for high-temperature studies up to 3000 K in high vacuum and the Paris–Edinburgh press suitable for high-pressure high-temperature studies in the range 0.1–7 GPa and temperatures up to 1500 K. These devices can be integrated in an experimental setup which combines various control and detection systems suitable to perform x-ray absorption spectroscopy, x-ray absorption temperature scans, and energy scanning x-ray diffraction (ESXD). The ESXD setup is based on a scintillator detector behind a fixed angle collimator aligned to the sample. The combination of these three measurements, which can be performed in rapid sequence on the sample during the experiment, provides an essential tool for structural investigations and in situ sample characterization. © 2000 American Institute of Physics.
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07.85.Qe Synchrotron radiation instrumentation
07.85.Nc X-ray and γ-ray spectrometers
29.30.Kv X- and γ-ray spectroscopy
61.05.cj X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.

Precise and direct determination of the elastic constants of a cylinder with a length equal to its diameter

F. J. Nieves, F. Gascón, and A. Bayón

Rev. Sci. Instrum. 71, 2433 (2000); http://dx.doi.org/10.1063/1.1150632 (7 pages) | Cited 1 time

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A cylinder made of a homogeneous isotropic material and with a length equal to its diameter is excited by axial percussion. Its axial displacement is detected by speckle interferometry. The two lowest frequencies, the first symmetric mode and first antisymmetric mode, are compared with the corresponding nondimensional natural frequencies, calculated to six significant figures using the Ritz method for 51 values of Poisson’s ratio. The values of both dynamic elastic constants (shear modulus and Poisson’s ratio) are found based on the quotient of the measured frequencies by using a table that is given. The method requires only one experiment and a simple calculator. The origin of the uncertainties is analyzed to improve the method’s precision. The systematic uncertainty of the results shows relative values of 0.23% for shear modulus and 0.59% for Poisson’s ratio. The values of the elastic constants calculated for a stainless steel test piece are compared with the values obtained by other methods. © 2000 American Institute of Physics.
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81.70.Bt Mechanical testing, impact tests, static and dynamic loads
46.80.+j Measurement methods and techniques in continuum mechanics of solids
07.60.Ly Interferometers
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy

Lock-in common-mode rejection demodulation: Measurement technique and applications to thermal-wave detection: Theoretical

Andreas Mandelis, Stefano Paoloni, and Lena Nicolaides

Rev. Sci. Instrum. 71, 2440 (2000); http://dx.doi.org/10.1063/1.1150633 (5 pages) | Cited 11 times

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The ability of conventional single-ended photothermal techniques to detect weak inhomogeneities in a given material is mainly limited by two instrumental factors: the signal-to-noise ratio (SNR) and the amplitude dynamic range. The amplitude level is limited by the output signal baseline, and may be too high to monitor relatively small variations introduced by the presence of weak inhomogeneities. The purpose of this work is to introduce a novel photothermal signal generation methodology, the principle of which can be broadly applied to any technique utilizing a lock-in analyzer demodulation scheme of periodic signal wave forms. Unlike the conventional single-ended periodic excitation wave form, which uses a 50% duty-cycle square wave or sinusoidal modulation of the pump laser heating beam, a more complicated periodic modulation wave form is employed, resulting in the equivalent of differential-signal demodulation. The new wave form takes advantage of the real-time differential action performed by the lock-in amplifier weighing function over the two half periods of the modulated signal. This results in enhanced signal dynamic range due to the efficient suppression of the baseline and a substantial improvement in the SNR. The main features of this technique are investigated with a theoretical model for an arbitrary repetitive signal wave form and, in particular, for a photothermal signal. The dependence of the signal on the wave form parameters is also discussed. © 2000 American Institute of Physics.
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07.20.-n Thermal instruments and apparatus
84.40.Ua Telecommunications: signal transmission and processing; communication satellites
81.70.Fy Nondestructive testing: optical methods
84.30.Ng Oscillators, pulse generators, and function generators

Lock-in common-mode rejection demodulation: Measurement technique and applications to thermal-wave detection. Experimental

Stefano Paoloni, Lena Nicolaides, and Andreas Mandelis

Rev. Sci. Instrum. 71, 2445 (2000); http://dx.doi.org/10.1063/1.1150634 (7 pages) | Cited 9 times

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A new signal generation methodology based on lock-in amplifier common mode rejection demodulation for materials nondestructive evaluation has been implemented experimentally with thermal waves in a photothermal radiometric apparatus. A procedure to calibrate the experiment is described in order to take into account instrumental time delay phase shifts between the reference and the optical excitation wave form. Some preliminary results obtained on Zr–2.5Nb shot peened samples are presented and compared to those obtained by temporally modulating the pump intensity as a 50% duty cycle square wave. The comparison shows the new measurement methodology to be a very promising technique for nondestructive evaluation and depth profiling applications, featuring high detectivity for low-dynamic-range and poor-signal to noise ratio signals, such as those obtained with thermal-wave diagnostics. © 2000 American Institute of Physics.
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07.20.-n Thermal instruments and apparatus
84.40.Ua Telecommunications: signal transmission and processing; communication satellites
81.70.Fy Nondestructive testing: optical methods
84.30.Ng Oscillators, pulse generators, and function generators

Parameter estimations for measurements of thermal transport properties with the hot disk thermal constants analyzer

Vlastimil Bohac, Mattias K. Gustavsson, Ludovit Kubicar, and Silas E. Gustafsson

Rev. Sci. Instrum. 71, 2452 (2000); http://dx.doi.org/10.1063/1.1150635 (4 pages) | Cited 24 times

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The objective of this work is to improve measurements of transport properties using the hot disk thermal constants analyzer. The principle of this method is based on the transient heating of a plane double spiral sandwiched between two pieces of the investigated material. From the temperature increase of the heat source, it is possible to derive both the thermal conductivity and the thermal diffusivity from one single transient recording, provided the total time of the measurement is chosen within a correct time window defined by the theory and the experimental situation. Based on a theory of sensitivity coefficients, it is demonstrated how the experimental time window should be selected under different experimental situations. In addition to the theoretical work, measurements on two different materials: poly(methylmethacrylate) and Stainless Steel A 310, with thermal conductivity of 0.2 and 14 W/mK, respectively, have been performed and analyzed based on the developed theory. © 2000 American Institute of Physics.
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07.20.Dt Thermometers
07.20.Hy Furnaces; heaters

Extended frequency range dielectric measurements of thin films

Frederick I. Mopsik

Rev. Sci. Instrum. 71, 2456 (2000); http://dx.doi.org/10.1063/1.1150663 (5 pages) | Cited 1 time

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A method is described to measure the dielectric constant and loss of thin films. It employs a sample holder based on precision 50 Ω air line and can be used from audio frequencies to 1 GHz with a single sample. It is shown to maximize the precision available from commercial instrumentation with minimal data correction. This is confirmed by regions in which the different instruments overlap their frequency coverage.
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84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
07.68.+m Photography, photographic instruments; xerography
77.55.-g Dielectric thin films

Versatile device for low temperature in situ generation of forces up to 25 kN: Application to hydrostatic pressure experiments

B. Salce, J. Thomasson, A. Demuer, J. J. Blanchard, J. M. Martinod, L. Devoille, and A. Guillaume

Rev. Sci. Instrum. 71, 2461 (2000); http://dx.doi.org/10.1063/1.1150664 (6 pages) | Cited 19 times

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We describe a versatile modular device built to generate forces up to 25 kN at cryogenic temperatures in order to achieve very fine in situ hydrostatic pressure tuning in the range 0–21 GPa. This device was designed to save time during measurements and protect the experimental setup by avoiding warming and cooling cycles to vary the pressure. The force is generated by a bellow operated with pressurized 4He and amplified mechanically. Diamond and sapphire anvil cells are used to perform electrical resistivity, magnetic susceptibility, and specific heat measurements under highly hydrostatic conditions by using helium as the transmitting medium. The pressure is determined by the ruby fluorescence technique. The performance of the device is illustrated by measurements of the superconducting transition of Pb and the magnetic transitions of CeRu2Ge2 in the range 0–10 GPa. This device is currently being adapted in a dilution fridge in order to be operated down to 50 mK. © 2000 American Institute of Physics.
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07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

Optical flow-through high pressure cell for light scattering investigations

Thorleif Berger and Werner Steffen

Rev. Sci. Instrum. 71, 2467 (2000); http://dx.doi.org/10.1063/1.1150636 (4 pages) | Cited 2 times

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An optical flow-through/stop-flow high pressure cell has been constructed for static and dynamic light scattering investigations. The cell is especially designed for investigations in supercritical fluids. Angular dependence of scattered light intensity can be measured in principle stepwise between 0° and 360°. Fused quartz as window material allows polarized as well as depolarized measurements to study relaxation functions due to translational or rotational motions. The temperature range 25–100 °C and the pressure range of up to 60 MPa make this cell well suited for studies of polymeric materials in supercritical solvents. Dynamic light scattering results of a solution of polydimethylsiloxane in sc-CO2 at a pressure of 40 MPa are presented to show the capabilities of the apparatus. © 2000 American Institute of Physics.
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07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
42.79.Ci Filters, zone plates, and polarizers
07.60.-j Optical instruments and equipment

High pressure reaction cell and transfer mechanism for ultrahigh vacuum spectroscopic chambers

A. E. Nelson and K. H. Schulz

Rev. Sci. Instrum. 71, 2471 (2000); http://dx.doi.org/10.1063/1.1150637 (5 pages) | Cited 2 times

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A novel high pressure reaction cell and sample transfer mechanism for ultrahigh vacuum (UHV) spectroscopic chambers is described. The design employs a unique modification of a commercial load-lock transfer system to emulate a tractable microreactor. The reaction cell has an operating pressure range of <1×10−4 to 1000 Torr and can be evacuated to UHV conditions to enable sample transfer into the spectroscopic chamber. Additionally, a newly designed sample holder equipped with electrical and thermocouple contacts is described. The sample holder is capable of resistive specimen heating to 400 and 800 °C with current requirements of 14 A (2 V) and 25 A (3.5 V), respectively. The design enables thorough material science characterization of catalytic reactions and the surface chemistry of catalytic materials without exposing the specimen to atmospheric contaminants. The system is constructed primarily from readily available commercial equipment allowing its rapid implementation into existing laboratories. © 2000 American Institute of Physics.
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82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
07.81.+a Electron and ion spectrometers
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
06.60.Ei Sample preparation (including design of sample holders)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

A method and device for measurement of a sedimentation constant of magnetorheological fluids

S. R. Gorodkin, W. I. Kordonski, E. V. Medvedeva, Z. A. Novikova, A. B. Shorey, and S. D. Jacobs

Rev. Sci. Instrum. 71, 2476 (2000); http://dx.doi.org/10.1063/1.1150638 (5 pages) | Cited 9 times

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An original procedure and device used for the estimation of a sedimentation constant of magnetorheological fluids have been developed. Experiments that vary the volume concentration and particle size of the dispersed phase, as well as the viscosity of the dispersion medium, show the flexibility of the proposed procedure. A procedure for using this device to estimate the yield stress of these fluids is also described. The results given by our device are shown to be in good agreement with flow curves generated by a commercial rheometer. © 2000 American Institute of Physics.
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83.85.Cg Rheological measurements—rheometry
83.80.Gv Electro- and magnetorheological fluids
82.70.Kj Emulsions and suspensions
47.80.-v Instrumentation and measurement methods in fluid dynamics

Measuring the surface tension of a liquid–gas interface by automatic stalagmometer

C. Molina, L. Victoria, and A. Arenas

Rev. Sci. Instrum. 71, 2481 (2000); http://dx.doi.org/10.1063/1.1150639 (6 pages) | Cited 1 time

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We present a variation of the stalagmometer method for automatically determining the surface tension of a liquid–gas interface using a pressure sensor to measure the pressure variation per drop. The presented method does not depend on a knowledge of the density of the problem liquid and obtains values with a measurement error in the range of 1%–2%. Its low cost and simplicity mean that the technique can be used in the teaching and instrumentation laboratory in the same way as other methods. © 2000 American Institute of Physics.
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68.03.Cd Surface tension and related phenomena
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.07.Tw Servo and control equipment; robots

Viscosity measurements based on experimental investigations of composite cantilever beam eigenfrequencies in viscous media

Christian Bergaud and Liviu Nicu

Rev. Sci. Instrum. 71, 2487 (2000); http://dx.doi.org/10.1063/1.1150640 (5 pages) | Cited 36 times

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Experimental investigations have been conducted to study the multimode dynamic response of composite cantilever beams in various viscous media and to determine their viscosity. Theoretical eigenfrequencies are computed using the analytical model proposed by Sader [J. Appl. Phys. 84, 64 (1998)] based on the analysis of the hydrodynamic function of cantilever beams. A good agreement is found between theory and experiment for the first two resonant frequencies of composite beams operated in air and in water. The same experimental approach is used to determine the viscosity of ultrapure ethanol. Thus, it is established that Sader’s model represents an accurate alternative for the determination of liquid viscosity in small volumes (about 50 μl) which might be of great importance for microfluidics applications. Finally, the limits of the method are underlined by monitoring the dynamic response of cantilever beams in silicon oil. © 2000 American Institute of Physics.
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47.80.-v Instrumentation and measurement methods in fluid dynamics
07.79.Lh Atomic force microscopes
back to top CHEMISTRY

Simultaneous measurement method of both shock state and stress profile in polymers in 1 GPa stress

Yasuhito Mori, Kota Hidaka, and Kunihito Nagayama

Rev. Sci. Instrum. 71, 2492 (2000); http://dx.doi.org/10.1063/1.1150641 (5 pages) | Cited 5 times

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A new procedure of recording both Hugoniot parameters and stress profile is proposed to study shock characteristics of polymers in 1 GPa stress region. The assembly consists of an in-material polyvinylidene fluoride (PVDF) stress gauge element and an optical prism pin. The PVDF gauge records the shock wave stress profile, while the prism pin records the arrival of shock front at the free surface of the target. Argon laser beam is focused onto the bottom face of the prism pin placed on the free surface so as to satisfy the condition of total internal reflection. Shock velocity can be estimated from the time difference of two signals, the PVDF gauge and the prism pin. The Hugoniot state can be calculated by the shock velocity and the projectile velocity regardless of the stress profile obtained by the PVDF gauge. A typical result for polytetrafluoroethylene (PTFE) specimen is shown with the impact velocity of PTFE flyer of 295 m/s. The obtained Hugoniot point coincides very well with the published data. Precision of the method was examined in detail, and estimated to be better than 2%. © 2000 American Institute of Physics.
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62.50.-p High-pressure effects in solids and liquids
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
64.30.-t Equations of state of specific substances
07.10.-h Mechanical instruments and equipment

Polymer microparticle arrays from electrodynamically focused microdroplet streams

K. C. Ng, J. V. Ford, S. C. Jacobson, J. M. Ramsey, and M. D. Barnes

Rev. Sci. Instrum. 71, 2497 (2000); http://dx.doi.org/10.1063/1.1150642 (3 pages) | Cited 4 times

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We describe instrumentation for forming two-dimensional arrays of polymer microparticles produced from electrodynamically focused microdroplet streams. A single-stage linear quadrupole was used to focus droplets/particles onto silanated glass slides mounted on a computer-driven two-dimensional translation stage. Center-to-center position stability was on the order of 1 μm. Applications to molecular sorting with polymer particles as host carriers are discussed. © 2000 American Institute of Physics.
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07.90.+c Other topics in instruments, apparatus, and components common to several branches of physics and astronomy (restricted to new topics in section 07)
47.55.D- Drops and bubbles
81.90.+c Other topics in materials science (restricted to new topics in section 81)
06.60.Sx Positioning and alignment; manipulating, remote handling
47.55.Kf Particle-laden flows
back to top BIOLOGY and MEDICINE

Broad bandwidth frequency domain instrument for quantitative tissue optical spectroscopy

Tuan H. Pham, Olivier Coquoz, Joshua B. Fishkin, Eric Anderson, and Bruce J. Tromberg

Rev. Sci. Instrum. 71, 2500 (2000); http://dx.doi.org/10.1063/1.1150665 (14 pages) | Cited 85 times

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Near-infrared (NIR) optical properties of turbid media, e.g., tissue, can be accurately quantified noninvasively using methods based on diffuse reflectance or transmittance, such as frequency domain photon migration (FDPM). Factors which govern the accuracy and sensitivity of FDPM-measured optical properties include instrument performance, the light propagation model, and fitting algorithms used to calculate optical properties from measured data. In this article, we characterize instrument, model, and fitting uncertaintics of an FDPM system designed for clinical use and investigate how each of these factors affects the quantification of NIR absorption (μa) and reduced scattering (μs′) parameters in tissue phantoms. The instrument is based on a 500 MHz, multiwavelength platform that sweeps through 201 discrete frequencies in as little as 675 ms. Phase and amplitude of intensity modulated light launched into tissue, i.e., diffuse photon density waves (PDW), are measured with an accuracy of ±0.30° and ±3.5%, while phase and amplitude precision are ±0.025° and ±0.20%, respectively. At this level of instrument uncertainty, simultaneous fitting of frequency-dependent phase and amplitude nonlinear model functions derived from a photon diffusion approximation provides an accurate and robust strategy for determining optical properties from FDPM data, especially for media with high absorption. In an optical property range that is characteristic of most human tissues in the NIR (5×10−3<μa<5×10−2 mm−1, 0.5<μs′<2 mm−1), we theoretically and experimentally demonstrate that the multifrequency, simultaneous-fit approach allows μa and μs′ to be quantified with an accuracy of ±5% and ±3%, respectively. Although exceptionally high levels of precision can be obtained using this approach (<1% of the estimated absorption and scattering values), we show that the absolute accuracy of optical property measurements is highly dependent on specific factors associated with instrument performance, model function relevance, and details of the fitting strategy used to calculate μa and μs′. © 2000 American Institute of Physics.
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87.64.K- Spectroscopy
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques

Design and characterization of a research electrohydraulic lithotripter patterned after the Dornier HM3

Robin O. Cleveland, Michael R. Bailey, Naomi Fineberg, Bruce Hartenbaum, Murtuza Lokhandwalla, James A. McAteer, and Bradford Sturtevant

Rev. Sci. Instrum. 71, 2514 (2000); http://dx.doi.org/10.1063/1.1150643 (12 pages) | Cited 52 times

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An electrohydraulic lithotripter has been designed that mimics the behavior of the Dornier HM3 extracorporeal shock wave lithotripter. The key mechanical and electrical properties of a clinical HM3 were measured and a design implemented to replicate these parameters. Three research lithotripters have been constructed on this design and are being used in a multi-institutional, multidisciplinary research program to determine the physical mechanisms of stone fragmentation and tissue damage in shock wave lithotripsy. The acoustic fields of the three research lithotripters and of two clinical Dornier HM3 lithotripters were measured with a PVDF membrane hydrophone. The peak positive pressure, peak negative pressure, pulse duration, and shock rise time of the focal waveforms were compared. Peak positive pressures varied from 25 MPa at a voltage setting of 12 kV to 40 MPa at 24 kV. The magnitude of the peak negative pressure varied from −7 to −12 MPa over the same voltage range. The spatial variations of the peak positive pressure and peak negative pressure were also compared. The focal region, as defined by the full width half maximum of the peak positive pressure, was 60 mm long in the axial direction and 10 mm wide in the lateral direction. The performance of the research lithotripters was found to be consistent at clinical firing rates (up to 3 Hz). The results indicated that pressure fields in the research lithotripters are equivalent to those generated by a clinical HM3 lithotripter. © 2000 American Institute of Physics.
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87.50.-a Effects of electromagnetic and acoustic fields on biological systems
87.56.B- Radiation sources
43.80.Vj Acoustical medical instrumentation and measurement techniques

Microtensile device for stress: Elongation tests on nonstandard specimens

F. P. Branca and F. Marinozzi

Rev. Sci. Instrum. 71, 2526 (2000); http://dx.doi.org/10.1063/1.1150644 (6 pages) | Cited 4 times

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Show Abstract
A microtensile device (MTD) especially designed to carry out test on nonstandard specimens such as thin wires, polymers, and biological samples is described. The use of a feedback control system in order to apply the load and simultaneously assure axial deformations allows for measurement with great accuracy even on specimens of only a few millimeters. Within the device, a laser interferometer gives high-resolution elongation measurements. The prototype allows for the evaluation of specimen stiffness, defined as the ratio of the applied load versus the specimen axial deformation. This measurement can be performed with an accuracy better than 1.5%, depending on the accuracy class of the load cell and its positioning in the MTD body, while the elongation measurement is affected by a systematic error of 0.1 μm/N proportional to the applied load. In order to compare the obtained results to commonly available data, some tests have been performed on specimens of well-known mechanical characteristics, such as optical fibers. A typical optical fiber Young modulus evaluation was (67±1.5) GPa. Other tests have been carried out on nonconventional (biological) specimens with the aim of demonstrating the MTD specific application field. © 2000 American Institute of Physics.
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81.70.Bt Mechanical testing, impact tests, static and dynamic loads
07.60.Ly Interferometers
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
07.10.Pz Instruments for strain, force, and torque
06.60.Sx Positioning and alignment; manipulating, remote handling

Imaging ferromagnetic tracers with an ac biosusceptometer

M. Moreira, L. O. Murta, and O. Baffa

Rev. Sci. Instrum. 71, 2532 (2000); http://dx.doi.org/10.1063/1.1150666 (7 pages) | Cited 5 times

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The aim of this work was to study the feasibility of obtaining images of the distribution of ferromagnetic tracers using an ac biosusceptometer (ACB). The images were generated by mapping the response of the ACB at short distances due to the presence of a ferrite powder dispersed in a planar gel matrix with different shapes. The ACB was scanned over the sample and the voltages generated by the variation in ferrite concentration were sampled. Methods to render and image the distribution of ferromagnetic particles were studied. The generalized Wiener parametric method gave the best results. The system has a potential to be used in functional images of the gastrointestinal tract where a moderate resolution is required. We conclude that this biomagnetic method can be successfully used to generate planar functional images of magnetic particles in the near field. © 2000 American Institute of Physics.
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87.63.-d Non-ionizing radiation equipment and techniques
87.57.N- Image analysis
07.55.Jg Magnetometers for susceptibility, magnetic moment, and magnetization measurements
back to top GRAVITY; GEOPHYSICS; ASTRONOMY and ASTROPHYSICS

GEO 600 triple pendulum suspension system: Seismic isolation and control

M. V. Plissi, C. I. Torrie, M. E. Husman, N. A. Robertson, K. A. Strain, H. Ward, H. Lück, and J. Hough

Rev. Sci. Instrum. 71, 2539 (2000); http://dx.doi.org/10.1063/1.1150645 (7 pages) | Cited 42 times

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In this article we describe aspects of the suspension system for each of the main optics (test masses) in the GEO 600 interferometric gravitational wave detector currently under construction in Germany. In particular we describe the triple pendulum, which is a key aspect of the overall system, discuss the details of the mechanical design, present transfer functions of the isolation performance, and display examples of impulse responses for the local control used to damp the low frequency modes of the triple pendulum. This local control is achieved using co-located sensing and feedback at the highest mass of the triple pendulum, providing a significant attenuation of local control noise to the fused silica test mass, the lowest mass of the triple pendulum. In order to enhance the vertical isolation, the triple pendulum will incorporate two stages of cantilever springs, and fused silica fibers will be used in the lowest pendulum stage in order to minimize thermal noise from the pendulum modes. It is expected that the thermal noise associated with the internal modes of the fused silica test mass (mass ∼ 6 kg) will set the sensitivity limit for GEO 600 from 50 to ∼ 200 Hz. The measured performance from individual stages of the prototype suspension system indicates that a seismic noise level which is a factor ∼3 lower than this thermal noise level at 50 Hz can be achieved. © 2000 American Institute of Physics.
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95.55.Ym Gravitational radiation detectors; mass spectrometers; and other instrumentation and techniques
04.80.Nn Gravitational wave detectors and experiments
07.60.Ly Interferometers
07.10.Fq Vibration isolation
45.80.+r Control of mechanical systems

Modeling of multistage pendulums: Triple pendulum suspension for GEO 600

M. E. Husman, C. I. Torrie, M. V. Plissi, N. A. Robertson, K. A. Strain, and J. Hough

Rev. Sci. Instrum. 71, 2546 (2000); http://dx.doi.org/10.1063/1.1150646 (6 pages) | Cited 5 times

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Extensive dynamic six degree-of-freedom modeling of a multiple pendulum suspension has been developed for application to the design and analysis of the planned suspensions for the main mirrors in GEO 600, the German/United Kingdom gravitational wave detector. Two models were developed independently, and results from both were compared with the experiment to verify their applicability. The models have been applied to investigate the optimization of parameters for achieving the desired modal behavior. In addition, the levels of cross coupling between degrees of freedom due to mechanical misalignments have been investigated and shown to be within acceptable limits. © 2000 American Institute of Physics.
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04.80.Nn Gravitational wave detectors and experiments

Vibration isolation support system for a truncated icosahedral gravitational wave antenna

W. F. Velloso, J. L. Melo, and O. D. Aguiar

Rev. Sci. Instrum. 71, 2552 (2000); http://dx.doi.org/10.1063/1.1150647 (8 pages) | Cited 5 times

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We designed a mechanical isolation system for an icosahedral resonant gravitational wave detector we plan to construct in Brazil. We have used the NASTRAN finite element software to perform the numerical analysis. Our results show that the designed system could allow a damping factor better than −200 dB in the spectral range of interest, which is adequate to the sensibility level we want for the antenna. © 2000 American Institute of Physics.
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04.80.Nn Gravitational wave detectors and experiments
95.55.Ym Gravitational radiation detectors; mass spectrometers; and other instrumentation and techniques
07.10.Fq Vibration isolation
45.80.+r Control of mechanical systems
back to top ELECTRONICS; ELECTROMAGNETIC TECHNOLOGY; MICROWAVES

A pulser for medium-frequency modulated direct-current reactive sputter deposition of insulators

G. T. Kiehne, M. Z. Lin, G. Wang, W. H. Xiang, H. Cao, and J. B. Ketterson

Rev. Sci. Instrum. 71, 2560 (2000); http://dx.doi.org/10.1063/1.1150648 (3 pages)

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We present the circuit design of a unit for medium-frequency modulated direct-current (dc) reactive sputter deposition of electrical insulators. The unit is connected in series between a commercial dc sputtering power supply and a sputtering cathode (target). It modulates the voltage applied to the sputtering cathode in a pulsed, asymmetric bipolar fashion. The pulsing effectively eliminates the problem of arcing at the target surface. The simple circuit is a low-cost, flexible alternative to commercially available units. To demonstrate its utility, we deposited a film of 5 SiO2/TiO2 bilayers, forming a highly reflective dielectric optical mirror with a stop band centered near a wavelength in air of 600 nm. © 2000 American Institute of Physics.
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81.15.Cd Deposition by sputtering
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables

A continuous motional series resonant frequency monitoring circuit and a new method of determining Butterworth–Van Dyke parameters of a quartz crystal microbalance in fluid media

A. Arnau, T. Sogorb, and Y. Jiménez

Rev. Sci. Instrum. 71, 2563 (2000); http://dx.doi.org/10.1063/1.1150649 (9 pages) | Cited 6 times

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A new electronic design for continuous monitoring of the motional series resonant frequency of a quartz crystal microbalance either in vacuum or in single-face contact with a fluid medium is presented. The motional resistance is directly measured and a simple method for measuring L and C parameters of the Butterworth–Van Dyke equivalent circuit is described. The results are in agreement with impedance analyzer measurements. © 2000 American Institute of Physics.
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06.30.Dr Mass and density
77.65.Fs Electromechanical resonance; quartz resonators
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
07.68.+m Photography, photographic instruments; xerography
07.10.Lw Balance systems, tensile machines, etc.

An innovative linear response time-to-digital converter with a branched propagation delay chain

Chih-Yao Chang, Wan-Li Sun, Nai-Chueh Wang, and Chung-Yee Leung

Rev. Sci. Instrum. 71, 2572 (2000); http://dx.doi.org/10.1063/1.1150650 (5 pages)

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Utilizing the propagation delay in a chain of logic elements to digitize short time intervals has a high potential in various applications because the method has an ultrashort measurement “dead time” and its complete timing circuit can be easily integrated in a single semiconductor chip. However, the existing single-lined chain suffers from serious nonlinearity due to the longer path lengths at the foldings which are unavoidable when the number of delay elements is large as high time resolution requires. We propose a new configuration in which the delay chain is branched. The delay elements of each branch evenly subdivide the corresponding larger folding path so all units have the same delay time. The proposed time-to-digital converter with an 81-delay-unit branched chain and a built-in calibration circuit has been implemented on a commercial programmable logic device. It is used to interpolate different time durations within the 100 ns period of a standard 10 MHz clock. The digital time deviates less than 0.3 ns throughout the entire range. A similar single-lined delay chain, constructed for comparison, exhibits timing error up to 32.7 ns. A major improvement in linearity has been achieved by our device. © 2000 American Institute of Physics.
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06.30.Ft Time and frequency
84.30.Sk Pulse and digital circuits
07.68.+m Photography, photographic instruments; xerography
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