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Oct 1998

Volume 69, Issue 10, pp. 3457-3708

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Phase measurement of light absorption and scatter in human tissue

B. Chance, M. Cope, E. Gratton, N. Ramanujam, and B. Tromberg

Rev. Sci. Instrum. 69, 3457 (1998); http://dx.doi.org/10.1063/1.1149123 (25 pages) | Cited 84 times

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Analog and digital technologies are presented for precise measurement of propagation delay of photons from source and detector placed on portions of the human body. The goal of the apparatus design is to quantify absorption (μa) and scattering (μs′) induced by biological pigments and biological structures, respectively. Body tissues are highly scattering with a mean distance between scatterers of less than a mm (at 700–850 nm). Significant absorption is mainly due to 5%–10% of the tissue volume occupied by blood. Measurement of μa and μs′ is done by both time and frequency domain equipment. This article focuses upon frequency domain equipment because of its simplicity, reduced noise bandwidth, versatility, and the strong analogy to very high frequency/ultrahigh frequency communication devices, particularly those using phase modulation. Comparisons are made of homodyne and heterodyne systems together with evaluation of single and multiple side band systems, with particular emphasis on methods for multiplexed optical and radio frequencies by frequency encoding or time-sharing technologies. The applications of these phase modulation systems to quantitative brain and muscle blood oximetry, functional activity of the forebrain, and other important problems of medical science, are presented. © 1998 American Institute of Physics.
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87.63.Hg Thermography
01.30.Rr Surveys and tutorial papers; resource letters
87.63.-d Non-ionizing radiation equipment and techniques
07.50.-e Electrical and electronic instruments and components
84.30.Qi Modulators and demodulators; discriminators, comparators, mixers, limiters, and compressors
85.60.Gz Photodetectors (including infrared and CCD detectors)
42.62.Be Biological and medical applications
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An investigation of continuous-angle laser light scattering

Kazunori Tsutsui, Keisuke Koya, and Tadaya Kato

Rev. Sci. Instrum. 69, 3482 (1998); http://dx.doi.org/10.1063/1.1149124 (5 pages) | Cited 3 times

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A continuous-angle laser light scattering instrument has been developed that consists of an ellipsoidal mirror and a charge-coupled device detector. Continuous and simultaneous measurement for angular dependence of scattered intensity is achieved over the wide scattering angle with high angular resolution. Data acquisition by the instrument is quite rapid compared to conventional light scattering instruments and it takes less than 1 s in most cases. Characteristics of this instrument are evaluated and static light scattering data for linear polystyrene are presented. © 1998 American Institute of Physics.
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07.60.-j Optical instruments and equipment
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
42.79.Pw Imaging detectors and sensors

Reflective optics for cosine-corrected irradiance measurements

Carsten Oppitz and Wolfgang Heering

Rev. Sci. Instrum. 69, 3487 (1998); http://dx.doi.org/10.1063/1.1149125 (4 pages) | Cited 2 times

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Most of the detectors commonly used for radiometric measurements have a more or less poor cosine response. By means of a reflective entrance optics in front of the detection system, we have reduced relative cosine errors below 5% up to zenith angles of 75°. Cosine correction is performed by a roughened polytetrafluoroethylene (PTFE) plate which diffusely reflects parts of the incident radiation into a light guide with the detector at its end. It provides for a neglectible wavelength cosine error dependence and a significantly better radiant efficiency. Originally designed for irradiance measurements of solar global radiation and its photobiological effective irradiance, the entrance optics may also be used for determination of radiant flux from lamps by integrating the lamp irradiance over an enveloping surface as it is done in spectrogoniometric measurements. © 1998 American Institute of Physics.
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07.60.Dq Photometers, radiometers, and colorimeters
96.60.Tf Solar electromagnetic emission
42.79.Wc Optical coatings
87.50.-a Effects of electromagnetic and acoustic fields on biological systems

Spatially resolved Stokes vector measurements

Fredrick M. Cady and Duane Krings

Rev. Sci. Instrum. 69, 3491 (1998); http://dx.doi.org/10.1063/1.1149126 (3 pages) | Cited 2 times

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A procedure for making spatially resolved, Stokes vector image maps of polarized light is described. The imaging system consists of a circular polarizer and a charge coupled device (CCD) camera. A series of four images are captured and the polarization maps are computed and displayed using MATLAB software. © 1998 American Institute of Physics.
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42.79.Pw Imaging detectors and sensors
42.79.Ci Filters, zone plates, and polarizers
07.60.Fs Polarimeters and ellipsometers

Interpretation of capillary generated spatial and angular distributions of x rays: Theoretical modeling and experimental verification using the European Synchrotron Radiation Facility Optical beam line

L. Vincze, K. Janssens, F. Adams, A. Rindby, and P. Engström

Rev. Sci. Instrum. 69, 3494 (1998); http://dx.doi.org/10.1063/1.1149127 (10 pages) | Cited 12 times

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Using a detailed ray-tracing code for capillary optics, interpretation is given for parallel bore hole and tapered capillary generated far-field images. These images can be used to indicate the presence of various types of surface imperfections (i.e., surface roughness or waviness) or shape distortions of the optical device. The capillary output patterns were recorded at the optical beam line of the European Synchrotron Radiation Facility by using a monochromatic, highly parallel incident synchrotron beam. Capillaries of various dimensions were studied, with inlet diameters in the range of 30–70 μm, outlet diameters of 22–42 μm, and capillary length values ranging from 10 to 23 cm. The far-field images were taken at a distance of 10–11 cm from the capillary exit using a high resolution charge coupled device camera. By comparisons of simulated and experimental capillary output patterns, the effects of surface roughness/waviness, as well as axial distortions are studied with respect to the angular distribution of the generated capillary beam. © 1998 American Institute of Physics.
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41.50.+h X-ray beams and x-ray optics
07.85.Qe Synchrotron radiation instrumentation
41.60.Ap Synchrotron radiation
42.79.Bh Lenses, prisms and mirrors
02.50.Ng Distribution theory and Monte Carlo studies

The University of New Mexico/Sandia National Laboratories small-angle scattering laboratory

Thomas P. Rieker and Paul F. Hubbard

Rev. Sci. Instrum. 69, 3504 (1998); http://dx.doi.org/10.1063/1.1149128 (6 pages) | Cited 9 times

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The University of New Mexico/Sandia National Laboratories small-angle scattering laboratory provides a wide q-range, 3×10−4 Å−1<q<0.7 Å−1, for the structural analysis of materials on length scales from a few angstrom to ∼0.1 μm. The wide q-range is accomplished by combining data from a Bonse-Hart spectrometer (3×10−4 Å−1<q<3×10−2 Å−1) and a 5 m pinhole (3×10−3 Å−1<q<0.7 Å−1) instrument. Automation of the data acquisition systems along with a variety of sample environments and sample changers yields flexible, high throughput instruments. © 1998 American Institute of Physics.
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07.85.Nc X-ray and γ-ray spectrometers
61.05.cf X-ray scattering (including small-angle scattering)
07.05.Hd Data acquisition: hardware and software
29.30.Kv X- and γ-ray spectroscopy
01.52.+r National and international laboratory facilities

Theoretical analysis of electron cyclotron resonance x-ray sources

R. Baskaran

Rev. Sci. Instrum. 69, 3510 (1998); http://dx.doi.org/10.1063/1.1149129 (5 pages) | Cited 10 times

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In this article, the important physical parameters which affect the electron current and energy in electron cyclotron resonance x-ray source are discussed. The electron trajectory in an empty cylindrical cavity (TE111 mode), magnetized with dc magnetic field is plotted for the electrons with and without the initial velocity. Magnetic field tapering effect on the electron acceleration and the maximum attainable energy of the electron is studied. The advantages of waveguide coupling over the coaxial coupling for exciting the TE111 mode of the cavity are discussed. © 1998 American Institute of Physics.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
52.50.Gj Plasma heating by particle beams
84.40.Az Waveguides, transmission lines, striplines

Silicon avalanche photodiodes as detectors for photon correlation experiments

Ekkehard Overbeck, Christian Sinn, Ivo Flammer, and Jaro Rička

Rev. Sci. Instrum. 69, 3515 (1998); http://dx.doi.org/10.1063/1.1149130 (9 pages) | Cited 6 times

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In view of time correlated photon-counting experiments using wavelengths at the red end of the electromagnetic spectrum, we developed a simple electronic circuit for periodical gated quenching of silicon avalanche photodiodes. We compare the performance of this device with commercially available passive and active quenching modules and a reference photomultiplier. The detection system’s nonlinearities, i.e., dead time and afterpulsing, lead to direct and indirect distortions of photocount correlation functions. We characterize this nonlinear behavior by measuring intensity auto- and cross-correlation functions and supply nonlinearity parameters for each of the four detection systems. In addition, transfer functions are given which allow an estimate for the highest count rates accessible for each detection system. © 1998 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)

A multidetection, multicoincidence spectrometer for (e,2e) and (e,3e) electron impact ionization measurements

A. Duguet, A. Lahmam-Bennani, M. Lecas, and B. El Marji

Rev. Sci. Instrum. 69, 3524 (1998); http://dx.doi.org/10.1063/1.1149131 (13 pages) | Cited 32 times

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A new spectrometer for the coincidence study of (e,2e) single ionization, and e,(3-1)e or (e,3e) double ionization by electron impact is described. The system is based on two double toroidal analyzers for the ejected electrons and a cylindrical electrostatic analyzer for the scattered electrons. It allows angular and energy distributions of the ejected electrons to be measured over almost the totality of the collision plane, using dual two-dimensional position sensitive detectors. The design and operation of the spectrometer is described with a special emphasis on the imaging properties of the system. The performance (energy and angular resolutions,…) and the calibration of the spectrometer are discussed and sample results for (e,2e), e,(3-1)e and (e,3e) experiments on the rare gases are presented. © 1998 American Institute of Physics.
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07.81.+a Electron and ion spectrometers
29.30.Aj Charged-particle spectrometers: electric and magnetic
29.30.Ep Charged-particle spectroscopy
34.80.Dp Atomic excitation and ionization
34.80.Gs Molecular excitation and ionization
07.05.Hd Data acquisition: hardware and software
06.20.F- Units and standards
29.40.Gx Tracking and position-sensitive detectors

Interdigital accelerating H structure in the multicharged ion linac

V. A. Bomko, N. I. Demchuk, A. F. Dyachenko, A. F. Kobets, Yu. P. Mazalov, A. V. Pipa, and B. I. Rudyak

Rev. Sci. Instrum. 69, 3537 (1998); http://dx.doi.org/10.1063/1.1149132 (4 pages)

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Two modifications of the interdigital accelerating H structure forming the basis for upgrading both the main and prestripper sections of the Kharkov multicharged ion linac (MILAC) are described. Possible application of this type of structure to heavy ion accelerator is discussed. It is shown that the use of the interdigital H structure in this particular case has enabled three major problems to be solved, namely: (i) to increase the operating wavelength from 2.1 m of the previously used Alvarez structure up to 6.3 m, (ii) to double the acceleration rate, and (iii) to increase the shunt impedance by 2–4 times. New methods and designs are described for tuning the cavities at an operating frequency and transforming the sinusoidal field distribution, peculiar to the H mode, into the homogeneously distributed field along the structure axis, with varying period lengths. Characteristics of the MILAC main and prestripper sections are given. © 1998 American Institute of Physics.
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29.20.-c Accelerators
29.27.-a Beams in particle accelerators

Application of capillary optics to neutron radiography

K. M. Podurets, D. F. R. Mildner, and V. A. Sharov

Rev. Sci. Instrum. 69, 3541 (1998); http://dx.doi.org/10.1063/1.1149133 (6 pages) | Cited 5 times

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We propose two neutron radiographic techniques that make use of the converging beam from a tapered monolithic lens. The first is a focusing technique that enables one to obtain an image of a given cross section within an object. The second technique is neutron radiography that uses a beam emanating from a near point source. Both methods provide an improvement in spatial resolution for neutron radiography. © 1998 American Institute of Physics.
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07.77.-n Atomic, molecular, and charged-particle sources and detectors
41.75.-i Charged-particle beams
41.85.-p Beam optics

Hot plasma production in quasisteady arc discharge for divertor plasma simulator

A. A. Kabantsev, V. B. Reva, and V. G. Sokolov

Rev. Sci. Instrum. 69, 3547 (1998); http://dx.doi.org/10.1063/1.1149134 (4 pages)

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This article describes a type quasisteady arc plasma source developed for investigation of edge plasma physics in a fusion device. The source is a modification of the gas-loaded washer-stack plasma gun [J. Osher, Rev. Sci. Instrum. 53, 1685 (1982)]. One of the principal features of describing the source is the formation of electrostatic thermobarrier for plasma electrons near the output of the plasma source. It has been created by changing the polarity of the voltage applied to the discharge as compared with the conventional case. In a new configuration of electrodes, the electrons are accelerated to the back of the injection direction of the plasma flow. A thermobarrier makes it possible to reach the following plasma parameters: Te ≈ 50 eV, n ≈ 5×1013 cm−3, Ti ≈ 200 eV, and q ≈ 1–10 kW/cm2. © 1998 American Institute of Physics.
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52.50.Dg Plasma sources
52.65.-y Plasma simulation
28.52.Av Theory, design, and computerized simulation
52.40.Hf Plasma-material interactions; boundary layer effects
52.80.Mg Arcs; sparks; lightning; atmospheric electricity

Decay rate measurements in a negative ion rich plasma

Kouichi Jimbo and Masashi Iima

Rev. Sci. Instrum. 69, 3551 (1998); http://dx.doi.org/10.1063/1.1149135 (4 pages)

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By artificially terminating the hydrogen arc discharge in the sheet plasma experiments, the decay rates of the negative and the positive saturation currents of a Langmuir probe could be measured. This technique made it possible to observe, under a deep potential well geometry, two single decay curves of saturation currents, which decayed at the same rate reciprocally with time in the negative ion dominant cold region. This result illustrates that the negative saturation current, which consisted of chiefly electrons, was still proportional to negative ion density. © 1998 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
52.25.Fi Transport properties
52.40.Hf Plasma-material interactions; boundary layer effects
52.80.Hc Glow; corona

Application of high performance inverter circuit to plasma generation and heating in fusion devices

Shinichi Watanabe, Yoshihiko Uesugi, Shigeyuki Ohsawa, and Shuichi Takamura

Rev. Sci. Instrum. 69, 3555 (1998); http://dx.doi.org/10.1063/1.1149136 (3 pages) | Cited 4 times

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We have constructed a rf power source using static induction transistor (SIT) inverters to generate high heat flux plasmas in the diverter plasma simulator, NAGDIS-II. Since the SIT can enlarge the operating frequency range of the high power inverter above 1 MHz with output power of several tens of kW, SIT inverters can be used to generate rf plasmas and to heat plasmas by exciting low frequency plasma waves, such as Alfven waves and ion cyclotron waves in plasma devices. The rf conversion efficiency of a SIT inverter with matched load is >85% for frequencies up to 1.2 MHz. The third harmonic antenna current is found to be less than −30 dB. Using four sets of inverter power supplies, we can generate more than 56 kW in continuous rf power or 80 kW in 1 s pulses to produce high heat flux plasmas in the diverter plasma simulator. © 1998 American Institute of Physics.
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28.52.Cx Fueling, heating and ignition
52.50.Dg Plasma sources
52.50.Gj Plasma heating by particle beams
84.30.Jc Power electronics; power supply circuits

High-Q oscillator torque magnetometer

R. D. Biggar and J. M. Parpia

Rev. Sci. Instrum. 69, 3558 (1998); http://dx.doi.org/10.1063/1.1149137 (5 pages) | Cited 8 times

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We describe a torque magnetometer for use at low temperatures based on a high-Q silicon torsional oscillator. The oscillator is fabricated using standard lithographic techniques from a single-crystal silicon wafer. The sample stage of the oscillator has an area of 0.57 cm2 and is suitable for deposition of thin magnetic film samples. Oscillator motion is detected through a capacitance measurement. The small torsion constant of the oscillator combined with a Q value >106 allow detection of magnetic moments as small as 10−13 A m2. Magnetometer sensitivity is measured using small superconducting open cylinders machined from aluminum. © 1998 American Institute of Physics.
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07.55.Jg Magnetometers for susceptibility, magnetic moment, and magnetization measurements
07.10.Cm Micromechanical devices and systems

Precision sample rotator with active angular position readout for a superconducting quantum interference device susceptometer

Anand Bhattacharya, M. T. Tuominen, and A. M. Goldman

Rev. Sci. Instrum. 69, 3563 (1998); http://dx.doi.org/10.1063/1.1149138 (5 pages) | Cited 2 times

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A technique has been devised for precise in situ sample angular positioning and readout in a commercial superconducting quantum interference device (SQUID) susceptometer. The axis of rotation is perpendicular to the applied magnetic field and the temperature range is from 2 K up to room temperature. The technique has an accuracy in angular position of about 0.3%, approximately one degree over one complete rotation. A small coil with an ac current excitation is fixed on the sample stage, and the ac SQUID response is used to determine the angular position of the stage. © 1998 American Institute of Physics.
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07.55.Jg Magnetometers for susceptibility, magnetic moment, and magnetization measurements
85.25.Dq Superconducting quantum interference devices (SQUIDs)
07.07.Tw Servo and control equipment; robots
06.60.Sx Positioning and alignment; manipulating, remote handling

A two-dimensional Couette viscometer for Langmuir monolayers

R. S. Ghaskadvi and Michael Dennin

Rev. Sci. Instrum. 69, 3568 (1998); http://dx.doi.org/10.1063/1.1149139 (5 pages) | Cited 20 times

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We have developed an apparatus that is capable of simultaneously measuring the viscosity of Langmuir monolayers and visualizing their flow. It consists of a circular trough with a nearly circular elastic barrier that can be rotated to generate two-dimensional Couette flow. The “inner cylinder” is a Teflon knife-edge disk that is hung by a thin wire. The torque on the inner cylinder is determined by measuring the angular displacement of the disk. A stepper motor controls the barrier rotation. Viscosity can be measured in two different ways: by oscillating the torsion pendulum and by generating Couette flow. The dynamic viscosity range of the apparatus is 10−4<η<103 g/s. Typical shear rates range from 10−4 to 101 s−1. A Brewster angle microscope is mounted on the apparatus. This is used to study various properties of the monolayer such as: velocity profiles, domain shape during shear, domain relaxation after shear, and size distribution of domains. © 1998 American Institute of Physics.
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68.18.-g Langmuir-Blodgett films on liquids

Experimental investigation for the time-dependent effect in electrorheological fluids under time-regulated high pulse electric field

Weijia Wen, D. W. Zheng, and K. N. Tu

Rev. Sci. Instrum. 69, 3573 (1998); http://dx.doi.org/10.1063/1.1149140 (4 pages) | Cited 2 times

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A new time-regulated high-voltage power supply is designed to investigate the dynamic process of the particle–particle interaction in electrorheological (ER) fluids. Its shortest acting time on the particle is less than 200 ns and the field strength can be adjusted linearly from 0 to 15 kV. At a field strength of 1.2 kV/mm, it is found that the initial response time of the glass microsphere is 18 ms and the respective chain and column formation times are measured to be about 125 and 900 ms. During particle aggregation, a sensitive shear stress device is applied to test the time dependence of ER effect and the results indicate that there exist three different stages of increasing effect. In addition, it is found that the aggregation of the microspheres becomes faster and the interaction among particles is much stronger under higher field strength. © 1998 American Institute of Physics.
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83.80.Gv Electro- and magnetorheological fluids
82.70.Dd Colloids
83.85.Cg Rheological measurements—rheometry

Thermoelectric properties of the Au/Pt thermocouple

Yong-Gyoo Kim, Kee Sool Gam, and Kee Hoon Kang

Rev. Sci. Instrum. 69, 3577 (1998); http://dx.doi.org/10.1063/1.1149141 (6 pages) | Cited 11 times

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An Au/Pt thermocouple having a gold-bridged junction instead of a Pt coil is fabricated and its thermoelectric properties are investigated at the Sn, Zn, Al, and Ag freezing points. Reproducibility is found to be excellent and standard deviation is as small as ±4 mK at the Ag fixed point. Immersion properties, which indicate homogeneity of the thermocouple wire, are also shown to be very good, with standard deviation estimated as about 10 mK. In order to investigate interchangeability, 20 sets of Au/Pt thermocouples are made and their emfs are measured at the same fixed points. Thermocouples from the same spool are reproducible within ±0.02 °C for the whole temperature range. For practical use of the Au/Pt thermocouple, an inverse function and a deviation function for calibration are proposed. The inverse function has two temperature ranges and is accurate within ±1 mK, while the deviation function is a third-order polynomial without a constant term. The Au/Pt thermocouple is stable at high temperatures for long periods. After 1500 h at 1000 °C, the thermal emf at the Ag fixed point is changed by about 0.9 μV (about 40 mK). After the other experiments, calibration uncertainties at the fixed points are evaluated. At the Ag fixed point, the maximum expanded uncertainty is calculated and is about ±30 mK at a confidence interval of 95%. It is shown that the gold-bridged Au/Pt thermocouple is reproducible, accurate, and stable. At present, the Korea Research Institute of Standards and Science (KRISS) uses Au/Pt thermocouples as secondary standard thermometers; they are supplied to industry as certified references. © 1998 American Institute of Physics.
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07.20.Dt Thermometers
06.20.F- Units and standards

Compact low-energy electron microscope for surface imaging

P. Adamec, E. Bauer, and B. Lencová

Rev. Sci. Instrum. 69, 3583 (1998); http://dx.doi.org/10.1063/1.1149142 (5 pages) | Cited 5 times

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A compact electrostatic low-energy electron microscope is described. The electron optical system of the microscope was optimized in order to reduce the number of correcting elements and thus to simplify construction and operation of the instrument. The lenses are biased so that the specimen can be kept close to ground potential. The electrostatic tetrode objective lens allows to achieve a resolution below 10 nm at 10 eV. For beam separation, a magnetic sector with small deflection angle was used. The separator requires only one coil winding for excitation and does not introduce significant aberrations. A three-lens projector system enables magnifications from 600 to 60 000 times. The microscope was built and tested. The weight of the whole mumetal shielded instrument is less than 20 kg so that it can be attached to almost any specimen chamber via a 6 in. Con-flat flange. The microscope was operated in the mirror, low-energy electron microscopy, and low-energy electron diffraction modes. In the experimental system without vibration damping, 30 nm resolution was demonstrated. © 1998 American Institute of Physics.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
41.85.Ne Electrostatic lenses, septa
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)

Atomic force microscopy improved resolution employing large scanning speeds: Effects of the double relaxation time

O. Teschke and E. F. Souza

Rev. Sci. Instrum. 69, 3588 (1998); http://dx.doi.org/10.1063/1.1149143 (5 pages) | Cited 5 times

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The minimum scanning speed of atomic force microscopes for improved atomic resolution has been measured in liquid media, and shown to be equal to 100 nm/s for mica immersed in water corresponding to the time spent scanning the distance between two neighbor ions (∼0.52 nm) of ∼5 ms. The scanning velocity dependence of the force acting on the tip in the double-layer region (∼135 nm) when it approaches the surface was also measured. The stationary component of this force, for scanning speeds up to 30 μm/s, was identified as the exchange of the liquid media with ϵ ≈ 80 by the tip with ϵ ≈ 6. As the tip approaches the surface and as well as when the tip images atomic features, this repulsive force shows a relaxation time of a few milliseconds, corresponding to the shielding of the surface charge by the solution, i.e., the double-layer relaxation time. Scanning surfaces at speeds higher than the ratio of the atomic features distance and this relaxation time results in a variable repulsive force acting on the tip, as a function the scanning speed, which might be used to improve the atomic imaging resolution. © 1998 American Institute of Physics.
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68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
07.79.Lh Atomic force microscopes

A microcontroller-based system for piezoscanner nonlinearity correction: Atomic force microscope

Geraldo Antônio Guerrera Cidade, Gilberto Weissmüller, and Paulo Mascarello Bisch

Rev. Sci. Instrum. 69, 3593 (1998); http://dx.doi.org/10.1063/1.1149144 (5 pages) | Cited 3 times

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Scanning probe microscopes use piezoelectric actuators (piezoscanners) as extremely sensitive and exact positioners for small scaled sample scannings. They are capable of making fine movements along the X, Y, and Z axes, with displacements that can vary from several hundreds of angstroms to some micrometers. For high amplitude sweeps, the displacement response results in visible distortions due to the intrinsic nonlinearity effects of the piezoelectric tube. This work proposes the nonlinearity correction by means of a microcontroller-based system which produces (in real time) the correction values using the piezoscanner quadratic transfer function, adapted to an atomic force microscope (AFM) of its own construction. The AFM is intended to be used with biological samples. Other correction methods are described. © 1998 American Institute of Physics.
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07.79.Lh Atomic force microscopes
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
87.64.Dz Scanning tunneling and atomic force microscopy
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
07.05.Dz Control systems
87.80.-y Biophysical techniques (research methods)
07.68.+m Photography, photographic instruments; xerography

Nonintrusive rigid body tracking technique for dry particulate flows. Part I. Theoretical aspects

Rajesh N. Dave and Bruce G. Bukiet

Rev. Sci. Instrum. 69, 3598 (1998); http://dx.doi.org/10.1063/1.1149145 (8 pages) | Cited 2 times

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A unique system to nonintrusively track a particle in three dimensions is presented. It is based on the principle of magnetic induction coupling and consists of small transmitters mounted inside the particle being tracked, and a set of receiving antennae surrounding the experimental apparatus. In Part I of the sequence of two papers, the focus is on the theoretical aspects, in particular, on developing a computational technique to solve the inverse problem, i.e., find the three-dimensional position as well as orientation of the particle from the voltages induced in the antennae. The computational technique is based on the Levenberg–Marquardt algorithm, along with a scheme for providing good initializations. Through simulated experiments that include various levels of added noise in the voltage readings, the success of this algorithm is demonstrated and the feasibility of the overall technique is established. It is also shown that a system with three mutually orthogonal transmitters provides accurate results even with the noise in the voltage data. Although this system is intended for use in experimental studies of dry granular flows, it has wide applicability due to its nonintrusive nature, and is particularly useful when optical tracking techniques are not feasible. © 1998 American Institute of Physics.
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83.85.-c Techniques and apparatus
83.80.Fg Granular solids
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems
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)

Nonintrusive rigid body tracking technique for dry particulate flows. Part II. Practical aspects and implementation

Rajesh N. Dave, J. Volcy, J. Agarwal, and V. Gupta

Rev. Sci. Instrum. 69, 3606 (1998); http://dx.doi.org/10.1063/1.1149146 (8 pages) | Cited 2 times

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A system, based on the principle of magnetic induction coupling, to track a particle nonintrusively in three dimensions is presented. It consists of small transmitters mounted inside the particle being tracked, and a set of receiving antennae surrounding the experimental apparatus. In Part I of the sequence of two papers, the focus is on the theoretical aspects, in particular, on developing a computational technique to solve the inverse problem of finding the three-dimensional position as well as orientation of the particle from the voltages induced in the antennae. In Part II the focus is on the actual system development, including all hardware and data acquisition aspects. The results presented here are comprehensive, as they include details of hardware/electronics, comparison of induced voltage model and actual measurements, and a set of actual tracking results. Through test experiments that include a variety of real-time trajectories, this system is tested and its success is demonstrated. Results of real trajectories of a single ball rising in a mass of other spheres in a vibrated bed are also shown. Although this system is intended for use in experimental studies of dry granular flows, it has wide applicability due to its nonintrusive nature, and is particularly useful when optical tracking techniques are not feasible. © 1998 American Institute of Physics.
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47.55.Kf Particle-laden flows
47.80.-v Instrumentation and measurement methods in fluid dynamics

Large scanning area near field optical microscopy

P. K. Wei and W. S. Fann

Rev. Sci. Instrum. 69, 3614 (1998); http://dx.doi.org/10.1063/1.1149147 (4 pages) | Cited 1 time

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A near field optical microscope with a scanning area up to 1 mm×1 mm was demonstrated. The scanning element is the tapered fiber probe and a cylindrical lens is used to focus the feedback laser. Instead of the vibrational amplitude, the vibrational angle signal is used to regulate the distance between the probe and sample. The microscope was employed to map out the evanescent wave on a channel waveguide. © 1998 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
07.60.Vg Fiber-optic instruments
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