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Nov 2001

Volume 72, Issue 11, pp. 4025-4314

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back to top OPTICS; ATOMS and MOLECULES; SPECTROSCOPY

Optical elements based on the use of renewable liquid films with magneto-electrostatic control

D. Ryutov and A. Toor

Rev. Sci. Instrum. 72, 4042 (2001); http://dx.doi.org/10.1063/1.1412857 (13 pages) | Cited 1 time

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A novel concept of capillary magneto-electrostatic (CAMEL) optics is presented. The concept is based on the use of thin liquid films pressed through a porous substrate and quickly pulled back after the optical pulse, thereby allowing one to create optical elements anew after every pulse. Possible optical elements include planar and focusing mirrors, reflecting diffraction gratings, and reflecting zone plates. A set of engineering equations required for design of the CAMEL optics is presented. © 2001 American Institute of Physics.
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42.79.Bh Lenses, prisms and mirrors
42.79.Dj Gratings
42.79.Ci Filters, zone plates, and polarizers
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
68.15.+e Liquid thin films
68.03.Kn Dynamics (capillary waves)
42.15.Eq Optical system design
41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems

Fast switching of magnetic fields in a magneto-optic trap

C. J. Dedman, K. G. H. Baldwin, and M. Colla

Rev. Sci. Instrum. 72, 4055 (2001); http://dx.doi.org/10.1063/1.1408935 (4 pages) | Cited 7 times

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Magneto-optic traps which employ current windings to generate pulsed magnetic fields require rapid switch-off times for many applications. Practical difficulties in attaining rapid switch-off of the magnetic field, including the generation of induced currents, are addressed. Several methods for minimizing the switch-off time are presented which do not require complex feedback mechanisms involving direct measurement of the magnetic field. © 2001 American Institute of Physics.
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37.10.De Atom cooling methods
37.10.Gh Atom traps and guides
37.10.Vz Mechanical effects of light on atoms, molecules, and ions
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems
34.80.Bm Elastic scattering
07.55.Ge Magnetometers for magnetic field measurements
85.70.Sq Magnetooptical devices

Design and construction of a space-borne optical tweezer apparatus

Andrew Resnick

Rev. Sci. Instrum. 72, 4059 (2001); http://dx.doi.org/10.1063/1.1406921 (7 pages) | Cited 2 times

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A compact optical tweezer package has been developed for use on a microscope to be flown on the International Space Station as part of a series of experiments in colloid crystallization. A brief introduction to the principles of single-beam optical tweezer operation will be presented, after which a detailed system layout will be shown. Special design requirements due to the spaceflight nature of the hardware will also be discussed. The tweezer apparatus is capable of trapping many particles through use of a two-axis acousto-optical deflector. The trap strength is sufficient to perform the required science (50 pN at Δn = 0.2). The trap beam behaves approximately as a diffraction limited single mode Gaussian beam of numerical aperture, NA=1.4, as shown through spot size measurements and confocal-type images of the focal region. This is the first time optical tweezers will be deployed in a microgravity environment. © 2001 American Institute of Physics.
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07.60.Pb Conventional optical microscopes
37.10.Vz Mechanical effects of light on atoms, molecules, and ions
81.10.Mx Growth in microgravity environments
07.87.+v Spaceborne and space research instruments, apparatus, and components (satellites, space vehicles, etc.)
81.10.Dn Growth from solutions
42.79.Fm Reflectors, beam splitters, and deflectors
42.79.Jq Acousto-optical devices

Accuracy assessment of a linear birefringence measurement system using a Soleil–Babinet compensator

Baoliang Wang and Walter Hellman

Rev. Sci. Instrum. 72, 4066 (2001); http://dx.doi.org/10.1063/1.1412261 (5 pages) | Cited 23 times

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This article describes a method for assessing the accuracy of a new linear birefringence measurement system based on photoelastic modulator technology. We used a Soleil–Babinet compensator in the experiment and observed that its retardation varies significantly across the optical aperture. To use this compensator as a meaningful retardation standard, we fixed the beam position relative to the Soleil–Babinet compensator before and after its calibration. Our results show that the birefringence measurement system is capable of providing accurate measurements for linear retardation below 125 nm with a relative uncertainty below 1%. Experimental results support the fact that this birefringence measurement system is self-calibrating for measuring linear retardation. © 2001 American Institute of Physics.
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07.60.Fs Polarimeters and ellipsometers
42.25.Lc Birefringence
06.20.F- Units and standards

Ultrashort pulse characterization using a scanning Fabry–Pérot étalon enabling rapid acquisition and retrieval of a sonogram at rates up to 1.52 Hz

I. G. Cormack, W. Sibbett, R. Ortega-Martinez, and D. T. Reid

Rev. Sci. Instrum. 72, 4071 (2001); http://dx.doi.org/10.1063/1.1406932 (9 pages) | Cited 1 time

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Rapid characterization of ultrashort pulses has been demonstrated by measuring a two-photon absorption sonogram trace. The use of a scanning Fabry–Pérot frequency filter has made it possible to acquire and retrieve a sonogram at rates as high as 1.52 Hz. We discuss details of the experimental setup, including the synchronization electronics and the acquisition/retrieval software. Excellent agreement is obtained between retrieved pulse data and independent experimental pulse measurements. © 2001 American Institute of Physics.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
07.60.Ly Interferometers
42.79.Ci Filters, zone plates, and polarizers
07.05.Hd Data acquisition: hardware and software

X-ray monochromator with an energy resolution of 8×10−9 at 14.41 keV

Makina Yabashi, Kenji Tamasaku, Seishi Kikuta, and Tetsuya Ishikawa

Rev. Sci. Instrum. 72, 4080 (2001); http://dx.doi.org/10.1063/1.1406925 (4 pages) | Cited 32 times

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An ultrahigh-resolution x-ray crystal monochromator providing a 120 μeV bandwidth at 14.41 keV is presented. The design, which uses four independent silicon crystals and has an output beam parallel to the incident beam, may be generalized to arbitrary energies. Fluxes of 1.3×106 photons/s (1.0×107 photons/s) in bandwidths of 120±15 μeV (140±15 μeV) were measured. The performance of the monochromator, including the preservation of coherence through it, was verified by measurement of a 9.6±2.0% enhancement in the coincidence rate (i.e., γ(2)−1 = 0.096±0.020) in an intensity correlation experiment. © 2001 American Institute of Physics.
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07.85.-m X- and γ-ray instruments
61.05.cp X-ray diffraction
back to top PARTICLE SOURCES, OPTICS and ACCELERATION, DETECTORS

An iterative procedure for the inversion of two-dimensional ion/photoelectron imaging experiments

Marc J. J. Vrakking

Rev. Sci. Instrum. 72, 4084 (2001); http://dx.doi.org/10.1063/1.1406923 (6 pages) | Cited 95 times

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We present an iterative method for the extraction of velocity and angular distributions from two-dimensional (2D) ion/photoelectron imaging experiments. This method is based on the close relationship which exists between the initial 3D angular and velocity distribution and the measured 2D angular and radial distributions, and gives significantly better results than other inversion procedures which are commonly used today. Particularly, the procedure gets rid of the center-line noise which is one of the main artifacts in many current ion/photoelectron imaging experiments. © 2001 American Institute of Physics.
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07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.-j Optical instruments and equipment
07.81.+a Electron and ion spectrometers
02.60.Ed Interpolation; curve fitting
07.05.Pj Image processing
32.80.Rm Multiphoton ionization and excitation to highly excited states

Operation of the SERSE superconducting electron cyclotron resonance ion source at 28 GHz

S. Gammino, G. Ciavola, L. Celona, D. Hitz, A. Girard, and G. Melin

Rev. Sci. Instrum. 72, 4090 (2001); http://dx.doi.org/10.1063/1.1405786 (8 pages) | Cited 33 times

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The SERSE source [P. Ludwig et al., Rev. Sci. Instrum. 69, 4082 (1998), and references therein] is a superconducting electron cyclotron resonance (ECR) ion source, operating at the Laboratori Nazionali del Sud in Catania since 1998; it is currently used as the main injector for the K-800 superconducting cyclotron. Its high magnetic field provides a high plasma confinement and large currents of highly charged ions, as compared to conventional sources. It can efficiently operate at the microwave frequency of 14 and 18 GHz [S. Gammino and G. Ciavola, Rev. Sci. Instrum. 71, 631 (2000); S. Gammino et al., ibid.70, 3577 (1999)] and has been used as a test bench for injection at 28 GHz. High-frequency operation is expected to create a higher plasma density, thus resulting in larger currents of multiply charged ions. In this article, we report the first operation of an ECR ion source at 28 GHz by using a gyrotron. The gyrotron itself and the waveguide line are described, along with the operational results (in xenon gas for the sake of simplicity). Given the limited amount of power (about 4 kW), which can be injected in the plasma chamber during dc-mode operation, the results are less outstanding than in the pulsed mode (up to 6.5 kW). However, in both cases the beam intensities are far better than the ones obtained by the other ECR ion sources operating at lower frequencies. © 2001 American Institute of Physics.
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29.25.Ni Ion sources: positive and negative
52.50.Sw Plasma heating by microwaves; ECR, LH, collisional heating
29.27.Ac Beam injection and extraction
29.20.dg Cyclotrons

Energy broadening due to photoion space charge in a high resolution laser photoelectron source

J. Bömmels, E. Leber, A. Gopalan, J. M. Weber, S. Barsotti, M.-W. Ruf, and H. Hotop

Rev. Sci. Instrum. 72, 4098 (2001); http://dx.doi.org/10.1063/1.1412861 (8 pages) | Cited 10 times

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The results of experimental and theoretical studies, aiming at a quantitative characterization of photoion-induced energy broadening effects in a laser photoelectron source, are reported. The electron source is based on two-step cw laser photoionization of potassium atoms in a collimated beam. In the experimental studies, the attachment spectra for the formation of (N2O)9O− cluster ions through a narrow vibrational Feshbach resonance (full width at half maximum 2.3 meV) were measured as a function of the photocurrent. The theoretical studies involved Monte Carlo simulations of the broadening effects and were based on potential distributions caused by realistic spatial distributions of the photoions. Using the corresponding electric field distribution, trajectories were calculated for a representative ensemble of electrons, and effective electron energy distributions were obtained from averages over the electron trajectories in the volume relevant for electron attachment. Furthermore, the effects of additional weak electric fields, applied along the atomic beam direction, have been simulated. For our geometry (ionization volume about 2 mm3) the effective space charge related energy width is found to be about 16 μeV/pA. © 2001 American Institute of Physics.
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07.81.+a Electron and ion spectrometers
07.77.Ka Charged-particle beam sources and detectors
32.80.Fb Photoionization of atoms and ions
34.80.Lx Recombination, attachment, and positronium formation
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.-j Optical instruments and equipment
back to top NUCLEAR PHYSICS, FUSION and PLASMAS

Reducing influence of ion current on measurements of electron energy distributions in collisional plasmas

V. I. Demidov, S. V. Ratynskaia, and K. Rypdal

Rev. Sci. Instrum. 72, 4106 (2001); http://dx.doi.org/10.1063/1.1408933 (4 pages) | Cited 4 times

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A method for reducing the influence of ion current on probe measurements of electron velocity distributions in plasmas has been developed and tested in noble gas afterglow plasmas. It is valid for diffusive transport of ions to the probe. Experiments have demonstrated high accuracy of the proposed method. © 2001 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
52.80.Hc Glow; corona
52.25.Fi Transport properties

Fiber optic catalytic probe for weakly ionized oxygen plasma characterization

D. Babič, I. Poberaj, and M. Mozetič

Rev. Sci. Instrum. 72, 4110 (2001); http://dx.doi.org/10.1063/1.1409567 (5 pages) | Cited 33 times

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Construction and operation of a novel fiber optic catalytic probe is presented. The probe is intended for measurements of atomic oxygen density in plasma postglows. The operation of the probe is based on a catalytic recombination of oxygen atoms and remote temperature sensing via optical fiber. Compared to the classical catalytic probes, the new approach results in smaller dimensions, better sensitivity, and higher immunity to the electromagnetic interference. Comparative measurements of atomic oxygen density performed simultaneously with both types of probes demonstrated a superior performance of the novel probes. © 2001 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
07.60.Vg Fiber-optic instruments
42.81.Pa Sensors, gyros
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Measurement of spurious impurity concentrations in ASDEX Upgrade by x-ray spectroscopy

D. Bolshukhin, R. Neu, D. Schlögl, and R. Dux

Rev. Sci. Instrum. 72, 4115 (2001); http://dx.doi.org/10.1063/1.1405792 (10 pages) | Cited 1 time

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A two channel multicrystal spectrometer of Bragg geometry was constructed for measurements of absolute photon fluxes of ASDEX Upgrade plasmas in the wavelength range from 0.5 up to 26 Å. The calibration of the spectrometer was done by an ab initio calculation using the absolute reflection data from literature of four crystals. The calibration was validated by the direct comparison with other absolute calibrated diagnostics at the ASDEX Upgrade as well as by using the impurity transport code STRAHL. The absolute impurity concentrations of elements from N up to Cu have been extracted. O and F appear to be main impurity components after C, which is routinely measured by an independent diagnostic. Despite the significantly lower concentration of Ar, it contributes measurably to Zeff and can account for main plasma impurities as well. Other impurities either have never been seen or appear only sporadically (like Fe and Cu) and normally do not contribute significantly to the plasma radiation in the soft x-ray range. © 2001 American Institute of Physics.
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52.70.La X-ray and γ-ray measurements
52.55.Fa Tokamaks, spherical tokamaks
07.85.Nc X-ray and γ-ray spectrometers
52.25.Vy Impurities in plasmas

Electronics and signal processing for the multichord far-infrared polarimeter of the RFX experiment

E. Zilli, F. Milani, M. O’Gorman, L. Giudicotti, and S. L. Prunty

Rev. Sci. Instrum. 72, 4125 (2001); http://dx.doi.org/10.1063/1.1412262 (14 pages) | Cited 1 time

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This article describes the realization and testing of the electronic system which forms part of the multichannel far-infrared (FIR) polarimeter for the RFX machine, a plasma confinement experiment with Reversed Field Pinch (RFP) configuration. The electronic system, which comprises the detectors, the signal-processing electronics, and the motion electronics for the half-wave plate movement, is described. Emphasis is placed in the analysis of the polarimeter signals, which permits an in-depth understanding of the performance of the data processing electronics and the role of the various sources of noise in the system. After a brief outline of the basic principle of the measurement, the choice of detectors and their characteristics are described in order to achieve the best performances at the FIR wavelength (λ = 118.8 μm) of interest. Various tests, which are described, confirmed the need for a specifically designed pyroelectric detector capable of operating in the hostile magnetic environment near the machine. The processing of the raw polarimeter signals to produce the required sum and difference signals and to convert them into dc signals with 3 ms time constant is presented. These signals are synchronous with a chopper signal on the FIR beam and are subsequently fed to a lock-in amplifier. An accurate analysis of the data processing procedure is described, which helps to clarify the understanding of the output signals that are eventually recorded in the data acquisition system. In particular, various sources of noise, such as thermal noise of the detectors, laser fluctuations, spurious signals at harmonics of the chopper frequency, and phase jitter of the chopper, are evaluated, discussed, and compared with the observed signals. Finally, the control circuitry for the movement of the half-wave plates, both for manual control and for the programmed sequences of zero-search and calibration performed by a PLC control system, is described. Calibration curves obtained during experiments are also reported. © 2001 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.58.Lq Z-pinches, plasma focus, and other pinch devices
07.60.Fs Polarimeters and ellipsometers
07.68.+m Photography, photographic instruments; xerography
07.05.Hd Data acquisition: hardware and software

Analytical simulation of microwave reflectometry of a plasma cylinder

L. G. Bruskin and A. Mase

Rev. Sci. Instrum. 72, 4139 (2001); http://dx.doi.org/10.1063/1.1409570 (6 pages)

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An analytical solution of a time-dependent two-dimensional (2D) full-wave equation is obtained for the case of microwave propagation in a plasma with axial symmetry. The 2D structure of the electromagnetic wave in a nonmagnetized plasma (or an ordinary wave in a magnetized plasma) is studied for the general case of arbitrary time dependence of the incident wave emitted by the horn. The solutions cover the cases of conventional microwave reflectometry as well as the ultrashort pulse reflectometry of fusion and processing plasma. Analytical expressions can be further applied to study plasma density fluctuations as well as effects of plasma curvature and multidimensionality. The 2D plasma cylinder model is deemed by the authors to be more realistic as compared to the one-dimensional plasma slab model previously employed in all the analytical and most numerical treatments since the plasma in the fusion toroidal devices, mirror machines, and plasma processing chambers can be considered axially symmetric on the scale relevant to microwave reflectometry. © 2001 American Institute of Physics.
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52.70.Gw Radio-frequency and microwave measurements
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
52.65.-y Plasma simulation
52.25.Gj Fluctuation and chaos phenomena
back to top MICROSCOPY and IMAGING

Time-resolved confocal scanning device for ultrasensitive fluorescence detection

Martin Böhmer, Francesco Pampaloni, Michael Wahl, Hans-Jürgen Rahn, Rainer Erdmann, and Jörg Enderlein

Rev. Sci. Instrum. 72, 4145 (2001); http://dx.doi.org/10.1063/1.1406926 (8 pages) | Cited 27 times

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A confocal laser-scanning microscope for ultrasensitive fluorescence lifetime imaging on surfaces is presented. The system employs a compact electronics for time-correlated single-photon counting (TCSPC), allowing for measuring fluorescence lifetime with 40 ps time resolution, and for continuously recording photon arrival times with 100 ns time resolution. Additionally developed driver electronics serve for synchronization of scanning and data acquisition, which is significant for achieving high spatial image resolution. The capabilities of the measurement system are demonstrated on imaging single molecules immobilized on glass substrates. Finally, it is shown how the TCSPC capabilities of the system can be used not only for lifetime imaging but also for multichannel measurements. © 2001 American Institute of Physics.
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07.60.Pb Conventional optical microscopes
87.64.mk Confocal
07.05.Hd Data acquisition: hardware and software
07.05.Pj Image processing
42.30.Wb Image reconstruction; tomography

Scanning superconducting quantum interference device microscope in a dilution refrigerator

Per G. Björnsson, Brian W. Gardner, John R. Kirtley, and Kathryn A. Moler

Rev. Sci. Instrum. 72, 4153 (2001); http://dx.doi.org/10.1063/1.1406931 (6 pages) | Cited 11 times

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We report on a scanning superconducting quantum interference device microscope operating at temperatures down to 20 mK in a dilution refrigerator. The instrument is designed for studying quantum mechanical coherence effects in mesoscopic systems and investigating magnetic effects on a mesoscopic length scale in novel materials. We have demonstrated the low-temperature operating capabilities of the instrument by studying superconducting tin disks and the superconducting transition of a thin-film tungsten sample and vortices in the same film. Looking forward, we discuss the applicability of the instrument to measurements of persistent currents in normal-metal rings. © 2001 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)
07.79.-v Scanning probe microscopes and components
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

Atomic force microscope chamber for in situ studies of ice

Salvador Zepeda, Yin Yeh, and Christine A. Orme

Rev. Sci. Instrum. 72, 4159 (2001); http://dx.doi.org/10.1063/1.1406933 (5 pages) | Cited 4 times

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To investigate the surface morphologies of biological systems in a controlled gaseous environment (e.g., the temperature, humidity and composition), most commercial atomic force microscopes require modification. We have designed a double-jacketed environmental chamber specifically for a Nanoscope IIIa (Digital Instruments, Santa Barbara, CA) force microscope. We use cold nitrogen and thermoelectric devices to control the temperature in the chamber; the nitrogen simultaneously serves to create an inert environment. We have also designed a temperature controlled sample stage utilizing thermoelectric devices for fine temperature regulation. A variation of this sample stage allows us to image samples in fluids at cold temperatures with an O-ringless configuration. The relative humidity within the chamber is also measured with commercially available relative humidity sensors. We investigate the surface morphology of ice Ih in its pure phase and shall extend the study to ice in the presence of biological molecules, such as antifreeze proteins. We present a detailed description of our design and our first images of polycrystalline ice and single crystals of ice grown in situ from the vapor. © 2001 American Institute of Physics.
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07.79.Lh Atomic force microscopes
68.37.Ps Atomic force microscopy (AFM)
06.60.Ei Sample preparation (including design of sample holders)
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
07.07.Tw Servo and control equipment; robots

Measuring normal and friction forces acting on individual fine particles

Stefan Ecke, Roberto Raiteri, Elmar Bonaccurso, Christof Reiner, Hans-Jörg Deiseroth, and Hans-Jürgen Butt

Rev. Sci. Instrum. 72, 4164 (2001); http://dx.doi.org/10.1063/1.1406934 (7 pages) | Cited 25 times

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Interparticle and surface forces are of great importance in many fields of pure and applied science. We present an apparatus to measure the normal and friction forces acting between a particle (radius of 0.5–20 μm) and another solid surface. The apparatus is based on the principle of an atomic force microscope. For quantitative friction measurements we propose a method to determine the lateral spring constants of atomic force microscope cantilevers with attached spherical particles. © 2001 American Institute of Physics.
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07.79.Lh Atomic force microscopes
07.10.Pz Instruments for strain, force, and torque
46.55.+d Tribology and mechanical contacts
68.35.Af Atomic scale friction

New two-dimensional friction force apparatus design for measuring shear forces at the nanometer scale

Linmao Qian, Gustavo Luengo, Denis Douillet, Magali Charlot, Xavier Dollat, and Eric Perez

Rev. Sci. Instrum. 72, 4171 (2001); http://dx.doi.org/10.1063/1.1412860 (7 pages) | Cited 7 times

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A device to study the friction of two molecularly smooth surfaces separated by an ultrathin liquid film is presented along with its design, calibration, and performance. The apparatus can move one of the surfaces and measure the friction force on the other one bidimensionally for both processes. A high mechanical impedance system (104 N/m) measures continuous friction forces where only stick–slip was previously observed. The frequency and travel distance of the movement can be varied over a wide range (frequency from 10−4 to 7 Hz and distance from 1 to 800 μm) to provide variations of the shear rate over seven orders of magnitude. The actual movement provided by piezoelectric bimorph drive can be affected by the friction forces and is measured by strain gauges. The friction forces are measured with an accuracy of ±2μN with a capacitance sensor. The mechanical design prevents the surfaces from rolling under force. The apparatus is tested with hexadecane. The potential applications of this apparatus and its limitations are discussed. © 2001 American Institute of Physics.
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07.10.Pz Instruments for strain, force, and torque
46.80.+j Measurement methods and techniques in continuum mechanics of solids
46.55.+d Tribology and mechanical contacts
68.35.Af Atomic scale friction

Shear-force distance control at megahertz frequencies for near-field scanning optical microscopy

A. Simon, R. Brunner, J. O. White, O. Hollricher, and O. Marti

Rev. Sci. Instrum. 72, 4178 (2001); http://dx.doi.org/10.1063/1.1406922 (5 pages) | Cited 5 times

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We show that the use of fiber overtone resonance modes up to 3 MHz for shear-force distance control has two advantages for near-field microscopy. The higher dither frequency allows a shorter feedback loop time delay, which in turn allows scanning speeds of 100 μm/s on a sample with, for example, a 150 nm height variation over a 1 μm distance. Experiments on a hard semiconductor device and on a soft polymer sample demonstrate a factor of 5 improvement in scanning speed when the dither frequency is increased by a factor of 20. The second advantage is a reduction of the minimum lateral force required for height regulation, which is important for soft samples. Modeling the piezoelectric detection system as a harmonic oscillator indicates a factor of 33 increase in lateral force sensitivity when using the third overtone resonance of a typical fiber tip. This result is confirmed experimentally by immersing the tip into water. © 2001 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
06.60.Sx Positioning and alignment; manipulating, remote handling
42.81.Pa Sensors, gyros
07.07.Tw Servo and control equipment; robots

Piezo-driven metrological multiaxis nanopositioner

Jong-Youp Shim and Dae-Gab Gweon

Rev. Sci. Instrum. 72, 4183 (2001); http://dx.doi.org/10.1063/1.1408932 (5 pages) | Cited 7 times

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We report on the development of a metrological multiaxis nanopositioning device, which is operated by the piezo-based inertial method, as a sample stage for scanning probe microscopy. It has long moving range, unlimited in principle, and nanometer (microradian) resolution. Two operation methods, inertial sliding and inertial walking, can be applied to the stage and the inertial operating method can make the stage have a simple and compact structure. By the structure and operation method high positioning stability can be obtained which is an important requirement for scanning probe microscopy. For a metrological nanopositioner, a three axes laser interferometric sensing scheme is adopted for planar motion and a 15 channel high voltage amplifier is designed and computer based digital-to-analog conversion is adopted. Therefore the nanopositioner can be feedback controlled with many choices of voltage wave forms and control methods. Design of the nanopositioner and piezo-driver and experimental results are presented. The device provides step sizes of 0.016–10 μm at frequency up to about 7 kHz. The rotational range is limited by the interferometer alignment, 0.2°, and the step size is 0.17–103 arcsec. © 2001 American Institute of Physics.
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07.79.-v Scanning probe microscopes and components
06.60.Sx Positioning and alignment; manipulating, remote handling
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
07.07.Tw Servo and control equipment; robots
back to top CONDENSED MATTER; MATERIALS

Axially uniform resonant cavity modes for potential use in electron paramagnetic resonance spectroscopy

Richard R. Mett, Wojciech Froncisz, and James S. Hyde

Rev. Sci. Instrum. 72, 4188 (2001); http://dx.doi.org/10.1063/1.1405796 (13 pages) | Cited 12 times

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This article is concerned with cylindrical transverse electric TE011 and rectangular TE102 microwave cavity resonators commonly used in electron paramagnetic resonance (EPR) spectroscopy. In the cylindrical mode geometry considered here, the sample is along the z axis of the cylinder, dielectric disks of 1/4 wavelength thickness are placed at each end wall, and the diameter of the cylinder is set at the cutoff condition for propagation of microwave energy in a cylindrical waveguide at the desired microwave frequency. The microwave magnetic field is exactly uniform along the sample in the region between the dielectric disks and the resonant frequency is independent of the length of the cylinder without limit. The rectangular TE102 geometry is analogous, but here the microwave magnetic field is exactly uniform in a plane. A uniform microwave field along a line sample is highly advantageous in EPR spectroscopy compared with the usual sinusoidal variation, and these geometries are called “uniform field” modes. Extensive theoretical analysis as well as finite element calculation of field patterns are presented. The perturbation of field patterns caused by sample insertion as functions of the overall length of the resonator and diameter of the sample is analyzed. The article is intended to provide a basis for design of practical structures in the range of 10 to 100 GHz. © 2001 American Institute of Physics.
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84.40.Az Waveguides, transmission lines, striplines
07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques

Low-frequency ac measurement of the Seebeck coefficient

F. Chen, J. C. Cooley, W. L. Hults, and J. L. Smith

Rev. Sci. Instrum. 72, 4201 (2001); http://dx.doi.org/10.1063/1.1406930 (6 pages) | Cited 13 times

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We have analyzed the sources of error in the measurement of the Seebeck coefficient and designed a low frequency ac method to reduce them. This method has high precision in a short time period compared to commonly used dc methods while it minimizes some major sources of error that other ac methods do not. Furthermore, the setup can be fit into a 3 mm diam × 7 mm Teflon pressure cell and has minimal side effects due to the heat conductance of the pressure medium. We have also proposed and tested several methods to calibrate the Seebeck coefficient of thermocouples under pressure. © 2001 American Institute of Physics.
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84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
07.20.-n Thermal instruments and apparatus
06.20.F- Units and standards
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells

High-pressure rotational deformation apparatus to 15 GPa

D. Yamazaki and Shun-ichiro Karato

Rev. Sci. Instrum. 72, 4207 (2001); http://dx.doi.org/10.1063/1.1412858 (5 pages) | Cited 25 times

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A new apparatus has been developed that allows large-strain plastic deformation experiments under high pressure with a controlled strain rate in simple shear deformation geometry. A modification is made to a Drickamer-type opposed anvil apparatus to allow torsion tests by attaching a rotation actuator composed of a dc servomotor and a gear box. A thin disk of a sample (less than ∼0.8 mm thick and to ∼4 mm diameter) can be sheared between two anvils under pressure by a rotation actuator. Specimens of Fe were sheared to strains exceeding γ∼6 at pressures up to ∼15 GPa. Nearly simple shear deformation was achieved when the initial sample thickness is less than ∼0.4 mm. This apparatus allows studies of plastic flow and deformation microstructures under high pressures. © 2001 American Institute of Physics.
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07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
81.70.Bt Mechanical testing, impact tests, static and dynamic loads
07.07.Tw Servo and control equipment; robots
47.85.Kn Hydraulic and pneumatic machinery

Mathematical analysis of coaxial disk cellular shear loading devices

Michael C. Wendl

Rev. Sci. Instrum. 72, 4212 (2001); http://dx.doi.org/10.1063/1.1409569 (6 pages)

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Coaxial disk devices are widely used at low Reynolds numbers to simulate cellular shear loading. Here, we develop a mathematical theory for analyzing fluid behavior in these instruments. It improves upon classical results by accounting for both unsteady dynamics and wall drag effects. All previous models are shown to be special cases of the present one. Most devices utilize a low aspect ratio, for which we find wall effects to be limited to small regions near the periphery. In these cases, classical theory yields acceptable precision over most of the domain. Investigators commonly simulate pulsatile effects using low-frequency sinusoidal forcing. Results indicate that fluid motion remains essentially harmonic, permitting the exact solution to be approximated by a simple separable expression. This approximation should be useful in analyzing specific configurations. A wavelike flow mode conjectured to exist at high Strouhal numbers is also discussed. © 2001 American Institute of Physics.
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87.17.Aa Modeling, computer simulation of cell processes
87.19.U- Hemodynamics
87.19.Wx Pneumodyamics, respiration
47.27.N- Wall-bounded shear flow turbulence
47.11.-j Computational methods in fluid dynamics
47.85.Np Fluidics
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