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Dec 2003

Volume 74, Issue 12, pp. 4989-5284

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Superconductor and magnet levitation devices

K. B. Ma, Y. V. Postrekhin, and W. K. Chu

Rev. Sci. Instrum. 74, 4989 (2003); http://dx.doi.org/10.1063/1.1622973 (29 pages) | Cited 45 times

Online Publication Date: 21 November 2003

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This article reviews levitation devices using superconductors and magnets. Device concepts and their applications such as noncontact bearings, flywheels, and momentum wheels are discussed, following an exposition of the principles behind these devices. The basic magneto–mechanical phenomenon responsible for levitation in these devices is a result of flux pinning inherent in the interaction between a magnet and a type II superconductor, described and explained in this article by comparison with behavior expected of a perfect conductor or a nearly perfect conductor. The perfect conductor model is used to illustrate why there is a difference between the forces observed when the superconductor is cooled after or before the magnet is brought into position. The same model also establishes the principle that a resisting force or torque arises only in response to those motions of the magnet that changes the magnet field at the superconductor. A corollary of the converse, that no drag torque appears when an axisymmetric magnet levitated above a superconductor rotates, is the guiding concept in the design of superconductor magnet levitation bearings, which is the common component in a majority of levitation devices. The perfect conductor model is extended to a nearly perfect conductor to provide a qualitative understanding of the dissipative aspects such as creep and hysteresis in the interaction between magnets and superconductors. What all these entail in terms of forces, torques, and power loss is expounded further in the context of generic cases of a cylindrical permanent magnet levitated above a superconductor and a superconductor rotating in a transverse magnetic field. Then we proceed to compare the pros and cons of levitation bearings based on the first arrangement with conventional mechanical bearings and active magnetic bearings, and discuss how the weak points of the levitation bearing may be partially overcome. In the latter half, we examine designs of devices using superconductor magnet levitation, focusing more on issues specific to the application. We note that applications of superconductor magnet levitation devices tend to be most attractive in situations where energy conservation is critical. The most advanced in development are flywheel kinetic energy storage systems incorporating superconductor magnet bearings. Variations in the designs to enhance the performance in some specific regards are examined case by case. Next we present a reaction wheel for attitude control on small satellites, similar in overall design to the flywheel kinetic energy storage systems, but with subtle differences in details of emphasis, due to the difference in purpose and environment. Finally, we take a brief look at the case of vibration isolation devices as an example of a rectilinear modification of the more familiar rotational bearing applications. © 2003 American Institute of Physics.
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84.71.Ba Superconducting magnets; magnetic levitation devices
85.70.Rp Magnetic levitation, propulsion and control devices
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back to top OPTICS; ATOMS and MOLECULES; SPECTROSCOPY; PHOTON DETECTORS

A dynamic infrared source

M. J. Persky

Rev. Sci. Instrum. 74, 5018 (2003); http://dx.doi.org/10.1063/1.1622974 (8 pages)

Online Publication Date: 21 November 2003

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A system is described that can be used for testing infrared focal plane cameras in situations where conventional blackbody sources are deficient. The system uses readily available components, electronics, and software. It can provide either a wide area or a point source of infrared flux that can be programmed to follow a prescribed temporal profile at higher rates than available from commercial blackbody sources and with excellent repeatability. Additionally, the system provides flux without suffering from the temporal noise characteristic of commercial, wide area, flat sheet sources that results from turbulence in front of the blackbody. The system consists of commercially available, rapid rise time infrared radiators, either coupled to an integrating sphere for broad area flux, or used individually with a pinhole and collimator as a point source. A programmable voltage supply provides the power versus time profile at frequencies to several Hertz. Transfer from a standard blackbody calibrates the flux levels. This article provides a description, testing results, and application examples. © 2003 American Institute of Physics.
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42.72.Ai Infrared sources
07.57.Hm Infrared, submillimeter wave, microwave, and radiowave sources
42.79.Pw Imaging detectors and sensors
42.87.-d Optical testing techniques

Brandaris 128: A digital 25 million frames per second camera with 128 highly sensitive frames

Chien Ting Chin, Charles Lancée, Jerome Borsboom, Frits Mastik, Martijn E. Frijlink, Nico de Jong, Michel Versluis, and Detlef Lohse

Rev. Sci. Instrum. 74, 5026 (2003); http://dx.doi.org/10.1063/1.1626013 (9 pages) | Cited 44 times

Online Publication Date: 21 November 2003

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A high-speed camera that combines a customized rotating mirror camera frame with charge coupled device (CCD) image detectors and is practically fully operated by computer control was constructed. High sensitivity CCDs are used so that image intensifiers, which would degrade image quality, are not necessary. Customized electronics and instruments were used to improve the flexibility and control precisely the image acquisition process. A full sequence of 128 consecutive image frames with 500×292 pixels each can be acquired at a maximum frame rate of 25 million frames/s. Full sequences can be repeated every 20 ms, and six full sequences can be stored on the in-camera memory buffer. A high-speed communication link to a computer allows each full sequence of about 20 Mbytes to be stored on a hard disk in less than 1 s. The sensitivity of the camera has an equivalent International Standards Organization number of 2500. Resolution was measured to be 36 lp/mm on the detector plane of the camera, while under a microscope a bar pattern of 400 nm spacing line pairs could be resolved. Some high-speed events recorded with this camera, dubbed Brandaris 128, are presented. © 2003 American Institute of Physics.
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42.79.Pw Imaging detectors and sensors
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

High resolution hard x-ray spectroscopy of femtosecond laser-produced plasmas with a CZT detector

L. M. Chen, P. Forget, R. Toth, J. C. Kieffer, A. Krol, C. C. Chamberlain, B. X. Hou, J. Nees, and G. Mourou

Rev. Sci. Instrum. 74, 5035 (2003); http://dx.doi.org/10.1063/1.1628824 (4 pages) | Cited 7 times

Online Publication Date: 21 November 2003

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We present measurement of characteristic Kα emission from Mo, Ag, and La targets irradiated by a 60 fs, 600 mJ, 10 Hz Ti:sapphire laser pulse at 1017–1019 W/cm2. These x-ray emissions can potentially be used in applications from laser-based hard x-ray sources to x-ray mammography so detailed knowledge of the spectra is required to assess imaging of the figure of merit. We show here that high resolving hard x-ray spectroscopy can be achieved, with resolving powers (E/ΔE) of 60 at 18 keV, with cadmium–zinc–telluride detection system. The Kα conversion efficiency from the laser light to the Kα photon was optimized thanks to this diagnostic and values as high as 2×10−5 were obtained. © 2003 American Institute of Physics.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.70.La X-ray and γ-ray measurements
52.38.Ph X-ray, γ-ray, and particle generation
52.59.Px Hard X-ray sources
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Investigation of the projectile ion velocity inside the interaction media by the x-ray spectromicroscopy method

O. N. Rosmej, S. A. Pikuz, J. Wieser, A. Blazevic, E. Brambrink, M. Roth, V. P. Efremov, A. Ya. Faenov, T. A. Pikuz, I. Yu. Skobelev, and D. H. H. Hoffmann

Rev. Sci. Instrum. 74, 5039 (2003); http://dx.doi.org/10.1063/1.1623003 (7 pages) | Cited 11 times

Online Publication Date: 21 November 2003

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A method for space resolved measurements of the fast heavy ion velocity during the interaction with matter are presented. The main idea is based upon the fact that the characteristic radiation from ions traveling in the stopping media undergoes the Doppler shift, which varies along the ion beam trajectory due to the ion deceleration. High spectrally (λ/Δλ=1000–3000) and spatially (up to 30–100 μm) resolved x-ray K-shell spectra of Ca projectile ions as well as of the ionized stopping media have been obtained using focusing spectrometers with spatial resolution (FSSR). Spherically bent crystals of quartz and mica with small curvature radii R = 150 mm and large apertures (15×50 mm) have been used as dispersive elements. Fast Ca+6 ions with energies of 5.9 and 11.4 MeV/u were stopped in quartz, SiO2 aerogels and CaF2 targets. High spectral and spatial resolution of the spectra allowed measuring the velocity of heavy projectile ions at different points along the beam trajectory. A method based on the utilization of two equal spectrometers at different angles of observation (along and downstream the ion beam propagation direction) is proposed to measure the absolute values of ion velocity inside the stopping media. The use of aerogel targets with extremely low volume density (0.15 g/cc) increases the ion stopping range up to 50 times in comparison to solid quartz. This provides the resolution of the stopping process dynamics. Experimentally it was found that Ca+6 ions with the initial energies of 5.9 or 11.4 MeV/u propagate in solid dense matter as Ca+17–Ca+19 down to the energies of 2.0–2.2 MeV/u. © 2003 American Institute of Physics.
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61.85.+p Channeling phenomena (blocking, energy loss, etc.)
78.70.-g Interactions of particles and radiation with matter

An efficient method for simultaneous measurement of the integrated reflectivity of crystals in multiple orders of reflection using the bremsstrahlung continuum from an x-ray tube and comparison of experimental results for mica with theoretical calculations

S. G. Lee, J. G. Bak, Y. S. Jung, M. Bitter, K. W. Hill, G. Hölzer, O. Wehrhan, and E. Förster

Rev. Sci. Instrum. 74, 5046 (2003); http://dx.doi.org/10.1063/1.1619546 (7 pages) | Cited 4 times

Online Publication Date: 21 November 2003

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This article describes an efficient method for the simultaneous measurement of the integrated reflectivity of a crystal in multiple orders of reflection at a predefined Bragg angle by using the bremsstrahlung continuum from an x-ray tube in combination with an energy-sensitive detector. The technique is demonstrated with a mica crystal for Bragg angles of 43°, 47°, and 50°. The measured integrated reflectivity for Bragg reflections up to the 24th order is compared with theoretical predictions, which are also presented in this article. © 2003 American Institute of Physics.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.70.Ck X-ray scattering
back to top PARTICLE SOURCES, OPTICS and ACCELERATION; PARTICLE DETECTORS

A combined source of electron bunches and microwave power

J. L. Xie, F. Y. Wang, X. P. Yang, B. Shen, W. Gu, and L. W. Zhang

Rev. Sci. Instrum. 74, 5053 (2003); http://dx.doi.org/10.1063/1.1623618 (5 pages)

Online Publication Date: 21 November 2003

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In this article, the possibility of using a high power klystron amplifier simultaneously as a microwave power source as usual and an electron bunches source by extracting the spent beam with a magnet and also as an oscillator by feedback is investigated. The purpose of this study is to demonstrate the feasibility of constructing a very compact electron linear accelerator or for other applications of electron bunches. The feasibility of the idea was first examined by computer simulation of the electron motion in a 5 MW klystron and the characteristics of the klystron spent beam. Experimental study was then carried out by installing a radio frequency cavity and a Faraday cage in sequence at the exit end of a bending magnet located at the top of the klystron collector. The energy and current of the chopped spent electron beam can then be measured. By properly choosing the feedback circuit elements, the frequency stability of the klystron in oscillator mode was proved to be good enough for linac operation. According to the results presented in this article, it is evident that an extremely compact linac for research and education with better affordability can be constructed to promote the applications of linacs. © 2003 American Institute of Physics.
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29.25.Bx Electron sources
07.57.Hm Infrared, submillimeter wave, microwave, and radiowave sources
29.20.-c Accelerators
84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)
29.27.Ac Beam injection and extraction

Optimal lookup table construction for charge division with respect to efficiency flatness

P. Van Esch and F. Millier

Rev. Sci. Instrum. 74, 5058 (2003); http://dx.doi.org/10.1063/1.1623607 (4 pages) | Cited 1 time

Online Publication Date: 21 November 2003

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Static lookup tables, as often used in the position calculation electronics in position sensitive detectors, suffer from the well-known problem that the propagation of digitization errors in the division leads to unequal efficiencies for the different output channels. In this article, we present a solution to the construction of such a lookup table which is optimal in the sense that the least possible efficiency errors are committed in the class of monotone lookup tables. The obtained resolution is comparable to what is obtained using the standard implementation of the fixed point division. After a theoretical explanation, we present some experimental results confirming our claim. © 2003 American Institute of Physics.
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29.40.Gx Tracking and position-sensitive detectors
07.68.+m Photography, photographic instruments; xerography

Device to increase the dynamic range of high-pressure ionization chambers used in environmental radiation monitoring

V. Balagi, K. R. Prasad, R. K. Jakati, and S. K. Kataria

Rev. Sci. Instrum. 74, 5062 (2003); http://dx.doi.org/10.1063/1.1628844 (3 pages)

Online Publication Date: 21 November 2003

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An electronic device that can raise the upper limit of detected gamma exposure from 5 mR/h up to 100 R/h, in the case of a high-pressure ionization chamber (HPIC), has been developed. The chamber has a 7 L sensitive volume filled with high-purity argon at 300 psi pressure and its current sensitivity is 16 nA/R/h. An empirical relationship between I and R has been used to program the electronic device. This device consists of an autoranging dc amplifier, an 8751 microcontroller, and an analog to digital converter/digital to analog converter. A single current reading obtained at 300 V is processed by the system to display the exposure rate instantaneously. Experiments have shown that the exposure rate values derived are comparable to the rates delivered within ±7.7%. The method has the advantage of using a single ion chamber over a very wide range and the device can be used with existing HPIC systems. Potential applications include area gamma monitoring in power reactors and other laboratories. © 2003 American Institute of Physics.
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29.40.Cs Gas-filled counters: ionization chambers, proportional, and avalanche counters
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
back to top NUCLEAR PHYSICS, FUSION and PLASMAS

Large-grazing-angle, multi-image Kirkpatrick–Baez microscope as the front end to a high-resolution streak camera for OMEGA

O. V. Gotchev, L. J. Hayes, P. A. Jaanimagi, J. P. Knauer, F. J. Marshall, and D. D. Meyerhofer

Rev. Sci. Instrum. 74, 5065 (2003); http://dx.doi.org/10.1063/1.1623621 (5 pages) | Cited 5 times

Online Publication Date: 21 November 2003

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A high-resolution x-ray microscope with a large grazing angle has been developed, characterized, and fielded at the Laboratory for Laser Energetics. It increases the sensitivity and spatial resolution in planar direct-drive hydrodynamic stability experiments, relevant to inertial confinement fusion research. It has been designed to work as the optical front end of the PJX—a high-current, high-dynamic-range x-ray streak camera. Optical design optimization, results from numerical ray tracing, mirror-coating choice, and characterization have been described previously [O. V. Gotchev, et al., Rev. Sci. Instrum. 74, 2178 (2003)]. This work highlights the optics’ unique mechanical design and flexibility and considers certain applications that benefit from it. Characterization of the microscope’s resolution in terms of its modulation transfer function over the field of view is shown. Recent results from hydrodynamic stability experiments, diagnosed with the optic and the PJX, are provided to confirm the microscope’s advantages as a high-resolution, high-throughput x-ray optical front end for streaked imaging. © 2003 American Institute of Physics.
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07.85.Tt X-ray microscopes
28.52.Cx Fueling, heating and ignition
28.52.Lf Components and instrumentation
52.57.Fg Implosion symmetry and hydrodynamic instability (Rayleigh-Taylor, Richtmyer-Meshkov, imprint, etc.)

Curvature wave-front sensors for electron density characterization in plasmas

K. L. Baker

Rev. Sci. Instrum. 74, 5070 (2003); http://dx.doi.org/10.1063/1.1628822 (6 pages) | Cited 3 times

Online Publication Date: 21 November 2003

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In this article we examine the use of a curvature wave-front sensor to accurately measure the Laplacian of the line-integrated electron density formed in laser-produced and Z-pinch plasma experiments. Specifically, we propose designs for single shot curvature wave-front sensors capable of quantitatively determining the electron density present in a high density plasma. Wave optics simulations of the proposed designs are presented and are shown to quantitatively reconstruct the phase of a light beam passing through the simulated plasma. A laboratory demonstration of the single shot curvature wave-front sensor is also presented. For this demonstration, a liquid-crystal spatial light modulator is used to introduce a spatially varying phase, thus simulating a phase profile that could occur when a probe passes through a plasma. The phase change measured by the curvature sensor is then computed and shown to accurately reproduce the phase written to the spatial light modulator. Merits associated with the use of a curvature sensor are also discussed. © 2003 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
52.58.Lq Z-pinches, plasma focus, and other pinch devices
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
42.79.Hp Optical processors, correlators, and modulators
42.79.Kr Display devices, liquid-crystal devices

Soft x-ray emission from postpulse expanding laser-produced plasmas

J. L. Weaver, U. Feldman, A. N. Mostovych, J. F. Seely, D. Colombant, and G. Holland

Rev. Sci. Instrum. 74, 5076 (2003); http://dx.doi.org/10.1063/1.1623619 (8 pages)

Online Publication Date: 21 November 2003

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A diagnostic spectrometer has been developed at the Naval Research Laboratory to measure the time resolved absolute intensity of radiation emitted from targets irradiated by the Nike laser. The spectrometer consists of a dispersive transmission grating of 2500 lines/mm or 5000 lines/mm and a detection system consisting of an absolutely calibrated Si photodiode array and a charge coupled device camera. In this article, this spectrometer was used to study the spatial distribution of soft x-ray radiation from low Z elements (primarily carbon) that lasted tens of nanoseconds after the main laser illumination was over. We recorded soft x-ray emission as a function of the target material and target orientation with respect to the incoming laser beam and the spectrometer line of sight. While a number of spectral features have been identified in the data, the instrument’s combined temporal and spatial resolution allowed observation of the plasma expansion from CH targets for up to ∼25 ns after the cessation of the main laser pulse. The inferred plasma expansion velocities are slightly higher than those previously reported. © 2003 American Institute of Physics.
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52.38.Ph X-ray, γ-ray, and particle generation
52.70.La X-ray and γ-ray measurements
07.85.Nc X-ray and γ-ray spectrometers
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Cross-calibrating spatial positions of light-viewing diagnostics using plasma edge sweeps in DIII-D

W. M. Solomon, K. H. Burrell, P. Gohil, R. Groebner, and D. Kaplan

Rev. Sci. Instrum. 74, 5084 (2003); http://dx.doi.org/10.1063/1.1623622 (6 pages) | Cited 1 time

Online Publication Date: 21 November 2003

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An experimental technique is presented that permits diagnostics viewing light from the plasma edge to be spatially calibrated relative to one another. By sweeping the plasma edge, each chord of each diagnostic sweeps out a portion of the light emission profile. A nonlinear least-squares fit to such data provides superior cross-calibration of diagnostics located at different toroidal locations compared with simple surveying. Another advantage of the technique is that it can be used to monitor the position of viewing chords during an experimental campaign to ensure that alignment does not change over time. Moverover, should such a change occur, the data can still be cross-calibrated and its usefulness retained. © 2003 American Institute of Physics.
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52.55.Fa Tokamaks, spherical tokamaks
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Infrared camera diagnostic for heat flux measurements on the National Spherical Torus Experiment

D. Mastrovito, R. Maingi, H. W. Kugel, and A. L. Roquemore

Rev. Sci. Instrum. 74, 5090 (2003); http://dx.doi.org/10.1063/1.1623625 (3 pages) | Cited 11 times

Online Publication Date: 21 November 2003

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An infrared imaging system has been installed on the National Spherical Torus Experiment at Princeton Plasma Physics Laboratory to measure the surface temperatures on the lower divertor and center stack. The imaging system is based on an Indigo Alpha 160×128 microbolometer camera with 12 bits/pixel operating in the 7–13 μm range with a 30 Hz frame rate and a dynamic temperature range of 0–700 °C. From these data and knowledge of graphite thermal properties, the heat flux is derived with a classic one-dimensional conduction model. Preliminary results of heat flux scaling are reported. © 2003 American Institute of Physics.
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52.55.Fa Tokamaks, spherical tokamaks
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Identification of short-lived and localized coherent structures in plasma turbulence by window biorthogonal decomposition

Lifang Dong, Qingli Zhang, and Long Wang

Rev. Sci. Instrum. 74, 5093 (2003); http://dx.doi.org/10.1063/1.1626006 (4 pages) | Cited 1 time

Online Publication Date: 21 November 2003

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An alternative biorthogonal decomposition technique called the window biorthogonal decomposition (WBD) technique is introduced to analyze the coherent structures in the tokamak plasma turbulence. It can spot the short-lived and localized coherent structures in spatiotemporal turbulence signal and extract them out of the incoherence background. As an example, the localized and short-lived coherent structures existing stochastically in the CT-6B tokamak radial direction are analyzed by WBD. © 2003 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.35.Ra Plasma turbulence
52.55.Fa Tokamaks, spherical tokamaks

A plasma-shielded, miniature Rogowski probe

E. Torbert, I. Furno, T. Intrator, and E. Hemsing

Rev. Sci. Instrum. 74, 5097 (2003); http://dx.doi.org/10.1063/1.1626010 (4 pages) | Cited 5 times

Online Publication Date: 21 November 2003

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The design and first results from an electrically isolated and plasma-shielded Rogowski probe, used in the reconnection scaling experiment (RSX), are presented. The probe is designed to withstand extreme thermal shock, plasma corrosion, and be vacuum sanitary, which is accomplished with a machinable boron nitride shell. The novel miniature design, with an inner detecting area of 0.79 cm2, allows accurate position detection of plasma current channels with ≈ 2 cm radius and to measure local current density profiles. The temporal resolution (<1 μs) is sufficiently high to resolve the dynamic evolution of RSX plasma current channels. © 2003 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
52.40.Kh Plasma sheaths
back to top MICROSCOPY and IMAGING

Microbeam of 100 keV x ray with a sputtered-sliced Fresnel zone plate

Nagao Kamijo, Yoshio Suzuki, Hidekazu Takano, Shigeharu Tamura, Masato Yasumoto, Akihisa Takeuchi, and Mitsuhiro Awaji

Rev. Sci. Instrum. 74, 5101 (2003); http://dx.doi.org/10.1063/1.1614882 (4 pages) | Cited 19 times

Online Publication Date: 21 November 2003

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Microfocusing of 100 keV x ray with a sputtered-sliced Fresnel zone plate (ss-FZP) has been performed at the 250-m-long beamline (20XU) of SPring-8. The ss-FZP with an outermost zone width 0.16 μm which is composed of 70 layers of alternating Cu and Al layers and having thickness ∼180 μm was fabricated and characterized. The minimum focal spot size attained for the first order focal beam was 0.5 μm with a focal distance 900 mm at a photon energy 100 keV. The total flux of the microprobe was ∼ 2×106 photons s−1 μm−2. © 2003 American Institute of Physics.
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42.79.Ci Filters, zone plates, and polarizers
07.85.Tt X-ray microscopes
41.50.+h X-ray beams and x-ray optics

Scanning vector Hall probe microscope

J. Fedor, V. Cambel, D. Gregušová, P. Hanzelka, J. Dérer, and J. Volko

Rev. Sci. Instrum. 74, 5105 (2003); http://dx.doi.org/10.1063/1.1623004 (6 pages) | Cited 1 time

Online Publication Date: 21 November 2003

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We present a scanning vector Hall probe microscope for imaging the entire magnetic field vector in close proximity to magnetic and superconducting samples. The microscope combines a large scanned area and a high space resolution of the magnetic field vector measured. A special feature of the equipment is a vacuum-tight sample space connected with a moving system via a flexible metal bellows. The microscope is based on a vector Hall sensor that consists of three separate Hall probes of an active area 5×5 μm2, patterned on three sides of a GaAs pyramid. The top of the pyramid serves as a tunneling contact and helps to control the sensor–sample separation. The sensor and the sample are placed in a helium cryostat with a temperature control in the range 10–300 K. The sensor scans an area up to 5×5 mm2 in the whole temperature interval with a spatial resolution ∼ 5 μm. © 2003 American Institute of Physics.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.55.-w Magnetic instruments and components

Higher harmonics imaging in tapping-mode atomic-force microscopy

Robert W. Stark and Wolfgang M. Heckl

Rev. Sci. Instrum. 74, 5111 (2003); http://dx.doi.org/10.1063/1.1626008 (4 pages) | Cited 51 times

Online Publication Date: 21 November 2003

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In tapping-mode atomic-force microscopy usually amplitude and phase of the cantilever motion are acquired. These signals are related to the fundamental oscillation frequency neglecting information at higher frequencies. However, the nonlinear contact between tip and sample induces higher frequency vibrations that are harmonics of the fundamental. In order to recover the available information the full tip motion has to be analyzed. The higher harmonics can be employed for image formation. A setup that consists of two independently operated lock-in amplifiers is used to detect higher harmonics in the dynamic atomic-force microscopy signal. Higher harmonic imaging proves to be useful to monitor the imaging conditions in tapping mode and can be applied for nanoscale imaging with a material contrast. © 2003 American Institute of Physics.
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07.79.Lh Atomic force microscopes
68.37.Ps Atomic force microscopy (AFM)
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)

Compensation of cross talk in the optical lever deflection method used in atomic force microscopy

Satoru Fujisawa and Hisato Ogiso

Rev. Sci. Instrum. 74, 5115 (2003); http://dx.doi.org/10.1063/1.1622972 (3 pages) | Cited 7 times

Online Publication Date: 21 November 2003

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Most atomic force microscopes employ the optical lever deflection method using a quadrant photodetector as the displacement sensor of the cantilever, which enables it to detect lateral force (or friction force) as well as normal force. Misalignment between the cantilever direction and the photodetector direction causes cross talk between the lateral force signal and normal force signal. We analyze systematically the type of cross talk, and then propose a compensation method by using a two-dimensional rotary stage. © 2003 American Institute of Physics.
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07.79.Lh Atomic force microscopes
85.60.Gz Photodetectors (including infrared and CCD detectors)
back to top CONDENSED MATTER; MATERIALS

Original superconducting quantum interference device (SQUID) design and measurement technique for flux noise source localization in SQUID systems

M. Lam Chok Sing, S. Flament, X. Ridereau, C. Gunther, L. Méchin, and D. Bloyet

Rev. Sci. Instrum. 74, 5118 (2003); http://dx.doi.org/10.1063/1.1622979 (5 pages) | Cited 1 time

Online Publication Date: 21 November 2003

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We present an original method for studying the low frequency flux noise due to vortices in superconducting quantum interference device (SQUID) systems. We use two SQUIDs connected to the same washer in order to study the correlation of their outputs. A dedicated electronic system has been built so as to operate both SQUIDs at the same time. It was thus possible to distinguish fluctuations due to vortices located in the film far from the SQUID from fluctuations originating from vortices located close to the SQUID itself. In this article, the experimental setup is described and some preliminary noise measurements are presented. © 2003 American Institute of Physics.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
06.60.Mr Testing and inspecting procedures

Particle-beam experiment to study heterogeneous surface reactions relevant to plasma-assisted thin film growth and etching

Wolfgang Jacob, Christian Hopf, Achim von Keudell, Matthias Meier, and Thomas Schwarz-Selinger

Rev. Sci. Instrum. 74, 5123 (2003); http://dx.doi.org/10.1063/1.1628845 (14 pages) | Cited 16 times

Online Publication Date: 21 November 2003

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An ultrahigh-vacuum-based particle-beam experiment to study heterogeneous surface reactions relevant to plasma–surface interaction processes is presented. The experiment comprises two radical beam sources and a source for low energy ions. As diagnostic tools real-time in situ ellipsometry and infrared spectroscopy are implemented. The infrared sensitivity for thin films is enhanced through application of an optical cavity substrate. The fluxes of the radical beam sources are quantified absolutely for the production of hydrogen atoms and methyl radicals. The ion source is also quantified for a wide variety of ionic species, e.g., He+, Ar+, H+, H2+, H3+, and CH3+. Ion energies from above 1 keV down to 1 eV are achievable. The setup allows one to investigate heterogeneous surface processes of one single species or simultaneous interaction of up to three different, individually controllable species with a surface of interest. By running the radical sources to produce hydrogen and methyl radicals and the ion source with the ions mentioned, microscopic surface processes relevant to deposition and erosion of hydrocarbon layers in low-pressure gas discharges were studied in great detail. Sample results for the hydrogen CH3 growth synergism, ion-assisted film growth, and chemical sputtering are presented to demonstrate the capability of the setup. © 2003 American Institute of Physics.
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52.77.Dq Plasma-based ion implantation and deposition
81.15.Cd Deposition by sputtering
52.77.Bn Etching and cleaning
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
81.65.Cf Surface cleaning, etching, patterning
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Flexible system for multiple plasma immersion ion implantation-deposition processes

Xiubo Tian, Ricky K. Y. Fu, Paul K. Chu, Andre Anders, Chunzhi Gong, and Shiqin Yang

Rev. Sci. Instrum. 74, 5137 (2003); http://dx.doi.org/10.1063/1.1626012 (4 pages) | Cited 5 times

Online Publication Date: 21 November 2003

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Multiple plasma immersion ion implantation-deposition offers better flexibility compared to other thin film deposition techniques with regard to process optimization. The plasmas may be based on either cathodic arc plasmas (metal ions) or gas plasmas (gas ions) or both of them. Processing parameters such as pulsing frequency, pulse duration, bias voltage amplitude, and so on, that critically affect the film structure, internal stress, surface morphology, and other surface properties can be adjusted relatively easily to optimize the process. The plasma density can be readily controlled via the input power to obtain the desirable gas-to-metal ion ratios in the films. The high-voltage pulses can be applied to the samples within (in-duration mode), before (before-duration mode), or after (after-duration mode) the firing of the cathodic arcs. Consequently, dynamic ion beam assisted deposition processes incorporating various mixes of gas and metal ions can be achieved to yield thin films with the desirable properties. The immersion configuration provides to a certain degree the ability to treat components that are large and possess irregular geometries without resorting to complex sample manipulation or beam scanning. In this article we describe the hardware functions of such a system, voltage–current behavior to satisfy the needs of different processes, as well as typical experimental results. © 2003 American Institute of Physics.
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52.77.Dq Plasma-based ion implantation and deposition
81.15.Jj Ion and electron beam-assisted deposition; ion plating
61.72.up Other materials
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
52.80.Mg Arcs; sparks; lightning; atmospheric electricity

Magnetic force and optical force sensing with ultrathin silicon resonator

Takahito Ono and Masayoshi Esashi

Rev. Sci. Instrum. 74, 5141 (2003); http://dx.doi.org/10.1063/1.1623627 (6 pages) | Cited 14 times

Online Publication Date: 21 November 2003

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In this article, we demonstrated magnetic and optical force measurements using an ultrathin silicon cantilever down to 20 nm or 50 nm in thickness. The cantilever was heated in an ultrahigh vacuum for enhancing the Q factor and a magnetic particle was mounted at the end of the cantilever using a manipulator. The vibration was measured by a laser Doppler vibrometer and its signal was fed to an opposed metal electrode for electrostatic self-oscillation. An application of a magnetic field with a coil exerted a force to the magnetic material, which results in the change of the resonant frequency. However, the change in the mechanical properties of the cantilever, due to mechanical instability and temperature variation, drifts the resonance peak. Force balancing between the magnetic force and an electrostatic force in the opposite phase can minimize the vibration amplitude. From the electrostatic force at the minimum point, the exerted force can be estimated. A magnetic moment of 4×10−20 J/T was measured by this method. The same technique was also applied to measure the optical force of ∼ 10−17 N, impinging on the cantilever by a laser diode. © 2003 American Institute of Physics.
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07.10.Cm Micromechanical devices and systems
07.55.-w Magnetic instruments and components
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.10.Pz Instruments for strain, force, and torque
37.10.Vz Mechanical effects of light on atoms, molecules, and ions

Permeation rate measurements by electrical analysis of calcium corrosion

R. Paetzold, A. Winnacker, D. Henseler, V. Cesari, and K. Heuser

Rev. Sci. Instrum. 74, 5147 (2003); http://dx.doi.org/10.1063/1.1626015 (4 pages) | Cited 36 times

Online Publication Date: 21 November 2003

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Highly sensitive permeation measurements are crucial for the characterization and development of polymeric substrates for flexible display applications. In particular, organic light-emitting devices require substrates with extremely low permeation rates for water and oxygen. Here we demonstrate a concept for measuring ultralow permeation rates. The amount of oxidative degradation in a thin Ca sensor is monitored by in situ resistance measurements. The benefits of this technique are demonstrated for polyester foils with single- and double-sided barrier coatings. A sensitivity limit is imposed by the quality of the encapsulation. The resulting base line contribution to the water vapor transmission rate of a glass reference is below 10−6 g/m2 day at accelerated test conditions. © 2003 American Institute of Physics.
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81.70.-q Methods of materials testing and analysis
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
85.60.Jb Light-emitting devices
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