bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative contactless photothermal monitoring of drying in foodstuff materials
Authors: Delgadillo-Holtfort I. , Bein B. K. , Pelzl J. , Correia Da Silva E.
Published: January 2003

In this work a quantitative method for the study of drying in foodstuff systems is presented. This study relies on the fact that changes in moisture content influence the effective thermal transport properties of porous or fibrous materials. Here, we analyze frequency dependent thermal wave signals recorded on the basis of infrared detection at several drying states by considering that the foodstuff system is not perfectly opaque at the surface. The consideration of transparency allows an asymptotic linear analysis that gives direct information about combinations of optical and thermal parameters. This therefore simplifies a further theoretical numerical approach for the signals within the scope of a two-layer model. Under the condition of constant optical properties at the system surface and neglecting the moisture dependence of thermal diffusivity in comparison with changes induced upon the thermal effusivity, the number of effective parameters necessary to follow the drying progress reduces to two: the thermal diffusion time at the drying surface layer and the thermal effusivity of the bulk.
Energy spectra and dynamics of surface states on silicon investigated by the photoacoustic method
Authors: Todorović D. M. , Smiljanić M.
Published: January 2003

The spectral and dynamic characteristics of surface energy states (SES) on a Si wafer are investigated by photoacoustic (PA) spectroscopy. The PA spectra were measured as a function of the wavelength and modulation frequency of the excitation optical beam by the PA spectrometer. The PA amplitude spectra of Si samples of various surface quality were studied at room temperature in the spectral range of the excitation optical energy beam from 0.7 to 1.5 eV and for various modulation frequencies. The difference in PA amplitude spectra of an as-received Si wafer and a Si wafer with a mechanically roughened surface for various modulation frequencies indicates the energy distribution and the dynamics of the SES. A change in the PA amplitude signal for various modulation frequencies indicates the temporal distribution of the SES for a fixed energy of excitation.
Plasma, thermal, and elastic waves in semiconductors
Authors: Todorović D. M.
Published: January 2003

The system of partially coupled plasma, thermal, and elastic wave equations and conditions for neglecting the coupling between them is analyzed. The treatment considers a semiconductor elastic medium with isotropic and homogeneous thermal and elastic properties. The solution of the coupled system of plasma, thermal and elastic equations is a very complex problem. In most practical cases partially coupled treatment is sufficient. Conditions where it is possible to neglect the coupling between the plasma, thermal, and elastic waves are considered in this work. Special cases for coupled thermal and elastic waves (the thermoelastic problem) and coupled plasma and elastic waves (the electronic deformation) are taken into consideration. An approximate quantitative analysis of the coupling effects is given.
Photoacoustic manipulation of particles and cells
Authors: Zharov Vladimir , Malinsky Taras , Alekhnovich Valentin
Published: January 2003

The aim of this study is to evaluate the capability of the photoacoustic (PA) effect for manipulation of nonbiological particles or living cells. The principal operation of such “PA tweezers” are based on laser generation pressure gradients in a medium surrounding the particles, that create forces acting on the particles. Depending on the spatial geometry of these forces, particles can be moved in desired directions (asymmetrical forces) or trapped (symmetrical forces). Evaluation of these forces was performed for the laser beam with the conventional circular geometry and a ring geometry. If the laser-induced forces push the particles or cells away from the laser beam, the ring geometry is more preferable for their trapping. The capabilities of such PA tweezers are discussed.
Photothermal trace detection in capillary electrophoresis for biomedical diagnostics and toxic materials (invited)
Authors: Faubel Werner , Heissler Stefan , Pyell Ute , Ragozina Natalia
Published: January 2003

Two applications of a near-field thermal lens capillary electrophoresis detector in the deep ultraviolet region (pump beam 257 nm wavelength) will be presented: (1) Capillary electrophoretic determination of the pharmaceuticals Tramadol, Verapamil, and Papaverin. Direct separation techniques were used for the different classes of substances with characteristic absorbance spectra. The combination of capillary electrophoresis and the highly sensitive detection with thermal lens spectroscopy permits the analysis of nanoliter volume samples common in biomedical diagnostics without any preconcentration step. (2) The determination of (nonfluorescent) nitro aromatic explosives in contaminated soil. These compounds are detected with the laboratory built thermal lens detector after their separation by micellar electrokinetic chromatography. Its shown that this type of detection makes it possible to obtain limits of detection 1–2 orders of magnitude lower than those obtained with classical absorption spectrometric detection.
Thermal and elastic characterizations by photothermal microscopy (invited)
Authors: Jumel Julien , Rochais Denis , Enguehard Franck , Lepoutre François
Published: January 2003

A photothermal microscope based on photoreflectance and interferometric techniques is used to measure, on the same field, the thermal properties and the thermoelastic response of samples heated by a focused intensity modulated laser beam. In imaging mode, this instrument provides two-dimensional thermal or mechanical qualitative maps. In characterization configuration thermal and thermoelastic properties, with resolutions of a few micrometers, can be quantitatively measured if careful analysis of the signals is made.
Comparative analysis of laser-based drug injection models
Authors: Latyshev Alexei S. , Zharov Vladimir P.
Published: January 2003

The aim of our study is to provide a mathematical model for laser-induced injection of topical drugs by focused 2.94 μm laser radiation. Having analyzed three feasible mechanisms of laser-induced drug injection, such as photoacoustic forcing, vacuum suction, and hydrodynamic collapse, we focused on the last mechanism. Computer-assisted simulation was made for various values of the crater diameter, surface tension, and dynamic viscosity. We demonstrate that the theoretical estimates of crater-collapse parameters agree quite well with experimental data.
Photothermally modulated ultrasound reflection
Authors: Netzelmann U. , Bruch D.
Published: January 2003

An intensity modulated laser beam is used to modulate the ultrasound reflection via a thermoelastic mechanism. Modulation frequencies in the range of 5 Hz–2 kHz are used. The ultrasonic reflection is measured in pulse-echo technique using broadband 80 MHz focusing transducers. The effect of the photothermal modulation is detected by lock-in technique after demodulation of the selected interface ultrasound signal using a peak detector and a sample-and-hold stage. Experiments are performed on a fused quartz slab with an embedded Mo sheet. Lack of adhesion between Mo and quartz is detected by the modulated technique with much more contrast than by the reflected ultrasound amplitude. Line scans of the heating laser beam across the ultrasonic beam and measurements as a function of the laser modulation frequency are in accordance with a thermoelastic process as dominant signal generation mechanism.
Laser modulated optical reflectance of thin semiconductor films on glass
Authors: Fotsing J. L. N. , Hoffmeyer M. , Chotikaprakhan S. , Dietzel D. , Pelzl J. , Bein B. K. , Cerqueira F. , Macedo F. , Ferreira J. A.
Published: January 2003

Semiconductor films, deposited by reactive magnetron sputtering on glass substrates, have been analyzed with the help of laser modulated optical reflectance. The results are discussed with respect to the thermal and charge carrier transport properties. Charge carrier surface recombination at the front surface and at the interface between semiconductor film and glass substrate have been identified both for microcrystalline and amorphous films.
Minimono: An ultracompact permanent magnet ion source for singly charged ions
Authors: Gaubert G. , Baru C. , Canet C. , Cornell J. , Dupuis M. , Farabolini W. , Flambard J. L. , Gorel P. , Jardin P. , Lecesne N. , Leherissier P. , Lemagnen F. , Leroy R. , Pacquet J. Y. , Saint-Laurent M. G. , Villari A. C. C.
Published: January 2003

Minimono is a 2.45 GHz electron cyclotron resonance ion source for singly charged ions which uses only permanent magnets. Measurements of ionization efficiencies, maximum currents extracted, and emittances for H+, He+3,4, N+, Ne+, Ar+, Kr+, S+, and Si+ were carried out. In the case of buckminster fullerenes, C60+, C602+, and C603+ ions were extracted. The results obtained, the general mechanical simplicity of this ion source, and its low cost make this source attractive for the production of stable and radioactive ions.
Symmetrically arranged quartz tuning fork with soft cantilever for intermittent contact mode atomic force microscopy
Authors: Akiyama T. , Staufer U. , de Rooij N. F. , Frederix P. , Engel A.
Published: January 2003

A self-sensing and -actuating probe for dynamic mode atomic force microscopy (AFM) based on a commercial quartz tuning fork and a microfabricated cantilever is presented. The U-shaped cantilever, exhibiting a sharp tip, is combined with the tuning fork in a symmetrical arrangement, such that each of the two legs of the cantilever is fixed to one of the prongs of the tuning fork. The tuning fork is used as an oscillatory force sensor. Its frequency and amplitude govern that of the tip vibration, while the cantilever determines the spring constant of the whole probe. The frequency of the tip vibration for AFM operations can be much higher than the resonance frequency of the cantilever. A probe comprising a silicon nitride cantilever (0.1 N/m) is used to image monoatomic terraces of graphite in the intermittent contact mode. A much softer cantilever (0.01 N/m) is used to analyze the topography of a microelectronic chip in the same mode. Moreover, a bacterial surface layer hexagonally packed intermediate layer of Deinococcus radiodurans is imaged in a buffer solution. The tip vibration was again generated by the tuning fork while the sample interaction was measured using the standard optical detection scheme in this experiment. These probes are suited for batch fabrication and assembly and, therefore, enlarge the applications for the tuning fork based AFM.
Ultrafast optical parametric amplifiers
Authors: Cerullo Giulio , De Silvestri Sandro
Published: January 2003

Over the last decade there have been spectacular developments in ultrafast laser technology, due to the introduction of solid state active materials and of new mode-locking and amplification techniques. These advances, together with the discovery of new nonlinear optical crystals, have fostered the introduction of ultrafast optical parametric amplifiers as a practical source of femtosecond pulses tunable across the visible and infrared spectral ranges. This article summarizes the recent progress in the development of ultrafast optical parametric amplifiers, giving the basic design principles for different frequency ranges and in addition presenting some advanced designs for the generation of ultrabroadband, few-optical-cycle pulses. Finally, we also briefly discuss the possibility of applying parametric amplification schemes to large-scale, petawatt-level systems.
Measurement of magnetic field pitch angle using motional Stark effect spectroscopy in the compact helical system
Authors: Takayama Sadatsugu , Ida Katsumi , Okamura Shouichi , Kado Shinichiro
Published: January 2003

A spectroscopy system, which consists of a zigzag charge coupled device and ferroelectric liquid crystal cells, has been developed to measure magnetic field pitch angles. The magnetic field pitch angle is derived from the polarization angle of σ and π components in the Hα line measured with polarization sensitive spectroscopy. By using the spectroscopy system, the location of zero pitch angle is measured to shift outboard due to the Pfirsh–Schluter current by 28±16 mm. This shift is consistent with that predicted by an equilibrium code.
Kinematic viscosity meter utilizing the phase of pressure gradient variation
Authors: Torigoe Ippei
Published: January 2003

A method is proposed for measuring the kinematic viscosity of a fluid. An exciter is mounted in a sensing channel and driven sinusoidally so as to vibrate the fluid within the channel. This vibration causes an axial pressure gradient variation that has two components: (1) a component proportional to the velocity and viscosity of fluid in the sensing channel and (2) a component proportional to the acceleration and density of the fluid. The ratio of these two components — the phase angle between the fluid velocity and the pressure gradient — is a function only of the vibration frequency and kinematic viscosity of the fluid. Since the frequency and phase of the fluid velocity vibration is known, the kinematic viscosity can be obtained from the phase of the pressure gradient variation. An experimental device that employs a loudspeaker as the vibration exciter and condenser microphones to detect the pressure gradient variation was constructed and several experiments were performed for air. The results show that the change in the kinematic viscosity due to a change in the air temperature can be measured successfully using the proposed kinematic viscosity meter utilizing the pressure gradient variation.
Improved microwave Hall effect measurements method
Authors: Prati E. , Faralli S. , Martinelli M. , Annino G. , Biasiol G. , Sorba L.
Published: January 2003

Measurements of the microwave Hall mobility of semiconductors have been performed by an improved contactless method at 20 GHz by using a bimodal cavity resonator and a two-channel vector network analyzer. Data analysis was performed by using generalized expressions for the mobility, taking into account different coupling values on the two ports and a nonlinear response due to high magnetic fields in samples with mobility from thousands of cm2/V s. For several samples, Hall microwave and dc measurements have been compared, confirming the reliability of the proposed method; the characterization of bulk n-ZnSe and modulation-doped n-Al0.33Ga0.67As/GaAs two-dimensional electron gas samples is in particular presented. This method appears particularly suitable for the experimental determination of magnetotransport properties of semiconductor materials, especially when good electric contacts are difficult to be realized.
A sensitive 10 T pulsed magnetometer
Authors: Kapustin G. A. , Kim Y. B. , Kim H. T. , Cho S. H.
Published: January 2003

An inductive magnetometer is described for measurements using the pulsed magnetic fields up to 10 T at room temperature. The sensing element of the magnetometer is a modification of a three-axis-compensated design. A distinctive feature of the magnetometer described is the independent compensation of signals induced by each of the spatial components of the pulsed magnetic field. Sensitivity of the magnetometer is 5×10−4 emu and is limited mainly by irreproducibility of the magnetometer compensation (10−6 of the signal from the working coil with an inner diameter of 4 mm). The magnetometer demonstrates high sensitivity for volume magnetization and magnetic susceptibility measurements (10−2 emu/cm3 and 10−7, accordingly, for samples with a volume of 60 mm3). As examples, the magnetization curves of some hard magnetics (bulk and thin films) and common diamagnetic materials are measured.
Nonlinear contact mechanics based on ring-down experiments with quartz crystal resonators
Authors: Berg Steffen , Prellberg Thomas , Johannsmann Diethelm
Published: January 2003

We report on the explicit derivation of a nonlinear spring constant and a nonlinear friction coefficient describing the interaction between an oscillating quartz plate and a tip touching its surface. The analysis is based on ring-down experiments. After the electrical excitation is turned off, the decay of the oscillation shows an amplitude-dependent resonance frequency and decay rate. This “chirp” does not occur when the quartz plate is out of contact. The chirp and the nonlinear decay rate are converted to a nonlinear spring constant κ1(x) and a nonlinear friction coefficient ξ1(ẋ) by means of a perturbation analysis.
Transmission of x-ray polarization through glass capillary fibers
Authors: Benenson R. E. , Bai Jianming , Gibson Walter M.
Published: January 2003

Synchrotron radiation beams at energies of 7, 8, and 11.5 keV were transmitted through straight and bent capillary fibers of the type used to focus or collimate x rays. The purpose was to learn if the multiple wall collisions during transmission would attenuate the polarization of the incident beam. The emergent polarization was determined using 90° Rayleigh–Thomson scattering by a carbon foil into a proportional counter. The results clearly showed that polarized x rays incident on a capillary fiber retained their polarization after transmission. Hence, focusing or collimating optics can be used with polarized x rays for background reduction in x-ray fluorescence measurements.
High-performance differential surface plasmon resonance sensor using quadrant cell photodetector
Authors: Zhang H. Q. , Boussaad S. , Tao N. J.
Published: January 2003

We describe a simple, stable, and high-resolution surface plasmon resonance (SPR) sensor using a quadrant cell photodetector. The sensor focuses a diode laser through a prism onto a gold film that is divided into two areas, one for reference and the other for sensing analyte. The angular shifts of the SPR generated in the two areas are detected with a quadrant cell photodetector. Because signals from the two areas are produced and detected with the same laser, optics, and photodetector, the difference in the SPR angular shifts eliminates errors due to thermal drift, mechanical noise, and laser fluctuations. It also removes the SPR angular shift due to the change in the refractive index of the bulk solution as an analyte solution is introduced into the sample cell each time, and thus gives an accurate detection of the specific adsorption of analyte.
Infrared photothermal radiometry of deep subsurface defects in semiconductor materials
Authors: Rodrı́guez M. E. , Garcia J. A. , Mandelis A.
Published: January 2003

Photothermal radiometry (PTR) signals obtained with a highly focused laser beam, were used to obtain amplitude and phase PTR two-dimensional and three-dimensional images of a high-resistivity Si wafer with a mechanical damage on the backsurface, probed from the front (intact) surface. The frequency chosen was 5 kHz, corresponding to an optimal phase resolution of the defect. It is shown that the position of the underlying damage is well resolved in both images, with the phase image showing the expected higher sensitivity in terms of a greater extent of the damage region compared to the amplitude image. The results indicate that the change in carrier lifetime is the major contrast mechanism which can thus be calibrated and labeled as a free-carrier recombination lifetime image (under the same surface recombination conditions).
Fundamental processes of surface enhanced Raman scattering detected with transient reflecting grating spectroscopy
Authors: Shibamoto Kohei , Katayama Kenji , Fujinami Masanori , Sawada Tsuguo
Published: January 2003

We investigated ultrafast photoexcited electrons dynamics in relation to the surface enhanced Raman scattering (SERS) effect, using the transient reflecting grating spectroscopy method. We observed that only SERS-active samples had transfer of photoexcited electrons from a metal surface to adsorbed molecules within 200 fs followed by return of these charge transferred electrons to the metal within several picoseconds. By analyzing charge transfer (CT) processes, we were able to identify the main influential factors of the adsorption state, stay time at adsorbed molecules, and quantity of CT carriers. That these obtained factors had correlations to each other may lead to clarification of the CT processes within several picoseconds with regard to the SERS enhancement mechanism.
Monitoring of gas diffusion in air using the TWI technique: Thermal diffusivity measurements made easy
Authors: Lima J. A. P. , da Silva M. G. , Masssunaga M. S. O. , Cardoso S. L. , Vargas H. , Marı́n E. , Miranda L. C. M.
Published: January 2003

The thermal wave interference technique (TWI) has been explored in recent years for the investigation of the thermal and transport properties of gases and liquids. In this article we address ourselves to the quantitative understanding of the transient thermal wave interference signal of air:hydrocarbon vapor mixtures. This is the situation one faces when placing a given portion of liquid hydrocarbon inside an initially air-filled thermal wave interference. What is observed in this case is the thermal wave interference signal decay as a function of the time as a result of the change of the gas thermal diffusivity with time due to the increase of the hydrocarbon vapor concentration in air. In this article we show that value of the thermal diffusivity of the saturated mixture is readily obtained from the saturation value of the normalized signal amplitude, without the need of performing the conventional L scan.
Photoacoustic determination of heat capacity per unit volume at room temperature of thin metallic foils
Authors: Gutiérrez-Juárez G. , Vargas-Luna M. , Camacho-Espinosa J. J. , Sosa M. , González-Solı́s J. L. , Bernal-Alvarado J. , Alvarado-Gil J. J.
Published: January 2003

A photoacoustic method for the determination of the heat capacity per unit volume (ρCp), at room temperature, for thin metallic foils is presented. The method is based on the use of a variant of a conventional photoacoustic cell.
Progress in phase angle thermography
Authors: Dillenz A. , Zweschper T. , Riegert G. , Busse G.
Published: January 2003

Phase angle thermography is basically spatially multiplexed photothermal radiometry. It provides images for remote detection and imaging of damage. For energy deposition one can use external heat sources (e.g., light or convective heating) or internal heat generation (e.g., electric current, microwaves, eddy current, or elastic wave). More complete information about defects is obtained by combining information from external and internal heating methods: Effects of intact thermal structure can be distinguished from defect specific thermal signatures. Our recent results relate to multifrequency excitation allowing for depth profiling from one lock-in-thermography measurement and, additionally, to modulated ultrasound frequency burst phase angle thermography where effects of standing elastic waves are eliminated. This way the applications for nondestructive evaluation become more reliable and faster.
Thermal lens determination of the temperature coefficient of optical path length in optical materials
Authors: Andrade A. A. , Catunda T. , Bodnar I. , Mura J. , Baesso M. L.
Published: January 2003

In this work thermal lens spectrometry is applied to determine the temperature coefficient of optical path length in several optical materials. Polymer, fluoride and low silica calcium aluminosilicate glasses and YAG, YVO4, YLF, LiSAF, and LiSGaF crystals were analyzed. The results showed the ability of the thermal lens method to obtain the absolute values of this so important optical parameter, which is crucial for those who work in the designing of solid state laser cavity.
Microscopic thermal characterization of composites
Authors: Jumel Julien , Lepoutre François , Roger Jean-Paul , Neuer Gunther , Cataldi Michel , Enguehart Franck
Published: January 2003

The microscopic thermoelastic properties of matrix and fibers of composites are often not known before and after the process of preparation. To master the final properties of the composite, it is essential to characterize these components in order to supply the code with realistic material parameters. This article illustrates how the photoreflectance microscopy is able to measure the thermal properties, at a microscopic scale.
Microscopic thermoelastic characterizations by interferometric photothermal microscopy
Authors: Jumel Julien , Lepoutre François , Rochais Denis , Enguehard Franck
Published: January 2003

Some publications have demonstrated that local thermoelastic behavior in materials can be revealed using a photothermal microscope coupled with an interferometer, but up to now the quantitative data that can be extracted from these measures are not established clearly. We present analysis of the signals, numerical simulations, and experimental results which demonstrate that the thermal diffusivity, the elastic anisotropy, and the principal directions of anisotropy orientation can be obtained with a microscopic resolution.
Highly sensitive detection of molecules at the liquid/liquid interface using total internal reflection–optical beam deflection based on photothermal spectroscopy
Authors: Fujinami Masanori , Murakawa Hiromi , Sawada Tsuguo
Published: January 2003

In this study, a highly sensitive and versatile method based on photothermal spectroscopy has been developed to monitor the molecular density at a liquid/liquid interface. The excitation under the total internal reflection (TIR) condition results in a formation of a thin thermal lens elongated along the interface. In order to measure the thermal lens effects effectively and to reduce the background, the probe beam is irradiated parallel to the interface and its deflection is detected, which is called an TIR-optical beam deflection (TIR-OBD). As a result, the detection limit in TIR-OBD is about 2 orders lower than that of TIR-thermal lens spectroscopy, in which the irradiation of the probe beam is perpendicular to the interface.
Microscopic characterization of functionally graded materials
Authors: Jumel Julien , Lepoutre François , Terrien Nicolas , Arnould Olivier , Roger Jean-Paul
Published: January 2003

Simple photothermal analysis and associated inversion procedures are proposed for thermal mapping of functionally graded materials whose thermal properties are varying parallel to the sample surface.
Ultrafast transient lens spectroscopy of photoisomerization dynamics of azocompounds in confined nanospace of cyclodextrins
Authors: Yui Hiroharu , Takei Masako , Hirose Yasushi , Sawada Tsuguo
Published: January 2003

The ultrafast photoisomerization dynamics of azocompounds encapsulated in the cavity of α-, β-, and γ-cyclodextrin (CD) was investigated by the ultrafast transient lens method regarding effects of special restriction and intermolecular interactions. As expected, the spatial restriction reduced the yield of photoisomerization, but the effect was not so remarkable, indicating that the host and guest were relatively freely bounded. This effect was more prominent in azo: γ-CD=2:2 system, where the two guest molecules were packed in parallel as a dimer. From the viewpoint of the confined nanospace as a new reaction field, we found that the azo: γ-CD=2:2 system induced a specific intermediate having a long lifetime, which was not observed in free solutions. We also found that the formation of hydrogen-bonding between CD and guest remarkably elongated the trans–cis transformation of guest molecules in Orange II/CD systems.
Autofocusing system for a photothermal microscope
Authors: Taillade Frédéric , Hoang N. N. , Jumel Julien , Lepoutre François
Published: January 2003

Photoreflectance and interferometric microscopy are rather new methods used for thermal and thermoelastic characterizations of materials at a microscopic scale. These methods make use of an intensity modulated laser beam (pump) to produce a thermal wave which is at the origin of thermal diffusion and elastic deformations. The measurements make use of the periodic signals of a photodiode which receives the flux of a second beam (probe) detecting the thermal wave and its elastic effects. The results are strongly sensitive to the spots of the probe and pump beams on the sample surface. To optimize the spatial resolution and the long term stability of the microscope, the focusing of the pump and probe beams has to be controlled. For that purpose, this article proposes a compact, cheap and robust autofocusing system.
Systematical analysis of laser beam modulated optical reflectance signals
Authors: Dietzel D. , Bein B. K. , Pelzl J.
Published: January 2003

Based on silicon as semiconductor reference material, the performance of the laser modulated optical reflectance signal is analyzed with respect to variations of the technical parameters of the measuring system and with respect to variations of the charge carrier lifetime related to ion implantation.
A vertical inertial coarse approach for variable temperature scanned probe microscopy
Authors: Silveira William R. , Marohn John A.
Published: January 2003

We have developed a variable temperature inertial coarse approach mechanism for use in scanned probe microscopy. This reliable micropositioner has a coarse range of 2.5 mm and can take individual steps of less than 10 nm from 4 to 300 K. This simple, compact device is both nonmagnetic and glueless. It is operational in both horizontal and vertical geometries and is driven by a low voltage sawtooth waveform. We report on the design and performance of the device.
A beam scattering instrument for the dynamics studies of surface-induced dissociation processes
Authors: Shukla Anil K. , Futrell Jean H.
Published: January 2003

A beam scattering instrument has been constructed to study the dynamics of ion-surface collisions, especially surface-induced dissociation of polyatomic ions. The instrument uses a bench top double focusing mass spectrometer as the source of a well-defined ion beam for transmission into a collision chamber. The primary ions are decelerated to desired ion energy (as low as 5 eV) by a series of tube lenses and collide the surface at 45°. Thus, the ion energy for surface-induced dissociations can be varied from ∼5 eV to ⩾1 keV. The secondary ions are energy and mass analyzed by a cylindrical energy analyzer and a quadrupole mass filter, respectively, and detected by a channel electron multiplier operating in pulse counting mode. The detector assembly can be rotated with respect to the collision center between the specular angle and surface parallel to measure intensity and energy distributions of scattered primary and fragment ions as a function of scattering angle. The newly constructed instrument has been tested for its performance and used to study the dissociation of ethanol molecular ions colliding with a self-assembled monolayer surface of fluorinated thiol on gold (111) crystal and first results are presented here.
A narrow-band wavelength-tunable laser system delivering high-energy 300 ps pulses in the near-infrared
Authors: Brandi F. , Velchev I. , Neshev D. , Hogervorst W. , Ubachs W.
Published: January 2003

We report on the operation of a novel laser system delivering high-energy pulses in the near-infrared region. The pulses are nearly Fourier-transform limited (time-bandwidth product of 0.48), providing narrow-band radiation (∼1.5 GHz), with an energy of 225 mJ and 10 Hz repetition rate. The pulse duration of 320 ps covers the intermediate region between Q-switched and mode-locked lasers, and provides high peak powers. The nearly Gaussian beam profile, with a beam quality factor of M2=2.5, enables tight focusing, reaching intensities exceeding 5×1013 W/cm2. The system operation is demonstrated near 780 nm, however, the tunability extends over the range 700–970 nm. The laser system is suitable for high-order harmonic generation in the extreme-ultraviolet region for high-resolution frequency domain spectroscopy.
Algorithms for correcting geometric distortions in delay-line anodes
Authors: Wilkinson Erik , Béland Stéphane , Penton Steven V. , Vallerga John V. , McPhate Jason B. , Sahnow David J.
Published: January 2003

Time-delay anodes are typically used in conjunction with microchannel plates to create photon counting, two-dimensional imaging detectors. The anode and associated electronics are used to compute the centroid of the charge cloud from the microchannel plate stack. The computation of event position is done in analog circuitry and then digitized to an appropriate number of bits. The analog nature of the time-delay anode makes it susceptible to a wide variety of outside influences resulting in variations in the correlation between physical space and the reported digital value. These variations, both local and global, must be corrected as part of the reduction of scientific data. If left uncorrected in spectral data, for example, these variations result in decreased spectral resolution, inaccurate wavelength identifications, and/or distorted spectral line profiles. This work presents successful algorithms for correcting the dominant distortions present in a time-delay anode. These algorithms were developed as part of the data reduction pipeline for the cosmic origins spectrograph (COS) far ultraviolet channel. COS is a fourth generation instrument for the Hubble Space Telescope.
Optical workstation with concurrent, independent multiphoton imaging and experimental laser microbeam capabilities
Authors: Wokosin David L. , Squirrell Jayne M. , Eliceiri Kevin W. , White John G.
Published: January 2003

Experimental laser microbeam techniques have become established tools for studying living specimens. A steerable, focused laser beam may be used for a variety of experimental manipulations such as laser microsurgery, optical trapping, localized photolysis of caged bioactive probes, and patterned photobleaching. Typically, purpose-designed experimental systems have been constructed for each of these applications. In order to assess the consequences of such experimental optical interventions, long-term, microscopic observation of the specimen is often required. Multiphoton excitation, because of its ability to obtain high-contrast images from deep within a specimen with minimal phototoxic effects, is a preferred technique for in vivo imaging. An optical workstation is described that combines the functionality of an experimental optical microbeam apparatus with a sensitive multiphoton imaging system designed for use with living specimens. Design considerations are discussed and examples of ongoing biological applications are presented. The integrated optical workstation concept offers advantages in terms of flexibility and versatility relative to systems implemented with separate imaging and experimental components.
Feedforward reduction of the microseism disturbance in a long-base-line interferometric gravitational-wave detector
Authors: Giaime J. A. , Daw E. J. , Weitz M. , Adhikari R. , Fritschel P. , Abbott R. , Bork R. , Heefner J.
Published: January 2003

Standing ocean waves driven by storms can excite surface waves in the ocean floor at twice the wave frequency. These traverse large distances on land and are called the double-frequency (DF) microseism. The Laser Interferometer Gravitational-wave Observatory (LIGO) detector relies on length servos to maintain optical resonance in its 4 km Fabry–Pérot cavities, which consist of seismically isolated in-vacuum suspended test mass mirrors in three different buildings. Correcting for the DF microseism motion can require tens of micrometers of actuation, a significant fraction of the feedback dynamic range. The LIGO seismic isolation design provides an external fine actuation system (FAS), which allows long-range displacement of the optical tables that support the test mass suspensions. We report on a feedforward control system that uses seismometer signals from each building to produce correction signals, which are applied to the FAS, largely removing the microseism disturbance independently of length control servos. The root-mean-squared displacement from the microseism near 0.15 Hz can be reduced by 10 dB on average.
High-sensitivity photothermal radiometry measurement using a mirrored liquid sample vessel for multireflection of a pumping beam
Authors: Yarai Atsushi , Okamoto Yoshitsugu , Nakanishi Takuji
Published: January 2003

A method to enhance the sensitivity of photothermal radiometry (PTR) measurement was proposed. This method features multireflection of a pumping laser beam on the inside of a liquid vessel. This is a new, effective, and extremely simple method for measurement of a lowly thermally emissive sample. Our experimental data were compared to that of the conventional PTR method. A dye (IR-140) was used as the impurity in a solvent, and we ascertained superior detectablity of the impurity in the sample vessel—a 12 mm diameter integrating sphere—to that of the conventional method by more than a magnitude of one. A theoretical “limit of detection” value for our technique was estimated to be 0.7 ppb when the power of the pumping beam was 500 mW.
A sum rule for associated Legendre polynomials with spherical triangles
Authors: Khachatourian Armik V. M. , Wistrom Anders O.
Published: January 2003

An explicit solution to the classical electrostatic problem of the electrostatic force between N conducting spheres requires the expansion of the electrostatic potential. The boundary conditions for the potentials are given by Gauss which requires an expansion of the inverse of the distance that encompasses six angles. A sum rule for this expansion is presented in terms of associated Legendre polynomials with complex exponentials.
Modified Michelson fiber-optic interferometer: A remote low-coherence distributed strain sensor array
Authors: Yuan Libo
Published: January 2003

A simple modified Michelson fiber-optic low-coherence interferometric quasi-distributed sensing system permitting absolute length measurement in remote reflective sensor array is proposed. The sensor reflective signals characteristics have been analyzed and the relationship between light signal intensities and sensors number was given for multiplexing potential evaluation. The proposed sensing scheme will be useful for the remote measurement of strain. An important application could be deformation sensing in smart structures. Experimentally, a three sensors array has been demonstrated.
Environmental chamber for powder x-ray diffractometers for use at elevated pressures and low temperatures
Authors: Koster van Groos A. F. , Guggenheim Stephen , Cornell Curt
Published: January 2003

An elevated-pressure, low-temperature environmental chamber was developed for the Bruker (Siemens) D-5000 theta-theta goniometer-based powder x-ray diffractometer. With minor modifications, the chamber is applicable to all models of theta-theta goniometers from any manufacturer. The chamber is capable of pressures to about 100 bars and temperatures from −50 °C to 200 °C (with silicone seals), based on conservative best estimates. Diffractometer scans may be made between 0° and 70° two theta.
A low-energy charged particle distribution imager with a compact sensor for space applications
Authors: Knudsen D. J. , Burchill J. K. , Berg K. , Cameron T. , Enno G. A. , Marcellus C. G. , King E. P. , Wevers I. , King R. A.
Published: January 2003

Low-energy plasmas having temperatures of order 1 eV or less are found commonly in the ionospheres and space environments of Earth and other planets. Measuring the density, temperature, drift velocities, phase-space anisotropies, and other properties of these plasmas presents numerous challenges. Examples are distortions of particle trajectories due to spacecraft wakes, spacecraft charging, and particle gyromotion in magnetized plasmas. Furthermore, these plasmas are known to organize into structures as small as tens of meters across, traversed by spacecraft in tens of milliseconds or less. The Suprathermal Plasma Imager (SPI) was developed to address these challenges. The SPI is optimized for measurements of particles with ∼1 eV energies, and of the suprathermal extension of those populations up to several hundred eV. The SPI is sensitive to particle flux intensities of order 6×105 cm−2 s−1 sr−1 eV−1 and greater. It produces 3024-pixel images corresponding to two-dimensional (angle/energy) cuts through plasma velocity distribution functions, with an image frame rate of up to 100 s−1. The SPI has a cylindrical sensor head measuring 37.5 mm in diameter and 14 cm long, with a mass of 350 g. The relatively small size and mass of the sensor allow it to be deployed easily on a boom, outside of the spacecraft’s electrical sheath and in a region where wake perturbations are reduced. The SPI sensor head contains no electronic circuitry, but instead creates a visible image of the particle distribution with a system of dc-biased grids, microchannel plates, and a phosphor screen. The phosphor image is transferred via an imaging fiber-optic cable to an instrument box in the main spacecraft body, where it is sampled with a charge-coupled device and support electronics. Inside the sensor, angle/energy images of incident particle distributions are formed by a pair of concentric hemispherical grids. The incident energies Ei accessible to the analyzer lie in the range 0⩽Ei⩽Emax where Emax≈qΔV/3, ΔV being the potential difference between the hemispheres. For an ideal analyzer, energy resolution ΔE/E is ⩽22% over most of the imaged energy range, degrading at energies below Emax/10. Angular resolution varies from 2° to 8° full width at half maximum between Emax and Emax/10. Energy and angular resolutions are degraded in the presence of a potential difference between the sensor and surrounding plasma. A 37.5-mm-diam version of the analyzer with a 0.86-mm-wide aperture has an ideal energy-dependent geometry factor of ≈5×10−4 eV sr cm2 for a square detector pixel of width 0.28 mm. Laboratory testing shows degraded energy resolution compared to ideal values, due in part to particle scattering within the analyzer. The SPI was tested successfully in flight on the GEODESIC auroral sounding rocket on 26 February 2000.
Phase shifting focused ion beam moiré method
Authors: Xie Huimin , Shang Haixia , Li Biao , Dai Fulong
Published: January 2003

In this article, a phase shifting technique for focused ion beam (FIB) moiré method is proposed, which is able to measure the full field in-plane deformation of an object in a micrometer scale. The FIB moiré is generated by the interference between a prepared specimen grating and FIB raster scan lines. The principle of phase shifting technique for FIB moiré is described in detail. With this method, phase shifting was realized in four steps from 0 to 2 π by shifting the focused ion beam controlled by a FIB system. This method is successfully used to measure the virtual deformation in a micro-electro-mechanical system structure with a 2500 lines/mm grating. The experiments prove the validity of this technique and show its ability of determine the full field strain with high accuracy.
Low noise temperature control: Application to an active cavity radiometer
Authors: Guillet Bruno , Robbes Didier , Méchin Laurence
Published: January 2003

We have designed low noise temperature sensing and control units with the objective of using them for the fabrication of far infrared active cavity radiometers. The sensing unit, first characterized at 300 K using industrial platinum resistance thermometers, has a noise level of ∼25–30 μKeff for a 3 h measuring time and in a 1 Hz bandwidth. Using YBCO superconducting thermometers, the noise level goes down to 2.5 μKeff, which is strongly limited by excess 1/f noise in the YBCO film at the superconducting transition. The sample holder used in the 90 K experiments is built with an auxiliary heating resistor, which enables an easy and accurate identification of the electrothermal model, even in the closed loop operation. Based on a design previously published by NIST, we estimate from these experimental results that the overall noise limitations of radiometers could be lowered by one order of magnitude.
Herriott Cell augmentation of a quadrature heterodyne interferometer
Authors: Antonsen Erik L. , Burton Rodney L. , Spanjers Gregory G. , Engelman Scott F.
Published: January 2003

A quadrature heterodyne interferometer is augmented with a Herriott Cell multipass reflector to increase instrument resolution, enable a separation of the phase shift due to neutral density from room vibrations, and optimize the diagnostic for small scale length measurements or for planar measurements. Analysis is used to illustrate retro-reflective planar measurement geometries attainable with the instrument and to show that phase front degradation and loss of scene beam intensity does not introduce a systematic measurement uncertainty. The diagnostic capability is demonstrated with measurements of the electron and neutral densities in the plasma exhaust from electric propulsion thrusters. Experimental data with up to 18 passes through plasma demonstrates that the instrument resolution to electron and neutral density increases almost linearly with number of passes, and that the Herriott Cell can be used to increase the signal of neutral density phase shifts relative to the noise of the phase shifts due to room vibrations. For the Pulsed Plasma Thruster plasma exhaust used to validate the instrument, the addition of the Herriott Cell reduces the density measurement uncertainty to equal or less than the uncertainty due to discharge irreproducibility.
Vibration of the cantilever in Force Modulation Microscopy analysis by a finite element model
Authors: Arinero R. , Lévêque G.
Published: January 2003

The resonance frequency of the cantilever beam of a Force Modulation Microscope is studied in function of the beam shape, the sample stiffness, and the contact model. We used a one dimensional finite element model for the cantilever beam, which permits the exact vibration of the beam to be treated in the contact mode, whatever its shape (rectangular as well as triangular beams) and excitation mode (by the beam holder, by the sample, by a localized, or distributed force). Based on a classic finite element scheme, it is simple to program and as rapid as the usual analytical models. We demonstrate that the mode of excitation of the beam strongly influences the cantilever’s frequency response in the contact mode. Anti-resonance is observed on the amplitude curves, which may perturb the measurements on some samples. We analyzed the true normal and tangential amplitude, for different beams and tip dimensions, in relation with the apparent amplitude of the vibration, as detected by the system. Experimental results on soft materials (polyurethane rubbers) give evidence of a nonsliding contact and underline the importance of an adequate treatment for the tangential forces, even in the linear domain. We assume a kind of viscosity of the contact, the effects of which are not visible for slow scan, but stick the tip and the sample together in the 10–100 kHz frequency range. This viscosity also induces an important damping of the resonance.
Magneto-optical imaging setup for single vortex observation
Authors: Goa P. E. , Hauglin H. , Olsen Å. A. F. , Baziljevich M. , Johansen T. H.
Published: January 2003

A recently developed high-resolution magneto-optical imaging (MOI) setup is reviewed. It is the first MOI system capable of resolving the individual vortices in a type-II superconductor. We give a detailed description of the whole setup, and discuss its measured properties in terms of magnetic sensitivity and signal-noise characteristics. A simple model for the image intensity distribution due to a vortex lattice is developed, and for the intensity profile across a single vortex, we find good agreement between model calculations and experimental data. The minimum vortex spacing resolved experimentally is 1.3 μm. Our analysis shows that increased resolution can most easily be achieved by increasing the light input intensity, but maximum resolution is ultimately limited by the effective extinction ratio through the optical system and mechanical vibrations in the setup.