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Review of Scientific Instruments

Issue 4 • Date Apr 2006

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Displaying Results 1 - 25 of 71
  • Issue Cover

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  • Issue Table of Contents

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  • Photoacoustic imaging in biomedicine

    Page(s): 041101 - 041101-22
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    Photoacoustic imaging (also called optoacoustic or thermoacoustic imaging) has the potential to image animal or human organs, such as the breast and the brain, with simultaneous high contrast and high spatial resolution. This article provides an overview of the rapidly expanding field of photoacoustic imaging for biomedical applications. Imaging techniques, including depth profiling in layered media, scanning tomography with focused ultrasonic transducers, image forming with an acoustic lens, and computed tomography with unfocused transducers, are introduced. Special emphasis is placed on computed tomography, including reconstruction algorithms, spatial resolution, and related recent experiments. Promising biomedical applications are discussed throughout the text, including (1) tomographic imaging of the skin and other superficial organs by laser-induced photoacoustic microscopy, which offers the critical advantages, over current high-resolution optical imaging modalities, of deeper imaging depth and higher absorption contrasts, (2) breast cancer detection by near-infrared light or radio-frequency–wave-induced photoacoustic imaging, which has important potential for early detection, and (3) small animal imaging by laser-induced photoacoustic imaging, which measures unique optical absorption contrasts related to important biochemical information and provides better resolution in deep tissues than optical imaging. View full abstract»

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  • Experimental study of moiré method in laser scanning confocal microscopy

    Page(s): 043101 - 043101-5
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    By integrating moiré method with laser scanning confocal microscopy (LSCM), a novel class of moiré patterns, i.e., LSCM moiré patterns, is presented and investigated by experiment in this article. The moiré patterns are formed by the interference of a 1200 line/mm cross-line holographic grating and the scanning lines of LSCM. The principles and conditions of forming LSCM moiré are described in detail. The measured parameters of moiré fringes from experimental images agree well with theoretical analysis. The experimental results verify the feasibility and reality of the proposed moiré method to be another effective and high accuracy technique for measuring and observing in-plane microdeformation at micrometer scale. View full abstract»

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  • Simple Hartmann test data interpretation for ophthalmic lenses

    Page(s): 043102 - 043102-5
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    This article describes a simple Hartmann test data interpretation that can be used to evaluate the performance of ophthalmic lenses. Considering each spot of the Hartmann pattern such as a single test ray, using simple ray tracing analysis, it is possible to calculate the power values from the lens under test at the point corresponding with each spot. The values obtained by this procedure are used to plot the power distribution map of the entire lens. We present the results obtained applying this method with single vision, bifocal, and progressive lenses. View full abstract»

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  • Second-order aberration corrected electron energy loss spectroscopy attachment for scanning electron microscopes

    Page(s): 043103 - 043103-6
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    At present transmission electron energy loss spectrum (EELS) analysis is only carried out in dedicated research instruments such as transmission electron microscopes (TEMs) or scanning transmission electron microscopes. This article presents a new design of second-order geometric aberration corrected EELS spectrometer attachment using split plates, which enables conventional scanning electron microscopes (SEMs) to provide TEM-like EELS spectra. Correction to a third-order dominant geometric aberration pattern has been achieved, which indicates that most of the second-order geometric aberration component is eliminated. This second-order aberration corrected spectrometer attachment design can enable SEMs to provide transmission EELS spectrums. View full abstract»

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  • Soft x-ray measurement of the toroidal pinch experiment RX reversed field pinch plasma using transition edge sensor calorimeter

    Page(s): 043104 - 043104-12
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    A superconductive transition edge sensor (TES) calorimeter is for the first time applied for the diagnostics of the reversed field pinch plasma produced in the toroidal pinch experiment RX (TPE-RX), and the instrumental system is fully described. The first result from the soft x-ray spectroscopy in 0.2–3 keV with an energy resolution ∼50 eV are also presented. The TES calorimeter is made of a thin bilayer film of titanium and gold with a transition temperature of 151 mK and its best energy resolution at our laboratory is 6.4 eV, while it was significantly degraded by about a factor of eight during the plasma operation. The TES microcalorimeter was installed in a portable adiabatic demagnetization refrigerator (ADR), which is originally designed for a rocket experiment. The detector box is carefully designed to shield the strong magnetic field produced by the ADR and TPE-RX. The ADR was directly connected to TPE-RX with a vacuum duct in the sideway configuration, and cooled down to 125 mK stabilized with an accuracy of 10 μK rms using an improved proportional, integral, and derivative (PID) control method. Thin aluminized Toray Lumirror or Parylene-N films were used for the IR to UV blocking filters of the incident x-ray window to allow soft x-rays coming into the detector with good efficiency. TPE-RX was operated with the plasma current of Ip=220 kA, and the wave forms of the TES output for every plasma shot lasting ∼80 ms were obtained with a digital oscilloscope. The wave forms were analyzed with the optimal filtering method, and x-ray signals were extracted. A total of 3472 counts of x-ray si- gnals were detected for 210 plasma shots during the flat-top phase of t=35–70 ms. Combined with the data measured with a lithium drifted silicon detector in the 1.3–8 keV range, spectral features are investigated using a spectral fitting package XSPEC. The obtained spectrum is well explained by thermal plasma emission, although an impurity iron-L line emissions at variously ionized states are dominant around 0.7–1.2 keV. At least three different temperature components ranging T=350–900 eV are required to account for the spectral shape, while the average temperature is consistent with the ruby laser Thomson scattering measurement. View full abstract»

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  • Novel time-of-flight electron spectrometer optimized for time-resolved soft-x-ray photoelectron spectroscopy

    Page(s): 043105 - 043105-6
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    We developed a time-of-flight electron spectrometer optimized for the detection of photoelectrons generated with femtosecond laser-generated extreme ultraviolet pulses. The low number of electrons requires an electrostatic lens design with a very high transmission over a broad energy range. We show that with an asymmetric lens geometry the chromatic aberration can be reduced and the overall transmission be increased. The setup can be further optimized employing a closed-loop optimization with an evolutionary algorithm to increase the throughput by varying the voltages applied to the lens plates. View full abstract»

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  • Coupling a versatile aerosol apparatus to a synchrotron: Vacuum ultraviolet light scattering, photoelectron imaging, and fragment free mass spectrometry

    Page(s): 043106 - 043106-10
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    An aerosol apparatus has been coupled to the Chemical Dynamics Beamline of the Advanced Light Source at Lawrence Berkeley National Laboratory. This apparatus has multiple capabilities for aerosol studies, including vacuum ultraviolet (VUV) light scattering, photoelectron imaging, and mass spectroscopy of aerosols. By utilizing an inlet system consisting of a 200 μm orifice nozzle and aerodynamic lenses, aerosol particles of ∼50 nm–∼1 μm in diameter can be sampled directly from atmospheric pressure. The machine is versatile and can probe carbonaceous aerosols generated by a laboratory flame, nebulized solutions of biological molecules, hydrocarbon aerosol reaction products, and synthesized inorganic nanoparticles. The sensitivity of this apparatus is demonstrated by the detection of nanoparticles with VUV light scattering, photoelectron imaging, and charged particle detection. In addition to the detection of nanoparticles, the thermal vaporization of aerosols on a heater tip leads to the generation of intact gas phase molecules. This phenomenon coupled to threshold single photon ionization, accessible with tunable VUV light, allows for fragment-free mass spectrometry of complex molecules. The initial experiments with light scattering, photoelectron imaging, and aerosol mass spectrometry reported here serve as a demonstration of the design philosophy and multiple capabilities of the apparatus. View full abstract»

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  • Characterization of a charge-coupled device array for Bragg spectroscopy

    Page(s): 043107 - 043107-10
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    The average pixel distance as well as the relative orientation of an array of six charge-coupled device (CCD) detectors have been measured with accuracies of about 0.5 nm and 50 μrad, respectively. Such a precision satisfies the needs of modern crystal spectroscopy experiments in the field of exotic atoms and highly charged ions. Two different measurements have been performed by illuminating masks in front of the detector array by remote sources of radiation. In one case, an aluminum mask was irradiated with x rays, and in a second attempt, a nanometric quartz wafer was illuminated by a light bulb. Both methods gave consistent results with a smaller error for the optical method. In addition, the thermal expansion of the CCD detectors was characterized between -105 and -40 °C. View full abstract»

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  • Silicon carbide nozzle for producing molecular beams

    Page(s): 043301 - 043301-8
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    A resistively heated nozzle of silicon carbide (SiC) ceramic was developed for the production of high speed molecular beams for space environment simulation. The nozzle is able to withstand temperatures in excess of 1800 °C and pressures to 30 bars. In a seeded beam of 1% argon in 99% hydrogen, a speed of 3.9 km/s was achieved for the argon component at a nozzle temperature of 1150 °C and a pressure of 23 bars. View full abstract»

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  • Double-decker femtosecond electron beam accelerator for pulse radiolysis

    Page(s): 043302 - 043302-5
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    A new concept of double-decker electron beam accelerator based on a photocathode radio-frequency (rf) gun was proposed for studying chemical kinetics and primary processes or reactions of radiation chemistry. The synchronized double-decker electron beams with time interval of 1.4 ns were generated in the rf gun by injecting two laser beams on the photocathode. The double-decker electron beams were accelerated by a booster linear accelerator (linac) up to 31.8 MeV with energy-phase correlation and compressed into femtosecond by rotating the bunch in the energy-phase distribution in magnetic fields. The normalized transverse emittance of both beams downstream of the linac was obtained to be 2.5±0.6 mm mrad for the up beam with bunch charge of 0.47 nC and 3.6±0.7 mm mrad for the down beam with bunch charge of 0.65 nC. The minimum relative energy spread was (0.14±0.03)% for the two beams. The compressed bunch length was obtained to be 430±25 fs for the up bunch and 510±20 fs for the down bunch. View full abstract»

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  • Dual beam experiment for simultaneous irradiation of surfaces with ion species of gaseous and solid-state elements

    Page(s): 043501 - 043501-10
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    The effects occurring under simultaneous bombardment of surfaces by ions of gaseous and solid elements is a new field for research, which is of great interest for applications ranging from cold plasma technologies to nuclear fusion in magnetically confined plasmas. A multitude of new effects has been observed originating from mixing of incident ion species and bulk material at the surface and, in some cases, from additional complex chemical interactions between the mixing species. To study these effects under controlled conditions a new dual beam experiment has been commissioned, particularly suited for in situ studies of surface sputtering and ion implantation processes. Thin films with negligible impurity level and surface roughness are used as targets. High energy ion beam analysis is used as a means of nondestructive elemental depth profiling and concentration measurements. This allows for the first time the fast quantification of the elemental composition change of a target sample in intervals between ion irradiation. The article describes the details of design and operation, as well as the accessible range of experimental conditions. View full abstract»

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  • Development of a 100 eV, high-flux ion beam acceleration system

    Page(s): 043502 - 043502-4
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    A new system of electrodes has been developed for a high-flux, steady-state ion source with a large irradiation area to study plasma-wall interaction in fusion reactors at energies in the 100 eV range. These electrodes are multiaperture triode electrodes—the sizes of which are smaller as compared with those used in similar applications for previous systems. In particular, these electrodes have a thickness of 0.5 mm and an aperture size of 0.9 mm in diameter with 0.5 mm gaps between them. The influence of the plasma sheath on the beam energy has to be estimated since the plasma sheath potential is comparable to the acceleration voltage in such a low energy region. Source plasma is produced by a hydrogen arc discharge, following which hydrogen ions are extracted by using the new electrode system. Ion fluxes of 1.5×1020–5.3×1020 H/m2 s with energies ranging from 28 to 102 eV/H were obtained. These values are comparable to those of conventional high-flux ion sources with higher energies. This low energy ion beam can be used to investigate the plasma-wall interaction in fusion reactors. View full abstract»

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  • Proton core imaging of the nuclear burn in inertial confinement fusion implosions

    Page(s): 043503 - 043503-9
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    A proton emission imaging system has been developed and used extensively to measure the nuclear burn regions in the cores of inertial confinement fusion implosions. Three imaging cameras, mounted to the 60-beam OMEGA laser facility [T. R. Boehly etal, Opt. Commun. 133, 495 (1997)], use the penetrating 14.7 MeV protons produced from D 3He fusion reactions to produce emission images of the nuclear burn spatial distribution. The technique relies on penumbral imaging, with different reconstruction algorithms for extracting the burn distributions of symmetric and asymmetric implosions. The hardware and design considerations required for the imaging cameras are described. Experimental data, analysis, and error analysis are presented for a representative symmetric implosion of a fuel capsule with a 17-μm-thick plastic shell and 18 atm D 3He gas fill. The radial burn profile was found to have characteristic radius Rburn, which we define as the radius containing half the D 3He reactions, of 32±2 μm (burn radii measured for other capsule types range from 20 to 80 μm). Potential sources of error due to proton trajectory changes from interactions with electric fields and scattering in capsule and camera hardware are estimated with simple analytic and Monte Carlo calculations; they are predicted to be small compared with statistical errors. Experimental tests were performed to look for any inconsistencies between results from different cameras and different imaging geometries, or- evidence of error due to ambient electric or magnetic fields, and none were found. View full abstract»

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  • Characterization and cross calibration of Agfa D4, D7, and D8 and Kodak SR45 x-ray films against direct exposure film at 4.0–5.5 keV

    Page(s): 043504 - 043504-7
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    Kodak direct exposure film (DEF) [B. L. Henke etal, J. Opt. Soc. Am. B 3, 1540 (1986)] has been the standard for moderate energy (1–10 keV) x-ray diagnostic applications among the high-energy-density and inertial confinement fusion research communities. However, market forces have prompted Kodak to discontinue production of DEF, leaving these specialized communities searching for a replacement. We have conducted cross-calibration experiments and film characterizations on five possible substitutes for Kodak DEF. The film types studied were Kodak’s Biomax MR (BMR) and SR45 along with Agfa’s D8, D7, and D4sc. None of the films tested matched the speed of DEF. BMR and D8 were closest but D8 exhibited lower noise, with superior resolution and dynamic range. Agfa D7, Agfa D4sc, and Kodak SR45 were significantly less sensitive than BMR and D8, however, the improvements they yielded in resolution and dynamic range warrant their use if experimental constraints allow. View full abstract»

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  • New model for ultracompact coaxial Marx pulse generator simulations

    Page(s): 043505 - 043505-7
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    This article describes a new simulation model developed with PSPICE in order to improve the ultra compact Marx generators designed at the French-German Research Institute of Saint-Louis (ISL). The proposed model is based on a Marx elementary unit and is an equivalent electric circuit that matches the actual configuration of the generator. It consists of a structural description of the elementary stage of a Marx generator including stray components. It also includes a behavioral model of the spark gap switches based on the Vlastos formula determining the arc resistance value. The prebreakdown delay is also taken into account. Experimental data have been used to validate the results of the simulations. An original indirect measurement, allowing the estimation of the spark gap resistance, is also proposed. View full abstract»

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  • Miniature hybrid plasma focus extreme ultraviolet source driven by 10 kA fast current pulse

    Page(s): 043506 - 043506-7
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    A miniature hybrid plasma focus device, operated in xenon gas medium and driven by a 10 kA fast current pulse, has been used to generate extreme ultraviolet radiation in the range of 6–15 nm. At present the radiation characteristics from xenon plasma were mainly assessed qualitatively using standard tools such as visible light framing camera, extreme ultraviolet (EUV) pinhole camera, and EUV photodiode. Strong pinching of xenon plasma is indicative from both visible and EUV imagings. The maximum size of the EUV emitting zone is estimated to be of the order of 0.21×1.55 mm and the estimated value is within the accepted value as benchmarked by industries. The EUV intensity measurement by photodiode showed fairly isotropic radiation at least in a half solid angle. This device can be developed further as a competent source for EUV metrology or lithography applications. View full abstract»

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  • Simple way to determine the edge of an electron-free sheath with an emissive probe

    Page(s): 043507 - 043507-3
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    A new technique to determine the edge of an electron-free sheath is presented. The technique takes advantage of the variation of the inflection point of the emissive probe I-V characteristic with electron emission. The edge of the electron-free sheath is identified as the position where the inflection point changes from increasing with emission to decreasing with emission. View full abstract»

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  • Method for measuring radial impurity emission profiles using correlations of line integrated signals

    Page(s): 043508 - 043508-6
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    A method of determining radial impurity emission profiles is outlined. The method uses correlations between line integrated signals and is based on the assumption of cylindrically symmetric fluctuations. Measurements at the reversed field pinch EXTRAP T2R show that emission from impurities expected to be close to the edge is clearly different in raw as well as analyzed data to impurities expected to be more central. Best fitting of experimental data to simulated correlation coefficients yields emission profiles that are remarkably close to emission profiles determined using more conventional techniques. The radial extension of the fluctuations is small enough for the method to be used and bandpass filtered signals indicate that fluctuations below 10 kHz are cylindrically symmetric. The novel method is not sensitive to vessel window attenuation or wall reflections and can therefore complement the standard methods in the impurity emission reconstruction procedure. View full abstract»

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  • Development of liquid-environment frequency modulation atomic force microscope with low noise deflection sensor for cantilevers of various dimensions

    Page(s): 043701 - 043701-8
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    We have developed a liquid-environment frequency modulation atomic force microscope (FM-AFM) with a low noise deflection sensor for a wide range of cantilevers with different dimensions. A simple yet accurate equation describing the theoretical limit of the optical beam deflection method in air and liquid is presented. Based on the equation, we have designed a low noise deflection sensor. Replaceable microscope objective lenses are utilized for providing a high magnification optical view (resolution: ≪3 μm) as well as for focusing a laser beam (laser spot size: ∼10 μm). Even for a broad range of cantilevers with lengths from 35 to 125 μm, the sensor provides deflection noise densities of less than

    11 fm/
     Hz
    in air and
    16 fm/
     Hz
    in water. In particular, a cantilever with a length of 50 μm gives the minimum deflection noise density of
    5.7 fm/
     Hz
    in air and
    7.3 fm/
     Hz
    in water. True atomic resolution of the developed FM-AFM is demonstrated by imaging mica in water. View full abstract»

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  • Energy resolved two-dimensional soft x-ray radiography with a micropattern gas detector

    Page(s): 043702 - 043702-8
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    This article discusses the use of energy resolved two-dimensional soft x-ray imaging (ERXI), in the range of 2–8 keV, to study and investigate composition and depth of different materials. This technique represents a new approach in which imaging is merged with multienergy analysis, performed with spectral scans in 25 energy subintervals. The detector used is a micropattern gas detector with gas electron multiplier as amplifying structure, pixel readout board with 144 pixels (12×12), and electronics for photon counting for each pixel. As the detector works in a proportional regime, images in adjustable energy windows (independently for each pixel) can be acquired. Energy resolution enhances the contrast and the imaging capability providing more information of the transparencies of the materials under investigations. Contact radiographies have been made with samples of four different materials: CaCl, organic fat matter, aluminum, and thin plastic tape. The resulting data transparency curves for these materials have been derived. These curves demonstrate the value of ERXI at high performances (high efficiency, high dynamics, and high contrast), potentially relevant for many future applications. View full abstract»

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  • Apertureless scanning near field optical microscope with sub-10 nm resolution

    Page(s): 043703 - 043703-11
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    We report on the implementation of a versatile dynamic mode apertureless scanning near field optical microscope (aSNOM) for nanoscopic investigations of optical properties at surfaces and interfaces. The newly developed modular aSNOM optomechanical unit is essentially integrable with a multitude of laser sources, homemade scanning probe microscopes (SPMs) as well as commercially available SPMs as demonstrated here. The instrument is especially designed to image opaque surfaces without a restriction to transparent substrates. In the description of the instrument we draw frequent attention to various possible artifact mechanisms, how to overcome them, and we present effective checks to ensure true near field optical contrast. Lateral optical contrast in optical amplitude and phase images below 10 nm is demonstrated. View full abstract»

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  • Cantilever temperature characterization in low temperature vacuum atomic force microscope

    Page(s): 043704 - 043704-4
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    The frequency response of an atomic force microscope silicon cantilever located in a vacuum cryostat chamber was investigated. The resonance frequency and the peak width were extracted by a Lorentzian fit of the resonance curves for different sample temperatures (15–310 K). Frequency shifts significantly less than one could expect from known temperature dependencies of Young’s modulus and the density of silicon were found. The estimations described in this article show that the temperature of a silicon cantilever is mainly defined by the temperature of its holder, mainly due to the thermal conductivity of silicon. Thermal radiation emission plays a minor role in cooling the cantilever. Furthermore, heat transport through tip-sample contact, as well as contact with the environmental gas, could be neglected. View full abstract»

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  • Design of a femtosecond laser assisted tomographic atom probe

    Page(s): 043705 - 043705-8
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    A tomographic atom probe (TAP) in which the atoms are field evaporated by means of femtosecond laser pulses has been designed. It is shown that the field evaporation is assisted by the laser field enhanced by the subwavelength dimensions of the specimen without any significant heating of the specimen. In addition, as compared with the conventional TAP, due to the very short duration of laser pulses, no spread in the energy of emitted ions is observed, leading to a very high mass resolution in a straight TAP in a wide angle configuration. At last, laser pulses can be used to bring the intense electric field required for the field evaporation on poor conductive materials such as intrinsic Si at low temperature. In this article, the performance of the laser TAP is described and illustrated through the investigation of metals, oxides, and silicon materials. View full abstract»

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Aims & Scope

Review of Scientific Instruments, published by the American Institute of Physics, is devoted to scientific instruments, apparatus, and techniques.

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Meet Our Editors

Editor
Albert T. Macrander
Argonne National Laboratory