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Dec 2007

Volume 78, Issue 12, Articles (12xxxx)

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Rev. Sci. Instrum. 78, 121301 (2007); http://dx.doi.org/10.1063/1.2821148 (15 pages)

A. Westphalen, M.-S. Lee, A. Remhof, and H. Zabel
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Perspective: Tools of modern magnetic materials research: Vector and Bragg magneto-optical Kerr effect for the analysis of nanostructured magnetic arrays [ Rev. Sci. Instrum. 78, 121301 (2007) ]

Wolfgang Kleemann

Rev. Sci. Instrum. 78, 120901 (2007); http://dx.doi.org/10.1063/1.2821150 (2 pages) | Cited 4 times

Online Publication Date: 12 December 2007

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Abstract Unavailable
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78.20.Ls Magneto-optical effects
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.75.-c Magnetic properties of nanostructures
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Invited article: Vector and Bragg Magneto-optical Kerr effect for the analysis of nanostructured magnetic arrays

A. Westphalen, M.-S. Lee, A. Remhof, and H. Zabel

Rev. Sci. Instrum. 78, 121301 (2007); http://dx.doi.org/10.1063/1.2821148 (15 pages) | Cited 21 times

Online Publication Date: 12 December 2007

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Experimental and theoretical aspects of obtaining the magnetic information carried by laser beams diffracted from an array of micro- or nanosized magnetic objects are reviewed. We report on the fundamentals of vector magneto-optic Kerr effect (MOKE), Bragg-MOKE, and second-order effects in the Kerr signal in longitudinal Kerr geometry as well as on an experimental setup used for vector and Bragg-MOKE experiments. The vector and Bragg-MOKE technique in combination with micromagnetic simulation is a reliable tool for measuring the complete magnetization vector and for characterizing the reversal mechanism of lateral magnetic nanostructures. We discuss the Bragg-MOKE effect for three standard domain configurations during the magnetization reversal process and present the expected behavior of the magnetic hysteresis loops.
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78.20.Ls Magneto-optical effects
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Jk Magnetization reversal mechanisms
75.50.Tt Fine-particle systems; nanocrystalline materials
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A hyperspectral fluorescence lifetime probe for skin cancer diagnosis

P. A. A. De Beule, C. Dunsby, N. P. Galletly, G. W. Stamp, A. C. Chu, U. Anand, P. Anand, C. D. Benham, A. Naylor, and P. M. W. French

Rev. Sci. Instrum. 78, 123101 (2007); http://dx.doi.org/10.1063/1.2818785 (7 pages) | Cited 23 times

Online Publication Date: 4 December 2007

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The autofluorescence of biological tissue can be exploited for the detection and diagnosis of disease but, to date, its complex nature and relatively weak signal levels have impeded its widespread application in biology and medicine. We present here a portable instrument designed for the in situ simultaneous measurement of autofluorescence emission spectra and temporal decay profiles, permitting the analysis of complex fluorescence signals. This hyperspectral fluorescence lifetime probe utilizes two ultrafast lasers operating at 355 and 440 nm that can excite autofluorescence from many different biomolecules present in skin tissue including keratin, collagen, nicotinamide adenine dinucleotide (phosphate), and flavins. The instrument incorporates an optical fiber probe to provide sample illumination and fluorescence collection over a millimeter-sized area. We present a description of the system, including spectral and temporal characterizations, and report the preliminary application of this instrument to a study of recently resected (<2 h) ex vivo skin lesions, illustrating its potential for skin cancer detection and diagnosis.
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42.62.Be Biological and medical applications
87.19.X- Diseases
87.15.M- Spectra of biomolecules
87.14.E- Proteins

KMC-1: A high resolution and high flux soft x-ray beamline at BESSY

F. Schaefers, M. Mertin, and M. Gorgoi

Rev. Sci. Instrum. 78, 123102 (2007); http://dx.doi.org/10.1063/1.2808334 (14 pages) | Cited 22 times

Online Publication Date: 4 December 2007

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The crystal monochromator beamline KMC-1 at a BESSY II bending magnet covers the energy range from soft (1.7 keV) to hard x-rays (12 keV) employing the (n,−n) double crystal arrangement with constant beam offset. The monochromator is equipped with three sets of crystals, InSb, Si (111), and Si (422) which are exchangeable in situ within a few minutes. Beamline and monochromator have been optimized for high flux and high resolution. This could be achieved by (1) a windowless setup under ultrahigh-vacuum conditions up to the experiment, (2) by the use of only three optical elements to minimize reflection losses, (3) by collecting an unusually large horizontal radiation fan (6 mrad) with the toroidal premirror, and (4) the optimization of the crystal optics to the soft x-ray range necessitating quasibackscattering crystal geometry (θBragg,max = 82°) delivering crystal limited resolution. The multipurpose beamline is in use for a variety of user facilities such as extended x-ray absorption fine structure, ((Bio-)EXAFS) near-edge x-ray absorption fine structure (NEXAFS), absorption and fluorescence spectroscopy. Due to the windowless UHV setup the k edges of the technologically and biologically important elements such as Si, P, and S are accessible. In addition to these experiments this beamline is now extensively used for photoelectron spectroscopy at high kinetic energies. Photon flux in the 1011–1012 photons/s range and beamline resolving powers of more than E/ΔE ≈ 100.000 have been measured at selected energies employing Si (nnn) high order radiation in quasibackscattering geometry, thus photoelectron spectroscopy with a total instrumental resolution of about 150 meV is possible. This article describes the design features of the beamline and reports some experimental results in the above mentioned fields.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
79.60.-i Photoemission and photoelectron spectra
78.70.Dm X-ray absorption spectra

Phase-locked scanning interferometer for frequency stabilization of multiple lasers

Alexei A. Tonyushkin, Adam D. Light, and Michael D. Di Rosa

Rev. Sci. Instrum. 78, 123103 (2007); http://dx.doi.org/10.1063/1.2818773 (7 pages) | Cited 1 time

Online Publication Date: 6 December 2007

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We report a simple scheme for stabilizing and tuning the length of a conventional piezo-driven optical cavity against the resonant transmission of a master laser. In contrast with other schemes, we drive the piezo at its mechanical resonance of 5 kHz over an amplitude equivalent to one free spectral range and use a feedback circuit that incorporates phase-sensitive detection of the master-laser transmission. The bandwidth of our cavity-lock circuit is limited only by the resonance frequency of the cavity piezo and is 1.4 kHz. The stabilized mean cavity length reaches in 30 s a minimum Allan deviation of ∼ 10 kHz (a length stability of 20 parts per trillion) equaling that of the polarization-stabilized He–Ne we use as our master laser. Here, we investigate the mechanical characteristics of the cavity, describe the lock circuit and its measured performance, and provide simple analytical relations between the phase-sensitive signal and cavity displacement. Our setup economizes the cost and amount of equipment necessary for stabilizing multiple continuous-wave lasers operating at different wavelengths.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking
07.60.Ly Interferometers

High-intensity xenon plasma discharge lamp for bulk-sensitive high-resolution photoemission spectroscopy

S. Souma, T. Sato, T. Takahashi, and P. Baltzer

Rev. Sci. Instrum. 78, 123104 (2007); http://dx.doi.org/10.1063/1.2818806 (4 pages) | Cited 21 times

Online Publication Date: 6 December 2007

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We have developed a highly brilliant xenon (Xe) discharge lamp operated by microwave-induced electron cyclotron resonance (ECR) for ultrahigh-resolution bulk-sensitive photoemission spectroscopy (PES). We observed at least eight strong radiation lines from neutral or singly ionized Xe atoms in the energy region of 8.4–10.7 eV. The photon flux of the strongest Xe I resonance line at 8.437 eV is comparable to that of the He Iα line (21.218 eV) from the He-ECR discharge lamp. Stable operation for more than 300 h is achieved by efficient air-cooling of a ceramic tube in the resonance cavity. The high bulk sensitivity and high-energy resolution of PES using the Xe lines are demonstrated for some typical materials.
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42.72.Bj Visible and ultraviolet sources
07.81.+a Electron and ion spectrometers
52.75.-d Plasma devices
52.80.-s Electric discharges

Compact soft x-ray spectrometer for plasma diagnostics at the Heidelberg Electron Beam Ion Trap

A. Lapierre, J. R. Crespo López-Urrutia, T. M. Baumann, S. W. Epp, A. Gonchar, A. J. González Martínez, G. Liang, A. Rohr, R. Soria Orts, M. C. Simon, H. Tawara, R. Versteegen, and J. Ullrich

Rev. Sci. Instrum. 78, 123105 (2007); http://dx.doi.org/10.1063/1.2818808 (8 pages) | Cited 6 times

Online Publication Date: 7 December 2007

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A compact flat-field soft x-ray grazing-incidence grating spectrometer equipped with a cryogenically cooled back-illuminated charge-coupled device camera was built and implemented at the Heidelberg Electron Beam Ion Trap. The instrument spans the spectral region from 1 to 37 nm using two different gratings. In slitless operation mode, it directly images a radiation source, in this case ions confined in an electron beam ion trap, with high efficiency and reaching hereby a resolving power of λ/Δλ ≅ 130 at 2 nm and of λ/Δλ ≅ 600 at 28 nm. Capable of automatized operation, its low noise and excellent stability make it an ideal instrument not only for spectroscopic diagnostics requiring wide spectral coverage but also for precision wavelength measurements.
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07.85.Nc X-ray and γ-ray spectrometers
52.70.La X-ray and γ-ray measurements
29.30.Kv X- and γ-ray spectroscopy

Recent progress in vacuum-ultraviolet polarization modulation spectroscopy using polarizing undulator at the TERAS BL5 beamline

Kazutoshi Yagi-Watanabe, Masahito Tanaka, Fusae Kaneko, and Kazumichi Nakagawa

Rev. Sci. Instrum. 78, 123106 (2007); http://dx.doi.org/10.1063/1.2817630 (10 pages) | Cited 3 times

Online Publication Date: 10 December 2007

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Polarization modulation spectroscopy using an Onuki-type undulator is a useful technique for circular dichroism study in the vacuum-ultraviolet region. We have been developing the vacuum-ultraviolet circular dichroism (vuv-CD) spectroscopy in TERAS BL5 beamline at AIST. This paper describes recent improvements in our instrumentation and methods of analysis to achieve precise and absolute measurements. The CD signal is usually accompanied by experimental artifacts, and elimination of all possible artifacts is the key issue for making reliable measurements. After improving beamline optical system, light flux monitor, and undulator operation method, the base line shift of the CD spectrum is suppressed less than 3×10−4. Sample manipulation and data processing procedures are also described and absolute CD spectrum can be obtained even for linear anisotropic sample. These progresses lead to more quantitative comparison of experimental with calculation on vuv-CD spectrum.
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07.60.Rd Visible and ultraviolet spectrometers
29.27.-a Beams in particle accelerators

Direct measurement of the matched spot size in a slow capillary discharge optical waveguide

Pavel S. Antsiferov, Mohamed R. Akdim, and Herman T. van Dam

Rev. Sci. Instrum. 78, 123107 (2007); http://dx.doi.org/10.1063/1.2821601 (3 pages) | Cited 1 time

Online Publication Date: 18 December 2007

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This communication presents direct method for experimental determining the matched spot size in a plasma optical waveguide, created in a slow capillary discharge. It can be used for Laser Wakefield Acceleration experiments in addition to interferometry for fast control of optical properties of discharge plasma. The measurements are done by means of the comparison of the laser beam size at the entrance and at the exit of the plasma channel. They are direct in the sense that the interpretation is made in terms of the refractive index without usage of the information about electron density distribution. The method can be used for matched spot size measurement in conditions of the nonlinear effects (transmission of high power laser pulses).
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52.25.-b Plasma properties
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.80.-s Electric discharges
52.38.Kd Laser-plasma acceleration of electrons and ions

Mid-infrared optical coherence tomography

Christopher S. Colley, Jeremy C. Hebden, David T. Delpy, Alison D. Cambrey, Robert A. Brown, Evgeny A. Zibik, Wing H. Ng, Luke R. Wilson, and John W. Cockburn

Rev. Sci. Instrum. 78, 123108 (2007); http://dx.doi.org/10.1063/1.2821609 (7 pages) | Cited 6 times

Online Publication Date: 18 December 2007

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A time domain optical coherence tomography (OCT) system is described that uses mid-infrared light (6–8 μm). To the best of our knowledge, this is the first OCT system that operates in the mid-infrared spectral region. It has been designed to characterize bioengineered tissues in terms of their structure and biochemical composition. The system is based upon a free-space Michelson interferometer with a germanium beam splitter and a liquid nitrogen cooled HgCdTe detector. A key component of this work has been the development of a broadband quantum cascade laser source (InGaAs/AlInAs containing 11 different active regions of the three well vertical transition type) that emits continuously over the 6–8 μm wavelength range. This wavelength range corresponds to the so called “mid-infrared fingerprint region” which exhibits well-defined absorption bands that are specifically attributable to the absorbing molecules. Therefore, this technology provides an opportunity for optical coherence molecular imaging without the need for molecular contrast agents. Preliminary measurements are presented.
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42.30.Wb Image reconstruction; tomography
07.60.Ly Interferometers

Portable x-ray fluorescence spectrometer for coating thickness measurement

Alain Carapelle, Karl Fleury-Frenette, Jean-Paul Collette, Henri-Pierre Garnir, and Philippe Harlet

Rev. Sci. Instrum. 78, 123109 (2007); http://dx.doi.org/10.1063/1.2822613 (3 pages) | Cited 3 times

Online Publication Date: 18 December 2007

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A handheld x-ray spectrometer has been realized and tested. The purpose of the device is to measure the thickness of coated samples in the range of 1–1500 nm in an industrial environment. Accuracy of ∼ 3% has been achieved in this range with a measurement time of 1 min. Automated software has been implemented to allow utilization by a nonspecialist operator. An automated calibration procedure, based on measurements of reference samples, is used.
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07.85.Nc X-ray and γ-ray spectrometers
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
06.20.fb Standards and calibration

Determination of neutral carbon concentration in electron cyclotron resonance generated plasma discharges

A. B. Ene, P. Lindner, R. Stirn, and U. Schumacher

Rev. Sci. Instrum. 78, 123110 (2007); http://dx.doi.org/10.1063/1.2823332 (7 pages) | Cited 1 time

Online Publication Date: 26 December 2007

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Carbon containing plasmas play an important role not only in plasma technology but also in thermonuclear fusion research. In order to understand and control the processes taking place in the plasma, the knowledge of the carbon ground state density is of major importance. It can be determined by absorption and emission spectroscopy. Detailed measurements were performed in the past to determine the silicon ground state density by means of spectroscopy of the self-absorbed spectral lines of the silicon ground state multiplet at 251 nm. The same procedure was applied for the determination of the carbon concentration, for which the carbon multiplet at 165 nm was analyzed and compared to a simulated spectrum. The ground state density was determined by two independent methods.
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52.80.-s Electric discharges
52.50.-b Plasma production and heating
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Design and operating characteristics of new type cold cathode ion source

A. Hassan, N. Bassal, and S. G. Zakhary

Rev. Sci. Instrum. 78, 123301 (2007); http://dx.doi.org/10.1063/1.2821236 (4 pages)

Online Publication Date: 10 December 2007

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In this work, the design and performance of new type ion source are described. The discharge mechanism of the source is based on creating an arc discharge through a saddle electric field inside the discharge tube. The saddle electric field is created by immersing an annular anode inside the discharge tube covered from the upper and lower ends with two flanges. These two flanges act as cathodes. The discharge tube is surrounded by a solenoid coil which produces an axial magnetic field (up to 400 G) measured at the center of the source. Measurements have been performed to find out the influence of arc power, pressure, discharge voltage, magnetic field, and extracting voltage on the ion source properties. The source yields an argon ion current of ∼ 0.6 mA and electron current of ∼ 4 mA at normal operating conditions (extraction voltage Vex = 7 kV, pressure of 5.5×10−4 Torr, Varc = 400 V, Iarc = 1 A, B = 200 G). It showed an energy spread of 20 eV at a discharge voltage of 400 V and an extraction voltage of 3 kV.
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07.77.Ka Charged-particle beam sources and detectors
29.25.Ni Ion sources: positive and negative

Femtosecond synchronism of x-rays and visible/infrared light in an x-ray free-electron laser

B. W. Adams

Rev. Sci. Instrum. 78, 123302 (2007); http://dx.doi.org/10.1063/1.2805114 (9 pages)

Online Publication Date: 12 December 2007

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A way is proposed to obtain ultrashort pulses of intense infrared/visible light in few-femtosecond synchronism with x-rays from an x-ray free-electron laser (XFEL). It makes use of the recently proposed emittance-slicing technique [ Emma et al., Phys. Rev. Lett. 92, 074801 (2004) ] to both restrict the duration of self-amplified spontaneous emission (SASE) to a few femtoseconds and to lead to a coherence enhancement of near-infrared transition undulator radiation (CTUR). The x-rays and the near-infrared light originate within the XFEL undulator from the same slice of electrons within a bunch and are therefore perfectly synchronized with each other. An example of realizing the scheme at the Linac Coherent Light Source is presented. A few side issues are explored briefly, such as the magnitude of the velocity term versus the acceleration term in the Lienard-Wiechert fields and the possible use of the CTUR as a diagnostic tool for the SASE process itself.
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41.60.Cr Free-electron lasers
06.60.Jn High-speed techniques (microsecond to femtosecond)
42.72.-g Optical sources and standards
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Fine positioning of a poloidal probe array

T. Yamada, Y. Nagashima, S. Inagaki, Y. Kawai, M. Yagi, S.-I. Itoh, T. Maruta, S. Shinohara, K. Terasaka, M. Kawaguchi, M. Fukao, A. Fujisawa, and K. Itoh

Rev. Sci. Instrum. 78, 123501 (2007); http://dx.doi.org/10.1063/1.2818796 (5 pages) | Cited 18 times

Online Publication Date: 4 December 2007

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Multipoint detection is an essential requirement for investigating plasma turbulence which is a highly nonlinear phenomenon in space and time. We have fabricated an array of 64-channel poloidal probes surrounding the linear cylindrical plasma named LMD-U in order to study turbulence properties, particularly the nonlinear mode couplings, in the domain of poloidal wave number and frequency. However, misalignments of probe tips produce spurious modes, which do not exist in the real plasma, to distort the precise wave number measurements. The paper presents the description of the 64-channel poloidal probe array with means to adjust the probe positions, with discussion on the effects of the misalignments on the wave number measurements.
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52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.35.Ra Plasma turbulence
52.70.-m Plasma diagnostic techniques and instrumentation

Two-dimensional signal reconstruction: The correlation sampling method

H. E. Roman

Rev. Sci. Instrum. 78, 123502 (2007); http://dx.doi.org/10.1063/1.2821142 (5 pages) | Cited 1 time

Online Publication Date: 6 December 2007

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An accurate approach for reconstructing a time-dependent two-dimensional signal from non-synchronized time series recorded at points located on a grid is discussed. The method, denoted as correlation sampling, improves the standard conditional sampling approach commonly employed in the study of turbulence in magnetoplasma devices. Its implementation is illustrated in the case of an artificial time-dependent signal constructed using a fractal algorithm that simulates a fluctuating surface. A statistical method is also discussed for distinguishing coherent (i.e., collective) from purely random (noisy) behavior for such two-dimensional fluctuating phenomena.
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52.35.Ra Plasma turbulence
52.30.-q Plasma dynamics and flow
02.50.-r Probability theory, stochastic processes, and statistics
05.40.Ca Noise
05.45.Df Fractals

A new emissive-probe method for electron temperature measurement in radio-frequency plasmas

Kouta Kusaba and Haruo Shindo

Rev. Sci. Instrum. 78, 123503 (2007); http://dx.doi.org/10.1063/1.2821200 (8 pages) | Cited 3 times

Online Publication Date: 13 December 2007

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A new method to measure electron temperature by an emissive probe has been proposed. The method is based on measurement of the functional relationship between the floating potential and the heating voltage of emissive probe. From the measured data of the floating potential change as a function of the heating voltage, the electron temperature could be determined by comparing with the theoretical curve obtained under the assumption of Maxwellian distribution. The overall characteristic of the floating potential change could be explained as a function of the heating voltage. The electron temperatures obtained by the present method were consistent with those measured by the rf-compensated Langmuir probe within the error. These experimental verifications were made in the electron density range of 2.6×1011–2.8×1012 cm−3. It was stressed that the present method is advantageous in that the probe is operated in a floating condition, hence applicable to plasmas produced in an insulated container.
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52.80.Pi High-frequency and RF discharges
52.50.Qt Plasma heating by radio-frequency fields; ICR, ICP, helicons
52.70.Ds Electric and magnetic measurements
52.25.-b Plasma properties

Neutron production from feedback controlled thermal cycling of a pyroelectric crystal

V. Tang, G. Meyer, J. Morse, G. Schmid, C. Spadaccini, P. Kerr, B. Rusnak, S. Sampayan, B. Naranjo, and S. Putterman

Rev. Sci. Instrum. 78, 123504 (2007); http://dx.doi.org/10.1063/1.2823973 (4 pages) | Cited 8 times

Online Publication Date: 26 December 2007

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The LLNL Crystal Driven Neutron Source is operational and has produced record ion currents of ∼ 10 nA and neutron output of 1.9(±0.3)×105 per thermal cycle using a crystal heating rate of 0.2 °C/s from 10 to 110 °C. A 3 cm diameter by 1 cm thick LiTaO3 crystal with a socket secured field emitter tip is thermally cycled with feedback control for ionization and acceleration of deuterons onto a deuterated target to produce D–D fusion neutrons. The entire crystal and temperature system is mounted on a bellows which allows movement of the crystal along the beam axis and is completely contained on a single small vacuum flange. The modular crystal assembly permitted experimental flexibility. Operationally, flashover breakdowns along the side of the crystal and poor emitter tip characteristics can limit the neutron source. The experimental neutron results extend earlier published work by increasing the ion current and pulse length significantly to achieve a factor-of-two higher neutron output per thermal cycle. These findings are reviewed along with details of the instrument.
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29.25.Dz Neutron sources
34.50.Fa Electronic excitation and ionization of atoms (including beam-foil excitation and ionization)
25.60.Pj Fusion reactions

Compact cantilever force probe for plasma pressure measurements

I. S. Nedzelskiy, C. Silva, H. Fernandes, P. Duarte, and C. A. F. Varandas

Rev. Sci. Instrum. 78, 123505 (2007); http://dx.doi.org/10.1063/1.2813897 (6 pages) | Cited 5 times

Online Publication Date: 28 December 2007

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A simple, compact cantilever force probe (CFP) has been developed for plasma pressure measurements. It is based on the pull-in phenomenon well known in microelectromechanical-system electrostatic actuators. The probe consists of a thin (25 μm) titanium foil cantilever (38 mm of length and 14 mm of width) and a fixed electrode separated by a 0.75 mm gap. The probe is shielded by brass box and enclosed into boron nitride housing with a 9 mm diameter window for exposing part of cantilever surface to the plasma. When the voltage is applied between the cantilever and the electrode, an attractive electrostatic force is counterbalanced by cantilever restoring spring force. At some threshold (pull-in) voltage the system becomes unstable and the cantilever abruptly pulls toward the fixed electrode until breakdown occurs between them. The threshold voltage is sensitive to an additional externally applied force, while a simple detection of breakdown occurrence can be used to measure that threshold voltage value. The sensitivity to externally applied forces obtained during calibration is 0.28 V/μN (17.8 V/Pa for pressure). However, the resolution of the measurements is ±0.014 mN (±0.22 Pa) due to the statistical scattering in measured pull-in voltages. The diagnostic temporal resolution is ∼ 10 ms, being determined by the dynamics of pull-in process. The probe has been tested in the tokamak ISTTOK edge plasma, and a plasma force of ∼ 0.07 mN (plasma pressure ∼ 1.1 Pa) has been obtained near the leading edge of the limiter. This value is in a reasonable agreement with the estimations using local plasma parameters measured by electrical probes. The use of the described CFP is limited by a heat flux of Q ∼ 106 W/m2 due to uncontrollable rise of the cantilever temperature (ΔT ∼ 20 °C) during CFP response time.
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52.25.-b Plasma properties
52.70.Ds Electric and magnetic measurements
52.55.Fa Tokamaks, spherical tokamaks
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A cryogenic Quadraprobe scanning tunneling microscope system with fabrication capability for nanotransport research

Tae-Hwan Kim, Zhouhang Wang, John F. Wendelken, Hanno H. Weitering, Wenzhi Li, and An-Ping Li

Rev. Sci. Instrum. 78, 123701 (2007); http://dx.doi.org/10.1063/1.2821610 (7 pages) | Cited 15 times

Online Publication Date: 10 December 2007

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We describe the development and the capabilities of an advanced system for nanoscale electrical transport studies. This system consists of a low temperature four-probe scanning tunneling microscope (STM) and a high-resolution scanning electron microscope coupled to a molecular-beam epitaxy sample preparation chamber. The four STM probes can be manipulated independently with subnanometer precision, enabling atomic resolution STM imaging and four-point electrical transport study of surface electronic systems and nanostructured materials at temperatures down to 10 K. Additionally, an integrated energy analyzer allows for scanning Auger microscopy to probe chemical species of nanostructures. Some testing results are presented.
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73.63.-b Electronic transport in nanoscale materials and structures
07.79.Cz Scanning tunneling microscopes
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
61.46.-w Structure of nanoscale materials

Simultaneous correction of flat field and nonlinearity response of intensified charge-coupled devices

Timothy C. Williams and Christopher R. Shaddix

Rev. Sci. Instrum. 78, 123702 (2007); http://dx.doi.org/10.1063/1.2821616 (6 pages) | Cited 4 times

Online Publication Date: 13 December 2007

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Intensified charge-coupled devices (ICCDs) are used extensively in many scientific and engineering environments to image weak or temporally short optical events. Care has to be taken in interpreting the images from ICCDs if quantitative results are required. In particular, nonuniform gain (flat field) and nonlinear response effects must be properly accounted for. Traditional flat-field corrections can only be applied in the linear regime of the ICCD camera, which limits the usable dynamic range. This paper reports a more general approach to image correction whereby the nonlinear gain response of each pixel of the ICCD is characterized over the full dynamic range of the camera. Image data can then be corrected for the combined effects of nonuniform gain and nonlinearity. The results from a two-color pyrometry measurement of soot field temperature are used to illustrate the capabilities of the new correction approach.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
42.79.Ls Scanners, image intensifiers, and image converters

Phase-referenced probe interferometer for biological surface profiling and displacement measurements

Christopher Fang-Yen, Mark C. Chu, H. Sebastian Seung, Ramachandra R. Dasari, and Michael S. Feld

Rev. Sci. Instrum. 78, 123703 (2007); http://dx.doi.org/10.1063/1.2823976 (3 pages) | Cited 2 times

Online Publication Date: 26 December 2007

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We present a probe-based, phase-referenced low coherence interferometer in which the reference field is provided by a fiber end reflection. A gradient-index microlens focuses light onto a sample and collects reflected light. We use the probe interferometer to measure surface profiles of the compound eye of a housefly (Musca domestica) and measure nanometer-scale vibrations in a test sample.
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42.66.-p Physiological optics
42.81.-i Fiber optics
42.62.Be Biological and medical applications
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Adaptation of the Bridgman anvil cell to liquid pressure mediums

A.-S. Rüetschi and D. Jaccard

Rev. Sci. Instrum. 78, 123901 (2007); http://dx.doi.org/10.1063/1.2818788 (6 pages) | Cited 9 times

Online Publication Date: 6 December 2007

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The advantage of Bridgman anvil pressure cells is their wide pressure range and the large number of wires which can be introduced into the pressure chamber. In these pressure cells, soft solid pressure mediums such as steatite are used. We have succeeded in adapting the Bridgman cell to liquid pressure mediums. With this breakthrough, it is now possible to measure in very good hydrostatic pressure conditions up to 7 GPa, which is about twice the pressure attainable in piston-cylinder cells. The pressure gradient in the cell, estimated from the superconducting transition width of lead, is reduced by a factor of 5 in the liquid medium with respect to steatite. By using nonmagnetic materials for the anvils and the clamp and due to the small dimensions of the latter, our device is specially suitable for magnetotransport measurements in dilution fridges. This pressure cell has been developed to measure very fragile and brittle samples such as organic conductors. Resistivity measurements of (TMTTF)2BF4 performed in a solid and a liquid pressure medium demonstrate the necessity of hydrostatic pressure conditions for the study of organic conductors at high pressures.
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07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells

Experimental requirements for measuring pneumatochemical impedances

P. Millet, C. Decaux, R. Ngameni, and M. Guymont

Rev. Sci. Instrum. 78, 123902 (2007); http://dx.doi.org/10.1063/1.2818800 (11 pages) | Cited 6 times

Online Publication Date: 12 December 2007

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Hydrogen storage remains a bottleneck process on the way to the hydrogen economy. For practical applications, metal hydride systems offer interesting features, in particular, the possibility of reversibly storing large amounts of hydrogen at low or moderate pressure. However, they still suffer from unfavorable specific energy, with mass-fraction values ranging from 0 up to 5 wt % whereas transport applications require 6 wt % and more. Besides this, higher sorption/desorption kinetics and better chemical stability over long-term cycling are also needed. This is why many studies are carried out in the research community on hydride-forming systems, to develop new materials meeting these requirements. Development and optimization of metal hydride reactors require coupled thermodynamic and kinetic characterization of metal-hydrogen systems. In particular, it is necessary to analyze the kinetics in terms of reaction mechanism, in order to identify the different steps of commonly observed multistep reaction paths, and to measure their individual rate parameters. By analyzing hydriding kinetics in the frequency (Fourier) domain, pneumatochemical impedance spectroscopy (PIS) now offers the possibility of measuring experimental impedances and identifying reaction steps. However, measurement of such impedances is indirect and nontrivial. The purpose of this paper is to detail the experimental requirements needed for correctly measuring gas-phase impedance diagrams. In particular, practical conditions of data sampling and data treatment are described. Experimental results obtained with the model LaNi5–H2(g) system are presented to illustrate the potentialities of PIS analysis.
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82.45.Rr Electroanalytical chemistry
84.60.-h Direct energy conversion and storage
82.40.-g Chemical kinetics and reactions: special regimes and techniques

Chemical vapor synthesis of nanocrystalline perovskites using laser flash evaporation of low volatility solid precursors

Markus Winterer, Vladimir V. Srdic, Ruzica Djenadic, Alexander Kompch, and Thomas E. Weirich

Rev. Sci. Instrum. 78, 123903 (2007); http://dx.doi.org/10.1063/1.2821234 (5 pages)

Online Publication Date: 20 December 2007

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One key requirement for the production of multinary oxide films by chemical vapor deposition (CVD) or nanocrystalline multinary oxides particles by chemical vapor synthesis (CVS) is the availability of precursors with high vapor pressure. This is especially the case for CVS where much higher production rates are required compared to thin films prepared by CVD. However, elements, which form low valent cations such as alkaline earth metals, are typically only available as solid precursors of low volatility, e.g., in form of β-diketonates. This study describes laser flash evaporation as precursor delivery method for CVS of nanocrystalline perovskites. Laser flash evaporation exploits the nonequilibrium evaporation of solid metal organic precursors of low vapor pressure by absorption of the infrared radiation of a CO2 laser. It is shown that stoichiometric, nanocrystalline particles consisting of SrZrO3 and SrTiO3 can be formed from corresponding mixtures of β-diketonates which are evaporated nonselectively and with high rates by laser flash evaporation.
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81.16.Mk Laser-assisted deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
42.62.-b Laser applications
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