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August 2009

Volume 80, Issue 8,  Articles (08xxxx)

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Cover image from Ramón Carriles, Dawn N. Schafer, Kraig E. Sheetz, Jeffrey J. Field, Richard Cisek, Virginijus Barzda, Anne W. Sylvester, and Jeffrey A. Squier, Rev. Sci. Instrum. 80, 081101 (2009).
A maize plant leaf expressing a protein tagged with YFP (RAB2A::YFP) is imaged using two-photon excitation fluorescence at an excitation wavelength of 1040 nm.

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INVITED REVIEW ARTICLE

Invited Review Article: Imaging techniques for harmonic and multiphoton absorption fluorescence microscopy

Ramón Carriles, Dawn N. Schafer, Kraig E. Sheetz, Jeffrey J. Field, Richard Cisek, Virginijus Barzda, Anne W. Sylvester, and Jeffrey A. Squier

Rev. Sci. Instrum. 80, 081101 (2009) (23 pages)

Online Publication Date: 5 August 2009

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We review the current state of multiphoton microscopy. In particular, the requirements and limitations associated with high-speed multiphoton imaging are considered. A description of the different scanning technologies such as line scan, multifoci approaches, multidepth microscopy, and novel detection techniques is given. The main nonlinear optical contrast mechanisms employed in microscopy are reviewed, namely, multiphoton excitation fluorescence, second harmonic generation, and third harmonic generation. Techniques for optimizing these nonlinear mechanisms through a careful measurement of the spatial and temporal characteristics of the focal volume are discussed, and a brief summary of photobleaching effects is provided. Finally, we consider three new applications of multiphoton microscopy: nonlinear imaging in microfluidics as applied to chemical analysis and the use of two-photon absorption and self-phase modulation as contrast mechanisms applied to imaging problems in the medical sciences.
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42.65.Ky, 42.62.Fi, 42.65.Jx
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OPTICS; ATOMS AND MOLECULES; SPECTROSCOPY; PHOTON DETECTORS

Collinear interferometer with variable delay for carrier-envelope offset frequency measurement

Monika Pawlowska, Filip Ozimek, Piotr Fita, and Czeslaw Radzewicz

Rev. Sci. Instrum. 80, 083101 (2009) (5 pages)

Online Publication Date: 18 August 2009

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We demonstrate a novel scheme for measuring the carrier-envelope offset frequency in a femtosecond optical frequency comb. Our method is based on a common-path interferometer with a calcite Babinet–Soleil compensator employed to control the delay between the two interfering beams of pulses. The large delay range (up to 8 ps) of our device is sufficient for systems that rely on spectral broadening in microstructured fibers. We show an experimental proof that the stability of a common-path arrangement is superior to that of the standard interferometers.
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07.60.Ly, 06.30.Ft, 06.60.Jn

Toward ultrafast time-resolved Debye–Scherrer x-ray diffraction using a laser-plasma source

U. Shymanovich, M. Nicoul, W. Lu, S. Kähle, A. Tarasevitch, K. Sokolowski-Tinten, and D. von der Linde

Rev. Sci. Instrum. 80, 083102 (2009) (3 pages)

Online Publication Date: 21 August 2009

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An elliptical glass capillary has been used to focus ultrashort Cu Kalpha x-ray pulses emitted from a femtosecond laser-produced plasma. Due to its high magnification (7×), the optic transforms the divergent x-ray emission of the plasma into a quasicollimated x-ray beam with a divergence of only 0.18°. As an application we demonstrate the possibility to perform Debye–Scherrer diffraction experiments with the simultaneous detection of several diffraction orders. This will allow one to extend time-resolved x-ray diffraction with femtosecond laser-plasma x-ray sources to a much wider range of materials, which are not easily available as single crystals.
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42.65.Re, 61.05.cp

Production of a single spin-rotational state [(J,M)=(2,2)] selected molecular oxygen (3Sigma<sub>g</sub><sup>-</sup>) beam by a hexapole magnet

Mitsunori Kurahashi and Yasushi Yamauchi

Rev. Sci. Instrum. 80, 083103 (2009) (4 pages)

Online Publication Date: 24 August 2009

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A state-selected O2(3Sigma<sub>g</sub><sup>-</sup>) molecular beam, in which nearly 100% of the molecules are in the spin-rotational state of (J,M)=(2,2), has been produced by combining a supersonic seeded O2 beam with a hexapole magnet. The (2,−2) beam has also been obtained by the state inversion of the (2,2) beam through the nonadiabatic passage in a reversing longitudinal magnetic field along the beam axis. The intensities of the other (2,M) states, which appear when applying additional transverse magnetic fields to the reversing field region, were well reproduced by the Majorana's formula for J=2. The (2,±2) beam, for which we can determine the spin and rotational angular momenta of O2 almost independently, is the most promising probe for studying the spin effects as well as the steric effects in O2 molecular scattering.
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37.20.+j

Error-reduced channeled spectroscopic ellipsometer with palm-size sensing head

Hiroshi Okabe, Masayuki Hayakawa, Junichi Matoba, Hitoshi Naito, and Kazuhiko Oka

Rev. Sci. Instrum. 80, 083104 (2009) (10 pages)

Online Publication Date: 25 August 2009

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This paper describes a newly developed prototype system of the channeled spectroscopic ellipsometer (CSE). The new system has a feature that the major systematic and random error sources of the previous CSEs are effectively reduced or compensated for. In addition, the prototype preserves the advantageous features of the CSE in that it has a palm-size sensing head and that its acquisition time is as fast as 20 ms. Its performance is experimentally examined by use of 12 films whose thicknesses are ranging approximately from 3 to 4000 nm. The film thicknesses measured by the new CSE show good agreements with the ones by the rotating-compensator spectroscopic ellipsometer. The stability of the film-thickness measurement of the new CSE against the temperature change from 5 to 45 °C is less than 0.11 nm. The CSE can open up new applications of the spectroscopic ellipsometers in which the compactness, the simplicity, and the rapid response are important.
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07.60.Fs, 77.55.+f

A compact molecular beam machine

Paul Jansen, David W. Chandler, and Kevin E. Strecker

Rev. Sci. Instrum. 80, 083105 (2009) (5 pages)

Online Publication Date: 31 August 2009

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We have developed a compact, low cost, modular, crossed molecular beam machine. The new apparatus utilizes several technological advancements in molecular beams valves, ion detection, and vacuum pumping to reduce the size, cost, and complexity of a molecular beam apparatus. We apply these simplifications to construct a linear molecular beam machine as well as a crossed-atomic and molecular beam machine. The new apparatus measures almost 50 cm in length, with a total laboratory footprint less than 0.25  m2 for the crossed-atomic and molecular beam machine. We demonstrate the performance of the apparatus by measuring the rotational temperature of nitric oxide from three common molecular beam valves and by observing collisional energy transfer in nitric oxide from a collision with argon.
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07.75.+h, 07.30.Cy
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PARTICLE SOURCES, OPTICS AND ACCELERATION; PARTICLE DETECTORS

Three-dimensional velocity map imaging: Setup and resolution improvement compared to three-dimensional ion imaging

S. Kauczok, N. Gödecke, A. I. Chichinin, M. Veckenstedt, C. Maul, and K.-H. Gericke

Rev. Sci. Instrum. 80, 083301 (2009) (10 pages)

Online Publication Date: 3 August 2009

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For many years the three-dimensional (3D) ion imaging technique has not benefited from the introduction of ion optics into the field of imaging in molecular dynamics. Thus, a lower resolution of kinetic energy as in comparable techniques making use of inhomogeneous electric fields was inevitable. This was basically due to the fact that a homogeneous electric field was needed in order to obtain the velocity component in the direction of the time of flight spectrometer axis. In our approach we superimpose an Einzel lens field with the homogeneous field. We use a simulation based technique to account for the distortion of the ion cloud caused by the inhomogeneous field. In order to demonstrate the gain in kinetic energy resolution compared to conventional 3D Ion Imaging, we use the spatial distribution of H+ ions emerging from the photodissociation of HCl following the two photon excitation to the V 1[summation]+ state. So far a figure of merit of approximately four has been achieved, which means in absolute numbers Deltav/v=0.022 compared to 0.086 at v[approximate]17 000  m/s. However, this is not a theoretical limit of the technique, but due to our rather short TOF spectrometer (15 cm). The photodissociation of HBr near 243 nm has been used to recognize and eliminate systematic deviations between the simulation and the experimentally observed distribution. The technique has also proven to be essential for the precise measurement of translationally cold distributions.
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82.50.-m, 82.20.Hf, 82.80.Dx

A fast, direct x-ray detection charge-coupled device

P. Denes, D. Doering, H. A. Padmore, J.-P. Walder, and J. Weizeorick

Rev. Sci. Instrum. 80, 083302 (2009) (5 pages)

Online Publication Date: 6 August 2009

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A charge-coupled device (CCD) capable of 200 Mpixels/s readout has been designed and fabricated on thick, high-resistivity silicon. The CCDs, up to 600  µm thick, are fully depleted, ensuring good infrared to x-ray detection efficiency, together with a small point spread function. High readout speed, with good analog performance, is obtained by the use of a large number of parallel output ports. A set of companion 16-channel custom readout integrated circuits, capable of 15 bits of dynamic range, is used to read out the CCD. A gate array-controlled back end data acquisition system frames and transfers images, as well as provides the CCD clocks.
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85.30.Tv, 29.40.-n

Experimental demonstration of high quality MeV ultrafast electron diffraction

Renkai Li, Chuanxiang Tang, Yingchao Du, Wenhui Huang, Qiang Du, Jiaru Shi, Lixin Yan, and Xijie Wang

Rev. Sci. Instrum. 80, 083303 (2009) (4 pages)

Online Publication Date: 18 August 2009

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The simulation optimization and an experimental demonstration of improved performances of mega-electron-volt ultrafast electron diffraction (MeV UED) are reported in this paper. Using ultrashort high quality electron pulses from an S-band photocathode rf gun and a polycrystalline aluminum foil as the sample, we experimentally demonstrated an improved spatial resolution of MeV UED, in which the Debye–Scherrer rings of the (111) and (200) planes were clearly resolved. This result showed that MeV UED is capable to achieve an atomic level spatial resolution and a ~100  fs temporal resolution simultaneously, and will be a unique tool for ultrafast structural dynamics studies.
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61.05.J-, 02.60.Pn, 85.60.Ha

Emittance characterization of a hot-cavity laser ion source at Holifield Radioactive Ion Beam Facility

Y. Liu, C. Baktash, J. R. Beene, Ch. Geppert, T. Gottwald, C. C. Havener, T. Kessler, H. F. Krause, D. R. Schultz, D. W. Stracener, C. R. Vane, K. Wies, and K. Wendt

Rev. Sci. Instrum. 80, 083304 (2009) (10 pages)

Online Publication Date: 18 August 2009

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The first investigation of the transverse emittance of a hot-cavity laser ion source based on all-solid-state Ti:sapphire lasers is presented. The emittances of 63Cu ion beams generated by three-photon resonant ionization are measured and compared with that of the 69Ga and 39K ion beams resulting from surface ionization in the same ion source. A self-consistent unbiased elliptical exclusion method is adapted for noise reduction and emittance analysis. Typical values of the rms and 90% fractional emittances of the Cu ion beams at 20 keV energy are found to be about 2 and 8  pi  mm mrad, respectively, for the ion currents of 2–40 nA investigated. The emittances of the laser-produced Cu ion beams are smaller than those of the surface-ionized Ga and K ion beams.
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29.25.Lg, 79.20.Rf, 33.80.Rv, 42.55.Rz
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NUCLEAR PHYSICS, FUSION AND PLASMAS

A dual-channel, curved-crystal spectrograph for petawatt laser, x-ray backlighter source studies

W. Theobald, C. Stoeckl, P. A. Jaanimagi, P. M. Nilson, M. Storm, D. D. Meyerhofer, T. C. Sangster, D. Hey, A. J. MacKinnon, H.-S. Park, P. K. Patel, R. Shepherd, R. A. Snavely, M. H. Key, J. A. King et al.

Rev. Sci. Instrum. 80, 083501 (2009) (9 pages)

Online Publication Date: 10 August 2009

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A dual-channel, curved-crystal spectrograph was designed to measure time-integrated x-ray spectra in the ~1.5 to 2 keV range (6.2–8.2 Å wavelength) from small-mass, thin-foil targets irradiated by the VULCAN petawatt laser focused up to 4×1020  W/cm2. The spectrograph consists of two cylindrically curved potassium-acid-phthalate crystals bent in the meridional plane to increase the spectral range by a factor of ~10 compared to a flat crystal. The device acquires single-shot x-ray spectra with good signal-to-background ratios in the hard x-ray background environment of petawatt laser-plasma interactions. The peak spectral energies of the aluminum Healpha and Lyalpha resonance lines were ~1.8 and ~1.0  mJ/eV sr (~0.4 and 0.25 J/Å sr), respectively, for 220 J, 10 ps laser irradiation.
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07.85.Nc, 52.38.Dx

Deconvolution-based correction of alkali beam emission spectroscopy density profile measurements

I. Pusztai, G. Pokol, D. Dunai, D. Réfy, G. Pór, G. Anda, S. Zoletnik, and J. Schweinzer

Rev. Sci. Instrum. 80, 083502 (2009) (8 pages)

Online Publication Date: 20 August 2009

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A deconvolution-based correction method of the beam emission spectroscopy (BES) density profile measurement is demonstrated by its application to simulated measurements of the COMPASS and TEXTOR tokamaks. If the line of sight is far from tangential to the flux surfaces, and the beam width is comparable to the scale length on which the light profile varies, the observation may cause an undesired smoothing of the light profile, resulting in a non-negligible underestimation of the calculated density profile. This effect can be reduced significantly by the emission reconstruction method, which gives an estimate of the emissivity along the beam axis from the measured light profile, taking the finite beam width and the properties of the measurement into account in terms of the transfer function of the observation. Characteristics and magnitude of the mentioned systematic error and its reduction by the introduced method are studied by means of the comprehensive alkali BES simulation code RENATE.
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52.70.Kz, 52.55.Fa, 52.65.-y

Operating a radio-frequency plasma source on water vapor

Sonca V. T. Nguyen, John E. Foster, and Alec D. Gallimore

Rev. Sci. Instrum. 80, 083503 (2009) (8 pages)

Online Publication Date: 24 August 2009

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A magnetically enhanced radio-frequency (rf) plasma source operating on water vapor has an extensive list of potential applications. In this work, the use of a rf plasma source to dissociate water vapor for hydrogen production is investigated. This paper describes a rf plasma source operated on water vapor and characterizes its plasma properties using a Langmuir probe, a residual gas analyzer, and a spectrometer. The plasma source operated first on argon and then on water vapor at operating pressures just over 300 mtorr. Argon and water vapor plasma number densities differ significantly. In the electropositive argon plasma, quasineutrality requires ni~=ne, where ni is the positive ion density. But in the electronegative water plasma, quasineutrality requires ni+=ni−+ne. The positive ion density and electron density of the water vapor plasma are approximately one and two orders of magnitude lower, respectively, than those of argon plasma. These results suggest that attachment and dissociative attachment are present in electronegative water vapor plasma. The electron temperature for this water vapor plasma source is between 1.5 and 4 eV. Without an applied axial magnetic field, hydrogen production increases linearly with rf power. With an axial magnetic field, hydrogen production jumps to a maximum value at 500 W and then saturates with rf power. The presence of the applied axial magnetic field is therefore shown to enhance hydrogen production.
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52.50.Dg, 52.70.Ds

A compact submicrosecond, high current generator

B. M. Kovalchuk, A. V. Kharlov, V. B. Zorin, and A. A. Zherlitsyn

Rev. Sci. Instrum. 80, 083504 (2009) (6 pages)

Online Publication Date: 26 August 2009

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Pulsed current generator was developed for experiments with current carrying pulsed plasma. Main parts of the generator are capacitor bank, low inductive current driving lines, and central load part. Generator consists of four identical sections, connected in parallel to one load. Capacitor bank is assembled from 24 capacitor blocks (100 kV, 80 nF), connected in parallel. It stores 9.6 kJ at 100 kV charging voltage. Each capacitor block incorporates a multigap spark switch, which is able to commute by six parallel channels. Switches operate in dry air at atmospheric pressure. The generator was tested with an inductive load and a liner load. At 17.5 nH inductive load and 100 kV of charging voltage it provides 650 kA of current amplitude with 390 ns rise time with 0.6  Omega damping resistors in discharge circuit of each capacitor block. The net generator inductance without a load was optimized to be as low as 15 nH, which results in extremely low impedance of the generator (~0.08  Omega). It ensures effective energy coupling with a low impedance load such as Z pinch. The generator operates reliably without any adjustments in 70–100 kV range of charging voltage. Jitter in delay between output pulse and triggering pulse is less than 5 ns at 70–100 kV charging voltage. Operation and handling are very simple, because no oil or purified gases are required for the generator. The generator has dimensions 5.24×1.2×0.18  m3 and total weight about 1400 kg, thus manifesting itself as simple, robust, and cost effective apparatus.
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84.30.Ng, 84.70.+p, 84.32.Ff, 84.32.Tt

Broadband, high dynamics and high resolution charge coupled device-based spectrometer in dynamic mode for multi-keV repetitive x-ray sources

C. Fourment, N. Arazam, C. Bonte, T. Caillaud, D. Descamps, F. Dorchies, M. Harmand, S. Hulin, S. Petit, and J. J. Santos

Rev. Sci. Instrum. 80, 083505 (2009) (10 pages)

Online Publication Date: 27 August 2009

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We present a new operating mode, using a charged coupled device as dispersionless spectrometer dedicated to repetitive x-ray sources in the multi-keV domain. This enables to get spectra with high statistics in a short acquisition time and a way compatible with the operation of other diagnostics requiring accumulation. Several reconstruction algorithms for the spreading events are discussed, and a near Fano-limited resolution is demonstrated by using single pixel events. In this case, a method to take into account partial canceling of the events is presented. Experimental characterization and detailed modeling of the detector are performed, which allow to determine absolute number of photon with ±35% accuracy. Characterization of the 5–25 keV x rays emitted by a short pulse laser-produced plasma is reported, as well as their dependency with the atomic number, the laser duration, and energy.
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52.59.Px, 52.50.Jm, 52.25.Os, 07.85.Fv

A contoured gap coaxial plasma gun with injected plasma armature

F. Douglas Witherspoon, Andrew Case, Sarah J. Messer, Richard Bomgardner, II, Michael W. Phillips, Samuel Brockington, and Raymond Elton

Rev. Sci. Instrum. 80, 083506 (2009) (15 pages)

Online Publication Date: 27 August 2009

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A new coaxial plasma gun is described. The long term objective is to accelerate 100–200  µg of plasma with density above 1017  cm−3 to greater than 200 km/s with a Mach number above 10. Such high velocity dense plasma jets have a number of potential fusion applications, including plasma refueling, magnetized target fusion, injection of angular momentum into centrifugally confined mirrors, high energy density plasmas, and others. The approach uses symmetric injection of high density plasma into a coaxial electromagnetic accelerator having an annular gap geometry tailored to prevent formation of the blow-by instability. The injected plasma is generated by numerous (currently 32) radially oriented capillary discharges arranged uniformly around the circumference of the angled annular injection region of the accelerator. Magnetohydrodynamic modeling identified electrode profiles that can achieve the desired plasma jet parameters. The experimental hardware is described along with initial experimental results in which approximately 200  µg has been accelerated to 100 km/s in a half-scale prototype gun. Initial observations of 64 merging injector jets in a planar cylindrical testing array are presented. Density and velocity are presently limited by available peak current and injection sources. Steps to increase both the drive current and the injected plasma mass are described for next generation experiments.
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52.50.-b, 52.30.Cv, 52.80.-s, 52.75.-d

A multichannel, frequency-modulated, tunable Doppler backscattering and reflectometry system

J. C. Hillesheim, W. A. Peebles, T. L. Rhodes, L. Schmitz, T. A. Carter, P.-A. Gourdain, and G. Wang

Rev. Sci. Instrum. 80, 083507 (2009) (8 pages)

Online Publication Date: 31 August 2009

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A novel multichannel Doppler backscattering system has been designed and tested for application on the DIII-D [J. L. Luxon, Fusion Sci. Technol. 48, 828 (2005)] and National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)] fusion plasma devices. Doppler backscattering measures localized intermediate wavenumber (k[perpendicular]rhoi~1–4,k[perpendicular]~2–15  cm−1) density fluctuations and the propagation velocity of turbulent structures. Microwave radiation is launched at a frequency that approaches a cutoff layer in the plasma and at an angle that is oblique to the cutoff layer. Bragg backscattering occurs near the cutoff layer for fluctuations with k[perpendicular][approximate]−2ki, where ki is the incident probe wave vector at the scattering location. The turbulence propagation velocity can be determined from the Doppler shift in the return signal together with knowledge of the scattering wavenumber. Ray tracing simulations are used to determine k[perpendicular] and the scattering location. Frequency modulation of a voltage-controlled solid state microwave source followed by frequency multiplication is used to create an array of finely spaced (Deltaf=350  MHz) frequencies spanning 1.4 GHz. The center of the array bandwidth is tunable within the range of ~53–78  GHz. This article details the system design, laboratory tests, and presents initial data from DIII-D plasmas.
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52.58.-c, 52.75.-d, 52.35.Ra
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MICROSCOPY AND IMAGING

Nanoscale phase transformation in Ge2Sb2Te5 using encapsulated scanning probes and retraction force microscopy

Harish Bhaskaran, Abu Sebastian, Andrew Pauza, Haralampos Pozidis, and Michel Despont

Rev. Sci. Instrum. 80, 083701 (2009) (6 pages)

Online Publication Date: 20 August 2009

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Encapsulated conducting probes that can sustain high currents are used to study the nanoscale properties of thin-film stacks comprising of a phase-change chalcogenide, Ge2Sb2Te5. Scaling studies on this promising candidate for random-access memory devices had thus far required extensive lithography and nanoscale growth. This seriously hampers rapid materials characterization. This article describes the use of two key techniques, an encapsulated conductive probe and its use in retraction mode, whereby the attractive force between tip and sample is used to maintain electrical contact. The effective transformation of nanoscale dots of amorphous Ge2Sb2Te5 into the crystalline state is achieved and the electrical conductivity of the transformed structures is probed. The use of retraction force microscopy in a robust manner is demonstrated by reading the conductivity of the crystalline dots. Both these techniques could enable rapid electrical characterization of nanoscale materials, without extensive nanopatterning, thus reducing material development cycles.
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64.70.K-, 73.21.La, 81.16.Nd, 73.61.Jc, 61.43.Dq, 68.55.ag

A versatile dual spot laser scanning confocal microscopy system for advanced fluorescence correlation spectroscopy analysis in living cell

Patrick Ferrand, Martina Pianta, Alla Kress, Alexandre Aillaud, Hervé Rigneault, and Didier Marguet

Rev. Sci. Instrum. 80, 083702 (2009) (8 pages)

Online Publication Date: 20 August 2009

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A fluorescence correlation spectroscopy system based on two independent measurement volumes is presented. The optical setup and data acquisition hardware are detailed, as well as a complete protocol to control the location, size, and shape of the measurement volumes. A method that allows to monitor independently the excitation and collection efficiency distribution is proposed. Finally, a few examples of measurements that exploit the two spots in static and/or scanning schemes are reported.
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87.64.kv, 87.64.M-, 87.18.-h

Combined holographic-mechanical optical tweezers: Construction, optimization, and calibration

Richard D. L. Hanes, Matthew C. Jenkins, and Stefan U. Egelhaaf

Rev. Sci. Instrum. 80, 083703 (2009) (7 pages)

Online Publication Date: 26 August 2009

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A spatial light modulator (SLM) and a pair of galvanometer-mounted mirrors (GMM) were combined into an optical tweezers setup. This provides great flexibility as the SLM creates an array of traps, which can be moved smoothly and quickly with the GMM. To optimize performance, the effect of the incidence angle on the SLM with respect to phase and intensity response was investigated. Although it is common to use the SLM at an incidence angle of 45°, smaller angles give a full 2pi phase shift and an output intensity which is less dependent on the magnitude of the phase shift. The traps were calibrated using an active oscillatory technique and a passive probability distribution method.
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42.40.Eq, 42.50.Wk, 42.79.Hp, 06.20.F-, 02.50.Ng, 42.79.Bh

Design of a variable temperature scanning force microscope

E. Nazaretski, K. S. Graham, J. D. Thompson, J. A. Wright, D. V. Pelekhov, P. C. Hammel, and R. Movshovich

Rev. Sci. Instrum. 80, 083704 (2009) (6 pages)

Online Publication Date: 31 August 2009

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We have developed the variable temperature scanning force microscope capable of performing both magnetic resonance force microscopy (MRFM) and magnetic force microscopy (MFM) measurements in the temperature range between 5 and 300 K. Modular design, large scanning area, and interferometric detection of the cantilever deflection make it a sensitive, easy to operate, and reliable instrument suitable for studies of the dynamic and static magnetization in various systems. We have verified the performance of the microscope by imaging vortices in a Nb thin film in the MFM mode of operation. MRFM spectra in a diphenyl-picryl-hydrazyl film were recorded to evaluate the MRFM mode of operation.
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07.79.Lh, 07.79.Pk, 75.70.Ak, 75.60.Ej

Wideband digital frequency detector with subtraction-based phase comparator for frequency modulation atomic force microscopy

Yuji Mitani, Mamoru Kubo, Ken-ichiro Muramoto, and Takeshi Fukuma

Rev. Sci. Instrum. 80, 083705 (2009) (3 pages)

Online Publication Date: 31 August 2009

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We have developed a wideband digital frequency detector for high-speed frequency modulation atomic force microscopy (FM-AFM). We used a subtraction-based phase comparator (PC) in a phase-locked loop circuit instead of a commonly used multiplication-based PC, which has enhanced the detection bandwidth to 100 kHz. The quantitative analysis of the noise performance revealed that the internal noise from the developed detector is small enough to provide the theoretically limited noise performance in FM-AFM experiments in liquid. FM-AFM imaging of mica in liquid was performed with the developed detector, showing its stability and applicability to true atomic-resolution imaging in liquid.
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07.79.Lh, 84.30.Qi
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CONDENSED MATTER; MATERIALS

Characterization of hydrogen storage materials by means of pressure concentration isotherms based on the mass flow method

Michael Bielmann, Shunsuke Kato, Philippe Mauron, Andreas Borgschulte, and Andreas Züttel

Rev. Sci. Instrum. 80, 083901 (2009) (7 pages)

Online Publication Date: 3 August 2009

Full Text: PDF (425 kB)

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The determination of the equilibrium thermodynamic parameters of hydrogen storage materials from quasiequilibrium pressure data using the mass flow pressure concentration isotherm (pcI) method is presented. The method bases on the acquisition of pcI curves at different flow rates using a thermal mass flow controller to determine the amount of ad/desorbed hydrogen. These measurements provide a set of corresponding quasiequilibrium pressure functions from, which the true equilibrium pressure of the hydride is calculated by extrapolation to zero flow. The governing thermodynamic parameters can then be determined to characterize the material by the construction of a van't Hoff plot, extracting enthalpy of reaction DeltaHr and entropy of reaction DeltaSr from the equilibrium pressure peq as a function of temperature. Naturally, true equilibrium can never be reached and therefore can only be approximated by measurement––a drawback that all experimental techniques share. This complication is alleviated by the flow-pcI approach at different flow rates. The compilation of the peq(T) data from pcI-measurements can be performed by different methods, whereas the so called Sieverts apparatus is most commonly used. In this paper, we elaborate the differences and advantages of the mass flow-pcI over the Sieverts Apparatus and present measurements and results on LaNi5 as a benchmark. Measurements at different flow rates are presented and equilibrium pressures at zero flow are achieved by extrapolation. The obtained results of DeltaHd=32.5  kJ mol−1 H2 and DeltaSd=115  J K−1 mol−1 H2 (desorption process) perfectly match literature values, emphasizing the excellent quality of the measurements and the performance of this measurement apparatus.
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84.60.-h, 82.60.Cx, 65.40.gd, 68.43.Mn, 68.43.Nr

The experimental realization of a two-dimensional colloidal model system

F. Ebert, P. Dillmann, G. Maret, and P. Keim

Rev. Sci. Instrum. 80, 083902 (2009) (12 pages)

Online Publication Date: 3 August 2009

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We present the technical details of an experimental method to realize a model system for two-dimensional (2D) phase transitions and the glass transition. The system consists of several hundred thousand colloidal superparamagnetic particles confined by gravity at a flat water-air interface of a pending water droplet where they are subjected to Brownian motion. The dipolar pair potential and, therefore, the system temperature are not only known precisely but also directly and instantaneously controllable via an external magnetic field H. In the case of a one-component system of monodisperse particles the system can crystallize upon application of H whereas in a two component system it undergoes a glass transition. Up to 10 000 particles are observed by video microscopy and image processing provides their trajectories on all relative length and time scales. The position of the interface is actively regulated thereby reducing surface fluctuations to less than 1  µm and the setup inclination is controlled to an accuracy of ±1  µrad. The sample quality being necessary to enable the experimental investigation of the 2D melting scenario, 2D crystallization, and the 2D glass transition, is discussed.
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75.30.Kz, 64.70.pm, 75.50.Tt, 75.50.Mm, 75.20.-g, 64.70.dj
FREE

A compact apparatus for studies of element and phase-resolved ferromagnetic resonance

D. A. Arena, Y. Ding, E. Vescovo, S. Zohar, Y. Guan, and W. E. Bailey

Rev. Sci. Instrum. 80, 083903 (2009) (7 pages)

Online Publication Date: 11 August 2009

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We present a compact sample holder equipped with electromagnets and high frequency transmission lines; the sample holder is intended for combined x-ray magnetic circular dichroism (XMCD) and ferromagnetic resonance measurements (FMR). Time-resolved measurements of resonant x-ray detected FMR during forced precession are enabled by use of a rf excitation that is phase-locked to the storage ring bunch clock. Several applications of the combined XMCD+FMR technique are presented, demonstrating the flexibility of the experimental design.
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07.55.-w, 76.50.+g, 78.20.Ls, 07.85.-m

Acoustic levitator for structure measurements on low temperature liquid droplets

J. K. R. Weber, C. A. Rey, J. Neuefeind, and C. J. Benmore

Rev. Sci. Instrum. 80, 083904 (2009) (8 pages)

Online Publication Date: 13 August 2009

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A single-axis acoustic levitator was constructed and used to levitate liquid and solid drops of 1–3 mm in diameter at temperatures in the range −40 to +40 °C. The levitator comprised (i) two acoustic transducers mounted on a rigid vertical support that was bolted to an optical breadboard, (ii) an acoustic power supply that controlled acoustic intensity, relative phase of the drive to the transducers, and could modulate the acoustic forces at frequencies up to 1 kHz, (iii) a video camera, and (iv) a system for providing a stream of controlled temperature gas flow over the sample. The acoustic transducers were operated at their resonant frequency of ~22  kHz and could produce sound pressure levels of up to 160 dB. The force applied by the acoustic field could be modulated to excite oscillations in the sample. Sample temperature was controlled using a modified Cryostream Plus and measured using thermocouples and an infrared thermal imager. The levitator was installed at x-ray beamline 11 ID-C at the Advanced Photon Source and used to investigate the structure of supercooled liquids.
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43.38.-p, 43.25.-x

A nanocell for quartz crystal microbalance and quartz crystal microbalance with dissipation-monitoring sensing

Gabriel Ohlsson, Christoph Langhammer, Igor Zorić, and Bengt Kasemo

Rev. Sci. Instrum. 80, 083905 (2009) (10 pages)

Online Publication Date: 14 August 2009

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A novel device for nanometer-confinement of soft matter in one dimension (1D) is presented. This nanocell, with very large (up to 106:1) cell-radius to cell-height ratio, is tailored as an accessory for quartz crystal microbalance (QCM) and QCM with dissipation-monitoring (QCM-D) sensing to study internal and interfacial energy dissipation phenomena in highly confined (in 1D) soft matter and fluid films (patent pending). The cell consists of two macroscopic plates (diameter of 9 mm), a top (the “lid”) and a bottom (the QCM-D sensor), separated by appropriate spacers with heights ranging from below 100 nm up to 10  µm. The surfaces of both the lid and the bottom plate can be mechanically or/and chemically modified, prior to cell assembly, in order to tailor desired interfacial properties for the experiment. The cell is mounted on a standard QCM-D sensor, an AT-cut quartz crystal (the quartz crystal is cut at an angle of 35° from its ZX-plane), forming the bottom plate. We illustrate theoretically and experimentally, as application examples, the use of this device for studies of dynamic mass loading and internal energy dissipation processes in thin films of ethylene glycol respective thin liquid crystal films around the nematic-isotropic phase transition.
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77.65.Fs

M-H loop tracer based on digital signal processing for low frequency characterization of extremely thin magnetic wires

M. Butta, G. Infante, P. Ripka, G. A. Badini-Confalonieri, and M. Vázquez

Rev. Sci. Instrum. 80, 083906 (2009) (4 pages)

Online Publication Date: 21 August 2009

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A high-sensitivity ac hysteresis loop tracer has been developed to measure the low frequency hysteresis loop of soft magnetic materials. It has been applied successfully to characterize straight pieces of amorphous glass-covered microwires with metallic nucleus down to 1.5  µm thick. Based on the electromagnetic induction law, the proposed design is extremely simple and exploits the capabilities of commercially available data acquisition cards together with digital signal processing in order to achieve high-sensitivity without the need of expensive analog equipment.
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07.55.-w, 75.60.Ej, 06.30.Ka, 07.50.Qx

Microgravity compatible equipment for inert gas condensation of metals during parabolic flights

S. Lösch, B. H. Günther, G. N. Iles, and U. Büngener

Rev. Sci. Instrum. 80, 083907 (2009) (5 pages)

Online Publication Date: 24 August 2009

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Agglomerates of nanosized metal particles can be deposited onto a variety of substrates using a custom-built, microgravity-compatible evaporation/condensation device. A metal aerosol with high solid loading is produced by rf-induction coil heating of a metal melt in a laminar inert gas flow. Valves and flow controllers operating in hypergravity and microgravity conditions allow powder samples to be prepared from such aerosols suppressing buoyancy and sedimentation effects. We present here the technical details for such a parabolic flight compatible metal aerosol source together with some initial results of nanoscale Ni agglomerates synthesized and deposited under microgravity conditions.
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81.16.-c, 81.10.Mx, 82.70.Rr, 81.20.Ev

Development of special rotor for centrifugal separation of isotopes in solid pure metals

Masao Ono, Masanori Sueyoshi, Satoru Okayasu, Ting Hao, Fumitaka Esaka, Takahito Osawa, Yusuke Iguchi, and Tsutomu Mashimo

Rev. Sci. Instrum. 80, 083908 (2009) (6 pages)

Online Publication Date: 28 August 2009

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A prototype rotor with two grooves for the multistage centrifugal isotope separation in solid state was developed to test a new idea. This idea is based on the sedimentation of constitutional atoms in solid. In the performance test using indium specimen, it is verified that the developed rotor can receive all injected molten-indium droplets from an automatic raw-material feeding system even at the high rotational speed of 97 000  rpm without the loss of rotational stability, and the received indium specimens can be transferred in/between two grooves through the plastic flow under the influence of strong centrifugal force even in the solid state. The isotope ratio of centrifuged indium specimens was analyzed employing the secondary ion mass spectrometry, and it is confirmed that intended isotope separation by the centrifugation is realized in the solid state. The developed rotor can be used to perform the isotope separation on at least solid metals under the conditions of up to 400 °C in specimen temperature and 0.4×106g in centrifugal force field.
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07.10.-h, 84.50.+d, 06.30.Bp
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CHEMISTRY

The design and application of virtual ion meter based on LABVIEW 8.0

Hu Meng (孟虎), Jiangyuan Li (李将渊), and Yonghuai Tang (汤永怀)

Rev. Sci. Instrum. 80, 084101 (2009) (5 pages)

Online Publication Date: 3 August 2009

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The virtual ion meter is developed based on LABVIEW 8.0 by homemade adjusting circuit, data acquisition (DAQ) board, and computer. This note provides details of the structure of testing system and flow chart of DAQ program. This virtual instrument system is applied to multitask testing such as determining rate constant of second-order reaction by pX, pX potentiometric titration, determining oscillating reaction by potential, etc. The result of application indicates that this test system not only has function of real-time data acquiring, displaying, storage, but also realizes remote monitoring and controlling test-control spots through internet, automatic analyzing and processing of data, reporting of result according to the different testing task; moreover, the veracity and repeatability of data processing result are higher than the results of manual data processing.
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07.05.Hd

A flow cell for in situ synchrotron x-ray diffraction studies of scale formation under Bayer processing conditions

Nathan A. S. Webster, Ian C. Madsen, Melissa J. Loan, Nicola V. Y. Scarlett, and Kia S. Wallwork

Rev. Sci. Instrum. 80, 084102 (2009) (5 pages)

Online Publication Date: 5 August 2009

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The design, construction, and commissioning of a stainless steel flow cell for in situ synchrotron x-ray diffraction studies of scale formation under Bayer processing conditions is described. The use of the cell is demonstrated by a study of Al(OH)3 scale formation on a mild steel substrate from synthetic Bayer liquor at 70 °C. The cell design allows for interchangeable parts and substrates and would be suitable for the study of scale formation in other industrial processes.
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89.20.Kk
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BIOLOGY AND MEDICINE

An open source/real-time atomic force microscope architecture to perform customizable force spectroscopy experiments

Donatello Materassi, Paolo Baschieri, Bruno Tiribilli, Giampaolo Zuccheri, and Bruno Samorì

Rev. Sci. Instrum. 80, 084301 (2009) (6 pages)

Online Publication Date: 10 August 2009

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We describe the realization of an atomic force microscope architecture designed to perform customizable experiments in a flexible and automatic way. Novel technological contributions are given by the software implementation platform (RTAI-LINUX), which is free and open source, and from a functional point of view, by the implementation of hard real-time control algorithms. Some other technical solutions such as a new way to estimate the optical lever constant are described as well. The adoption of this architecture provides many degrees of freedom in the device behavior and, furthermore, allows one to obtain a flexible experimental instrument at a relatively low cost. In particular, we show how such a system has been employed to obtain measures in sophisticated single-molecule force spectroscopy experiments [Fernandez and Li, Science 303, 1674 (2004)]. Experimental results on proteins already studied using the same methodologies are provided in order to show the reliability of the measure system.
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07.79.Lh, 87.64.Dz, 87.14.E-
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ELECTRONICS; ELECTROMAGNETIC TECHNOLOGY; MICROWAVES

Flexible electronics sensors for tactile multiscanning

Wen-Yang Chang, Te-Hua Fang, Yu-Tang Shen, and Yu-Cheng Lin

Rev. Sci. Instrum. 80, 084701 (2009) (8 pages)

Online Publication Date: 7 August 2009

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Flexible electronics sensors are designed and fabricated for tactile multiscanning and large area applications. The algorithm matrix is derived for multiscanning switch of tactile sensing. The thixotropy materials, bump, and resistance material are printed on the polyimide substrate. A gap between the top electrode and the resistance layers provides a buffer distance to increase the radius of curvature for large bending. Experiment results show that a flexible electronics sensor with a printed a resistance layer and an algorithm matrix performed the multiscanning functions. The membrane without a bump had a delay time of about 0.2 s at the transient response and took a longer time to reach the stable state after a force is applied. For printing thick structures on the flexible substrates, diffusion effects, and dimensional shrinkages can be reduced by using a thixotropy material with a high viscosity. The probability distribution density of the printed resistance values, a thickness of about 23.2  µm, at two standard deviations from the mean values is about 81.2%. Feasibility studies show that screen printing is appropriate for large area applications and is a low-cost technology for fabricating flexible electronics sensors.
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07.07.Df

Millimeter wave detection of nuclear radiation: An alternative detection mechanism

N. Gopalsami, H. T. Chien, A. Heifetz, E. R. Koehl, and A. C. Raptis

Rev. Sci. Instrum. 80, 084702 (2009) (4 pages)

Online Publication Date: 17 August 2009

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We present a nuclear radiation detection mechanism using millimeter waves as an alternative to conventional detection. It is based on the concept that nuclear radiation causes ionization of air and that if we place a dielectric material near the radiation source, it acts as a charge accumulator of the air ions. We have found that millimeter waves can interrogate the charge cloud on the dielectric material remotely. This concept was tested with a standoff millimeter wave system by monitoring the charge levels on a cardboard tube placed in an x-ray beam.
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29.40.-n
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THERMOMETRY; THERMAL DIFFUSIVITY; ACOUSTIC; PHOTOTHERMAL AND PHOTOACOUSTIC

Systematic error of diode thermometer

Predrag S. Iskrenovic

Rev. Sci. Instrum. 80, 084901 (2009) (5 pages)

Online Publication Date: 24 August 2009

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Semiconductor diodes are often used for measuring temperatures. The forward voltage across a diode decreases, approximately linearly, with the increase in temperature. The applied method is mainly the simplest one. A constant direct current flows through the diode, and voltage is measured at diode terminals. The direct current that flows through the diode, putting it into operating mode, heats up the diode. The increase in temperature of the diode-sensor, i.e., the systematic error due to self-heating, depends on the intensity of current predominantly and also on other factors. The results of systematic error measurements due to heating up by the forward-bias current have been presented in this paper. The measurements were made at several diodes over a wide range of bias current intensity.
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07.20.Dt, 47.80.Fg, 85.30.Kk
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GENERAL INSTRUMENTS

Demonstration of microcantilever array with simultaneous readout using an in-plane photonic transduction method

Weisheng Hu, Ryan Anderson, Yusheng Qian, Jigou Song, Jong Wook Noh, Seunghyun Kim, and Gregory P. Nordin

Rev. Sci. Instrum. 80, 085101 (2009) (7 pages)

Online Publication Date: 6 August 2009

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We demonstrate a microcantilever array with an in-plane photonic transduction method for simultaneous readout of each microcantilever. The array is fabricated on a silicon-on-insulator substrate. Rib waveguides in conjunction with a compact waveguide splitter network comprised of trench-based splitters and trench-based bends route light from a single optical input to each microcantilever on the chip. Light propagates down a rib waveguide integrated into the microcantilever and, at the free end of the microcantilever, crosses a small gap. Light is captured in static asymmetric multimode waveguides that terminate in Y-branches, the outputs of which are imaged onto an InGaAs line scan camera. A differential signal for each microcantilever is simultaneously formed from the two outputs of the corresponding Y-branch. We demonstrate that reasonable signal uniformity is obtained with a scaled differential signal for seven out of nine surviving microcantilevers in an array.
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42.82.Et, 42.79.Gn

Method for reducing response time in sensor measurement

Oscar Casas and Francesc I. Rillo

Rev. Sci. Instrum. 80, 085102 (2009) (5 pages)

Online Publication Date: 11 August 2009

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Transients are present in sensor and instrumentation systems. They are caused by energy transference and are typically modeled as first-order systems. If too long, transients may suppose a critical factor for these systems unless they are analyzed (e.g., in terms of consumption). This work presents a new method for estimating the final value of a first-order system transient. Since this problem may be harmful, mainly to autonomous systems, the method equations are composed of simple operations that can be implemented on microcontrollers or similar interfaces with low computational capacity. The experimental results validate the theoretical models of the method and prove that, when the system coexists with disturbances, it is possible to estimate the final value in around 60% of the time we would have to wait until reaching it, in the worst case scenario.
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07.07.Df, 84.30.Bv

Fine calibration of the residual dissipation in a surface forces apparatus using a capacitive sensor

Samuel Leroy, Frédéric Restagno, and Élisabeth Charlaix

Rev. Sci. Instrum. 80, 085103 (2009) (6 pages)

Online Publication Date: 12 August 2009

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The design of a dynamic surface force apparatus using a capacitive sensor has been useful in the past to study the nanorheological behavior of thin liquid films confined between a sphere and a plane. This allows a precise measurement of the hydrodynamical boundary condition of liquids down to some molecular sizes. However for thick liquid films, the viscous force is decreased and the dissipation due to the flow of air in the capacitive sensor becomes of the same order of magnitude than the force due to the liquid flow. In the present paper we present an original technique to characterize this residual force due to the capacitive sensor and we show that a precise subtraction of this force extends the precision of the device to the case of thick liquid films of low viscosity. This correction should be of major importance to extend the capability of surface forces apparatus to measure very large boundary slippage of simple liquids.
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68.15.+e, 07.07.Df, 66.20.-d, 83.50.Lh, 47.85.Dh

A simple, compact, and rigid piezoelectric step motor with large step size

Qi Wang and Qingyou Lu

Rev. Sci. Instrum. 80, 085104 (2009) (4 pages)

Online Publication Date: 14 August 2009

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We present a novel piezoelectric stepper motor featuring high compactness, rigidity, simplicity, and any direction operability. Although tested in room temperature, it is believed to work in low temperatures, owing to its loose operation conditions and large step size. The motor is implemented with a piezoelectric scanner tube that is axially cut into almost two halves and clamp holds a hollow shaft inside at both ends via the spring parts of the shaft. Two driving voltages that singly deform the two halves of the piezotube in one direction and recover simultaneously will move the shaft in the opposite direction, and vice versa.
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07.79.-v, 85.50.-n, 84.50.+d, 06.60.Sx

High-resolution laser lithography system based on two-dimensional acousto-optic deflection

Manuel Koechlin, Gorazd Poberaj, and Peter Günter

Rev. Sci. Instrum. 80, 085105 (2009) (6 pages)

Online Publication Date: 19 August 2009

Full Text: PDF (419 kB)

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We present an advanced high-resolution, compact laser lithography system for fast prototyping of complex integrated optics devices comprising microring resonators and photonic crystal structures. Precise and flexible structuring of photoresist patterns is achieved by combing three linear stages (xyz) for sample positioning and a two-dimensional acousto-optical deflector for laser beam steering and intensity control. A continuous wave diode laser operating at a wavelength of 375 nm is used to illuminate all types of photoresists including SU-8. Using a microscope objective with a numerical aperture of 1.40, structure widths of ~200  nm can be obtained. The write-field covered by acousto-optic deflection can be as large as 200×200  µm2 when using an objective with a focal length of 4.5 mm. With a two-step lithography process, gaps as small as 150 nm between adjacent structures have been achieved, yielding superior photoresist masks for microring resonators with coupling ports.
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42.82.Cr, 78.20.Hp, 85.85.+j

Determination of three-dimensional orientations of ferroelectric single crystals by an improved rotating orientation x-ray diffraction method

Fei Li (李飞), Li Jin (靳立), Zhuo Xu (徐卓), and Zhenqi Guo (郭振琪)

Rev. Sci. Instrum. 80, 085106 (2009) (5 pages)

Online Publication Date: 19 August 2009

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X-ray diffraction (XRD) techniques are widely used in determining crystallographic orientations. In this paper we describe a two-step method to determine the three-dimensional orientations of ferroelectric single crystals based on an improved rotating orientations XRD method. This method could be readily carried out on standard x-ray laboratory equipment. Taking into account the geometric relationship in crystallography, we obtain an equation to find the expected crystallographic plane and simplify the determining process. The application of this method to LiNbO3 and xPb(Mg1/3Nb2/3)O3–(1−x)PbTiO3 ferroelectric single crystals demonstrates that it is a fast, flexible, and waste-free method for crystallographic orientation. Explanations of the scanning diffraction patterns and evaluation of the determining accuracy are presented. This method is also applicable to other nonferroelectric single crystal systems and would benefit the orientation-related issues.
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77.80.-e, 61.50.-f

A uniaxial tension system and its applications in testing of thin films and small components

Wenwang Wu, Xide Li, and Liang Liu

Rev. Sci. Instrum. 80, 085107 (2009) (6 pages)

Online Publication Date: 20 August 2009

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The aim of this investigation is to develop a uniaxial tension system for testing very small samples that allows observation of the gauge section by optical or atomic force microscopy. Major parts of the system consist of a pair of identical piezoelectric actuators, two symmetrical double-cantilevered force sensors, and two symmetrical universal coupling joints. It can accomplish both-end loaded uniaxial tension to produce centrosymmetric deformations of the tested objects in the field of view and can apply tensile loads in the range from 7.8  µN to 15 N to the samples. Sample extensions from submicrometers to 100  µm can be measured with displacement resolution of several tens of nanometers. The system's performance is demonstrated by tests of a polycrystalline aluminum alloy thin sheet, a mica thin sheet, and a fibril of bamboo.
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81.70.-q, 82.45.Mp, 07.79.Lh

Knot undulator to generate linearly polarized photons with low on-axis power density

S. Qiao, Dewei Ma, Donglai Feng, S. Marks, R. Schlueter, S. Prestemon, and Z. Hussain

Rev. Sci. Instrum. 80, 085108 (2009) (4 pages)

Online Publication Date: 21 August 2009

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Heat load on beamline optics is a serious obstacle for devices designed to generate pure linearly polarized photons in third generation synchrotron radiation facilities. For permanent magnet undulators, this problem can be overcome by implementing a figure-eight design configuration. As yet there has been no good method to tackle this problem for electromagnetic elliptical undulators. Here, a novel design and operational mode is suggested, which can generate pure linearly polarized photons with very low on-axis heat load. Additionally, the minimum photon energy capability of linearly polarized photons can be significantly extended by this method.
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29.27.Eg, 29.20.dk, 41.60.Ap

Development and performance test of a soft x-ray polarimeter and ellipsometer for complete polarization analysis

Takashi Imazono, Kazuo Sano, Yoji Suzuki, Tetsuya Kawachi, and Masato Koike

Rev. Sci. Instrum. 80, 085109 (2009) (8 pages)

Online Publication Date: 21 August 2009

Full Text: PDF (429 kB)

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A new apparatus for polarimetric and ellipsometric measurements based on the rotating-analyzer method in the soft x-ray region has been designed, constructed, and installed in the soft x-ray beamline (BL-11) at the SR Center of Ritsumeikan University, Shiga, Japan. It can realize the optical configurations for the complete polarization analysis by using six independently movable drive shafts. A demonstration of the capabilities of the apparatus has been performed using Mo/Si multilayer polarizers deposited by an ion beam sputtering method. It is for the first time shown that the degree of linear polarization of monochromatized light from the BL-11 is approximately 87% at 92 eV since the beamline has been constructed.
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07.85.-m, 07.60.Fs, 42.15.Eq, 42.82.Cr, 81.15.Cd

Friction on the microscale

K. B. Paul and L. Malkinski

Rev. Sci. Instrum. 80, 085110 (2009) (4 pages)

Online Publication Date: 31 August 2009

Full Text: PDF (217 kB)

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A new method is presented for measurements of friction of microsized particles on surfaces. Specifically in this work, the particles are alumina with diameters between [approximate]1 and 50  µm and the surfaces are InP, Si, and Cr. Friction is analyzed, its components are determined, and the friction coefficients are estimated from the experimental results. The technique and the specific instrument allow measurements of coefficients of friction for spherical particles with radii as small as 1  µm. For smaller sizes, the instrument needs to be modified by using a more powerful power supply, actuator with extended frequency and amplitude ranges, cooling of the actuator and the power supply, and the related mechanical modifications of the sample holder.
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07.10.-h, 46.55.+d
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NOTES

A compact surface decontamination system for surface-sensitive magnetic imaging

M. Konoto, H. Akoh, and Y. Tokura

Rev. Sci. Instrum. 80, 086101 (2009) (3 pages)

Online Publication Date: 5 August 2009

Full Text: PDF (416 kB)

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A surface decontamination system for application in surface sensitive magnetic imaging tools, such as a spin-polarized scanning electron microscope, is described. Adsorbed contaminant is chemically decomposed with the use of active oxygen in a compact vacuum chamber mounted in a microscope. The present method is especially suitable for fragile magnetic surfaces of complex oxide materials to which the conventional physical etching widely used for magnetic metals could cause serious structural damage. We have succeeded in detecting magnetic signals from a decontaminated oxide surface and visualizing domain images with sufficient magnetic contrast to analyze detailed domain structures.
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52.77.Bn, 52.75.-d, 81.65.Cf, 75.70.Ak, 75.70.Kw, 75.50.Dd

Monolithic time to amplitude converter for time correlated single photon counting

D. Resnati, I. Rech, A. Gallivanoni, and M. Ghioni

Rev. Sci. Instrum. 80, 086102 (2009) (3 pages)

Online Publication Date: 10 August 2009

Full Text: PDF (150 kB)

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Time correlated single photon counting techniques allow in depth examinations of very important chemical and biological processes involving complex interactions of biomolecules. Understanding of these processes is of the utmost importance to address vital medical issues such as the origin and growth of tumors. Modern developments of fluorescence analysis techniques require compact, low cost, and high performance instrumentation, and a major path to these goals is the successful integration of the electronics. In this paper we present a fully monolithic time to amplitude converter, built in standard 0.35  µm CMOS technology, characterized by good time resolution (60 ps), low differential nonlinearity (better than 0.5% rms), short dead time (80 ns), low power dissipation (60 mW), and low area occupation (1.8×1.4  mm2).
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07.57.-c, 07.60.Dq, 85.40.-e

Versatile piezoelectric pulsed molecular beam source for gaseous compounds and organic molecules with femtomole accuracy for UHV and surface science applications

Alexander Schießer and Rolf Schäfer

Rev. Sci. Instrum. 80, 086103 (2009) (2 pages)

Online Publication Date: 14 August 2009

Full Text: PDF (162 kB)

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This note describes the construction of a piezoelectric pulsed molecular beam source based upon a design presented in an earlier work [D. Proch and T. Trickl, Rev. Sci. Instrum. 60, 713 (1988)]. The design features significant modifications that permit the determination of the number of molecules in a beam pulse with an accuracy of 1×1011 molecules per pulse. The 21 cm long plunger-nozzle setup allows the molecules to be brought to any point of the UHV chamber with very high intensity. Furthermore, besides typical gaseous compounds, also smaller organic molecules with a vapor pressure higher than 0.1 mbar at room temperature may serve as feed material. This makes the new design suitable for various applications in chemical and surface science studies.
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07.77.Gx, 37.20.+j

A simple ac bridge for detecting small resistance change

Xiaohui Song, Yirong Jin, Xin Zhang, Yude Yu, and Dian-lin Zhang

Rev. Sci. Instrum. 80, 086104 (2009) (2 pages)

Online Publication Date: 18 August 2009

Full Text: PDF (254 kB)

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A simple ac resistance bridge is proposed. The stability of the design is better than 10−6, which is especially suitable for detecting tiny changes of resistance. An example of magnetoresistance measurement for a 220 nm Au film shows the good performance of the bridge.
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07.50.-e, 73.40.Cg

A high performance normally closed solenoid-actuated cold valve

I. A. J. Taminiau, O. W. B Benningshof, and R. Jochemsen

Rev. Sci. Instrum. 80, 086105 (2009) (3 pages)

Online Publication Date: 26 August 2009

Full Text: PDF (228 kB)

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An electromagnetically driven normally closed valve for liquid helium is presented, which is meant to regulate the input flow to a 1 K pot. An earlier design is modified to be normally closed (not actuated) and tuned for durability and reliability. A new feature is presented which prevents seat deformation at room temperature and provides comfort and durability for intensive use.
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07.20.Mc, 07.10.-h

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