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Jul 2005

Volume 76, Issue 7, Articles (07xxxx)

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An apparatus to investigate the fragmentation of molecular dications by electron impact

G. Alberti, E. Fainelli, F. Maracci, M. Mastropietro, R. Platania, and L. Avaldi

Rev. Sci. Instrum. 76, 073101 (2005); http://dx.doi.org/10.1063/1.1946988 (10 pages) | Cited 4 times

Online Publication Date: 22 June 2005

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An experimental setup to study the fragmentation of molecular dications formed via inner shell ionization by electron impact is described. The main components of the setup are a cylindrical mirror analyzer, CMA, used to detect the Auger electrons, which mark the molecular site where the ionization occurred and select the state of the dication, and a time of flight mass spectrometer, TOF-MS, used to detect the parent doubly charged ion or its fragments. The fragmentation is studied via Auger electron-ion and Auger electron-ion-ion coincidence experiments. The results of the measurements used to characterize the spectrometer are presented and discussed. Then the potentialities of the setup are described via selected examples of its applications.
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07.75.+h Mass spectrometers
34.80.Gs Molecular excitation and ionization

Development of a thermal neutron focusing device using neutron supermirrors

Toyotaka Osakabe and Kazuhiko Soyama

Rev. Sci. Instrum. 76, 073102 (2005); http://dx.doi.org/10.1063/1.1947883 (5 pages) | Cited 1 time

Online Publication Date: 22 June 2005

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Neutron focusing is an indispensable technique used to compensate for weak signals in experiments under extreme conditions with tiny samples. We describe the development of a thermal neutron focusing device for a typical triple-axis neutron spectrometer. The device has a length of 400 mm and is placed between the second collimator and the sample position. The focal length is 150 mm from the downstream end of the device. The optic has 18 pieces of the circular blade consisting of 3m NiC/Ti neutron supermirrors. The extensions of the end of each blade meet at the sample position, namely the focal point. Neutrons undergo successive reflection through the same angle from the inner surface of each blade and arrive at the sample position. The test results show that the gain of the neutron intensity at the sample position increases by a factor of 2 or more for the neutron energy below 30.5 meV.
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29.30.Hs Neutron spectroscopy
28.20.Cz Neutron scattering
42.79.Bh Lenses, prisms and mirrors

An algorithm for extremely complicated interference pattern evaluation

J. Olejníček, J. Píchal, J. Blažek, and P. Špatenka

Rev. Sci. Instrum. 76, 073103 (2005); http://dx.doi.org/10.1063/1.1942534 (6 pages) | Cited 1 time

Online Publication Date: 23 June 2005

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A description of an easy algorithm for evaluation of interference patterns recording the light beam deflection in phase objects is presented in this paper. The method is suitable for digitizing and evaluating complicated interference patterns containing heavily distorted, double or closed interference fringes. The created algorithm and evaluation procedure result from the lines’ approximation and Delaunay triangulation. They were applied to a complex interference pattern taken in the pinch discharge burning in low-pressure deuterium. The results obtained were used for calculation of electron density values in the discharge channel. The influence of the phase shift deformation outside the region under study on the accuracy of results and on electron density estimation inside the shock wave of the pinch was also analyzed. The gathered data were verified with a calculation of the electron temperature in the discharge channel, which was performed providing kinetic and magnetic pressure equilibriums.
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07.60.Ly Interferometers
52.80.-s Electric discharges
42.87.Bg Phase shifting interferometry
52.25.-b Plasma properties
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Noise suppression of a differential detector under high levels of illumination, relevant to terahertz electro-optic sampling

N. C. J. van der Valk, R. N. Schouten, and P. C. M. Planken

Rev. Sci. Instrum. 76, 073104 (2005); http://dx.doi.org/10.1063/1.1947667 (5 pages)

Online Publication Date: 23 June 2005

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In electro-optic detection of terahertz transients, the photodiodes of a differential detector are often illuminated with optical powers on the order of several milliwatts. We present measurements that show that the response of the photodiodes at these power levels is distorted, giving rise to frequency-dependent amplitude and phase changes in the electrical signal from these diodes. We find that these distortions significantly reduce the ability of the detector to suppress laser amplitude noise. Surprisingly, this occurs at power levels at which the dc output of each photodiode shows no sign of saturation. Based on our measurements, we provide experimenters with recommendations to improve the amplitude noise suppression of a differential detector under high levels of illumination.
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85.60.Dw Photodiodes; phototransistors; photoresistors
42.55.Px Semiconductor lasers; laser diodes
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

Novel technique for high-precision Bragg-angle determination in crystal x-ray spectroscopy

J. Braun, H. Bruhns, M. Trinczek, J. R. Crespo López-Urrutia, and J. Ullrich

Rev. Sci. Instrum. 76, 073105 (2005); http://dx.doi.org/10.1063/1.1947878 (6 pages) | Cited 7 times

Online Publication Date: 27 June 2005

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A novel technique for a high-precision large acceptance determination of the Bragg angle in crystal x-ray spectroscopy is presented and demonstrated. The method exploits visible light beams as fiducials reflected on the x-ray crystal’s surface to ensure exact knowledge of the position on the crystal at which the x rays are reflected, replacing entrance slits, thus making flat crystals suitable for low x-ray fluxes. It can be shown that many error sources arising from uncertainties in the determination of geometrical properties are eliminated in this way. A flat crystal x-ray spectrometer based on this technique has been designed, built, and tested using the most precisely known wavelengths emitted by highly charged ions, namely H- and He-like argon. The result for the 1s2p math→1s2 math w-line of He-like argon exhibits a statistical uncertainty of 3.8 ppm and an estimated systematic error of about 3 ppm, thus becoming the most accurate measurement of the He-like resonance transition in highly charged ions. It is shown that achieving a systematic error of below 1 ppm is feasible with this method. Therefore, our technique should allow reaching total accuracies approaching 1 ppm on transitions of mid-Z highly charged ions, which would provide challenging tests for state-of-the-art theoretical predictions.
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07.85.Nc X-ray and γ-ray spectrometers
32.30.Rj X-ray spectra

A multichannel, high-resolution, UV spectrometer for laser-fusion applications

W. R. Donaldson, M. Millecchia, and R. Keck

Rev. Sci. Instrum. 76, 073106 (2005); http://dx.doi.org/10.1063/1.1946087 (5 pages) | Cited 1 time

Online Publication Date: 1 July 2005

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A 63-channel, ultraviolet (UV) spectrometer has been designed and tested. With an input energy of 1 μJ per channel, 63 spectra can be acquired simultaneously on a single, multibeam laser shot. The spectrometer has a dispersion at the detector plane of 8.6×10−2 pm/μm and a spectral window of 2.4 nm at λ = 351 nm. The wavelength resolution varies from 2.5 pm at the center of the field of view to 6 pm at the edge.
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07.60.Rd Visible and ultraviolet spectrometers
52.57.-z Laser inertial confinement

Fully reflective deep ultraviolet to near infrared spectrometer and entrance optics for resonance Raman spectroscopy

B. Schulz, J. Bäckström, D. Budelmann, R. Maeser, M. Rübhausen, M. V. Klein, E. Schoeffel, A. Mihill, and S. Yoon

Rev. Sci. Instrum. 76, 073107 (2005); http://dx.doi.org/10.1063/1.1946985 (12 pages) | Cited 8 times

Online Publication Date: 1 July 2005

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We present the design and performance of a new triple-grating deep ultraviolet to near-infrared spectrometer. The system is fully achromatic due to the use of reflective optics. The minimization of image aberrations by using on- and off- axis parabolic mirrors as well as elliptical mirrors yields a strong stray light rejection with high resolution over a wavelength range between 165 and 1000 nm. The Raman signal is collected with a reflective entrance objective with a numerical aperture of 0.5, featuring a Cassegrain-type design. Resonance Raman studies on semiconductors and on correlated compounds, such as LaMnO3, highlight the performance of this instrument, and show diverse resonance effects between 1.96 and 5.4 eV.
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07.60.Rd Visible and ultraviolet spectrometers
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
42.15.Eq Optical system design
42.79.Bh Lenses, prisms and mirrors
42.79.Dj Gratings
78.30.Hv Other nonmetallic inorganics

A compact laser head with high-frequency stability for Rb atomic clocks and optical instrumentation

Christoph Affolderbach and Gaetano Mileti

Rev. Sci. Instrum. 76, 073108 (2005); http://dx.doi.org/10.1063/1.1979493 (5 pages) | Cited 10 times

Online Publication Date: 1 July 2005

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We present a compact and frequency-stabilized laser head based on an extended-cavity diode laser. The laser head occupies a volume of 200 cm3 and includes frequency stabilization to Doppler-free saturated absorption resonances on the hyperfine components of the math D2 lines at 780 nm, obtained from a simple and compact spectroscopic setup using a 2 cm3 vapor cell. The measured frequency stability is ⩽ 2×10−12 over integration times from 1 s to 1 day and shows the potential to reach 2×10−13 over 102−105 s. Compact laser sources with these performances are of great interest for applications in gas-cell atomic frequency standards, atomic magnetometers, interferometers and other instruments requiring stable and narrow-band optical sources.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
06.20.F- Units and standards
06.30.Ft Time and frequency
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Simulation results on a resistive plate chamber for a bakelite thickness of 1 mm up to 3 mm

J. T. Rhee and M. Jamil

Rev. Sci. Instrum. 76, 073301 (2005); http://dx.doi.org/10.1063/1.1927091 (4 pages) | Cited 4 times

Online Publication Date: 22 June 2005

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The performance of bakelite electrodes with thicknesses of 1, 2, and 3 mm in a double-gap resistive plate chamber (RPC) have been tested by GEANT-based Monte Carlo simulation. Results show that the thickness of bakelite plays an important role in detecting particle signals. For checking the efficiency of these RPCs, gamma particles in the range 0.01–100 MeV have been simulated through different bakelite setups. For an isotropic gamma source, a sensitivity sγ<3.5×10−2 at <100 MeV by a 1 mm bakelite double-gap RPC has been observed. For the same gamma source with a 2 mm bakelite RPC, a sensitivity sγ<4.0×10−2 at <100 MeV has been measured, whereas for 3 mm bakelite RPC, sensitivity results were sγ<4.44×10−2 at <100 MeV. Similar characteristics of bakelite electrodes have been observed for a parallel gamma source configuration.
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29.40.Gx Tracking and position-sensitive detectors
29.40.Cs Gas-filled counters: ionization chambers, proportional, and avalanche counters

Design of a standing-wave multicell radio frequency cavity beam monitor for simultaneous position and emittance measurement

Jin-Soo Kim, Roger Miller, and Christopher Nantista

Rev. Sci. Instrum. 76, 073302 (2005); http://dx.doi.org/10.1063/1.1946407 (9 pages) | Cited 2 times

Online Publication Date: 22 June 2005

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High precision, nondisruptive emittance measurement through second moment monitoring requires precise beam position at the measurement location. We present the design and analysis of a multicavity standing wave structure for a pulse-to-pulse beam position-emittance measurement system in which the quadrupole and the dipole standing wave modes resonate at harmonics of a presumed beam bunch train frequency. As an application for the Next Linear Collider (NLC) beams, an optimized nine-cavity standing-wave structure is designed for simultaneous high precision beam position and emittance measurement. It operates with the π-phase advance quadrupole mode resonating at the 16th harmonic (11.424 GHz) of the NLC bunch frequency and the 3π/4-phase advance dipole mode at the 12th harmonic (8.568 GHz). The output powers from these modes are estimated for the NLC beams. Measurement resolution is estimated to be on the micron scale for rms beam size and on the nanometer scale for beam position.
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29.27.Fh Beam characteristics
29.20.-c Accelerators

A large distributed digital camera system for accelerator beam diagnostics

L. Catani, A. Cianchi, G. Di Pirro, and K. Honkavaara

Rev. Sci. Instrum. 76, 073303 (2005); http://dx.doi.org/10.1063/1.1946667 (6 pages) | Cited 1 time

Online Publication Date: 23 June 2005

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Optical diagnostics, providing images of accelerated particle beams using radiation emitted by particles impinging a radiator, typically a fluorescent screen, has been extensively used, especially on electron linacs, since the 1970's. Higher intensity beams available in the last decade allow extending the use of beam imaging techniques to perform precise measurements of important beam parameters such as emittance, energy, and energy spread using optical transition radiation (OTR). OTR-based diagnostics systems are extensively used on the superconducting TESLA Test Facility (TTF) linac driving the vacuum ultraviolet free electron laser (VUV-FEL) at the Deutsches Elektronen-Synchrotron facility. Up to 30 optical diagnostic stations have been installed at various positions along the 250-m-long linac, each equipped with a high-performance digital camera. This paper describes the new approach to the design of the hardware and software setups required by the complex topology of such a distributed camera system.
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42.79.Pw Imaging detectors and sensors
29.27.Eg Beam handling; beam transport
41.85.-p Beam optics
29.27.Fh Beam characteristics
41.75.Fr Electron and positron beams
41.60.Cr Free-electron lasers

Low jitter metal vapor vacuum arc ion source for electron beam ion trap injections

Glenn E. Holland, Craig N. Boyer, John F. Seely, J. N. Tan, J. M. Pomeroy, and J. D. Gillaspy

Rev. Sci. Instrum. 76, 073304 (2005); http://dx.doi.org/10.1063/1.1948396 (6 pages) | Cited 6 times

Online Publication Date: 27 June 2005

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We describe a metal vapor vacuum arc (MeVVA) ion source containing eight different cathodes that are individually selectable via the control electronics which does not require moving components in vacuum. Inside the vacuum assembly, the arc plasma is produced by means of a 30 μs pulse (26 kV,125 A) delivering 2.4 mC of charge to the cathode sample material. The trigger jitter is minimized (<200 ns) to improve the capture efficiency of the ions which are injected into an ion trap. During a single discharge, the over-damped pulse produces an ion flux of 8.4×109 ions/cm2, measured by an unbiased Faraday cup positioned 20 cm from the extractor grid, at discharge rates up to 5 Hz. The electronic triggering of the discharge is via a fiber optic interface. We present the design, fabrication details, and performance of this MeVVA, recently installed on the National Institute of Standards and Technology electron beam ion trap (EBIT).
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.80.Vp Discharge in vacuum
52.50.Dg Plasma sources
52.70.-m Plasma diagnostic techniques and instrumentation

Production of a MeV proton with 30 mJ laser energy by optimizing the focusing spot using a deformable mirror

Takuya Nayuki, Takashi Fujii, Yuji Oishi, Kei Takano, Xiaofang Wang, Alexander Alekseevitch Andreev, Koshichi Nemoto, and Ken-ichi Ueda

Rev. Sci. Instrum. 76, 073305 (2005); http://dx.doi.org/10.1063/1.1942527 (5 pages) | Cited 3 times

Online Publication Date: 1 July 2005

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The production of energetic protons using a polyimide tape of 7.5 μm thickness was carried out with laser pulses of 30 mJ energy and 80 fs duration. A deformable mirror system with a genetic algorithm (GA) was developed to optimize the laser-focusing spot. The fitness values used in the GA were measured from the focusing intensities under the low-gain condition of the power amplifier, or from x-ray in situ signals emitted from the target. Although we obtained a diffraction-limited size of 2 μm (full width at half maximum) using the former value, a precise compensation using the latter value was essential to accelerate protons whose flux was 106/MeV/shot to a maximum energy of 1.1±0.3 MeV with laser pulses of only 30 mJ energy since a laser spot that is too tight may be sensitive to wave-front distortion caused by residual thermal lenses of the power amplifier.
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07.77.Ka Charged-particle beam sources and detectors
29.25.-t Particle sources and targets
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.79.Bh Lenses, prisms and mirrors
02.60.Pn Numerical optimization
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Behavior of liquid lithium jet irradiated by 1 MeV electron beams up to 20 kW

J. A. Nolen, C. B. Reed, V. J. Novick, J. R. Specht, J. M. Bogaty, P. Plotkin, and Y. Momozaki

Rev. Sci. Instrum. 76, 073501 (2005); http://dx.doi.org/10.1063/1.1942530 (6 pages) | Cited 1 time

Online Publication Date: 22 June 2005

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Experiments were conducted to demonstrate the stable operation of the windowless liquid lithium target under extreme thermal loads that are equivalent to uranium beams from the proposed Rare Isotope Accelerator (RIA) driver linac. The cross section of the windowless liquid lithium target was 5 mm×10 mm and the velocity of the liquid lithium was varied up to 6 m/s. Thermal loads up to 20 kW within a beam spot of 1 mm in diameter were applied on the windowless liquid lithium target by 1 MeV electron beams. The maximum power density and total power deposited within the target was equivalent to that of a 200 kW, 400 MeV/u uranium beam. It was demonstrated that the windowless liquid lithium target flowing at as low as 1.8 m/s stably operates at a beam energy deposition up to 20 kW without disruption or excess vaporization.
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07.77.Ka Charged-particle beam sources and detectors
29.27.-a Beams in particle accelerators
29.25.Pj Polarized and other targets
61.80.Fe Electron and positron radiation effects

Analysis of γγ directional correlation data taken with a multi-detector system

J. Y. Zevallos-Chávez, F. A. Genezini, C. B. Zamboni, M. T. F. da Cruz, M. N. Martins, V. R. Vanin, Z. O. Guimarães-Filho, and P. R. Pascholati

Rev. Sci. Instrum. 76, 073502 (2005); http://dx.doi.org/10.1063/1.1938527 (5 pages) | Cited 1 time

Online Publication Date: 22 June 2005

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When performed with a multi-detector system, γγ directional correlation measurements need to be corrected differently for each independent detector pair, especially when those detectors have different active volumes and subtend different solid angles with respect to the radioactive source. We show here a method, which is suitable for setups containing dissimilar detectors. Successful tests were made for four γγ cascades, from math, math and math.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
29.40.Wk Solid-state detectors

A new method on recycling coefficient measurement using impurity pellet injection in a large helical device

Hideaki Nozato, Shigeru Morita, and Motoshi Goto

Rev. Sci. Instrum. 76, 073503 (2005); http://dx.doi.org/10.1063/1.1946567 (5 pages) | Cited 1 time

Online Publication Date: 23 June 2005

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Recycling coefficients of carbon, aluminum, and titanium were evaluated using a new technique combining impurity pellet injection with high-spatial resolution bremsstrahlung measurement in hydrogen and helium plasmas on the large helical device. The recycling coefficient of impurities was investigated by measuring absolute intensities with the visible bremsstrahlung array. The time evolution of the bremsstrahlung signals was modeled by an impurity transport code adjusting the diffusion coefficient, convective velocity, and recycling coefficient. As a result, a finite value of the recycling coefficient was required in the case of carbon, whereas aluminum and titanium were explained as nonrecycled particles. It was also clarified that the recycling coefficient of carbon had a larger value in hydrogen plasmas (R = 0.5–0.65) than in helium plasmas (R = 0–0.2), suggesting the formation of hydrogen molecules.
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52.25.Vy Impurities in plasmas
52.25.Fi Transport properties
52.55.Jd Magnetic mirrors, gas dynamic traps
52.58.-c Other confinement methods

Two-dimensional density and density fluctuation diagnostic for the edge plasma in fusion devices

S. Zoletnik, G. Petravich, A. Bencze, M. Berta, S. Fiedler, K. McCormick, and J. Schweinzer

Rev. Sci. Instrum. 76, 073504 (2005); http://dx.doi.org/10.1063/1.1947727 (12 pages) | Cited 7 times

Online Publication Date: 23 June 2005

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A technique is described for the two-dimensional measurement of electron density profile and fluctuations in edge regions of magnetically confined fusion plasmas. The method is based on existing lithium beam beam emission spectroscopy technique, two-dimensional resolution is achieved by electrostatically scanning the beam. If scanning is performed faster than the lifetime of the turbulent structures in the plasma, the diagnostic is capable of measuring the structure of electron density fluctuations as well. The beam strength of currently available beams makes the detection of single fluctuation events impossible, but the full two-dimensional spatial structure of correlations can still be determined. The article describes the technique and fast beam deflection tests up to 250 kHz. The capabilities of such a diagnostic for fluctuation measurement are explored by simulating measurement signals. Measurement of both the two-dimensional density profile, fluctuation correlation function and poloidal flow velocity are demonstrated at the Wendelstein 7-AS stellarator. The shape of the density profile, the radial and poloidal correlation lengths and the flow velocity are in agreement with expectations and previous Langmuir probe measurement.
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52.70.Nc Particle measurements
52.25.Gj Fluctuation and chaos phenomena
52.40.Hf Plasma-material interactions; boundary layer effects
52.55.Jd Magnetic mirrors, gas dynamic traps
52.30.-q Plasma dynamics and flow
52.35.Ra Plasma turbulence

In situ characterization of high-intensity laser beams on OMEGA

R. A. Forties and F. J. Marshall

Rev. Sci. Instrum. 76, 073505 (2005); http://dx.doi.org/10.1063/1.1947782 (4 pages) | Cited 4 times

Online Publication Date: 23 June 2005

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This article details a means of inferring high-intensity laser beam shapes as applied to the 60-beam ultraviolet (UV) (351 nm) OMEGA laser system [ T. R. Boehly et al., Opt. Commun. 133, 495 (1997) ]. Measurements of the shape, location, and relative fluence of beams on the OMEGA laser system are obtained from x-ray images of the emission from 4‐mm‐diam, Au-coated pointing targets irradiated by the focused beams. The images are digitally recorded with an array of up to eight pinhole cameras. The image of each beam is corrected for the effect of view angle and conversion efficiency from UV to x rays, and fit to an elliptical super-Gaussian. The best-fit values from multiple views are combined to obtain values of the beam’s shape, beam-to-beam relative peak fluence, beam position, and errors thereof. This method allows the beam-to-beam balance and beam pointing to be further improved, if so desired, by providing measurements of these quantities at the target.
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28.52.Cx Fueling, heating and ignition

Vacuum photodiode detectors for soft x-ray ITER plasma tomography

Yu. V. Gott and M. M. Stepanenko

Rev. Sci. Instrum. 76, 073506 (2005); http://dx.doi.org/10.1063/1.1951588 (5 pages) | Cited 6 times

Online Publication Date: 27 June 2005

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A special type of vacuum photodiode detector (VPD) for x-ray tomography of (ITER) plasma is described. Laboratory experiments demonstrate that VPD has high sensitivity to thermal x-rays and low sensitivity to hard gamma rays and neutrons. It was shown that in ITER environment the signal due to thermal x-rays will surpass the background signal by more than a factor of 100.
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52.70.La X-ray and γ-ray measurements
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
28.52.Lf Components and instrumentation
28.52.Av Theory, design, and computerized simulation
52.75.-d Plasma devices
85.60.Dw Photodiodes; phototransistors; photoresistors
85.60.Gz Photodetectors (including infrared and CCD detectors)

A software package to manipulate space dependencies and geometry in magnetic confinement fusion

J.-M. Moret

Rev. Sci. Instrum. 76, 073507 (2005); http://dx.doi.org/10.1063/1.1946608 (15 pages) | Cited 1 time

Online Publication Date: 12 July 2005

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Improvement in the performance of magnetic confinement devices for nuclear fusion relies on the optimization of the geometry of the plasma: either the two-dimensional (2D) cross-section shape in tokamaks with toroidal symmetry or the 3D magnetic configuration in stellerators. The variation in time and space of the plasma parameters in these devices is measured using tomographic or imaging systems with a large number of detectors. To integrate the geometrical manipulations required for the analysis of experimental data, the description of the confining magnetic field configuration and the modeling and simulation of the physical processes within the plasma, an object oriented software package has been developed. Classes in this package are used to describe several coordinate systems, including magnetic flux coordinates, the geometry of the measurement systems, the configuration of the magnetic field and space, and time dependent functions representing plasma parameters. Methods applied on these classes can then easily implement coordinate system transformations, as well as interpolation of and integro-differential calculus on, space and time dependent functions. The geometrical description and characteristics of the magnetic flux surfaces have a natural representation in this environment, allowing the ready computation of the intersection of measurement viewing lines with a coordinate mesh and with flux surfaces, as well as the calculation of the corresponding transfer matrix used in tomographic inversion. The selected numerical methods used in these manipulations and their performances are also presented.
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52.70.-m Plasma diagnostic techniques and instrumentation
52.55.Fa Tokamaks, spherical tokamaks
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Nanometer scale marker for fluorescent microscopy

Takashi Hiraga, Yoshinori Iketaki, Takeshi Watanabe, Hideyuki Ohyi, Kazumasa Kobayashi, Noritaka Yamamoto, Toshiko Mizokuro, and Masaaki Fujii

Rev. Sci. Instrum. 76, 073701 (2005); http://dx.doi.org/10.1063/1.1946627 (4 pages) | Cited 8 times

Online Publication Date: 23 June 2005

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To establish a calibration method of optical performance in fluorescence microscopy, we fabricated a fluorescent nanometer-scale marker by combining a dry dye method for polymer film and fine lithography. The marker has a 50 nm line-and-space fluorescent pattern, finer than the optical diffraction limit. A spin-coated poly(methyl methacrylate) thin film on a silicon wafer was densely doped with Rhodamine 6G using a simple vacuum process, named the vapor-transportation method, and then the pattern was formed on the film using electron-beam lithography. The figure accuracy of the fabricated marker was calibrated by electron microscopes. Using this marker, one can quantitatively evaluate the optical properties; i.e., the contrast-transfer function, the point-spread function, magnification, and so on. To show practical use of the marker, we demonstrated the evaluation of a fluorescent microscope system.
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07.60.Pb Conventional optical microscopes
06.20.F- Units and standards
42.30.Lr Modulation and optical transfer functions
42.82.Cr Fabrication techniques; lithography, pattern transfer
81.16.Nd Micro- and nanolithography

Nondestructive evaluation of rice using two-dimensional imaging of photoluminescence

T. Katsumata, T. Suzuki, H. Aizawa, E. Matashige, S. Komuro, and T. Morikawa

Rev. Sci. Instrum. 76, 073702 (2005); http://dx.doi.org/10.1063/1.1947879 (4 pages) | Cited 1 time

Online Publication Date: 23 June 2005

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Evaluation technique of rice using photoluminescence (PL) imaging has been developed based on the visible light PL with broad peak at a wavelength of λ = 462 nm from starchy foods under illumination of ultraviolet (UV) light at λ = 365 nm. Peak intensity of PL varies with variety and source of the rice. Two-dimensional (2D) images of PL from rice reveal the uniformity of the rice product. Blended rice from different species can be detected using 2D PL image. Brightness over the 2D PL images of rice with a single breed from a single source distributes according to a Gaussian distribution curve. Deviation from a Gaussian distribution curve estimated as χ2 value and correlation coefficient increases in a rice specimen of various species of blended rice. Image processing of PL images from specimens reveals contamination and∕or mixing of other species or foreign objects. A 2D PL imaging technique is potentially useful for nondestructive and quick evaluation and quality control of the rice products.
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07.05.Pj Image processing
89.90.+n Other topics in areas of applied and interdisciplinary physics (restricted to new topics in section 89)
78.55.-m Photoluminescence, properties and materials
81.70.Fy Nondestructive testing: optical methods

Spatial-temporal modeling for electrical impedance imaging of a mixing process

R. M. West, S. Meng, R. G. Aykroyd, and R. A. Williams

Rev. Sci. Instrum. 76, 073703 (2005); http://dx.doi.org/10.1063/1.1947882 (10 pages) | Cited 2 times

Online Publication Date: 27 June 2005

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The use of electrical tomography techniques for process visualization and investigation is a well-known example of a nonlinear, ill-posed, and underdetermined inverse problem. Hence stable and reliable solution is not possible using measured data alone, but requires regularization through prior information. The rôle of a Bayesian approach is therefore of fundamental importance, and when coupled with Markov chain Monte Carlo (MCMC) sampling, it can provide valuable statistical information about solution behavior and reliability, which is in contrast to most current approaches which provide only a single image reconstruction with unquantified errors. For many applications of dynamic electrical impedance imaging, some degree of both spatial and temporal smoothness is expected. Often temporal smoothness is ignored and only spatial smoothing is used. In the current application, the addition of an aliquot to a mixing vessel, smoothness is not appropriate prior information. Instead an aliquot prior is proposed, parameterized in terms of location, size, and resistivity. This approach leads to data-driven and adaptive smoothing, in contrast to the more usual global smoothing of standard regularization methods. Of further interest is the inclusion of temporal prior information: it is known that the aliquot moves and disperses in a specific manner. With this added temporal information, imaging is improved as are derived process parameters.
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84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
64.75.-g Phase equilibria
02.30.Zz Inverse problems
02.70.Uu Applications of Monte Carlo methods
02.50.Ga Markov processes

Time-gated imaging for multifocus second-harmonic generation microscopy

Minoru Kobayashi, Katsumasa Fujita, Osamu Nakamura, and Satoshi Kawata

Rev. Sci. Instrum. 76, 073704 (2005); http://dx.doi.org/10.1063/1.1947047 (4 pages) | Cited 2 times

Online Publication Date: 29 June 2005

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We developed a scanning second-harmonic generation (SHG) microscope with a time-gated image intensifier. The combination of a microlens array scanner and the gated image intensifier allows us to perform simultaneous time-resolved detection of SHG at multiple positions in a sample. By tuning the time delay of the gated detection from pulsed laser illumination by a mode-locked Ti:sapphire laser, background noise originating from the image intensifier dark current, fluorescence from the sample, and stray light are effectively reduced.
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07.60.Pb Conventional optical microscopes
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Ls Scanners, image intensifiers, and image converters
42.79.Bh Lenses, prisms and mirrors

Optimization of phase contrast imaging using hard x rays

S. Zabler, P. Cloetens, J.-P. Guigay, J. Baruchel, and M. Schlenker

Rev. Sci. Instrum. 76, 073705 (2005); http://dx.doi.org/10.1063/1.1960797 (7 pages) | Cited 26 times

Online Publication Date: 29 June 2005

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X ray radiography and tomography are important tools in medicine as well as in life science and materials science. Not long ago an approach called in-line holography based on simple propagation became possible using partially coherent synchrotron beams like the ones available at the European Synchrotron Radiation Facility (ESRF). Theoretical and experimental work by Cloetens et al. [Appl. Phys. Lett 75, 2912 (1999)] have shown that quantitative retrieval of the optical phase, from a set of radiographs taken at different sample-to-detector distances, is feasible. Mathematically speaking we are dealing with a direct method based on linearization in order to solve an inverse nonlinear problem. The phase retrieval can be combined with classical tomography in order to obtain a three-dimensional representation of the object’s electron density (holotomography). In order to optimize the image contrast for the numerical phase retrieval process, we have carried out calculations resulting in an optimized choice of value and number of the sample-to-detector distances as well as of the photon energy. These results were then confirmed by experiments on the ESRF long beamline ID19.
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07.85.-m X- and γ-ray instruments
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