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Nov 2009

Volume 80, Issue 11, Articles (11xxxx)

Issue Cover Spotlight Figure

Rev. Sci. Instrum. 80, 111101 (2009); http://dx.doi.org/10.1063/1.3224703 (17 pages)

R. Vijay, M. H. Devoret, and I. Siddiqi

Poincaré sections of an RF-driven Josephson junction oscillator. Right: Oscillator biased near the upper bifurcation point (IRF=IB+) where two attractors OL and OH coexist. The transition from OL to OH forms the basis of a sensitive threshold amplifier. Left: Oscillator biased outside the bistable region where a single attractor exists.

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Invited Review Article: The Josephson bifurcation amplifier

R. Vijay, M. H. Devoret, and I. Siddiqi

Rev. Sci. Instrum. 80, 111101 (2009); http://dx.doi.org/10.1063/1.3224703 (17 pages) | Cited 15 times

Online Publication Date: 17 November 2009

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We review the theory, fabrication, and implementation of the Josephson bifurcation amplifier (JBA). At the core of the JBA is a nonlinear oscillator based on a reactively shunted Josephson junction. A weak input signal to the amplifier couples to the junction critical current I0 and results in a dispersive shift in the resonator plasma frequency ωp. This shift is enhanced by biasing the junction with a sufficiently strong microwave current Irf to access the nonlinear regime where ωp varies with Irf. For a drive frequency ωd such that Ω = 2Q(1−ωd/ωp)>math, the oscillator enters the bistable regime where two nondissipative dynamical states OL and OH, which differ in amplitude and phase, can exist. The sharp I0 dependent transition from OL to OH forms the basis for a sensitive digital threshold amplifier. In the vicinity of the bistable regime (Ω<math), analog amplification of continuous signals is also possible. We present experimental data characterizing amplifier performance and discuss two specific applications—the readout of superconducting qubits (digital mode) and dispersive microwave magnetometry (analog mode).
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85.25.Cp Josephson devices
85.25.Dq Superconducting quantum interference devices (SQUIDs)
84.30.Le Amplifiers
84.30.Ng Oscillators, pulse generators, and function generators
84.40.-x Radiowave and microwave (including millimeter wave) technology
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A threshold photoelectron-photoion coincidence spectrometer with double velocity imaging using synchrotron radiation

Xiaofeng Tang, Xiaoguo Zhou, Mingli Niu, Shilin Liu, Jinda Sun, Xiaobin Shan, Fuyi Liu, and Liusi Sheng

Rev. Sci. Instrum. 80, 113101 (2009); http://dx.doi.org/10.1063/1.3250872 (10 pages) | Cited 10 times

Online Publication Date: 2 November 2009

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A novel threshold photoelectron-photoion coincidence (TPEPICO) imaging spectrometer at the U14-A beamline of the Hefei National Synchrotron Radiation Laboratory is presented. A set of open electron and ion lenses are utilized to map velocity imaging of photoelectrons and photoions simultaneously, in which a repelling electric field using an extra lens is applied to magnify images of photoelectrons instead of traditional accelerating electric field in order to suppress the contribution of energetic electrons in the threshold photoelectron spectroscopy (TPES) and the mass-selected TPEPICO spectroscopy. The typical energy resolution of TPES is measured to be 9 meV (full width at half maximum), as shown on the 2P1/2 ionization of argon. The measured mass resolving power for the present TPEPICO imaging spectrometer is above 900 of M/ΔM. Subsequently as a benchmark, oxygen molecule is photoionized by monochromatic synchrotron radiation at 20.298 eV and dissociates to an oxygen atomic ion and a neutral oxygen atom, and the translation energy distribution of oxygen atomic ion is measured by the time-sliced imaging based on mass-selected TPEPICO experiment. The kinetic energy resolution of the present ion velocity imaging is better than 3% of ΔE/E.
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07.81.+a Electron and ion spectrometers
07.75.+h Mass spectrometers
07.85.Nc X-ray and γ-ray spectrometers

Internal frequency conversion extreme ultraviolet interferometer using mutual coherence properties of two high-order-harmonic sources

S. Dobosz, H. Stabile, A. Tortora, P. Monot, F. Réau, M. Bougeard, H. Merdji, B. Carré, Ph. Martin, D. Joyeux, D. Phalippou, F. Delmotte, J. Gautier, and R. Mercier

Rev. Sci. Instrum. 80, 113102 (2009); http://dx.doi.org/10.1063/1.3257676 (6 pages) | Cited 1 time

Online Publication Date: 3 November 2009

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We report on an innovative two-dimensional imaging extreme ultraviolet (XUV) interferometer operating at 32 nm based on the mutual coherence of two laser high order harmonics (HOH) sources, separately generated in gas. We give the first evidence that the two mutually coherent HOH sources can be produced in two independent spatially separated gas jets, allowing for probing centimeter-sized objects. A magnification factor of 10 leads to a micron resolution associated with a subpicosecond temporal resolution. Single shot interferograms with a fringe visibility better than 30% are routinely produced. As a test of the XUV interferometer, we measure a maximum electronic density of 3×1020 cm−3 1.1 ns after the creation of a plasma on aluminum target.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
07.60.Ly Interferometers
51.70.+f Optical and dielectric properties

Electro-optic measurement of terahertz pulse energy distribution

J. H. Sun, J. G. Gallacher, G. J. H. Brussaard, N. Lemos, R. Issac, Z. X. Huang, J. M. Dias, and D. A. Jaroszynski

Rev. Sci. Instrum. 80, 113103 (2009); http://dx.doi.org/10.1063/1.3245342 (4 pages)

Online Publication Date: 5 November 2009

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An accurate and direct measurement of the energy distribution of a low repetition rate terahertz electromagnetic pulse is challenging because of the lack of sensitive detectors in this spectral range. In this paper, we show how the total energy and energy density distribution of a terahertz electromagnetic pulse can be determined by directly measuring the absolute electric field amplitude and beam energy density distribution using electro-optic detection. This method has potential use as a routine method of measuring the energy density of terahertz pulses that could be applied to evaluating future high power terahertz sources, terahertz imaging, and spatially and temporarily resolved pump-probe experiments.
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78.20.Jq Electro-optical effects
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
84.40.-x Radiowave and microwave (including millimeter wave) technology
07.50.Hp Electrical noise and shielding equipment

Extended Kalman filter estimates the contour length of a protein in single molecule atomic force microscopy experiments

Vicente I. Fernandez, Pallav Kosuri, Vicente Parot, and Julio M. Fernandez

Rev. Sci. Instrum. 80, 113104 (2009); http://dx.doi.org/10.1063/1.3252982 (7 pages) | Cited 1 time

Online Publication Date: 6 November 2009

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Atomic force microscopy force spectroscopy has become a powerful biophysical technique for probing the dynamics of proteins at the single molecule level. Extending a polyprotein at constant velocity produces the now familiar sawtooth pattern force-length relationship. Customarily, manual fits of the wormlike chain (WLC) model of polymer elasticity to sawtooth pattern data have been used to measure the contour length Lc of the protein as it unfolds one module at a time. The change in the value of Lc measures the number of amino acids released by an unfolding protein and can be used as a precise locator of the unfolding transition state. However, manual WLC fits are slow and introduce inevitable operator-driven errors which reduce the accuracy of the Lc estimates. Here we demonstrate an extended Kalman filter that provides operator-free real time estimates of Lc from sawtooth pattern data. The filter design is based on a cantilever-protein arrangement modeled by a simple linear time-invariant cantilever model and by a nonlinear force-length relationship function for the protein. The resulting Kalman filter applied to sawtooth pattern data demonstrates its real time, operator-free ability to accurately measure Lc. These results are a marked improvement over the earlier techniques and the procedure is easily extended or modified to accommodate further quantities of interest in force spectroscopy.
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87.80.Nj Single-molecule techniques
87.80.Dj Spectroscopies
87.14.E- Proteins
87.15.bk Structure of aggregates
87.15.H- Dynamics of biomolecules
36.20.Ey Conformation (statistics and dynamics)

Continuous wave terahertz wave spectrometer based on diode laser pumping: Potential applications in high resolution spectroscopy

Tadao Tanabe, Srinivasa Ragam, and Yutaka Oyama

Rev. Sci. Instrum. 80, 113105 (2009); http://dx.doi.org/10.1063/1.3258202 (4 pages) | Cited 1 time

Online Publication Date: 9 November 2009

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We constructed a high resolution terahertz (THz) spectroscopic system with an automatic scanning control using a continuous wave (cw) THz wave generator based on difference frequency generation method by excitation of phonon-polariton mode in GaP. The pump and signals lasers were compact, tunable external cavity laser, and distributed feedback (DFB) lasers, respectively. The generated THz waves were tuned automatically by changing the temperature of the DFB laser using a system control. We present the water vapor transmission characteristics of the THz wave and also absorption spectrum of a white polyethylene in the frequency range of 1.97–2.45 THz. The spectroscopic measurements performed at an output power level of 2 nW, which was obtained with a 15-mm-long GaP crystal at 2 THz. The advantage of this cw THz spectrometer is wide frequency tuning range (0.7–4.42 THz) with an estimated linewidth of full width at quarter maximum <8 MHz and this system has a potential application in high resolution spectroscopy.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques

Photoacoustic beam profiling of pulsed lasers

Martín González, Guillermo Santiago, Verónica Slezak, and Alejandro Peuriot

Rev. Sci. Instrum. 80, 113106 (2009); http://dx.doi.org/10.1063/1.3246782 (5 pages) | Cited 1 time

Online Publication Date: 9 November 2009

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We introduce a beam profiler of pulsed lasers based on the photoacoustic technique. The method assumes that the initial pressure distribution inside the acoustic cell follows the laser intensity pattern if absorbed energy relaxes rapidly. This initial pressure condition can be described as a superposition of acoustic modes of different amplitudes and phases. We analyze how to reconstruct the intensity profile of the laser beam from the recorded acoustic signals. Finally, we present preliminary results obtained with a frequency doubled Nd:YAG laser that excites NO2–CF2Cl2 mixtures.
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42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect

Modification of a commercial cavity ring-down spectroscopy NO2 detector for enhanced sensitivity

Patricia Castellanos, Winston T. Luke, Paul Kelley, Jeffrey W. Stehr, Sheryl H. Ehrman, and Russell R. Dickerson

Rev. Sci. Instrum. 80, 113107 (2009); http://dx.doi.org/10.1063/1.3244090 (6 pages)

Online Publication Date: 11 November 2009

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Nitrogen dioxide (NO2) plays a central role in atmospheric chemistry, air pollution, and biogeochemical cycles. Many analytical techniques have been developed to detect NO2, but only chemiluminescence-based instruments are commonly, commercially available. There remains a need for a fast, light, and simple method to directly measure NO2. In this work we describe the modification and characterization of a small, commercially available cavity ring-down spectroscopy (CRDS) NO2 detector suitable for surface and aircraft monitoring. A metal oxide scrubber was added to remove NO2, and provide a chemical zero, improving the detection limit (3σ of the background noise) from several parts per billion by volume (ppbv) to 0.06 ppbv, integrated over 60 s. Known interferences by water and particles were removed using Nafion tubing and a 1 μm Teflon® filter, respectively. A 95% response time of 18±1 s was observed for a step change in concentration. The CRDS detector was run in parallel to an ozone chemiluminescence device with photolytic conversion of NO2 to NO. The two instruments measured ambient air in suburban Maryland. A least-squares fit to the comparison data resulted a slope of 0.960±0.002 and R of 0.995, showing agreement within experimental uncertainty.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
82.80.Dx Analytical methods involving electronic spectroscopy
82.50.-m Photochemistry

A new dual-purpose ultrahigh vacuum infrared spectroscopy apparatus optimized for grazing-incidence reflection as well as for transmission geometries

Y. Wang, A. Glenz, M. Muhler, and Ch. Wöll

Rev. Sci. Instrum. 80, 113108 (2009); http://dx.doi.org/10.1063/1.3257677 (6 pages) | Cited 13 times

Online Publication Date: 13 November 2009

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A newly designed ultrahigh vacuum (UHV) infrared spectroscopy apparatus dedicated to the spectroscopic characterization of oxides, singles crystals as well as powders, is described. It combines a state-of-the-art vacuum Fourier transform infrared (FTIR) spectrometer (Bruker, VERTEX 80v) with a novel UHV system (PREVAC) consisting of load-lock, distribution, measurement, and magazine chambers. The innovative design allows carrying out both reflection-absorption IR spectroscopy experiments at grazing incidence on well-defined oxide single crystal surfaces and FTIR transmission measurements for powder particles. A further unique feature of the apparatus is the entirely evacuated optical path to avoid background signals from gas phase H2O, CO2, and other species, thus creating the possibility to record high-quality IR data with high sensitivity and stability, an essential prerequisite for monitoring molecular species adsorbed on oxide single-crystal surfaces. The unique performance of this new apparatus with regard to the spectroscopic characterization of adsorbates on oxide single crystals as well as on powder particles is demonstrated by case studies for two different materials, TiO2 and ZnO.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
07.30.-t Vacuum apparatus

Hyperfine spectroscopy of the 1s5−2p9 transition of 39Ar

J. Welte, I. Steinke, M. Henrich, F. Ritterbusch, M. K. Oberthaler, W. Aeschbach-Hertig, W. H. Schwarz, and M. Trieloff

Rev. Sci. Instrum. 80, 113109 (2009); http://dx.doi.org/10.1063/1.3257691 (4 pages) | Cited 2 times

Online Publication Date: 19 November 2009

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We report on the first experimental determination of the hyperfine structure of the 1s5−2p9 transition in 39Ar. We give a detailed description of the sample preparation, spectroscopy cell cleaning, and spectroscopic setup. The resulting set of parameters consists of the hyperfine constants of the levels involved and the isotopic shift between 39Ar and 40Ar. With the achieved precision all laser frequencies necessary for the implementation of atom trap trace analysis for 39Ar, i.e., laser cooling and repumping frequencies, are now known.
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31.30.Gs Hyperfine interactions and isotope effects
32.70.Jz Line shapes, widths, and shifts
37.10.De Atom cooling methods

The photon analysis, delivery, and reduction system at the FERMI@Elettra free electron laser user facility

M. Zangrando, A. Abrami, D. Bacescu, I. Cudin, C. Fava, F. Frassetto, A. Galimberti, R. Godnig, D. Giuressi, L. Poletto, L. Rumiz, R. Sergo, C. Svetina, and D. Cocco

Rev. Sci. Instrum. 80, 113110 (2009); http://dx.doi.org/10.1063/1.3262502 (5 pages)

Online Publication Date: 20 November 2009

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The FERMI@Elettra free electron laser (FEL) user facility is currently under construction at the Sincrotrone Trieste laboratory in Trieste (Italy). It will cover the wavelength range from 100 to about 5 nm in the fundamental and 3 or 1 nm using the third harmonic. We report the layout of the photon beam diagnostics section, the radiation transport system to the experimental area, and the photon beam distribution system. Due to the peculiar characteristics of the emitted FEL radiation (high peak power, short pulse length, and statistical variation of the emitted intensity and distribution), the realization of the diagnostics system is particularly challenging. The end users are interested in parameters such as the radiation pulse intensity and spectral distribution, as well as in the possibility to attenuate the intensity. In order to accomplish these tasks, a photon analysis, delivery, and reduction system is now under development and construction and is presented here. This system will work on-line producing pulse-resolved information and will let users keep track of the photon beam parameters during the experiments.
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41.60.Cr Free-electron lasers
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
29.27.Fh Beam characteristics
41.85.Qg Particle beam analyzers, beam monitors, and Faraday cups
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.62.-b Laser applications

Intense SrF radical beam for molecular cooling experiments

Ming-Feng Tu, Jia-Jung Ho, Chih-Chiang Hsieh, and Ying-Cheng Chen

Rev. Sci. Instrum. 80, 113111 (2009); http://dx.doi.org/10.1063/1.3262631 (5 pages) | Cited 1 time

Online Publication Date: 30 November 2009

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We have developed a continuous SrF radical beam for the loading of helium buffer gas cooling. The SrF molecules are efficiently generated by high-temperature chemical reaction of the solid precursor SrF2 with boron in a graphite oven. The beam properties are characterized with laser-induced fluorescence spectroscopic method. We obtain a molecular flux of up to 2.1×1015 sr−1 s−1 at the detection region for all rotational states. The dependence of the flux on oven temperature suggests that even higher flux is possible if a higher temperature in the oven is achieved.
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33.80.-b Photon interactions with molecules
33.50.Dq Fluorescence and phosphorescence spectra
33.20.Sn Rotational analysis
37.10.-x Atom, molecule, and ion cooling methods
37.20.+j Atomic and molecular beam sources and techniques
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Repetitive production of positron emitters using deuterons accelerated by multiterawatt laser pulses

Masatoshi Fujimoto (藤本正俊), Koji Matsukado (松門宏治), Hironori Takahashi (高橋宏典), Yoichi Kawada (河田陽一), Shinji Ohsuka (大須賀慎二), and Shin-Ichiro Aoshima (青島紳一郎)

Rev. Sci. Instrum. 80, 113301 (2009); http://dx.doi.org/10.1063/1.3256113 (5 pages) | Cited 1 time

Online Publication Date: 9 November 2009

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Positron emitters 11C, 13N, and 15O, which can be used in positron emission tomography, were produced using deuterons accelerated by irradiation of laser pulses ∼ 70 TW in peak power and ∼ 30 fs in duration with a repetition of 10 Hz during a period of as long as 200 s. Every laser pulse irradiates the fresh surface of a long strip of a solid-state thin film. Deuterons contained in the film are accelerated in the relativistic plasma induced by the pulse. The deuterons are repetitively incident on solid plates, which are placed near the film, to produce positron emitters by nuclear reactions. The radioactivities of the activated plates are measured after the termination of laser irradiation. In activation of graphite, boron-nitride, and melamine plates, the products had total activities of 64, 46, and 153 Bq, respectively. Contamination in the setup was negligible even after several thousands of laser shots. Our apparatus is expected to greatly contribute to the construction of a compact PET diagnostic system in the future.
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07.77.Ka Charged-particle beam sources and detectors
41.75.Fr Electron and positron beams
87.57.uk Positron emission tomography (PET)
29.25.Bx Electron sources

Direct high-resolution ion beam-profile imaging using a position-sensitive Faraday cup array

Lauri Panitzsch, Michael Stalder, and Robert F. Wimmer-Schweingruber

Rev. Sci. Instrum. 80, 113302 (2009); http://dx.doi.org/10.1063/1.3246787 (6 pages) | Cited 3 times

Online Publication Date: 10 November 2009

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Ion sources have wide-spread use in a multitude of applications. For many, an accurate knowledge, or better, an accurate imaging, of the beam profile and intensity is an important criterion. We are developing an ion source to calibrate instruments for space-based measurements of solar wind and suprathermal particles in the energy range from below 1 keV/nuc to above 200 keV/nuc. In order to establish accurate beam profiles for calibration purposes, we have developed a new method based on an array of very small (∅ = 0.3 mm) Faraday cups. Here, we describe the experimental setup and discuss how to achieve several requirements such as a large thermal load due to the ∼ 40W of beam power.
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29.40.Gx Tracking and position-sensitive detectors
06.20.fb Standards and calibration
07.77.Ka Charged-particle beam sources and detectors
29.25.Ni Ion sources: positive and negative

A short pulse (7 μs FWHM) and high repetition rate (dc-5kHz) cantilever piezovalve for pulsed atomic and molecular beams

Daniel Irimia, Dimitar Dobrikov, Rob Kortekaas, Han Voet, Daan A. van den Ende, Wilhelm A. Groen, and Maurice H. M. Janssen

Rev. Sci. Instrum. 80, 113303 (2009); http://dx.doi.org/10.1063/1.3263912 (6 pages) | Cited 7 times

Online Publication Date: 23 November 2009

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In this paper we report on the design and operation of a novel piezovalve for the production of short pulsed atomic or molecular beams. The high speed valve operates on the principle of a cantilever piezo. The only moving part, besides the cantilever piezo itself, is a very small O-ring that forms the vacuum seal. The valve can operate continuous (dc) and in pulsed mode with the same drive electronics. Pulsed operation has been tested at repetition frequencies up to 5 kHz. The static deflection of the cantilever, as mounted in the valve body, was measured as a function of driving field strength with a confocal microscope. The deflection and high speed dynamical response of the cantilever can be easily changed and optimized for a particular nozzle diameter or repetition rate by a simple adjustment of the free cantilever length. Pulsed molecular beams with a full width at half maximum pulse width as low as 7 μs have been measured at a position 10 cm downstream of the nozzle exit. This represents a gas pulse with a length of only 10 mm making it well matched to for instance experiments using laser beams. Such a short pulse with 6 bar backing pressure behind a 150 μm nozzle releases about 1016 particles/pulse and the beam brightness was estimated to be 4×1022 particles/(s str). The short pulses of the cantilever piezovalve result in a much reduced gas load in the vacuum system. We demonstrate operation of the pulsed valve with skimmer in a single vacuum chamber pumped by a 520 l/s turbomolecular pump maintaining a pressure of 5×10−6 Torr, which is an excellent vacuum to have the strong and cold skimmed molecular beam interact with laser beams only 10 cm downstream of the nozzle to do velocity map slice imaging with a microchannel-plate imaging detector in a single chamber. The piezovalve produces cold and narrow (Δv/v = 2%–3%) velocity distributions of molecules seeded in helium or neon at modest backing pressures of only 6 bar. The low gas load of the cantilever valve makes it possible to design very compact single chamber molecular beam machines with high quality cold and intense supersonic beams. The high speed cantilever piezovalve may find broad applicability in experiments where short and strong gas pulses are needed with only modest pumping, the effective use of (expensive) samples, or the production of cold atomic and molecular beams.
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07.77.-n Atomic, molecular, and charged-particle sources and detectors
29.40.-n Radiation detectors
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
29.25.-t Particle sources and targets
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Electron density measurements of a field-reversed configuration plasma using a novel compact ultrastable second-harmonic interferometer

F. Brandi, F. Giammanco, W. S. Harris, T. Roche, E. Trask, and F. J. Wessel

Rev. Sci. Instrum. 80, 113501 (2009); http://dx.doi.org/10.1063/1.3258199 (4 pages) | Cited 3 times

Online Publication Date: 9 November 2009

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A compact high-sensitivity second-harmonic interferometer for line-integrated electron density measurements on a large plasma machine is presented. The device is based on a fiber coupled near-infrared continuous-wave Nd:YAG laser and is remotely controlled. The performances of the instrument are tested on the Irvine field-reversed configuration machine, and a sensitivity of few 1014 cm−2 in measuring line integrated electron density is demonstrated with a time resolution of a few microseconds. The interferometer is self calibrated, has an impressive stability, and it does not require any further alignment after proper installation. These features make this device a real turn-key system suitable for electron density measurement in large plasma machines.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
07.60.Ly Interferometers
52.55.Lf Field-reversed configurations, rotamaks, astrons, ion rings, magnetized target fusion, and cusps

Metastable helium density probe for remote plasmas

Naoto Miura and Jeffrey Hopwood

Rev. Sci. Instrum. 80, 113502 (2009); http://dx.doi.org/10.1063/1.3258198 (5 pages)

Online Publication Date: 11 November 2009

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Helium metastable atom density was spatially determined by a modified electrostatic probe in a remote plasma. The probe structure was similar to that of a guard ring probe. Opposite polarity voltages were applied to the inner probe and the guard ring to shield both electrons and ions from the vicinity of the inner probe. Therefore, the inner probe current is due to secondary electrons generated by the de-exciting helium metastable atom flux. The photoelectron current was removed by shielding and orienting the probe 90° to the direction of the plasma-generated photon flux. Helium metastable atom density on the order of 107 cm−3 was measured. Limitations on the use of this technique are revealed by comparisons with simulated metastable distributions.
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52.70.Ds Electric and magnetic measurements
52.25.Fi Transport properties

Soft x-ray virtual diagnostics for tokamak simulations

J. S. Kim, L. Zhao, I. N. Bogatu, Y. In, A. Turnbull, T. Osborne, M. Maraschek, and K. Comer

Rev. Sci. Instrum. 80, 113503 (2009); http://dx.doi.org/10.1063/1.3245344 (7 pages) | Cited 1 time

Online Publication Date: 11 November 2009

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The numerical toolset, FAR-TECH Virtual Diagnostic Utility, for generating virtual experimental data based on theoretical models and comparing it with experimental data, has been developed for soft x-ray diagnostics on DIII-D. The virtual (or synthetic) soft x-ray signals for a sample DIII-D discharge are compared with the experimental data. The plasma density and temperature radial profiles needed in the soft x-ray signal modeling are obtained from experimental data, i.e., from Thomson scattering and electron cyclotron emission. The virtual soft x-ray diagnostics for the equilibriums have a good agreement with the experimental data. The virtual diagnostics based on an ideal linear instability also agree reasonably well with the experimental data. The agreements are good enough to justify the methodology presented here for utilizing virtual diagnostics for routine comparison of experimental data. The agreements also motivate further detailed simulations with improved physical models such as the nonideal magnetohydrodynamics contributions (resistivity, viscosity, nonaxisymmetric error fields, etc.) and other nonlinear effects, which can be tested by virtual diagnostics with various stability modeling.
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52.70.-m Plasma diagnostic techniques and instrumentation
52.65.Kj Magnetohydrodynamic and fluid equation
52.55.Fa Tokamaks, spherical tokamaks
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
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Pr3+-doped fluoro-oxide lithium glass as scintillator for nuclear fusion diagnostics

Yasunobu Arikawa, Kohei Yamanoi, Tomoharu Nakazato, Elmer Surat Estacio, Toshihiko Shimizu, Nobuhiko Sarukura, Mitsuo Nakai, Takayoshi Norimatsu, Hiroshi Azechi, Takahiro Murata, Shigeru Fujino, Hideki Yoshida, Kei Kamada, Yoshiyuki Usuki, Toshihisa Suyama, et al.

Rev. Sci. Instrum. 80, 113504 (2009); http://dx.doi.org/10.1063/1.3254444 (4 pages) | Cited 5 times

Online Publication Date: 13 November 2009

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Experimental results are presented on the neutron scintillating properties of a custom-designed Pr3+(praseodymium)-doped lithium (Li) glass. Luminescence was observed at 278 nm wavelength, originating from the 5d-4f transition. Time-resolved measurements yielded about 20 ns decay times for ultraviolet and x-ray excitation while much faster decay times of about 6 ns were observed for alpha particle and neutron excitation. Actual time-of-flight data in laser fusion experiments at the GEKKO XII facility of the Institute of Laser Engineering, Osaka University reveal that it can clearly discriminate fusion neutrons from the much stronger x-rays signals. This material can promise improved accuracy in future scattered neutron diagnostics.
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29.40.Mc Scintillation detectors
78.60.-b Other luminescence and radiative recombination

Design, construction, and calibration of a three-axis, high-frequency magnetic probe (B-dot probe) as a diagnostic for exploding plasmas

E. T. Everson, P. Pribyl, C. G. Constantin, A. Zylstra, D. Schaeffer, N. L. Kugland, and C. Niemann

Rev. Sci. Instrum. 80, 113505 (2009); http://dx.doi.org/10.1063/1.3246785 (8 pages) | Cited 9 times

Online Publication Date: 18 November 2009

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A three-axis, 2.5 mm overall diameter differential magnetic probe (also known as B-dot probe) is discussed in detail from its design and construction to its calibration and use as diagnostic of fast transient effects in exploding plasmas. A design and construction method is presented as a means to reduce stray pickup, eliminate electrostatic pickup, reduce physical size, and increase magnetic signals while maintaining a high bandwidth. The probe’s frequency response is measured in detail from 10 kHz to 50 MHz using the presented calibration method and compared to theory. The effect of the probe’s self-induction as a first order correction in frequency, O(ω), on experimental signals and magnetic field calculations is discussed. The probe’s viability as a diagnostic is demonstrated by measuring the magnetic field compression and diamagnetism of a sub-Alfvénic ( ∼ 500 km/s,MA ∼ 0.36) flow created from the explosion of a high-density energetic laser plasma through a cooler, low-density, magnetized ambient plasma.
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52.70.-m Plasma diagnostic techniques and instrumentation

Modified proton radiography arrangement for the detection of ultrafast field fronts

K. Quinn, P. A. Wilson, B. Ramakrishna, L. Romagnani, G. Sarri, C. A. Cecchetti, L. Lancia, J. Fuchs, A. Pipahl, T. Toncian, O. Willi, R. J. Clarke, D. Neely, M. Notley, P. Gallegos, et al.

Rev. Sci. Instrum. 80, 113506 (2009); http://dx.doi.org/10.1063/1.3262630 (5 pages)

Online Publication Date: 25 November 2009

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The experimental arrangement for the investigation of high-field laser-induced processes using a broadband proton probe beam has been modified to enable the detection of the ultrafast motion of field fronts. It is typical in such experiments for the target to be oriented perpendicularly with respect to the principal axis of the probe beam. It is demonstrated here, however, that the temporal imaging properties of the diagnostic arrangement are altered drastically by placing the axis (or plane) of the target at an oblique angle to the transverse plane of the probe beam. In particular, the detection of the motion of a laser-driven field front along a wire at a velocity of (0.95±0.05)c is described.
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07.68.+m Photography, photographic instruments; xerography
07.77.Ka Charged-particle beam sources and detectors
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Improvement of windowed type environmental-cell transmission electron microscope for in situ observation of gas-solid interactions

Tadahiro Kawasaki, Kouta Ueda, Mikio Ichihashi, and Takayoshi Tanji

Rev. Sci. Instrum. 80, 113701 (2009); http://dx.doi.org/10.1063/1.3250862 (5 pages) | Cited 4 times

Online Publication Date: 2 November 2009

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We have developed an improved, windowed type environmental-cell (E-cell) transmission electron microscope (TEM) for in situ observation of gas-solid interactions, such as catalytic reactions at atmospheric pressure. Our E-cell TEM includes a compact E-cell specimen holder with mechanical stability, resulting in smoother introduction of the desired gases compared with previous E-cell TEMs. In addition, the gas control unit was simplified by omitting the pressure control function of the TEM pre-evacuation chamber. This simplification was due to the successful development of remarkably tough thin carbon films as the window material. These films, with a thickness of <10 nm, were found to withstand pressure differences >2 atm. Appropriate arrangement of the specimen position inside the E-cell provided quantitatively analyzable TEM images, with no disturbances caused by the windowed films. As an application, we used this E-cell TEM to observe the dynamic shape change in a catalytic gold nanoparticle supported on TiO2 during the oxidation of CO gas.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.65.Mq Oxidation
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
68.55.aj Insulators

Development of a surface conductivity measurement system for ultrahigh vacuum transmission electron microscope

H. Minoda, K. Hatano, and H. Yazawa

Rev. Sci. Instrum. 80, 113702 (2009); http://dx.doi.org/10.1063/1.3251272 (4 pages)

Online Publication Date: 2 November 2009

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The surface conductivity measurement system using a micro-four-point probe (M4PP) had been developed for the ultrahigh vacuum transmission electron microscope (UHV-TEM). Since the current distribution in the sample crystals during the current voltage measurement by the M4PP is localized within the depth of several micrometers from the surface, the system is sensitive to the surface conductivity, which is related with the surface superstructure. It was installed in the main chamber of the TEM and the surface conductivity can be measured in situ. The surface structures were observed by reflection electron microscopy and diffraction (REM-RHEED). REM-RHEED enables us to observe the surface superstructures and their structure defects such as surface atomic steps and domain boundaries of the surface superstructure. Thus the effects of the defects on the surface conductivity can be investigated. In the present paper we present the surface conductivity measurement system and its application to the Si(111)-math×math-Ag surface prepared on the Si(111) vicinal surfaces. The result clearly showed that the surface conductivity was affected by step configuration.
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06.30.Ka Basic electromagnetic quantities
73.25.+i Surface conductivity and carrier phenomena
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
68.37.Lp Transmission electron microscopy (TEM)
68.35.B- Structure of clean surfaces (and surface reconstruction)

Single-shot measurement of terahertz temporal waveform using pulse-front tilting by a direct vision dispersion prism

Yoichi Kawada, Takashi Yasuda, Atsushi Nakanishi, Hironori Takahashi, and Shin-ichiro Aoshima

Rev. Sci. Instrum. 80, 113703 (2009); http://dx.doi.org/10.1063/1.3257617 (4 pages) | Cited 1 time

Online Publication Date: 3 November 2009

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We demonstrated a single-shot measurement of terahertz temporal waveform using pulse-front tilting by a direct vision dispersion prism (DVDP). An advantage of this technique is the simplicity with which an electro-optic terahertz imaging optical system can be changed into a single-shot measurement system by inserting a DVDP in the probe beam path. In this technique, control of the angle of pulse-front tilting is very important. We precisely designed DVDP and measured the angle of the pulse-front tilting by interference measurement. We obtained a terahertz temporal waveform with a single shot with a time window of 3.2 ps.
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07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
42.79.Bh Lenses, prisms and mirrors

A diffraction-limited scanning system providing broad spectral range for laser scanning microscopy

Jiun-Yann Yu (游鈞彥), Chien-Sheng Liao (廖建盛), Zong-Yan Zhuo (卓宗衍), Chen-Han Huang (黃貞翰), Hsiang-Chen Chui (崔祥辰), and Shi-Wei Chu (朱士維)

Rev. Sci. Instrum. 80, 113704 (2009); http://dx.doi.org/10.1063/1.3254021 (5 pages) | Cited 4 times

Online Publication Date: 10 November 2009

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Diversified research interests in scanning laser microscopy nowadays require broadband capability of the optical system. Although an all-mirror-based optical design with a suitable metallic coating is appropriate for broad-spectrum applications from ultraviolet to terahertz, most researchers prefer lens-based scanning systems despite the drawbacks of a limited spectral range, ghost reflection, and chromatic aberration. One of the main concerns is that the geometrical aberration induced by off-axis incidence on spherical mirrors significantly deteriorates image resolution. Here, we demonstrate a novel geometrical design of a spherical-mirror-based scanning system in which off-axis aberrations, both astigmatism and coma, are compensated to reach diffraction-limited performance. We have numerically simulated and experimentally verified that this scanning system meets the Marechàl condition and provides high Strehl ratio within a 3°×3° scanning area. Moreover, we demonstrate second-harmonic-generation imaging from starch with our new design. A greatly improved resolution compared to the conventional mirror-based system is confirmed. This scanning system will be ideal for high-resolution linear/nonlinear laser scanning microscopy, ophthalmoscopic applications, and precision fabrications.
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07.79.-v Scanning probe microscopes and components
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Bh Lenses, prisms and mirrors
42.15.Fr Aberrations
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