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Apr 2010

Volume 81, Issue 4, Articles (04xxxx)

Issue Cover Spotlight Figure

Rev. Sci. Instrum. 81, 041301 (2010); http://dx.doi.org/10.1063/1.3400212 (8 pages)

Yejun Feng, R. Jaramillo, Jiyang Wang, Yang Ren, and T. F. Rosenbaum

Modern high-pressure experiments in condensed matter physics involve instrumentations varying in length scale over eight orders of magnitude. Pictured are the synchrotron at the Advanced Photon Source (diameter 350 m), x-ray diffractometer (0.5 m), cryogenic high-pressure cell (5 cm), diamond anvil (3 mm), gasket (800 µm), sample (70 µm), and crystalline ruby ball (10 µm).

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Invited Article: High-pressure techniques for condensed matter physics at low temperature

Yejun Feng, R. Jaramillo, Jiyang Wang, Yang Ren, and T. F. Rosenbaum

Rev. Sci. Instrum. 81, 041301 (2010); http://dx.doi.org/10.1063/1.3400212 (8 pages) | Cited 4 times

Online Publication Date: 20 April 2010

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Condensed matter experiments at high pressure accentuate the need for accurate pressure scales over a broad range of temperatures, as well as placing a premium on a homogeneous pressure environment. However, challenges remain in diamond anvil cell technology, including both the quality of various pressure transmitting media and the accuracy of secondary pressure scales at low temperature. We directly calibrate the ruby fluorescence R1 line shift with pressure at T = 4.5 K using high-resolution x-ray powder diffraction measurements of the silver lattice constant and its known equation of state up to P = 16 GPa. Our results reveal a ruby pressure scale at low temperatures that differs by 6% from the best available ruby scale at room T. We also use ruby fluorescence to characterize the pressure inhomogeneity and anisotropy in two representative and commonly used pressure media, helium and methanol:ethanol 4:1, under the same preparation conditions for pressures up to 20 GPa at T = 5 K. Contrary to the accepted wisdom, both media show equal levels of pressure inhomogeneity measured over the same area, with a consistent ΔP/P per unit area of ±1.8 %/(104 μm2) from 0 to 20 GPa. The helium medium shows an essentially constant deviatoric stress of 0.021±0.011 GPa up to 16 GPa, while the methanol:ethanol mixture shows a similar level of anisotropy up to 10 GPa, above which the anisotropy increases. The quality of both pressure media is further examined under the more stringent requirements of single crystal x-ray diffraction at cryogenic temperature. For such experiments we conclude that the ratio of sample-to-pressure chamber volume is a critical parameter in maintaining sample quality at high pressure, and may affect the choice of pressure medium.
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62.50.-p High-pressure effects in solids and liquids
81.40.Vw Pressure treatment
78.60.-b Other luminescence and radiative recombination
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back to top Optics; Atoms and Molecules; Spectroscopy; Photon Detectors

Absolute optical extinction measurements of single nano-objects by spatial modulation spectroscopy using a white lamp

Pierre Billaud, Salem Marhaba, Nadia Grillet, Emmanuel Cottancin, Christophe Bonnet, Jean Lermé, Jean-Louis Vialle, Michel Broyer, and Michel Pellarin

Rev. Sci. Instrum. 81, 043101 (2010); http://dx.doi.org/10.1063/1.3340875 (12 pages) | Cited 7 times

Online Publication Date: 7 April 2010

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This article describes a high sensitivity spectrophotometer designed to detect the overall extinction of light by a single nanoparticle (NP) in the 10−4–10−5 relative range, using a transmission measurement configuration. We focus here on the simple and low cost scheme where a white lamp is used as a light source, permitting easy and broadband extinction measurements (300–900 nm). Using a microscope, in a confocal geometry, an increased sensitivity is reached thanks to a modulation of the NP position under the light spot combined with lock-in detection. Moreover, it is shown that this technique gives access to the absolute extinction cross-sections of the single NP provided that the incident electromagnetic field distribution experienced by the NP is accurately characterized. In this respect, an experimental procedure to characterize the light spot profile in the focal plane, using a reference NP as a probe, is also laid out. The validity of this approach is discussed and confirmed by comparing experimental intensity distributions to theoretical calculations taking into account the vector character of the tightly focused beam. The calibration procedure permitting to obtain the absolute extinction cross-section of the probed NP is then fully described. Finally, the force of the present technique is illustrated through selected examples concerning spherical and slightly elongated gold and silver NPs. Absolute extinction measurements are found to be in good consistency with the NP size and shape independently obtained from transmission electron microscopy, showing that spatial modulation spectroscopy is a powerful tool to get an optical fingerprint of the NP.
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42.62.Fi Laser spectroscopy
07.60.-j Optical instruments and equipment
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)

A new optical front-end compensation technique for suppression of spurious signal in photoreflectance spectroscopy using an antiphase signal

Q. Li, H. H. Tan, and C. Jagadish

Rev. Sci. Instrum. 81, 043102 (2010); http://dx.doi.org/10.1063/1.3368598 (4 pages) | Cited 2 times

Online Publication Date: 14 April 2010

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A new optical front-end compensation technique to suppress the unwanted, spurious signal in photoreflectance (PR) spectroscopy is developed. In this approach an optical compensation signal, which is amplitude-matched to and in antiphase to the spurious signal, is introduced and directed to the photodetector. The combination of the compensation signal and the spurious signal results in a dc output from the photodetector which is thereafter suppressed by the lock-in amplifier, leaving only the true PR signal to be recovered and amplified. A high spurious signal suppression efficiency is demonstrated and the advantages of the technique are discussed.
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85.60.Gz Photodetectors (including infrared and CCD detectors)

Molecular beam-thermal hydrogen desorption from palladium

R. F. M. Lobo, F. M. V. Berardo, and J. H. F. Ribeiro

Rev. Sci. Instrum. 81, 043103 (2010); http://dx.doi.org/10.1063/1.3385686 (5 pages)

Online Publication Date: 14 April 2010

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Among the most efficient techniques for hydrogen desorption monitoring, thermal desorption mass spectrometry is a very sensitive one, but in certain cases can give rise to uptake misleading results due to residual hydrogen partial pressure background variations. In this work one develops a novel thermal desorption variant based on the effusive molecular beam technique that represents a significant improvement in the accurate determination of hydrogen mass absorbed on a solid sample. The enhancement in the signal-to-noise ratio for trace hydrogen is on the order of 20%, and no previous calibration with a chemical standard is required. The kinetic information obtained from the hydrogen desorption mass spectra (at a constant heating rate of 1 °C/min) accounts for the consistency of the technique.
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68.43.Nr Desorption kinetics
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Broadband femtosecond circular dichroism spectrometer with white-light polarization control

Anton Trifonov, Ivan Buchvarov, Andreas Lohr, Frank Würthner, and Torsten Fiebig

Rev. Sci. Instrum. 81, 043104 (2010); http://dx.doi.org/10.1063/1.3340892 (6 pages) | Cited 4 times

Online Publication Date: 15 April 2010

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A broadband, femtosecond transient circular dichroism (TRCD) spectrometer has been developed and tested in the wavelength range from 350 to 700 nm. The spectrometer uses a femtosecond probe white light with well-defined circular polarization. The latter is modulated by the polarization of a narrowband seed pulse. We have implemented a dual-beam probe geometry with phase-locked detection technique to increase the signal-to-noise ratio and to reduce optical artifacts. The spectrometer allows the acquisition of TRCD spectra with subpicosecond time resolution and typical noise levels of 10−4 absorbance units. The performance of this instrument has been demonstrated on bis(merocyanine) nanorod aggregates in tetrahydrofurane/methylcyclohexane solution. The case study confirmed that this spectrometer is effective for the investigation of chiral properties in various molecular and nanostructural systems that have transient spectra in the UV-visible spectral range.
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07.60.Rd Visible and ultraviolet spectrometers
42.25.Ja Polarization

Ultrasensitive near-infrared cavity ring-down spectrometer for precise line profile measurement

Bo Gao, Wei Jiang, An-Wen Liu, Yan Lu, Cun-Feng Cheng, Guo-Sheng Cheng, and Shui-Ming Hu

Rev. Sci. Instrum. 81, 043105 (2010); http://dx.doi.org/10.1063/1.3385675 (5 pages) | Cited 6 times

Online Publication Date: 15 April 2010

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A cavity ring-down (CRD) spectrometer is built with a continuous-wave Ti:sapphire ring laser. Using a pair of R ∼ 0.999 95 high-reflective mirrors, the noise-equivalent minimum detectable absorption loss reaches 7×10−11/cm over the spectral range of 780–830 nm. A thermal-stabilized Fabry-Perot interferometer is applied to calibrate the CRD spectrum with an accuracy of 1×10−4 cm−1. The quantitative measurement is carried out for the line profile measurements of some overtone absorption lines of C2H2 near 787 nm. Doppler determined line shape has been observed with milli-Torr acetylene gas in the ring-down cavity. The instrumental line width is estimated from the line profile fitting to be <1×10−4 cm−1. It demonstrates that the CRD spectrometer with extremely high sensitivity is also very suitable for quantitative measurements including precise line profile studies in the near-infrared.
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33.70.Jg Line and band widths, shapes, and shifts
33.20.Ea Infrared spectra
07.60.Ly Interferometers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
82.80.Gk Analytical methods involving vibrational spectroscopy
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques

Development of a scanning angle total internal reflection Raman spectrometer

Kristopher J. McKee and Emily A. Smith

Rev. Sci. Instrum. 81, 043106 (2010); http://dx.doi.org/10.1063/1.3378682 (6 pages) | Cited 2 times

Online Publication Date: 21 April 2010

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A scanning angle total internal reflection (SATIR) Raman spectrometer has been developed for measuring interfacial phenomena with chemical specificity and high axial resolution perpendicular to the interface. The instrument platform is an inverted optical microscope with added automated variable angle optics to control the angle of an incident laser on a prism/sample interface. These optics include two motorized translation stages, the first containing a focusing lens and the second a variable angle galvanometer mirror. The movement of all instrument components is coordinated to ensure that the same sample location and area are probed at each angle. At angles greater than the critical angle, an evanescent wave capable of producing Raman scatter is generated in the sample. The Raman scatter is collected by a microscope objective and directed to a dispersive spectrometer and charge-coupled device detector. In addition to the collected Raman scatter, light reflected from the prism/sample interface is collected to provide calibration parameters that enable modeling the distance over which the Raman scatter is collected for depth profiling measurements. The developed instrument has an incident angle range of 25.5°–75.5°, with a 0.05° angle resolution. Raman scatter can be collected from a ZnSe/organic interface over a range of roughly 35–180 nm. Far from the critical angle, the achieved axial resolution perpendicular to the focal plane is approximately 34 nm. This is roughly a 30-fold improvement relative to confocal Raman microscopy.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
07.79.-v Scanning probe microscopes and components

The extreme ultraviolet split and femtosecond delay unit at the plane grating monochromator beamline PG2 at FLASH

F. Sorgenfrei, W. F. Schlotter, T. Beeck, M. Nagasono, S. Gieschen, H. Meyer, A. Föhlisch, M. Beye, and W. Wurth

Rev. Sci. Instrum. 81, 043107 (2010); http://dx.doi.org/10.1063/1.3374166 (7 pages) | Cited 2 times

Online Publication Date: 22 April 2010

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An extreme ultraviolet split and femtosecond delay unit based on grazing incidence Mach–Zehnder geometry has been designed and implemented on the plane grating monochromator beamline PG2 at FLASH, the Free Electron Laser at DESY. This device splits the FLASH radiation into two beams, which can independently be steered, filtered and temporally delayed between −5.1 and +5.1 ps with uncertainty in the temporal accuracy of 210 as. To demonstrate the performance of this device, we have performed longitudinal coherence studies of FLASH radiation as well as measured the pulse length by nonlinear two-photon double-ionization in helium.
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41.60.Cr Free-electron lasers
42.79.Dj Gratings
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

A rotating-compensator based reflectance difference spectrometer for fast spectroscopic measurements

C. G. Hu, L. D. Sun, J. M. Flores-Camacho, M. Hohage, C. Y. Liu, X. T. Hu, and P. Zeppenfeld

Rev. Sci. Instrum. 81, 043108 (2010); http://dx.doi.org/10.1063/1.3379289 (11 pages)

Online Publication Date: 23 April 2010

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We present a new type of reflectance difference (RD) spectrometer for fast spectroscopic measurements based on a rotating-compensator (RC) design. The instrument uses a 1024 element Si photodiode linear array for simultaneous multiwavelength detection. High quality RD spectra covering a spectral range from 1.5 to 4.5 eV can be acquired within a few seconds. A detailed description of the working principle, the instrumentation, and the algorithms used for data collection and reduction is presented, followed by a discussion of errors introduced by lamp instability and optical imperfections of the compensator. Finally, to demonstrate the performance of the new RCRD spectrometer, we illustrate its application for the in situ, real-time monitoring of the initial stages of organic thin film growth of para-sexiphenyl (p-6P) on the Cu(110)-(2×1)O surface.
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07.60.Fs Polarimeters and ellipsometers
78.40.Me Organic compounds and polymers
68.55.am Polymers and organics

Ion imaging in a high-gradient magnetic guide

V. D. Vaidya, M. Traxler, C. Hempel, R. R. Mhaskar, and G. Raithel

Rev. Sci. Instrum. 81, 043109 (2010); http://dx.doi.org/10.1063/1.3386583 (7 pages)

Online Publication Date: 23 April 2010

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We study a photoionization method to detect and image a narrow beam of cold atoms traveling along a high-gradient two-wire magnetic guide that is continuously on. Ions are accelerated in a compact acceleration region, directed through a drift region several centimeters in length, and detected using a position-sensitive ion detector. The potentials of several electrodes can be varied to adjust the imaging properties. Using ion trajectory simulations as well as experiments, we study the passage of the ions through the detection system, the magnification of the detection system, and the time-of-flight characteristics.
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37.20.+j Atomic and molecular beam sources and techniques
37.10.De Atom cooling methods
32.80.Fb Photoionization of atoms and ions
37.10.Gh Atom traps and guides

Fourier transform approach in modulation technique of experimental measurements

M. V. Khazimullin and Yu. A. Lebedev

Rev. Sci. Instrum. 81, 043110 (2010); http://dx.doi.org/10.1063/1.3327844 (8 pages) | Cited 1 time

Online Publication Date: 27 April 2010

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An application of Fourier transform approach in modulation technique of experimental studies is considered. This method has obvious advantages compared with traditional lock-in amplifiers technique—simple experimental setup, a quickly available information on all the required harmonics, high speed of data processing using fast Fourier transform algorithm. A computationally simple, fast and accurate Fourier coefficients interpolation (FCI) method has been implemented to obtain a useful information from harmonics of a multimode signal. Our analysis shows that in this case FCI method has a systematical error (bias) of a signal parameters estimation, which became essential for the short data sets. Hence, a new differential Fourier coefficients interpolation (DFCI) method has been suggested, which is less sensitive to a presence of several modes in a signal. The analysis has been confirmed by simulations and measurements of a quartz wedge birefringence by means of the photoelastic modulator. The obtained bias, noise level, and measuring speed are comparable and even better than in lock-in amplifier technique. Moreover, presented DFCI method is expected to be promised candidate for using in actively developing imaging systems based on the modulation technique requiring fast digital signal processing of large data sets.
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42.30.Kq Fourier optics
42.70.Ce Glasses, quartz
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
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A near infrared instrument to monitor relative hemoglobin concentrations of human bone tissue in vitro and in vivo

Syed Mahfuzul Aziz, Faram Khambatta, Tharshan Vaithianathan, John C. Thomas, Jillian M. Clark, and Ruth Marshall

Rev. Sci. Instrum. 81, 043111 (2010); http://dx.doi.org/10.1063/1.3398450 (7 pages) | Cited 1 time

Online Publication Date: 30 April 2010

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A continuous wave near infrared instrument has been developed to monitor in vivo changes in the hemoglobin concentration of the trabecular compartment of human bone. The transmitter uses only two laser diodes of wavelengths 685 and 830 nm, and the receiver uses a single silicon photodiode operating in the photovoltaic mode. The functioning of the instrument and the depth of penetration of the near infrared signals was determined in vitro using tissue-equivalent phantoms. The instrument achieves a depth of penetration of approximately 2 cm for an optode separation of 4 cm and, therefore, has the capacity to interrogate the trabecular compartment of human bone. The functioning of the instrument was tested in vivo to evaluate the relative oxy-hemoglobin (HbO2) and deoxy-hemoglobin (Hb) concentrations of the proximal tibial bone of apparently healthy, normal weight, adult subjects in response to a 3 min on, 5 min off, vascular occlusion protocol. The traces of the relative Hb and HbO2 concentrations obtained were reproducible in controlled conditions. The instrument is relatively simple and flexible, and offers an inexpensive platform for further studies to obtain normative data for healthy cohorts, and to evaluate disease-specific performance characteristics for cohorts with vasculopathies of bone.
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87.50.wp Therapeutic applications
87.14.E- Proteins
72.40.+w Photoconduction and photovoltaic effects
85.60.Dw Photodiodes; phototransistors; photoresistors
42.62.Be Biological and medical applications
back to top Particle Sources, Optics and Acceleration; Particle Detectors

An electrostatic deceleration lens for highly charged ions

J. Rajput, A. Roy, D. Kanjilal, R. Ahuja, and C. P. Safvan

Rev. Sci. Instrum. 81, 043301 (2010); http://dx.doi.org/10.1063/1.3379242 (5 pages)

Online Publication Date: 19 April 2010

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The design and implementation of a purely electrostatic deceleration lens used to obtain beams of highly charged ions at very low energies is presented. The design of the lens is such that it can be used with parallel as well as diverging incoming beams and delivers a well focused low energy beam at the target. In addition, tuning of the final energy of the beam over a wide range (1 eV/q to several hundred eV/q, where q is the beam charge state) is possible without any change in hardware configuration. The deceleration lens was tested with Ar8+, extracted from an electron cyclotron resonance ion source, having an initial energy of 30 keV/q and final energies as low as 70 eV/q have been achieved.
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42.79.Bh Lenses, prisms and mirrors
41.85.-p Beam optics

Measurements and effects of backstreaming ions produced at bremsstrahlung converter target in Dragon-I linear induction accelerator

Haijun Yu, Jun Zhu, Nan Chen, Yutong Xie, Xiaoguo Jiang, and Cheng Jian

Rev. Sci. Instrum. 81, 043302 (2010); http://dx.doi.org/10.1063/1.3379132 (4 pages)

Online Publication Date: 22 April 2010

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Positive ions released from x-ray converter target impacted by electron beam of millimeter spot size can be trapped and accelerated in the incident beam’s potential well. As the ions move upstream, the beam will be pinched first and then defocused at the target. Four Faraday cups are used to collect backstreaming ions produced at the bremsstrahlung converter target in Dragon-I linear induction accelerator (LIA). Experimental and theoretical results show that the backstreaming positive ions density and velocity are about 1021/m3 and 2–3 mm/μs, respectively. The theoretical and experimental results of electron beam envelope with ions and without ions are also presented. The discussions show that the backstreaming positive ions will not affect the electron beam focusing and envelope radius in Dragon-I LIA.
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29.20.Ej Linear accelerators

An all solid-state, rolled strip pulse forming line with low impedance and compact structure

Shi Yang, Hui-Huang Zhong, Bao-Liang Qian, and Han-Wu Yang

Rev. Sci. Instrum. 81, 043303 (2010); http://dx.doi.org/10.1063/1.3398438 (5 pages) | Cited 1 time

Online Publication Date: 23 April 2010

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An all solid-state and compact pulsed strip pulse forming line (PFL) is investigated both theoretically and experimentally. The electromagnetic field distribution and the pulse formation in the strip PFL are analyzed numerically. Based on the theoretical analysis and numerical results, a rolled strip PFL with output voltage of 20 kV, pulse duration of 230 ns, and characteristic impedance of 0.5 Ω was designed and manufactured. We use the Mylar film and copper as the dielectric and conductor of the strip PFL. The dimension of the strip line is 23 000×400×1.6 mm3 in the case in which the strip line is unrolled, and the strip line is finally rolled into a cylinder of diameter of 311 mm for the experiment. The dimension and weight are about ten times smaller than those of traditional dielectric (oil or pure water) PFL with the same electrical parameters. Two experiments were performed using the strip line. One was for a transmission line experiment, and the other was for a PFL experiment. In the experiment of transmission line, the transmission time of the voltage signal was 115 ns, and the signal had almost no distortion, which verified the design. In the PFL experiment, results gave a 17.8 kV, 270 ns (full width at half maximum) voltage pulse which was a quasisquare wave on the water load of 0.5 Ω. The current going through the load is about 35.6 kA.
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84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables
84.40.Az Waveguides, transmission lines, striplines
41.20.-q Applied classical electromagnetism

High Voltage-Cylinder Sector Analyzer 300/15: A cylindrical sector analyzer for electron kinetic energies up to 15 keV

J. Rubio-Zuazo, M. Escher, M. Merkel, and G. R. Castro

Rev. Sci. Instrum. 81, 043304 (2010); http://dx.doi.org/10.1063/1.3398441 (8 pages) | Cited 3 times

Online Publication Date: 26 April 2010

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We have developed an energy analyzer, High Voltage-Cylinder Sector Analyzer 300/15, for electron kinetic energies up to 15 keV. It is especially suited for hard x-ray photoelectron spectroscopy, but also for ultraviolet and soft x-ray photoelectron spectroscopy (ultraviolet photoemission spectroscopy, x-ray photoemission spectroscopy), Auger electron spectroscopy, and reflection high energy electron spectroscopy. The analyzer is based on a cylinder sector with 90° deflection, 300 mm slit-to-slit distance, and a four-element pre-retarding lens system with 50 mm sample-to-lens distance. The result is a very compact design of the analyzer that is easily integrated into a multipurpose experiment with different techniques. A low noise/low drift electronics is capable of continuous energy scans from 0 to 15 keV using nonlinear lens curves. The first analyzer is allocated at the Spanish CRG SpLine beamline at the ESRF at an end station where simultaneous surface x-ray diffraction is possible. The analyzer is operated routinely since 2006 up to 15 keV electron kinetic energy, expanding the achievable electron kinetic energy range compared to other commercial analyzers. In this work we present a detailed description of the developed electron analyzer. The analyzer capabilities, in terms of energy resolution and transmission, are shown by using an electron gun, an ultraviolet-discharge lamp, and hard x-ray synchrotron radiation as excitation sources.
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61.05.js X-ray photoelectron diffraction
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

The DCU laser ion source

P. Yeates, J. T. Costello, and E. T. Kennedy

Rev. Sci. Instrum. 81, 043305 (2010); http://dx.doi.org/10.1063/1.3374123 (14 pages) | Cited 7 times

Online Publication Date: 27 April 2010

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Laser ion sources are used to generate and deliver highly charged ions of various masses and energies. We present details on the design and basic parameters of the DCU laser ion source (LIS). The theoretical aspects of a high voltage (HV) linear LIS are presented and the main issues surrounding laser-plasma formation, ion extraction and modeling of beam transport in relation to the operation of a LIS are detailed. A range of laser power densities (I ∼ 108–1011 W cm−2) and fluences (F = 0.1–3.9 kJ cm−2) from a Q-switched ruby laser (full-width half-maximum pulse duration ∼ 35 ns, λ = 694 nm) were used to generate a copper plasma. In “basic operating mode,” laser generated plasma ions are electrostatically accelerated using a dc HV bias (5–18 kV). A traditional einzel electrostatic lens system is utilized to transport and collimate the extracted ion beam for detection via a Faraday cup. Peak currents of up to I ∼ 600 μA for Cu+ to Cu3+ ions were recorded. The maximum collected charge reached 94 pC (Cu2+). Hydrodynamic simulations and ion probe diagnostics were used to study the plasma plume within the extraction gap. The system measured performance and electrodynamic simulations indicated that the use of a short field-free (L = 48 mm) region results in rapid expansion of the injected ion beam in the drift tube. This severely limits the efficiency of the electrostatic lens system and consequently the sources performance. Simulations of ion beam dynamics in a “continuous einzel array” were performed and experimentally verified to counter the strong space-charge force present in the ion beam which results from plasma extraction close to the target surface. Ion beam acceleration and injection thus occur at “high pressure.” In “enhanced operating mode,” peak currents of 3.26 mA (Cu2+) were recorded. The collected currents of more highly charged ions (Cu4+–Cu6+) increased considerably in this mode of operation.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.50.Dg Plasma sources
52.40.Mj Particle beam interactions in plasmas
52.70.-m Plasma diagnostic techniques and instrumentation
back to top Nuclear Physics, Fusion and Plasmas

Fast integrator based data acquisition system for the SST-1 Thomson scattering system

Kiran Patel and Ajai Kumar

Rev. Sci. Instrum. 81, 043501 (2010); http://dx.doi.org/10.1063/1.3374110 (5 pages)

Online Publication Date: 12 April 2010

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An operational transconductance amplifier based fast charge-integrating module (FCIM) is designed and developed for an easy acquisition of fast Thomson scattered and background signal. FCIM based data acquisition technique can be used for the measurement of charge pulses of <20 ns duration. The response of the module is tested using a standard pulsed charge-generating module. The measuring charge range of the module depends on the integrating capacitor. Comparison of the performance of FCIM to commercially available module shows that it has better dynamic range with higher sensitivity and less measurement error. The module is quite cost effective and has many new features.
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52.55.Fa Tokamaks, spherical tokamaks
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.70.Ds Electric and magnetic measurements
84.30.-r Electronic circuits
52.25.-b Plasma properties
84.30.Le Amplifiers

Measurement of type-I edge localized mode pulse propagation in scrape-off layer using optical system of motional Stark effect diagnostics in JT-60U

T. Suzuki, N. Oyama, and N. Asakura

Rev. Sci. Instrum. 81, 043502 (2010); http://dx.doi.org/10.1063/1.3378752 (5 pages) | Cited 1 time

Online Publication Date: 14 April 2010

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Propagation of plasma ejected by type-I edge localized mode (ELM) has been measured in scrape-off layer (SOL) of the JT-60U tokamak, using optical system of motional Stark effect (MSE) diagnostics as beam emission spectroscopy (BES) diagnostics through a new technique developed. This MSE/BES system measures Dα emission from heating neutral beam excited by collisions with the ejected plasma, as well as background light (e.g., bremsstrahlung). While spatio-temporal change in the beam emission gives information on propagation of the ejected plasma, the background light that is observed simultaneously in all spatial channels veils the information. In order to separate the beam emission and the background light, a two-wavelength detector is newly introduced into the MSE/BES system. The detector observes simultaneously at the same spatial point in two distinct wavelengths using two photomultiplier tubes through two interference filters. One of the filters is adjusted to the central wavelength of the beam emission for the MSE diagnostics, and the other is outside the beam emission spectrum. Eliminating the background light, temporal change in the net beam emission in the SOL has been evaluated. Comparing conditionally averaged beam emission with respect to 594 ELMs in a discharge at five spatial channels (0.02–0.3 m outside the main plasma near equatorial plane), radial velocity of the ELM pulse propagation in SOL is evaluated to be 0.8–1.8 km/s ( ∼ 1.4 km/s for least-mean-squared fitting).
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52.40.Hf Plasma-material interactions; boundary layer effects
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.70.-m Plasma diagnostic techniques and instrumentation

Space-resolved vacuum ultraviolet spectrometer system for edge impurity and temperature profile measurement in HL-2A

Zhengying Cui, Shigeru Morita, Bingzhong Fu, Yuan Huang, Ping Sun, Yadong Gao, Yuan Xu, Chunfeng Dong, Ping Lu, Quanming Wang, Xuantong Ding, Qingwei Yang, and Xuru Duan

Rev. Sci. Instrum. 81, 043503 (2010); http://dx.doi.org/10.1063/1.3378288 (8 pages)

Online Publication Date: 15 April 2010

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A 1 m normal incidence vacuum ultraviolet (VUV) spectrometer has been developed for spatial distribution measurement of edge impurity line emission in the wavelength range of 300–3200 Å on HL-2A tokamak. A vertical profile of the impurity line emission is measured with a space-resolved slit placed between an entrance slit and a grating of the spectrometer. Two concave 1200 grooves/mm gratings blazed at 800 and 1500 Å are set on a rotatable holder in the spectrometer, which gives wavelength dispersion of 0.12 mm/Å. A back-illuminated charge-coupled device is used as a detector with an image size of 6.7×26.6 mm2 (26×26 μm2/pixel). An excellent spatial resolution of 2 mm is obtained with good spectral resolution of 0.15 Å when the space-resolved slit of 50 μm in width is used. The space-resolved spectra thus provide three radial profiles of emission line intensity, ion temperature, and poloidal rotation. The electron temperature can be measured by the intensity ratio, e.g., CIII 2s2-2s3p (386 Å)/2s2-2s2p (977 Å). The sensitivity of the spectrometer is calibrated in situ by using the VUV bremsstrahlung continuum radiation emitted from the tokamak plasma. A good performance of the spectrometer system for the edge impurity and temperature profile measurements is presented with results on Ohmic and H-mode discharges.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.55.Fa Tokamaks, spherical tokamaks
52.25.Vy Impurities in plasmas
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
07.60.Rd Visible and ultraviolet spectrometers
52.80.-s Electric discharges

Pulsed current wave shaping with a transmission line by utilizing superposition of a forward and a backward voltage wave for fast capillary Z-pinch discharge

Y. Sakai, S. Takahashi, M. Watanabe, G.-H. Kim, and E. Hotta

Rev. Sci. Instrum. 81, 043504 (2010); http://dx.doi.org/10.1063/1.3397348 (4 pages)

Online Publication Date: 22 April 2010

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By using a water transmission line, current wave shaping was demonstrated for a fast capillary Z-pinch discharge recombination soft x-ray laser study. The pulsed power system consists of a water capacitor, a gap switch, a transmission line, and a capillary plasma load. A voltage wave initiated at the water capacitor propagates toward the capillary load through the transmission line. Control of the pulse delay that occurred in the transmission line provides the superposition of the forward and the backward voltage waves effectively in order to perform current wave shaping with higher current amplitude and rapid current decay.
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52.58.Lq Z-pinches, plasma focus, and other pinch devices
52.70.La X-ray and γ-ray measurements
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables
back to top Microscopy and Imaging

Development of high-speed polarizing imaging system for operation in high pulsed magnetic field

I. Katakura, M. Tokunaga, A. Matsuo, K. Kawaguchi, K. Kindo, M. Hitomi, D. Akahoshi, and H. Kuwahara

Rev. Sci. Instrum. 81, 043701 (2010); http://dx.doi.org/10.1063/1.3359954 (5 pages) | Cited 1 time

Online Publication Date: 12 April 2010

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A high-speed polarizing microscope system combined with a 37 T pulse magnet has been developed. This system was applied to successfully visualize the field-induced collapse of charge-orbital ordering in a layered manganite La1/2Sr3/2MnO4. Quantitative analyses of the obtained polarizing microscope images provided clear evidence of this transition in contrast to rather moderate changes in magnetization and magnetoresistance. The ability of this system to carry out quantitative analysis was further tested through the observation of Faraday rotation in a Tb3Ga5O12 crystal. The Verdet constant determined from the polarizing images is in reasonable agreement with that in literature. Local intensity analyses of the images indicate that we can investigate magneto-optical signals within an accuracy of 0.85% in an area of 9.6×9.6 μm2.
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07.60.Pb Conventional optical microscopes
78.20.Ls Magneto-optical effects
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

MEMS-based high speed scanning probe microscopy

E. C. M. Disseldorp, F. C. Tabak, A. J. Katan, M. B. S. Hesselberth, T. H. Oosterkamp, J. W. M. Frenken, and W. M. van Spengen

Rev. Sci. Instrum. 81, 043702 (2010); http://dx.doi.org/10.1063/1.3361215 (7 pages) | Cited 5 times

Online Publication Date: 12 April 2010

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The high speed performance of a scanning probe microscope (SPM) is improved if a microelectromechanical systems (MEMS) device is employed for the out-of-plane scanning motion. We have carried out experiments with MEMS high-speed z-scanners (189 kHz fundamental resonance frequency) in both atomic force microscope and scanning tunneling microscope modes. The experiments show that with the current MEMS z-scanner, lateral tip speeds of 5 mm/s can be achieved with full feedback on surfaces with significant roughness. The improvement in scan speed, obtained with MEMS scanners, increases the possibilities for SPM observations of dynamic processes. Even higher speed MEMS scanners with fundamental resonance frequencies in excess of a megahertz are currently under development.
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07.79.Cz Scanning tunneling microscopes
07.79.Lh Atomic force microscopes
07.10.Cm Micromechanical devices and systems

Design of a laser-assisted tomographic atom probe at Münster University

Ralf Schlesiger, Christian Oberdorfer, Roland Würz, Gerd Greiwe, Patrick Stender, Michael Artmeier, Patrick Pelka, Frank Spaleck, and Guido Schmitz

Rev. Sci. Instrum. 81, 043703 (2010); http://dx.doi.org/10.1063/1.3378674 (8 pages) | Cited 10 times

Online Publication Date: 22 April 2010

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To benefit from the latest technical improvements in atom probe analysis, a new tomographic atom probe has been built at the University of Münster, Germany. The instrument utilizes a femtosecond laser system with a high repetition rate combined with the ability of using a micrometer-sized extraction electrode and a wide angle configuration. Since field evaporation is triggered by laser pulses instead of high-voltage pulses, the instrument offers the ability to expand the range of analyzed materials to poorly conducting or insulating materials such as oxides, glasses, ceramics, and polymeric materials. The article describes the design of the instrument and presents characterizing measurements on metals, semiconductors, and oxide ceramic.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Influence of feedback parameters on ferroelectric domain imaging with piezoresponse force microscopy

Huifeng Bo, Yi Kan, Xiaomei Lu, Song Peng, Xiaofei Wang, Yunfei Liu, Wei Cai, Ruoshi Xue, and Jinsong Zhu

Rev. Sci. Instrum. 81, 043704 (2010); http://dx.doi.org/10.1063/1.3387342 (6 pages) | Cited 1 time

Online Publication Date: 22 April 2010

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The piezoresponse (PR) amplitude and phase signals for antiparallel ferroelectric domains were investigated with different feedback parameters. It is found that the drive frequency and setpoint can strongly alternate the PR image contrast, while the drive phase can be considered as a constant adding to the PR phase signal. The PR amplitude is proportional to the drive amplitude while the PR phase is drive amplitude independent. The larger piezoelectric vibration amplitude and fitting piezoelectric constants (PCs) obtained by vectorial analysis compared with the known values are originated from the sample resonance, and the local electrostatic force can lead to a nonlinear shift in the measured PCs from the theoretical expectations.
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77.80.Dj Domain structure; hysteresis
77.65.Bn Piezoelectric and electrostrictive constants
77.84.Ek Niobates and tantalates
07.79.Lh Atomic force microscopes
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