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Mar 2009

Volume 80, Issue 3, Articles (03xxxx)

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The estimation of charge footprint size of ultraviolet photon counting imaging detector with induction readout

Xinghua Zhang, Baosheng Zhao, Feifei Zhao, Yong’an Liu, Zhenhua Miao, Xiangping Zhu, and Qiurong Yan

Rev. Sci. Instrum. 80, 033101 (2009); http://dx.doi.org/10.1063/1.3090891 (5 pages) | Cited 4 times

Online Publication Date: 5 March 2009

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The structure and work principle of an ultraviolet photon counting imaging detector based on wedge and strip anode with induction readout mode are introduced. Two methods of estimating the charge footprint size are presented. One way is theoretical calculation and simulation. The physical course of electrons is simulated from the microchannel plate output side to the readout anode. The calculated results show that the final charge footprint size is sensitive to the thickness of ceramic and not sensitive to the charge footprint size on the Ge layer. The other way is experimental image estimation. The final charge footprint size can be estimated according to the position where the light line of resolution board image begins to bend. Both methods show that the charge footprint size is sensitive to the ceramic substrate. The two methods are simple and effective for estimation of charge footprint size of photon counting imaging detector with induction readout.
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42.79.Pw Imaging detectors and sensors
85.60.Gz Photodetectors (including infrared and CCD detectors)
42.50.Ar Photon statistics and coherence theory
42.30.Va Image forming and processing
42.79.Ls Scanners, image intensifiers, and image converters

Portable UV-visible spectrometer for measuring absorbance and dichroism of Langmuir monolayers at air-water interfaces.

Andrey Tronin, Joseph Strzalka, Venkata Krishnan, Ivan Kuzmenko, H. Christopher Fry, Michael Therien, and J. Kent Blasie

Rev. Sci. Instrum. 80, 033102 (2009); http://dx.doi.org/10.1063/1.3089807 (7 pages) | Cited 4 times

Online Publication Date: 10 March 2009

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An UV-visible spectrometer for measuring absorbance and dichroism of Langmuir monolayers under in situ conditions is described. The spectrometer utilizes a stand-alone multipass sensor, which is placed in a Langmuir trough and coupled with light source and spectrometer head via fiber optics. Implementation of the multipass scheme in the absorbance sensor makes it possible to obtain reliable quantitative spectroscopic data of the Langmuir monolayers with absorbance as low as 1 mOD. Such high sensitivity makes the developed sensor very useful for UV-visible spectral studies of a wide variety of chromophores. The new technique was applied to several model systems: fatty acid monolayers containing amphiphilic dyes DiI or BODIPY and also a monolayer of a synthetic amphiphilic porphyrin-binding peptide BBC16. Implementation of UV-visible absorbance spectroscopy measurements in situ together with x-ray scattering technique was used to confirm the bound state of the chromophore, and determine the exact position of the latter in the peptide matrix. Fiber optics design of the spectrometer provides portability and compatibility with other experimental techniques making it possible to study samples with a geometry unsuitable for conventional spectroscopic measurements and located in experimental environments with spatial limitations, such as synchrotron x-ray scattering stations.
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07.60.Rd Visible and ultraviolet spectrometers
07.60.Vg Fiber-optic instruments
42.81.Pa Sensors, gyros
42.15.Eq Optical system design
82.80.Dx Analytical methods involving electronic spectroscopy

Preparation and characterization of planar deuterium cryotargets

Haile Lei, Jun Li, Yongjian Tang, and Yuanqiong Liu

Rev. Sci. Instrum. 80, 033103 (2009); http://dx.doi.org/10.1063/1.3082018 (4 pages)

Online Publication Date: 10 March 2009

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Using a planar-cryotarget system with the cooling power provided by a Gifford–McMahon cryocooler, the deuterium vapor is condensed to form liquid in a cylinder target cell. The liquefaction processes of deuterium are examined by the Mach–Zehnder interference and infrared spectra. The infrared-absorption spectra of deuterium show a strong absorption peak around 3040 nm at 19 K. The thickness distribution of the condensed deuterium in the target cell is determined from Mach–Zehnder interference images by developing a new mathematical treatment method in combination with the digital-image processing technique.
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07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
78.30.-j Infrared and Raman spectra
42.30.-d Imaging and optical processing

Asymmetric Fabry–Pérot fiber-optic pressure sensor for liquid-level measurement

Tao Lű, Zhengjia Li, Danqing Xia, Kaihua He, and Guangyong Zhang

Rev. Sci. Instrum. 80, 033104 (2009); http://dx.doi.org/10.1063/1.3093808 (4 pages) | Cited 3 times

Online Publication Date: 11 March 2009

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It is demonstrated that an asymmetric Fabry–Pérot fiber-optic pressure sensor is capable to precisely measure liquid levels. They are directly proportional to pressures that can modulate cavity length of Fabry–Pérot cavity. As a result, the sensor can operate over a linear region of an interference fringe that enables liquid-levels interrogation by measuring the reflected intensity. Experimental results show the resolving power of 0.4 mm, sensitivity of 2.4 mV/mm, and precision of 1 mm over range of 2.3 m (water) can be achieved. The sensor can measure liquid levels accurately, continuously, and automatically in flammable and explosive circumstances.
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42.81.Pa Sensors, gyros
07.60.Vg Fiber-optic instruments
47.70.Pq Flames; combustion
47.80.Fg Pressure and temperature measurements
07.60.Ly Interferometers
07.60.Hv Refractometers and reflectometers

In-line extreme ultraviolet polarizer with hybrid configuration

Minghong Yang, Xinling Tong, Yan Sun, Desheng Jiang, Ciming Zhou, and Dongsheng Zhang

Rev. Sci. Instrum. 80, 033105 (2009); http://dx.doi.org/10.1063/1.3095679 (4 pages)

Online Publication Date: 11 March 2009

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A novel hybrid Au-multilayer-Au in-line extreme ultraviolet (EUV) optical polarizer is presented in this paper. Different from all-Mo/Si multilayer EUV polarizer, this polarizer is based on the concept that Au surfaces work as reflecting elements for in-line optics routine, while polarization effect is realized by polarizing multilayer. Simulation shows that the proposed polarizer with 80°-70°-80° angle configuration has about 30% of transmission and 12 eV of bandwidth half maximum, which enables more throughput and broader bandwidth than the all-multilayer one.
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42.79.Ci Filters, zone plates, and polarizers
42.79.Wc Optical coatings

Illumination-induced errors associated with suns-VOC measurements of silicon solar cells

Thomas Roth, Jochen Hohl-Ebinger, Daniela Grote, Evelyn Schmich, Wilhelm Warta, Stefan W. Glunz, and Ronald A. Sinton

Rev. Sci. Instrum. 80, 033106 (2009); http://dx.doi.org/10.1063/1.3095441 (7 pages) | Cited 1 time

Online Publication Date: 12 March 2009

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ISC-VOC curves measured by the suns-VOC method are widely used for solar cell characterization due to its being unaffected by series resistance effects. A common setup for this measurement system uses a xenon photoflash for illumination purposes, resulting in a fast acquisition of the suns-VOC measurement data during the decaying edge of one flash. However, the use of a xenon photoflash accompanies also several disadvantages. Measurement errors are expected from the imperfect illumination homogeneity on the measurement stage. Also the discrepancy of the flash spectrum compared to the standard AM 1.5G spectrum leads to spectral mismatch between the sample and monitor cells when their spectral response differs. In addition, the divergence of the flash light leads to different illumination densities on the sample and the monitor cell if the height of these two cells differs. In this article these photoflash-caused measurement errors are investigated in detail, analyzing the resulting deviation in illumination density. The error due to an inhomogeneous illumination is negligible under most circumstances, while the error due to a spectral mismatch has to be considered but can be reduced drastically if an additional short-pass filter is used. The measurement error due to different cell highs should be taken into account but can be accounted for using an analytical correction.
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84.60.Jt Photoelectric conversion
72.80.Cw Elemental semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance

Switching of 800 nm femtosecond laser pulses using a compact PMN-PT modulator

Peter Adany, E. Shane Price, Carey K. Johnson, Run Zhang, and Rongqing Hui

Rev. Sci. Instrum. 80, 033107 (2009); http://dx.doi.org/10.1063/1.3093811 (5 pages) | Cited 2 times

Online Publication Date: 13 March 2009

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A voltage-controlled birefringent cell based on ceramic PMN-PT material is used to enable fast intensity modulation of femtosecond laser pulses in the 800 nm wavelength window. The birefringent cell based on a PMN-PT compound has comparatively high electro-optic response, allowing for a short interaction length of 3 mm and thus very small size, low attenuation of 0.16 dB, and negligible broadening for 100 fs optical pulses. As an application example, agile wavelength tuning of optical pulses is demonstrated using the soliton self-frequency shift in a photonic crystal fiber. By dynamically controlling the optical power into the fiber, this system switches the wavelength of 100 fs pulses from 900 nm to beyond 1120 nm with less than 5 μs time. In addition, a feedback system stabilizes the wavelength drift against external conditions resulting in high wavelength stability.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.55.Tv Photonic crystal lasers and coherent effects

Development of a microfocus x-ray tube with multiple excitation sources

Shuji Maeo, Markus Krämer, and Kazuo Taniguchi

Rev. Sci. Instrum. 80, 033108 (2009); http://dx.doi.org/10.1063/1.3095551 (5 pages) | Cited 1 time

Online Publication Date: 16 March 2009

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A microfocus x-ray tube with multiple targets and an electron gun with a focal spot size of 10 μm in diameter has been developed. The electron gun contains a LaB6 cathode and an Einzel lens. The x-ray tube can be operated at 50 W (50 kV, 1 mA) and has three targets, namely, Cr, W, and Rh on the anode that can be selected completely by moving the anode position. A focal spot size of 10 μm in diameter can be achieved at 0.5 mA current. As demonstration of the usability of a multiexcitation x-ray tube, the fluorescence x-rays have been measured using a powder specimen mixed of TiO2, Co, and Zr of the same quantity. The differences of excitation efficiency have clearly appeared according to the change in excitation source. From the results discussed here, it can be expected that the presented x-ray tube will be a powerful tool in microx-ray fluorescence spectrometers and various x-ray instruments.
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07.85.-m X- and γ-ray instruments
84.47.+w Vacuum tubes

Instrument response standard in time-resolved fluorescence

Rafal Luchowski, Zygmunt Gryczynski, Pabak Sarkar, Julian Borejdo, Mariusz Szabelski, Peter Kapusta, and Ignacy Gryczynski

Rev. Sci. Instrum. 80, 033109 (2009); http://dx.doi.org/10.1063/1.3095677 (6 pages) | Cited 5 times

Online Publication Date: 17 March 2009

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The fluorescence of LDS 798 dye in aqueous solution has a very short lifetime of 24ps, independent of excitation wavelength. The time response of common photon counting detectors depends on the wavelength of the registered photon. In lifetime measurements, the instrument response function (IRF) is usually approximated by the temporal profile of the scattered excitation light. Because λExc is typically much shorter than λEm, a systematic error may be present in these measurements. We demonstrate that the fluorescence decay of LDS 798 is a better approximation of IRF, in particular, for avalanche photodiodes used in the near infrared spectral region.
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78.55.Kz Solid organic materials
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
85.60.Dw Photodiodes; phototransistors; photoresistors
78.47.jd Time resolved luminescence
78.47.D- Time resolved spectroscopy (>1 psec)

A velocity map imaging detector with an integrated gas injection system

O. Ghafur, W. Siu, P. Johnsson, M. F. Kling, M. Drescher, and M. J. J. Vrakking

Rev. Sci. Instrum. 80, 033110 (2009); http://dx.doi.org/10.1063/1.3085799 (6 pages) | Cited 12 times

Online Publication Date: 18 March 2009

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We present the design of a velocity map imaging spectrometer where the target gas is injected from a capillary that is integrated in the repeller plate of the ion optics assembly that drives electrons/ions formed by ionization or dissociation to a two-dimensional detector. The geometry of this design allows the use of gas densities in the interaction region that are two to three orders of magnitude higher than the densities that are used in standard velocity map imaging spectrometers, making the detector suitable for working with weak light sources such as newly developed attosecond pulse sources, or (quasi-)cw sources such as synchrotrons. In a test where monoenergetic photoelectrons were generated by six-photon ionization of Xe (utilizing the second harmonic of a neodymium doped Nd:YAG), the kinetic energy resolution of the spectrometer was found to be ΔE/E = 1.8%. This number was found to be in good agreement with Monte Carlo simulations.
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41.85.-p Beam optics
29.25.Ni Ion sources: positive and negative

Laser-induced atomic fragment fluorescence spectroscopy: A facile technique for molecular spectroscopy of spin-forbidden states

Qun Zhang, Yang Chen, and Mark Keil

Rev. Sci. Instrum. 80, 033111 (2009); http://dx.doi.org/10.1063/1.3103645 (5 pages) | Cited 1 time

Online Publication Date: 25 March 2009

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Spectra of spin-forbidden and spin-allowed transitions in the mixed b 3Πu ∼ A 1Σu+ state of Na2 are measured separately by two-photon excitation using a single tunable dye laser. The two-photon excitation produces Na∗(3p) by photodissociation, which is easily and sensitively detected by atomic fluorescence. At low laser power, only the A 1Σu+ state is excited, completely free of triplet excitation. At high laser power, photodissociation via the intermediate b 3Πu triplet state becomes much more likely, effectively “switching” the observations from singlet spectroscopy to triplet spectroscopy with only minor apparatus changes. This technique of perturbation-assisted laser-induced atomic fragment fluorescence may therefore be especially useful as a general vehicle for investigating perturbation-related physics pertinent to the spin-forbidden states, as well as for studying allowed and forbidden states of other molecules.
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33.50.Dq Fluorescence and phosphorescence spectra
33.80.Gj Diffuse spectra; predissociation, photodissociation

Tandem demodulation lock-in amplifier based on digital signal processor for dual-modulated spectroscopy

Jianhuan Qin, Zhiming Huang, Yujian Ge, Yun Hou, and Junhao Chu

Rev. Sci. Instrum. 80, 033112 (2009); http://dx.doi.org/10.1063/1.3098948 (7 pages)

Online Publication Date: 25 March 2009

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Dual-modulated spectroscopy is one of the most powerful methods in the measurement of modulation spectroscopy. Here we develop a tandem lock-in amplifier (LIA) based on digital signal processor to implement a novel algorithm of tandem demodulation. The theoretical analysis of demodulation algorithm is presented, and the implementation of this tandem LIA is described in detail. Compared to the traditional demodulating way with two LIAs in cascade, this tandem LIA eliminates the extra quantization error of redundant analog-to-digital and digital-to-analog conversions and removes the limitation to the time constant in the commercial LIA, hence lowers the requirement of frequency ratio in dual-modulated spectroscopy. The applications are given as examples in the photoreflectance (PR) measurements of GaAs (100) thin film and GaSb bulk material, respectively, at the different optical energy regions. The experimental results indicate that this tandem is well capable of PR spectra measurement with good PR lineshapes and reasonable signal noise ratio. A brief comparison of GaAs PR results between tandem LIA and two LIAs is made to prove the efficiency and advantages of the tandem LIA.
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07.60.Rd Visible and ultraviolet spectrometers
07.05.Hd Data acquisition: hardware and software

Adaptive spatially resolving detector for the extreme ultraviolet with absolute measuring capability

Markus Benk and Klaus Bergmann

Rev. Sci. Instrum. 80, 033113 (2009); http://dx.doi.org/10.1063/1.3097883 (6 pages)

Online Publication Date: 26 March 2009

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A spatially resolving detector for the extreme ultraviolet (XUV) and soft x-ray spectral region is presented. Principle of operation is conversion of XUV radiation to visible light by a scintillator crystal. Luminescence is detected using charge coupled device camera and imaging optics. Single layer and multilayer coatings are applied to match the system to different spectral regions of interest. Field of view and spatial resolution can be adapted to the application. Calibration of the system enables to absolutely measure in-band radiation flux on the scintillator. The setup is designed for the characterization and optimization of XUV sources and XUV optical systems. Measurements, carried out to characterize the focus in a soft x-ray microscope, are presented as an application example.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)
29.40.Mc Scintillation detectors
42.79.Wc Optical coatings
42.72.Bj Visible and ultraviolet sources
07.85.Tt X-ray microscopes
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Radiochromic film imaging spectroscopy of laser-accelerated proton beams

F. Nürnberg, M. Schollmeier, E. Brambrink, A. Blažević, D. C. Carroll, K. Flippo, D. C. Gautier, M. Geißel, K. Harres, B. M. Hegelich, O. Lundh, K. Markey, P. McKenna, D. Neely, J. Schreiber, et al.

Rev. Sci. Instrum. 80, 033301 (2009); http://dx.doi.org/10.1063/1.3086424 (13 pages) | Cited 22 times

Online Publication Date: 10 March 2009

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This article reports on an experimental method to fully reconstruct laser-accelerated proton beam parameters called radiochromic film imaging spectroscopy (RIS). RIS allows for the characterization of proton beams concerning real and virtual source size, envelope- and microdivergence, normalized transverse emittance, phase space, and proton spectrum. This technique requires particular targets and a high resolution proton detector. Therefore thin gold foils with a microgrooved rear side were manufactured and characterized. Calibrated GafChromic radiochromic film (RCF) types MD-55, HS, and HD-810 in stack configuration were used as spatial and energy resolved film detectors. The principle of the RCF imaging spectroscopy was demonstrated at four different laser systems. This can be a method to characterize a laser system with respect to its proton-acceleration capability. In addition, an algorithm to calculate the spatial and energy resolved proton distribution has been developed and tested to get a better idea of laser-accelerated proton beams and their energy deposition with respect to further applications.
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29.20.Ej Linear accelerators

Single-turn extraction from a K110 AVF cyclotron by flat-top acceleration

Satoshi Kurashima, Nobumasa Miyawaki, Susumu Okumura, Ikuo Ishibori, Takayuki Nara, Takashi Agematsu, Ken-ichi Yoshida, Watalu Yokota, Yoshiteru Nakamura, Kazuo Arakawa, and Mitsuhiro Fukuda

Rev. Sci. Instrum. 80, 033302 (2009); http://dx.doi.org/10.1063/1.3093810 (9 pages) | Cited 2 times

Online Publication Date: 13 March 2009

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Single-turn extraction from the Japan Atomic Energy Agency AVF cyclotron with a K number of 110 using a flat-top (FT) acceleration system has been achieved to reduce the energy spread of an ion beam for microbeam formation with energy up to hundreds of MeV and to increase extraction efficiency from the cyclotron. In order to generate a FT waveform voltage using the fifth-harmonic frequency on a dee electrode, a FT resonator was designed using MAFIA code to achieve downsizing and low power consumption. The FT resonator, coupled to the main resonator through a coupling capacitor, covered the full range of the fifth harmonic frequency from 55 to 110 MHz. Various ion beams, accelerated using different acceleration harmonic modes of h = 1 and 2, such as 220 MeV 12C5+ (h = 2), 260 MeV 20Ne7+ (h = 2), and 45 MeV H+ (h = 1), were developed by FT acceleration. A clear turn separation of the beam bunches was successfully observed at the extraction region of the large-scale AVF cyclotron with number of revolutions greater than 200. As a result, high extraction efficiency (over 95%) from the cyclotron was achieved. Single-turn extraction was confirmed by counting the number of beam bunches out of the cyclotron for an injected beam pulsed by a beam chopping system in the injection line. The energy spread of the 260 MeV 20Ne7+ beam was measured using an analyzing magnet, and we verified a reduction in the energy spread from ΔE/E = 0.1% to 0.05% by single-turn extraction after FT acceleration.
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29.20.dg Cyclotrons
29.27.Ac Beam injection and extraction
41.75.Ak Positive-ion beams
29.27.Eg Beam handling; beam transport
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Fast optical spectrometer for the charge exchange diagnostic on RFX-mod

E. Gazza and M. Valisa

Rev. Sci. Instrum. 80, 033501 (2009); http://dx.doi.org/10.1063/1.3089812 (5 pages) | Cited 1 time

Online Publication Date: 5 March 2009

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A new fast visible spectrometer built for the charge exchange diagnostic system of the RFX-mod Reversed Field pinch experiment is described. The optical mounting is of the Littrow type. The spectral resolution is defined by a 3000 grooves/mm, 180×143 mm2 wide reflection grating, and a focal length of 400 mm. The collimating optics is based on a commercial high quality f/2.8 telephoto lens, so that the input fibers can be vertically stacked without space in between. The detector is a two-dimensional charge coupled device back-illuminated sensor to ensure high quantum efficiency. Thus the spectrometer combines high speed, high spectral resolution, and excellent imaging quality.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
07.60.Rd Visible and ultraviolet spectrometers
52.25.Fi Transport properties
52.58.Lq Z-pinches, plasma focus, and other pinch devices

Improved double planar probe data analysis technique

Young-chul Ghim(Kim) and Noah Hershkowitz

Rev. Sci. Instrum. 80, 033502 (2009); http://dx.doi.org/10.1063/1.3089811 (4 pages) | Cited 2 times

Online Publication Date: 6 March 2009

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Plasma electron number density and ion number density in a dc multidipole weakly collisional Ar plasma are measured with a single planar Langmuir probe and a double planar probe, respectively. A factor of two discrepancy between the two density measurements is resolved by applying Sheridan’s empirical formula [ T. E. Sheridan, Phys. Plasmas 7, 3084 (2000) ] for sheath expansion to the double probe data.
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52.70.Ds Electric and magnetic measurements
52.25.-b Plasma properties
52.40.Kh Plasma sheaths

An experimental setup to study the expansion dynamics of laser blow-off plasma plume in variable transverse magnetic field

Ajai Kumar, Vishnu Chaudhari, Kiran Patel, Sony George, S. Sunil, R. K. Singh, and Ranjeet Singh

Rev. Sci. Instrum. 80, 033503 (2009); http://dx.doi.org/10.1063/1.3095545 (6 pages) | Cited 4 times

Online Publication Date: 18 March 2009

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In the present work we report generation of uniform and variable pulsed magnetic field in synchronization with pulsed plasma for the study of the expansion dynamics of laser blow-off (LBO) plasma plume. The experimental procedure for optimizing various parameters of the setup, e.g., the production of pulsed field and its synchronization with pulsed plasma and diagnostics system, is also reported. Until now the effect of magnetic field was studied using fixed field. The present setup, however, provides variable and uniform field in synchronization with the setup. A low cost time sequencing control module has been developed for the above purpose. Although the main emphasis is on the technical aspect of the setup, salient features of the effect of transverse magnetic field on the evolution features of the neutral and ionic species are also reported briefly. It is observed that LBO generated plume have a stronger correlation with the magnetic field in comparison to the conventional laser produced plasma experiments as reported earlier.
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52.38.Fz Laser-induced magnetic fields in plasmas
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.70.Ds Electric and magnetic measurements
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Fast imaging system on Tore Supra

A. Géraud, S. Salasca, J. M. Verger, T. Alarcon, G. Agarici, S. Bremond, J. P. Chenevois, M. Geynet, J. B. Migozzi, and C. Reux

Rev. Sci. Instrum. 80, 033504 (2009); http://dx.doi.org/10.1063/1.3098944 (4 pages) | Cited 1 time

Online Publication Date: 26 March 2009

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A new endoscope aiming at transferring the image of a poloidal section of the Tore Supra plasma to a fast camera able to record frames at a speed up to 4800 frames per second at full resolution, or much faster for a limited number of pixel, has been installed on Tore Supra. First movies showing the light emission associated to fast phenomena such as plasma start up, disruptions or gas and pellet injections have been produced.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.55.Fa Tokamaks, spherical tokamaks

Measurements of spatial line emission profiles in the main scrape-off layer of the DIII-D tokamak

M. Groth, R. M. Ellis, N. H. Brooks, M. E. Fenstermacher, C. J. Lasnier, W. H. Meyer, and J. M. Moeller

Rev. Sci. Instrum. 80, 033505 (2009); http://dx.doi.org/10.1063/1.3103575 (9 pages) | Cited 1 time

Online Publication Date: 27 March 2009

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A video camera system is described as that measures the spatial distribution of visible line emission emitted from the main scrape-off layer (SOL) of plasmas in the DIII-D tokamak. A wide-angle lens installed on an equatorial port and an in-vessel mirror, which intercepts part of the lens’ view, provide simultaneous tangential views of the SOL on the low-field and high-field sides of the plasma’s equatorial plane. Tomographic reconstruction techniques are used to calculate the two-dimensional (2D) poloidal profiles from the raw data, and one-dimensional (1D) poloidal profiles simulating chordal views of other optical diagnostics from the 2D profiles. The 2D profiles can be compared with SOL plasma simulations; the 1D profiles with measurements from spectroscopic diagnostics. Sample results are presented, which elucidate carbon transport in plasmas with toroidally uniform injection of methane and argon transport in disruption mitigation experiments with massive gas jet injection.
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52.55.Fa Tokamaks, spherical tokamaks
52.65.-y Plasma simulation
52.70.-m Plasma diagnostic techniques and instrumentation
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Etching gold tips suitable for tip-enhanced near-field optical microscopy

Lior Eligal, Ferhat Culfaz, Vincent McCaughan, Nicholas I. Cade, and David Richards

Rev. Sci. Instrum. 80, 033701 (2009); http://dx.doi.org/10.1063/1.3090174 (3 pages) | Cited 7 times

Online Publication Date: 5 March 2009

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We describe a simple method of fabricating gold tips for tip-enhanced near-field optical microscopy using a single step direct current electrochemical etch. Smooth gold tips with a radius of curvature ∼ 40 nm and with an aspect ratio suitable for shear force measurement have been produced in a few minutes. A detailed analysis of the etching process has enabled production of reproducible high quality tips. Near field images of single quantum dots using tips etched with this technique are shown.
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07.79.Fc Near-field scanning optical microscopes
42.86.+b Optical workshop techniques
81.65.Cf Surface cleaning, etching, patterning
82.45.-h Electrochemistry and electrophoresis
42.70.-a Optical materials

Evaluation of the irising effect of a slow-gating intensified charge-coupled device on laser-induced incandescence measurements of soot

Christopher R. Shaddix and Timothy C. Williams

Rev. Sci. Instrum. 80, 033702 (2009); http://dx.doi.org/10.1063/1.3089224 (6 pages) | Cited 1 time

Online Publication Date: 16 March 2009

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Intensified charge-coupled devices (ICCDs) are used extensively in many scientific and engineering environments to image weak or temporally short optical events. To optimize the quantum efficiency of light collection, many of these devices are chosen to have characteristic intensifier gate times that are relatively slow, on the order of tens of nanoseconds. For many measurements associated with nanosecond laser sources, such as scattering-based diagnostics and most laser-induced fluorescence applications, the signals rise and decay sufficiently fast during and after the laser pulse that the intensifier gate may be set to close after the cessation of the signal and still effectively reject interferences associated with longer time scales. However, the relatively long time scale and complex temporal response of laser-induced incandescence (LII) of nanometer-sized particles (such as soot) offer a difficult challenge to the use of slow-gating ICCDs for quantitative measurements. In this paper, ultraviolet Rayleigh scattering imaging is used to quantify the irising effect of a slow-gating scientific ICCD camera, and an analysis is conducted of LII image data collected with this camera as a function of intensifier gate width. The results demonstrate that relatively prompt LII detection, generally desirable to minimize the influences of particle size and local gas pressure and temperature on measurements of the soot volume fraction, is strongly influenced by the irising effect of slow-gating ICCDs.
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42.79.Pw Imaging detectors and sensors
85.60.Gz Photodetectors (including infrared and CCD detectors)
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
42.65.Es Stimulated Brillouin and Rayleigh scattering
82.33.Vx Reactions in flames, combustion, and explosions

Thermal imaging with tapping mode using a bimetal oscillator formed at the end of a cantilever

Sang-Jin Kim, Takahito Ono, and Masayoshi Esashi

Rev. Sci. Instrum. 80, 033703 (2009); http://dx.doi.org/10.1063/1.3095680 (6 pages) | Cited 3 times

Online Publication Date: 16 March 2009

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Thermal detection based on the thermal shift of the resonant frequency of a bimetal resonator (Al/Si) is presented and demonstrated. The bimetal oscillator with a tip is fabricated at the end of a commercial silicon cantilever. The bimetal oscillator and the silicon cantilever have a resonance frequency of 441 and 91 kHz, respectively, and the measured temperature coefficients of the resonant frequency are −127×10−6/K and −115×10−6/K, respectively. It is demonstrated that self-oscillated resonant frequency of the bimetal oscillator changes in response to heat from a microheat source. Simultaneous measurements of topography and temperature profile with the temperature resolution of 0.12 K on a glass substrate heated using a thin chromium film microheater are successfully demonstrated. These results show potential abilities of the mechanical resonant thermal sensor.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
07.20.Dt Thermometers
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Hollow-pyramid based scanning near-field optical microscope coupled to femtosecond pulses: A tool for nonlinear optics at the nanoscale

Michele Celebrano, Paolo Biagioni, Margherita Zavelani-Rossi, Dario Polli, Massimiliano Labardi, Maria Allegrini, Marco Finazzi, Lamberto Duò, and Giulio Cerullo

Rev. Sci. Instrum. 80, 033704 (2009); http://dx.doi.org/10.1063/1.3095556 (8 pages) | Cited 5 times

Online Publication Date: 20 March 2009

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We describe an aperture scanning near-field optical microscope (SNOM) using cantilevered hollow pyramid probes coupled to femtosecond laser pulses. Such probes, with respect to tapered optical fibers, present higher throughput and laser power damage threshold, as well as greater mechanical robustness. In addition, they preserve pulse duration and polarization in the near field. The instrument can operate in two configurations: illumination mode, in which the SNOM probe is used to excite the nonlinear response in the near field, and collection mode, where it collects the nonlinear emission following far-field excitation. We present application examples highlighting the capability of the system to observe the nonlinear optical response of nanostructured metal surfaces (gold projection patterns and gold nanorods) with sub-100-nm spatial resolution.
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07.79.Fc Near-field scanning optical microscopes
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

An instrument for combining x-ray multiple diffraction and x-ray topographic imaging for examining crystal microcrystallography and perfection

X. Lai, C. Y. Ma, K. J. Roberts, L. P. Cardoso, A. O. dos Santos, D. Bogg, and M. C. Miller

Rev. Sci. Instrum. 80, 033705 (2009); http://dx.doi.org/10.1063/1.3103571 (6 pages)

Online Publication Date: 27 March 2009

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Diffraction imaging using x-ray topography (XRT) and x-ray multiple diffraction (XRMD) provide valuable tools for examining the growth defects in crystals and the distributions from ideal lattice symmetry (microcrystallography). The topographic x-ray multiple diffraction microprobe (TMDM) combines the complementary aspects of both techniques enabling XRT and XRMD studies within the same instrument providing a useful resource for the structural characterization of materials that are not very stable in vacuum and electron beam environments. The design of the TMDM instrument is described together with data taken on GaAs (001) and potassium dihydrogen phosphate (001).
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07.85.Jy Diffractometers
61.05.C- X-ray diffraction and scattering
61.50.-f Structure of bulk crystals
61.72.Dd Experimental determination of defects by diffraction and scattering
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