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May 2012

Volume 83, Issue 5 (partial)

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back to top Optics; Atoms and Molecules; Spectroscopy; Photon Detectors

Detection of nanosecond-scale, high power THz pulses with a field effect transistor

S. Preu, H. Lu, M. S. Sherwin, and A. C. Gossard

Rev. Sci. Instrum. 83, 053101 (2012); http://dx.doi.org/10.1063/1.4705986 (6 pages)

Online Publication Date: 1 May 2012

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We demonstrate detection and resolution of high power, 34 ns free electron laser pulses using a rectifying field effect transistor. The detector remains linear up to an input power of 11 ± 0.5 W at a pulse energy of 20 ± 1 μJ at 240 GHz. We compare its performance to a protected Schottky diode, finding a shorter intrinsic time constant. The damage threshold is estimated to be a few 100 W. The detector is, therefore, well-suited for characterizing high power THz pulses. We further demonstrate that the same detector can be used to detect low power continuous-wave THz signals with a post detection limited noise floor of 3.1 μW/math. Such ultrafast, high power detectors are important tools for high power and high energy THz facilities such as free electron lasers.
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41.60.Cr Free-electron lasers
42.60.-v Laser optical systems: design and operation

Realization of autofocusing system for laser direct writing on non-planar surfaces

Jianbo Luo, Yiyong Liang, and Guoguang Yang

Rev. Sci. Instrum. 83, 053102 (2012); http://dx.doi.org/10.1063/1.4709407 (5 pages)

Online Publication Date: 2 May 2012

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This paper presents an autofocusing system for laser direct writing on non-planar surfaces, including focus error signal detection and focusing control. The focus error signal detection is based on modified confocal techniques, which features easy implementation, independence of the tilt angles of non-planar surfaces, and excellent suppression of common-mode noise or variable system factors. We also present a macro/micro dual-drive mechanism and its synchronous operation for focusing control on non-planar surfaces. Finally, a performance evaluation of the autofocusing system is presented. The uniform line width of 2.1 μm for a pattern on a convex spherical substrate with a curvature radius of 100 mm shows the autofocusing system performs well.
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42.62.-b Laser applications

Enhancing photocurrent transient spectroscopy by electromagnetic modeling

H. Diesinger, M. Panahandeh-Fard, Z. Wang, D. Baillargeat, and C. Soci

Rev. Sci. Instrum. 83, 053103 (2012); http://dx.doi.org/10.1063/1.4710996 (6 pages)

Online Publication Date: 3 May 2012

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The shape and duration of photocurrent transients generated by a photoconductive switch depend on both the intrinsic response of the active material and the geometry of the transmission line structure. The present electromagnetic model decouples both shape forming contributions. In contrast to previously published work, it accounts for the particular operating mode of transient spectroscopy. The objective is to increase the time resolution by two approaches, by optimizing structural response and by deconvolving it from experimental data. The switch structure is represented by an effective transimpedance onto which the active material acts as current generator. As proof of concept, the response of a standard microstrip switch is modeled and deconvolved from experimental data acquired in GaAs, yielding a single exponential material response and hence supporting the validity of the approach. Beyond compensating for the response deterioration by the structure, switch architectures can be a priori optimized with respect to frequency response. As an example, it is shown that a microstrip gap that can be deposited on materials incompatible with standard lithography reduces pulse broadening by an order of magnitude if it is provided with transitions to coplanar access lines.
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41.20.Jb Electromagnetic wave propagation; radiowave propagation
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
11.55.-m S-matrix theory; analytic structure of amplitudes

An in situ set up for the detection of CO2 from catalytic CO oxidation by using planar laser-induced fluorescence

J. Zetterberg, S. Blomberg, J. Gustafson, Z. W. Sun, Z. S. Li, E. Lundgren, and M. Aldén

Rev. Sci. Instrum. 83, 053104 (2012); http://dx.doi.org/10.1063/1.4711130 (5 pages)

Online Publication Date: 4 May 2012

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We report the first experiment carried out on an in situ setup, which allows for detection of CO2 from catalytic CO oxidation close to a model catalyst under realistic reaction conditions by the means of planar laser-induced fluorescence (PLIF) in the mid-infrared spectral range. The onset of the catalytic reaction as a function of temperature was followed by PLIF in a steady state flow reactor. After taking into account the self-absorption of CO2, a good agreement between the detected CO2 fluorescence signal and the CO2 mass spectrometry signal was shown. The observed difference to previously measured onset temperatures for the catalytic ignition is discussed and the potential impact of IR-PLIF as a detection technique in catalysis is outlined.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
42.62.-b Laser applications

Response of large area avalanche photodiodes to low energy x rays

T. R. Gentile, M. Bales, U. Arp, B. Dong, and R. Farrell

Rev. Sci. Instrum. 83, 053105 (2012); http://dx.doi.org/10.1063/1.4714348 (9 pages)

Online Publication Date: 8 May 2012

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For an experiment to study neutron radiative beta-decay, we operated large area avalanche photodiodes (APDs) near liquid nitrogen temperature to detect x rays with energies between 0.2 keV and 20 keV. Whereas there are numerous reports of x ray spectrometry using APDs at energies above 1 keV, operation near liquid nitrogen temperature allowed us to reach a nominal threshold of 0.1 keV. However, due to the short penetration depth of x rays below 1 keV, the pulse height spectrum of the APD become complex. We studied the response using monochromatic x ray beams and employed phenomenological fits of the pulse height spectrum to model the measurement of a continuum spectrum from a synchrotron. In addition, the measured pulse height spectrum was modelled using a profile for the variation in efficiency of collection of photoelectrons with depth into the APD. The best results are obtained with the collection efficiency model.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.Dw Photodiodes; phototransistors; photoresistors
07.85.Nc X-ray and γ-ray spectrometers

Fourier transform infrared spectroscopy approach for measurements of photoluminescence and electroluminescence in mid-infrared

Y. G. Zhang, Y. Gu, K. Wang, X. Fang, A. Z. Li, and K. H. Liu

Rev. Sci. Instrum. 83, 053106 (2012); http://dx.doi.org/10.1063/1.4717673 (7 pages)

Online Publication Date: 11 May 2012

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An improved Fourier transform infrared spectroscopy approach adapting to photoluminescence and electroluminescence measurements in mid-infrared has been developed, in which diode-pumped solid-state excitation lasers were adopted for photoluminescence excitation. In this approach, three different Fourier transform infrared modes of rapid scan, double modulation, and step scan were software switchable without changing the hardware or connections. The advantages and limitations of each mode were analyzed in detail. Using this approach a group of III–V and II–VI samples from near-infrared extending to mid-infrared with photoluminescence intensities in a wider range have been characterized at room temperature to demonstrate the validity and overall performances of the system. The weaker electroluminescence of quantum cascade lasers in mid-infrared band was also surveyed at different resolutions. Results show that for samples with relatively strong photoluminescence or electroluminescence out off the background, rapid scan mode is the most preferable. For weaker photoluminescence or electroluminescence overlapped with background, double modulation is the most effective mode. To get a better signal noise ratio when weaker photoluminescence or electroluminescence signal has been observed in double modulation mode, switching to step scan mode should be an advisable option despite the long data acquiring time and limited resolution.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
42.70.Hj Laser materials
78.30.Fs III-V and II-VI semiconductors
78.55.Cr III-V semiconductors
78.55.Et II-VI semiconductors
78.60.Fi Electroluminescence

A versatile and reconfigurable setup for all-terahertz time-resolved pump-probe spectroscopy

A. Y. Elezzabi and P. Maraghechi

Rev. Sci. Instrum. 83, 053107 (2012); http://dx.doi.org/10.1063/1.4717732 (6 pages)

Online Publication Date: 14 May 2012

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A versatile optical setup for all-terahertz (THz) time resolved pump-probe spectroscopy was designed and tested. By utilizing a dual THz pulse generator emitter module, independent and synchronized THz radiation pump and probe pulses were produced, thus eliminating the need for THz beam splitters and the limitations associated with their implementation. The current THz setup allows for precise control of the electric fields splitting ratio between the THz radiation pump and probe pulses, as well as in-phase, out-of-phase, and polarization dependent pump-probe spectroscopy. Since the present THz pump-probe setup does not require specialized THz radiation optical components, such as phase shifters, polarization rotators, or wide bandwidth beam splitters, it can be easily implemented with minimal alterations to a conventional THz time domain spectroscopy system. The present setup is valuable for studying the time dynamics of THz coherent phenomena in solid-state, chemical, and biological systems.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
42.79.Fm Reflectors, beam splitters, and deflectors

An apparatus for immersing trapped ions into an ultracold gas of neutral atoms

Stefan Schmid, Arne Härter, Albert Frisch, Sascha Hoinka, and Johannes Hecker Denschlag

Rev. Sci. Instrum. 83, 053108 (2012); http://dx.doi.org/10.1063/1.4718356 (10 pages)

Online Publication Date: 17 May 2012

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We describe a hybrid vacuum system in which a single ion or a well-defined small number of trapped ions (in our case Ba+ or Rb+) can be immersed into a cloud of ultracold neutral atoms (in our case Rb). This apparatus allows for the study of collisions and interactions between atoms and ions in the ultracold regime. Our setup is a combination of a Bose-Einstein condensation apparatus and a linear Paul trap. The main design feature of the apparatus is to first separate the production locations for the ion and the ultracold atoms and then to bring the two species together. This scheme has advantages in terms of stability and available access to the region where the atom-ion collision experiments are carried out. The ion and the atoms are brought together using a moving one-dimensional optical lattice transport which vertically lifts the atomic sample over a distance of 30 cm from its production chamber into the center of the Paul trap in another chamber. We present techniques to detect and control the relative position between the ion and the atom cloud.
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37.10.Ty Ion trapping
42.50.Wk Mechanical effects of light on material media, microstructures and particles
37.10.Vz Mechanical effects of light on atoms, molecules, and ions
37.10.Rs Ion cooling
34.50.-s Scattering of atoms and molecules
37.10.Jk Atoms in optical lattices

Multiplex and simultaneous measurement of displacement and temperature using tapered fiber and fiber Bragg grating

Chongke Ji, Chun-Liu Zhao, Juan Kang, Xinyong Dong, and Shangzhong Jin

Rev. Sci. Instrum. 83, 053109 (2012); http://dx.doi.org/10.1063/1.4718360 (5 pages)

Online Publication Date: 17 May 2012

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A simple method to work out the multiplexing of tapered fiber based sensors is proposed and demonstrated. By cascading a tapered fiber with a fiber Bragg grating (FBG), the sensor head is provided with a wavelength identification, different FBGs provide the sensor heads with different reflective peaks and they can be distinguished in optical spectrum. By compositing several such sensor heads with a multi-channel beam splitter, a star-style topological structure sensor for multipoint sensing is achieved. At the same time, the output intensity at the peak wavelength is sensitive to one external physical parameter applied on the related FBG-cascaded tapered fiber and the central wavelength of the peak is only sensitive to temperature, so that that parameter and temperature can be measured simultaneously. A sensor for dual-point measurement of the displacement and temperature simultaneously is experimentally demonstrated by using a 2 × 2 coupler in this paper. Experiment results show that the sensor works well and the largest sensitivities reach to 0.11 dB/μm for displacement in the range of 0–400 μm, and ∼0.0097 nm/°C for temperature between 20 °C and 70 °C.
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42.81.Pa Sensors, gyros
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
42.79.Dj Gratings

Time-resolved near-edge x-ray absorption fine structure spectroscopy on photo-induced phase transitions using a tabletop soft-x-ray spectrometer

P. Grossmann, I. Rajkovic, R. Moré, J. Norpoth, S. Techert, C. Jooss, and Klaus Mann

Rev. Sci. Instrum. 83, 053110 (2012); http://dx.doi.org/10.1063/1.4718936 (4 pages)

Online Publication Date: 17 May 2012

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We present a table-top soft-x-ray spectrometer for the wavelength range λ = 1–5 nm based on a stable laser-driven x-ray source, making use of a gas-puff target. With this setup, optical light-pump/soft-x-ray probe near-edge x-ray absorption fine structure (NEXAFS) experiments with a temporal resolution of about 230 ps are feasible. Pump-probe NEXAFS measurements were carried out in the “water-window” region (2.28 nm–4.36 nm) on the manganite Pr0.7Ca0.3MnO3, investigating diminutive changes of the oxygen K edge that derive from an optically induced phase transition. The results show the practicability of the table-top soft-x-ray spectrometer on demanding investigations so far exclusively conducted at synchrotron radiation sources.
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07.60.-j Optical instruments and equipment
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
back to top Particle Sources, Optics and Acceleration; Particle Detectors

Experimental investigation on focusing characteristics of a He-Ne laser using circular Fresnel zone plate for high-precision alignment of linear accelerators

Tsuyoshi Suwada, Masanori Satoh, Souichi Telada, and Kaoru Minoshima

Rev. Sci. Instrum. 83, 053301 (2012); http://dx.doi.org/10.1063/1.4709497 (9 pages)

Online Publication Date: 3 May 2012

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We experimentally investigate the focusing characteristics of a He–Ne laser at the focal region for the high-precision alignment of long-distance linear accelerators using a circular Fresnel zone plate. The laser wave passing through the Fresnel zone plate having a focal length of 66.7 m propagates for a 268-m-long distance at atmospheric pressure. A new laser-based alignment system using Fresnel zone plates as the alignment targets is discussed. The transverse displacement of the focused spot of the laser is measured as a function of the displacement of the target by a detector installed at the focal point. Systematic studies on the focusing characteristics and alignment precision have been successfully conducted in this experiment. The experimental results are in good agreement with theoretical calculations, and the alignment precision of the target is determined to be less than ±30 μm. In this study, we perform a detailed experimental investigation on the laser propagation and focusing characteristics using the circular Fresnel zone plate at the focal region along with theoretical calculations.
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29.20.Ej Linear accelerators
42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.79.Ci Filters, zone plates, and polarizers

Demonstration of charge breeding in a compact room temperature electron beam ion trap

G. Vorobjev, A. Sokolov, A. Thorn, F. Herfurth, O. Kester, W. Quint, Th. Stöhlker, and G. Zschornack

Rev. Sci. Instrum. 83, 053302 (2012); http://dx.doi.org/10.1063/1.4719668 (5 pages)

Online Publication Date: 18 May 2012

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For the first time, a small room-temperature electron beam ion trap (EBIT), operated with permanent magnets, was successfully used for charge breeding experiments. The relatively low magnetic field of this EBIT does not contribute to the capture of the ions; single-charged ions are only caught by the space charge potential of the electron beam. An over-barrier injection method was used to fill the EBIT's electrostatic trap with externally produced, single-charged potassium ions. Charge states as high as K19+ were reached after about a 3 s breeding time. The capture and breeding efficiencies up to 0.016(4)% for K17+ have been measured.
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29.27.Bd Beam dynamics; collective effects and instabilities
41.75.Fr Electron and positron beams
back to top Nuclear Physics, Fusion and Plasmas

Central electron temperature estimations of TJ-II neutral beam injection heated plasmas based on the soft x ray multi-foil technique

D. Baião, F. Medina, M. Ochando, K. McCarthy, F. Tabarés, I. Pastor, and C. Varandas

Rev. Sci. Instrum. 83, 053501 (2012); http://dx.doi.org/10.1063/1.4714340 (5 pages)

Online Publication Date: 8 May 2012

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The core electron temperature (Te0) of neutral beam heated plasmas is determined in TJ-II stellarator by using soft x ray detectors with beryllium filters of different thickness, based on the method known as the foil absorption technique. Te0 estimations are done with the impurity code IONEQ, making use of complementary information from the TJ-II soft x ray tomography and the VUV survey diagnostics. When considering the actual electron density and temperature profile shapes, an acceptable agreement is found with Thomson scattering measurements for 8 different magnetic configurations. The impact of the use of both neutral beam injectors on the Te0 measurements is addressed. Also, the behaviour of Te0 during spontaneous profile transitions is presented.
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52.55.Jd Magnetic mirrors, gas dynamic traps
52.70.La X-ray and γ-ray measurements
52.25.Vy Impurities in plasmas
52.50.Gj Plasma heating by particle beams

Quantitative measurement of hard x-ray spectra for high intensity laser produced plasma

Z. Zhang, H. Nishimura, T. Namimoto, S. Fujioka, Y. Arikawa, M. Nishikino, T. Kawachi, A. Sagisaka, H. Hosoda, S. Orimo, K. Ogura, A. Pirozhkov, A. Yogo, Y. Okano, H. Kiriyama, et al.

Rev. Sci. Instrum. 83, 053502 (2012); http://dx.doi.org/10.1063/1.4717677 (5 pages)

Online Publication Date: 10 May 2012

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X-ray line spectra ranging from 17 to 77 keV were quantitatively measured with a Laue spectrometer, composed of a cylindrically curved crystal and a detector. Either a visible CCD detector coupled with a CsI phosphor screen or an imaging plate can be chosen, depending on the signal intensities and exposure times. The absolute sensitivity of the spectrometer system was calibrated using pre-characterized laser-produced x-ray sources and radioisotopes. The integrated reflectivity for the crystal is in good agreement with predictions by an open code for x-ray diffraction. The energy transfer efficiency from incident laser beams to hot electrons, as the energy transfer agency for specific x-ray line emissions, is derived as a consequence of this work.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.59.Px Hard X-ray sources
52.70.La X-ray and γ-ray measurements
back to top Microscopy and Imaging

Experimental and simulation study of undesirable short-period deformation in piezoelectric deformable x-ray mirrors

Hiroki Nakamori, Satoshi Matsuyama, Shota Imai, Takashi Kimura, Yasuhisa Sano, Yoshiki Kohmura, Kenji Tamasaku, Makina Yabashi, Tetsuya Ishikawa, and Kazuto Yamauchi

Rev. Sci. Instrum. 83, 053701 (2012); http://dx.doi.org/10.1063/1.4709499 (6 pages)

Online Publication Date: 3 May 2012

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To construct adaptive x-ray focusing optics whose optical parameters can be varied while performing wavefront correction, ultraprecise piezoelectric deformable mirrors have been developed. We computationally and experimentally investigated undesirable short-period deformation caused by piezoelectric actuators adhered to the substrate during mirror deformation. Based on the results of finite element method analysis, shape measurements, and the observation of x-ray reflection images, a guideline is developed for designing deformable mirrors that do not have short-period deformation errors.
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41.50.+h X-ray beams and x-ray optics
42.79.Bh Lenses, prisms and mirrors
07.07.Tw Servo and control equipment; robots

Development of a pulse programmer for magnetic resonance imaging using a personal computer and a high-speed digital input–output board

Seitaro Hashimoto, Katsumi Kose, and Tomoyuki Haishi

Rev. Sci. Instrum. 83, 053702 (2012); http://dx.doi.org/10.1063/1.4711132 (6 pages)

Online Publication Date: 7 May 2012

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We have developed a pulse programmer for magnetic resonance imaging (MRI) using a personal computer and a commercially available high-speed digital input–output board. The software for the pulse programmer was developed using C/C++ and .NET Framework 2.0 running under the Windows 7 operating system. The pulse programmer was connected to a digital MRI transceiver using a 32-bit parallel interface, and 128-bit data (16 bits × 8 words) for the pulse sequence and the digitally detected MRI signal were transferred bi-directionally every 1 μs. The performance of the pulse programmer was evaluated using a 1.0 T permanent magnet MRI system. The acquired MR images demonstrated the usefulness of the pulse programmer. Although our pulse programmer was developed for a specially designed digital MRI transceiver, our approach can be used for any MRI system if the interface for the transceiver is properly designed. Therefore, we have concluded that our approach is promising for MRI pulse programmers.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
84.30.Ng Oscillators, pulse generators, and function generators

Retrofitting an atomic force microscope with photothermal excitation for a clean cantilever response in low Q environments

Aleksander Labuda, Kei Kobayashi, Yoichi Miyahara, and Peter Grütter

Rev. Sci. Instrum. 83, 053703 (2012); http://dx.doi.org/10.1063/1.4712286 (8 pages)

Online Publication Date: 10 May 2012

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multimedia

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It is well known that the low-Q regime in dynamic atomic force microscopy is afflicted by instrumental artifacts (known as “the forest of peaks”) caused by piezoacoustic excitation of the cantilever. In this article, we unveil additional issues associated with piezoacoustic excitation that become apparent and problematic at low Q values. We present the design of a photothermal excitation system that resolves these issues, and demonstrate its performance on force spectroscopy at the interface of gold and an ionic liquid with an overdamped cantilever (Q < 0.5). Finally, challenges in the interpretation of low-Q dynamic AFM measurements are discussed.
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07.79.Lh Atomic force microscopes

Design and analysis of multi-color confocal microscopy with a wavelength scanning detector

Dukho Do, Wanhee Chun, and Dae-Gab Gweon

Rev. Sci. Instrum. 83, 053704 (2012); http://dx.doi.org/10.1063/1.4717679 (6 pages)

Online Publication Date: 10 May 2012

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Spectral (or multi-color) microscopy has the ability to detect the fluorescent light of biological specimens with a broad range of wavelengths. Currently, the acousto-optic tunable filter (AOTF) is widely used in spectral microscopy as a substitute for a multiple-dichroic mirror to divide excitation and emission signals while maintaining sufficient light efficiency. In addition, systems which utilize an AOTF have a very fast switching speed and high resolution for wavelength selection. In this paper, confocal-spectral microscopy is proposed with a particular spectrometer design with a wavelength-scanning galvano-mirror. This enables the detection of broadband (480–700 nm) fluorescence signals by a single point detector (photomultiplier tube) instead of a CCD pixel array. For this purpose, a number of optical elements were applicably designed. A prism is used to amplify the dispersion angle, and the design of the relay optics matches the signals to the diameter of the wavelength-scanning galvano-mirror. Also, a birefringent material known as calcite is used to offset the displacement error at the image plane depending on the polarization states. The proposed multi-color confocal microscopy with the unique detection body has many advantages in comparison with commercial devices. In terms of the detection method, it can be easily applied to other imaging modalities.
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42.79.Pw Imaging detectors and sensors
07.60.Pb Conventional optical microscopes
42.79.Bh Lenses, prisms and mirrors
42.79.Ci Filters, zone plates, and polarizers
42.79.Jq Acousto-optical devices

Quantitative scheme for full-field polarization rotating fluorescence microscopy using a liquid crystal variable retarder

John F. Lesoine, Ji Youn Lee, Jeffrey R. Krogmeier, Hyeonggon Kang, Matthew L. Clarke, Robert Chang, Dan L. Sackett, Ralph Nossal, and Jeeseong Hwang

Rev. Sci. Instrum. 83, 053705 (2012); http://dx.doi.org/10.1063/1.4717682 (9 pages)

Online Publication Date: 16 May 2012

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We present a quantitative scheme for full-field polarization rotating fluorescence microscopy. A quarter-wave plate, in combination with a liquid crystal variable retarder, provides a tunable method to rotate polarization states of light prior to its being coupled into a fluorescence microscope. A calibration of the polarization properties of the incident light is performed in order to correct for elliptical polarization states. This calibration allows the response of the sample to linear polarization states of light to be recovered. Three known polarization states of light can be used to determine the average fluorescent dipole orientations in the presence of a spatially varying dc offset or background polarization-invariant fluorescence signal. To demonstrate the capabilities of this device, we measured a series of full-field fluorescence polarization images from fluorescent analogs incorporated in the lipid membrane of Burkitts lymphoma CA46 cells. The fluorescent lipid-like analogs used in this study are molecules that are labeled by either a DiI (1,1′-Dioctadecyl 3,3,3′,3′-Tetramethylindocarbocyanine) fluorophore in its head group or a Bodipy (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) molecule in its acyl chain. A spatially varying contrast in the normalized amplitude was observed on the cell surface, where the orientation of the DiI molecules is tangential to the cell membrane. The internally labeled cellular structures showed zero response to changes in linear polarization, and the net linear polarization amplitude for these regions was zero. This instrument provides a low cost calibrated method that may be coupled to existing fluorescence microscopes to perform investigations of cellular processes that involve a change in molecular orientations.
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87.64.M- Optical microscopy
42.79.Ci Filters, zone plates, and polarizers
42.79.Kr Display devices, liquid-crystal devices
87.64.kv Fluorescence
back to top Condensed Matter; Materials

A furnace with rotating load frame for in situ high temperature deformation and creep experiments in a neutron diffraction beam line

H. M. Reiche, S. C. Vogel, P. Mosbrucker, E. J. Larson, and M. R. Daymond

Rev. Sci. Instrum. 83, 053901 (2012); http://dx.doi.org/10.1063/1.4708619 (7 pages)

Online Publication Date: 2 May 2012

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A resistive furnace combined with a load frame was built that allows for in situ neutron diffraction studies of high temperature deformation, in particular, creep. A maximum force of 2700 N can be applied at temperatures up to 1000 °C. A load control mode permits studies of, e.g., creep or phase transformations under applied uni-axial stress. In position control, a range of high temperature deformation experiments can be achieved. The examined specimen can be rotated up to 80° around the vertical compression axis allowing texture measurements in the neutron time-of-flight diffractometer HIPPO (High Pressure – Preferred Orientation). We present results from the successful commissioning, deforming a Zr-2.5 wt.% Nb cylinder at 975 °C. The device is now available for the user program of the HIPPO diffractometer at the LANSCE (Los Alamos Neutron Science Center) user facility.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
62.50.-p High-pressure effects in solids and liquids
64.70.K- Solid-solid transitions
62.20.Hg Creep
81.40.Lm Deformation, plasticity, and creep

Development of a simultaneous Hugoniot and temperature measurement for preheated-metal shock experiments: Melting temperatures of Ta at pressures of 100 GPa

Jun Li, Xianming Zhou, Jiabo Li, Qiang Wu, Lingcang Cai, and Chengda Dai

Rev. Sci. Instrum. 83, 053902 (2012); http://dx.doi.org/10.1063/1.4716459 (7 pages)

Online Publication Date: 14 May 2012

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Equations of state of metals are important issues in earth science and planetary science. A major limitation of them is the lack of experimental data for determining pressure-volume and temperature of shocked metal simultaneously. By measuring them in a single experiment, a major source of systematic error is eliminated in determining from which shock pressure release pressure originates. Hence, a non-contact fast optical method was developed and demonstrated to simultaneously measure a Hugoniot pressure-volume (PH-VH) point and interfacial temperature TR on the release of Hugoniot pressure (PR) for preheated metals up to 1000 K. Experimental details in our investigation are (i) a Ni–Cr resistance coil field placed around the metal specimen to generate a controllable and stable heating source, (ii) a fiber-optic probe with an optical lens coupling system and optical pyrometer with ns time resolution to carry out non-contact fast optical measurements for determining PH-VH and TR. The shock response of preheated tantalum (Ta) at 773 K was investigated in our work. Measured data for shock velocity versus particle velocity at an initial state of room temperature was in agreement with previous shock compression results, while the measured shock data between 248 and 307 GPa initially heated to 773 K were below the Hugoniot evaluation from its off-Hugoniot states. Obtained interfacial temperatures on release of Hugoniot pressures (100–170 GPa) were in agreement with shock-melting points at initial ambient condition and ab initio calculations of melting curve. It indicates a good consistency for shock melting data of Ta at different initial temperatures. Our combined diagnostics for Hugoniot and temperature provides an important approach for studying EOS and the temperature effect of shocked metals. In particular, our measured melting temperatures of Ta address the current controversy about the difference by more than a factor of 2 between the melting temperatures measured under shock and those measured in a laser-heated diamond anvil cell at ∼100 GPa.
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07.20.Dt Thermometers
07.20.Ka High-temperature instrumentation; pyrometers
42.79.Bh Lenses, prisms and mirrors
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
back to top Biology and Medicine

Humidity-controlled preparation of frozen-hydrated biological samples for cryogenic coherent x-ray diffraction microscopy

Yuki Takayama and Masayoshi Nakasako

Rev. Sci. Instrum. 83, 054301 (2012); http://dx.doi.org/10.1063/1.4718359 (6 pages)

Online Publication Date: 17 May 2012

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Coherent x-ray diffraction microscopy (CXDM) has the potential to visualize the structures of micro- to sub-micrometer-sized biological particles, such as cells and organelles, at high resolution. Toward advancing structural studies on the functional states of such particles, here, we developed a system for the preparation of frozen-hydrated biological samples for cryogenic CXDM experiments. The system, which comprised a moist air generator, microscope, micro-injector mounted on a micromanipulator, custom-made sample preparation chamber, and flash-cooling device, allowed for the manipulation of sample particles in the relative humidity range of 20%–94%rh at 293 K to maintain their hydrated and functional states. Here, we report the details of the system and the operation procedure, including its application to the preparation of a frozen-hydrated chloroplast sample. Sample quality was evaluated through a cryogenic CXDM experiment conducted at BL29XUL of SPring-8. Taking the performance of the system and the quality of the sample, the system was suitable to prepare frozen-hydrated biological samples for cryogenic CXDM experiments.
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87.80.Fe Micromanipulation of biological structures
87.64.Bx Electron, neutron and x-ray diffraction and scattering
07.85.Tt X-ray microscopes
back to top Electronics; Electromagnetic Technology; Microwaves

A digitally configurable measurement platform using audio cards for high-resolution electronic transport studies

D. B. Gopman, D. Bedau, and A. D. Kent

Rev. Sci. Instrum. 83, 054701 (2012); http://dx.doi.org/10.1063/1.4709498 (4 pages)

Online Publication Date: 7 May 2012

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We report on a software-defined digitally configurable measurement platform for determining electronic transport properties in nanostructures with small readout signals. By using a high-resolution audio analog-to-digital/digital-to-analog converter in a digitally compensated bridge configuration we significantly increase the measurement speed compared to established techniques and simultaneously acquire large and small signal characteristics. We characterize the performance (16 bit resolution, 100 dB dynamic range at 192 kS/s) and demonstrate the application of this measurement platform for studying the transport properties of spin-valve nanopillars, a two-terminal device that exhibits giant magnetoresistance and whose resistance can be switched between two levels by applied magnetic fields and by currents applied by the audio card. The high resolution and fast sampling capability permits rapid acquisition of deep statistics on the switching of a spin-valve nanopillar and reduces the time to acquire the basic properties of the device – a state-diagram showing the magnetic configurations as function of applied current and magnetic field – by orders of magnitude.
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84.40.Ua Telecommunications: signal transmission and processing; communication satellites

The investigation of a compact auto-connected wire-wrapped pulsed transformer

Yuwei Wang, Jiande Zhang, Dongqun Chen, Shengguang Cao, Da Li, and Tianyang Zhang

Rev. Sci. Instrum. 83, 054702 (2012); http://dx.doi.org/10.1063/1.4719918 (6 pages)

Online Publication Date: 18 May 2012

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For the power conditioning circuit used to deliver power efficiently from flux compression generator (FCG) to the load with high impedance, an air-cored and wire-wrapped transformer convenient in coaxial connection to the other parts is investigated. To reduce the size and enhance the performance, an auto-connection is adopted. A fast and simple model is used to calculate the electrical parameters of the transformer. To evaluate the high voltage capability, the voltages across turns and the electric field distribution in the transformer are investigated. The calculated and the measured electrical parameters of the transformer show good agreements. And the safe operating voltage is predicted to exceed 500 kV. In the preliminary experiments, the transformer is tested in a power conditioning circuit with a capacitive power supply. It is demonstrated that the output voltage of the transformer reaches −342 kV under the input voltage of −81 kV.
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84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables
back to top Thermometry; Thermal Diffusivity; Acoustics; Photothermal and Photoacoustic

Development of a continuous testing apparatus for temperature reduction performance of cool coatings

Zhongnan Song, Yunxing Shi, Weidong Zhang, Jianrong Song, Jian Qu, Yanwen Li, and Zhongde Wang

Rev. Sci. Instrum. 83, 054901 (2012); http://dx.doi.org/10.1063/1.4709494 (5 pages)

Online Publication Date: 2 May 2012

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The working principle of a continuous testing apparatus for the temperature reduction performance of cool coatings is presented in this work. The apparatus consists of infrared reflector type lamps, an adiabatic box, and a data acquisition system. It was calibrated with the different conventional reference panels. The tests for dynamic and steady state temperature reduction performances were illustrated with two cool coatings. Results obtained directly from the simultaneous measurement are in good agreement with those calculated from separate measurements, thus confirming this apparatus as a valuable experimental tool for research and development of cool coatings.
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07.05.Hd Data acquisition: hardware and software
07.20.Dt Thermometers
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