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Feb 2007

Volume 78, Issue 2, pp. 1-029901-1

Issue Cover Spotlight Figure

Rev. Sci. Instrum. 78, 021101 (2007); http://dx.doi.org/10.1063/1.2437069 (25 pages)

Seth M. Foreman, Kevin W. Holman, Darren D. Hudson, David J. Jones, and Jun Ye
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Erratum: “Modulated photoluminescence spectroscopy with a step-scan Fourier transform infrared spectrometer” [Rev. of Sci. Instrum. 77, 063104 (2006)]

Jun Shao, Wei Lu, Xiang Lü, Fangyu Yue, Zhifeng Li, Shaoling Guo, and Junhao Chu

Rev. Sci. Instrum. 78, 1 (2007); http://dx.doi.org/10.1063/1.2670354 (1 page)

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99.10.Cd Errata
78.55.-m Photoluminescence, properties and materials
78.30.-j Infrared and Raman spectra
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Remote transfer of ultrastable frequency references via fiber networks

Seth M. Foreman, Kevin W. Holman, Darren D. Hudson, David J. Jones, and Jun Ye

Rev. Sci. Instrum. 78, 021101 (2007); http://dx.doi.org/10.1063/1.2437069 (25 pages) | Cited 57 times

Online Publication Date: 28 February 2007

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Three distinct techniques exist for distributing an ultrastable frequency reference over optical fibers. For the distribution of a microwave frequency reference, an amplitude-modulated continuous wave (cw) laser can be used. Over kilometer-scale lengths this approach provides an instability at 1 s of ∼ 3×10−14 without stabilization of the fiber-induced noise and ∼ 1×10−14 with active noise cancellation. An optical frequency reference can be transferred by directly transmitting a stabilized cw laser over fiber and then disseminated to other optical and microwave regions using an optical frequency comb. This provides an instability at 1 s of 2×10−14 without active noise cancellation and 3×10−15 with active noise cancellation [Recent results reduce the instability at 1 s to 6×10−18.] Finally, microwave and optical frequency references can be simultaneously transmitted using an optical frequency comb, and we expect the optical transfer to be similar in performance to the cw optical frequency transfer. The instability at 1 s for transfer of a microwave frequency reference with the comb is ∼ 3×10−14 without active noise cancellation and <7×10−15 with active stabilization. The comb can also distribute a microwave frequency reference with root-mean-square timing jitter below 16 fs integrated over the Nyquist bandwidth of the pulse train ( ∼ 50 MHz) when high-bandwidth active noise cancellation is employed, which is important for remote synchronization applications.
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06.20.fb Standards and calibration
42.81.-i Fiber optics
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Fast scanning of a pulsed terahertz signal using an oscillating optical delay line

Yun-Sik Jin, Seok-Gy Jeon, Geun-Ju Kim, Jung-Il Kim, and Chae-Hwa Shon

Rev. Sci. Instrum. 78, 023101 (2007); http://dx.doi.org/10.1063/1.2437764 (5 pages) | Cited 8 times

Online Publication Date: 5 February 2007

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We describe a fast measurement of a pulsed terahertz signal generated by a femtosecond laser and a photoconductive antenna using an oscillating optical delay line. The method to measure the amplitude of the retroreflector in the oscillating optical delay line is proposed and the displacement of the retroreflector is exactly calculated to acquire the optical delay time in the fast scan mode. With the different oscillation frequency and amplitude of the retroreflector, the pulsed terahertz signals are measured and analyzed. The comparison of the temporal waveform and frequency spectrum between the fast scan mode and the slow scan mode shows a good agreement with the decrease in the scanning time from 60 to 1 s at a signal to noise ratio of 430.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
85.60.-q Optoelectronic devices

Candlestick oven with a silica wick provides an intense collimated cesium atomic beam

A. Pailloux, T. Alpettaz, and E. Lizon

Rev. Sci. Instrum. 78, 023102 (2007); http://dx.doi.org/10.1063/1.2437140 (6 pages) | Cited 2 times

Online Publication Date: 5 February 2007

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This article shows that readily available glass and silica fibers and braids are suitable capillary structure for recirculating ovens, such as candlestick ovens, becoming then an alternative wick material to conventional metal based capillary structures. In order to study wettability and capillarity of metallic liquid cesium on borosilicate and silica microstructures, samples were selected, prepared, and tested experimentally. The contact angle of cesium on silica glass was roughly measured: θ = 35°±10°. A commercially available silica braid was then introduced inside a candlestick oven to transfer the metallic liquid cesium from the cold reservoir to the hot emission point of the candlestick. A collimated cesium atomic beam of intensity of 2×1016 at./s sr was obtained, stable and reproducible. Furthermore, this modified oven is easy to handle daily.
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07.20.Hy Furnaces; heaters
68.03.Cd Surface tension and related phenomena
68.08.Bc Wetting

Thermal beam of metastable krypton atoms produced by optical excitation

Y. Ding, S.-M. Hu, K. Bailey, A. M. Davis, R. W. Dunford, Z.-T. Lu, T. P. O’Connor, and L. Young

Rev. Sci. Instrum. 78, 023103 (2007); http://dx.doi.org/10.1063/1.2437193 (4 pages) | Cited 4 times

Online Publication Date: 8 February 2007

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A room-temperature beam of krypton atoms in the metastable 5s[3/2]2 level is demonstrated via an optical excitation method. A Kr-discharge lamp is used to produce vacuum ultraviolet photons at 124 nm for the first-step excitation from the ground level 4p6 1S0 to the 5s[3/2]1 level. An 819 nm Ti:sapphire laser is used for the second-step excitation from 5s[3/2]1 to 5s[3/2]2 followed by a spontaneous decay to the 5s[3/2]2 metastable level. A metastable atomic beam with an angular flux density of 3×1014 s−1 sr−1 is achieved at the total gas flow rate of 0.01 cm3/s at STP (or 3×1017 at./s). The dependences of the flux on the gas flow rate, laser power, and lamp parameters are investigated.
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32.80.Rm Multiphoton ionization and excitation to highly excited states
31.50.Df Potential energy surfaces for excited electronic states

Characterization of a derivative photoacoustic spectrometer

Lina Guo, Zhilie Tang, Yongheng He, and Hanchao Zhang

Rev. Sci. Instrum. 78, 023104 (2007); http://dx.doi.org/10.1063/1.2472594 (4 pages) | Cited 1 time

Online Publication Date: 16 February 2007

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A design of derivative photoacoustic spectrometer is presented in this article. It mainly includes a wavelength-intensity splitter and a complementary chopper. In our design, a dual wavelength derivative method is introduced to implement a derivative operation. Through the wavelength-intensity splitter, two beams are obtained and then complementarily modulated by the complementary chopper to satisfy the first derivative requirements as well as to achieve the differential of photoacoustic signals. As examples, the first derivative photoacoustic spectra of He–Ne laser and xenon lamp are also presented in this article. The results show that the first derivative photoacoustic spectrum can provide a superior fine spectral structure and spectral resolution compared to the photoacoustic absorption spectrum.
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43.58.Kr Spectrum and frequency analyzers and filters; acoustical and electrical oscillographs; photoacoustic spectrometers; acoustical delay lines and resonators
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect

Synchronizing fast electrically driven phenomena with synchrotron x-ray probes

Alexei Grigoriev, Dal-Hyun Do, Paul G. Evans, Bernhard Adams, Eric Landahl, and Eric M. Dufresne

Rev. Sci. Instrum. 78, 023105 (2007); http://dx.doi.org/10.1063/1.2668989 (4 pages) | Cited 4 times

Online Publication Date: 26 February 2007

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Time scales of long-range physical processes in solids are typically in the range of picoseconds to nanoseconds. These times are commensurate with the time resolution of structural probes based on modern synchrotron x-ray sources. Several processes of technological and scientific interest can be driven by applied electric fields, but synchronizing electrically driven phenomena with an x-ray probe poses a technical challenge. We describe the synchronization of a well-defined number of fast electrical pulses with the time structure of synchrotron x rays to probe the dynamics of thin films and nanostructures. This synchronization technique yields x-ray transient signals with 600 ps transitions in ferroelectric thin films, with a contribution of approximately 320 ps due to timing jitter in the synchronization.
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77.55.-g Dielectric thin films
77.80.Fm Switching phenomena
75.60.Jk Magnetization reversal mechanisms
07.85.Qe Synchrotron radiation instrumentation

Mobile spectroscopic system for trace gas detection using a tunable mid-IR laser

V. Vaičikauskas, M. Kaučikas, V. Švedas, and Z. Kuprionis

Rev. Sci. Instrum. 78, 023106 (2007); http://dx.doi.org/10.1063/1.2668940 (6 pages) | Cited 2 times

Online Publication Date: 27 February 2007

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We describe a mobile spectroscopic system for trace gas analysis based on the open path differential absorption spectrometer and the photoacoustic spectrometer. The first method allows long distance measurements (up to a few kilometers) while the second one provides local in situ detection of pollutants. The open path system is based on the nanosecond (f = 10 Hz, τ ≈ 5 ns) lamp pumped Nd:YAG laser and a tunable two cascade optical parametric generator operating in the 5–12 μm spectral region. This source was mounted into the lidar setup based on the coaxial transmitter/receiver. The photoacoustic system was constructed using the same laser as well as a nonresonant photoacoustic cell.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
42.68.Kh Effects of air pollution
82.80.Dx Analytical methods involving electronic spectroscopy
42.79.Qx Range finders, remote sensing devices; laser Doppler velocimeters, SAR, and LIDAR
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.65.Yj Optical parametric oscillators and amplifiers
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Lifetime of anode polymer in magnetically insulated ion diodes for high-intensity pulsed ion beam generation

X. P. Zhu, Z. H. Dong, X. G. Han, J. P. Xin, and M. K. Lei

Rev. Sci. Instrum. 78, 023301 (2007); http://dx.doi.org/10.1063/1.2437760 (8 pages) | Cited 4 times

Online Publication Date: 5 February 2007

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Generation of high-intensity pulsed ion beam (HIPIB) has been studied experimentally using polyethylene as the anode polymer in magnetically insulated ion diodes (MIDs) with an external magnetic field. The HIPIB is extracted from the anode plasma produced during the surface discharging process on polyethylene under the electrical and magnetic fields in MIDs, i.e., high-voltage surface breakdown (flashover) with bombardments by electrons. The surface morphology and the microstructure of the anode polymer are characterized using scanning electron microscopy and differential scanning calorimetry, respectively. The surface roughening of the anode polymer results from the explosive release of trapped gases or newly formed gases under the high-voltage discharging, leaving fractured surfaces with bubble formation. The polyethylene in the surface layer degrades into low-molecular-weight polymers such as polyethylene wax and paraffin under the discharging process. Both the surface roughness and the fraction of low molecular polymers apparently increase as the discharging times are prolonged for multipulse HIPIB generation. The changes in the surface morphology and the composition of anode polymer lead to a noticeable decrease in the output of ion beam intensity, i.e., ion current density and diode voltage, accompanied with an increase in instability of the parameters with the prolonged discharge times. The diode voltage (or surface breakdown voltage of polymer) mainly depends on the surface morphology (or roughness) of anode polymers, and the ion current density on the composition of anode polymers, which account for the two stages of anode polymer degradation observed experimentally, i.e., stage I which has a steady decrease of the two parameters and stage II which shows a slow decrease, but with an enhanced fluctuation of the two parameters with increasing pulses of HIPIB generation.
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52.75.Fk Magnetohydrodynamic generators and thermionic convertors; plasma diodes
52.50.Dg Plasma sources
52.80.Qj Explosions; exploding wires
29.25.Ni Ion sources: positive and negative
07.77.Ka Charged-particle beam sources and detectors
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials

Spatial charge cloud size of microchannel plates

M. Saito, Y. Saito, K. Asamura, and T. Mukai

Rev. Sci. Instrum. 78, 023302 (2007); http://dx.doi.org/10.1063/1.2472595 (7 pages) | Cited 3 times

Online Publication Date: 22 February 2007

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We examine the spatial evolution of charge clouds emitted by microchannel plates (MCPs). A model of this evolution is presented, along with a comparison to experimental results. We also present an experimental method to measure the charge cloud radius in which the radial charge cloud distribution is assumed to be Gaussian. When a charge cloud is released from the MCP, its initial size is determined by the number and distribution of excited channels. The size of the charge cloud is examined as a function acceleration voltage, distance between MCP and anode, and MCP bias voltage. Since electrons released from the MCP have various initial energies and angular divergence, the charge cloud size increases as it travels away from the MCP. Space charge effects also contribute to the growth of the charge cloud. The experimental results are in close agreement with our model, which includes these effects. From experiment, we also derive an approximate expression for charge cloud radius as a function of acceleration voltage and distance between MCP and anode. This expression can be used for the practical design and optimization of a position sensing system comprised of multiple anodes.
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77.22.Jp Dielectric breakdown and space-charge effects

High precision electrostatic potential calculations for cylindrically symmetric lenses

David Edwards, Jr.

Rev. Sci. Instrum. 78, 023303 (2007); http://dx.doi.org/10.1063/1.2437757 (11 pages)

Online Publication Date: 26 February 2007

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A method is developed for a potential calculation within cylindrically symmetric electrostatic lenses using mesh relaxation techniques, and it is capable of considerably higher accuracies than currently available. The method involves (i) creating very high order algorithms (orders of 6, 8, and 10) for determining the potentials at points in the net using surrounding point values, (ii) eliminating the effect of the large errors caused by singular points, and (iii) reducing gradients in the high gradient regions of the geometry, thereby allowing the algorithms used in these regions to achieve greater precisions—(ii) and (iii) achieved by the use of telescopic multiregions. In addition, an algorithm for points one unit from a metal surface is developed, allowing general mesh point algorithms to be used in these situations, thereby taking advantage of the enhanced precision of the latter. A maximum error function dependent on a sixth order gradient of the potential is defined. With this the single point algorithmic errors are able to be viewed over the entire net. Finally, it is demonstrated that by utilizing the above concepts and procedures, the potential of a point in a reasonably high gradient region of a test geometry can realize a precision of less than 10−10.
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41.85.Ne Electrostatic lenses, septa

Characterization of one-dimensional position sensitive detectors with improved efficiency and position resolution for neutron spectrometers

S. S. Desai and A. M. Shaikh

Rev. Sci. Instrum. 78, 023304 (2007); http://dx.doi.org/10.1063/1.2671005 (6 pages) | Cited 1 time

Online Publication Date: 27 February 2007

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Development and characterization of one-dimentional (1D) position sensitive detectors (PSDs) with improved efficiency and position resolution for neutron scattering applications are reported. The PSDs are characterized for energy resolution, count rate capability, sensitivity, efficiency, position resolution, and uniformity of response over the sensitive length. The studies are carried out to verify the dependence of position resolution on detector geometry, electronic noise, and stopping power of the fill gas. One of the PSDs is mounted on the small angle neutron scattering spectrometer and spectra from CTAB micelle sample are recorded using 5.4 Å neutrons. A gain of factors 1.1 and 1.2 is obtained compared to earlier in house made 1D PSD and LND-made 1D PSD, respectively. The diffraction patterns from standard vanadium, nickel, and silicon samples are recorded on a powder diffractometer using newly designed PSDs. Gain in efficiency obtained at shorter wavelength of 0.783 Å is by a factor of 1.6. All high pressure PSDs show improvement in the position resolution by 2–3 mm. It is observed that 1D PSD filled with isobutane as stopping gas improves the gamma tolerance and position resolution at lower partial pressures as compared to Kr. It is advantageous to use two or more 36C-type PSDs stacked together. It is economic and gives better efficiency due to scanning more beam height.
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29.40.Gx Tracking and position-sensitive detectors
29.30.Hs Neutron spectroscopy
07.50.Hp Electrical noise and shielding equipment
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Spectroscopic comparison between 1200 grooves/mm ruled and holographic gratings of a flat-field spectrometer and its absolute sensitivity calibration using bremsstrahlung continuum

Malay Bikas Chowdhuri, Shigeru Morita, Motoshi Goto, Hiroaki Nishimura, Keiji Nagai, and Shinsuke Fujioka

Rev. Sci. Instrum. 78, 023501 (2007); http://dx.doi.org/10.1063/1.2437742 (7 pages) | Cited 27 times

Online Publication Date: 5 February 2007

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A flat-field extreme ultraviolet (EUV) spectrometer with a varied line spacing groove grating (1200 grooves/mm at grating center) has been developed to study the emission spectra from highly ionized medium Z impurities in large helical device (LHD). It covers a wavelength range of 50–500 Å using a mechanically ruled grating, which was later replaced by a newly developed laminar-type holographic grating for comparative studies. Differences in spectral resolution, intensities of higher order spectra, and sensitivities of the spectrometer were studied between the two gratings by observing the emission spectra of LHD plasmas. Although the achieved resolution was alike between them, i.e., Δλ ∼ 0.24 Å at 200 Å, the holographic grating was much superior in suppressing the higher order light than the ruled grating. The relative sensitivity between the two gratings was evaluated using continuum radiation from LHD plasmas. As a result, it was found that the holographic grating has a flat response in the full wavelength range, but the sensitivity of the ruled grating drops sharply below 200 Å. A new technique for the absolute calibration of the EUV holographic grating spectrometer was tried by combining the continuum radiation with a branching ratio of C IV lines (3p-3s: 5800 Å/3p-2s: 312 Å), and an accurate absolute sensitivity has been successfully obtained.
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07.60.Rd Visible and ultraviolet spectrometers
06.20.fb Standards and calibration
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.25.Vy Impurities in plasmas
52.55.Jd Magnetic mirrors, gas dynamic traps

Measurement of electric field and gradient in the plasma sheath using clusters of floating microspheres

T. E. Sheridan, M. R. Katschke, and K. D. Wells

Rev. Sci. Instrum. 78, 023502 (2007); http://dx.doi.org/10.1063/1.2437114 (5 pages) | Cited 10 times

Online Publication Date: 8 February 2007

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A method for measuring the time-averaged vertical electric field and its gradient in the plasma sheath using clusters with n = 2 or 3 floating microspheres of known mass is described. The particle charge q is found by determining the ratio of the breathing frequency to the center-of-mass frequency for horizontal (in-plane) oscillations. The electric field at the position of the particles is then calculated using the measured charge-to-mass ratio, and the electric-field gradient is determined from the vertical resonance frequency. The Debye length is also found. Experimental results are in agreement with a simple sheath model.
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52.70.Nc Particle measurements
52.40.Kh Plasma sheaths
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)

A tetrode based fast pulsed microwave source for electron cyclotron resonance breakdown experiments

Vipin K. Yadav, K. Sathyanarayana, D. Purohit, and D. Bora

Rev. Sci. Instrum. 78, 023503 (2007); http://dx.doi.org/10.1063/1.2671793 (4 pages)

Online Publication Date: 26 February 2007

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To study electron cylotron resonance (ECR) breakdown and afterglow plasma in an experimental linear plasma system, a pulsed microwave source with rapid rise and fall of microwave power is desired. A pulsed microwave source with fast rise and fall capability for ECR breakdown experiments has been designed and tested for performance in the system. A tetrode, controlled by a modulator card, is used as a fast switch to initiate microwave power from a conventional magnetron operating at 2.45 GHz. The typical rise time of microwave power is ∼ 3 μs and a fall time of ∼ 10 μs. Using this scheme in a realistic pulsed microwave source at 800 W power, ECR breakdown of neutral gas is achieved and the plasma delay and fall time are observed from the plasma density measurements using a Langmuir probe. The design details of the fast rise pulsed microwave source are presented in this article with initial experimental results.
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84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)
84.47.+w Vacuum tubes
52.80.Pi High-frequency and RF discharges
52.80.Hc Glow; corona
52.50.Dg Plasma sources
52.70.Ds Electric and magnetic measurements

Cryogenic pellet launcher adapted for controlling of tokamak plasma edge instabilities

P. T. Lang, P. Cierpka, J. Harhausen, J. Neuhauser, C. Wittmann, ASDEX Upgrade Team, K. Gál, S. Kálvin, G. Kocsis, J. Sárközi, T. Szepesi, C. Dorner, and G. Kauke

Rev. Sci. Instrum. 78, 023504 (2007); http://dx.doi.org/10.1063/1.2437116 (9 pages) | Cited 4 times

Online Publication Date: 27 February 2007

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One of the main challenges posed recently on pellet launcher systems in fusion-oriented plasma physics is the control of the plasma edge region. Strong energy bursts ejected from the plasma due to edge localized modes (ELMs) can form a severe threat for in-vessel components but can be mitigated by sufficiently frequent triggering of the underlying instabilities using hydrogen isotope pellet injection. However, pellet injection systems developed mainly for the task of ELM control, keeping the unwanted pellet fueling minimized, are still missing. Here, we report on a novel system developed under the premise of its suitability for control and mitigation of plasma edge instabilities. The system is based on the blower gun principle and is capable of combining high repetition rates up to 143 Hz with low pellet velocities. Thus, the flexibility of the accessible injection geometry can be maximized and the pellet size kept low. As a result the new system allows for an enhancement in the tokamak operation as well as for more sophisticated experiments investigating the underlying physics of the plasma edge instabilities. This article reports on the design of the new system, its main operational characteristics as determined in extensive test bed runs, and also its first test at the tokamak experiment ASDEX Upgrade.
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52.55.Fa Tokamaks, spherical tokamaks
52.55.Pi Fusion products effects (e.g., alpha-particles, etc.), fast particle effects
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.40.Hf Plasma-material interactions; boundary layer effects
28.52.Av Theory, design, and computerized simulation
28.52.Fa Materials
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Unstable amplitude and noisy image induced by tip contamination in dynamic force mode atomic force microscopy

H.-Y. Nie and N. S. McIntyre

Rev. Sci. Instrum. 78, 023701 (2007); http://dx.doi.org/10.1063/1.2437196 (5 pages) | Cited 6 times

Online Publication Date: 5 February 2007

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Liquid 1-decanethiol was confined on an atomic force microscope (AFM) tip apex and the effect was investigated by measuring amplitude-distance curves in dynamic force mode. Within the working distance in the dynamic force mode AFM, the thiol showed strong interactions bridging between a gold-coated probe tip and a gold-coated Si substrate, resulting in unstable amplitude and noisy AFM images. We show that under such a situation, the amplitude change is dominated by the extra forces induced by the active material loaded on the tip apex, overwhelming the amplitude change caused by the geometry of the sample surface, thus resulting in noise in the image the tip collects. We also show that such a contaminant may be removed from the apex by pushing the tip into a material soft enough to avoid damage to the tip.
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07.79.Lh Atomic force microscopes

Measuring material softening with nanoscale spatial resolution using heated silicon probes

B. A. Nelson and W. P. King

Rev. Sci. Instrum. 78, 023702 (2007); http://dx.doi.org/10.1063/1.2435589 (8 pages) | Cited 42 times

Online Publication Date: 7 February 2007

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This article describes the use of heated silicon atomic force microscopy probes to perform local thermal analysis (LTA) of a thin film of polystyrene. The experiments measure film softening behavior with 100 nm spatial resolution, whereas previous research on LTA used probes that had a resolution near 10 μm, which was too large to investigate some types of features. This article demonstrates four methods by which heated silicon probes can perform thermal analysis with nanoscale spatial resolution. The polystyrene softening temperature measured from nanoscale LTA techniques is 120 °C, compared to 100 °C, measured with bulk ellipsometry. The discrepancy is attributed to the thermal contact resistance at the end of the silicon probe tip, on the order of 107K/W, which modulates heat flow between the tip and sample and governs the fundamental limits of this technique. The use of a silicon probe for LTA enables bulk fabrication, parallelization for high-throughput analysis, and fabrication of a sharp tip capable of nanoscale spatial resolution.
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07.79.Lh Atomic force microscopes

Image processing for resonance frequency mapping in atomic force modulation microscopy

R. Arinéro, G. Lévêque, P. Girard, and J. Y. Ferrandis

Rev. Sci. Instrum. 78, 023703 (2007); http://dx.doi.org/10.1063/1.2432264 (6 pages) | Cited 2 times

Online Publication Date: 8 February 2007

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It has been demonstrated that the resonance frequency of the cantilever in atomic force modulation microscopy can be used to study local mechanical properties. We developed a numerical method to achieve mapping of the resonance frequency without significant modification of the device. By making the assumption that the resonance spectrum can be approximated by a Lorentzian curve, we established analytical expressions of the resonance frequency and the width of the curve (damping) depending on the real and imaginary parts of the vibration at a single frequency. Then, resonance frequency and damping images were produced from the recording of both the real and imaginary part images of the complex amplitude. The results on a standard high-impact polystyrene sample are shown.
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42.30.Va Image forming and processing
68.37.Ps Atomic force microscopy (AFM)

Real-time image compression for high-speed particle tracking

King-Yeung Chan, Dominik Stich, and Greg A. Voth

Rev. Sci. Instrum. 78, 023704 (2007); http://dx.doi.org/10.1063/1.2536719 (5 pages) | Cited 3 times

Online Publication Date: 27 February 2007

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High-speed particle tracking with digital video creates very large data rates and as a result experimenters are forced to make compromises between spatial resolution, temporal resolution, and the duration over which data is acquired. The images produced in particle tracking experiments typically contain a large amount of black space with relatively few bright pixels and this suggests the possibility of image compression. This paper describes a system for real-time compression of high-speed video. A digital circuit placed between the camera (500 Hz, 1280×1024 pixels) and frame grabber compresses data in real-time by comparing input pixels with a threshold value and outputs a vector containing the brightness and position of the bright pixels. In a typical experiment, the compression ratio for an image ranges from 100 to 1000 and varies dynamically depending on the number of filtered pixels. The reduced data rate makes it possible to write directly to the hard disk. While previously data could only be acquired for 6.5 s into 4 GB of dedicated video RAM, the new system could acquire full resolution data continuously for up to a week into a 600 GB hard drive.
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84.40.Ua Telecommunications: signal transmission and processing; communication satellites
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Basic building units and properties of a fluorescence single plane illumination microscope

K. Greger, J. Swoger, and E. H. K. Stelzer

Rev. Sci. Instrum. 78, 023705 (2007); http://dx.doi.org/10.1063/1.2428277 (7 pages) | Cited 25 times

Online Publication Date: 28 February 2007

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The critical issue of all fluorescence microscopes is the efficient use of the fluorophores, i.e., to detect as many photons from the excited fluorophores as possible, as well as to excite only the fluorophores that are in focus. This issue is addressed in EMBL’s implementation of a light sheet based microscope [single plane illumination microscope (SPIM)], which illuminates only the fluorophores in the focal plane of the detection objective lens. The light sheet is a beam that is collimated in one and focused in the other direction. Since no fluorophores are excited outside the detectors’ focal plane, the method also provides intrinsic optical sectioning. The total number of observable time points can be improved by several orders of magnitude when compared to a confocal fluorescence microscope. The actual improvement factor depends on the number of planes acquired and required to achieve a certain signal to noise ratio. A SPIM consists of five basic units, which address (1) light detection, (2) illumination of the specimen, (3) generation of an appropriate beam of light, (4) translation and rotation of the specimen, and finally (5) control of different mechanical and electronic parts, data collection, and postprocessing of the data. We first describe the basic building units of EMBL’s SPIM and its most relevant properties. We then cover the basic principles underlying this instrument and its unique properties such as the efficient usage of the fluorophores, the reduced photo toxic effects, the true optical sectioning capability, and the excellent axial resolution. We also discuss how an isotropic resolution can be achieved. The optical setup, the control hardware, and the control scheme are explained in detail. We also describe some less obvious refinements of the basic setup that result in an improved performance. The properties of the instrument are demonstrated by images of biological samples that were imaged with one of EMBL’s SPIMs.
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07.60.Pb Conventional optical microscopes
87.64.M- Optical microscopy

In-plane rigid-body vibration mode characterization with a nanometer resolution by stroboscopic imaging of a microstructured pattern

Patrick Sandoz, Jean-Michel Friedt, and Emile Carry

Rev. Sci. Instrum. 78, 023706 (2007); http://dx.doi.org/10.1063/1.2472604 (9 pages) | Cited 8 times

Online Publication Date: 28 February 2007

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This article introduces an improved approach for the characterization of in-plane rigid-body vibration, based on digital processing of stroboscopic images of the moving part. The method involves a sample preparation step, in order to pattern a periodic microstructure on the vibrating device, for instance, by focused ion beam milling. An image processing method has then been developed to perform the optimum reconstruction of this a priori known object feature. In-plane displacement and rotation are deduced simultaneously with a high resolution (10−2 pixel and 0.5×10−3 rad, respectively). The measurement principle combines phase measurements—that provide the high resolution—with correlation—that unwraps the phase with the proper phase constants. The vibration modes of a tuning fork are used for demonstrating the capabilities of the method. For applications allowing the sample preparation, the proposed methodology is more convenient than common interference methods or image processing techniques for the characterization of the vibration modes, even for amplitudes in the nanometer range.
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07.10.-h Mechanical instruments and equipment
42.30.Va Image forming and processing
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System for continuous production of nanophase materials using a microwave-driven polyol process

Steven H. Gold, Ralph W. Bruce, Arne W. Fliflet, David Lewis, III, Lynn K. Kurihara, and M. A. Imam

Rev. Sci. Instrum. 78, 023901 (2007); http://dx.doi.org/10.1063/1.2435588 (6 pages)

Online Publication Date: 7 February 2007

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A prototype system is described for the large scale, continuous production of nanophase metals, metal oxides, and other nanophase materials using the polyol process. The polyol process employs an organic solvent such as ethylene glycol to reduce a metal oxide/metal salt at high temperature to the metal oxide or metal. The system employs a 6 kW, 2.45 GHz microwave source to rapidly heat the continuously flowing solution to a desired process temperature as it flows through a silica tube placed along the center line of a section of waveguide.
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81.16.-c Methods of micro- and nanofabrication and processing
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment

Three-terminal capacitance cell for stopped-flow measurements of very dilute solutions

Martin Tjahjono, Thomas Davis, and Marc Garland

Rev. Sci. Instrum. 78, 023902 (2007); http://dx.doi.org/10.1063/1.2437134 (6 pages) | Cited 3 times

Online Publication Date: 9 February 2007

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A capacitance cell has been designed, constructed, and tested for stopped-flow measurements of very dilute low-relative permittivity liquid solutions. The capacitance cell utilizes a three-terminal design and is connected to ultrahigh sensitivity capacitance bridge. The cell was designed for operating conditions T ≈ 243.15–373.15 K and P ≈ 0–1 MPa and tested with pure anhydrous cyclohexane and with dilute acetone/cyclohexane solutions at 298.15 K and 0.1 MPa under an argon blanket in a thermostated bath with a temperature variation of <0.001 K. Details of the design and materials of construction are reported. The measured relative permittivity of cyclohexane was 2.015 565, in agreement with the literature, and the long term variation of the measurement was ±5×10−6. The relative permittivities of the acetone/cyclohexane solutions were very linear (R2 = 0.9997) in the measured interval of 0.001–0.008 mole fraction. These measurements confirm that the design specifications for stability and resolution/sensitivity of better than 1×10−5 have been realized. Finally, the present online capacitance cell was connected online to an ultrasensitive densitometer and ultrasensitive refractometer and binary acetone/cyclohexane solutions were measured. The measurements of density, refractive index, and relative permittivity were combined to provide a dipole moment of acetone of 2.750±0.005 D, which is in good agreement with literature.
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47.80.-v Instrumentation and measurement methods in fluid dynamics
82.47.-a Applied electrochemistry
77.22.Ch Permittivity (dielectric function)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Equipment for hydrogen absorption-desorption cycling characterization of hydride forming materials

G. Meyer, P. Arneodo Larochette, A. Baruj, F. J. Castro, P. Lacharmoise, E. Zacur, and B. A. Talagañis

Rev. Sci. Instrum. 78, 023903 (2007); http://dx.doi.org/10.1063/1.2437160 (6 pages) | Cited 1 time

Online Publication Date: 9 February 2007

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Hydrogen storage materials suffer different degradation processes when they are cycled, forming and decomposing their associated hydride phases. In order to study these processes, we have designed and built an automated apparatus specifically developed for cycling samples of hydride forming materials by changing the external hydrogen pressure. Instead of the standard open configuration involving a high-pressure, high-quality gas bottle and a vacuum pump, the equipment uses another hydride forming material (in our case LaNi5) as a source and sink of hydrogen. The resulting closed-loop configuration eliminates hydrogen waste and ensures that extremely high purity gas is used during the whole experiment, thanks to the purifying properties of the selected hydride as source/sink. Hydrogen pressure is set by changing the source/sink temperature. Cycles can be performed as fast as one cycle every 5 min, a period comparable with typical good hydride forming material kinetics. An example of application of the apparatus is given for 1000 absorption/desorption cycles on a Mm0.8Ca0.2Ni5 sample.
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84.60.Ve Energy storage systems, including capacitor banks
68.43.Mn Adsorption kinetics
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