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Nov 1997

Volume 68, Issue 11, pp. 3945-4289

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Review of high-power microwave source research

Steven H. Gold and Gregory S. Nusinovich

Rev. Sci. Instrum. 68, 3945 (1997); http://dx.doi.org/10.1063/1.1148382 (30 pages) | Cited 64 times

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This article reviews the state-of-the-art in high-power microwave source research. It begins with a discussion of the concepts involved in coherent microwave generation. The main varieties of microwave tubes are classified into three groups, according to the fundamental radiation mechanism involved: Cherenkov, transition, or bremsstrahlung radiation. This is followed by a brief discussion of some of the technical fundamentals of high-power microwave sources, including power supplies and electron guns. Finally, the history and recent developments of both high-peak power and high-average power sources are reviewed in the context of four main areas of application: (1) plasma resonance heating and current drive; (2) rf acceleration of charged particles; (3) radar and communications systems; and (4) high-peak power sources for weapons-effect simulation and exploratory development. © 1997 American Institute of Physics.
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84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)
07.57.Hm Infrared, submillimeter wave, microwave, and radiowave sources
01.30.Rr Surveys and tutorial papers; resource letters
41.60.-m Radiation by moving charges
52.50.Gj Plasma heating by particle beams
84.40.Ua Telecommunications: signal transmission and processing; communication satellites
29.27.-a Beams in particle accelerators

Parametric optimization of discharge pumped XeCl lasers

Maxime Makarov

Rev. Sci. Instrum. 68, 3975 (1997); http://dx.doi.org/10.1063/1.1148379 (14 pages) | Cited 2 times

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The data gained on discharge pumped XeCl laser systems over the last 15 years were analyzed to identify common inherent regularities. It is obvious that there are three major classes of phenomena involved, namely: the electrical processes in the pumping circuit, the plasma-chemical kinetics, and the discharge contraction. It has been demonstrated that under certain conditions they can be considered separately. Such an approach allows one to estimate a priori the optimal pumping conditions and the electrical circuit parameters to obtain the required laser energy. The results presented could be used in the engineering calculations of high-performance excimer laser systems to significantly reduce the cost of the design and the optimization stages. © 1997 American Institute of Physics.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.By Design of specific laser systems

Shot-noise-limited radio-frequency lock-in photodetection with a continuous wave mode-locked laser

D. Yu. Paraschuk, T. A. Kulakov, O. Yu. Nedopekin, N. V. Chigarev, and X. Y. Pan

Rev. Sci. Instrum. 68, 3989 (1997); http://dx.doi.org/10.1063/1.1148370 (3 pages) | Cited 6 times

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We have developed quite a simple and original lock-in photodetection system that works at a fixed radio frequency. The system includes a photodetector, a frequency down converter and a standard low-frequency lock-in amplifier. The resonant implementation of the radio-frequency attachment provides high gain and high selectivity, which have enabled us to attain the shot-noise-limited sensitivity to relative optical power change δP/P ≃ 4×10−8 Hz−1/2 at a detection frequency of 6.2 MHz in measurements with a cw mode-locked Nd:yttrium aluminum garnet laser. We have realized the precise position-sensitive photodetection for laser pointing noise measurements and picosecond photoacoustic spectroscopy of solids. © 1997 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
42.60.Fc Modulation, tuning, and mode locking
84.30.Le Amplifiers
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Device for the simultaneous application of uniaxial stress and hydrostatic pressure: Application to semiconductor lasers

F. Widulle, J. Th. Held, M. Huber, H. D. Hochheimer, R. T. Kotitschke, and A. R. Adams

Rev. Sci. Instrum. 68, 3992 (1997); http://dx.doi.org/10.1063/1.1148371 (4 pages) | Cited 2 times

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The design of a device for the simultaneous application of uniaxial stress and hydrostatic pressure is presented. Shown in detail is the design of the part that applies the uniaxial force to the sample and first results of the simultaneous application of uniaxial stress and hydrostatic pressure to a semiconductor laser. © 1997 American Institute of Physics.
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07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
42.55.Px Semiconductor lasers; laser diodes

A new design for a versatile Fabry-Pérot interferometer for Brillouin spectroscopy

Klaus Weishaupt, Stefan H. Anders, Reinhold G. Eberle, and Martin Pietralla

Rev. Sci. Instrum. 68, 3996 (1997); http://dx.doi.org/10.1063/1.1148372 (5 pages) | Cited 3 times

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We present a new design of a Fabry-Pérot interferometer for Brillouin spectroscopy. Emphasis is placed on a quick change of the free spectral range without losing alignment, the possibility of switching the multipass arrangement from 3 to 5 pass and back, and finally on a simple and inexpensive construction. Besides this the new interferometer shows very good long term stability and is easy to handle. These features were not available before in this combination. The performance of the instrument will be demonstrated. © 1997 American Institute of Physics.
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07.60.Ly Interferometers
07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
07.05.Dz Control systems

Developments of widely tunable light sources for picosecond time-resolved resonance Raman spectroscopy

Yuki Uesugi, Yasuhisa Mizutani, and Teizo Kitagawa

Rev. Sci. Instrum. 68, 4001 (1997); http://dx.doi.org/10.1063/1.1148373 (8 pages) | Cited 13 times

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Two systems of widely tunable light sources for picosecond time-resolved resonance Raman (ps-TR3) spectroscopy have been constructed using a 1 kHz ps-Ti:sapphire laser/regenerative amplifier system. Performance of the systems was examined in terms of pulse duration, spectral width, pulse energy, and shot-to-shot stability. One system, consisting of white light continuum seeder and β-barium borate optical parametric amplifier, demonstrated tunability in the 500–660 nm range with 1.3–2.1 ps pulse duration and 15 μJ pulse energy. The other system, consisting of a lithium triborate optical parametric generator in type II noncritical phase matching configuration and β-barium borate optical parametric amplifier, was found to yield visible pulses as high as 18 μJ with 1.5–2.4 ps of pulse duration in the 520–630 nm region. The shot-to-shot stability of generated pulses is less than 10% for both systems. Capability of the present systems is demonstrated by observing ps-TR3 spectra of nickel octaethylporphyrin in coordinating and noncoordinating solvents. © 1997 American Institute of Physics.
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07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.-j Optical instruments and equipment
42.72.-g Optical sources and standards
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.65.Yj Optical parametric oscillators and amplifiers
42.60.Fc Modulation, tuning, and mode locking
06.60.Jn High-speed techniques (microsecond to femtosecond)

X-ray absolute intensity measurement at HASYLAB ultrasmall angle x-ray scattering beamline BW4

A. Endres, U. Lode, G. v. Krosigk, M. Bark, S. Cunis, R. Gehrke, and W. Wilke

Rev. Sci. Instrum. 68, 4009 (1997); http://dx.doi.org/10.1063/1.1148374 (5 pages) | Cited 4 times

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In order to obtain small angle scattering intensities in absolute units, measurements of the incident beam intensity and the intensity transmitted through the sample are required. For this purpose the scattering intensity of a calibrated polyethylene (LUPOLEN) standard is used. For the determination of the absolute photon flux and the correction of the scattering patterns obtained with a two dimensional position sensitive detector we use the detector response function. A set of data measured subsequently at the standard and at a given sample can be evaluated in a program that calculates a pattern in absolute units corrected by means of the detector response. This program also calculates the absolute photon flux, determines automatically the center coordinates of the incident beam, and calculates the scattering vectors that belong to the different positions on the detector. © 1997 American Institute of Physics.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors

An apparatus for fabrication of optical waveguides by electromigration

H. S. Monteiro, J. C. Said, J. F. Mendes, and R. Srivastava

Rev. Sci. Instrum. 68, 4014 (1997); http://dx.doi.org/10.1063/1.1148375 (3 pages) | Cited 1 time

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We present an apparatus for fabricating ion exchanged glass waveguides with reproducible characteristics. It consists of a vertical furnace with a uniform temperature zone, which is flat to within 1 °C over the sample length, a silica crucible for containing molten salt, a metallic sample holder made of either aluminum or stainless steel, and a motor-driven sample lowering system. The time and temperature are accurately controlled to produce waveguides of desired index profiles. © 1997 American Institute of Physics.
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42.86.+b Optical workshop techniques
42.79.Gn Optical waveguides and couplers
81.05.Kf Glasses (including metallic glasses)
07.20.Hy Furnaces; heaters
82.30.Hk Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)

Monte Carlo calculations for the design of Mott scattering spin polarimeters

S. Qiao and A. Kakizaki

Rev. Sci. Instrum. 68, 4017 (1997); http://dx.doi.org/10.1063/1.1148381 (5 pages) | Cited 6 times

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Using the Monte Carlo method, we have calculated, for 50 keV electrons incident on a gold target, the dependence of the effective Sherman asymmetry function and scattered intensity on the target thickness and inelastic energy loss window for scattering angles from 90° to 180°. Our results show that, when the gold target is thicker than 700 Å or the inelastic energy loss window is larger than 1200 eV, the scattered intensity is maximum at a scattering angle of about 120°, and the effective Sherman function is almost constant over a wide range of scattering angles. Thus, for Mott scattering spin polarimeters, the electron detectors should be positioned at ±120°, and the larger the collection angle for scattered electrons, the higher the efficiency of the Mott polarimeter. © 1997 American Institute of Physics.
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29.40.-n Radiation detectors
29.27.Hj Polarized beams
02.70.Rr General statistical methods
34.80.Nz Spin dependence of cross sections; polarized beam experiments
79.20.Kz Other electron-impact emission phenomena

Instrumentation for charged particle traps

S. S. Rajput and S. C. Garg

Rev. Sci. Instrum. 68, 4022 (1997); http://dx.doi.org/10.1063/1.1148376 (5 pages) | Cited 3 times

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This article reports the design and its special features for various grid biases for a retarding potential analyzer instrument aboard Indian satellite SROSS-C2 to ensure trouble free functioning of electron and ion traps. The polarities of the various grid biases, identify the difference between ion traps and electron traps. A new concept of generating bias sweeps on line for future missions has been proposed. © 1997 American Institute of Physics.
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94.80.+g Instrumentation for space plasma physics, ionosphere, and magnetosphere
07.77.Ka Charged-particle beam sources and detectors
07.87.+v Spaceborne and space research instruments, apparatus, and components (satellites, space vehicles, etc.)

A time detector design for MeV particles using secondary electron emission and microchannel plates

Z. Fang and D. J. O’Connor

Rev. Sci. Instrum. 68, 4027 (1997); http://dx.doi.org/10.1063/1.1148003 (8 pages)

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In this article we present some basic considerations in the design of a time detector for high energy (0.2–1.0 MeV) particle detection. Based on these considerations, a novel time detector design is proposed in order to overcome some of the problems in existing designs. Improvement in the timing resolution (<50 ps) and efficiency (>70% for 4.0 MeV α particles) is expected and a compact detector structure with ultrahigh vacuum compatibility is achieved. The new design employs a novel form of crossed electric and magnetic fields to deflect the electrons emitted from a thin foil to form a timing signal. In this design electrons are transported in a grid-free region and the energetic particle needs to pass through the grid once only. The electric field was produced by three metal plates forming a triangular prism. The magnetic field was generated by a coil pair which creates a uniform field in the electron transport region. Computer simulation and numerical analysis were performed to calculate the electric and magnetic field as well as the electron trajectory and flight time. The detector timing resolution is analyzed and the spread in electron initial energy contributes a significant portion. To avoid the complicated numerical details in field and trajectory calculations, we use an empirical approach in this article to illustrate the design principle. Some experimental results are presented to compare with the calculations. © 1997 American Institute of Physics.
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29.30.-h Spectrometers and spectroscopic techniques
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
29.40.-n Radiation detectors
85.60.Ha Photomultipliers; phototubes and photocathodes

Two-color polarimeter for electron density measurement on large tokamaks

Yasunori Kawano and Akira Nagashima

Rev. Sci. Instrum. 68, 4035 (1997); http://dx.doi.org/10.1063/1.1148377 (3 pages) | Cited 7 times

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A two-color laser polarimeter on large tokamaks such as ITER has been proposed for electron density measurement based on the midplane Faraday rotation. The two-color scheme in the polarimeter eliminates the Faraday rotation at vacuum windows from measured polarization angles. Two CO2 lasers which have different wavelengths of 10.6 and 9.27 μm are favorable as light sources of the two-color laser polarimeter for large tokamaks. A couple of photoelastatic modulators are used for stable polarization measurement even though the intensity and the propagation axis of an incident laser beam are changed. © 1997 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
07.60.Fs Polarimeters and ellipsometers
52.55.Fa Tokamaks, spherical tokamaks
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy

Electron density profile reconstruction from multichannel microwave interferometer data at W7-AS

J. P. T. Koponen and O. Dumbrajs

Rev. Sci. Instrum. 68, 4038 (1997); http://dx.doi.org/10.1063/1.1148378 (5 pages) | Cited 9 times

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A multichannel microwave interferometer has been built for the W7-AS fusion experiment in order to study temporal phenomena in plasma density. For this reason, electron density profile reconstruction methods based on regularization functionals were studied. Simulations showed, that the minimum Fisher-information approach (adapted from tomography) gives better results than the maximum entropy approach. This is due to the fact, that in the minimum Fisher-information method the reconstructed distribution is inherently assumed to be continuous, whereas the maximum entropy method the distribution is assumed to be noncontinuous. The profiles reconstructed from multichannel interferometer data are in good agreement with the profiles measured by other diagnostic systems. © 1997 American Institute of Physics.
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52.70.Gw Radio-frequency and microwave measurements
52.55.Jd Magnetic mirrors, gas dynamic traps
02.60.Ed Interpolation; curve fitting
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment

Use of Langmuir probes in a weakly ionized, steady-state plasma with strong magnetic field

D. Batani, S. Alba, P. Lombardi, and A. Galassi

Rev. Sci. Instrum. 68, 4043 (1997); http://dx.doi.org/10.1063/1.1148346 (8 pages) | Cited 2 times

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This article describes the use of Langmuir probes to measure plasma parameters in low density, low temperature plasmas with a strong applied magnetic field. The experiment has been performed at the Physics Department of Milan’s University on the steady-state toroidal machine “Thorello.” Results have been analyzed by taking into account instrumental and ionic sheath effects. Finally, experimental results have been compared with direct measurements of the electron distribution function in Thorello. © 1997 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
52.55.Jd Magnetic mirrors, gas dynamic traps
52.40.Hf Plasma-material interactions; boundary layer effects

Improvement of q-profile measurement by fast observation of pellet ablation at ASDEX Upgrade

H. W. Müller, P. T. Lang, K. Büchl, M. Kaufmann, B. V. Kuteev, P. J. McCarthy, V. Mertens, I. Miroshnikov, W. Schneider, and H. Zohm

Rev. Sci. Instrum. 68, 4051 (1997); http://dx.doi.org/10.1063/1.1148386 (10 pages) | Cited 9 times

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The q-profile measurement presented in this article is based on the observation of pellets injected into the plasma and viewed with a fast-framing camera. The pellets sublimate in the plasma and the ablated material is ionized. The ions move along the magnetic field lines, while an ablation cloud is forming. This ablation cloud contains a small fraction of neutral particles which emit visible light after collisional excitation. It is therefore possible to visualize the magnetic field lines along which the pellet passes. The inclination angle of the magnetic field lines with respect to the torus midplane can be determined from this observation. The results are compared with the inclination angles delivered by an equilibrium code. Further analysis shows that it is not meaningful to determine the q-profile from the data of only the pellet ablation, in the case of an elongated plasma as in ASDEX Upgrade. However, the accuracy of the q-profile determined by an equilibrium code, especially in the plasma center, can be greatly improved by using the pellet measurements as additional input data. © 1997 American Institute of Physics.  
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52.70.Ds Electric and magnetic measurements
52.25.Fi Transport properties

Cantilever magnetometry in pulsed magnetic fields

M. J. Naughton, J. P. Ulmet, A. Narjis, S. Askenazy, M. V. Chaparala, and A. P. Hope

Rev. Sci. Instrum. 68, 4061 (1997); http://dx.doi.org/10.1063/1.1148347 (5 pages) | Cited 21 times

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The technique of cantilever magnetometry is shown to be functional in pulsed magnetic fields. Employing micromachined single crystal silicon cantilevers and capacitance detection, we demonstrated a utilizable sensitivity to magnetic moment of 2.5×10−12 Am2 in magnetic fields to 36 T, representing an improvement of more than a factor of 10 over competing technologies. Torque magnetization measurements on microcrystals of anisotropic superconductors are presented as evidence of the feasibility of the technique in long pulse magnets of pulse duration ∼ 0.1–1 s. © 1997 American Institute of Physics.
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07.55.Jg Magnetometers for susceptibility, magnetic moment, and magnetization measurements
07.10.Cm Micromechanical devices and systems
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
74.25.Ha Magnetic properties including vortex structures and related phenomena

Improved dc SQUID read-out electronics with low 1/f noise preamplifier

Dietmar Drung

Rev. Sci. Instrum. 68, 4066 (1997); http://dx.doi.org/10.1063/1.1148348 (9 pages) | Cited 23 times

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An improved read-out electronics without flux modulation for dc superconducting quantum interference devices (dc SQUIDs) is presented where the preamplifier is directly coupled to the SQUID. Compared to our previous designs, the 1/f voltage and current noise levels of the preamplifier were reduced by about a factor of 4 (rms) by using bipolar matched transistors instead of operational amplifiers at the input. Three types of flux-locked-loop electronics were developed and successfully tested: a low-power (120 mW) version for large multichannel arrays, a high-speed version with a 15 MHz bandwidth and a very fast (300 ns) reset mode, and a low-noise (0.44 nV/math) version with a fast and precise bias reversal circuit. The flux-locked-loop electronics are compatible with each other, so that only one type of low-power (180 mW) control unit is required to operate them. All essential specifications of practical SQUID systems (noise, dynamic behavior, and temperature stability) were determined by using liquid-helium and liquid-nitrogen cooled SQUIDs, respectively. © 1997 American Institute of Physics.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
84.30.Le Amplifiers
07.55.Ge Magnetometers for magnetic field measurements

An automated susceptometer for the measurement of linear and nonlinear magnetic ac susceptibility

A. Bajpai and A. Banerjee

Rev. Sci. Instrum. 68, 4075 (1997); http://dx.doi.org/10.1063/1.1148349 (5 pages) | Cited 38 times

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A completely automated ac susceptometer is constructed to measure phase resolved linear and nonlinear ac susceptibility. Measurements over a wide range of experimental variables, such as ac and superimposed dc fields up to 300 Oe, frequency from 1 Hz to 100 kHz, and temperature from 77 to 300 K are made using only a lock-in amplifier (LIA), a PC, and some simple electronic circuits. A temperature-measurement and control unit is built utilizing the analog–digital input and digital–analog output of the LIA. Using a proportional and integral algorithm, a control accuracy better than 50 mK is achieved. The overall sensitivity of the setup is better than 10−7 emu and a reproducibility better than 0.1% is achieved in the system. © 1997 American Institute of Physics.
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07.55.Jg Magnetometers for susceptibility, magnetic moment, and magnetization measurements

Temperature measurement of fine wires by photothermal radiometry

T. Borca-Tasciuc and G. Chen

Rev. Sci. Instrum. 68, 4080 (1997); http://dx.doi.org/10.1063/1.1148350 (4 pages) | Cited 4 times

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This work reports temperature measurement of fine wires using the photothermal radiometry (PTR) technique. In this method, a laser is employed to create a small periodic temperature perturbation on the wire and thus a small modulation of the thermal emission signal from the wire. The temperature of the wire is derived from the ratio of the photothermal emission signals at two different wavelengths. Temperature measurement is performed on an electrically heated metallic wire of 127 μm in diameter. A calibration procedure is developed to account for the emissivity difference at the two signal wavelengths. The measured temperatures by the PTR technique are in good agreement with the thermocouple readings at different laser modulation frequencies. The possibility of extending the technique to optical fibers is discussed based on Mie scattering theory. Calculations suggest that the PTR technique can be used to measure temperature of optical fibers during the fiber drawing process by choosing an appropriate excitation laser and the signal wavelengths. © 1997 American Institute of Physics.
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07.20.Dt Thermometers
07.60.Dq Photometers, radiometers, and colorimeters
42.81.Cn Fiber testing and measurement of fiber parameters
06.20.F- Units and standards

Development of a calorimetric technique for measuring absorption cross section of rigid bodies—Case study: carbon fiber

Kristan P. Gurton and Charles W. Bruce

Rev. Sci. Instrum. 68, 4084 (1997); http://dx.doi.org/10.1063/1.1148388 (6 pages)

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A balanced calorimetric device has been developed to measure the absorption cross section of a single macroscopic sized particle (in this case a carbon fiber) at a microwave frequency of 35 GHz, as a function of size and orientation with respect to the electric field. The technique used is based on simple thermodynamic principles that relate the electromagnetic absorption of a particle to its thermal response. A single particle is irradiated in a fixed volume of gas by an approximate plane wave. Absorption by the particle results in a change in the ambient pressure that is proportional to the absorption cross section of the particle. Comparison of measured quantities with recently developed theory agree well.
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07.20.Fw Calorimeters
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)

Orthogonal superposition measurements using a rheometer equipped with a force rebalanced transducer

J. Vermant, P. Moldenaers, J. Mewis, M. Ellis, and R. Garritano

Rev. Sci. Instrum. 68, 4090 (1997); http://dx.doi.org/10.1063/1.1148351 (7 pages) | Cited 9 times

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The design of a device for rheological orthogonal superposition measurements on fluids is discussed. Superposing a small amplitude oscillatory motion on a steady or transient shear flow provides a technique to probe flow-induced microstructural changes in situ by means of mechanical spectroscopy. Oscillations perpendicular to the main shear flow possess intrinsic advantages over the parallel case. It is shown that the closed loop system of a force rebalanced transducer of an existing rheometer can be modified to drive an orthogonal oscillatory motion and to measure the material response. Nonhomogeneous flow, annular pumping or cavitation can occur and have to be avoided by means of a suitable flow cell. A double walled Couette cell, open at the bottom is suggested for that purpose. The device is evaluated with Newtonian fluids and with a viscoelastic polymer solution. The apparatus has two major advantages. First the forces associated with the main shear flow can be measured simultaneously with the orthogonal moduli. Second, the present design is implemented on an instrument already capable of performing parallel superposition measurements, hence the two superposition modes are available on a single instrument. The relative simplicity of the proposed modification could boost the use of orthogonal superposition measurements and facilitate the development of new applications, e.g., to probe the time evolution of the flow-induced anisotropy in complex systems. © 1997 American Institute of Physics.
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83.85.Cg Rheological measurements—rheometry
47.80.-v Instrumentation and measurement methods in fluid dynamics
47.50.-d Non-Newtonian fluid flows
47.35.-i Hydrodynamic waves
07.07.Mp Transducers

Fluorescent imaging system for global measurement of liquid film thickness and dynamic contact angle in free surface flows

M. F. G. Johnson, R. A. Schluter, and S. G. Bankoff

Rev. Sci. Instrum. 68, 4097 (1997); http://dx.doi.org/10.1063/1.1148352 (6 pages) | Cited 11 times

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Fluorescent dye dissolved in a liquid flow was used to outline liquid-gas free boundaries and, with digital imaging, to observe quantitatively surface wave propagation and pattern formation, as well as contact-line velocity and contact angle in thin film flows on horizontal and inclined substrates. Using the relatively inexpensive system described here, a fluid depth measurement with a precision of ±0.02 mm is obtained routinely in flows of several millimeters depth over an area of approximately one square meter, and essentially unlimited continuous time spans. Dynamic contact angles are measured, for the first time, on liquid fronts with significant three-dimensional curvature such as rivulets draining down an inclined plate at any speed or global location. Procedures to normalize results quantitatively for any nonuniformities of the incident illumination are given. Estimates of the contribution to the experimental error by other effects, such as variations in dye concentration and temperature, and image digital register capacity, are also discussed. Illustrative results for two fluids and several dyes are given. Refinements to decrease the local error further to ±0.005 mm or less are described. © 1997 American Institute of Physics.
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47.80.-v Instrumentation and measurement methods in fluid dynamics
68.15.+e Liquid thin films
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
68.03.Cd Surface tension and related phenomena
42.79.Pw Imaging detectors and sensors
47.35.-i Hydrodynamic waves
07.60.Pb Conventional optical microscopes

A new system for two-dimensional analysis of hydrogen on solid surfaces

K. Ishikawa, M. Yoshimura, K. Ueda, and Y. Sakai

Rev. Sci. Instrum. 68, 4103 (1997); http://dx.doi.org/10.1063/1.1148353 (4 pages) | Cited 10 times

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This article reports the development of a two-dimensional analyzer, which enables us to observe the distribution of hydrogen on surfaces. A micro-focused electron beam with low primary electron energy (<1 keV) is scanned over a sample surface, in conjunction with a time-of-flight type electron-stimulated desorption spectroscope, to obtain clear H+ ion images of a specimen surface. A line scan analysis of H+ ions on an integrated circuit and a scanning electron-stimulated desorption image of H+ ions on a Cu mesh are presented as demonstrations. © 1997 American Institute of Physics.
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82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
79.20.La Photon- and electron-stimulated desorption
07.75.+h Mass spectrometers
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics

Rapid acquisition, analysis, and display of fluorescence lifetime-resolved images for real-time applications

Peter C. Schneider and Robert M. Clegg

Rev. Sci. Instrum. 68, 4107 (1997); http://dx.doi.org/10.1063/1.1148354 (13 pages) | Cited 36 times

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Fluorescence lifetime-resolved imaging (FLI) is a relatively new technique of fluorescence imaging whereby the spatial distribution of fluorescence decay times can be determined directly at every pixel of an image simultaneously. The fluorescence decay times of many chromophores can act as sensitive gauges of their molecular environments. By employing measurement techniques that are quantitatively related to the radiative dynamics of the dye molecules (in the nanosecond time range), additional physical parameters are available for discerning different fluorophores with disparate lifetimes, or for characterizing a single fluorophore in different surroundings. Many physical processes such as molecular aggregation, binding of dyes to macromolecular species, inclusion of chromophores in specific cellular organwelles, fluorescence resonance energy transfer, and dynamic quenching determine the excited-state lifetime of a fluorophore. The FLI technique provides a way to measure these processes directly at 103–106 pixels in an image. In addition, if image domains differ with respect to the mean fluorescence lifetime, FLI can be used to improve the contrast of a fluorescence image. By measuring the fluorescence lifetime one can determine whether fluorescence intensity differences from different locations in an image can be attributed to differences in dye concentration or whether physical spectroscopic effects such as local differences in the rate of dynamic quenching are responsible. All the above applications provide new possibilities for biology and medical diagnostics. However the speed of data acquisition and analysis in current FLI instrumentation is limited in general to several minutes; for real-time applications (in order to follow rapid changes of microscopic samples or make in vivo endoscopic medical diagnosis) the present instruments are too slow. We present here a FLI apparatus that is capable of acquiring, processing, and displaying fluorescence lifetime-resolved images in quasi-real time. We also present rapid algorithms for analyzing the data in real time. © 1997 American Institute of Physics.
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87.64.K- Spectroscopy
07.05.Hd Data acquisition: hardware and software
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.-j Optical instruments and equipment
07.60.Rd Visible and ultraviolet spectrometers
78.47.-p Spectroscopy of solid state dynamics
07.60.Pb Conventional optical microscopes

High-contrast piezoelectric fiber resonance detection for near-field optical microscopy

A. Débarre, A. Richard, and P. Tchénio

Rev. Sci. Instrum. 68, 4120 (1997); http://dx.doi.org/10.1063/1.1148355 (4 pages) | Cited 1 time

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We describe a simple, piezoelectric shear-force detection for controlling the tip–sample distance in near-field optical microscopes. The fiber is glued to a V-shaped piezoelectric cantilever and the assembly is fixed to a piezoelectric plate. The piezoelectric plate excites the fiber at resonance, while the piezoelectric cantilever of small mass detects the fiber motion with a high sensitivity. When the fiber approaches within, typically, 10–20 nm above the sample, shear forces cause the signal to reduce. The only signal processing before injecting it into the feedback loop is demodulation by a lock-in amplifier. The high signal-to-background allows the fiber resonance to be identified easily. We demonstrate the performance of our system with shear-force images of two test patterns. © 1997 American Institute of Physics.
Show PACS
07.79.Fc Near-field scanning optical microscopes
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
06.60.Sx Positioning and alignment; manipulating, remote handling
07.10.Pz Instruments for strain, force, and torque
07.07.Tw Servo and control equipment; robots
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