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Dec 1999

Volume 70, Issue 12, pp. 4457-4738

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back to top OPTICS; ATOMS and MOLECULES; SPECTROSCOPY

Performance of the advanced photon source 1-BM beamline optics

J. C. Lang, G. Srajer, J. Wang, and P. L. Lee

Rev. Sci. Instrum. 70, 4457 (1999); http://dx.doi.org/10.1063/1.1150096 (6 pages) | Cited 14 times

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Bending magnet beamlines at third-generation synchrotron sources combined with well-designed optics offer unique capabilities for providing high x-ray fluxes into relatively small focal spots. This article provides a description of the x-ray optics used in the Advanced Photon Source 1-BM beamline. The performance of these optics in terms of the delivered flux ( 9×1011 ph/s/100 mA at 10 keV), energy resolution [ΔE/E ≈ 1.5×10−4 with Si(111)], and focusing properties (spot size ≈0.25×0.60 mm) is compared with that expected from ideally reflecting and shaped optics. © 1999 American Institute of Physics.
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07.85.Qe Synchrotron radiation instrumentation
41.85.Lc Particle beam focusing and bending magnets, wiggler magnets, and quadrupoles
29.20.db Storage rings and colliders
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors

True near-field optical characters of a GaAlAs semiconductor laser diode

Sy-Hann Chen, Din Ping Tsai, Yung-Fu Chen, and Pang-Ming Ong

Rev. Sci. Instrum. 70, 4463 (1999); http://dx.doi.org/10.1063/1.1150097 (3 pages)

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In this research we have taken advantage of near-field scanning optical microscopy, a recently developed technique, to test the optical nature of GaAlAs semiconductor laser diodes working at 780 nm. With this method, both the images of the topographic and the near-field intensity of the laser diodes can be simultaneously obtained. With the obtained results, we can analyze the variety of the geometric structure, the local near-field optical intensity, the propagating modes, and the near-field mode-field diameter at different working states of the laser diodes. Hereby, we can find the factors that affected the radiation cavity of the laser diode and explore its alive state. © 1999 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
07.79.Fc Near-field scanning optical microscopes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Low-cost device for ratiometric fluorescence measurements

Yordan Kostov and Govind Rao

Rev. Sci. Instrum. 70, 4466 (1999); http://dx.doi.org/10.1063/1.1150098 (5 pages) | Cited 9 times

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An all-solid-state, low-cost device for fluorescent wavelength-ratiometric detection is described. Ultrabright light-emitting diodes were used as light sources. This allowed electronic modulation of the light, simple optical configuration, and miniaturization of the instrument. Narrow-bandpass interference filters were used for wavelength separation. Detection was accomplished by high-sensitivity, large-surface PIN photodiodes. An integrating double-ramp technique with fixed upper and lower thresholds was employed for conversion of the light intensities into time intervals. The duty ratio of the output signal was a function of the fluorescence intensity ratio. Additionally, the concentration of the fluorophore could be measured. The device could be easily designed as a battery-operated version. It could be used for a variety of ratiometric fluorescence measurements. © 1999 American Institute of Physics.
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82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
07.60.Rd Visible and ultraviolet spectrometers
87.64.K- Spectroscopy
85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.Jb Light-emitting devices
42.79.Ci Filters, zone plates, and polarizers
85.60.Dw Photodiodes; phototransistors; photoresistors

Spectrophotometers intercomparison for spectrocolorimetric scale harmonization

Olivério D. D. Soares and José L. C. Costa

Rev. Sci. Instrum. 70, 4471 (1999); http://dx.doi.org/10.1063/1.1150099 (11 pages) | Cited 1 time

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An in situ comparison of spectrophotometer scales of wavelength, spectral bandwidth, and regular spectral transmittance was made in 1997/98 towards the harmonization of spectrocolorimetric scales for the measurements in transmittance mode. It used a set of three neutral density glass filter standards and a crystal with sharp absorption bands as wavelength and spectral bandwidth standard. Measurements by 22 laboratories with a great diversity of instrumentation constituted a good testing reference data to examine the aspects in scale harmonization. The intercomparison reflects a widespread misunderstanding about levels of accuracy achieved and a generalized lack of use of service standard coverage in checking uncertainty levels along the range of the concerned metrological scales. The spectral bandwidth scale is usually not taken in appropriated attention. It is demonstrated that relative small discrepancies in the spectral bandwidth setting lead to large uncertainties in the measurements that may overexceed computed uncertainty values derived from wavelength and spectral transmittance scale uncertainties. © 1999 American Institute of Physics.  
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07.60.Dq Photometers, radiometers, and colorimeters
06.20.F- Units and standards

Electron trapping materials for use in a picosecond infrared streak camera

Wenhui Fan, Xun Hou, Li Du, Lihong Niu, Wei Zhao, and Xiaoqiu Zhang

Rev. Sci. Instrum. 70, 4482 (1999); http://dx.doi.org/10.1063/1.1150100 (5 pages) | Cited 1 time

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We describe our research on the employment of an infrared upconversion screen made of electron trapping material (ETM) in combination with the high sensitivity of the S-20 photocathode responsive to visible radiation to produce a streak camera arrangement capable of viewing and recording infrared incident pulses. The ETM-based upconversion screen converts 800–1600 nm infrared radiation to visible light which is viewed or recorded by the S-20 photocathode. The peak values of the upconversion efficiency are located at 1165 nm for CaS:Eu, Sm and 1060 nm for CaS:Ce, Sm. The present experiment showed time resolution was 12.3 ps for a CaS:Eu, Sm screen and 8.4 ps for a CaS:Ce, Sm screen. The minimum detectability is 4.8×10−9 J/mm2 (minimum detectability of the coupled visible streak camera is 8.3×10−10 J/mm2). Other parameters, such as spatial resolution and dynamic range, have also been measured and analyzed. The results show ETM can be used in the measurement of infrared ultrafast phenomena up to picosecond time domain. In consideration of the limited number of trapped electrons in ETM, the infrared-sensitive streak camera consisting of an ETM-based upconversion screen is suitable to operate in the single shot mode. © 1999 American Institute of Physics.
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07.68.+m Photography, photographic instruments; xerography
06.60.Jn High-speed techniques (microsecond to femtosecond)
42.79.Pw Imaging detectors and sensors
85.60.Gz Photodetectors (including infrared and CCD detectors)

Systematic and statistical errors in correlation estimators obtained from various digital correlators

Z. Kojro, A. Riede, M. Schubert, and W. Grill

Rev. Sci. Instrum. 70, 4487 (1999); http://dx.doi.org/10.1063/1.1150101 (10 pages) | Cited 2 times

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A number of commercially available digital correlators is discussed with respect to algorithms, systematic errors, and statistical errors. Special attention has been paid to the determination of an influence of the temporal integration of measured signals on autocorrelation functions measured in digital correlators. A calculation of the standard deviation for statistical errors in correlation estimators has been performed. The result is compared with the experiment. Favorable noise properties of the multiple-tau correlator which have been reported in the literature are not confirmed. © 1999 American Institute of Physics.
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84.40.Ua Telecommunications: signal transmission and processing; communication satellites
06.20.Dk Measurement and error theory
02.50.-r Probability theory, stochastic processes, and statistics

A new high transmission infinite range mass selector for cluster and nanoparticle beams

B. von Issendorff and R. E. Palmer

Rev. Sci. Instrum. 70, 4497 (1999); http://dx.doi.org/10.1063/1.1150102 (5 pages) | Cited 48 times

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A new mass selection technique has been developed, which allows one to size-select charged particles from atoms to nanoparticles of almost unlimited size. It provides a mass resolution of m/Δm = 20–50 and a transmission of about 50% for the selected size, both independent of mass. The technique is based on the time-of-flight principle, but differs fundamentally from time-of-flight mass selection normally used. The basic idea is to use time-limited high voltage pulses to displace laterally a preaccelerated ion beam, without changing its direction or shape. As the movement of the ions perpendicular to their original beam direction is independent of their forward velocity, mass resolution and calibration does not depend on the ion beam energy. A mass selector of this type has been implemented successfully into a cluster deposition experiment and has proven to be reliable and simple to operate. © 1999 American Institute of Physics.
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07.75.+h Mass spectrometers
07.77.-n Atomic, molecular, and charged-particle sources and detectors
back to top CHARGED PARTICLE SOURCES, OPTICS and ACCELERATION

Self-excitation and operational characteristics of the crossed-field secondary emission electron source

Y. M. Saveliev, W. Sibbett, and D. M. Parkes

Rev. Sci. Instrum. 70, 4502 (1999); http://dx.doi.org/10.1063/1.1150103 (13 pages) | Cited 5 times

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We have investigated the crossed-field secondary emission (CFSE) electron source which is of a magnetron type with smooth cylindrical electrodes and axial applied magnetic field. It initiates at the negative slope d∣U∣/dt<0 of the high voltage pulse U ∼ 10–40 kV, but further current production is maintained by a self-sustained secondary electron emission regardless to the voltage pulse shape. The output electron beam is tubular with a thin ∼1 mm wall. This article is concerned mainly with the identification of the mechanisms governing the excitation and generation of the electron beam and with the determination of the principles upon which the “optimal” CFSE electron source should be designed. We have demonstrated that the CFSE diode starts operation in a self-excitation regime (i.e., without application of the primary current) provided there is a partial trapping of the multiplying electrons inside the diode boundaries. The required axial decelerating force can be established with the use of either axial electric or nonuniform magnetic fields. Amongst all of the practical methods tested (shifting of the anode with respect to the cathode, double diode, diodes with ferromagnetic parts, use of the nonuniform external magnetic field), the diode with a ferromagnetic ring insert inside the cathode cylinder has been shown to be the most successful. It has generated an ∼240 A electron beam with a perveance of ∼85 μA/V3/2. The operating range of the CFSE diode is limited by both low and high magnetic fields. The lower limit arises from a necessity to comply with a Hull cutoff condition. The upper limit is determined by the time required for development of an electron avalanche. A secondary electron emission mechanism of current production in the CFSE diode allows the diode to operate in an oscillating regime when the applied magnetic field is higher but close to the Hull cutoff value. It has thus been possible to generate 100% density modulated electron beams at a modulation frequency of ∼ 107 Hz in our present experiments with the possibility of further increases up to ∼ 108 Hz. A geometrical scaling law for the CFSE diodes has been deduced empirically. It states that the perveance of the output electron beam is proportional to the geometrical factor X = (Dk/de)(math−0.8), where Dk is the cathode diameter, de is an effective diode gap, and Ld is the diode length. The scaling law provides a tool for designing the CFSE diodes and predicting the ultimate beam currents. For a practical size of device, this electron current could be as high as ∼1 kA.
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07.77.Ka Charged-particle beam sources and detectors
29.25.Bx Electron sources

Simultaneous energy distribution and ion fraction measurements using a linear time-of-flight analyzer with a floatable drift tube

V. A. Morozov and F. W. Meyer

Rev. Sci. Instrum. 70, 4515 (1999); http://dx.doi.org/10.1063/1.1150104 (8 pages) | Cited 12 times

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A technique for simultaneous energy distribution and ion fraction measurements using a linear time-of-flight analyzer with a floatable drift tube is described. Analytical expressions for the relative collection efficiency and viewing region of the apparatus are developed as functions of the analyzed particle reduced energy and dimensionless apparatus parameters. The method was applied to studies of large-angle scattering of singly charged oxygen ions incident on Au(110), and carried out at the Oak Ridge National Laboratory’s Multicharged Ion Research Facility. Energy distributions of the scattered projectiles and the negative ion fraction are presented as a function of scattered projectile energy. As a by-product of the measurements, the relative ion detection efficiency of the particle detector was reconstructed as a function of ion impact energy on the detector. © 1999 American Institute of Physics.
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07.75.+h Mass spectrometers
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
34.35.+a Interactions of atoms and molecules with surfaces
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.-j Optical instruments and equipment

Construction of a variable-frequency radio-frequency quadrupole linac for the RIKEN heavy-ion linac

O. Kamigaito, A. Goto, Y. Miyazawa, T. Chiba, M. Hemmi, M. Kase, S. Kohara, Y. Batygin, E. Ikezawa, T. Nakagawa, and Y. Yano

Rev. Sci. Instrum. 70, 4523 (1999); http://dx.doi.org/10.1063/1.1150105 (9 pages) | Cited 7 times

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A new type of variable-frequency radio-frequency quadrupole (RFQ) linac has been constructed as a new preinjector for the RIKEN heavy-ion linac (RILAC). The RFQ resonator, based on a folded-coaxial structure with a movable shorting plate, is compact even in a low frequency region below 20 MHz. It accelerates ions with mass-to-charge ratios of 5.3 to 26.4 in the energy range up to 450 keV per charge, by varying its resonant frequency from 17.4 to 39.0 MHz. Moreover, the power loss is small in the low frequency region; the rf power consumption in cw mode is 7 kW at 17.4 MHz, and it increases to 30 kW at 39.0 MHz at the maximum intervane voltage of 36.8 kV. We initiated this project in 1991, and installed the new preinjector consisting of an electron cyclotron resonance ion source of 18 GHz and this RFQ in 1996. Since the installation, the beam intensity has become larger by more than 1 order of magnitude than that formerly obtained with the Cockcroft–Walton preinjector. Recently, the maximum power of the beam extracted from the RILAC and that from the ring cyclotron has reached 560 W and 2 kW, respectively. © 1999 American Institute of Physics.
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29.27.Ac Beam injection and extraction
29.20.-c Accelerators

Efficient, compact power supply for repetitively pulsed, “triggerless” cathodic arcs

André Anders, Robert A. MacGill, and Thomas A. McVeigh

Rev. Sci. Instrum. 70, 4532 (1999); http://dx.doi.org/10.1063/1.1150106 (4 pages) | Cited 16 times

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A power supply for “triggerless,” repetitively pulsed cathodic arcs has been developed. It is based on a thyristor-switched, high-voltage, high-current, pulse-forming network (PFN). It can provide high pulsed currents (up to 2 kA), with duration of 600 μs, and pulse repetition rate of up to 10 Hz. Higher repetition rates are possible at lower current. The rectangular pulse shape and amplitude are reproducible to within a few percent. Cathodic arc initiation is extremely reliable because the charging voltage is much higher than the minimum starting voltage for the triggerless arc initiation method. The energy utilization efficiency is very high by intentionally mismatching load and PFN impedances and by using an efficiency-enhancing diode; the stored energy is dissipated primarily in the arc.
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables

Single-ion detection using nuclear track detector CR-39 plastic

Ken-ichi Hara, Meishoku Koh, Takashi Matsukawa, Takashi Tanii, and Iwao Ohdomari

Rev. Sci. Instrum. 70, 4536 (1999); http://dx.doi.org/10.1063/1.1150107 (3 pages) | Cited 3 times

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We have developed a technique for detecting single-ions that uses CR-39 plastic. Chemical etching of the plastic enables us to visualize both the incident sites and the existence of the single-ion incidences as etch pits. Using this technique, we obtained a singularity rate of 88.3%. © 1999 American Institute of Physics.
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29.40.Gx Tracking and position-sensitive detectors
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
back to top NUCLEAR PHYSICS, FUSION and PLASMAS

Photocathode source for studying two-dimensional fluid phenomena with magnetized electron columns

D. Durkin and J. Fajans

Rev. Sci. Instrum. 70, 4539 (1999); http://dx.doi.org/10.1063/1.1150108 (3 pages) | Cited 5 times

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Magnetized electron columns are a valuable experimental tool used to study two-dimensional (2D) fluid phenomena. Traditionally, the electrons have been generated with thermionic sources, typically limiting the initial electron distribution to one filled circle and thereby restricting the range of accessible fluid phenomena. Here, we describe a new electron source based on a cesium antimonide photocathode that can generate more complicated initial electron distributions. Experiments so far have focused on the stability of 2D vortex patterns. © 1999 American Institute of Physics.
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85.60.Ha Photomultipliers; phototubes and photocathodes
07.77.Ka Charged-particle beam sources and detectors
47.80.-v Instrumentation and measurement methods in fluid dynamics
47.32.C- Vortex dynamics

The drift source: A negative ion source module for direct current multiampere ion beams

A. Simonin, G. Delogu, C. Desgranges, and M. Fumelli

Rev. Sci. Instrum. 70, 4542 (1999); http://dx.doi.org/10.1063/1.1150109 (3 pages) | Cited 1 time

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The concept of a modular large size ion source is under investigation in our laboratory for the development of the very intense (tens of amperes) negative ion (D−) beams needed for neutral beam injection in thermonuclear fusion research. The basic idea is to develop a compact small ion source producing the required ion flux (20–30 mA/cm2) over a total surface of about 200 cm2 and designed in such a way that it can easily be juxtaposed with other identical modules. A large negative ion source of any size (up to several m2) and shape could be realized as a set of several modules. The anticipated advantage of this concept is the minimization of the risk inherent in a large extrapolation in size (e.g., ≈1.0 m2 for an ignition device to test engineering concepts) of the present ion sources. In this context, we have developed and tested a source module, called the DRIFT source, whose main properties are presented in this article. The particular magnetic field configuration of this module ensures, in a simplified way, a very good plasma confinement allowing operation of the source at very low filling pressures. Up to now, a D− current of 1 A (20 mA/cm2) 50 keV energy, 1 s pulse length, was obtained with cesium vapor seeding at 0.15 Pa source pressure with an arc power of 2.5 kW/l (12 kW). © 1999 American Institute of Physics.
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29.25.Ni Ion sources: positive and negative
41.75.Cn Negative-ion beams
07.77.Ka Charged-particle beam sources and detectors

Nonstationary signal analysis of magnetic islands in plasmas

E. D. Taylor, C. Cates, M. E. Mauel, D. A. Maurer, D. Nadle, G. A. Navratil, and M. Shilov

Rev. Sci. Instrum. 70, 4545 (1999); http://dx.doi.org/10.1063/1.1150110 (7 pages) | Cited 8 times

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Rotating magnetic islands produce fluctuations on a variety of diagnostics in magnetic fusion energy plasmas. The analysis of these fluctuations requires the calculation of the amplitude, phase, and frequency of the oscillations. These three spectral quantities generally evolve in time, necessitating nonstationary signal analysis techniques. The Hilbert transform offers an efficient and accurate method of calculating these three quantities from one diagnostic signal. This feature allows the Hilbert transform to determine the success of the active rotation control of magnetic islands, and to calculate the profile of the diagnostic measurements in a frame of reference co-rotating with the magnetic island. Comparisons to quadrature and spectrogram techniques demonstrate the accuracy of the Hilbert transform method. © 1999 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
52.55.Fa Tokamaks, spherical tokamaks
52.25.Gj Fluctuation and chaos phenomena
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
84.40.Ua Telecommunications: signal transmission and processing; communication satellites
02.30.Uu Integral transforms
02.30.Vv Operational calculus

Fast bolometric measurements on the TCV tokamak

I. Furno, H. Weisen, J. Mlynar, R. A. Pitts, X. Llobet, Ph. Marmillod, and G. P. Pochon

Rev. Sci. Instrum. 70, 4552 (1999); http://dx.doi.org/10.1063/1.1150111 (5 pages) | Cited 12 times

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The design and first results are presented from a bolometric diagnostic with high temporal resolution recently installed on the TCV tokamak. The system consists of two pinhole cameras viewing the plasma from above and below at the same toroidal location. Each camera is equipped with an AXUV-16ELO linear array of 16 p–n junction photodiodes, characterized by a flat spectral sensitivity from ultraviolet to x-ray energies, a high temporal response (<0.5 μs), and insensitivity to low-energy neutral particles emitted by the plasma. This high temporal resolution allows the study of transient phenomena such as fast magnetohydrodynamic (MHD) activity hitherto inaccessible with standard bolometry. In the case of purely electromagnetic radiation, good agreement has been found when comparing results from the new diagnostic with those from a standard metal foil bolometer system. This comparison has also revealed that the contribution of neutrals to the foil bolometer measurements can be extremely important under certain operating conditions, precluding the application of tomographic techniques for reconstruction of the radiation distribution. © 1999 American Institute of Physics.
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52.55.Fa Tokamaks, spherical tokamaks
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)

Setup for potential bias experiments on the Saha Institute of Nuclear Physics tokamak

J. Ghosh, R. Pal, and P. K. Chattopadhyay

Rev. Sci. Instrum. 70, 4557 (1999); http://dx.doi.org/10.1063/1.1150112 (5 pages) | Cited 2 times

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An experimental setup for studying the influence of the radial electric field on very low qa plasma on the Saha Institute of Nuclear Physics tokamak is presented. A high current, high voltage pulsed power supply, using a semiconductor controlled rectifier (SCR) as a dc switch is developed and used to bias a tungsten electrode inserted inside the plasma. The electrode’s exposed length and its position inside the plasma are controlled by a double bellows assembly to optimize the electrode-exposed length. We show that using the force commutation method to turn the SCR off to get the power pulse desired has good potential for carrying out similar kinds of studies, especially in a low budget small tokamak. © 1999 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
52.55.Fa Tokamaks, spherical tokamaks
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables
52.40.Hf Plasma-material interactions; boundary layer effects
52.25.Fi Transport properties
back to top BASIC PHENOMENA

Superconducting magnetic shields for SQUID applications

J. R. Claycomb and J. H. Miller

Rev. Sci. Instrum. 70, 4562 (1999); http://dx.doi.org/10.1063/1.1150113 (7 pages) | Cited 10 times

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We investigate the shielding of superconducting and μ-metal forms in axial and transverse directed background magnetic noise fields. Analytical expressions are obtained for the improvement in signal-to-noise ratio obtained by placing a superconducting disk in the presence of a dipole source and a uniform noise field. Axial and transverse shielding factors are then compared for identical superconducting and μ-metal cylinders. The signal-to-noise ratio is found to be infinite at certain points inside a superconducting cylinder as well as a superconducting cylinder with a central partition. Shielding factors obtained here are relevant to SQUID measurements of small dipole source fields in the presence of large background noise fields such as those encountered in biomagnetism and nondestructive evaluation. © 1999 American Institute of Physics.
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07.55.Ge Magnetometers for magnetic field measurements
85.25.Dq Superconducting quantum interference devices (SQUIDs)
07.55.Nk Magnetic shielding in instruments

Selection criteria for microphones used in pulsed nonresonant gas-phase photoacoustics

I. G. Calasso and M. W. Sigrist

Rev. Sci. Instrum. 70, 4569 (1999); http://dx.doi.org/10.1063/1.1150114 (10 pages) | Cited 12 times

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Theoretical and experimental investigations aimed at optimizing the detection performance in nonresonant pulsed photoacoustic (PA) studies in the gas phase by selecting microphones with appropriate characteristics are presented. An analytical function is introduced that allows the simulation of the measured signal-to-noise-ratio (SNR) for given microphone specifications. The crucial parameters for maximum SNR are the microphone responsivity, its bandwidth, and noise characteristics. Good agreement between calculated and measured PA signal shapes and their fast Fourier transform spectra is obtained. Comparisons of experimental data recorded in a gas mixture of 100 ppm ethylene buffered in synthetic air with various condenser and electret microphones with different characteristics confirm our theoretical predictions. The peak amplitude of the recorded microphone signal increases with decreasing laser beam radius rb. However, for standard microphones with a bandwidth of ≈20 kHz, there is no reason to use rb<0.5 mm because the spectral composition of the signal shape for frequencies <20 kHz remains unchanged. A large microphone bandwidth of a few 100 kHz is advantageous for resolving the temporal evolution of the PA signal but it can be disadvantageous for trace gas monitoring due to an enhanced noise level. Our simulation permits the selection of the most appropriate microphone for maximum SNR under given experimental conditions. Finally, an analysis on the pressure dependence of the responsivity of a selected microphone is presented that is of interest when performing trace gas measurements at reduced pressure to enhance the detection selectivity. © 1999 American Institute of Physics.
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43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
43.38.Kb Microphones and their calibration
82.80.Kq Energy-conversion spectro-analytical methods (e.g., photoacoustic, photothermal, and optogalvanic spectroscopic methods)
43.58.Kr Spectrum and frequency analyzers and filters; acoustical and electrical oscillographs; photoacoustic spectrometers; acoustical delay lines and resonators

Direct scanning tunneling microscope detection of laser induced ultrasonic pulses with nanometer resolution

J. Jersch, F. Demming, I. Fedotov, and K. Dickmann

Rev. Sci. Instrum. 70, 4579 (1999); http://dx.doi.org/10.1063/1.1150115 (3 pages) | Cited 1 time

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We show the use of scanning tunneling microscope (STM) with a self-designed wide-bandwidth current preamplifier (50 MHz) for direct registration of ultrasonic pulses induced by nanosecond laser pulses in substrate. The changes in tip–sample separation caused by ultrasonic vibrations are seen as perturbations in tunneling current. At moderate incident laser pulse energy of 1–2 mJ ultrasonic waves in glass rod and silica wafer were observed. This wide-band signal, low noise registration in addition with nanometer spatial resolution of a STM opens new possibilities in investigations of ultrasonic near-field distribution, elastic material properties on a nanometer scale, and measurements of the ultrasound velocity in laser ultrasonics. © 1999 American Institute of Physics.
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07.79.Cz Scanning tunneling microscopes
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
43.35.Yb Ultrasonic instrumentation and measurement techniques
back to top MICROSCOPY and IMAGING

Operation of a separated-type x-ray interferometer for phase-contrast x-ray imaging

Akio Yoneyama, Atsushi Momose, Eiichi Seya, Keiichi Hirano, Tohoru Takeda, and Yuji Itai

Rev. Sci. Instrum. 70, 4582 (1999); http://dx.doi.org/10.1063/1.1150116 (5 pages) | Cited 4 times

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Aiming at large-area phase-contrast x-ray imaging, a separated-type x-ray interferometer system was designed and developed to produce 25×20 mm interference patterns. The skew-symmetric optical system was adopted because of the feasibility of alignment. The rotation between the separated crystal blocks was controlled within a drift of 0.06 nrad using a feedback positioning system. This interferometer generated a 25×15 mm interference pattern with 0.07 nm synchrotron x-rays. A slice of a rabbit’s kidney was observed, and its tubular structure could be revealed in a measured phase map. © 1999 American Institute of Physics.
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07.85.Qe Synchrotron radiation instrumentation
87.64.-t Spectroscopic and microscopic techniques in biophysics and medical physics
07.07.Tw Servo and control equipment; robots

Application to dielectric, metallic, and magnetic samples of a transmission mode scanning near field optical microscope with normal force distance regulation on bent optical fibers

T. David, C. Chicanne, N. Richard, J. R. Krenn, F. Scheurer, K. Ounadjela, M. Hehn, Y. Lacroute, and J. P. Goudonnet

Rev. Sci. Instrum. 70, 4587 (1999); http://dx.doi.org/10.1063/1.1150117 (8 pages) | Cited 4 times

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We have developed a scanning near field optical microscope (SNOM) based on bent optical fiber probes with a normal force atomic force microscopies (AFM) regulation. The optical fibers are used both as optical probes and AFM cantilevers. This SNOM was especially developed for transmission mode SNOM and it offers the possibility to realize simultaneously all AFM modes imaging and optical analysis. The fiber is used to illuminate the sample and the detection is performed through an inverted optical microscope. This article presents results obtained on dielectric, metallic, and magnetic samples with submicronic features. We have resolved the object of 80 nm in size, separated by 40 nm, and we illustrate the capabilities of our SNOM in investigating, locally, the variation of the optical properties of periodic samples, even though contaminant, and for a large variety of samples. © 1999 American Institute of Physics.
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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
07.79.Lh Atomic force microscopes
68.35.B- Structure of clean surfaces (and surface reconstruction)
07.79.Fc Near-field scanning optical microscopes

Low temperature ultrahigh vacuum cross-sectional scanning tunneling microscope for luminescence measurements

Yoonho Khang, Yeonjoon Park, Miquel Salmeron, and Eicke R. Weber

Rev. Sci. Instrum. 70, 4595 (1999); http://dx.doi.org/10.1063/1.1150118 (5 pages) | Cited 5 times

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We have constructed a scanning tunneling microscope with simultaneous light collection capabilities in order to investigate the opto-electronic properties of semiconductors. The microscope has in situ sample cleavage mechanism for cross-sectional sample. In order to reach low temperature (4 K), we used a specially designed cryostat. The efficiency of light collection generated in the tip-surface junction was greatly improved by use of a small parabolic mirror with the tip located at its focal point. © 1999 American Institute of Physics.
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07.79.Cz Scanning tunneling microscopes
78.60.Hk Cathodoluminescence, ionoluminescence
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials

Vibration compensation for high speed scanning tunneling microscopy

D. Croft and S. Devasia

Rev. Sci. Instrum. 70, 4600 (1999); http://dx.doi.org/10.1063/1.1150119 (6 pages) | Cited 40 times

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Low scanning speed is a fundamental limitation of scanning tunneling microscopes (STMs), making real time imaging of surface processes and nanofabrication impractical. The effective scanning bandwidth is currently limited by the smallest resonant vibrational frequency of the piezobased positioning system (i.e., scanner) used in the STM. Due to this limitation, the acquired images are distorted during high speed operations. In practice, the achievable scan rates are much less than 1/10th of the resonant vibrational frequency of the STM scanner. To alleviate the scanning speed limitation, this article describes an inversion-based approach that compensates for the structural vibrations in the scanner and thus, allows STM imaging at high scanning speeds (relative to the smallest resonant vibrational frequency). Experimental results are presented to show the increase in scanning speeds achievable by applying the vibration compensation methods. © 1999 American Institute of Physics.
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07.79.Cz Scanning tunneling microscopes
07.10.Fq Vibration isolation
07.05.Dz Control systems
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Improved laser-heated pedestal growth system for crystal growth in medium and high isostatic pressure environment

D. Reyes Ardila, J. P. Andreeta, C. T. M. Ribeiro, and M. Siu Li

Rev. Sci. Instrum. 70, 4606 (1999); http://dx.doi.org/10.1063/1.1150120 (3 pages) | Cited 6 times

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A modified apparatus for single-crystal-fiber growth in an isostatic gaseous environment and for a large range of pressure (100 mbar up to 100 bar) using a floating-zone-type method known as laser-heated pedestal growth is described. The difficulties and advantages of its design are discussed through examples of crystal growth of some oxide materials. © 1999 American Institute of Physics.
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81.10.Fq Growth from melts; zone melting and refining
42.62.-b Laser applications
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