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Aug 2000

Volume 71, Issue 8, pp. 2959-3233

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back to top OPTICS; ATOMS and MOLECULES; SPECTROSCOPY

Submillimeter resolution in one-dimensional position measurements of γ-ray photons by using a CsI(Tl) scintillator coupled to a linear array of silicon drift detectors

C. Fiorini, C. Labanti, and F. Perotti

Rev. Sci. Instrum. 71, 2979 (2000); http://dx.doi.org/10.1063/1.1305815 (5 pages) | Cited 1 time

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We present the one-dimensional (1D) position and energy resolution results obtained by a γ-ray detector based on a single CsI(Tl) scintillator coupled to a linear array of silicon drift detectors (SDDs). The present prototype has been realized in order to investigate the basic performances of this new architecture in view of the realization of Anger cameras for 2D imaging in nuclear medicine, based on the use of SDDs instead of photomultiplier tubes. The SDD provides a high value of quantum efficiency to the scintillation light, typical of a silicon photodetector, and is moreover characterized by a lower value of electronics noise with respect to conventional silicon photodiodes, thanks to the low value of output capacitance. At 122 keV the present detector shows a position resolution better than 0.5 mm FWHM, and an energy resolution of about 13% FWHM. The experimental setup is described and the most significant experimental results are presented. © 2000 American Institute of Physics.
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29.40.Gx Tracking and position-sensitive detectors
29.40.Mc Scintillation detectors
87.56.Da Ancillary equipment
87.57.U- Nuclear medicine imaging
29.40.Wk Solid-state detectors
87.63.-d Non-ionizing radiation equipment and techniques

Obtaining frequency markers of variable separation with a spherical mirror Fabry-Perot interferometer

Dmitry Budker, Simon M. Rochester, and Valeriy V. Yashchuk

Rev. Sci. Instrum. 71, 2984 (2000); http://dx.doi.org/10.1063/1.1304879 (4 pages) | Cited 4 times

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A compact (L ≈ 5 cm) spherical Fabry-Pérot interferometer with adjustable mirror spacing is used to produce interference fringes with frequency separation (c/2L)/N, N≲20. These fringes are used as frequency markers in a Doppler-free saturation spectroscopy experiment. The conditions for observation of the fringes are discussed in terms of the eigenmodes of the cavity with high transverse indices. © 2000 American Institute of Physics.
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07.60.Ly Interferometers
42.79.Bh Lenses, prisms and mirrors

The use of pressure controlled Fabry-Pérot interferometer with linear scanning of data for Brillouin-type experiments

Tomasz Błachowicz

Rev. Sci. Instrum. 71, 2988 (2000); http://dx.doi.org/10.1063/1.1304872 (4 pages) | Cited 2 times

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The article presents results from work with Fabry-Pérot interferometers in Brillouin laser light scattering experiments, where optical signals of very low level intensity are observed. The information presented here can be useful in other types of optical experiments where scanning in the Fabry-Pérot interferometer spectral range has to be used. In such situations the shape of spectral lines as well as their relative distances can be detected. The key to the solution presented here is the use of a silicon-membrane pressure sensor coupled to a pressure chamber. It makes it possible to view spectral lines equally spaced after nonlinear flow of air from a chamber where the Fabry-Pérot interferometer is placed. Linear scanning in the spectral range equal to a frequency of about 150 GHz is possible. The method can be applied to Fabry-Pérot’s etalons, very frequently produced some years ago. Now it should find new fields of application, in a simple and cost effective way, in student laboratories as well as in other research institutions. © 2000 American Institute of Physics.
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07.60.Ly Interferometers
78.35.+c Brillouin and Rayleigh scattering; other light scattering
42.65.Es Stimulated Brillouin and Rayleigh scattering
07.60.Rd Visible and ultraviolet spectrometers

High power solid state single-frequency pulsed laser for Doppler velocimeters

A. Ludmirsky, E. Moshe, Y. Horovitz, M. Fraenkel, Z. Henis, and I. B. Goldberg

Rev. Sci. Instrum. 71, 2992 (2000); http://dx.doi.org/10.1063/1.1304876 (3 pages) | Cited 1 time

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A high power solid state single-frequency pulsed oscillator/amplifier laser system developed for Doppler velocimeters is described. The oscillator is based on a continuous wave diode pumped Nd:YAG single frequency laser, operating at a wavelength of 1064 nm. The output of the laser is chopped into pulses of 100 ns to 10 μs duration and 10 Hz repetition rate by a Pockels cell and polarizers. The pulses are amplified by a double pass flash-pumped Nd:YAG amplifier to kW power levels. The amplified laser pulses are frequency doubled with high efficiency to 532 nm in a periodically poled KTiOPO4 crystal. This ladder system is useful for many velocimeter applications and its utilization in an optically recording velocity interferometer system is described. © 2000 American Institute of Physics.
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42.60.By Design of specific laser systems
42.55.Rz Doped-insulator lasers and other solid state lasers
07.60.Ly Interferometers
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
06.30.Gv Velocity, acceleration, and rotation
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
47.80.-v Instrumentation and measurement methods in fluid dynamics

dc and ac optical nulling bridges for sensitive transmittance measurements

V. Argueta-Díaz, M. Trejo-Valdez, and A. García-Valenzuela

Rev. Sci. Instrum. 71, 2995 (2000); http://dx.doi.org/10.1063/1.1305509 (9 pages) | Cited 3 times

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We present a formal comparison between dc and ac nulling optical bridges. We consider their performance in monitoring over long periods of time (several minutes), small and slow (in a time scale of seconds) changes in transmittance of an optical component. We consider two fundamentally different ac optical bridges (OB), an amplitude modulated optical bridge (AM-OB), and a switching optical bridge (Sw-OB). For each OB, we derive a general expression for the minimum detectable change in transmittance (∣ΔT∣min), taking into account all the important noises. It is found that under optimum conditions the dc- and AM-OB have similar detection limits imposed by the 1/f noise of the photodetectors. It is shown that the Sw-OB can in principle overcome the 1/f noise of the detector and approach the shot-noise limit; however, it is sensitive to switching device imperfections (to first order in smallness), which could easily prevent achieving a detection limit below the 1/f noise. It is also shown that the Sw-OB has intrinsic advantages over the dc- and AM-OB for its use in remote sensors. It can eliminate more efficiently noise induced along the propagation of light from the sensing point to the photodetector. We conclude that when using low power optics (P ⩽ 1 mW) and considering a bench instrument, the dc- and AM-OB can be used for a target resolution down to ∣ΔT∣min ≈ 10−5–10−6. The Sw-OB optical bridges should be chosen if ∣ΔT∣min ≈ 10−6–10−8 is to be attempted. In any case, strict conditions are to be met before considering approaching the detection limits imposed by electronic noises. These conditions are discussed in detail. In particular, atmospheric isolation will be needed in general below ∣ΔT∣min ≈ 10−4. © 2000 American Institute of Physics.
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07.60.-j Optical instruments and equipment

Compact fiber-optic fluorosensor using a continuous-wave violet diode laser and an integrated spectrometer

Ulf Gustafsson, Sara Pålsson, and Sune Svanberg

Rev. Sci. Instrum. 71, 3004 (2000); http://dx.doi.org/10.1063/1.1305814 (3 pages) | Cited 15 times

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A compact fluorosensor with a fiber-optic measurement probe was developed, employing a continuous-wave violet diode laser as an exciting source and an integrated digital spectrometer for the monitoring of fluorescence signatures. The system has the dimensions 22×13×8 cm3, and features 5 nm spectral resolution and an excellent detectivity. Results from measurements on vegetation and human premalignant skin lesions are reported, illustrating the potential of the instrument. © 2000 American Institute of Physics.
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42.81.Pa Sensors, gyros
07.60.Rd Visible and ultraviolet spectrometers
42.79.Pw Imaging detectors and sensors
42.62.Be Biological and medical applications
87.63.L- Visual imaging
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy

Radiometric analysis of the light coupled by optimally cut plastic optical fiber amplitude modulating reflectance displacement sensors

S. Hadjiloucas, J. J. Irvine, and J. W. Bowen

Rev. Sci. Instrum. 71, 3007 (2000); http://dx.doi.org/10.1063/1.1304858 (3 pages) | Cited 1 time

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A radiometric analysis of the light coupled by optical fiber amplitude modulating extrinsic-type reflectance displacement sensors is presented. Uncut fiber sensors show the largest range but a smaller responsivity. Single cut fiber sensors exhibit an improvement in responsivity at the expense of range. A further increase in responsivity as well as a reduction in the operational range is obtained when the double cut sensor configuration is implemented. The double cut configuration is particularly suitable in applications where feedback action is applied to the moving reflector surface. © 2000 American Institute of Physics.
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42.81.Pa Sensors, gyros
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
07.60.Hv Refractometers and reflectometers
back to top PARTICLE SOURCES, OPTICS and ACCELERATION

Effective initial sorting of undulator magnets

Takashi Tanaka and Hideo Kitamura

Rev. Sci. Instrum. 71, 3010 (2000); http://dx.doi.org/10.1063/1.1304878 (6 pages)

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A new method to optimize undulator magnet arrangement is considered. Field-integral values of magnet blocks instead of magnetic flux distributions are used to determine the magnet arrangement for the purpose of not only reducing integrated multipole but also improving spectral intensity. A system composed of a fast-rotating coil and a lock-in amplifier has been constructed for fast and accurate measurement of field integrals. A ten-period test undulator has been assembled with the best and the worst arrangements determined by the optimization method. Undulator performances such as integrated multipoles, orbit deviations, and phase errors have been measured at various gap values, which showed a good agreement with expectations in both cases. © 2000 American Institute of Physics.
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29.27.Eg Beam handling; beam transport
41.85.Lc Particle beam focusing and bending magnets, wiggler magnets, and quadrupoles
07.85.Qe Synchrotron radiation instrumentation
07.55.Db Generation of magnetic fields; magnets

Design of a scanning atom probe with improved mass resolution

A. Cerezo, T. J. Godfrey, M. Huang, and G. D. W. Smith

Rev. Sci. Instrum. 71, 3016 (2000); http://dx.doi.org/10.1063/1.1304877 (8 pages) | Cited 6 times

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A design for a high mass resolution scanning atom probe is described, which utilizes a two-conductor microelectrode held at 10–100 μm from the specimen. Field evaporation pulses are applied to the part of the counter-electrode closest to the specimen, while the output is maintained at ground. If the gap between the two conductors is small, field evaporated ions pass through the microelectrode while the pulse voltage is essentially constant, and thus the resultant spread in ion energies is small and the mass resolution in time-of-flight mass spectrometry is correspondingly improved. Initial results indicate improvements of 4–5 times over the mass resolution obtained with a simple counter electrode. © 2000 American Institute of Physics.
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82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
07.75.+h Mass spectrometers
79.70.+q Field emission, ionization, evaporation, and desorption
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

A new type of rocket-borne neutral atom analyzer

K. Asamura, T. Mukai, Y. Saito, Y. Kazama, and S. Machida

Rev. Sci. Instrum. 71, 3024 (2000); http://dx.doi.org/10.1063/1.1304874 (7 pages) | Cited 1 time

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A new-type analyzer for measurement of energetic neutral atoms (ENAs) in an energy range of 4–40 keV is described. Incoming ENAs are ionized by electron stripping at passage of an ultrathin carbon foil. After post-acceleration (by 3 kV), the particles are guided to a time-of-flight (TOF) section over a wide energy-per-charge bandwidth by means of electrostatic deflection without any potential sweeping for electrodes. Then, their velocity is measured by the TOF technique, with which species can also be identified, because the particle energies are limited to a certain range by the electrostatic deflector and acceleration upon entering the TOF section. A unique feature in the present analyzer is in the rejection method of extreme ultraviolet (EUV) contamination. In contrast to conventional usage of serrated electrodes for EUV attenuation, one of the electrostatic deflection plates is machined to be so flat that EUV photons are guided to a photon trap regardless of wavelength. The TOF device can also be used in a coincidence mode for noise suppression. The present instrument was flown on a sounding rocket, and has successfully measured ENAs precipitating into the low-latitude upper atmosphere from the magnetosphere. © 2000 American Institute of Physics.
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94.80.+g Instrumentation for space plasma physics, ionosphere, and magnetosphere
07.87.+v Spaceborne and space research instruments, apparatus, and components (satellites, space vehicles, etc.)

Filamentless operation of a high-power electron bombardment furnace used for refractory metals atom beam generation

M. S. Bhatia, A. S. Dongare, V. K. Mago, and B. Lal

Rev. Sci. Instrum. 71, 3031 (2000); http://dx.doi.org/10.1063/1.1305813 (6 pages)

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Filamentless operation of a 10 kW electron bombardment vacuum furnace in the temperature range 2000–3000 K is described. This novel mode of operation was useful in obtaining low magnetic field ambient around the furnace. This enabled us to carry out sensitive measurement of atomic properties of refractory metal atoms with the help of well-collimated neutral atomic beams. In this furnace, the necessary electron emission was derived from the innermost heat shield, which was coated with a low work-function metal and placed closer to the boat to attain high enough temperatures. The destabilizing effect of high degree of electrothermal feedback was effectively countered by using a nonlinear ballast consisting of a bank of tungsten lamps. The ionized fraction in the atomic beam was removed with the help of biased grids. This furnace has provided uninterrupted service to many users over the last few years. © 2000 American Institute of Physics.
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07.20.Hy Furnaces; heaters
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
07.77.Gx Atomic and molecular beam sources and detectors
07.07.Tw Servo and control equipment; robots

A computer-controlled Gerdien atmospheric ion counter

K. L. Aplin and R. G. Harrison

Rev. Sci. Instrum. 71, 3037 (2000); http://dx.doi.org/10.1063/1.1305511 (5 pages) | Cited 13 times

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Accurate measurements of atmospheric ions are desirable in order to investigate atmospheric aerosol processes. A cylindrical capacitor ion counter is described which has a flexible computerized control system, to allow selection of ion mobility by changing the bias voltage across the capacitor. Ion measurements obtained correlate well with the ionization rate measured with an adjacent Geiger counter in clean air. Measurements of air ions using the device in current and voltage decay modes show consistent results. The collecting electrode is exposed directly in the air stream to be sampled, eliminating diffusive losses in intake tubes. The system can measure ion concentrations from 20 ions cm−3 (including typical atmospheric concentrations) and can sample ions rapidly. These characteristics enable comprehensive air conductivity measurements to be made. © 2000 American Institute of Physics.
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93.85.-q Instruments and techniques for geophysical research: Exploration geophysics
92.60.Mt Particles and aerosols
92.60.Ls Ion chemistry of the atmosphere
07.05.Dz Control systems

A highly sensitive electron spectrometer for crossed-beam collisional ionization: A retarding-type magnetic bottle analyzer and its application to collision-energy resolved Penning ionization electron spectroscopy

Yoshihiro Yamakita, Hideyasu Tanaka, Ryo Maruyama, Hideo Yamakado, Fuminori Misaizu, and Koichi Ohno

Rev. Sci. Instrum. 71, 3042 (2000); http://dx.doi.org/10.1063/1.1305819 (8 pages) | Cited 11 times

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A highly sensitive electron energy analyzer which utilizes a “magnetic bottle” combined with a retarding electrostatic field has been developed for Penning ionization electron spectroscopy. A beam of metastable rare-gas atoms is crossed with a continuous supersonic sample beam in the source region of the analyzer. The emitted electrons are collected by an inhomogeneous magnetic field (the magnetic bottle effect) with a high efficiency of nearly 4π solid angle, which is more than 103 times higher than that of a conventional hemispherical analyzer. The kinetic energy of electrons is analyzed by scanning the retarding field in a flight tube of the analyzer in the presence of a weak magnetic field. The velocity of the metastable atoms can also be resolved by a time-of-flight method in the present instrument. Examples of Penning ionization electron energy spectra as a function of collision energy are presented for Ar and N2 with metastable He∗(2 3S) atoms. This instrument has opened the possibility for extensive studies of Penning ionization electron spectroscopy for low-density species, such as clusters, ions, electronically excited species, unstable or transient species, and large molecules with low volatility. © 2000 American Institute of Physics.
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07.81.+a Electron and ion spectrometers
34.50.Fa Electronic excitation and ionization of atoms (including beam-foil excitation and ionization)
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.-j Optical instruments and equipment
37.20.+j Atomic and molecular beam sources and techniques

Direct imaging of highly charged ions in an electron beam ion trap

J. V. Porto, I. Kink, and J. D. Gillaspy

Rev. Sci. Instrum. 71, 3050 (2000); http://dx.doi.org/10.1063/1.1305521 (9 pages) | Cited 11 times

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We have directly observed the ion cloud distribution in an electron beam ion trap using visible and ultraviolet fluorescence from lines in the ground term of Ar13+, Xe31+ and Xe32+ ions. Using a gated intensified charge coupled device camera, we have the capability to measure both static and dynamic ion cloud distributions. The images provide information about the trapped highly charged ions which is difficult to obtain by other methods. To demonstrate the usefulness of the technique, we took images of static ion clouds under different conditions and compared the distributions to a simple model. We also recorded time resolved images which show that we can monitor the relaxation of the ion cloud toward equilibrium when the trapping conditions are suddenly changed. The information provided by such measurements can be used to improve models of ion cloud dynamics and, combined with modeling, these techniques can help improve measurements of atomic data using electron beam ion traps.
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37.20.+j Atomic and molecular beam sources and techniques

Beamlet–beamlet interaction in a multi-aperture negative ion source

Yukio Fujiwara, Masaya Hanada, Yoshikazu Okumura, Kazuhiro Watanabe, and Kenichi Kawai

Rev. Sci. Instrum. 71, 3059 (2000); http://dx.doi.org/10.1063/1.1305515 (6 pages) | Cited 10 times

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Beamlet–beamlet interaction in an acceleration region of a multi-aperture hydrogen negative ion source was experimentally studied. Deflection angle of beamlets was measured in the case of both five-row beamlets and three-row beamlets at the beam energy ranging from 86 to 178 keV. The deflection angle of beamlets at the edge of a beam was about 3 mrad larger than that at the center of the beam. The deflection angle was independent of beam energy at the same perveance. Repulsive force due to the beamlet–beamlet interaction proved to be inversely proportional to the square of distance approximately. From a beam trajectory calculation, shaping of a grid was confirmed to be effective to compensate the beamlet–beamlet interaction. © 2000 American Institute of Physics.
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29.25.Ni Ion sources: positive and negative
07.77.Ka Charged-particle beam sources and detectors
back to top NUCLEAR PHYSICS, FUSION and PLASMAS

A new device for dynamic sampling of radon in air

J. C. Lozano, V. Gómez Escobar, and F. Vera Tomé

Rev. Sci. Instrum. 71, 3065 (2000); http://dx.doi.org/10.1063/1.1305820 (7 pages)

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A new system is proposed for the active sampling of radon in air, based on the well-known property of activated charcoal to retain radon. Two identical carbon-activated cartridges arranged in series remove the radon from the air being sampled. The air passes first through a desiccant cell and then the carbon cartridges for short sampling times using a low-flow pump. The alpha activity for each cartridge is determined by a liquid scintillation counting system. The cartridge is placed in a holder into a vial that also contains the appropriate amount of scintillation cocktail, in a way that avoids direct contact between cocktail and charcoal. Once dynamic equilibrium between the phases has been reached, the vials can be counted. Optimum sampling conditions concerning flow rates and sampling times are determined. Using those conditions, the method was applied to environmental samples, straightforwardly providing good results for very different levels of activity. © 2000 American Institute of Physics.
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07.88.+y Instruments for environmental pollution measurements
29.40.Mc Scintillation detectors
89.60.-k Environmental studies
87.55.N- Radiation monitoring, control, and safety

Spectral resolution for a five-element, filtered, x-ray detector array using the method of Backus and Gilbert

D. L. Fehl, F. Biggs, G. A. Chandler, and W. A. Stygar

Rev. Sci. Instrum. 71, 3072 (2000); http://dx.doi.org/10.1063/1.1304869 (8 pages) | Cited 7 times

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The generalized method of Backus and Gilbert (BG) is described and applied to the inverse problem of obtaining the spectrum from a five-channel, filtered array of x-ray detectors. This diagnostic is routinely fielded on the Z facility at Sandia National Laboratories to study soft x-ray photons (∼100–2300 eV), emitted by high density Z-pinch plasmas. The BG method defines spectral resolution limits on the system of response functions that are in good agreement with a classical unfold method, based on a histogram representation of the source spectrum. The resolution so defined is independent of the source spectrum. For noise-free, simulated data the BG approximating function is also in reasonable agreement with the source spectrum (150 eV blackbody) and the unfolded spectrum. This function may be used as an initial trial function for iterative methods or a regularization model.© 2000 American Institute of Physics.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
07.85.Nc X-ray and γ-ray spectrometers
52.70.La X-ray and γ-ray measurements

Valve and nozzle design for injecting a shell-on-shell gas puff load into a z pinch

Y. Song, P. Coleman, B. H. Failor, A. Fisher, R. Ingermanson, J. S. Levine, H. Sze, E. Waisman, R. J. Commisso, T. Cochran, J. Davis, B. Moosman, A. L. Velikovich, B. V. Weber, D. Bell, et al.

Rev. Sci. Instrum. 71, 3080 (2000); http://dx.doi.org/10.1063/1.1305817 (5 pages) | Cited 19 times

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We have developed a dual-plenum gas valve coupled to a double shell nozzle for the generation of “shell-on-shell” gas loads in z-pinch plasma radiation source experiments. The gas density profiles of the nozzles have been characterized with laser interferometry. This valve/nozzle combination has been successfully fielded on the Double-EAGLE and Saturn pulsed-power generators. The design and characterization of the shell-on-shell valve/nozzle are presented in this article. © 2000 American Institute of Physics.
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52.55.Ez Theta pinch
52.30.-q Plasma dynamics and flow
back to top BASIC PHENOMENA

Correlation-based phase noise measurements

Enrico Rubiola and Vincent Giordano

Rev. Sci. Instrum. 71, 3085 (2000); http://dx.doi.org/10.1063/1.1304871 (7 pages) | Cited 10 times

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In the characterization of the phase noise of a component, it is common practice to measure the cross-spectrum density at the output of two phase detectors that simultaneously compare the component output signal to a common reference. This technique, which is based on correlation and averaging, allows the rejection of the phase detector noise. On the other hand, it is known that the interferometer exhibits lower noise floor and higher conversion gain than other phase detectors suitable to radio-frequency and microwave bands. Thus, we experimented on an improved instrument in which the phase noise of a component is measured by correlating and averaging the output of two interferometers. The measurement sensitivity, given in terms of noise floor, turns out to be limited by the temperature uniformity of the instrument, instead of the absolute temperature T. This feature makes the instrument suitable to investigate the spectrum Sφ(f) of phase fluctuations below kBT/Po, i.e., the thermal energy kBT referred to the carrier power Po. The described method is suitable to the implementation of instruments in a wide frequency range, from some 100 kHz to 40 GHz and beyond. In principle, this method can also be exploited for the measurement of amplitude noise. Theory and experimental proof are given. © 2000 American Institute of Physics.
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84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
07.50.Hp Electrical noise and shielding equipment
back to top MICROSCOPY and IMAGING

An innovative approach to multiparticle three-dimensional imaging

D. Strasser, X. Urbain, H. B. Pedersen, N. Altstein, O. Heber, R. Wester, K. G. Bhushan, and D. Zajfman

Rev. Sci. Instrum. 71, 3092 (2000); http://dx.doi.org/10.1063/1.1305514 (7 pages) | Cited 16 times

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An innovative technique for three-dimensional imaging is presented, which uses the ratio of intensities of a pair of two-dimensional images to extract timing information. The principal advantage of this method is the ability to measure position and time for an almost unlimited number of particles hitting the detector simultaneously. The detector is capable of subnanosecond time resolution and position resolution of about 50 μm. The photodissociation of H2+ is used to demonstrate the capability of the detector. © 2000 American Institute of Physics.
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07.77.-n Atomic, molecular, and charged-particle sources and detectors
33.80.Gj Diffuse spectra; predissociation, photodissociation

Ferromagnetic resonance spectroscopy with a micromechanical calorimeter sensor

John Moreland, Markus Löhndorf, Pavel Kabos, and R. D. McMichael

Rev. Sci. Instrum. 71, 3099 (2000); http://dx.doi.org/10.1063/1.1305508 (5 pages) | Cited 10 times

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We describe a new type of ferromagnetic resonance (FMR) spectroscopy that is based on a calorimeter sensor. We use an atomic force microscopy cantilever coated with a ferromagnetic thin film as a bimaterial sensor to measure absorption of microwaves at 9.17 GHz. The spectra show a peak in the cantilever deflection as a function of applied magnetic field corresponding to a peak in the absorbed microwave power that occurs at the FMR resonance of the ferromagnetic film. The saturation magnetization Meff and the damping factor α were determined from the FMR microwave absorption spectra for Co, NiFe, and Ni thin films. The data correlate well with conventional FMR spectra taken with a tuned cavity spectrometer. Our instrument can detect magnetic moments as small as 1.3×10−12 A m2 (1.3×10−9 emu) with prospects for sensitivity improvements to the 1×10−16 A m2 (1×10−12 emu) level. The technique provides a potentially superior way to make quantitative measurements of saturation magnetization of thin-film samples with very small total magnetic moments.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
07.20.Fw Calorimeters
07.10.Cm Micromechanical devices and systems
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.79.Lh Atomic force microscopes

Noncontact scanning force microscopy based on a modified tuning fork sensor

Hagen Göttlich, Robert W. Stark, Johannes D. Pedarnig, and Wolfgang M. Heckl

Rev. Sci. Instrum. 71, 3104 (2000); http://dx.doi.org/10.1063/1.1304881 (4 pages) | Cited 17 times

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Distance control using a tuning fork setup for the detection of shear forces is a standard configuration in scanning near-field optical microscopy (SNOM). Based on this concept, a modified sensor was developed, where a standard silicon tip for atomic force microscopy (AFM) is attached to the front end of one prong of a 100 kHz quartz tuning fork oscillator. Comparison of force curves of a standard tapping-mode AFM cantilever, a conventional fiber tip SNOM sensor and the novel AFM tip shear force sensor demonstrate an enhanced stability and sensitivity of the new sensor. Due to the rigid sensor design the force curves of the AFM tip shear force sensor indicate a perfect noncontact behavior under normal conditions in air. Noncontact images show a comparable resolution to conventional force microscopy. © 2000 American Institute of Physics.
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07.79.Lh Atomic force microscopes
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.10.Pz Instruments for strain, force, and torque

Microscope system for use in high magnetic fields

James M. Valles, Sarah Wasserman, James M. Denegre, and Kimberly L. Mowry

Rev. Sci. Instrum. 71, 3108 (2000); http://dx.doi.org/10.1063/1.1304880 (3 pages) | Cited 4 times

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We describe a microscope system, with video output, that operates within the confines and the high magnetic field of the 195 mm wide bore, 20 T resistive magnet at the National High Magnetic Field Laboratory. The accessibility of this system allows the user to vary the field of view and focus in situ and to produce images with up to 10 micron resolution. It allows for temperature regulation of samples to within 1 °C and in situ sample manipulation. Images of a biological specimen, Xenopus laevis embryos, in high magnetic field are presented. © 2000 American Institute of Physics.
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07.60.Pb Conventional optical microscopes
87.64.M- Optical microscopy
42.79.Pw Imaging detectors and sensors

High throughput aperture near-field scanning optical microscopy

Phan Ngoc Minh, Takahito Ono, and Masayoshi Esashi

Rev. Sci. Instrum. 71, 3111 (2000); http://dx.doi.org/10.1063/1.1304867 (7 pages) | Cited 17 times

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This article presents a simple measurement setup for characterization of a combined near-field scanning optical and atomic force microscopy (NSOM/AFM) using an aperture Si based probe. A technological approach has been found for the fabrication of a miniature aperture at the apex of a SiO2 tip on a Si cantilever for NSOM using a “low temperature oxidation and selective etching” (LOSE) technique. The optical transmission efficiency (throughput) of the fabricated probe was measured to be about 10−2 when the aperture size was approximately 100 nm, which is several orders of magnitude higher than that of conventional optical fibers and is also higher than other published throughput on micromachined tips due to a large curvature angle of the SiO2 tip. An extension of the LOSE technique for the fabrication of a tip with a tiny aperture having a metal nanowire at the center of the aperture for a multipurpose NSOM probe is also presented. Using the proposed measurement setup and the fabricated probe, NSOM and corresponding AFM images in contact and tapping modes of several surfaces are obtained. © 2000 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
07.79.Lh Atomic force microscopes
07.10.Cm Micromechanical devices and systems
42.86.+b Optical workshop techniques
81.65.Mq Oxidation
81.65.Cf Surface cleaning, etching, patterning

Method to produce high-resolution scanning near-field optical microscope probes by beveling optical fibers

T. Held, S. Emonin, O. Marti, and O. Hollricher

Rev. Sci. Instrum. 71, 3118 (2000); http://dx.doi.org/10.1063/1.1304866 (5 pages) | Cited 19 times

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A new two-step method to fabricate scanning near-field optical microscope (SNOM) probes with an aperture size clearly below 100 nm has been developed. For the first step, a chemical etching process is used in which an optical fiber is dipped with its acrylate jacket into hydrofluoric acid to get a suitable tapered shape of the fiber. The second step consists of beveling the etched fiber using a modified micropipette beveler to obtain a tip diameter in the nanometer range as well as a smooth surface to allow a good aluminum metallization by evaporation. By varying the beveling angle tapered shapes with different cone angles can be obtained. First transmission experiments with our probes show an optical resolution below 80 nm. In comparison to fiber tips obtained by a standard heating and pulling method, the transmission efficiency of these tips is up to three orders of magnitude higher due to the optimized tapered shape. © 2000 American Institute of Physics.  
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07.79.Fc Near-field scanning optical microscopes
07.60.Vg Fiber-optic instruments
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