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Apr 2003

Volume 74, Issue 4, pp. 2255-2616

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back to top OPTICS; ATOMS and MOLECULES; SPECTROSCOPY; PHOTON DETECTORS

Phase-locked-loop-based delay-line-free picosecond electro-optic sampling system

Gong-Ru Lin and Yung-Cheng Chang

Rev. Sci. Instrum. 74, 2255 (2003); http://dx.doi.org/10.1063/1.1536256 (7 pages)

Online Publication Date: 26 March 2003

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A delay-line-free, high-speed electro-optic sampling (EOS) system is proposed by employing a delay-time-controlled ultrafast laser diode as the optical probe. Versatile optoelectronic delay-time controllers (ODTCs) based on modified voltage-controlled phase-locked-loop phase-shifting technologies are designed for the laser. The integration of the ODTC circuit and the pulsed laser diode has replaced the traditional optomechanical delay-line module used in the conventional EOS system. This design essentially prevents sampling distortion from misalignment of the probe beam, and overcomes the difficulty in sampling free-running high-speed transients. The maximum tuning range, error, scanning speed, tuning responsivity, and resolution of the ODTC are 3.9π (700°), <5% deviation, 25–2405 ns/s, 0.557 ps/mV, and ∼1 ps, respectively. Free-running wave forms from the analog, digital, and pulsed microwave signals are sampled and compared with those measured by the commercial apparatus. © 2003 American Institute of Physics.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.79.-e Optical elements, devices, and systems

Large aperture compound lenses made of lithium

J. T. Cremer, M. A. Piestrup, H. R. Beguiristain, C. K. Gary, and R. H. Pantell

Rev. Sci. Instrum. 74, 2262 (2003); http://dx.doi.org/10.1063/1.1556948 (5 pages) | Cited 6 times

Online Publication Date: 26 March 2003

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We have measured the intensity profile and transmission of x rays focused by a series of biconcave parabolic unit lenses fabricated in lithium. For specified focal length and photon energy lithium compound refractive lenses (CRL) have a larger transmission, aperture size, and gain compared to aluminum, kapton, and beryllium CRLs. The lithium compound refractive lens was composed of 335 biconcave, parabolic unit lenses each with an on-axis radius of curvature of 0.95 mm. Two-dimensional focusing was obtained at 8.0 keV with a focal length of 95 cm. The effective aperture of the CRL was measured to be 1030 μm with on-axis (peak) transmissions of 27% and an on-axis intensity gain of 18.9. © 2003 American Institute of Physics.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
41.50.+h X-ray beams and x-ray optics

The Stark ball: A programmable multipolar environment

K. B. MacAdam and C. S. Hwang

Rev. Sci. Instrum. 74, 2267 (2003); http://dx.doi.org/10.1063/1.1544085 (9 pages) | Cited 2 times

Online Publication Date: 26 March 2003

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A device is described and mathematically analyzed which creates electrostatic multipole potentials at least up to rank 3 in a 2 cm diam spherical region. The fields in the Stark ball are produced by the application of programmed voltages to 24 conducting rods that are inserted symmetrically in an empty 5 cm conducting cavity. Three mutually orthogonal unobstructed paths through the center of the device between the rods are provided for access of light and particle beams, and four other tetrahedrally located openings can be added for beams, detectors, or imaging. The device is intended for application in atom or molecule trapping and cooling, recoil-ion momentum spectroscopy, particulate analysis, reactive scattering, and coherent control. Potential distributions can be established, altered, and rotated on subnanosecond time scales, and frequencies higher than 20 GHz can be introduced via the same electrodes. Uniform fields, i.e., first-rank multipoles, quadrupole, and octupole potentials can be programmed and superposed with arbitrary and independent time profiles, so that the device may be applied to the study of orientational properties of complex anisotropic molecules, pollens, grains of dust, and other particulates. The device is nonmagnetic. An extensive analysis of fields in the center region, fringing fields, and multipole purity up to rank 7 has been carried out, and recipes are given for pure (l,m) = (1,0), (2,0), and (3,0) multipoles. The principles and methods laid out here and applied to a “truncated octahedron” can be applied to the design of electrostatic environments having fewer or more independent electrodes in any polyhedral geometry. © 2003 American Institute of Physics.
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41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
back to top PARTICLE SOURCES, OPTICS and ACCELERATION; PARTICLE DETECTORS

Highly charged ion beams at eV kinetic energies

H. Lebius, A. Brenac, B. A. Huber, L. Maunoury, F. Gustavo, and D. Cormier

Rev. Sci. Instrum. 74, 2276 (2003); http://dx.doi.org/10.1063/1.1556952 (4 pages) | Cited 4 times

Online Publication Date: 26 March 2003

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An experimental setup that furnishes slow highly charged ion beams is described. A 14.5 GHz CAPRICE electron cyclotron resonance ion source provides highly charged ions at a kinetic energy of 10 to 20 keV per charge. The kinetic energy is reduced in a deceleration system, which consists of two stages, each of which is built up by two electrostatic zoom lenses. The ion beam can be decelerated down to a kinetic energy of 1 eV/charge. Typical beam currents, measured at the experiment with an emittance of (20 π mm mrad) are about 100 pA, even for the highest measured charge states (Ar16+). © 2003 American Institute of Physics.
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41.75.Ak Positive-ion beams
29.25.Ni Ion sources: positive and negative
41.85.Ne Electrostatic lenses, septa

Accurate Monte Carlo calculation of Boersch energy and angle spreading

F. H. Read and N. J. Bowring

Rev. Sci. Instrum. 74, 2280 (2003); http://dx.doi.org/10.1063/1.1544422 (8 pages) | Cited 3 times

Online Publication Date: 26 March 2003

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The effects of stochastic electron–electron interactions have been studied by a computational technique that attempts to avoid systematic errors, leaving only the random errors that are inherent in a Monte Carlo calculation. The technique has been applied to the energy and angle spreading in a converging round beam. The results are compared with previous analytical results. © 2003 American Institute of Physics.
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41.75.Fr Electron and positron beams
02.70.Uu Applications of Monte Carlo methods

Mini rf-driven ion sources for focused ion beam systems

X. Jiang, Q. Ji, A. Chang, and K. N. Leung

Rev. Sci. Instrum. 74, 2288 (2003); http://dx.doi.org/10.1063/1.1556944 (5 pages) | Cited 13 times

Online Publication Date: 26 March 2003

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Mini rf-driven ion sources with 1.2 cm and 1.5 cm inner chamber diameter have been developed at Lawrence Berkeley National Laboratory. Several gas species have been tested including argon, krypton, and hydrogen. These mini ion sources operate in inductively coupled mode and are capable of generating high current density ion beams at tens of watts of absorbed rf power. Since the plasma potential is relatively low in the plasma chamber, these mini ion sources can function reliably without any perceptible sputtering damage of the chamber wall. The mini rf-driven ion sources will be combined with electrostatic focusing columns, and are capable of producing nanofocused ion beams for micromachining and semiconductor fabrications. © 2003 American Institute of Physics.
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29.25.Ni Ion sources: positive and negative

Flat-top acceleration system for the variable-energy multiparticle AVF cyclotron

Mitsuhiro Fukuda, Satoshi Kurashima, Susumu Okumura, Nobumasa Miyawaki, Takashi Agematsu, Yoshiteru Nakamura, Takayuki Nara, Ikuo Ishibori, Kenichi Yoshida, Watalu Yokota, Kazuo Arakawa, Yukio Kumata, Yasushi Fukumoto, and Katsuhiko Saito

Rev. Sci. Instrum. 74, 2293 (2003); http://dx.doi.org/10.1063/1.1556941 (7 pages) | Cited 7 times

Online Publication Date: 26 March 2003

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A flat-top acceleration system appropriate to minimization of energy spread in an ion beam was investigated for the JAERI AVF cyclotron. A combination of the fundamental- and the fifth-harmonic voltages to obtain a homogeneous energy gain distribution of accelerated particles is ideally suited to a variable-energy multiparticle cyclotron using acceleration harmonics of 1, 2, and 3. The flat topping of the energy gain distribution using the fifth harmonics has the advantages of minimizing amplifier power, reducing power dissipation in a resonator, and increasing the energy gain per turn. The flat-top acceleration system was designed to reduce the energy spread to 0.02%, which fulfills a beam focusing condition for production of a microbeam with a beam spot diameter of 1 μm. Tolerable fluctuations of acceleration voltages, required to achieve the energy spread of 0.02%, were 2.0×10−4 for the fundamental voltage and 1.0×10−3 for the fifth-harmonic voltage. Both fundamental- and fifth-harmonic phases were required to be stabilized within 0.2 rf degrees. The tolerance of the magnetic excitation was 1.9×10−5. In order to enhance compactness of the flat-topping cavity and to make a substantial saving of the amplifier power, optimum geometric parameters of the flat-topping cavity were determined by a cold model test and a calculation using the MAFIA code. A full range of the fifth-harmonic frequency, 55–110 MHz, was covered by the flat-top system, which enables us to apply the flat-top acceleration to a wide range of energy. © 2003 American Institute of Physics.
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29.20.dg Cyclotrons
29.27.Eg Beam handling; beam transport
back to top NUCLEAR PHYSICS, FUSION and PLASMAS

High-repetition-rate, hard x-ray radiation from a laser-produced plasma: Photon yield and application considerations

A. Sjögren, M. Harbst, C.-G. Wahlström, S. Svanberg, and C. Olsson

Rev. Sci. Instrum. 74, 2300 (2003); http://dx.doi.org/10.1063/1.1544054 (12 pages) | Cited 17 times

Online Publication Date: 26 March 2003

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We present an experimental study of hard x rays produced in laser-produced plasmas. The laser used is a 1 kHz system, delivering 0.7 mJ for 25 fs onto a solid target. The x-ray spectrum was measured with calibrated germanium detectors, allowing a very good estimate of the absolute number of photons emitted from the plasma over a wide energy range; from 7 keV to 0.5 MeV. Assuming a bi-Maxwellian electron distribution with temperatures of 4.5 and 63 keV, theoretical calculations support the experimental findings. The imaging characteristics of the x-ray source were investigated experimentally employing image plates and theoretically based on the electron distribution. © 2003 American Institute of Physics.
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52.59.Px Hard X-ray sources
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Plasma emission tomographic reconstruction in the large helical device

Y. Liu, A. Yu. Kostrioukov, and B. J. Peterson

Rev. Sci. Instrum. 74, 2312 (2003); http://dx.doi.org/10.1063/1.1544080 (6 pages) | Cited 9 times

Online Publication Date: 26 March 2003

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Both one-dimensional (1D) and two-dimensional (2D) tomographic reconstruction of the total radiation power distribution from the large helical device (LHD) was based on the data obtained from absolute extreme ultraviolet silicon photodiodes. Two arrays (16 and 19 channels) installed in the normal LHD cross section (constant toroidal angle) provided simple and reliable 1D poloidally symmetric radiation profile reconstruction. The data obtained from two other arrays (20 and 20 channels) were used for 2D reconstruction of the radiation distribution in a semitangential plasma cross section. Using a 2D peeling away algorithm, improved by a feedback procedure, enabled reconstruction of several Fourier harmonics at each magnetic flux surface. These measurement and analysis techniques have enabled us to visualize asymmetries in plasma emission due to pellet and gas fueling. © 2003 American Institute of Physics.
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52.55.Jd Magnetic mirrors, gas dynamic traps
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Separatrix shape measurement on field-reversed configuration plasmas

Hiroshi Gota, Takahiko Akiyama, Kayoko Fujimoto, Yasunori Ohkuma, Tsutomu Takahashi, and Yasuyuki Nogi

Rev. Sci. Instrum. 74, 2318 (2003); http://dx.doi.org/10.1063/1.1561599 (6 pages) | Cited 5 times

Online Publication Date: 26 March 2003

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In order to determine the separatrix shapes of field-reversed configuration plasmas with high accuracy, an iterative method that compares measured magnetic fluxes with the solution of the Grad–Shafranov equation is discussed in detail. Several suggestions for successfully treating the iterative method are given using numerical simulation and a mock-up experiment where conductors with three kinds of shape are inserted into the coil instead of the plasma. The iterative method is also applied to the field-reversed configuration plasma, and it is found that the separatrix shape has distinct ends and the axial location of the X point can be determined. © 2003 American Institute of Physics.
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52.55.Lf Field-reversed configurations, rotamaks, astrons, ion rings, magnetized target fusion, and cusps
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.65.Kj Magnetohydrodynamic and fluid equation
52.40.Hf Plasma-material interactions; boundary layer effects
52.65.-y Plasma simulation

Reconnection scaling experiment: A new device for three-dimensional magnetic reconnection studies

I. Furno, T. Intrator, E. Torbert, C. Carey, M. D. Cash, J. K. Campbell, W. J. Fienup, C. A. Werley, G. A. Wurden, and G. Fiksel

Rev. Sci. Instrum. 74, 2324 (2003); http://dx.doi.org/10.1063/1.1544051 (8 pages) | Cited 20 times

Online Publication Date: 26 March 2003

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The reconnection scaling experiment (RSX), a linear device for studying three-dimensional magnetic reconnection in both collisional and collisionless laboratory plasmas, has been constructed at Los Alamos National Laboratory. Advanced experimental features of the RSX that lead to scientific advantages include the use of simple technology (commercial plasma guns) to create plasma and current channels. Physics motivations, design and construction features of the RSX, are presented. Basic plasma parameters that characterize the RSX are shown together with preliminary measurements of visible light emission during the merging of two parallel current channels. © 2003 American Institute of Physics.
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52.75.-d Plasma devices

Spatial deconvolution technique to obtain velocity profiles from chord integrated spectra

R. P. Golingo and U. Shumlak

Rev. Sci. Instrum. 74, 2332 (2003); http://dx.doi.org/10.1063/1.1556956 (6 pages) | Cited 9 times

Online Publication Date: 26 March 2003

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Passive spectroscopy is used to measure the plasma parameters on the ZaP experiment at the University of Washington. Twenty spectral intensities, which are functions of the plasma’s density, velocity, and temperature along the viewing chord, are recorded on a charged coupled device. The instrument function is different for each viewing chord. A deconvolution technique based on a shell model, which includes the effects of the instrument function, is developed to deduce the local plasma parameters. The error analysis for this technique is also developed. The technique is able to model complicated plasma parameter profiles and is able to deduce the local plasma parameters and position of the plasma. © 2003 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.58.Lq Z-pinches, plasma focus, and other pinch devices
52.25.-b Plasma properties
06.20.Dk Measurement and error theory

Neutral particle analyzer/isotope separator for measurement of hydrogen isotope composition of JET plasmas

V. I. Afanasyev, A. Gondhalekar, P. Yu. Babenko, P. Beaumont, P. De Antonis, A. V. Detch, A. I. Kislyakov, S. S. Kozlovskij, M. I. Mironov, M. P. Petrov, S. Ya. Petrov, F. V. Tschernyshev, and C. H. Wilson

Rev. Sci. Instrum. 74, 2338 (2003); http://dx.doi.org/10.1063/1.1542664 (15 pages) | Cited 11 times

Online Publication Date: 26 March 2003

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This article describes a neutral particle analyzer/isotope separator (ISEP) developed for measurement of the relative hydrogen isotope composition of Joint European Torus (JET) plasmas. The ISEP deployed on the JET can be regarded as a prototype of an instrument proposed for measurement of the spatial profile of the ratio of the density of deuterium and tritium ions in the plasma, nD(r)/nT(r), in the International Thermonuclear Experimental Reactor (ITER). The ISEP makes simultaneous measurements of the energy distribution of efflux of hydrogen isotope atoms (H, D, and T) from the plasma. From such measurements it is possible to deduce the radial profile of the relative hydrogen isotope ion composition of the plasma and radial transport of ions of one isotope across the plasma of another isotope species. The main elements of the ISEP are (a) use of a thin carbon foil for reionization of the incident atoms, thereby eliminating gas stripping cells and gas sources of conventional neutral particle analyzers (NPAs), (b) acceleration of secondary ions in order to access the regime of higher detection efficiency of the NPA and to better separate ion pulses from neutron/γ-ray induced pulses in scintillator detectors, (c) E‖B dispersion of the secondary ions in specially designed nonuniform magnetic and electric fields to provide focusing in the detector plane, increased throughput and greater contrast between neighboring isotopes, and (d) counting of energy and mass analyzed secondary ions using detectors consisting of thin [1 ⩽ t (μm) ⩽ 7] CsI(Tl) scintillators deposited directly on miniature thin window photomultiplier tubes mounted in vacuum. The ISEP has high contrast between atoms of neighboring masses ( ≥ 103 for E ≈ 5 keV and much greater at higher energies), and high detection efficiency (0.06 ⩽ ε ⩽ 0.83 for atoms of 5 ⩽  (keV) ⩽ 150. ISEP detectors have very low sensitivity to neutrons and γ rays ( ⩽ 10−7 of ion sensitivity), making it feasible to use the ISEP in JET DT experiments without any shielding. Only a modest amount of neutron/γ-ray shielding would be required in the ITER for similar applications of the ISEP. The initial experiments on JET plasmas using the ISEP demonstrate well the capabilities of the instrument for measurement of the hydrogen isotope composition of the plasma and the energy distribution function of isotope ions. © 2003 American Institute of Physics.
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52.55.Fa Tokamaks, spherical tokamaks
52.70.Nc Particle measurements

Optimization of the number of soft x-ray arrays and detectors for the SST-1 tokamak by the tomographic method

A. K. Chattopadhyay, C. V. S. Rao, and R. Srivatsan

Rev. Sci. Instrum. 74, 2353 (2003); http://dx.doi.org/10.1063/1.1544052 (4 pages) | Cited 1 time

Online Publication Date: 26 March 2003

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An x-ray imaging system for tomographic reconstruction of two-dimensional emissivity is being developed for the SST-1 tokamak. In this article it is shown that for circular plasma, which will be generated in the first phase of operation of the machine, 7 arrays and 115 detectors are adequate to reconstruct the simulated data. Sawtooth phenomena depicted by both the Wesson model and the Kadomtsev model and the disruption phenomenon associated with m=2 mode are reconstructed well with the help of this imaging system. © 2003 American Institute of Physics.
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52.55.Fa Tokamaks, spherical tokamaks
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.70.La X-ray and γ-ray measurements

Three different simple detector manipulators for spatial measurements in a plasma discharge device

Shunjiro Shinohara

Rev. Sci. Instrum. 74, 2357 (2003); http://dx.doi.org/10.1063/1.1556949 (4 pages) | Cited 1 time

Online Publication Date: 26 March 2003

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Simple and convenient novel manipulators with two dimensions and three dimensions were demonstrated for measuring various parameters directly in a cylindrical vacuum chamber. Examples of experimental data are presented to prove the usefulness of the systems in a plasma device. Three different mechanisms with neither internal driving nor differentially pumped systems for achieving varying degrees of accuracy were proposed: In one of the two three-dimensional driving systems, detectors were introduced along the axial direction with an arbitrary rotation with respect to the axis by the use of two small-diameter bellows. The other system allowed motion along the radial direction with the capability of arbitrary rotation by small-diameter bellows. In the two-dimensional system, detectors could be scanned vertically using a sliding flange in addition to a radial motion mechanism. © 2003 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements

Rapid multiplexed data acquisition: Application to three-dimensional magnetic field measurements in a turbulent laboratory plasma

M. Landreman, C. D. Cothran, M. R. Brown, M. Kostora, and J. T. Slough

Rev. Sci. Instrum. 74, 2361 (2003); http://dx.doi.org/10.1063/1.1544417 (8 pages) | Cited 14 times

Online Publication Date: 26 March 2003

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Multiplexing electronics have been constructed to reduce the cost of high-speed data acquisition at the Swarthmore Spheromak Experiment (SSX) and Redmond Plasma Physics Laboratory. An application of the system is described for a three-dimensional magnetic probe array designed to resolve magnetohydrodynamic time scale and ion inertial spatial scale structure of magnetic reconnection in a laboratory plasma at SSX. Multiplexing at 10 MHz compresses 600 pick-up coil signals in the magnetic probe array into 75 digitizer channels. An external master timing system maintains synchronization of the multiplexers and digitizers. The complete system, calibrated and tested with Helmholtz, line current, and magnetofluid fields, reads out the entire 5×5×8 probe array every 800 ns with an absolute accuracy of approximately 20 G, limited mainly by bit error. © 2003 American Institute of Physics.
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52.55.Ip Spheromaks
52.70.Ds Electric and magnetic measurements
07.05.Hd Data acquisition: hardware and software
52.35.Ra Plasma turbulence
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.35.Vd Magnetic reconnection

Conical x-ray crystal spectrometer for time integrated and time resolved measurements

U. Andiel, K. Eidmann, F. Pisani, K. Witte, I. Uschmann, O. Wehrhan, and E. Förster

Rev. Sci. Instrum. 74, 2369 (2003); http://dx.doi.org/10.1063/1.1556953 (6 pages) | Cited 8 times

Online Publication Date: 26 March 2003

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We present a new x-ray spectrometer setup based on a conically curved mica crystal in the von Hámos configuration. An x-ray sensitive charge coupled device or streak camera can be easily coupled in a perpendicular orientation to the spectrally resolved x-ray line focus. Shifting the crystal along its axis of symmetry allows one to change the dispersion and the signal flux density on the detector. A large spectral range at high resolution and adjustable signal intensity is accessible with this setup. © 2003 American Institute of Physics.
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52.70.La X-ray and γ-ray measurements
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
07.85.Nc X-ray and γ-ray spectrometers
52.25.-b Plasma properties
06.60.Jn High-speed techniques (microsecond to femtosecond)
42.79.Pw Imaging detectors and sensors

X-ray crystal spectrometer with a charge-coupled-device detector for ion temperature measurements in the Large Helical Device

Shigeru Morita and Motoshi Goto

Rev. Sci. Instrum. 74, 2375 (2003); http://dx.doi.org/10.1063/1.1556942 (13 pages) | Cited 23 times

Online Publication Date: 26 March 2003

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A Johann-type x-ray crystal spectrometer has been designed using a ray tracing calculation and constructed for ion temperature measurement in the plasma center of a large helical device (LHD) using Doppler broadening of a He-like resonance line of ArXVII, TiXXI, CrXXIII, or FeXXV. Four curved quartz (2020), (2023), (3140), and (2243) crystals are set in a quadrangular rotary crystal holder for measuring the x-ray line from such four different elements. Each of the crystals can be externally selected through a computer network. The curved crystals with a radius of 3 m are fabricated by gluing thin quartz (0.7 mmt) on an accurately ground cylindrical blue glass plate. The curvature of the crystals was checked by scanning a sharp pin along the crystal surface. As a result, an excellent agreement with the designed cylindrical curvature was obtained with an accuracy of 1 μm. A secular change of the curved crystal surface structure was found by measuring the curvature of the curved crystal fabricated 15 years earlier. A charge-coupled-device (CCD) detector is used instead of a usually used proportional counter to increase the count rate and to avoid the influence of magnetic field leakage from the LHD. The influence of magnetic fields on the proportional counter was investigated in a range of B ⩽ 1.5 kG. The use of the CCD brought us a large increment of more than ten times in the count rate compared with the multiwire proportional counter. The ion temperature thus has been successfully observed in a time interval of 20 ms with small error bars. The lowest measured ion temperature was 0.2–0.3 keV for ArXVII and TiXXI, which indicates an excellent spectral resolution of the crystal spectrometer. Finally, the influence of the chord integration on the measured ion temperature is discussed as a function of central electron temperature and density profile with analysis from impurity transport calculations. © 2003 American Institute of Physics.
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07.85.Nc X-ray and γ-ray spectrometers
52.70.La X-ray and γ-ray measurements
52.25.-b Plasma properties

Versatile high resolution crystal spectrometer with x-ray charge coupled device detector

R. Barnsley, N. J. Peacock, J. Dunn, I. M. Melnick, I. H. Coffey, J. A. Rainnie, M. R. Tarbutt, and N. Nelms

Rev. Sci. Instrum. 74, 2388 (2003); http://dx.doi.org/10.1063/1.1533105 (21 pages) | Cited 9 times

Online Publication Date: 26 March 2003

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A family of Johann configuration curved crystal spectrometers has been designed to share the basic engineering features of compactness, modularity, facility of alignment and focus, and incorporation of solid-state charge coupled device detector arrays. These detectors have intrinsically low noise, useful energy resolution, two-dimensional position sensitivity, and readout modes that are programmable. The spectrometers, although relatively compact, with a Rowland circle diameter in the range 0.5–2 m, can still have sufficient resolving power, dispersion, and throughput to be invaluable in high resolution studies of atomic and plasma sources. This article discusses the basic design features and performance of these doubly dispersive spectrometers and illustrates their versatility by applications to studies of a wide range of laboratory x-ray sources such as line emission from highly ionized atoms in the extended plasmas of Tokamaks and nearly point plasmas produced by focused laser irradiation of solids and in beam-foil experiments and electron beam ion traps. © 2003 American Institute of Physics.
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07.85.Nc X-ray and γ-ray spectrometers
42.79.Pw Imaging detectors and sensors
52.70.La X-ray and γ-ray measurements
52.50.Dg Plasma sources
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Magnetic diagnostics for ITER/BPX plasmas (invited)

G. Vayakis and C. Walker

Rev. Sci. Instrum. 74, 2409 (2003); http://dx.doi.org/10.1063/1.1534388 (9 pages) | Cited 15 times

Online Publication Date: 26 March 2003

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The measurement requirements and expected performance of the International Thermonuclear Experimental Reactor (ITER) magnetics system are summarized. The constraints of a burning plasma experiment (BPX) on tokamak magnetic diagnostic system designs are listed and illustrated using the parameters and design of sensors being developed for the ITER device. Design principles to meet the constraints are discussed, with an emphasis on radiation effects, reliability, and redundancy for sensors and subsystems. The remaining research and development for the ITER system is outlined. © 2003 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
52.55.Fa Tokamaks, spherical tokamaks
07.55.-w Magnetic instruments and components
28.52.Lf Components and instrumentation
back to top MICROSCOPY and IMAGING

Thermal conductivity calibration for hot wire based dc scanning thermal microscopy

Stéphane Lefèvre, Sebastian Volz, Jean-Bernard Saulnier, Catherine Fuentes, and Nathalie Trannoy

Rev. Sci. Instrum. 74, 2418 (2003); http://dx.doi.org/10.1063/1.1544078 (6 pages) | Cited 23 times

Online Publication Date: 26 March 2003

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Thermal conductivity characterization with nanoscale spatial resolution can be performed by contact probe techniques only. The technique based on a hot anemometer wire probe mounted in an atomic force microscope is now a standard setup. However, no rigorous calibration procedure is provided so far in basic dc mode. While in contact with the sample surface, the electrical current I injected into the probe is controlled so that electrical resistance or the wire temperature is maintained by the Joule effect. The variation in current is assumed to be linearly related to the heat flux lost towards the sample and traditional calibration is carried out by relating the thermal conductivity of a set of samples to the measured current I. We provide analytical and numerical thermal modeling of the tip and sample to estimate the key heat transfer in a conductivity calibration procedure. A simple calibration expression is established that provides thermal conductivity as a function of the probe current or voltage measured. Finally, experimental data allow us to determine the unknown quantities of the parametric form obtained, i.e., the mean tip–sample contact radius and conductance. © 2003 American Institute of Physics.
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07.79.-v Scanning probe microscopes and components
07.20.-n Thermal instruments and apparatus

Standard sample probes for characterizing optical apertures in near-field scanning optical microscopy

Joseph M. Imhof, Eun-Soo Kwak, and David A. Vanden Bout

Rev. Sci. Instrum. 74, 2424 (2003); http://dx.doi.org/10.1063/1.1556951 (5 pages) | Cited 2 times

Online Publication Date: 26 March 2003

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A quick, cost effective, semiquantitative means for gauging the quality of near-field scanning optical microscopy (NSOM) probe apertures has been demonstrated by employing a nanoperforated thin metal film standard sample. Small 182 nm holes were created by evaporating gold over dispersed latex spheres with subsequent removal of the spheres. The size of the NSOM aperture can be determined from a deconvolution of the image size and the known sample size and geometry. Results from the standard correlate well with aperture size measurements made from scanning electron micrographs.© 2003 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes

Two linear beetle-type scanning tunneling microscopes

J. M. MacLeod, Antje Moffat, J. A. Miwa, A. G. Mark, G. K. Mullins, R. H. J. Dumont, G. E. Constant, and A. B. McLean

Rev. Sci. Instrum. 74, 2429 (2003); http://dx.doi.org/10.1063/1.1544423 (9 pages) | Cited 18 times

Online Publication Date: 26 March 2003

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Two beetle-type scanning tunneling microscopes are described. Both designs have the thermal stability of the Besocke beetle and the simplicity of the Wilms beetle. Moreover, sample holders were designed that also allow both semiconductor wafers and metal single crystals to be studied. The coarse approach is a linear motion of the beetle towards the sample using inertial slip–stick motion. Ten wires are required to control the position of the beetle and scanner and measure the tunneling current. The two beetles were built with different sized piezolegs, and the vibrational properties of both beetles were studied in detail. It was found, in agreement with previous work, that the beetle bending mode is the lowest principal eigenmode. However, in contrast to previous vibrational studies of beetle-type scanning tunneling microscopes, we found that the beetles did not have the “rattling” modes that are thought to arise from the beetle sliding or rocking between surface asperities on the raceway. The mass of our beetles is 3–4 times larger than the mass of beetles where rattling modes have been observed. We conjecture that the mass of our beetles is above a “critical beetle mass.” This is defined to be the beetle mass that attenuates the rattling modes by elastically deforming the contact region to the extent that the rattling modes cannot be identified as distinct modes in cross-coupling measurements. © 2003 American Institute of Physics.
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07.79.Cz Scanning tunneling microscopes

Susceptibility of atomic force microscope cantilevers to lateral forces

John Elie Sader

Rev. Sci. Instrum. 74, 2438 (2003); http://dx.doi.org/10.1063/1.1544421 (6 pages) | Cited 29 times

Online Publication Date: 26 March 2003

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V-shaped cantilevers are used widely in the atomic force microscope (AFM) due to their perceived enhanced resistance to lateral forces in comparison to rectangular cantilevers. In this article, we rigorously investigate this premise, and in so doing establish that, contrary to established operating principles and intuition, V-shaped AFM cantilevers are generally more prone to the effects of lateral forces than rectangular AFM cantilevers. This finding suggests that rectangular cantilevers should be used in place of V-shaped cantilevers in applications where the effects of lateral forces are to be minimized. © 2003 American Institute of Physics.
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07.79.Lh Atomic force microscopes

In situ scanning tunneling microscopy of individual supported metal clusters at reactive gas pressures from 10−8 to 104 Pa

A. Kolmakov and D. W. Goodman

Rev. Sci. Instrum. 74, 2444 (2003); http://dx.doi.org/10.1063/1.1544086 (7 pages) | Cited 18 times

Online Publication Date: 26 March 2003

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An experimental apparatus has been designed and an approach developed for imaging individual oxide supported nanoparticles with scanning tunneling microscopy (STM) during their nucleation, growth, alloying, and “real world” chemical, thermal, and other in situ treatments. By careful selection of the tunneling conditions and using the STM tip to index the surface, it is demonstrated that preselected individual particles can be imaged at elevated temperatures while changing the reactive gas pressure over 12 orders of magnitude. The experimental challenges due mainly to tunnel junction instabilities, a relatively weak cluster-support interaction, and sample drift are considered and strategies to overcome these obstacles proposed. Using Au and Ag clusters deposited on TiO2(110) as a model system, the potential of the method is demonstrated for exploring on a particle-by-particle basis cluster growth, alloying, thermal coarsening, and the evolution of particle morphology in a reactive gas environment. An additional advantage of the approach is that a wide cluster size distribution can be synthesized and surveyed on the same substrate. The size effects on cluster morphology therefore can be probed in situ for a wide variety of treatments on preselected clusters. © 2003 American Institute of Physics.
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68.47.Jn Clusters on oxide surfaces
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
61.46.-w Structure of nanoscale materials
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