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Microscopy in solid state science (1993)

McGibbon, A. J. ; Brown, L. M. ; Bleloch, A. L. ; [weitere]

New York, NY [u.a.] : Wiley-Blackwell

Microscopy Research and Technique 24 (1993), S. 299-315

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ISSN: 1059-910X

Schlagwort(e): STEM ; PEELS ; HAADFI ; Nanolithography ; Super-resolution ; STM ; Life and Medical Sciences ; Cell & Developmental Biology

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Allgemeine Naturwissenschaft

Notizen: The Microstructural Physics group at the Cavendish Laboratory is actively involved in a considerable number of research projects which cover a broad range of materials science. In this paper, we describe briefly several such projects, with particular emphasis given to the application of parallel-detection electron energy loss spectroscopy (PEELS) on a scanning transmission electron microscope (STEM) to the analysis of materials such as stainless steels, catalysts, and high temperature superconductors. In addition, we describe a number of related projects that are currently being carried out in the group, particularly those which utilise and develop novel STEM imaging and analytical techniques. © 1993 Wiley-Liss, Inc.

Zusätzliches Material: 19 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/jemt.1070240404

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Helium, iron, and electron particle transport and energy transport studies on the Tokamak Fusion Test Reactor (1993)

Synakowski, E. J. ; Efthimion, P. C. ; Rewoldt, G. ; [weitere]

New York, NY : American Institute of Physics (AIP)

Physics of Fluids 5 (1993), S. 2215-2228

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ISSN: 1089-7666

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Results from helium, iron, and electron transport studies on the Tokamak Fusion Test Reactor (TFTR) [Plasma Phys. Controlled Nucl. Fusion Res. 26, 11 (1984)] in L-mode and supershot deuterium plasmas with the same toroidal field, plasma current, and neutral beam heating power are presented. They are compared to results from thermal transport analysis based on power balance. Particle diffusivities and thermal conductivities are radially hollow and larger than neoclassical values, except possibly near the magnetic axis. The ion channel dominates over the electron channel in both particle and thermal diffusion. A peaked helium profile, supported by inward convection that is stronger than predicted by neoclassical theory, is measured in the supershot. The helium profile shape is consistent with predictions from quasilinear electrostatic drift-wave theory. While the perturbative particle diffusion coefficients of all three species are similar in the supershot, differences are found in the L mode. Quasilinear theory calculations of the ratios of impurity diffusivities are in good accord with measurements. Theory estimates indicate that the ion heat flux should be larger than the electron heat flux, consistent with power balance analysis. However, theoretical values of the ratio of the ion to electron heat flux can be more than a factor of 3 larger than experimental values. A correlation between helium diffusion and ion thermal transport is observed and has favorable implications for sustained ignition of a tokamak fusion reactor.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.860755

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3

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Ion cyclotron range of frequency heating on the Tokamak Fusion Test Reactorf| (1993)

Taylor, G. ; Bell, M. G. ; Biglari, H. ; [weitere]

New York, NY : American Institute of Physics (AIP)

Physics of Fluids 5 (1993), S. 2437-2444

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ISSN: 1089-7666

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The complete ion cyclotron range of frequency (ICRF) heating system for the Tokamak Fusion Test Reactor (TFTR) [Fusion Tech. 21, 1324 (1992)], consisting of four antennas and six generators designed to deliver 12.5 MW to the TFTR plasma, has now been installed. Recently a series of experiments has been conducted to explore the effect of ICRF heating on the performance of low recycling, supershot plasmas in minority and nonresonant electron heating regimes. The addition of up to 7.4 MW of ICRF power to full size (R∼2.6 m, a∼0.95 m), helium-3 minority, deuterium supershots heated with up to 30 MW of deuterium neutral-beam injection has resulted in a significant increase in core electron temperature (ΔTe=3–4 keV). Simulations of equivalent deuterium–tritium (D–T) supershots predict that such ICRF heating should result in an increase in βα(0)∼30%. Direct electron heating has been observed and has been found to be in agreement with theory. The ICRF heating has also been coupled to neutral-beam heated plasmas fueled by frozen deuterium pellets. In addition ICRF heated energetic ion tails have been used to simulate fusion alpha particles in high-recycling plasmas. Up to 11.4 MW of ICRF heating has been coupled into a hydrogen minority, high-recycling helium plasma and the first observation of the toroidal Alfvén eigenmode (TAE) instability driven by the energetic proton tail has been made in this regime.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.860728

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4

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The ROSAT Wide Field Camera all-sky survey of extreme-ultraviolet sources – I. The Bright Source Catalogue (1993)

Pounds, K. A. ; Allan, D. J. ; Barber, C. ; [weitere]

Oxford University Press

In: Monthly Notices of the Royal Astronomical Society. 1993; 260(1): 77-102. Published 1993 Jan 01. doi: 10.1093/mnras/260.1.77.

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Publikationsdatum: 1993-01-01

Print ISSN: 0035-8711

Digitale ISSN: 1365-2966

Thema: Physik

Publiziert von Oxford University Press im Namen von The Royal Astronomical Society.

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Spectroscopic and photometric observations of supernova 1987A - VII. Days 793 to 1770 (1993)

Caldwell, J. A. R. ; Menzies, J. W. ; Banfield, R. M. ; [weitere]

Oxford University Press

In: Monthly Notices of the Royal Astronomical Society. 1993; 262(2): 313-324. Published 1993 May 15. doi: 10.1093/mnras/262.2.313.

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Publikationsdatum: 1993-05-15

Print ISSN: 0035-8711

Digitale ISSN: 1365-2966

Thema: Physik

Publiziert von Oxford University Press im Namen von The Royal Astronomical Society.

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6

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Improvement of FMR linewidth in Bi-substituted lutetium iron garnet thin films for the MSW-optical-mode interaction : 37th Annual conference on magnetism and magnetic materials (1993)

Silliman, S. D. ; Gualtieri, D. M. ; Stancil, D. D.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 73 (1993), S. 6460-6462

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Thin films of bismuth-substituted lutetium iron garnet (BiLuIG) for the magnetostatic wave (MSW)-optical-mode interaction can be grown by liquid-phase epitaxy from the standard PbO-based melt system developed for yttrium iron garnet (YIG). The addition of MgO to the melt to counteract the effect of lea on the ferromagnetic resonance (FMR) linewidth is investigated. BiLuIG thin films were grown on paramagnetic gadolinium gallium garnet substrates with varying amounts of MgO added. The ferromagnetic resonance linewidth, optical waveguide absorption, and MSW passband were measured. The addition of magnesium reduced the FMR linewidth from an average of 3 Oe down to under 1 Oe, with little effect on other parameters.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.352579

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7

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Reducing quasi-ergodic behavior in Monte Carlo simulations by J-walking: Applications to atomic clusters (1990)

Frantz, D. D. ; Freeman, D. L. ; Doll, J. D.

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 93 (1990), S. 2769-2784

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ISSN: 1089-7690

Quelle: AIP Digital Archive

Thema: Physik , Chemie und Pharmazie

Notizen: A method is introduced that is easy to implement and greatly reduces the systematic error resulting from quasi-ergodicity, or incomplete sampling of configuration space, in Monte Carlo simulations of systems containing large potential energy barriers. The method makes possible the jumping over these barriers by coupling the usual Metropolis sampling to the Boltzmann distribution generated by another random walker at a higher temperature. The basic techniques are illustrated on some simple classical systems, beginning for heuristic purposes with a simple one-dimensional double well potential based on a quartic polynomial. The method's suitability for typical multidimensional Monte Carlo systems is demonstrated by extending the double well potential to several dimensions, and then by applying the method to a multiparticle cluster system consisting of argon atoms bound by pairwise Lennard-Jones potentials. Remarkable improvements are demonstrated in the convergence rate for the cluster configuration energy, and especially for the heat capacity, at temperatures near the cluster melting transition region. Moreover, these improvements can be obtained even in the worst-case scenario where the clusters are initialized from random configurations.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.458863

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8

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Photodissociation dynamics of the N3 radical (1993)

Continetti, R. E. ; Cyr, D. R. ; Osborn, D. L. ; [weitere]

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 99 (1993), S. 2616-2631

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ISSN: 1089-7690

Quelle: AIP Digital Archive

Thema: Physik , Chemie und Pharmazie

Notizen: The dissociation dynamics of the B˜ 2Σu+ state of N3 were investigated using fast radical beam photodissociation coupled with a new coincidence wedge-and-strip-anode particle detector. With this detector, detailed photofragment kinetic energy and angular distributions can be measured as a function of excitation energy. Calibration of the detector by studies of the predissociation of the O2 B 3Σu− state is discussed. Methods of extracting the center-of-mass kinetic energy and angular distributions are presented. The photodissociation results for N3 show that from the vibrationless level of the B˜ 2Σu+ state in N3, both spin-allowed [N3→N(2D)+N2(1Σg+)] and spin-forbidden [N3→N(4S)+N2(1Σg+)] dissociation processes occur. Bend excitation in the B˜ 2Σu+ state, however, enhances the spin-allowed dissociation process considerably. The kinetic energy distributions reveal partially resolved vibrational structure in the N2 fragment, and indicate substantial rotational excitation of the N2. This implies that bent geometries play a major role in the dissociation of the N3 B˜ state. Possible mechanisms for the spin-forbidden and spin-allowed dissociation channels are discussed.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.465224

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9

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Fast beam photodissociation of the CH2NO2 radical (1993)

Cyr, D. R. ; Leahy, D. J. ; Osborn, D. L. ; [weitere]

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 99 (1993), S. 8751-8764

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ISSN: 1089-7690

Quelle: AIP Digital Archive

Thema: Physik , Chemie und Pharmazie

Notizen: The photodissociation of the nitromethyl radical, CH2NO2, has been studied using a fast beam photofragment translational spectrometer. In these experiments, a fast beam of mass selected, internally cold nitromethyl radicals is formed via negative ion photodetachment of CH2NO−2 and subsequently dissociated. The recoiling photofragments are detected in coincidence using a microchannel plate detector equipped with a time- and position-sensing anode. Two dissociation product channels are observed at each of three dissociation wavelengths investigated in the range 240–270 nm and are identified as (I) CH2NO2→CH2NO+O and (II) CH2NO2→H2CO+NO. In marked contrast to the ultraviolet photodissociation of CH3NO2, no evidence is found for simple C–N bond fission to give (III) CH2NO2→CH2+NO2. Translational energy and angular distributions were obtained for the two observed channels. The translational energy distribution of channel (I) peaks at only 5–8 kcal/mol, while the distribution for channel (II) peaks at ∼60 kcal/mol. The angular distributions for both channels are largely isotropic. The nature of the electronic excitation and dissociation dynamics are considered at length. The upper state in the electronic transition is assigned to the 1 2B1 state. Results of attempts to model various aspects of the dissociation dynamics as statistical processes on the ground state surface indicate this mechanism is very unlikely. Instead, both dissociation channels are believed to occur primarily on excited state surfaces, and mechanisms for these processes are proposed.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.465597

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Use of trilevel resists for high-resolution soft-x-ray projection lithography (1990)

Berreman, D. W. ; Bjorkholm, J. E. ; Becker, M. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 56 (1990), S. 2180-2182

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: A projection optical system with 20:1 reduction has been used with radiation at ∼36 nm to evaluate resists for use in soft-x-ray projection lithography. The high absorption of soft x rays by carbon-based polymers requires that an imaging resist layer be very thin. The sensitivities and contrasts of several such resists are reported. By incorporating a thin imaging layer into a trilayer resist scheme, we have exposed, developed, and transferred features as small as 0.2 μm into silicon.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.102961

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