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  • American Institute of Physics  (29)
  • American Institute of Physics (AIP)  (16)
  • Wiley-Blackwell
  • 1
    Electronic Resource
    Electronic Resource
    Magnetohydrodynamic turbulence in the solar wind (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 4154-4160 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low frequency fluctuations in the solar wind magnetic field and plasma velocity are often highly correlated, so much so that the fluctuations may be thought of as originating near the Sun as nearly perfect Alfvén waves. Power spectra of these fluctuations from 10−7 Hz to several Hz to suggest that the medium is turbulent. Near 1 AU, fluctuations below 10−5 Hz have a relatively flat slope (∼−1) and contain most of the energy in the fluctuating fields. From 10−5 Hz to ∼0.1 Hz, the spectra exhibit a power law inertial range similar to that seen in ordinary fluid turbulence. At the highest frequencies, the rapid fall-off of the power suggests that strong dissipation is occurring. From in situ measurements, it is clear that the fluctuations emanate from the solar corona. The turbulent cascade appears to evolve most rapidly in the vicinity of velocity shears and current sheets. Numerical solutions of both the compressible and incompressible equations of magnetohydrodynamics in both Cartesian and spherical geometry corroborate this interpretation. There are conflicting interpretations of observations suggesting that much of the power in magnetic field fluctuations resides in quasi-two-dimensional structures and simulations have helped to elucidate some of these issues. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873680
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  • 2
    Electronic Resource
    Electronic Resource
    Measurements on rotating ion cyclotron range of frequencies induced particle fluxes in axisymmetric mirror plasmas (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 2947-2954 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A comparison of phenomenological features of plasmas is made with a special emphasis on radio-frequency induced transport, which are maintained when a set of two closely spaced dual half-turn antennas in a central cell of the Phaedrus-B axisymmetric tandem mirror [J. J. Browning et al., Phys. Fluids B 1, 1692 (1989)] is phased to excite electromagnetic fields in the ion cyclotron range of frequencies (ICRF) with m=−1 (rotating with ions) and m=+1 (rotating with electrons) azimuthal modes. Positive and negative electric currents are measured to flow axially to the end walls in the cases of m=−1 and m=+1 excitations, respectively. These parallel nonambipolar ion and electron fluxes are observed to be accompanied by azimuthal ion flows in the same directions as the antenna-excitation modes m. The phenomena are argued in terms of radial particle fluxes due to a nonambipolar transport mechanism [Hojo and Hatori, J. Phys. Soc. Jpn. 60, 2510 (1991); Hatakeyama et al., J. Phys. Soc. Jpn. 60, 2815 (1991), and Phys. Rev. E 52, 6664 (1995)], which are induced when azimuthally traveling ICRF waves are absorbed in the magnetized plasma column. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872427
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  • 3
    Electronic Resource
    Electronic Resource
    Vertical viewing of electron-cyclotron emissions for diagnosing fast-electron dynamics in TEXT-U : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 427-429 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A system for vertically observing the second-harmonic electron-cyclotron emissions from the TEXT-U tokamak in conjunction with fundamental electron-cyclotron heating is described. Using external collection optics and heterodyne receivers, measurements of the distribution function can be performed over two-thirds of the plasma radius and on transport time scales. Observations are typically of electrons with energy E〈100 keV and either steep or shallow pitch angle, depending upon the toroidal viewing angle relative to the plasma current. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146368
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  • 4
    Electronic Resource
    Electronic Resource
    Field-induced phase switching and electrically driven strains in sol-gel derived antiferroelectric (Pb,Nb)(Zr,Sn,Ti)O3 thin layers (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1171-1177 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Tin-modified lead zirconate titanate thin layers were prepared by a sol-gel method. A room- temperature antiferroelectric (AFE) phase composition Pb0.99Nb0.02[(Zr0.58Sn0.42)0.96Ti0.04] 0.98O3 was prepared and examined for weak- and high-field dielectric properties as a function of temperature, with emphasis on field-induced AFE-ferroelectric (FE) switching characteristics. Thin layers processed with a lead oxide cover coat were found to be free of any secondary phases and showed improved properties. Room-temperature values of dielectric constant K'=390 and saturation polarization Ps=20 μC/cm2 were obtained with field-induced strains up to 0.15% in submicron grain structures. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360353
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  • 5
    Electronic Resource
    Electronic Resource
    Magnetic field pitch angle diagnostic using the motional Stark effect (invited) : Eighth topical conference on high—temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2914-2919 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Stark effect has been employed in a novel technique for obtaining the pitch angle profile and q(r) using polarimetry measurements of the Doppler shifted Hα emission from a hydrogen diagnostic neutral beam. As a neutral beam propagates through a plasma, collisions of the beam particles with the background ions and electrons will excite beam atoms, leading to emission of radiation. The motional Stark effect, which arises from the electric field induced in the atom's rest frame due to the beam motion across the magnetic field (E=Vbeam×B), causes a wavelength splitting of several angstroms and polarization of the emitted radiation. The Δm=±1 transitions, or σ components, from the beam fluorescence are linearly polarized parallel to the direction of the local magnetic field when viewed transverse to the fields. Since the hydrogen beam provides good spatial localization and penetration, the pitch angle can be obtained anywhere in the plasma. A photoelastic modulator (PEM) is used to modulate the linearly polarized light. Depending on the orientation of the PEM, it can measure the sine or cosine of the angle of polarization. Two PEM's are used to measure both components simultaneously. Results of q(r) for both Ohmic and NBI heated discharges have been obtained in the Princeton Beta Experiment (PBX-M) tokamak, with an uncertainty of ∼6% for q(0).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141776
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  • 6
    Electronic Resource
    Electronic Resource
    Neutral probe beam q-profile measurements in PDX and PBX-M (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1635-1637 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Using the fast ion diagnostic experiment technique, a neutral probe beam (NPB) can be aimed to inject tangent to a magnetic surface. The resultant ion orbit shifts, due to conservation of canonical toroidal angular momentum, can be measured with a multi-sight-line charge exchange analyzer to yield direct measurements of radial magnetic flux profiles, current-density profiles, the radial position of the magnetic axis, flux surface inner and outer edges, q profiles, and central-q time dependencies. An extensive error analysis was performed on previous PDX q measurements in circular plasmas and the resulting estimated contributions of various systematic effects are discussed. Preliminary results of fast ion orbit shift measurements at early times in indented PBX-M plasmas are given. Methods for increasing the absolute experimental precision of similar measurements in progress on PBX-M are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140169
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  • 7
    Electronic Resource
    Electronic Resource
    Equilibrium q-profile determination and stability analysis from magnetic field pitch angle measurements using motional Stark effect polarimetry : Eighth topical conference on high—temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2932-2934 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The motional Stark effect polarimetry technique has been used to measure the magnetic pitch angle in a variety of PBX-M plasma conditions. For high aspect ratio, circular plasmas, the q profile can be obtained directly from the γp profile using the cylindrical expression q(r)=(rBT/RBp). In strongly shaped PBX-M plasmas, the magnetic pitch angle data are used as an internal constraint on the plasma equilibrium calculated by solving the Grad–Shafranov equation, subject to external flux measurements. Thus, an accurate determination of q(r) depends upon detailed knowledge of the plasma equilibrium. Discussion of uncertainties in the equilibrium determination and their effect on q(r) will be presented. The equilibrium solutions using the pitch angle data are required for MHD stability calculations, which are being used to investigate the relationship between internal kink modes and plasma shape.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141780
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  • 8
    Electronic Resource
    Electronic Resource
    Adsorption and decomposition of diethylgermane on Si(111) 7×7 (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 2002-2004 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Germanium was deposited on Si(111) 7×7 by the adsorption and thermal decomposition of diethylgermane [(CH3CH2)2GeH2] (DEG). The DEG reaction products were CH2(large-closed-square)CH2 and H2, which desorbed at 700 and 800 K, respectively, as observed by laser-induced thermal desorption and temperature programmed desorption techniques. The desorption of atomic Ge was also monitored at approximately 1200 K. The production of ethylene was consistent with a β-hydride elimination mechanism for the surface ethyl groups, i.e., Ge—CH2CH3→GeH+CH2(large-closed-square)CH2. The initial sticking coefficient of DEG decreased with increasing surface temperature and a saturation coverage was obtained after exposures of E(approximately-greater-than)700 L at 200 K. This saturation behavior indicates that DEG may be useful for the controlled growth of Ge atomic layers on silicon surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107124
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  • 9
    Electronic Resource
    Electronic Resource
    Chemical vapor deposition of silicon carbide thin films on titanium carbide, using 1,3 disilacyclobutane (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 3097-3098 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Silicon carbide (SiC) thin films were deposited on titanium carbide (TiC) substrates by pyrolysis of 1,3 disilacyclobutane (C2H8Si2), at atmospheric pressure, in an inverted-vertical cold-wall chemical vapor deposition reactor. The growth rate, morphology, and crystallinity of the films were studied, at constant C2H8Si2 flow rate, as a function of substrate temperature (810 °C≤Ts≤1285 °C). The growth rate increased with increasing Ts. Film morphologies were dependent on Ts and slight differences in TiC substrate orientation at Ts≥1015 °C. A smooth, soft as-grown morphology was obtained at 810 °C. Hard, rough as-grown surfaces were obtained at Ts≥1066 °C. Films grown at Ts ≥1066 °C contained a SiC primary phase and a Si-rich second phase. Epitaxial growth of β-SiC was obtained only at 1210 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109147
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  • 10
    Electronic Resource
    Electronic Resource
    Enhanced slow-wave beach heating of mirror plasmas with two-ion species (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 1475-1485 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Plasma heating in the ion-cyclotron range of frequencies has been examined in a beach-heating configuration of the central cell of the Phaedrus-B tandem mirror [Phys. Rev. Lett. 51, 1955 (1983)] during scans of the ion species ratio of hydrogen–helium (H–He) and hydrogen–deuterium (H–D) plasmas. Observed changes in the radial profiles of wave magnetic field and plasma parameters during the scans provide evidence of varied fast- and slow-wave eigenmode excitation and absorption. These changes are shown to be in agreement with those expected from wave accessibility considerations. Optimal peak parameters in the plasma core, ne=1.0×1013 cm−3, Te(parallel)=20 eV, Ti(parallel)=140 eV, Ti⊥=450 eV, and β=0.26 at midplane, were obtained for moderate helium or deuterium ion fractions (puffed nHe/ne=nD/ne ∼0.25). These parameters represent a significant increase in plasma energy density over that obtained under the same conditions with "pure'' hydrogen plasmas: ne=7.0×1012 cm−3, Te(parallel)=25 eV, Ti(parallel)=80 eV, Ti⊥=300 eV, and β=0.12.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860058
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