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  • 1
    Electronic Resource
    Electronic Resource
    Heating of a plasma with a frequency feedback system
    Amsterdam : Elsevier
    Physics Letters A 48 (1974), S. 193-194 
    Details
    ISSN: 0375-9601
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0375-9601(74)90539-8
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  • 2
    Electronic Resource
    Electronic Resource
    Determination of average ion energy in turbulently heated plasmas by secondary emission detector
    Amsterdam : Elsevier
    Physics Letters A 57 (1976), S. 339-340 
    Details
    ISSN: 0375-9601
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0375-9601(76)90601-0
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  • 3
    Electronic Resource
    Electronic Resource
    Present and future JET ICRF antennae
    Amsterdam : Elsevier
    Fusion Engineering and Design 24 (1994), S. 1-21 
    Details
    ISSN: 0920-3796
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0920-3796(94)90034-5
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  • 4
    Electronic Resource
    Electronic Resource
    Development of the JET ICRH plant
    Amsterdam : Elsevier
    Fusion Engineering and Design 24 (1994), S. 23-46 
    Details
    ISSN: 0920-3796
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0920-3796(94)90035-3
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  • 5
    Electronic Resource
    Electronic Resource
    High-resolution, high-sensitivity NMR of nanolitre anisotropic samples by coil spinning (2007)
    [s.l.] : Nature Publishing Group
    Nature 447 (2007), S. 694-697 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Nuclear magnetic resonance (NMR) can probe the local structure and dynamic properties of liquids and solids, making it one of the most powerful and versatile analytical methods available today. However, its intrinsically low sensitivity precludes NMR analysis of very small samples—as ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature05897
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  • 6
    Electronic Resource
    Electronic Resource
    Relaxation without spin diffusion in fractal systems: Polymers in glassy solutions (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 9239-9251 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We describe the nuclear relaxation of protons by paramagnetic centers in glassy solutions of polymers. Both the protons and the paramagnetic radicals are on the polymers, and the solvent is fully deuterated. Two cases have been analyzed, that when the relaxing centers are randomly distributed, and that when each polymer has a single center grafted at one end. The analysis was made for dilute and semi-dilute solutions of polymers. Experiments performed on poly-2 vinyl pyridine (P2VP) and on polystyrene yield results in agreement with theory, both as regards the NMR and the polymer models. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475216
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  • 7
    Electronic Resource
    Electronic Resource
    Radio-frequency-sheath-driven edge plasma convection and interaction with the H mode (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 3603-3617 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is shown that radio-frequency (rf) antenna sheaths can bias the edge plasma potential and drive steady-state convective cells in the scrape-off layer (SOL). The resulting E×B convective flow opposes the direction of the sheared flow in the SOL induced by the radially decaying Bohm sheath potential. A two-dimensional fluid simulation shows that the interaction of the opposing poloidal flows produces secondary vortices, which connect the edge of the confined plasma to the antenna limiters, when the antenna–plasma separation is typically of order a few times the local electron skin depth at the antenna. Estimates for typical tokamak edge parameters suggest that the transit time of particles and energy across these vortices is rapid enough to cause the broadening of SOL density and temperature profiles observed during high-power heating with ion cyclotron range of frequency (ICRF) antennas in monopole phasing. Radio-frequency-sheath-driven convection is also a good candidate to explain the phasing dependence of the global confinement properties of ICRF H modes on the Joint European Torus (JET) [Fusion Technol. 11, 13 (1987)]. A comparison of the JET H-mode data with the theoretical modeling supports this idea and suggests that ICRF convection may be a useful tool to spread the heat deposition in the divertor and to extend the lifetime of the H mode.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860832
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  • 8
    Electronic Resource
    Electronic Resource
    Joint European Torus results with both fast and lower-hybrid wave consequences for future devices (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2111-2121 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Heating and current drive studies were performed during the JET [Phys Fluids B 3, 2209 (1991)] 1990/91 operation using two large systems capable of generating either fast waves in the ion cyclotron range of frequencies (ICRF) or slow waves at a frequency above the lower-hybrid resonance (LH). The maximum wave power coupled to the torus reached 22 MW for ICRH and 2.4 MW for LH. The results obtained in plasma heating experiments qualify ICRH as a prime candidate for heating reactor grade plasmas. A centrally localized deposition profile in the cyclotron damping regime was demonstrated in a wide range of plasma density resulting in (i) record value nd τE Ti0 (approximately-equal-to) 7.8 × 1020 m−3 sec keV in "thermal'' conditions Ti = Te (approximately-equal-to) 11 keV at high central densities generated by pellet injection; (ii) large normalized confinement 2.5 ≤ τE/τGoldston≤4. The large values of τE/τGoldston are reached in H-mode discharges (I≤1.5 MA) with large bootstrap current fraction IBS/I ≤ 0.7 ± 0.2; (iii) the highest to date D–3He fusion power (140 kW) generated with 10–14 MW of ICRH in the L-mode regime at the 3He cyclotron frequency. All specific impurity generations have been reduced to negligible levels by proper antenna design and the generic difficulty of wave–plasma coupling has been greatly reduced using feedback loops controlling in real time the antenna circuits and the plasma position.Current drive efficiencies γ=ICD〈ne〉R/P (approximately-equal-to) 0.4 × 1020 m−2 A/W have been reached in 1.5 MA L-mode plasma with zero loop voltage by combining LHCD and ICRH. Fast electrons are driven by LHCD alone to tail temperatures of up to 70 keV. The fast electron density is peaked in the plasma center at lower densities (ne0 ≤ 2.6 × 1019 m−3) and high field (Bφ ∼ 3.1 T). In these conditions, the fast electrons are further accelerated (even at zero loop voltage) to tail temperatures above 150 keV by heating the plasma with ICRF in monopole phasing. Direct electron damping of the fast wave on the fast electrons created by LH appears to be the driving mechanism of this synergism which produces fast wave current drive even without phasing the ICRH antennas. Finally, the first results obtained in the minority current drive regime are reported. The sawtooth instability is considerably modified when the resonance is located near the q=1 resonance. The effect is reversed from stabilization to destabilization when the phase of the ICRH antennas is reversed from +90° to −90°.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860483
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  • 9
    Electronic Resource
    Electronic Resource
    Silicon Substitution for Aluminum in Calcium Silicate Hydrates (1999)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: 27Al MAS and multiquantum (MQ) MASNMR (magic-angle spinning nuclear magnetic resonance) spectroscopy were used to study the substitution of silicon by aluminum in calcium silicate hydrates (C-S-H), which are the main component of hydrated portland cement. Synthetic C-S-H samples were prepared, and their chemical stability was studied. Two-dimensional 3Q-MASNMR spectra revealed the chemical shift and quadrupolar parameters (deltaiso, nuQ) that labeled aluminum sites in the C-S-H. Tetrahedral aluminum was observed in the bridging and nonbridging sites of the silicate chains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb01912.x
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  • 10
    Electronic Resource
    Electronic Resource
    NMR studies on nuclear ordering in metallic copper below 1 ΜK (1980)
    Springer
    Journal of low temperature physics 39 (1980), S. 417-450 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: The nuclear spin system of metallic copper in a poly crystalline sample consisting of thin wires has been studied using a cryostat in which a dilution refrigerator and two copper nuclear stages operate in series. The spin system was cooled to 50 nK, which is an all-time low-temperature record. The NMR absorption curves were measured in external fields from zero to B ext = 15 mT and at entropies corresponding to polarizations up to 0.9. The line shapes reveal the effect of indirect exchange interaction corresponding to an antiferromagnetic value of Σ j J ij /γ2\ħ 2Μ 0 ϱ = −0.42 ± 0.05. This result was obtained both from the interference of the isotopic absorption lines at 15 mT and from the shift of the second harmonic in fields below 2 mT. Thus, an antiferromagnetic transition in zero field at about 200 nK is expected. The Curie—Weiss θ points to a transition temperature of 150 nK; the inverse static susceptibility vs temperature curve clearly predicts antiferromagnetism. However, no evidence of such a transition was found in NMR spectra measured with the excitation transverse to the copper wires, although the entropy was reduced to about 0.45 R ln 4, with the corresponding temperatures well below 100 nK. On the other hand, in measurements during which the excitation was parallel to the wires, a clear saturation of susceptibility to a constant value could be seen as a sudden change in the apparent relaxation rate at the lowest entropies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00115631
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