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  • 1
    Electronic Resource
    Electronic Resource
    TFTR Thomson scattering system (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1015-1017 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The TFTR Thomson scattering system has been operational since January 1984. The diagnostic uses two ruby lasers and two spectrometer-detector systems to provide profiles at two times in a discharge. The two scattering lines consist of 76 spatial channels which span the 200-cm vacuum vessel along a major radius. The detectors are gated, intensified CCD arrays with single photoelectron sensitivity. Te(R) and Ne(R) profiles are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138255
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  • 2
    Electronic Resource
    Electronic Resource
    Approaches to ultrafast neutron detectors (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1096-1097 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We discuss two approaches to obtain neutron detectors of very high temporal resolution. In the first approach, a uranium-coated cathode is used in a streak tube configuration. Secondary electrons accompanying the fission fragments from a neutron-uranium reaction are accelerated, focused through a pinhole, and streaked. Calculations show that 20-ps time resolution can be obtained. In the second approach, a uranium-coated cathode is integrated into a transmission line. State-of-the-art technology indicates that a time resolution of 20 ps can be obtained by gating the cathode with a fast electric pulse.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138234
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetostatic wave propagation losses in thorium-substituted YIG (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3724-3726 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: YIG films were grown with thorium added to the melt in varying concentrations with a maximum Th/Y ratio of 0.487. The effect of the addition of thorium on the propagation of magnetostatic forward volume waves at X band was studied using a differential path delay line. It was found that the addition of thorium increased the propagation loss. For Th/Y ratios greater than 0.0428, magnetostatic forward volume waves could not be detected after propagation over a 1-cm path length. Although the variations in thorium content resulted in a range of lattice mismatches including both positive and negative values, there was no observable minimum in the loss corresponding to zero mismatch. It was also observed that the addition of thorium increased the dc conductivity, but calculations showed that the conductivity was not large enough to produce significant eddy current losses. We feel that the addition of thorium increased the amount of Fe2+ present in the films, thus activating the valence-exchange loss mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.334949
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  • 4
    Electronic Resource
    Electronic Resource
    Advances in laser fluorescence scattering with Balmer series dye lasers (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1012-1014 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The spatial distribution of neutral deuterium has been determined in a reversed field pinch by fluorescence scattering. The first series of measurements, with a resolution of 4 cm were made with the laser tuned to the Dα, n=2−3(6561 A(ring)) transition. The second set of measurements, with both 4 and 2 cm resolution were performed with the laser tuned to the Dβn=2−4(4861 A(ring)) wavelength. The improvement in signal to noise obtained was substantial, being increased by a factor of (approximately-equal-to)2.5 in general. This is believed to be the first such measurement at this wavelength. The advantages of using this transition are such that this technique can be extended to measure the electron density near the plasma edge.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138254
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  • 5
    Electronic Resource
    Electronic Resource
    Ultrafast turnoff laser triggered gating system for microchannel-plate intensified x-ray spectrometers (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 818-820 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A laser triggered photoconductive switch based microchannel-plate (MCP) gating system has been developed. The gating pulse provided to the MCP has a fall time on the order of 200 ps. Use of this system has resulted in increased signal-to-noise ratio on three MCP intensified x-ray spectrometers during recent x-ray experiments at the Novette laser facility. The x-ray signals of interest have a duration of approximately 300 ps while background in the same spectral region continues for several nanoseconds. As a result, signal-to-noise ratio is maximized by turning the MCP off just after the signals of interest are recorded. The MCP's are turned on by charging to approximately 1 kV with a slow rise-time (500 ns) pulse and rapidly gated off by a photoconductive switch connected to the MCP through transmission lines. Staggering the turnoff times of three microstrip lines across the MCP by 250 ps provides some time resolution. Details of the system, including pulse charging system, trigger beam delivery optics, and system diagnostics will be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138183
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  • 6
    Electronic Resource
    Electronic Resource
    Photodissociation of chlorine isocyanate (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 1317-1322 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Gaseous ClNCO exhibits a continuous ultraviolet absorption feature peaked near 250 nm. Photolysis of this compound at 249 nm produces bright blue emission identified as the A 2Σ+→X 2Π transition in NCO. The excited NCO arises from a collisional process in which N(2D) atoms, produced directly by the photodissociation, react with the parent ClNCO. The rate constant for this process is k=(2.1±0.2)×10−11 cm3 s−1. From production of N(2D) by the 249 nm photolysis, the heat of formation of gaseous ClNCO is inferred to be ΔHf(ClNCO)≥52.9 kcal mol−1. ClNCO is metastable with respect to the ground electronic states of NCl and CO by 8.2 kcal mol−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.448962
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  • 7
    Electronic Resource
    Electronic Resource
    Raman scattering study of phase transitions in NH4SCN (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 5624-5632 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Raman spectra (30–3300 cm−1) of a single crystal and of polycrystalline forms of NH4SCN are presented in the temperature range 135 to −175 °C. The polarization behavior of the Raman bands reveals the antipolar arrangements of SCN− ions in the room temperature phase. Above 86.5 °C the spectra do not show polarization behavior due to the formation of polycrystalline domains. Other changes observed in the entire spectrum at this phase transition are attributed to reorientation of SCN− ions between two equivalent configurations. At the next phase transition around 112 °C the lattice modes of SCN− ions are affected. The characteristics are those of a second-order displacive phase transition. A new phase transition observed at −70 °C is characterized by the strengthening of the hydrogen-bond networks in the lattice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.448598
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  • 8
    Electronic Resource
    Electronic Resource
    An EXAFS study of the structure of the metal–support interface in highly dispersed Rh/Al2O3 catalysts (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 5742-5754 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Four highly dispersed and fully reduced rhodium on alumina catalysts with different particle sizes in the range 6–12 A(ring) were investigated with the EXAFS technique in order to derive information about the structure of the metal–support interface. This information can only be obtained when the signal-to-noise ratio of the experimental EXAFS data is high enough and accurate reference compounds and a modified way of data analysis are used. With the aid of phase and amplitude corrected Fourier transforms it was possible to detect a small additional signal which could be ascribed to a Rh–O bond. Since the catalysts were fully reduced and since the intensity of the small signal increased with decreasing particle size, the oxygen neighbor was assigned to be originated from the metal–support interface. From the intensity of the Rh–O bond it was estimated that, on the average, each interfacial rhodium atom is surrounded by 2–3 oxygen ions of the support. The detected Rh–O bond has a coordination distance of 2.7 A(ring) which is about 0.6 A(ring) larger than the first coordination distance in Rh2O3 (2.05 A(ring)). The coordination distance of 2.7 A(ring) can be explained by assuming an interaction between metallic rhodium (atomic radius 1.34 A(ring)) and ionic oxygen belonging to the support (ionic radius 1.4 A(ring)). This would possibly imply an ion-induced dipole bonding between the metal particle and the support.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.448563
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  • 9
    Electronic Resource
    Electronic Resource
    Compressibility as a feature of field reversal maintenance in the reversed-field pinch (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 898-902 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Five different codes have been used to simulate the identical problem in reversed-field pinch (RFP) dynamics using the resistive magnetohydrodynamic (MHD) model in three dimensions with the same set of initial and boundary conditions. Three codes are compressible, while two are incompressible. The assumption of incompressibility was made in the spirit of reducing the model so that, for example, the codes would run faster while retaining the relevant physics. The results show that the three compressible codes agree quite well with each other and the two incompressible codes agree with each other also, but the compressible and incompressible models show qualitatively different behavior. Most importantly, for a certain set of boundary and initial conditions, the compressible codes predict field reversal maintenance while the incompressible codes do not. Thus compressibility is an important feature of RFP physics. This is in contrast to tokamak physics where the strong toroidal field enforces incompressibility at low poloidal beta.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865060
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  • 10
    Electronic Resource
    Electronic Resource
    Multiple-frequency electron-cyclotron heating of hot-electron rings in a bumpy torus (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 1932-1936 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The use of multiple-frequency microwave power for electron-cyclotron heating significantly increased the ring stored energy in the SM-1 simple mirror device. Multiple-frequency electron-cyclotron heating (MFECH) was used on the ELMO Bumpy torus (EBT) in an effort to increase its hot-electron beta. No substantial improvement in the ring parameters was observed in a series of two-frequency ECH experiments, with frequency separations up to 90 MHz, in contrast to the dramatic improvement found in the axisymmetric SM-1 experiment. The toroidal canting of the EBT mirror sectors introduces asymmetries that destroy the superadiabatic behavior of the energetic electrons, reduce microwave heating efficiency, and produce additional ring losses. These effects qualitatively explain the different multiple-frequency heating results obtained in EBT and SM-1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.864937
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