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Alternating current (ac) losses in conductor-on-rounded-core (CORC) cables of YBCO high-temperature superconducting (HTS) tapes are a significant challenge in HTS power applications. This study employs two finite element analysis (FEA) models to investigate the contributions from different ac loss components and provide approaches for reducing ac losses in cables. An FEA model based on the T-A formulation treats the cross section of thin superconducting layers as 1D lines and, therefore, only can predict the ac loss generated by the perpendicular magnetic field. In contrast, the model based on H-formulation can be performed on the actual 2D rectangular cross section HTS tapes to provide the total ac losses generated by magnetic fluxes penetrating from both the edges and surfaces of HTS tapes, although this model requires more computing time and memory. The 1D and 2D simulation models were validated by cross comparing the results from both models and by comparing sub-section and full cross section models. Subsequently, two models relate cable design and operational parameters to the surface and edge losses of a two-layer CORC cable by considering the (1) relative contributions of edge and surface losses to the overall ac losses; (2) effect of the current distribution between inner and outer HTS layers on ac losses; (3) impact of the tape alignment on ac losses in each HTS layer; (4) influence of the thickness of HTS layers on ac losses; (5) effect of size and number of inter-tape gaps on ac losses; and (6) contribution frequency on the ac losses. The research results given in this paper are therefore not only valuable to suggest strategies for reducing ac loss in multi-layer cables but also for developing more accurate and effective methods to calculate ac loss in CORC HTS cables. [ABSTRACT FROM AUTHOR]

Molecular anions are appealing targets for study because, compared with their neutral and cationic counterparts, they can be probed with conventional laboratory lasers without the need for multiphoton ionization schemes, and they provide spectroscopic details on the corresponding neutral molecules. Here, we describe a section of a modular instrument designed to perform high-throughput photoelectron and photodetachment spectroscopy of gas-phase anions, with future provision for time-resolved and isomer-selective spectroscopy. The instrument framework allows for the incorporation and adaptation of several ion sources, as demonstrated here with plasma (electric) discharge sources providing variable hard to soft ion generation conditions. The generated anions are separated according to their mass-to-charge ratio through time-of-flight mass spectrometry ( m / z Δ m / z = 500–600) and are focused into a set of perpendicular velocity-map imaging electrodes ( Δ E E ≈ 4 %), where mass-selected anions are probed using laser light and the ejected electrons are velocity-map imaged. Instrument performance is demonstrated through the acquisition of photodetachment and photoelectron spectra for CH2CN−, showing sharp resonances in the vicinity of the detachment threshold assigned to rovibrational states of a dipole-bound anion and broader lifetime-limited spectral features at photon energies well above the threshold assigned to prompt autodetachment from a temporary anion resonance. Similar measurements could be performed on any molecular anions generated in the sources. [ABSTRACT FROM AUTHOR]

A new method for the deposition of stacks of YBCO layers on the same substrate is studied using the multiple ion beam-assisted deposition (IBAD) templates. The analysis reveals that the resetting of the surface texture helps in the manufacture of new types of structures in the coated conductors.

The study presents the quantification of the tape interaction and the AC losses that are observed in the YBCO coated conductor coils. The losses are found to decrease in the presence of an externally applied magnetic field.

This paper presents a study of the total ac loss characteristics of a rolling-assisted biaxially textured substrate (RABiTS) YBa2Cu3O7 (YBCO) sample exposed to a parallel ac magnetic field. The results have shown that, for a given applied magnetic field and transport current, a RABiTS YBCO tape can generate very different magnitudes of ac loss, depending on whether the transport current and applied field have the same phase or opposite phase. The results of this study are very important for the optimization of the design of a RABiTS YBCO cable because they can suggest an appropriate arrangement of RABiTS tapes in a cable to minimize the cable ac loss. In this study, both experimental and finite-element method simulation approaches were employed. A modeling model that takes the magnetic field dependent permeability and ferromagnetic loss of the substrate into account reproduced well the experimental data for both self-field and total ac losses. [ABSTRACT FROM AUTHOR]

In this paper we present a finite element model using the commercial COMSOL® software package for calculating the ac loss in bifilar stacks of high temperature superconducting tape. In the model, the current-voltage relationship characterizing the superconducting properties is assumed to follow a power law. The calculations were performed for infinite bifilar stacks with different values of layer-to-layer separation D. With appropriate settings for the boundary conditions, the numerical results agree well with the analytical data obtained from a recently proposed model [J. R. Clem, Phys. Rev. B 77, 134506 (2008)]. The numerical approach was also used to investigate the end effects in a bifilar stack to answer the following question: how many layers away from the end of a stack are required before the environment of a given layer is identical to that in an infinite stack? We find that the answer to this question depends strongly on the value of D. Based on this study, a model for calculating the ac loss in bifilar noninductively wound coils with a finite number of turns is proposed. [ABSTRACT FROM AUTHOR]

Yttrium barium copper oxide (YBCO) coated conductors are now the most promising high-temperature superconducting tapes in terms of current capacity and price. One form of these conductors utilizes YBCO films on Ni–W metallic tapes and is being considered for a number of power engineering applications. In these applications, the conductor will carry an ac current, leading to energy losses, which are the focus of significant technical and experimental efforts. Our measurements of the ac losses of YBCO/Ni–W conductors carrying ac currents in applied dc magnetic fields have revealed a complex interaction between the magnetic materials present, the geometry of the conductor, the ac and dc magnetic fields, and the electromagnetic “history” of the sample. The investigation of this interaction is the main subject of this paper. [ABSTRACT FROM AUTHOR]

Sub-Doppler spectra of the A [SUP3]II-X[SUP3]∑ [SUP-](0,0) and (1,0) bands of the PH radical have been recorded using an injection seeded single mode optical parametric oscillator in a supersonic jet expansion. Most of the rotational lines in these laser-induced fluorescence spectra exhibit clear splittings or asymmetry due to hyperfine structure. An analysis of this structure is presented in terms of the electronic structure and bonding of the molecule. Comparisons are drawn with the corresponding A [SUP3]II state of the NH radical, and some shortcomings in the accepted methods for interpretation are highlighted and discussed. [ABSTRACT FROM AUTHOR]

The total ac loss characteristics of a rolling-assisted biaxially textured substrate (RABiTS) Y[Ba.sub.2][Cu.sub.3][O.sub.7] (YBCO) sample exposed to a parallel ac magnetic field is studied. The results have shown that a RABiTS YBCO tape has generated very different magnitudes of ac loss, depending on whether the transport current and applied fields have the same phase or opposite phase.

"Physics behind music: an introduction" by Bryan H. Suits is a book that successfully combines physics and music. Unlike other books on the subject, Suits uses familiar aspects of music as a starting point to explain various physical principles. The book covers topics such as rates of processes, frequencies, pitch, auditory illusions, vibrating rods, wavepackets, non-linear physics, sound in pipes and tubes, room acoustics, electronic sound production, and more. Each chapter includes a summary, suggestions for additional reading, and problems with selected answers. The book is accessible to non-experts and is recommended for interested readers or as supplementary material for a physics course. [Extracted from the article]

By use of a free-jet expansion which incorporates a heated nozzle, we have recorded the laser excitation spectrum of the 460 nm band system of NiCl2 at rotational resolution. The rotational temperature in these recordings was about 12 K. Several bands have been recorded and analyzed for three isotopomers, 58Ni35Cl2, 60Ni35Cl2, and 58Ni35Cl37Cl in natural abundance. Spin components with Ω values of 0 and 1 have been identified in both the upper and lower states of the transition. Accurate values for all three vibrational intervals ν1, ν2, and ν3 have been determined for nickel dichloride in the upper state and for the bending wave number ν2 in the lower state. The results show that the molecule is linear in both states involved in the transition and that the lower (ground) state is 3Σ-g in character. Evidence is presented from the nickel isotope shifts to show that the transition is vibronically induced through the bending vibration and that the upper state is vibronically 3Πu in character; it probably derives from an electronic 3Δg state. The zero-point averaged bond lengths are determined for both states as r0′=0.209 435(13) nm and r0″=0.205 317(14) nm. The fine structure parameters for the X 3Σ-g state are interpreted in terms of low lying 1Σ+g and 3Πg states, which are shown to lie a few thousand reciprocal centimeters above the ground state. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We present high resolution, infrared laser absorption spectra of (DF)3 in a slit supersonic jet expansion. In contrast to previous structureless near IR spectra of (HF)3, the (DF)3 data reveal clear rotational structure characteristic of a cyclic, 6-membered ‘‘ring,’’ and therefore provide the first accurate experimental evidence for the equilibrium geometry of any hydrogen fluoride oligomer beyond the well-studied dimer. Furthermore, the spectra display homogeneous rotational fine structure 2–3 orders of magnitude in excess of what could be anticipated from a single vibrational band. Analysis of this fine structure elucidates a novel IVR mechanism which involves single hydrogen bond cleavage, and consequent opening of the (DF)3 ring on the 40 ps time scale. [ABSTRACT FROM AUTHOR]