AC Loss and Voltage Signal in a Pancake Coil Made of Coated Conductor With Ferromagnetic Substrate
The voltage signal and the AC loss in a pancake coil made of a coated conductor tape with magnetic substrate is measured. The experimental data have been analyzed with the help of numerical calculations. It is found that while for a single tape the AC loss is dominated by the substrate, for the coil it is dominated by the superconducting layer. Moreover, the substrate increases the AC loss generated in the superconducting material, making it similar to a slab. A compensation method for the voltage signal is also described, thanks to which the contribution from the substrate and the superconducting layer can be distinguished.
Magnetic properties of finite superconducting cylinders. I. Uniform applied field
A model for the calculation of the magnetic levitation force for finite type-II superconductors in the critical state is presented in a series of two papers. In the first paper, we describe the main features of the model and understand the effect of demagnetizing fields in the magnetic properties of finite superconductors by considering the case of a superconducting cylinder in the presence of a homogeneous applied field. Field and current profiles are calculated from a minimization of the magnetic energy in the superconductor after a change in the applied field. Results are presented for both constant and field-dependent critical currents. The procedure is general enough to be applied to the case of nonuniform applied fields, as long as the cylindrical geometry is preserved.
Geomagnetic Polarity Epochs: Sierra Nevada Data, 3
Available paleomagnetic and radiometric results for about 60 igneous rocks 3.6 m.y. old or less are consistent with the following geomagnetic polarity epoch time scale: Brunhes normal polarity epoch, 0.0 to 0.85±0.15 million years; Matuyama reversed polarity epoch, 0.85±0.15 to 2.4±0.1 million years; Gauss normal polarity epoch, 2.4±0.1 to 3.35±0.1 million years; Gilbert reversed polarity epoch, 3.35±0.1 million years to (?). A brief interval of normal polarity (the Olduvai event) occurs within the Matuyama reversed epoch at about 1.9 m.y., and a brief interval of reversed polarity (the Mammoth event) occurs within the Gauss normal epoch at about 3.06 m.y. Data for twelve units from eastern California and Nevada, reported here for the first time, are particularly useful in defining the Gauss-Gilbert boundary and for recognizing the Mammoth event.