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A laboratory-scale EMS-based HTS maglev vehicle operating over a 1.5 m guideway has been successfully constructed. The fully integrated system consists of a vehicle chassis, four dependent magnetic circuits, four distance sensors, and control and power amplification circuits. As key component of the system, each magnetic circuit includes a U-shape iron core with one HTS coil forming each pole. Eight HTS coils made of Bi-2223 multi-filamentary tape were used to provide the magnetic motive force. Several questions relating to the unique characteristics of the HTS material in a controlled magnetic circuit are discussed. The most important consideration for such applications is that the anisotropic critical current of the Bi-2223/Ag tape depends strongly on the magnetic field. The commercially available FEA software ANSYS was used to simulate the field distribution along the magnetic circuit and HTS coil winding, and thereby identify how the magnetic circuit alters the field distribution in the coil winding and therefore also the critical current. A general optimization process is described for finding the best position in the U-shape iron core to hold the HTS coils. In this process the critical current of the HTS tape and the force–current characteristic of the magnetic circuit are considered synthetically. The results demonstrate the feasibility and stability of HTS material in a typical maglev system and other similar controllability applications. � 2005 Elsevier B.V. All rights reserved. PACS: 84.71.Ba

AC losses in multi-filamentary tapes depend on various parameters. Among them, the overall tape width and thickness are expected to have an important influence. In order to study this geometrical effect, five Bi-2223/Ag tapes with different aspect ratios from 5 to 26 have been prepared. AC losses have been measured at 77 K when a perpendicular AC magnetic field is applied. It has been found that at any frequencies the magnetic loss per cycle increases as the aspect ratio increases. For AC magnetic loss, with increasing frequency from 3 to 9000 Hz the losses as a function of frequency show a maximum if the field amplitude is much less than the full penetration field or increase continuously if the field amplitude is larger.

Change in the quadrupole splitting of 151 Eu nucleus in the Mossbauer spectra of an EuBa 2 Cu 3 O 7− x thick film at 105 K has been observed when an AC electric current passes the thick film. It has been found that the quadrupole splitting of 151 Eu nucleus increases with increasing the frequency of the electric current passing the thick film and that the relationship between the quadrupole splitting of Eu nucleus in the superconducting thick film and temperature before the superconducting transition can also obey the formula presented by Heubes and Christiansen. This phenomenon may be attributed to the hysteresis loss of the alternating current passing the superconducting regions in the EuBa 2 Cu 3 O 7− x thick film.

Mossbauer spectra of Fe-57 in a thick film YBa2(Cu0.97Fe0.03)(3)O7-x irradiated by a large dose of gamma-rays from Co-60 have been measured. The variation of the relative intensities of some subspectra of Fe-57 in the. Mossbauer spectra of the thick film YBa2(Cu0.97Fe0.03)(3)O7-x after irradiation can be observed. This variation indicates that the change of the coordination environment around some Fe atoms in the lattice occurs due to irradiation. The relative intensity of subspectrum D1(Fe) at the Cu(1) site decreases and that of subspectrum D4(Fe) at the Cu(1) site increases. This may be because of the possible oxygen atom hopping between the coordination environments of D1(Fe) and D4(Fe) in the lattice caused by irradiation. The effect of irradiation on the coordination environment around the Fe atom at the Cu(2) site is not appreciable. (C) 1997 Elsevier Science B.V.

Laser-induced voltage pulses of several tens volts have been observed in YBa 2 Cu 3 O 7−δ films with a tilted orientation at room temperature. In this paper, we present the experiment results concerning the dependence of the response time on the film thickness, the tilt angles and the way of irradiation.

The epitaxial Tl 2 Ba 2 CaCu 2 O 8 films were prepared by magnetic sputtering on (100) SrTiO 3 substrates but with a tilt angle ( α =0°,10°,20°). Through analysis of SEM and X-ray diffraction, we studied the surface topography and structure of the films: the smaller the tilt angle of the substrate, the smoother the film surface and the better the film texture along C-axis. Voltage pulses can be observed on TlBaCaCuO films with a tilt orientation(10° and 20°). The amplitude of signals is related to the structure of the films.