Helical resonators containing high T c ceramic superconductors

Abstract

Resonators are the single most important ingredient in microwave and radio frequency circuits. We have produced some helical resonators using a bulk Ba2YCu3O7 high Tc ceramic superconductor. These resonators, which operate at 77 K and cover the frequency range from 0.1 to 2.0 GHz, outperform their all copper counterparts by at least a factor of 5 in unloaded Q.

High-temperature superconducting thick films

“…Given the differences in the grain microstructure of the films prepared below and above the peritectic temperature, the performance agrees qualitatively with the resistively shunted junction model for sintered materials where there is poor coupling between grains and where R s is poor in comparison with melttextured YBCO thick films [5]. In an early study of fine-grained sintered YBCO there was seen to be a welldefined power dependence in the material which, being fine grained, contained a large number of grain boundaries per unit volume [73]. It is now recognized that the coupling between the grains in such materials is poor.…”

A radio-frequency coil for the microwave characterization of vortex dynamics in thin film superconductors

“…One important advantage of this kind of resonator is that it provides a high quality factor, Q, in a reasonably small volume. 43,45 The complex physical structure of the helical resonator makes it very difficult to analyze and exact solutions to the problem do not exist. Nevertheless, there have been a number of attempts to interpret it, two of the more successful being the sheath 49 and the tape 50 models.…”

“…1,27 A number of helical resonators have been developed from either thick films [43][44][45][46] or copper wire, 43,45 with different forms as those of a bulk wire helix supported by thin-walled quartz, 44 or a helix on a tubular yttria-stabilized zirconia substrate, 46 amongst others. The resonant frequencies, that depend on the total length of wound wire, lie between a few MHz and several GHz.…”