S.J. Penn

A simple process for manufacturing barium zirconate crucibles

A simple method is reported for making crucibles. crucibles are favoured for making high quality HTS single crystals. A problem with is that it is highly refractory requiring very high sintering temperatures in order to achieve high density. The process reported uses widely available yttria stabilized zirconia substrates upon which barium containing materials are reacted.

Design of rf receiver coils fabricated from high temperature superconductor for use in whole body imaging equipment

Abstract The application of HTS to Magnetic Resonance receive coils needs to be tailored to the frequency of operation and the volume of interest. We report on the limits of achievable performance and the relative importance of parameters involved in designing receiver coils. The gulf between achieved and expected performance is identified by reference to examples of thick film HTS coils compared to copper mimics.

Measurements of material and circuit properties using a microstrip ring-resonator circuit on zirconia at 77K

By using a thick-film microstrip ring-resonator circuit formed on a yttria-stabilised zirconia substrate and by measuring the frequencies of a number of resonant harmonics of the circuit, both at room temperature and when cooled with liquid nitrogen, material properties of the substrate such as the thermal expansion and dielectric constant, the dielectric constant of liquid nitrogen and the surface resistance of the conductor have been determined. This data is necessary for the accurate design of thick-film superconducting microwave circuits. Measurements have been carried out up to the 21st. harmonic of the resonator (0.5->10.4GHz) using both silver and YBa2Cu3Ox thick-film superconductor as the microstrip line and ground plane. This method has proved to be versatile and accurate, provided that a variety of factors are taken into account to enable an accurate analysis of the microstrip ring-resonator to be made. This paper presents a theoretical and experimental evaluation of the microstrip ring resonator.

RF power dependence of YBCO thick films

The dependence of Q on incident power has been measured for an all-thick-film YBa/sub 2/Cu/sub 3/O/sub x/ cavity resonating in the TE/sub 011/ mode at 5.66 GHz and 77 K. The high unloaded Q of 715000 measured at low incident power levels decreases as the power level is increased, but remains over 200000 with 1.4 W incident on the cavity, which corresponds to 0.7 W dissipated in the cavity. The data have been used to calculate the RF power dependence of the R/sub s/ of thick-film YBa/sub 2/Cu/sub 3/O/sub x/, which is shown to be approximately linear for RF fields between 0 and 0.5 mT.<<ETX>>

High Q dielectric resonators using YBa/sub 2/Cu/sub 3/O/sub x/ thick films and polycrystalline dielectrics

The combination of high Q dielectric resonators and high temperature superconducting (HTS) films offer many advantages in the area of cellular and satellite communications. The high cost of single crystal dielectrics and HTS thin films may be unattractive in certain applications. Superconducting thick films and polycrystalline ceramic dielectrics offer a high performance, low cost alternative to high Q thin film/single crystal dielectric resonators. Results on polycrystalline dielectrics show that Qs well in excess of 10/sup 5/ at 10 GHz and 77 K can be achieved in a design made compact by the use of a HTS thick film shield.

Thermal cycling, critical current vs. strain, and finite element modelling of 1, 7, 19 and 37 filament Ag/Bi-Sr-Ca-Cu-O (BSCCO) tapes

Transport critical current, I/sub c/, distribution measurements, thermal cycling experiments and critical current vs. strain (I/sub c/ vs. /spl epsiv/) experiments were carried out on silver clad 1, 7, 19 and 37 filament Bi-Sr-Ca-Cu-O (BSCCO) tapes. The transport critical current distribution of silver clad Bi-Sr-Ca-Cu-O tapes are measured using a measurement system capable of making 10 /spl mu/m steps along 120 mm long tapes. The tapes are subjected to thermal cycling and repeat measurements of the I/sub c/ are made. The critical current vs. strain experiments are carried out by centre point loading of the tapes. Elastic-Plastic Finite Element Modelling (FEM) of a monocore tape is carried out. Our analyses show the variation of the transverse stress, /spl sigma//sub yy/, across the width of the tape.