Microwave characterization of normal and superconducting states of MOCVD made YBCO tapes

Abstract

We have used a microwave, non-contact, non-destructive, dielectric resonator (DR) technique to characterize complex conductivity of different quality YBCO/Hastelloy tapes for the purpose of exploring such a technique as a potential quality control method for fabrication of YBCO tapes. The tapes were deposited at different temperatures on Hastelloy-supported oxide buffer layers using the MOCVD technique. The buffer stack consisted of aluminum oxide (Al2O3), yttrium oxide (Y2O3), and textured ion beam assisted deposition-MgO and LaMnO3 layers. Two dielectric resonators (DRs), the single post DR, consisting of high-permittivity barium zirconium titanate ceramic operating at 13 GHz in quasi-TE01δ mode, and the rod DR, consisting of rutile single crystal disk operating at 9.4 GHz in-TE011 mode, were designed to meet sensitivity requirements for characterization of conductivity of the superconductor at normal and superconducting states, respectively. For calculations of complex conductivity from experimental data of Q-factor and resonant frequency shift, a commercial electromagnetic simulator HFSS, based on finite elements analysis, was used. The theoretical Q-factor and resonant frequency on conductivity functions obtained from full wave numerical simulations of microwave fields were matched with the experimental data to determine conductivity of the YBCO tapes in both normal and superconducting states. In addition, for comparison purposes, 280 nm thick high-quality YBCO epitaxial film deposited on a dielectric substrate was also characterized, including frequency dependence of the complex conductivity. Discussion about feasibility of using DR microwave techniques as a quality control tool via measurements of conductivity versus temperature slope of the YBCO/Hastelloy tape in normal state is included. Also, microwave conductivity values of Hastelloy substrate as a function of temperature are reported.

Evaluation of the nonlinear surface resistance of REBCO coated conductors for their use in the FCC-hh beam screen

“…The resonator was designed to operate in the TE 011 mode. This mode is typically used for microwave characterization due to its azimuthal currents, which make resonator parameters (quality factor and resonant frequency) insensitive to the electrical contact between the samples under test and the lateral walls [28][29][30][31]. Given the dimensions of the REBCO-CCs, the radius of the cavity was chosen to be R = 5.5 mm.…”

Superconducting cavity in a high magnetic field

“…Superconducting radio-frequency (SRF) science and technology involves the application of superconducting properties to radio frequency systems. Due to the ultralow electrical resistivity, which allows an RF resonator to obtain an extremely high quality (Q) factor, SRF resonant cavities can be used in a broad scope of applications such as particle accelerators [1,2], material characterization [3,4], and quantum devices [5,6]. However, the presence of an external magnetic field will destroy the superconducting state above the critical field, which limits scientific productivity in many areas such as high energy particle accelerators [7,8], and axion dark matter research [9][10][11][12].…”

“…We chose to use pure YBCO over other rare-earth barium copper oxide (ReBCO) materials which have a high concentration of gadolinium atoms. The RF surface resistance of those ReBCO materials (∼ 1mΩ) [4] could be higher than that of YBCO (∼ 0.1 mΩ) at zero field [20] because gadolinium is paramagnetic, introducing an additional energy loss mechanism due to rotating spins. The substrate and buffer layers of the tape were designed to act as template layers to provide the biaxial texture for the YBCO film.…”

Maintaining high Q-factor of superconducting YBa$_2$Cu$_3$O$_{7-x}$ microwave cavity in a high magnetic field

“…In this work, we preferred to use pure YBCO to other rare-earth barium copper oxide (ReBCO) materials which have a high concentration of the gadolinium atoms. The RF surface resistance of those ReBCO materials could be higher than that of YBCO because gadolinium is paramagnetic [14,16].…”