Accuracy issues in surface resistance measurements of high temperature superconductors using dielectric resonators

Abstract

Reproducible and accurate measurements of the surface resistance of high temperature superconductors are essential for the development and commercialization of the next generation of high performance cryoelectronic systems. Dielectric resonators are the best, most accurate technique for this measurement and have been suggested for the international standard technique. This paper discusses tradeoffs amongst the various types of dielectric resonators including choices of the dielectric rod, the metallic enclosure, the electrical measurements of Q-factor, resonant frequency and coupling coefficients, and other issues to ensure reproducible and accurate measurements.

Accurate microwave technique of surface resistance measurement of large-area HTS films using sapphire quasi-optical resonator

“…The most probable error of -measurement is evaluated by the known expression [4] and is about 5%. It can be further reduced by using an advanced measurement technique.…”

“…In a case when both CEP's are formed of HTS samples (normal metal), we obtain (2) From the electrodynamic solution of the field structure in the QDR with CEP, the expression for -quality is obtained [7] where " " denotes the wave mode, or , and , , are the azimuthal, radial and axial numbers, respectively. From (2) and (3), it follows that (4) where is the height of a dielectric cylinder and 10 H m. The expressions for and depend on dimensions of the resonator and the wave mode within it. Here they are not cited because they are extremely clumsy.…”

“…For the classical microwave band (with frequencies less than 25 GHz,) the standard technique based on a sapphire (Al O ) resonator with the lower mode oscillations has been proposed [4]. Of two basic types of a dielectric resonator (DR), a Hakki-Coleman resonator [5].…”

Microwave properties of HTS films: measurements in the millimeter wave range

“…Using the above-mentioned approach, 3,16 the minimum value of R s available for measurement can also be calculated:…”

“…2 A well-known technique of surface resistance R s measurement based on a sapphire ͑Al 2 O 3 ͒ resonator with lower mode oscillations was used in the classic microwave band ͑Ͻ25 GHz͒. 3 Various types of the Hakki-Coleman dielectric resonator have the advantage of being able to evaluate the total energy dissipation. 4 The dimensions of dielectric resonators operating in the millimeter wavelength range ͑Ͼ25 GHz͒ and utilizing lower-mode oscillations ͑waves͒ become unacceptably small.…”