Superconducting cavity in a high magnetic field

Abstract

A high Q-factor microwave resonator in a high magnetic field could be of great use in a wide range of applications, from accelerator design to axion dark matter research. The natural choice of material for the superconducting cavity to be placed in a high field is a high temperature superconductor (HTS) with high critical field (>100 T) and high depinning frequency (>10 GHz). The deposition, however, of a high-quality, grain-aligned HTS film on a three-dimensional surface is technically challenging. As a technical solution, we introduce a polygon-shaped resonant cavity with commercial YBa2Cu3O7−x (YBCO) tapes covering the entire inner wall. We then measured the Q-factor at 4 K at 6.93 GHz as a function of an external DC magnetic field. We demonstrated that the maximum Q-factor of the superconducting YBCO cavity was about 6 times higher than that of a copper cavity and showed no significant degradation up to 8 T. This is the first indication of the possible applications of HTS technology to the research areas requiring low loss in a strong magnetic field at high radio frequencies.

Direct Detection of Dark Matter -- APPEC Committee Report

“…University of Western Australia -UWA) but also in Europe (QUAX [397,398] at INFN Legnaro) to extend the sensitivity of cavity experiments to mass ranges up to ∼70 µeV, maybe even beyond. These are mainly based on the challenging tasks of increasing magnetic field and volume [399,400], improving on detection technology to (sub) quantum limited detection of (quantum squeezed) signals in the 100 MHz to 10 GHz regime [401,402] and by increasing the Q-factor of cavities using superconducting foils [397,403] or using the dielectric cavity approach. Here, low loss dielectric movable cylinders or bars (photonic band-gap cavity) are placed inside a copper cavity, like this increasing the Q-factor by a significant decrease of the losses from the walls of the copper cavity.…”

Superconducting detectors for rare event searches in experimental astroparticle physics

“…They plan to upgrade the magnet to a 25 T HTS magnet with a 10 cm bore that is under development [253,254]. For the superconducting cavity, they demonstrated a cavity quality factor 6 times higher than that of their copper cavity using a polygon-shaped cavity with commercial YBCO tapes covering the entire inner wall [255]. For the quantumlimited amplifiers, R&D on JPAs is ongoing [256].…”

Impact of the superconductors properties on the measurement sensitivity of resonant-based axion detectors

“…The high Q needed to increase P a→γ ph pushes toward the study of new methods to reduce the cavity losses. The best results are obtained with either superconductive [8,9,10] or dielectric resonant cavities [11,12]. Since in metallic cavities Q ∝ R −1 s , being R s the surface resistance of the conductive walls of the cavity, materials with low R s must be employed.…”

“…In [8] the Q-factor of copper and NbTi haloscopes (tuned at ∼ 9.08 GHz) have been measured, showing that with a NbTi cavity the figure of merit B 2 Q at ∼ 6 T is ∼ 5 times larger than what reached with a Cu cavity. The first RE-Ba 2 Cu 3 O 7−δ (RE-BCO) cavity, with RE a rare earth element such as Y, was shown in [9] to exhibit Q ≈ 3.25 × 10 5 at 6.93 GHz and up to 8 T, which is more than 6 times larger than with a Cu cavity. Recently [10], a different configuration for a RE-BCO cavity was presented and its performances compared with one coated with Nb 3 Sn, both working at ∼ 9 GHz: the RE-BCO haloscope reached Q ∼ 7 × 10 4 at ∼ 12 T which was shown to be only 1.75 times larger than that obtained with the equivalent Cu cavity.…”