Improvement of RF Magnetic Field Strength and Tunable Frequency Range by Using HTS Modified Split-Type RF Coil for NMR

A high-temperature superconductor (HTS) radio frequency (RF) coil that improved not only the RF magnetic strength but also the tunable resonant frequency range was developed for nuclear magnetic resonance (NMR) spectroscopy. The HTS coil consisted of four individual half-wavelength resonators and was fabricated using a YBa2Cu3Oythin film on sapphire substrates. The RF magnetic field strength of the fabricated HTS coil was 1.7 times higher than that of a previously developed HTS coil (HTS split-type coil), and the tunable resonant frequency range was 10 times wider. The measured quality factor (Q) of the proposed HTS coil at 11 K was 15 times higher than that of a commercial copper coil at 20 K. The SNR of 1H nuclei measured with the HTS coil was 1.5 times higher than that with the copper coil.