Thin-film HTS probe coils for magnetic-resonance imaging

Several planar coil designs, with integral resonating capacitors, are reported using large-area sputtered YBCO films. One design utilizes a distributed interdigital capacitor, while a second exploits capacitive coupling of two films on opposite sides of a dielectric. Devices of the first design made on LaAlO/sub 3/ have achieved Q>10/sup 4/ at 18.5 MHz, possibly limited by the loss tangent of this substrate. Identical coils made with silver films have Q=10. With the second design, Q>10/sup 4/ was achieved at the even lower frequency of 5.7 MHz.>