Josephson junction array for high-frequency current probe

We propose the use of a high-T_c Josephson junction array for the measurement of high-frequency magnetic fields with high spatial resolution. In this application, the magnetic field B is converted to the voltage V by using the V-B relationship of the bicrystal junction. For the design of the array, the parameter dependence of the conversion efficiency dV/dB is examined both theoretically and experimentally. The eight-junction array fabricated with an area of 120 × 50 μm² showed the conversion efficiency dV/dB = 70 and 260 V/T at T = 77 and 60 K, respectively. The value of dV/dB = 260 V/T indicates that the array is more sensitive, up to 7 GHz, than the conventional induction coil having the same area.