Sensitivity Enhancement of Superconducting Quantum Interference Devices through the Use of Fractional-Turn Loops

A new ``fractional-turn'' configuration for superconducting quantum interference devices provides enhanced sensitivity, with large loop area and low loop inductance. By operating the new configuration at optimum bias frequency (300 MHz or higher), inherent field sensitivities of 10−15 T (10−11 G) or better can reasonably be expected. The operational sensitivity of an instrument using such a device would probably be limited by externally generated noise in most applications. The configuration is readily adaptable to measurements of both diagonal and offdiagonal components of the field gradient.