Asymmetric Bias Injection Technique for Drung-Type Superconducting Quantum Interference Devices

Abstract

An asymmetric bias current injection method is developed to reduce bias-caused noise in Drung-type SQUID (superconducting quantum interference devices) without adding extra coils. A measuring scheme for ∂Φ/∂ I b is tested, and it is demonstrated that the reduction is from 100 to 150 times that attained by the conventional SQUID biasing method. It is revealed that the direction of APF (additional positive feedback) coil winding is important in attaining this reduction.