Development of a dc-SQUID Amplifier with Intra-Coil Resistors
摘要
We have developed a dc-SQUID amplifier with intra-coil resistors based on second-order parallel gradiometers. The measured results show that intra-coil resistors can significantly increase the flux–voltage transfer coefficient VΦ as well as smooth out resonances and produce a smooth flux–voltage (V–Φ) characteristic curve. It has been observed through a comparison of various intra-coil damping resistors that the flux–voltage transfer coefficient VΦ as a function of the resistance of the intra-coil resistors rises as the corresponding electrical conductance increases. The measured results of the flux noise at 4.2 K demonstrate explicitly that the flux–voltage transfer coefficient can greatly increase detection sensitivity and successfully reduce the noise contribution from the electronics operating at room temperature.