Increasing the linear flux range of SQUID amplifier using self-feedback effect

Superconducting quantum interference devices (SQUIDs) are low-noise amplifiers that are essential for the readouts of translation edge sensors (TESs). The linear flux range is an important parameter for SQUID amplifiers, especially those controlled by high-bandwidth digital flux-locked-loop circuits. A large linear flux range helps to accurately measure the input signal and also allows increasing the multiplexing factor in the time-division multiplexed (TDM) readout scheme of the TES array. We report an improvement of the linear flux range of a SQUID using self-feedback effect. When an asymmetric SQUID loop is designed, a voltage-biased SQUID shows an asymmetric current-flux (I-Φ) response curve. The linear flux range is improved alongside the I-Φ curve with a shallow slope. The experimental results agree well with the numerical simulations. The asymmetric SQUID will sever as a building block in the development of the TDM readout systems for large TES arrays.