Low-T-c SQUIDs with a built-in heater module to remove flux trapping

We have fabricated low-T-c SQUIDs (superconducting quantum interference dev ices) that have a built-in heater module next to the Josephson junctions to remove trapped Aux by using only a low heating power. To suppress the gene ration of magnetic fields, the heater module comprises a double-layer consi sting of a heater, which is a narrow Nb film, and an Al electrode. The modu le can be fabricated together with the SQUID without complicating the proce ss. The Nb heater is transformed to normal metal with sufficient resistance when a current above the critical current flows through it. We demonstrate d that the heater module could reliably remove trapped flux with 24 mW with out increasing any noise of the SQUID or causing re-trapping.