REDUCTION OF LOW-FREQUENCY EXCESS NOISE IN SUPERCONDUCTING QUANTUM INTERFERENCE DEVICES BY APPLYING HIGH-FREQUENCY MAGNETIC-FIELDS

We have investigated a possible reduction of low-frequency excess nois e and the dependence of the flux signal on temperature changes in dire ct current superconducting quantum interference devices, de SQUIDs, ge nerated by trapped flux. Niobium thin film de SQUIDs, carefully cooled down in a well shielded environment, have been exposed to switching t ransients. The thereby generated low-frequency excess noise and in som e case an excess white noise, could substantially be reduced by applyi ng a rf magnetic field of sufficiently high frequency to the SQUID. Th e temperature dependence of the flux signal of the SQUID and the magne tic field dependence of the drift could also be reduced in these cases , where the drift is caused by movement of trapped vortices. (C) 1996 American Institute of Physics.