摘要 : The authors present the results of measurements of the noise of open-loop and flux-locked DC SQUIDs (superconducting quantum interference devices) at frequencies from 100 kHz to 10/sup -4/ Hz. The SQUIDs studied in this work were ... 展开 The authors present the results of measurements of the noise of open-loop and flux-locked DC SQUIDs (superconducting quantum interference devices) at frequencies from 100 kHz to 10/sup -4/ Hz. The SQUIDs studied in this work were low-1/f-noise devices. Measurements were made in DC magnetic fields of 2*10/sup -3/ G using conventional shielding and also in an ultralow magnetic field environment of 10/sup -7/ G using expanded superconducting foil shields and a feedback-controlled slow cooling technique. The open-loop results are consistent with the earlier work of C.D. Tesche (1985). Some of the runs in the moderate-background-field environment (those with reduced shielding) showed a metastable structure in which switching between the metastable states was stimulated by electromagnetic interference. A description of the apparatus used for obtaining the various noise measurements is provided. 收起