Low- and High-Tc Squids and Some Applications

摘要: DC Superconducting QUantum Interference Devices are routinely fabricated from Nb films with an integrated input coil to couple in magnetic flux the signal source. Typical dc SQUIDs operated at 4.2 K have a noise of 10−6 Φ0 Hz−1/2, where is quantum, corresponding energy 10−32 JHz−1. With aid superconducting transformer field can approach 1 fT Hz−1/2. High-Tc thin YBa2Cu3O7-x (YBCO) achieved energies below 10−30 JHz−1 77 and, multilayer transformers, 10 Hz−1/2 frequencies down few Hz. An rf SQUID made YBCO and around GHz has 16 above 100 A recent theory for predicts levels good agreement experiment. Two issues relevant operation high-Tc unshielded environment increase low-frequency arising entry vortices into realization long-baseline gradiometers. The applications low-Tc nuclear quadrupole resonance, scanning microscopy geophysics discussed.