TOWARDS PRACTICAL QUANTUM-LIMITED SQUIDS FOR A GRAVITATIONAL-WAVE ANTENNA

Nearly quantum-limited Superconducting QUantum Interference Devices (S QUIDs) have to be used in resonant mass gravitational wave antennas to reach a displacement sensitivity of the order of 10(-21) m/root Hz in a bandwidth of 100 Hz around the resonance frequency of about 900 Hz. The design of these de SQUIDs will be described. The possible use of Double Relaxation Oscillation SQUIDs (DROSs) was also studied. We show that SQUIDs with a relatively large hole size can reach the quantum l imit at low temperatures. The large hole size facilitates the coupling between the SQUID and the inductive transformer circuit of the antenn a.