USE OF LOW-NOISE DC-SQUIDS IN FUNDAMENTAL PHYSICS EXPERIMENTS

The noise performance of dc-SQUIDs (Superconducting Quantum Interferen ce Devices), which nowadays can reach values close to the quantum limi t, makes them very attractive as amplifiers for experiments using low temperatures and demanding for extremely high sensitivity. After revie wing the working principle of the de-SQUID, we describe a thin-film de vice with a new structure, which allowed us to reach an energy sensiti vity of 5.5 (h) over bar at 0.9 K and a good coupling with a large inp ut coil. At last we discuss some fundamental physics experiments which take advantage from the SQUID use.