SQUID

For other uses, see Squid (disambiguation).

A SQUID (superconducting quantum interference device) is a very sensitive magnetometer used to measure extremely weak magnetic fields, based on superconducting loops containing Josephson junctions.

SQUIDs are sensitive enough to measure magnetic fields as low as 5×10−18 T with a few days of averaged measurements (see orders of magnitude (magnetic field)). Their noise levels are as low as 3 fT·Hz−1⁄2. For comparison, a typical refrigerator magnet produces 10−2 T, and some processes in animals produce very small magnetic fields between 10−9 T and 10−6 T. SERF atomic magnetometers, invented in the early 2000s are potentially more sensitive and do not require cryogenic refrigeration but are orders of magnitude larger in size (~1 cm3) and must be operated in a near-zero magnetic field.

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