Superconducting Quantum Interference Device- SQUID
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SQUID is an extremely sensitive device used to measure the magnetic and paramagnetic properties of materials. The SQUID sensor consists of a superconducting circuit separated by a parallel Josephson junctions. The sensor is connected to a pickup coil inside a superconducting magnet. When the sample is moved inside the magnet and pickup coil this triggers an quantum interference pattern in the squid detector which causes voltage proportional to the change in magnetic flux caused by the sample. Thus extremely small magnetic properties are amplified into a measurable voltage.
In this animation you should notice the following:
- The squid magnetometer is a superconducting loop connected to an pickup coil located inside a superconducting magnet.
- When there is no magnetic flux, or change in magnetism the squid loop has superconducting current flow, but no voltage.
- When a magnetic sample is moved in the pickup coil the loop is disrupted and a net voltage appears across the circuit.
- The bias voltage is actually the voltage that is applied to cancel out the effects of the magnetic sample and maintain the superconducting loop.