Physics Group - II (3110018)

BE | Semester-1   Winter-2019 | 02-01-2020

Q5) (a)

Write short note on SQUID.

  • A SQUID (for superconducting quantum interference device) is a very sensitive magnetometer used to measure extremely subtle magnetic fields, based on superconducting loops containing Josephson junctions.
  • A SQUID is formed by connecting two Josephson junctions in parallel. 
  • When current is passed into this arrangemnt, it splits flowing across the two opposite arc.
  • The current through the circuit will have a periodicity which is very sensitive to the magnetic flux passing normally through the closed circuit.
  • As a result, extremely small magnetic flux can be detected with this device.
  • This device can also be used to detect voltages as small as 10-15 V. Magnetic field changes as small as 10-21 T can be detected. Weak magnetic fields produced by biological currents such as those in the brain can also be detected using SQUIDs.
  • SQUID detectors are used to measure the levels of iron in liver – so that iron built up can be treated before much harm is done to the body.