superconduct. solenoid crop3.jpg (3041 bytes)

superconduct. solenoid crop2.jpg (6089 bytes) In the maser studies the value of the magnetic field required to establish three-level maser action in a Ruby crystal was obtained. A coil was fabricated from Niobium wire which became superconducting at liquid helium temperatures and the dimensions  of the solenoid required to establish the correct magnetic field was calculated.

The solenoid was immersed in liquid helium and energised by an external D.C. supply. The correct value of the magnetic field required for maser action was established in the solenoid. A subsidary magnetic field was used for quenching the superconductivity in the Niobium wire that completed the circuit formed by the windings of the coil. This magnetic field and the D.C. supply were removed and the D.C.current was then diverted through the coils of the solenoid. This current kept circulating during the time the solenoid was kept at liquid helium temperatures.