PRODUCTION OF MAGNETIC FIELDS BY SUPERCONDUCTING SOLENOIDS
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.