Induced axial oscillations in superconducting dipole windings

When superconducting accelerator magnets wound from a multi-stranded conductor are energized, a periodic variation appears in the magnetic field along the axis. This oscillation is present in all components of the field and has a period that is equal to the transposition pitch of the superconducting cable. Such axial variations have been observed even in windings which are not carrying any transport current. A magnetic field was applied to a portion of a dipole winding using a second magnet. Axial oscillations were induced along the total length of the windings including the portion not in the applied field. The amplitude of these oscillations varied with the amount of inert winding inside the energizing magnet and with the angle of the applied field. These field variations could be completely eliminated in the external portion of the coil by heating a small section of the winding above the transition temperature. >