Interaction between current imbalance and magnetization in LHC cables

The quality of the magnetic field in superconducting accelerator magnets is associated with the properties of the superconducting cable, Current imbal ances due to coupling currents DeltaI, as large as 100 A, are induced by sp atial variations of the field sweep rate and contact resistances. During in jection at a constant field all magnetic field components show a decay beha vior. The decay is caused by a diffusion of coupling currents into the whol e magnet. This results in a redistribution of the transport current among t he strands and causes a demagnetization of the superconducting cable. As so on as the field is ramped up again after the end of injection, the magnetiz ation rapidly recovers from the decay and follows the course of the origina l hysteresis curve. In order to clarify the interactions between the change s in current and magnetization during injection we performed a number of ex periments. A magnetic field with a spatially periodic pattern was applied t o a superconducting wire in order to simulate the coupling behavior in a ma gnet. This model system was placed into a stand for magnetization measureme nts and the influence of different powering conditions was analyzed.