Minimum quench energy measurements on single strands for LHC main magnets

The stability of magnet conductors can be characterized by their minimum quench energies (MQE), i.e. the minimum energy pulse of small extent and short duration needed to initiate a quench. The MQE of a considerable number of prototype strands for the superconducting LHC magnets have been measured at BNL within the framework of the US-CERN accelerator collaboration. The main interest of this work was to study the effect of different strand designs, copper to superconductor ratios (Cu/Se) and the source of the niobium-titanium alloy on MQE. Although MQE varied significantly between the strands, the measurements revealed that except for Cu/Se ratio, these above stated parameters do not affect MQE in a consistent way. Numerical simulations indicate that these tests made with a restricted helium volume and heat exchange surface were quasi-adiabatic in nature, and hence the influence of the cooling even in superfluid helium was minimal.