Thermally Enhanced Cable Insulation for the Nb-Ti High Luminosity LHC Inner Triplet Model

Abstract

Abstract-A new concept of polyimide electrical insulation for superconducting cables of accelerator magnets was developed in the last years. Its enhanced He II permeability allows a significant improvement of the heat extraction from the coil. This cable insulation concept is used for the quadrupole magnet prototype for the insertion region of the High Luminosity-Large Hadron Collider project. It aims at pushing the limits of the Nb-Ti technology to withstand high heat deposition.Cable samples wrapped with the new insulation scheme were characterized from the thermal standpoint, as well as from the electrical and mechanical ones. In particular, heat transfer measurements from insulated cables towards the helium cooling bath were performed in a coil-like configuration. Various wrapping schemes were tested in different mechanical conditions, and a model was developed to explain the experimental results. The paper summarizes the main results of all these investigations.

Heat transfer through cable insulation of Nb–Ti superconducting magnets operating in He II

“…Besides the effect of the pressure applied during the test, several other mechanisms can influence the micro-channels topology and dimensions. For instance the curing cycle [29], the plastic deformation due to the applied pressure [30] as well as to creep effect [29], or the stress induced by the differential thermal contractions of the coil components. All these mechanisms affect the micro-channels among the insulation tapes, thus making hard to precisely determine their shape and dimension from a mechanical standpoint.…”