Design of a High Toughness Epoxy for Superconducting Magnets and Its Key Properties

Nb
₃
Sn accelerator magnets are poised to enable the luminosity upgrade of the Large Hadron Collider (LHC) at CERN, improving its potential for exploring physics beyond the standard model of particle physics. The prototype Nb
₃
Sn magnets consistently need 10-25 quenches to achieve their best performance. A hypothesis is that the long training of these magnets may at least be partially induced by epoxy cracking and bonding failures. In 2018, we showed that several existing epoxies have a higher toughness and less tendency to crack at low temperatures than CTD-101K, the epoxy resin with which almost all Nb
₃
Sn accelerator magnets have been impregnated. Here we explore a new high toughness formulation for reducing quench training of Nb
₃
Sn accelerator magnets, through combining two amine curing agents to achieve a good glass transition temperature (T
_g
), adding a viscosity reducer to achieve low viscosity, and experimenting a coupling agent for improved bonding strengths. We report results of comprehensive materials tests, including thermal shock, tensile, compressive, shear tests, viscosity and T
_g
tests.