A new ductile, tougher resin for impregnation of superconducting magnets

Abstract

A major remaining challenge for Nb3Sn high field magnets is their training due to random temperature variations in the coils. The main objective of our research is to reduce or eliminate it by finding novel impregnation materials in replacement of the epoxies currently used. An organic olefin-based thermosetting dicyclopentadiene (DCP) resin, C10H12, commercially available in Japan as TELENE® by RIMTEC, was used to impregnate a short Nb3Sn undulator coil developed by ANL and FNAL. This magnet reached short sample limit after only two quenches, compared with ~100 when CTD-101K® was used. Ductility, i.e. the ability to accept large strains, and toughness were identified as key properties to achieve these results. In addition, we have been investigating whether mixing TELENE with high heat capacity ceramic powders such as Gd2O3, Gd2O2S, and HoCu2, increases the specific heat (Cp) of impregnated Nb3Sn superconducting magnets. The viscosity, heat capacity, thermal conductivity, and other physical properties of TELENE with high-Cp powder fillers were measured in this study as a function of temperature and magnetic field. The TELENE-87wt%Gd2O2S had a peak in Cp between 4.3 K and 5.3 K at fields between 0 and 8 T. We have also investigated the effect on the mechanical properties of pure and mixed TELENE under 10 Gy of gamma ray irradiation at the Takasaki Advanced Radiation Research Institute in Takasaki, Japan. TELENE-87wt%Gd2O2S exhibited exceptional radiation resistance. Impregnating an undulator coil with TELENE mixed with Gd2O2S powder will verify whether the coils’ thermal stability further improves, or whether its low diffusivity will require engineering the material with high-thermal conductivity components. Short magnet training will lead to better magnet reliability, lower magnet margins, lower risk and substantial saving in accelerators’ commissioning costs. 

Training-free demonstration of a 5.4 T Nb3Sn Canted–Cosine–Theta accelerator dipole impregnated with paraffin wax

“…The Paul Scherrer Institut (PSI) recently initiated a series of cable-in-groove training experiments (BOX) [12], and reported encouraging results with wax impregnated materials [13]. Other approaches to reduce magnet training are also being explored, such as ductile resins [14] and high heat capacity fillers [15].…”