Division of accelerators, cryogenics and magnetism

Use of Nb₃Sn Rutherford cables in accelerator magnets enables reaching magnetic fields in the 11 to 16 T range, but they often suffer from a long training process. The BOX (BOnding eXperiment) facility was developed to systematically investigate training parameters at a small scale. It aims to be representative of accelerator magnets, in particular those of the canted-cosine-theta (CCT) type. The BOX test samples consist of a flat holder comprising a serpentine-like channel in which a short Nb₃Sn Rutherford cable of about 1 meter is heat treated and impregnated. A Lorentz force similar to those in accelerator magnets is generated in the cable by applying an external magnetic field of 7 to 11 T, and powering the cable at full current of up to 25 kA using a superconducting transformer. The experiment has shown a training behavior similar to that in full-size coils for epoxy resins such as CTD-101k, mix 61 and Araldite MY750. Furthermore, the experiment has proven to be a powerful tool in demonstrating potential solutions for reducing training in magnets including use of alumina fillers and impregnation with paraffin wax. In this contribution, we show test results on a series of new samples with fine-grained filler materials in the resin, which aim to be compatible with vacuum impregnation. We also show new results on the introduction of a sliding/debonding layer between the cable and the channel wall.