Investigating high radio-purity electroformation capabilities at Boulby Underground Laboratory

Extreme radiopurity is key for rare-event searches in particle physics, including searches for Dark Matter (DM) and neutrinoless double beta-decay. Electroformed copper (EFCu) is the material of choice for manufacturing ultra-high radiopurity structures for experiments and radio-assay programs. In particular, EFCu produced in clean-rooms at underground laboratories maximises radiopurity by avoiding cosmogenic activation. SNOLab in Canada is working towards establishing the world's largest underground electroforming facility by hosting the Electroformed CUprum Manufacturing Experiment (ECUME). ECUME aspires to deliver a 140 cm in diameter spherical proportional counter for use in direct DM searches, with construction scheduled to start early in 2021. Through Birmingham's contribution to ECUME, the unique opportunity arises for Boulby Underground Laboratory, and the UK in general, to acquire expertise on high radio-purity EFCu, towards establishing an underground electroforming capability. This development will further strengthen Boulby's world-leading ultra-low background material assay facility and the capacity to support and host future experimental activities.