Shape memory alloy-based rings for ultra high vacuum applications in particle accelerators

Shape Memory Alloy (SMA) rings were analyzed for possible applications as beam-pipe couplers in particle accelerators. The tightening performance of NiTiNb rings, in terms of contact pressure and clamping/unclamping mechanisms, was studied by both numerical simulations and experimental tests. The results revealed that the contact pressure is not significantly affected by the initial pipe-ring assembly clearance. In addition, thermal dismounting and subsequent re-clamping is obtained by exploiting the two-way shape memory recovery capabilities of the SMA rings. Finally, the vacuum performance of selected coupling geometries was experimentally assessed by using special prototype vacuum chambers. Results revealed that the leak rate constraints for UHV applications in particle accelerators (<10^-10 mbar l s^-1) were always satisfied. Thanks to these features, these connectors can be used in future high-energy particle accelerators, especially in restricted access areas, where thermally induced mounting and dismounting operations can be operated remotely.