Shape-memory alloy rings as tight couplers between ultrahigh-vacuum pipes: Design and experimental assessment

The ultrahigh-vacuum (UHV) coupling performance of NiTiNb shape memory alloy (SMA) rings was investigated by finite element (FE) simulations and experimental measurements. The contact pressure at the interface between the SMA ring and the vacuum pipe was measured and good agree- ments with the FE results were obtained. Furthermore, a design method was proposed that involves the FE results and a vacuum sealing model. Finally, leak rate measurements were carried out to assess the sealing performance of selected coupling configurations. The main result found was that the leak rate constraints for UHV applications could be easily satisfied (leak rate <10 10 mbar l s 1), which opens the possibility of remotely clamping/unclamping the tight couplers by well-defined changes in their temperature. Possible applications in the field of particle accelerators and, in particu- lar, in restricted access areas were considered.