Particle radiation effects on Shape Memory Alloy couplers for Ultra-High Vacuum sealing: a preliminary study

A new shape memory alloy (SMA)-based coupling system for ultra-high vacuum (UHV) applications in particle in accelerators is currently under investigation at the European organization for nuclear research (CERN). The use of such technology in some restricted-access radioactive areas within CERN accelerators could result in noticeable advantages, especially during maintenance operations. Bolt-free SMA couplers, can be activated remotely by temperature changes, resulting in significant reduction of the radiation doses collected by the technical personnel. The functional performance of SMA-based prototype systems, in terms of leak tightness, thermal mounting/dismounting and thermal outgassing properties, has been already verified. Radiation-induced microstructural damages usually cause losses in the mechanical properties, such as embrittlement in conventional engineering metals. The particle radiation effects on the functional characteristics of SMAs, in terms of microstructural transition mechanisms, represent a key issue for their application in critical accelerators areas. To this aim, specific research activities are being carried out at CERN for capturing the evolution of SMA mechanical and functional properties during and/or after particle irradiation. In this preliminary study, a few selected SMA-based prototype UHV chambers, have been exposed to a high-energy mixed particle field (up to similar to 140 kGy of absorbed dose) at the CERN high-energy accelerator mixed-field (CHARM) facility. The results, in terms of post-irradiation measurements, have revealed that leak tightness and thermal dismounting are unaffected by irradiation.