Aim and features of the simplified parametric mock-up of a fast shutter developed for ITER optical diagnostics

Highlights: • Full functional mock-up model with a reduced geometry complexity. • Mass–stiffness-equivalent model for an identical mechanical behaviour of the mock-up. • Changeable mechanical properties by adding masses and plates for experimental tests. - Abstract: To optimise the mechanical behaviour of the fast shutter intended for ITER diagnostics, a simplified parametric mock-up was developed in addition to the full-scale prototype that was designed to conform to the harsh ITER environment. This parametric shutter is to be used for mechanical tests in air and vacuum conditions at Forschungszentrum Jülich, Germany. The main idea was to reduce the structure complexity but to retain the mechanical properties like characteristic dimensions, the distribution of mass and stiffness, and to make them easy to change. For this reason, a basic mass–stiffness-equivalent geometry was abstracted into a simple beam structure. The main feature of the simplified shutter is its adjustable geometry which allows modification of the shutter mechanical (especially dynamic) behaviour. The paper mainly focuses on numerical studies of possible ways to change by simple means the shutter mass–stiffness distribution thus influencing its mechanical performance according to the developed test programme. Results show that attachment of simple parts on the mock-up is sufficient to change preload, relevant natural frequencies and system stiffness in the required range. Numerical simulations have been conducted to estimate the impact of manufacturing tolerances on the mechanical performance of the shutter and to derive requirements on manufacturing tolerances.