Lightweight fast rotating Fermi-chopper, proof of principle for a scalable array chopper

The concept of the Fermi chopper array based on small Fermi rotors is explored. The advantages of such an array would be very low stored kinetic energy even for very fast running large area choppers and emerging possibilities for new and very flexible focussing schemes. The work comprises the investigation of a drive concept with a small motor and the design of a precise phase control. Further the rotor mechanics (stress and deformation) at high rotation frequencies has been optimised by FE-calculations. A chopper concept is studied with a small high speed motor connected to the rotor by means of an elastic shaft. This concept is comparable to the model of the “de Laval” or “Jeffcott” rotor.The development from a first layout of the Fermi rotor to a prototype aiming at high running speeds up to 1000 Hz is described and results for transmission, blocking and pulse shapes obtained at the ESS test beamline are reported