Design, manufacturing and first measurements of a hybrid permanent magnet undulator for free electron laser

The hybrid permanent magnet undulator for the LISA-FEL (free electron laser) experiment (INFN, Frascati, Italy) has been designed and manufactured. A computerized driving system has been developed in order to lighten the mechanical structure and gain accuracy in positioning of the jaws during gap variation. The NdFeB permanent magnet blocks have been measured and sorted in order to reduce magnetic field errors along the undulator axis. The field integrals are minimized by the electronic control, which feeds the correction coils with a gap-dependent current. The first results of mechanical tests and magnetic field measurements confirm the good performance and reliability of the device.<>