Development of cryogenically cooled permanent magnet undulators for PETRA IV

Abstract Cryogenically cooled permanent magnet undulators (CPMUs) are an improvement of the in-vacuum undulators (IVUs) which are widely used at various synchrotron radiation facilities and free-electron lasers in order to improve the photon flux towards shorter wavelengths. Especially beamlines with the need for high energy photons will benefit from shorter period insertion devices (IDs). For the planned ultra-low emittance photon source PETRA IV at Deutsches Elektronen-Synchrotron (DESY), we are designing CPMUs with a hybrid magnet structure based on PrFeB magnet material. First prototyping was done on magnet keepers and the pole-tuning mechanism. In addition, options for force-compensation are assessed. Crucial components are the link rods connecting the in-vacuum girders with load bearing out-of-vacuum girders. Simulations on the impact of their arrangement on the bending of the magnet structure and their thermal behaviour are presented.