Development of cryogenic undulators and measurement equipment for PETRA IV

DESY is planning to upgrade its current storage ring PETRA III into the ultra-low emittance photon source PETRA IV. The current H6BA cell design for the PETRA IV lattice will allow for insertion devices of up to 4 m length in the standard straight sections. In order to allow some beamlines to not only benefit from the performance improvements by the machine but also from the undulators, we started looking into using advanced undulator schemes as well. We decided to start the design of cryogenically cooled permanent magnet undulators (CPMUs) based on (Nd,Pr)FeB magnets for PETRA IV, since this technique has already been proven successfully by various other facilities. We will present the planned design for the magnet keepers, the pole tuning mechanism as well as a testbed for keepers under cryogenic conditions. We will also show a preliminary design for the in-situ Hall-probe bench currently developed for the upcoming PETRA IV CPMUs.