Nd2Fe14B and Pr2Fe14B magnets characterisation and modelling for cryogenic permanent magnet undulator applications

Cryogenic permanent magnet undulators take benefit from improved magnetic properties of RE2Fe14B (Rare Earth based magnets) at cryogenic temperatures for achieving short period high magnetic field. In particular, using Praseodymium instead of Neodymium generally employed for insertion devices avoids limitation due to Spin Reorientation Transition phenomenon. Magnetic properties of magnet samples (Nd2Fe14B and Pr2Fe14B) versus temperature have been investigated and applied to a 20 mm period Nd2Fe14B (BH50) and to a 18 mm period Pr2Fe14B (CR53) systems. Four period undulators have been built, characterised and compared to the models.