Bahrdt, J.; Frentrup, W.; Gaupp, A.; Scheer, M.; Weingartner, R.; O'Shea, F.; Grüner, F.: Cryogenic Undulator for a Table Top FEL. In: Garrett, R... [Ed.] : SRI 2009 : the 10th International Conference on Synchrotron Radiation Instrumentation ; Melbourne, Australia, 27 September - 2 October 2009Melville, NY: American Inst. of Physics, 2010 (AIP conference proceedings ; 1234). - ISBN 978-0-7354-0782-4, p. 499-502
Abstract:
A laser plasma accelerator is under development at the Max-Planck-Institut für Quantenoptik in Garching. This accelerator will be part of an X-ray table top FEL in the future. The FEL radiation will be produced with a small period in-vacuum undulator. The coercivity of the magnetic material has to be sufficiently high in order to avoid demagnetization due to electron losses. The best performance can be achieved with a cryogenic permanent magnet undulator design. (Nd0.2Pr0.8)2Fe14B magnets are suited for low temperatures since they do not suffer from a spin reorientation. A new (Nd0.2Pr0.8)2Fe14B material has been characterized at various temperatures and the results are presented. Based on this material a 20 period prototype with a period length of 9mm and a magnetic gap of 2.5mm is currently under construction.