• F.H. O'Shea, G. Marcus, J.B. Rosenzweig
  UCLA, Los Angeles, California
• J. Bahrdt, A. Gaupp
  BESSY GmbH, Berlin
• F.J. Grüner, R. Weingartner
  LMU, Garching

The fundamentals of insertion device physics demand that to have access to ever higher photon energies either the beam energy must increase or the undulator period must decrease. Recent advances in accelerator technology have increased beam energies and at the same time insertion device technology has developed creative ways of producing light of the desired energy, characteristics and quality. This paper describes the simulation work for the design of a 9 mm period in-vacuum planar undulator using a new rare-earth magnetic material.