Seed level requirement for improving the temporal coherence of a Free-Electron Laser G. Lambert, T. Hara, M. Labat, T. Tanikawa, Y. Tanaka, M. Yabashi, D. Garzella, B. Carré and M. E. Couprie EPL, 88 5 (2009) 54002 Published online: 15 December 2009 DOI: 10.1209/0295-5075/88/54002