Free electron laser with curved parallel plate waveguide Minghong Wang, Pukun Liu, Huishan Yu, Ruixin Dong and Zheng Liang Eur. Phys. J. Appl. Phys., 37 2 (2007) 169-173 Published online: 17 January 2007 DOI: 10.1051/epjap:2007008