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Nature Photonics 2, 555–559 (1 September 2008) | doi:10.1038/nphoton.2008.134

A compact free-electron laser for generating coherent radiation in the extreme ultraviolet region

Tsumoru Shintake , Hitoshi Tanaka , Toru Hara , Takashi Tanaka , Kazuaki Togawa , Makina Yabashi , Yuji Otake , Yoshihiro Asano , Teruhiko Bizen , Toru Fukui , Shunji Goto , Atsushi Higashiya , Toko Hirono , Naoyasu Hosoda , Takahiro Inagaki , Shinobu Inoue , Miho Ishii , Yujong Kim , Hiroaki Kimura , Masanobu Kitamura , Toshiaki Kobayashi , Hirokazu Maesaka , Takemasa Masuda , Sakuo Matsui , Tomohiro Matsushita , Xavier Mar|[eacute]|chal , Mitsuru Nagasono , Haruhiko Ohashi , Toru Ohata , Takashi Ohshima , Kazuyuki Onoe , Katsutoshi Shirasawa , Tetsuya Takagi , Sunao Takahashi , Masao Takeuchi , Kenji Tamasaku , Ryotaro Tanaka , Yoshihito Tanaka , Takanori Tanikawa , Tadashi Togashi , Shukui Wu , Akihiro Yamashita , Kenichi Yanagida , Chao Zhang , Hideo Kitamura & Tetsuya Ishikawa

Single-pass free-electron lasers based on self-amplified spontaneous emission are enabling the generation of laser light at ever shorter wavelengths, including extreme ultraviolet, soft X-rays and even hard X-rays. A typical X-ray free-electron laser is a few kilometres in length and requires an electron-beam energy higher than 10|[nbsp]|GeV (refs|[nbsp]|6, 8). If such light sources are to become accessible to more researchers, a significant reduction in scale is desirable Here, we report observations of brilliant extreme-ultraviolet radiation from a 55-m-long compact self-amplified spontaneous-emission source, which combines short-period undulators with a high-quality electron source operating at a low acceleration energy of 250|[nbsp]|MeV. The radiation power reaches saturation at wavelengths ranging from 51 to 61|[nbsp]|nm with a maximum pulse energy of 30|[nbsp]||[micro]|J. The ultralow emittance (0.6|[pi]||[nbsp]|mm|[nbsp]|mrad) of the electron beam from a CeB6 thermionic cathode is barely degraded by a multiple-stage bunch compression system that dramatically enhances the beam current from 1 to 300|[nbsp]|A. This achievement expands the potential for generating X-ray free-electron laser radiation with a compact 2-GeV machine.