Date: Wed, 21 Dec 2011 09:47:06 +0900 From: Norihiro SeiDear FEL Community, I am glad that I inform you an experimental achievement of a seventh-harmonic FEL oscillation at the National Institute of Advanced Industrial Science and Technology (AIST) in Japan. An FEL team at the AIST has developed higher-harmonic FEL oscillations using the storage ring NIJI-IV and its infrared FEL beamline. We have already achieved the third-harmonic FEL oscillations in a wavelength region of 852-1551nm. Using high-reflectivity dielectric mirrors, the fifth- and seventh-harmonic FEL oscillations were achieved at wavelengths of approximately 890 nm. The characteristics of the higher-harmonic FELs were described in the following article: N. Sei, H. Ogawa, and K. Yamada, "Operation of higher harmonic oscillations in free-electron lasers," Opt. Express 20, 308-316 (2012). Our results would be helpful to recognize again the usefulness of the higher-harmonic FEL oscillation. The higher-harmonic FEL oscillation technique is useful for realizing a resonator-type FEL with lower electron-beam energy in the EUV and x-ray regions. I expect that a high-power resonator-type FEL with the higher harmonics will be applied to the photolithography at a wavelength of 13 nm or less. Although a press release from the AIST cannot be carried out, I thank for what I can inform you our results at this place. I hope that your research is going well. Yours sincerely, Norihiro Sei Research Institute of Instrumentation Frontier National Institute of Advanced Industrial Science and Technology 1-1-1 Umezono, Tsukuba, Ibaraki Japan 305-8568 (TEL) +81-29-861-5680 (FAX) +81-29-861-5683