Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan.
RIKEN SPring-8 Center, 1-1-1 Koto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.
J Synchrotron Radiat. 2019 Sep 1;26(Pt 5):1406-1411. doi: 10.1107/S1600577519007057. Epub 2019 Aug 5.
Intense sub-micrometre focusing of a soft X-ray free-electron laser (FEL) was achieved by using an ellipsoidal mirror with a high numerical aperture. A hybrid focusing system in combination with a Kirkpatrick-Baez mirror was applied for compensation of a small spatial acceptance of the ellipsoidal mirror. With this system, the soft X-ray FEL pulses were focused down to 480 nm × 680 nm with an extremely high intensity of 8.8×10 W cm at a photon energy of 120 eV, which yielded saturable absorption at the L-edge of Si (99.8 eV) with a drastic increase of transmittance from 8% to 48%.
通过使用高数值孔径的椭圆反射镜实现了软 X 射线自由电子激光（FEL）的超强亚微米聚焦。采用混合聚焦系统与 Kirkpatrick-Baez 镜相结合，用于补偿椭圆反射镜的小空间接收。利用该系统，软 X 射线 FEL 脉冲在光子能量为 120 eV 时聚焦到 480nm×680nm，强度高达 8.8×10Wcm，在 Si 的 L 边（99.8eV）处产生饱和吸收，透过率从 8%急剧增加到 48%。
