Soft x-ray nanobeam formed by an ellipsoidal mirror


Yoko Takeo, Akihiro Suzuki, Hiroto Motoyama, Yoshinori Takei, Takehiro Kume, Yusuke Matsuzawa, Yasunori Senba, Hikaru Kishimoto, Haruhiko Ohashi and Hidekazu Mimura

Ellipsoidal mirrors are promising optical devices for soft x-ray focusing. A fabrication process consisting of master fabrication and replication has been developed to produce ellipsoidal mirrors with wide apertures of approximately 10 mm. In the present study, the focusing performance of an ellipsoidal mirror was evaluated using soft x-rays in the soft x-ray beamline BL25SU-a of SPring-8. The focus sizes were measured at photon energies of 300, 400, and 500 eV. A quantitative figure error of the ellipsoidal mirror was also evaluated by analyzing the wavefield of the focused beam retrieved using ptychography. The figure error distributions measured at different photon energies agreed with each other at a root mean square level of 1 nm. The developed focusing system can be used for various types of microscopy, allowing the use of a wide range of x-ray energies.
The present study was supported by Grants-in-Aid for Scientific Research (A) (Grant Nos. 15H02041 and 19H00736) and JSPS Fellows (Grant No. 17J04201) from the Ministry of Education, Sports, Culture, Science and Technology, Japan (MEXT). The present research was carried out under SPring-8 Proposal Nos. 2017A1262 and 2017B1688.