Takanori KIYOKURA,¹ Fumihiko MAEDA,¹ Yoshio WATANABE,¹ Yoshinori IKETAKI,² Koumei NAGAI,²Yoshiaki HORIKAWA,² Masaharu OSHIMA,³ Eiji SHIGEMASA⁴ and Akira YAGISHITA⁴

¹NTT Basic Research Laboratories, 3-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198 Japan, ²Olympus Optical Co., Ltd., 2-3 Kuboyamacho, Hachioji, Tokyo, 192-8512 Japan, ³Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656 Japan, ⁴High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki, 305-0801 Japan

(Received June 13, 2000; Accepted June 30, 2000)

The throughput of a Schwarzschild objective using undulator synchrotron radiation was measured. Conventionally, the throughput was estimated from the squared reflectivity of one multilayer mirror and from the obstruction ratio. However, we evaluated the transmission ratio from the input and output photon flux using a precisely calibrated monochromatic beam from an undulator light source. It was found that the objective has a maximum throughput of 8.5% at a wavelength of 13.9 nm.

Key words : Schwarzschild objective multilayer, synchrotron radiation, throughput, soft X-ray, monochromator