title: Performance of Y2O3∕Al multilayer coatings for the He-II radiation at 30.4 nm.
abstract: We briefly report on the performance and stability of periodic multilayer mirrors containing Y(2)O(3) and Al layers designed for normal incidence reflection at the He-II emission line (30.4 nm). We found that Y(2)O(3)∕Al multilayer coatings had higher reflectivity (24.9%) at 30.4 nm and significantly lower reflectivity (1.3%) at 58.4 nm than the conventional coatings such as Mo∕Si. Furthermore, we investigated the temporal stability of the Y(2)O(3)∕Al multilayer coatings. Our sample was kept under vacuum, dry N(2) purge, and normal atmosphere for over three months, and there were no measurable changes in the reflectivity. These results suggest that we can use Y(2)O(3)∕Al multilayer coatings as standard mirrors for the He-II radiation.
authors: Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan. go@eps.s.u-tokyo.ac.jp
authors: Go
authors: G
authors: Murakami
authors: Kouichi
authors: K
authors: Sakai
authors: Tatsuro
authors: T
authors: Homma
authors: Kazuo
authors: K
authors: Yoshioka
authors: Ichiro
authors: I
authors: Yoshikawa
authors: Satoshi
authors: S
authors: Ichimaru
authors: Hisataka
authors: H
authors: Takenaka