Open AccessGrowth of nano‐dots on the grazing‐incidence mirror surface under FEL irradiation
Author(s) -
Kozhevnikov I. V.,
Buzmakov A. V.,
Siewert F.,
Tiedtke K.,
Störmer M.,
Samoylova L.,
Sinn H.
Publication year - 2016
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s160057751502202x
Subject(s) - irradiation , incidence (geometry) , nano , optics , physics , materials science , nuclear physics , composite material
A new phenomenon on X‐ray optics surfaces has been observed: the growth of nano‐dots (40–55 nm diameter, 8–13 nm height, 9.4 dots µm −2 surface density) on the grazing‐incidence mirror surface under irradiation by the free‐electron laser (FEL) FLASH (5–45 nm wavelength, 3° grazing‐incidence angle). With a model calculation it is shown that these nano‐dots may occur during the growth of a contamination layer due to polymerization of incoming hydrocarbon molecules. The crucial factors responsible for the growth of nano‐dots in the model are the incident peak intensity and the reflection angle of the beam. A reduction of the peak intensity ( e.g. replacement of the FEL beam by synchrotron radiation) as well as a decrease of the incident angle by just 1° (from 3° to 2°) may result in the total disappearance of the nano‐dots. The model calculations are compared with surface analysis of two FLASH mirrors.