Narrow-bandpass multilayer mirrors for an extreme-ultraviolet Doppler telescope

We have developed narrow-bandpass MoSi/Si multilayer mirrors for a Japanese sounding-rocket program. A high spectral resolution lambda/Delta lambda ex ceeding 40 was achieved by a two-mirror telescope with a multilayer coating . The single telescope had two bandpasses in the extreme-UV range for detec ting a coronal high-velocity flow; the wavelength at peak reflectance (here after peak wavelength) in one of the bandpasses was 210.2 Angstrom, situate d on the blue side of the target's Fe XIV 211.3-Angstrom coronal emission l ine, and the peak wavelength in the other was 213.3 Angstrom on the red sid e. A high uniformity in a peak wavelength of less than 1 Angstrom was achie ved over a primary (secondary) mirror surface 158 (96) mm in diameter. The ratio of the reflectance for the Fe XIV line at 211 Angstrom to that for an intense He II line as a contaminant at 304 Angstrom in the telescope syste m became 2 x 10(5) owing to a wave trap consisting of a single Si layer on the MoSi/Si multilayer. The narrow-bandpass (similar to 5-Angstrom) telesco pe was launched on 31 January 1998 by sounding rocket S520CN-22, and images of the whole-Sun corona at Fe XIV 211 Angstrom were successfully obtained. (C) 1999 Optical Society of America.