Metal multilayer mirrors for EUV wide field telescopes
Metal multilayer mirrors have been designed for the ALEXIS satellite, which is to carry six wide field telescopes to perform an all-sky survey in three or four narrow wavelength bands in the EUV. Comprised of alternating layers of molybdenum and silicon, the mirrors are optimized to provide maximum reflectivity at angles from 11.5 to 17/degree/ off normal incidence and at wavelengths of 133, 171, or 186A. Simultaneously, the mirrors use a ''wavetrap'' described below to suppress reflectivity at 304A, where the extremely strong geocoronal line of He II causes severe background problems. Low reflectivity at 304A is achieved by superposing two layer pairs that provide destructive interference with an effective 2d spacing of 152A. The Mo layers in this wavetrap must be very thin, about 10A each, in order to allow the shorter wavelengths desired for peak reflectivity to penetrate without significant attenuation. Because refraction changes the effective angle of passage through the wavetrap, a joint optimization between layer thicknesses in the deep layers and the wavetrap layers must be performed for each target peak wavelength. For the 186A mirror, the optimum design from substrate upward is 40 layer pairs, each 74A Si and 31A Mo, followed by 2 layer pairs, each 55A Si and 10A Mo. Calculations predict this design will have a peak reflectivity at 186A of 35 percent and a 304A reflectivity less than 10/sup /minus/5/, if available optical constants are correct and the multilayer can be fabricated without difficulty. We will present details of the calculations and laboratory measurements of the reflectivity performance attained with prototype mirrors. 6 refs., 2 figs.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 5892434
- Report Number(s):
- LA-UR-89-2381; CONF-890836-2; ON: DE89015262
- Resource Relation:
- Conference: 33. SPIE annual international technical symposium on optical and optoelectronic applied science and engineering, San Diego, CA, USA, 6-11 Aug 1989; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
MIRRORS
DESIGN
TELESCOPES
EXTREME ULTRAVIOLET RADIATION
LAYERS
MOLYBDENUM
OPTICS
REFLECTIVITY
SATELLITES
SILICON
SPACE VEHICLE COMPONENTS
ELECTROMAGNETIC RADIATION
ELEMENTS
METALS
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
SEMIMETALS
SURFACE PROPERTIES
TRANSITION ELEMENTS
ULTRAVIOLET RADIATION
640100* - Astrophysics & Cosmology