| Description |
In optical or visible spectrum, most materials used for reflection have refractive index greater than 1, while for X-rays this index slightly less than 1 for all materials. The highly energetic X-ray photons are absorbed in the coating material at normal incidence, used for visible light optics. Therefore, the imaging optics in X-rays make use of total external reflection at grazing incidence angle. But the energy dependence of the critical angle for the total external reflection limits the practical use of the standard reflecting optics to low energies (E< 15 keV). The solution to the problem, is the development of super mirrors (mirrors that can reflect hard X-rays) using multilayer coatings. Thin film multilayer coatings can be deposited on glass or other substrates using alternate layers of materials having high and low atomic number Z. Reflections from such multilayer mirrors satisfy Bragg’s equation mλ=2dsinƟ. This increases the reflectivity range, extending the imaging capabilities to a wide band of energies in the hard X-ray regime. Here, I present the work done for developing such multilayered mirror systems for a hard X-ray telescope.
I also present the work done for calibration of optics of ASTROSAT’s Soft X-ray Telescope pre-vibration, post-vibration and post thermovac tests.
|