Grazing incidence optics for X-ray astronomy

Abstract

Cosmic X-ray sources are usually very weak and their detection, therefore, needs large area telescopes to gather light and sensitive detectors to enhance quantum efficiency. Conventional telescopes for visible light use refracting or reflective optics which is impractical for X-ray wavelengths because photon energies are greater than the binding energies of the typical atomic electrons leading to a refractive index for Xrays being less than unity. Thus single surface reflectivity for near-normal incidence is negligible for X-rays. However, by Snell's Laws, total external reflection occurs and X-rays can be reflected from a surface up to a critical angle (usually about a degree for energies below 10 keV) given by cosine θ = n. This is known as the grazing angle. X-ray telescopes are made to exploit the grazing incidence from a set of co-axial and confocal shells of paraboloidal and hyperboloidal mirThe paper was based on presentation at XXXV OSI symposium held at Thiruvananthapuram during 16-18 January 2011.

Адаптивная И Активная Рентгеновская Оптика

“…Многие астрофизические объекты, такие как скопление галактик, черные дыры в активных ядрах галактик (AGN), галактические объекты (остатки сверхновых звезд, нейтронные звезды), излучают, флуоресцируют или отражают РЛ [80]. зеркал с уменьшающимися радиусами ( " зеркальные оболочки"), вложенные друг в друга наподобие русской матрешки, причем угол скольжения уменьшается от внешней оболочки к внутренней [82] (рис.…”

Adaptive and active X-ray optics

“…Many astrophysical objects, such as a galaxy cluster, black holes in active galactic nuclei (AGN), galactic objects (supernova remnants, neutron stars), radiate, fluoresce or reflect X-ray [80].…”

An X-ray view of quasars

“…A simple power-law was found to characterise the 3 to 50 keV X-ray emission of AGN. A soft X-ray (< 1 keV) bump in the power-law X-ray spectrum of a Seyfert was also first discovered with the low-energy detectors on board HEAO-1 (Singh et al 1985) A veritable revolution in X-ray astronomy occurred when Einstein Observatory carrying the first X-ray telescope with focusing optics necessary to produce images (see Aschenbach (1985); Singh (2005Singh ( , 2011 for an overview of X-ray imaging optics) was launched in 1978. Hundreds of extragalactic point-like Xray sources, as well as diffuse and extended sources over 0.2 − 4 keV were imaged with superb spatial resolution of a few arcsec.…”