Focusing X-Ray Optics for Astronomy

Table 1

Various types of optics for X-ray telescopes.

Type	Best angular resolution (half power diam.)	Energy band	Status	Astronomical applications
Grazing incidence reflection	0.5 arcsec (actual)	0.15–10 keV	Currently operating***	Imaging and spectroscopy of all type objects
Grazing incidence reflection with ML coatings**	0.4 to 1 arcmin	5–>80 keV	Balloon experiments, NuSTAR in 2012	Broad band imaging of all type objects
Lobster-eye (grazing incidence)	Few arcmin	0.2–5 keV	Small payload prototypes	Wide Field monitoring and surveys
Laue Crystal Lens	~1 to 2 arcmin	Few % variable in 0.1–1 MeV band	Balloon and laboratory experiments	Hard X-ray, soft gamma-ray spectroscopy, nuclear lines
Normal incidence reflection with ML coatings**	<1 arcsec (actual)	<0.25 keV ~1% bandwidth	Recent missions, for example, TRACE	Imaging soft X-ray lines in the solar corona
Diffractive-refractive	10 to 100* microarcsec	>4 keV∼10–20% bandwidth	Laboratory experiments	Central regions of galaxies + jets nearby stars
Interferometer	0.1* microarcsec	0.2 to 10 keV	Laboratory experiments	Imaging the environments of super massive black holes

* Expected resolution. ** multilayer coatings. *** In 2010, the Chandra X-Ray Observatory, XMM-Newton, Suzaku, and Swift XRT Total telescope areas at 1 keV are, respectively, 0.09 m², 0.43 m² (3 tel), 0.18 m² (4 tel), and 0.015 m².