Astronomical soft x-ray mirrors reflectivity enhancement by multilayer coatings with carbon overcoating

Pareschi, G.; Cotroneo, Vincenzo; Spiga, D.; Vernani, Dervis; Barbera, Marco; Artale, Maria Antonella; Collura, A.; Varisco, Salvatore; Grisoni, Gabriele; Valsecchi, Giuseppe; Negri, B.

doi:10.1117/12.556838

Cited by 26 publications

(23 citation statements)

References 7 publications

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“…A substrate and rib thickness of 150 μm and wafer thickness of 750 μm enables a pore structure of 0.6 × 1.5 mm with ∼70% aperture efficiency, which results in a low energy collecting area of ∼70 cm 2 for an XOU. An overcoat of carbon on the iridium-coated reflecting surfaces of HPOs can provide enhanced low energy reflectivity [15].…”

Section: X-ray Opticsmentioning

confidence: 99%

“…An inner annular radius of 0.67 m, limited by the MSC launch adapter, accommodates HPOs with small grazing angles such that the collecting area at 10 keV is ∼0.8 m 2 . If multi-layer coatings are used on the inner HPO the high energy response can be extended to give ∼0.1 m 2 at 30 keV [15]. An outer aperture radius of 2.1 m can be accommodated within the launcher fairing including a baffle skirt of width ∼16 cm.…”

Section: X-ray Opticsmentioning

confidence: 99%

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XEUS: the physics of the hot evolving universe

et al. 2008

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Section: X-ray Opticsmentioning

confidence: 99%

Section: X-ray Opticsmentioning

confidence: 99%

XEUS: the physics of the hot evolving universe

et al. 2008

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“…Pareschi et al 17 have recently shown that a thin Coating of Carbon, overimposed to the gold coating, can fill this gap and increase the effective area in the 2 -3 keV band. 17,18 This possibility will be seriously considered.…”

Section: Opticsmentioning

confidence: 99%

POLARIX: a small mission of x-ray polarimetry

Costa¹,

Bellazzini

Soffitta³

et al. 2006

SPIE Proceedings

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X-Ray Polarimetry can be now performed by using a Micro Pattern Gas Chamber in the focus of a telescope. It requires large area optics for most important scientific targets. But since the technique is additive a dedicated mission with a cluster of small telescopes can perform many important measurements and bridge the 40 year gap between OSO-8 data and future big telescopes such as XEUS. POLARIX has been conceived as such a pathfinder. It is a Small Satellite based on the optics of JET-X. Two telescopes are available in flight configuration and three more can be easily produced starting from the available superpolished mandrels. We show the capabilities of such a cluster of telescopes each equipped with a focal plane photoelectric polarimeter and discuss a few alternative solutions.Keywords: X-ray Astronomy, Polarimetry, Telescope, Detectors POLARIMETRY: BIG HOPES MEAGRE RESULTS.A long term theoretical analysis has foreseen the possibility to test models of X-ray sources and to derive relevant parameters of the models themselves by measuring the linear polarization of X-rays. In the first years the polarization deriving from the emission process was outlined. On 1985 Sunyaev and and Titarchuk demonstrated that in a hot accretion disk the scattered photons have an energy much higher than the original photons and thence the Chandrasekhar limit of 11.7 % could be exceeded. In 1988 Meszaros et al. stated "Polarimetry would add to energy and time two further observable quantities (the amount and the angle of polarization) constraining any model and interpretation: a theoretical/observational break-through". This very attractive perspective pushed some investigators to develop instrumentation aimed to perform this measurements. This was mainly based on Bragg Diffraction at 45 o and on Compton/Thomson scattering in a certain range of angles around 90 o . Bragg crystal is an excellent analyzer of polarization (100% modulation) but is effective in a very narrow interval around the energy that fulfils the Bragg condition for that particular crystal and that particular angle. A flat Bragg crystal at 45 o set before the focal plane of an X-ray telescope acts as a newtonian secondary mirror and a detector in the secondary focal plane detects the source in the thin band defined by the Bragg (plus higher orders if in the band). The whole is rotated and the source brightness is modulated depending on the amount of polarization.The scattering polarimetry is effective only when scattering exceeds photoabsorption. A well of detectors surrounds the scatterer and the polarization is measured by the angular distribution of the out-coming photons.

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“…Subsequently, Pareschi et al [4] pointed out that the deliberate employment of a low density external film over any mirror acts to reduce the photoelectric absorption when the mirror is in the total external reflection regime. In such a case the effective area of the mirror could intentionally be increased between 1 and 4 keV.…”

Section: Introductionmentioning

confidence: 99%

Influence of a carbon over-coat on the X-ray reflectance of XEUS mirrors

Lumb

Christensen²,

Jensen³

et al. 2007

Optics Communications

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We describe measurements of the X-ray reflectance in the range 2 to 10 keV of samples representative of coated silicon wafers that are proposed for the fabrication of the XEUS (X-ray Evolving Universe Spectrometer) mission. We compare the reflectance of silicon samples coated with bare Pt, with that for samples with an additional 10nm thick carbon over-coating. We demonstrate a significant improvement in reflectance in the energy range ~1 to 4 keV, and at a grazing incidence angle of 10 mrad (0.57°). We consider the resulting effective area that could be attained with an optimized design of the XEUS telescope. Typically an improvement of 10 to 60 % in effective area, depending on photon energy, can be achieved using the carbon overcoat.

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Astronomical soft x-ray mirrors reflectivity enhancement by multilayer coatings with carbon overcoating

Cited by 26 publications

References 7 publications

XEUS: the physics of the hot evolving universe

XEUS: the physics of the hot evolving universe

POLARIX: a small mission of x-ray polarimetry

Influence of a carbon over-coat on the X-ray reflectance of XEUS mirrors

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