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|Authors: ||Sironi, Giorgia|
|Internal Tutor: ||TREVES, ALDO|
|Co-tutor: ||CITTERIO, OBERTO|
|Title: ||Analysis of X-ray telescope angular resolutions: application to NHXM.|
|Abstract: ||X-ray Astronomy is a young eld of research. Since the rst X-ray observation performed by means of a rocket ight in the '60s, the greatest leap forward in Xray telescopes performances was brought in the '70s when the imaging capability was introduced thanks to the use of grazing incidence optics. The excellent results of grazing incidence telescopes in the soft x-ray imaging are well-known and represented by the results obtained with emissions ROSAT, Chandra and XMMNewton.
However, the extension of the imaging capability to the hard X-rays (E 10 keV) will allow the observations of sources critical for their role in cosmology like
AGN, and clusters of galaxies. In the last decade the aim of extending the imaging
capability to hard X-rays (E 10 keV) brings to the development of speci c and
challenging missions, in this thesis the reference mission is New Hard X-ray Mission
(NHXM), a mission of the Italian Space Agency, which development is in cooperation
with the INAF-Astronomical Observatory of Merate (OAB) and with Media Lario Tech. for the studies concerning the NHXM Wolter-like optics production. Wolter-like optics, the de-facto standard for the realization of high resolution focusing telescopes, are manufactured by Nickel-Cobalt eletroforming. Once the optics theoretical performances have been optimized by means of the opportune optical design strong image degradation can still be caused by surface errors e ect generated in the manufacturing process. When surface pro le errors are on macroscopical length scale ( mm) their e ects on optical performance scan be evaluated considering geometrical optics and simulating the optical path of incident photons by means of ray-tracing codes. In this case the imaging capability degradation is independent from photons energy. Further image degradation e ects are due to the microroughness of the reflection surface which e ect behaviour follows the X-ray scattering laws. The XRS e ect is to spread a fraction, increasing with photons energy, of the incident radiation around the direction of the reflected beam. When hard X-ray are considered the requirements to limit the XRS e ects are to have reflection surface with small surface errors also on microscopical length scale ( m scale).
My Ph.D. research deals with the development of methods allowing estimating and
controlling the X-ray Wolter-like telescopes optics angular resolution degradation
caused by optics surface errors. My activities are separable in two fields:
The effects on angular resolution at high energy of the optical surface microrougness
variation. This point had been met changing the reflecting layer substrate in the replica process of manufacturing.
The development of two new metrological devices, capable of estimating the
angular resolution degradation, due to mandrels and mirror shells shape errors.
The two presented points requires the multi-instrumental complete optics surface
characterization, covering the surface errors wavelengths scale in the broad interval 1 m -1 m.
The thesis discussion is organized as follow: Presentation of the NHXM mission and of its target observational sources
Description of the Wolter-like optics geometry, manufacturing process, and
characteristic surface errors (Chapter 2)
Study of the angular resolution energy dependent term in function of Gold layer
thinning in Ni-Co electroformed replica process (Chapter 3)
Development of a new mandrel metrological device (Chapter 6)
Development of a new mirror shells metrological device (Chapter 7)
Conclusions about the followed research plan (Chapter 8)|
|Subject MIUR : ||FIS/05 ASTRONOMIA E ASTROFISICA|
|Issue Date: ||2010|
|Doctoral course: ||Astronomia e Astrofisica|
|Publisher: ||Università degli Studi dell'Insubria|
|Citation: ||Sironi, G.Analysis of X-ray telescope angular resolutions: application to NHXM. (Doctoral Thesis, Università degli Studi dell'Insubria, 2010).|
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