Deconvolution-based PSF reconstruction method for NewAthena silicon pore optics MMs calibrated at BEaTriX
Le résumé fourni par la source
The Beam Expander Testing X-ray (BEaTriX) facility is an advanced experimental setup designed to test silicon pore optics mirror modules (SPO MMs) for the NewAthena telescope at the energies 4.51 keV and 1.49 keV. The 4.51 keV energy line has been operational since 2022, while the other is under developement. Its novel design allows measurements of the point spread function (PSF) and of the effective area with the required accuracy. The 4.51 keV line at BEaTriX can be operated in two configurations: one with higher flux used for the effective area measurement and another with tighter beam collimation used for the half-energy width (HEW) measurement. In this paper, we present a deconvolution--based method to mathematically derive the PSF of a perfectly collimated X-ray beam, using the PSF information acquired with the high-flux configuration. This approach offers the possibility to primarily use the high-flux configuration for the MM characterization. We used the Richardson--Lucy deconvolution algorithm to reconstruct the PSF of a perfectly collimated X-ray beam. The deconvolution kernel, which models the angular distribution of the BEaTriX beam, was derived from a Hartmann test in high-flux configuration, accounting for the finite source size, dispersivity of the beam expander, figure errors of the collimating mirror, and misalignments. Using this kernel and performing a deconvolution to the measured high-flux image, we are able to obtain the intrinsic PSF of the MM for an ideally collimated beam. The images reconstructed using the deconvolution method were used to calculate the qualification parameters (i.e., full width at half maximum, FWHM, and HEW) for an SPO MM. To validate the reliability of the reconstruction approach, the mathematically deconvolved image is convolved back to the modeled beam kernel. This operation, as expected, yields the experimental PSF obtained in the high-flux configuration. As a further validation, the deconvolved PSF was compared with independent measurements acquired at the PANTER X-ray test facility, demonstrating a very good agreement.
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