2026/07/22 by Yue Yu, Jooyun Woo, Ipek Altunyurt +34
#physics.ins-det #astro-ph.IM
We present the design optimization for maximizing the effective area of a custom X-ray optic for the International Axion Observatory (IAXO) and BabyIAXO, including its novel hybrid configuration that enables full coverage of the 700-mm-diameter magnetic bore with minimal stress imposed on the mirrors; shell layout optimized for axion spectra and spatial distribution; and the coating recipes that enhance reflectivity in the energy range of interest. We evaluate how these design choices improve the observation signal-to-noise ratio (SNR) of BabyIAXO and IAXO by calculating the broad-band effective area and simulating the point spread function (PSF) and focal spot at the detector plane. The cost-effective and scalable optic offers an energy response from 0.03--15 keV, achieving an effective area that exceeds 2400 cm2 near 1 keV - the peak of the ABC axion spectrum - and remains above 1700 cm2 around 3 keV - the peak of the Primakoff axion spectrum. It yields a half-power diameter (HPD) of ∼ 46′′ for an on-axis point source at infinity, and a focal-spot HPD of ∼ 120′′ for the radial distribution expected for axion signals within the approximately 3′-radius solar core. A relatively generous fabrication-error budget is also summarized. The custom optic, accounting for fabrication errors, is anticipated to deliver a more than 55-fold enhancement in the SNR.