Development of x-ray focusing telescope for HUBS

The Hot Universe Baryon Surveyor (HUBS) mission will carry an imaging X-ray telescope (IXT) for covering an energy range from 0.5 keV to 10 keV to study the hot baryon evolution. In this paper, we report the optical design for HUBS mission and the latest developments at IPOE, Tongji Univeristy. For HUBS mission, we had designed a three-stage conic-approximation type to simplify the manufacturing process. The basic process of imaging X-ray telescopes based on thermal glass slumping has been introduced. Nearly ten prototypes have been fabricated for the process optimization over the years. In August 2018, an IXT prototype with 21 layers was measured at the PANTER X-ray test facility, indicating an HPD of 111″ and an effective area of 39 cm2 at 1.49 keV. In September 2019, the latest prototype with 3 layers reached to an HPD of 58″ at 1.49 keV.