Development of high reflective mirrors for space-based EUV polarimeter

Understanding the coronal magnetism is important to answer long-standing questions in the solar physics, such as the problem of high coronal temperatures, the acceleration of solar energetic particles, and the dynamics behind the solar eruptions that drive the geospace weather. Our recent study has reported coronal emission lines in the extreme-ultraviolet (EUV) which are, in principle, sensitive to the weak magnetic field of the solar corona via the Hanle effect. However, measurements of the coronal magnetic field have remained sporadic till date, due to the challenges faced in designing and manufacturing high-reflectivity and high-polarizing optics for successful operation in the EUV spectral range. In this work, thin-film fabrication of highly reflective mirrors is performed in EUV spectral range between 740 to 800 Å using the beamline facility of the RRCAT, Indore. The properties of the fabricated mirrors are studied in terms of their long-term stability, throughput and polarizing power.