Study of a Superconducting Magnetic Diverter for the ATHENA X-Ray Space Telescope

Abstract

The advanced telescope for high energy astrophysics (ATHENA) is an X-ray telescope of the European space agency which is planned to be launched in 2028. It will carry out observations in the X-ray band, exploiting two focal plane detectors where X-ray photons will be focused by silicon pore optics. Previous X-ray missions have shown a serious issue with soft protons and ions (below 150 keV/n), which could enter the telescope mirror aperture and be concentrated toward the focal plane. These particles must be blocked or diverted to avoid excess background loading on the detectors. The proposed solution is to deflect protons away from the instruments field of view by means of magnets located between the optics and the focal plane. A 160000 amp-turns HTS superconducting toroidal magnet, composed by three or four round coils located between 0.6 and 1.2 m from the focal plane, can efficiently deflect most of the incoming particles. The rejection rate for protons till 120 keV is better than 99%, to be compared with about 80% of a previously proposed diverter based on permanent magnets. The magnetic field requirement at the detectors level (B <; 1 mT) is widely satisfied, as well as the mass budget of 110 kg. Challenging aspects related to the operation and reliability of the superconducting magnet will be discussed.