Calliope 60Co gamma irradiation facility for space qualification at ENEA-casaccia research centre (Rome)

Abstract

Optical and electronic components used on spacecrafts and satellites are exposed to a large variety of environments, often rich in high fluxes of energetic particles, which may cause serious degradation and damaging effects.1–5 The Space experiment radiation environment is characterized by several kind of primary particles. The main sources of Space radiation are galactic cosmic rays, energetic electrons and protons, trapped in the Van Allen Belts, and particles associated to the solar activity (electron, protons and heavy ions). Cosmic rays are charged particles (protons, electrons and heavy ions) whose flux (10-28-103 m-2 sr-1 s-1 GeV-1) and particle energy (from tens to 1014 MeV) vary depending on their solar, galactic and extra galactic origin.6–8 The galactic cosmic rays flux strongly depends on the solar activity: it is low when the solar activity is high because the solar wind does not allow particles to easily enter the solar system. The charged particles of galactic cosmic rays are also influenced by the Earth magnetic field which provides a partial radiation shielding for spacecraft. However, cosmic rays, as well as solar emitted particles, have free access over the polar regions where the magnetic field lines are open to interplanetary Space: the result is that the galactic cosmic ray fluxes are higher at the Poles and lower at the equator.9 The Van Allen belts mainly consist of MeV protons and keV electrons trapped in the Earth magnetic field, with a toroid spatial distribution around the Earth.10 Trapped electrons are positioned in two regions: the former extends to about 2.4 Earth radii and contain electrons with energy lower than 5 MeV while the latter, the outer, goes from about 2.8 to 12 radii and include electrons with energy up to 7 MeV. Finally, the Sun is the source of different kinds of particles such as those produced by the solar wind coming from upper atmosphere of the Sun, and by the solar flares and the coronal mass ejection processes, sporadically occurring.9,11,12