Shielding an MCP Detector for a Space-Borne Mass Spectrometer Against the Harsh Radiation Environment in Jupiter’s Magnetosphere

Detectors of scientific instruments on spacecraft flying through Jupiter radiation belts need to be protected from high fluxes of penetrating radiation by means of radiation shields. Electrons constitute the most difficult component of Jupiter's magnetosphere to shield from, because of their abundance, penetration depth in matter, and intensity of bremsstrahlung radiation generated upon interaction with the shielding material. For the Neutral and Ion Mass spectrometer (NIM) of the Particle Environment Package (PEP) instrument suite on board the European Space Agency's mission JUpiter Icy moons Explorer (JUICE), we devised a shielding design made of an aluminum and tantalum stack to reduce the radiation-induced noise on its Micro-Channel Plate (MCP) detector. To predict the expected radiation background in the mass spectra in space, we manufactured a flight-like shielded detector and submitted it to radiation testing at the Paul Scherrer Institut with an electron beam in the energy range ~ 30 to ~ 345 MeV. The results of this test provide a verification of the NIM capability to fulfill its science requirements in the mission's worst-case scenario (the Europa flyby), and give insights into new directions of optimization of shielding elements' design for NIM and similar instrument bound to operate in a harsh radiation environment.