Testing the Radiation Hardness of Thick-Film Resistors for a Time-Of-Flight Mass Spectrometer at Jupiter with 18 MeV Protons

The Neutral and Ion Mass Spectrometer onboard ESA Jupiter mission JUICE employs thick-film resistors (from ~1 Ω to ~1 MQ), screen-printed on ceramic elements, to realize high-voltage ion optical elements and decontamination heaters. Despite the relevant space heritage, these materials were never employed before in a radiation environment comparable to Jupiter's magnetosphere. With this study, we prove the suitability of these materials for the NIM instrument by means of irradiation up to ~ 16-85 Mrad in vacuum with 18 MeV protons. To allow an accurate calculation of the dose, the chemical composition of the samples is determined by Laser Mass Spectrometry. Thanks to a custom-designed irradiation station, the temperature and the electrical parameters of the sample are monitored in real-time during the irradiation, or the sample can be subject to high-voltages representative of the operating conditions in space. All in all, the materials proved to be radiation-hard in the investigated dose range, with few exceptions where permanent damages occur.