Dose Measurements and Simulations of the RADFETs Response Onboard the Alphasat CTTB Experiments

Abstract

On July 25, 2013, the Alphasat satellite was launched, carrying the component technology test-bed (CTTB) to assess the space radiation effects in electronic components. Embedded in each of the three experimental boards of the CTTB, are radiation-sensitive metal-oxide–silicon field-effect transistors (RADFETs) to measure the radiation levels at the Alphasat geostationary orbit (GEO). In this work, values of accumulated dose are presented for the RADFETs onboard the Alphasat CTTB experiments up to July 16, 2018. These values were calculated from the threshold voltage shift and from temperature data transmitted to Earth, and using the model derived, previously, from the ESAPMOS4 RADFETs calibration campaign conducted at the European Space Research and Technology Centre (ESTEC) Cobalt-60 facility. These results show that the current accumulated doses are between 1.9 and 3.2 krad and the average dose rates are between 40 and 70 mrad/h. We also present a polynomial function that allows converting voltages into doses for a wide range of values and for different temperatures. The quality of this conversion is tested against Geant4 simulations of the expected dose in the CTTB components for the space radiation environment at the Alphasat orbit. The simulated doses were obtained for three GEO radiation models: AE8, AE9, and IGE-2006.