COTS MOS Dosimetry on the MeMOSat Board, Results After 2.5 Years in Orbit

• Main Authors: Lipovetzky, José, Garcia-Inza, Mariano, Cañete, Macarena Rodríguez, Redin, Gabriel, Carbonetto, Sebastián, Echarri, Martín, Golmar, Federico, Marlasca, Fernando Gomez, Barella, Mariano, Sanca, Gabriel A, Levy, Pablo, Faigón, Adrián
• Format: Journal Article
• Language: English
• Published: 30.06.2020
• Subjects: Physics - Applied Physics; Physics - Instrumentation and Detectors
• DOI: 10.48550/arxiv.2007.00143

We present the results after 2.5 years in or-bit of Total Ionizing Dose (TID) measurements done using Metal Oxide Semiconductor (MOS) dosimeters on the MeMOSat board. The MeMOSat board was launched on July 19th 2014 at the BugSat-1 "Tita" microsatellite developed by Satellogic to stay at LEO. We used as dosimeters p-channel Commercial Off The Shelf (COTS) MOS transistors with gate oxides of 250~nm. Before launch, a subset of transistors with similar drain current to voltage (I-V)curves where selected from a group of 100 devices. The temperature dependence of the (I-V) curves was studied to find the minimum temperature coefficient biasing point. Then, a calibration subgroup of sensors was irradiated using a $^{60}$Co gamma source to study their response to TID, showing responsivities of $\sim$75~mV/krad when the sensors are irradiated without gate bias. Also, the post irradiation response of the sensors was monitored, in order to include a correction for low dose rate irradiations, yielding 30~mV/krad. A biasing and reading circuit was developed in order to allow the reading of up to 4 sensors.The threshold voltage was monitored during different periods of the mission. After 2.5 years in orbit,the threshold voltage of the sensor mounted on the MeMOSat Board had a V$_\mathrm{T}$ shift of approximately 35~mV corresponds to a dose of 1.2~krads.