Speaker
Description
Multilayer or Z-graded radiation shielding has been proposed to reduce the weight of satellite radiation shielding in comparison to conventional aluminium shielding. Especially for CubeSats, which are mass and volume-constrained and rely on non-radiation hard commercial off-the-shelf (COTS) components, multilayer shielding could enable longer mission durations and missions to higher orbits. Simulations with Geant4 show up to a 30% reduction in required shielding mass compared to conventional aluminium shielding to achieve the same total ionising dose (TID) behind an optimised two-layer shield consisting of polyethylene on top of lead.
To verify the performance of such a multilayer shield in space, a compact and low-power multilayer radiation shielding experiment is proposed. It uses RadFET total dose sensors to passively accumulate ionising dose behind different aluminium shielding thicknesses and polyethylene-lead multilayer shielding configurations.
The readout is done by pushing 10 or 17 µA into each of the RadFETs one at a time while measuring the voltage drop across the RadFET. The current source of the readout circuit must be precise and stable while the leakage current of the switching matrix must be low enough to not influence the measurement. These requirements must be maintained despite fluctuations in temperature and the radiation environment.
A prototype of the readout electronics was successfully tested under Co-60 irradiation up to 30 krad of ionising dose. A qualification model of the circuit has since been designed and assembled. The mechanical manufacturing is expected to be complete before SPACEMON 2025. A full electrical and mechanical qualification model is scheduled for proton irradiation testing in summer 2025.
The instrument is being developed as part of the RADICS collaboration between Aalto University and the University of Turku in Finland and was designed to fly on the proposed Foresail-2 CubeSat of the Finnish Centre of Excellence for Sustainable Space.
Additionally, work has started on a compact internal radiation monitor to observe the actual radiation environment that reaches the internal electronics of satellites. The plan is to measure the total ionising dose, displacement damage and flux of high LET particles using a RadFET, GaAs diode and a silicon plate detector. Feedback from the community is welcomed to help define requirements for this new instrument, inform design decisions and discuss flight opportunities.
