Speaker
Description
Since early 2000’s GEANT4 knows an increasing use for the modelling of the space environment effects on space systems. New domains of applications recently appear of reached an operational level, like for instance in 3D internal charging analysis or in the prediction of the Single Events Effects (SEE/SEU) in electronic devices. These outline new usages, needs and challenges. It is proposed to illustrate this wtith three examples issued from application cases of SpaceSuite’s tools.
With simulation kernels like ESA/GRAS, GEANT4 is more and more intensively used on realistic and complex geometries. In an industrial context, the temptation to directly import them from mechanical CAD models, through the STEP-AP format and convert it into GDML is high. But up to recently, this was remaining quite complicated. Generally, it may lead to a sever negative impact on the simulation performances. Due to the difference of geometrical approaches (Brep versus GDML) a direct conversion is generally done through a tesselation of surfaces deeply impacting GEANT4 simulations in terms of CPU time for large systems. In most of the cases, direct Monte-Carlo simulation are unreachable with realistic geometries.
SpaceSuite/EDGE CAD tool, with the recent evolutions of its STEP-AP importer, aims to address these issues with improved geometrical simplification capabilities and a new and innovative detessalation function. This last one allows, in most of the cases, to convert back to canonical CSG shapes from tesselated closed surfaces. It deeply optimises the geometry and reduces significantly the CPU time for the simulation. Moreover, tests have shown that an improper and direct tesselation may lead to significant errors or divergences in the final physical results. Examples, including CAD simplifications, and impacts on the simulations cost will be presented and discussed.
In the domain of the predictions of Single Event (SEE/SEU) on electronic devices, GEANT4 offers several key possibilities, directly exploited by the new SEE-U single event prediction tools recently developed by Artenum and ONERA in the frame of the SpaceSuite-O project. Through a fine 3D computation of the deposited energy of the incoming particles, with GEANT4, it is possible to numerically evaluate the SEU cross-sections of technologies depending on the size and the position of the transistors, independently on experimental measurements. Moreover, the set MoOra/GRAS/GEANT4 offers to compute the energy particle spectrum after shielding. EDGE’s Sector Shielding analysis module, SAAM, allows to rebuild the detailed equivalent aluminium shielding in each point inside a spacecraft. Combining both it is then possible to evaluate in situ the final Software Event Rate for the selected device, opening by this strong optimisations possibilities. Examples and first results will be presented and discussed.
Last, Internal Charging is an increasing risk factor, especially for missions passing through the radiations belts. If the initial particles charges and doses rates inside your sensitive components can be computed with MoOra/GRAS/GEANT4, a simple static view of deposited charges is not enough for a proper evaluation of the electrostatic risk, the dynamics and migration of charges inside the dielectric to be consider for a proper evaluation of E-fields and currents. To handle this, MoOra and the SPIS-IC plasma code has been interfaced in order to model precisely in 3D and dynamically the internal charge evolutions and the charging risk. Concrete examples on scientific experiments will be presented and briefly discussed.
