Geant4 Model of Transmission of Low Energy Particles through Ultrathin Carbon Foils for Space Plasma Instrumentation

Abstract

Carbon foils have been used in space physics flight instrumentation for decades, and they are the primary mechanism behind SWAPI, an instrument on NASA IMAP. SWAPI is designed to measure solar wind particles of H++ and He+. However, during coronal mass ejections or other solar events, a model of the carbon foil and the simulation of particles through it could predict how particles of different species interact with SWAPI. A Geant4 model of a carbon foil was created and compared against published multiple scattering data, where it aligned well with the experimental results. Then, this model was updated to fit the configuration of the Space Physics' Laboratory's absolute beam monitor (ABM). SIMION simulations of the ABM informed the development of its electric fields, and flight calibration data was used as a basis of comparison. The ABM model is not as accurate compared to the scattering data, and this is likely due to missing physics lists and processes, as Geant4 has limited options for low-energy physics. In the future, a full integration of SIMION with Geant4 geometry and physics can be pursued. Additionally, further research can be done to find the best low-energy physics lists for this application.