Development and Validation of the GEANT4 Model of the Electron Proton Helium Instrument on Board the SOHO Spacecraft Utilizing the Accelerator Measurements at the Hahn‐Meitner Institute Berlin

Abstract Context. The Electron Proton Helium INstrument (EPHIN) aboard SOlar and Heliospheric Observatory is a particle telescope that measures energetic protons and helium above 4 MeV/nuc and electrons above 150 keV. While a calibration of EPHIN has been performed before launch, it has only partially been assessed reducing the accuracy of the detector and dead layer thicknesses of each detector. However, these parameters are crucial for the correct representation of the instrument in simulation runs which are necessary for detailed analysis of the instruments measurements in space. Aims. An accurate representation of EPHINs detector geometry has been derived from the calibration results. These improvements compared to previous detector models will allow for lower systematic uncertainties as well as new data products for the EPHIN data at high energies. Methods. EPHIN was calibrated using a 4He beam aimed at a gold target. The various particle populations produced in the target were then filtered using a rigidity filter. The measured energy loss distributions in each individual detector have been compared to GEANT4 simulations. The thicknesses and dead layer thicknesses of each detector have been varied in the simulation setup to achieve best agreements between simulation and calibration. Results. Good agreements between simulation and calibration have been reached. Most energy loss distribution fall within a 3 % margin, compared to differences of more than 10 % in earlier models.