Overcoming the Challenges of Measuring Energetic Particles in the Inner Belt: A Geant4-based Performance of an Energetic Particle Detector Instrument, REPTile-2

Abstract:

Following the retirement of community-supported Van Allen Probes mission, the quest for high quality energetic particle measurements in the radiation belts is likely to be taken on by smaller missions like CubeSat in the foreseeable future. Here we introduce Relativistic Electron Proton Telescope integrated little experiment-2 (REPTile-2), a low-mass, miniaturized (~1U) solid-state charged particle telescope that aims to undertake this challenging task. It incorporates detailed pulse-height analysis to enable 60 electron channels and 60 proton channels and includes anticoincidence detectors to minimize unwanted background contaminations. Monte-Carlo simulations of the particles’ interaction with the model instrument are analyzed extensively to derive the logic/binning equations and characterize the instrument response. Our analysis shows that REPTile-2 can measure ~0.3-~3.5MeV electrons and ~6.7-35 MeV protons with energy resolutions as low as 0.02 MeV for electrons and ~0.2 MeV for protons. In addition, contaminations due to electronic limitations are considered. The pileup effect on REPTile-2 is modelled using theoretical equations and is confirmed to be insignificant. We will present a comprehensive description of the REPTile-2 design and emphasize the importance of extensive Geant4-based analysis in empowering the design of new energetic particle instruments. These high-quality energetic particle measurements will enable new scientific understanding of the inner radiation belt, where unwanted contamination from the unforgiving penetration of highly energetic protons (tens of MeV to GeV) has been inevitable, and provide detailed specifications of the inner belt electrons and protons that are crucial for space weather modeling.