Reconstruction of high energy thunderstorm radiation effects on soil matrix using Monte Carlo simulations

Due to their electromagnetic properties, thunderclouds can act as natural particle accelerators. Electrons accelerated in the thunderclouds can reach energies up to tens of MeV. Large populations of high energetic electrons formed by avalanche growth driven by electric fields in the Earth atmosphere called Relativistic Runaway Electron Avalanches (RREA) propagate through matter. They are decelerated and deflected in the course of collisions with particles in the atmosphere and emit gamma rays known as bremsstrahlung. The produced gamma rays can further trigger photonuclear reactions in the air and soil. This article reports on the work of project CRREAT (Research Centre of Cosmic Rays and Radiation Events in the Atmosphere), studying various lightning-related phenomena in various ways, both in situ and in the laboratory. This paper focuses on the simulation of the laboratory experiments at the Microtron accelerator in Prague and the neutron generator in Ostrava, where we irradiated various soil samples with 20 MeV electron beams. Experiments showed which radionuclides can be formed during the reactions of high-energy electrons with various soils and can be as targeted products in the thunderstorm radiation effect analysis. Radionuclides produced in exposed samples were measured using a high-purity germanium (HPGe) detector. A computer simulation was done with a simple source and sample geometry using the general-purpose 3D Monte Carlo code PHITS.