Geant4 simulation of the solar neutron telescope at Sierra Negra, Mexico

Abstract

The solar neutron telescope (SNT) at Sierra Negra (19.0°N, 97.3°W and 4580 m.a.s.l) is part of a worldwide network of similar detectors (Valdés-Galicia et al., (2004) [1]). This SNT has an area of 4 m 2; it is composed by four 1 m×1 m×30 cm plastic scintillators (Sci). The Telescope is completely surrounded by anti-coincidence proportional counters (PRCs) to separate charged particles from the neutron flux. In order to discard photon background it is shielded on its sides by 10 mm thick iron plates and on its top by 5 mm lead plates. It is capable of registering four different channels corresponding to four energy deposition thresholds: E>30, >60, >90 and >120 MeV. The arrival direction of neutrons is determined by gondolas of PRCs in electronic coincidence, four layers of these gondolas orthogonally located underneath the SNT, two in the NS direction and two in the EW direction. We present here simulations of the detector response to neutrons, protons, electrons and gammas in range of energies from 100 to 1000 MeV. We report on the detector efficiency and on its angular resolution for particles impinging the device with different zenith angles. The simulation code was written using the Geant4 package (Agostinelli et al., (2003) [2]), taking into account all relevant physical processes.