Physics of auroral phenomena : proceedings of the 33rd Annual seminar, Apatity, 02 - 05 March, 2010 / [ed.: A.G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2011. - 206 с. : ил.

E.A. Maurchev at al. Fig. 2. Visualization of neutron monitor model with a graphic system FreeWRL. In the figure the neutron monitor 6 - NM-64 is placed in a particles beam with random incident positions (particles fall on the monitor from above). Modeling technique For the calculations presented in given work the software package Geant4 (version 9.2. p.2 [1]) installed on OS SuSe Linux 11.2 was used. Also the library of data G4NDL 3.13 (Neutron Data Library) [2] which is based on calculation of cross sections ENDF/B-VI and which also includes cross sections for thermal scattering was installed. For visualization of modeled system graphic interface DAWN was used. In describing the physics o f interactions we used a standard list of physical processes, based on ready-made models (Bertini cascades and model exact calculation of low energy neutron interactions with matter [3]). Calculation results In Fig. 3 typical multiplicity spectra of secondary neutrons depending on primary particle (n, p) energy are presented. For calculation of the neutron monitor response function first o f all, the information is necessary on neutrons which have reached the detector and have interacted with nuclei 10 B. In Fig. 4 the typical energy spectrum of secondary neutrons which have reached the detector, obtained as a result o f the first modeling experiment (energy of a primary neutron 100 MeV) is presented. It should be noted, that at increase o f primary particle energy a spectrum form remains constant, and the amplitude varies only. Fig. 3. Multiplicity spectra of secondary neutrons resulting in the irradiation o f a system: polythene-lead-polythene by the incident neutrons (A) and protons (B) beam with a random angular distribution. 84