Physics of auroral phenomena : proceedings of the 34th Annual seminar, Apatity, 01 - 04 March, 2011 / [ed.: A. G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2011. - 231 с. : ил.

Yu. V. Balabin, E.A. Maurchev for thermal scattering. In all calculations the neutron fluence in the detector volume (i.e. the actual proportional counter tube) was scored using a Sensitive Detector class. In order to determine the counter response, He (n,p) H + 0,764 MeV reaction was used. For physics processes the built-in physics list QGSPBERTHP (recommended for such applications), which includes various interaction model was applied. Fig. 1. A unit (one detector) o f a neutron spectrometer is shown (in section). Polyethylene shield is marked 1, protection box from thermal neutron is marked 2, neutron detector SNM-18 (filled with He3 gas counter) is marked 3. This unit is shown without polyethylene moderator, which covers above the counter tube into gap of protection. Lines are neutron tracks in response modeling. Neutron initial position and angular distribution are random into some value limits to avoid “empty” tracks when neutrons pass by the box. a C«C. -O £ s z; у «Р Яa оU4>-O 3 Z _______ 3 EE 104 10* Energy, eV Fig. 2. A neutron detection efficiency depending on moderator thickness obtained as a result of first part of modeling. 1, 2, 3 lines represent efficiencies for moderator thickness of 2 cm, 4 cm and 8 cm respectively. Efficiency is given as N particle per 1000 initial ones. Fig. 3. A neutron detection efficiency depending on incident direction relative to vertical one obtained as a result of modeling. 1, 2, 3 lines represent efficiencies for incident direction with angles 0, 15 and 45 degrees respectively. Efficiency is given as N particle per 1000 initial ones. As a result of modeling of neutron detection efficiency depending on thickness o f the polyethylene plate closing an upper of the counter (polyethylene moderator) for the first experiment and depending on incident 104 15 degrees - 45 degrees I A j JW Energy, eV | " 0 degrees