Speaker
Description
On the Zugspitze mountain (2650 m a.s.l.), Germany, the Institute of Radiation Protection operates a Bonner Sphere Spectrometer (BSS), running continuously since 2004, to measure the neutron energy distribution of secondary cosmic rays. These measurements are highly affected by various environmental parameters, and in particular by the amount of snow in the near environment. To quantify this effect, Geant4 is used to simulate the neutron radiation field in this environment.
In a first step, the radiation field was simulated at 5 km a.s.l.. For this purpose the Earth atmosphere was adopted as a cylinder with a height of 100 km and a diameter of 6,000 km, consisting of several layers with temperature, density and air composition according to the 1976 U. S. Standard Atmosphere. At the top of this cylinder a surface source was placed covering the whole cylinder cross section and emitting primary cosmic rays (protons and alphas). Energy and angular distribution was implemented using a modulated local interstellar (LIS) spectrum with local cutoff rigidity and a cosine law angular distribution.
In a second step, the cylinder was reduced to 200 km in diameter to enhance the particle fluence, and the radiation field obtained in the first-step simulation was used as an input field at 5 km a.s.l. For this step, the ground level environment (mountain, housing of measurement location, several snow depths) will also be implemented.
This presentation shows the first results of this project, and further plans will be discussed.
