Diploma Thesis of Michael Moser

Title: Solar Neutron Telescope Gornergrat: Monte Carlo Simulation of Detector Properties
Abstract: The Solar Neutron Telescope (SONTEL) at Gornergrat was built in 1998 to detect high-energy neutrons produced during energetic processes at the Sun. In 1999 it was upgraded by adding a facility to detect the direction of the incident neutrons.

In order to interpret the SONTEL recordings during solar neutron events, it is necessary to know the relationship between the counting rates and the primary particle flux penetrating the Earth's atmosphere. This relationship can hardly be determined experimentally. Also in particle beam calibrations the atmospheric cascade of primary cosmic ray particles cannot realistically be reproduced. An analytical treatment is too difficult since the complex properties of the atmosphere and of the detector have to be considered.

Within the scope of this work, we therefore developed a Monte Carlo application to determine the detector properties of SONTEL at Gornergrat theoretically. The Monte Carlo code is based on CERN's GEANT3 libraries which allow to simulate the interaction processes of radiation with matter. From this application we first determined the efficiencies of the various SONTEL channels. The same code also allowed to simulate the average counting rates. As input we used secondary cosmic ray spectra from literature adapted to Gornergrat altitude. For the simulation of the detector response to Ground Level Enhancements (GLE), we developed another GEANT3 application to determine the corresponding secondary particle spectra above the detector. We simulated the detector response for two historic solar particle events, i.e. the solar neutron event of June 3, 1982, and the solar proton event of April 15, 2001. The latter has been recorded by SONTEL at Gornergrat, providing the possibility for a verification of the theoretical results.

Advisor: Prof. Dr. Erwin O. Flückiger, Physikalisches Institut, Universität Bern
Date: November 20, 2002
Download: The diploma thesis and the Monte Carlo applications are available for download:

A password is required to download the GEANT3/4 codes. Please contact the author.