P. Vojtyla, A COMPUTER-SIMULATION OF THE COSMIC-MUON BACKGROUND INDUCTION IN A GEGAMMA-SPECTROMETER USING GEANT, Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms, 100(1), 1995, pp. 87-96
A computer simulation of the cosmic-muon background induction in a HPG
e gamma-spectrometer using GEANT3.15 is described. Relative contributi
ons of muon interaction mechanisms in parts of a detector shield were
investigated. The direct muon ionisation in the Ge-diode, production o
f delta-electrons, direct e(-)e(+)-pair production, muon decay and muo
n bremsstrahlung contribute to the induced lower-energy background by
2.5%, 81.2%, 10.0%, 4.0% and 2.3%, respectively. For muons with moment
a below approximate to 0.7 GeV/c the muon decay is the most contributi
ng mechanism. The contribution of the delta-electron production reache
s a maximum at 1.7 GeV/c and extends to the highest momenta. Above app
roximate to 70 GeV/c the direct e(-)e(+)-pair production dominates. Ab
out 97% of muon primary interaction vertices are situated in shield ma
terials. An inner shield layer that is 4.7 cm thick contains 90% of al
l the vertices. A 3 mm thick Cd-Cu shield lining accounts for 15% of a
ll events. The simulated spectrum agrees well with an experimental one
. Limitations of the standard GEANT for simulating the background indu
ction by cosmic rays are discussed as well.