EXPERIMENTAL AND SIMULATED COSMIC MUON INDUCED BACKGROUND OF A GE SPECTROMETER EQUIPPED WITH A TOP SIDE ANTICOINCIDENCE PROPORTIONAL CHAMBER

Background of a well-type ground-based low-level high purity germanium spectrometer was reduced using a single top side anticoincidence prop ortional chamber. The chamber suppressed the total background (40-1500 keV) of 34 cpm by a factor of 2.2. To assess the efficiency of the an ticoincidence chamber in reducing the cosmic muon induced background M onte Carlo simulations were done using GEANT3. With the sea-level cosm ic muon flux distribution, a total muon induced background of 47 cpm ( 0-1500 keV) and a background reduction factor of 4.2 were computed. Go od agreement between the measured and simulated spectra was obtained. Some general features of the background induction by muons are discuss ed. Muons with momenta from about 1 to 10 GeV/c contribute mostly to t he background. For muons with momenta below 1 GeV/c the muon decay is the most contributing mechanism.