Influence of shield parameters on cosmic-muon induced backgrounds of Ge γ-spectrometers

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Beam interactions with materials and atoms, 1996-04, Vol.111 (1), p.163-170
• Main Author: Vojtyla, Pavol
• Format: Article
• Language: English
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/0168-583X(95)01267-2

Computer simulations using GEANT 3.21 with shields of various parameters are performed to investigate how shield parameters can influence the cosmic-muon induced background of a typical low-level HPGe γ-spectrometric system. It was found that the background increases with increasing inner shield dimensions to reach a saturated value for very large dimensions when the composition of the shield (bulk material, thickness, lining and proportion between height and width) is not changed. The background for a large shield is almost twice that for a tight one. The background does not depend significantly on the position of the detector inside a shield and on the shape (cylinder or rectangular) provided the inner dimensions are the same. There is a strong dependence on bulk material and lining. Backgrounds are lower below ≈500 keV but higher above ≈500 keV and in the 511 keV annihilation peak for higher- Z materials. Several types of lining are simulated and compared. Best results are obtained for a lead shield lined with 2 mm of tin.