Background Measurements with Different Shielding and Anticoincidence Systems

Abstract

ABSTRACT. Extremely low background count rates are a necessary condition for both the measurement of 39Ar concentrations in ground and ocean water and of 14C activities in small samples using gas proportional counting techniques. A systematic comparison of the performance of three different designs of shielding systems in four different installations has been made.Background values of selected gas proportional counters were measured, compared and separated into their various components. Acceptably low backgrounds were obtained in all the systems tried. The performance of a Nail shield in a surface laboratory was found to be at least equal to the best obtained with a gas ariticoincidence detector in a deep underground labora-

Stability of a New, Multichannel, Low-Level Liquid Scintillation Counter System, Kvartett

“…Background measurements with a set of gas proportional counters under different active and passive shields have demonstrated convincingly that an active guard consisting of a 102-mm-thick annular NaI(Tl) scintillation detector (Loosli, Forster and Otlet 1986) gives the best active shield. This can be explained by the fact that the NaI(Tl) detector not only eliminates the muon background component but also largely suppresses the background contribution of the secondary gamma rays produced by energetic cosmic muons and protons in the thick passive shield surrounding the sample detector.…”

Liquid Scintillation Counting in the London Underground

“…Massive physical shielding (ie, deep underground siting) to reduce the cosmic-ray contribution to background count rates in low-level liquid scintillation counting has been reported by various authors (Schotterer & Oeschger, 1980;Calf & Airey, 1982;Loosli, Forster & Otlet, 1986;Kahn & Long, 1989). At the 12th International Radiocarbon Conference held in Trondheim, the potential of the London Underground as a site for liquid scintillation counting was considered (Bowman, 1986).…”