The University of Arizona
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Surface and underground ultra low-level liquid scintillation spectrometry.

Wolfango Plastino, Lauri Kaihola

Abstract


Cosmic background and its variation have been removed in the Gran Sasso National Laboratory (National Institute of Nuclear Physics) by its 1400-m rock overburden. Stable, high-performance liquid scintillation counting conditions are obtained when any remaining variable components of the environmental background, such as radon, are eliminated. The ultra low-level liquid scintillation spectrometer Quantulus (super TM) has an anti-Compton guard detector (guard for short) that allows monitoring of gamma radiation in the background. The guard detector efficiency in radiocarbon background reduction is 8% in the Gran Sasso National Laboratory, while 80% is observed in surface laboratories. Thus, atmospheric pressure variations in surface laboratories cause variation in cosmic radiation flux. The Quantulus anti-Compton detector is highly efficient in detecting cosmic radiation, and the sample count rate remains stable in long-term counting. Also, correlation of sample backgrounds with environmental gamma radiation in various laboratories is examined.

Keywords


absolute age;C 14;carbon ;Compton radiation;cosmic rays;Europe ;gamma rays;Gran Sasso National Laboratory;instruments ;isotopes ;Italy ;liquid scintillation methods;methods ;monitoring ;Quantulus ;radioactive isotopes;Southern Europe;underground installations

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