Experiments at Modane underground laboratory or the swan song of radiocarbon ß-counting by gas proportional counter
Résumé
ABSTRACT In 1991, a 14 C ß-counting installation with four proportional CO 2 gas counters was tested at the Modane underground laboratory, 1700 m below the summit of Pointe du Fréjus, reducing the muon flux to 4 muons per square meter and per day. With cosmic radiation attenuated by a factor of 2.10 6 , the background level of the counters was reduced by 65 to 85% while its variability was reduced by a factor of 30–80 depending on the type of counter. The dating limit of these counters extends to well beyond 60,000 years.