Copenhagen Natural Radiocarbon Measurements I.1

Journal/Book: SCIENCE July 3 1953 Vol. 118 No. 3053 pages 6-11. 1953;

Abstract: Carbon -14 Dating Laboratory Juliane Mariesvej 36 Copenhagen Denmark 1 The authors wish to express their gratitude to the Carlsberg Foundation for sponsoring the construction of the dating apparatus and the pertaining equipment. The series of investigations presented here were likewise carried out with financial Support from the Carlsberg Foundation. Moreover our sincere thanks are due Professor P. Brandt Rehberg head of the Zoophyeiological Laboratory where the apparatus is installed for the hospitality granted and for his kind interest in the work. Several firms have aided the project by placing equipment or chemicals at our disposal at a reduced price or free of Charge. We with to express our appreciation to Brüel and Kjær Copenhagen for electronics equipment ; Norsk Hydro Oslo for supplying argon gas ; British Petrol Co. Copenhagen for supplying butane gas ; Det Danske Stålvalseværk Frederiksværk for the steel plates forming the shield ; and Radiation Counter Laboratories Skokie Ill. for a Set of 24 a-c counters. 2 On leave of absence from the Los Alamos Scientific Laboratories. A fellowship and travel grant from the Danish Rask Ørsted Fond and a grant in aid from the Wenner Gren Foundation for Anthropological Research are gratefully acknowledged. CONSTRUCTION of a C14 dating apparatus in Copenhagen began in the fall of 1951 and the first unknown samples were dated in the summer of 1952. The technique used is largely that developed by Anderson Arnold and Libby (1) and later modified by Kulp (2). The only significant deviation from the classical set up is the use of a double screen wall counter as described by Anderson and Levi (3). This instrument (Fig. 1) consists of two independent detector units in a common envelope and a triple sample cylinder. The sample is mounted an the middle section of the cylinder while the two outer sections provide the areas for the background countings. As in the conventional screen wall the positions of the sample cylinder can be alternated between two extremes. In one position the sample an the middle section is exposed to detector A and a background area to detector B (ef. Fig. 1) ; in the other position the sample is exposed to B and the other background to A. This arrangement has two advantages. First the counting time necessary to arrive at a given statistical accuracy is reduced by 1/2 and second background and sample counts are registered simultaneously whereby the effect an the net count of possible temporal fluctuations in the background is eliminated. ... ___MH

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