Update on the Performance of the SUERC In Situ Cosmogenic 14C Extraction Line

Abstract

In this paper, we describe improvements to the in situ cosmogenic radiocarbon extraction system at SUERC made since 2004, highlighting the factors that potentially control the reduction of analytical variability. We also present new results on system blanks and of measurements of in situ 14C in shielded quartz and a surface quartz sample used at the University of Arizona as an in situ 14C standard (PP-4). The SUERC in situ 14C extraction system was built in 2001 and is based on a combustion technique following the design of the extraction system at the University of Arizona. Our preliminary results suggest that the continuous running of the extraction system and the monitoring of gas collecting time and of the temperature of the cryogenic traps used in the gas cleaning steps are key to maintaining low and stable system blanks. Our latest average system blank is 2.02 +/- 0.23 x 105 14C atoms. This is consistent with those recently published by the University of Arizona and ETH in situ 14C labs. Measurements of in situ 14C concentrations in sample PP-4 yield an average of 3.82 +/- 0.23 x 105 atoms g-1 quartz, again consistent with published values.