Status of the NSF-Arizona AMS laboratory

Investigation into Background Levels of Small Organic Samples at the NERC Radiocarbon Laboratory

“…As described in Donahue et al (1997), we also observed an increase of background levels below 1 mg C from 0.13 ± 0.05 to 1.20 ± 0.04 pMC Figure 5 A) 14 C activity expressed as pMC based on 14/13 ratio versus carbon content in AMS target; B) pMC based on 14/13 ratio versus inverse carbon mass in target. Data points obtained by individual combustion of small amounts of acid-alkali-acid pretreated bituminous coal; isotopic ratios were corrected for AMS-measured δ 13 C and normalized to the corresponding averaged value of HOxII >400 µg C; no procedural blank correction was applied.…”

Poisson and non-Poisson uncertainty estimations of 10Be/9Be measurements at LLNL–CAMS

“…We use these data to calculate (1) the routine 9 Be 3+ beam currents and (2) the statistical, systematic (''additional'' or ''excess'' errors above counting statistics), and total uncertainties using statistical methods similar to Burr et al [15] and Donahue et al [16] following the treatment of Bevington and Roberts [12]. Statistical errors can be quantified for measurements drawn from a parent population with a Poisson distribution [12]; for such a population, the average statistical uncertainty on an individual sample from counting statistics with unequal errors (s st ) can be approximated by the equation:…”

“…Statistical errors should be, therefore, primarily dictated by the number of counts collected in the detector, which is, in turn, related to AMS system performance, e.g., the ionization yield and efficiency of the ion source, and transport efficiency of the AMS system [13,14]. However, non-statistical, systematic uncertainties above counting errors, e.g., ''random machine error'' [15], are only rarely quantified [15][16][17][18], and the accuracy of the isotopic ratio measurements is generally not independently confirmed. Furthermore, measurement uncertainties are inherently linked with the performance of the AMS system as well as sample preparation.…”

Accelerator Mass Spectrometry for 14 C Dating

“…The most well known, [53] include the 3 MV Tandetron in Oxford, the 3 MV Pelletron at VERA in Vienna, [54] the 2.5 MV Tandetron in Groningen, [55] the 3 MV Tandetron at the Leibniz Labor in Kiel, [56] the 2 MV Tandetron STAR at ANSTO in Sidney, [57] the 2.5 MV Tandetron and the 3 MV Pelletron at the NSF-Arizona AMS laboratory in Tucson, [58] and the two Tandetrons at the Nagoya University Center for Chronological Research in Japan. [59] Other facilities are based on higher terminal voltage accelerators [60].…”