In accelerator systems, beam lines are generally equipped with diagnostic elements, such as Faraday cups and beam profile monitors (BPM), to optimize beam transport. These diagnostic elements, or at least commercial ones, are designed to only work with continuous beams, and their typical maximum sensitivity is about few tens of pA. Thus, in the case of diagnosis of rare isotope beams in accelerator mass spectrometry (AMS), Faraday cups and BPMs are not suitable on the high-energy side of the tandem accelerator, after energy-mass-charge analysis. For example, in 14C AMS, even for a modern sample, the expected counting rate is a few tens of Hz; in these conditions, a commercial BPM cannot be used. On the other hand, checking the shape and the position of the rare isotope beam hitting the detector can be important in order to better identify signals in the detector itself, thus also helping in reducing the measurement background.

This paper presents a prototype BPM especially designed for low-intensity beams. The BPM is based on a multiwire proportional chamber characterized by 2 grids of anode wires, oriented perpendicular to each other in order to measure both the x and the y coordinates of the particle impact point. Details about the design and the electronics of the device are given, and the first test measurements are discussed.

This paper reports the results of tree-ring dating and accelerator mass spectrometry (AMS) wiggle-matching for wooden Buddhist statues stored at the Eungjindang Hall of Neunggasa Temple, South Korea. Among 23 statues, 10 were successfully dated by tree rings. The cutting date of logs used for the statues was determined as some time between late fall 1684 and early spring 1685 when the bark ring (AD 1684) completed latewood formation. The 95.4% confidence interval of a radiocarbon date (cal AD 1688–1713, 2 σ), which was obtained by wiggle-matching 7 samples of a statue, is similar to the dendro-date (AD 1684). A historical document recorded that the statues in the Eungjindang of Neunggasa were dedicated in July 1685. The dendro-date and written record indicate that Eungjindang statues were made within 3–8 months after log cutting. This seems rather short if we consider the period required for natural drying to avoid defects such as cracking and crooking.

Over the past decades, analysis of occluded carbon in phytoliths (opaline silica mineral bodies that form in and between plant cells) has become a workhorse of paleoclimate and archaeological studies. Since different plant types exhibit distinctive phytolith morphologies, their assemblages are used in identifying vegetation histories or food culture adaptations. A few direct radiocarbon AMS measurements of phytoliths have been carried out, but these measurements are difficult due to the low concentrations of phytoliths in some plant species, and the small amount of C per phytolith (<2%). In addition, no phytoliths samples of a known 14C age are available to verify measurement accuracy and precision, and to check sample preparation protocols. Background corrections are also difficult to address due to the lack of suitable material. In this work, we designed a procedure to quantify a suitable blank using SiO2 powder samples (close to the opal structure, and free of 14C). The full phytolith extraction showed high carbon contamination components: a) ∼3 μg of modern C and ∼2 μg of dead C. We also performed accuracy tests on large phytolith-occluded carbon samples extracted from soils and harvested plants. The unexpected 14C ages in some of the results triggered further investigations of possible sources of carbon contamination.

The “calibration” of arbitrarily defined (in some sense, “conventional”) ages, given in conventional radiocarbon years BP, is now becoming necessary because the term “radiocarbon age” is used less often in archaeological and Quaternary practice. The standard calibration procedure is inappropriate here because Mangerud's boundaries are not measurement results. Thus, another approach to the problem is proposed in order to model the natural situation of many, uniformly distributed, dated samples, which should be similarly divided by the original and “calibrated” boundary. However, the result depends on the value of the typical measurement error and is not unequivocal.

Efforts to extract weak geomagnetic excursion signals from Chinese loess-paleosol 10Be have generally been unsuccessful due to the complexities of its accumulation, because the geomagnetic and climate (precipitation and dust) signals contained in loess-paleosol sequence are tightly overprinted. Here, we present a reconstruction of geomagnetic relative paleointensities for the past 130 kyr from 10Be records in 2 Chinese loess-paleosol sections using a correction based on the correlation of 10Be with magnetic susceptibility (SUS) to remove the climatic contamination. Both these records reveal the Laschamp and Blake events, which lie in the loess and paleosol (L1SS1 and S1SS3) horizons corresponding to mid-MIS 3 and 5e, respectively. The good agreement between our results and other geomagnetic intensities reconstructions from Atlantic and Pacific sediments indicates that our method is robust. Our study suggests the potential application of loess-paleosol 10Be for reconstructing geomagnetic intensity variations spanning the whole Quaternary.

We performed accelerator mass spectrometry (AMS) radiocarbon dating and wiggle-matching of 2 wood samples from charred trunks of trees (samples A and B) collected from an ignimbrite deposit on the northeastern slope of the Baitoushan Volcano on the border of China and North Korea. The obtained calendar years for the eruption are cal AD 945–960 for sample A and cal AD 859–884 and cal AD 935–963 for sample B in the 2-σ range. These results are unable to determine the precise eruption age. The reason for the difference in reported ages may be due to volcanic gas emission prior to the huge eruption.

Submicron-sized airborne particulate matter (PM) is not collected well on regular quartz or glass fiber filter papers. We used a micro-orifice uniform deposit impactor (MOUDI) to fractionate PM into 6 size fractions and deposit it on specially designed high-purity thin aluminum disks. The MOUDI separated PM into fractions 56–100, 100–180, 180–320, 320–560, 560–1000, and 1000–1800 nm. Since the MOUDI has a low flow rate (30 L/min), it takes several days to collect sufficient carbon on 47-mm foil disks. The small carbon mass (20–200 μg C) and large aluminum substrate (∼25 mg Al) present several challenges to production of graphite targets for accelerator mass spectrometry (AMS) analysis. The Al foil consumes large amounts of oxygen as it is heated and tends to melt into quartz combustion tubes, causing gas leaks. We describe sample processing techniques to reliably produce graphitic targets for 14C AMS analysis of PM deposited on Al impact foils.

An on-line measurement system was installed at the MICADAS in Zurich, using an elemental analyzer (EA) as a combustion unit to enable direct radiocarbon measurement of samples containing carbon in the range of 5–100 μg possible with minimum effort. The samples are combusted in small capsules and the gaseous combustion products are separated by the EA. The carbon dioxide leaving the EA in a high helium flow is concentrated on a small external trap containing X13 zeolite adsorber material. This new concept, avoiding a cryogenic trapping for the enrichment step, allows the construction of a very compact system able to work even with the smallest samples. Concentrated on the external trap, the carbon dioxide is flushed into the gas-tight syringe of our gas inlet system using a low helium stream. The gas mixture is measured with the MICADAS gas ion source. Several different sample capsules were analyzed to minimize the major blank contribution coming from the sample vessel. The best results were achieved with 25-μL tin capsules, which contained only 0.34 ± 0.13 μg carbon at 65 pMC. This work describes the development of the on-line system and the protocol for measurement runs. Results are presented for on-line measurements of reference materials and a comparison is performed with typical dating samples measured previously as graphite targets. Finally, relevance and limitations of on-line measurements are discussed.

Paired radiocarbon and stable carbon analyses have been carried out on aragonite shells and organic soft bodies of snails from the Chinese Loess Plateau in order to explore the possibility of using these kinds of samples as environmental and chronological indicators. Results show that the soft bodies exhibit 14C concentrations similar to those of plant leaves, indicating that carbon in the soft bodies is fixed from organic diets. The aragonite shells are depleted in 14C compared to the soft bodies due to ingestion of 14C-depleted carbonate. This depletion shows a consistent pattern across the Chinese Loess Plateau, implying a good potential for the snail shells to be applicable for 14C dating with a simple correction. The δ13C values measured for aragonite shells display a linear relationship with those obtained for the soft bodies with a constant offset. In addition, the carbon derived from organic diets accounts for more than 70% of the total shell carbon. This fact suggests that stable carbon isotope composition of aragonite shells mainly reflects that of organic diet, and could be used as a reliable indicator of paleodiet in the Chinese Loess Plateau.

After introducing the liquid scintillation counting (LSC) method and graphite target preparation for accelerator mass spectrometry (AMS) measurements in the Zagreb Radiocarbon Laboratory, the existing database software designed only for gas proportional counting (GPC) (using a DOS operating system) could not satisfy the requirements for parallel conduction of several techniques. This has been enabled recently by the development of the new relational database ZAGRADA, which—using SQL scripts and constraints defined by primary and foreign keys—enforces high data integrity and provides better performances in data filtering and sorting. The structural scheme of this database conceptually comprises 4 basic modules with data on the samples, chemical pretreatment and preparation, measurements and data on the final results. A user-friendly graphical user interface has been designed to perform various actions and data manipulation to the database. The implementation of a new database for 14C samples has significant contribution to scientific research performed in the Radiocarbon and Tritium Laboratory and to quality assurance and quality control, and will enable better and easier communication with customers.

Actinide isotopes are present in environmental samples at ultra-trace levels (236U concentration is quoted to be on the order of pg/kg or fg/kg). Their detection requires the resolution of mass spectrometry (MS) techniques, but only accelerator mass spectrometry (AMS) has the sensitivity required. In order to perform the isotopic ratio measurements of actinides, such as 236U/238U, an upgrade of the Center for Isotopic Research on Cultural and Environmental Heritage accelerator (CIRCE) in Caserta, Italy, has been performed. The system was originally equipped for radiocarbon AMS measurements. The main difficulty of AMS measurement of 236U is the intense neighboring beam of 238U. Although most of the 238U ions are suppressed by means of magnetic and electrostatic elements, a small fraction of this intense beam can interfere with the rare isotopes. This paper reports the preliminary results of the 236U/238U isotopic ratio measurement limit (<5.6 x 10–11), aimed also to better understand the origin of background ions. For this purpose, a large 16-strip silicon detector providing spatial resolution has been used. In addition, calculations to assess the performance of the system obtained by adding a high-resolution time of flight-energy (TOF-E) detector are discussed.

The relationship between temperature and time required for collagenization using modern bone samples was investigated. Gelatinized samples of bone collagen were filtered to selectively collect different molecular weight fractions. The results of this study suggest that heating to 70 ° for a duration of 12 hr provides the optimal conditions for gelatinization.

The Radiocarbon Dating Laboratory at the University of Illinois has been using the pyrolysis-combustion technique to separate pyrolysis-volatile (Py-V) or low molecular weight and pyrolysis-residue (Py-R) or high molecular weight compounds for 14C dating of organic remains since 2003. We have applied this method to human collagen dating to examine the 14C age difference between low and high molecular weight organic compounds. Results show that both fractions of late prehistoric period human bones from Illinois archaeological sites yield identical 14C dates but that Py-V or low molecular weight fractions of Archaic period human bones appear to be slightly contaminated. In this case, Py-V components or low molecular weight collagen fraction yield older 14C dates, which could result from contamination from old organic-rich sediments. The pyrolysis-combustion technique provides an economical alternative method to date bones that have not been satisfactorily dated using conventional purification techniques.

The Bayesian CAR (continuous autoregressive) model for accelerator mass spectrometry (AMS) data analysis delivers uncertainties with less scatter and bias. Better detection and estimation of the instrumental error of the AMS machine are also achieved. Presently, the main disadvantage is the several-hour duration of the analysis. The Markov chain Monte Carlo (MCMC) program for CAR model analysis, car4ams, has been made freely available under the GPL license. Included in the package is an R program that analyzes the car4ams output and summarizes the results in graphical and spreadsheet formats. We describe the main properties of the CAR analysis and the use of the 2 parts of the program package for radiocarbon AMS data analysis.

Gas-accepting ion sources for radiocarbon accelerator mass spectrometry (AMS) have permitted the direct analysis of CO2 gas, eliminating the need to graphitize samples. As a result, a variety of analytical instruments can be interfaced to an AMS system, processing time is decreased, and smaller samples can be analyzed (albeit with lower precision). We have coupled a gas chromatograph to a compact 14C AMS system fitted with a microwave ion source for real-time compound-specific 14C analysis. As an initial test of the system, we have analyzed a sample of fatty acid methyl esters and biodiesel. Peak shape and memory was better then existing systems fitted with a hybrid ion source while precision was comparable. 14C/12C ratios of individual components at natural abundance levels were consistent with those determined by conventional methods. Continuing refinements to the ion source are expected to improve the performance and scope of the instrument.

Liquid scintillation counting (LSC) for radiocarbon dating is a less expensive method than accelerator mass spectrometry (AMS), provides a high degree of accuracy, and is less prone to contamination due to the larger sample sizes. However, to obtain high precision, a long counting time is needed. The Gliwice Radiocarbon Laboratory is seeking to obtain an increased counting capacity with 2–3 mL benzene samples than we presently can achieve with our 2 Quantulus systems. We are therefore investigating the possibility of using a simple, single-phototube LS system (ICELS) for dating samples younger than 5000 yr. We present the first results of this investigation, including the measurement of 3 VIRI and 3 FIRI intercomparison samples.

Radiocarbon accelerator mass spectrometry (AMS) measurements are always carried out relative to internationally accepted standards with known 14C activities. The determination of accurate 14C concentrations relies on the fact that standards and unknown samples must be measured under the same conditions. When this is not the case, data reduction is either performed by splitting the collected data set into subsets with consistent measurement conditions or by applying correction factors.

This paper introduces a mathematical framework that exploits the intrinsic variability of an AMS system by combining arbitrary measurement parameters into a normalization function. This novel approach allows the en-masse reduction of large data sets by providing individual normalization factors for each data point. Both general features and practicalities necessary for its efficient application are discussed.

We present a status report of the accelerator mass spectrometry (AMS) facility at the University of California, Irvine, USA. Recent spectrometer upgrades and repairs are discussed. Modifications to preparation laboratory procedures designed to improve sample throughput efficiency while maintaining precision of 2–3‰ for 1-mg samples (Santos et al. 2007c) are presented.

Mazar and Bronk Ramsey (2008) recently proposed that the Iron I/IIA transition in the Levant took place during the first half of the 10th century. In the first part of this article, we challenge their method and conclusions. We argue against the inclusion of charcoal in their model, which could lead to an “old wood effect.” We also argue that in dealing with a transition date, all available data must be taken into consideration. In the second part of the article, we propose Bayesian Model I for the Iron I/IIA transition, which is based on 2 sets of data—for the periods immediately before and after this transition. Our model, along with the other 11 published Bayesian models for this transition that used only short-lived samples, agrees with the Low Chronology system for the Iron Age strata in the Levant and negates all other proposals, including Mazar's Modified Conventional Chronology. The Iron I/IIA transition occurred during the second half of the 10th century. In the third part of the article, we present a new insight on the Iron I/IIA transition. We propose that the late Iron I cities came to an end in a gradual process and interpret this proposal with Bayesian Model II.

Mazar and Bronk Ramsey (2008) recently challenged Sharon et al. (2007; also Boaretto et al. 2005) and us (e.g. Finkelstein and Piasetzky 2003, 2007a,b) regarding the date of transition from the Iron I to the Iron IIA in the Levant. While we and Sharon et al. placed this transition in the second half of the 10th century BCE, Mazar and Bronk Ramsey positioned it “during the first half of the 10th century BCE” and argued that “the second half of the 10th century BCE should be included in the Iron IIA” (Mazar and Bronk Ramsey 2008:178). We discuss some problems in the methodology of Mazar and Bronk Ramsey that may have influenced their results. In particular, we discuss 1) the exclusion of data; 2) the inclusion of data (charcoal samples); and 3) show that even according to Mazar and Bronk Ramsey, excluding these samples position the late Iron I/IIA transition in the late 10th century. Finally, we present our own 2 Bayesian models for the Iron I/IIA transition.

Calibration is a core element of radiocarbon dating and is undergoing rapid development on a number of different fronts. This is most obvious in the area of 14C archives suitable for calibration purposes, which are now demonstrating much greater coherence over the earlier age range of the technique. Of particular significance to this end is the development of purely terrestrial archives such as those from the Lake Suigetsu sedimentary profile and Kauri tree rings from New Zealand, in addition to the groundwater records from speleothems. Equally important, however, is the development of statistical tools that can be used with, and help develop, such calibration data. In the context of sedimentary deposition, age-depth modeling provides a very useful way to analyze series of measurements from cores, with or without the presence of additional varve information. New methods are under development, making use of model averaging, that generate more robust age models. In addition, all calibration requires a coherent approach to outliers, for both single samples and where entire data sets might be offset relative to the calibration curve. This paper looks at current developments in these areas.