Status report of the first AMS laboratory in the Czech Republic at the Nuclear Physics Institute, Řež

Combining atmospheric Δ14CO2 data sets from different networks or laboratories requires secure knowledge on their compatibility. In the present study, we compare Δ14CO2 results from the Heidelberg low-level counting (LLC) laboratory to 12 international accelerator mass spectrometry (AMS) laboratories using distributed aliquots of five pure CO2 samples. The averaged result of the LLC laboratory has a measurement bias of –0.3±0.5‰ with respect to the consensus value of the AMS laboratories for the investigated atmospheric Δ14C range of 9.6 to 40.4‰. Thus, the LLC measurements on average are not significantly different from the AMS laboratories, and the most likely measurement bias is smaller than the World Meteorological Organization (WMO) interlaboratory compatibility goal for Δ14CO2 of 0.5‰. The number of intercomparison samples was, however, too small to determine whether the measurement biases of the individual AMS laboratories fulfilled the WMO goal.

Funding was received from NA-22 to investigate transitioning iodine isotopic analyses to an accelerator mass spectrometry (AMS) system. The present method uses gas-phase chemistry followed by thermal ionization mass spectrometry (TIMS). It was anticipated that the AMS approach could provide comparable data, with improved background levels and superior sample throughput. An aqueous extraction method was developed for removal of iodine species from high-volume air filters. Ethanol and sodium hydroxide, plus heating and ultrasonic treatment, were used to successfully extract iodine from loaded high-volume air filters. Portions of the same filters were also processed in the traditional method and analyzed by TIMS for comparison. Aliquot parts of the aqueous extracts were analyzed by AMS at the Swiss Federal Institute of Technology. Idaho National Laboratory (INL) personnel visited several AMS laboratories in the US, Spain, and Switzerland. Experience with AMS systems from several manufacturers was gained, and relationships were developed with key personnel at the laboratories. Three batches of samples were analyzed in Switzerland, and one in Spain. Results show that the INL extraction method successfully extracted enough iodine from high-volume air filters to allow AMS analysis. Comparison of the AMS and TIMS data is very encouraging; while the TIMS showed about forty percent more atoms of 129I, the 129/127 ratios tracked each other very well between the two methods. The time required for analysis is greatly reduced for the aqueous extraction/AMS approach. For a hypothetical batch of thirty samples, the AMS methodology is about five times faster than the traditional gas-phase chemistry and TIMS analysis. As an additional benefit, background levels for the AMS method are about 1000 times lower than for TIMS. This results from the fundamental mechanisms of ionization in the AMS system and cleanup of molecular interferences. We showed that an aqueous extraction of high-volume air filters, followed by isotopic analysis by AMS, can be used successfully to make iodine measurements with results comparable to those obtained by filter combustion and TIMS analysis.

A first international (36)Cl interlaboratory comparison has been initiated. Evaluation of the final results of the eight participating accelerator mass spectrometry (AMS) laboratories on three synthetic AgCl samples with (36)Cl/Cl ratios at the 10(-11), 10(-12), and 10(-13) level shows no difference in the sense of simple statistical significance. However, more detailed statistical analyses demonstrate certain interlaboratory bias and underestimation of uncertainties by some laboratories. Following subsequent remeasurement and reanalysis of the data from some AMS facilities, the round-robin data indicate that (36)Cl/Cl data from two individual AMS laboratories can differ by up to 17%. Thus, the demand for further work on harmonising the (36)Cl-system on a worldwide scale and enlarging the improvement of measurements is obvious.

ABSTRACTThe accelerator mass spectrometry (AMS) center at Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering, Bucharest, is based on the latest-generation 1 MV Tandetron® accelerator, produced by High Voltage Engineering Europa (HVEE), The Netherlands. The AMS center became fully functional at the start of 2013, and at the end of 2015 the laboratory established the RoAMS international code and it was added to the list of AMS laboratories maintained by Radiocarbon journal. An important aspect in the establishment of a new AMS laboratory is the declaration and documentation of the adopted protocols and to demonstrate the reliability and reproducibility of the measurements in comparison to internationally recognized reference materials. In this paper, we present the dating results on the Sixth International Radiocarbon Intercomparison (SIRI) samples that were pretreated, graphitized, and measured in our laboratory. The newly developed sample preparation laboratory can handle sample materials as (1) organic materials, (2) wood, (3) bones, and (4) carbonates. The results of our measurements are in very good agreement with the SIRI consensus values and confirm the reliability of our sample preparation laboratory and also the good performance of the HVEE AMS system. The blank levels for the SIRI materials are 0.277±0.045/0.333±0.046 percent modern carbon (pMC) for wood samples, 0.441±0.038 pMC for bone collagen, and 0.239±0.030 pMC for carbonate materials, considering an average mass of 1 mg sample graphite.

Accelerator mass spectrometry (AMS) represents an ultrasensitive analytical method for measurement of long-lived radionuclides, namely 14C, 10Be, 26Al, 41Ca, 129I, and 236U. It provides information about isotopic ratios up to 10–16 in samples of mass from several miligrams to tens of micrograms. The first AMS laboratory in the Czech Republic was built in Nuclear Physics Institute, Řež, in collaboration with Archaeological Institute, Prague (both Czech Academy of Sciences) and Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, and equipped with AMS MIELA (Ionplus AG, Switzerland). This review summarizes history, principles, and use of this unique analytical method.

Low energy AMS of americium and curium

A new radiocarbon accelerator mass spectrometry (AMS) laboratory for carbon cycle studies has been established at the University of California, Irvine. The 0.5MV AMS system was installed in mid-2002 and has operated routinely since October of that year. This paper briefly describes the spectrometer and summarizes lessons learned during the first year of operation. In the process of setting up the system, we identified and largely suppressed a previously unreported 14C AMS background: charge exchange tails from 14N beams derived from nitrogen-containing molecular ions produced near the entrance of the accelerator.

ABSTRACTThe complex geographical scenario of Mexico allowed the cultural diversification and development of multiple cultures such as Tolteca, Teotihuacan, Mexica, and Maya, among others. Despite this rich cultural heritage, radiometric dating of Mexican cultural samples with radiocarbon (14C) began only in the 1980s and with accelerator mass spectrometry (AMS) in 2013. Analysis of 14C with AMS is the most widely used technique to date archaeological objects and cultural heritage. Since 2013, the Accelerator Mass Spectrometry Laboratory (LEMA) facility of the Institute of Physics at UNAM (IF-UNAM) has supported archaeological research in Mexico, but also investigation in other areas such as geology, physics, chemistry, and environmental sciences through the analysis of 14C, 10Be, 26Al, 129I, and Pu. The absolute dating with 14C continues to be the core of LEMA’s work, where different geographical scenarios of the country and climatic conditions present very diverse analytical challenges. This work presents a basic description of the AMS system of the LEMA laboratory and describes some applications that are currently being developed.

Preparation of new 10Be and 26Al AMS standard reference materials

ABSTRACTThe radiocarbon (14C) calibration curve so far contains annually resolved data only for a short period of time. With accelerator mass spectrometry (AMS) matching the precision of decay counting, it is now possible to efficiently produce large datasets of annual resolution for calibration purposes using small amounts of wood. The radiocarbon intercomparison on single-year tree-ring samples presented here is the first to investigate specifically possible offsets between AMS laboratories at high precision. The results show that AMS laboratories are capable of measuring samples of Holocene age with an accuracy and precision that is comparable or even goes beyond what is possible with decay counting, even though they require a thousand times less wood. It also shows that not all AMS laboratories always produce results that are consistent with their stated uncertainties. The long-term benefits of studies of this kind are more accurate radiocarbon measurements with, in the future, better quantified uncertainties.

Preparation of 26Al AMS standards

Accelerator Mass Spectrometry (AMS) provides high sensitivity measurements (typically at or below 1 part in $10^{12}$) for rare, long-lived radioisotopes when isobars (other elements with the same atomic weight as the isotope of interest) can be eliminated. In AMS laboratories, established techniques are used for the removal of the interfering isobars of some light isotopes. However, for smaller, lower-energy AMS systems separating the abundant isobars of many isotopes, such as the sulfur-36 in measurements of chlorine-36, remains a challenge. For some heavy isotopes, such as strontium-90 and cesium-135,137, even high energy accelerators are unable to separate the interfering isobars. The Isobar Separator for Anions (ISA), which has been integrated into a second injection line of the 3 MeV tandem accelerator system at the A. E. Lalonde AMS Laboratory, will provide a universal way to measure rare radioisotopes without the interference of abundant isobars. The ISA is a radiofrequency quadrupole (RFQ) reaction cell system, including a DC deceleration region, a combined cooling and reaction cell, and a DC acceleration region. The deceleration region accepts a mass analyzed beam from the ion source (with energy 20-35 keV) and reduces the energy to a level that the reaction cell can accept. RFQ segments along the length of the cell create a potential well which limits the divergence of the traversing ions. DC rod offset voltages on these RFQ segments maintain a controlled ion velocity through the cell. The cell is filled with an inert cooling gas that has been experimentally selected to provide the lowest ion energy and the highest transmission, and with nitrogen dioxide, a reaction gas chosen to preferentially react with the interfering isobar. In the case of chlorine-36, the sulfur-36 isobar has been shown to be reduced by over $10^{6}$. Preliminary characterization of the ISA and its incoming and outgoing ion beams will be presented.

First AMS measurements of 60Fe/Fe isotopic ratios at the Cologne 10 MV tandem accelerator

ABSTRACTAugusto Moreno is credited with establishing the first radiocarbon (14C) laboratory in Mexico in the 1950s, however, 14C measurement with the accelerator mass spectrometry (AMS) technique was not achieved in our country until 2003. Douglas Donahue from the University of Arizona, a pioneer in using AMS for 14C dating, participated in that experiment; then, the idea of establishing a 14C AMS laboratory evolved into a feasible project. This was finally reached in 2013, thanks to the technological developments in AMS and sample preparation with automated equipment, and the backing and support of the National Autonomous University of Mexico and the National Council for Science and Technology. The Mexican AMS Laboratory, LEMA, with a compact 1 MV system from High Voltage Engineering Europa, and its sample preparation laboratories with IonPlus automated graphitization equipment, is now a reality.

High-resolution as well as high-precision age estimation is particularly important for Quaternary research to realize its main aim of better understanding of global environmental changes of the past and realistic prediction of the changes in the near future. Among several dating methods that are applicable to Quaternary samples, radiocarbon (14C) dating has been commonly used since its development in late 1940s.A new 14C detection technique, accelerator mass spectrometry (AMS), has been developed since 1977. The method directly detects and counts 14C atoms, instead of counting β-ray emitted in the decay of 14C, and therefore requires only a few mg of carbon for 14C measurements. Nowadays, AMS 14C dating is widely used and more than sixty AMS 14C facilities are in operation in the world. In Japan, eight facilities for AMS 14C dating have been in use since 2004.As one of the eight AMS 14C measurement systems in Japan, the Nagoya University AMS group has started routine 14C measurements with the firstly introduced Tandetron AMS system since 1983 and also with the secondly established Tandetron AMS since 1999. The second system has an excellent performance of the standard deviation (one sigma) of the 14C/12C ratios of around ±0.2% to ±0.4% (±17-±30 14C yrs) and that of the corresponding 13C/12C ratios of ±0.03% to ±0.07%, as are tested for HOxII targets. By using this AMS system, we are now trying to provide accurate ages to the Quaternary events. Briefly discussed in this article are, (1) a consistency test of the established IntCal98 and IntCal04 14C data sets with the 14C-concentration records in Japanese tree rings ; (2) programs of high accuracy and precision age estimation by 14C wiggle matching techniques for wood samples ; (3) investigations of 14C reservoir effect for marine samples from the Japanese Archipelago.