Single-stage Accelerator Mass Spectrometer Research Articles

RADIOCARBON AND TRITIUM MEASUREMENTS AT THE GXNU-AMS FACILITY

ABSTRACT A single-stage accelerator mass spectrometer (GXNU-AMS) developed for radiocarbon and tritium measurements was installed and commissioned at Guangxi Normal University in 2017. After several years of operational and methodological upgrades, its performance has been continuously improved and applied in multidisciplinary fields. Currently, the measurement sensitivity for radiocarbon and tritium is 14C/12C ∼ (3.14 ± 0.05) ×10–15 and 3H/1H ∼ (1.23 ± 0.17)×10–16, respectively, and the measurement accuracy is ∼0.6%, which can meet the measurement requirements in the nuclear, earth, environmental and life science fields. This study presents the performance characteristics of GXNU-AMS and several interesting application studies.

Efficient radiocarbon measurements on marine and terrestrial samples with single stage Accelerator Mass Spectrometry at the Atmosphere and Ocean Research Institute, University of Tokyo

A single stage Accelerator Mass Spectrometer (National Electrostatic Corporation, YS-AMS) at the Atmosphere and Ocean Research Institute (AORI), University of Tokyo has operated smoothly since 2013. The average annual operation hours exceeded 8000 h/year for the last two years, allowing for measurement of up to 2912 samples/year (including standards). A newly developed in-house automated system increased the throughput dramatically, with a total of 16,000 samples measured to date. A 14C/12C measurement precision on standard material is better than 0.1 % due to and improved operation software system and an increased number of standards measured per run. Results have improved geochronological information for paleoenvironmental, biological, and geohazard studies.

A single-stage accelerator mass spectrometer and its applications at Guangxi Normal University

GXNU-AMS, a compact 14C accelerator mass spectrometer jointly developed by the Guangxi Normal University and China Institute of Atomic Energy, was installed and commissioned in Guangxi Normal University in 2017. It is the first original single-stage AMS facility and one of the lowest designed energy AMS systems in China. Without the traditional mode of a SF6 pressure tank, the terminal of the system was designed as an open insulated high-voltage platform, which reduces the accelerator size to ∼2.5 m × 4.5 m. Helium gas stripping was used for eliminating the interference of molecular ions, and the maximum operating voltage is ∼200 kV. During several years of operation, its performance has been continuously improved and it has been applied in multidisciplinary fields. Currently, the measurement accuracy of the instrument is ∼0.6 % and the measurement sensitivity is 14C/12C ∼ 3 × 10−15 (equivalent to a 14C age of approximately 47,000 years.), which can meet the measurement requirements in the fields of life sciences and archaeology. In this study, the performance characteristics and operation of GXNU-AMS are discussed and several application studies being conducted by the GXNU-AMS group are presented.

Radiocarbon generation and atmospheric release assessment from nuclear power plant with RBMK type reactors

The article provides the results of the estimation of 14C nuclide generation and release from the systems and structures of RBMK-1500 reactors operated at Ignalina NPP. The main circulation circuit and gaseous circuit of this type of reactor are the primary sources of 14C generation and airborne release, evaluated to be 0.491 and 0.367 TBq per one calendar year (10.5 months of effective reactor operation at 1350 MWe power), respectively. The analysis of the operation specifics of these systems showed that they don’t provide an effective barrier to contain 14C due to the 14CO2 chemical form of radiocarbon in RBMK reactors, i.e., 100% release (0.858 TBq/year) have been evaluated available for atmospheric release. These results have been compared with the atmospheric releases evaluated from the 14C activity concentration measured in Scots pine tree (Pinus Sylvestris L.) ring samples by single stage accelerator mass spectrometer (SSAMS, NEC, USA) at Vilnius Radiocarbon facility, resulting to airborne release value of 1 TBq/year for one RBMK-1500 reactor. Slightly higher value reproduced from the tree ring samples indicates that the reactor graphite stack might be also a source of 14C releases of about 0.14–0.24 TBq/year. Based on similar design features the results of the study can be easily projected to the RBMK-1000 reactors rescaling 14C source term according to the lower reactor power.

Radiocarbon Characterization study of Atmospheric PM2.5 in Beijing during the 2014 APEC Summit

ABSTRACTRadiocarbon (14C) has become a unique and powerful tracer in source apportionment of atmospheric carbonaceous particles. In this study, the Asia Pacific Economic Cooperation summit (APEC) held in Beijing in 2014 was used as a demonstration to research the source apportionment of atmosphere PM2.5. We used a 200 kV single stage accelerator mass spectrometer recently completed at China Institute of Atomic Energy (CIAE). The PM2.5 samples related to above case were collected, and the characteristics of radiocarbon in organic carbon (OC) and elemental carbon (EC) in samples were analyzed using the AMS. The results show that the Before-APEC pollution emission mode is different from the During-APEC and After-APEC pollution emission modes. For Before-APEC, During-APEC and After-APEC, the average values of fossil carbon fraction of OC are 0.463, 0.431 and 0.615, respectively, and those of EC are 0.644, 0.561 and 0.687. The fossil source contributions of traffic activities using fossil fuels to OC and EC are 15.8 % and 21.9 %, respectively. The fossil source contributions of industrial activities to OC and EC are 38.0 % and 8.2 %, respectively. It is about 7–10 days that is needed to take to regenerate the PM2.5 pollution caused by human activities.

Assessment of the Contamination by 14C Airborne Releases in the Vicinity of the Ignalina Nuclear Power Plant

ABSTRACTA radiocarbon (14C) activity analysis in the tree rings around Ignalina nuclear power plant (INPP) has been carried out with the aim to test the hypothesis to use 14C tree-ring analysis data as a tool for the reconstruction of gaseous releases from NPP to the environment. The INPP has been in decommissioning state since the end of 2009. Tree-ring samples for 14C analysis were collected 7 yr after final power unit shutdown from the INPP vicinity. The samples from 5 sampling locations were collected, prepared and measured using the Single Stage Accelerator Mass Spectrometer (SSAMS). Data analysis represents observable Ignalina NPP influence by 14C increase up to 15 pMC (percent modern carbon) in tree rings. Good correlations of the 14C concentrations and wind direction were obtained. The main purpose of this article was to match 14C measurement data along with the atmospheric dispersion modeling of emissions in order to retrospectively characterize the emission source.

Performance of Home-Made Single-Stage 14C AMS System at CIAE

ABSTRACTThe second home-made single stage accelerator mass spectrometer (SSAMS) system dedicated to radiocarbon (14C) measurements was built after the first SSAMS system was moved to Guangxi Normal University. With some improvements to the second SSAMS system, the performance has been improved. With the conditions of total ion energy of 200KeV, ions charge states of 1+ and helium as stripper gas, 14C measurements with precision of 0.5% and a background level of 0.5 pMC were achieved. Details of the system and the experimental performance are given here.

Small- to ultra-small-scale radiocarbon measurements using newly installed single-stage AMS at the University of Tokyo

Small- to ultra-small-scale radiocarbon (14C) measurements are an essential technique for compound-specific radiocarbon measurements of fatty acids and amino acids. The Atmosphere and Ocean Research Institute at the University of Tokyo installed an NEC 250 kV single-stage accelerator mass spectrometer (AMS) in March 2013. We improved the pretreatment method to reduce modern and 14C-dead carbon contaminations. The modern and 14C-dead carbon contaminations from combustion and graphitization were estimated to be 0.37 ± 0.13 μgC and lower than 1.62 μgC, respectively. Furthermore, we examined an AMS measurement method that can be used to obtain a stable beam current intensity. As a result, we succeeded in conducting small- to ultra-small-scale 14C measurements. Typically, a sample of 100 µg of carbon (μgC) can be measured with a current of 25 μA in a low-energy Faraday cup for 30 min or more, whereas a sample of 10 μgC can be measured with a current of 1 μA in a low-energy Faraday cup for 15 min or more.

Positive ion SIMS-SSAMS for trace analysis of materials

By using a single-stage accelerator mass spectrometer (SSAMS) as a detector for a secondary ion mass spectrometry (SIMS) instrument, spatially resolved trace analysis of elements and isotopes in solid materials is significantly improved. This is especially true for masses greater than ∼90 u, where a mass resolving power in excess of 10,000 is generally needed to separate abundant molecular isobars from atomic ions of interest, particularly when the atomic species are present in trace quantities. Prior techniques using SIMS in high-resolution mode can suffer from residual molecular interferences that effect detection limits and isotope analysis precision. The 300 kV SSAMS at the U.S. Naval Research Laboratory typically measures +1 ions up to mass 300 u, as they are more abundant for most elements. Additionally, there can be no molecule fragments in a lower charge state at the same m/q and E/q. Interferences from higher charge states either injected into the SSAMS or generated by the stripper tube are limited to mimicking masses below ∼120 u. Molecule fragments can also be chosen for analysis, when a molecular ion is more abundant than an atomic one. Electrostatic peak switching through the SIMS and SSAMS magnets enables rapid cycling up to ±6.5% about a central mass during a depth profile measurement. For typical operating conditions using Ar gas in the stripper tube, molecular ions are reduced by 4–6 orders of magnitude while better than 20% of desired ions are transmitted. These numbers depend on gas thickness in the stripper, mass of the ion, and molecule involved. Cross sections for molecule destruction and ion transmission, and charge state +1 ion yields are described for a number of different stripper gases and ions. Example trace analysis measurements demonstrate the instrument’s capabilities.

Aerosol source (biomass, traffic and coal emission) apportionment in Lithuania using stable carbon and radiocarbon analysis

ABSTRACTIn the present study, a combination of the stable carbon isotope ratio (13C/12C) with radiocarbon data (14C) allowed us to perform the aerosol source apportionment. Filter samples of PM1 were collected during the warm and cold periods in rural and urban sites in Lithuania. The 14C/12C ratio of total carbon (TC) was measured using the single stage accelerator mass spectrometer quantifying of fossil and non-fossil derived aerosol emissions. The δ13C value was measured using an elemental analyser interfaced with an isotope ratio mass spectrometer. We have found that the highest fraction of contemporary carbon (fc = 0.82) was measured during a warm period in a rural location. A higher fraction of fossil fuel-derived carbon was observed for air masses transported from highly industrialized Western European regions during both seasons. Isotope mass balance calculations revealed that the traffic emissions composed 15 and 25 % in rural and urban sites, respectively, and did not change during either season. Input from coal-derived aerosol particles was estimated to be 15 % at an urban site during the cold period. The combination of the stable carbon isotope ratio with the radiocarbon data allowed us to distinguish coal, liquid fossil fuel combustion, and non-fossil derived aerosol particle emissions.

Annual Variations of 14C Concentration in the Tree Rings in the Vicinity of Ignalina Nuclear Power Plant

ABSTRACTIn this paper we analyze the radiocarbon (14C) concentration changes over the whole operational period of the Ignalina Nuclear Power Plant (INPP) including the post-shutdown decommissioning. Environmental samples from the vicinity of the INPP and a rural area as background of pine tree rings were analyzed with the single stage accelerator mass spectrometer (SSAMS). The analysis shows the local influence of the INPP from 3 to 7 pMC. The whole time span from 1983 to 2015 is divided into three periods representing the early and late operational and post-shutdown stages of the INPP with different 14C profiles in analyzed samples. The influence of the maintenance of the INPP and radioactive waste management activities are indicated and discussed.

Reprint Of: Enhanced spatially-resolved trace analysis using combined SIMS–single-stage AMS

Abstract Secondary ion mass spectrometry (SIMS) provides spatially resolved trace analysis of solid materials, but can be complicated by unresolved abundant molecular isobars. By adding a 300-kV single-stage accelerator mass spectrometer (SSAMS) as a detector for a Cameca ims 4f SIMS, one can measure more abundant positive ions from the SIMS while removing molecular isobars, thus improving very low abundance trace element and isotope analysis. This paper describes important features and capabilities of such an integrated system at the Naval Research Laboratory using charge state +1 ions. Transmission loss is compared to molecule destruction as gas flow to the molecule-destruction cell increases. As most measurements tolerate more modest abundance sensitivities than for 14C analysis, a lower gas flow is acceptable, so good transmission of 20–50% for ions of interest can be maintained for a broad range of ion masses. This new instrument has measured isotope ratios for uranium, lead, rare earths, and other elements from particulates and localized regions, with molecule destruction enabling the measurement at low SIMS mass resolving power and thus high transmission, as examples will show. This new and world-unique instrument provides improved capabilities for applications in nuclear and other forensics, geochemistry, cosmochemistry, and the development of optical, electronic, multifunctional, and structural materials.

Enhanced spatially-resolved trace analysis using combined SIMS–single-stage AMS

Abstract Secondary ion mass spectrometry (SIMS) provides spatially resolved trace analysis of solid materials, but can be complicated by unresolved abundant molecular isobars. By adding a 300-kV single-stage accelerator mass spectrometer (SSAMS) as a detector for a Cameca ims 4f SIMS, one can measure more abundant positive ions from the SIMS while removing molecular isobars, thus improving very low abundance trace element and isotope analysis. This paper describes important features and capabilities of such an integrated system at the Naval Research Laboratory using charge state +1 ions. Transmission loss is compared to molecule destruction as gas flow to the molecule-destruction cell increases. As most measurements tolerate more modest abundance sensitivities than for 14C analysis, a lower gas flow is acceptable, so good transmission of 20–50% for ions of interest can be maintained for a broad range of ion masses. This new instrument has measured isotope ratios for uranium, lead, rare earths, and other elements from particulates and localized regions, with molecule destruction enabling the measurement at low SIMS mass resolving power and thus high transmission, as examples will show. This new and world-unique instrument provides improved capabilities for applications in nuclear and other forensics, geochemistry, cosmochemistry, and the development of optical, electronic, multifunctional, and structural materials.

Measurement of Uranium Isotopes in Particles of U3O8 by Secondary Ion Mass Spectrometry-Single-Stage Accelerator Mass Spectrometry (SIMS-SSAMS).

A commercial secondary ion mass spectrometer (SIMS) was coupled to a ± 300 kV single-stage accelerator mass spectrometer (SSAMS). Positive secondary ions generated with the SIMS were injected into the SSAMS for analysis. This combined instrument was used to measure the uranium isotopic ratios in particles of three certified reference materials (CRM) of uranium, CRM U030a, CRM U500, and CRM U850. The ability to inject positive ions into the SSAMS is unique for AMS systems and allows for simple analysis of nearly the entire periodic table because most elements will readily produce positive ions. Isotopic ratios were measured on samples of a few picograms to nanograms of total U. Destruction of UH(+) ions in the stripper tube of the SSAMS reduced hydride levels by a factor of ∼3 × 10(4) giving the UH(+)/U(+) ratio at the SSAMS detector of ∼1.4 × 10(-8). These hydride ion levels would allow the measurement of (239)Pu at the 10 ppb level in the presence of U and the equivalent of ∼10(-10236)U concentration in natural uranium. SIMS-SSAMS analysis of solid nuclear materials, such as these, with signals nearly free of molecular interferences, could have a significant future impact on the way some measurements are made for nuclear nonproliferation.

Origin Identification of Carbonaceous Aerosol Particles by Carbon Isotope Ratio Analysis

We applied stable carbon isotope ratio (^(13)C/^(12)C) and radiocarbon (^(14)C) analysis for the quantification of three main aerosol sources (coal, biomass and liquid fossil fuel derived aerosol emissions). Submicron aerosol samples (PM1) were collected from 27^(th) October, 2014 to 19^(th) January, 2015 at a suburban site of Vilnius city (Lithuania). To determine fossil and non-fossil contributions to submicron carbonaceous aerosol particles, ^(14)C measurements of total carbon (TC) were performed using single stage accelerator mass spectrometer (SSAMS, NEC, USA). The concentrations of TC and δ^(13)C in PM_1 fraction were measured using elemental analyzer interfaced to isotope ratio mass spectrometer (EA-IRMS). The TC concentration during measurement period ranged from 1.3 to 9.6 μg m^(-3). The variation of TC concentrations can be explained by the influence of long-range transport and dispersion properties of the boundary layer (mixed layer depth). We found that biomass-derived aerosol sources are prevailing in Vilnius during wintertime and ranged from 57% to 84% of total carbonaceous aerosol fraction. Applying isotope mass balance calculations the traffic emissions were estimated to be 15 ± 7% and coal combustion made up 14 ± 9% in PM_1. To provide better information about the pollution sources, the carbon isotope analysis along air mass transport pattern was performed. Our results demonstrated that the high contribution to PM_1 from coal burning (up to 40%) was observed for air masses transported from highly industrialized Western Europe regions. Combination of stable carbon isotope ratio with the radiocarbon data allow to distinguish coal from liquid fossil fuel in the aerosol particle emissions.

160 keV 26Al-AMS with a single-stage accelerator mass spectrometer

Proof-of-principle 26Al-AMS analysis is achieved with a single-stage accelerator mass spectrometer (SSAMS) utilising very low ion energy. The SSAMS operates by discriminating against atomic isobar interference in a negative ion source and suppressing molecules with thick gas stripper. Resulting 1+ ions counting is with a surface barrier detector. The NEC designed SSAMS for 14C analysis is a popular model accelerator mass spectrometer and the developed further capability might be a significant addition to established 26Al-AMS capacity. Measurements at these energies should also be sufficient for alternative 26Al positive-ion mass spectrometry (PIMS).

Performance of the rebuilt SUERC single-stage accelerator mass spectrometer

The SUERC bipolar single-stage accelerator mass spectrometer (SSAMS) has been dismantled and rebuilt to accommodate an additional rotatable pre-accelerator electrostatic spherical analyser (ESA) and a second ion source injector. This is for the attachment of an experimental positive-ion electron cyclotron resonance (ECR) ion source in addition to a Cs-sputter source. The ESA significantly suppresses oxygen interference to radiocarbon detection, and remaining measurement interference is now thought to be from 13C injected as 13CH molecule scattering off the plates of a second original pre-detector ESA.

Radiocarbon measurements at LAC-UFF: Recent performance

In 2012 a single stage accelerator mass spectrometer from NEC was installed at the Radiocarbon Laboratory of Universidade Federal Fluminense (LAC-UFF), Niterói, Brazil. Here, we present a status report of our facility. We discuss some modifications applied to our combustion protocol in an attempt to reduce our procedural blank, mostly to processed organic samples. Measurements of reference materials indicate low precision and accuracy that are partially related to beam optics through the acceleration tube. We observed that once the beam current intensity increases the measured 13C+/12C+ becomes erratic. Therefore, in order to maintain the AMS-δ13C values within reasonable values, so that fractionation corrections using the spectrometer 13C+/12C+ values does not affect the final 14C results, we are forced to limit the 12C− beam intensity to ⩽30μA. This requirement was confirmed during our accuracy tests, when measuring selected annual tree-rings wood samples from a Parana pine (Araucaria angustifolia) between 1927 and 1997 previously measured at the Keck Carbon Cycle AMS Facility (KCCAMS), at the University of California, Irvine (UCI). At the LAC-UFF tree-ring wood samples were processed and measured in 4 different batches during a period of about 5months. The 14C results were later compared to the high-precision data obtained at KCCAMS/UCI and reached a good agreement. Recently a problem associated with graphitization yield were finally identified and new measurements with secondary standards are promising.

Single-stage accelerator mass spectrometer radiocarbon-interference identification and positive-ionisation characterisation

A single-stage accelerator mass spectrometer (SSAMS) is a good alternative to conventional spectrometers based on tandem electrostatic acceleration for radiocarbon measurement and permits experimentation with both negative and positive carbon ions. However, such 14C AMS of either polarity ions is limited by an interference. In the case of anion acceleration we have newly determined this to be summed 13C and 16O by improvising an additional Wien filter on our SSAMS deck. Also, 14C AMS might be improved by removing its dependency on negative-ionisation in a sputter ion source. This requires negative-ionisation of sample atoms elsewhere to suppress the 14N interference, which we accomplish by transmitting initially positive ions through a thin membrane. The ionisation dependence on ion-energy is found to be consistent with previous experimentation with vapours and thicker foils.

14C AMS at Suerc: Improving QA Data with the 5MV Tandem and 250KV SSAMS

In 2003, a National Electrostatics Corporation (NEC) 5MV tandem accelerator mass spectrometer was installed at SUERC, providing the radiocarbon laboratory with 14C measurements to 4–5‰ repeatability. In 2007, a 250kV single-stage accelerator mass spectrometer (SSAMS) was added to provide additional 14C capability and is now the preferred system for 14C analysis. Changes to the technology and to our operations are evident in our copious quality assurance data: typically, we now use the 134-position MC-SNICS source, which is filled to capacity. Measurement of standards shows that spectrometer running without the complication of on-line δ13C evaluation is a good operational compromise. Currently, 3‰ 14C/13C measurements are routinely achieved for samples up to nearly 3 half-lives old by consistent sample preparation and an automated data acquisition algorithm with sample random access for measurement repeats. Background and known-age standard data are presented for the period 2003–2008 for the 5MV system and 2007–2008 for the SSAMS, to demonstrate the improvements in data quality.