Accelerator Mass Spectrometry System Research Articles

Reaching environmental levels of 244Pu by accelerator mass spectrometry at the Centro Nacional de Aceleradores

244Pu (T1/2 = 81 My) is the longest-lived, most minor, and the most understudied Pu isotope. The anthropogenic production of 244Pu is linked to nuclear detonations. Reported 244Pu/239Pu atom ratios in environmental samples range from below 10−6 to above 10−3. This work discusses the performance of the 1 MV Accelerator Mass Spectrometry system at the Centro Nacional de Aceleradores (CNA, Seville, Spain) to analyse 244Pu at environmental levels. The presence of 232Th traces in the Pu sample limits the sensitivity of the technique through the formation of the diatomic trication (232Th12C)3+, of mass 244 u, which must be suppressed by adjusting the stripper gas pressure. A244Pu background of 0.0075 fg (2 × 104 at) is demonstrated for samples that have undergone a chemical treatment. The reliability of the technique is proved through the analysis of three reference sediments provided by the International Atomic Energy Agency (IAEA-412, IAEA-465, IAEA-385). 244Pu results are complemented with 239Pu, 240Pu, 241Pu and 236U and their relative isotopic abundances are discussed.

Characterization of meteoric 10Be in certified reference materials for use in internal control standards

In recent decades, interest in the measurement of 10Be has increased due to its relevance in various fields of science. Trace amounts of 10Be produced from meteoric sources require sensitive accelerator mass spectrometry (AMS) measurements and robust sample preparation. The extraction, separation, and preparation of the appropriate oxide form for AMS require extensive and careful laboratory processing and certified reference materials to validate the chemical performance of the protocols used and the calibration of the AMS system in the measurement. In this work, the meteoric 10Be concentrations in two certified reference materials are characterized to establish their suitability as internal control standards for laboratory chemical preparation and AMS measurements of this radioisotope in our laboratory and the whole AMS community.

Development of pixelated silicon detector for AMS study

A pixelated silicon detector (PSD) has been developed for the position-sensitive detector on a focal plane of an accelerator mass spectrometry (AMS) system in Yamagata University (YU). The YU-AMS system measures the relative abundances of the carbon isotopes 14C, 13C, and 12C for radiocarbon dating. The beam of the rare isotope 14C is transported to the focal plane of the AMS system. When the focal plane detector is position-sensitive to the beam, it can be utilized for beam diagnostics on the AMS beamline to achieve 14C measurement with high accuracy. To investigate the characteristics of the PSD, α particles from 241Am were irradiated on the PSD. A beam test using 14C was also performed to evaluate the size and position of the 14C beam on the focal plane of the YU-AMS system.

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

The first accelerator mass spectrometry (AMS) laboratory in the Czech Republic has been established and put into routine operation in February 2022. Here we briefly describe the facilities available, namely a 300 kV multi-isotope low-energy AMS system (MILEA) capable of determination 10Be, 14C, 26Al, 41Ca, 129I, isotopes of U, especially 236U, Pu and other actinoids, and accessories for 14C measurements, which include a gas interface system, a preparative gas chromatography system for compound-specific radiocarbon dating analysis, and an isotope-ratio mass spectrometer. The first results achieved for separation and measurement of the above radionuclides (except for 41Ca) are also reported, with the main focus on 14C measurements. A specimen breakdown of 729 graphitised samples analysed for 14C so far is presented, as well as a proof of measurement stability of the MILEA system obtained by analysis of radiocarbon standards and analytical blanks. For the other radionuclides, well proven or novel procedures for sample preparation and measurement are presented.

10Be at iThemba LABS using a silicon nitride membrane stack as absorber for isobar suppression

10Be is an important isotope for accelerator mass spectrometry (AMS) because of the demand for cosmogenic radionuclide dating methods in the earth science and paleo-sciences community. At the iThemba Laboratory for Accelerator Based Science (iThemba LABS) we implemented full suppression of the interfering isobar 10B using a silicon nitride foil-stack, utilizing the 2+ charge state for high efficiency. We demonstrate the performance of this newly established AMS system using standards and test samples. We further present the results of an inter-comparison between iThemba LABS and the Center for Accelerator Mass Spectrometry/Lawrence Livermore National Laboratory, on AMS samples prepared from purified quartz at the University of Vermont. The results for 10Be from the laboratories are in close agreement, fully consistent with cross-calibration between them. AMS results for 26Al are in similarly good agreement, demonstrating the performance and accuracy of iThemba LABS for the most commonly measured in situ produced cosmogenic nuclides.

Optimal design and fabrication of a RF cavity for accelerator mass spectrometry system cyclotron

Optimal design and fabrication of a RF cavity for accelerator mass spectrometry system cyclotron

Present status of the YU-AMS system and its operation over the past 10 years

In 2009, Yamagata University installed a compact 14C accelerator mass spectrometry (YU-AMS) system and an automated graphitization line. The YU-AMS system is based on a 0.5 MV pelletron accelerator (1.5SDH-1) developed by National Electrostatics Corporation (NEC). A second automated graphitization line and an additional ion source of the YU-AMS system were installed in 2014. Approximately 2,000 samples have been measured per year using the system since 2010. The long-term stability of the system from 2010 to 2021 was assessed by measuring the IAEA-C6 and IAEA-C7 standard samples graphitized by the automated graphitization line.

Atmospheric deposition of 10Be in Altzomoni rainfall

The optimization of preparation techniques for 10Be in rainfall samples and the approaches applied to improve the measurement of this radionuclide with the accelerator mass spectrometry (AMS) system were carried out at LEMA-UNAM. A radiochemical procedure has been realized to measure 10Be in smaller samples than those reported in similar studies, reducing the sample volume from 2 L to 250 mL. The 10Be concentrations in the dissolved and particulate fraction of rain from the high-altitude rural site Altzomoni (Mexico) during 2017–2018 were determined for the first time at LEMA. The results show that the presence of particulate material is four orders of magnitude greater than the content of 10Be in the rainfall from Altzomoni. This work shows a mean concentration of (1.9 ± 0.2) × 104 and (3.3 ± 0.6) × 108 atoms per gram of rainfall in dissolved and particulate fractions.

Determination of Radiocarbon Content in Bio-Oil Samples by Mini Carbon Dating System in the Gliwice Radiocarbon and Mass Spectrometry Laboratory

Abstract The applications of isotopes are used by many European countries to investigate environmental changes. A compact modern accelerator mass spectrometry (AMS) system known as Mini Carbon Dating System (MICADAS) is used in Gliwice Radiocarbon and Mass Spectrometry Laboratory for determining the 14C content in different environmental samples including liquid fuels. For radiocarbon measurement using MICADAS, the liquid samples are accurately prepared using the tin capsules for liquids for combustion in elemental analyser (EA) and graphitisation in the AGE system. In this study, the determination of 14C content in three different bio-oil samples and one reference sample of 100% biomass was conducted. Bio-oil samples were prepared using tin capsules for liquids sealed in the second capsules for solids to avoid sample evaporation while the reference sample was prepared using the tin capsule for solids for combustion in EA and graphitisation in the AGE system. Based on the 14C measurement results, one of the bio-oils was not produced from the analysed reference biomass. Two others were determined as a mixture of bio- and fossil components, and based on 14C the bio-carbon content was calculated. For all samples, the 14C measurement showed reproducible and reliable results.

236U analyses with the ETH Zurich MILEA prototype system

Compact, low energy accelerator mass spectrometry (AMS) has evolved over the past years as one of the most sensitive, selective, and robust techniques for the analysis of heavy and long lived radionuclides. In this study, we focus on the analytical capabilities of the compact AMS system MILEA, mainly for 236U analyses. First, the setup of the system for actinide analyses is presented and the special technical setup for 23xU/238U (x = 3, 6, 5) is discussed. Then, the background and sensitivity for 236U/238U are studied in detail, and finally results from the first routine runs are presented and discussed. Our results show that the ETH Zurich MILEA system is ideally suited for fast, reliable, high sensitivity, and almost background free analyses of 236U/238U in environmental samples allowing the analysis of larger batches of samples with reasonably small sample sizes or volumes.

Performance of the 1 MV Accelerator Mass Spectrometry system at the Centro Nacional de Aceleradores for the analysis of 233U at environmental levels

233U (T1/2 = 0.159 My) has aroused much interest in the last few years because of the potential of 233U/236U to inform about anthropogenic U sources. The reported 233U/238U atom ratios in general environmental samples are in the 10−12–10−6 range. We demonstrate that 233U/238U abundance sensitivities at the 5 × 10−11 level can be achieved at the 1 MV Accelerator Mass Spectrometry system at the Centro Nacional de Aceleradores (CNA, Seville, Spain). Unresolved 234U, 235U and 232Th molecular fragments are identified as the main233U background contributors and procedures to subtract them are proposed. 233U/238U and 236U/238U atom ratios were analysed in the IAEA reference materials coded Soil-6, 300, 385, 410, and 412 at the CNA and at the 600 kV ETH AMS system for intercomparison. 233U/238U atom ratios for samples 412 and 385 were only reported by the ETH.

Hydrogen isotope ratio measurement by AMS at CIAE

Knowledge of the ratio of hydrogen isotopes contributes to many research fields. We have developed an accelerator mass spectrometry (AMS) method allowing simultaneous measurement of D/H and T/H ratios. We present a novel TiH2 sample preparation method suitable for the preparation of AMS targets and we describe the measurement technique developed with our in-house 300 kV AMS system at CIAE. We achieved a H+ transmission efficiency of 65 % and T/H measurement background of 2 × 10−15. Measurement of isotopic standard samples gave linear relationships between the measured and nominal values for both T/H and D/H.

Characterization of the isobar separator for anions integrated into the A. E. Lalonde laboratory’s 3 MV AMS system

Accelerator Mass Spectrometry (AMS) of isotopes with abundant negative ion-forming isobars often requires the use of large accelerators to achieve high sensitivity measurements. The Isobar Separator for Anions (ISA) is a radio frequency quadrupole (RFQ) reaction cell system that can provide selective isobar suppression in the low energy system, prior to injection into an accelerator. A commercial version from Isobarex Corp. has been installed in a second injection line of the 3 MV tandem accelerator system at the A. E. Lalonde AMS Laboratory, University of Ottawa. Here, we present the characterization of the ISA for its optimization of S– suppression and Cl– transmission. He gas was selected as a cooling buffer gas, as it provided the best Cl– transmission of ∼50 % through the ISA column. These tests use NO2 as a reaction gas due to its well-known exothermic reaction with S– but endothermic reaction with Cl–. More than six orders of magnitude reduction of S to Cl has been observed.

Initial tests of 26Al fluoride target matrix on MILEA AMS system

In this study, the possibility of using a superhalogenide ion AlF4- extracted from Na3AlF6 based target materials for 26Al/27Al measurements by Accelerator Mass Spectrometry (AMS) was investigated. Determination of 26Al by usual mass spectrometric methods is generally hampered by the presence of the isobar 26Mg. However, the AMS method enables significant suppression of this interference, particularly by negative ion formation. After initial current tests in a caesium sputtering ion source of the Tandetron system, performance of the fluoride materials was analysed on the MILEA AMS system at ETH Zürich. The AlF4- current was used to evaluate the performance of the respective samples. Additives as PbF2 were tested to increase the extracted ion currents and samples containing MgF2 were used to investigate the presence of isobaric ions. Subsequently, the ionization efficiency of AlF4- was determined by recording the 27Al2+ current on the high energy side and the signals of 26Al2+ were investigated with the gas ionization detector.

Small accelerators and their applications in the CANAM research infrastructure at the NPI CAS

The Nuclear Physics Institute (NPI) of the Czech Academy of Sciences (CAS) operates, among other facilities, a Tandetron linear accelerator, TR-24 and U-120M cyclotrons, and an MT25 microtron. A new accelerator mass spectrometry (AMS) instrument, MILEA, has recently been acquired. Except for the MT25, all facilities are synergic parts of the Centre of Accelerators and Nuclear Analytical Methods Research Infrastructure (CANAM RI) ( http://canam.ujf.cas.cz ). This paper demonstrates the instrumental, scientific and application capabilities of the devices for many fundamental nuclear physics experiments and a wide spectrum of applications. The Tandetron Laboratory has a full arsenal of ion-beam analytical methods, ion-beam nano- and microstructuring techniques, as well as tools for the doping and synthesis of new progressive materials using energetic ion beams. It uniquely utilises ion beams for 3D elemental mapping; it studies internal morphology using ion-microprobe methods applicable in many scientific branches. The TR-24 and U-120M cyclotrons provide the primary beams of accelerated ions as well as the generated secondary fast neutrons, including the necessary instrumentation and the target technology, and enable fundamental experiments in nuclear physics, astrophysics, dosimetry, etc. The microtron MT25 is a source of relativistic electrons (the primary electron beam), the secondary photon beam (bremsstrahlung) and neutrons from photonuclear reactions which are used, e.g. for analysis and preservation of cultural heritage. The MILEA AMS system offers a highly sensitive isotopic ratio measurement of very long-lived radionuclides at levels up to 10–15.

LAC-UFF STATUS REPORT: CURRENT PROTOCOLS AND RECENT DEVELOPMENTS

ABSTRACTThe Radiocarbon Laboratory of the Fluminense Federal University was installed in 2009, and its NEC Single Stage Accelerator Mass Spectrometry system has been operational since 2012. As the first14C-AMS facility in Latin America, the LAC-UFF became a reference center for radiocarbon (14C) dating in Brazil. Over the years we have implemented pretreatment protocols for several kinds of materials, such as cellulose, soil, bone, and biofuels. In the present paper we describe our current protocols for the preparation of these types of samples. Moreover, after 10 years of operation, with the aim of expanding the range of materials we are able to analyze, we report the results of several tests to improve accuracy, precision and background levels. For example, here we discuss how isotopic fractionation during the graphitization and measurement steps has been controlled. Concerning results interpretation, our research group has been using OxCal chronological models to analyze different contexts such as stromatolite growth, tree rings, soil deposition and marine reservoir effect (MRE) determination.

14C-AMS IN MEXICO AND PRE-COLUMBIAN ARCHAEOLOGY

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.

Perspectives for low energy reactions measurements at the new LEMA beam-line

Towards the end of 2017, a new beam line was commissioned at the Laboratorio Nacional de Espectrometría de Masas con Aceleradores (LEMA) at Instituto de Física of the Universidad Nacional Autónoma de México (IFUNAM). Initially, LEMA was a 1 MV tandetron accelerator just dedicated to Accelerator Mass Spectrometry (AMS); nowadays, the new line adopted the main characteristics of the AMS system in a natural way: i.e., it has a high precision measurement of the beam energy and a very high and stable current (tens of μ A) depending of charge state of each isotope. The precise low energy limit around 400 keV opens a window to study reactions in the region of interest for Astrophysics. At the same time, the LEMA beam-line allows to develop experiments combining nuclear reactions with AMS, as well the developing of all of kind of Ion Beam Analysis (IBA) studies. In this work the main characteristics of the line, the ancillary systems and the perspectives for low energy measurements for nuclear studies and applications are described.

Analysis of 14C concentration in teeth to estimate the year of birth in the Mexican population

The 14C analysis of permanent teeth employing nuclear techniques has a direct application in Forensic Sciences since teeth are the hardest part of the human body and can survive natural decay or extreme conditions. After the first Accelerator Mass Spectrometry Laboratory AMS-LEMA at UNAM, our research group is interested in reproducing 14C analysis on teeth as other countries to estimate age in the Mexican population samples. One of the main goals of this exploratory study is to know the best methodology considering relevant biological factors based on differences in tissues (enamel and dentin) that allows us to know the year of birth through the 14C concentration comparing the yield between 14C analyses from carbonate in enamel and collagen in dentin. In this study, Accelerator Mass Spectrometry (AMS) has been performed in 22 contemporary teeth samples (each one donated from 1 different adult), participating 22 individuals by informed consent to enable a new tool and improve forensic practices in Mexico. Carbon is extracted, converted to graphite, and pressed into a cathode. The sample is taken to an AMS system, where carbon isotopes are separated, counted, and the 14C/12C and 13C/12C ratios determined. Our results for standards and teeth samples from Mexican people are in good agreement with the expected values; they are also useful to set up the best conditions for studies in dentin and enamel. However, this is a destructive technique for dental organs; it is not suitable for individuals born previous 1950. New challenges in sample preparation processes are to be solved to take advantage of the nuclear techniques developed in the last 50 years and make new contributions to society.

Development the Miniaturized AMS System and Its Analysis Technique

Accelerator mass spectrometry(AMS) is the most sensitive analytical technique for measuring long-lived radionuclides, which is widely used in the fields of environment, geology, archaeology and physics. In recent years, the miniaturization of AMS device has been greatly developed in the world. In order to develop miniaturized AMS devices and their analysis technology, China institute of atomic energy has independently developed a single-stage AMS device with an acceleration voltage of 0.2 MV and a tandem AMS device with an terminal voltage of 0.3 MV, respectively. Based on the single-stage AMS device, the high efficiency transport technique and background eliminating method have been developed for 14C measurement, and realized the high sensitivity measurement of 14C. The measurement sensitivity reaches 14C/12C (atomic number ratio)=2×10–15. Using the 0.3 MV tandem AMS device, the gas stripping conditions, background eliminating and detection methods of 129I at low ion energy were systematically studied, and the high efficient transmission and high sensitive measurement methods of 129I were established, the sensitivity is 129I/127I=1×10–14. This is the first time to develop miniaturized AMS devices in China, which lays the foundation for the localization of AMS.