[en] Ultra-sensitive isotopic analysis of noble gases is excluded from the capabilities of accelerator mass spectrometry (AMS) facilities based on electrostatic tandem accelerators using negative-ion injection, due to the instability of elemental negative ions of noble gases. Detection of rare medium and heavy radionuclides which require isobaric discrimination is also constrained for tandem-accelerator AMS facilities by their achievable ion energy. Our group has been developing and using a method of accelerator mass spectrometry based on an electron cyclotron resonance (ECR) ion source producing highly-charged positive ions and the superconducting heavy-ion linear accelerator ATLAS at Argonne National Laboratory (Illinois, USA).

[en] High Voltage Engineering Europa B.V. (HVE) has designed a 300 kV AMS system for the measurement of ¹⁴C and of non-radiocarbon isotope species like ³H, ¹⁰Be, ²⁶Al, ⁴¹Ca, ¹²⁹I and actinides. The system features an electrostatic analyzer (ESA) as well as a high resolution analyzing magnet in the low-energy spectrometer, a 300 kV, vacuum insulated tandem accelerator and a high energy (HE) spectrometer comprising two high resolution magnets and an ESA in between. The layout of the system is shown. Located after the terminal stripper is an electrostatic deflector acting as charge state selector (CSS). The CSS fundamentally reduces a specific class of measurement background, especially beneficial for actinides.

[en] The Institute for Structure and Nuclear Astrophysics (ISNAP) at the University of Notre Dame in the United States has for many years concentrated its research efforts in experimental Nuclear Astrophysics as well as Nuclear structure and its effects on stellar reaction rates. This research effort centers on the use of three electrostatic accelerators present at Notre Dame (a 10MV FN Tandem, a 5MV single ended high-intensity vertical 5U accelerator and a 3MV Tandem accelerator dedicated to material analysis). Since 2006 an Accelerator Mass Spectrometry (AMS) program based on the 10MV FN Tandem accelerator has been dedicated to Nuclear Astrophysics as well as Nuclear forensics and Environmental science measurements. The available beam energy and experimental beam time combined with the availability of a gas-filled magnet (GFM) and Time-of-Flight (ToF) section and an array of available detectors provides a setup unique in North America dedicated to technical developments and sample measurements.

[en] Nuclear energy continues being commonly used nowadays in spite of the general tendency to substitute it by cleaner ways of energy production. In any case, one of the disadvantages of this method of energy production is the necessity of environmental control of the radioactivity especially close to the vicinity of nuclear facilities. Another important drawback is the large amount of residues that it produces. These are originated either in the normal activity of the nuclear power plants and/or on the decommissioning of these plants. A big part of these residues will need to be stored in special facilities especially designed for this purpose. In order to optimise this process, it is very important to characterize them very well so that only the ones that strictly need this storage treatment are sent to these special stores. This would reduce strongly the amount of material that must be treated as radioactive and, consequently, the loading rhythm of the stores and their economic and social impact. The long-lived radionuclides fulfil two important characteristics: they remain for a very long time in the nuclear residues and, in many cases, they are very difficult to detect by radiometric methods, as these do not have always enough sensitivity. In spite of this, the knowledge of their activities is essential for their appropriate evaluation. In these cases, a maximum level is fixed although the real level of the radionuclide in the residue will be much lower. The lack of sensitivity is clearly also an inconvenient for environmental samples.

[en] The 6 MV Pelletron tandem accelerator was designed and constructed for multi-nuclide AMS at the University of Tsukuba in 2016¹). It has two MC-SNICSs for the routine measurement. A five-electrode AE—-E gas ionization detector is installed on the end station of the rare-particle detection system. We have developed ultrasensitive detection techniques for ¹⁰Be, ¹⁴C (graphite and CO₂), ²⁶Al, ³⁶Cl, ⁴¹Ca, ⁹⁰Sr and ¹²⁹I in isotopic-ratio ranges of 10^-10 to 10^-15. In the case of ³⁶Cl AMS, we developed the sulfur removal method to reduce ³⁶S contamination. AgCl samples are pressed into an AgBr backing in a large Cu sample cathode (6 mm diameter) in order to reduce ³⁶S contamination”). ³⁶ClCl measurements are performed with a carbon foil (4.8 ug cm’) and an 8+ charge state at 6.0 MV, with ³⁶Cl⁸⁺ being injected into the detector at 54.0 MeV.

[en] Development of capabilities and methods of analysis using AMS has provided a tool for extremely high sensitivity analysis of a wide range of heavy isotopes including fission products, such as I-129 and Tc-99, and activation/decay products such as plutonium isotopes (239, 240, 241, 242 and 244), Pa-231, Np-237, Am-241 and the uranium isotopes U-236 and U-233. The 1MV VEGA AMS system at ANSTO's Centre for Accelerator Science (CAS) has one of the highest sensitivities in the world for rare heavy isotopes, which offers a significant advantage in investigation of trace signatures of nuclear contamination in the environment [1]. Achievement of sub-femtogram detection limits for a wide range of isotopes is possible this system. The ability to interrogate a wide range of anthropogenic nuclear isotopes allows the potential to distinguish nuclear material signatures of local contamination sources from global fallout background and identify the relative contributions. Significantly, with this improved tool for investigation it has become possible to not only characterise and quantify environmental deposition of plutonium contamination, but also the interaction of such contamination with biota and food webs by examining uptake in organisms living and feeding within contaminated zones. This information can then be used to inform radiological dose models for humans and wildlife and provide a basis for managing contaminated zones. Additionally, organ specific uptake can be determined to understand the interaction between contaminant form and biological uptake. Here a couple of recent examples of the application of the VEGA AMS Actinides capability are presented.

[en] The development of Accelerator Mass Spectrometry (AMS) has led to remarkable advances in the ability to detect at very low isotopic ratio several radionuclides of great interest in many scientific fields. However, expanding the application range of AMS to new radionuclides may require the use of isobaric separation techniques different from those commonly used in conventional AMS. Separation techniques based on DE/dx separation in foils or gases, gas ionization detectors or gas-filled magnets in many cases require larger accelerators. These currently limit the extension of AMS to a wider variety of radionuclides, despite the quality and imagination of AMS scientists who routinely apply these techniques to separate isobars from ''classical'' radionuclides. To be successful, any new isobaric separation technique will need to be integrable into existing AMS systems without major modification of installed equipment and will also need to provide efficient transmission of the radionuclide of interest to preserve the current ability of AMS to measure, in reasonable time and on milligram samples, isotopic ratios inaccessible by other techniques. Other important features to consider will be the cost and reliability of the additional equipment to be installed, the relative lengthening of the AMS line that may be required and the flexibility of these new techniques to be quickly programmed by the user to handle a wide range of radionuclides, ideally without requiring modification to hardware.

[en] The necessity to use negative ions for injection into AMS systems which use tandem accelerators has, from its beginning, led to the use of molecular anions (negative ions) to inject the analyte atom. This strategy is required for those elements, typically metals, which have weak binding of an electron to the neutral atom and so produce very low (nA or less) beams from a sputter source. Early work used oxide beams, for example BeO [1], and oxides continue to be commonly used. While oxides provide stable target materials and beams, they are electrically insulating, so require mixing with a conducting binder. They also require powerful ion sources to generate usable currents and the presence of 3 oxygen isotopes can, in some cases, cause ambiguities in the beam that is mass-selected for injections. In 2009, Zhao et al. [2] published the results of an extensive investigation of molecular anions using fluorine, covering much of the periodic table. Not only is fluorine a mono-isotopic element, but the binding properties of molecular fluorine anions show a stoichiometric relationship which can provide useful isobar discrimination.

[en] MALT (Micro Analysis Laboratory, Tandem accelerator), The University of Tokyo, is an ion beam analysis facility equipped with a 5MV tandem accelerator, a Cs-sputter negative ion source, mass analysis system, multi-Faraday cups for the stable isotope measurements, and final detectors designed for each bam analysis techniques. Among various beam analysis methods including NRA (Nuclear Reaction Analysis), ERDA (Elastic Recoil Detection Analysis), and PIXE (Particle Induced X-ray Emission), AMS (Accelerator Mass Spectrometry) is the most promising at MALT. Actually 70% of whole machine time is used for AMS. Since the completion of MALT facility in 1993, AMS for various nuclides had been developed, ¹⁰Be, ²⁶Al, ³⁶Cl, ⁴¹Ca, ¹²⁹I, and ²³⁶U as well as ¹⁴C. MALT is a pioneer of non-radiocarbon AMS in Japan. In Japan, there are 14 running accelerators for AMS, of which 8 accelerators are dedicated for ¹⁴C.

[en] Applications of accelerator mass spectrometry (AMS) for determination of long-lived naturally occurring and man-made radionuclides at ultra-trace levels are continuously increasing in mutual synergy with research and development of technology and related fields. New, smaller and multipurpose AMS systems are being designed and produced following intensive scientific progress, bringing significant economic advantages. To acquire a system in line with the above trend, a consortium of Nuclear Physics Institute (NPI) of the Czech Academy of Sciences (CAS), Faculty of Nuclear Sciences and Physical Engineering of the Czech Technical University in Prague (CTU in Prague — FNSPE) and the Institute of Archaeology of the Czech Academy of Sciences, Prague has been established. The consortium is actually finalizing the first installation of a new Multi-Isotope Low-Energy AMS (MILEA) system outside of the country of its developers — Jonplus AG and ETH Zurich, Switzerland. MILEA system combines the established ion source technology and the vacuum insulated accelerator of the well-known device MICADAS (upgraded to 300 kV terminal voltage) with the well-proven concept of the high energy mass spectrometer layout of the ETH “TANDY” instrument. In contrast to the mentioned devices, MILEA consists of 90° low energy ESA and LE injector, and uses two analysing magnets and ESA at the high energy side, all in achromatic arrangement. Helium is used as a stripper gas. To compensate focal plane positions in multi- nuclide arrangement it uses e.g. a set of quadrupole lenses just behind the accelerator, or a set of positionable Faraday cups with various combinations of integrators after the first analysing magnet. At the back-end, an improved low-noise AE-Eres gas ionization detector provides outstanding separation and identification of interfering particles.