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Natural plutonium from supernovaeThe rapid neutron capture process (r-process) produces many of the heavy chemical elements, but the astrophysical settings where it occurs remain unclear. Leading candidates are neutron star mergers and some types of supernovae. Wallneret al.analyzed the plutonium content of a deep-sea crust sample, identifying a few dozen atoms of the r-process isotope plutonium- 244 that were delivered to Earth within the past few million years. There was a simultaneous signal of iron-60, which is known to be produced in supernovae. Comparing the ratios of these isotopes constrains the relative contributions of supernovae and neutron star mergers to r-process nucleosynthesis.Science, this issue p.742

Since the 1956 completion of nuclear testing at the Montebello Islands, Western Australia, this remote uninhabited island group has been relatively undisturbed (no major remediations) and currently functions as high-value marine and terrestrial habitat within the Montebello/Barrow Islands Marine Conservation Reserves. The former weapons testing sites, therefore, provide a unique opportunity for assessing the fate and behaviour of Anthropocene radionuclides subjected to natural processes across a range of shallow-marine to island-terrestrial ecological units (ecotopes). We collected soil, sediment and biota samples and analysed their radionuclide content using gamma and alpha spectrometry, photostimulated luminescence autoradiography and accelerator mass spectrometry. We found the activity levels of the fission and neutron-activation products have decreased by ~hundred-fold near the ground zero locations. However, Pu concentrations remain elevated, some of which are high relative to most other Australian and international sites (up to 25,050 Bq kg−1 of 239+240+241Pu). Across ecotopes, Pu ranked from highest to lowest in the following order: island soils > dunes > foredunes > marine sediments > and beach intertidal zone. Low values of Pu and other radionuclides were detected in all local wildlife tested including endangered species. Activity concentrations ranked (highest to lowest) terrestrial arthropods > terrestrial mammal and reptile bones > algae > oyster flesh > whole crab > sea turtle bone > stingray and teleost fish livers > sea cucumber flesh > sea turtle skin > teleost fish muscle. The three detonations (one from within a ship and two from 30 m towers) resulted in differing contaminant forms, with the ship detonation producing the highest activity concentrations and finer more inhalable particulate forms. The three sites are distinct in their 240/239Pu and 241/239Pu atom ratios, including the Pu transported by natural process or within migratory living organisms.

The VEGA 1MV accelerator at ANSTO is designed to be a highly versatile AMS instrument. In this paper we focus on describing those aspects of the system that are designed to optimise its performance for actinides isotopic analysis, in particular the implementation of fast isotope cycling and multiple isotope detection methods to enable isotope detection across a wide range of rates and currents. Charge state yields are reported in the energy range from 0.3 to 1.0 MeV with helium gas stripping, showing that the highest yield for the 3+ charge state occurs around 1 MeV and exceeds 40%. Accuracy and precision for uranium isotope ratios are shown to approach 1% over a wide range of concentrations and isotope ratios. The ionisation efficiency for plutonium is shown to exceed 3%, leading to overall detection efficiency over 1%. In the absence of background, this leads to sub-attogram detection limits for several Pu isotopes including 244Pu.

The release of plutonium (Pu) from the 2011 Fukushima accident has raised questions on how prevalent it is in the environment and how its cycling into the biosphere compares with that from the previous Nagasaki and global-fallout sources. Here, we report on systematic sampling and analysis of soils, earthworms, and wild boar as markers of Pu in the deposition areas near the Fukushima Daiichi Nuclear Power Station (FDNPS) and Nagasaki. Highly-sensitive Accelerator Mass Spectrometry (AMS) methods were used to distinguish the Pu sourced from the FDNPS accident, and Nagasaki-detonation, from worldwide fallout Pu. We primarily used 241Pu/239Pu atom ratios, as the other typically-used Pu measures (240Pu/239Pu atom ratios, activity concentrations) were less sensitive and did not distinguish the FDNPS Pu from background in most study samples. Near the FDNPS, results indicate that five years after the accident, 0.4% – 2% of the Pu in the local soils (0-5cm) had originated from the FDNPS releases, the remainder being from global fallout. The trace amounts of FDNPS Pu (e.g., 0.02-0.04 Bq kg-1239Pu estimated in local ~3km deposition) contrasted sharply with the 134+137Cs content which was about 106 times greater than background in the same samples. The accident also contributed new Pu of ~0.3% – 3% in earthworms and ~1% – 10% in wild boar near the FDNPS. The soil and wild boar data from across the study sites consistently indicate only low levels of new accident-Pu and do not support the concept of a substantial undiscovered deposit of Pu near the FDNPS. Unlike sparsely-taken individual soil samples that might miss a Pu hotspot, the wild boar samples represent the integration of uptake throughout their entire foraging areas. Near Nagasaki, our measurements in 2016 show a lasting legacy of Pu sourced from the 1945 detonation (~93% soils, ~88% earthworm, ~96% boar in samples 134,137Cs in samples from near the FDNPS. The results demonstrate progress in increasing the sensitivity of AMS methods, including the use of 241Pu/239Pu atom ratios, to compare recent and past nuclear contamination events and suggest that the Nagasaki-detonation Pu will be distinguishable in the environment long after the FDNPP-accident Pu is not.

Nuclides synthesized in massive stars are ejected into space via stellar winds and supernova explosions. The solar system (SS) moves through the interstellar medium and collects these nucleosynthesis products. One such product is (60)Fe, a radionuclide with a half-life of 2.6 My that is predominantly produced in massive stars and ejected in supernova explosions. Extraterrestrial (60)Fe has been found on Earth, suggesting close-by supernova explosions ∼2 to 3 and ∼6 Ma. Here, we report on the detection of a continuous interstellar (60)Fe influx on Earth over the past ∼33,000 y. This time period coincides with passage of our SS through such interstellar clouds, which have a significantly larger particle density compared to the local average interstellar medium embedding our SS for the past few million years. The interstellar (60)Fe was extracted from five deep-sea sediment samples and accelerator mass spectrometry was used for single-atom counting. The low number of 19 detected atoms indicates a continued but low influx of interstellar (60)Fe. The measured (60)Fe time profile over the 33 ky, obtained with a time resolution of about ±9 ky, does not seem to reflect any large changes in the interstellar particle density during Earth’s passage through local interstellar clouds, which could be expected if the local cloud represented an isolated remnant of the most recent supernova ejecta that traversed the Earth ∼2 to 3 Ma. The identified (60)Fe influx may signal a late echo of some million-year-old supernovae with the (60)Fe-bearing dust particles still permeating the interstellar medium.

Organic spring deposits have the potential to provide to outstanding records of palaeoenvironmental and climatic change, particularly in arid and semi-arid environments where establishing robust records of environmental change is challenging due to a lack of classic sedimentary records, e.g. perennial lakes and extensive wetlands. However, despite the potential of organic spring deposits a number of studies demonstrate complications in the application of standard 14C techniques which has, in several cases, led to confusing chronologies. This implies that dynamic carbon pathways commonly occur within spring systems. Because of the importance of springs as critical palaeoenvironmental archives, this study sought to better understand the behaviour of 14C and other radionuclides used in geochronology within organic springs, and ultimately, establish a protocol for building reliable chronologies in these environments. To do this, we utilised multiple geochronological methodologies to investigate cores collected from three springs in the Kimberley region of northwest Australia. This included 14C dating of different carbon fractions, 210Pb dating, the application of 239+240Pu, and novel, high spatial resolution, luminescence techniques as indicators of geochronological structure. The natural sensitivity-corrected luminescence (Ln/Tn) signal indicated the studied springs contained a relatively complete stratigraphic record, however 14C results were found to be convoluted by contamination attributed to a combination of roots, groundwater fluctuations and allochthonous input of “old” carbon affecting ages. Whilst it was found that no single carbon fraction is universally reliable in dynamic spring environments, dating the stable polycyclic aromatic carbon (SPAC), isolated by hydrogen pyrolysis (HyPy) pre-treatment, appeared to remove the effects of post-depositional modification which otherwise perturbed the age of carbon fractions with respect to sedimentary development of the spring. By contrast, the ability of 210Pb and 239+240Pu to provide detailed chronologies for recent spring sediments (i.e. the past 100 years) was found to be complicated due to the behaviour of springs as an open system with regards to uranium. Therefore, it may not be possible to construct 210Pb chronologies in many spring environments. Overall, the results of this study indicate that it is possible to construct 14C based chronologies in spring systems, however it is necessary to understand the effects of physical and biological processes within springs on 14C pathways. In particular, the application of HyPy pre-treatment of SPAC appears to offer a viable approach to constructing chronologies in these environments. Furthermore, although this study pertains to springs, the sources of geochronological complexity described here are not exclusive to these systems and our results are therefore more widely applicable.

This study presents the first measurements of anthropogenic plutonium (239Pu and 240Pu) concentrations and atom ratios (240Pu/239Pu) for Tasmania, in sediment collected from Bathurst Harbour, in the Tasmanian Wilderness World Heritage Area, Australia. The weighted mean 240Pu/239Pu atom ratio measured at this site was 0.172 ± 0.007 which is consistent with published data from mainland Australia and global and Southern Hemisphere averages. The 240Pu/239Pu atom ratios ranged between 0.11 and 0.21 with the earliest recorded 240Pu/239Pu atom ratios being the lowest, suggesting an influence of low atom ratio fallout from nuclear testing in Australia. Post-moratorium fallout 240Pu/239Pu atom ratios were consistent with other records. Lead-210 (210Pb) sediment chronologies indicate sediment accumulation rates have increased since the early part of the 19th century at this location.

The Centre for Accelerator Science at ANSTO operates four tandem accelerator systems for Accelerator Mass Spectrometry (AMS) and Ion Beam Analysis (IBA). The latest addition to the fleet is SIRIUS, a 6 MV combined IBA and AMS system. Following initial ion beam testing, conditioning and debugging software and hardware, SIRIUS is now commissioned. Details of the instrument design and performance data for 10 Be, 26 Al and 36 Cl are presented.

Plutonium (Pu) has been released in Japan by two very different types of nuclear events – the 2011 Fukushima accident and the 1945 detonation of a Pu-core weapon at Nagasaki. Here we report on the use of Accelerator Mass Spectrometry (AMS) methods to distinguish the FDNPP-accident and Nagasaki-detonation Pu from worldwide fallout in soils and biota. The FDNPP-Pu was distinct in local environmental samples through the use of highly sensitive 241Pu/239Pu atom ratios. In contrast, other typically-used Pu measures (240Pu/239Pu atom ratios, activity concentrations) did not distinguish the FDNPP Pu from background in most 2016 environmental samples. Results indicate the accident contributed new Pu of ~0.4%–2% in the 0–5 cm soils, ~0.3%–3% in earthworms, and ~1%–10% in wild boar near the FDNPP. The uptake of Pu in the boar appears to be relatively uninfluenced by the glassy particle forms of fallout near the FDNPP, whereas the 134,137Cs uptake appears to be highly influenced. Near Nagasaki, the lasting legacy of Pu is greater with high percentages of Pu sourced from the 1945 detonation (~93% soils, ~88% earthworm, ~96% boar). The Pu at Nagasaki contrasts with that from the FDNPP in having proportionately higher 239Pu and was distinguished by both 240Pu/239Pu and 241Pu/239Pu atom ratios. However, compared with the contamination near the Chernobyl accident site, the Pu amounts at all study sites in Japan are orders of magnitude lower. The dose rates from Pu to organisms in the FDNPP and Nagasaki areas, as well as to human consumers of wild boar meat, have been only slightly elevated above background. Our data demonstrate the greater sensitivity of 241Pu/239Pu atom ratios in tracing Pu from nuclear releases and suggest that the Nagasaki-detonation Pu will be distinguishable in the environment for much longer than the FDNPP-accident Pu.

We present new chironomid and stable isotope (δ13C and δ15N) data from Little Llangothlin Lagoon, Australia that provides more detail on changes in this wetland since European settlement ca. 1840 AD. We also examine how the updated Holocene paleoecological record provides insights for management of this Ramsar-listed wetland. The current management strategy for Little Llangothlin is to restore the wetland and catchment to its natural state. This strategy is intended to protect the values that allowed it to be listed as a Ramsar wetland; i.e. its role as a drought refuge for waterbirds and to preserve or enhance threatened ecological communities. There are clear conflicts between the Ramsar listing criteria, management objectives and the management strategy in light of information provided by the palaeoecological record. In particular, restoration of terrestrial ecosystems through reforestation may jeopardise the wetlands role as a drought refuge. Some activities, such as artificial raising of the water level in 1989 are intended to restore, but actually introduced a state that did not exist prior to human settlement. We recommend a more integrated management approach that heeds the information provided by the palaeoecological record and focuses more on maintenance or enhancement of ecosystem services and biodiversity.

The Centre for Accelerator Science (CAS) facility at ANSTO has been expanded with a new 6 MV tandem accelerator system supplied by the National Electrostatic Corporation (NEC). The beamlines, end-stations and data acquisition software for the accelerator mass spectrometry (AMS) were custom built by NEC for rare isotope mass spectrometry, while the beamlines with end-stations for the ion beam analysis (IBA) are largely custom designed at ANSTO. An overview of the 6 MV system and its performance during testing and commissioning phase is given with emphasis on the IBA end-stations and their applications for materials modification and characterisation.

Radionuclides from 1950s weapons testing at the Montebello Islands, Western Australia, may impact sea turtle embryos incubating within eggs laid in contaminated sands or be taken up into adult body tissues where they can contribute to radiation dose over a turtles' 60+ year lifespan. We measured plutonium in all local samples including turtle skin, bones, hatchlings, eggshells, sea sediments, diet items and beach sands. The amount of Pu in developing embryos/hatchling samples was orders of magnitude lower than that in the surrounding sands. These contaminated sands caused most dose to eggs (external dose from 137Cs, 152Eu), while most of the dose to adults was from internalised radionuclides (98%). While current dose rates are relatively low, local dose rates were high for about ten years following the 1950s detonations and may have resulted in lethality or health impacts to a generation of turtles that likely carry biomarkers today.

This study examines mangrove substrate production within a mangrove basin forest in the Tweed Estuary, northern New South Wales, Australia. This is achieved using high resolution dating of 239+240Pu, 236U and 210Pb in mangrove sediments to examine both the modes and rates of mangrove substrate production. Results show a shift in the mode of substrate production occurred approximately 70 years ago in response to human modification of the Tweed Estuary (hydrologic changes). At that time, mangrove substrate production shifted from being dominated by sedimentation processes (fine silt accumulation) to being dominated by biological processes (mangrove root production). Since that time, mangrove peat has been accreting at the study site at the same rate as local sea level rise (SLR), implying current rates of peat substrate development are tuned to increasing sea level. A further implication of the shift to biological accretion at rates corresponding with SLR is that the studied mangrove basin is sequestering C at increasing rates due to subsurface root production.

A new 1 MV NEC pelletron AMS system at ANSTO is presented. The spectrometer comprises large radius magnets for actinide measurements. A novel feature of the system is fast switching between isotopes both at low and high energy sections allowing measurements of up to 8 isotopes within a single sequence. Technical details and layout of the spectrometer is presented. Performance data for 14C, 10Be, 26Al and actinides demonstrate the system is ready for routine AMS measurements.

Nuclear forensic analysis was conducted on two uranium samples confiscated during a police investigation in Victoria, Australia. The first sample, designated NSR-F-270409-1, was a depleted uranium powder of moderate purity (∼ 1000 μg/g total elemental impurities). The chemical form of the uranium was a compound similar to K2(UO2)3O4 · 4H2O. While aliquoting NSR-F-270409-1 for analysis, the body and head of a Tineid moth was discovered in the sample. The second sample, designated NSR-F-270409-2, was also a depleted uranium powder. It was of reasonably high purity (∼ 380 μg/g total elemental impurities). The chemical form of the uranium was primarily UO3 · 2H2O, with minor phases of U3O8 and UO2. While aliquoting NSR-F-270409-2 for analysis, a metal staple of unknown origin was discovered in the sample. The presence of 236U and 232U in both samples indicates that the uranium feed stocks for these samples experienced a neutron flux at some point in their history. The reactor burn-up calculated from the isotopic composition of the uranium is consistent with that of spent fuel from natural uranium (NU) fueled Pu production. These nuclear forensic conclusions allow us to categorically exclude Australia as the origin of the material and greatly reduce the number of candidate sources.

The mobility of plutonium (Pu) in soils, and its uptake into a range of wildlife, were examined using recent and ∼25 year old data from the Taranaki area of the former Maralinga weapons test site, Australia. Since its initial deposition in the early 1960s, the dispersed Pu has been incorporated into the soil profile and food chain through natural processes, allowing for the study of Pu sequestration and dynamics in relatively undisturbed semi-arid conditions. The data indicate downward mobility of Pu in soil at rates of ∼0.2–0.3 cm per year for the most mobile fraction. As a result, while all of the Pu was initially deposited on the ground surface, approximately 93% and 62% remained in the top 0–2 cm depth after 25- and 50-years respectively. No large-scale lateral spreading of the Taranaki plume was observed. Pu activity concentrations in 0–1 cm soils with biotic crusts were not elevated when compared with nearby bare soils, although a small number of individual data suggest retention of Pu-containing particles may be occurring in some biotic crusts. Soil-to-animal transfer, as measured by concentration ratios (CRwo-soil), was 4.1E−04 (Geometric Mean (GM)) in mammals, which aligns well with those from similar species and conditions (such as the Nevada Test Site, US), but are lower than the GM of the international mammal data reported in the Wildlife Transfer Database (WTD). These lower values are likely due to the presence of a low-soluble, particulate form of the Pu in Maralinga soils. Arthropod concentration ratios (3.1E−03 GM), were similar to those from Rocky Flats, US, while values for reptiles (2.0E−02 GM) were higher than the WTD GM value which was dominated by data from Chernobyl. Comparison of uptake data spanning approximately 30 years indicates no decrease over time for mammals, and a potential increase for reptiles. The results confirm the persistence of bioavailable Pu after more than 50 years since deposition, and also the presence of larger-sized particles which currently affect CRwo-soil calculations, and which may serve as an ongoing source of bioavailable Pu as they are subjected to weathering into the future.

We have investigated sulphur hexafluoride as a stripper gas in tandem accelerators by using the ANTARES accelerator system at ANSTO to measure charge state distributions for this gas. Results are reported at 4 MV terminal voltage for injected negative ions ranging from carbon to uranium oxide. For iodine and thorium the distributions are extended across a range of energies of practical use for accelerator mass spectrometry, ion beam analysis and other accelerator applications. Charge state distributions using sulphur hexafluoride are found to have mean charge states up to 1 charge unit higher than, and to be broader than, corresponding distributions for argon gas, except in the case of carbon beams. As a result, SF6 is shown to provide significantly higher yields for charge states of heavy ions above the mean charge state. We now perform actinide AMS measurements with 9% yield to the 5+ charge state, compared to 4–5% achieved previously with argon gas.

The British government performed a number of nuclear weapon tests on Australian territory from 1952 through to 1963 with the cooperation of the Australian government. Nine fission bombs were detonated in South Australia at Emu Junction and Maralinga, and a further three fission weapons were detonated in the Monte Bello Islands off the coast of Western Australia. A number of soil samples were collected by the Australian Radiation Laboratories in 1972 and 1978 during field surveys at these nuclear weapon test sites. They were analysed by gamma spectrometry and, for a select few samples, by alpha spectrometry to measure the remaining activities of fission products, activation products and weapon materials. We have remeasured a number of these Montebello Islands and Emu Junction soil samples using the ANTARES AMS facility, ANSTO. These samples were analysed for plutonium and uranium isotopic ratios and isotopic concentrations. Very low 240 Pu/ 239 Pu ratios were measured at both sites (∼0.05 for Alpha Island and ∼0.02 for Emu Field), substantially below global fallout averages. Well correlated but widely varying 236 U and plutonium concentrations were measured across both sites, but 233 U did not correlate with these other isotopes and instead showed correlation with distance from ground zero, indicating in situ production in the soils.

We have used a tandem accelerator to measure charge state distributions at 4.1 MeV for negative ions ranging from carbon to uranium oxide passing through the gases helium, argon and xenon. The gas density was varied over a wide range to observe the onset of equilibrium stripping conditions. Using a 12° electrostatic deflector after the accelerator, charge states from 1+ to 8+ have been measured. For carbon, the charge state is seen to strip progressively from a low charge of around 1+ towards equilibrium with increasing gas thickness. However, for all the other ions, there is a high probability of multiple electron loss in single collisions with the gas, leading to mean charge states greater than 2 even at very low gas stripper pressure. This effect is observed to be gas-independent.

A number of electronic systems are used on the ANTARES accelerator at ANSTO to implement its fast cycling accelerator mass spectrometry (AMS) capability. The fast cycling system was originally installed and commissioned in 1993 and has recently been updated. This paper describes the more significant of the electronic systems, such as the controller (“sequencer”), the high-voltage power supply (“bouncer”), the fast electrostatic beam chopper, and those used for measurement of the pulsed ion beam current. The sequencer, a programmable 15-bit digital pulse generator, generates the timing and sequencing of the control signals for bouncing voltage selection, beam chopping, Faraday cup current measurement, and rare isotope event measurement. The new sequencer is implemented using a National Instruments FPGA (field programmable gate array) card, programmed using LabVIEW 2010. This device has the benefits of host CPU-independent operation, simple interfacing (PCI), a small footprint, off-the-shelf availability at modest cost, and ease of functionality upgrade. The sequencer provides 15 synchronous digital signals, whose “on” and “off” transitions can be independently specified, in both number and time, with a time resolution of between 0.5 and 128 ms, and with the total duration between repetitions adjustable between 65.5 ms and 8.4 s per cycle. It is hosted by a generic PC because of the low-cost and ubiquity of these. The stand-alone FPGA-based approach ensures that the sequencer determinism is unaffected by processes executing in the host CPU. DOI: 10.2458/azu_js_rc.55.16276

Isobaric interference represents one of the major limitations in mass spectrometry. For a few cases in AMS with tandem accelerators, isobaric interference is completely excluded like the well-known major isotopes 14C, 26Al, 129I. Additional isotopes are 55Fe (t1/2 = 2.74 years), 68Ge (t1/2 = 270.9 days) and 202Pb (t1/2 = 52.5 kyr), with 68Ge and 202Pb never been used in AMS so far. Their respective stable isobars, 55Mn, 68Zn and 202Hg do not form stable negative ions. The exceptional sensitivity of AMS for 55Fe, 68Ge and 202gPb offers important insights into such different fields like nuclear astrophysics, fundamental nuclear physics and technological applications. VERA, a dedicated AMS facility is well suited for developing procedures for new and non-standard isotopes. AMS measurements at the VERA facility established low backgrounds for these radionuclides in natural samples. Limits for isotope ratios of

Measurements of the isotopic ratios of plutonium and uranium are utilised by the safeguards community, environmental radioactivity and remediation studies, oceanography research, and in the U-series dating of geological samples. Accelerator Mass Spectrometry offers the advantages of high selectivity and sensitivity for such ratio measurements, but suffers from a poorer ionisation and transmission efficiency than some other mass spectrometric techniques. In addition, the ionisation efficiency achieved in caesium-sputter ion sources can be variable depending on the chemical form and geometry of the target used, yielding actinide negative ion beam rates with efficiencies ranging from 0.05% to 0.5%. In this paper we investigate the impact of the crystal structure of the target material, chemical composition and the geometry of the target in order to determine conditions which will allow us to maximise beam output and increase the efficiency of AMS measurements in future. We also examine target stability and “burn in time” (the time taken to generate a stable beam current) in conjunction with these measurements in order to maintain a high precision of measurement during the measurement period.

The nuclear safeguards system which is used to monitor compliance with the Nuclear Non-proliferation Treaty relies to a significant degree on the analysis of environmental samples. Undeclared nuclear activities can be detected through determination of the isotopic ratios of uranium and plutonium in such samples. It is necessary to be able to measure plutonium at the femtogram level in this application, and measure the full suite of uranium isotopes (233–238U) where the total uranium content may be at the nanogram level. In this paper we describe the development of our accelerator mass spectrometry system for such analyses, with particular reference to recent improvements in our methods. The commissioning of a fast isotope cycling system for actinides has led to improved precision, with reproducibility of 4% for actinide isotope ratios. The background level for the key rare isotope 236U is found to be 8.8 fg, for total uranium content in the nanogram range, and is limited by 236U contamination rather than ion mis-identification. For plutonium the background is at the low femtogram level.

A method for detection of radiocarbon at low levels is described and the results of tests are presented. We refer to this method as ion charge exchange mass spectrometry (ICE-MS). The ICE-MS instrument is a two stage mass spectrometer. In the first stage, molecular interferences which would otherwise affect radiocarbon detection at mass 14 are eliminated by producing high charge state ions directly in the ion source (charge state ⩾2). 14N interference is eliminated in the second stage by converting the beam to negative ions in a charge exchange cell. The beam is mass-analysed at each stage. We have built a test apparatus consisting of an electron cyclotron resonance ion source and a pair of analysing magnets with a charge exchange cell in between, followed by an electrostatic analyser to improve the signal to background ratio. With this apparatus we have measured charge exchange probabilities for (Cn+ → C−) from 4.5 to 40.5 keV (n = 1–3). We have studied the sources of background including assessment of limits for nitrogen interference by searching for negative ions from charge exchange of 14N ions. Our system has been used to detect 14C in enriched samples of CO2 gas with 14C/12C isotopic ratio down to the 10−9 level. Combined with a measured sample consumption rate of 4 ng/s, this corresponds to a capability to detect transient signals containing only a few μBq of 14C activity, such as may be obtained from chromatographic separation. The method will require further development to match the sensitivity of AMS with a gas ion source; however, even in its present state its sensitivity is well suited to tracer studies in biomedical research and drug development.

Soil and sediment samples from the Sydney basin were measured to ascertain fallout radionuclide activity concentrations and atom ratios. Caesium-137 ((137)Cs) was measured using gamma spectroscopy, and plutonium isotopes ((239)Pu and (240)Pu) were quantified using accelerator mass spectrometry (AMS). Fallout radionuclide activity concentrations were variable ranging from 0.6 to 26.1 Bq/kg for (137)Cs and 0.02-0.52 Bq/kg for (239+240)Pu. Radionuclides in creek sediment samples were an order of magnitude lower than in soils. (137)Cs and (239+240)Pu activity concentration in soils were well correlated (r(2) = 0.80) although some deviation was observed in samples collected at higher elevations. Soil ratios of (137)Cs/(239+240)Pu (decay corrected to 1/1/2014) ranged from 11.5 to 52.1 (average = 37.0 ± 12.4) and showed more variability than previous studies. (240)Pu/(239)Pu atom ratios ranged from 0.117 to 0.165 with an average of 0.146 (±0.013) and an error weighted mean of 0.138 (±0.001). These ratios are lower than a previously reported ratio for Sydney, and lower than the global average. However, these ratios are similar to those reported for other sites within Australia that are located away from former weapons testing sites and indicate that atom ratio measurements from other parts of the world are unlikely to be applicable to the Australian context.

The uranium isotope 233 U is not usually observed in alpha spectra from environmental samples due to its low natural and fallout abundance. It may be present in samples from sites in the vicinity of nuclear operations such as reactors or fuel reprocessing facilities, radioactive waste disposal sites or sites affected by clandestine nuclear operations. On an alpha spectrum, the two most abundant alpha emissions of 233 U (4.784 MeV, 13.2%; and 4.824 MeV, 84.3%) will overlap with the 234 U doublet peak (4.722 MeV, 28.4%; and 4.775 MeV, 71.4%), if present, resulting in a combined 233+234 U multiplet. A technique for quantifying both 233 U and 234 U from alpha spectra was investigated. A series of groundwater samples were measured both by accelerator mass spectrometry (AMS) to determine 233 U/ 234 U atom and activity ratios and by alpha spectrometry in order to establish a reliable 233 U estimation technique using alpha spectra. The Genie™ 2000 Alpha Analysis and Interactive Peak Fitting (IPF) software packages were used and it was found that IPF with identification of three peaks ( 234 U minor, combined 234 U major and 233 U minor, and 233 U major) followed by interference correction on the combined peak and a weighted average activity calculation gave satisfactory agreement with the AMS data across the 233 U/ 234 U activity ratio range (0.1–20) and 233 U activity range (2–300 mBq) investigated. Correlation between the AMS 233 U and alpha spectrometry 233 U was r 2 = 0.996 (n = 10).

We examined the distribution of plutonium (Pu) in the tissues of mammalian wildlife inhabiting the relatively undisturbed, semi-arid former Taranaki weapons test site, Maralinga, Australia. The accumulation of absorbed Pu was highest in the skeleton (83% ± 6%), followed by muscle (10% ± 9%), liver (6% ± 6%), kidneys (0.6% ± 0.4%), and blood (0.2%). Pu activity concentrations in lung tissues were elevated relative to the body average. Foetal transfer was higher in the wildlife data than in previous laboratory studies. The amount of Pu in the gastrointestinal tract was highly elevated relative to that absorbed within the body, potentially increasing transfer of Pu to wildlife and human consumers that may ingest gastrointestinal tract organs. The Pu distribution in the Maralinga mammalian wildlife generally aligns with previous studies related to environmental exposure (e.g. Pu in humans from worldwide fallout), but contrasts with the partitioning models that have traditionally been used for human worker-protection purposes (approximately equal deposition in bone and liver) which appear to under-predict the skeletal accumulation in environmental exposure conditions.

This paper presents an overview of ANTARES operations, describing (1) technical upgrades that now allow routine 0.3–0.4% 14 C precision for 1 mg carbon samples and 1% precision for 100 micrograms, (2) proficiency at 236 U measurements in environmental samples, (3) new developments in AMS of platinum group elements and (4), some major application projects undertaken over the period of the past three years. Importantly, the facility is poised to enter into a new phase of expansion with the recent delivery of a 2 MV 14 C tandem accelerator system from High Voltage Engineering (HVE) and a stable isotope ratio mass spectrometer from Micromass Inc. for combustion of organic samples and isotopic analysis.

Modern forensic science has to deal not only with homicides and other traditional crimes but also with more global threats such as smuggling of nuclear materials, clandestine production of weapons of mass destruction, stockpiling of illicit drugs by state-controlled groups and war crimes. Forensic applications have always benefited from the use of advanced analytical tools that can characterise materials found at crime scenes. In this paper we will discuss the use of accelerator mass spectrometry as an ultra sensitive tool for the crime labs of the third millennium.

Soil samples collected from locations in Kosovo where depleted uranium (DU) ammunition was expended during the 1999 Balkan conflict were analysed for uranium and plutonium isotopes content ( 234 U, 235 U, 236 U, 238 U, 238 Pu, 239 + 240 Pu ). The analyses were conducted using gamma spectrometry ( 235 U, 238 U ), alpha spectrometry ( 238 Pu, 239 + 240 Pu ), inductively coupled plasma–mass spectrometry (ICP—MS) ( 234 U, 235 U, 236 U, 238 U ) and accelerator mass spectrometry (AMS) ( 236 U ). The results indicated that whenever the U concentration exceeded the normal environmental values (~2 to 3 mg/kg) the increase was due to DU contamination. 236 U was also present in the released DU at a constant ratio of 236 U (mg/kg)/ 238 U (mg/kg) =2.6×10 −5 , indicating that the DU used in the ammunition was from a batch that had been irradiated and then reprocessed. The plutonium concentration in the soil (undisturbed) was about 1 Bq/kg and, on the basis of the measured 238 Pu/ 239 + 240 Pu , could be entirely attributed to the fallout of the nuclear weapon tests of the 1960s (no appreciable contribution from DU).

A certified reference material (CRM) for radionuclides in seawater, IAEA-381 (Irish Sea Water), is described and the results of certification are presented. The material has been certified for nine radionuclides (40K, 90Sr, 137Cs, 237Np, 238Pu, 239Pu,240Pu, 239,240Pu and 241Am). Information on massic activities with the corresponding 95% confidence intervals are given for eight radionuclides (3H, 125Sb, 234U, 235U, 236U, 238U, 241Pu and 244Cm). Less reported radionuclides include 60Co, 99Tc, and 242Pu. The CRM may be used for quality assurance/quality control of the analysis of radionuclides in environmental water samples, for the development and validation of analytical methods and for training purposes. The material is available from the IAEA in 5 kg units.

We have implemented a fast switching electrostatic system on the actinides beamline on the ANTARES accelerator at ANSTO, to improve the precision of analyses by accelerator mass spectrometry. This high-energy bouncing system is based on a pair of deflector plates, deflecting in the orbit plane, set at the entrance and exit of the analysing magnet. The design of deflector plates is unique, and it was modelled by SIMION in order to minimize field inhomogenity and fringe field effects. The pair of deflector plates are supplied by a high-voltage amplifier driven by an EPICS-enabled control unit, with two 4 W power supplies providing up to ±10 kV modulation. The high-energy bouncing system is synchronized with the existing low-energy bouncing system. To measure the isotopic ratio with the new system, the magnetic fields of the injector and analysing magnets are set to transmit selected isotopes along the beam line with zero voltage applied. The other isotopes of interest are transmitted by keeping the magnetic fields constant and modulating the voltages on the injector magnet chamber and on the high-energy deflector plates.

We have measured the low-energy yield of 36Cl from Ti for proton energies from 35 to 150 MeV. Thin Ti foil irradiations were performed at the Harvard University Cyclotron Laboratory and 36Cl concentrations were determined using the ANTARES AMS facility at ANSTO. Cross-sections ranged smoothly with energy from 0.32±0.05 mb at 35 MeV to 5.3±0.4 mb at 150 MeV. Results for E

The long-lived uranium isotope 236U (T1/2=23.4 Ma) is produced by 235U neutron capture and builds up to high levels in nuclear fuel. It has been distributed in the environment as a result of nuclear activities including nuclear explosions, accidents at nuclear plants, dumping of nuclear waste and releases from nuclear facilities. 236U is a potentially useful tracer of irradiated uranium for nuclear safeguards or other applications, due to its virtual absence in natural samples (236U:238U ratio ∼10−10 in uranium ore). We have measured 236U in soil and sediment reference materials (IAEA 375, 135 and 300) by accelerator mass spectrometry (AMS). The AMS system on the ANTARES accelerator has been upgraded to make such measurements possible. The system, including sample preparation procedures, is described and the results discussed.

The status and capabilities of the ANTARES AMS facility after 10 years are reviewed. The common AMS radioisotopes, 10 Be, 14 C, 26 Al, 36 Cl and 129 I, are routinely analysed. A capability for the detection of 236 U and other actinide isotopes has been developed. The measurement program includes support to Quaternary science projects at Australian universities and to ANSTO projects in global climate change and nuclear safeguards.

Little is known about the transition to the Modern Economy in non-European settings. Southeast Asia provides a rare opportunity to evaluate this transition through analysis of the tradeware production system that operated at the site of Sisatchanalai in central northern Thailand. Sisatchanalai is the largest and longest lived (A.C. 1100–1650) stoneware production complex in continental Southeast Asia. Based on the timing and nature of changes in tradeware production, we suggest that the political and economic structures present in Thailand during this era precluded its incorporation into the European periphery. Like Japan and China, Thailand successfully defined its own terms for subsequent European interaction.

The ANTARES AMS facility is fully operational and supports a research program in environmental science, with emphasis on global climate change and nuclear safeguards. A measurement program for external projects involving Australian and overseas institutions is also carried out, mainly in Quaternary science studies.

The 14C bomb-pulse signature has been measured by AMS on cross-dateable teak samples from N- and S-hemisphere locations in the tropics. Excellent agreement is found with the atmospheric 14C content in the period 1955 to 1980 for the respective hemispheres. These results demonstrate that 14C measurements can be used to facilitate growth rate determinations in tropical trees.

In conjunction with an extensive radiocarbon program, ANTARES has also carried out AMS measurement of the radioisotopes 26 Al and 36 Cl with the recent addition of 129 I. Development of an AMS measurement capability for 10 Be and for the actinides is underway. These projects pose a range of technical challenges both in spectrometer performance and in sample preparation. This paper discusses the special aspects of the facility that have been developed to meet these needs, with emphasis on 36 Cl, 129 I and plans for future actinide measurements.

The ANTARES AMS Centre at Lucas Heights Research Laboratories is currently used for measurements of the long-lived radioisotopes 14C, 26Al, 36Cl and 129I, with measurement of 10Be and actinides under development. Improved precision for 14C (to 0.5%) has been achieved with the recent commissioning of a 59 sample ion source coupled with automated data acquisition. We have developed rigorous data evaluation methods which are invaluable in assessing reproducibility and aid in the identification of physical problems with the system. Low backgrounds, in the accelerator and in the sample preparation laboratories, have allowed us to measure very old samples (to 50 000 years BP) and are also vital for high-accuracy dating of small samples.

The acid insoluble residue of twenty-nine gold-bearing and ten barren jasperoids from Carlin, Nevada, were analysed by electron paramagnetic resonance powder spectroscopy (EPR), and by simultaneous proton-induced X-ray emission (PIXE) and proton-induced gamma ray emission (PIGME) spectroscopy. The mineralised samples are characterised by high Li, F, AI, K, Ti, Rb, V, Y, and Zr values in general and by significantly higher Rb/Al and V/Al ratios in particular. The chemical differences are largely caused by the abundance and type of sericite present. Significant differences in EPR intensity exist between the mineralised and barren jasperoids.

The ANTARES accelerator mass spectrometry facility at Lucas Heights Research Laboratory is operational and AMS measurements of 14C, 26Al and 36Cl are being carried out routinely. Measurement of 129I recently commenced and capabilities for other long-lived radioisotopes such as 10Be are being established. The overall aim of the facility is to develop advanced programs in Quaternary science, global climate change, biomedicine and nuclear safeguards.

Recent results of 14 C analyses at the ANTARES AMS Centre are presented. Test measurements of 14 C blanks demonstrate an ultimate sensitivity of the order of 10 −15 ( 14 C/ 12 C ratio). Measurements of unknowns have been made with a precision in the range 1–1.5% using a “slow cycling” mode of operation where the injection magnet field is changed to inject 14 C and 13 C alternately. Results are presented for a series of log coffins from cave burials in NW Thailand.

As the debate on the role played by aluminium in Alzheimer's disease remains a controversial one, the mechanism and degree of uptake of aluminium into brain tissue is not well understood nor quantified. We report here results from the initial phase of our study of aluminium uptake and retention in tissues of rats following oral administration of a tracer dose of 26Al. An account of our biomedical findings in old rats will be described elsewhere. For a young rat population, we find 26Al retention in the liver to be 7 times that in the brain. A description of our experience in performing aluminium measurements of biological tissues is described and interpretation of the findings are given.

The ANTARES AMS facility at the Lucas Heights Research Laboratories is operational and AMS measurements of 14C and 26Al are performed routinely. Measurement programs for a variety of other long-lived cosmogenic radioisotopes are being implemented on specialised beamlines. The overall aim of the facility is to establish an AMS centre for advanced studies in global change and Quaternary science. Other projects in biomedicine and nuclear safeguards monitoring are also being developed.

The original Rutgers FN tandem accelerator has been modified for high-precision high-throughput AMS analyses at the ANTARES AMS Center. The status of this work and future plans are discussed, with emphasis on 14 C. Isotopic ratios are measured at ANTARES by sequentially injecting stable isotopes and the radioisotope, and the systems developed for this purpose are described. Progress with a new injection platform and high intensity, multi-sample ion source is also given.

Microsecond isomers in the exotic proton-richN=82, 83 nuclei153Yb,153Lu,154Lu and154Hf have been identified byγ-ray spectroscopy following mass analysis of102Pd+245 MeV54Fe reaction products using the Daresbury Recoil Separator. The decays of the isomers, interpreted asπh 11 2/ andπh 11 2/ vf7/2 states, are characterized. The reduced E2 transition rates indicate that half-filling of theπh11/2 subshell occurs just belowZ=71, and results for theN=83 odd-odd isotones are also consistent with this finding.

The growth of photochemical native oxides on x = 0.3 bulk wafers of n-type Hg1−xCdxTe has been studied with relation to growth temperature, gas flow rate, oxidizing ambient, and the wavelengths of ultraviolet radiation needed to drive the process. The growth was found to proceed with a relationship of thickness ∝ (time)1/3 for both O2 and N2O ambients. An observed inverse relationship between thickness, and both growth temperature and gas flow rate, indicates a growth process that is either competing with parasitic quenching of the excited oxidizing species produced, or a diffusion controlled process, in which different growth conditions produce oxides with a variety of diffusion characteristics. The physical and optical properties of the photochemical oxides were found to be similar to anodic oxides. Rutherford backscattering spectra have shown the composition of the films to be highly dependent on growth conditions with films grown in O2 ambients generally showing a higher mercury content than those grown in N2O. Further, for growths in O2 atmospheres, those carried out at lower temperatures result in more mercury in the oxide and at the oxide/mercury cadmium telluride interface when compared to those grown at higher temperatures.