ANSTO :: Browsing by Author "Tuniz, C"

Browsing by Author "Tuniz, C"

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14C AMS measurements of the bomb pulse in N- and S- hemisphere tropical trees
(Elsevier, 1997-03-02) Murphy, JO; Lawson, EM; Fink, D; Hotchkis, MAC; Hua, Q; Jacobsen, GE; Smith, AM; Tuniz, C
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. © 1997 Elsevier B.V.
14C analyses at the ANTARES AMS Centre: dating the log coffins of northwest Thailand
(Elsevier, 1994-06-03) Hotchkis, MAC; Fink, D; Jacobsen, GE; Lawson, EM; Shying, ME; Smith, AM; Tuniz, C; Barbetti, M; Grave, P; Quan, HM; Head, J
Recent results of 14C analyses at the ANTARES AMS Centre are presented. Test measurements of 14C blanks demonstrate an ultimate sensitivity of the order of 10−15 (14C/12C 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 14C and 13C alternately. Results are presented for a series of log coffins from cave burials in NW Thailand. © 1994 Elsevier B.V.
14C in uranium and thorium minerals: a signature of cluster radioactivity?
(Springer Nature, 1999-06-01) Bonetti, R; Guglielmetti, A; Poli, G; Sacchi, E; Fink, D; Hotchkis, MAC; Jacobsen, GE; Lawson, EM; Hua, Q; Smith, AM; Tuniz, C
Various uranium and thorium minerals have been analysed with accelerator mass spectrometry to determine their 14C content. It is found that, whenever the contribution from secondary reactions such as the 11B(α,p)14C is sufficiently low, the 14C concentration is consistent with that expected from 14C (spontaneous) cluster radioactivity from radium isotopes of the uranium and thorium natural series. © Springer-Verlag 1999
59Ni production rates in mesosiderites measured with AMS
(Wiley, 1993-07-01) Fink, D; Tuniz, C; Herzog, G; Albrecht, A; Fifield, LK; Allen, GL; Paul, M
The cosmogenic radionuclide 59 Ni(t1/2=76ka) has great potential as a monitor of thermal neutrons in metal-rich extraterrestrial materials. In deep samples from larger meteoroids (which can support a big neutron flux) containing >1% or so of nickel, thermal neturon capture on 58Ni (delta th=4.6b) is the dominate production mechanism. Near the surface of millimeter-sized bodies production occurs via primary proton, fast neutron, and a reaction channels on Fe, Co, and Ni. We have applied AMS to the measurement of 59Ni activities (see [1] for details) in four samples from the metal phase to f the mesosiderites Estherville (fall,1879) and Budulan(find). The activities range from 1.5 to 3.5 dmp/g-Ni. Related work is described in [2,3]. To discuss neutron fluxes in Budulan, we must correct the measured 59Ni activities for terrestrial age. By using measured 41Ca activities (13-19 dpm/kg-Fe [4]) and a maximum production rate PFe(41Ca), in stony irons of 21dpm/kg-Fe [5] we deduce a maximum terrestrial age of 35 ka. After correction for this terrestrial age and normalization of L-chondrite composition [6], the production rates of 59Ni,PFe(59Ni), range from 5-13 dpm/g-Ni; these values are 2-3x greater than those reported in [7] for large irons and ~10x those for chondrites. Albrecht et al. [4] and Fink et al. [8] present 41Ca data in the silicate and metal phases from the same Estherville and Budulan samples. If thermal neutron production were solely responsible for PFe(59Ni) and PS2(41Ca) (the latter corrected for spalliation of oxidized iron in pyroxene), the thermal neutron fluxes, o, inferred from each nuclide in a sample should be the same. We deduce ratios of o(59Ni)/o(41Ca) that range from 0.75 to 1.65. Differences in epithermal yields can account for only a minor fraction of this variation as the ratio of the total resonant neutron absorption intergrals for 40Ca and 58Ni is within 10% of the ratio of the thermal neutron cross sections alone. A twofold change in Budulan's terrestrial age alters the flux ratio by 10% at most. Like 41Ca[9,10], PFe(59Ni) can be used to estimate shielding depths and lower limits on the preatmospheric radius. Calculations by [11] give a maximum value for PFe(59Ni) of 22 atoms/min/g-Ni at the center of an L chondrite with a radius of 300 g/cm2. The 10Be and 26A1 activities in Estherville [5] and respective semi-empirical production rate formulas [12] set a maximum meteoroid radius of 300 g/cm2. Our measured value for 59Ni implies a lower radius limit of 150 g/cm2 and shielding depths of 60-150g/cm2. Similarly, we suggest a radius of 200< R < 400 g/cm2 and shielding depths from 40-200 g/cm2 for Budalan. We infer that the above samples originated at relatively large depths (except for perhaps Budulan 2428) in meteoroids with preatmospheric radii >30cm, assuming a mesosiderite density of 5.5 g/cm3. Interestingly, those samples (Budulan2357 and Estherville 3311) having 41Ca production rates that indicate a higher degree of shielding have flux rations equal to or less than 1; the other two samples have 41Ca contents typical of near-surface exposure and have ratios o(59Ni)/o(41Ca) larger than unity. This correlation indicates that P59 from fast neutron reactions on 60,61Ni enhances 59Ni production at near-surface regions.
Accelerator mass spectrometry analyses of environmental radionuclides: sensitivity, precision and standardisation
(Elsevier, 2000-10-01) Hotchkis, MAC; Fink, D; Tuniz, C; Vogt, S
Accelerator Mass Spectrometry (AMS) is the analytical technique of choice for the detection of long-lived radionuclides which cannot be practically analysed with decay counting or conventional mass spectrometry. AMS allows an isotopic sensitivity as low as one part in 1015 for 14C (5.73 ka), 10Be (1.6 Ma), 26Al (720 ka), 36Cl (301 ka), 41Ca (104 ka), 129I (16 Ma) and other long-lived radionuclides occurring in nature at ultra-trace levels. These radionuclides can be used as tracers and chronometers in many disciplines: geology, archaeology, astrophysics, biomedicine and materials science. Low-level decay counting techniques have been developed in the last 40–50 years to detect the concentration of cosmogenic, radiogenic and anthropogenic radionuclides in a variety of specimens. Radioactivity measurements for long-lived radionuclides are made difficult by low counting rates and in some cases the need for complicated radiochemistry procedures and efficient detectors of soft β-particles and low energy x-rays. The sensitivity of AMS is unaffected by the half-life of the isotope being measured, since the atoms not the radiations that result from their decay, are counted directly. Hence, the efficiency of AMS in the detection of long-lived radionuclides is 106–109 times higher than decay counting and the size of the sample required for analysis is reduced accordingly. For example, 14C is being analysed in samples containing as little as 20 μg carbon. There is also a world-wide effort to use AMS for the analysis of rare nuclides of heavy mass, such as actinides, with important applications in safeguards and nuclear waste disposal. Finally, AMS microprobes are being developed for the in-situ analysis of stable isotopes in geological samples, semiconductors and other materials. Unfortunately, the use of AMS is limited by the expensive accelerator technology required, but there are several attempts to develop compact AMS spectrometers at low (⩽0.5 MV) terminal voltages. Recent advances in AMS will be reviewed with highlights from the scientific programs at Lucas Heights and other AMS centres. © 2000 Elsevier Science Ltd.
Accelerator mass spectrometry ultrasensitive analysis for global science
(CRC Press, 1998-03-25) Tuniz, C; Kutschera, W; Fink, D; Herzog, GF; Bird, JR
This extensive undertaking, Accelerator Mass Spectrometry, conducts an elaborate and comprehensive summary of one of the foremost catalysts of progress in scientific research. Accelerator mass spectrometry (AMS), an innovative analytical technique, measures rare atoms at unprecedented levels of sensitivity, revolutionizing the science of radiocarbon dating and accessing new natural radioisotopes as environmental tracers and chronometers. This book demonstrates how AMS is applied in the studies of extraterrestrial materials, the earth sciences, the future of the global environment, and the history of mankind. This compendium also highlights the significant impact of AMS on several fields of scientific investigation, spurring remarkable studies in global climate change, ancient artifacts, pollution, nuclear safeguards, geochronology, and materials characterization. The myriad of sample types and variety of applications in this examination include: Meteorites from Mars Ancient air trapped in Antarctic ice The Shroud of Turin The dating of human bones The colonization of the Americas and Australia Ancient rock art The crown of Charlemagne Cancerogenic effects of cooked meat The consequences of the Chernobyl accident The role of aluminum in Alzheimer's Disease This unique edition has compiled the diverse set of scientific literature into a single volume, suitable as a text or resource on the major AMS-related outcomes, issues, and methods.
Accelerator mass spectrometry: ultra-sensitive analysis for global science
(Elsevier B. V., 2001-08-07) Tuniz, C
Accelerator mass spectrometry (AMS) is the analytical technique of choice for the detection of long-lived radionuclides that cannot be practically analysed with decay counting or conventional mass spectrometry. AMS has been used for the analysis of 14C, 10Be, 36Cl and other cosmogenic radionuclides in archaeology, geology and environmental science. In addition, the ultrasensitivity of AMS is being applied in biomedicine to study the exposure of human tissues to chemicals and biomolecules at attomole levels. AMS is also being considered for the detection of anthropogenic radionuclides, such as 129I and 236U, in environmental samples for the verification of the nuclear non-proliferation agreements. The state of the art of AMS is reviewed with examples from some recent applications. © 2001 Elsevier Science Ltd.
AMS at ANTARES – the first 10 years
(Elsevier, 2000-10) Lawson, EM; Elliott, G; Fallon, J; Fink, D; Hotchkis, MAC; Hua, Q; Jacobsen, GE; Lee, P; Smith, AM; Tuniz, C; Zoppi, U
The status and capabilities of the ANTARES AMS facility after 10 years are reviewed. The common AMS radioisotopes, 10Be, 14C, 26A1, 36C1 and 129I, are routinely analysed. A capability for the detection of 236U 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. © 2000 Elsevier Science B.V.
AMS measurement of 129I, 36C1 and 14C in underground waters from Mururoa and Fangataufa atolls
(Elsevier, 2000-10) Jacobsen, GE; Hotchkis, MAC; Fink, D; Child, DP; Tuniz, C; Sacchi, E; Levins, DM; Povinec, PP; Mulsow, S
AMS analyses of 36Cl, 129I and 14C in underground water have been performed as part of IAEA’s assessment of the radiological situation at Mururoa and Fangataufa atolls. The samples consisted of waters from monitoring wells, and from two cavity-chimneys created by underground nuclear tests. The water samples from the monitoring wells contained varying concentrations of radionuclides, with the highest concentrations of radionuclides found in the two test cavity-chimneys. A comparison of the concentrations of radionuclides determined by AMS, 36Cl and 129I, and with radionuclides determined using conventional methods, 3H, 90Sr and 137Cs, shows a reasonable correlation. However, some differences in behaviour, mainly attributed to differences in the sorption characteristics of the elements, are discernible. The concentrations of radionuclides in the underground environment were used to validate geosphere transport models. © 2000 Elsevier Science B.V.
AMS radiocarbon analysis of microsamples
(Australian Institute of Nuclear Science and Engineering, Australian Nuclear Science & Technology Organisation and Australian Museum, 1997-02-12) Jacobsen, GE; Hua, Q; Tarshishi, J; Fink, D; Hotchkis, MAC; Lawson, EM; Smith, AM; Tuniz, C
The ANTARES AMS Centre has two chemistry laboratories dedicated to preparing targets for measurement. Target preparation encompasses a variety of activities ranging from the curation of incoming samples to the numerous steps involved in the purification and processing of dissimilar samples. One of the two laboratories is set up for the physical and chemical pretreatment of 14C samples. Treatments include cleaning by sonification, sorting, grinding and sieving, and chemical treatments such as the standard AAA treatment, and solvent extraction. Combustion and graphitisation are also carried out in this laboratory. The second laboratory is a clean room and is dedicated to the combustion, hydrolysis and graphitisation of 14C samples as well as processing targets for the other isotopes. Combustion is achieved by heating the sample to 900 deg C in the presence of CuO, the resulting gas is purified by passing over Ag and Cu wire at 600 deg C. Graphitisation is carried out by reducing the CO{sub 2} with an iron catalyst (600 deg C) in the presence of zinc (400 deg C) and a small amount of hydrogen. Samples such as charcoal, shell, bone, wood, sediment, seawater and groundwater, containing 0.3-1 mg or more of original carbon, are processed routinely for radiocarbon analysis. The current 14C chemistry background for 1 mg carbon is approx. 0.3 percent of modern carbon (pMC) enabling materials` dating up to 45 000 BP.
The ANTARES AMS Centre : a status report
(Cambridge University Press, 2016-07-18) Tuniz, C; Fink, D; Hotchkis, MAC; Jacobsen, GE; Lawson, EM; Smith, AM; Hua, Q; Drewer, P; Lee, P; Levchenko, VA; Bird, R; Boldeman, JW; Barbetti, M; Taylor, G; Head, J
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. © the Department of Geosciences, The University of Arizona
The ANTARES AMS Centre at the Lucas Heights Research Laboratories
(Elsevier, 1994-06-03) Tuniz, C; Fink, D; Hotchkis, MAC; Jacobsen, GE; Lawson, EM; Smith, AM; Bird, JR; Boldeman, JW
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. © 1994 Elsevier B.V.
Applications of accelerator physics and ANSTO
(Australian Institute of Physics, 1998-04) Tuniz, C
The Australian Nuclear Science and Technology Organisation (ANSTO) is involved in advanced research programs based on the use of nuclear science and technology for materials microanalysis. This paper is a review of accelerator-based probes to characterise environmental, biological, and industrial materials. Most examples are inspired by the ANSTO research program.
Beeswax as dental filling on a Neolithic human tooth
(Public Library of Science, 2012-09-19) Bernardini, F; Tuniz, C; Coppa, A; Mancini, L; Dreossi, D; Eichert, D; Turco, G; Biasotto, M; Terrasi, F; De Cesare, N; Hua, Q; Levchenko, VA
Evidence of prehistoric dentistry has been limited to a few cases, the most ancient dating back to the Neolithic. Here we report a 6500-year-old human mandible from Slovenia whose left canine crown bears the traces of a filling with beeswax. The use of different analytical techniques, including synchrotron radiation computed micro-tomography (micro-CT), Accelerator Mass Spectrometry (AMS) radiocarbon dating, Infrared (IR) Spectroscopy and Scanning Electron Microscopy (SEM), has shown that the exposed area of dentine resulting from occlusal wear and the upper part of a vertical crack affecting enamel and dentin tissues were filled with beeswax shortly before or after the individual's death. If the filling was done when the person was still alive, the intervention was likely aimed to relieve tooth sensitivity derived from either exposed dentine and/or the pain resulting from chewing on a cracked tooth: this would provide the earliest known direct evidence of therapeutic-palliative dental filling. © 2012, The Authors
Environmental monitoring in support of international nuclear safeguards and test ban agreements
(The Institution of Engineers Australia, 1994-05-01) Boldeman, JW; Tuniz, C
Long-lived radioisotopes introduced into the environment by tests of nuclear weapons and by the operation of nuclear fuel reprocessing plants can be analysed with ultra-high sensitivity by accelerator mass spectrometry (AMS). Isotopic concentrations of 106 atoms per gram and isotopic ratios of 1 part in 1015 can be detected in milligram samples taken from selected environmental media. ANSTO is setting up specialized beamlines at the ANTARES AMS system for the ultrasensitive analysis of long-lived radioisotopes, such as 129I, produced by nuclear activities and for the direct detection of uranium, plutonium and other actinides. It is believed that these new analytical methods will be valuable in the verification of compliance with the terms of international safeguards and nuclear test ban treaties.
Equipment and methodology for high precision, high throughput 14C AMS analyses at ANTARES
(Elsevier, 1994-06-03) Smith, AM; Fink, D; Hotchkis, MAC; Jacobsen, GE; Lawson, EM; Shying, ME; Tuniz, C; Watt, GC; Fallon, J; Ellis, PJ
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 14C. 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. © 1994 Elsevier B.V.
Exposure history of the Torino meteorite
(Wiley, 1996-03) Wieler, R; Graf, T; Signer, P; Vogt, S; Herzog, GF; Tuniz, C; Fink, D; Fifield, LK; Klein, J; Middleton, R; Jull, AJT; Pellas, P; Masarik, J; Dreibus, G
We determined He, Ne, Ar, 10Be, 26Al, 36Cl, and 14C concentrations, as well as cosmic-ray track densities and halogen concentrations in different specimens of the H6 chondrite Torino, in order to constrain its exposure history to cosmic radiation. The Torino meteoroid had a radius of ∼20 cm and travelled in interplanetary space for 2.5–10 Ma. Earlier, Torino was part of a larger body. The smallest possible precursor had a radius of 55 cm and a journey through space longer than ∼65 Ma. If the first-stage exposure took place in a body with a radius of >3 m or in the parent asteroid, then it lasted nearly 300 Ma. The example of Torino shows that it is easy to underestimate first-stage exposure ages when constructing two-stage histories. © 1999-2021 John Wiley & Sons, Inc.
First 26Al analyses at the ANTARES AMS Centre: uptake via oral ingestion of 26Al in rats
(Elsevier, 1994-06-03) Fink, D; Walton, J; Hotchkis, MAC; Jacobsen, GE; Lawson, EM; Smith, AM; Tuniz, C; Wilcox, D
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. © 1994 Elsevier B.V.
Forensic applications of 14C bomb-pulse dating
(Elsevier, 2004-08-01) Zoppi, U; Skopec, Z; Skopec, J; Jones, G; Fink, D; Jacobsen, GE; Tuniz, C; Williams, AA
After a brief review of the basics of 14C bomb-pulse dating, this paper presents two unique forensic applications. Particular attention is dedicated to the use of the 14C bomb-pulse to establish the time of harvest of illicit drugs such as heroin and opium. Preliminary measurements of 14C concentrations in milligram samples taken from seized drugs are presented. 14C bomb-pulse dating can determine whether drug distribution originates from stockpiles or recent manufacture, and support the action of law enforcement authorities against criminal organisations involved in drug trafficking. In addition, we describe the dating of wine vintages for a number of authenticated single label vintage red wines from the Barossa Valley – South Australia. Our results show that radiocarbon dating can be used to accurately determine wine vintages and therefore reveal the addition of unrelated materials of natural and synthetic origin. © 2004 Elsevier B.V.
High-precision radiocarbon measurements at the ANTARES AMS Centre
(Elsevier, 1996-06-01) Hotchkis, MAC; Fink, D; Hua, Q; Jacobsen, GE; Lawson, EM; Smith, AM; Tuniz, C
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. © 1996 Elsevier Science B.V.

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