Browsing by Author "Kitchen, R"

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    Accelerator mass spectrometry on SIRIUS: new 6MV spectrometer at ANSTO
    (Elsevier, 2016-07-08) Wilcken, KM; Fink, D; Hotchkis, MAC; Garton, D; Button, D; Mann, M; Kitchen, R
    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 10Be, 26Al and 36Cl are presented.
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    Accelerator mass spectrometry on SIRIUS: new 6MV spectrometer at ANSTO
    (University of Jyväskylä, Finland, 2016-07-03) Wilcken, KM; Fink, D; Hotchkis, MAC; Garton, D; Button, D; Mann, M; Kitchen, R
    As a part of Australian Federal Government funding in 2009 to establish a centre for accelerator science a new 6 MV state of the art accelerator – SIRIUS – was purchased. The system is now commissioned and comprises ion sources and beam lines to cater for a wide variety of both IBA and AMS applications. The ion source used for AMS (MC-SNICS) is the latest incarnation followed by 45 degree spherical ESA(R=0.3 m) and double focusing injection magnet (R=1 m, ME=20) prior the accelerator. At the terminal we have a choice of 2 stripper gasses and/or stripper foils. The high-energy spectrometer for AMS consists of a 1.27 m radius analyzing magnet with ME=176, 45 degree ESA (R=3.81m), followed by a switching magnet and 3 beam lines: one with a standard multianode ionization chamber; one with an absorber cell in front of the detector; whereas the third beam line has a time-of- ight detector. Details of the instrument design and performance data for 10Be, 26Al and 36Cl will be presented. © The Authors
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    Actinides isotopic analysis using a 1 MV AMS system
    (University of Jyväskylä, Finland, 2016-07-03) Hotchkis, MAC; Child, DP; Wilcken, KM; Kitchen, R
    The VEGA 1 MV AMS system at ANSTO has been custom-designed to cover analysis of a wide range of long-lived radioisotopes, including routine radiocarbon analysis and multiple-isotope analysis of actinides. The system incorporates 1.0 m radius injection and analysing magnets with o -axis cups on high and low mass sides. Following the analysing magnet, rare isotope beams pass through a 1m radius spherical electrostatic analyser and a 120 1 m radius magnet. The detector station consists of a two-anode gas detector, with o -axis options to direct isotopes to either a Faraday cup or an electron multiplier ion counter. All three analysing magnets are fitted with electrostatic bouncer systems. At the LE end, the bouncer works in the usual way for all isotope combinations of interest, including 12C-13C-14C and actinides. The HE bouncers are used to transmit a range of masses of interest for actinides analysis, for example mass 239 to 244 Pu isotopes. For uranium analysis, the less rare isotopes can be directed to o axis cups or the ion counter. Software has been implemented to enable a high degree of exibility in analysing up to 8 isotopes at a time. In this paper we present details of the system and its performance and applications. © The Authors
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    From carbon to actinides: a new universal 1MV accelerator mass spectrometer at ANSTO
    (Elsevier, 2015-10-15) Wilcken, KM; Hotchkis, MAC; Levchenko, VA; Fink, D; Hauser, T; Kitchen, R
    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. © 2015 Elsevier B.V.
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    Negative ionisation efficiencies for 10Be, 26Al and Pu with MCSNICS at ANSTO
    (Australian Nuclear Science and Technology Organisation, 2021-11-17) Wilcken, KM; Child, DP; Hotchkis, MAC; Mann, M; Simon, KJ; Koll, D; Wallner, A; Hauser, T; Kitchen, R
    Low overall detection efficiency for actinides and cosmogenic isotopes (Al, Be) is the limiting factor affecting precision and sensitivity for applications where the amount of available sample material is small and/or rare isotope concentration is low. Due to low ionisation efficiencies for these isotopes it is not uncommon that more than 99% of the rare isotopes in the sample do not contribute to the statistical precision of the measurement. Optimising ion transmission and detection efficiency in the AMS measurement offers some room for improvement but these avenues are already close to their theoretical limits. On the other hand, optimising the performance and operation of the negative ion Cs-sputter sources has significant scope for improvement but is challenging. One often needs to compromise between competing requirements, for example, maintaining high sputtering rate to allow expedient consumption of the sample material but at the same time keeping the source insulators clean for longevity. The lack of a well-understood theoretical model for the negative ionisation process adds to the engineering challenges. Negative ionisation efficiencies above 30% have been demonstrated for radiocarbon [1] but remain often more than an order of magnitude lower for Be, Al and actinides. This is sometimes taken to be an inherent limitation of the technique, rather than a challenge to be addressed. Here we present details of the modified MC-SNICS sources at ANSTO, including engineering modifications that have improved longevity and stability. With attention to a combination of ion source running conditions, sample masses and sample binders the total efficiency for Pu measurements was increased up to 1.5%, corresponding to a negative ionisation yield of 4%. For Aland BeO- negative ion source yields are 0.2% and 3%, respectively.