Browsing by Author "Watt, GC"

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    The ANSTO isotope cycling system
    (Cambridge University Press, 2016-02-09) Watt, GC; Boronkay, S; Smith, AM; Hotchkis, MAC
    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 μs, 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. © 2013 Arizona Board of Regents on behalf of the University of Arizona
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    Application of the CORIS360 Gamma Ray Imager at a light source
    (JACoW Publishing, 2021-05-24) Tan, YRE; Boardman, DA; Chartier, L; Guenette, MC; Ilter, M; Watt, GC
    The CORIS360 is a gamma-ray imager developed at Australian Nuclear Science and Technology (ANSTO) for identifying and localising sources of radiation typically from gamma emitting radionuclides. The low EMI and low noise power supply features of the imaging technology have enabled it to have a low energy detection threshold and to detect photons as low as 20 keV. This report shall present the initial measurements performed at the Australian Synchrotron, in the storage ring and beamlines, where the imager is able to detect radiation from all sources of synchrotron radiation (dipole, wiggler and undulator). The radiation imaging results from the injection system and scrapers (to dump the stored beam) will be discussed. Future developments for imaging in pulsed radiation environments and time varying environments will also be discussed. © 2021 JACoW
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    Charge transport properties of CdMnTe radiation detectors
    (EDP Sciences, 2012-04-11) Rafiei, R; Boardman, DA; Reinhard, MI; Sarbutt, A; Kim, KH; Watt, GC; Uxa, S; Prokopovich, DA; Belas, E; Bolotnikov, AE; James, RB
    Growth, fabrication and characterization of indium-doped cadmium manganese telluride (CdMnTe) radiation detectors have been described. Alpha-particle spectroscopy measurements and time resolved current transient measurements have yielded an average charge collection efficiency approaching 100 %. Spatially resolved charge collection efficiency maps have been produced for a range of detector bias voltages. Inhomogeneities in the charge transport of the CdMnTe crystals have been associated with chains of tellurium inclusions within the detector bulk. Further, it has been shown that the role of tellurium inclusions in degrading charge collection is reduced with increasing values of bias voltage. The electron drift velocity was calculated from the rise time distribution of the preamplifier output pulses at each measured bias. From the dependence of drift velocity on applied electric field the electron mobility was found to be μn = (718 ± 55) cm2/Vs at room temperature. © 2012 the Authors, published by EDP Sciences.
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    Digital coincidence counting - initial results
    (Elsevier, 2000-08-01) Butcher, KSA; Watt, GC; Alexiev, D; van der Gaast, H; Davies, JB; Mo, L; Wyllie, HA; Keightley, JD; Smith, D; Woods, MJ
    Digital Coincidence Counting (DCC) is a new technique in radiation metrology, based on the older method of analogue coincidence counting. It has been developed by the Australian Nuclear Science and Technology Organisation (ANSTO), in collaboration with the National Physical Laboratory (NPL) of the United Kingdom, as a faster more reliable means of determining the activity of ionising radiation samples. The technique employs a dual channel analogue-to-digital converter acquisition system for collecting pulse information from a 4π beta detector and an NaI(Tl) gamma detector. The digitised pulse information is stored on a high-speed hard disk and timing information for both channels is also stored. The data may subsequently be recalled and analysed using software-based algorithms. In this letter we describe some recent results obtained with the new acquistion hardware being tested at ANSTO. The system is fully operational and is now in routine use. Results for 60Co and 22Na radiation activity calibrations are presented, initial results with 153Sm are also briefly mentioned. © 2000, Elsevier Ltd.
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    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.
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    High-purity CdMnTe radiation detectors: a high-resolution spectroscopic evaluation
    (Intistute of Electrical Engineers, 2013-02-07) Rafiei, R; Reinhard, MI; Kim, KH; Prokopovich, DA; Boardman, DA; Sarbutt, A; Watt, GC; Bolotnikov, AE; Bignell, LJ; James, RB
    The charge transport properties of a high-purity CdMnTe (CMT) crystal have been measured at room temperature down to a micron-scale resolution. The CMT crystal, doped with indium, was grown by the vertical Bridgman technique. To reduce the residual impurities in the Mn source material, the growth process incorporated a five-times purification process of MnTe by a zone-refining method with molten Te solvent. The resulting 2.6 mm thick crystal exhibited an electron mobility-lifetime product of μnτn=2.9 × 10-3 cm2V-1. The velocity of electron drift was calculated from the rise time distribution of the preamplifier's output pulses at each measured bias. The electron mobility was extracted from the electric field dependence of the drift velocity and at room temperature it has a value of μn=(950±90) cm2/Vs. High-resolution maps of the charge collection efficiency have been measured using a scanning microbeam of 5.5 MeV 4He2+ ions focused to a beam diameter <; 1 μm and display large-area spatial uniformity. The evolution of charge collection uniformity across the detector has been highlighted by acquiring measurements at applied biases ranging between 50 V and 1100 V. Charge transport inhomogeneity has been associated with the presence of bulk defects. It has been demonstrated that minimizing the content of impurities in the MnTe source material is highly effective in achieving major improvements in the CMT detector's performance as compared to previous data. © 2013, IEEE.