Browsing by Author "Wyllie, HA"

Now showing 1 - 11 of 11
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    Calibration and operation of the AAEC working standard of measurement for the activity of radionuclides, Part 2 - ion chamber analysis
    (Australian Atomic Energy Commission, 1986-05) Wyllie, HA
    As a secondary method for the determination of radioactivity the ion chamber is both convenient and precise. The equations used in the calibration of the equipment and in the calculation of unknown activities are fully derived and it is shown that the experimental procedure outlined is the optimum for both precision and convenience.
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    Campion's coincidence-counting corrections revisited
    (Australian Nuclear Science and Technology Organisation, 1994-10) Wyllie, HA
    Detailed derivations are given of some of Campion's formulae. Improved versions of some formulae are also derived. Efficiency extrapolation is dealt with briefly.
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    Coincidence counting corrections for dead time losses and accidental coincidences
    (Australian Atomic Energy Commission, 1987-04) Wyllie, HA
    An equation is derived for the calculation of the radioactivity of a source from the results of coincidence counting, taking into account the dead-time losses and accidental coincidences. The derivation is an extension of the method of J. Bryant [Int. J. Appl. Radiat. Isot. 14:143 1963]. The improvement on Bryant's formula has been verified by experiment.
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    Coincidence-counting corrections for accidental coincidences, set dead time and intrinsic dead time
    (Australian Nuclear Science and Technology Organisation, 1991-12) Wyllie, HA
    An equation is derived for calculating the radioactivity of a source from the results of coincidence counting taking into account dead-time losses and accidental coincidences. The corrections allow for the extension of the set dead time in the β channel by the intrinsic dead time. Experimental verification shows improvement over a previous equation.
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    Correction for intrinsic and set dead-time losses in radioactivity counting
    (Australian Nuclear Science and Technology Organisation, 1992-12) Wyllie, HA
    Equations are derived for the determination of the intrinsic dead time of the components which precede the paralysis unit in a counting system for measuring radioactivity. The determination depends on the extension of the set dead time by the intrinsic dead time. Improved formulae are given for the dead-time correction of the count rate of a radioactive source in a single-channel system. A variable in the formulae is the intrinsic dead time which is determined concurrently with the counting of the source. The only extra equipment required in a conventional system is a scaler.
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    Derivation of the dead-time correction equation for a radioactivity detector.
    (Australian Nuclear Science and Technology Organisation, 2009-09) Wyllie, HA
    When a radioactive source is being counted, a detected disintegration cannot be recorded during a Dead-Time period. In this report experiments are described which show that the graph of the distribution of detected disintegrations during Dead-Time periods is a horizontal line. Based on this observation, an alternative derivation is produced of the widely used Dead-Time correction equation for a radioactivity detector.
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    The determination of barium-133 by efficiency extrapolation.
    (Australian Nuclear Science and Technology Organisation, 2009-08) Wyllie, HA
    A β-efficiency-extrapolation method for the determination of radioactivity makes use of a coincidence-counting system with two β-counting channels. In one channel, the efficiency is reduced by a linear gate which is controlled by a wave-form composer. The intermittent closing of the gate is a random process.
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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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    The preparation of radioactive sources with radioactivities of less than 110 kilobecquerels.
    (Australian Nuclear Science and Technology Organisation, 1989-03) Wyllie, HA
    A description is given of the various radioactive sources prepared in the ANSTO Radioisotope Standards Laboratory and the procedures associated with their preparation. ANSTO is authorised by CSIRO to maintain the Commonwealth standard of activity of radionuclides. Counting sources are required for the standardisation of solutions of radionuclides. Calibration sources are required for equipment used to detect radioactivity such as gamma-ray spectrometers and can be supplied to clients in other organisations. The maximum radioactivity supplied is 110 kBq.
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    The production of ultra-thin layers of ion-exchange resin and metallic silver by electrospraying
    (Australian Atomic Energy Commission, 1988-10) Wyllie, HA
    Highly efficient radioactive sources for use in radioisotope metrology have been prepared on ultra-thin layers of electrosprayed ion-exchange resin. The efficiency of these sources can be reduced for the purpose of radioactivity standardisation by coating them with conducting silver layers which are also produced by electrospraying. A description is given of improvements to the electrospraying methods together with details of the rotating oscillating source-mount turntable.
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    Radioactivity determination by coincidence counting. Part 1 - setting up the equipment and the standardisation of cobalt-60
    (Australian Nuclear Science and Technology Organisation, 1987-11) Wyllie, HA
    The 4 pi β-γ coincidence counting equipment used in the Lucas Heights radioisotope standards laboratory for international comparisons is described in detail. A radioactivity standard is a method rather than a material object; as such it can be specified clearly only by discussing fully the setting-up and operation of one particular set of equipment. This manual is written for persons who are setting up such equipment for the first time.