Browsing by Author "Altzitzoglou, T"

Now showing 1 - 4 of 4
  • No Thumbnail Available
    Item
    Comparison of triple-to-double coincidence ratio (TDCR) efficiency calculations and uncertainty assessments for Tc-99
    (Elsevier, 2010-07) Zimmerman, BE; Altzitzoglou, T; Rodrigues, D; Broda, R; Cassette, P; Mo, L; Ratel, G; Simpson, BRS; van Wyngaardt, WM; Watjen, C
    A comparison exercise for data analysis was recently conducted by the Liquid Scintillation Counting Working Group (LSCWG) of the International Committee on Radionuclide Metrology (ICRM) to evaluate the uncertainties involved in applying different analysis methodologies (including computer programs) for the triple-to-double coincidence ratio (TDCR) method. The goals of the comparison were to (1) study differences in calculation results from different TDCR analysis programs, (2) investigate differences in analysis techniques and uncertainty assessment philosophies between laboratories, and (3) study the effect of not taking asymmetry of photomultiplier tube (PMT) efficiencies into account on the calculated activity. To achieve this, a single set of TDCR data for the pure beta emitter 99Tc, was distributed to the participants, who analyzed the data according to their normal procedures and report the activity concentration of the 99Tc solution from their results. The results indicate that the presently used programs are generally able to calculate the same activity values, assuming that the correct input parameters are used and that not taking PMT asymmetry into account in the calculations can lead to significant (0.6% for 99Tc) errors in reported results. The comparison also highlighted the need for a more rigorous approach to estimating and reporting uncertainties. © 2010, Elsevier Ltd.
  • Thumbnail Image
    Item
    Evidence against solar influence on nuclear decay constants
    (Elsevier B. V., 2016-10-10) Pommé, S; Stroh, H; Paepen, J; Van Ammel, R; Marouli, M; Altzitzoglou, T; Hult, M; Kossert, K; Nähle, O; Schrader, H; Juget, F; Bailat, CJ; Nedjadi, Y; Bochud, F; Buchillier, T; Michotte, C; Courte, S; van Rooy, MW; van Staden, MJ; Lubbe, J; Simpson, BRS; Fazio, A; De Felice, P; Jackson, TW; van Wyngaardt, WM; Reinhard, MI; Golya, J; Bourke, S; Roy, T; Galea, R; Keightley, JD; Ferreira, KM; Collins, SM; Ceccatelli, A; Unterweger, MP; Fitzgerald, R; Bergeron, DE; Pibida, L; Verheyen, L; Bruggeman, M; Vodenik, B; Korun, M; Chisté, V; Amiot, MN
    The hypothesis that proximity to the Sun causes variation of decay constants at permille level has been tested and disproved. Repeated activity measurements of mono-radionuclide sources were performed over periods from 200 days up to four decades at 14 laboratories across the globe. Residuals from the exponential nuclear decay curves were inspected for annual oscillations. Systematic deviations from a purely exponential decay curve differ from one data set to another and are attributable to instabilities in the instrumentation and measurement conditions. The most stable activity measurements of alpha, beta-minus, electron capture, and beta-plus decaying sources set an upper limit of 0.0006% to 0.008% to the amplitude of annual oscillations in the decay rate. Oscillations in phase with Earth's orbital distance to the Sun could not be observed within a to range of precision. There are also no apparent modulations over periods of weeks or months. Consequently, there is no indication of a natural impediment against sub-permille accuracy in half-life determinations, renormalisation of activity to a distant reference date, application of nuclear dating for archaeology, geo- and cosmochronology, nor in establishing the SI unit becquerel and seeking international equivalence of activity standards. © 2016 The Authors. Published by Elsevier B.V.
  • Thumbnail Image
    Item
    On decay constants and orbital distance to the Sun—part III: beta plus and electron capture decay
    (IOP Publishing, 2016-11-28) Pommé, S; Stroh, H; Paepen, J; Van Ammel, R; Marouli, M; Altzitzoglou, T; Hult, M; Kossert, K; Nähle, O; Schrader, H; Juget, F; Bailat, C; Nedjadi, Y; Bochud, F; Buchillier, T; Michotte, C; Courte, S; van Rooy, MW; van Staden, MJ; Lubbe, J; Simpson, BRS; Fazio, A; De Felice, P; Jackson, TW; van Wyngaardt, WM; Reinhard, MI; Golya, J; Bourke, S; Roy, T; Galea, R; Keightley, JD; Ferreira, KM; Collins, SM; Ceccatelli, A; Verheyen, L; Bruggeman, M; Vodenik, B; Korun, M; Chisté, V; Amiot, MN
    The hypothesis that seasonal changes in proximity to the Sun cause variation of decay constants at permille level has been tested for radionuclides disintegrating through electron capture and beta plus decay. Activity measurements of 22Na, 54Mn, 55Fe, 57Co, 65Zn, 82+85Sr, 90Sr, 109Cd, 124Sb, 133Ba, 152Eu, and 207Bi sources were repeated over periods from 200 d up to more than four decades at 14 laboratories across the globe. Residuals from the exponential nuclear decay curves were inspected for annual oscillations. Systematic deviations from a purely exponential decay curve differ from one data set to another and appear attributable to instabilities in the instrumentation and measurement conditions. Oscillations in phase with Earth's orbital distance to the sun could not be observed within 10−4–10−5 range precision. The most stable activity measurements of β+ and EC decaying sources set an upper limit of 0.006% or less to the amplitude of annual oscillations in the decay rate. There are no apparent indications for systematic oscillations at a level of weeks or months. © The Authors CC BY 3.0 licence
  • No Thumbnail Available
    Item
    Results of the CCRI(II)-S12.H-3 supplementary comparison: comparison of methods for the calculation of the activity and standard uncertainty of a tritiated-water source measured using the LSC-TDCR method
    (Elsevier B. V., 2018-04) Cassette, P; Altzitzoglou, T; Anthohe, A; Rossi, M; Arinc, A; Capogni, M; Galea, R; Gudelis, A; Kossert, K; Lee, KB; Liang, J; Nedjadi, Y; Oropesa Verdecia, P; Shilnikova, T; van Wyngaardt, WM; Ziemek, T; Zimmerman, BE
    A comparison of calculations of the activity of a 3H2O liquid scintillation source using the same experimental data set collected at the LNE-LNHB with a triple-to-double coincidence ratio (TDCR) counter was completed. A total of 17 laboratories calculated the activity and standard uncertainty of the LS source using the files with experimental data provided by the LNE-LNHB. The results as well as relevant information on the computation techniques are presented and analysed in this paper. All results are compatible, even if there is a significant dispersion between the reported uncertainties. An output of this comparison is the estimation of the dispersion of TDCR measurement results when measurement conditions are well defined. © 2017 Elsevier Ltd.