Program - Brookhaven National Laboratory

LE 5 5:00 PM
Method of Best Representation for Averages in Data Evaluation
M. Birch and B. Singh
Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1, Canada
A novel statistical approach to the averaging procedures in data evaluation is developed based on producing
a mean probability density function to represent the data set. This Method of Best Representation (MBR)
is shown to have desirable properties including being robust to outliers and agreement with the standard
weighted average (weighting by the reciprocal of the square of the uncertainty in the measurement) in
the case of non-discrepant data. Examples from isotopic half-life and gamma-ray intensity data will be
discussed to illustrate the method.
LE 6 5:15 PM
New Model for ab initio Calculation of Atomic Radiations in Nuclear Decay
A.E. Stuchbery, T. Kibédi, B.Q. Lee, K.A. Robertson,
Department of Nuclear Physics, Research School of Physics and Engineering, The Australian National
University, Canberra, ACT 0200, Australia
F.G. Kondev
Argonne National Laboratory, Argonne, Illinois 60439, USA
Unstable atomic nuclei release excess energy through various radioactive decay processes by emitting particles
(e.g. neutron, alpha, beta) or electromagnetic radiation (gamma-ray photons). Most of the applications
of nuclear isotopes make use of the interactions of their radiations passing through material, which depend
on the type (photons, neutral or charged particles) and the transferred energy. The ionizing radiation
produced by radioisotopes goes beyond the alpha, beta and gamma radiation from the nuclear decay. A
cascade of Auger electrons is often emitted in the atomic relaxation process following a nuclear event.
This radiation is particularly important for medical applications [1]. Since the early 70s, when the use of
Auger electrons for cancer therapy was first suggested (see the review by Howell [2]), considerable advances
have been made in understanding the radiobiological effect of low energy electrons. On the other hand,
a comparison of the calculated Auger yields for selected radioisotopes [3] has identified significant differences
between the various computational models. These differences stem from differences in the physical
assumptions of the models as well as differences in the adopted atomic transition rates and energies. In
this paper we review the current knowledge on Auger emission rates in nuclear decay and present a new
ab initio model which evaluates the transition energies and rates from first principles using the GRASP2k
[4] and RATIP [5] codes. A full Monte Carlo approach was adopted to treat the stochastic nature of the
creation of the primary atomic vacancies after nuclear decay, as well as for the subsequent propagation of
vacancies. Our first numerical results on selected medical radioisotopes will be presented.
[1] A.L. Nichols, S.M. Qaim, R.C. Noy, Summary Report Technical Meeting on Intermediate-term Nuclear
Data Needs for Medical Applications: Cross Sections and Decay Data, AEA Nuclear Data Section,
INDC(NDS)-0596 (2011) [2] R.W. Howell, Journal of Radiation Biology, 84, 959 (2008) [3] B.Q. Lee, T.
Kibédi, A.E. Stuchbery, K.A. Robertson, Computational and Mathematical Methods in Medicine (2012), in
press, doi:10.1155/2012/651475 [4] P. Jönsson, X. He, C. Froese Fischer, I. P. Grant, Computer Physics
Communications 177, 597 (2007) [5] S. Fritzsche, Computer Physics Communications 183, 1525 (2012)
LE 7 5:30 PM
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