cea-01807987
https://cea.hal.science/cea-01807987
https://cea.hal.science/cea-01807987/document
https://cea.hal.science/cea-01807987/file/article_XavierMougeot_radioprotection.pdf
doi:10.1051/radiopro/2014017
[CEA] CEA - Commissariat à l'énergie atomique
[DRT] Direction de la recherche technologique
[LIST] Laboratoire d'Intégration des Systèmes et des Technologies
[DM2I] Département Métrologie Instrumentation & Information
[DIN] Département d'Instrumentation Numérique
Calculation of beta spectral shapes
Mougeot, Xavier
Bé, Marie-Martine
Bisch, Charlène
[PHYS.NUCL] Physics [physics]/Nuclear Theory [nucl-th]
ART
beta spectrum
Beta particles
$^{129}$I
$^{58}$Co
$^{99}$Tc
metrology
ionizing radiations
shape factor
transition
atomic exchange
spectral shape
Classical beta spectra calculations are briefly described, highlighting the usual assumptions and limitations. To go beyond these usual assumptions, the numerical resolution of the Dirac equation for the atomic and beta electrons is necessary. This allowed us to determine the parameters $\lambda_i$ involved in the theoretical shape factors exactly. A systematic comparison between theoretical and experimental shape factors led us to disqualify the usual $\lambda_i$ = 1 assumption for all forbidden transitions. The usual $\xi$-approximation was proved to be incorrect for numerous first forbidden non-unique transitions, and for all higherorder non-unique transitions. A more accurate screening correction was defined and the atomic exchange effect was taken into account, an effect which is always neglected in usual calculations. The beta spectra of $^{63}$Ni and $^{241}$Pu, recently measured down to very low energies, are well reproduced in our calculations. The exchange effect was demonstrated to have a great influence on the spectral shape within this energy range.
2014-10
2020-02-11
en
Radioprotection
EDP Sciences