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Ciclo de Seminarios 2015

2015 26 JUN

Viernes 26 de Junio
10:30 hs. - Auditorio Emma Pérez Ferreira
Edificio TANDAR
" 244Pu and  60Fe on Earth - are there signatures of recent supernovæ?"
Dr. Anton Wallner (*)
Dept. of Nuclear Physics, Research School of Physics and Engineering, The Australian National University
RESUMEN: Accelerator mass spectrometry (AMS) represents a sensitive technique for studying long-lived radionuclides through ultra-low isotope ratio measurements. In this talk I will highlight applications related to nuclear astrophysics. Direct observation and detection of freshly synthesized material from space is a powerful tool for understanding nucleosynthesis. Here I will report on the detection of live interstellar radionuclides trapped in terrestrial archives. "How were the heavy elements from iron to uranium made?" It is clear that half of these elements including all actinides are made in a process requiring high neutron densities (r-process). Their sites and history, however, still remain unclear. Candidates are supernova (SN) explosions or neutron-star mergers, the latter at least 100 times less frequent than SN. New data using AMS suggest an unexpected low abundance of interstellar 244Pu (t1/2=81 Myr). Another isotope produced in SNe is 60Fe (t1/2=2.6 Myr). A previous measurement at TU Munich of an Ocean crust-sample showed an enhanced 60Fe signal of possibly extraterrestrial origin - a close-by SN about 2-3 Myr ago? We have started a similar program at the ANU resulting in an exceptional sensitivity for 60Fe detection. I will discuss a new approach to determine 60Fe's disputed half-life value. In addition, we have analyzed several deep-sea sediments, crusts and nodules for extraterrestrial 60Fe. I will present new data and will relate them to potential exposure of Earth to recent SNe

* El Dr. Wallner es doctor de la Universidad de Viena, posdoc de la Universidad Técnica de Munich y actualmente es profesor de la Universidad Nacional de Australia. Su campo de investigación comprende la medición de datos nucleares fundamentales para reactores de fusión y fisión nuclear, estudio experimental de nucleosíntesis estelar y busqueda de rastros de explosiones supernovas en la Tierra.
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