resumo
At the ISOLDE facility at CERN, thick targets are bombarded with highly energetic pulsed protons to produce radioactive ion beams (RIBs). The isotopes produced in the bulk of the material have to diffuse out of the grain and effuse throughout the porosity of the material to a transfer line which is connected to an ionizer, from which the charged isotopes are extracted and delivered for physics experiments. Calcium oxide (CaO) powder targets have been used to produce mainly neutron deficient argon and carbon RIBs over the past decades. Such targets presented unstable yields, either decaying over time or low from the beginning of operation. These problems were suspected to come from the degradation of the target microstructure (sintering due to high temperature and/or high proton intensity). In this work, a CaO microstructural study in terms of sintering was conducted on a nanostructured CaO powder synthesized from the respective carbonate. Taking the results of this study, several changes were made at ISOLDE in terms of the CaO target production, handling and operation in order to produce and maintain the nanostructured CaO. The new target, the first nanostructured target to be operated at ISOLDE, showed improved yields of (exotic) Ar and more importantly a stable yield over the whole operation time, while operating with lower temperatures. This contradicts the ISOL paradigm of using the highest possible temperature regardless of the target's microstructure degradation. (C) 2014 Published by Elsevier B.V.
palavras-chave
RADIOACTIVE-ION-BEAMS; FACILITY; RELEASE; ONLINE; YIELDS; GASES; DECAY
categoria
Instruments & Instrumentation; Nuclear Science & Technology; Physics
autores
Ramos, JP; Gottberg, A; Mendonca, TM; Seiffert, C; Senos, AMR; Fynbo, HOU; Tengblad, O; Briz, JA; Lund, MV; Koldste, GT; Carmona-Gallardo, M; Pesudo, V; Stora, T
nossos autores
Ana Maria de Oliveira e Rocha Senos
Colaboradoragradecimentos
The author J.P. Ramos gratefully acknowledges Bernard Crepieux, Michael Owen and Ermanno Barbero for the technical support and the financial support from Agenda de Inovacao, S.A. (AdI) and CERN, through the Grant SFRH/ BEST/ 51352/ 2011 for the traineeship at CERN.