Speaker
Joao Pedro Ramos
(University of Aveiro)
Description
Calcium oxide powder targets have been successfully used at ISOLDE-CERN to produced neutron deficient exotic argon isotopes and carbon isotopes, released as CO and CO2 molecules. Such targets outperform other related targets used to produce the same beams, such as MgO sintered powder or TiOx fibers. However, either some CaO target units displayed slow release rates (or low absolute yields) from the beginning or a rapid decrease over time when operated under proton irradiation.[1] We found that the good performance of the ISOLDE historical targets was related to a structure of a nanometric scale.[2,3] Its fast degradation was mainly caused by sintering due to the high operation temperatures and/or high proton intensities being responsible for the fast drop of the yields. Taking this into account, systematic studies of: the synthesis conditions, sintering kinetics and the air reactivity of the nanometric powder were performed; all in order to improve/maintain the target nanostructural properties. A new production and operation methods were proposed and tested at ISOLDE in order to improve the release properties, in terms of diffusion and effusion of isotopes. Improved yields of exotic Ar beams and no sign of degradation were observed during the operation of the CaO #469, target unit of this year.
References:
[1] Ravn, H. L. et al. Bunched Release of Gases from Oxide Targets. Nuclear Instruments and Methods in Physics Research B: Beam Interactions with Materials and Atoms 1997, 126, 176-181.
[2] Stora, T. et al., Nanostructured Target for Isotope Production, WO 2010/034364 A1, 2010.
[3] Fernandes, S. Submicro- and Nanostructured Porous Materials for Productin of High-Intensity Exotic Radioactive Ion Beams; PhD Thesis; École Polytechnique Fédérale de Lausanne: Lausanne, 2011.
Primary author
Joao Pedro Ramos
(University of Aveiro)
Co-authors
Ana Maria Rocha Senos
(University of Aveiro, PT)
Thierry Stora
(CERN)
