Vila Franca do Campo, Portugal
Vila Franca do Campo, Portugal

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Gottberg A.,CERN | Gottberg A.,CSIC - Institute for the Structure of Matter | Mendonca T.M.,CERN | Mendonca T.M.,IN Institute of Nanosciences and Nanotechnologies | And 19 more authors.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2014

The suppression of isobaric contaminations is of growing importance for many scientific programs using radioactive isotopes produced at isotope separation on-line (ISOL) facilities, such as ISOLDE-CERN. A solid tungsten proton-to-neutron converter has been used for ten years to produce neutron-rich fission fragments from an UCx target while suppressing the production of neutron-deficient isobaric contaminants. The remaining contamination is mainly produced by primary protons that are scattered by the heavy neutron converter and finally impinge on the UCx target itself. Therefore, the knowledge of the energy-dependant cross-sections of proton and neutron induced fission events is crucial in order to evaluate future converter concepts. In this paper, an improved neutron converter prototype design is presented together with the experimentally assessed radioisotope production of Rb, Zn, Cu, Ga and In that validate the converter concept aiming at beams of higher purity neutron-rich isotopes. The experimentally derived release efficiencies for isotopes produced by the 1.4 GeV protons available at ISOLDE are used to evaluate the Monte Carlo code FLUKA and the cross-section codes TALYS and ABRABLA, respectively. © 2014 Published by Elsevier B.V.


Mendona T.M.,IN Institute of Nanosciences and Nanotechnologies | Mendona T.M.,CNRS Neel Institute | Tavares P.B.,University of Trás os Montes e Alto Douro | Correia J.G.,Technological and Nuclear Institute of Portugal | And 4 more authors.
Physica C: Superconductivity and its Applications | Year: 2011

An alternative sol-gel route for synthesizing precursors of mercury based superconductors is presented. This route is based on urea as a combustion agent and has been applied in the synthesis of HgBa2Ca2Cu 3O8+δ (Hg-1223). Moreover, the effects of the precursor preparation on the synthesis of Hg-1223 were studied. This method is further compared with other sol-gel routes used in the synthesis of this family of compounds. © 2011 Elsevier B.V. All rights reserved.


Mendonca T.M.,IN Institute of Nanosciences and Nanotechnologies | Mendonca T.M.,CNRS Neel Institute | Correia J.G.,Technological and Nuclear Institute of Portugal | Correia J.G.,University of Lisbon | And 10 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

Lattice sites and collective ordering of oxygen atoms in HgBa 2CaCu2O6+δ were studied using the perturbed angular correlation (PAC) technique at ISOLDE/CERN. The electric field gradients (EFG) at 199mHg nuclei have been measured as functions of oxygen doping on the Hg planes, above and below Tc. In comparison with the results obtained for oxygen and fluorine doping in Hg-1201, the analysis shows a different oxygen ordering exhibited by Hg-1212. Moreover, for all studied cases, the experimental results show that at a local scale there is non uniform oxygen distribution. A series of ab initio EFG calculations allowed to infer that at low concentrations, regions without oxygen coexist with regions where O2δ dumbbell molecules are located at the center of the Hg mesh. On the other side, at high concentrations, O2δ dumbbell molecules coexist with single Oδ atoms occupying the center of the Hg mesh. The present results suggest that oxygen sits on the Hg planes in the form of a molecule and not as a single atom. © 2011 American Physical Society.


Mendonca T.M.,IN Institute of Nanosciences and Nanotechnologies | Mendonca T.M.,CNRS Neel Institute | Correia J.G.,Technological and Nuclear Institute of Portugal | Haas H.,Technological and Nuclear Institute of Portugal | And 6 more authors.
Journal of Superconductivity and Novel Magnetism | Year: 2011

The electric field gradients at 199mHg nuclei have been measured via the perturbed angular correlation (PAC) technique, allowing a full characterization of the Hg neighborhood charge distribution at high oxygen doping on the Hg planes. The PAC technique has been applied to investigate the effect of high oxygen pressure during the measurement. Polycrystalline HgBa 2CaCu 2O 6+δ (Hg-1212) samples have been annealed at 152 bar pressurized oxygen. The influence of oxygen pressure during the experiment was then investigated by measuring the samples at atmospheric pressure and under 152 bar oxygen pressure. The present set of PAC experiments shows that at high oxygen concentrations there is a non-uniform oxygen distribution. Moreover, the Hg environment is not free from oxygen and the results hint to a new type of ordering. © 2010 Springer Science+Business Media, LLC.


Hodak R.,ASCR Institute of Physics Prague | Mendonca T.M.,IN Institute of Nanosciences and Nanotechnologies | Mendonca T.M.,CERN | Stora T.,CERN
AIP Conference Proceedings | Year: 2014

Intense relativistic (anti)neutrino beams are an unique tool required to study fundamental properties of neutrinos such as neutrino oscillation parameters, as well as their Majorana or Dirac nature, the lepton number conservation hypothesis and the absolute neutrino mass scale. Such beams originate from acceleration of β-decaying radioactive ions ("Beta beams"). A molten fluoride salt target has been developed for the production of the required rates of low-Q baseline isotope 18Ne for the Beta beams project. The prototyped unit has been tested on-line at ISOLDE-CERN. In this contribution an overview of the prototyping and on-line tests is presented. © 2013 AIP Publishing LLC.


Hodak R.,Comenius University | Stora T.,CERN | Mendonca T.M.,CERN | Mendonca T.M.,IN Institute of Nanosciences and Nanotechnologies
AIP Conference Proceedings | Year: 2011

We discuss a design study devoted to a construction of the Beta beams facility at CERN, a next generation European facility aiming for a production of pure and collimated ultra-relativistic beam of electron (anti)neutrinos with help of accelerated β-decaying radioactive ions circulating in a storage decay ring. This high intense source of (anti)neutrinos directed towards a remote underground neutrino detector will allow to measure neutrino oscillations with high accuracy offering a unique chance for establishing a value of the β13 mixing angle and CP violating phase. Recently, a significant progress have been achieved on the conceptual design of high power targets required for a production and an extraction of two baseline isotopes, 6He and 18Ne, at the unexampled rate of several 10 13ions/s. There is a possibility to produce these isotopes using the so-called Isotope Separation On Line (ISOL) method at the ISOLDE facility (CERN). The 6He production is realized by taking advantage of the 9Be(n,α)6He reaction and with help of spallation neutrons and porous BeO target material. The production of 18Ne through the 19F(p,2n)18Ne reaction at required intensities is even more challenging. Currently, a molten salt (NaF) loop target is proposed for a production of high rate of 18Ne required for the Beta beams project. The progress on the design study associated with new data and plans for future is briefly presented. © 2011 American Institute of Physics.

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