227 research outputs found
Nuclear structure of Ac-231
The low-energy structure of 231Ac has been investigated by means of gamma ray
spectroscopy following the beta-decay of 231Ra. Multipolarities of 28
transitions have been established by measuring conversion electrons with a
mini-orange electron spectrometer. The decay scheme of 231Ra --> 231Ac has been
constructed for the first time. The Advanced Time Delayed beta-gamma-gamma(t)
method has been used to measure the half-lives of five levels. The moderately
fast B(E1) transition rates derived suggest that the octupole effects, albeit
weak, are still present in this exotic nucleus
The sensitivity of LaBr3:Ce scintillation detectors to low energy neutrons: Measurement and Monte Carlo simulation
AbstractThe neutron sensitivity of a cylindrical ⊘1.5in.×1.5in. LaBr3:Ce scintillation detector was measured using quasi-monoenergetic neutron beams in the energy range from 40keV to 2.5MeV. In this energy range the detector is sensitive to γ-rays generated in neutron inelastic and capture processes. The experimental energy response was compared with Monte Carlo simulations performed with the Geant4 simulation toolkit using the so-called High Precision Neutron Models. These models rely on relevant information stored in evaluated nuclear data libraries. The performance of the Geant4 Neutron Data Library as well as several standard nuclear data libraries was investigated. In the latter case this was made possible by the use of a conversion tool that allowed the direct use of the data from other libraries in Geant4. Overall it was found that there was good agreement with experiment for some of the neutron data bases like ENDF/B-VII.0 or JENDL-3.3 but not with the others such as ENDF/B-VI.8 or JEFF-3.1
Shapes of the Pb ground states from beta decay studies using the total absorption technique
The beta decay of Pb has been studied using the total absorption
technique at the ISOLDE(CERN) facility. The beta-decay strength deduced from
the measurements, combined with QRPA theoretical calculations, allow us to
infer that the ground states of the Pb isotopes are spherical.
These results represent the first application of the shape determination method
using the total absorption technique for heavy nuclei and in a region where
there is considerable interest in nuclear shapes and shape effects
Experimental validation of gallium production and isotope-dependent positron range correction in PET
Abstract Positron range (PR) is one of the important factors that limit the spatial resolution of positron emission tomography (PET) preclinical images. Its blurring effect can be corrected to a large extent if the appropriate method is used during the image reconstruction. Nevertheless, this correction requires an accurate modelling of the PR for the particular radionuclide and materials in the sample under study. In this work we investigate PET imaging with 68Ga and 66Ga radioisotopes, which have a large PR and are being used in many preclinical and clinical PET studies. We produced a 68Ga and 66Ga phantom on a natural zinc target through (p,n) reactions using the 9-MeV proton beam delivered by the 5-MV CMAM tandetron accelerator. The phantom was imaged in an ARGUS small animal PET/CT scanner and reconstructed with a fully 3D iterative algorithm, with and without PR corrections. The reconstructed images at different time frames show significant improvement in spatial resolution when the appropriate PR is applied for each frame, by taking into account the relative amount of each isotope in the sample. With these results we validate our previously proposed PR correction method for isotopes with large PR. Additionally, we explore the feasibility of PET imaging with 68Ga and 66Ga radioisotopes in proton therapy.We acknowledge support from the Spanish
MINECO through projects FPA2010-17142,
FPA2013-41267-P, CSD-2007-00042 (CPAN), and
the RTC-2015-3772-1 grant. We also acknowledge
support from Comunidad de Madrid via the TOPUS
S2013/MIT-3024 project
Seafloor geomorphology of the Passage of Lanzarote (West Africa Margin): Influences of the oceanographic processes
The seafloor morphology of the Passage of Lanzarote has been analysed with the aim to know
the active processes on the bottom surface related to the oceanographic context. Multibeam bathymetric
data and high and very high resolution seismic profiles obtained in the SUBVENT2 cruise have been
used. Five main morphological groups have been analysed: (a) Volcanic or diapiric submarine hills; (b)
Tectonic features on the continental slope (linear scarps and a rhombohedral depression) related to
normal faults; (c) Submarine venting at top of diapirs initially triggered circular depressions; (d)
Sedimentary instabilities (gullies, canyons, mass transport deposits) are present specially on the
Fuerteventura-Lanzarote ridge; and (e) Contouritic bottom features both erosive (central valley,
marginal valleys) and depositional (plastered drifts) are on the central part of the passage, and are
generated by the interaction of MW and the interface MW-AAIW with seafloor.Versión del edito
Evidence of a new state in Be observed in the Li -decay
Coincidences between charged particles emitted in the -decay of
Li were observed using highly segmented detectors. The breakup channels
involving three particles were studied in full kinematics allowing for the
reconstruction of the excitation energy of the Be states participating
in the decay. In particular, the contribution of a previously unobserved state
at 16.3 MeV in Be has been identified selecting the +
He + He+n channel. The angular correlations between the
particle and the center of mass of the He+n system favors spin and
parity assignment of 3/2 for this state as well as for the previously known
state at 18 MeV.Comment: 13 pages, 6 figure
Características geomorfológicas del Pasaje de Lanzarote (Región oriental de las Islas Canarias)
The Passage of Lanzarote is an example of a wide oceanic corridor. It extends between the
eastern Canary Islands and the Western Africa continental margin. Seafloor morphology of this
passage has been analyzed with the aim to know the morphogenetic processes related to both the
oceanography and the geology. Multibeam bathymetric data and high and very high resolution
seismic profiles obtained in the SUBVENT2 cruise have been used. Five main morphological groups
were analyzed: (a) Volcanic or diapiric submarine hills; (b) Tectonic features on the continental slope
(linear scarps and a rhomboid-like depression) related to normal faults at the top of buried diapirs;
(c) Giant circular depressions initially triggered by submarine venting at the top of diapirs; (d)
Sedimentary instabilities and canyons (gullies, canyons, mass transport deposits) that are present
specially on the Fuerteventura-Lanzarote ridge must be related to the high energy geological
processes, both constructive and dismantling, associated to the evolution of these volcanic domains;
and (e) Contouritic features both erosive (central channel, contourite channels) and depositional
(mounded and plastered drifts) that occur in the central part of the bottom surface of the passage,
and are generated by the interaction of the MW and the interface MW-AAIW with the seafloor.Versión del edito
Searching for ß-delayed protons from 11 Be
ISOLDE Workshop and Usersmeeting. Wednesday 05 December - Friday 07 December 2018 .CERN ( ISOLDE User Support. PH Departmen - CERN/CH-1211 Geneve 23). --.https://indico.cern.ch/event/736872/contributions
Study of beta-delayed 3-body and 5-body breakup channels observed in the decay of ^11Li
The beta-delayed charged particle emission from ^11Li has been studied with
emphasis on the three-body n+alpha+^6He and five-body 2alpha+3n channels from
the 10.59 and 18.15 MeV states in ^11Be. Monte Carlo simulations using an
R-matrix formalism lead to the conclusion that the ^AHe resonance states play a
significant role in the break-up of these states. The results exclude an
earlier assumption of a phase-space description of the break-up process of the
18.15 MeV state. Evidence for extra sequential decay paths is found for both
states.Comment: 16 pages, 9 figures. Submitted to Nuclear Physics
Publisher's note:Half-life of the<b> 15/2<sup>+</sup></b> state of <b><sup>135</sup>I: </b>a test of <b>E2</b> seniority relations [Phys. Rev. C <b>95</b>, 021302(R) (2017)]
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