2016 IEEE Nuclear Science Symposium, Medical Imaging Conference and Room-Temperature Semiconductor Detector Workshop (NSS/MIC/RTSD), 2016
Ultra fast inorganic scintillators, like LaBr3(Ce) are key detectors in Nuclear Physics and medic... more Ultra fast inorganic scintillators, like LaBr3(Ce) are key detectors in Nuclear Physics and medical applications. On the other hand, fully digital acquisition systems, for which the pulses from the detectors are sampled at high rates, are being increasingly used. We present new digital pulse processing algorithms to extract time and energy signals from nuclear pulses produced by ultrafast detectors. We compare the results of the fully digital acquisition chain (DDAQ) to state-of-the-art results obtained with traditional electronics, based upon constant fraction discriminators (CFD), time to digital converters and multichannel analyzers. For this purpose, we have performed coincidence measurements using relatively large (1″×1.5″×1”) truncated cone and cylindrical LaBr3(Ce) and CeBr3 crystals coupled to ultra fast photomultipliers (PMTs). Coincidence measurements with Co-60 and Na-22 sources are acquired. The main advantage of fully digital processing is that many different algorithms...
The low energy structure of 65 Co was studied by means of γ-and fast-timing spectroscopy at the I... more The low energy structure of 65 Co was studied by means of γ-and fast-timing spectroscopy at the ISOLDE/CERN facility. The known level scheme of 65 Co populated following the β − decay of 65 Fe was expanded. The experimental results were compared with large scale shell-model calculations. The measured long lifetime of the (1/2 − 1) level confirms its nature as a highly collective state with proton excitations across the Z=28 gap and neutrons across the N=40 sub-shell.
The lifetime of the 0 + 3 state in 66 Ni, two neutrons below the N=40 sub-shell gap, has been mea... more The lifetime of the 0 + 3 state in 66 Ni, two neutrons below the N=40 sub-shell gap, has been measured. The transition B(E2;0 + 3 → 2 + 1) is one of the most hindered E2 transitions in the Ni isotopic chain and it implies that, unlike 68 Ni, there is a spherical structure at low excitation energy. We have performed extensive shell-model calculations that correctly predict this result, obtaining a spherical 0 + state at the correct energy and with an extremely low B(E2;0 + 3 → 2 + 1) value.
Neutron-rich light nuclei and their reactions play an important role for the creation of chemical... more Neutron-rich light nuclei and their reactions play an important role for the creation of chemical elements. Here, data from a Coulomb dissociation experiment on 20,21 N are reported. Relativistic 20,21 N ions impinged on a lead target and the Coulomb dissociation cross section was determined in a kinematically complete experiment. Using the detailed balance theorem, the 19 N(n, γ) 20 N and 20 N(n, γ) 21 N excitation functions and thermonuclear reaction rates have been determined. The 19 N(n, γ) 20 N rate is up to a factor of 5 higher at T < 1 GK with respect to previous theoretical calculations, leading to a 10 % decrease in the predicted fluorine abundance.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2016
Positron range (PR) is one of the important factors that limit the spatial resolution of positron... more 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 68 Ga and 66 Ga radioisotopes, which have a large PR and are being used in many preclinical and clinical PET studies. We produced a 68 Ga and 66 Ga 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 68 Ga and 66 Ga radioisotopes in proton therapy.
The beta decay of exotic nuclei is directly connected to many different and highly relevant issue... more The beta decay of exotic nuclei is directly connected to many different and highly relevant issues. While along the years a hundred of nuclei have been identified as beta delayed proton (β-p) emitters only eight have been found to be β-2p emitters and the β-3p decay mode although energetically allowed has so far not been observed [1].
ABSTRACT We have investigated the levels in 65Fe populated in the β decay of 65Mn, with several n... more ABSTRACT We have investigated the levels in 65Fe populated in the β decay of 65Mn, with several new transitions and levels identified. Using the Advanced Time-Delayed Method we have measured the lifetime of the first two excited states with preliminary results of T1/2(363.7keV) = 95(2) ps and T1/2(455.6keV) = 340(30) ps. Also reported here are preliminary values for the β-delayed neutron branch of Pn = 5(1)% and an upper limit for the β-feeding to the ground state of &lt; 8%.
Proceedings of the Conference on Advances in Radioactive Isotope Science (ARIS2014), 2015
The neutron-rich nucleus 81Ga was populated from the β-decay of 81Zn produced at the ISOLDE (CERN... more The neutron-rich nucleus 81Ga was populated from the β-decay of 81Zn produced at the ISOLDE (CERN) facility. The analysis of β-gated γ-ray singles and γ-γ coincidences permits to extend significantly the level scheme of 81Ga as well as to provide a new half-life for 81Zn. A preliminary upper limit was obtained for the half-life of the first excited state in 81Ga.
We have studied one-proton-removal reactions of about 500 MeV/u 17 Ne beams on a carbon target at... more We have studied one-proton-removal reactions of about 500 MeV/u 17 Ne beams on a carbon target at the R 3 B/LAND setup at GSI by detecting beam-like 15 Op and determining their relative-energy distribution.
Two-proton decay of the unbound T z = −2 nucleus 16 Ne, produced in one-neutron knockout from a 5... more Two-proton decay of the unbound T z = −2 nucleus 16 Ne, produced in one-neutron knockout from a 500 MeV/u 17 Ne beam, has been studied at GSI. The ground state, at a resonance energy 1.388(15) MeV, (Γ = 0.082(15) MeV) above the 14 O+p+p threshold, and two narrow resonances at E r = 3.220(46) MeV and 7.57(6) MeV have been investigated. A comparison of the energy difference between the first excited 2 + state and the 0 + ground state in 16 Ne with its mirror nucleus 16 C reveals a small Thomas-Ehrman shift (TES) of +70(46) keV. A trend of the TES for the T = 2 quintet is obtained by completing the known data with a prediction for 16 F obtained from an IMME analysis. The decay mechanisms of the observed three resonances were revealed from an analysis of the energy and angular correlations of the 14 O+p+p decay products. The ground state decay can be considered as a genuine three-body (democratic) mode and the excited states decay sequentially via states in the intermediate nucleus 15 F, the 3.22 MeV state predominantly via the 15 F ground-state resonance, while the 7.57 MeV state decays via the 5/2 + resonance in 15 F at 2.8 MeV above the 14 O+p+p threshold. Further, from an analysis of angular correlations, the spin-parity of the 7.57 MeV state has been determined as I π = 2 + and assigned as the third 2 + state in 16 Ne based on a comparison with 16 C.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2013
We report on the time response of a novel inorganic scintillator, CeBr 3. The measurements were p... more We report on the time response of a novel inorganic scintillator, CeBr 3. The measurements were performed using a cylindrical crystal of 1-in. in height and 1-in. in diameter at 22 Na and 60 Co photon energies. The time response was measured against a fast reference BaF 2 detector. Hamamatsu R9779 and Photonis XP20D0 fast photomultipliers (PMTs) were used. The PMT bias voltages and Constant Fraction Discriminator settings were optimized with respect to the timing resolution. The Full Width at Half Maximum (FWHM) time resolution for an individual CeBr 3 crystal coupled to Hamamatsu PMT is found here to be as low as 119 ps at 60 Co energies, which is comparable to the resolution of 107 ps reported for LaBr 3 (Ce). For 511 keV photons the measured FWHM time resolution for CeBr 3 coupled to the Hamamatsu PMT is 164 ps.
In this work, we investigate PET imaging with 68 Ga and 66 Ga after proton irradiation on a natur... more In this work, we investigate PET imaging with 68 Ga and 66 Ga after proton irradiation on a natural zinc foil. The nuclides 68 Ga and 66 Ga are ideally suited for off line PET monitoring of proton radiotherapy due to their beta decay half lives of 67.71(9) minutes and 9.49(3) hours, respectively, and suitable fl end point energy. The purpose of this work is to explore the feasibility of PET monitoring in hadrontherapy treatments, and to study how the amount of activity and the positron range affect the PET image reconstruction. Profiting from the low energy reaction threshold for production via (p,n) reactions, both 68 Ga and 66 Ga gallium isotopes have been produced by activation on a natural zinc target by a proton pencil beam. In this way, it is possible to create detailed patterns, such as the Derenzo inspired one employed here. The proton beam was produced by the 5 MV tandetron accelerator at CMAM in Madrid. The energy of this beam (up to 10 MeV) is similar to the residual energy of the protons used for therapy at the distal edge of their path. The activated target was imaged in an ARGUS small animal PETtCT scanner and reconstructed with a fully 3D iterative algorithm, with and without positron range corrections.
A new level scheme of 80 Ga has been determined. This nucleus was populated following the β − dec... more A new level scheme of 80 Ga has been determined. This nucleus was populated following the β − decay of 80 Zn at ISOLDE, CERN. The proposed level scheme is significantly different compared to the previously reported one and contains 26 levels up to 3.4 MeV in excitation energy. The present study establishes that the previously identified 1.9-s β −-decaying 6 − isomer is the ground state of 80 Ga and the 1.3-s β −-decaying 3 − isomer lies at an excitation energy of 22.4 keV. A new isomeric level was identified at 707.8 keV and its half-life was measured to be 18.3(5) ns, allowing the 685.4-keV transition de-exciting this state to be assigned an M2 multipolarity. The newly measured spectroscopic observables are compared with shell-model calculations using the jj44bpn and JUN45 interactions.
After the successful commissioning of the Radioactive beam EXperiment (REX) at ISOLDE (CERN) in 2... more After the successful commissioning of the Radioactive beam EXperiment (REX) at ISOLDE (CERN) in 2002, first physics experiments were performed in 2003 which focussed on the neutron-rich Mg isotopes in the vicinity of the "island of inversion". After introducing the REX facility and the modern γ spectrometer MINIBALL first preliminary results will be presented showing the high potential and physics opportunities offered by this new radioactive beam facility.
ABSTRACT We report on the results of the β-decay of 81Zn. The experiment was performed at the CER... more ABSTRACT We report on the results of the β-decay of 81Zn. The experiment was performed at the CERN ISOLDE facility in the framework of a systematic ultra-fast timing investigation of neutron-rich nuclei populated in the decay of Zn. The present analysis included β-gated γ-ray singles and γ-γ coincidences from the decay of 81Zn to 81Ga and leads to a new and much more extensive level scheme of 81Ga. A new half-life of 81Zn is provided.
Fission and Properties of Neutron-Rich Nuclei, 2003
The first experiments using post-accelerated radioactive ion beams from REX-ISOLDE have taken pla... more The first experiments using post-accelerated radioactive ion beams from REX-ISOLDE have taken place during 2002 after approximately six years of development. The novel techniques used for the production of the radioactive ion beam as well as at the experimental set-up are described in this paper. It is attempted to show that REX-ISOLDE is a unique machine for experiments in nuclear
The current evaluation of the triple-reaction rate assumes that the decay of the 7.65 MeV, 0 þ st... more The current evaluation of the triple-reaction rate assumes that the decay of the 7.65 MeV, 0 þ state in 12 C, commonly known as the Hoyle state, proceeds sequentially via the ground state of 8 Be. This assumption is challenged by the recent identification of two direct-decay branches with a combined branching ratio of 17ð5Þ%. If correct, this would imply a corresponding reduction in the triple-reaction rate with important astrophysical consequences. We have used the 11 Bð 3 He; dÞ reaction to populate the Hoyle state and measured the decay to three particles in complete kinematics. We find no evidence for direct-decay branches, and hence our data do not support a revision of the triple-reaction rate. We obtain an upper limit of 5 Â 10 À3 on the direct decay of the Hoyle state at 95% C.L., which is 1 order of magnitude better than a previous upper limit.
The mirror β +-decay of 61 Ga was investigated by means of βand γ-ray spectrometry at the ISOLDE-... more The mirror β +-decay of 61 Ga was investigated by means of βand γ-ray spectrometry at the ISOLDE-PSB facility using laser ionisation and mass-separation. The results for the 61 Ga half-life and the Q EC value are 168(3) ms and 9255(50) keV, respectively. The β-decay strength to the ground and low-lying excited states of the daughter 61 Zn was deduced. The experimental results are in a good agreement with large-scale shell model calculations.
2016 IEEE Nuclear Science Symposium, Medical Imaging Conference and Room-Temperature Semiconductor Detector Workshop (NSS/MIC/RTSD), 2016
Ultra fast inorganic scintillators, like LaBr3(Ce) are key detectors in Nuclear Physics and medic... more Ultra fast inorganic scintillators, like LaBr3(Ce) are key detectors in Nuclear Physics and medical applications. On the other hand, fully digital acquisition systems, for which the pulses from the detectors are sampled at high rates, are being increasingly used. We present new digital pulse processing algorithms to extract time and energy signals from nuclear pulses produced by ultrafast detectors. We compare the results of the fully digital acquisition chain (DDAQ) to state-of-the-art results obtained with traditional electronics, based upon constant fraction discriminators (CFD), time to digital converters and multichannel analyzers. For this purpose, we have performed coincidence measurements using relatively large (1″×1.5″×1”) truncated cone and cylindrical LaBr3(Ce) and CeBr3 crystals coupled to ultra fast photomultipliers (PMTs). Coincidence measurements with Co-60 and Na-22 sources are acquired. The main advantage of fully digital processing is that many different algorithms...
The low energy structure of 65 Co was studied by means of γ-and fast-timing spectroscopy at the I... more The low energy structure of 65 Co was studied by means of γ-and fast-timing spectroscopy at the ISOLDE/CERN facility. The known level scheme of 65 Co populated following the β − decay of 65 Fe was expanded. The experimental results were compared with large scale shell-model calculations. The measured long lifetime of the (1/2 − 1) level confirms its nature as a highly collective state with proton excitations across the Z=28 gap and neutrons across the N=40 sub-shell.
The lifetime of the 0 + 3 state in 66 Ni, two neutrons below the N=40 sub-shell gap, has been mea... more The lifetime of the 0 + 3 state in 66 Ni, two neutrons below the N=40 sub-shell gap, has been measured. The transition B(E2;0 + 3 → 2 + 1) is one of the most hindered E2 transitions in the Ni isotopic chain and it implies that, unlike 68 Ni, there is a spherical structure at low excitation energy. We have performed extensive shell-model calculations that correctly predict this result, obtaining a spherical 0 + state at the correct energy and with an extremely low B(E2;0 + 3 → 2 + 1) value.
Neutron-rich light nuclei and their reactions play an important role for the creation of chemical... more Neutron-rich light nuclei and their reactions play an important role for the creation of chemical elements. Here, data from a Coulomb dissociation experiment on 20,21 N are reported. Relativistic 20,21 N ions impinged on a lead target and the Coulomb dissociation cross section was determined in a kinematically complete experiment. Using the detailed balance theorem, the 19 N(n, γ) 20 N and 20 N(n, γ) 21 N excitation functions and thermonuclear reaction rates have been determined. The 19 N(n, γ) 20 N rate is up to a factor of 5 higher at T < 1 GK with respect to previous theoretical calculations, leading to a 10 % decrease in the predicted fluorine abundance.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2016
Positron range (PR) is one of the important factors that limit the spatial resolution of positron... more 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 68 Ga and 66 Ga radioisotopes, which have a large PR and are being used in many preclinical and clinical PET studies. We produced a 68 Ga and 66 Ga 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 68 Ga and 66 Ga radioisotopes in proton therapy.
The beta decay of exotic nuclei is directly connected to many different and highly relevant issue... more The beta decay of exotic nuclei is directly connected to many different and highly relevant issues. While along the years a hundred of nuclei have been identified as beta delayed proton (β-p) emitters only eight have been found to be β-2p emitters and the β-3p decay mode although energetically allowed has so far not been observed [1].
ABSTRACT We have investigated the levels in 65Fe populated in the β decay of 65Mn, with several n... more ABSTRACT We have investigated the levels in 65Fe populated in the β decay of 65Mn, with several new transitions and levels identified. Using the Advanced Time-Delayed Method we have measured the lifetime of the first two excited states with preliminary results of T1/2(363.7keV) = 95(2) ps and T1/2(455.6keV) = 340(30) ps. Also reported here are preliminary values for the β-delayed neutron branch of Pn = 5(1)% and an upper limit for the β-feeding to the ground state of &lt; 8%.
Proceedings of the Conference on Advances in Radioactive Isotope Science (ARIS2014), 2015
The neutron-rich nucleus 81Ga was populated from the β-decay of 81Zn produced at the ISOLDE (CERN... more The neutron-rich nucleus 81Ga was populated from the β-decay of 81Zn produced at the ISOLDE (CERN) facility. The analysis of β-gated γ-ray singles and γ-γ coincidences permits to extend significantly the level scheme of 81Ga as well as to provide a new half-life for 81Zn. A preliminary upper limit was obtained for the half-life of the first excited state in 81Ga.
We have studied one-proton-removal reactions of about 500 MeV/u 17 Ne beams on a carbon target at... more We have studied one-proton-removal reactions of about 500 MeV/u 17 Ne beams on a carbon target at the R 3 B/LAND setup at GSI by detecting beam-like 15 Op and determining their relative-energy distribution.
Two-proton decay of the unbound T z = −2 nucleus 16 Ne, produced in one-neutron knockout from a 5... more Two-proton decay of the unbound T z = −2 nucleus 16 Ne, produced in one-neutron knockout from a 500 MeV/u 17 Ne beam, has been studied at GSI. The ground state, at a resonance energy 1.388(15) MeV, (Γ = 0.082(15) MeV) above the 14 O+p+p threshold, and two narrow resonances at E r = 3.220(46) MeV and 7.57(6) MeV have been investigated. A comparison of the energy difference between the first excited 2 + state and the 0 + ground state in 16 Ne with its mirror nucleus 16 C reveals a small Thomas-Ehrman shift (TES) of +70(46) keV. A trend of the TES for the T = 2 quintet is obtained by completing the known data with a prediction for 16 F obtained from an IMME analysis. The decay mechanisms of the observed three resonances were revealed from an analysis of the energy and angular correlations of the 14 O+p+p decay products. The ground state decay can be considered as a genuine three-body (democratic) mode and the excited states decay sequentially via states in the intermediate nucleus 15 F, the 3.22 MeV state predominantly via the 15 F ground-state resonance, while the 7.57 MeV state decays via the 5/2 + resonance in 15 F at 2.8 MeV above the 14 O+p+p threshold. Further, from an analysis of angular correlations, the spin-parity of the 7.57 MeV state has been determined as I π = 2 + and assigned as the third 2 + state in 16 Ne based on a comparison with 16 C.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2013
We report on the time response of a novel inorganic scintillator, CeBr 3. The measurements were p... more We report on the time response of a novel inorganic scintillator, CeBr 3. The measurements were performed using a cylindrical crystal of 1-in. in height and 1-in. in diameter at 22 Na and 60 Co photon energies. The time response was measured against a fast reference BaF 2 detector. Hamamatsu R9779 and Photonis XP20D0 fast photomultipliers (PMTs) were used. The PMT bias voltages and Constant Fraction Discriminator settings were optimized with respect to the timing resolution. The Full Width at Half Maximum (FWHM) time resolution for an individual CeBr 3 crystal coupled to Hamamatsu PMT is found here to be as low as 119 ps at 60 Co energies, which is comparable to the resolution of 107 ps reported for LaBr 3 (Ce). For 511 keV photons the measured FWHM time resolution for CeBr 3 coupled to the Hamamatsu PMT is 164 ps.
In this work, we investigate PET imaging with 68 Ga and 66 Ga after proton irradiation on a natur... more In this work, we investigate PET imaging with 68 Ga and 66 Ga after proton irradiation on a natural zinc foil. The nuclides 68 Ga and 66 Ga are ideally suited for off line PET monitoring of proton radiotherapy due to their beta decay half lives of 67.71(9) minutes and 9.49(3) hours, respectively, and suitable fl end point energy. The purpose of this work is to explore the feasibility of PET monitoring in hadrontherapy treatments, and to study how the amount of activity and the positron range affect the PET image reconstruction. Profiting from the low energy reaction threshold for production via (p,n) reactions, both 68 Ga and 66 Ga gallium isotopes have been produced by activation on a natural zinc target by a proton pencil beam. In this way, it is possible to create detailed patterns, such as the Derenzo inspired one employed here. The proton beam was produced by the 5 MV tandetron accelerator at CMAM in Madrid. The energy of this beam (up to 10 MeV) is similar to the residual energy of the protons used for therapy at the distal edge of their path. The activated target was imaged in an ARGUS small animal PETtCT scanner and reconstructed with a fully 3D iterative algorithm, with and without positron range corrections.
A new level scheme of 80 Ga has been determined. This nucleus was populated following the β − dec... more A new level scheme of 80 Ga has been determined. This nucleus was populated following the β − decay of 80 Zn at ISOLDE, CERN. The proposed level scheme is significantly different compared to the previously reported one and contains 26 levels up to 3.4 MeV in excitation energy. The present study establishes that the previously identified 1.9-s β −-decaying 6 − isomer is the ground state of 80 Ga and the 1.3-s β −-decaying 3 − isomer lies at an excitation energy of 22.4 keV. A new isomeric level was identified at 707.8 keV and its half-life was measured to be 18.3(5) ns, allowing the 685.4-keV transition de-exciting this state to be assigned an M2 multipolarity. The newly measured spectroscopic observables are compared with shell-model calculations using the jj44bpn and JUN45 interactions.
After the successful commissioning of the Radioactive beam EXperiment (REX) at ISOLDE (CERN) in 2... more After the successful commissioning of the Radioactive beam EXperiment (REX) at ISOLDE (CERN) in 2002, first physics experiments were performed in 2003 which focussed on the neutron-rich Mg isotopes in the vicinity of the "island of inversion". After introducing the REX facility and the modern γ spectrometer MINIBALL first preliminary results will be presented showing the high potential and physics opportunities offered by this new radioactive beam facility.
ABSTRACT We report on the results of the β-decay of 81Zn. The experiment was performed at the CER... more ABSTRACT We report on the results of the β-decay of 81Zn. The experiment was performed at the CERN ISOLDE facility in the framework of a systematic ultra-fast timing investigation of neutron-rich nuclei populated in the decay of Zn. The present analysis included β-gated γ-ray singles and γ-γ coincidences from the decay of 81Zn to 81Ga and leads to a new and much more extensive level scheme of 81Ga. A new half-life of 81Zn is provided.
Fission and Properties of Neutron-Rich Nuclei, 2003
The first experiments using post-accelerated radioactive ion beams from REX-ISOLDE have taken pla... more The first experiments using post-accelerated radioactive ion beams from REX-ISOLDE have taken place during 2002 after approximately six years of development. The novel techniques used for the production of the radioactive ion beam as well as at the experimental set-up are described in this paper. It is attempted to show that REX-ISOLDE is a unique machine for experiments in nuclear
The current evaluation of the triple-reaction rate assumes that the decay of the 7.65 MeV, 0 þ st... more The current evaluation of the triple-reaction rate assumes that the decay of the 7.65 MeV, 0 þ state in 12 C, commonly known as the Hoyle state, proceeds sequentially via the ground state of 8 Be. This assumption is challenged by the recent identification of two direct-decay branches with a combined branching ratio of 17ð5Þ%. If correct, this would imply a corresponding reduction in the triple-reaction rate with important astrophysical consequences. We have used the 11 Bð 3 He; dÞ reaction to populate the Hoyle state and measured the decay to three particles in complete kinematics. We find no evidence for direct-decay branches, and hence our data do not support a revision of the triple-reaction rate. We obtain an upper limit of 5 Â 10 À3 on the direct decay of the Hoyle state at 95% C.L., which is 1 order of magnitude better than a previous upper limit.
The mirror β +-decay of 61 Ga was investigated by means of βand γ-ray spectrometry at the ISOLDE-... more The mirror β +-decay of 61 Ga was investigated by means of βand γ-ray spectrometry at the ISOLDE-PSB facility using laser ionisation and mass-separation. The results for the 61 Ga half-life and the Q EC value are 168(3) ms and 9255(50) keV, respectively. The β-decay strength to the ground and low-lying excited states of the daughter 61 Zn was deduced. The experimental results are in a good agreement with large-scale shell model calculations.
Uploads
Papers by Luis M Fraile