45 research outputs found
New accurate measurements of neutron emission probabilities for relevant fission products
We have performed new accurate measurements of the beta-delayed neutron emission probability for ten isotopes of the elements Y, Sb, Te and I. These are fission products that either have a significant contribution to the fraction of delayed neutrons in reactors or are relatively close to the path of the astrophysical r process. The measurements were performed with isotopically pure radioactive beams using a constant and high efficiency neutron counter and a low noise beta detector. Preliminary results are presented for six of the isotopes and compared with previous measurements and theoretical calculations.Postprint (published version
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
Fine structure of the Gamow-Teller resonance revealed in the decay of Ho-150 2(-) isomer
The γ rays following the 72s 150Ho 2- Gamow-Teller β decay have been investigated with the CLUSTER CUBE setup, an array of six EUROBALL CLUSTER Ge detectors in close cubic geometry, providing a γ ray detection sensitivity of 2×10-5 per β-parent decay for γ-ray energies up to 5 MeV. The fine structure of the Gamow-Teller resonance at 4.4-MeV excitation in 150Dy has been studied. The resolved levels are compared with Shell Model predictions
First determination of β -delayed multiple neutron emission beyond A=100 through direct neutron measurement: The P2n value of Sb 136
Conceptual design of a hybrid neutron-gamma detector for study of Ăź-delayed neutrons at the RIB facility of RIKEN
The conceptual design of the BRIKEN neutron detector at the radioactive ion beam factory (RIBF) of the RIKEN Nishina Center is reported. The BRIKEN setup is a complex system aimed at detecting heavy-ion implants, Ăź particles, Âż rays and Ăź-delayed neutrons. The whole setup includes the Advanced Implantation Detection Array (AIDA), two HPGe Clover detectors and up to 166 3He-filled counters embedded in a high-density polyethylene moderator. The design is quite complex due to the large number and different types of 3He-tubes involved and the additional constraints introduced by the ancillary detectors for charged particles and Âż rays. This article reports on a novel methodology developed for the conceptual design and optimisation of the 3He-counter array, aiming for the best possible performance in terms of neutron detection. The algorithm is based on a geometric representation of two selected detector parameters of merit, namely, the average neutron detection efficiency and the efficiency flatness as a function of a reduced number of geometric variables. The response of the neutron detector is obtained from a systematic Monte Carlo simulation implemented in GEANT4. The robustness of the algorithm allowed us to design a versatile detection system, which operated in hybrid mode includes the full neutron counter and two clover detectors for high-precision gamma spectroscopy. In addition, the system can be reconfigured into a compact mode by removing the clover detectors and re-arranging the 3He tubes in order to maximize the neutron detection performance. Both operation modes shows a rather flat and high average efficiency. In summary, we have designed a system which shows an average efficiency for hybrid mode (3He tubes + clovers) of 68.6% and 64% for neutron energies up to 1 and 5 MeV, respectively. For compact mode (only 3He tubes), the average efficiency is 75.7% and 71% for neutron energies up to 1 and 5 MeV, respectively. The performance of the BRIKEN detection system has been also quantified by means of Monte Carlo simulations with different neutron energy distributions.Postprint (author's final draft
SEOM-GECP-GETTHI Clinical Guidelines for the treatment of patients with thymic epithelial tumours (2021)
Thymic epithelial tumours (TET) represent a heterogeneous group of rare malignancies that include thymomas and thymic carcinoma. Treatment of TET is based on the resectability of the tumour. If this is considered achievable upfront, surgical resection is the cornerstone of treatment. Platinum-based chemotherapy is the standard regimen for advanced TET. Due to the rarity of this disease, treatment decisions should be discussed in specific multidisciplinary tumour boards, and there are few prospective clinical studies with new strategies. However, several pathways involved in TET have been explored as potential targets for new therapies in previously treated patients, such as multi-tyrosine kinase inhibitors with antiangiogenic properties and immune checkpoint inhibitors (ICI). One third of patient with thymoma present an autoimmune disorders, increasing the risk of immune-related adverse events and autoimmune flares under ICIs. In these guidelines, we summarize the current evidence for the therapeutic approach in patients with TET and define levels of evidence for these decisions
Measurement of the heaviest Beta-delayed 2-neutron emitter: 136Sb
The Beta-delayed neutron emission probability, Pn , of very exotic nuclei is crucial for the understanding of nuclear structure properties of many isotopes and astrophysical processes such as the rapid neutron capture process (r-process). In addition Beta-delayed neutrons are important in a nuclear power reactor operated in a prompt sub-critical, delayed critical condition, as they contribute to the decay heat inducing fission reactions after a shut down. The study of neutron-rich isotopes and the measurement of Beta-delayed one-neutron emitters (Beta1n) is possible thanks to the Rare Isotope Beam (RIB) facilities, where radioactive beams allow the production of exotic nuclei of interest, which can be studied and analyzed using specific detection systems. This contribution reports two recent measurements of Beta-delayed neutron emitters which
allowed the determination of half-lives and the neutron branching ratio of isotopes in the mass region above A = 200 and N > 126, and a second experiment which confirmed 136Sb as the heaviest double neutron emitter (Beta2n) measured so far.Postprint (published version
Measurement of very low (alpha,n) cross sections of astrophysical interest
The reactions 13C(alpha, n)16O and 22Ne(alpha, n)25Mg are the primary sources of neutrons for the astrophysical s-process. The feasibility of cross section measurements within the respective Gamow windows is discussed in quantitative terms for a 4p neutron counter, based on 3He tubes and a neutron moderator, placed in an underground lab.Postprint (published version
Ăź-delayed neutron emission studies
The study of beta-delayed neutron emission plays a major role in different fields such as nuclear technology, nuclear astrophysics and nuclear structure. However the quality of the existing experimental data nowadays is not sufficient for the various technical and scientific applications and new high precision measurements are necessary to improve the data bases. One key aspect to the success of these high precission measurements is the use of a very pure ion beam that ensures that only the ion of interest is produced. The combination of the IGISOL mass separator with the JYFLTRAP Penning trap is an excellent tool for this type of measurement because of the ability to deliver isobarically and even isomerically clean beams. Another key feature of the installation is the non-chemical selectivity of the IGISOL ion source which allows measurements in the important region of refractory elements. This paper summarises the beta-delayed neutron emission studies that have been carried out at the IGISOL facility with two different neutron detectors based on 3He counters in a polyethylene moderator: the Mainz neutron detector and the BEta deLayEd Neutron detector.Postprint (published version
Conceptual design of the BRIKEN detector: A hybrid neutron-gamma detection system for nuclear physics at the RIB facility of RIKEN
BRIKEN is a complex detection system to be installed at the RIB-facility of the RIKEN Nishina
Center. It is aimed at the detection of heavy-ion implants, Ăź-particles, Âż-rays and Ăź-delayed neu-
trons. The whole detection setup involves the Advanced Implantation Detection Array (AIDA), two
HPGe Clover detectors and a large set of 166 counters of 3He embedded in a high-density polyethy-
lene matrix. This article reports on a novel methodology developed for the conceptual design and
optimisation of the 3He-tubes array, aiming at the best possible performance in terms of neutron
detection. The algorithm is based on a geometric representation of two selected parameters of merit,
namely, average neutron detection efficiency and efficiency flatness, as a function of a reduced num-
ber of geometric variables. The response of the detection system itself, for each configuration, is
obtained from a systematic MC-simulation implemented realistically in Geant4. This approach has
been found to be particularly useful. On the one hand, due to the different types and large number
of 3He-tubes involved and, on the other hand, due to the additional constraints introduced by the
ancillary detectors for charged particles and gamma-rays. Empowered by the robustness of the al-
gorithm, we have been able to design a versatile detection system, which can be easily re-arranged
into a compact mode in order to maximize the neutron detection performance, at the cost of the
gamma-ray sensitivity. In summary, we have designed a system which shows, for neutron energies up
to 1(5) MeV, a rather flat and high average efficiency of 68.6%(64%) and 75.7%(71%) for the hybrid
and compact modes, respectively. The performance of the BRIKEN system has been also quantified
realistically by means of MC-simulations made with different neutron energy distributions