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Neutron destruction reactions of the cosmic γ-ray emitter Al26 are of importance to determine the amount of Al26 ejected into our galaxy by supernova explosions and for Al26 production in asymptotic giant branch stars. We performed a new measurement of the Al26(n,α) reaction up to 160-keV neutron energy at the neutron time-of-flight facilities n_TOF at CERN and GELINA at EC-JRC. We provide strengths for ten resonances, six of them for the first time. We use our data to calculate astrophysical reactivities for stellar temperatures up to 0.7 GK. Our results resolve a discrepancy between the two previous direct measurements of this reaction, and indicate higher stellar destruction rates than the most recently recommended reactivity., We thank P. Black (University of Edinburgh) for support in design and construction of the detection system and P. Morrall (Daresbury Laboratory) for production of the B and LiF reference samples. This Letter was supported by the Austrian Science Fund (FWF), Project No. J3503, by JRC-IRMM through the EUFRAT Program, by the U.K. Science and Technologies Facilities Council (STFC), Projects No. ST/L005824/1 and No. ST/M006085/1, the European Research Council ERC-2015-STG Grant No. 677497, and the Cost Action “ChETEC” (Grant No. CA16117).

The 26 Al ( n , p ) 26 Mg reaction is the key reaction impacting on the abundances of the cosmic ¿ -ray emitter 26 Al produced in massive stars and impacts on the potential pollution of the early solar system with 26 Al by asymptotic giant branch stars. We performed a measurement of the 26 Al ( n , p ) 26 Mg cross section at the high-flux beam line EAR-2 at the n_TOF facility (CERN). We report resonance strengths for eleven resonances, nine being measured for the first time, while there is only one previous measurement for the other two. Our resonance strengths are significantly lower than the only previous values available. Our cross-section data range to 150 keV neutron energy, which is sufficient for a reliable determination of astrophysical reactivities up to 0.5 GK stellar temperature.

Tesis (Dr. en Física)--Universidad Nacional de Córdoba, Facultad de Matemática, Astronomía, Física y Computación, 2019. Actualmente, se cuenta con modernas técnicas para el tratamiento del cáncer incluidas dentro del marco de la radioterapia, conocidas como radioterapias no-convencionales. Estas técnicas fueron investigadas bajo el mismo precepto que todas las terapias de cáncer que utilizan radiaciones ionizantes: realizar la conformación de la dosis en el interior del paciente de la forma más precisa posible, sin dañar tejidos sanos o radio-sensibles. Entre estas técnicas no-convencionales, se encuentra la hadronterapia, que consiste básicamente en la utilización de partı́culas cargadas pesadas (protones, partı́culas alfa, iones de carbono, etc) para la conformación de dosis en pequeños volumenes. Las principales ventajas de la hadronterapia, se deben a la naturaleza del depósito de energı́a descripto por la fı́sica del problema. Dada la alta transferencia lineal de energı́a que poseen los iones utilizados en hadronterapia, los daños biológicos resultan superiores a los de la radioterapia convencional, y por ende es necesario contar con herramientas que permitan establecer el “control / verificación del rango de los iones” en el interior del paciente durante el procedimiento de irradiación. Para este fin, es necesario identificar procesos fı́sicos que produzcan alguna señal interpretable desde el exterior del paciente que sea potencialmente útil para monitorear el haz terapéutico. Una posibilidad consiste en aprovechar las propiedades del agua lı́quida equivalente a las del tejido blando, y analizar los procesos nucleares que den lugar a estados excitados del núcleo de oxı́geno con consecuente emisión foto-nuclear. En este trabajo de tesis, se investigó un nuevo enfoque basado en la posibilidad de monitorear el haz de terapia por medio de algún elemento no presente, en forma natural, en el tejido biológico; que al interactuar de alguna forma con la radiación incidente produzca alguna consecuencia correlacionada con los procesos de interés. Asimismo, se analiza la potencial detección de fotones de aniquilación en la radioterapia convencional debido a la inclusión de nanopartı́culas de oro en el material tejido-equivalente a modo de aproximación experimental a la detección, y correlación con el proceso de irradiación. En términos de hadronterapia, y particularmente la protonterapia, se estudia la factibilidad de aprovechar la fusión nuclear entre protones de energı́as bajas (respecto de las energı́as incidentes de terapia) y el isótopo de boro 11, dando lugar a dos significativas ventajas: la mejora dosimétrica debido a la emisión de partı́culas alfa resultantes del proceso de fusión; y la verificación online e in-situ del rango de los protones, con la consecuente herramienta de diagnóstico por imágenes médicas, debido a la emisión de fotones gamma prompt (“rápidos”). Nowadays, different techniques are being used for the treatment of cancer in the framework of radiotherapy, thoroughly known as non-conventional radiotherapies. These techniques were researched with the same goal than most cancer therapies utilizing ionizing radiation: conforming the dose inside the patient in the more accurate way possible, sparing healthy or radiosensitive tissues. Among these non-conventional techniques is the hadrontherapy, consisting mainly in using heavy charged particles (protons, alpha particles, carbon ions, etc) to perform the dose conformation in small volumes. The principal advantages of hadrontherapy are due to the nature of the energy deposition mechanism of the charged particles in matter, as described by the physics of the problem. Given the high linear energy transfer (LET) the ions used in hadrontherapy possess, the biological damage is higher than the conventional radiotherapy, and for this reason it is necessary to provide tools that allows the medical physicists to establish the “control / verification of the range of the ions” inside the patient during the irradiation procedure. To this aim, it is necessary to identify physical processes that leads to an interpretable signal outside the patient that are potentially useful for the therapeutic beam monitoring. A posibility consists of taking advantage of the water-equivalent properties of the biological tissue, and analyze the nuclear processes with excited states of the oxygen nuclei with the consecuent emission of a photo-nuclear photon. In this thesis work, a new approach is studied, based on the possibility of monitoring the therapeutic beam using an element not naturally present in the biological tissue, and whose interaction with the ionizing radiation used in the therapy produces a consequence correlated with the process of interest. These are called the “theranostics” methods. Likewise, the potential detection of annihilation photons in conventional radiotherapy is analyzed, using gold nanoparticles inside a tissue-equivalent material, mostly as an experimental approach to the detection and correlation with the irradiation process. In terms of hadrontherapy, particularly regarding protontherapy, this work shows the feasibility of taking advantage of the so-called proton-boron fusion, consisting of using the low-energy protons (respect therapy incident energies) interaction with boron 11 isotopes, which leads to two significant advantages: dosimetric improvement due to the alpha particles produced in the reaction; and an online and in-situ verification of the range of the protons, with the consequent tool for medical imaging, due to the emission of prompt-gamma photons. Fil: Geser, Federico Alejandro. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación; Argentina.

First measurements of double-polarization observables in $\omega$ photoproduction off the proton are presented using transverse target polarization and data from the CEBAF Large Acceptance Spectrometer (CLAS) FROST experiment at Jefferson Lab. The beam-target asymmetry $F$ has been measured using circularly polarized, tagged photons in the energy range 1200 - 2700 MeV, and the beam-target asymmetries $H$ and $P$ have been measured using linearly polarized tagged photons in the energy range 1200 - 2000 MeV. These measurements significantly increase the database on polarization observables. The results are included in two partial-wave analyses and reveal significant contributions from several nucleon ($N^\ast$) resonances. In particular, contributions from new $N^\ast$ resonances listed in the Review of Particle Properties are observed, which aid in reaching the goal of mapping out the nucleon resonance spectrum., Comment: Two authors added, figures updated

We investigate resonance states in three-cluster continuum of some light nuclei $^{9}$Be, $^{9}$B, $^{10}$B, $^{11}$B and $^{11}$C. These nuclei are considered to have a three-cluster configuration consisting of two alpha-particles and neutron, proton, deuteron, triton and nucleus $^{3}$He. In this study, we make use two different microscopic three-cluster models. The first model employs the Hyperspherical Harmonics basis to numerate channels and describe three-cluster continuum. The second model is the well-known complex scaling method. The nucleon-nucleon interaction is modeled by the semi-realistic Minnesota and Hasegawa-Nagata potentials. Our main aim is to find the Hoyle-analog states in these nuclei or, in other words, whether it is possible to synthesize these nuclei in a triple collision of clusters. We formulate the criteria for selecting such states and apply them to resonance states, emerged from our calculations. We found that there are resonance states obeying the formulated criteria which make possible syntheses of these nuclei in a stellar environment., 15 pages, 15 figures, submitted to Phys. Rev. C

In order to explore the nature of collective modes in weakly bound nuclei, we have investigated deformation effects and surface flow patterns of isovector dipole modes in a shape-coexisting nucleus $^{40}$Mg. The calculations were done in a fully self-consistent continuum finite-amplitude Quasiparticle Random Phase Approximation (QRPA) in a large deformed spatial mesh. An unexpected result of pygmy and giant dipole modes having disproportionate deformation splittings in strength functions was obtained. Furthermore, the transition current densities demonstrate that the long-sought core-halo oscillation in pygmy resonances is collective and compressional, corresponding to the lowest excitation energy and the simplest quantum flow topology. Our calculations show that surface flow patterns become more complicated as excitation energies increase., Comment: 5 pages, 4 figures, accepted for Phys.Rev.C (Rapid Comm.)

The $^{63}$Ni($n, \gamma$) cross section has been measured for the first time at the neutron time-of-flight facility n\_TOF at CERN from thermal neutron energies up to 200 keV. In total, capture kernels of 12 (new) resonances were determined. Maxwellian Averaged Cross Sections were calculated for thermal energies from kT = 5 keV to 100 keV with uncertainties around 20%. Stellar model calculations for a 25 M$_\odot$ star show that the new data have a significant effect on the $s$-process production of $^{63}$Cu, $^{64}$Ni, and $^{64}$Zn in massive stars, allowing stronger constraints on the Cu yields from explosive nucleosynthesis in the subsequent supernova. The Ni63(n,γ) cross section has been measured for the first time at the neutron time-of-flight facility n_TOF at CERN from thermal neutron energies up to 200 keV. In total, capture kernels of 12 (new) resonances were determined. Maxwellian averaged cross sections were calculated for thermal energies from kT=5–100 keV with uncertainties around 20%. Stellar model calculations for a 25M⊙ star show that the new data have a significant effect on the s-process production of Cu63, Ni64, and Zn64 in massive stars, allowing stronger constraints on the Cu yields from explosive nucleosynthesis in the subsequent supernova. The $^{63}$Ni($n, \gamma$) cross section has been measured for the first time at the neutron time-of-flight facility n\_TOF at CERN from thermal neutron energies up to 200 keV. In total, capture kernels of 12 (new) resonances were determined. Maxwellian Averaged Cross Sections were calculated for thermal energies from kT = 5 keV to 100 keV with uncertainties around 20%. Stellar model calculations for a 25 M$_\odot$ star show that the new data have a significant effect on the $s$-process production of $^{63}$Cu, $^{64}$Ni, and $^{64}$Zn in massive stars, allowing stronger constraints on the Cu yields from explosive nucleosynthesis in the subsequent supernova.

International audience; The 18O(p,α)15N and 17O(p,α)14N reactions are of primary importance in several as-trophysical scenarios, including nucleosynthesis inside Asymptotic Giant Branch stars and oxygen and nitrogen isotopic ratios in meteorite grains. They are also key reactions to understand exotic systems such as R-Coronae Borealis stars and novae. Thus, the measurement of their cross sections in the low energy region can be crucial to reduce the nuclear uncertainty on theoretical predictions, because the resonance parameters are poorly determined. The Trojan Horse Method, in its newly developed form particularly suited to investigate low-energy resonances, has been applied to the 2H(18O,α15N)n and 2H(17O,α14N)n reactions to deduce the 18O(p,α)15N and 17O(p,α)14N cross sections at low energies. Resonances in the 18O(p,α)15N and 17O(p,α)14N excitation functions have been studied and the resonance parameters deduced.

International audience; The 18O(p, α)15N and 17O(p, α)14N reactions are of primary importance in several as-trophysical scenarios, including nucleosynthesis inside Asymptotic Giant Branch stars and oxygen and nitrogen isotopic ratios in meteorite grains. They are also key reactions to understand exotic systems such as R-Coronae Borealis stars and novae. Thus, the measurement of their cross sections in the low energy region can be crucial to reduce the nuclear uncertainty on theoretical predictions, because the resonance parameters are poorly determined. The Trojan Horse Method, in its newly developed form particularly suited to investigate low-energy resonances, has been applied to the 2H(18O, α15N)n and 2H(17O, α14N)n reactions to deduce the 18O(p, α)15N and 17O(p, α)14N cross sections at low energies. Resonances in the 18O(p, α)15N and 17O(p, α)14N excitation functions have been studied and the resonance parameters deduced.

The resonance scattering method in inverse kinematics on infinite target has been applied to two systems, 18O + alpha and 9Be + alpha, in order to test and to optimize an experimental apparatus in view of a set of resonance scattering experiments to be performed with 8Li and 9Li radioactive ion beams delivered by the facility EXCYT. The scattering excitation functions, deduced for the two systems, were compared with previous results reported in literature. Results show that reliable stopping power data are essential for the application of this technique.