We discuss the possibility of finding an upper bound on the seesaw scale using the cosmological bound on the cold dark matter relic density. We investigate a simple relation between the origin of neutrino masses and the properties of a dark matter candidate in a simple theory where the new symmetry breaking scale defines the seesaw scale. Imposing the cosmological bounds, we find an upper bound of order multi-TeV on the lepton number violation scale. We investigate the predictions for direct and indirect detection dark matter experiments and the possible signatures at the Large Hadron Collider.
I will talk about a family of alpha'-corrected solutions of the Heterotic Superstring effective action describing four-dimensional black holes which are sourced by five branes, strings and Kaluza-Klein monopoles. I will then focus!
on small black holes, discussing if higher-curvature corrections can render the horizon regular or not.!
Mapping gluonic states in the light sector is a challenge,
and has led to controversies in the past. In particular, the experiments have reported two different states with exotic signature, \pi_1(1400) and \pi_1(1600), which couple separately
to \eta \pi and \eta' \pi. This picture is not compatible with the Lattice QCD estimates for hybrid states, nor with most phenomenological models.
We consider the most recent partial wave analysis of the \eta pi system performed by COMPASS. We fit it with a coupled-channel amplitude which enforces the unitarity and analyticity of the S-matrix. We provide
a robust extraction of a single exotic \pi_1 resonant pole, with mass and width 1564 +- 24 +- 86 MeV and 492 +- 54 +- 102 MeV, which couples to both \eta(') pi channels. We find no evidence for a second exotic state. We also provide the resonant parameters of the a_2(1320) and a'_2(1700).
We briefly summarize current experimental and theoretical results on the two important processes of the low-energy hadron physics involving neutral pions: the Dalitz decay of $\pi^0$ and the rare decay $\pi^0\to e^+e^-$. As novel results we present the complete set of radiative corrections to the Dalitz decays $\eta^{(\prime)}\to\ell^+\ell^-\gamma$ beyond the soft-photon approximation, i.e.\ over the whole range of the Dalitz plot and with no restrictions on the energy of a radiative photon. The corrections inevitably depend on the $\eta^{(\prime)}\to\gamma^*\gamma^{(*)}$ transition form factors. For the singly-virtual transition form factor appearing e.g.\ in the bremsstrahlung correction, recent dispersive calculations are used. For the one-photon-irreducible contribution at the one-loop level (for the doubly-virtual form factor), we use a vector-meson-dominance-inspired model while taking into account the $\eta$-$\eta^\prime$ mixing.
After recalling that the sharpened version of the WGC proposed by Ooguri and Vafa implies that any stable non-SUSY AdS vacuum is in the swampland, we will present several consequences that this may have for the SM and some of its extensions. First, we will argue why it is interesting to consider compatifications of the SM to 2D on $T^2/Z_N$. From these we can conclude that the SM is not robust against the appearance of AdS vacua in 2D and hence would be, by itself, inconsistent with quantum gravity. However, if the SM is embedded at some scale into a supersymmetric version, these AdS vacua present in the non-SUSY case disappear or become unstable, suggesting that the WGC favors supersymmetry. Finally, we present different scenarios in which embedding the orbifold action into different gauge symmetries can lead to additional constraints.
The Standard Model of particles physics (SM), which describes the strong, weak and electromagnetic interactions, has shown to be very successful. However, there are clear indications that the SM is not the ultimate theory of elementary particle interactions since it has troubles to explain some phenomena such as the neutrino masses. It is known that some of these problems could be resolved considering a gauge theory with invariance under a larger group than the SM gauge group. Thereby the Standard Model would be the low-energy limit of this new gauge theory. We call them Grand Uni ed theories (GUTs). Most of GUTs have important implications in Cosmology, for example an explication for the baryon asymmetry of the universe, new dark matter candidates, an approach to the earliest universe energies... We will introduce Grand Uni cation and we will discuss its role in Cosmology. Furthermore, we shall present an uni fied model based on gauge group SU(4)_CxSU(4)_RL.
Based on the quasi-local energy definition of Brown and York, we compute the integral of the trace of the extrinsic curvature over a codimension-2 hypersurface. In particular, we study the difference between the uncompactified Minkowski spacetime and the toroidal Kaluza-Klein compactification. For the latter, we find that this quantity interpolates between zero and the value for the uncompactified spacetime, as the size of the compact dimension increases. Thus, the quasi-local energy is able to discriminate between the two spacetimes.
It has been recently argued that the presence of any non-SUSY AdS stable vacua implies that a theory cannot be consistently coupled to gravity (Ooguri-Vafa conjecture). The application of this conjecture to the SM and its compactifications to two or three dimensions has lead to interesting predictions on low energy physics. One of these predictions is an upper bound on the Higgs vev, determined by the cosmological constant, that appears when trying to avoid the formation of an AdS minima around the neutrino scale. We will show that, when the number of quark/lepton generations is bigger or equal than three, the Higgs vev is also bounded from below by $\Lambda_{\text{QCD}}$. These bounds force the EW and QCD scale to be relatively close. They also imply that the Higgs vev is stable against quantum corrections, leading to a reassessment of the SM hierarchy problem.
The MnuSSM is a simple supersymmetric extension of the Standard Model (SM) capable of predicting neutrino physics in agreement with experiment. In this paper we perform the complete one-loop renormalization of the neutral scalar sector of the MnuSSM with one and three generations of right-handed neutrinos in a mixed on-shell/DR scheme. The renormalization procedure is discussed in detail, emphasizing conceptual differences to the minimal (MSSM) and next-to-minimal (NMSSM) supersymmetric standard model regarding the field renormalization and the treatment of non-flavor-diagonal soft mass parameters, which have their origin in the breaking of R-parity. We calculate the full one-loop corrections to the neutral scalar masses of the MnuSSM. The one-loop contributions are supplemented by available MSSM higher-order corrections. We obtain numerical results for a SM-like Higgs boson mass consistent with experimental bounds. Corrections genuine for the MnuSSM are discussed in example scenarios. Finally we show that the MnuSSM can accomodate a Higgs boson that could explain an excess of diphoton events at ∼96GeV, as reported by CMS, as well as the 2σ excess of bb events observed at LEP at a similar mass scale.
The RG-2 flow is the two-loop approximation for the world-sheet non
linear sigma model renormalization group flow. The first truncation of
the flow is the well known Ricci flow, at two loops higher order
curvature terms appear, changing almost completely the behaviour of
the evolution equation. In this talk we study the RG-2 flow in the
context of general relativity. Considering a time symmetric foliation
of an asymptotically flat spacetime we show that the area A of a
closed two dimensional surface S is monotonous under the RG-2 flow,
refining and extending the previous results already known for the
Ricci flow, we also discuss about the possibility of extending the
result to all loops. We show that the inequality relating the area of
the surface S and the Hawking mass already found for the Ricci flow is
still satisfied when we make evolve the area under the new flow.
The cold dark matter (CDM) scenario has proved successful in cosmology.
However, we lack a fundamental understanding of its microscopic nature. Moreover, the
apparent disagreement between CDM predictions and subgalactic-structure observations
has prompted the debate about its behaviour at small scales. These problems could be
alleviated if the dark matter is composed of ultralight fields m ∼ 10 −22 eV, usually known
as fuzzy dark matter (FDM). Some specific models, with axion-like potentials, have been
thoroughly studied and are collectively referred to as ultralight axions (ULAs) or axion-like
particles (ALPs). In this work we consider anharmonic corrections to the mass term coming from a repulsive quartic self-interaction. Whenever this anharmonic term dominates, the field behaves as radiation instead of cold matter, modifying the time of matter-radiation equality. Additionally, even for high masses, i.e. masses that reproduce the cold mat-
ter behaviour, the presence of anharmonic terms introduce a cut-off in the matter power
spectrum through its contribution to the sound speed. We analyze the model and derive
constraints using a modified version of class and comparing with CMB and large-scale
structure data.
We characterise the geometrical nature of smooth supertranslations
defined on a generic non-expanding horizon (NEH) embedded in vacuum. To this
end we consider the constraints imposed by the vacuum Einstein’s equations on the
NEH structure, and discuss the transformation properties of their solutions under
supertranslations. We present a freely specifiable data set which is both necessary
and sufficient to reconstruct the full horizon geometry, and is composed of objects
which are invariant under supertranslations. We conclude that smooth supertranslations
do not transform the geometry of the NEH, and that they should be regarded
as pure gauge. Our results apply both to stationary, and non-stationary states of a
NEH, the later ones being able to describe radiative processes taking place on the
horizon. As a consistency check we repeat the analysis for BMS supertranslations
defined on null infinity, I. Using the same framework as for the NEH we recover the
well known result that BMS supertranslations act non-trivially on the free data on
I. The full analysis is done in exact, non-linear, general relativity.
La caracterización de los blancos utilizados en experimentos de física nuclear resulta fundamental en la interpretación de los resultados de éstos. Dos tipos de desviaciones respecto a los blancos diseñados, inhomogeneidades y presencia de impurezas, pueden alterar la composición inicialmente planificada. Las técnicas IBA constituyen una herramienta de caracterización idónea para medir los blancos que se utilizarán posteriormente (o que hayan sido usados) en experimentos de reacciones nucleares. Se presentarán diferentes ejemplos de caracterización de blancos.
Based on recent experimental and theoretical hints on possible formation of a resonant four-neutron system we study effects of appearance of such an aggregates in neutron rich baryon matter inside neutron stars. For this purpose we employ a relativistic mean field approach which includes nucleons, Δ-isobars as well as light nuclear clusters. Our analysis demonstrates that tetraneutrons existing as the Bose-Einstein condensate can appear even despite their short lifetime and strong effects of the Pauli blocking. This significantly affects the equation of state of cold baryonic matter and observable characteristics of neutrons stars. Tetraneutron driven suppression of Δ-baryons is another important result of our study. The most prominent manifestation of the tetraneutron condensation in neutron stars is related to suppression of the superconducting phase which can be concluded from analysis of the nucleon-nucleon pairing gap and density of pairs.
Tl-205 is most abundant stable isotope of thallium in the Earth. It is produced mainly during the slow (s) process of nucleosynthesis by neutron capture. During some stages of the s process, and due to the high temperatures involved, it becomes stable and decays to Pb-205. This isotope of lead is radioactive, and it is produced only by the s-process, and therefore it is thought that it could be used as a "clock" of the process. The Tl-205 abundance is strongly dependent on its neutron capture rate, and by means of the mechanism mentioned before, so it is the abundance of Pb-205. Having considered this, the ANT group of the UPC carried out the measurement of the capture cross section of Tl-205 in the n_TOF experiment at CERN this last summer, aiming to improve both the accuracy and precision of the cross section for nucleosynthesis calculations. In this talk, besides explaining more in detail the astrophyisical motivations, a description of the measurement process, and some preliminary results, will be shown.
Chairs: Juan Antonio Aguilar Saavedra, Carmen Garcia, Sven Heinemeyer
Chair: Sergio Pastor
El uso de las técnicas nucleares de análisis ha experimentado un auge extraordinario en las últimas décadas en el campo del Patrimonio Cultural. Hoy en día, su uso en el estudio de objetos de interés para el Patrimonio se ha vuelto esencial. Desde los años 90, el grupo de investigación en Física Nuclear Aplicada del Centro Nacional de Aceleradores ha realizado un esfuerzo importante para desarrollar diferentes técnicas analíticas no destructivas para el estudio de objetos de arte y arqueológicos. Estos esfuerzos se centraron inicialmente en el uso de las técnicas IBA (Ion Beam Analysis) y, últimamente, en el desarrollo de equipos portátiles de fluorescencia de rayos X (XRF), incluidas las versiones con microhaces gracias a la implementación de lentes policapilares (μXRF y XRF confocal).
En esta comunicación se presentarán los diferentes métodos e instrumentación desarrollados en los últimos años en el CNA, e ilustraremos con varias aplicaciones sus capacidades para el análisis de diferentes tipos de objetos: joyas, monedas, pinturas, vidrios, etc. Se mostrarán las ventajas y limitaciones de las diferentes técnicas y también se presentarán ejemplos de cómo la combinación de varios de estos métodos puede superar algunas de esas limitaciones.
En este trabajo se ha estudiado la técnica de seguimiento de marcadores fiduciales emisores de positrones para detectar y corregir movimiento en adquisiciones de tomografía por emisión de positrones (PET). El objetivo es poder realizar adquisiciones PET con animales despiertos. Esto evitaría el uso de anestesia y sus efectos en el funcionamiento normal del cerebro bajo estudio.
Se han estudiado distintas métricas para determinar el movimiento tanto en el espacio del sinograma como en el de la imagen retroproyectada. Se ha probado que varias de estas métricas, basadas en la distribución no uniforme del escáner, son capaces de detectar instantes en los que el animal se encuentra quieto. El método del centroide de líneas de respuestas ha sido el más rápido.
Mediante la generación de datos con trazado de rayos y simulaciones Montecarlo con Penelo-PET, se ha estudiado cómo afectan factores como el ruido o la resolución del escáner, en la correcta localización de los marcadores. Con ello se pretende poder estimar la actividad óptima de las fuentes dependiendo del estudio que se quiere realizar. Para la correcta localización de las fuentes se ha utilizado un nuevo filtro, que hemos denominado pseudo-FBP, que mejora el contraste obtenido con la retroproyección estándar, sin aumentar mucho el tiempo de cálculo.
Por último, se ha caracterizado el movimiento de los cuatro marcadores colocados sobre una rata en una adquisición con FDG mediante el PET Super-Argus. Para ello se ha usado el algoritmo Kabsch para determinar el movimiento de sólido rígido de la imagen retroproyectada. El uso de las imágenes retroproyectadas de cada instante de tiempo (en lugar de las imágenes reconstruidas que requieren entre uno y dos órdenes de magnitud más de tiempo de cálculo) es un gran avance en este campo, dado que abre las puertas a su uso en futuros estudios en vivo.
En resumen, en este trabajo mostramos cómo es posible estimar y caracterizar de manera rápida y eficiente el movimiento en PET mediante el uso de marcadores fiduciales emisores de positrones colocados sobre el animal en estudio.
Neutrons are intentionally used or incidentally created in various scenarios. Depending on the neutron energy, this kind of radiation can dominate the total dose received. Thus, the detection of neutrons, for radiation protection purposes, is an important issue in areas such as basic research, nuclear power plants, healthcare, industrial applications, defense and homeland security. The commercially available detectors for area monitoring are based on polyethylene moderated proportional counters [KNO10]. They were designed in the late nineties, according to the ICRP74 recommendations [ICRP74], in order to measure the ambient to dose equivalent H(10).
For continuous neutron fields, commercial surveys fits well the recommended response up to 10 or 20 MeV [IAEA2001]. At higher energies, the response of most of the commercial dosimeters present underestimations of the ambient dose (H(10)). This is a major concern in modern medical applications, such as proton therapy, where secondary neutrons are produced with energies spanning from 60 up to 250 MeV[AGO98, FAR15, MAR16].
For pulsed fields, i. e. when the neutron intensity presents large variations in short periods of time, there are currently several concerns about the reliability of commercial neutron dosimeters [KLE06, CAR14]. This is a major issue for the radiation protection in the new particle accelerator technologies, for example synchrotrons and medical linacs, where beam losses produce short bursts of secondary neutron radiation; or pulsed neutron facilities for basic research and applications, such as spallation and fusion sources, high intensity lasers, among others.
At UPC, provided the experience gained by our group in the design of complex neutron detectors for research in nuclear physics, we have started a project for the design of improved ambient neutron dosimeters. The new designs are intended for application in pulsed fields and proton therapy. The status and future of the project is presented.
Las nanopartículas de lantánidos constituyen un prometedor grupo de agentes para imagen multimodal. Por sus propiedades fisicoquímicas podrían ser útiles en diferentes técnicas diagnósticas; bioluminiscencia, resonancia magnética (MRI), tomografía computarizada (CT) y tomografía por emisión de positrones (PET). En el presente trabajo se marcaron nanopartículas de trifluoruro de lantano con Flúor-18 para estudios de imagen por PET/CT.
Se obtuvo el [18F]fluoruro por bombardeo de un target líquido 18O(p,n)18F en el ciclotrón del CNA. La actividad se transfirió a un módulo de síntesis dentro una celda blindada de la Unidad de Radiofarmacia. La reacción de marcaje tuvo lugar a temperatura ambiente. Antes de inyectarlas al animal, se analizaron las nanopartículas por radiocromatografía en capa fina, para asegurar la pureza radioquímica. Los controles de pH y la estabilidad in vitro en plasma humano se llevaron a cabo en estudios anteriores. Se inyectaron 4 MBq de nanopartículas radiactivas por la vena lateral de la cola de un ratón sano BALB/c y se realizó el estudio PET estático de 15 minutos seguido del estudio CT. El animal permaneció anestesiado durante ambos estudios, por lo que las imágenes funcionales PET pudieron superponerse a las imágenes anatómicas del CT.
Muchas de las técnicas de imagen médica se basan en el uso de radiación ionizante. En particular la tomografía por emisión de positrones (PET) permite obtener imágenes tridimensionales de calidad tras suministrarle al paciente un fármaco con un marcador emisor de positrones.
Actualmente, la producción de isótopos radioactivos destinados a imagen y tratamientos médicos tiene lugar principalmente en aceleradores de partículas convencionales. Recientemente se ha propuesto el empleo de láseres ultraintensos de femtosegundo los cuales, a través de la interacción láser-plasma, son capaces de acelerar partículas ligeras en un rango de energías suficiente como para generar estos isótopos mediante reacciones nucleares.
El Laboratorio Láser de Aceleración y Aplicaciones (L2A2) de la Universidad de Santiago de Compostela dispone de un láser de femtosegundo capaz de operar con una tasa de disparo de 10 Hz, con el que se pretende conseguir un haz de protones continuo de hasta 10 MeV. La focalización del láser sobre un blanco primario, alcanzando intensidades de en torno a 10^19 W/cm2, permite por diversos mecanismos físicos la generación de un haz de partículas ligeras (protones, deuterones, etc) que, al incidir sobre un blanco secundario, dan lugar a la producción de isótopos radioactivos.
En esta charla presentaremos el dispositivo experimental instalado en el L2A2 para este fin describiendo en particular los sistemas de focalización, el blanco de aceleración y su control y los sensores de caracterización de los protones acelerados.
En protonterapia, la verificación de rango in vivo usando un escáner PET se basa en la comparación entre la actividad medida y la actividad estimada de emisores de positrones inducidos por el haz de protones en los principales elementos del cuerpo humano: carbono, oxígeno, nitrógeno, calcio y fósforo. La exactitud con la que se conoce dicha estimación depende de la exactitud de la simulación Monte Carlo correspondiente, que a su vez depende de la exactitud con la que se conocen las secciones eficaces de interés [1]. Una revisión de los datos experimentales disponibles en EXFOR [2,3] muestra que para determinadas reacciones no existen datos en todo el rango de energías del haz de protones (hasta 250 MeV) y que, además, existen diferencias significativas entre las distintas medidas. Esto es particularmente serio para el caso de emisores β+ de vida media corta (<20 s), para los que básicamente no existen datos por encima de 55 MeV.
En este trabajo se ha desarrollado un método para medir las tasas de producción de emisores de positrones de vida media larga, 11C y 13N, en carbono, nitrógeno y oxígeno. El método consiste en la irradiación de paquetes de láminas delgadas ricas en C, N y O, de tal forma que el haz de protones se degrada a su paso por ellas. La medida de la actividad producida en cada lámina se mide entonces en un escáner PET operado en modo dinámico para obtener las curvas de actividad correspondientes. El método se ha aplicado de forma satisfactoria en el CNA para protones por debajo de 18 MeV, para los que se han medido las reacciones 16O(p, )13N y 14N(p, )11C. Se presentarán dichos resultados además de los planes para realizar medidas a mayores energías en haces clínicos.
Este método no es aplicable a los emisores de vida media corta, ya que el decaimiento se produciría por completo antes de poder colocar las láminas irradiadas en el escáner PET. Por tanto se está diseñando, en colaboración con KVI-CART, otro dispositivo experimental basado en la irradiación con una haz pulsado y las medidas de la actividad correspondiente mediante detectores centelleadores entre pulso y pulso. La clave en este caso son las correcciones por la posición de la aniquilación de los positrones, ya que los valores Q son de hasta 16 MeV. Se presentarán las simulaciones Monte Carlo correspondientes a dicho montaje experimental y se discutirán los experimento de validación de la técnica que se pretende llevar a cabo en el CNA mediante el estudio de las reacciones 31P(p,p2n)29P y 40Ca(p,2pn)38mK por debajo de 18 MeV.
We propose a new interpretation of Peccei-Quinn symmetry within the Standard Model, identifying it with the axial B+L symmetry i.e. U(1)PQ≡U(1)γ5(B+L). This new interpretation retains all the attractive features of Peccei-Quinn solution to strong CP problem but in addition also leads to several other new and interesting consequences. Owing to the identification U(1)PQ≡U(1)γ5(B+L) the axion also behaves like Majoron inducing small seesaw masses for neutrinos after spontaneous symmetry breaking. Another novel feature of this identification is the phenomenon of spontaneous (and also chiral) proton decay with its decay rate associated with the axion decay constant. Low energy processes which can be used to test this interpretation are pointed out.
In this seminar, we apply the formalism known as hybrid loop quantum cosmology to the physically interesting case of fermionic cosmological perturbations. Within this formalism, we study the possible splitting procedures between the cosmological geometry and the perturbations, leading to different Hamiltonian dynamics. The geometry is quantized by methods inspired in loop quantum gravity, whereas the perturbations are quantized by usual techniques of quantum field theory in curved spacetimes. We then discuss the freedom available to define creation and annihilation operators for the fermionic degrees of freedom and determine the sufficient and necessary conditions that this definition must satisfy in order to provide a quantum theory with good properties in the matter sector.
In the present work we study a model with an SU(2)_L x SU(2)_R x U(1)_X$ symmetry, with two scalar doublets. We start from a massless lagrangian, but by using the Coleman-Weinberg mechanism we obtain masses for both the gauge bosons and the scalars. We also calculate the renormalized effective potential, depending on the masses and couplings of the model. With this formalism we obtain two sets of gauge bosons, corresponding to the L and R sectors, in addition to the two scalars. We analyse the mass ratio of these sectors in order to obtain a hyerarchy between them. With an appropriate choice of parameters we can have the L particles in the SM range, while the R particles have much higher masses.
Axion and axion-like particle models are typically affected by a strong fine-tuning problem in conceiving the electroweak and the Peccei-Quinn breaking scales. Within the context of the Minimal Linear ${\sigma}$ Model, axion-like particle constructions are identified where this hierarchy problem is solved, accounting for a TeV Peccei-Quinn breaking scale and a pseudoscalar particle with a mass larger than 10 MeV. Potential signatures at the LHC are discussed.
The talk would be bases on "J. Alonso-González, L. Merlo, F. Pobbe, S. Rigolin and O. Sumensari, <<testable axion-like="" in="" linear ${\sigma}$ model="" minimal="" particles="" the="">>, arXiv:1807.08643 [hep-ph]”.</testable>
We consider an effective non-linear Electroweak Chiral Lagrangian containing three would-be Goldstone bosons: w^a which transform non-linearly as a triplet under SU(2)_L X SU(2)_R and a Higgs singlet h plus its couplings to fermions via Yukawa interactions. This low energy model is valid for the range M_h,M_W,M_Z << s << 3 TeV.
Since the nex-to-leading order corrections due to fermion loops are proportional to the mass of the fermion we have performed the calculation for the heaviest fermion: top quark. We present both the finite and divergent part to the one-loop contribution, finding an agreement with other authors for the latter.
We consider Type IIA compactifications on Calabi-Yau orientifolds
with non-trivial background fluxes and mobile D6-branes. In this context, we investigate whether some known examples of stable type IIA vacua are kept in the presence of open string degrees of freedom.
In this talk, I will present the study of the decay of 8B into highly excited states of 8Be with the aim of determining the branching ratios. Our interest lies in the 2+ doublet at 16.6 and 16.9 MeV populated via β+ and electron capture (EC) respectively and also the so far unobserved EC-delayed proton emission via the 17.640 MeV state, that has a theoretical branching ratio of 2.3·10-8. The 2+ doublet is interesting due to the high isospin mixing [1], leading to dominant configurations as 7Li+p and 7Be+n respectively
I will discuss the aims of the experiment, the setup and I will give the results obtained so far in the analysis.
[1] P. von Brentano, Phys. Rep. 264 (1996) 57
The neutron research activities with the Tandem Pelletron Accelerator at CNA in Seville (Spain) is based on the development of neutron sources with different energy and angular distributions, which could be generated by 7Li(p,n) and D(D,n) reactions. The neutron beam characterization is done using the Time of Flight technique (TOF). The TOF technique allows measuring neutron induced cross section as a function of the neutron energy, which can be obtained from the flight time that a neutron spends to travel over known path. To implement TOF technique one needs pulsed ion beams.
In order to provide pulsed beams, CNA team and NEC staff are currently working on a chopping/bunching system installation and commissioning, as well as the addition of new equipment to better monitor and control the beam in a new neutron line. The beam chopper consists of a pair of electrically deflecting plates, mounted in parallel to the initial ion beam. One plate is normally polarized with dc voltage deflecting the beam on an absorbing beam catcher. The second one is supplied with an electronic switch. Both work together producing an oscillation of the beam in the transverse direction, thus creating a beam pulse. The bunching unit, being made up involving a pair of tubular electrodes, is mounted coaxially to the ion beam, after the pulsing unit. The electrodes are supplied with radiofrequency voltage phase locked to the different frequencies of the chopping system. The entrance and the exit gaps of the tubular bunching electrodes are used for the time compression of the beam pulse. The other new devices are: a beam profile monitor (BPM), two magnetic steerers, two manual slits, a Faraday cup, and a Pick-Up.
The chopping/bunching system has been designed to deal with a primary beam of protons or deuterium. The first tests with protons show a pulsed beam with a FWHM of the order of ns and expected frequency.
These promising results will lead the way to various research lines in Seville, among them are nuclear energy production, radiation protection, cancer therapy by neutron irradiation, radio- biological and nuclear structure research.
Los SiPMs ocupan un lugar importante en la detección de radiación para experimentos de física nuclear e imagen médica. Aparecen nuevos modelos cada pocos meses con características mejoradas. Analizamos en este trabajo los últimos modelos de SiPM de Hamamatsu y SensL que introducen mejoras en la PDE con respecto a los modelos anteriores. Se han acoplado a varios cristales centelladores, LYSO, PrLuAG, CeGAG y CsI. El PrLUAG es un cristal notablemente más rápido que el LYSO, presenta su pico de emisión en los 310 nm, lo que pone a prueba la sensibilidad espectral de los SiPMS en el extremo de su respuesta. El CEGAG presenta una gran emisión de fotones, por lo que cabría esperar buena resolución energética por su parte.
Se han probado diferentes combinaciones y tamaños de cristales centelladores con cuatro SiPMs de Hamamatsu: S13360-3050CS, S13360-66050CS, S13360-6075Cs, S14160-6050HS, y dos SiPMs de SensL: MicroES-SMA-30035TSV y MicroFJ-SMA-60035.
Los resultados obtenidos muestran que, la mejora en la PDE de los nuevos SiPMs, se traduce en mejores resoluciones en energía, 8% (CeGAGG), 10% (LYSO) y 16% (PrLUAG), utilizando el modelo S13360-6075CS de Hamamatsu. En todos los casos el factor más limitante se ha encontrado la diferencia entre las secciones transversales de los cristales probados (10x10 mm2) y del SiPM (6x6 mm2). Los resultados con CsI (6x6mm2) son reveladores a este respecto. Con respecto a la resolución temporal, para las combinaciones favorables de SiPMs y cristales se han conseguido valores de resolución en torno a 250 ps (FWHM,CRT), en este caso los mejores resultados se obtienen con SiPM de SensL.
In this work we summarize some recent experiments carried out at the three different irradiation facilities from the Centro Nacional de Aceleradores, using either gamma radiation from a Co-60 source, or protons and neutrons from the particle accelerators. In addition, the main characteristics of a new chamber which will be available at CNA in the near future and specially designed to irradiate at elevated and cryogenic temperatures will be shown and discussed.
Los haces de neutrones pulsados suponen una valiosa herramienta en física nuclear, con aplicaciones en un amplio abanico de campos [1-7]. Estos haces de neutrones, producidos actualmente mediante aceleradores de partículas convencionales [8-11], se caracterizan mediante “tiempo de vuelo” (TOF, por sus siglas en inglés), lo que nos permite conocer el espectro energético de nuestro haz de neutrones. El uso de esta técnica está limitado por la resolución temporal que podamos obtener, la intensidad de cada pulso, y la frecuencia con las que podamos producirlos.
En las últimas décadas, el desarrollo de láseres de pulso ultracorto (femtosegundo) y alta potencia (> 1019 W/cm2) ha abierto la puerta a un gran número de nuevas aplicaciones [12]. Gran parte de los recursos de investigación se han invertido en el estudio de la aceleración de haces de iones asistidos por láser, dirigiendo la mayoría de los esfuerzos en la optimización en la producción de las distintas especies de partículas. El uso de estos haces en la producción de neutrones ha permitido alcanzar valores por pulso competitivos respecto a las fuentes tradicionales [13-14] lo que podría convertir a este tipo de fuentes láser en una interesante alternativa para la comunidad de haces pulsados. Sin embargo, hasta ahora, estos neutrones no han sido utilizados para llevar a cabo ningún experimento de física nuclear.
En este contexto, nuestro grupo de investigación desde la Universidad de Sevilla, y en colaboración con otros grupos de investigación con amplia experiencia en producción, detección y uso de haces pulsados de neutrones en instalaciones convencionales, se ha propuesto realizar una serie de experimentos con el objetivo de producir y caracterizar haces de neutrones pulsados asistidos por láser, optimizando las técnicas de detección, análisis y diagnóstico utilizadas actualmente en fuentes de neutrones convencionales para implementarlas en sistemas de producción láser con el propósito de asentar la viabilidad de llevar a cabo experimentos de física nuclear en este tipo de fuentes e identificar las ventajas y desventajas de este método de producción respecto a los sistemas convencionales.
Para ello, se pretende realizar experimentos en diferentes instalaciones láser tanto en España (L2A2 en Santiago de Compostela y CLPU en Salamanca) como en Europa (CILEX en Paris y LEX Photonics en Munich).
Referencias
[1] Barbagallo M. et al., Phys. Rev. Lett. 117, 152701 (2016). [2] Guerrero C. et al., Phys. Rev. C 85, 044616 (2012).
[3] Lederer C. et al., Phys. Rev. Lett. 110, 022501 (2013).
[4] Lerendegui-Marco J., et al. Phys. Rev. C 97, 024605 (2018). [5] Mendoza E. et al., Phys. Rev. C 97, 054616 (2018).
[6] Praena, J. et al., Nucl. Data Sheets. 120, 205–207. (2014).
[7] Sato, H. et al., Nucl. Instrum. and Meth A. 605(1-2), 36-39. (2009).
[8] Bensussan A. and J. M.Salome. Nucl. Instrum. and Meth. 155(1-2), 11-23 (1978). [9] Guerrero, C. et al. Eur. Phys. J. A. 49, 27 (2013).
[10] Lederer, C. et al Phys. Rev. C 85, 055809 (2012).
[11] Mastinu, P. et al. Phys. Procedia, 26, 261-273 (2012).
[12] Danson, C. et al., High Power Laser Sci., 3. e3, 1-14. (2015).
[13] Pomerantz I. et al., Phys Rev Lett 113, 184801 (2014).
[14] Roth M. et al., Phys Rev Lett 110, 044802. (2013).
By using a non-relativistic independent particle approach we investigate the mechanism promot- ing 34 as new magic number. We carried out Hartree-Fock plus Bardeen-Cooper-Schrieffer and Quasi-particle Random Phase Approximation calculations by consistently using the same finite- range interaction in all the three steps of our approach. We used two Gogny-like interactions, with and without tensor terms. We find that the shell closure for N = 34 neutrons appears in isotones with proton number smaller than 26. The smaller is the proton number, the more evident is the shell closure at N = 34. An ideal nucleus to investigate this effect is 48Si , as it has been recently suggested.
The neutron capture reactions in 244Cm and 246Cm isotopes open the path of the formation of heavier Cm isotopes and heavier elements such as Bk and Cf in a nuclear reactor. In addition, both isotopes are two of the minor actinides with a large contribution to the decay heat and to the neutron emission in irradiated fuels proposed for the transmutation of the nuclear waste and fast critical reactors. The available experimental data for both isotopes is very scarce due to the difficulties in performing the measurements: high intrinsic activity of the samples and the limited facilities capable of providing isotopically enriched samples. We measure the neutron capture cross section measurement with isotopically enriched samples of 244Cm and 246Cm provided by JAEA. The measurement covers the range from 1 eV to 250 eV. The measure was done in to difference experimental areas with different detectors: In Experimental Area 2 (EAR-2) with C6D6 and also in experimental Area 1 (EAR-1) with the Total Absorption Calorimeter.
Chair: Sergio Pastor
Chairs: Juan Antonio Aguilar Saavedra, Carmen Garcia, Sven Heinemeyer
Casino del Tormes (C/ La Pesca, 5, 37008 Salamanca)