Joaquin Gomez Camacho

The structure and decay of the most neutron-rich beryllium isotope, Be 16, has been investigated following proton knockout from a high-energy B 17 beam. Two relatively narrow resonances were observed for the first time, with energies of 0.84 (3) and 2.15 (5) MeV above the two-neutron decay threshold and widths of 0.32 (8) and 0.95 (15) MeV, respectively. These were assigned to be the ground (J π= 0+) and first excited (2+) state, with E x= 1.31 (6) MeV. The mass excess of Be 16 was thus deduced to be 56.93 (13) MeV, some 0.5 MeV more bound than the only previous measurement. Both states were observed to decay by direct two-neutron emission. Calculations incorporating the evolution of the wave function during the decay as a genuine three-body process reproduced the principal characteristics of the neutron-neutron energy spectra for both levels, indicating that the ground state exhibits a strong …

NUCLEAR REACTIONS 3 He (32 S, α) 31 S, E= 128 MeV; measured reaction products, Eγ, Iγ; deduced γ-ray energies, levels, T 1/2, resonances. Comparison with the shell-model code NuShellX calculations. Modern Markov chain Monte Carlo-based Bayesian statistical techniques. The Doppler Shift Lifetimes (DSL2) facility at the TRIUMF Isotope Separator and Accelerator (ISAC-II) facility.

The characteristics of the fast neutron beams produced in the HiSPANoS facility at Centro Nacional de Aceleradores (CNA) are presented. The neutrons are generated by deuteron beams from a 3 MV tandem accelerator in either continuous (5 μ A) or pulsed (2 ns width, 500 kHz and 4% duty cycle) mode. In this work, the pulsed mode was used in a time-of-flight characterization of the produced neutron beams in terms of yield, flux, energy resolution, and background. The results were then validated through their comparison with previously published data. Quasi-monoenergetic neutron beams between 2 and 6 MeV are produced by means of the 2 H (d, n) 3 H e reaction, featuring a neutron yield of 10 6 n/sr/μ C at the target, with an energy resolution of about 7% at 150 cm. Neutron beams with broad energy distributions are produced by deuteron irradiation of thick beryllium and lithium targets, resulting in maximum …

miniBELEN is a modular and transportable neutron moderated counter with a nearly flat neutron detection efficiency up to 10 MeV. Modularity implies that the moderator can be reassembled in different ways in order to obtain different types of response. The detector has been developed in the context of the Measurement of Alpha Neutron Yields (MANY) collaboration, which is a scientific effort aiming to carry out measurements of (????, ????) production yields, reaction cross-sections and neutron energy spectra. In this work we present and discuss several configurations of the miniBELEN detector. The experimental validation of the efficiency calculations using 252Cf sources and the measurement of the 27Al(????, ????) 30P reaction is also presented.

The discrepancy between experimental data and theoretical calculations in one-nucleon removal reactions at intermediate energies (quantified by the so-called “quenching factors”) and its dependence on the isospin asymmetry of the nuclei has been an open problem in nuclear physics for the last fifteen years. In this work, we propose an explanation for this long-standing problem, which relies on the inclusion of the process of core destruction due to its interaction with the removed nucleon. To include this effect, we extend the commonly used eikonal formalism via an effective nucleon density, and apply it to a series of nucleon knockout reactions. The effect of core destruction is found to depend strongly on the binding energy of the removed nucleon, leading to a significant reduction of the cross section for deeply bound nucleons, which reduces the isospin dependence of the “quenching factors”, making them more …

In this work, the effect of nucleon-core absorption on nucleon removal reaction is explored through the use of complex nucleon-core interactions. Results are presented for exclusive breakup reactions, where absorption is explored through the use of a binormal basis in the continuum-discretized coupled-channel method, and for stripping nucleon knockout reactions, where absorption is considered through the application of an effective density in the eikonal approximation. Both methods show an increased effect of nucleon-core absorption when removing a deeply-bound nucleon, which leads to smaller cross sections, a reduction that is larger than in the weakly-bound case.

miniBELEN-10A is a modular and transportable moderated neutron counter with a nearly flat detection efficiency up to 8 MeV. The detector was designed to carry out measurements of (α, n) reactions in the context of the Measurement of Alpha Neutron Yields (MANY) project. In this work we present the results of the commissioning of miniBELEN-10A using the relatively well-known thick-target neutron yields from 27Al(α, n)30P.

In this work, we present an extension of the Continuum-Discretized Coupled-Channel formalism to include the effects of absorption and excitation of the core through its interaction with the removed particle in the description of nuclear breakup reactions. This extension is performed via the inclusion of a complex energy-dependent interaction between core and removed particle and the use of a binormal basis to ensure orthogonality. The formalism is applied to neutron breakup reactions with a 12C target at 70 MeV per nucleon for the loosely-bound 11Be nucleus and the more deeply-bound 41Ca nucleus, finding a moderate reduction in the cross section for the weakly-bound case and a strong reduction for the more deeply-bound case. Possible implications for the interpretation of intermediate-energy knockout reactions are discussed.

Configuration localised states (CLS) based on the zeroes of orthogonal polynomials were introduced some time ago for 1D systems [Phys. Rev. A 61, 042504 (2000)]. Recently two algebraic approaches based on a discrete variable representation were proposed to describe 3D systems: the 3D harmonic oscillator discrete variable representation (HO-DVR) approach and the U(4)-UGA [Mol. Phys. 118, e1662959 (2020)]. Both of them together with the CLS are based on the harmonic oscillator basis. A comparison between the three ways of generating a DVR is timely. For that purpose, here, first the CLS method based on zeroes of orthogonal polynomials is generalised so as to be applied to 3D systems and, then, its results are compared with the algebraic DVR methods. It is shown that the CLS states obtained from the zeroes of orthogonal polynomials are equivalent to the localised states of the HO-DVR approach, while …

The Centro Nacional de Aceleradores is a user-oriented accelerator facility in Seville, Spain. Its main facilities are a 3 MV tandem accelerator, an 18 MeV proton Cyclotron, a tandetron used for AMS, a compact accelerator used for radiocarbon measurements, a Co irradiator and a PET/CT scanner. The technical specifications and research applications of these facilities are described. A neutron beam line associated to a charged pulsed beam in the tandem allows for time of flight measurements which determine the neutron energy. The use of an adequate stripper gas in the AMS tandetron permits to measure heavy radionuclides with very low detection levels, allowing to perform environmental studies using these radionuclides as tracers. The use of the microbeam in the tandem accelerator allows to apply the ion beam-induced current technique to investigate the spectroscopic properties and radiation …

In 1985, Hussein and McVoy [Nuc. Phys. A445 (1985) 124] elucidated a formula for the evaluation of the nonelastic breakup (“stripping”) contribution in inclusive breakup reactions. The formula, based on the spectator core model, acquires a particularly simple and appealing form in the eikonal limit, to the extent that it has become the standard procedure to analyze single-nucleon knockout reactions at intermediate energies. In this contribution, a critical assessment of this formula is presented and its connection with other, noneikonal expressions discussed. Some calculations comparing the different formulae are also presented for the one-nucleon removal of O+Be reaction at several incident energies.

In 1985, Hussein and McVoy [Nuc. Phys. A445 (1985) 124] elucidated a formula for the evaluation of the nonelastic breakup ("stripping") contribution in inclusive breakup reactions. The formula, based on the spectator core model, acquires a particularly simple and appealing form in the eikonal limit, to the extent that it has become the standard procedure to analyze single-nucleon knockout reactions at intermediate energies. In this contribution, a critical assessment of this formula is presented and its connection with other, noneikonal expressions discussed. Some calculations comparing the different formulae are also presented for the one-nucleon removal of O+Be reaction at several incident energies.

Small and Medium Particle Accelerator Facilities (SMPAF) play a very important role in the landscape of European research. They can accelerate a variety of nuclei, at energies in the MeV range, and have a cross-disciplinary application field. They are generally installed in research centres, which may be either national centres, or depend on research or university institutions. In most cases, they are open to external users, so a proper knowledge by the community of the possibilities provided by these facilities is of great importance.SMPAF, unlike other user-focused accelerators facilities such as synchrotrons, have different characteristics. While they share some common techniques (mostly associated to Ion Beam Techniques applied to materials science), there are additional techniques (medical science, neutrons, irradiation with swift heavy ions, detectors tests, low-energy nuclear physics, etc.) that are developed …

Este documento describe una instalación de protonterapia. La iniciativa de este proyecto surge de un grupo de profesionales motivados y animados por el beneficio que conllevarıa disponer de una instalación de este tipo en el ámbito de la sanidad pública. El grupo de trabajo que ha alumbrado este libro blanco cuenta entre sus miembros con radioterapeutas, oncólogos, radiofısicos y fısicos con variadas, y dilatadas, formación y experiencia. Esto ha permitido abordar su elaboración con una óptica multidisciplinar que se ve reflejada en los distintos tópicos considerados. Los miembros del grupo de trabajo son los siguientes:

The nature of the 1− and 2− excited states in Be 10 is studied using the Be 11 (p, d) transfer reaction in inverse kinematics at 10A MeV at TRIUMF ISAC-II, in particular to assess whether either of them can be considered as an excited halo state. The angular distributions for both states are extracted using deuteron-γ coincidences and analyzed using a transfer model taking into account one-step and two-step processes. A good fit of the angular distributions is obtained considering only the one-step process, whereby an inner p 3/2 neutron of Be 11 is removed, leaving the halo neutron intact. Higher-order processes however cannot be rejected. The small spectroscopic factors extracted suggest that the structure of both states is not uniquely halo-like, but rather display a more complex configuration mixing cluster and halo structures. Further insights are limited, as this experiment specifically probed the halo-like (but not …

An algebraic method based on a discrete variable representation (DVR) scheme is applied to describe 1D potentials. The approach is based on the algebraic realisation of the coordinate and momentum in the framework of a complete basis associated with the 1D Morse potential. The diagonalisation of the matrix representations of the coordinate and momentum in this scheme provides discrete bases that establish the DVR approach, allowing the matrix representation of the Hamiltonian to be expressed in a simple form in terms of diagonal matrices through the use of the transformation coefficients. The advantage of this approach is that it may be suitable for any potential using only algebraic means at an affordable computational cost. Application to obtain the solutions associated with the Lennard-Jones potential and the ab initio potential of the H2 molecule is presented. Reliable, accurate vibrational energies as …

HiSPANoS (HiSPAlis Neutron Source) is the first accelerator-based neutron facility in Spain, installed at the Centro Nacional de Aceleradores (CNA), where different experiments have been performed related to nuclear astrophysics, detector characterization, electronic devices irradiation, imaging, etc. An upgrade of the neutron facility has been carried out recently, installing a pulsing system at the 3 MV tandem accelerator at CNA. Such system, composed by a chopper and buncher unit, can provide nanosecond proton and deuteron pulsed beams. A new experimental line dedicated to neutron time-of-flight (n-TOF) technique has been installed at the tandem accelerator. Proton and deuterium pulse width of 1 ns have been measured with a repetition rate in the range of 62.5 kHz to 2 MHz. The commissioning of the n-TOF line has consisted of the measurement of the neutron field generated by 7 Li (p, n) reaction with …

Two algebraic approaches based on a discrete variable representation are introduced and applied to describe the Stark effect in the non-relativistic Hydrogen atom. One approach consists of considering an algebraic representation of a cutoff 3D harmonic oscillator where the matrix representation of the operators r2 and p2 are diagonalized to define useful bases to obtain the matrix representation of the Hamiltonian in a simple form in terms of diagonal matrices. The second approach is based on the U(4) dynamical algebra which consists of the addition of a scalar boson to the 3D harmonic oscillator space keeping constant the total number of bosons. This allows the kets associated with the different subgroup chains to be linked to energy, coordinate and momentum representations, whose involved branching rules define the discrete variable representation. Both methods, although originating from the harmonic oscillator basis, provide different convergence tests due to the fact that the associated discrete bases turn out to be different. These approaches provide powerful tools to obtain the matrix representation of 3D general Hamiltonians in a simple form. In particular, the Hydrogen atom interacting with a static electric field is described. To accomplish this task, the diagonalization of the exact matrix representation of the Hamiltonian is carried out. Particular attention is paid to the subspaces associated with the quantum numbers n=2,3 with m=0.

A specially prepared Si/He thin solid film was investigated as a suitable target for experimental studies on nuclear reactions involving He targets. For that purpose, the elastically scattered He recoil coming from the reaction Li + He at incident energy of 5.5 MeV was measured. The differential cross section of Li on He has been found to be fully consistent with previous measurements in the literature. The prospective advantages of using these solid He targets in experiments at radioactive beam facilities are discussed.

An algebraic approach based on the unitary algebra is proposed to describe 3D systems for effective potentials. Our approach is based on the 3D vibron model where the addition of a scalar boson is introduced into the space of a 3D harmonic oscillator. Our approach is based on the mapping between the dynamical symmetry and the harmonic oscillator states. A minimisation procedure is used in order to determine the coefficients involved in the algebraic expansions. This allows the kets associated with the different subgroup chains to be linked to energy, coordinate and momentum representations. As an application of this approach the eigensystem of the 3D-Morse potential is analysed in detail. The analyses of inertia moments as well as the dipole moment strengths are also included. To show the convenience of this approach, a comparison with one ab-initio calculation for vibrational and rotational levels …