arXiv subjects

Pablo Torres-Sánchez

Publications and source records attributed to Pablo Torres-Sánchez.

7 recordsLinked to original sources

arXiv2026

Direct Experiments of Neutron Capture on Stable and Unstable Isotopes for Stellar Nucleosynthesis Studies

Neutron-capture reactions provide essential nuclear-physics input for modeling the synthesis of heavy elements in stars. The growing precision of stellar spectroscopy and isotopic measurements in presolar SiC grains now demands cross sections with improved accuracy over the full energy range, and access to unstable nuclei relevant to slow (s-) process branchings and the intermediate (i-) process. This article reviews recent progress in direct neutron-capture measurements, focusing on time-of-flight (TOF) experiments at CERN n_TOF and complementary activation techniques. Substantial advances have been achieved for stable s-only and bottleneck isotopes, significantly improving constraints on s-process models. In parallel, the combination of high instantaneous neutron fluxes and advanced detector systems has facilitated first-time measurements of several radioactive branching-point nuclei. Feasibility studies, however, reveal current limitations related to sample availability, background conditions, and restricted energy coverage. In this context, the complementarity between TOF and activation emerges as a central strategy. Future developments, including high-flux facilities and novel inverse-kinematics experiments in ion storage rings, are expected to extend the boundaries of neutron-capture measurements, overcoming current limitation

nucl-ex↗

arXiv2025

Measurement of the $^{35}Cl(n, p)^{35}S$ cross-section at the CERN n\_TOF facility from subthermal energy to 120 keV

Background: The $^{35}Cl(n, p)^{35}S$ reaction is of special interest in three different applications. First, in Boron Neutron Capture Therapy due to the presence of $^{35}Cl$ in brain and skin tissue. Second, it is involved in the creation of $^{36}S$, whose astrophysical origin remains unresolved. Third, in the designing of fast nuclear reactors of new generation based on molten salts. Purpose: To measure the $^{35}Cl(n, p)^{35}S$ cross-section from thermal energy to 120 keV, determine the resonance parameters in this range and Maxwellian Averaged Cross-Section (MACS). Method: We made use of the Time-of-Flight technique with microMEGAS detectors at Experimental Area 2 (EAR-2) of n\_TOF facility at CERN. The $^{10}B(n, α)^{7}Li$ and $^{235}U(n, f)$ reactions were used as references. Rutherford Back-scattering Spectrometry technique was performed at Centro Nacional de Aceleradores (CNA) in Sevilla, in order to accurately determine the masses of the irradiated samples. Results: We obtain a thermal cross-section of $0.470 \pm 0.009$ barns. The $1/v$ energy dependence of the cross-section is observed up to the first resonance at 0.398 keV, the resonances up to 120 keV are analyzed and MACS calculated for $k_{B} T$ from 1 to 100 keV. Conclusions: The $^{35}Cl(n, p)^{35}S$ cross-section has been obtained over a wide energy range for the first time, with high accuracy across the aforementioned range. The thermal cross-section and first two resonances are in agreement with latest evaluation in ENDF/B-VIII.1, while lower resonance strength was found for high energy resonances. These data are used to calculate the MACS for different $k_{B} T$.

nucl-ex↗

arXiv2025

Measurement of neutron total cross-section of Mg and MgF$_{2}$ at MONNET (JRC-Geel) from transmission with fine multi-scattering corrections

Neutron-transmission measurements through samples of magnesium fluoride (MgF$_2$) and pure magnesium were performed to obtain the (n, tot) cross section for all isotopes involved, $^{19}$F and $^{24-26}$Mg. Lithium-glass detectors were used in conjunction with the neutron time-of-flight technique. The measurement campaign was performed at the MONNET fast-neutron source of the European Commission Joint Research Centre (JRC-Geel, Belgium). Highly precise corrections for multiple scattering were calculated using a sophisticated iterative method based on Monte Carlo simulations with the MCNP6.3 code, accounting for the effects of the experimental setup. With the SAMMY code, an R-Matrix analysis of the experimental data was performed. The extracted cross-sections, resonance spin and parity as well as the limitations of the method are carefully discussed.

nucl-ex↗

arXiv2025

First experimental results and optimization study of the portable neutron-gamma imager GN-Vision

GN-Vision is a compact, dual-modality imaging device designed to simultaneously localize the spatial origin of $γ$-ray and slow neutron sources, with potential applications in nuclear safety, security, and hadron therapy. The system utilizes two position-sensitive detection planes, combining Compton imaging techniques for $γ$-ray visualization with passive collimation for imaging slow and thermal neutrons (energies below 100 eV). This paper presents the first experimental outcomes from the initial GN-Vision prototype, focused on the development of its neutron imaging capabilities. Following this experimental assessment, we explore the device$'$s performance potential and discuss several Monte Carlo simulation-based optimizations aimed at refining the neutron collimation system. These optimizations seek to improve real-time imaging efficiency and cost-effectiveness, enhancing GN-Vision$'$s applicability for future practical deployments.

physics.ins-det↗

arXiv2024

Towards Real Time Compton Imaging in Demanding Conditions

Compton cameras are radiation detectors that provide spatial information on the origin of the γ-ray sources based on the Compton scattering effect. Many applications require these detectors to be used at high counting rate. As such, the preprocessing of the detections as well as the imaging algorithms are required to be time-efficient in order for the data to be processed in real time. In this work, optimizations to the preprocessing of events in Compton cameras based on monolithic crystals, with special focus on event identification, were implemented using a parallelizable algorithm. Regarding imaging, an established 3D back projection algorithm was parallelized and implemented using SYCL. The parallel implementation of the algorithm was included without and with several optimizations such as the pre-computing values, discarding low impact contributions based on angle, and selecting an efficient shape of the image universe. The implementations were tested with Intel CPUs, GPUs, and NVIDIA GPUs. An outlook into the study of algorithms to reconstruct the position of interaction within Compton cameras based on monolithic crystals into segmented regions and other next steps is included.

physics.ins-det↗

arXiv2024

The i-TED Compton Camera Array for real-time boron imaging and determination during treatments in Boron Neutron Capture Therapy

This paper explores the adaptation and application of i-TED Compton imagers for real-time dosimetry in Boron Neutron Capture Therapy (BNCT). The i-TED array, previously utilized in nuclear astrophysics experiments at CERN, is being optimized for detecting and imaging 478 keV gamma-rays, critical for accurate BNCT dosimetry. Detailed Monte Carlo simulations were used to optimize the i-TED detector configuration and enhance its performance in the challenging radiation environment typical of BNCT. Additionally, advanced 3D image reconstruction algorithms, including a combination of back-projection and List-Mode Maximum Likelihood Expectation Maximization (LM-MLEM), are implemented and validated through simulations. Preliminary experimental tests at the Institut Laue-Langevin (ILL) demonstrate the potential of i-TED in a clinical setting, with ongoing experiments focusing on improving imaging capabilities in realistic BNCT conditions.

physics.med-ph↗

arXiv2023

Fast neutron production at the LNL Tandem from the $^7$Li($^{14}$N,xn)X reaction

Fast neutron beams are of relevance for many scientific and industrial applications. This paper explores fast neutron production using a TANDEM accelerator at the Legnaro National Laboratories, via an energetic ion beam (90 MeV $^{14}N$) onto a lithium target. The high energy models for nuclear collision of FLUKA foresee large neutron yields for reactions of this kind. The experiment aimed at validating the expected neutron yields from FLUKA simulations, using two separate and independent set-ups: one based on the multi-foil activation technique, and the other on the time of flight technique, by using liquid scintillator detectors. The results of the experiment show clear agreement of the measured spectra with the FLUKA simulations, both in the shape and the magnitude of the neutron flux at the measured positions. The neutron spectrum is centered around the 8 MeV range with mild tails, and a maximum neutron energy spanning up to 50 MeV. These advantageous results provide a starting point in the development of fast neutron beams based on high energy ion beams from medium-sized accelerator facilities.

nucl-ex↗