Secondary neutrons generated during proton or photon cancer treatments can contribute to unwanted radiation doses, especially critical for young patients. We have developed neutron dosimeters such as LINrem and LINdos for accurate out-of-field dose measurements in hadron therapy.

In the scope of the AEI national grant and ERC Proof-of-Concept grant GNVISION, we are adapting our imaging and detection systems for ion-range verification in proton therapy, improving treatment accuracy and minimizing dose to healthy tissue. Projects such as PRIDE integrate proton computed tomography and range verification into a single device, with potential to become clinical tools.

Environmental Radioactivity and Climate Applications

We are applying our nuclear detection expertise to study the effects of climate change, particularly ocean acidification. Through the REMO project, we use radiotracers to investigate how acidification affects calcium uptake in corals and mollusks, species that build their skeletons from calcium carbonate and are especially sensitive to changes in seawater chemistry.

In collaboration with the University of Costa Rica, we also study beryllium-7 in soils and aerosols as a tracer for atmospheric circulation and seasonal patterns, providing insights into environmental processes that link climate, chemistry, and radiation.

From the Cosmos to the Clinic

Across all these areas—from neutron-capture reactions in the hearts of stars to neutron dosimetry in cancer therapy with the ERC-AMA, ERC-GNVISION and LINrem projects—our research links the most fundamental questions in astrophysics with practical applications in energy, health, and the environment.

Our work demonstrates how advances in neutron physics and nuclear astrophysics not only expand our understanding of the Universe, but also deliver tangible benefits to society.

• HENSA is a high-efficiency neutron spectrometer based on an enhanced Bonner Sphere design, capable of measurements from thermal neutrons up to GeV energies. It is used for underground background characterization, cosmic-ray neutron mapping, and high-energy neutron measurements in medical and space-weather contexts.

• We lead long-term neutron background studies at Spain’s underground laboratory (LSC) and map cosmic-ray neutrons across the country, from sea level to mountain altitudes, to understand their variation with geomagnetic conditions.

• We are also investigating neutron bursts from lightning discharges in collaboration with the UPC Lightning Research Group, as well as neutron fields in pulsed accelerator environments.

We also study neutron-deficient mercury isotopes, which exhibit shape coexistence—different nuclear shapes existing at similar energies. By comparing beta-decay strength distributions with nuclear radius measurements, we explore the interplay between nuclear shape and decay properties.

Our expertise in Total Absorption Gamma-ray Spectroscopy (TAGS) allows us to investigate beta strength in nuclei near the proton drip line, with implications for the rapid proton-capture process (rp-process) occurring in explosive astrophysical environments such as type-I X-ray bursts.

Neutrino Properties and Reactor Antineutrinos

Beta decay is a powerful tool not only for nuclear structure and astrophysics, but also for probing the fundamental properties of the weak interaction and neutrinos. Nuclear reactors produce vast numbers of electron antineutrinos, which have been key to studying neutrino oscillations. However, differences between predicted and observed spectra—the so-called reactor antineutrino anomaly—have sparked debate about possible new physics, such as sterile neutrinos.

Our group has led the use of TAGS measurements to obtain precise beta-intensity distributions for the most important fission products contributing to reactor antineutrino fluxes. By combining these data through the summation method, we have reduced the predicted-vs-measured flux discrepancy from about 6% to roughly 2%, challenging the existence of the anomaly. We are now extending this program to measure beta spectra shapes of key isotopes, which could explain both the residual flux difference and the observed distortion around 6 MeV.

Nuclear Data for Energy Safety and Technology

Accurate nuclear decay data are critical for predicting decay heat—the residual energy released after a reactor shuts down. Decay heat represents about 7% of reactor power during operation and nearly all the heat after shutdown, making it a key safety parameter for cooling system design and emergency planning. Our high-precision beta-decay measurements directly improve these predictions, with impact on reactor safety, fuel management, and accident analysis.

A central question in modern science is how the elements heavier than iron were formed in the Universe. Nearly all such elements are produced inside stars through neutron-capture processes, which take place in different astrophysical environments and under very different conditions.

The slow neutron-capture process (s-process) occurs in environments such as asymptotic giant branch (AGB) stars, where neutron capture happens more slowly than radioactive beta decay. This process builds many of the stable isotopes we find today. This recent PRL-article describes one of the most challenging (n,g) experiments conducted at CERN n_TOF to assess the origin of the heaviest s-only nucleus Pb-204.  However, certain radioactive nuclei act as branching points in the s-process path, where the competition between neutron capture and beta decay determines the final abundance patterns. Studying these nuclei requires extremely precise measurements of their neutron-capture cross sections, which is technically challenging due to the small quantities available, possible contamination, and high gamma-ray backgrounds from their own radioactivity. Advances and new ideas for this type of experiments are reported in this article, and a summary with all the s-process branching nuclei measured at CERN n_TOF is available in this review article.

To overcome these challenges, our group has designed and built innovative detection systems such as the i-TED gamma-ray imager, which greatly suppresses background and allows neutron-capture measurements on highly radioactive and rare samples. With this technology, we have carried out landmark experiments at CERN’s n_TOF facility on isotopes such as ⁷⁹Se and ⁹⁴Nb, providing unique insights into the temperature, neutron density, and timescales of the s-process. These measurements are essential for stellar modelling and for understanding the chemical evolution of our Galaxy.

At CERN n_TOF we are pioneering new detector concepts like STAR, an array of solid-state organic scintillators coupled to silicon photosensors, capable of handling the very high neutron fluxes required for experiments on extremely small, highly radioactive samples. These developments will enable measurements that have previously been beyond experimental reach.

Beyond the s-Process: The i- and r-Processes

While the s-process explains many heavy isotopes, others—especially in the germanium-to-molybdenum region—cannot be explained by any mix of s- and r-processes. The intermediate neutron-capture process (i-process) has been proposed to account for these cases. It occurs under neutron densities between those of the s- and r-processes, such as during helium-shell flashes in rapidly accreting white dwarfs.

Validating the i-process requires neutron-capture data on short-lived isotopes that can only be produced at rare-isotope beam facilities. We are developing ultra-sensitive activation techniques at the NEAR station of n_TOF, capable of working with nanogram-scale samples. In parallel, we are developing the CYCLING station at CERN n_TOF , a dedicated cyclic activation setup to investigate i-process isotopes with unprecedented sensitivity.

The rapid neutron-capture process (r-process) produces the heaviest neutron-rich nuclei in the Universe and occurs in extreme environments such as neutron-star mergers and possibly certain types of supernovae. The detection in 2017 of gravitational waves and electromagnetic emission from a neutron star merger, revealing freshly synthesized heavy elements, was a watershed moment in the field.

The r-process path runs through nuclei far from stability, where experimental data are scarce. Our group plays a leading role in the BRIKEN collaboration at RIKEN, which has measured hundreds of new beta-decay half-lives and beta-delayed neutron probabilities. These measurements feed directly into r-process simulations, helping to identify the astrophysical sites and conditions where the process occurs. This recent PRL-article describes some of the most exciting recent results in this field.

(α, n) Reactions and Neutron Sources

Alpha-induced neutron production plays a central role in nuclear astrophysics, underground rare-event experiments, nuclear technology, and security applications. The available data for many isotopes are incomplete or inconsistent.

We co-lead the MANY collaboration in Spain, which is building comprehensive datasets for (α, n) reactions using advanced detectors like miniBELEN at accelerator facilities in Madrid (CMAM) and Seville (CNA). These measurements support s- and r-process modelling, background reduction in underground experiments, and the design of advanced nuclear systems.