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n_TOF Collaboration(Balibrea-Correa, J. et al), Domingo-Pardo, C., Giubrone, G., Tain, J. L., & Tarifeño-Saldivia, A. (2020). Measurement of the alpha ratio and (n, gamma) cross section of U-235 from 0.2 to 200 eV at n_TOF. Phys. Rev. C, 102(4), 044615–18pp.
Abstract: We measured the neutron capture-to-fission cross-section ratio (alpha ratio) and the capture cross section of U-235 between 0.2 and 200 eV at the nTOF facility at CERN. The simultaneous measurement of neutron-induced capture and fission rates was performed by means of the nTOF BaF2 Total Absorption Calorimeter (TAC), used for detection of gamma rays, in combination with a set of micromegas detectors used as fission tagging detectors. The energy dependence of the capture cross section was obtained with help of the Li-6(n, t) standard reaction determining the n_TOF neutron fluence; the well-known integral of the U-235(n, f) cross section between 7.8 and 11 eV was then used for its absolute normalization. The alpha ratio, obtained with slightly higher statistical fluctuations, was determined directly, without need for any reference cross section. To perform the analysis of this measurement we developed a new methodology to correct the experimentally observed effect that the probabilities of detecting a fission reaction in the TAC and the micromegas detectors are not independent. The results of this work have been used in a new evaluation of U-235 performed within the scope of the Collaborative International Evaluated Library Organisation (CIELO) Project, and are consistent with the ENDF/B-VIII.0 and JEFF-3.3 capture cross sections below 4 eV and above 100 eV. However, the measured capture cross section is on average 10% larger between 4 and 100 eV.
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n_TOF Collaboration(Gawlik, A. et al), Domingo-Pardo, C., Tain, J. L., & Tarifeño-Saldivia, A. (2021). Radiative Neutron Capture Cross-Section Measurement of Ge Isotopes at n_TOF CERN Facility and Its Importance for Stellar Nucleosynthesis. Acta Phys. Pol. A, 139(4), 383–388.
Abstract: This manuscript summarizes the results of radiative neutron capture cross-section measurements on two stable germanium isotopes, Ge-70 and Ge-73. Experiments were performed at the n_TOF facility at CERN via the time-of-flight technique, over a wide neutron energy range, for all stable germanium isotopes (70,72,73,74, and 76). Results for Ge-70 [Phys. Rev. C 100, 045804 (2019)] and Ge-73 [Phys. Lett. B 790, 458 (2019)] are already published. In the field of nuclear structure, such measurements allow to study excited levels close to the neutron binding energy and to obtain information on nuclear properties. In stellar nucleosynthesis research, neutron induced reactions on germanium are of importance for nucleosynthesis in the weak component of the slow neutron capture processes.
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Martins, A., da Mota, A. F., Stanford, C., Contreras, T., Martin-Albo, J., Kish, A., et al. (2024). Simple strategy for the simulation of axially symmetric large-area metasurfaces. J. Opt. Soc. Am. B, 41(5), 1261–1269.
Abstract: Metalenses are composed of nanostructures for focusing light and have been widely explored in many exciting applications. However, their expanding dimensions pose simulation challenges. We propose a method to simulate metalenses in a timely manner using vectorial wave and ray tracing models. We sample the metalens's radial phase gradient and locally approximate the phase profile by a linear phase response. Each sampling point is modeled as a binary blazed grating, employing the chosen nanostructure, to build a transfer function set. The metalens transmission or reflection is then obtained by applying the corresponding transfer function to the incoming field on the regions surrounding each sampling point. Fourier optics is used to calculate the scattered fields under arbitrary illumination for the vectorial wave method, and a Monte Carlo algorithm is used in the ray tracing formalism. We validated our method against finite -difference time domain simulations at 632 nm, and we were able to simulate metalenses larger than 3000 wavelengths in diameter on a personal computer.
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Tarifeño-Saldivia, A., & Soto, L. (2014). Effects of gas chamber geometry and gas flow on the neutron production in a fast plasma focus neutron source. Plasma Phys. Control. Fusion, 56(12), 125013–5pp.
Abstract: This work reports that gas chamber geometry and gas flow management substantially affect the neutron production of a repetitive fast plasma focus. The gas flow rate is the most sensitive parameter. An appropriate design of the gas chamber combined with a suitable flow-rate management can lead to improvements in the neutron production of one order of magnitude working in a fast repetitive mode.
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Martin-Luna, P., Esperante, D., Prieto, A. F., Fuster-Martinez, N., Rivas, I. G., Gimeno, B., et al. (2024). Simulation of electron transport and secondary emission in a photomultiplier tube and validation. Sens. Actuator A-Phys., 365, 114859–10pp.
Abstract: The electron amplification and transport within a photomultiplier tube (PMT) has been investigated by developing an in-house Monte Carlo simulation code. The secondary electron emission in the dynodes is implemented via an effective electron model and the Modified Vaughan's model, whereas the transport is computed with the Boris leapfrog algorithm. The PMT gain, rise time and transit time have been studied as a function of supply voltage and external magnetostatic field. A good agreement with experimental measurements using a Hamamatsu R13408-100 PMT was obtained. The simulations have been conducted following different treatments of the underlying geometry: three-dimensional, two-dimensional and intermediate (2.5D). The validity of these approaches is compared. The developed framework will help in understanding the behavior of PMTs under highly intense and irregular illumination or varying external magnetic fields, as in the case of prompt gamma-ray measurements during pencil-beam proton therapy; and aid in optimizing the design of voltage dividers with behavioral circuit models.
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Morales, A. I., & Tuzon, P. (2022). Misconceptions, Knowledge, and Attitudes Towards the Phenomenon of Radioactivity. Sci. Educ., 31, 405–426.
Abstract: The teaching of the phenomenon of radioactivity is considered a key ingredient in the path towards developing critical thinking skills in many secondary science education curricula. Despite being one of the basic concepts in general physics courses, the scientific teaching literature of the last 40 years reports a great deal of misconceptions and conceptual errors related to radioactivity that seemingly appear regardless of the educational level and context. This study reports the first cross-sectional diagnostic study in Spain to secondary education students and pre-service teachers. Data were collected in the year 2019 through a questionnaire adapted from a previously validated one to explore the main misconceptions, attitudes, and knowledge status on the topic on a sample of 191 secondary school students and 29 Physics-and-Chemistry trainee teachers in the Spanish region of Valencia. Open and closed questions were used to categorize the entity itself, its properties, and the main misconceptions related to radioactivity. The responses were analysed using conventional statistical methods. The results indicate an evolution from a widespread dissenting notion on the phenomenon, which is staunchly related to danger, hazard, and destruction in the lowest educational levels, towards a more rational, relative, and multidimensional perspective in the highest ones. On the other hand, the ideas, emotions, and attitudes of the inquired individuals are in good agreement with the main misconceptions reported in the literature.
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ANTARES Collaboration(Aguilar, J. A. et al), Bigongiari, C., Dornic, D., Emanuele, U., Gomez-Gonzalez, J. P., Hernandez-Rey, J. J., et al. (2010). Zenith distribution and flux of atmospheric muons measured with the 5-line ANTARES detector. Astropart Phys., 34(3), 179–184.
Abstract: The ANTARES high-energy neutrino telescope is a three-dimensional array of about 900 photomultipliers distributed over 12 mooring lines installed in the Mediterranean Sea. Between February and November 2007 it acquired data in a 5-line configuration. The zenith angular distribution of the atmospheric muon flux and the associated depth-intensity relation are measured and compared with previous measurements and Monte Carlo expectations. An evaluation of the systematic effects due to uncertainties on environmental and detector parameters is presented.
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ANTARES Collaboration(Aguilar, J. A. et al), Bigongiari, C., Dornic, D., Emanuele, U., Gomez-Gonzalez, J. P., Hernandez-Rey, J. J., et al. (2011). A fast algorithm for muon track reconstruction and its application to the ANTARES neutrino telescope. Astropart Phys., 34(9), 652–662.
Abstract: An algorithm is presented, that provides a fast and robust reconstruction of neutrino induced upward-going muons and a discrimination of these events from downward-going atmospheric muon background in data collected by the ANTARES neutrino telescope. The algorithm consists of a hit merging and hit selection procedure followed by fitting steps for a track hypothesis and a point-like light source. It is particularly well-suited for real time applications such as online monitoring and fast triggering of optical follow-up observations for multi-messenger studies. The performance of the algorithm is evaluated with Monte Carlo simulations and various distributions are compared with that obtained in ANTARES data.
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ANTARES Collaboration(Aguilar, J. A. et al), Bigongiari, C., Dornic, D., Emanuele, U., Gomez-Gonzalez, J. P., Hernandez-Rey, J. J., et al. (2011). Time calibration of the ANTARES neutrino telescope. Astropart Phys., 34(7), 539–549.
Abstract: The ANTARES deep-sea neutrino telescope comprises a three-dimensional array of photomultipliers to detect the Cherenkov light induced by upgoing relativistic charged particles originating from neutrino interactions in the vicinity of the detector. The large scattering length of light in the deep sea facilitates an angular resolution of a few tenths of a degree for neutrino energies exceeding 10 TeV. In order to achieve this optimal performance, the time calibration procedures should ensure a relative time calibration between the photomultipliers at the level of similar to 1 ns. The methods developed to attain this level of precision are described.
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ANTARES Collaboration(Aguilar, J. A. et al), Bigongiari, C., Emanuele, U., Gomez-Gonzalez, J. P., Hernandez-Rey, J. J., Mangano, S., et al. (2010). Measurement of the atmospheric muon flux with a 4 GeV threshold in the ANTARES neutrino telescope. Astropart Phys., 33(2), 86–90.
Abstract: A new method for the measurement of the muon flux in the deep-sea ANTARES neutrino telescope and its dependence on the depth is presented. The method is based oil the observation of coincidence signals in adjacent storeys of the detector. This yields an energy threshold of about 4 GeV. The main sources of optical background are the decay of K-40 and the bioluminescence in the sea water. The K-40 background is used to calibrate the efficiency of the photo-multiplier tubes.
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