Measurement of the neutron capture cross section of the ²³⁵U at the n_TOF facility

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Física Teórica II, leída el 08-11-2017Las actuales y futuras demandas de energía requieren el desarrollo de nuevas fuentes de producción así como la mejora de las ya existentes. El primer y crucial ingrediente para el diseño de los reactores nucleares y el ciclo de combustible son los datos nucleares. A la hora de diseñar y evaluar la seguridad de los reactores nucleares es necesario una gran cantidad de datos nucleares para distintos materiales. Los ingenieros y físicos deben afrontar diferentes variantes de los reactores nucleares y realizar grandes cálculos para estimar el rendimiento de los sistemas nucleares críticos. Para tener estimaciones fiables, estos estudios deben incoporar las secciones eficaces más precisas que se conocen, habitualmente incluidas en las librerias evualadas tales como ENDF/B-VII.1, JENDL-4.0a o JEFF-3.2. Estas librer¿¿as evaluadas son probadas con experimentos integrales y de esta manera se valida los actuales datos y secciones eficaces nucleares. Estas librer¿¿as predicen de manera muy precisa para la mayoria de sistemas nucleares cr¿¿ticos su comportamiento. Sin embargo, la buena estimación en estos experimentos integrales crea la falsa sensación de optimismo debido a la compensación de errores, calibraciones de los datos y discrepancias entre librer¿¿as. El objetivo de este manuscrito es presentar el análisis y resultados de la medida de la sección eficaz de captura del 235 U llevado a cabo en la instalación n TOF del CERN en el rango de energ¿¿as del neutrón desde 0.2 a 200 eV. Estos datos han sido utilizados para el desarrollo de una nueva libreria evaluada de secciones eficaces de neutrones que será usada en el diseño y desarrollo de nuevos reactores nucleares.Depto. de Física TeóricaFac. de Ciencias FísicasTRUEunpu

First measurement of the 94Nb(n,γ) cross section at the CERN n_TOF facility

One of the crucial ingredients for the improvement of stellar models is the accurate knowledge of neutron capture cross-sections for the different isotopes involved in the s-,r- and i- processes. These measurements can shed light on existing discrepancies between observed and predicted isotopic abundances and help to constrain the physical conditions where these reactions take place along different stages of stellar evolution. In the particular case of the radioactive 94Nb, the 94Nb(n,γ) cross-section could play a role in the determination of the s-process production of 94Mo in AGB stars, which presently cannot be reproduced by state-of-the-art stellar models. There are no previous 94Nb(n,γ) experimental data for the resolved and unresolved resonance regions mainly due to the difficulties in producing highquality samples and also due to limitations in conventional detection systems commonly used in time-of-flight experiments. Motivated by this situation, a first measurement of the 94Nb(n,γ) reaction was carried out at CERN n_TOF, thereby exploiting the high luminosity of the EAR2 area in combination with a new detection system of small-volume C6D6-detectors and a high quality 94Nb-sample. The latter was based on hyper-pure 93Nb material activated at the high-flux reactor of ILL-Grenoble. An innovative ring-configuration detection system in close geometry around the capture sample allowed us to significantly enhance the signal-to-background ratio. This set-up was supplemented with two conventional C6D6-detectors and a highresolution LaCl3(Ce)-detector, which will be employed for addressing reliably systematic effects and uncertainties. At the current status of the data analysis, 18 resonance in 94Nb+n have been observed for the first time in the neutron energy range from thermal up to 10 keV.European Research Council (ERC)European Union’s Horizon 2020 research and innovation programme (ERC Consolidator Grant project HYMNS, with grant agreement No. 681740)ICJ220-045122-IMCIN/AEI/ 10.13039/501100011033European Union NextGenerationEU/PRTRSpanish Ministerio de Ciencia e Innovación under grants PID2019-104714GB-C21, FPA2017-83946-C2-1-P, FIS2015-71688-ERCCSICPIE-201750I2

Thermal neutron background at Laboratorio Subterráneo de Canfranc (LSC)

The thermal neutron background at Laboratorio Subterráneo de Canfranc (LSC) has been determined using several He proportional counter detectors. Bare and Cd shielded counters were used in a series of long measurements. Pulse shape discrimination techniques were applied to discriminate between neutron and gamma signals as well as other intrinsic contributions. Montecarlo simulations allowed us to estimate the sensitivity of the detectors and calculate values for the background flux of thermal neutrons inside Hall-A of LSC. The obtained value is (3.5±0.8)×10 n/cms, and is within an order of magnitude compared to similar facilities.This work was supported partially by the Spanish Ministerio de Ciencia e Innovación and its Plan Nacional de I+D+i de Física de Partículas projects: FPA2016-76765-P and FPA2018-096717-B-C21. The authors want to acknowledge the help provided by the staff at LSC in the preparation and support for this work

Measurement of the α ratio and (n, γ) cross section of 235U from 0.2 to 200 eV at n_TOF

We measured the neutron capture-to-fission cross-section ratio (α ratio) and the capture cross section of 235U between 0.2 and 200 eV at the n_TOF facility at CERN. The simultaneous measurement of neutron-induced capture and fission rates was performed by means of the n_TOF BaF2 Total Absorption Calorimeter (TAC), used for detection of γ 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 6 Li(n,t) standard reaction determining the n_TOF neutron fluence; the well-known integral of the 235U(n, f ) cross section between 7.8 and 11 eV was then used for its absolute normalization. The α 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 235U 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.Ministerio de Economía, Industria y Competitividad de España. FPA2014-53290-C2-1, FPA2016-76765- P y FPA2017-82647-P7º Programa Marco CHANDA de la Comisión Europea. FP7-60520

74 Ge(n, ¿) cross section below 70 keV measured at n_TOF CERN

The version of record os available online at:https://doi.org/10.1140/epja/s10050-022-00878-5Neutron capture reaction cross sections on 74Ge are of importance to determine 74Ge production during the astrophysical slow neutron capture process. We present new resonancedataon74Ge(n,¿)reactionsbelow70keVneutron energy. We calculate Maxwellian averaged cross sections, combining our data below 70 keV with evaluated cross sections at higher neutron energies. Our stellar cross sections are in agreement with a previous activation measurement performed at Forschungszentrum Karlsruhe by Marganiec et al., once their data has been re-normalised to account for an update in the reference cross section used in that experimentPeer ReviewedArticle escrit per 123 autors/autores C. Lederer-Woods, O. Aberle, J. Andrzejewski, L. Audouin, V. Bécares, M. Bacak, J. Balibrea, M. Barbagallo, S. Barros, U. Battino, F. Bečvář, C. Beinrucker, E. Berthoumieux, J. Billowes, D. Bosnar, M. Brugger, M. Caamaño, F. Calviño, M. Calviani, D. Cano-Ott, R. Cardella, A. Casanovas, D. M. Castelluccio, F. Cerutti, Y. H. Chen, E. Chiaveri, N. Colonna, G. Cortés, M. A. Cortés-Giraldo, L. Cosentino, L. A. Damone, M. Diakaki, C. Domingo-Pardo, R. Dressler, E. Dupont, I. Durán, B. Fernández-Domínguez, A. Ferrari, P. Ferreira, P. Finocchiaro, V. Furman, K. Göbel, A. R. García, A. Gawlik-Ramięga, T. Glodariu, I. F. Gonçalves, E. González-Romero, A. Goverdovski, E. Griesmayer, C. Guerrero, F. Gunsing, H. Harada, T. Heftrich, S. Heinitz, J. Heyse, D. G. Jenkins, E. Jericha, F. Käppeler, Y. Kadi, T. Katabuchi, P. Kavrigin, V. Ketlerov, V. Khryachkov, A. Kimura, N. Kivel, M. Kokkoris, M. Krtička, E. Leal-Cidoncha, H. Leeb, J. Lerendegui-Marco, S. Lo Meo, S. J. Lonsdale, R. Losito, D. Macina, J. Marganiec, T. Martínez, C. Massimi, P. Mastinu, M. Mastromarco, F. Matteucci, E. A. Maugeri, E. Mendoza, A. Mengoni, P. M. Milazzo, F. Mingrone, M. Mirea, S. Montesano, A. Musumarra, R. Nolte, A. Oprea, N. Patronis, A. Pavlik, J. Perkowski, I. Porras, J. Praena, J. M. Quesada, K. Rajeev, T. Rauscher, R. Reifarth, A. Riego-Perez, P. C. Rout, C. Rubbia, J. A. Ryan, M. Sabaté-Gilarte, A. Saxena, P. Schillebeeckx, S. Schmidt, D. Schumann, P. Sedyshev, A. G. Smith, A. Stamatopoulos, G. Tagliente, J. L. Tain, A. Tarifeño-Saldivia, L. Tassan-Got, A. Tsinganis, S. Valenta, G. Vannini, V. Variale, P. Vaz, A. Ventura, V. Vlachoudis, R. Vlastou, A. Wallner, S. Warren, M. Weigand, C. Weiss, C. Wolf, P. J. Woods, T. Wright, P. ŽugecPostprint (published version

Advances and new ideas for neutron-capture astrophysics experiments at CERN n_TOF

The version of record of this article, first published in [The Europen Physics Journal A], is available online at Publisher’s website: http://dx.doi.org/10.1140/epja/s10050-022-00876-7This article presents a few selected developments and future ideas related to the measurement of (n,¿) data of astrophysical interest at CERN n_TOF. The MC-aided analysis methodology for the use of low-efficiency radiation detectors in time-of-flight neutron-capture measurements is discussed, with particular emphasis on the systematic accuracy. Several recent instrumental advances are also presented, such as the development of total-energy detectors with ¿ - ray imaging capability for background suppression, and the development of an array of small-volume organic scintillators aimed at exploiting the high instantaneous neutron-flux of EAR2. Finally, astrophysics prospects related to the intermediate i neutron-capture process of nucleosynthesis are discussed in the context of the new NEAR activation areaPeer ReviewedArticle escrit per 139 auors/autores C. Domingo-Pardo, V. Babiano-Suarez, J. Balibrea-Correa, L. Caballero, I. Ladarescu, J. Lerendegui-Marco, J. L. Tain, A. Tarifeño-Saldivia, O. Aberle, V. Alcayne, S. Altieri, S. Amaducci, J. Andrzejewski, M. Bacak, C. Beltrami, S. Bennett, A. P. Bernardes, E. Berthoumieux, M. Boromiza, D. Bosnar, M. Caamaño, F. Calviño, M. Calviani, D. Cano-Ott, A. Casanovas, F. Cerutti, G. Cescutti, S. Chasapoglou, E. Chiaveri, N. M. Chiera, P. Colombetti, N. Colonna, P. Console Camprini, G. Cortés, M. A. Cortés-Giraldo, L. Cosentino, S. Cristallo, S. Dellmann, M. Di Castro, S. Di Maria, M. Diakaki, M. Dietz, R. Dressler, E. Dupont, I. Durán, Z. Eleme, S. Fargier, B. Fernández, B. Fernández-Domínguez, P. Finocchiaro, S. Fiore, F. García-Infantes, A. Gawlik-Ramięga , G. Gervino, S. Gilardoni, E. González-Romero, C. Guerrero, F. Gunsing, C. Gustavino, J. Heyse, W. Hillman, D. G. Jenkins, E. Jericha, A. Junghans, Y. Kadi, K. Kaperoni, F. Käppeler, G. Kaur, A. Kimura, I. Knapová, U. Köster, M. Kokkoris, M. Krtička, N. Kyritsis, C. Lederer-Woods, G. Lerner, A. Manna, T. Martínez, A. Masi, C. Massimi, P. Mastinu, M. Mastromarco, E. A. Maugeri, A. Mazzone, E. Mendoza, A. Mengoni, P. M. Milazzo, I. Mönch, R. Mucciola, F. Murtas, E. Musacchio-Gonzalez, A. Musumarra, A. Negret, A. Pérez de Rada, P. Pérez-Maroto, N. Patronis, J. A. Pavón-Rodríguez, M. G. Pellegriti, J. Perkowski, C. Petrone, E. Pirovano, J. Plaza, S. Pomp, I. Porras, J. Praena, J. M. Quesada, R. Reifarth, D. Rochman, Y. Romanets, C. Rubbia, A. Sánchez, M. Sabaté-Gilarte, P. Schillebeeckx, D. Schumann, A. Sekhar, A. G. Smith, N. V. Sosnin, M. Stamati, A. Sturniolo, G. Tagliente, D. Tarrío, P. Torres-Sánchez, J. Turko, S. Urlass, E. Vagena, S. Valenta, V. Variale, P. Vaz, G. Vecchio, D. Vescovi, V. Vlachoudis, R. Vlastou, T. Wallner, P. J. Woods, T. Wright, R. Zarrella, P. ŽugecPostprint (published version

miniBELEN: a modular neutron counter for (a, n) reactions

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 (a, n) 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(a, n) 30P reaction is also presented.This work has been supported by the Spanish Ministerio de Economía y Competitividad under grants FPA2017-83946- C2-1 & C2-2 and PID2019-104714GB-C21 & C22, the Generalitat Valenciana Grant PROMETEO/2019/007, both cofounded by FEDER (EU), and the SANDA project funded under H2020-EURATOM-1.1 Grant No. 847552. The authors acknowledge the support from Centro de Microanálisis de Materiales (CMAM) - Universidad Autónoma de Madrid, for the beam time proposal (Comissioning of neutron detector systems for (a,݊n) reaction measurements) with code P01156, and its technical staff for their contribution to the operation of the accelerator.Article signat per 41 autors/es: N. Mont-Geli, A. Tarifeño-Saldivia, L.M. Fraile, S. Viñals, A. Perea, M. Pallàs, G. Cortés, E. Nácher, J.L. Tain, V. Alcayne, A. Algora, J. Balibrea-Correa, J. Benito, M.J.G. Borge, J.A. Briz, F. Calviño, D. Cano-Ott, A. De Blas, C. Domingo-Pardo, B. Fernández, R. Garcia, G. García, J. Gómez-Camacho, E.M. González-Romero, C. Guerrero, J. Lerendegui-Marco, M. Llanos, T. Martínez, E. Mendoza, J.R. Murias, S.E.A. Orrigo, A. Pérez de Rada, V. Pesudo, J. Plaza, J.M. Quesada, A. Sánchez, V. Sánchez-Tembleque, R. Santorelli, O. Tengblad, J.M. Udías and D. Villamarín.Postprint (published version