Commissionning of the n_TOF-Ph2 facility

The white spectrum neutron time-of-flight facility n_TOF is operating at CERN since 2001. The neutron beam has a very high instantaneous flux and high resolution in energy and it is delivered in the experimental area located 187 m downstream from the spallation target. The intense neutron fluence per proton burst results in a much enhanced signal to background ratio for neutron capture and fission reactions on radioactive isotopes, thus making the facility well suited for accurate measurement of neutron-induced reaction cross-sections. This is especially true to highly radioactive targets which are of major importance in new nuclear energy system such as Gen-IV reactors, especially those with fast spectrum. Combined with state-of-the-art detectors and with advanced data acquisition systems, the innovative characteristics of the n_TOF neutron beam allow collecting data on a variety of stable and radioactive isotopes of interest for nuclear astrophysics and for applications to advanced reactor technologies.Peer ReviewedPostprint (published version

Reachability in High Treewidth Graphs

Reachability is the problem of deciding whether there is a path from one vertex to the other in the graph. Standard graph traversal algorithms such as DFS and BFS take linear time to decide reachability however their space complexity is also linear. On the other hand, Savitch's algorithm takes quasipolynomial time although the space bound is $O(\log^2 n)$. Here, we study space efficient algorithms for deciding reachability that runs simultaneously in polynomial time. In this paper, we show that given an $n$ vertex directed graph of treewidth $w$ along with its tree decomposition, there exists an algorithm running in polynomial time and $O(w\log n)$ space, that solves reachability in the graph

FSK-based Simultaneous Wireless Information and Power Transfer in Inductively Coupled Resonant Circuits Exploiting Frequency Splitting

Inductively coupled resonant circuits are affected by the so-called frequency splitting phenomenon at short distances. In the area of power electronics, tracking of one of the peak frequencies is state-of-the-art. In the data transmission community, however, the frequency splitting effect is often ignored. Particularly, modulation schemes have not yet been adapted to the bifurcation phenomenon. We argue that binary frequency shift keying (2-ary FSK) is a low-cost modulation scheme which well matches the double-peak voltage transfer function $H(s)$, particularly when the quality factor $Q$ is large, whereas most other modulation schemes suffer from the small bandwidths of the peaks. Additionally we show that a rectified version of 2-ary FSK, coined rectified FSK (RFSK), is even more attractive from output power and implementation points of view. Analytical and numerical contributions include the efficiency factor, the impulse response, and the bit error performance. A low-cost incoherent receiver is proposed. Theoretical examinations are supported by an experimental prototype

Monte Carlo simulations for the study of a moderated neutron detector

This work presents the Monte Carlo simulations performed with the MCNPX and GEANT4 codes for the design of a BEta deLayEd Neutron detector, BELEN-20. This detector will be used for the study of beta delayed neutron emission and consists of a block of polyethylene with dimensions 90x90x80 cm3 and 20 cylindrical 3He gas counters. The results of these simulations have been validated experimentally with a 252Cf source in the laboratory at UPC, Barcelona. Also the first experiment with this detector has been carried out in November 2009 in JYFL, Finland. In this experiment the neutron emission probability after beta decay of the fission products 88Br, 94;95Rb, and 138I has been measured; this data is still under analysis. Simulations with MCNPX and GEANT4 have been performed in order to obtain the efficiency of the BELEN-20 detector for each of the above nuclei using the neutron energy distribution corresponding to each nucleus.Peer ReviewedPostprint (published version

The 236U neutron capture cross-section measured at the n TOF CERN facility

The 236U isotope plays an important role in nuclear systems, both for future and currently operating ones. The actual knowledge of the capture reaction of this isotope is satisfactory in the thermal region, but it is considered insufficient for Fast Reactor and ADS applications. For this reason the 236U(n, gamma ) reaction cross section has been measured for the first time in the whole energy region from thermal energy up to 1MeV at the n TOF facility with two different detection systems: an array of C6D6 detectors, employing the total energy deposited method, and a 4p total absorption calorimeter (TAC), made of 40 BaF2 crystals. The two n TOF data sets agree with each other within the statistical uncertainty in the Resolved Resonance Region up to 800 eV, while sizable differences (up to 20%) are found relative to the current evaluated data libraries. Moreover two new resonances have been found in the n TOF data. In the Unresolved Resonance Region up to 200 keV, the n TOF results show a reasonable agreement with previous measurements and evaluated data.Postprint (published version

High precision measurement of the radiative capture cross section of 238U at the n TOF CERN facility

The importance of improving the accuracy on the capture cross-section of 238U has been addressed by the Nuclear Energy Agency, since its uncertainty significantly affects the uncertainties of key design parameters for both fast and thermal nuclear reactors. Within the 7th framework programme ANDES of the European Commission three different measurements have been carried out with the aim of providing the 238U(n, gamma) cross-section with an accuracy which varies from 1 to 5%, depending on the energy range. Hereby the final results of the measurement performed at the n TOF CERN facility in a wide energy range from 1 eV to 700 keV will be presented.Postprint (published version

Measurement of the 241Am neutron capture cross section at the n TOF facility at CERN

New neutron cross section measurements of minor actinides have been performed recently in order to reduce the uncertainties in the evaluated data, which is important for the design of advanced nuclear reactors and, in particular, for determining their performance in the transmutation of nuclear waste.We have measured the 241Am(n,gamma ) cross section at the n TOF facility between 0.2 eV and 10 keV with a BaF2 Total Absorption Calorimeter, and the analysis of the measurement has been recently concluded. Our results are in reasonable agreement below 20 eV with the ones published by C. Lampoudis et al. in 2013, who reported a 22% larger capture cross section up to 110 eV compared to experimental and evaluated data published before. Our results also indicate that the 241Am(n,gamma ) cross section is underestimated in the present evaluated libraries between 20 eV and 2 keV by 25%, on average, and up to 35% for certain evaluations and energy ranges.Postprint (published version

Neutron-induced fission cross sections of Th 232 and U 233 up to 1 GeV using parallel plate avalanche counters at the CERN n_TOF facility

The neutron-induced fission cross sections of 232 Th and 233 U were measured relative to 235 U in a wide neutron energy range up to 1 GeV (and from fission threshold in the case of 232 Th , and from 0.7 eV in case of 233 U ), using the white-spectrum neutron source at the CERN Neutron Time-of-Flight (n_TOF) facility. Parallel plate avalanche counters (PPACs) were used, installed at the Experimental Area 1 (EAR1), which is located at 185 m from the neutron spallation target. The anisotropic emission of fission fragments were taken into account in the detection efficiency by using, in the case of 233 U , previous results available in EXFOR, whereas in the case of 232 Th these data were obtained from our measurement, using PPACs and targets tilted 45 ° with respect to the neutron beam direction. Finally, the obtained results are compared with past measurements and major evaluated nuclear data libraries. Calculations using the high-energy reaction models INCL + + and ABLA07 were performed and some of their parameters were modified to reproduce the experimental results. At high energies, where no other neutron data exist, our results are compared with experimental data on proton-induced fission. Moreover, the dependence of the fission cross section at 1 GeV with the fissility parameter of the target nucleus is studied by combining those ( p , f ) data with our ( n , f ) data on 232 Th and 233 U and on other isotopes studied earlier at n_TOF using the same experimental setup.Peer ReviewedArticle escrit per 81 autors/autores: D. Tarrío , L. Tassan-Got, I. Duran, L. S. Leong, C. Paradela, L. Audouin, E. Leal-Cidoncha, C. Le Naour, M. Caamaño, A. Ventura, S. Altstadt, J. Andrzejewski, M. Barbagallo, V. Bécares, F. Becvá ˇ ˇr,F. Belloni, E. Berthoumieux, J. Billowes, V. Boccone, D. Bosnar, M. Brugger, M. Calviani, F. Calviño, D. Cano-Ott, C. Carrapiço, F. Cerutti, E. Chiaveri,M. Chin, N. Colonna, G. Cortés, M. A. Cortés-Giraldo, M. Diakaki, C. Domingo-Pardo, N. Dzysiuk, C. Eleftheriadis, A. Ferrari, K. Fraval, S. Ganesan, A. R. García, G. Giubrone, M. B. Gómez-Hornillos, I. F. Gonçalves, E. González-Romero,E. Griesmayer, C. Guerrero, F. Gunsing, P. Gurusamy, D. G. Jenkins, E. Jericha, Y. Kadi, F. Käppeler,† D. Karadimos, P. Koehler, M. Kokkoris, M. Krticka, J. Kroll, C. Langer, C. Lederer, H. Leeb, R. Losito, A. Manousos, J. Marganiec, T. Martínez, C. Massimi, P. F. Mastinu,M. Mastromarco, M. Meaze, E. Mendoza, A. Mengoni, P. M. Milazzo, F. Mingrone, M. Mirea,,† W. Mondalaers, A. Pavlik, J. Perkowski, A. Plompen, J. Praena, J. M. Quesada, T. Rauscher, R. Reifarth, A. Riego, M. S. Robles, F. Roman, C. Rubbia, R. Sarmento, P. Schillebeeckx,S. Schmidt, G. Tagliente, J. L. Tain, A. Tsinganis, S. Valenta, G. Vannini, V. Variale, P. Vaz, R. Versaci, M. J. Vermeulen, V. Vlachoudis, R. Vlastou,A. Wallner, T. Ware, M. Weigand, C. Weiß, T. J. Wright, P. ŽugecPostprint (published version

Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality

Past, present and future of the n_TOF facility at CERN

Postprint (published version