Investigation of 14.1 MeV neutrons interaction with C, Mg, Cr

This paper is dedicated to n+12C, n+24Mg, n+52Cr -reactions investigation at 14.1 MeV neutron energy. Characteristics of these reactions have been calculated using TALYS code to estimate perspectives of using of this code in data interpretation in the TANGRA project. This project is performed in Frank Laboratory of Neutron Physics (FLNP JINR) to investigate properties of (n,xγ)-type reactions, important for fundamental and practical applications

Investigation of 14.1 MeV neutrons interaction with C, Mg, Cr

358-362This paper is dedicated to n+12C, n+24Mg, n+52Cr -reactions investigation at 14.1 MeV neutron energy. Characteristics of these reactions have been calculated using TALYS code to estimate perspectives of using of this code in data interpretation in the TANGRA project. This project is performed in Frank Laboratory of Neutron Physics (FLNP JINR) to investigate properties of (n,xγ)-type reactions, important for fundamental and practical applications

Response function of a BGO detector for γ-rays with energies in the range from 0.2 MeV to 8 MeV

This work is devoted to determination of the response function of a BGO detector of γ-rays, which is used in experiments aimed at investigation of inelastic scattering of neutrons with energies of 14.1 MeV on various nuclei. A function is constructed to describe the Monte-Carlo simulated response of a gamma-detector, which allows taking into account all possible mechanisms of interaction of γ-rays with matter, as well as the geometric parameters of the detector. For all components of the function, an analytical form of their energy dependencies is selected and its parameters are determined in the case of registration of γ-quanta with energies in the range from 0.2 MeV to 8 MeV

Response function of a BGO detector for γ-rays with energies in the range from 0.2 MeV to 8 MeV

427-430This work is devoted to determination of the response function of a BGO detector of γ-rays, which is used in experiments aimed at investigation of inelastic scattering of neutrons with energies of 14.1 MeV on various nuclei. A function is constructed to describe the Monte-Carlo simulated response of a gamma-detector, which allows taking into account all possible mechanisms of interaction of γ-rays with matter, as well as the geometric parameters of the detector. For all components of the function, an analytical form of their energy dependencies is selected and its parameters are determined in the case of registration of γ-quanta with energies in the range from 0.2 MeV to 8 MeV

Neutron capture measurement at the n TOF facility of the 204Tl and 205Tl s-process branching points

Neutron capture cross sections are one of the fundamental nuclear data in the study of the s (slow) process of nucleosynthesis. More interestingly, the competition between the capture and the decay rates in some unstable nuclei determines the local isotopic abundance pattern. Since decay rates are often sensible to temperature and electron density, the study of the nuclear properties of these nuclei can provide valuable constraints to the physical magnitudes of the nucleosynthesis stellar environment. Here we report on the capture cross section measurement of two thallium isotopes, 204Tl and 205Tl performed by the time-of-flight technique at the n TOF facility at CERN. At some particular stellar s-process environments, the decay of both nuclei is strongly enhanced, and determines decisively the abundance of two s-only isotopes of lead, 204Pb and 205Pb. The latter, as a long-lived radioactive nucleus, has potential use as a chronometer of the last s-process events that contributed to final solar isotopic abundances

80Se(n,?) cross-section measurement at CERN n TOF

Radiative neutron capture cross section measurements are of fundamental importance for the study of the slow neutron capture (s-) process of nucleosynthesis. This mechanism is responsible for the formation of most elements heavier than iron in the Universe. Particularly relevant are branching nuclei along the s-process path, which are sensitive to the physical conditions of the stellar environment. One such example is the branching at $^{79}$Se (3.27 × 10$^{5}$ y), which shows a thermally dependent β-decay rate. However, an astrophysically consistent interpretation requires also the knowledge of the closest neighbour isotopes involved. In particular, the $^{80}$Se(n,γ) cross section directly affects the stellar yield of the "cold" branch leading to the formation of the s-only $^{82}$Kr. Experimentally, there exists only one previous measurement on $^{80}$Se using the time of flight (TOF) technique. However, the latter suffers from some limitations that are described in this presentation. These drawbacks have been significantly improved in a recent measurement at CERN n TOF. This contribution presents a summary of the latter measurement and the status of the data analysis

First results of the140ce(N,ү)141ce cross-section measurement at n_tof

An accurate measurement of the140Ce(n,ү) energy-dependent cross-section was performed at the n_TOF facility at CERN. This cross-section is of great importance because it represents a bottleneck for the s-process nucleosynthesis and determines to a large extent the cerium abundance in stars. The measurement was motivated by the significant difference between the cerium abundance measured in globular clusters and the value predicted by theoretical stellar models. This discrepancy can be ascribed to an overestimation of the140Ce capture cross-section due to a lack of accurate nuclear data. For this measurement, we used a sample of cerium oxide enriched in140Ce to 99.4%. The experimental apparatus consisted of four deuterated benzene liquid scintillator detectors, which allowed us to overcome the difficulties present in the previous measurements, thanks to their very low neutron sensitivity. The accurate analysis of the p-wave resonances and the calculation of their average parameters are fundamental to improve the evaluation of the140Ce Maxwellian-averaged cross-section

First results of the Am-241(n,f) cross section measurement at the Experimental Area 2 of the n_TOF facility at CERN

This research is co-financed by Greece and the European Union (European Social Fund-ESF) through the Operational Programme Human Resources Development, Education and Lifelong Learning in the context of the project "Strengthening Human Resources Research Potential via Doctorate Research" (MIS-5000432), implemented by the State Scholarships Foundation (IKY). Also, the authors would like to acknowledge the support of the European Commission under the CHANDA project (7th Framework Programme).Feasibility, design and sensitivity studies on innovative nuclear reactors that could address the issue of nuclear waste transmutation using fuels enriched in minor actinides, require high accuracy cross section data for a variety of neutron-induced reactions from thermal energies to several tens of MeV. The isotope Am-241 (T-1/2= 433 years) is present in high-level nuclear waste (HLW), representing about 1.8 % of the actinide mass in spent PWR UOx fuel. Its importance increases with cooling time due to additional production from the beta-decay of Pu-241 with a half-life of 14.3 years. The production rate of 241Am in conventional reactors, including its further accumulation through the decay of Pu-241 and its destruction through transmutation/incineration are very important parameters for the design of any recycling solution. In the present work, the Am-241(n,f) reaction cross-section was measured using Micromegas detectors at the Experimental Area 2 of the n_TOF facility at CERN. For the measurement, the U-235(n,f) and U-238(n,f) reference reactions were used for the determination of the neutron flux. In the present work an overview of the experimental setup and the adopted data analysis techniques is given along with preliminary results.European Union (European Social Fund-ESF) through the Operational Programme Human Resources Development, Education and Lifelong Learning MIS-5000432European Commission under the CHANDA project (7th Framework Programme

Monte Carlo simulations and n-p differential scattering data measured with Proton Recoil Telescopes

The authors wish to thank the National Center of the INFN for Research and Development in Information and Communication Technologies (CNAF) for their computational support.The neutron-induced fission cross section of U-235, a standard at thermal energy and between 0.15 MeV and 200 MeV, plays a crucial role in nuclear technology applications. The long-standing need of improving cross section data above 20 MeV and the lack of experimental data above 200 MeV motivated a new experimental campaign at the n_TOF facility at CERN. The measurement has been performed in 2018 at the experimental area 1 (EAR1), located at 185 m from the neutron-producing target (the experiment is presented by A. Manna et al. in a contribution to this conference). The U-235(n,f) cross section from 20 MeV up to about 1 GeV has been measured relative to the H-1(n,n)H-1 reaction, which is considered the primary reference in this energy region. The neutron flux impinging on the U-235 sample (a key quantity for determining the fission events) has been obtained by detecting recoil protons originating from n-p scattering in a C2H4 sample. Two Proton Recoil Telescopes (PRT), consisting of several layers of solid-state detectors and fast plastic scintillators, have been located at proton scattering angles of 25.07 degrees and 20.32 degrees, out of the neutron beam. The PRTs exploit the Delta E-E technique for particle identification, a basic requirement for the rejection of charged particles from neutron-induced reactions in carbon. Extensive Monte Carlo simulations were performed to characterize proton transport through the different slabs of silicon and scintillation detectors, to optimize the experimental set-up and to deduce the efficiency of the whole PRT detector. In this work we compare measured data collected with the PRTs with a full Monte Carlo simulation based on the Geant-4 toolkit

Setup for the measurement of the U-235(n,f) cross section relative to n-p scattering up to 1 GeV

The neutron induced fission of U-235 is extensively used as a reference for neutron fluence measurements in various applications, ranging from the investigation of the biological effectiveness of high energy neutrons, to the measurement of high energy neutron cross sections of relevance for accelerator driven nuclear systems. Despite its widespread use, no data exist on neutron induced fission of U-235 above 200 MeV. The neutron facility n_TOF offers the possibility to improve the situation. The measurement of U-235(n,f) relative to the differential n-p scattering cross-section, was carried out in September 2018 with the aim of providing accurate and precise cross section data in the energy range from 10 MeV up to 1 GeV. In such measurements, Recoil Proton Telescopes (RPTs) are used to measure the neutron flux while the fission events are detected and counted with dedicated detectors. In this paper the measurement campaign and the experimental set-up are illustrated