Measurements of high-energy neutron-induced fission of (nat)Pb and (209)Bi

This is an Open Access article distributed under the terms of the Creative Commons Attribution-Noncommercial License 3.0, which permits unrestricted use, distribution, and reproduction in any noncommercial medium, provided the original work is properly citedThe CERN Neutron Time-Of-Flight (n_TOF) facility is well suited to measure low cross sections as those of neutron-induced fission in subactinides. The cross section ratios of (nat)Pb and (209)Bi relative to (235)U and (238)U were measured using PPAC detectors and a fragment coincidence method that allows us to identify the fission events. The present experiment provides first results for neutron-induced fission up to 1 GeV. Good agreement is found with previous experimental data below 200 MeV. The comparison with proton-induced fission indicates that the limiting regime where neutron-induced and proton-induced fission reach equal cross sections is close to 1 GeV

Towards the high-accuracy determination of the 238U fission cross section at the threshold region at CERN - N-TOF

The 238U fission cross section is an international standard beyond 2 MeV where the fission plateau starts. However, due to its importance in fission reactors, this cross-section should be very accurately known also in the threshold region below 2 MeV. The 238U fission cross section has been measured relative to the 235U fission cross section at CERN - n-TOF with different detection systems. These datasets have been collected and suitably combined to increase the counting statistics in the threshold region from about 300 keV up to 3 MeV. The results are compared with other experimental data, evaluated libraries, and the IAEA standards

Nuclear astrophysics at n-TOF facility, CERN

The innovative feature of the n-TOF facility at CERN, in the two experimental areas, (20 m and 200 m flight paths), allow for an accurate determination of the neutron capture cross section for radioactive samples or for isotopes with small neutron capture cross section, of interest for Nuclear Astrophysics. This contribution presents an overview on the astrophysical program carried on at the n-TOF facility, the main results and their implications

Measurement of the Neutron Capture Cross Section of 234U in n_TOF at CERN

Accurate and reliable neutron capture cross sections are needed in many research areas, including stellar nucleosynthesis, advanced nuclear fuel cycles, waste transmutation, and other applied programs. In particular, the accurate knowledge of 234U(n,γ) reaction cross section is required for the design and realization of nuclear power stations based on the thorium fuel cycle. We have measured the neutron capture cross section of 234U at the recently constructed neutron time-of-flight facility n TOF at CERN [2] in the energy range from 0.03 eV to 1 MeV with high accuracy due to a combination of features unique in the world: A high instantaneous neutron fluence and excellent energy resolution of the n TOF facility, an innovative Data Acquisition System based on flash ADCs [3] and the use of a high performance 4π BaF2 Total Absorption Calorimeter (TAC) as a detection device [4, 5]. In this paper, we will describe the experimental apparatus including the various TAC components and its performance. We also will present results from the 234U(n,γ) measurement. A sample of 38.7 mg of 234U3O8 was pressed into a pellet and doubly encapsulated between Al and Ti foils which were 0.15 mm and 0.2 mm thick, respectively. Monte-Carlo simulations with GEANT4 [6] of the detector response have been performed. After the background subtraction and correction with dead time and pile-up, the capture yield from 0.03 eV up to 1.5 keV was derived. Preliminary analysis of the capture yield in terms of R-matrix resonance parameters is discussed.JRC.D.5-Neutron physic