The new vertical neutron beam line at the CERN n_TOF facility design and outlook on the performance

Abstract

At the neutron Lime-of-flight facility n_TOF at CERN a new vertical beam line was constructed in 2014, in order to extend the experimental possibilities at this facility to an even wider range of challenging cross-section measurements of interest in astrophysics, nuclear technology and medical physics. The design of the beam line and the experimental hall was based on FLUKA Monte Carlo simulations, aiming at maximizing the neutron flux, reducing the beam halo and minimizing the background from neutrons interacting with the collimator or back-scattered in the beam dump. \ud The present paper gives an overview on the design of the beam line and the relevant elements and provides an outlook on the expected performance regarding the neutron beam intensity, shape and energy resolution, as well as the neutron and photon backgroundsPostprint (author's final draft

Be7(n,α)HeBarbagallo1, Musumarra2, Coséntino3 et al. 2016Phys. Rev. Lett.Self Cite1022341View full textAdd to dashboardCite

“…The energy calibration of the detectors was performed by means of the 6 Liðn; tÞ 4 He reaction, measured with the final detector configuration a few days before the insertion of the 7 Be samples. The same measurement provided an indication of the upper neutron energy limit of the measurement, which was determined by the recovery time of the Si detectors after the γ flash from the spallation target [17]. Therefore, the present results are limited to neutron energies below 10 keV.…”

“…The recent construction of a second, high-flux experimental area at n_TOF (EAR2), CERN [15,16], offered the unique opportunity to perform a first time-of-flight measurement of the 7 Beðn; αÞ 4 He cross section over a wider energy range. The neutron beam in the new measuring station, located 20 m above the spallation target [17], is characterized by an extremely high luminosity (10 7 neutrons=pulse), wide energy range (10 meV < E n < 100 MeV), good energy resolution (ΔE=E ∼ 10 −3 up to 10 keV), and low repetition rate (< 0.8 Hz). All these features make EAR2 ideal for measurements on isotopes only available in very small amounts, with short half-lives, or both, as indeed is the case for 7 Be.…”

Study of a data analysis method for the angle resolving silicon telescope

“…The second is to investigate its applicability on the artificially generated dataset resembling the first experimental dataset from n_TOF to which the the method is to be applied at a later date: that of the 12 C(n, p) reaction (section 3). In doing this we aim (1) to provide the future users of the method with all the necessary steps and considerations to be taken into account in extracting the optimal set of physical parameters from a given measurement; (2) to provide an honest assessment of the direct applicability of the method to a dataset of a given level of uncertainties, in particular the one expected from the 12 C(n, p) measurement, and (3) to provide alternative solutions in case the direct application proves to be unreliable due to the level of uncertainties in the extracted results (section 4). Since we develop the method having a specific 12 C(n, p) reaction in mind, it cannot be overemphasized that the procedure is aimed at and designed for the particular detector setup, based on the ∆E-E telescoping principle, rather than for the particular reaction of even the type of reaction.…”

“…i j (x, E, χ, E(1) , E(2) ) ≡ d 4 N i j (x, E, χ, E (1) , E (2) ) d 2 N (x, E, χ)dE (1) dE(2) , Illustrative example: the reaction products leaving the daughter nucleus in any of its excited states may leave a clear signature in the deposited energy spectrum if the energy separation of the excited states is sufficient.…”

Design of back-streaming white neutron beam line at CSNS

“…These facilities have specific characteristics of neutron beam intensities, energy resolutions, associated instrumentation and data acquisition systems, and dedicated experimental programs. The CERN n_TOF provides an intense pulsed neutron beam in a wide energy spectrum and a good energy resolution with a time-of-flight (TOF) distance of 185 m that stands today among the world's leading facilities for measuring neutron-induced cross section [2][3]. The LANSCE/WNR provides a continuous intense neutron beam with energy ranging from about 0.1 MeV to more than 600 MeV using the 800-MeV proton beam from the LANSCE linac and has six flight paths instrumented for a variety of measurements [4].…”