Abstract
At the neutron time-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.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 backgrounds.
Highlights
The neutron time-of-flight facility n_TOF at CERN [1,2] is a pulsed white neutron source for high-accuracy neutron crosssection measurements over a wide neutron energy range
The neutron beam is shaped by two collimators:
The beam line design of the vertical flight path was based on extensive Monte Carlo simulation studies [12,13], which were performed with the FLUKA code [14,15], using the graphical interface FLAIR [16]
Summary
The neutron time-of-flight facility n_TOF at CERN [1,2] is a pulsed white neutron source for high-accuracy neutron crosssection measurements over a wide neutron energy range. At the facility in operation since 2000 the measurements take place in an experimental area placed at the end of a horizontal beam line, 200 m in length. The experimental conditions and neutron beam characteristics at this horizontal flight path are presented in full detail in Ref. The horizontal 200 m flight path, with its record instantaneous neutron beam intensity, has allowed very important cross-sections to be measured, getting unprecedented energy resolution in both neutron capture [5,6] and fission [7] as well as extending the measurement range to previously unreachable neutron energies [8]. In order to extend the experimental possibilities at the n_TOF facility for cross-section measurements of very low mass samples ( o 1 mg), reactions with small cross-sections or highly radioactive samples [9], an additional vertical flight path of 20 m with a significantly higher neutron flux was designed and constructed in 2014.
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