The n_TOF Facility at CERN: Status and Perspectives

Abstract

The outstanding features of the existing CERN n_TOF neutron beam are the very high instantaneous neutron flux, excellent n_TOF resolution, low intrinsic backgrounds and coverage of a wide range of neutron energies, from thermal to a few GeV. These characteristics provide a unique possibility to perform neutron-induced cross-section and angular distribution measurements for applications such as nuclear astrophysics, nuclear reactor technology and basic nuclear physics. This paper presents in detail all the characteristics of the present neutron beam in the different available configurations, which correspond to two different collimation systems and two choices of neutron moderator. The features include shape and intensity of the neutron flux, beam spatial profile, in-beam background components and the energy resolution broadening. The description of these features is based upon both dedicated measurements as well as Monte Carlo simulations, and includes an estimation of the systematic uncertainties in the mentioned quantities. The overall efficiency of the experimental program and the range of possible measurements will be expanded in the near future with the construction of a second experimental area (EAR-2), vertically located 20 m on top of the present n_TOF spallation target. This upgrade, which will benefit from a neutron flux 25 times higher than the existing one, will provide a substantial improvement in measurement sensitivities and will open the possibility to measure neutron cross-section of isotopes with very short halflives or available in very small quantities. The technical study for the construction of this new neutron beam will be presented, highlighting the main advantages compared to the presently existing Experimental Area (EAR-1).