Speaker
Description
The European Laboratory for Particle Physics (CERN) is equipped with a top-class, high-brightness, neutron spallation source dedicated to high-resolution neutron time-of-flight experiments: the n_TOF Facility.
During CERN’s Long Shutdown 2 (LS2, 2019-2021), the n_TOF neutron spallation target has been exchanged and the facility is now operating with its third-generation target [1]. The neutron production target is based on a segmented pure Pb (>99.9%) core, cooled by gaseous nitrogen at atmospheric pressure. The target has been designed for a single bunch proton beam impacting on the production target at 20 GeV/c with up to 1013 protons/bunch, and with a bunch length of 6 ns RMS. The produced neutrons span 11 orders of magnitude in kinetic energy, from sub-thermal to GeV and are serving two time-of-flight experimental stations plus an irradiation station. The initially fast neutrons are moderated by two independent moderator circuits, each one dedicated to an experimental station, that can be filled with either by demineralized water or by borated water in saturation.
The contribution will detail the physics optimization and engineering design processes that brought the facility from the second-generation target to the current evolutionary one. The work will include a description of the new target design features, its mechanical assembly, and its compliance with safety and physics performance requirements as well as the R&D which has been carried out, including beam testing at the CERN’s HiRadMat facility [2]. The contribution will also detail the first hardware results coming from the 2021 facility commissioning, first radiation protection assessments in the target zone and from early operation in 2022.
The paper will also discuss the plans for an autopsy of the second-generation target to investigate the status of the water-cooled monolithic Pb core after 10 years of operation and its impact on the radioactive waste characterization and in the operation of the third-generation target.
[1] R. Esposito et al., Design of the third-generation lead-based neutron spallation target for the neutron time-of-flight facility at CERN, Phys. Rev. Accel. Beams 24, 093001 (2021)
[2] R. Esposito and M. Calviani, Design of the third-generation neutron spallation target for the CERN’s n_TOF facility, J. Neutron Res. 22, 221 (2020)