Abstract
The neutron time-of-flight (n_TOF) facility at the European Laboratory for Particle Physics (CERN) is a pulsed white-spectrum neutron spallation source producing neutrons for two experimental areas: the Experimental Area 1 (EAR1), located 185 m horizontally from the target, and the Experimental Area 2 (EAR2), located 20 m above the target. The target, based on pure lead, is impacted by a high-intensity 20-GeV/c pulsed proton beam. The facility was conceived to study neutron-nucleus interactions for neutron kinetic energies between a few meV to several GeV, with applications of interest for nuclear astrophysics, nuclear technology, and medical research. After the second-generation target reached the end of its lifetime, the facility underwent a major upgrade during CERN's Long Shutdown 2 (LS2, 2019-2021), which included the installation of the new third-generation neutron target. The first and second-generation targets were based on water-cooled massive lead blocks and were designed focusing on EAR1, since EAR2 was built later. The new target is cooled by nitrogen gas to avoid erosion-corrosion and contamination of cooling water with radioactive lead spallation products. Moreover, the new design is optimized also for the vertical flight path and EAR2. This paper presents an overview of the target design focused on both physics and thermo-mechanical performance, and includes a description of the nitrogen cooling circuit and radiation protection studies.
Highlights
AND MOTIVATIONSThe neutron time-of-flight (n_TOF) facility at the European Laboratory for Particle Physics (CERN) is a neutron source capable of providing high-intensity pulsed white-spectrum neutrons covering almost 11 orders of magnitude, from thermal neutrons to several GeV
This paper presents an overview of the target design focused on both physics and thermomechanical performance, and includes a description of the nitrogen cooling circuit and radiation protection studies
The generated neutrons travel inside vacuum tubes along two flight paths directed to two experimental areas, Experimental Area 1 (EAR1) and Experimental Area 2 (EAR2), where cutting-edge experimental setups for neutron-induced reaction studies are in place
Summary
The neutron time-of-flight (n_TOF) facility at the European Laboratory for Particle Physics (CERN) is a neutron source capable of providing high-intensity pulsed white-spectrum neutrons covering almost 11 orders of magnitude, from thermal neutrons to several GeV. The facility operated with EAR1 and a first-generation spallation target (Target #1) from 2000 to 2004 [7]. During 2014, the second experimental area (EAR2) was built 20 m above the spallation target, the neutron beam characteristics in EAR2 were not optimal since the target shape was not conceived for this experimental area. All these aspects triggered the design of a new thirdgeneration spallation target (Target #3), to be installed during the Long Shutdown 2 (LS2), a three-year stop of the CERN accelerators, and with the objective of starting operation in 2021. The beam size on target is assumed to be 15 mm (rms)
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