The neutron time-of-flight facility, nTOF, has been operating at CERN since 2001. nTOF is a pulsed neutron source coupled to a 200-metre flight path. It is designed to study neutron-nucleus interactions for neutron energies ranging from a few meV to several GeV. The wide energy range and high-intensity neutron beams produced at nTOF are used to make precise measurements of neutron-related processes.
To produce neutrons, a pulsed beam of protons from the Proton Synchrotron (PS) is directed at a lead target. When the beam hits, every proton yields about 300 neutrons. The initially fast neutrons are slowed down, first by a lead target, and then by a slab containing water. Some neutrons slow more than others as they pass through the targets, which creates a range of neutron energies (a "neutron spectrum") from the meV region up to the GeV region.
These neutrons are guided through an evacuated beam pipe to an experimental area 185 metres from the target. In a typical experiment, a sample is placed in the neutron beam and the reaction products detected. This allows the team to reconstruct the reaction probability as a function of the incident neutron energy.
Neutron time-of-flight measurements contribute in an important way to understanding nuclear data. Only a few time-of-flight facilities exist worldwide, each with its own characteristics. The strength of nTOF is the large energy range it can cover, and the high number of neutrons per pulse.
Data produced by nTOF are used in astrophysics to study stellar evolution and supernovae. Intense neutron beams are also important in hadrontherapy (the treatment of tumors with beams of hadrons) and studies of how to incinerate radioactive nuclear waste.
n_TOF – L’usine à neutrons
Astrophysique, environnement et applications médicales
L’installation de mesure du temps de vol des neutrons (n_TOF) est une source de neutrons qui fonctionne au CERN depuis 2001. Il s’agit d’une installation unique en son genre dans laquelle sont produits des neutrons avec des gammes d’énergie très large et dans des faisceaux très intenses. Le système permet des mesures fines des processus impliquant des neutrons, ce qui présente un intérêt pour plusieurs disciplines.
Ainsi, en astrophysique nucléaire, les données produites par n_TOF sont utilisées pour étudier l’évolution stellaire normale ainsi que les supernovas. Les faisceaux de neutrons intenses sont aussi d’importance critique pour l’étude des processus d’incinération des déchets nucléaires radioactifs et une meilleure compréhension des effets des rayonnements dans les traitement des tumeurs par faisceaux de hadrons (hadrothérapie).
n_TOF is a pulsed neutron source coupled to a 200 m flight path designed to study neutron-nucleus interactions for neutron kinetic energies ranging from a few meV to several GeV. The neutron kinetic energy is determined by time-of-flight, hence the name n_TOF.
The study of neutron-induced reactions is of large importance in a wide variety of research fields, ranging from stellar nucleosynthesis, symmetry breaking effects in compound nuclei, and the investigation of nuclear level densities, to applications of nuclear technology, including the transmutation of nuclear waste, accelerator driven systems and nuclear fuel cycle investigations.