CERN n_TOF

CERN n_TOF
Name	n_TOF
Caption	Neutron Time-of-Flight facility at CERN
Established	2001
Location	Meyrin, Switzerland
Operating org	CERN

CERN n_TOF The n_TOF facility at CERN is a neutron time-of-flight experimental installation dedicated to precision neutron-induced reaction measurements relevant to nuclear astrophysics, nuclear reactor design, radiation protection and medical physics. Located at the CERN Meyrin site, the facility uses a high-energy proton beam from the Proton Synchrotron (PS) to produce neutrons via spallation and measures reaction cross sections with high resolution and low background. n_TOF serves an international user community spanning national laboratories, universities, and research institutes such as CERN, Los Alamos National Laboratory, Oak Ridge National Laboratory, Institut Laue–Langevin, and GSI.

Overview

n_TOF was conceived to address precision measurements of neutron capture, fission, and scattering cross sections that impact models in s-process, r-process, and nuclear applications like Generation IV reactor concepts and transmutation studies. The facility's distinguishing features include a long flight path to achieve excellent energy resolution, a pulsed proton driver from the PS Booster, and advanced detection systems drawn from collaborations with institutions such as INFN, CNRS, CEA, and TU Delft. The program has influenced evaluations in nuclear data libraries like ENDF/B, JEFF, and JENDL.

Facility and Experimental Setup

The core layout comprises a spallation target station, neutron moderators, and two experimental areas at differing flight paths: the long-path experimental area and a shorter, high-flux station. Protons accelerated by the Proton Synchrotron strike a heavy metal spallation target (typically lead or tantalum) producing a neutron spectrum moderated by materials such as graphite or water, with beam transport through shielding built from concrete and iron blocks. Instrumentation includes total energy detectors, segmented silicon detectors, ionization chambers, and scintillation arrays developed in partnership with groups from ETH Zurich, Politecnico di Milano, University of Manchester, and CEA Saclay. Time-of-flight measurement uses timing references from the PS extraction and high-precision timing electronics provided by collaborators like CERN BE Department and GSI electronics groups.

Research Program and Methods

n_TOF's research program covers neutron capture, (n,γ), neutron-induced fission, (n,f), neutron-induced charged-particle reactions, (n,p) and (n,α), and neutron scattering for structural and dosimetric applications. Methods combine time-of-flight spectroscopy, activation techniques, and coincidence measurements using calorimetric detectors such as the C6D6 liquid scintillators and total absorption calorimeters developed with Università di Bologna, LPC Caen, and University of Lisbon. Experimental campaigns often integrate Monte Carlo simulations with codes like GEANT4, FLUKA, and deterministic transport tools from NEA Data Bank partners to model neutron transport, detector response, and background suppression. Results feed into astrophysical reaction-rate calculations alongside theoretical models from groups working with KADoNiS and statistical-model codes such as TALYS.

Key Results and Discoveries

n_TOF has produced high-precision cross sections for isotopes central to nucleosynthesis: measurements on 187Os, 186Os, 151Sm, and radioactive isotopes like 79Se and 60Fe have refined s-process branching analyses and cosmic chronometers. The facility provided benchmark fission cross sections for actinides including 235U, 238U, and 239Pu employed in reactor physics and criticality safety. Studies on minor actinides, e.g., 241Am and 243Am, informed transmutation strategies considered by MYRRHA and European Spallation Source planning. n_TOF also reported neutron-induced reaction data for medically relevant isotopes such as 99Mo production routes and for dosimetry materials used by ESA and ITER diagnostic teams.

Collaborations and User Community

The user base comprises hundreds of scientists from over 100 institutions across Europe, North America, and Asia, including recurring participants from CERN, INFN, CNRS, PSI, JAEA, and Kyoto University. n_TOF operates under a proposal-driven access model similar to major facilities like ITER and ESS, with experiments reviewed by an external program committee and supported by technical teams from CERN Accelerator and detector groups. Collaborative outputs appear in journals alongside contributions from networks such as the European Nuclear Education Network and projects funded by the European Union's framework programs.

Future Upgrades and Developments

Planned upgrades include increased proton intensity from the PS complex, enhanced moderator and target designs, and new detection systems to improve sensitivity to weak or radioactive samples, coordinated with partners like ENEA, SCK CEN, and CEA. Developments aim to extend capabilities for radioactive ion-beam activation, compact moderator stations for low-energy neutrons, and improved data acquisition integrating FPGA-based electronics from institutions such as CERN BE Department and GSI. These upgrades target expanded impact on fields tied to astrophysical modeling, advanced reactor fuel cycles, and isotope production for nuclear medicine.

Category:Particle physics facilities Category:Nuclear physics