V. Vlachoudis

Neutron capture cross section of unstable 63Ni: implications for stellar nucleosynthesis.

The 63Ni(n,γ) cross section has been measured for the first time at the neutron time-of-flight facility n_TOF at CERN from thermal neutron energies up to 200 keV. In total, capture kernels of 12 (new) resonances were determined. Maxwellian averaged cross sections were calculated for thermal energies from   kT=5-100  keV with uncertainties around 20%. Stellar model calculations for a 25M⊙ star show that the new data have a significant effect on the s-process production of 63Cu, 64Ni, and 64Zn in massive stars, allowing stronger constraints on the Cu yields from explosive nucleosynthesis in the subsequent supernova.

The Neutron Time Of Flight Facility at CERN

The neutron Time of Flight (n_TOF) facility at CERN is a high flux neutron source obtained by the spallation of 20 GeV/c protons onto a solid lead target. The proton beam is delivered by the Proton Synchrotron (PS)1) capable of providing up to four sharp bunches (6 ns) with an intensity of 71012 protons per bunch, within a 14.4 s supercycle. The outstanding characteristics of this facility: high neutron flux of 106 n/cm2/71012 p. at 182.5 m, wide spectral function from 1 eV up to 250 MeV, low repetition rates and an excellent energy resolution of 2 × 10–4 open new possibilities for high precision neutron induced cross section measurements, using samples of modest mass. The facility was commissioned in Nov. 2000 and Apr. 2001, with performances similar to those predicted by Monte Carlo simulations.

The Neutron Time-Of-Flight Facility n_TOF At CERN: Phase II

Neutron‐induced reactions are studied at the neutron time‐of‐flight facility n_TOF at CERN. The facility uses 6∼ns wide pulses of 20 GeV/c protons impinging on a lead spallation target. The large neutron energy range and the high instantaneous neutron flux combined with high resolution are among the key characteristics of the facility. After a first phase of data taking during the period 2001–2004, the facility has been refurbished with an upgraded spallation target and cooling system for a second phase of data taking which started in 2009. Since 2010, the experimental area at 185 m where the neutron beam arrives, has been modified into a worksector of type A, allowing the extension of the physics program to include neutron‐induced reactions on radioactive isotopes.

Neutron research at the N_TOF facility (CERN): Results and perspectives

In the first ten years of operation, the neutron time-of-flight facility n_TOF at CERN has produced a large body of new and accurate data on neutron capture and fission cross sections, relevant to Nuclear Astrophysics and advanced nuclear technologies. In the next phase, with the construction of a second experimental area with a shorted flight path, the focus of the Collaboration will partially shift from high-resolution measurements of stable or long-lived isotopes, to high-flux measurements of isotopes of relatively short half-life, very low-cross sections, or available in very small quantities. The main results obtained so far at n_TOF and the future perspectives are here presented.