NEAR: A New Station to Study Neutron-Induced Reactions of Astrophysical Interest at CERN-n_TOF

Abstract

We present NEAR, a new experimental area at the CERN-n_TOF facility and a possible setup for cross section measurements of interest to nuclear astrophysics. This was recently realized with the aim of performing spectral-averaged neutron-capture cross section measurements by means of the activation technique. The recently commissioned NEAR station at n_TOF is now ready for the physics program, which includes a preliminary benchmark of the proposed idea. Based on the results obtained by dedicated Monte Carlo simulations and calculation, a suitable filtering of the neutron beam is expected to enable measurements of Maxwellian Averaged Cross Section (MACS) at different temperatures. To validate the feasibility of these studies we plan to start the measurement campaign by irradiating several isotopes whose MACS at different temperatures have recently been or are planned to be determined with high accuracy at n_TOF, as a function of energy in the two time-of-flight measurement stations. For instance, the physical cases of 88Sr(n,γ), 89Y(n,γ), 94Zr(n,γ) and 64Ni(n,γ) are discussed. As the neutron capture on 89Y produces a pure β-decay emitter, we plan to test the possibility to perform activation measurements on such class of isotopes as well. The expected results of these measurements would open the way to challenging measurements of MACS by the activation technique at n_TOF, for rare and/or exotic isotopes of interest for nuclear astrophysics.

First measurement of the 94Nb(n,γ) cross section at the CERN n_TOF facility

“…The next steps in the data analysis comprise the implementation of a Bayesian-based algorithm for reliably addressing the different background components, the determination of the capture-yield by applying the pulse-height weighting technique [15] and the final R-matrix analysis of the resolved resonances. Additionally it is foreseen to perform a complementary measurement at the n_TOF NEAR station [16] via activation, once the facility is fully characterized and operational, for validating the results from this experimental campaign at several stellar temperatures via activation.…”

Nuclear astrophysics activities at the n_TOF facility at CERN

“…Feasibility studies are ongoing to demonstrate the possibility of producing Maxwellianlike neutron spectra at different stellar temperatures by means of a neutron moderator/filter assembly, see for instance ref. [7].…”

New perspectives for neutron capture measurements in the upgraded CERN-n_TOF Facility

“…A new experimental area, so-called NEAR Station, has been installed during the recent upgrade next to the spallation target. It features an extremely high neutron flux that opens the door to (n,γ) activation measurements on short-lived radioactive isotopes or on very small mass samples [10,11].…”