Activation studies and radiation safety for the N_tof experiment

The Neutron Time Of Flight (n_TOF) facility, whose installation is about to be completed at CERN, will use a high intensity proton beam (7E12 protons per bunch, 1 or 4 bunches allowed per 14.4 s at 20 GeV/c), which through the spallation process onto a solid lead target (80 x 80 x 60 cm3), produces a high flux of neutrons, charged particles, and photons. Intensive simulation studies with the FLUKA Monte Carlo code were undertaken to calculate the radioactivity induced in the target and in the surrounding structures as well as in the cooling water. Shielding calculations were also performed for the various critical locations along the 200 m long tunnel which houses the proton beam line, the target and the TOF tube. In particular, extensive simulations were required to define the shielding of the target area and the dimensions of the access labyrinths.