Activation detector measurements at the hadron absorber of the NuMI neutrino beamline at Fermilab

Two-dimensional distributions of the production rates of radionuclides in aluminum and gold activation detectors, placed behind the hadron absorber of the NuMI beamline at Fermilab were obtained in an experiment for shielding data as a dump in a proton-beam-energy domain above 100 GeV. The production rates of ⁷Be, ²²Na, and ²⁴Na in the aluminum activation detectors and those of ¹⁸⁵Os, ¹⁹⁴Au, and ¹⁹⁶Au in the gold activation detectors were obtained from the γ-ray spectra of HPGe counters. It was concluded that in these distributions showed some peaks that can be attributed to a lack of shielding caused by the gaps for arraignment and cooling in the hadron absorber. The radionuclides in the activation detectors were mainly produced by neutrons, protons and pions, according to analyses of calculated results by the PHITS code. (author)