Production of Radionuclides in the Cooling Water for Electromagnetic Horns at the J-PARC Neutrino Experimental Facility

The cooling water for the electromagnetic horns is exposed to intense high-energy protons, neutrons and charged pions at the J-PARC neutrino experimental facility. These high-energy particles produce various radionuclides in the cooling water; dominant radionuclides were H and Be, and various -emitting nuclides were also detected by a Ge detector. Specific activities of individual nuclides in the circulating cooling-water were determined and compared with the results obtained by Monte Carlo calculations. The results demonstrated that H and Be were directly produced in water by nuclear spallation of oxygen in water molecules, and that other nuclides were produced in metal components and transferred into water, in accordance with the observations at other high-energy accelerator facilities.