Operating Experience with Meson Production Targets at Triumf

High power targets are required for operation at beam powers in excess of 1 MW for spallation neutron sources and neutrino factories. TRIUMF has been operating beryllium and graphite meson production targets for many years. Although the proton beam power of 100 kW at 500 MeV is lower, the beam densities and fluences are higher than most operating solid targets. Other high power accelerators have used rotating targets or larger beam spots. The beam size on the TRIUMF targets is maintained at ∼ 0.15 cm²and this beam density leads to proton fluences of 10²³protons/cm²per year. The beryllium targets are rectangular rods immersed in a water-cooled stainless steel jacket. The graphite targets consist of pie-shaped segments bonded to a water-cooled copper saddle. Operating experience shows that the graphite targets suffer thermal damage above beam currents of 120 μA but operate for long periods at 100 μA. The beryllium targets can operate to 200 μA and appear to survive radiation damage beyond 10 dpa. This paper will describe the operating experience with these targets and present some thermal and radiation calculations.