Cavitation in high-power pulsed spallation neutron sources

Futakawa, Masatoshi  ; Tanaka, Nobuatsu*

High-power pulsed spallation neutron sources are being developed in the world. A mercury target is installed at MLF (Materials and Life science experimental Facility) in J-PARC (Japan Proton Accelerator Research Complex), which will promote innovative science. At the moment the proton beams bombard the mercury target, pressure waves will be generated in mercury by thermally shocked heat deposition. Cavitation will be induced through the pressure wave propagation in mercury and eroded the vessel inner surface contacting with mercury, i.e. pitting damage. The eroded vessel wall is damaged by cyclic fatigue because pulsed proton beams strike the target repeatedly. In the paper, the effects of pitting damage, cyclic fatigue damage and mercury environment on the lifetime of the mercury target, and mitigation techniques for pressure waves and cavitation damage are described.