Cavitation erosion induced by proton beam bombarding mercury target for high-power spallation neutron sources

• The effects of gas-bubble injection into the mercury were investigated to mitigate the pressure wave.
• The bubbles will be workable to suppress the cavitation inception in the macroscopic time-scale.
• In the microscopic time-scale, the bubbles certainly mitigate the cavitation intensity.

A liquid mercury target system for a megawatt-class spallation neutron source is being developed in the world. Proton beam is injected to the mercury target to induce spallation reaction. The moment the proton beams bombard the target, pressure waves are generated in the mercury by the thermally shocked heat deposition. The pressure waves excite the mercury target vessel and negative pressure that may cause cavitation along the vessel wall. Gas-bubbles will be injected into the flowing mercury to mitigate the pressure waves and suppress the cavitation inception. The injected gas-bubbles conditions were examined and the effects were predicted experimentally and theoretically from the viewpoints of macroscopic time-scale and microscopic time-scale, i.e. in the former is dominant the interaction between the structural vibration and the pressure in mercury, and in the later is essential the pressure wave propagation process.