Development on mercury pump for JSNS

A permanent magnet rotating type induction pump (PM pump) was developed to provide mercury to a liquid mercury target system in Japan Spallation Neutron Source (JSNS). Mechanical pumps, such as a gear pump and a centrifugal pump, have risk of leakage of mercury from the seal parts. Induction pumps can avoid mercury leakage because they have no seal parts. The PM pump could be compact compared with a conventional induction pump; however, power loss must be reduced to avoid overheating of the system. Then optimizations for the thickness of mercury duct wall and width of the duct were carried out to reduce heat loss due to the eddy current in the duct generated by the induction, and to reduce flow-induced loss. As for the flow-induced loss, backflow would occur at the outside of the duct because of the difference in the Lorentz force between inside and outside of the duct. Consequently, the developed PM pump could have sufficient performance for the target system in JSNS and operate with low vibration.