New Design of High Power Mercury Target Vessel of J-PARC

Abstract

A mercury target vessel for the spallation neutron source at the J-PARC, which the mercury vessel was covered with the water shroud, was improved to realize the operation at the high beam power in two steps. In the first step to realize the stable operation at 500 kW, the basic structure of the initial design was followed and the connection method between the mercury vessel and the water shroud was changed to prevent the failure from the connection. The service operation at the beam power of 500 kW was realized in the about eight months. In the second step to realize the stable operation at 1 MW, the new structure which only rear ends of vessels were connected was investigated. The new structure which has the cooling of the mercury vessel to reduce thermal stress and the thick internal and external vessels of the water shroud to increase the stiffness for the internal pressure was adopted. The stresses in each vessel were lower than the allowable stress based on the elastic design criteria and it was confirmed that the operation with a beam power of 1 MW could be conducted.