Design of control system of neutron beam shutters for 1MW spallation neutron source at Japan Proton Accelerator Research Complex (J-PARC)

The 1-MW spallation neutron source constructed in the Materials and Life Science Experimental Facility under the Japan Proton Accelerator Research Complex (J-PARC) project provides neutrons available for variety of neutron scattering experiments conducted at neutron instruments through neutron beam lines, where neutrons are produced by 3-GeV proton induced spallation reactions in a mercury target followed by moderation through a super-critical hydrogen moderator surrounded by a reflector. Neutron beam shutter systems were installed at the neutron beam line to extract and/or shield neutrons. The shutter control system was designed in order that users were able to open/close shutters at experimental halls during a beam-time and facility's personnel could move shutters for adjustment at vicinity of neutron shutter drive mechanism room in maintenance period. It was also designed to keep the primary condition that personnel was allowed to enter the instrument room when the shutter was closed. This condition was integrated in the Personnel Protection System (PPS) to secure the safety of personnel. Components were designed to enhance reliability of the control system as follows: a shutter close position was detected by two kinds of devices of a mechanical limit switch and a rotary encoder, and the power supply for the shutter system was connected with an uninterruptible power supply (UPS) to prevent loss of signals in case of a power failure. (author)