Engineering design of JSNS shutter system

Neutron beam shutter system of Japan Spallation Neutron Source (JSNS) in the J-PARC has been designed under a particular precondition that every shutter should be controlled and maintained independently. This is very important from the viewpoints of usability and flexibility of a beam-line. To satisfy this precondition, a compact ball screw jack system sustaining a shutter gate by two shafts with rigid flanges was designed. Every shutter gate contains an insert as a beam-line component. An allowance of misalignment for the insert was evaluated by Monte Carlo simulations, and 1 mrad which corresponds to maximum beam loss at 2% was set as a target value. Alignment for an insert within 1 mrad in a vertical plane was achieved by an ex-situ adjustment at installation work. For the alignment in a horizontal plane, on the other hand, an in-situ adjustment mechanism was developed to meet the target value.