Background: The Multi-purpose Reflectometer (MR) is one of the three spectrometers in the first-phase construction of the China Spallation Neutron Source (CSNS). The neutron beam line switch plays an important role in MR of the neutron beam. Purpose: This study aims to design high precision and high reliability switching control of the neutron beam line in MR that guarantees the security of operators and devices. Methods: A programmable logic controller (PLC) is employed as kernel processor

a step motor as driving component

and a high precision circular grating for position-feedback. Redundancy of the protective design and error handling is taken to ensure that the system is working steadily and safely. Results: Simulation test showed that the system can deal with error condition safely and maintain a stable running. A repeat positioning accuracy of 16.2″ is achieved during the no load test. Conclusion: The results of tests show that the design of our neutron beam line switch control system can satisfy the experiment requirements in MR. Abstract