Driving system design and precision test of the VSANS detector trolleys

Abstract

BackgroundThe Very Small Angle Neutron Scattering (VSANS) instrument of China Spallation Neutron Source (CSNS) is a world-class SANS instrument with several detectors. It is necessary that the three 3He detectors move accurately and smoothly forward and backward in the vacuum scattering tank.PurposeThis study aims to create high-precision detector trolleys with a positioning accuracy of ≤200 μm in the traveling range of 5 m.MethodsThree detector trolleys supported by double guide rails with rack-pinion mechanism were designed, fabricated and aligned. They were motorized by three servo motors meshing with the rack-pinion system fixed on one side of the guide rail at the bottom of the detector tank. The rotation of the motors to maintain the smoothness of the action was realized by planetary gear reducer. The parallelism of the left and right sides of the guide rails was controlled within 50 μm during the 12 m stroke, and the reverse clearance of the rack and pinion was controlled within 100 μm to provide high motion accuracy of the detector trolleys.ResultsThe results of five round-trip repeat positioning tests of the detector trolleys demonstrate that the bidirectional repeated positioning accuracy of the detector trolleys is within 140 μm, and their positioning accuracy is within 167 μm.ConclusionsThree detector trolleys supported by double guide rails and powered by a rack-pinion mechanism are constructed for the CSNS-VSANS instrument. The positioning accuracy is better than 200 μm which meets the precision requirements of SANS experiments.

Keywords

• very small angle neutron scattering instrument
• rack-pinion mechanism
• accuracy test