Background: Multi-purpose Reflectometer (MR) is one of the three spectrometers under construction at China Spallation Neutron Source (CSNS). The reflection arm is a key component in MR

which is used to carry the neutron detector. The size of the reflection arm is 1750 mm×1000 mm×800mm (L×W×H)

and the weight is 1200kg. The reflection arm should rotate around the sample center with a rotation range of 130°

and the accuracy of the rotation should be higher than 0.001°. Purpose: This study aims to design the structure with the combination of air bearing support and friction wheel drive for the movement request of heavy load

large travel and high precision in the reflection arm. Methods: A high precision rotation stage with air bearing support is developed to verify the feasibility of this structure in which no contact and friction between reflection arm and granite floor when the air bearing works. The air floating stage is supported by three sets of air bearings

which is placed on a granite platform with the size of 1000mm×2000mm

a sample stage base is located on one side of the granite platform

a sheet steel is used to connect the air floating stage and the cross roller bearing which is installed in the sample stage base

a friction wheel is installed in the side of the air floating stage. The rotation range of the air floating stage is 45°

and the load of the air floating stage under test is 800kg. Results: The accuracy test indicates that the rotation stage with air bearing support can offer the repeatability positioning accuracy of 0.00031°

and the positioning accuracy of 0.0009° within the scope of whole rotation range. Conclusion: These results show that the structure with the combination of air bearing support and friction wheel drive can satisfy the movement requirement of the reflection arm in MR. Abstract