Design of imaging system for CSNS near-target beam diagnostics

Introduction China Spallation Neutron Source (CSNS) is an accelerator-based pulsed neutron source which produces neutron with spallation reaction induced by proton bombarding tungsten target. With increasing beam powers and influences on target, near-target monitoring becomes extreme necessary. In this situation, an optical imaging system for proton beam diagnostics and monitoring near the target is being developed at CSNS, which can provide real-time images of the beam on target and beam distribution information. Target imaging system design and development In the design of CSNS target imaging system, coating of Cr^3+:Al_2O_3 is used to convert particle radiation into emission light. According to the geometry limits of CSNS target station, a special optical system was designed and fabricated to collect the emission light. When the proton beams strike on the target, the coating on the target will be excited, emitting luminescence at the same time. The mirrors and lenses of the optical system image the distribution of emission light into a radiation-hard imaging fiber, which transmits the images to the GigE camera located at low-dose area outside of the target station. Software was written on the LabView platform to control the camera and analyze the images on line. Mock-up of the imaging system was manufactured to test and evaluate the performances of the system. Some important characteristics of the system were obtained and studied. Conclusion Tests on the mock-up of the system present reliably expectation for beam diagnostics. The imaging system has been installed at CSNS recently. More work will be continued to improve the properties of the system.