Abstract: China Spallation Neutron Source (CSNS) is a large scientific experimental device of proton accelerator in operation in China. It is of great significance to ensure the normal operation and scientific research output of the equipment and the radiation safety of the staff and the public, and to ensure the air activation level at a monitored and controllable state. The previous understandings of accelerator air activation at home and abroad are almost coming from references and theoretical calculations. Due to lack of specific research and design, no air induced radionuclides and their concentrations have been measured in previous domestic accelerators’ air activation monitoring. Late of 2019, an online air activation monitoring system was developed in CSNS, which successfully detected the major radionuclides and their activity concentrations in air activation. This paper introduces the research and development of the system and the monitoring results, and puts forward some views on the monitoring and evaluation of accelerator air activation.

Key words: accelerator, air activation, radionuclides, gamma spectrum, activation concentration