Which VISA do I apply?

I am a student, with US citizenship, and currently studying in University of Gothenburg in Sweden. I will go to China as part of a project. The project is a collaboration between my current project supervisor/professor in Sweden and a professor in Chinese Academy of Science in Beijing. However, I am NOT admitted to the Chinese Academy of Science in Beijing. The duration is expect to around a month.

Which type do I need to apply? Thank you.