Institute of Plasma Physics;
Hefei Institutes of Physical Science;
Chinese Academy of Sciences;
Hefei 230031;
People’s Republic of China;
University of Science and Technology of China;
Hefei 230026;
People’s Republic of China;
Key Laboratory of Photovoltaic and Energy Conservation Materials;
Chinese Academy of Sciences;
Hefei 230031;
People’s Republic of China;
tungsten sputtering source; carbon impurity; wall conditioning; PWI; EAST;