1. School of Resources and Environmental Engineering, Hefei University of Technology, Hefei, Anhui Province, PR China;
2. Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, PR China;
3. Center of Medical Physics and Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, PR China;
4. Anhui Province Key Laboratory of Medical Physics and Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, PR China