1. Departamento de Física, Universidade Federal de Pernambuco, Recife 50670-901, Brazil
2. College of Physical Science and Technology, Bohai University, Jinzhou 121013, People’s Republic of China
3. Varian Medical Systems, a Siemens Healthineers Company, Helsinki 00100, Finland
4. Dipartimento di Fisica, Sapienza Università di Roma, Roma 00185, Italy