1 Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Napoli, Naples, Italy.
2 Radiation Biophysics Laboratory, Department of Physics "E. Pancini," Università di Napoli Federico II, Naples, Italy.
3 Department of Radiation Oncology, David Geffen School of Medicine, University of California at Los Angeles (UCLA), Los Angeles, CA, United States.
4 Radiation Safety Unit, Biology and Environmental Chemistry Division, Sustainable System Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI), Komae, Tokyo, Japan.