1. Department of Electrical and Electronic Engineering, and the Schlesinger Family Center for Compact Accelerators, Radiation Sources and Applications (FEL), Ariel University, 40700 Ariel, Israel
2. Physics Department, Technion—Israel, Institute of Technology, Haifa 3200003, Israel
3. Institute of Applied Physics, Russian Academy of Sciences, 603950 Nizhny Novgorod, Russia