Ragnar Hellborg is emeritus Full professor of Applied Physics at the Department of Physics, University of Lund in Sweden. He has worked in the field of applied physics using electrostatic accelerators for more than 50 years.Harry J Whitlow is Full professor of Physics and Director of the Louisiana Accelerator Center at the University of Louisiana at Lafayette, USA. He has a long career in applying Mevion accelerator-based methods to a wide range of fundamental and applied problems.