Calculation of Electron Beam Potential Energy from RF Photocathode Gun

In this paper, we consider the contribution of potential energy to beam dynamics as simulated by PARMELA at low energies (10-30MeV). We calculate the potential energy of the relativistic electron beam using the static coulomb potential in the rest frame (the first order approximation as used in the PARMELA code). We found that the potential energy contribution to the beam dynamics could be very significant, particularly with the high charge beams generated by an RF photocathode gun. Our results show that when the potential energy is counted correctly and added to the kinetic energy from PARMELA, the total energy is conserved. Results of potential and kinetic energy simulations for short beams (∼ 1mm) at various charges (1-100nC) generated by a high current RF photocathode gun are presented.