Electromagnetic Shock-Induced Current Due to Charge Impact on a Conductor

When a charged particle strikes a conducting surface and is removed upon impact, an electromagnetic shock is generated at the location of impact. This purely electromagnetic effect was shown in our recent extension [1] of the classical Ramo-Shockley theorem (RS) [2] . RS gives the induced surface current assuming nonrelativistic velocities and electrostatic fields. In this paper, we provide a comparison of the electromagnetic shock-induced current with the classical RS for an infinitely long charged rod striking an infinite, perfectly conducting plate in the single and parallel plate geometries. The electromagnetic shock-induced currents are calculated assuming a constant velocity of the charge before impact, and the classical induced current in the parallel-plate geometry assumes that the charge in transit is subject to an RF voltage. We note that the induced current due to the electromagnetic shock is comparatively small for low impact energies (less than 100 eV, such as those found in multipactor discharges [3] ) but becomes significant for relativistic impact velocities. The electromagnetic shock thus could have a considerable effect on beam loading in relativistic magnetrons and in magnetically insulated line oscillators (MILOs) [4] , but is relatively unimportant in multipactor discharges [3]