A new compensating element for a femtosecond photoelectron gun

Design and analysis of a new compensating element for improving the electro n pulse front and compressing the pulse duration in a femtosecond photoelec tron gun are described. The compensating element is a small metallic cylind rical cavity in which an external voltage is applied in such a way that a s pecial electric field forms and interacts with the electron pulse. This ele ctric field reduces the distances between the faster and slower electrons i nside the cavity and efficiently compensates for electron pulse broadening caused by the photoelectron energy spread and space charge effects. Poisson 's equation and the equation of motion are solved to obtain the electron tr ajectories. Results highlight the important design parameters of the new co mpensating element and show its feasibility in compressing electron pulses in the femtosecond regime. (C) 2001 American Institute of Physics.