A charged particle beam transport system and method for linear accelerators includes a lens stack having two electrodes serially arranged along an acceleration axis between a charged particle source, and a linear accelerator. After producing and extracting a bunch of charged particles (i.e. particle beam) from the particle source, a voltage difference between the two electrodes is ramped in time to longitudinally compress the particle beam to be shorter than the pulsewidth of acceleration pulses produced in the accelerator. Additional electrodes may be provided in the lens stack for performing transverse focusing of the charged particle bunch and controlling a final beam spot size independent of the current and energy of the particle beam. In a traveling wave accelerator embodiment having a plurality of independently switchable pulse-forming lines, beam transport can also be controlled by triggering multiple adjacent lines simultaneously so that the physical size of the accelerating electric field is longer than the charged particle bunch, as well as by controlling trigger timing of the pulse-forming lines to perform alternating phase focusing.
FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 The United States Government has rights in this invention pursuant to Contract No. DE-AC52-07NA27344 between the United States Department of Energy and Lawrence Livermore National Security, LLC for the operation of Lawrence Livermore National Laboratory.