A neutron radiography system having a high energy neutron generator (100) of the type comprising an ion accelerator (106) and a tritium target (110) located downstream of the accelerator. The generator is disclosed in a housing (22) containing a moderator medium (140) adapted to absorb part of the energy of the neutrons, thereby creating thermal neutrons. A neutron flux booster (130) comprised of a high neutron cross section material, such as depleted uranium, is disposed between the target and the moderator medium such that collisions of high energy neutrons produced at the target will collide with the uranium to release additional high energy neutrons from the booster into the moderator medium. A collimator (40) is disposed in communication with the moderator material for discharging thermal neutrons from the moderator medium.