The angular distribution of characteristic X-rays using a partial-transmission tungsten target was analyzed. Twenty four tallies were modeled to cover a 360 envelope around the target. The Monte Carlo N-Particle (MCNP5) simulation results revealed that the characteristic X-ray flux is not always isotropic around the target. Rather, the flux mainly depends on the target thickness and the energy of the incident electron beam. A multi-energy photon generator is proposed to emit high-energy characteristic X-rays, where the target acts as a filter for the low-energy characteristic X-rays. (C) 2013 Elsevier Ltd. All rights reserved.