Axial Energy Distribution in Disc-Shaped Tantalum and Aluminium Bremsstrahlung Conversion Targets

The axial distribution of energy deposited in bremsstrahlung conversion targets is modelled using the Monte Carlo N-Particle (MCNP™) code. Systems comprising a disc-shaped target, segmented axially, and a point source of paraxial, monoenergetic electrons (2, 7, 10, or 14 MeV) are considered. Thick tantalum and aluminium targets and also tantalum targets of optimum thickness are modelled. Energy density, as a function of depth within the target, is found to depend on overall target thickness and to exhibit a maximum value at a particular depth. The far-field radiation polar diagram is calculated for X-rays exiting the target through its output face.