Modelling electron-beam converter interactions in laser-driven X-ray radiography*

Short-pulse laser-plasma interactions provide a possible route to high-performance X-ray radiography. This scheme involves two main stages: the laser-target interaction which generates an electron beam with energies in the MeV range, and conversion of the electron beam to X-rays via bremsstrahlung. Here we focus on modelling of the latter process.

 

Modelling of the x-ray yield is conventionally achieved via Monte-Carlo particle transport simulations, using codes such as MCNP, GEANT4, and PENELOPE. However, it has been known for some time that electric fields generated within the electron-beam converter material may decelerate the electron beam and therefore reduce the x-ray yield, and this is not modelled by such codes.

 

In this presentation we discuss progress towards modelling the impact of the electric field via extending the VPIC particle-in-cell code to model bremsstrahlung and other high-energy processes, and development of semi-analytic models that would provide a computationally inexpensive method for estimating the impact of these fields on the x-ray yield.