I am simulating a partial-transmission target by sending 100 keV electrons onto a 6 um tungsten target. I then have a collimator, some air, and water in which I collect the dose distribution.
The conversion of electrons to photons in the tungsten is a very inefficient process. I have tried some techniques to improve my statistics. For example, I split the tungsten into layers and used importance biasing in each layer. While this did work, due to only air being between my target and my water detector, I find my biased photons too correlated resulting in dose distribution artefacts. I was wondering if there was a way to use biasing such that I create more photons from the electron interactions in the tungsten. I have been looking through the BIASING options but I am unclear of the correct solution.