Distribution of Electrons vs. Velocity angle

These plots show the correlation between the energy of electrons, and longitudinal momentum, vs. the velocity angle. There are two selection criteria for dumping particles, the electron must be inside the simulation box, and they must have a gamma > 1. Additionally I have limited the plot axis so only the nearest 45^o from the target rear surface normal. The normalisation on the color bar scale may not be accurate at this point, I've not normalized over the d theta component, but that doesn't affect the distribution.

The velocity angle is calculated as

theta=tan^-1(p_perp/p_x)

where

p_perp=sqrt(p_y² +p_z²)

The simulation was a 2D simulation and the normalization for the 3rd dimension is 1m, so please bear this in mind. This is the default normalization for Epoch and I've not changed it.