Hi John,
I tried what you suggested and I see many more arrows and they appear clustered around the tip.
I´m not sure what the different colours mean, but it looks good. However, now I find that the electrons are not curving in this field. In addition, I try to launch the electrons from a particular position, but I do not see the track from this position and only after there is some interaction in the sample. I think maybe as the material properties were defined in the GDML file previously, then some bug has crept in as I now define the material properties within the program. I have also tried increasing the size of the simulation (up to mm), but this does not seem to change these problems. I will continue to check what might be wrong.
Best Wishes
Chris
