Adapting electron cooler example to PICMI

[cchall]

I was asked by @bruhwiler to share one of our Warp input scripts for simulating space charge neutralization in a magnetized electron cooler. We would like to see if we can adapt this script to use the PICMI standard, which might include expanding some areas the standard covers.

The script can be found here: https://github.com/radiasoft/rswarp/blob/master/examples/picmi_test_input/magnetized_cooler.py

It include a custom ionization routine and injection function, also defined in the same rswarp repo. The script attempts to pip install the two non-standard dependencies of rswarp and rsoopic (which includes cross section definitions).

This example also includes installation of several internal conductors to represent electrodes. Looking through the Standard I did not see anything yet about specifying internal boundary conditions, like Conductors in Warp.