1. The problem statement, all variables and given/known data I'm trying to create a simple excel simulation for runaway electrons using a given energy-loss per unit distance equation (Bethe formula). I'm stepping through time (pico-seconds) and giving the the electric field some initial value at a distance of 1mm and from there basically using energy and equations from special relativity to calculate other parameters. I'm having serious issues setting the spreadsheet up correctly I've been trying for a few weeks now and keep having problems with circular references. I've literally got no idea how to fix it so if someone could please help, it would be greatly appreciated. 2. Relevant equations 3. The attempt at a solution The equation given above is only correct for kinetic energies greater than the kinetic energy which causes the peak of the graph below, so i had to find a linear fit to approximate the beginning portion of the graph. I'm starting to doubt if my physics is correct. Spreadsheet is attached! please take a look if possible. Ps:- not sure if this was the correct place to post.