Multiple changes to speed up the code

This MR aims to speed up the radiation damage code. It does multiple things:

• Moves the check for radiation flag outside of one loop to allow better compiler optimisation
• Reduces the number of conditions by retrieving the correct maps at the beginning of the loops
• Uses std::abs, std::sqrt and std::pow consistently in the code
• Removes debug messages from the innermost loops
• Pass few objects by const references
• Replaces comparison of strings to comparison of enums

cc @bnachman