Time evolution of energy spectra. Empirical probability distribution functions (and fitted power laws) of recorded energies at various times throughout the experiment, for a) electrons all with 2 eV energy; b) protons with 2 eV initial energies; c) electrons with 200 eV energies and d) protons with 200 eV initial energy. For key to output times for each spectra and accompanying power law, see legend.