Radiation induced defects in graphite.

The Raman intensity ratio I/I for: (a) graphite-rich pencil rods irradiated using x-ray doses up to 20 Gy; (b) a restricted view of the I/I response for the same group of media, limited to x-ray doses of no more than 6 Gy; (c1 and c2) an extended group of graphite-rich media irradiated using Co gamma-rays; (d) a restricted view of the I/I response for a restricted group of the media shown in (c), with Co gamma-ray doses limited to no more than 20 Gy; (e) 2B graphite-rich pencil rods irradiated using 6 MeV electrons, and: (f) irradiation of a subset of the media by thermal (0.025 eV) neutrons. The fluctuation of I/I with dose for carbon-rich human hair of nominal diameter 60 μm is indicated by the dashed line in (c) and (d).