Megagray dosimetry (or monitoring of very large radiation doses)

A number of suitably calibrated plastic and dyed films and solid-state systems can provide mapping of very intense radiation fields with high spatial resolution and reasonable limits of uncertainty of absorbed dose assessment. Although most systems of this type suffer from rate dependence and temperature dependence of response when irradiated with charged particle beams at high dose rates, a few are stable, easily calibrated, and capable of faithful imaging of detailed dose profiles, even at doses up to 106 Gy and dose rates up to 108 Gy.s-1. Candidates include certain undyed plastic films (e.g., polyhalostyrenes), some dyed cellulosics, radiochromic dye films (e.g., Nylon-base 'Trogamid' films) and pure LiF crystals. (author)