Problems with solid dosimeters

The report describes problems concerning 'stopping power and LET' and 'reading of absorbed dose' which have been identified in performing research and development of exoelectron dosimeters (TSEDs). These problems are critical to almost all types of solid dosimeters. It is widely known that TSEDs, as well as TLDs, show excessive response to photons in the range of 50-500 KeV. A number of additional difficult problems will occur in the case of alpha and beta rays, which are high in LET, and X-rays and gamma rays, which are low in energy. According to measurements, TSED appears to respond proportionally to the incident beta ray stopping power dE/dx at the surface of a sample, instead of the absorbed dose. This phenomenon is related with the fact that exoelectrons are released only from a very thin surface layer. It has also been revealed that exoelectrons associated with absorbed dose or exoelectron sources at depth of more than 800-1000 A cannot reach the surface, and the absorbed dose at deeper portions cannot be detected as signals. (Nogami, K.)