Improvements in the Use of Ceramic BeO for TLD

Several types of commercially available ceramic BeO are evaluated for thermoluminescence and combined thermoluminescence-exoelectron dosimetry (TLD-TSEE). The ceramic Thermalox 995 is superior in nearly all respects. Physical and chemical treatments which enhance or reduce sensitivity and stability of TSEE exert often similar influences on the TL. A thin surface region, which is rich in impurities, suppresses spurious emissions of both light and electrons and allows combined TL and TSEE measurements to be made on the same BeO disk. The luminescence is a maximum at 260 nm requiring a reader with a u.v.-sensitive photomultiplier tube. The characteristics important for TLD are as follows: a lower exposure limit of 1 mR with supralinearity starting at 10 R; only 10 % fading after 3 months at 300C and 90 % relative humidity, but rapid bleaching in laboratory fluorescent lighting of 50 % in 30 min; and an energy dependence of response similar to that of LiF TLD.