Superlinear dose dependence of high temperature thermoluminescence peaks in Al₂O₃:C

We report on strong superlinearity of high temperature (300-700°C) thermoluminescence (TL) peaks in α-Al₂O₃:C powder. The main dosimetric peak at ∼200°C, previously found to exhibit slight superlinearity, is now shown to yield a slope of ∼1.15 on a log(intensity) vs. log(dose) curve. Higher temperature peaks at ∼320, 450 and 650°C, previously reported following UV and X-ray excitation, have now been observed after beta irradiation and showed stronger superlinearity. Using a blue filter, the weak peak at ∼320°C started about quadratically and the slope on the log-log scale decreased gradually from 2 to about unity at ∼100 Gy. The two higher temperature peaks at ∼450 and ∼650°C also exhibited a strong superlinear dose dependence in this dose range, with an average slope of ∼2. Roughly similar behaviour has been found when a UV filter was used. The possible explanation of the strong superlinearity is discussed.