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

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