Infrared and visible thermoluminescence signals of Tm-doped CaF2 measured by a semiconductor photodiode

A silicon semiconductor photodiode was used to measure the TL-signal of TLD-300 (CaF2:Tm) detectors irradiated with 60Co gamma rays and 226Ra alpha particles. The applied dose values varied from 0.12 to 14.3 Gy for gamma rays and from about 50 to 300 Gy for alpha particles. Because of the infrared sensitivity of the photodiode the infrared emission of the planchet and the TLD-detector produced a high output signal above about 200 degrees C. In addition to this background signal an infrared emission from the TLD-300 detectors could be detected. This infrared TL-signal exhibited the same dose dependences as the visible signal, but the amplitude was higher than that of the visible TL-signal. For the applied photodiode the ratio of the infrared TL-signal to the visible TL-signal was about 24 for the 100 degrees C peak, about 15 for the 150 degrees C peak and 6 for the 240 degrees C peak.