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KMgF 3 fluoroperovskite doped with thulium at different concentrations were synthesized by the solid-state reaction method. The phase composition and the thermal stability up to 600 °C of the polycrystals were analyzed by X-ray diffraction and thermogravimetric analysis, respectively. The KMgF 3 at 1.0 mol% of Tm polycrystals showed the best thermal stability and did not present another phase. The gamma radiation (0.1–10 kGy) effect in thulium-doped KMgF 3 produced the F color centers, and their aggregates such as F 2 , and F 3 centers. The F centers, and the potassium vacancies (V K −) in the fluoroperosvkites were analyzed by the optical absorption and emission measurements. Optical absorption at 275 nm and 443 nm were assigned to F and F 2 , respectively, in undoped KMgF 3. Tm-doped fluoroperovskite shows the optical absorption bands at 277, 393, 432, and 577 nm, which were ascribed to the F, F 3 , F 2 and V K − centers, respectively. When the F band for undoped polycrystals was excited at 275 nm, a clear emission associated with F 2 and F 3 centers was observed. In the case of Tm-doped, an enhancement of the blue emission at 457 nm occurred and a UV band (354 nm) was observed upon exciting the F band. The blue emission of thulium was overlapped with the F 3 color center band. The emission bands at 457 and 354 nm were ascribed to 1D 2 - 3F 4 and 1D 2 - 3H 6 transitions of Tm in KMgF 3. The optical absorption and glow curves were investigated too. The glow curves were assisted by the color centers, vacancies, and thulium impurity. Thermal bleaching shows that the F center was the main participant to give rise to the TL intensity of the glow curves. Thulium acts as a deep electron trap in the bandgap of the KMgF 3 fluoroperovskites forming TL peak at the higher temperature, from 430 to 408 °C. The absorption, emission, and thermoluminescence glow peaks of the undoped and Tm-doped KMgF 3 were compared. • Thulium-doped KMgF 3 polycrystals were synthesized by solid-state reaction method. • Optical absorption at 275 and 443 nm were assigned to F and F 2 , respectively, in KMgF 3. • KMgF 3 :Tm shows OA at 277, 393, 432, and 577 nm, ascribed to F, F 3 , F 2 and V K − centers. • Emission at 457 and 354 nm were assigned to 1D 2 - 3F 4 and 1D 2 - 3H 6 transitions of Tm in KMgF 3. • Thermal bleaching shows F center has the main influence on the TL glow curves. [ABSTRACT FROM AUTHOR]

It is commonly believed that gamma photon irradiation to water does not produce light in water if the gamma photon energy is lower than the Cerenkov-light threshold and imaging of gamma photon is impossible because the produced electrons from gamma photons do not emit light. However, we found that the light is produced in water and the imaging of produced light in water was possible with gamma photon irradiation even at lower energy than the Cerenkov-light threshold. We irradiated gamma photons with lower energy than the Cerenkov-light threshold (260 keV for electrons in water) from 99mTc (gamma photon energy of 140.5 keV) to water phantom, optical imaging was carried out with a charge-coupled device (CCD) camera. Also we conducted imaging of the gamma photons irradiation to acrylic and plastic scintillator blocks. The optical images of water were observed from 3600 s exposure time, and the intensity of the luminescence was linearly increased with time although the intensity was ~0.001% of that with the plastic scintillator block. The optical imaging of water during irradiation of gamma photons lower energy than the Cerenkov-light threshold was possible and it could be a new method for distribution measurements of gamma photons in water. • The optical imaging of water was possible during irradiation of gamma photons lower energy than the Cerenkov-light threshold. • The intensity of the luminescence was ~0.001% of that with the plastic scintillator block. [ABSTRACT FROM AUTHOR]