The growth of LaBrs：Ce^3＋ crystal by the vertical Bridgman process in a nonvacuum atmosphere was reported. According to the dehydration procedure of LaBr3·7H2O and CeBr3·7H2O investigated by differential t...The growth of LaBrs：Ce^3＋ crystal by the vertical Bridgman process in a nonvacuum atmosphere was reported. According to the dehydration procedure of LaBr3·7H2O and CeBr3·7H2O investigated by differential thermal analysis/thermogravimetry （DTA/TG）, anhydrous LaBr3 and CeBr3 were prepared by heating LaBr3·7H2O and CeBr3·7H2O at 240-260℃ for 5-6 h in dried HBr atmosphere. Using the feed materials prepared from the anhydrous lanthanon bromides, a 0.5 mole fraction Ce^3＋ doped LaBr3 crystal with size ofФ25 mm×50 mm had been grown by vertical Bridgman process successfully. By sealing the feed material in a platinum crucible, the crystal could be grown in a nonvacuum atmosphere as the oxidization and volatilization of the melt could be avoided. The crystal was grown with the optimum conditions such as a growth rate of 0.5-1.0 mm/h and a temperature gradient of around 30℃/cm across solid-liquid interface under a furnace temperature of 850-880℃. The crystal was characterized by DTA/TG, X-ray diffraction （XRD）, optical transmission, photoluminescence and X-ray stimulated luminescence measurement. The Bridgman process was confirmed to be promising for growing transparent LaBr3：Ce^3＋ crystal with high optical quality.展开更多
In recent years,LaBr_(3)(Ce)crystals and silicon photomultipliers(SiPMs)have been increasingly used in radiation imaging.This study involved the establishment of a detector model with a monolithic LaBr_(3)(Ce)crystal ...In recent years,LaBr_(3)(Ce)crystals and silicon photomultipliers(SiPMs)have been increasingly used in radiation imaging.This study involved the establishment of a detector model with a monolithic LaBr_(3)(Ce)crystal and SiPM array forγ-radiation imaging on the GEANT4 platform.The optical process included in the detector model was defined by key parameters,such as the emission spectrum,scintillation yield,and intrinsic resolution of the LaBr_(3):5%Ce crystal,as well as the detection efficiency of the SiPM array.The response of the detector model to^(57)Co flooded field irradiation was simulated and evaluated.The radiation images generated by the detector model exhibited a compression effect that was very close to that on images acquired by the physical detector.The spatial resolution of the simulated detector closely approximates that of the physical experiment.A detector model without the optical process was also established for comparison with a detector using the optical process.Both were used in a near-field modified uniform redundant array(MURA)imaging system to acquire images of a point source and a ring source of^(57)Co at the center of the field-of-view of the imaging system.The spatial resolution and signal-to-noise ratio of the images that were reconstructed using the two detector models were determined and compared.Compared with the detector model without optical processes,although the images from the proposed detector model have slightly inferior signal-to-noise ratios and more artifacts,they are more consistent with the reconstructed versions of images acquired in real physical experiments.The results confirm that the detector model can be used to design aγ-radiation imaging detector and to develop an imaging algorithm that can significantly shorten the development time and reduce the cost.展开更多
基金supported by the Scientific & Techni-cal Project of Zhejiang Province, China (No 2005C31029)the Doctor Science Foundation of Ningbo City, China(No 2005A610021)
文摘The growth of LaBrs：Ce^3＋ crystal by the vertical Bridgman process in a nonvacuum atmosphere was reported. According to the dehydration procedure of LaBr3·7H2O and CeBr3·7H2O investigated by differential thermal analysis/thermogravimetry （DTA/TG）, anhydrous LaBr3 and CeBr3 were prepared by heating LaBr3·7H2O and CeBr3·7H2O at 240-260℃ for 5-6 h in dried HBr atmosphere. Using the feed materials prepared from the anhydrous lanthanon bromides, a 0.5 mole fraction Ce^3＋ doped LaBr3 crystal with size ofФ25 mm×50 mm had been grown by vertical Bridgman process successfully. By sealing the feed material in a platinum crucible, the crystal could be grown in a nonvacuum atmosphere as the oxidization and volatilization of the melt could be avoided. The crystal was grown with the optimum conditions such as a growth rate of 0.5-1.0 mm/h and a temperature gradient of around 30℃/cm across solid-liquid interface under a furnace temperature of 850-880℃. The crystal was characterized by DTA/TG, X-ray diffraction （XRD）, optical transmission, photoluminescence and X-ray stimulated luminescence measurement. The Bridgman process was confirmed to be promising for growing transparent LaBr3：Ce^3＋ crystal with high optical quality.
基金supported by the National Natural Science Foundation of China (Nos. 41874121 and U19A2086)the major scientific instruments and equipment development project of the Ministry of Science and Technology,People’s Republic of China (No.2012YQ180118)+1 种基金the Sichuan Science and Technology Program (No.2018JY0181)Sichuan Science and Technology Miao-zi Project(Nos. 2021JDRC0107 and 2021JDRCO068)
文摘In recent years,LaBr_(3)(Ce)crystals and silicon photomultipliers(SiPMs)have been increasingly used in radiation imaging.This study involved the establishment of a detector model with a monolithic LaBr_(3)(Ce)crystal and SiPM array forγ-radiation imaging on the GEANT4 platform.The optical process included in the detector model was defined by key parameters,such as the emission spectrum,scintillation yield,and intrinsic resolution of the LaBr_(3):5%Ce crystal,as well as the detection efficiency of the SiPM array.The response of the detector model to^(57)Co flooded field irradiation was simulated and evaluated.The radiation images generated by the detector model exhibited a compression effect that was very close to that on images acquired by the physical detector.The spatial resolution of the simulated detector closely approximates that of the physical experiment.A detector model without the optical process was also established for comparison with a detector using the optical process.Both were used in a near-field modified uniform redundant array(MURA)imaging system to acquire images of a point source and a ring source of^(57)Co at the center of the field-of-view of the imaging system.The spatial resolution and signal-to-noise ratio of the images that were reconstructed using the two detector models were determined and compared.Compared with the detector model without optical processes,although the images from the proposed detector model have slightly inferior signal-to-noise ratios and more artifacts,they are more consistent with the reconstructed versions of images acquired in real physical experiments.The results confirm that the detector model can be used to design aγ-radiation imaging detector and to develop an imaging algorithm that can significantly shorten the development time and reduce the cost.
