The GECAM series of satellites utilizes LaBr_(3)(Ce),LaBr_(3)(Ce,Sr),and NaI(Tl)crystals as sensitive materials for gamma-ray detectors(GRDs).To investigate the nonlinearity in the detection of low-energy gamma rays a...The GECAM series of satellites utilizes LaBr_(3)(Ce),LaBr_(3)(Ce,Sr),and NaI(Tl)crystals as sensitive materials for gamma-ray detectors(GRDs).To investigate the nonlinearity in the detection of low-energy gamma rays and address the errors in the calibration of the E-C relationship,comprehensive tests and comparative studies of the three aforementioned crystals were conducted using Compton electrons,radioactive sources,and mono-energetic X-rays.The nonlinearity test results of the Compton electrons and X-rays demonstrated substantial differences,with all three crystals presenting a higher nonlinearity for X/-rays than for Compton electrons.Despite the LaBr_(3)(Ce)and LaBr_(3)(Ce,Sr)crystals having higher absolute light yields,they exhibited a noticeable nonlinear decrease in the light yield,especially at energies below 400 keV.The NaI(Tl)crystal demonstrated an"excess"light output in the 6-200 keV range,reaching a maximum"excess"of 9.2%at 30 keV in the X-ray testing and up to 15.5%at 14 keV during Compton electron testing,indicating a significant advantage in the detection of low-energy gamma rays.Furthermore,we explored the underlying causes of the observed nonlinearity in these crystals.This study not only elucidates the detector responses of GECAM,but also initiates a comprehensive investigation of the nonlinearity of domestically produced lanthanum bromide and sodium iodide crystals.展开更多
The intense blue emitting phosphors Sr2MgSiO5∶Ce 3+ were synthesized by high temperature solid state reaction method,and their luminescence properties were studied.The intense blue-emission band present a peak fixed ...The intense blue emitting phosphors Sr2MgSiO5∶Ce 3+ were synthesized by high temperature solid state reaction method,and their luminescence properties were studied.The intense blue-emission band present a peak fixed at 420 nm,which consists of two peaks located at 408 and 445 nm,respectively.The two peaks are originated from the transition 5d→ 2F 5/2（4f）and 5d→ 2F 7/2（4f）of Ce 3+ ions.The energy level difference value of the two emission bands is 2 038 cm-1,which is consistent with the theoretic value（2 000 cm-1）between the ground state:2F 5/2 and 2F 7/2 of Ce 3+ ions.The excitation spectra extend from 250 to 400 nm and the peak positions around 365 nm.In addition,the effect of the concentration of Ce 3+ ions and the role of charge compensation of different ions to the emission intense were investigated,the experiment results suggest that when the proportion of Ce 3+ ions to Sr2MgSiO5 were 0.03（molar ratio）,the strongest emission was obtained.Li+,Na+,K+ and Cl-ions can all enhance the intensity of the emissions;especially Cl-ions gave the best improvement.展开更多
Undoped and Eu3+-doped Sr2CeO4 luminescent materials were prepared by sol-gel method. The structure and uncommon photoluminescence of Sr2CeO4∶Eu3+ phosphors were investigated in detail by powder X-ray diffraction (XR...Undoped and Eu3+-doped Sr2CeO4 luminescent materials were prepared by sol-gel method. The structure and uncommon photoluminescence of Sr2CeO4∶Eu3+ phosphors were investigated in detail by powder X-ray diffraction (XRD), Raman spectrum, and photoluminescence spectrum, respectively. The XRD results demonstrate that the as-prepared Sr2CeO4 phosphor is single phase and well crystallized. For Sr2CeO4∶Eu3+ phosphor, its excitation spectrum consists of a broad intense band from host and Eu3+-O2-charge transfer and a number of small peaks from Eu3+ ion. The broad emission band originated from Sr2CeO4 host and Eu3+ emission lines in the blue, green, and red regions coexist. Not only the characteristic transition lines from the lowest excited 5D0 level of Eu3+ but also those from higher energy levels 5DJ (J=1, 2) of Eu3+ ions are observed. These unusual luminescence properties result from the low vibration energy of Sr2CeO4 host-lattice and different energy transfer process from host to activator.展开更多
基金This work was supported by the National Key Research and Development Program(Nos.2022YFB3503600 and 2021YFA0718500)Strategic Priority Research Program of the Chinese Academy of Sciences(Nos.XDA15360102)National Natural Science Foundation of China(Nos.12273042 and 12075258).
文摘The GECAM series of satellites utilizes LaBr_(3)(Ce),LaBr_(3)(Ce,Sr),and NaI(Tl)crystals as sensitive materials for gamma-ray detectors(GRDs).To investigate the nonlinearity in the detection of low-energy gamma rays and address the errors in the calibration of the E-C relationship,comprehensive tests and comparative studies of the three aforementioned crystals were conducted using Compton electrons,radioactive sources,and mono-energetic X-rays.The nonlinearity test results of the Compton electrons and X-rays demonstrated substantial differences,with all three crystals presenting a higher nonlinearity for X/-rays than for Compton electrons.Despite the LaBr_(3)(Ce)and LaBr_(3)(Ce,Sr)crystals having higher absolute light yields,they exhibited a noticeable nonlinear decrease in the light yield,especially at energies below 400 keV.The NaI(Tl)crystal demonstrated an"excess"light output in the 6-200 keV range,reaching a maximum"excess"of 9.2%at 30 keV in the X-ray testing and up to 15.5%at 14 keV during Compton electron testing,indicating a significant advantage in the detection of low-energy gamma rays.Furthermore,we explored the underlying causes of the observed nonlinearity in these crystals.This study not only elucidates the detector responses of GECAM,but also initiates a comprehensive investigation of the nonlinearity of domestically produced lanthanum bromide and sodium iodide crystals.
文摘The intense blue emitting phosphors Sr2MgSiO5∶Ce 3+ were synthesized by high temperature solid state reaction method,and their luminescence properties were studied.The intense blue-emission band present a peak fixed at 420 nm,which consists of two peaks located at 408 and 445 nm,respectively.The two peaks are originated from the transition 5d→ 2F 5/2（4f）and 5d→ 2F 7/2（4f）of Ce 3+ ions.The energy level difference value of the two emission bands is 2 038 cm-1,which is consistent with the theoretic value（2 000 cm-1）between the ground state:2F 5/2 and 2F 7/2 of Ce 3+ ions.The excitation spectra extend from 250 to 400 nm and the peak positions around 365 nm.In addition,the effect of the concentration of Ce 3+ ions and the role of charge compensation of different ions to the emission intense were investigated,the experiment results suggest that when the proportion of Ce 3+ ions to Sr2MgSiO5 were 0.03（molar ratio）,the strongest emission was obtained.Li+,Na+,K+ and Cl-ions can all enhance the intensity of the emissions;especially Cl-ions gave the best improvement.
基金Project supported bythe JSTUFoundation of Science Research (KYY05039)
文摘Undoped and Eu3+-doped Sr2CeO4 luminescent materials were prepared by sol-gel method. The structure and uncommon photoluminescence of Sr2CeO4∶Eu3+ phosphors were investigated in detail by powder X-ray diffraction (XRD), Raman spectrum, and photoluminescence spectrum, respectively. The XRD results demonstrate that the as-prepared Sr2CeO4 phosphor is single phase and well crystallized. For Sr2CeO4∶Eu3+ phosphor, its excitation spectrum consists of a broad intense band from host and Eu3+-O2-charge transfer and a number of small peaks from Eu3+ ion. The broad emission band originated from Sr2CeO4 host and Eu3+ emission lines in the blue, green, and red regions coexist. Not only the characteristic transition lines from the lowest excited 5D0 level of Eu3+ but also those from higher energy levels 5DJ (J=1, 2) of Eu3+ ions are observed. These unusual luminescence properties result from the low vibration energy of Sr2CeO4 host-lattice and different energy transfer process from host to activator.
