We investigated the cathode luminescence characteristics of CsI(Na)and CsI(Tl)crystals by the spectrum and structure properties at room temperature.We fabricated three different sizes of CsI(Na)and CsI(Tl)crystals and...We investigated the cathode luminescence characteristics of CsI(Na)and CsI(Tl)crystals by the spectrum and structure properties at room temperature.We fabricated three different sizes of CsI(Na)and CsI(Tl)crystals and measured their luminescence spectra under cathode rays.We found that CsI(Na)cathode luminescence peaks appear at 420 and 305 nm,and CsI(Tl)cathode luminescence peaks are 540 and 410 nm,the grain size affects CsI(Na)luminescence significantly,and the Na-related420 nm luminescence intensified relatively when the average grain size reaches^20μm,which becomes weak when the grain size is down to nano-scale.But the cathode luminescence spectra of CsI(Tl)crystals with different size have no obvious changes.Our explanations for these phenomena are that the different impurities in the same host material CsI lead to different luminescence mechanisms.These cathode luminescence characteristics indicate the suitability of CsI(Na)and CsI(Tl)crystals to match photomultiplier tube for large area crystal detector development.展开更多
An intrinsic sensor （diameter 16 ram, thickness 300 μm ） based on chemical vapor deposition derived polycrystailine diamond was developed. Ultra low dark current under 100 pA and high n/γ discrimination of 15.8 we...An intrinsic sensor （diameter 16 ram, thickness 300 μm ） based on chemical vapor deposition derived polycrystailine diamond was developed. Ultra low dark current under 100 pA and high n/γ discrimination of 15.8 were obtained on this device, which enable it to be used for neutron detection in multi-radiation field. Moreover, the neutron sensitivity of this detector was characterized theoretically and experimentally. And for fast and ultra-fast neutron, the detection sensitivity is in the magnitude of 10^-17 to 10^-16 C cm^2/n with good stability and negligible pump effect. All these results indicate that the as-prepared sensor to be ideal for fast and ultra-fast neutron monitoring, and it may pave the way to build neutron detector with low cost and large sensitive area with diamond.展开更多
Recently, Sandia Laboratories developed a neutron scatter camera to detect special nuclear materials. This camera exhibits the following advantages: high efficiency, direction discrimination, neutron-gamma discriminat...Recently, Sandia Laboratories developed a neutron scatter camera to detect special nuclear materials. This camera exhibits the following advantages: high efficiency, direction discrimination, neutron-gamma discrimination ability, and wide field of view. However, using the direct projection method, the angular resolution of this camera is limited by uncertainties in the energies estimated from pulse height and time of flight measurements. In this study, we established an eight-element neutron scatter camera and conducted the experiment with a ^(252)Cf neutron source. The results show that it has an angular resolution better than 8°(1s) and a detection efficiency of approximately 2.6′10-4. Using maximum likelihood expectation maximization method, the image artifact was eliminated, and the angular resolution was improved. We proposed an average scattering angle method to estimate the scattering energy of neutrons and Compton gamma rays. As such, we can obtain a recognizable image and energy spectrum of the source with some degradation of energy and image resolutions. Finally, a newly measured light response function based on the MPD^(-4) device was used for image reconstruction. Although we did not obtain a better result than that of the standard light response function, we have observed the effects of light response function on image reconstruction.展开更多
基金supported by the Fundamental Research Funds for the Central Universities(Grant No.11QG14)
文摘We investigated the cathode luminescence characteristics of CsI(Na)and CsI(Tl)crystals by the spectrum and structure properties at room temperature.We fabricated three different sizes of CsI(Na)and CsI(Tl)crystals and measured their luminescence spectra under cathode rays.We found that CsI(Na)cathode luminescence peaks appear at 420 and 305 nm,and CsI(Tl)cathode luminescence peaks are 540 and 410 nm,the grain size affects CsI(Na)luminescence significantly,and the Na-related420 nm luminescence intensified relatively when the average grain size reaches^20μm,which becomes weak when the grain size is down to nano-scale.But the cathode luminescence spectra of CsI(Tl)crystals with different size have no obvious changes.Our explanations for these phenomena are that the different impurities in the same host material CsI lead to different luminescence mechanisms.These cathode luminescence characteristics indicate the suitability of CsI(Na)and CsI(Tl)crystals to match photomultiplier tube for large area crystal detector development.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11175142,11175141 and 11105106)the National Hi-Tech Project of China (Grant No. 2009AA050705)the State Key Laboratory of Multiphase Flow (Xi’an Jiaotong University)
文摘An intrinsic sensor （diameter 16 ram, thickness 300 μm ） based on chemical vapor deposition derived polycrystailine diamond was developed. Ultra low dark current under 100 pA and high n/γ discrimination of 15.8 were obtained on this device, which enable it to be used for neutron detection in multi-radiation field. Moreover, the neutron sensitivity of this detector was characterized theoretically and experimentally. And for fast and ultra-fast neutron, the detection sensitivity is in the magnitude of 10^-17 to 10^-16 C cm^2/n with good stability and negligible pump effect. All these results indicate that the as-prepared sensor to be ideal for fast and ultra-fast neutron monitoring, and it may pave the way to build neutron detector with low cost and large sensitive area with diamond.
基金supported by the National Natural Science Fundation of China(Grant Nos.1110510611375144&11275153)
文摘Recently, Sandia Laboratories developed a neutron scatter camera to detect special nuclear materials. This camera exhibits the following advantages: high efficiency, direction discrimination, neutron-gamma discrimination ability, and wide field of view. However, using the direct projection method, the angular resolution of this camera is limited by uncertainties in the energies estimated from pulse height and time of flight measurements. In this study, we established an eight-element neutron scatter camera and conducted the experiment with a ^(252)Cf neutron source. The results show that it has an angular resolution better than 8°(1s) and a detection efficiency of approximately 2.6′10-4. Using maximum likelihood expectation maximization method, the image artifact was eliminated, and the angular resolution was improved. We proposed an average scattering angle method to estimate the scattering energy of neutrons and Compton gamma rays. As such, we can obtain a recognizable image and energy spectrum of the source with some degradation of energy and image resolutions. Finally, a newly measured light response function based on the MPD^(-4) device was used for image reconstruction. Although we did not obtain a better result than that of the standard light response function, we have observed the effects of light response function on image reconstruction.
