A model for theoretical analysis of nonlinear (or high gain) mode of photoconductive semiconductor switches (PCSS's) is proposed.The switching transition of high gain PCSS's can be described with an optically...A model for theoretical analysis of nonlinear (or high gain) mode of photoconductive semiconductor switches (PCSS's) is proposed.The switching transition of high gain PCSS's can be described with an optically activated charge domain. The switching characteristics including rise time,delay and their relationship to electric field strength,optical trigger energies are discussed.The formation and radiation transit,accumulation of the charge domain are related with the triggering and sustaining phases of PCSS's,respectively.The results of the mathematical model on this mechanism agree with experimental results.展开更多
Radiation affects the environment and local human activity in any location of the earth＇s surface. Due to this fact, the aim of this study was to monitor the ionizing radiation and rain intensity using portable devic...Radiation affects the environment and local human activity in any location of the earth＇s surface. Due to this fact, the aim of this study was to monitor the ionizing radiation and rain intensity using portable devices. During May 23 to October 2, 2015, it was made measures the intensity of gamma radiation from 30 keV to 10.0 MeV at a height of 25 meters in Sao Jos6 dos Campos city, SP, Brazil. It was used a crystal of sodium iodide scintillator 3 - 3 inches coupled to a photomultiplier and associated electronic. The measurements were made continually with minute＇s interval throughout the period and it was monitored rain intensity every minute at the same height of the tower. In this job, it was possible to correlate rain-radiation and it was observed which gamma radiation has a directly proportional relationship with rain and visible frequency of 1 day.展开更多
The temperature dependence of BGO coupled with photomultiplier tube R5610A-01 was studied in the range of-30–30℃. The temperature coefficient of the BGO and R5610 A as a whole was tested to be-1.82%/℃. And the temp...The temperature dependence of BGO coupled with photomultiplier tube R5610A-01 was studied in the range of-30–30℃. The temperature coefficient of the BGO and R5610 A as a whole was tested to be-1.82%/℃. And the temperature coefficient of the gain of the R5610 A is-0.44%/℃ which was tested in the same situation using a blue LED. Thus the temperature coefficient of BGO's light yield can be evaluated as-1.38%/℃.展开更多
Knowledge of the temporal-spatial distribution of water content in atmosphere and water phase change in cloud is important for atmospheric study. For this purpose, we have developed a high resolution full-spectrum wat...Knowledge of the temporal-spatial distribution of water content in atmosphere and water phase change in cloud is important for atmospheric study. For this purpose, we have developed a high resolution full-spectrum water Raman lidar that can collect Raman signals from ice, water droplets and water vapor simultaneously. A double-grating polychromator and a 32-channel photomultiplier-tube detector are used to obtain a spectral resolution of-0.19 nm in the full Raman spectrum range of water, Preliminary observations present the water Raman spectrum characteristics of both the mixed-phase cloud and humid air under cloudless condition.展开更多
Signal-induced noise(SIN) in a photomultiplier tube(PMT) introduces bias into the Na density results that are retrieved from the backscattered signals of Na resonance fluorescence lidar systems. The response character...Signal-induced noise(SIN) in a photomultiplier tube(PMT) introduces bias into the Na density results that are retrieved from the backscattered signals of Na resonance fluorescence lidar systems. The response characteristics of a PMT when stimulated by a series of light pulses with a fixed width of 1 μs are therefore used to develop a precise SIN model to estimate the relative error caused by SIN. Unless the strong signals that are returned from the lower atmosphere are excluded, the measured density results are always smaller than the actual values, and the resulting relative error may be 50% or more. Three potential solutions to reduce the SIN were quantified for comparison, including use of a chopper system, use of a gated circuit, and separation of the laser beam and the telescope receiver. When optimized parameters are used for these technologies, the relative error can then be reduced to less than 2%.展开更多
BaFe10A12O19/poly（m-toluidine） （BFA/PMT） composites were synthesized by in-situ polymerization of m-toluidine in the presence of BaFe10Al2O19 particles. The structure, composition and morphology of the obtained sa...BaFe10A12O19/poly（m-toluidine） （BFA/PMT） composites were synthesized by in-situ polymerization of m-toluidine in the presence of BaFe10Al2O19 particles. The structure, composition and morphology of the obtained samples were characterized by using XRD, FT-IR, UV-visible spectroscopy, SEM and TEM techniques. Their electrical conductivity, magnetic property and microwave absorbing property were measured by the four-probe meter, the vibrating sample magnetometer and the vector network analyzer, respectively. The results indicated that BFA particles were coated effectively by PMT polymer and some interactions between PMT and BFA particles existing in the composites. The conductivity of BFA/PMT composite is smaller than that of pure polymers and its saturation magnetization is a little smaller than that of pure BFA. The influence of the constitution and film thickness of absorbent on its microwave absorbing property is evident. The microwave absorbing properties of the BFA/PMT composites are better than those of pure BFA and PMT. When optimizing the mass rate of BFA/PMT to 0.3, the absorbent with 2 mm film thickness has the minimum reflection loss of -28.26 dB at approximate 14.24 GHz, and the maximum available bandwidth of 8.8 GHz, respectively. The results show that these composites can be used as advancing absorption and shielding materials due to their favorable microwave absorbing property.展开更多
The activity of tritiated water has been standardized by two liquid scintillation counting methods:The CIEMAT/NIST method with the54Mn-standard efficiency tracing and the triple-to-double coincidence ratio(TDCR)method...The activity of tritiated water has been standardized by two liquid scintillation counting methods:The CIEMAT/NIST method with the54Mn-standard efficiency tracing and the triple-to-double coincidence ratio(TDCR)method.The samples were prepared with Ultima Gold TM AB liquid scintillation cocktail in low-potassium glass vials.In the application of the CIEMAT/NIST method,the computer program EMILIA was used to calculate the efficiency of3H and54Mn according to the KL1L2L3M atomic rearrangement model.And the detection efficiency of the TDCR counter was calculated using TDCR07 code,which makes it possible to allow for the potential asymmetry between the three photomultiplier tubes.The influence of stopping power and k B factor is discussed in the paper.When a power approach is adopted for the stopping power for electrons below 1ke V and k B is chosen to be 0.0075 cm/Me V,the relative deviation will be only 0.3%between the two methods.展开更多
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
For a quantitative understanding of light interaction with fruit tissue, it is critical to obtain two fundamental parameters： the absorption coefficient and the scattering coefficient of the tissue. This study was to...For a quantitative understanding of light interaction with fruit tissue, it is critical to obtain two fundamental parameters： the absorption coefficient and the scattering coefficient of the tissue. This study was to investigate the optical properties of kiwifruit tissue at the wavelength of 632.8 nm. The total reflectance and total transmittance of kiwifruit tissue from three parts （including the flesh part, the seed part, and the seed-base part） were measured using a single integrating sphere system. Based on the measured spectral signals, the absorption coefficient pa and the reduced scattering coefficient Ps＇ of kiwifruit tissue were calculated using the inverse adding-doubling （lAD） method. Phantoms made from Intralipid 20% and India ink as well as a Biomimic solid phantom were used for system validation The mean values of μa and μs＇ of different parts of the kiwifruit were 0.031-0.308 mm-1 and 0.120-0.946 mm-1, respectively. The results showed significant differences among the Pa and Ps＇ of the three parts of the kiwifruit. The results of this study confirmed the importance of studying the optical properties for a quantitative understanding of light interaction with fruit tissue. Further investigation of fruit optical properties will be extended to a broader spectral region and different kinds of fruits.展开更多
文摘A model for theoretical analysis of nonlinear (or high gain) mode of photoconductive semiconductor switches (PCSS's) is proposed.The switching transition of high gain PCSS's can be described with an optically activated charge domain. The switching characteristics including rise time,delay and their relationship to electric field strength,optical trigger energies are discussed.The formation and radiation transit,accumulation of the charge domain are related with the triggering and sustaining phases of PCSS's,respectively.The results of the mathematical model on this mechanism agree with experimental results.
文摘Radiation affects the environment and local human activity in any location of the earth＇s surface. Due to this fact, the aim of this study was to monitor the ionizing radiation and rain intensity using portable devices. During May 23 to October 2, 2015, it was made measures the intensity of gamma radiation from 30 keV to 10.0 MeV at a height of 25 meters in Sao Jos6 dos Campos city, SP, Brazil. It was used a crystal of sodium iodide scintillator 3 - 3 inches coupled to a photomultiplier and associated electronic. The measurements were made continually with minute＇s interval throughout the period and it was monitored rain intensity every minute at the same height of the tower. In this job, it was possible to correlate rain-radiation and it was observed which gamma radiation has a directly proportional relationship with rain and visible frequency of 1 day.
基金supported by the National Basic Research Program of China(Grant No.2010CB833002)the Strategic Priority Research Program on Space Science of the Chinese Academy of Sciences(Grant No.XDA04040202-4)
文摘The temperature dependence of BGO coupled with photomultiplier tube R5610A-01 was studied in the range of-30–30℃. The temperature coefficient of the BGO and R5610 A as a whole was tested to be-1.82%/℃. And the temperature coefficient of the gain of the R5610 A is-0.44%/℃ which was tested in the same situation using a blue LED. Thus the temperature coefficient of BGO's light yield can be evaluated as-1.38%/℃.
基金supported by the National Natural Science Foundation of China (Grant No. 40731055)
文摘Knowledge of the temporal-spatial distribution of water content in atmosphere and water phase change in cloud is important for atmospheric study. For this purpose, we have developed a high resolution full-spectrum water Raman lidar that can collect Raman signals from ice, water droplets and water vapor simultaneously. A double-grating polychromator and a 32-channel photomultiplier-tube detector are used to obtain a spectral resolution of-0.19 nm in the full Raman spectrum range of water, Preliminary observations present the water Raman spectrum characteristics of both the mixed-phase cloud and humid air under cloudless condition.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41404120, 41521063 & 41327801)
文摘Signal-induced noise(SIN) in a photomultiplier tube(PMT) introduces bias into the Na density results that are retrieved from the backscattered signals of Na resonance fluorescence lidar systems. The response characteristics of a PMT when stimulated by a series of light pulses with a fixed width of 1 μs are therefore used to develop a precise SIN model to estimate the relative error caused by SIN. Unless the strong signals that are returned from the lower atmosphere are excluded, the measured density results are always smaller than the actual values, and the resulting relative error may be 50% or more. Three potential solutions to reduce the SIN were quantified for comparison, including use of a chopper system, use of a gated circuit, and separation of the laser beam and the telescope receiver. When optimized parameters are used for these technologies, the relative error can then be reduced to less than 2%.
基金supported by the National Nature Science Foundation of China (21071125)the Natural Science Foundation of Zhejiang Province(Y4100022,Y4090636)the Science and Technology Key Project of Zhejiang Province (2010C11053)
文摘BaFe10A12O19/poly（m-toluidine） （BFA/PMT） composites were synthesized by in-situ polymerization of m-toluidine in the presence of BaFe10Al2O19 particles. The structure, composition and morphology of the obtained samples were characterized by using XRD, FT-IR, UV-visible spectroscopy, SEM and TEM techniques. Their electrical conductivity, magnetic property and microwave absorbing property were measured by the four-probe meter, the vibrating sample magnetometer and the vector network analyzer, respectively. The results indicated that BFA particles were coated effectively by PMT polymer and some interactions between PMT and BFA particles existing in the composites. The conductivity of BFA/PMT composite is smaller than that of pure polymers and its saturation magnetization is a little smaller than that of pure BFA. The influence of the constitution and film thickness of absorbent on its microwave absorbing property is evident. The microwave absorbing properties of the BFA/PMT composites are better than those of pure BFA and PMT. When optimizing the mass rate of BFA/PMT to 0.3, the absorbent with 2 mm film thickness has the minimum reflection loss of -28.26 dB at approximate 14.24 GHz, and the maximum available bandwidth of 8.8 GHz, respectively. The results show that these composites can be used as advancing absorption and shielding materials due to their favorable microwave absorbing property.
基金supported by the National Natural Science Foundation of China(Grant Nos.91126002 and 11405071)the National Science and Technology Major Project of China(Grant No.2012ZX06004-005)
文摘The activity of tritiated water has been standardized by two liquid scintillation counting methods:The CIEMAT/NIST method with the54Mn-standard efficiency tracing and the triple-to-double coincidence ratio(TDCR)method.The samples were prepared with Ultima Gold TM AB liquid scintillation cocktail in low-potassium glass vials.In the application of the CIEMAT/NIST method,the computer program EMILIA was used to calculate the efficiency of3H and54Mn according to the KL1L2L3M atomic rearrangement model.And the detection efficiency of the TDCR counter was calculated using TDCR07 code,which makes it possible to allow for the potential asymmetry between the three photomultiplier tubes.The influence of stopping power and k B factor is discussed in the paper.When a power approach is adopted for the stopping power for electrons below 1ke V and k B is chosen to be 0.0075 cm/Me V,the relative deviation will be only 0.3%between the two methods.
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Project supported by the National Natural Science Foundation of China(No.31401289)the Zhejiang Provincial Natural Science Foundation of China(No.LQ12C10001)the Education Department of Zhejiang Province(No.Y201122219),China
文摘For a quantitative understanding of light interaction with fruit tissue, it is critical to obtain two fundamental parameters： the absorption coefficient and the scattering coefficient of the tissue. This study was to investigate the optical properties of kiwifruit tissue at the wavelength of 632.8 nm. The total reflectance and total transmittance of kiwifruit tissue from three parts （including the flesh part, the seed part, and the seed-base part） were measured using a single integrating sphere system. Based on the measured spectral signals, the absorption coefficient pa and the reduced scattering coefficient Ps＇ of kiwifruit tissue were calculated using the inverse adding-doubling （lAD） method. Phantoms made from Intralipid 20% and India ink as well as a Biomimic solid phantom were used for system validation The mean values of μa and μs＇ of different parts of the kiwifruit were 0.031-0.308 mm-1 and 0.120-0.946 mm-1, respectively. The results showed significant differences among the Pa and Ps＇ of the three parts of the kiwifruit. The results of this study confirmed the importance of studying the optical properties for a quantitative understanding of light interaction with fruit tissue. Further investigation of fruit optical properties will be extended to a broader spectral region and different kinds of fruits.
