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71.
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《Journal of Nuclear Science and Technology》2013,50(10):917-931
A phoswich-type neutron detector was developed in order to measure high-energy cosmic ray neutron spectra in aircraft. The neutron detector consists of an EJ309 organic liquid scintillator that is 121.7mm in diameter and 121.7mm in length and is covered with a 15mm thick EJ299-13 outer plastic scintillator. The neutron response functions of the detector are required for the unfolding method to obtain the energy spectrum. The neutron response functions were created based on MCNPX simulations using an anticoincidence mode with the experimental light-output correlations with particle energies, uniformity of light collection and energy resolutions. The light-output correlation with particle energy, the uniformity of light collection and the energy resolutions were evaluated based on experiments. Measurements of neutron response functions were performed using four quasi-monoenergetic neutron beams from 40 to 80 MeV p-Li reactions to verify the calculated results. The calculated response functions show good agreement with the measurements. The angular response of the phoswich detector was confirmed to be isotropic from the calculation. The photon response functions of the detector were also calculated and agreed well with the measurements for 6.129MeV photons. Neutron and photon response matrices were created up to 300 and 50 MeV, respectively, over a wide energy range for experimental flights. 相似文献
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LIU Yanping CHEN Zhaoyang BA Weizhen FAN Yanwei GUO Qi YU Xuefeng CHANG Aiming LU Wu DU Yanzhao 《核技术(英文版)》2008,19(2):113-116
Alkaline earth sulfides (MgS, CaS and BaS) crystal doped with rare-earth ions is an optically stimulated luminescence dosimeter with very high sensitivity, short time constant of the optically stimulated luminescence (OSL)separated perfectly from the stimulation. In this paper, an OSL dosimeter is described. It has linear dose response from 0.01 to 1000 Gy. The equipment, relatively simple and small in size is promising for applications in space exploration and for high dose irradiation and dangerous irradiation conditions. 相似文献
75.
为了解C60(OH)x经呼吸道进入体内后的分布情况,用放射性标记技术和单光子发射计算机断层(Single photon emission computed tomography,SPECT)成像技术,研究了99mTc-C60(OH)x经气管滴注后在SD大鼠体内分布、吸收和代谢的情况,及其与纳米颗粒粒径的依赖关系.用99mTc标记了富勒烯多羟基衍生物C60(OH)x(x=22,24),标记率为93%.标记物在体外和体内都有良好的稳定性.比较了99mTc-C60(OH)x和Na99mTcO4经气管滴注后在SD大鼠体内的SPECT成像.结果表明,与水溶性的小分子Na99mTcO4不同,纳米尺度的99mTc-C60(OH)x标记物大多滞留于肺中,且清除缓慢;少部分99mTc-C60(OH)x能迅速通过肺泡-毛细管屏障进入血液,主要分布于肝、骨和脾中,并通过肾代谢排泄,显示了纳米颗粒生物分布的主要特征.由此可见,纳米颗粒穿越气血屏障的能力与颗粒物的粒径相关.研究结果为纳米颗粒的呼吸毒性研究提供了重要基础资料. 相似文献
76.
Xixiang Zhu Hengxing Xu Yongtao Liu Jia Zhang Miaosheng Wang Ilia N. Ivanov Olga S. Ovchinnikova Bin Hu 《Advanced materials (Deerfield Beach, Fla.)》2019,31(49)
A new approach to generate a two‐photon up‐conversion photoluminescence (PL) by directly exciting the gap states with continuous‐wave (CW) infrared photoexcitation in solution‐processing quasi‐2D perovskite films [(PEA)2(MA)4Pb5Br16 with n = 5] is reported. Specifically, a visible PL peaked at 520 nm is observed with the quadratic power dependence by exciting the gap states with CW 980 nm laser excitation, indicating a two‐photon up‐conversion PL occurring in quasi‐2D perovskite films. Decreasing the gap states by reducing the n value leads to a dramatic decrease in the two‐photon up‐conversion PL signal. This confirms that the gap states are indeed responsible for generating the two‐photon up‐conversion PL in quasi‐2D perovskites. Furthermore, mechanical scratching indicates that the different‐n‐value nanoplates are essentially uniformly formed in the quasi‐2D perovskite films toward generating multi‐photon up‐conversion light emission. More importantly, the two‐photon up‐conversion PL is found to be sensitive to an external magnetic field, indicating that the gap states are essentially formed as spatially extended states ready for multi‐photon excitation. Polarization‐dependent up‐conversion PL studies reveal that the gap states experience the orbit–orbit interaction through Coulomb polarization to form spatially extended states toward developing multi‐photon up‐conversion light emission in quasi‐2D perovskites. 相似文献
77.
The third order nonlinear optical, electric and dielectric properties of an organic stilbazolium derivative of 4-N,N-dimethylamino-N′-methylstilbazolium p-methoxybenzenesulfonate (DSMOS) crystal are reported. The nonlinear refractive index (n2), two photon absorption coefficient (β) and third order optical susceptibility χ(3) have been measured by Z-scan technique using Gaussian beam from the Nd:YAG laser at 1064 nm. The results show a large negative nonlinear refractive index (n2 = −1.122 × 10−9 cm2/W) with a molecular two photon absorption coefficient β value of 3.625 × 10−6 cm/W. The low dielectric constant observed in the high frequency region indicates the suitability of the sample for electro-optic applications. The surface features are also investigated by atomic force microscopy (AFM). 相似文献
78.
论证了在三能级系统中经由受激拉曼绝热过程产生太赫兹,分析了基本模型和泵浦激光与太赫兹产生相干的三能级的理论,并应用在横向激励二氧化碳激光光学泵浦重水分子中,可以产生波长为385μm的太赫兹辐射。产生的太赫兹脉冲功率表现为蒸汽压的函数,并得到了最高太赫兹功率。该技术提供了一种鲁棒性非常好的产生太赫兹的方法。 相似文献
79.
80.
可调谐多波长布里渊掺铒光纤激光器将光纤中的SBS非线性放大同掺铒光纤的线性放大相结合得到室温稳定的多波长输出,具有波长间隔一致、线宽窄、功率谱相对平坦等优点。设计了一种基于光纤布拉格(FBG)反射的线性可调谐多波长布里渊掺铒光纤激光器。该线性腔激光器的一端利用光纤布拉格光栅作为反射镜,有效抑制了腔内自激模的影响,增加激光器输出波长数。布里渊泵浦信号进入布里渊增益介质之前经过掺铒光纤放大器的两次放大,降低了布里渊增益的阈值。该多波长激光器实现了1 530~1 560 nm之间30 nm可调谐范围的输出。在布里渊泵浦信号功率2 mW,980 nm泵源抽运功率60 mW情况下,1 540~1 554 nm范围内,获得了波长间隔0.088 nm的16个波长的输出。 相似文献