The effects of atomic number Z on the energy distribution of hot electrons generated by the interaction of 60fs, 130mJ, 800nm, and 7×10^17W/cm^2 laser pulses with metallic targets have been studied experimentally...The effects of atomic number Z on the energy distribution of hot electrons generated by the interaction of 60fs, 130mJ, 800nm, and 7×10^17W/cm^2 laser pulses with metallic targets have been studied experimentally. The results show that the number and the effective temperature of hot electrons increase with the atomic number Z of metallic targets, and the temperature of hot electrons are in the range of 190-230keV, which is consistent with a scaling law of hot electrons temperature.展开更多
Amino acids are the building blocks of proteins,which are the most abundant macromolecules in living cells.From the standpoint of the photon interaction cross sections of amino acids,the mass attenuation coefficients,...Amino acids are the building blocks of proteins,which are the most abundant macromolecules in living cells.From the standpoint of the photon interaction cross sections of amino acids,the mass attenuation coefficients,half and tenth value layers,mean free path,effective atomic and electronic cross sections,effective atomic number,and effective electron density of fifteen essential amino acids have been determined for 133Ba,137Cs,and 60Co gamma-ray sources.The MCNP-4C code and the XCOM program have been used to calculate these parameters.The results have been compared to the available experimental and theoretical data.The theoretical results agreed with the experimental data,with RD values of ≤±7%.In the energy region of 81-1332.5 keV,it was found that the μm,σa,and revalues of the amino acids decreased as the photon energy increased,and the increasing density of amino acids had no steady effect on these quantities.Additionally,results demonstrated that the HVL,TVL,and MFP values increased with the increase in photon energy.The μm,σa,and Zeff values of aspartic acid were the highest among those of all amino acids,and they were the lowest for isoleucine.The Zeff value of each sample containing H,C,N,and O atoms was nearly constant in the studied energy region.The Neffvalues of the studied amino acids varied in the range of 3.14×10^23-3.44×10^23 electron/g.Furthermore,the Neffvalues were approximately independent of the amino acid type in this energy region.展开更多
In this work, the Styrene-butadiene rubber (SBR)/lead oxide and the Styrene-butadiene rubber (SBR)/lead nitrate composites were prepared as gamma-radiation shielding materials. The investigated materials were prepared...In this work, the Styrene-butadiene rubber (SBR)/lead oxide and the Styrene-butadiene rubber (SBR)/lead nitrate composites were prepared as gamma-radiation shielding materials. The investigated materials were prepared with three different weight percentage of lead oxide and lead nitrate (30, 50 and 70 wt%). The mass attenuation coefficients (μ<sub>m</sub>) for all composite samples were measured experimentally at 511 and 661.6 keV photon energies. The measurements were made by performing transmission experiments with a 3'' × 3'' NaI (Tl) scintillation detector, which had an energy resolution of 7% at 0.662 MeV for the gamma-rays from the decay of <sup>137</sup>Cs. The effective atomic numbers (Z<sub>eff</sub>) and the effective electron densities (N<sub>eff</sub>) were determined experimentally. Also they were determined theoretically using the obtained μ<sub>m</sub> values for the studied composites samples by WinXCom program. The obtained results show that the experimental values of the composites are found to be in a good agreement with the theoretical values. It is recognized that the mass attenuation coefficient (μ<sub>m</sub>), effective atomic numbers (Z<sub>eff</sub>) and the effective electron densities (N<sub>eff</sub>) are increased in the composite samples which contain lead oxides than which contain lead nitrates. Finally, the Styrene-butadiene rubber (SBR)/lead oxide is better than Styrene-butadiene rubber (SBR)/lead nitrate polymer as gamma radiation shielding.展开更多
利用1064nm Nd:YAG激光器研究了激光诱导铁条等离子体的特征参数。为了减小测量误差和谱线自发辐射跃迁几率不确定性带来的计算误差,采用改进的迭代Boltzmann方法精确求解铁等离子体的电子温度为8058K。Lorentz函数拟合Fe I 376.553nm...利用1064nm Nd:YAG激光器研究了激光诱导铁条等离子体的特征参数。为了减小测量误差和谱线自发辐射跃迁几率不确定性带来的计算误差,采用改进的迭代Boltzmann方法精确求解铁等离子体的电子温度为8058K。Lorentz函数拟合Fe I 376.553nm得到等离子体的电子数密度为8.7×1017 cm-3。分析表明等离子体的加热机制主要是逆轫致过程,其吸收系数是0.14cm-1。实验数据证实激光诱导铁等离子体处于局部热力学平衡状态和光学薄状态。展开更多
准确测量气态靶区的有效靶原子密度能够提升离子与气体和离子与等离子体靶相互作用实验结果的精度和对物理过程的认识.实验中利用离子加速器引出的100 ke V质子束穿过一定长度的氢气靶,对质子的剩余能量进行了精确测量,获得了在气体靶...准确测量气态靶区的有效靶原子密度能够提升离子与气体和离子与等离子体靶相互作用实验结果的精度和对物理过程的认识.实验中利用离子加速器引出的100 ke V质子束穿过一定长度的氢气靶,对质子的剩余能量进行了精确测量,获得了在气体靶内的质子能损数据,结合已有的能损研究结果,重新标定了气体靶区内的有效靶原子密度.分别比较了能损、电离型真空计IonIVac ITR 90和薄膜电容型真空计Varian CDG-500的实验测量结果,对比了修正后的电离型真空计有效气压曲线,结果发现质子束能损的测量方式具有原位、高准确性、在线监测等突出优势,为诊断气态靶有效原子密度提供了新的方法.展开更多
In this work, linear and mass attenuation coefficients, half and tenth-value layers, effective atomic number and electron density of different types of concretes were determined at 316.51, 468.07, 511, 662, 1173 and 1...In this work, linear and mass attenuation coefficients, half and tenth-value layers, effective atomic number and electron density of different types of concretes were determined at 316.51, 468.07, 511, 662, 1173 and 1332 keV using MCNP-4C code and Win XCom programs. The MCNP-4C and Win XCom results agreed well with each other, with differences of \±1.9%. The results agreed with available experimental data, too, with differences of \±6%.The MCNP-4C results showed better agreement with the experimental data than the Win XCom results. Also, it was found that the effective electron density of studied concretes varies in the range of(2.83–3.2) 9 10^(23)electron/g.展开更多
目的通过模体实验探究第三代双源CT不同能量组合对物质电子密度/有效原子序数(Electron Density/Effective Atomic Number,Rho/Z)检测的准确性与重复性误差,为临床应用提供准确指导。方法使用西门子SOMATOM Force CT不同双能量组合对Cat...目的通过模体实验探究第三代双源CT不同能量组合对物质电子密度/有效原子序数(Electron Density/Effective Atomic Number,Rho/Z)检测的准确性与重复性误差,为临床应用提供准确指导。方法使用西门子SOMATOM Force CT不同双能量组合对Catphan 600标准模体的CTP404模块进行扫描。并通过syngo.via工作站测量不同能量组合的Rho/Z和CT值。并记录每次扫描的容积CT剂量指数和剂量长度乘积。各组数均进行组内一致性检验,单独样本t检验。并对所有参数进行优劣解距离法(Technique for Order Preference by Similarity to an ideal Solution,TOPSIS)综合分析。结果五种双能量组合下,Rho/Z和CT值组内测量一致性较高。经单独样本t检验,电子密度测量值与实际值有明显差异(P<0.05)的占90%,无明显差异(P>0.05)的情况占10%;有效原子序数测量值与实际值有明显差别(P<0.05)的情况占48.6%,无明显差异(P>0.05)的情况占51.4%。TOPSIS分析得出80/Sn150 kV组为最优组合。结论80/Sn150 kV组既可以保证测量的准确度,又可以最大限度地缩减辐射剂量,值得应用推广。展开更多
基金Project supported by the National Natural Science Foundation of China （Grant No 10275056） and the Science and Technology 0ffice of Sichuan, China （Grant 04JY029-097）.
文摘The effects of atomic number Z on the energy distribution of hot electrons generated by the interaction of 60fs, 130mJ, 800nm, and 7×10^17W/cm^2 laser pulses with metallic targets have been studied experimentally. The results show that the number and the effective temperature of hot electrons increase with the atomic number Z of metallic targets, and the temperature of hot electrons are in the range of 190-230keV, which is consistent with a scaling law of hot electrons temperature.
文摘Amino acids are the building blocks of proteins,which are the most abundant macromolecules in living cells.From the standpoint of the photon interaction cross sections of amino acids,the mass attenuation coefficients,half and tenth value layers,mean free path,effective atomic and electronic cross sections,effective atomic number,and effective electron density of fifteen essential amino acids have been determined for 133Ba,137Cs,and 60Co gamma-ray sources.The MCNP-4C code and the XCOM program have been used to calculate these parameters.The results have been compared to the available experimental and theoretical data.The theoretical results agreed with the experimental data,with RD values of ≤±7%.In the energy region of 81-1332.5 keV,it was found that the μm,σa,and revalues of the amino acids decreased as the photon energy increased,and the increasing density of amino acids had no steady effect on these quantities.Additionally,results demonstrated that the HVL,TVL,and MFP values increased with the increase in photon energy.The μm,σa,and Zeff values of aspartic acid were the highest among those of all amino acids,and they were the lowest for isoleucine.The Zeff value of each sample containing H,C,N,and O atoms was nearly constant in the studied energy region.The Neffvalues of the studied amino acids varied in the range of 3.14×10^23-3.44×10^23 electron/g.Furthermore,the Neffvalues were approximately independent of the amino acid type in this energy region.
文摘In this work, the Styrene-butadiene rubber (SBR)/lead oxide and the Styrene-butadiene rubber (SBR)/lead nitrate composites were prepared as gamma-radiation shielding materials. The investigated materials were prepared with three different weight percentage of lead oxide and lead nitrate (30, 50 and 70 wt%). The mass attenuation coefficients (μ<sub>m</sub>) for all composite samples were measured experimentally at 511 and 661.6 keV photon energies. The measurements were made by performing transmission experiments with a 3'' × 3'' NaI (Tl) scintillation detector, which had an energy resolution of 7% at 0.662 MeV for the gamma-rays from the decay of <sup>137</sup>Cs. The effective atomic numbers (Z<sub>eff</sub>) and the effective electron densities (N<sub>eff</sub>) were determined experimentally. Also they were determined theoretically using the obtained μ<sub>m</sub> values for the studied composites samples by WinXCom program. The obtained results show that the experimental values of the composites are found to be in a good agreement with the theoretical values. It is recognized that the mass attenuation coefficient (μ<sub>m</sub>), effective atomic numbers (Z<sub>eff</sub>) and the effective electron densities (N<sub>eff</sub>) are increased in the composite samples which contain lead oxides than which contain lead nitrates. Finally, the Styrene-butadiene rubber (SBR)/lead oxide is better than Styrene-butadiene rubber (SBR)/lead nitrate polymer as gamma radiation shielding.
基金Supported by Scientific Research Program Funded by Shaanxi Provincial Education Department(2013JK0620,2013JK0640)Xi’an Science and Technology Planning Project(CX12189WL02,CX12189WL01)Natural Science Foundation Fund of Shaanxi Province(2012jq5006)
文摘基于1064nm Nd:YAG激光器,对比研究了紫铜和黄铜等离子的特征参数。洛仑兹函数拟合Cu I 324.75nm得到紫铜和黄铜等离子体的电子密度分别是3.6×1017 cm-3和3.3×1017 cm-3。为了减小谱线自发辐射跃迁几率不确定性和测量误差带来的计算误差,采用改进型迭代玻耳兹曼算法精确求解紫铜等离子体和黄铜等离子体的电子温度分别是6316K和6051K,分析表明,两种等离子体特征参数的差异主要是由于黄铜中的锌元素的电离能(9.39eV)大于铜元素的电离能(7.72eV)而造成的。实验数据证实激光诱导的紫铜和黄铜等离子体满足局部热力学平衡模型和光学薄模型。
基金Supported by the Young Scientists Fund of the National Natural Science Foundation of China(61108061)the Xi'an University of Posts and Telecommunications Foundation for Young Teachers+1 种基金Xi'an Science and Technology Planning Project(CX12189WL02)Scientific Research Program Funded by Shaanxi Provincial Education Department(2013JK0607,2013JK0620)
文摘利用1064nm Nd:YAG激光器研究了激光诱导铁条等离子体的特征参数。为了减小测量误差和谱线自发辐射跃迁几率不确定性带来的计算误差,采用改进的迭代Boltzmann方法精确求解铁等离子体的电子温度为8058K。Lorentz函数拟合Fe I 376.553nm得到等离子体的电子数密度为8.7×1017 cm-3。分析表明等离子体的加热机制主要是逆轫致过程,其吸收系数是0.14cm-1。实验数据证实激光诱导铁等离子体处于局部热力学平衡状态和光学薄状态。
文摘In this work, linear and mass attenuation coefficients, half and tenth-value layers, effective atomic number and electron density of different types of concretes were determined at 316.51, 468.07, 511, 662, 1173 and 1332 keV using MCNP-4C code and Win XCom programs. The MCNP-4C and Win XCom results agreed well with each other, with differences of \±1.9%. The results agreed with available experimental data, too, with differences of \±6%.The MCNP-4C results showed better agreement with the experimental data than the Win XCom results. Also, it was found that the effective electron density of studied concretes varies in the range of(2.83–3.2) 9 10^(23)electron/g.
文摘目的通过模体实验探究第三代双源CT不同能量组合对物质电子密度/有效原子序数(Electron Density/Effective Atomic Number,Rho/Z)检测的准确性与重复性误差,为临床应用提供准确指导。方法使用西门子SOMATOM Force CT不同双能量组合对Catphan 600标准模体的CTP404模块进行扫描。并通过syngo.via工作站测量不同能量组合的Rho/Z和CT值。并记录每次扫描的容积CT剂量指数和剂量长度乘积。各组数均进行组内一致性检验,单独样本t检验。并对所有参数进行优劣解距离法(Technique for Order Preference by Similarity to an ideal Solution,TOPSIS)综合分析。结果五种双能量组合下,Rho/Z和CT值组内测量一致性较高。经单独样本t检验,电子密度测量值与实际值有明显差异(P<0.05)的占90%,无明显差异(P>0.05)的情况占10%;有效原子序数测量值与实际值有明显差别(P<0.05)的情况占48.6%,无明显差异(P>0.05)的情况占51.4%。TOPSIS分析得出80/Sn150 kV组为最优组合。结论80/Sn150 kV组既可以保证测量的准确度,又可以最大限度地缩减辐射剂量,值得应用推广。
