Pre-neutron fragment mass yields in the vicinity of the thermal neutron energy are highly important for applications because of the larger fission cross sections of the^(235)U(n,f)and^(239)Pu(n,f)reactions.In this pap...Pre-neutron fragment mass yields in the vicinity of the thermal neutron energy are highly important for applications because of the larger fission cross sections of the^(235)U(n,f)and^(239)Pu(n,f)reactions.In this paper,preneutron fragment mass yields at incident energies from thermal up to 20 MeV are systematically studied using an empirical fission potential(EFP)model,the potential parameters of which are obtained from the measured data.The energy dependences of the peaks and valleys of the pre-neutron fragment mass yields are described by exponential and linear functions for the^(235)U(n,f)and^(239)Pu(n,f)reactions,respectively.The energy dependences of the evaporation neutrons,which play a crucial role in the reasonable description of pre-neutron fragment mass yields,are also obtained from the fission cross sections.The pre-neutron fragment mass yields in this study are not only consistent with the results of previous studies in regions of several Me Vs but also agree well with existing measured data at incident energies from thermal up to 20 MeV.The results show that the feasibility of this EFP model is verified in this extended energy region.展开更多
The pre-neutron-emission mass distributions for reaction232Th(n, f) up to 60 MeV are systematically studied with an empirical fission potential model. The energy dependences of the peaks and valleys of the pre-neutron...The pre-neutron-emission mass distributions for reaction232Th(n, f) up to 60 MeV are systematically studied with an empirical fission potential model. The energy dependences of the peaks and valleys of the pre-neutronemission mass distributions are described by the exponential expressions based on the newly measured data. The energy dependence of evaporation neutrons before scission, which plays a crucial role for the reasonable description of the mass distribution, is also considered. Both the double-humped and triple-humped shape of the measured pre-neutronemission mass distributions for reaction232Th(n, f) are reasonably well reproduced at incident energies up to 60 MeV.The mass distributions at unmeasured energies and the critical energies at which the humped pre-neutron-emission mass distributions are transformed into each other are also predicted.展开更多
Abstract： The pre-neutron-emission mass distributions for reaction ^238U（n, f） up to 60 MeV are systematically studied with an empirical fission potential model. The energy dependence of the peaks and valleys of th...Abstract： The pre-neutron-emission mass distributions for reaction ^238U（n, f） up to 60 MeV are systematically studied with an empirical fission potential model. The energy dependence of the peaks and valleys of the pre-neutronemission mass distributions is described by an exponential form based on the newly measured data. The energy dependence of evaporation neutrons before scission is also considered, which plays a crucial role in the reasonable description of the mass distributions. The measured ^238U（n, f） are reasonably well reproduced up to 60 predicted using this approach. data of the pre-neutron-emission mass distributions for reaction MeV. The mass distributions at unmeasured energies are also展开更多
ABE-CYCIAE是一种基于标准AB雷姆仪的扩展型中子雷姆仪,该设备将用于HI-13串列加速器升级工程的中子在线监测。设备采用一根BF3管进行中子探测,使用聚乙烯及掺硼聚乙烯作为主要的慢化材料。通过使用MCNP软件对中子能量响应曲线进行模拟...ABE-CYCIAE是一种基于标准AB雷姆仪的扩展型中子雷姆仪,该设备将用于HI-13串列加速器升级工程的中子在线监测。设备采用一根BF3管进行中子探测,使用聚乙烯及掺硼聚乙烯作为主要的慢化材料。通过使用MCNP软件对中子能量响应曲线进行模拟,计算的热中子到100 Me V的中子能量响应能较好的符合ICRP74号报告给出的注量剂量转换曲线。BF3管输出的脉冲信号经过电荷灵敏前置放大器放大,并由50 Hz陷波器除去工频干扰后,送入主放大器和计数器进行成型放大和计数。展开更多
以一种高压电源的前置稳压电路作为研究对象,重点分析稳压控制电路的抗中子抗辐射能力。对导致中子辐照前后输出电压变化量的因素进行分析,并对关键元器件晶体管进行辐照效应分析和试验验证,提出了晶体管优化和采用达林顿晶体管结构2种...以一种高压电源的前置稳压电路作为研究对象,重点分析稳压控制电路的抗中子抗辐射能力。对导致中子辐照前后输出电压变化量的因素进行分析,并对关键元器件晶体管进行辐照效应分析和试验验证,提出了晶体管优化和采用达林顿晶体管结构2种加固措施。通过电路仿真和制作样机,得到在1 Me V等效中子2×10;n/cm;中子注量后的仿真和实测结果与理论分析值相吻合,验证了抗辐射加固措施的有效性。展开更多
A dynamical Langevin model is employed to evaluate the excess of the neutron emission in the fission ofheavy nuclei ^(240)Cf,^(246)Cf,^(254)Cf,^(240)U relative to the standard statistical-model prediction at various s...A dynamical Langevin model is employed to evaluate the excess of the neutron emission in the fission ofheavy nuclei ^(240)Cf,^(246)Cf,^(254)Cf,^(240)U relative to the standard statistical-model prediction at various saddle-to-scissionfriction strengths.It is shown that when the neutron-to-proton ratio N/Z of the system increases,the sensitivityof the excess to the friction decreases substantially,and it almost disappears for ^(240)U.We suggest that using thosecompound systems with low N/Z favors an accurate determination for the saddle-to-scission friction strength based onthe measurement of the pre-scission neutron multiplicity.展开更多
The evaporation residue cross section anisotropy of the fission fragment angular distribution, pre-scission neutron multiplicity and the pre-saddle and post-saddle contributions of the pre-scission neutron multiplicit...The evaporation residue cross section anisotropy of the fission fragment angular distribution, pre-scission neutron multiplicity and the pre-saddle and post-saddle contributions of the pre-scission neutron multiplicity were analyzed within a stochastic approach based on one-, two- and three-dimensional Langevin equations for the compound nucleus ^224Th formed via a complete fusion. In these calculations, dissipation was generated through the chaos weighted wall and window friction formula. Comparison of the theoretical results with the experimental data showed that three-dimensional Langevin equations with dissipation generated through the chaos weighted wall and window friction formula make it possible to reproduce satisfactorily the above-mentioned experimental data.展开更多
Using the stochastic Langevin model coupled with a statistical decay model, we study the influence of pre-equilibrium（PE） emission on probing postsaddle friction（β） with neutrons. A postsaddle friction value of（...Using the stochastic Langevin model coupled with a statistical decay model, we study the influence of pre-equilibrium（PE） emission on probing postsaddle friction（β） with neutrons. A postsaddle friction value of（14-16.5） ×10^21s^-1 and（11-13） ×10^21s^-1 is obtained from comparing calculated and measured prescission neutron multiplicities of heavy fissioning systems ^248 Fm and ^256Fm in the absence and presence of the deformation factor.Moreover, it is found that a larger β is required to fit multiplicity data after the PE effect is accounted for, and that the effect becomes stronger when more energy is removed by PE particles. Our findings suggest that, to more accurately determine the postsaddle friction strength through the measurement of prescission neutrons, in addition to incorporating the contribution of PE evaporation source into the experimental multi-source analysis for particle energy spectra in coincidence with fission fragments, on the theoretical side, it is very important to make a precise evaluation of the energy that PE emission carries away from excited compound systems produced in heavy-ion fusion reactions.展开更多
基金Supported by the National Natural Science Foundation of China(12065003)the Natural Science Foundation of Guangxi(2019GXNSFDA185011)+2 种基金the Key Laboratory of Neutron Physics China Academy of Engineering Physics(2018BA03)the Scientific Research and Technology Development Project of Guilin(20210104-2)the Central Government Guides Local Scientic and Technological Development Funds of China(Guike ZY22096024)。
文摘Pre-neutron fragment mass yields in the vicinity of the thermal neutron energy are highly important for applications because of the larger fission cross sections of the^(235)U(n,f)and^(239)Pu(n,f)reactions.In this paper,preneutron fragment mass yields at incident energies from thermal up to 20 MeV are systematically studied using an empirical fission potential(EFP)model,the potential parameters of which are obtained from the measured data.The energy dependences of the peaks and valleys of the pre-neutron fragment mass yields are described by exponential and linear functions for the^(235)U(n,f)and^(239)Pu(n,f)reactions,respectively.The energy dependences of the evaporation neutrons,which play a crucial role in the reasonable description of pre-neutron fragment mass yields,are also obtained from the fission cross sections.The pre-neutron fragment mass yields in this study are not only consistent with the results of previous studies in regions of several Me Vs but also agree well with existing measured data at incident energies from thermal up to 20 MeV.The results show that the feasibility of this EFP model is verified in this extended energy region.
基金Supported by Guangxi University Science and Technology Research Projects under Grant No.2013ZD007Guangxi Natural Science Foundation under Grant No.2012GXNSFAA053008+1 种基金National Natural Science Foundation of China under Grant No.11265004the Th-based Molten Salt Reactor Power System of the Strategic Pioneer Science and Technology Projects from the Chinese Academy of Sciences
文摘The pre-neutron-emission mass distributions for reaction232Th(n, f) up to 60 MeV are systematically studied with an empirical fission potential model. The energy dependences of the peaks and valleys of the pre-neutronemission mass distributions are described by the exponential expressions based on the newly measured data. The energy dependence of evaporation neutrons before scission, which plays a crucial role for the reasonable description of the mass distribution, is also considered. Both the double-humped and triple-humped shape of the measured pre-neutronemission mass distributions for reaction232Th(n, f) are reasonably well reproduced at incident energies up to 60 MeV.The mass distributions at unmeasured energies and the critical energies at which the humped pre-neutron-emission mass distributions are transformed into each other are also predicted.
基金Supported by Guangxi University Science and Technology Research Projects(2013ZD007)Guangxi Natural Science Foundation(2012GXNSFAA053008)National Natural Science Foundation of China(11265004)
文摘Abstract： The pre-neutron-emission mass distributions for reaction ^238U（n, f） up to 60 MeV are systematically studied with an empirical fission potential model. The energy dependence of the peaks and valleys of the pre-neutronemission mass distributions is described by an exponential form based on the newly measured data. The energy dependence of evaporation neutrons before scission is also considered, which plays a crucial role in the reasonable description of the mass distributions. The measured ^238U（n, f） are reasonably well reproduced up to 60 predicted using this approach. data of the pre-neutron-emission mass distributions for reaction MeV. The mass distributions at unmeasured energies are also
文摘ABE-CYCIAE是一种基于标准AB雷姆仪的扩展型中子雷姆仪,该设备将用于HI-13串列加速器升级工程的中子在线监测。设备采用一根BF3管进行中子探测,使用聚乙烯及掺硼聚乙烯作为主要的慢化材料。通过使用MCNP软件对中子能量响应曲线进行模拟,计算的热中子到100 Me V的中子能量响应能较好的符合ICRP74号报告给出的注量剂量转换曲线。BF3管输出的脉冲信号经过电荷灵敏前置放大器放大,并由50 Hz陷波器除去工频干扰后,送入主放大器和计数器进行成型放大和计数。
文摘以一种高压电源的前置稳压电路作为研究对象,重点分析稳压控制电路的抗中子抗辐射能力。对导致中子辐照前后输出电压变化量的因素进行分析,并对关键元器件晶体管进行辐照效应分析和试验验证,提出了晶体管优化和采用达林顿晶体管结构2种加固措施。通过电路仿真和制作样机,得到在1 Me V等效中子2×10;n/cm;中子注量后的仿真和实测结果与理论分析值相吻合,验证了抗辐射加固措施的有效性。
基金Supported by the Foundation of Nanjing University of Finance and Economics under Grant No.C0836
文摘A dynamical Langevin model is employed to evaluate the excess of the neutron emission in the fission ofheavy nuclei ^(240)Cf,^(246)Cf,^(254)Cf,^(240)U relative to the standard statistical-model prediction at various saddle-to-scissionfriction strengths.It is shown that when the neutron-to-proton ratio N/Z of the system increases,the sensitivityof the excess to the friction decreases substantially,and it almost disappears for ^(240)U.We suggest that using thosecompound systems with low N/Z favors an accurate determination for the saddle-to-scission friction strength based onthe measurement of the pre-scission neutron multiplicity.
基金support of the Research Committee of the Persian Gulf University
文摘The evaporation residue cross section anisotropy of the fission fragment angular distribution, pre-scission neutron multiplicity and the pre-saddle and post-saddle contributions of the pre-scission neutron multiplicity were analyzed within a stochastic approach based on one-, two- and three-dimensional Langevin equations for the compound nucleus ^224Th formed via a complete fusion. In these calculations, dissipation was generated through the chaos weighted wall and window friction formula. Comparison of the theoretical results with the experimental data showed that three-dimensional Langevin equations with dissipation generated through the chaos weighted wall and window friction formula make it possible to reproduce satisfactorily the above-mentioned experimental data.
基金Supported by National Nature Science Foundation of China(11575044)
文摘Using the stochastic Langevin model coupled with a statistical decay model, we study the influence of pre-equilibrium（PE） emission on probing postsaddle friction（β） with neutrons. A postsaddle friction value of（14-16.5） ×10^21s^-1 and（11-13） ×10^21s^-1 is obtained from comparing calculated and measured prescission neutron multiplicities of heavy fissioning systems ^248 Fm and ^256Fm in the absence and presence of the deformation factor.Moreover, it is found that a larger β is required to fit multiplicity data after the PE effect is accounted for, and that the effect becomes stronger when more energy is removed by PE particles. Our findings suggest that, to more accurately determine the postsaddle friction strength through the measurement of prescission neutrons, in addition to incorporating the contribution of PE evaporation source into the experimental multi-source analysis for particle energy spectra in coincidence with fission fragments, on the theoretical side, it is very important to make a precise evaluation of the energy that PE emission carries away from excited compound systems produced in heavy-ion fusion reactions.
