A measurement of the ^235U prompt fission neutron spectrum (PFNS) by the recoil proton method was performed at the Institute of Nuclear Physics and Chemistry, China. Details of the method, which include the calculatio...A measurement of the ^235U prompt fission neutron spectrum (PFNS) by the recoil proton method was performed at the Institute of Nuclear Physics and Chemistry, China. Details of the method, which include the calculation and validation of the response matrix, are presented. The PFNS for ^235U in the energy range 1–12 MeV, induced by thermal neutrons, was obtained. The measured spectrum in the low-energy region was in good agreement with previous work and the ENDF/B-VII library, except for minor differences. In the high-energy region, however, the relative height of the measured spectrum was greater, and an analysis of the experiment indicated uncertainties of 13% at 10 MeV and 24% at 12 MeV. Experimental results showed that the recoil proton method could be used to measure prompt fission neutron spectra. Some directions for future work are included.展开更多
An attempt is made to improve the evaluation of the prompt fission neutron emis- sion from 233U（n, f） reaction for incident neutron energies below 6 MeV. The multi-modal fission approach is applied to the improved v...An attempt is made to improve the evaluation of the prompt fission neutron emis- sion from 233U（n, f） reaction for incident neutron energies below 6 MeV. The multi-modal fission approach is applied to the improved version of Los Alamos model and the point by point model. The prompt fission neutron spectra and the prompt fission neutron as a function of fragment mass （usually named ＂sawtooth＂ data） v（A） are calculated independently for the three most dominant fission modes （standard I, standard II and superlong）, and the total spectra and v（A） are syn- thesized. The multi-modal parameters are determined on the basis of experimental data of fission fragment mass distributions. The present calculation results can describe the experimental data very well, and the proposed treatment is thus a useful tool for prompt fission neutron emission prediction.展开更多
The complete-fusion reaction^(204)Pb(^(48)Ca,2n)^(250)No was used to study two activities of^(250)No with distinct half-lives.A total of 1357 events were observed in the SFiNx neutron detection system.The average numb...The complete-fusion reaction^(204)Pb(^(48)Ca,2n)^(250)No was used to study two activities of^(250)No with distinct half-lives.A total of 1357 events were observed in the SFiNx neutron detection system.The average number of neutrons emitted per spontaneous fission of^(250)No was determined to be(4.1±0.1).The unusually symmetrical shape of the prompt neutron multiplicity distribution was restored and presented for the first time.Statistical tests were performed to compare the prompt neutron multiplicity distributions associated with the ground state and K-isomer state decays.展开更多
The prompt fission neutron spectra for the neutron-induced fission of 235U at En 5 MeV are calculated using nuclear evaporation theory with a semi-empirical model, in which the nonconstant and con- stant temperatures ...The prompt fission neutron spectra for the neutron-induced fission of 235U at En 5 MeV are calculated using nuclear evaporation theory with a semi-empirical model, in which the nonconstant and con- stant temperatures related to the Fermi gas model are taken into account. The calculated prompt fission neutron spectra reproduce the experimental data well. For the n（thermal）＋235 U reaction, the average nuclear temperature of the fission fragment, and the probability distribution of the nuclear temperature, are discussed and compared with the Los Alamos model. The energy carried away by γ rays emitted from each fragment is also obtained and the results are in good agreement with the existing experimental data.展开更多
Hypersphere World-Universe Model (WUM) envisions Matter carried from Universe into World from fourth spatial dimension by Dark Matter Particles (DMPs). Luminous Matter is byproduct of Dark Matter (DM) annihilation. WU...Hypersphere World-Universe Model (WUM) envisions Matter carried from Universe into World from fourth spatial dimension by Dark Matter Particles (DMPs). Luminous Matter is byproduct of Dark Matter (DM) annihilation. WUM introduces Dark Epoch (spanning from Beginning of World for 0.4 billion years) when only DMPs existed, and Luminous Epoch (ever since for 13.8 billion years). Big Bang discussed in standard cosmological model is, in our view, transition from Dark Epoch to Luminous Epoch due to Rotational Fission of Overspinning DM Supercluster’s Cores and annihilation of DMPs. WUM solves a number of physical problems in contemporary Cosmology and Astrophysics through DMPs and their interactions: Angular Momentum problem in birth and subsequent evolution of Galaxies and Extrasolar systems—how do they obtain it;Fermi Bubbles—two large structures in gamma-rays and X-rays above and below Galactic center;Mysterious Star KIC 8462852 with irregular dimmings;Coronal Heating problem in solar physics—temperature of Sun’s corona exceeding that of photosphere by millions of degrees;Cores of Sun and Earth rotating faster than their surfaces;Diversity of Gravitationally-Rounded Objects in Solar system and their Internal Heat;Lightning Initiation problem—electric fields observed inside thunderstorms are not sufficient to initiate sparks;Terrestrial Gamma-Ray Flashes—bursts of high energy X-rays and gamma rays emanating from Earth. Model makes predictions pertaining to Masses of DMPs, proposes New Types of their Interactions. WUM reveals Inter-Connectivity of Primary Cosmological Parameters and calculates their values, which are in good agreement with the latest results of their measurements.展开更多
Hypersphere World-Universe Model (WUM) envisions Matter carried from the Universe into the World from the fourth spatial dimension by Dark Matter Particles (DMPs). Luminous Matter is a byproduct of Dark Matter (DM) se...Hypersphere World-Universe Model (WUM) envisions Matter carried from the Universe into the World from the fourth spatial dimension by Dark Matter Particles (DMPs). Luminous Matter is a byproduct of Dark Matter (DM) self-annihilation. WUM introduces Dark Epoch (spanning from the Beginning of the World for 0.45 billion years) and Luminous Epoch (ever since for 13.77 billion years). Big Bang discussed in Standard Cosmology (SC) is, in our view, transition from Dark Epoch to Luminous Epoch due to Rotational Fission of Overspinning DM Supercluster’s Cores and self-annihilation of DMPs. WUM solves a number of physical problems in SC and Astrophysics through DMPs and their interactions: Angular Momentum problem in birth and subsequent evolution of Galaxies and Extrasolar systems;Fermi Bubbles—two large structures in gamma-rays and X-rays above and below Galactic center;Coronal Heating problem in solar physics—temperature of Sun’s corona exceeding that of photosphere by millions of degrees;Cores of Sun and Earth rotating faster than their surfaces;Diversity of Gravitationally-Rounded objects in Solar system and their Internal Heating. Model makes predictions pertaining to Rest Energies of DMPs, proposes New Type of their Interactions. WUM reveals Inter-Connectivity of Primary Cosmological Parameters and calculates their values, which are in good agreement with the latest results of their measurements.展开更多
The prompt fission neutron spectra for the neutron-induced fission of 233U for low energy neutrons （below 6 MeV） are calculated using nuclear evaporation theory with a semi-empirical method, in which the partition o...The prompt fission neutron spectra for the neutron-induced fission of 233U for low energy neutrons （below 6 MeV） are calculated using nuclear evaporation theory with a semi-empirical method, in which the partition of the total excitation energy between the fission fragments for the nth＋233U fission reactions is determined by the available experimental and evaluation data. The calculated prompt fission neutron spectra agree well with the experimental data. The proportions of high-energy neutrons of prompt fission neutron spectrum versus incident neutron energies are investigated with the theoretical spectra, and the results are consistent with the systematics. The semi-empirical method could be a useful tool for the prompt evaluation of fission neutron spectra.展开更多
Properties of prompt fission neutrons from 238U（n, f） are calculated for incident neutron egies below 6 MeV using the multi-modal model, including the prompt fission neutron spectrum, thnere average prompt fission n...Properties of prompt fission neutrons from 238U（n, f） are calculated for incident neutron egies below 6 MeV using the multi-modal model, including the prompt fission neutron spectrum, thnere average prompt fission neutron multiplicity, and the prompt fission neutron multiplicity as a function of the fission fragment mass v（A） （usually named ＂sawtooth＂ data） The three most dominant fission modes are taken into account. The model parameters are determined on the basis of experimental fission fragment data. The predicted results are in good agreement with the experimental data.展开更多
基金supported by the National Natural Science Foundation of China(No.11775196)the Chinese Special Project for ITER(No.2015GB108006)
文摘A measurement of the ^235U prompt fission neutron spectrum (PFNS) by the recoil proton method was performed at the Institute of Nuclear Physics and Chemistry, China. Details of the method, which include the calculation and validation of the response matrix, are presented. The PFNS for ^235U in the energy range 1–12 MeV, induced by thermal neutrons, was obtained. The measured spectrum in the low-energy region was in good agreement with previous work and the ENDF/B-VII library, except for minor differences. In the high-energy region, however, the relative height of the measured spectrum was greater, and an analysis of the experiment indicated uncertainties of 13% at 10 MeV and 24% at 12 MeV. Experimental results showed that the recoil proton method could be used to measure prompt fission neutron spectra. Some directions for future work are included.
基金supported by the State Key Development Program for Basic Research of China (Nos. 2008CB717803, 2009GB107001, and2007CB209903)the Research Fund for the Doctoral Program of Higher Education of China (No. 200610011023)
文摘An attempt is made to improve the evaluation of the prompt fission neutron emis- sion from 233U（n, f） reaction for incident neutron energies below 6 MeV. The multi-modal fission approach is applied to the improved version of Los Alamos model and the point by point model. The prompt fission neutron spectra and the prompt fission neutron as a function of fragment mass （usually named ＂sawtooth＂ data） v（A） are calculated independently for the three most dominant fission modes （standard I, standard II and superlong）, and the total spectra and v（A） are syn- thesized. The multi-modal parameters are determined on the basis of experimental data of fission fragment mass distributions. The present calculation results can describe the experimental data very well, and the proposed treatment is thus a useful tool for prompt fission neutron emission prediction.
文摘The complete-fusion reaction^(204)Pb(^(48)Ca,2n)^(250)No was used to study two activities of^(250)No with distinct half-lives.A total of 1357 events were observed in the SFiNx neutron detection system.The average number of neutrons emitted per spontaneous fission of^(250)No was determined to be(4.1±0.1).The unusually symmetrical shape of the prompt neutron multiplicity distribution was restored and presented for the first time.Statistical tests were performed to compare the prompt neutron multiplicity distributions associated with the ground state and K-isomer state decays.
基金Supported by IAEA-CRP(15905)the State Key Laboratory of Nuclear Physics and Technology,Peking University(SKL-NPT)
文摘The prompt fission neutron spectra for the neutron-induced fission of 235U at En 5 MeV are calculated using nuclear evaporation theory with a semi-empirical model, in which the nonconstant and con- stant temperatures related to the Fermi gas model are taken into account. The calculated prompt fission neutron spectra reproduce the experimental data well. For the n（thermal）＋235 U reaction, the average nuclear temperature of the fission fragment, and the probability distribution of the nuclear temperature, are discussed and compared with the Los Alamos model. The energy carried away by γ rays emitted from each fragment is also obtained and the results are in good agreement with the existing experimental data.
文摘Hypersphere World-Universe Model (WUM) envisions Matter carried from Universe into World from fourth spatial dimension by Dark Matter Particles (DMPs). Luminous Matter is byproduct of Dark Matter (DM) annihilation. WUM introduces Dark Epoch (spanning from Beginning of World for 0.4 billion years) when only DMPs existed, and Luminous Epoch (ever since for 13.8 billion years). Big Bang discussed in standard cosmological model is, in our view, transition from Dark Epoch to Luminous Epoch due to Rotational Fission of Overspinning DM Supercluster’s Cores and annihilation of DMPs. WUM solves a number of physical problems in contemporary Cosmology and Astrophysics through DMPs and their interactions: Angular Momentum problem in birth and subsequent evolution of Galaxies and Extrasolar systems—how do they obtain it;Fermi Bubbles—two large structures in gamma-rays and X-rays above and below Galactic center;Mysterious Star KIC 8462852 with irregular dimmings;Coronal Heating problem in solar physics—temperature of Sun’s corona exceeding that of photosphere by millions of degrees;Cores of Sun and Earth rotating faster than their surfaces;Diversity of Gravitationally-Rounded Objects in Solar system and their Internal Heat;Lightning Initiation problem—electric fields observed inside thunderstorms are not sufficient to initiate sparks;Terrestrial Gamma-Ray Flashes—bursts of high energy X-rays and gamma rays emanating from Earth. Model makes predictions pertaining to Masses of DMPs, proposes New Types of their Interactions. WUM reveals Inter-Connectivity of Primary Cosmological Parameters and calculates their values, which are in good agreement with the latest results of their measurements.
文摘Hypersphere World-Universe Model (WUM) envisions Matter carried from the Universe into the World from the fourth spatial dimension by Dark Matter Particles (DMPs). Luminous Matter is a byproduct of Dark Matter (DM) self-annihilation. WUM introduces Dark Epoch (spanning from the Beginning of the World for 0.45 billion years) and Luminous Epoch (ever since for 13.77 billion years). Big Bang discussed in Standard Cosmology (SC) is, in our view, transition from Dark Epoch to Luminous Epoch due to Rotational Fission of Overspinning DM Supercluster’s Cores and self-annihilation of DMPs. WUM solves a number of physical problems in SC and Astrophysics through DMPs and their interactions: Angular Momentum problem in birth and subsequent evolution of Galaxies and Extrasolar systems;Fermi Bubbles—two large structures in gamma-rays and X-rays above and below Galactic center;Coronal Heating problem in solar physics—temperature of Sun’s corona exceeding that of photosphere by millions of degrees;Cores of Sun and Earth rotating faster than their surfaces;Diversity of Gravitationally-Rounded objects in Solar system and their Internal Heating. Model makes predictions pertaining to Rest Energies of DMPs, proposes New Type of their Interactions. WUM reveals Inter-Connectivity of Primary Cosmological Parameters and calculates their values, which are in good agreement with the latest results of their measurements.
基金Supported by National Natural Science Foundation of China(11205246,91126010,91226102)
文摘The prompt fission neutron spectra for the neutron-induced fission of 233U for low energy neutrons （below 6 MeV） are calculated using nuclear evaporation theory with a semi-empirical method, in which the partition of the total excitation energy between the fission fragments for the nth＋233U fission reactions is determined by the available experimental and evaluation data. The calculated prompt fission neutron spectra agree well with the experimental data. The proportions of high-energy neutrons of prompt fission neutron spectrum versus incident neutron energies are investigated with the theoretical spectra, and the results are consistent with the systematics. The semi-empirical method could be a useful tool for the prompt evaluation of fission neutron spectra.
基金Supported by State Key Development Program for Basic Research of China (2008CB717803,2009GB107001,2007CB209903)Research Fund for the Doctoral Program of Higher Education of China (200610011023)
文摘Properties of prompt fission neutrons from 238U（n, f） are calculated for incident neutron egies below 6 MeV using the multi-modal model, including the prompt fission neutron spectrum, thnere average prompt fission neutron multiplicity, and the prompt fission neutron multiplicity as a function of the fission fragment mass v（A） （usually named ＂sawtooth＂ data） The three most dominant fission modes are taken into account. The model parameters are determined on the basis of experimental fission fragment data. The predicted results are in good agreement with the experimental data.
