The Monte Carlo code CASCADE for the calculation of inelastic hadron- and nucleus-nucleus interactions at energies from several
tens of MeV up to several tens of GeV and for modelling of nuclear-physical processes accompanying the transport of particles
and nuclei in matter is improved by considering a more detailed model of decay of highly excited residual (after-intranuclear-cascade)
nuclei. Results of calculations are in good agreement with experiment. However, there are some deviations for light-isotope
production, which prompt the necessity of developing more correct models of evaporation and strong asymmetric high-energy
fission. 相似文献
Investigation of fossil charged-particle tracks in various mineral phases of extraterrestrial samples is a powerful method for research the early stages of the solar system. Examination of fossil charged-particle tracks in the phosphate and olivine crystals of 5 pallasites coupled with U content determination allowed the estimation of the contributions of all possible track sources to the total track density and calculation of a value of model fission-track age.
Phosphate crystals from all studied pallasites were established to contain fossil tracks due to galactic cosmic rays (VH, VVH nuclei); induced fission of U and Th by cosmic rays; spontaneous fission of 238U; spontaneous fission of extinct short-lived 244Pu nuclei presented in significant quantities in the early solar system. The discovery of a high track density attributed to the extinct 244Pu pointed obviously to the high value of the fission-track age. Model fission-track ages of (4.37±0.02) Gyr for the Marjalahti pallasite; (4.37±0.01) Gyr for the Omolon pallasite; (4.19±0.02) Gyr for the Bragin pallasite; (4.18±0.03) Gyr for the Krasnoyarsk pallasite; (4.21±0.02) Gyr for the Brenham pallasite were calculated. The comparison of represented data with petrographic analyses allowed us to interpret a value of fission-track age as the time of the last intensive shock/thermal event in the cosmic history of a pallasite. 相似文献
Investigation of the 246Cm spontaneous ternary decay into nearly equal clusters using polyethyleneterephthalate track detectors has been carried out. The possibility of ternary cluster decay has been found out to be of less than 10−6 with respect to all fission modes of 246Cm. 相似文献
The quartz glass open chromatographic columns with thermal gradient, which usually were used for the investigation of chemical properties of short-lived Z104 nuclides, were first used as the track detectors of spontaneously fissioning isotopes of elements 104, 105 and 106. The recoil nuclei of these elements were captured by the flow of gaseous chlorides then go to the quartz tube with reducing thermal gradient 400°C-100°C. The quartz tube was etched in 40% HF. The tracks due to spontaneous fission of isotopes 259104, 262105 and 263106 which were etched at the internal wall of quartz tubes were counted under optical microscope. 相似文献
As President of the Kaiser Wilhelm Society and its successor, the Max Planck Society, from 1946 until 1960, Otto Hahn (1879–1968)
sought to portray science under the Third Reich as a purely intellectual endeavor untainted by National Socialism. I outline
Hahn’s activities from 1933 into the postwar years, focusing on the contrast between his personal stance during the National
Socialist period, when he distinguished himself as an upright non-Nazi, and his postwar attitude, which was characterized
by suppression and denial of Germany’s recent past. Particular examples include Hahn’s efforts to help Jewish friends; his
testimony for colleagues involved in denazification and on trial in Nuremberg; his postwar relationships with émigré colleagues,
including Lise Meitner; and his misrepresentation of his wartime work in the Kaiser Wilhelm Institute for Chemistry. 相似文献
The emission probabilities per fission of α-particles, tritons and protons have been measured in fast neutron induced fission of 235U. The measurements were carried out at neutron energies of 120, 180, 230 and 550 keV. AΔE-E semiconductor detector telescope was used to identify different light charged particles and the fission fragments were detected with an ionization chamber. The three-parameter data corresponding to the pulse heights from the ΔE-E detectors and the ion-chamber were recorded event by event on magnetic tape and were analyzed off-line by computer. No significant variation in the most probable energy () and the standard deviation (σE) of the energy spectra of different light charged particles with incident neutron energy was observed, although was seen to have a slightly higher value beyond En = 230 keV. The yield of α-particles in fission induced by neutrons of En ~ 200 keV was found to be higher by about 20 % than that in thermal neutron induced fission. The yields of tritons and protons were found to increase significantly with neutron energy. 相似文献