Values Of Total Kinetic Energy Research Articles

A Design Scenario Approach for Choosing Protection Works against Rockfall Phenomena

Proximity remote sensing techniques, both land- and drone-based, allow for a significant improvement of the quality and quantity of raw data employed in the analysis of rockfall phenomena. In particular, the large amount of data these techniques can provide allows for the use of probabilistic approaches to rock mass characterization, with particular reference to block volume and shape definition. These, in return, are key parameters required for a proper rockfall hazard assessment and the optimization of countermeasures design. This study aims at providing a sort of guide, starting from the data gathering phase to the processing, up to the implementation of the outputs in a probabilistic-based scenario, which is able to associate a probability of not being exceeded with total kinetic energy values. By doing so, we were able to introduce a new approach for the choice of design parameters and the evaluation of the effectiveness of mitigation techniques. For this purpose, a suitable case study located in Varaita Valley (Cuneo, Italy) has been selected. The area has been surveyed, and a model of the slope and a digital model of the rock faces have been defined. The results show that a 6.5 m3 block has a probability of not being exceeded of 75%; subsequent simulations show that the level of kinetic energy involved in such a rockfall is extremely high. Some mitigation techniques are discussed.

Impact of nuclear dissipation on the fission dynamics within the Langevin approach

The impact of nuclear dissipation on the dynamics of nuclear fission at low excitation energy is studied with a three-dimensional Langevin approach in which the two-center shell model is adopted to describe the nuclear shape and the single-particle potential. With three types of formulas for the friction tensor, such as the wall formula, the wall-and-window formula with and without the term related to the mass asymmetry change, the fragment mass and the total kinetic energy (TKE) distributions in low-energy fission are calculated. The calculated fragment mass distributions are almost identical for both with the wall formula and with the wall-and-window model without the term related to the mass asymmetry change, and both the results are consistent with the evaluated mass yields and the calculated results with the GEF model. Our study found that the term related to the mass asymmetry change in the window formula leads to an unreasonable shift of the peak position of the mass distribution. The TKE values calculated with the wall model are slightly larger than those with the wall-and-window model due to the more compact configuration obtained with the pure wall model. Moreover, the influences of the strength of friction tensor on the fragment distribution, the scission configuration, and the fission time distribution are investigated. With the present model the fission fragment mass distributions of U, Np, Pu, and Am isotopes are well reproduced and the systematic dependence of the averaged TKE on the Coulomb parameter is also well reproduced.

Kinetic energy distribution for photofission of light actinides

The scission point model has been used to calculate the total kinetic energy (TKE) as a function of fission fragments for photofission reactions. By comparing the calculated TKE values with the available experimental data, the deformation parameters of the fission fragments are obtained in the scission point model. The results show that the deformation parameters of the fission fragments have a large change near the symmetrical region. TKE distribution has been investigated for neutron-induced fission, spontaneous fission, and photofission to predict actinide TKE distribution. This indicates that the TKE distribution depends on the mass and atomic number of compound nuclei and, of course, the excitation energy. The odd-even effect plays an important role in predicting TKE distribution behavior. Also, TKE distribution has a similar trend for all isotopes and the TKE distribution of spontaneous fission is significantly different from the TKE distribution of photofission. At last, the total kinetic energy distributions for the photofission fragments of light actinides are evaluated in the scission point model.

Properties of fission fragments forZ=112−116superheavy nuclei

The dynamical cluster decay model (DCM) is applied to understand the dynamics of $^{48}\mathrm{Ca}+^{238}\mathrm{U},^{244}\mathrm{Pu},^{248}\mathrm{Cm}$ reactions at comparable excitation energies across the barrier. To understand the capture stage of $^{286}112^{*},\phantom{\rule{0.16em}{0ex}}^{292}114^{*}$, and $^{296}116^{*}$ nuclei, the compound nucleus formation probability is calculated. The indication of ${P}_{CN}l1$ in the DCM framework demonstrates the fact that some competing process such as quasifission may occur at the capture stage of the $^{48}\mathrm{Ca}$ induced reactions. To understand this further, the comparative decay analysis of $^{286}112^{*},\phantom{\rule{0.16em}{0ex}}^{292}114^{*}$ and $^{296}116^{*}$, nuclei is carried out using ${\ensuremath{\beta}}_{2i}$ deformations within hot optimum orientation criteria, and the calculated fission cross sections find nice agreement with available data. The fission mass distribution shows a double humped structure where a symmetric peak observed around the Sn region appears to find its genesis in a symmetric quasifission component. On the other hand, the emergence of peaks around Pb in the decay of $Z=112$, 114, and 116 nuclei signify the possible presence of asymmetric quasifission. Higher and broader asymmetric quasifission peaks are observed for $^{296}116^{*}$ and $^{292}114^{*}$ nuclei as compared to $^{286}112^{*}$ nucleus. Beside this, the total kinetic energy (TKE) distribution of the decay fragments is also explored by using different proximity potentials, such as Prox-77, Prox-88, and Prox-00. Prox-88 seems to perform better and the calculated TKE values find relatively better comparison at lower angular momentum states. The possible role of different radii of the decaying nuclei is also exercised to understand the $\overline{\mathrm{TKE}}$ dynamics of $^{48}\mathrm{Ca}+^{238}\mathrm{U},^{244}\mathrm{Pu},^{248}\mathrm{Cm}$ reactions.

Prompt fission neutron emission calculations and description of sub-barrier fission cross section resonances for 234U()

Abstract Prompt emission quantities of 234U( n , f ) (average quantities as a function of fragment mass, average quantities as a function of total kinetic energy (TKE) and total average quantities) have been calculated within the Point-by-Point model. The recently measured fission fragment distributions at incident energies (En) ranging from 0.2 MeV to 5 MeV have been used. The insensibility of the fragment pair multiplicity ν pair to the partition of total excitation energy (TXE) between complementary fully accelerated fission fragments has been confirmed. This gives confidence in the predicted total average prompt emission data as a function of En and of average quantities as a function of TKE at different incident energies of 234U( n , f ). The systematic behavior of experimental ratios ν H / ν pair as a function of heavy fragment mass number A H together with the TXE partition based on modeling at scission allow the parameterization of the excitation energy ratio E H ⁎ / TXE . This opens up the possibility to provide ν ( A ) of 234U in the absence of any experimental data. For the first time the calculation of 〈 ν 〉 ( TKE ) at many En revealed two interesting aspects: the slope d TKE / d ν does not vary with En and the flattening of 〈 ν 〉 at low TKE values is more pronounced at low incident energies. The correlation between the sub-barrier resonant behavior of the fission cross section of fertile actinides (characterizing the pre-scission stage) and the visible fluctuations of their fission fragment and prompt neutron emission data (characterizing the post-scission stage), already discussed in the case of 238U( n , f ) is outlined and quantitatively supported by 234U( n , f ), too. The pronounced vibrational resonances in the experimental fission cross section of 234U placed below 1 MeV can be described by the statistical model for reaction cross section calculation including the optical model for fission.

Fission and binary fragmentation reactions inSe80+Pb208andSe80+Th232systems

Fission and binary fragmentation of the excited nuclear systems of Z=116 and 124 were investigated using the reactions induced by Se80 beams on Pb208 and Th232 targets at bombarding energies ranging from 470 to 630 MeV. The mass and kinetic energy of the binary reaction products were reconstructed by measuring their velocities by the time-of-flight method and the angles of emission using multiwire proportional chambers. Total neutron multiplicities were measured in coincidence with the fragments, using an array of neutron detectors. The fragment mass-energy correlation was studied for the two systems. The average total kinetic energy (TKE) of fragments for the Se80+Pb208 system agrees with earlier measurements and with Viola's systematics in the mass symmetric region for compound nucleus fission, whereas for the Se80+Th232 system, the TKE values are significantly lower. This is also consistent with higher values of total neutron multiplicities observed for the case of Se80+Th232 at comparable available energies. From an extrapolation of the measured total neutron multiplicities for the mass symmetric region to zero compound nucleus excitation energy, the average number of prompt neutrons expected to be emitted in the spontaneous fission of the superheavy Z=116 has been estimated to be νtotsf=10±2, which is consistent with the value derived for the same compound nucleus populated in the Fe56+Th232 reaction in an earlier work. In the case of the Se80+Th232 system, similar analysis was carried out by taking the average TKE from Viola's systematics for estimating the available energy for particle emission corresponding to compound nucleus fission. In this way, by extrapolating the observed neutron multiplicities to zero compound nucleus excitation energy, a value of νtotsf=15±2 was obtained for the spontaneous fission of the superheavy Z=124 nucleus. The increase in the average number of neutrons emitted in fission as a function of the atomic number of the nucleus in the superheavy mass region was confirmed by comparing the results of the present work with published data.3 MoreReceived 2 May 2006DOI:https://doi.org/10.1103/PhysRevC.75.024604©2007 American Physical Society

Prompt neutron emission from the spontaneous fission of 260Md.

We have made the first measurement of the number of neutrons emitted from the spontaneous fission of a nuclide in which very high fragment energies dominate the fission process. In bombardments of $^{254}\mathrm{Es}$, we produced a large sample of 28-d $^{260}\mathrm{Md}$, which was neutron counted in a 1-m-diameter spherical tank containing a Gd-doped scintillator solution. The average number of neutrons emitted per fission is only 2.58\ifmmode\pm\else\textpm\fi{}0.11, substantially less than for other actinides. A linear dependence of neutron multiplicity on fragment-excitation energy is observed to the highest values of total kinetic energy.

Coulomb effects in low energy fission

The structures in the total kinetic energy (TKE) distributions in cold fission of234U and236U are interpreted in terms of the Coulomb interaction energy (C) between fragments at the scission point. The maximal value ofC, C max, corresponding to the most compact scission configuration, is calculated for several mass fragmentations. It is shown that withQ being constant,C max increases if one increases the charge asymmetry for a given primary fragmentation. This condition produces oscillations with a period of approximately 5 amu ofC max as a function of the light fragment mass which are correlated with the observed oscillations of the maximal value of TKE. Moreover, the enhancement of the yields of the more asymmetric charge fragmentation for a given fragmentation is explained.

Mass and kinetic energy distribution in cold fission of233U,235U and239Pu induced by thermal neutrons

The time-of-flight technique was used to measure the mass and kinetic energy distribution of fragments from fission of233U,235U and239Pu, induced by thermal neutrons at the Grenoble High Flux Reactor. The data array is presented as equal probability lines in the high kinetic energy regions. The fluctuations observed in those experimental lines are explained by a static scission configuration model, in which the most important influence comes from the Coulomb interaction energy between the two fragments. The highest values of total kinetic energy are obtained for fragmentations with heavy fragmentsZ=50–52,N=80–82 and light fragmentsZ=40–42,N=60–64.