Influence of angular momentum on evaporation residue cross section as a probe of nuclear dissipation

By calculating the excess of the evaporation residue cross sections of the ^200Pb nucleus over that predicted by the standard statistical model as a function of nuclear viscosity coefficient using a Langevin equation combined with a statistical decay model, it is found that high angular momentum not only amplifies the dissipation effects on the excess of the evaporation residue cross sections, but also considerably increases the sensitivity of this excess to the nuclear viscosity coefficient. These results suggest that on the experimental side, to accurately obtain the information of nuclear dissipation inside the saddle point by measuring the evaporation residue cross section, it had better populate those compound systems with high spins.

Spin distribution of evaporation residue cross section within a stochastic approach

The Langevin equation including particle emission was used to reproduce the recently measured spin distribution of evaporation residue cross sections in the reaction ^16O＋^184W at beam energies of 84, 92, 100, 108, 116 and 120 MeV. By comparing the theoretical calculations with the experimental data, the validity of the stochastic approach to dissipative fission is verified. Moreover, a pre-saddle nuclear viscosity coefficient of 5×10^21 s^-1 is extracted.

Numerical Simulation of Heat Transfer Performance for Ultra-Thin Flat Heat Pipe

The heat transfer performance of ultra-thin flat heat pipes with#180 copper mesh wick was studied by numerical simulation for different heating powers.The length,width and height of the ultra-thin flat heat pipe are 80 mm,8.5 mm and 1 mm,respectively.The temperature distribution and flow characteristics of ultra-thin flat heat pipes were simulated by coupling porous media model and user-defined function(UDF)in FLUENT.To validate the accuracy of the numerical model,the simulation results of the ultra-thin flat heat pipe are compared with the experimental data in predicting the evaporation section temperature.The numerical model has good accuracy for the one-dimensional heat transfer method of ultra-thin flat heat pipes.The velocity,pressure drop of the wick and total temperature difference have the same variation trend.With the increase of heating power,the temperature difference of ultra-thin flat heat pipes increases,and the pressure drop and the liquid velocity in the wick also increase.

Surveying the role of excitation energy in probing nuclear dissipation

A dynamical Langevin model is employed to calculate the excess of the evaporation residue cross sections of the ^194Pb nucleus over that predicted by the standard statistical model as a function of nuclear dissipation strength. It is shown that large excitation energy can increase the effects of nuclear dissipation on the excess of the evaporation residues and the sensitivity of this excess to the dissipation strength,and that more higher excitation energies have little contribution to further raising this sensitivity. These results suggest that on the experimental side,producing those compound systems with moderate excitation energy is sucient for a good determination of the pre-saddle nuclear dissipation strength by measuring the evaporation residue cross section,and that forming an extremely highly excited system does not considerably improve the sensitivity of evaporation residues to the dissipation strength.

Study of different features offission dynamics of ^(224)Th produced in fusion reactions within a stochastic approach

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.