Nuclear structure around ~(80)Zr

Recent years have witnessed intense activity concerning the study of nuclei with equal numbers of neutrons and protons (N = Z). Exotic properties have been exhibited in the N = Z nuclei, especially in those with atomic masses around 80. In the present paper, the projected shell model(PSM)together with a relativistic Hartree-Bogoliubov (RHB) theory is used to study the nuclear structure near the N = Z line in the mass A ≈ 80 region. For three Zr isotopes 80,82,84Zr, the projected potential energy surfaces an...     

Nuclear structure around ~(80)Zr

Recent years have witnessed intense activity concerning the study of nuclei with equal numbers of neutrons and protons (N = Z). Exotic properties have been exhibited in the N = Z nuclei, especially in those with atomic masses around 80. In the present paper, the projected shell model(PSM)together with a relativistic Hartree-Bogoliubov (RHB) theory is used to study the nuclear structure near the N = Z line in the mass A ≈ 80 region. For three Zr isotopes 80,82,84Zr, the projected potential energy surfaces and ground state bands are calculated. It is shown that shape coexistence occurs in all of these nuclei. Moreover, we find that the residual neutron-proton interaction strongly affects the ground state band of 80Zr; however, it slightly modifies those of 82Zr and 84Zr.     

Angular momentum dependence of quasifission dynamics in the reaction ~(48)Ca+~(244)Pu

The quasifission dynamics in the reaction ~(48)Ca+~(244)Pu is investigated in the framework of time-dependent Hartree-Fock(TDHF)theory. The calculations are performed in three-dimensional Cartesian coordinate without any symmetry restrictions. The full Skyrme energy functional is incorporated in our TDHF implementation. The quasifission dynamics is quite sensitive to the angular momentum of colliding system. The contact time of quasifission decreases as a function of angular momentum and then forms a plateau with small oscillations. The quasifission process is accompanied by an important multi-nucleon transfer. The quantum shell effect plays a crucial role in the mass and charge of quasifission fragments. The mass-angle distribution of the fragments is calculated, which can be compared directly with future experiments.     

Heat convection and transport barriers in low-magnetic-shear rijnhuizen tokamak project plasmas

Layers of reduced electron heat transport ("transport barriers") have been observed in the Rijnhuizen Tokamak Project when the plasma is dominantly heated by electron cyclotron heating (ECH). Experiments into the properties of the transport barriers are reported. Modulation of the ECH power was used to probe electron heat transport in the barriers by means of propagating electron temperature perturbations. The observed propagation shows that transport inside the barriers is dominated by heat convection. This convection is inward, i.e., up the temperature gradient.     

Calculations of thermal conductivity of complex (dusty) plasmas using homogenous nonequilibrium molecular simulations

The heat conductivity of three-dimensional Yukawa dusty plasma liquids (YDPLs) has been investigated by employing a homogenous nonequilibrium molecular dynamics (HNEMD) technique at a low normalized force field strength (F*). The obtained results for plasma heat conductivity with suitable normalizations are measured over a wide range of various plasma states of the Coulomb coupling (Γ) and screening length (κ) in a canonical ensemble (NVT). The calculations for lattice correlations (Ψ) show that our YDPLs system remains in a nonideal strongly coupled regime for a complete range of Γ. It has been shown that the presented Yukawa system obeys a simple analytical temperature demonstration of λ₀ with a normalized Einstein frequency. The employed HNEMD algorithm is found to have a more efficient method than that of different earlier numerical methods and it gives more satisfactory results for lower to intermediate Γ with small system sizes at low F*. The obtained simulation results at nearly equilibrium F* (=?0.002) are in reasonable agreement with different earlier numerical results and with the present reference set of data showed deviations within less than ±15% for most of the present data points and generally underpredicted the λ₀ by 2–22%, depending on (Γ, κ).     

Momentum injection in tokamak plasmas and transitions to reduced transport

The effect of momentum injection on the temperature gradient in tokamak plasmas is studied. A plausible scenario for transitions to reduced transport regimes is proposed. The transition happens when there is sufficient momentum input so that the velocity shear can suppress or reduce the turbulence. However, it is possible to drive too much velocity shear and rekindle the turbulent transport. The optimal level of momentum injection is determined. The reduction in transport is maximized in the regions of low or zero magnetic shear.     

Langevin study of neutron emission in the reactions ^16O＋^181Ta and ^19F＋^178Hf^＊

The pre-scission neutrons measured in the reactions 16O 181Ta and 19F 178Hf are studied via a Langevin equation coupled with a statistical decay model. We find that because of the mass asymmetry of different entrance channels, the spin distributions of compound nuclei would be different, consequently, the measured neutrons in these two reactions would also different. This means that the entrance channel will affect the particle emission in the fission process of hot nuclei.     

Double folding analysis of ~(3)He elastic and inelastic scattering to low lying states on ~(90)Zr,~(116)Sn and ~(208)Pb at 270 MeV

The experimental data on elastic and inelastic scattering of 270 MeV~3 He particles to several low lying states in~(90)Zr,~(116)Sn and~(208)Pb are analyzed within the double folding model(DFM). Fermi density distribution(FDD) of target nuclei is used to obtain real potentials with different powers. DF results are introduced into a modified DWUCK4 code to calculate the elastic and inelastic scattering cross sections. Two choices of potentials form factors are used; Woods Saxon(WS) and Woods Saxon Squared(WS~2) for real potential, while the imaginary part is taken as phenomenological Woods Saxon(PWS) and phenomenological Woods Saxon Squared(PWS~2). This comparison provides information about the similarities and differences of the models used in calculations.     

Simulation of the fission dynamics of the excited compound nuclei ~(206)Po and ~(168)Yb produced in the reactions ~(12)C+~(194)Pt and ~(18)O+~(150)Sm

A two-dimensional dynamical model based on the Langevin equation was used to study the fission dynamics of the compound nuclei ~(206)Po and ~(168)Yb produced in the reactions ~(12)C+~(194)Pt and ~(18)O+~(150)Sm,respectively.The fission cross section and average pre-scission neutron multiplicity were calculated for the compound nuclei ~(206)Po and ~(168)Yb,and results of the calculations compared with the experimental data.The elongation coordinate was used as the first dimension and the projection of the total spin of the compound nucleus onto the symmetry axis,K,considered as the second dimension in the Langevin dynamical calculations.In the two-dimensional calculations,a constant dissipation coefficient of K and a non-constant dissipation coefficient have been used to reproduce the abovementioned experimental data.It is shown that the two-dimensional Langevin equation can satisfactorily reproduce the fission cross section and average pre-scission neutron multiplicity for the compound nuclei ~(206)Po and ~(168)Yb by using constant values of the dissipation coefficient of K equal to γκ=0.18(MeV zs)~(-1/2) and γκ= 0.20(MeV zs)~(-1/2)for the compound nuclei ~(206)Po and ~(168)Yb,respectively.     

Shape coexistence close to N=50 in the neutron-rich isotope ~(80)Ge investigated by IBM-2

The properties of the low-lying states,especially the relevant shape coexistence in~(80)Ge,close to one of most neutron-rich doubly magic nuclei at N=50 and Z=28,have been investigated within the framework of the proton-neutron interacting model(IBM-2).Based on the fact that the relative energy of the d neutron boson is different from that of the proton boson,the calculated energy levels of low-lying states and E2 transition strengths can reproduce the experimental data very well.Particularly,the first excited state 0_2~+,which is intimately related to the shape coexistence phenomenon,is reproduced quite nicely.Theρ~2(E0,0_2~+→0_1~+)transition strength is also predicted.The experimental data and theoretical results indicate that both collective spherical andγ-soft vibration structures coexist in~(80)Ge.     

Experimental research into the two-proton emissions from ~(17,18) Ne,~(28) P and ~(28,29)S

Two-proton emissions from the excited states of 17,18Ne, 28P and 28,29S were investigated experimentally by the radioactive beams bombarding on the 197Au target via the Coulomb excitation. The complete-kinematics measurements were actualized by the stacks of silicon-strip detectors and CsI+PIN array detectors. The invariant mass of final systems as well as the relative momentum, opening angle, and relative energy of the two emitted protons was reconstructed under the framework of relativ istic kinematics. V...     

Nucleon momentum distribution of ~(56)Fe from the axially deformed relativistic mean-field model with nucleon-nucleon correlations

Nucleon momentum distribution(NMD), particularly its high-momentum components, is essential for understanding the nucleonnucleon(NN) correlations in nuclei. Herein, we develop the studies of NMD of ~(56)Fe from the axially deformed relativistic mean-field(RMF) model. Moreover, we introduce the effects of NN correlation into the RMF model from phenomenological models basing on deuteron and nuclear matter. For the region k k_F, the effects of deformation on the NMD of the RMF model are investigated using the total and single-particle NMDs. For the region k k_F, the high-momentum components of the RMF model are modified by the effects of NN correlation, which agree with the experimental data. Comparing the NMD of relativistic and non-relativistic mean-field models, the relativistic effects on nuclear structures in momentum space are analyzed. Finally, by analogizing the tensor correlations in deuteron and Jastrow-type correlations in nuclear matter, the behaviors and contributions of NN correlations in ~(56)Fe are further analyzed, which helps clarify the effects of the tensor force on the NMD of heavy nuclei.     

Contribution to the evaluation of transport coefficients in plasmas containing krypton and sodium

Electrical and thermal conductivities for low-temperature (2000 K to 20000 K) and high-pressure (0.1 MPa to 2.5 MPa) krypton plasma with some sodium (1% and 10%) as additive are presented. The plasma is treated as weakly non-ideal and having attained the local thermodynamical equilibrium states. The problem of the plasma non-ideality according to standard criteria is of the plasma Debye radius, with an improved cut-off length. Use is made of a previously derived modified Debye radius with the Landau length instead of the smallest ionic radii which allowed to regard the plasmas investigated as weakly non-ideal. This alteration in the evaluation of the Debye radius profoundly alters the equilibrium plasma compositions and their transport coefficients.     

Effect of hydrogen plasma implantation on the micro-structure and magnetic properties of hcp-Co_(80)~(57)Fe_4Ir_(16) thin films

We present detailed investigations of structural and static/dynamic magnetic properties of hydrogenated hcpCo_(80)~(57)Fe_4Ir_(16) soft magnetic thin films. Two different kinds of defects, i.e., destructive and non-destructive, were demonstrated by controlling the negative bias voltage of the hydrogenation process. Our results show that the structure and magnetic properties of our sample can be tuned by the density of the induced defects. These results provide better understanding of the hydrogenation effect and thus can be used in the future for materials processing to meet the requirements of different devices.     

Study of ~3He inelastic scattering on ~(13)C and ~(14)C at 37.9 MeV

The differential cross sections of elastic and inelastic scattering of ³He ions on ¹³C and ¹⁴C have been studied at an energy of 37.9 MeV with a double folding model based on M3Y-Reid effective nucleon-nucleon interaction. The resulted parameters have been used for the standard Distorted Wave Born Approximation calculations of angular distributions corresponding to different excitations levels of ¹³C and ¹⁴C and deformation parameters have been deduced.     

An Investigation of ~4He+~(12)C and ~4He+~(16)O Reactions Using the Cluster Model

The α-target semimicroscopic single folding potentials have been derived by folding a composite (repul-sive and attractive) effective α-α interaction with the α-cluster distribution density in the target nuclei. The obtained potentials are considered as the real part of the nuclear optical model potentials, while the imaginary parts are phe-nomenologicaly expressed using the Woods-Saxon form. Nine sets of measured experimental data of the 4He+12C and 4 He+16O elastic rainbow scattering over the energy range 80-240 MeV are analyzed using the obtained potentials. The data are successfully reproduced using the extracted potentials. The resulted reaction cross sections are also investigated and compared with the available corresponding data.     

Polarization and fundamental sensitivity of ~(39)K(~(133)Cs)-~(85)Rb-~(21)Ne co-magnetometers

The hybrid optical pumping spin exchange relaxation free(HOPSERF)atomic co-magnetometers make ultrahigh sensitivity measurement of inertia achievable.The wall relaxation rate has a big effect on the polarization and fundamental sensitivity for the co-magnetometer,but it is often neglected in the experiments.However,there is almost no work about the systematic analysis of the influence factors on the polarization and the fundamental sensitivity of the HOPSERF co-magnetometers.Here we systematically study the polarization and the fundamental sensitivity of 39K-85Rb-21Ne and 133Cs-85Rb-21Ne HOPSERF co-magnetometers with low polarization limit and the wall relaxation rate.The 21Ne number density,the power density and wavelength of pump beam will affect the polarization greatly by affecting the pumping rate of the pump beam.We obtain a general formula on the fundamental sensitivity of the HOPSERF co-magnetometers due to shot-noise and the fundamental sensitivity changes with multiple systemic parameters,where the suitable number density of buffer gas and quench gas make the fundamental sensitivity highest.The fundamental sensitivity 7.5355×10^-11 rad·s^-1·Hz^-1/2 of 133Cs-85Rb-21Ne co-magnetometer is higher than the ultimate theoretical sensitivity 2×10^-10 rad·s^-1·Hz^-1/2 of K-21Ne co-magnetometer.     

Heat transport in a two-dimensional complex (dusty) plasma at melting conditions

The heat transport in a two-dimensional complex (dusty) plasma undergoing a phase transition was studied experimentally. A single layer of highly charged polymer microspheres was suspended in a plasma sheath. A part of this lattice was heated by two counterpropagating focused laser beams that moved rapidly around in the lattice and provided short intense random kicks to the particles. Above a threshold, the lattice locally melted. The spatial profiles of the particle kinetic temperature were analyzed to find a thermal conductivity, which did not depend on temperature.