1996 Vol. 20, No. 4
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By using a detection system combining Time-of-Flight(TOF)method with(△E-E)technique,the excitation functions,the dependence of energy coherence widthΓon product mass A and the dependence of Γon the degree of freedom of neutron excess N/Z for some elements and their isotope products in the dissipative process of reaction 19F+51V at energies from 102.25MeV to 109.50 MeV(in 250 keV steps)were presented and discussed for the first time.
The azimuthal Structure of partivles produced in pp collisions at 400 GeV/c was investigated by using different methods.The analytic results of one and two-dimensional scaled factorial moments indicate that the intermittent effect is stronger for two-dimensional analysis.It is not contradictory with jet-like multiparticle production mechanism. However,the analytic results of other methods show that the azimuthal structure seems to be of stochastic nature and no evidence of the jet-like multiparticle production mechanism is observed.
The inclusive energy spectra of intermediate-mass fragments(IMF)(3≤Z≤9)have been measured in the range from 20°to 155°for 40Ar+159Tb reaction at 25MeV/u.At backward angles,the spectra of IMF show a characteristic of statistic evaporation and can be well fitted by a moving source with same parameters.The obtained source velocity and temperature are in agreement with the corresponding values of hot nuclei produced in an incomplete-fusion process.Therefore,it seems that there IMF are statistically evaporated from a same source.The experimental results have for compared with the predictions of the statistical model using GEMINI code.
The anisotropy of azimuthal distribution for the final state particles in the center-of-mass coordinate systems where the z axis is rotated to various polar angles in the reaction plane is studied.A method to determine the flow angle is proposed. Studying the polar angle distributions for collisions of1.2AGeV Ar+KC,1.2AGeV Ne+NaF and 2.1AGeV Ne+NaF at the Bevalac streamer chamber in the coordinate systems with the z axis rotated to the now angles,we can estimate the fraction of the anisotropic emission particles to all the final state particles and the degree of concentration around the flow direction quantitatively.
The macro-microscopic model is applied to study the properties of the nuclei far from stability line.Some results are obtained,e.g.proton and neutron drip line,changes of proton and neutron density distributions,the rms radii and neutron skin thickness with isospins.The calculated results of some exotic nuclei are compared with those of relativistic mean-field approach.Brief discussions for proton radioactivity are given.
A form of densities suitable for applications of extended Thomas-Fermi(ETF)method is proposed.With SkM* force parameters,ground state properties of some Spherical nuclei are calculated.The results,in a general way,are better than those with ordinarily parametrized densities. Further application of the expectation value method(EVM)can also reproduce Hatree-Fock(H-F)results.
The variation of equipotential lines of interaction potential with the intuitively gives the information about the fluctuation of the potential in intermediate energy heavy ion collisions.At the early stage of collisions the potential value in the central region of the system could be positive.The followed irregular deformation of equipotential lines in the region,especially the appearance of the negative curvatUre of the equipotential lines causes the chaotic nucleonic motion.The phase difference of the neighbouring nucleons increases with time exponentially,and the phase space of nucleons thus separates and caussd the multifragmentation.
The analytical limits of a speacial potential of the Bohr Hamiltonian are discussed in detail.A new formula for the axial symmetric,triakial deformed and the γ-soft nuclei is presented.The nuclear γ deformation can be identified with this formula.The calculations of some nuclear yrast lines seproduce the experiment al results very Well,and the degree of the nuclear γ deformation is obtained.
The effects of radial expansion energy on the mean field and nucleon-nucleon cross section are studied by using Skyrme interaction.It is found that radial expansion energy is Strongly influenced by mean field,and on the contrary,the dependence on the nucleon-nucleon cross section was smaller.
Applying the method proposed by R.Crespo and J.A.Tostevin to p-3He elastic scattering,we study the treatment of Coulomb interaction of momentum space.The differential cross sections and spin observables at 500 and 300 MeV are calculated with R=7fm.The present results are compared with those given in V-P method.It shows that the applicable range of angular momentum and momentum transfer in R-J method are wider than those in V-P method.
The different choices for phase space variables in the study of anomalous scaling in high energy multiparticle production are discussed. In order to overcome the shortcomings of the transverse variables currently used,a set of new transverse variables are introduced,which has some advantage in the anomalous scaling study of high energy multiparticle production. The probability distributions as well as the numerical characteristics of these variables are given and the independency between them are discussed.The corresponding cumulate variables are given.
A quark-quark potential is derived from the linear expression of the Lagrangian Which is invariant under the SU(3)L×SU(3)R infinitesimal transformation,and further used to make a qualitative analysis on the Λ-N interaction.The result shows that the SU(3)chiral scalar fields are important in explaining the spin-dependence feature of the Λ-N interaction.
Electron beam transverse temperatures on HIRFL-CSR electron cooler are deduced from motion equations of single electron in themagnetic field. Some important conclusions have Been drawn.
The beam dynamics in RF thermionic guns is studied using simulation method in this paper.A RF thermionic gun simulation code is compiled.It is a versatile multiparticle trace code,besides use for RF thermionic guns,capable of simulations of photocathode RF guns and standing wave accelerators.During our simulation,the Schottky effect and beam load effect are calculated using iterative method, and space charge effect is treated at every time step by splitting the electron bunch into discs of variable radii and considering the mirror effect of the cathode surface.The dynamics calculations are done in a rectangular coordinate system(x, y, z),so that dis-axisymmetrical fields, such as the quadrupole components of RF fields of the coupling slots, can be taken into account.Our simulation results have been compared with those of PARMELA and experiments of BFEL laboratory,showing very good agreement with each other.
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