1993 Vol. 17, No. 4
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Cross sections for some (n,d*),(n,t) and (n,n'α)reactions have been measured by using the activation method relative to cross sections of 27Al(n,α)24Na or 93Nb(n,2n)92mNb reactions in neutron energies around 14MeV.In this paper some of the published cross section data have also been listed and compared with our results.The neutron energies were determined by the method of cross section ratios for the reactions of 90Zr(n,2n) 89m+gZr and 93Nb(n,2n)92mNb.
The experiment results of unstable nucliaes decay by using the light charged particle correlation function obtained in 12C 46.7MeV/u+58Ni experiment are reported.Under the assumption of statistical equilibrium,the nuclear temperatures are extracted,and the influence of the reaction mechanism on the nuclear temperature are also investigated.
The monoenergetic slow positron beam was first used to study the crystalliation process of metallic glasses.The measurement of Doppler broadening spectra as a function of positron energy was made on the samples of metallic glass Pd79.5Ni4Si16.5 in various states.It is shown that there are a number of the vacancy-like defects in the as-quenched state sample.Its crystallization started at the sample surface.Slow position beam turned out to be an effective probe to study the structural change of metallic glasses.
In this paper the transport of charged particle beams in nonlinear periodic fields is studied.By means of mapping method the emittance plots of beams matched with the nonlinear periodic fields can be obtained.The variance of emittance plots and envelopes of these beams are periodic and their periods are equal to the period of field.
The advanced properties of RFQ are commented in this paper.The contribution of the design research on the beam dynamics to these advanced properties is described.Five design limits are given.The main developments of RFQ's beam dynamics and r.f structures in the last 10 years are presented.
The possible isomorphic relations between W algebras from various conformal reductions of WZNW model are investigated and the criterion for the isomorphism of W algebras is given.In the special case of sl3 WZNW theory,we show explicitly the isomorphism between W[(111)2] and W[(12)1] and discuss the constraint-gauge condition transmutation between the O'Raifeartaigh gauges and the transmutation of conformal weights under the isomorphism transformation.
We show the dressing transformations of the basic field and the classical chiral operators in the Bosonic Superconformal Toda model.After quantization,we obtain the related quantum algebra.
In Dirac-Brueckner calculations for nuclear matter,the average binding energy per nucleon versus density curve is not uniquely defined if coupling to anti-particle is neglected.According to the Hugenholtz-Van Hove theorem,a constraint requires that the nucleon separation energy equals to the fermi energy at saturation density.Choosing saturation energy as empirical value EB/A=－15.8MeV,the self-consistent calculation leads to the saturation density kf=1.41fm－1 and effective mass m*=0.52m,in compressive coefficient k=208MeV.Applying the first law of thermodynamics,self-consistent effective mass (real scalar potential) and the binding energy per nucleon as function of the nuclear density can be obtained.With the realistic nucleon-nucleon interaction (Bonn potential),the vector potential can be obtained from solving the RBBG equation,which weakly depends on the momentum.The cross section and spin observables of the nucleon-nucleus scattering are studied with this new self-consistent relativistic microscopic optical potential.
Level structures of neutron-rich even-even nuclei around A～100 and 150 regions have been studied by observing the prompt gamma rays from the spontaneous fission of 252Cf.The highest spin is up to 10～14.The character of nuclear structures and shape phase transitions of some isotope chains are discussed.
The expression of quantum correction of the multidimensional fission rate at finite temperature is obtained by a path integral method.
The spin transverse response functions for 40Ca and 12C in different approximations have been calculated.By using the coupled RPA equations for polarization propagator including the delta degree of freedom,the influence of the delta on the response function has been investigated.The results show that they are reduced explicitly.Introducing the energy dependent effective nucleon mass,which embodies the manybody ef ects,the satisfactory results are obtained.
The influence of the parameters of the relativistic optical potential on the nucleon scattering properties,such as cross sections,angular distributions and spin observables etc.,is studied based on a set of global Dirac phenomenological optical potentials.It is shown that,in contrast with the case at low energies.the total scattering cross sections vary slowly as the energy and weakly depend on the potentials at Ep<200MeV.The differential cross sections and spin observables depend not only on the volume integrals of the optical potentials,but also on their strengths and shapes.The applicability of the relativistic microscopic optical potentia based on Walecka model in the medium energy region is also discussed in this paper.
In the structure function approach,we calculate the threshold behaviours for e++e－→τ++τ－,which including QED radiative corrections from initial correction,vacuum polarization effect,Coulomb effect and final state correction.This theoretical prediction for threshold behaviours of τ-pair production is useful for BES new measurement of lepton τ mass.
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