1996 Vol. 20, No. 5
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The High spin isomer(HSI)in 144Pm was produced and separated by using the high spin isomer beam facility.Based on the measurements of γ-γ coincidence, γ-ray excitation functions and isotropies,the decay level scheme of the HSI was established for the first time including 19 new high spin levels and 29 new γ-transitions assigned to 144Pm by this work.The HSI-γ correlation measurement indicated that the halflife of the HSI is longer than 2μs.From the systematic comparisons and the deformed independent particle model calculations for the N=83 isotones,the most possible particle configuration of π(1h211/2d5/2)v(1i13/21h9/22f7/2) and the spin-parity of Jπ=27+ were assigned to this HSI corresponding to an oblate deformation with β=－0.18.
The in-plane and out-of-plane emission of light particles from 40Ar+197Au collisions at 25MeV/u was studied by means of coincidence measurement of light particles with two fission fragments.An in-plane enhancement was observed for mid-rapidity p,d,t,α particles,indicating a rotation effect in this reaction system.This enhancement becomes more obvious with the increase of mass of the particles,or with the increase of the impact parameters.It was also found that in-plane emission is dominant for projectile-like particles.
Gamma family events with visible energies higher than 1015eV usually form halos in the emulsion chambers,which bring up some problems for further investigating the characteristics of superhigh energy nuclear interactions. At present,only a few gross quantities are used for describing the halo events.On the other hand,there are some fine structures inside the halo, which can give us more information.We have measured all the showers one by one in the superhigh energy family events and compared the results with those obtained by the method of halo measurements.Analyses and discussions are made forsome special events.
The attenuation lengths of hadron fluxes with visible energies higher than 4TeV have been observed in thick type iron emulsion chambers exposed at Mt. Kanbala with high detecting efficiency for hadrons.Uncorrelated hadrons as well as hadrons in family events with visible energies of ΣEγ>500TeV、100TeV≤ΣEγ≤500TeV and 30TeV≤ΣEγ<100TeV are measured.Preliminary results indicate that the attenuation lengths of hadrons in iron in these four cases are different.A brief discussion is given.
In this paper,we discuss that the mass of stellar, nucleon, and the dark matter particles are connected by a large number A～1019,and the strong interaction might be phenomenologically connected with the gravitation also by this large number in a deeper level.
The rare decays t→cV(V=Z,γ,g)induced through loop diagrams are calculated in a minimal Technicolor model(MTC) with a massless weak doublet recently presented by C.D.Carone and H. Georgi.We find that these new contributions can enhance the SM branching fractions by as much as 3—4 orders of magnitude,i.e.,B(t→cZ)≈10,B(t→cγ)≈10－9, B(t→cg)≈10－6 for the favorable values of the parameters.It might provide a unique window to detect the virtual effects of technipions in MTC theory.
In the frame of the random neck rupture and multichannel fission model,thefragment yield,average total kinetic energy distributions and prompt neutron multiplicities of the neutron induced 233,235,238U(n,f)fission covering the incident neutron energy range from thermal to 6 MeV are calculated.The theoretical results are in accord with the experimental data.
FolloWing the intrabeam scattering(IBS)theory of Bjorken and Mtingwa,more general formulae for the growth rates of horizontal,vertical emittance and longitudinal momentum spread are deduced in a simpler form of elliptic integrals.The formulae are applied to the proposed HIRFL-CSR. By means of numerical integration,continuous variations of emittances and momentum spread with time are obtained.The results show that the IBS growth rates are not rapid enough to be a design constraint of CSR lattice.
The RVUU model is used to study dynamical processes of the kaon and pion produced in heavy ion collisions.We include the nuclear medium effect on kaon and pion in the model, and simulate pion production and kaon subthreshold production process in heavy ion collisions at 1 GeV/nucleon.The calculated results show that the attractive pion optical potential changes the final pion momentum spectrum,increasing transverse momentum spectrum at the low momentum region.At the same time it also apparently enhances kaon abundance and modifies kaon momentum distribution.It illustrates that both kaon and pion final state dynamic processes should be considered in order to make a reasonable comment on the signals in heavy ion collisions.
Relativistic mean field theory in the rotating frame is used to describe superdeformed nuclei. Nuclear currents and the resulting spatial components of the vector meson fields are fully taken into account.It is shown that the filling of specific orbitals can lead to bands with deexcitation γ-ray energies differing by at most a few keV in nuclei with two mass units difference.The results is in a good agreement with the recent experimental data over a range of angular momenta.
The well known axial rotor plus quasiparticle model for odd nuclei is generalized to odd-odd nuclei.The proton-neutron interactions are considered in the base-space of the model for the first time.The method presented in this paper is used for several realistic nuclei in A=160 area.The results agree with experimental data qualitatively.A possible mechanism for Signature inversion of odd-odd nuclei is also discussed.
Technical specifications of Beam-line 4W1C and X-ray diffuse scattering station at Beijing Synchrotron Radiation Facility(BSRF)were discussed. Double focussed monochromatic X-ray beam,with energy resolution of 4.4×10－4 and beam spot of 0.5mm(H)×0.3mm(V),was obtained with a bent crystal mdnochromator shaped in triangular and a cylindric mirror.Nonspecular X-ray scattering from quasiperiodic amorphous multilayer was studied.The scattering maximums formed intensity streaks in the reciprocal space having the quasiperiodic character.Intensity modulations were observed and simulations based on atomic scattering gave satisfactory results.
According to the principle of"uniform magnetization",the 3-dimensional magnetic fields of the permanent magnet linear peridic system─hybrid insenion devices are analysed.The approximate analytical expressions of 3-dimensions are given.By applying these expressions,the magnetic field distributions in 3-dimensions of hybrid insertion devices can be calculated,and the calculation error is about 5%.This method conduces to design and optimization of the permanent magnet insertion devices.
Based on our Month Carlo Calculation model of heavy ion track structure,the radial dose distribution around an energetic heavy ion path and the maximum radial effect range in the liquid water are calculated.The results are compared with the experiments and other δ-ray theoretical calculation.This is useful for obtaiaing the relations between lesion intensity and range of cells and heavy ion parameters,and the biological effect mechanisms of heavy ion irradiation.
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