1987 Vol. 11, No. 1
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The method and arrangement determining the energy spectrum of primary cosmic rays by measuring the Cerenkov radiation were described. The integral power index γ=1.80±0.11 of energy spectrum of primary cosmic rays wa measured at the energy range of 2.9×1014－4.0×1015eV.
In this paper the structure and the induced readout characteristics of a new type of plastic streamer tube is introduced. The relation between charge distribution spectra and high voltage on the induced strips and the charge distribution on the adjacent strips have been studied. The spatial resolution has also been measured and calculated. It is pointed out that the two peak effect in the distribution spectra is caused by the nearer and farther streamers from two sides of anode wire to strips. At last, some preliminary results of the induced pads as a readout mode are reported.
This paper presents the characteristics, structure and parameters of the permanent magnet quadrupole lenses which have been used as a beam transport element in our linac. The methods of connection and adjustment are discussed. After transporting 15MeV electron beams by 43cm, a improvement of 50%—80% of the primary beam profile was obtained.
An array of 9 BGO crystals of 20×20×200mm3 equipped with photomultiplier readout was assembled and tested. Radioactive γ and neutron sources, (p,γ) reactions by low energy protons from Van de Graaff accelerator and (n,γ) reactions by thermal neutrons from nuclear reactor were employed to produce photons in the energy range from 0.5 to 21MeV. The energy response of the array is shown to be linear over the whole range. Data on the energy resolution follow an E1/2 dependence at low energies, and deviate from it at 4.43MeV and higher energies. Results from the lateral energy deposition of showers were compared with the predictions of the Monte Carlo simulation and found to be in good agreement. Our study demonstrates the feasibility of calibration and monitoring of BGO electromagnetic calorimeter by means of radioactive sources and low energy (p,γ) reactions.
In this paper, the coulomb disintegration cross-section and decay rate of the atom (π+Ω－) are calculated by using perturbation expansion of the quantized composite field theory and relativistic B-S wave function for spin (0－3/2) electromagnetic bound system. The disintegration cross-section of the high energy atom (π+Ω－) in screened coulomb field of nuclei is about σ=Z4/3×2.9×10－18cm2, and the calculation result of the decay rate is w[(π+Ω－)→π+Λ0K－]/w[Ω－→Λ0K－]=1+O(α).
We derived a new formula for the mass plitting of N and Δ on the basis of the Skyrme model with the consideration of the soft pion effect. The results showed that the soft-pion fluctuation cannot be ignored in the evaluation of the ground state energy of some hadron like nuleon etc. The results obtained are better than that of Adkins et al. (1984).
The method developed by D.J.E.Callaway is applied to Ising model on a two-dimensional triangular lattice. A fixed point and critical exponent are found. The results are consistent with one of the exact theories very well. Obviously this method show superiority to that obtained by some other approximate methods. The method is also applied to Z2 gauge theory on a 2-dimensional triangular lattice, no fixed points are found, in agreement with other methods.
The mechanism of high-energy A'－A collision (A>A',A'1/3>>1) and the space-time evolution of the fluid formed in the collision are analysed. The corresponding 1+1 dimensional hydrodynamical equations are established. The average rapidity distributions are estimated and compared with some cosmic ray events. The origin of the nonsymmetry of rapidity distribution is explained.
We have performed an experimental study of the α-fragments emitted from collisions between emulsion nuclei and heavy-ion projectiles at beam energies beyond 1A GeV. It is shown that the transverse momentum distributions of relativistic α-particles give evidence for two effective temperatures emission in high-energy heavy-ion collisions. The data might take on a new signature for the phase transition from hadron matter to quark matter.
In this paper, the descending equations of cochains defined on simplexes are generalized to the general chains. We have also explained geometrically in some detail that the topological non-trivialness of physical quantities can descend from higher dimension to lower dimension through the surface term.
Using cumulant expansion method, we obtain gloun condensation for pure SU (2) gauge theory analytically.
In the framework of relativistic Dirac's equation, a fermion elastic scattering from a nucleus has been discussed. The cross sections, analyzing power and spinrotation parameters for 500MeV proton scattered from He4,Ca40,48 and Pb208 have been calculated in the eikonal approximation. The agreement between theoretical and experimental results is satifactory.
In the framework of the eikonal theory and using the first order π-nucleus optical potential, the elastic and inelastic scatterings of π± from well-deformed nuclei are discussed. The virtual excitations to the low-lying levels are taken into account in the calculations of the elastic scatterings by using the closure approximation. The theoretical results of pion scatterings from 152Sm at Tπ=180MeV are compared with the data.
The special design and the technique of developing the 10MeV Beijing proton linac to 35MeV are described. The performance level of major components and the beam test results of whole machine are presented.
Energy spectra and angular distributions of the particles emitted from 12C+64Ni reaction at eight energies in the region of 36.5MeV—69.4MeV are measured. The angular distributions of α particles change from forward peaked one to that peaked near by the grazing angle with decreasing incident energy. This result show that the emission mechanism of non-evaporation α particle is different in different energy regions.
The angular distributions of fission fragments are measured for systems of 120MeV 14N+118Sn with mica track detectors and gold-surfacebarrier silicon detectors. The measured angular distributions can be fitted by the standard theory of fission angular distributions on the basis of statistical model. The effective moments of inertia of fissioning nuclei at saddle point are derived from angular distribution anisotropies. The shapes of saddle point of fissioning nuclei in the region of Z2/A<30 are discussed.
In the coincidence measurement between α-particles and projectile-like fragments in the reaction of 82.7MeV 16O on 27Al,the contour plot of the C-α coincidence in the velocity plane and the coincident angular correlation are obtained. Different mechanisms of α-particle emission are analysed. A possible reaction mechanism of incomplete DIC is descussed.
The continuous variable representation and the geometrical interpretation of the Elliott SU(3) model are given by virtue of the generator coordinate method. It is pointed out that the carrier subspace of collective states of the dynamical group SU(3) in the Elliott model is spanned by the β and γ vibration states as well as the rotation states.
The features of d-d and d-3H equivalent local potentials are studied by using single channel RGM and two-channel RGM, respectively. The results show that those equivalent potentials have energy and state dependences (containing odd-even l-dependence and s-dependence), which are useful in choosing the phenomenological optical model parameters of light nuclei.
A systematic analysis on the νi13/2 pair in the even Pt isotopes has been carefully done. Comparisons between the experimental data and Nilsson cranked model results with different parameters κ,μ show. 1)An improved κ,μ set, which can nicely fit the 185Au data, seems also applicable in Pt isotopes too. 2)The νi13/2 alignment only could not explain the big up-bend phenomenon in 184Pt,πh9/2 alignment must be taken into considevation as well. 3) Deviations between experimental data and theoretical calculations indicate that dimensional potential energy surface calculation of ε2, ε4 and γ, is needed.
The mechanism of the formation of the band 2 in nuclei 156Er and 158Er has been discussed in the framwork of VMI model.
In the paper we give a new transformation in the reduced gravity, which is associated with the Virasoro algebra without the center term. To compare with the Geroch group it is easy to establish the relationship between the Virasoro algebra and the Kac-Moody algebra in the theory of the reduced gravity. Then we point out that the transformation can be adopted to generated the new solutions of the Ernst equation from the old ones.
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