1981 Vol. 5, No. 5
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A picture of the tribaryon system is proposed based on the papers [1—3]. It is considered that proton, neutron and A hyperon from the basic particles of SU(3) group and form the basic particles of SU(6) group on account for spin. It turns out that there exist "unitary energy band" structure in the tribaryon system. From the mass formula of T33 breaking, one can find that the SU(6) symmetry gives the mass relations between different spin levels of the same strangeness analog states. Finally, simple calculations are made and tbere is no discrepancy between tbe results and the experimental data.
An α particle model of light nuclei is proposed. The physical picture of the model is clear, its wave functions are simpler and convenient for some applications. When it is used in the problems of multiple scattering, each term in the series of the multiple scattering expansion can be integrated out analytically. The experiments of elastic electron scattering can be well fited by using the model wave functions. The investigations of the model indicate that the usual rigid a particle model is the classical homologue of our model.
A relativistic equation of motion for many-body system is established. The relativistic potential is a certain rearrangement of the irreducible series of many-body B-S equation. Considering the two-body irreducible B-S kernels only the many-body potential is expressed as a sum of two-body ones.
Using the definition of irreducible tensor operators of the Lie group SU(n), we ive a method of calculating the irreducible representations of the graded Lie algebra U(m/n). We also give some simple examples of irreducible representations of U(3/2) and SU(m/n).
The dependence of parallel plate spark chamber efficiency on pressure, gap widths and applied voltage has been studied in the pressure range 200—700 mm Hg of neon. The dependence of the threshold voltage on pressure, gap widths has also been studied in the same range. It is shown that the efficiency increases when the product of pressure P and gap with d and voltage increase, and the threshold voltage of the spark chamber follows Paschen's Law.
We have designed and operated a test module of multistep avalanche chamber with effective detection area of 9 by 9 cm2. Argon-acetone mixture gas is provided by a simple gas mixing system, and mixture ratio can be modulated by gas flow. The performance of the chamber has been investigated by use of 55Fe 5.9 keV X-ray source at acetone concentration in argon of 2.7％, and the effect of acetone concentration to the chamber has been measured.
A scintillation counter array localization system, i.e, scintillation counter hodoscope, was studied and made for selecting events and triggering the streamer chamber in 1980. With this facility the penetrating position of the charged particles can be determined and it can be used as a trigger counter too. As soon as the charged particles penetrated this array and other scintillation telescope, the generated coincidence signal triggers the control system of the streamer chamber with the time delay 74 ns.On the other hand, this system also has a ability of selecting charged particle number penetrating the counter array, thus, the streamer chamber is able to record the event with certain multiplicity.This hodoscope contains a 8×8 scintillation counter array. Each plastic scintillator (type ST401) has the dimensions of 40×5×0.6 cm3 and the type of photomultipliers used is GDB50. The array area is 40×40 cm2.The fast electronics and data handling system were made by ourselves. The whole system works well during the test with the on-line microcomputer TRS-80 and is not expensive.
Two large area plastic scintillation counters (50cm×50cm and 50cm×100cm, 0.5cm thick) have been built with the scintillator type ST-401 made in China. The characteristic parameters of the counters, such as the attenuation length and the detection efficiency have been measured. The results show that the quality of the counters is desirable and that they can be used as trigger counters in experiments of high energy physics.
By using the time aepenaent projection operator to the intrinsic aegreea or freedom, the general theoretical framework of the coupling equations of the relative motion in classical limit, oscillective oscillations and single particle excitations are formulated. For a coupling system simultenously involving the degrees of freedom of the relative motion and the intrinsic excitations (including collective oscillations and single particle excitations). In the first order Born approximation and the random phase approximation of the matrix element of the interaction between phonons and single particle (neglecting the higher terms of the interactions between relative and the phonons, single particle.) the simple coupling equations, which are physically clear and easy for computations, are obtained.These theoretical formulations are expected to be useful for the descriptions of the transport process for the inelastic collision between heavy ions as well as nuclear fission.
Isomeric cross section ratio for the 197Au (n, 2n) reaction at 15 MeV is measured by the activation method. Using the Huizenga and Vandenbosch method, the isomeric ratio is calculated for the reaction. From the comparison of the measured and theoretically calculated isomeric ratio, the values of the spin cut-off factor and nuclear moment of inertia are determined.
Angular distribution of the scattering of 31.2 MeV-α-particle by the nucleus 10,11B is measured. Our results show that there is anomalous phenomenon in the case of 10B but there is not in 11B. Calculations and analysis are made with the optical model adding the Regge-Pole model. The results show that for the nucleus of 1p-shell, such as α+16O, the result of the calculation agrees very well with the experimental measurements but it fails in α+10B. As to the analysis with the double v-power optieal model for α+16O, the agreement is somewhat a little worse than the former's and the result for α+10B agrees only qualitatively with the experimental measurement. It is well known that the analysis with these models for α+40Ca agrees very well with the experimental data. Thus we may come to the conclusion that the mechanism of ALAS of the nucleus of 2s-1d shell is different from that of 1p-shell, and the mechanisms of ALAS of the nuclei of 1p-shell are also different.
Using the square of W-S potential as the real part of optic potential instead of normal W-S potential, we improve the theoretical calculation for the differential cross sections of elastic scattering and single proton transfer reaction. It turns out that the improved theoretical result fit the data better than before.
The beta decay energies (Wapstra and Bos, 1977) of about 1,000 isobaric nuclei (10≤A≤253) are carefully analyzed. Weighted least squares method is used to determine the parameters of the mass parabola——the location of the moat β-stable nuclei Z0, the curvature parameter b and even-add mass difference △E. Several mass formulae are compared with the resultes of the present paper.
According to the principle of the "uniform magnetization" and harmonic analytic method, the fields of the ring structure system with multi-segmented and trapezoidal magnet are analysed. The 3-dimensional expression of the field at any point of the space is given, and the 2-dimensional expression of the fundamental component of multipole, harmonic and leakage field is also given.The comparisons between the property of segmental and trapezoidal magnet are discussed.
The initial photon energy 14.4 keV and the energy of the survival photons passed through a medium were measured with a γ ray spectrometer composed of a recoilless nuclear γ ray source and a nuclear resonant absorber. The peak positions of the γ ray spectrum lines of these two measurements were compared and the energy change of the photon was determined. The experimental results show that for a 0.4g/cm2. Al absorber two peak positions coincide with each other within the accuracy of 3×10-10 eV.
A small MSAC, with effective area 7.4×8cm2, has been designed, build and tested. Each grid wire is insolated with others. Energy resolution of the PA gap for X-ray detection is about 19% (FWHM) at 5.9 keV. Avalanche mechanism has been discussed.
The energy spectra of the alpha particles from the reaction 141Pr (n, α) 138La at 0°, 30°, 60°, 120°, 150° and 180° are measured and the angular distributions of the alpha particles are given. It shows that the predominant mechanism of the reaction at En=14 MeV is precompound emission.
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