2005 Vol. 29, No. 7
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In a 16ΛO γ-ray spectroscopy experiment with HYPERBALL, two γ-ray transitions from the 6.6MeV excited 1－2 state to both ground-states spin-doublet members 1－1 and 0－ have been observed. The measured ground-state doublet spacing is 26.4 ± 1.6(stat) ± 0.5(syst)keV. Thus a small but nonzero strength of the tensor interaction between a Λ and a nucleon is deduced to be T=+0.03MeV. The excitation energy of the 1－2 state is also determined to be 6561.7 ± 1.1(stat) ± 1.7(syst) keV.
Within the framework of the Brueckner-Hartree-Fock approach, the effects of a microscopic nuclear three-body force on the critical density for kaon condensation in neutron star matter and on the composition of the kaon condensed phase have been investigated. The nuclear three-body force turns out to affect considerably both the critical density for kaon condensation and the composition of the kaon condensed phase in neutron stars via its strongly effect on the high-density behavior of nuclear symmetry energy. It is shown that inclusion of the three-body force contribution in the symmetry energy leads to a reduction of the critical density for kaon condensation and the three-body force effect on the critical density decreases as the proton strangeness content increases. The kaon condensed phase of neutron star matter turns out to be proton-rich instead of neutron-rich. The three-body force contribution results in a significant reduction of the proton and kaon fractions in the kaon condensed phase and makes the condensed neutron star matter to be more symmetric in neutrons and protons as compared with the results without including the three-body force. Our results are also compared with other theoretical predictions and discussed in connection with the possible implications for the study of neutron star structure.
Using algebraic dynamics, the Landau system in a rotating magnetic field has been solved and the general geometric phase is calculated. The classical correspondence between the quantum geometric phase and Hannay angle related to gauge potentials is established. The relation between nonadiabaticity and nonperiodicity is investigated numerically.
Cross sections for (n,2n) reactions are measured on chromium isotopes at the neutron energies of 13.5—14.6MeV using the activation technique. The data of the cross sections are reported for the following reactions: 50Cr (n,2n)49 Cr and 52Cr (n,2n)51 Cr. The cross sections of 50Cr (n,2n)49 Cr reaction are 3.4±0.2,6.8±0.3,21.5±1.0 and 25.0±1.2mb at the neutron energies of 13.5±0.3 ,14.1±0.2,14.4±0.3 and 14.6±0.3MeV incident neutron energies,respectively.The cross sections of 185±10,193±9,258±13 and 332±16mb for 52Cr (n,2n)51 Cr reaction are given at the neutron energies of 13.5±0.3 ,14.1±0.2,14.4±0.3 and 14.6±0.3MeV,respectively.The samples wrapped in cadmium foil are irradiated in order to avoid the effect of 50Cr (n, g)51Cr reaction induced by thermal neutron to 52Cr (n,2n)51Cr reaction,and the measured results are compared with published data. Neutron energies are determined by the method of cross-section ratios of 90Zr(n,2n) 89m+gZr and 93 Nb(n,2n) 92mNb reactions, and the neutron fluencies are determined using the monitor reaction 93 Nb(n,2n) 92mNb.
The reactor neutron cross-section for 181Hf (n,γ) 182Hf reaction has been measured with the activation method at the heavy water research reactor of China Institute of Atomic Energy. Thermal ionization mass spectrometry was used to determine the 182Hf/180Hf and 181Hf/180Hf atom ratios of the irradiated sample. The reactor neutron cross-section for 181Hf (n,γ) 182Hf reaction is 80.0±5.6 b, given by 14.80±0.60 b for the 180Hf (n,γ) 181Hf reaction as a reference.
One-dimensional time-dependent classical harmonic oscillator is a nonautonomous system with an SU(1,1) dynamical symmetry. By means of algebraic dynamics method, we have obtained its exact solution for the first time. As the time-dependent stiffness of the harmonic oscillator assumes some elementary functions, such as power functions, trigonal functions, exponential functions etc., the exact solutions become analytic. The recently proposed "analytic approximation solution" is proved to be a good approximation to the corresponding analytic solution under some conditions.
We calculate the energy spectra and eigenfunctions of nucleons in a constant magnetic field. Concrete solutions of the Dirac equation including the anomalous magnetic moment (AMM) of nucleons are provided in the chiral representation. They are then used to investigate the equation of state (EOS) and particle ratios on the inner shell layer of neutron stars. The results show that the magnetic energy of strong field will increase the inner shell layer of neutron stars,but the matter remains to be a neutron-rich matter. It is found that the AMM has evident effects on the proton polarization.
This paper is based on a suggestion by Franco and Yin that the phase of the ucleon-nucleon scattering amplitude should vary with momentum transfer .The intermediate energy proton elastic scattering on 4He is studied applying the KMT multiple scattering theory with microscopic moenteum space optical potential.The results show that the phase leads to differential cross section and polarization are in better agreement with experimental data.
In the framework of the resonating group method, the non-local YN interaction and Λ-core interaction in the chiral SU(3) quark model are obtained, and the binding energies BΛof light hypernuclei 5ΛHe ,4ΛHe and 4ΛH are calculated. It is shown that the chiral SU(3) quark model can well-describe not only the ΛN scattering but also the binding energies of light hypernuclei. The resultant binding energies BΛ of light hypernuclei by using the non-local YN interaction in terms of the resonating group method are more accurate than those by using the non-local YN interaction in terms of the resonating groupmethod are more accurate than those by using the generator coordinate method. As aresult,a set of model parameters is more accurately determined for the future hypernucleus and multi-quark system studies.
Systematic calculations on spontaneous fission half-lives of heavy nuclei are carried out by Swiatecki's formula with renewed parameters and by its generalized form. A new formula with only four parameters is also proposed for spontaneous fission half-lives.Experimental half-lives are well reproduced by the three formulae. We have found from systematics of available data that there is a long lifetime line of spontaneous fission N=Z+52 for heavy elements with Z≥90. The new formula can be used to predict the spontaneous fission half-lives of heavy nuclei not far away from this long lifetime line.
A multi-ring semiconductor detector has been developed for the measurement of the angular distributions of nuclear reactions induced by secondary ion beams in inverse kinematics. The advantages of the multi-ring detector are generally discussed and the manufacturing procedure is presented. The detector has 11 independent rings formed in a φ100 mm silicon wafer with the thickness of 300μm. Aφ7 mm hole is cut in the center in order to avoid recording the beam at 0°directly. The active area and the energy resolution of each ring are typically 450 mm2 and 32 keV in FWHM (5.156 MeV αparticles), respectively. The detector is used in the angular distribution measurement of 11C(d,n)12N reaction and the performance is briefly described.
A cosmic-ray testing station (CORTS) in laboratory has been installed, and the performance of a prototype of CMS RE1/2 RPC was tested. The RPC's efficiency is about 85%, the time resolution is 0.87±0.08ns, and the spatial resolution is 1.5 times the width of read-out strip, which are in consistent with the results obtained using the muon beam at CERN. The comparison makes clear that cosmic-ray test can provide reliably the basic parameters which describe the RPC performance.
We presented in this paper the calculating method of the energy response matrix of the detectors of the Hard X-ray Modulation Telescope, with both laboratory measurements and simulations. Using this matrix and the direct demodulation technique we have successfully restored the spectra of the radioactive sources from data collected in the laboratory. This shows that the energy response matrix is reliable.
The Combined Scintillator Detection System is compsed of Pb fiter leaf and plastic sintillator detector. Using direct current scale, the neutron sensitivity of detecion system composed of Pb fiter leaf and ST401, ST1422 and ST1423 detector,respectively has been studied at the neutron energy 0.565 MeV, 1.20 MeV, 2.50 MeV, 3.50 MeV, 5.00 MeV and 14.16 MeV. From the experiment results we get the relation of the detector's sensitivity and the thickness of Pb fiter leaf, the thickness of scintillator, and the neutrons energy. By the experiment and calculation the neutron energy response of three kinds of combined scintillator detection system is obtained.
With the Lie algebraic methods, the charged particle trajectories in electrostatic analyzers are analyzed,and the third order solutions obtained. In this paper, we briefly describe the Lie algebraic methods and the procedures of calculating the nonlinear orbits. The procedures are: first, set up the Hamiltonian; then expand the Hamiltonian into a sum of homogeneous polynomials of different degrees; next, calculate the Lie map associating to the Hamiltonian; finally, apply the Lie map on the particle initial coordinates in the phase space, and obtain the particle nonlinear trajectories of the first order,the second order, and the third order approximations respectively. Higher orders solutions could be obtained if needed.
A multi-cell thermionic RF gun injector based on X-band(11.43GHz) Disk-and-Washer(DAW) accelerating structure has been developed. The influence to the RF characteristic of the washer supports and the mode overlap problem of DAW structure are analysed in this paper. Becaus DAW accelerating structure has a large coupling coefficient and the next nearest neighbour coupling can't be ignored, a special tuning method was developed. The results of dynamic simulation of this injector are given. Simulation shows the gun can accelerate electron beams of 40mA to 5—6MeV, with an emittance of 3.4π.mm.mrad. Manufacture and brazing of the RF gun have been finished, and the cold test results of it are also presented.
This paper present the structural design and functional analysis of a new kind of 1.2MeV industrial electron accelerator. PIC(Particle-In-Cell) method is used to simulate this accelerator and to optimize the desing, the results show that the optics property of this accelerator has been improved. This electron accelerator is used for desulfuration and denitrogenation in environmental industry.This application purifies flue gases of the thermal power station from Sulphurous oxide and Nitrogen oxide in order to reduce the pollution in the air.
The biological equivalent dose of the heavy ion treatment planning and the calculation of the relative biological effectiveness based on the Local Effect Model are briefed in the first part. Then the experimental results tested with biological system are reported and compared with the calculated results. The overall agreement in the target region as well as outside the target show the reliability and the ability of sparing critical structures close to the target of the heavy ion treatment planning.
High resolution scattergrams of China map profile are etched on the CR-39 film within a small area of hundreds of microns×hundreds of microns by the AS-LIBB single proton microbeam, according to the coordinates of the standard images, which are acquired by the home-developed image-processing program. The testing results show that the single particle detection efficiency for this facility is over 98%, and the target-positioning accuracy is within 3mm. Moreover, the near-path traversing algorithm for stage control is optimal for irradiating scattergrams of picture profile, and the dots on CR-39 film for the measured results and the expected values are quite identical. Therefore, this single particle irradiation system meets to the demands of etching micron-dimensional pictures on CR-39 film in dot manner with single particles and the needs of the biological cell irradiation experiments.
Monte Carlo Hamiltonian (MCH) method is applied to the study of the non S states in the quantum mechanical system with inverse potential, and the hydrogen system is taken as an example. The validity and efficiency of MCH is verified. New suggestion for computing the statistical errors is provided. The spectrum and reduced wave functions are consistent with the analytic results.
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