2005 Vol. 29, No. 5
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RIKEN has produced the new element Z=113 by cold-fusion reaction. Here we systematically study the new nuclide 278113 and its α-Decay chain using deformed relativistic mean-field theory with three sets of force parameters,TMA,NL-Z2 and NL3.The results are compared with those of the Skyrme-Hartree-Fock model, Moller et al and also with the new experimental data. The experimental decay energies are well reproduced with RMF.This not only shows the alidity of self-consistent field theoretical model in researching the ground state properties of superheavy nuclei, but also shows that prolate deformation is important for the ground state of these nuclei.
The coupling Schrodinger equations describing the evolution of c`c states in nuclear matter are analytically and systematically solved via perturbation method，and the correlation between charmonium formation and nuclear absorption is investigated. After calculating J/ψ and ψ′suppression in nucleon-nucleus collisions and comparing with experiment data, it is found that the formation time effect plays an important rule in charmonium suppression, especially in ψ′suppression.
Using the improved lattice gauge field Hamiltonian and the truncated eigenvalue equation method, we compute the 0++ glueball wave function of three-dimensional U(1) lattice gauge theory up to the 3rd order. The scaling behavior of the 3rd order result is much better than the one of the 2nd order result.
The experimental set-up, methods and results on the synthesis and identification of the new isotope 265 107Bh are presented in this paper. The new isotope was produced by the complete fusion-evaporation reaction of 243Am with 168MeV 26Mg at the Sector Focus Cyclotron of Heavy Ion Research Facility Lanzhou. The reaction products were transported and collected using helium-jet technique and a set of rotating wheel system. The identification of the new isotope was made by observing of correlated a-particle decays chain between the new isotope 265Bh and its 261Db and 257Lr daughters. A total of 8 correlated decay events of 265Bh and 4 decay events of 264Bh were observed. The new nuclide 265Bh has a half-life of 0.94+0.70 -0.31s and decays by alpha-particle emission with decay energy of Ea=(9.24±0.05)MeV. The half-life and a decay energy of 265Bh from this experiment are consistent with theoretical predictions.
We insert the isospin degree of freedom into the momentum dependent interaction to obtain an isospin and momentum dependent interaction given in a form practically usable in isospin dependent quantum molecular dynamics model. We investigate the isospin effect of momentum dependent interaction on the observable in the intermediate energy heavy ion collisions. It is found that momentum dependent interaction with and without isospin dependence, lead to significant different predictions on the nuclear stopping (momentum dissipation) and isospin fractionation ratio. In particular the momentum dependent interaction with the isospin degree of freedom induces the reductions for the strong dependence of nuclear stopping on the two-body collisions and the sensitive dependence of isospin fractionation ratio on the symmetry potential. However it does not change obviously above features for the nuclear stopping and isospin fractionation ratio as the good probe of in-medium nucleon nucleon cross section and symmetry potential respectively. The isospin dependence of momentum dependent interaction is thus important for studying accurately the equation of state of isospin asymmetry nuclear matter.
The overlapping cylinder model (OCM) is used in this letter to describe the rapidity (or pseudorapidity) distributions of charged particles produced in nucleus-nucleus collisions at high energies. For the fixed target experiments at present accelerator energies, the same relative strengths of longitudinal flows are observed and two completely overlapping cylinders can give a description of the experimental data. A stronger longitudinal flow is observed and two partly overlapping cylinders are needed at higher energy (above 4A TeV). The (pseudo)rapidity distributions calculated by the overlapping cylinder model are in agreement with the available experimental data.
We examine the two-pion Hanbury-Brown-Twiss (HBT) interferometry for the expanding sources of quark-gluon plasma evolution with the Bjorken cylinder geometry.The two-pion HBT correlation functions are calculated using quantum probability amplitudes in a path-integral formalism and the HBT radius is extracted both for the expanding source and the static source.We find that the HBT radius for the freeze-out emission case is substantially greater than that for the without absorption of multiple scattering case. The expanding velocity of the source leads to a smaller HBT radius. The effect of expanding velocity for the Bjorken cylinder source with zero width of the transition temperature is smaller than those of the corresponding spherical source.
The statistical property is studied for the resonance matter produced in relativistic heavy-ion collision. The relation between chemical potential of the resonant particle and net particle density is discussed. The total particle density and the energy density are calculated, and the relations between these densities and the net baryon density are analyzed. The ratio of the total particle density to the normal nuclear density(0.16fm)is estimated. It is about 5－8 in RHIC energy region and 3－6 in the SPS energy region. Finally, the character of the hadronic component at different regions is studied. It is found that in three temperature regions which correspond to the AGS, SPS and RHIC energy region, respectively, the main hadronic component is baryon, strange particle and meson, respectively.
Design of cell structure and layer arrangement of the BESⅢ drift chamber are presented. The effect of stereo angles and the layers at axial-stereo boundaries on the drift-time-to-distance relation are discussed. In addition, the optimization of layer radius is performed based on the drift-time-to-distance relation.
Using a proportional tube, the gas gain of the helium-based gas mixture He/C3H8(60/40) was measured with 55Fe 5.9keV X-ray source as a function of the anode wire high voltage, gas temperature, gas pressure and gas mixture ratio. The gas mixtures of He/CH4(60/40) and Ar/CO2/CH4(89/10/1) were also tested for comparison.
The lateral distributions, as measured by ARGO array, of the extensive air showers induced by γ and hadrons with energy range from 100GeV to 10 TeV, zenith angle from 0° to 45°, were studied using Monte Carlo generated data. Several parameters such as average lateral distribution, minimum tree length and so on, which could be used to the difference of the lateral distributions between the showers induced by γ and hadrons were obtained. These parameters were used as the input for an artificial neural network, which was then trained to study the γ/hadron discrimination power. The result indicated that using this method could effectively separate the showers induced by γ-rays and hadrons.
The measurement method and principle of dipole magnet reproducibility for Cooling-storage-ring are introduced. How the position and number of steel sheet affect the reproducibility of magnet is investigated. In the end, the reproducibility of CSRm dipoles reaches to less than ±2×10-4, which can meet the acquirements of CSR. In addition, the measurement repeatability and the sources causing errors are also analyzed.
The TESLA positron injector linac with an L-band TW normal conducting structure has been studied, which offers both higher shunt impedance and larger aperture. Main parameters of this injector linac have been designed by systematical beam modeling, and a satisfactory positron beam transmission and the beam performance at the output of the injector linac have been obtained.
Plasma could be produced when intense electron beams striking on converter target materials, such as Ta. The beam space charge may draw an ion current out of the plasma, which could substantially affect the final focus of beam on the target. This is called backstreaming ions effect. Since focus-spot is a key point for good radiography in X-ray machine research, the backstreaming ions effect gets much concerns. Based on our analyses, it is believed that generally the backstreaming ions are mainly from thermal desorption of contaminant on the Ta target surface. The ion emission is restricted by the space-charge effect, not by the ions source power.
E5-4 experimental electron gun system is the improved version of BEPC gun system. Firstly,some theoretical analyses on E5-4 gun are performed.Beam testing result is then introduced. The test is based on Y796 cathode-grid assembly, new power supply system and new pulser system. Impacts of different parameters on beam current are analyzed. This experimental electron gun system has performed an important directive role on the research and manufacturing of BEPCII electron gun system
A 4-rod RFQ cavity was simulated with MAFIA code for the design of a high current, high duty factor RFQ accelerator. The influence of distance, wide, height and shape of stems on the cavity's RF property were studied. The structure parameters of the RFQ cavity were optimized by the requirements of the shunt impedance and the electromagnetic field distribution in the RFQ accelerator. Based on the simulation result, then a cold cavity model was built, measured and the result was compared with the simulation.
Measurement of electron bunch length through its generated coherent diffraction radiation (CDR) via optical autocorrelation is a new non-intercepting frequency domain diagnostics technique developed in accelerator fields recently. In this paper, the CDR emitted by femto-second electron bunches provided by the SINAP linac are analyzed and numerically calculated, experimental designs on CDR generation and bunch length measurement are presented, and the beam splitter affected interferogram is simulated. As a result, broad band continuous and high intensity CDR covering a range from far-infrared to mm-wave region can be obtained by directly using these bunches. CDR energy is mainly concentrated near the beam axis and can be up to several millijoules for Gaussian bunches. We use a far-infrared Michelson interferometer and a Golay detector to measure the autocorrelation interferogram of CDR, considering the interference effects caused by the beam splitter, the electron bunch length can be easily obtained, from which one can derive its electron density distribution.
The effects of hydrogen plasma treatment on He-implantation-induced cavities in silicon during subsequent annealing were studied.Silicon samples were first implanted at room temperature with He ions of different energies (40,160 and 1550keV) at the same dose of 5×1016cm-2,and then were exposed to high density ECR hydrogen plasma for 30 min at temperature of 250°C.XTEM was applied to study the formation of cavities after an annealing at 800°C for 1h. The results clearly show that the effects of plasma hydrogenation on thermal growth of cavities depend strongly on the He ion energy. No effects were clearly seen in 40 keV He-implantation-induced cavities and a slightly effects were observed in that of 1550 keV He implantation. However,in the case of 160 keV He implantation,additional H plasma treatment could assist the growth of cavities. Further analyses show that the effects were possibly related to the role of hydrogen introduced by plasma hydrogenation.
This paper derived the formulation of the real efficient emission coefficient secondary electron under the condition that high energy primary electron incident on metal obliquely .It shows that the coefficient is reversely proportional to the cosine of the incident angle
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