2005 Vol. 29, No. 8

Particle and field theory
Study on the Muon Backgroud in the Underground Laboratory of KIMS
ZHU Jing-Jun, KANG Ke-Jun, LI Yuan-Jing, LI Jin
2005, 29(8): 721-726.
KIMS is a group aiming at the search for WIMP. In WIMP search experiment, the muon is one important background. We measure the muon flux in Yangyang laboratory where is located at 700m underground. The structure and performance test of muon detector is described. The analysis on muon hit position and angle distribution has been performed. The simulations of muon flux have been done. The muon flux in the laboratory is found to be about (7.0±0.4)×10-8/s/cm2/sr.
Normalization Constants of the Twist-3 Distribution Amplitudes of the Pion and Kaon From the QCD Sum Rules
WU Xing-Hua, ZHOU Ming-Zhen, HUANG Tao
2005, 29(8): 727-730.
In this paper we calculate the normalization constants m_{0π}^p and m_{0K}^p of the twist-3 distribution amplitudes of the pion and kaon from the QCD sum rules,instead of using the equations of motion. We find that m_{0π}^p=1.00±0.17GeV and m_{0K}^p=1.46±0.23 GeV after including αs corrections to the perturbative part of the sum rules. They are close to the phenomenological values. For the pion case, this shows that the value obtained in QCD sum rules is only 50% of that determined by the equation of motion.
Green Function Solution to the Doublet Potential Equations of the Moving Dyons
LI Kang, WANG Jian-Hua
2005, 29(8): 731-735.
After reviewing the doublet 4 dimensional potentials of the electromagnetic field theory in the presence of magnetic charge (or effective magnetic charge), we give out the electromagnetic (EM) duality symmetric Maxwell equation and the relationship between the field strength and the doublet potentials, then using the Green’s function method we find the Lorentz invariant retarded solutions to the field equations, at last, we obtain the explicit expression of the generalized Lienard-Wiechert potentials.
Nuclear and ion Physics
Experimental Study of High-Spin Band Structures of 183Au
SONG Li-Tao, ZHOU Xiao-Hong, ZHANG Yu-Hu, GUO Ying-Xiang, LEI Xiang-Guo, ZHENG Yong, LIU Min-Liang, de Angelis
2005, 29(8): 736-740.
High-spin states in 183Au have been studied experimentally using heavy-ion-induced fusion-evaporation reaction and standard in-beam γ-ray spectroscopic techniques. The level scheme of 183Au was revised and extended. A rotational band proposed as the unfavored signature branch of the πi13/2 band has been observed for the first time. Interaction properties between the two negative-signature bands of the πh9/2-πf7/2 system have been discussed for the light odd-A Au nuclei.
A General Formula Used to Deduct the Effect of Excited State to Base State Was Deduced in Measurement of Cross Section of Nuclear Reaction
ZHOU Feng-Qun, LUO Jun-Hua, YI Yan-Ling, TUO Fei, KONG Xiang-Zhong
2005, 29(8): 741-744.
According to the regulation of growing and decay of artificial radioactive nuclide, a general formula used to deduct the effect of excited state to ground state was deduced. Therefore, the problem of effect of excited state to ground state was solved in the measurement of cross section of nuclear reaction.
Phenomenological Analysis of Energy Shifts and Widths of Kaonic Atoms
LIANG Chun-Tian, CAI Cong-Hai
2005, 29(8): 745-751.
We analyze kaonic atoms in terms of the phenomenological optical potential of Woods-Saxon form. By fitting data of kaonic atoms, we obtain an optimal set of optical potential parameters. Comparing this optical potential near surface of nucleus with other optical potentials obtained in some successful research works, we find that they are in rather good agreement with each other. On the other hand, the imaginary part of our potential between kaon and nucleus is similar to that between nucleon and nucleus, but the real part of the potential between kaon and nucleus is much deeper and narrower in radial distribution.
Energy Level Statistics of the SO(6) Limit of Super-Symmetry U(6/4)in the IBFM
BAI Hong-Bo, ZHANG Jin-Fu, ZHOU Xian-Rong
2005, 29(8): 752-756.
The energy levels of the SO(6) limit of super-symmetry U(6/4) belonging to odd-A nucleus are calculated with the interacting boson-fermion model. Its emphasis is to study the statistical properties of the nearest neighbor spacing distribution(NSD) and the spectral rigidity(△ ).And the factors that affect the properties of level statistics are also investigated. The calculated results indicate that the finite boson number N effect is prominent. When N has a value close to a realistic one, both the interaction strength of subgroup SOBF(5) and the spin play an important role in the energy level statistics. However, in the case of N close to infinite, the statistics all tend to be Poisson type.
Quark-Gluon Mixed Vacuum Condensates in Dyson-Schwinger Equations
ZHOU Li-Juan, MA Wei-Xing
2005, 29(8): 757-760.
Based on Dyson - Schwinger Equations of quark propagator, we calculate quark-gluon mixed vacuum condensates 〈0│:qgs σμνGμνq:│0〉and quark vacuum condensates 〈0│:qq:│0〉which are not only related to virtuality of quark in vacuum state but also characterizes the space width of quark distribution in the vacuum. The existence of these vacuum condensates reflects in a direct way the non-perturbative structure of QCD vacuum. Our calculated results on the mixed condensates lead to quark virtualities of λ2u,d=0.7GeV2 for u, d quarks, and 2s=1.6GeV2for s quark which are consistent with other's calculations used completely different methods.
Special Role of Neutron-Halo Structure in the Fragmentation Reactions
LIU Jian-Ye, GUO Wen-Jun, REN Zhong-Zhou, XING Yong-Zhong, ZUO Wei, LI Xi-Guo
2005, 29(8): 761-765.
Baced on the quantum molecular dynamics model the special role of neutron-Halo structure in the fragmentation reactions was studied. In order to compare and protrude the special roleof neuron halo structure 11Li in the fragmentation reactions we also studied the fragmentation reactions induced by the stable nucleus 11B with the same mass and the same incident channel condition. We found that the special neutron-halo structure of 11Li is beneficial for the fragmentation reactions in the lower energy region, compared to that induced by stable nucleus 11B. However the beneficial role of neutron-halo 11Li on the fragmentation reactions decreases up to be canceled as the increase of beam energy. The beneficial role of neutron-halo 11Li on the fragmention reactions also decreases as the increases of target mass and impact parameter.
Measures of Charge Fluctuation in Nucleonic and Nuclear Collisions
FENG Ao-Qi, WU Yuan-Fan
2005, 29(8): 766-769.
The dependencies of all suggested measures for charge fluctuation on the size of rapidity window are compared using the nucleonic and nuclear collision models—PYTHIA and RQMD. It is found that such dependency is model dependent. However, the charge correlations have the best measure for the effects of global charge conservation and short-range rapidity correlation and is therefore recommended.
Detection Technology and Methods
Irradiation Test of FPGA for BES-Ⅲ
CHEN Yi-Xin, LIANG Hao, XUE Jun-Dong, HOU Long, LIU Bao-Ying, LOU Qiang, YU Xiao-Qi, ZHOU You-Zhao
2005, 29(8): 770-774.
The irradiation effect of FPGA, applied in Front-end Electronics for experiments of High-Energy Physics, is a serious problem. The performance of FPGA, used in the front-end card of Muon Counters of BES-III project, needs to be evaluated under irradiation. SEUs on Altera ACEX 1K FPGA, observed in the experiment under the irradiation of γ ray, 14 and 2.5MeV neutrons, was investigated. We calculated involved cross-section and provided reasonable analysis and evaluation for the result of the experiment. The conclusion about feasibility of applying ACEX 1K FPGA in the front-end card of the readout system of Muon Counters for BES-III was given.
Beam Test of the Time Resolution of the BESⅢ Endcap TOF
AN Shao-Hui, WU Chong, LI Xin, CHEN Hong-Fang, HENG Yue-Kun, SUN Zhi-Jia, WANG Yi-Fang, LI Cheng
2005, 29(8): 775-780.
The Endcap TOF(ETOF)of Beijing Spectrometer(BESⅢ) consists of 2×48 pieces of trapezoidal scintillator (BC408). Its main physics goal is to reach the intrinsic time resolution of 80ps and to realize the 2σ π/k separation at momentum up to 1GeV/c. In this paper, the performance of one ETOF module under different conditions, such as with different packing material、operating voltage and shape of scintillator, is tested by the beam of 800MeV electrons at IHEP. The primary results show that the intrinsic time resolution of ETOF with Tyvek paper wrapping is between 70-90ps.
Using the Q of TOF to Identify the Particles
LIU Fang, HE Kang-Lin, SUN Sheng-Sen, YANG Fan, ZHENG Zhi-Peng, LI Jin
2005, 29(8): 781-786.
Time of flight counter (TOF) is one of the main subdetectors of Beijing SpectrometerII (BESII) for identification of charge particles. Time of flight and pulse amplitude are measured from the time of flight counters, when the particle hits on the TOF. Based on Di-mu sample from BESII, the correction of pulse amplitude Q is studied. Using the hadron sample of J/ψ, the relation between the corrected Pulse amplitude and βγ value is analyzed. A conclusion is that it is feasible to use the pulse amplitude Q0 of TOF to identify the particles. Finally the efficiency and error efficiency is given while the pulse amplitude is used to identify the particles.
Monte Carlo Study of Methods for Off-Line Calibration of ARGO-YBJ Experiment
ZHOU Yuan, HE Hui-Hai, MU Jun
2005, 29(8): 787-792.
In the YBJ-ARGO experiment, the hit time of detector-units can’t be calibrated manually due to the massive number of detector-units. Two methods of off-line calibration, named concentric circle method and characteristic plane method, are developed. Their calibration precision is estimated using the simulation data and the data of the 50m2 RPC carpet. It shows that concentric circle method can be used to calibrate the detector-units which have the same distance from the centre of the array,while the characteristic plane method, which has a good precision, is suitable for off-line calibration of all the detector-units, especially, under different experiment conditions.
Accurate Computation on High Order Modes of Axial-symmetric Cavity with The Third Order Vector Finite-Element Method
CAO Liang, HUANG Wen-Hui
2005, 29(8): 793-796.
In this paper, the third order vector finite-element method is presented which achieves remarkable improvement on the precision of numerical computation for high order modes of RF cavities. Compared with Cafe , which is a numerical computing program for high order modes of axial-symmetric cavities employing the second order vector finite-element method, our method is quicker and more precise in computing curve boundaries. Thus the program meshmatrix3 is obtained for computing high order modes of axial-symmetric cavities with the third order vector finite-element method. It is shown that our meshmatrix3 works satisfyingly.
The Design and Simulation of a Cooling System of High Current 4-rod RFQ Cavity
ZHU Kun, GUO Zhi-Yu, FANG Jia-Xun, GUO Jiu-Fang
2005, 29(8): 797-801.
To develop a high current neutron generator, preliminary studies on a high current, high duty factor 4-rod RFQ accelerator has been carried out in the Institute of Heavy Ion Physics,Peking University. This paper discusses the design of a cooling system of the RFQ cavity. Finite element program ANSYS was used to analyze the cooling system. The power density was simulated by MAFIA and used as the boundary condition of ANSYS. Due to the different meshing methods between MAFIA and ANSYS, a program was written to transfer the result of MAFIA to ANSYS. Then a thermal analysis model of RFQ cavity was built by using ANSYS. The design of the cooling system was analyzed and checked by using this model, and then the structure of cooling system is determined. Simulation results showed that the design of the cooling system makes RFQ accelerator working at proper temperature and long time steadily.
Extraction System for RFQ Cooler and Buncher
HUANG Wen-Xue, WANG Yue, XU Hu-Shan, SUN Zhi-Yu, LI Zhan-Kui, XIAO Guo-Qing, ZHAN Wen-Long
2005, 29(8): 802-805.
Two different systems, static electric guide and miniature RFQ (Radiofrequency Quadrupole), for ion extraction from a RFQ cooler and buncher have been discussed. By fluid dynamics calculation, the mass flow rate and possibly available vacuum of the being designed static electric extraction system have also been evaluated. We have made conclusions that the miniature RFQ should be used for a low helium buffer gas pressure to obtain a good beam quality, but for a higher gas pressure the static electric guide must be used. In addition, because the being designed RFQ cooler and buncher will always work in a relatively high gas pressure, the recycling and reusing of the high purity helium gas must be considered.
Researches on the Electromagnetic Field in RF Superconducting Cavities
HAO Jian-Kui, HUANG Sen-Lin, ZHU Feng, QUAN Sheng-Wen, ZHAO Kui
2005, 29(8): 806-809.
Q-drop phenomenon usually occurs in RF superconducting cavities made from high pure niobium at high field level. This is caused by the enhancement of local magnetic field at the surface of the niobium cavities. To study the electromagnetic performances of the superconducting cavities at high field, a series of experiments are designed with single cell niobium cavity. By the measurements of the peak surface magnetic field of the cavity, the defects in the cavity can be located with special method. Effective treatments can be used to improve the properties of the superconducting cavities.
Study of the Ion Beam Extraction and Transmission from ECRIS
SUN Liang-Ting, CAO Yun, ZHAO Hong-Wei, ZHANG Zi-Min, FENG Yu-Cheng, LI Jin-Yu
2005, 29(8): 810-817.
Experiments concerning the ion beam extraction and transmission have been done in Institute of Modern Physics on the Lanzhou Electron Cyclotron Resonance Ion Source No.3 experimental platform. We have studied the influences of the plasma electrode extraction aperture, the biased voltage on the screening electrode and the Glaser lens. The emphasis is put on the research how to extract the ions produced in the source more efficiently and how to make the extracted ion beam transmit with less loss. In this paper, the results of the experiments are presented. With the results obtained, systematic analysis has been made and a general physical image has also been bought forward in this paper.
Calculating RF Parameters of Individual Cell by Electronic Field Distribution of a Coupled Cavity Chain
SHI Jia-Ru, ZHENG Shu-Xin, CHEN Huai-Bi, TANG Chuan-Xiang
2005, 29(8): 818-823.
Electric field distribution of a coupled cavity chain is used to calculate RF Parameters of individual cell in the chain. When the characteristic frequencies of a coupled cavity chain and the electric field distribution of each mode are known, by equivalent circuit model, one can solve the RF parameters of each individual cell and the coupling factors between them. This method is useful in designing and tuning a cavity chain of a linear accelerator, especially a non-periodic long structure. A description of the mathematical model and calculating experience are presented.
Synchrotron radiation,applications of nuclear techniquees,etc
FTIR Study of C-Implanted SiO2 after High-Energy Pb-ion Irradiation
ZHAO Zhi-Ming, WANG Zhi-Guang, SONG Yin, JIN Yun-Fan, SUN You-Mei
2005, 29(8): 824-829.
SiO2 films were firstly implanted at room temperature (RT) with 120 keV C-ions to a dose of 2.0×1017, 5.0×1017 or 8.6×1017 C cm-2, and then the C-doped SiO2 films were irradiated at RT with 950 MeV Pb ions to a fluence of 5.0×1011, 1.0×1012 or 3.8×1012 Pb cm-2, respectively. The Fourier Transformation Infrared (FTIR) spectra of these samples were measured using a Spectrum GX IR spectroscopy. From the obtained micro-FTIR Spectra, we found that significant chemical bonds such as Si-C and Si(C)-O-C bonds were formed in the C doped SiO2 films after high-energy Pb ion irradiation. It was also found that CO2 molecule was formed in the high dose C-doped SiO2 films after large fluence Pb ion irradiations. The existence of a large number of Si-C bonding and CO2 molecule implies that nano-sized Si cluster and/or SiC grains may form in the C doped SiO2 films after high-energy Pb ion irradiation.