2006 Vol. 30, No. 9

Particle and field theory
Efficiency Correction to HOWL Generator of J/ψ→ Baryon Antibaryon Decays
PING Rong-Gang, LI Hai-Bo
2006, 30(9): 819-823.
A kind of Monte-Carlo generator based on the transition amplitude information is developed to study the detection efficiency correction to the pure phase space(HOWL) generator. Monte-Carlo(MC) simulations for the J/ψ→pp, ΛΛ, pX decays are carried out, and the results show that angular distributions for the decayed particles can well be reproduced. Compared with the HOWL generator, we find that the generator based on amplitude information will make a large correction to the detection efficiency. Therefore we recommend that a generator with a full transition information be used to simulate the long sequential decays.
Performance of CRTNT Fluorescence Light Detector for Sub-EeV Cosmic Ray Observation
BAI Yun-Xiang, XIAO Gang, CAO Zhen
2006, 30(9): 824-827.
Cosmic Ray Tau Neutrino Telescopes (CRTNT) for sub-EeV cosmic ray measurement is discussed. Performances of a stereoscope configuration with a tower of telescopes plus two side-triggers are studied. This is done by using a detailed detector simulation driven by Corsika. Detector aperture as a function of shower energy above 1017eV is calculated. Event rate of about 20k per year for the second knee measurement is estimated. Event rate for cross calibration with detectors working on higher energy range is also estimated. Different configurations of the detectors are tried for optimization.
Why is the 3×3 Neutrino Mixing Matrix Almost Unitary in Realistic Seesaw Models?
XING Zhi-Zhong, ZHOU Shun
2006, 30(9): 828-832.
A simple extension of the standard model is to introduce n heavy right-handed Majorana neutrinos and preserve its SU(2)L \times U(1)Y gauge symmetry. Diagonalizing the (3+n)×(3+n) neutrino mass matrix, we obtain an exact analytical expression for the effective mass matrix of νe, νμand ντ. It turns out that the 3×3 neutrino mixing matrix V, which appears in the leptonic charged-current weak interactions, must not be exactly unitary. The unitarity violation of V is negligibly tiny, however, if the canonical seesaw mechanism works to reproduce the correct mass scale of light Majorana neutrinos. A similar conclusion can be drawn in the realistic Type-Ⅱ seesaw models.
Two Renormalization Approaches for the Dyson-Schwinger Equations in the Infrared
SHI Yuan-Mei, PING Jia-Lun, HE Han-Xin
2006, 30(9): 833-837.
Two renormalization approaches: the analytic continuation approach and the subtraction approach, are used to obtain the infrared behavior of gluon and ghost propagators in the coupled gluon and ghost Dyson-Schwinger equations,where the three-gluon and gluon-ghost vertices are taken to be bare. The results show that the two renormalization approaches give the same results in the infrared analysis of propagators.
Study of Solving a Toda Dynamic System with Loop Algebra
ZHU Qiao, YANG Zhan-Ying, SHI Kang-Jie, WEN Jun-Qing
2006, 30(9): 838-843.
In this paper, we construct a Toda system with Loop algebra, and prove that the Lax equation L=[L,M] can be solved by means of solving a regular Riemann-Hilbert problem. In our system, M in Lax pair is an antisymmetrical matrix, while L=L++M, and L+ is a quasi-upper triangular matrix of loop algebra. In order to check our result, we exactly solve a R-H problem under a given initial condition as an example.
Nuclear and ion Physics
(n,2n),(n,p) and (n,α) Reactions Cross-Sections Measurement on Selenium Isotopes at Neutron Energy of 14MeV
HE Guo-Zhu, TUO Fei, KONG Xiang-Zhong
2006, 30(9): 844-847.
Cross sections for 82Se(n,2n)81m,gSe,76Se(n,2n)75Se,78Se(n,p)78As,76Se(n,p)76As,74Se(n,p)74As and 80Se(n,α)77Ge reactions have been measured at neutron energy of 14MeV using activation technique. Neutrons were produced by reaction 3H(d,n)4He and neutron flux were monitored by reaction 93Nb(n,2n)92mNb. The results of the present work are compared with the previous reported data.
Three-Body Force Rearrangement Contribution to Single Nucleon Potential in Nuclear Matter
ZUO Wei, LUO Pei-Yan, LI Bao-An, CHEN Ji-Yan, Lombardo U
2006, 30(9): 848-853.
Within the framework of microscopic Brueckner-Hatree-Fock,the contribution of the three-body force (TBF) rearrangement to the single nucleon potential is calculated. The TBF rearrangement effects on the momentum and the density dependence of the single nucleon potential are investigated. The influence of the TBF rearrangement on the effective mass of nucleon is also discussed. It is shown that the rearrangement contribution of TBF is repulsive and momentum-dependent. The TBF rearrangement effect and its momentum dependence increase rapidly as increasing density and momentum. At high densities and high momenta, the repulsive rearrangement contribution reduces strongly the attraction of the single nucleon potential and enhances considerably the momentum dependence of the single nucleon potential.
SD Pair Shell Model: Collectivity of Low-Lying State for Even-Even Pt Isotopes
LI Qiong, XIA Bing-Shu, LUO Yan-An, PAN Feng, NING Ping-Zhi
2006, 30(9): 854-857.
The SD pair shell model was applied to study the even-even Pt isotopes. The results show that collectivity of low-lying states for the Pt isotopes can be reproduced approximately with a three parameter Hamiltonian.
Macroscopic-Microscopic Calculation on the Ground State Properties of Superheavy Odd-Even Nuclei
ZHI Qi-Jun, REN Zhong-Zhou
2006, 30(9): 858-862.
Using the macroscopic-microscopic model, we systematically calculate the ground state properties of superheavy odd-even nuclei with proton number Z=95—113. The theoretical binding energies and alpha-decay energies are in good agreement with the experimental data and with the results from relativistic mean-field (RMF) model. The reliability of macroscopic-microscopic model which is used in superheavy nuclei is further confirmed by our calculations and comparisons. The calculations show that the deformations play important role for the properties of superheavy nuclei. The predicted properties of some unknown nuclei are useful for future experimental research.
Medium-Induced Parton Splitting Probability
XIANG Wen-Chang, DING Heng-Tong, ZHOU Dai-Cui
2006, 30(9): 863-867.
The parton shower evolution law in the hot and dense matter is studied by using the spectrum of parton radiative energy loss. At the same energy, the numerical results indicate that the splitting probability of parton, in the medium, is large than those in the vacuum. And when the density of medium is higher, the splitting probability of parton is larger. This result is in agreement with the suppression of leading particles production in BNL/RHIC,it indicates that the hot and dense matter has already been produced at RHIC energy.
Effect of Friction on Neutron Emission in Fission of Heavy Nuclei
JIA Ying, BAO Jing-Dong
2006, 30(9): 868-871.
By using the {c,h,α} parameterization to describe the deformation process of heavy nuclei, a Langevin equation for fission dynamics with neutron emission is presented and the Monte-Carlo calculations of pre-scission neutron multiplicities are performed. The effect of different damping coefficients on the result is compared, especially the distributions of neutron emission when the system first and last passes the saddle point are distinguished.
Detection Technology and Methods
Radiation Hardness Properties of Plastic Scintillators
WU Chong, ZHAO Li, HENG Yue-Kun, ZHAO Xiao-Jian, SUN Zhi-Jia, WU Jin-Jie, ZHAO Yu-Da, WANG Feng-Mei, XUE Sheng-Tian
2006, 30(9): 872-875.
Using 60Co radioactive source, the radiation damage properties of three kinds of plastic scintillators, BC-408, EJ-200 and BC-404 were studied. By the study of the variation of transmission spectra,emission spectra and light yield, it can be found that the scintillators have good irradiation hardness at low dose. When the dose is over 1.44×104Gy, the transmission spectrum becomes worse and the light output decrease very much. However, the emission spectrum is unchanged.
Nuclear Counter Effect of Silicon Photodiode Used in CsI(Tl) Crystal Calorimeter
WANG Zhi-Gang, SHAN Li-Min, SHANG Lei, XIE Wen-Jie, QIN Gang, LIU Chun-Xiu, YU Bo-Xiang, DONG Ming-Yi, CAI Xiao, ZHOU Li, XIA Xiao-Mi, LAI Yuan-Fen, WANG Man
2006, 30(9): 876-879.
We investigated the nuclear counter effect of the silicon photodiode mounted on a CsI(Tl) crystal detector due to the leakage of electromagnetic shower through the rear end of the crystal. Using electron beams at IHEP, we have tested its effect on the energy measurement by the CsI(Tl) calorimeter for BESⅢ experiment. The results are found to be in good agreement with that of GEANT simulation and the effect for the BESⅢ calorimeter is negligible.
Mechanism and Application of the Super-Periodic Structural Resonance in Storage Rings
FANG Shou-Xian, QIN Qing
2006, 30(9): 880-887.
The traditional stability diagram for lattice design described in the space of the gradients of a focusing and a defocusing magnet is extended to study more complicated cases, in which the basic cell included in the super-periodic structure has more than two gradients as variables. With the method developed here, it is easy to understand the mechanism and the physics hidden behind these structural resonances and the method can be used to guide the choice of the working points of a given lattice. Applications on the real machines are given as examples, with the simulation results on dynamic aperture.
Transverse Phase Space Measurement Based on Computerized Tomography
DU Ying-Chao, XIANG Dao, HUANG Wen-Hui, HE Xiao-Zhong, CHENG Cheng, DU Tai-Bin, TANG Chuan-Xiang, LIN Yu-Zheng
2006, 30(9): 888-891.
Precise measurements of emittance and transverse phase space are essential to generation and applications of high brightness electron beams. Compared to the quadrupole-scanning technique which treats the phase space distributions as ellipses and only measure the sigma matrices that define the ellipses, the measurement of transverse phase space based on CT(computerized tomography) measures the actual phase space distributions while making no a priori assumptions about the distributions. This process is capable of reconstructing transverse phase space distributions that are not elliptical. The theories of CT based measurements are studied. The preliminary experiment result is presented which is in good agreement with that obtained from quadruple scanning.
Research on Depolarization of Transversely Polarized Gas Target Induced by High Energy e-Beam
WANG Si-Guang, ZHOU Shu-Hua, YE Yun-Xiu, YE Zhen-Yu, MAO Ya-Jun
2006, 30(9): 892-895.
High frequency electromagnetic fields induced by high-energy e-beam can cause resonance depolarization of the HERMES transversely polarized gas target. This paper presents the research results on the mechanism of depolarization and the position where resonance σ24 takes place. About 3% depolarization has been saved after avoiding such resonance by fixing the magnet field far from resonance position according to the measured results.
Balun Technology for Bipolar Pulsed Power Supply
CHEN Jin-Hui, HAN Qian, KANG Wen
2006, 30(9): 896-901.
A new type slotted pipe kicker with advantage of low coupling impedance is adopted for the major upgrading of the Beijing Electron Positron Collider (BEPCⅡ). A bipolar pulsed power supply is needed for the new type kicker. In order to avoid difficulties caused by the floating-thyratron scheme, a balun is introduced into the LC series resonance circuit with a grounded thyratron. The current balance degree between primary and secondary coils must be considered for the balun as a high-voltage fast-pulsed transformer for the special purpose. The unbalanced currents include magnetizing current and equivalent current of eddy-current loss in core. A nanocrystalline tape-wound toroid annealed in transverse magnetic field is chosen for the balun. To reduce leakage inductance, a simply parallel flat structure is adopted in design of transformer primary and secondary conductors. The test results on the prototype confirm the design theory and current balance degree of the balun reaches the design target of D<1%.
Study of Extraction Property of RF Ion Source
SUN Zhen-Wu, HUO Yu-Ping, LI Yu-Xiao, LI Tao
2006, 30(9): 902-906.
Effects of geometry parameters of extraction electrode, extraction voltage and oscillator power on the extraction property of RF ion source are measured and the experimental results are analyzed. It turns out that the RF ion source has a good extraction property. There is the best D/d on condition that other parameters don't change. The D/d rising is beneficial to the ion beam focusing from over focusing. Focusing degree increases and extraction beam intensity drops with b/D increasing. Focusing degree rises with B/d decreasing and the rising tendency slows down when B/d is smaller than 4. The suitable ranges of D/d, b/D and B/d are respectively 1.6—2.1,0.7—1.1 and 4—7 when considering comprehensively the focusing degree, the extraction beam intensity and the pressure. Change of extraction voltage and oscillator power has opposite effect on the ion source performance and they have respectively best operation values.
Research on New BPM Used to “Dragon Ⅰ”
XU Tie-Zheng, XIE Yu-Tong, GAO Feng, DAI Wen-Hua, GU Zhan-Jun, WANG Li-Ming, WANG Hua-Cen, LI Jing
2006, 30(9): 907-911.
The principle of beam position monitoring of button was introduced briefly. It was compared with beam bugs in principle. Based on the result in simulation experiment, a new structure of button was design, and some mistakes in the primary design was correctted. In the realy beam experiment of “Dragon Ⅰ”, the beam waveform and position were monitored. Compared the position curve between button and beam bugs, that indicated the data that got form button is credible. In the experiment, the button have an accuracy of 0.5mm, which is adequate for beam position measurement of “Dragon Ⅰ”.
Synchrotron radiation,applications of nuclear techniquees,etc
Calibration of XRD Detector and Filter on the 3B3 Medium Energy X-Ray Beam in BSRF
CUI Yan-Li, YI Rong-Qing, DU Hua-Bing, ZHAO Yi-Dong, CUI Ming-Qi, ZHENG Lei
2006, 30(9): 912-915.
The sensitivity of XRD detector in 2.1—6.0keV energy range has been calibrated on the 3B3 medium energy X-ray beam at the BSRF for the first time in our country, and the uncertainty is less than 7%. In addition, the calibration precision of filter thickness has been improved by using the 3B3 medium energy X-ray beam, and the uncertainty of the filter thickness is less than 3.6%.
Study on the Convergent Function of a Cylinder Capillary Transmitting X-Ray
LI Yu-De, LIN Xiao-Yan, WANG Da-Chun
2006, 30(9): 916-919.
The power density gain and equivalent length of cylinder capillary with different lengths and radii are calculated with a simulation program. In experiment, with 8.04keV X-ray source the power density gain and equivalent length of cylinder capillary are measured and the experiment results are compared with the simulation. The conclusion is drawn that a cylinder capillary has great application prospect on crystal diffraction.
Physical Property Measurement of Therapeutic Carbon Ion Beam in the Shallow-Seated Tumor Therapy Terminal at HIRFL
DAI Zhong-Ying, LI Qiang, YAN Zheng, JIN Xiao-Dong, HU Zheng-Guo, XIAO Guo-Qing
2006, 30(9): 920-924.
For the first time the physical properties of therapeutic carbon-ion beam supplied by the shallow-seated tumor therapy terminal at the Heavy Ion Research Facility in Lanzhou (HIRFL) are measured. For a 80.55MeV/u 12C ion beam delivered to the therapy terminal, the homogeneity of irradiation fields is 73.48%, when the beam intensity varied in the range of 0.001—0.1nA (i.e. 1×106—1×108 particles per second). The stability of the beam intensity within a few minutes is estimated to be 80.87%. The depth-dose distribution of the beam at the isocenter of the therapy facility is measured, and the position of the high-dose Bragg peak is found to be located at the water-equivalent depth of 13.866mm. Based on the relationship between beam energy and Bragg peak position, the corresponding beam energy at the isocenter of the therapy terminal is evaluated to be 71.71MeV/u for the original 80.55MeV/u 12C ion beam, which consisted basically with calculation. The readout of the previously-used air-free ionization chamber regarding absorbed dose is calibrated as well in this experiment. The results indicate that the performance of the therapy facility should be optimized further to meet the requirements of clinical trial.
Conformal Irradiation to Moving Targets in Heavy Ion Radiotherapy with Raster-Scanning Beam Delivery System: (II) Feasibility Experiments
LI Qiang
2006, 30(9): 925-929.
Within the framework of the pilot heavy-ion therapy facility at GSI equipped with an active beam delivery system of advanced raster scanning technique, a feasibility study on actively conformal heavy-ion irradiation to moving tumors has been experimentally conducted. Laterally, real-time corrections to the beam scanning parameters by the raster scanner, leading to an active beam tracing, compensate for the lateral motion of a target volume. Longitudinally, a mechanically driven wedge energy degrader (called depth scanner) is applied to adjust the beam energy so as to locate the high-dose Bragg peak of heavy ion beam to the slice under treatment for the moving target volume. It has been experimentally shown that compensations for lateral target motion by the raster scanner and longitudinal target shift by the depth scanner are feasible.