2014 Vol. 38, No. 1

Particle and field theory
Pseudospin symmetry of the Dirac equation for a Möbius squareplus Mie type potential with a Coulomb-like tensor interaction via SUSYQM
Akpan N, Eno J
2014, 38(1): 013101. doi: 10.1088/1674-1137/38/1/013101
We investigate the approximate solution of the Dirac equation for a combination of Möbius square and Mie type potentials under the pseudospin symmetry limit by using supersymmetry quantum mechanics. We obtain the bound-state energy equation and the corresponding spinor wave functions in an approximate analytical manner. We comment on the system via various useful figures and tables.
Scalar glueball in a soft-wall model of AdS/QCD
LI Xue-Feng, ZHANG Ai-Lin
2014, 38(1): 013102. doi: 10.1088/1674-1137/38/1/013102
The scalar glueball is investigated in a soft-wall model of AdS/QCD. Constraints of the mass of the scalar glueball are given through an analysis of a relation between the bulk mass and the anomalous dimension. The mass of the ground scalar glueball is located at 0.96-0.07+0.04 GeV<mG<1.36-0.10+0.05 GeV. In terms of a background dilaton field Φ(z)=cz2, the two-point correlation function for the scalar gluon operator is obtained. The two-point correlation function at Δ=4 gives a different behavior compared with the one in QCD.
Meson decays in an extended Nambu—Jona-Lasinio model with heavy quark flavors
DENG Hong-Bo, CHEN Xiao-Lin, DENG Wei-Zhen
2014, 38(1): 013103. doi: 10.1088/1674-1137/38/1/013103
In a previous work, we proposed an extended Nambu-Jona-Lasinio (NJL) model including heavy quark flavors. In this work, we will calculate strong and radiative decays of vector mesons in this extended NJL model, including light ρ, ω, K*, φ and heavy D*, D*s, B*, B*s.
Projectile fragment emission in the fragmentation of 56Fe on C, Al and CH2 targets at 471 A MeV
LI Yan-Jing, ZHANG Dong-Hai, YAN Shi-Wei, WANG Li-Chun, CHENG Jin-Xia, LI Jun-Sheng
2014, 38(1): 014001. doi: 10.1088/1674-1137/38/1/014001
The emission angle and the transverse momentum distributions of projectile fragments produced in the fragmentation of 56Fe on CH2, C and Al targets at 471 A MeV are measured. It is found that for the same target, the average value and width of the angular distribution decrease with an increase of the projectile fragment charge; for the same projectile fragment, the average value of the distribution increases and the width of the distribution decreases with increasing the target charge number. The transverse momentum distribution of a projectile fragment can be explained by a single Gaussian distribution and the averaged transverse momentum per nucleon decreases with the increase of the charge of projectile fragment. The cumulated squared transverse momentum distribution of a projectile fragment can be explained well by a single Rayleigh distribution. The temperature parameter of the emission source of the projectile fragment, calculated from the cumulated squared transverse momentum distribution, decreases with the increase of the size of the projectile fragment.
Big deformation in 17C
FAN Guang-Wei, CAI Xiao-Lu, HAN Ti-Fei, LI Xue-Chao, REN Zhong-Zhou, XU Wang
2014, 38(1): 014101. doi: 10.1088/1674-1137/38/1/014101
Reaction and interaction cross sections of 17C on a carbon target have been re-analyzed using the modified Glauber model. The analysis with a deformed Woods-Saxon density/potential suggests a big deformation structure for 17C. The existence of a tail in the density distribution supports the possibility of it being a one-neutron halo structure. Under a deformed core plus a single-particle assumption, analysis shows a dominant d-wave of the valence neutron in 17C.
Simulation of energy scan of pion interferometry in central Au+Au collisions at relativistic energies
ZHANG Zheng-Qiao, ZHANG Song, MA Yu-Gang
2014, 38(1): 014102. doi: 10.1088/1674-1137/38/1/014102
We present a systematic analysis of two-pion interferometry for the central Au+Au collisions at √sNN=3, 5, 7, 11, 17, 27, 39, 62, 130 and 200 GeV/c with the help of a multiphase transport (AMPT) model. Emission source-size radius parameters Rlong, Rout, Rside and the chaotic parameter λ are extracted and compared with the experimental data. Transverse momentum and azimuthal angle dependencies of the HBT radii are also discussed for central Au+Au collisions at 200 GeV/c. The results show that the HBT radii in central collisions do not change much above 7 GeV/c. For central collisions at 200 GeV/c, the radii decrease with the increasing of transverse momentum pT but are not sensitive to the azimuthal angle. These results provide a theoretical reference for the energy scan program of the RHIC-STAR experiment.
particle and nuclear astrophysics and cosmology
Transition density of the large mass hyperon star
ZHAO Xian-Feng, JIA Huan-Yu
2014, 38(1): 015101. doi: 10.1088/1674-1137/38/1/015101
The difference between the transition density of a larger mass hyperon star (for example, the neutron star PSR J1614-2230) and that of a smaller mass hyperon star is investigated in the framework of the relativistic mean field theory. We see that the transition density ρ0H increases with the increase of xω (i.e. the mass of the neutron star). For the nucleons parts, the neutrons make the main contribution to the transition density as the baryon density ρ=ρ0H. With the increase of the xω (i.e. the mass of the neutron star), the relative particle number density of neutrons decreases while that of protons increases. For the parts of hyperons, the Λ and Ξ- make the main contributions to the transition density as the baryon density ρ=ρ0H. The relative particle number density of Λ decreases while that of Ξ- increases with the increase of the xω (i.e. the mass of the neutron star). For the hyperons Σ-, Σ0 and Σ-, the total contributions are less than 16 per cent.
Effects of ultra-strong magnetic field on electron capture rates of 55Co and 56Ni in the magnetar surrounding
DU Jun, LUO Zhi-Quan, LI Ping-Ping
2014, 38(1): 015102. doi: 10.1088/1674-1137/38/1/015102
The electron capture rates of 55Co and 56Ni in the ultra-strong magnetic field at four typical temperature-density points have been calculated using the nuclear shell model and Landau energy levels quantized approximate correction. The results show that the electron capture rates of 55Co and 56Ni are increased greatly in the ultra-strong magnetic field, and even exceed two orders of magnitude in the range from 4.414× 1013G to 2.207× 1017G. The change rate of electron abundance, Ýe, of 55Co and 56Ni under the condition of B=4.414× 1015G in the magnetar surrounding has been calculated and discussed, the proportions of Ýe of 55Co and 56Ni in the total Ýe have been reduced by 50 percent in all more than the condition without a magnetic field.
Detection Technology , Electronics and Methods
Experimental research on performances of the imaging plates applied in gamma-ray imaging
QI Jian-Min, ZHANG Fa-Qiang, CHEN Jin-Chuan, XIE Hong-Wei
2014, 38(1): 016001. doi: 10.1088/1674-1137/38/1/016001
Experimental studies on the basic characteristics of IPs applied in γ-ray imaging are carried out by utilizing isotopic γ-ray sources. The 1.25 MeV γ-ray sensitivity of the BAS-MS and BAS-TR imaging plates and their enhanced sensitivity by covering appropriate Compton conversion foils are measured based on the studies of the image intensity linear calibration, time attenuation laws and the influence of scanning parameter settings. The energy-dependent γ-ray sensitivity of the IPs is also obtained by the studies of the measured sensitivity and the Monte Carlo simulated energy deposition in the IPs' sensitive layer. Furthermore, a method of a sandwich detection structure as well as its primary experimental validations are presented in order to increase the gamma-to-neutron ratio in a γ/n mixed radiation field.
Study on the optimization of the water Cherenkov detector array of the LHAASO project for surveying VHE gamma ray sources
LI Hui-Cai, CHEN Ming-Jun, JIA Huan-Yu, GAO Bo, YAO Zhi-Guo, YUO Xiao-Hao, ZHOU Bin, ZHU Feng-Rong
2014, 38(1): 016002. doi: 10.1088/1674-1137/38/1/016002
It is prpopsed that a water Cherenkov detector array, LHAASO-WCDA, is to be built at Shangri-la, Yunnan Province, China. As one of the major components of the LHAASO project, the main purpose of it is to survey the northern sky for gamma ray sources in the energy range of 100 GeV—30 TeV. In order to design the water Cherenkov array efficiently to economize the budget, a Monte Carlo simulation is carried out. With the help of the simulation, the cost performance of different configurations of the array are obtained and compared with each other, serving as a guide for the more detailed design of the experiment in the next step.
Proposal of the readout electronics for the WCDA in the LHAASO experiment
ZHAO Lei, LIU Shu-Bin, AN Qi
2014, 38(1): 016101. doi: 10.1088/1674-1137/38/1/016101
The LHAASO (Large High Altitude Air Shower Observatory) experiment is proposed for a very high energy gamma ray source survey, in which the WCDA (Water Cherenkov Detector Array) is one of the major components. In the WCDA, a total of 3600 PMTs are placed under water in four ponds, each with a size of 150 m× 150 m. Precise time and charge measurement is required for the PMT signals, over a large signal amplitude range from a single P.E. (photo electron) to 4000 P.E. To fulfill the high requirement of a signal measurement in so many front end nodes scattered in a large area, special techniques are developed, such as multiple gain readout, hybrid transmission of clocks, commands and data, precise clock phase alignment and new trigger electronics. We present the readout electronics architecture for the WCDA and several prototype modules, which are now being tested in the laboratory.
Study of the efficiency of event start time determination at BESⅢ
GUAN Ying-Hui, ZHENG Yang-Heng, WANG Yi-Fang
2014, 38(1): 016201. doi: 10.1088/1674-1137/38/1/016201
A method to estimate the efficiency of event start time determination at BESⅢ is developed. This method estimates the efficiency at the event level by combining the efficiencies of various tracks (e, μ, π, K, p, γ) in a Bayesian way. Efficiencies results and the difference between data and MC at the track level are presented in this paper. For a given physics channel, event start time efficiency and systematic error can be estimated following this method.
Mode control in a high gain relativistic klystron amplifier with 3 GW output power
WU Yang, XIE Hong-Quan, XU Zhou
2014, 38(1): 017001. doi: 10.1088/1674-1137/38/1/017001
Higher mode excitation is very serious in the relativistic klystron amplifier, especially for the high gain relativistic amplifier working at tens of kilo-amperes. The mechanism of higher mode excitation is explored in the PIC simulation and it is shown that insufficient separation of adjacent cavities is the main cause of higher mode excitation. So RF lossy material mounted on the drift tube wall is adopted to suppress higher mode excitation. A high gain S-band relativistic klystron amplifier is designed for the beam current of 13 kA and the voltage of 1 MV. PIC simulation shows that the output power is 3.2 GW when the input power is only 2.8 kW.
Instantaneous electron beam emittance measurement system based on the optical transition radiation principle
JIANG Xiao-Guo, WANG Yuan, ZHANG Kai-Zhi, YANG Guo-Jun, SHI Jin-Shui, DENG Jian-Jun, LI Jin
2014, 38(1): 017002. doi: 10.1088/1674-1137/38/1/017002
One kind of instantaneous electron beam emittance measurement system based on the optical transition radiation principle and double imaging optical method has been set up. It is mainly adopted in the test for the intense electron-beam produced by a linear induction accelerator. The system features two characteristics. The first one concerns the system synchronization signal triggered by the following edge of the main output waveform from a Blumlein switch. The synchronous precision of about 1 ns between the electron beam and the image capture time can be reached in this way so that the electron beam emittance at the desired time point can be obtained. The other advantage of the system is the ability to obtain the beam spot and beam divergence in one measurement so that the calculated result is the true beam emittance at that time, which can explain the electron beam condition. It provides to be a powerful beam diagnostic method for a 2.5 kA, 18.5 MeV, 90 ns (FWHM) electron beam pulse produced by Dragon I. The ability of the instantaneous measurement is about 3 ns and it can measure the beam emittance at any time point during one beam pulse. A series of beam emittances have been obtained for Dragon I. The typical beam spot is 9.0 mm (FWHM) in diameter and the corresponding beam divergence is about 10.5 mrad.
Development of a superconducting solenoid for CADS
WU Wei, WNAG Zhi-Jun, WU Bei-Ming, HAN Shao-Fei, NI Dong-Sheng, MEI En-Ming, YANG Wen-Jie, ZHU Li, ZHENG Shi-Jun, YANG Tong-Jun, YANG Xiao-Liang, MA Li-Zhen, HE Yuan
2014, 38(1): 017003. doi: 10.1088/1674-1137/38/1/017003
A superconducting focusing solenoid has been designed and developed for the China Accelerator Driven System (CADS). In order to meet the requirement of focusing strength and fringe field while minimizing the physical size of the solenoid, the novel optimizing design method based on a linear programming method was employed. In this report, the design of the solenoid including magnetic field optimization, mechanical design and quench protection will be introduced. The solenoid has been fabricated and tested. The testing results show that the central field reached 8.4 T and the stray field was lower than 50 Gauss in the cavity zone.
Synchrotron radiation,applications of nuclear techniquees,etc
Physical design of FEL injector based on the performance-enhanced EC-ITC RF gun
HU Tong-Ning, CHEN Qu-Shan, PEI Yuan-Ji, LI Ji, QIN Bin
2014, 38(1): 018101. doi: 10.1088/1674-1137/38/1/018101
To meet the requirements of high performance THz-FEL (Free Electron Laser), a compact scheme of FEL injector was proposed. A thermionic cathode was chosen to emit electrons instead of a photo-cathode with its complex structure and high cost. The effective bunch charge was improved to ~200 pC by adopting an enhanced EC-ITC (External Cathode Independently Tunable Cells) RF gun to extract micro-bunches; back bombardment effects were almost eliminated as well. Constant gradient accelerator structures were designed to improve energy to ~14 MeV, while the focusing system was applied for emittance suppressing and bunch state maintenance. The physical design and beam dynamics of the key components for the FEL injector were analyzed. Furthermore, start-to-end simulations with multi-pulses were performed using homemade MATLAB and Parmela. The results show that continual high brightness electron bunches with a low energy spread and emittance could be obtained stably.
Experimental study of the plasma window
SHI Ben-Liang, HUANG Sheng, ZHU Kun, LU Yuan-Rong
2014, 38(1): 018201. doi: 10.1088/1674-1137/38/1/018201
The plasma window is an advanced apparatus that can work as the interface between a vacuum and a high pressure region. It can be used in many applications that need atmosphere-vacuum interface, such as a gas target, electron beam welding, synchrotron radiation and a spallation neutron source. A test bench of the plasma window is constructed in Peking University. A series of experiments and the corresponding parameter measurements have been presented in this article. The experiment result indicates the feasibility of such a facility acting as an interface between a vacuum and a high pressure region.
Design of data acquisition system and algorithm research for omnidirectional gamma-ray positioning equipment
HU Ting-Ting, SHUAI Lei, WANG Pei-Lin, FENG Bao-Tong, ZHANG Yi-Wen, SUN Yun-Hua, LI Xiao-Hui, WEI Shu-Jun, SHAN Bao-Ci, WEI Long
2014, 38(1): 018202. doi: 10.1088/1674-1137/38/1/018202
This article introduces the design and performance of the data acquisition system used in an omnidirectional gamma-ray positioning system, along with a new method used in this system to obtain the position of radiation sources in a large field. This data acquisition system has various built-in interfaces collecting, in real time, information from the radiation detector, the video camera and the GPS positioning module. Experiments show that the data acquisition system is capable of carrying out the proposed quantitative analysis to derive the position of radioactive sources, which also satisfies the requirements of high stability and reliability.