2014 Vol. 38, No. 8

An exclusive event generator for e+e- scan experiments
PING Rong-Gang
2014, 38(8): 083001. doi: 10.1088/1674-1137/38/8/083001
An exclusive event generator is designed for e+e- scan experiments, including initial state radiation effects up to the second order correction. The generator is coded within the framework of BesEvtGen. There are seventy hadronic decay modes available, with effective center-of-mass energy coverage from the two pion mass threshold up to about 6 GeV. The accuracy achieved for the initial state radiation correction reaches the level achieved by the KKMC generator. The uncertainty associated with the calculation of the correction factor to the initial state radiation is dominated by the measurements of the energy-dependent Born cross section.
Meson polarized distribution function and mass dependence ofthe nucleon parton densities
A. Mirjalili, K. Keshavarzian
2014, 38(8): 083101. doi: 10.1088/1674-1137/38/8/083101
The polarized distribution functions of mesons, including pion, kaon and eta, using the proton structure function, are calculated. We are looking for a relationship between the polarized distribution of mesons and the polarized structure of nucleons. We show that the meson polarized parton distributions leads to zero total spin for the concerned mesons, considering the orbital angular momentum of quarks and gluons inside the meson. Two separate Monte Carlo algorithms are applied to compute the polarized parton distributions of the kaon. Via the mass dependence of quark distributions, the distribution function of the eta meson is obtained. A new method by which the polarized sea quark distributions of protons are evolved separately -which cannot be performed easily using the standard solution of DGLAP equations -is introduced. The mass dependence of these distributions is obtained, using the renormalization group equation which makes their evolutions more precise. Comparison between the evolved distributions and the available experimental data validates the suggested solutions for separated evolutions.
Astrophysical S-factor of the 12C(α,γ) 16O reaction at solar energies
H. Sadeghi, R. Ghasemi, H. Khalili
2014, 38(8): 084101. doi: 10.1088/1674-1137/38/8/084101
The astrophysical S-factor of the 4He+12C radiative capture is calculated in the potential model at the energy range 0.1-2.0 MeV. Radiative capture 12C(α,γ) 16O is extremely relevant for the fate of massive stars and determines if the remnant of a supernova explosion becomes a black hole or a neutron star. Because this reaction occurs at low energies, the experimental measurements are very difficult and perhaps impossible. In this paper, radiative capture of the 12C(α,γ) 16O reaction at very low energies is taken as a case study. In comparison with other theoretical methods and available experimental data, good agreement is achieved for the astrophysical S-factor of this process.
Three-body force effect on the properties of nuclear matter underthe gap and continuous choices within the BHF approach
ANG Pei, ZUO Wei
2014, 38(8): 084102. doi: 10.1088/1674-1137/38/8/084102
We have calculated and compared the three-body force effects on the properties of nuclear matter under the gap and continuous choices for the self-consistent auxiliary potential within the Brueckner-Hartree-Fock approach by adopting the Argonne V18 and the Bonn B two-body potentials plus a microscopic three-body force (TBF). The TBF provides a strong repulsive effect on the equation of state of nuclear matter at high densities for both the gap and continuous choices. The saturation point turns out to be much closer to the empirical value when the continuous choice is adopted. In addition, the dependence of the calculated symmetry energy upon the choice of the self-consistent auxiliary potential is discussed.
Pseudorapidity distributions of the produced charged particles in nucleus-nucleus collisions at low energies at the BNL relativisticheavy ion collider
JIANG Zhi-Jin, MA Ke, ZHANG Hai-Li, CAI Liu-Mei
2014, 38(8): 084103. doi: 10.1088/1674-1137/38/8/084103
The revised Landau hydrodynamic model is used to discuss the pseudorapidity distributions of the produced charged particles in Au+Au and Cu+Cu collisions at energies of √sNN=19.6 and 22.4 GeV respectively at the BNL Relativistic Heavy Ion Collider. It is found that the revised Landau hydrodynamic model alone can give a good description of the experimental measurements. This is different from the result with the same collisions but at the maximum energy of √sNN=200 GeV, where in addition to the revised Landau hydrodynamic model, the effects of leading particles have to be taken into account in order to explain the experimental observations. This can be attributed to the different degrees of transparency of participants at the different incident energies.
Impact parameter dependence of the scaling of anisotropic flowsin intermediate energy heavy-ion collisions
YAN Ting-Zhi, LI Shan
2014, 38(8): 084104. doi: 10.1088/1674-1137/38/8/084104
The scaling behaviors of anisotropic flows of light charged particles are studied for 25 MeV/u 40Ca+40Ca collisions at different impact parameters by the isospin-dependent quantum molecular dynamics model. The nucleon-number scaling of elliptic flow exists and the scaling of the ratios of v4/v22 and v3/(v1v2) is applicable to collisions at almost all impact parameters except for peripheral collisions.
particle and nuclear astrophysics and cosmology
Multi-wavelength study of MGRO J2019+37
HOU Chao, CHEN Song-Zhan, YUAN Qiang, CAO Zhen, HE Hui-Hai, SHENG Xiang-Dong
2014, 38(8): 085001. doi: 10.1088/1674-1137/38/8/085001
MGRO J2019+37, within the Cygnus region, is a bright extended source revealed by Milagro at 12-35 TeV. This source is almost as bright as the Crab Nebula in the northern sky, but is not confirmed by ARGO-YBJ around the TeV scale. Up to now, no obvious counterpart at low energy wavelengths has been found. Hence, MGRO J2019+37 is a rather mysterious object and its VHEγ-ray emission mechanism is worth investigating. In this paper, a brief summary of the multi-wavelength observations from radio to γ-rays is presented. All the available data from XMM-Newton and INTEGRAL at X-ray, and Fermi-LAT atγ-ray bands, are used to get constraints on its emission flux at low energy wavelengths. Then, its possible counterparts and the VHE emission mechanism are discussed.
Detection Technology , Electronics and Methods
Onsite data processing and monitoring for the Daya Bay experiment
LIU Ying-Biao, HE Miao, LIU Bei-Jiang, WANG Meng, MA Qiu-Mei, QI Fa-Zhi, ZENG Shan
2014, 38(8): 086001. doi: 10.1088/1674-1137/38/8/086001
The Daya Bay Reactor Neutrino Experiment started running on September 23, 2011. The offline computing environment, consisting of 11 servers at Daya Bay, was built to process onsite data. With the current computing ability, onsite data processing is running smoothly. The Performance Quality Monitoring system (PQM) has been developed to monitor the detector performance and data quality. Its main feature is the ability to efficiently process multiple data streams from the three experimental halls. The PQM processes raw data files from the Daya Bay data acquisition system, generates and publishes histograms via a graphical web interface by executing the user-defined algorithm modules, and saves the histograms for permanent storage. The fact that the whole process takes only around 40 minutes makes it valuable for the shift crew to monitor the running status of all the sub-detectors and the data quality.
Magnetic shielding for DAMPE electromagnetic calorimeter PMTs
WANG Pei-Long, ZHANG Yun-Long, WANG Xiao-Lian, XU Zi-Zong
2014, 38(8): 086002. doi: 10.1088/1674-1137/38/8/086002
The magnetic characteristics of R5610A-01 photomultiplier tubes are studied in this paper. The experimental data shows that the gain of R5610A-01 loses about 53% when the magnetic field is 3 Gs along its +X axis. A cylinder of one-layer permalloy strip is able to reduce the effect of a 3 Gs magnetic field on the PMT gain to less than 1%.
High efficiency event-counting thermal neutron imagingusing a Gd-doped micro-channel plate
TIAN Yang, YANG Yi-Gang, PAN Jing-Sheng, LI Yu-Lan, LI Yuan-Jing
2014, 38(8): 086003. doi: 10.1088/1674-1137/38/8/086003
An event-counting thermal neutron imaging detector based on 3 mol % natGd2O3-doped micro-channel plate (MCP) has been developed and tested. A thermal neutron imaging experiment was carried out with a low flux neutron beam. Detection efficiency of 33% was achieved with only one doped MCP. The spatial resolution of 72 μm RMS is currently limited by the readout anode. A detector with larger area and improved readout method is now being developed.
Proton irradiation effect on SCDs
YANG Yan-Ji, LU Jing-Bin, WANG Yu-Sa, CHEN Yong, XU Yu-Peng, CUI Wei-Wei, LI Wei, LI Zheng-Wei, LI Mao-Shun, LIU Xiao-Yan, WANG Juan, HAN Da-Wei, CHEN Tian-Xiang, LI Cheng-Kui, HUO Jia, HU Wei, ZHANG Yi, LU Bo, ZHU Yue, MA Ke-Yan, WU Di, LIU Yan, ZHANG Zi-Liang, YIN Guo-He, WANG Yu
2014, 38(8): 086004. doi: 10.1088/1674-1137/38/8/086004
The Low Energy X-ray Telescope is one of the main payloads on the Hard X-ray Modulation Telescope satellite. Swept charge devices (SCDs) are selected as detectors for the Low Energy X-ray Telescope. As SCDs are sensitive to proton irradiation, irradiation tests were carried out on the HI-13 accelerator at the China Institute of Atomic Energy. The beam energy was measured to be 10 MeV at the SCD. The proton fluence delivered to the SCD was 3×108 protons cm2 over two hours. By comparing the performance before and after irradiation, it is concluded that proton irradiation affects both the dark current and the charge transfer inefficiency of the SCD. The energy resolution of the proton-irradiated SCD is 212 eV@5.9 keV at -60℃, while it before irradiated is 134 eV. Moreover, better performance can be reached by lowering the operating temperature of the SCD in orbit.
Waveform digitizing for LaBr3/NaI phoswich detector
SHE Rui, JI Jian-Feng, FENG Hua, LI Hong, HAN Dong
2014, 38(8): 086005. doi: 10.1088/1674-1137/38/8/086005
The detection efficiency of phoswich detector starts to decrease when Compton scattering becomes significant. Events with energy deposit in both scintillators, if not rejected, are not useful for spectral analysis as the full energy of the incident photon cannot be reconstructed with conventional readout. We show that once the system response is carefully calibrated, the full energy of those double deposit events can be reconstructed using a waveform digitizer as the readout. Our experiment suggests that the efficiency of a photopeak at 662 keV can be increased by a factor of 2 using our LaBr3/NaI phoswich detector.
Design and simulation of a wire position monitor for cryogenicsystems in an ADS linac
ZHU Hong-Yan, DONG Lan, LI Bo
2014, 38(8): 087001. doi: 10.1088/1674-1137/38/8/087001
This paper introduces the design and simulation of a Wire Position Monitor (WPM) used in the cryogenic system of an Accelerator Driven System (ADS). The WPM is designed to monitor the contraction of cold masses during the cooling-down operation. In this paper, POISSON-2D electrostatic field software is used to calculate the best characteristic impedance for the WPM. Furthermore, the time domain signal of different end structures is theoretically analyzed and simulated. The coupling of electrodes and the influence of signal carrier size, which may influence the induced signal, are also discussed. Finally, the linearity of the induced voltage and the sensitivity of the WPM are analyzed. The time domain simulation results are consistent with the theoretical analysis. The influences of the coupling and carrier size are very small, and the linearity of the normalized voltage is good within r/2.
Characterizing a proton beam with two different methods inbeam halo experiments
JIANG Hong-Ping, FU Shi-Nian, PENG Jun, CHENG Peng, HUANG Tao, LI Peng, LI Fang, LI Jian, LIU Hua-Chang, LIU Mei-Fei, MENG Ming, MENG Cai, MU Zhen-Cheng, RONG Lin-Yan, OUYANG Hua-Fu, SUN Biao, WANG Bo, TIAN Jian-Min, WANG Biao, WANG Sheng-Chang, YAO Yuan, XU Tao-Guang, XU Xin-An, XIN Wen-Qu, ZHAO Fu-Xiang, ZENG Lei, ZHOU Wen-Zhong
2014, 38(8): 087002. doi: 10.1088/1674-1137/38/8/087002
In beam halo experiments, it is very important to correctly characterize the RFQ output proton beam. In order to simulate the beam dynamics properly, we must first know the correct initial beam parameters. We have used two different methods, quadrupole scans and multi-wire scanners to determine the transverse phase-space properties of the proton beam. The experimental data were analyzed by fitting to the 3-D nonlinear simulation code IMPACT. For the quadrupole scan method, we found that the RMS beam radius and the measured beam-core profiles agreed very well with the simulations. For the multi-wire scanner method, we choose the case of a matched beam. By fitting the IMPACT simulation results to the measured data, we obtained the Courant-Snyder parameters and the emittance of the beam. The difference between the two methods is about eight percent, which is acceptable in our experiments.
First experimental research in low energy proton radiography
WEI Tao, YANG Guo-Jun, LI Yi-Ding, LONG Ji-Dong, HE Xiao-Zhong, ZHANG Xiao-Ding, JIANG Xiao-Guo, MA Chao-Fan, ZHAO Liang-Chao, YANG Xing-Lin, ZHANG Zhuo, WANG Yuan, PANG Jian, LI Hong, LI Wei-Feng, ZHOU Fu-Xin, SHI Jin-Shui, ZHANG Kai-Zhi, LI Jin, ZHANG Lin-Wen, DENG Jian-Jun
2014, 38(8): 087003. doi: 10.1088/1674-1137/38/8/087003
Proton radiography is a new scatheless diagnostic tool providing a potential development direction for advanced hydrotesting. Recently a low energy proton radiography system has been developed at the Chinese Academy of Engineering Phyiscs (CAEP). This system has been designed to use an 11 MeV proton beam to radiograph thin static objects. This system consists of a proton cyclotron coupled to an imaging beamline, which is the first domestic beamline dedicated to proton radiography experiments. Via some demonstration experiments, the radiography system is confirmed to provide clear pictures with spatial resolution ~ 100 μm within 40 mm field-of-view.
Calculations for shortening the bunch length in storage rings using a harmonic cavity
FAN Hao, WU Cong-Feng, HE Duo-Hui
2014, 38(8): 087004. doi: 10.1088/1674-1137/38/8/087004
Using the Hefei Light Source phase Ⅱ project (HLS-Ⅱ) as an example, a theoretical analysis of shortening the bunch lengths using a higher harmonic cavity (HHC) is given. The threshold voltage of an active HHC and the threshold tuning angle of a passive HHC are first analysed. The optimum tuning angle for the constant detuning scenario and the optimum harmonic voltage for the constant voltage scenario are presented. The calculated results show that the reduced bunch length is about half that of the nominal bunch. The bunch lengths vary from 11 mm at 0.1 A to 7 mm at 0.4 A for the constant detuning scenario, while the bunch lengths are around 7 mm over the beam current range for the constant voltage scenario. In addition, the synchrotron frequency spread is increased. It indicates that HHC may be used to reduce the bunch length and increase the Landau damping of synchrotron oscillations in a storage ring.
Mechanical design and analysis of a low beta squeezedhalf-wave resonator
HE Shou-Bo, ZHANG Cong, YUE Wei-Ming, WANG Ruo-Xu, XU Meng-Xin, WANG Zhi-Jun, HUANG Shi-Chun, HUANG Yu-Lu, JIANG Tian-Cai, WANG Feng-Feng, ZHANG Sheng-Xue, HE Yuan, ZHANG Sheng-Hu, ZHAO Hong-Wei
2014, 38(8): 087005. doi: 10.1088/1674-1137/38/8/087005
A superconducting squeezed type half-wave resonator (HWR) of β=0.09 has been developed at the Institute of Modern Physics, Lanzhou. In this paper, a basic design is presented for the stiffening structure for the detuning effect caused by helium pressure and Lorentz force. The mechanical modal analysis has been investigated the with finite element method (FEM). Based on these considerations, a new stiffening structure is proposed for the HWR cavity. The computation results concerning the frequency shift show that the low beta HWR cavity with new stiffening structure has low frequency sensitivity coefficient df/dp and Lorentz force detuning coefficient KL, and stable mechanical properties.
Synchrotron radiation,applications of nuclear techniquees,etc
An analysis of undulator optimization in self-seedingfree electron lasers
2014, 38(8): 088101. doi: 10.1088/1674-1137/38/8/088101
A simple analysis is given for the optimum length of undulator in a self-seeding free electron laser (FEL). The obtained relations show the correlation between the undulator length and the system parameters. The power required for the seeding in the second part of the undulator and the overall efficiency of monochromatizating the seeding determine the length of the first part of the undulator; the magnitude of seeding power dominates the length of the second part of the undulator; the whole length of the undulator in a self-seeding FEL is determined by the overall efficiency for getting coherent seed, and is about half as long again as that of SASE, not including the dispersion section. The requirement of the dispersion section strength is also analyzed.
Evolutionary genetic optimization of the injector beamdynamics for the ERL test facility at IHEP
2014, 38(8): 088102. doi: 10.1088/1674-1137/38/8/088102
The energy recovery linac test facility (ERL-TF), a compact ERL-FEL (free electron laser) two-purpose machine, has been proposed at the Institute of High Energy Physics, Beijing. As one important component of the ERL-TF, the photo-injector was designed and preliminarily optimized. In this paper an evolutionary genetic method, non-dominated sorting genetic algorithm Ⅱ, is applied to optimize the injector beam dynamics, especially in the high-charge operation mode. Study shows that using an incident laser with rms transverse size of 1-1.2 mm, the normalized emittance of the electron beam can be kept below 1 mm·mrad at the end of the injector. This work, together with the previous optimization of the low-charge operation mode by using the iterative scan method, provides guidance and confidence for future construction and commissioning of the ERL-TF injector.
Beam dynamics simulations of the injector for a compact THz source
LI Ji, PEI Yuan-Ji, SHANG Lei, FENG Guang-Yao, HU Tong-Ning, CHEN Qu-Shan, LI Cheng-Long
2014, 38(8): 088103. doi: 10.1088/1674-1137/38/8/088103
Terahertz radiation has broad application prospects due to its ability to penetrate deep into many organic materials without the damage caused by ionizing radiations. A free electron laser (FEL)-based THz source is the best choice to produce high-power radiation. In this paper, a 14 MeV injector is introduced for generating high-quality beam for FEL, is composed of an EC-ITC RF gun, compensating coils and a travelling-wave structure. Beam dynamics simulations have been done with ASTRA code to verify the design and to optimize parameters. Simulations of the operating mode at 6 MeV have also been executed.
Neutronic calculations for CANDU thorium systems usingMonte Carlo techniques
M. Saldideh, M. Shayesteh, M. Eshghi
2014, 38(8): 088201. doi: 10.1088/1674-1137/38/8/088201
In this paper, we have investigated the prospects of exploiting the rich world thorium reserves using Canada Deuterium Uranium (CANDU) reactors. The analysis is performed using the Monte Carlo MCNP code in order to understand how much time the reactor is in criticality conduction. Four different fuel compositions have been selected for analysis. We have obtained the infinite multiplication factor, k, under full power operation of the reactor over 8 years. The neutronic flux distribution in the full core reactor has already been investigated.
A simulation study of a dual-plate in-room PET system for dose verification in carbon ion therapy
CHEN Ze, HU Zheng-Guo, CHEN Jin-Da, ZHANG Xiu-Ling, GUO Zhong-Yan, XIAO Guo-Qing, SUN Zhi-Yu, HUANG Wen-Xue, WANG Jian-Song
2014, 38(8): 088202. doi: 10.1088/1674-1137/38/8/088202
During carbon ion therapy, lots of positron emitters such as 11C, 15O, 10C are generated in irradiated tissues by nuclear reactions, and can be used to track the carbon beam in the tissue by a positron emission tomography (PET) scanner. In this study, an dual-plate in-room PET scanner has been designed and evaluated based on the GATE simulation platform to monitor patient dose in carbon ion therapy. The dual-plate PET is designed to avoid interference with the carbon beamline and with patient positioning. Its performance was compared with that of four-head and full-ring PET scanners. The dual-plate, four-head and full-ring PET scanners consisted of 30, 60, 60 detector modules, respectively, with a 36 cm distance between directly opposite detector modules for dose deposition measurements. Each detector module consisted of a 24×24 array of 2 mm×2 mm×18 mm LYSO pixels coupled to a Hamamatsu H8500 PMT. To estimate the production yield of positron emitters, a 10 cm×15 cm×15 cm cuboid PMMA phantom was irradiated with 172, 200, 250 MeV/u 12C beams. 3D images of the activity distribution measured by the three types of scanner are produced by an iterative reconstruction algorithm. By comparing the longitudinal profile of positron emitters along the carbon beam path, it is indicated that use of the dual-plate PET scanner is feasible for monitoring the dose distribution in carbon ion therapy.
Tritium and helium analyses in thin films by enhancedproton backscattering
FU Tao, AN Zhu, ZHU Jing-Jun, LIU Man-Tian, MAO Li
2014, 38(8): 088203. doi: 10.1088/1674-1137/38/8/088203
In order to study how to reliably perform quantitative tritium and helium analyses in thin film samples using enhanced proton backscattering (EPBS), several EPBS spectra for some samples consisting of non-RBS light elements (i.e., T, 4He, 12C, 16O, natSi), medium and heavy elements have been measured and analyzed using analytical SIMNRA and Monte Carlo-based CORTEO codes. The non-RBS cross sections needed in the CORTEO code are taken from the ENDF/B-Ⅶ.1 database and the calculations of SigmaCalc code and are incorporated into the CORTEO code. All non-RBS cross section data over the entire proton incident energy-scattering angle plane are obtained by interpolation. It is quantitatively observed that in EPBS analysis the multiple and plural scattering effects have little impact on the energy spectra for light elements and the RBS cross sections of light elements can be used in the SIMNRA code for dual scattering calculations. It is also observed that the results given by the CORTEO code are higher than the results of the SIMNRA code in the low energy part of EPBS spectra, and are in better agreement with the experimental data. Tritium and helium analyses in thin film samples using EPBS can be performed reliably when the multiple and plural scattering contributions are completely accounted.