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2018 Vol. 35, No. 3

Nuclear Physics
Status of the Chiral Magnetic Effect Search in Relativistic Heavy-ion Collisions
ZHAO Jie, TU Zhoudunming, WANG Fuqiang
2018, 35(3): 225-242. doi: 10.11804/NuclPhysRev.35.03.225
Abstract:
Quark interactions with topological gluon fields in QCD can yield local P and CP violations which could explain the matter-antimatter asymmetry in our universe. Effects of P and CP violations can result in charge separation under a strong magnetic field, a phenomenon called the chiral magnetic effect (CME). Experimental measurements of the CME-induced charge separation in heavy-ion collisions are dominated by physics backgrounds. Major theoretical and experimental efforts have been devoted to eliminating or reducing those backgrounds. We review the current status of these efforts in the search for the CME in heavy-ion collisions.
Evidence for Rotational to Vibrational Evolution Along the Yrast Line in the Odd-A Rare-earth Nuclei
ZHOU Houbing, HUANG Shan, DONG Guoxiang, SHEN Zixu, LU Huijin, WANG Lele, SUN Xiaojun, XU Furong
2018, 35(3): 243-249. doi: 10.11804/NuclPhysRev.35.03.243
Abstract:
The phase transition of nuclei with increasing angular momentum (or spin) and excitation energy is one of the most fundamental topics of nuclear structure research. The odd-N nuclei with A ≈160 are widely considered belonging to the well-deformed region, and their excitation spectra are energetically favored to exhibit the rotational characteristics. In this work, however, the evidence suggesting that the nuclei changes from rotation to vibration along the yrast lines as a function of spin was found. The simple method, named as E-Gamma Over Spin (E-GOS) curves, would be used to discern the evolution from rotational to vibrational structure in nuclei for various spin ranges. Meanwhile, in order to understand the band structure properties of nuclei, theoretical calculations have been performed for the yrast bands of the odd-A rare-earth nuclei within the framework of the total routhian surface (TRS) model. The TRS plots predict that the 165Yb and 157Dy isotopes have large quadrupole shapes at low spin states. At higher rotational frequency (~ >0.50 MeV), a clear reduction of the quadrupole deformation is indicated by the present results, and the isotopes become rigid in the γ deformation.
Strong-coupling Critical Point Symmetries for Axially-symmetric Odd-A Nuclei
AN Siyu, JIANG He, DONG Wenting, ZHANG Yu
2018, 35(3): 250-256. doi: 10.11804/NuclPhysRev.35.03.250
Abstract:
In view of the successful application of the methods based on critical point symmetries (CPSs) in nuclear shape phase transitions, the new CPSs named SX(n) are established in this work for axially-symmetric odd-A nuclei through extending the original X(n) CPSs with n=3,4,5, which were used to describe the spherical to prolate shape phase transitions in even-even nuclei, in the strong-coupling scheme. By comparing the spectral structures in between the X(n) and the SX(n) CPSs, it is revealed that the dynamical structures of SX(n) are closer to the rigid rotor and less changed with the model dimension in comparison with X(n). Moreover, these features of SX(n) are preliminarily verified by checking the rotational structures of 150,151,152,153Sm and 172,173,174,175Os nuclei.
Systematic Study of Proton Radioactivity Based on Two-potential Approach with Folding Potentials
CHEN Jiulong, CHENG Junhao, DENG Jungang, LI Xiaohua
2018, 35(3): 257-263. doi: 10.11804/NuclPhysRev.35.03.257
Abstract(1249) PDF (288KB)(143)
Abstract:
In the present work, we systematically study the half-lives of proton radioactivity for 51 ≤ Z ≤ 83 nuclei within the two-potential approach. The total emitted proton-daughter nucleus interaction potential is composed of the microscopic nuclear potential obtained by single folding the density of the daughter nucleus with the DDM3Y effective interaction, the realistic Coulomb potential obtained by single folding the charge density of the daughter nucleus with the proton-proton Coulomb interaction and the centrifugal potential. We extend our study to predict proton radioactivity half-lives of 16 nuclei in the same region within a factor of 4.11. In addition, the Geiger-Nuttall law for proton radioactivity is researched. The results indicate that the Geiger-Nuttall law can be used to describe the proton radioactivity isotopes with same angular momentum.
Imprint on the Neutron Star Global Properties by Part of the Equation of State
ZHANG Na, WEN Dehua
2018, 35(3): 264-269. doi: 10.11804/NuclPhysRev.35.03.264
Abstract(1284) PDF (561KB)(113)
Abstract:
Because of the complicacy of the interaction between the nucleon-nucleon for high density matters, up to now the equation of state (EOS) of the unsymmetrical high-density nuclear matter is still uncertain. In order to investigate the imprint on the global properties by some special part of the EOS, we designedly modify part of the EOS and explore the corresponding effect on the stellar properties, especially on the radius of the typical neutron star (1.4 M) and the maximum stellar mass of the neutron star sequence for a given EOS. It is further proved by our calculation that the EOS around 2 times of the saturation nuclear density has an obvious imprint on the stellar radius of a typical neutron star. In addition, we also investigate the dependence of the mass-radius curve and its slope (dM/dR) on the EOS. It is found that the slope (dM/dR) is mainly determined by the EOS above the saturation nuclear density. In fact, the investigations above will provide some useful theoretical reference. This is expected to conversely constrain the EOS of dense matter by using the future astronomic observation data of neutron star.
Accelerator
Ion Optics Design of the Isochronous Modes for the HIAF/Sring
WU Bo, YANG Jiancheng, GE Wenwen, XIA Jiawen, SHEN Guodong, YAN Xinliang
2018, 35(3): 270-277. doi: 10.11804/NuclPhysRev.35.03.270
Abstract:
The Spectrometer Ring, as the most important experiment terminal of the High Intensity heavy-ion Accelerator Facility (HIAF) project, is a key device to obtain high-quality radioactive ion beams (RIBs) for atomic physics, nuclear physics experiments and accelerator technology researches. Three operation modes including the isochronous mode, the normal mode and the internal target mode, have been designed for the SRing. In the isochronous mode, the SRing operates under a special ion optics and could be used for precision mass measurement of short-lived nuclei with half-life shorter than several tens of microseconds. This study aims to design the ion optics for the isochronous mode and improve the mass resolving power of the SRing with higher-order ion-optical correction scheme for isochronism while preserve a large momentum acceptance of SRing. The ion optics and the higher-order correction for the isochronous mode are calculated with the code MAD-X and GICOSY respectively. Three ion optics with γt=1.43, 1.67, 1.83 settings have been calculated. The code MCOADI which utilizes the matrixes generated by the code GICOSY is used for particles tracking to verify the correction results. For the ion-optical setting of γt=1.43 with a momentum acceptance of ±0.20%, the mass resolving power of the SRing could be improved from R=1.6×104 to R=1.2×106, after isochronous higher-order corrections.
Research on Plasma Discharge for Plasma Processing of a 1.3 GHz Single-cell SRF Cavity
YANG Lei, WU Andong, LU Liang, LI Yongming, XU Xianbo, CHEN Long, LI Chenxing, SUN Liepeng, LI Chunlong, MA Wei, HE Tao, XING Chaochao, HE Yuan
2018, 35(3): 278-286. doi: 10.11804/NuclPhysRev.35.03.278
Abstract:
Field emission limits the accelerating gradient increase in SRF cavities. In order to reduce field emission of SRF cavities, the plasma processing experimental setup of a 1.3 GHz single-cell SRF cavity is designed and built to carry out plasma processing discharge research at room temperature. The electromagnetic field distribution is simulated and the external quality factor is optimized to provide a suitable discharge condition using CST software. It is explored that the physical property of Ar/Ar-O2 discharge and the variation trend of electron excitation temperature with the changes of pressure, forward power and O2 content in experiment. The result of residual gas analysis indicates that Ar/O2 plasma processing can eliminate the carbide of the inner surface of cavity.
Availability Designs and Analyses of Solid-state Amplifiers for CiADS
GAO Penghui, WANG Zhijun, SUN Liepeng, JIA Yongzhi, QIN Yuanshuai, HE Yuan, HUANG Guirong
2018, 35(3): 287-293. doi: 10.11804/NuclPhysRev.35.03.287
Abstract(1217) PDF (588KB)(109)
Abstract:
One of the challenging technologies of ADS is the high availability requirement. The availability design of the solid-state amplifier is the preparation for ADS. Firstly the availability requirement of CiADS is proposed as 0.8. The distribution result of the solid-state amplifier is 0.999 according to this requirement. Then the availability result shows the preliminary design of solid-state amplifiers can not reach the availability requirement. At last the power loss is considered to build the k/N redundancy model of the main amplifier and the mean time between failure (MTBF) is calculated for various redundancy models. The reliability block diagram of the solid-state amplifier is set up by Reliasoft and the simulation results show that the 25/28 redundancy model can meet the requirement 0.999 when MTBF of other components reaches 171 702 hours with the certain maintenance.
Analysis and Test of New Tuning Algorithm for Low Beta Superconducting Cavity
MA Tengfei, XUE Peng, KEN Fong, WANG Xianwu, HUANG Guirong, GAO Zheng, GONG Zheng, ZHU Zhenglong
2018, 35(3): 294-301. doi: 10.11804/NuclPhysRev.35.03.294
Abstract:
For the purposes of keeping the resonant cavity steady in a complex electromagnetic environment and maintaining stable amplitude and phase, a new tuning algorithm for superconducting RF cavity operated in self-excited phase-locked mode has been developed. The quadrature voltage was employed to control the tuner under the phase-locked condition, so as to eliminate phase measurement between the input and the output. This paper demonstrates the principle of this "Minimum Q" tuning algorithm and presents an analysis of the stability of the system. The algorithm is applied to the superconducting accelerator of the Institute of Modern Physics' ADS project. The "Minimum Q" tuning algorithmnot only simplifies the number of signal sampling but also improves the control accuracy and anti-interference ability of the system, while enables the cavity to overcome the helium pressure fluctuation which caused by power overshoot. It ensures that the frequency of the superconducting cavity is stable at 162.5 MHz, and the frequency error is less than 17 Hz.
Nuclear Technology
Shielding Design for BRing and High-energy Experimental Terminal in HIAF
LI Wuyuan, XU Junkui, YANG Yao, SU Youwu, YAN Weiwei, YANG Bo, MAO Wang, XU Chong, WANG Lijun
2018, 35(3): 302-307. doi: 10.11804/NuclPhysRev.35.03.302
Abstract(1123) PDF (862KB)(134)
Abstract:
High Intensity heavy-ion Accelerator Facility (HIAF) is designed by the Institute of Modern Physics, Chinese Academy of Sciences, which can accelerate particles from proton up to uranium. To guarantee the radiation safety of HIAF during operation, the FLUKA code and extrapolation method were adopted to calculate the shielding thickness. The calculations were based on proton, carbon and uranium particles when losing on the Booster Ring (BRing) and the high-energy experimental terminal. The results indicate that the shielding thickness required for accelerating protons was the largest. Basing on the results, a method for estimating the lateral shielding of a high-energy proton/heavy-ion accelerator was proposed. A good agreement shows between the estimated results and the FLUKA calculated results, the validity and accuracy of the method were verified.
Design of the Data Transfer System for Radio Frequency Transmitter Based on FPGA and W5100
HAN Xiaodong, XU Zhe, CONG Yan, LI Shilong, ZHANG Ruifeng, YI Xiaoping
2018, 35(3): 308-312. doi: 10.11804/NuclPhysRev.35.03.308
Abstract:
Radio frequency system is the power core of Heavy Ion Medical Machine. Transmitter, as a key component of the high frequency system, depends heavily on the monitoring system to ensure its stability and reliability. In order to perform a reliable transmission of remote monitoring data of transmitter working state, a data transmission system based on field programmable gate array (FPGA) and network interface chip (W5100) is proposed. The system consists of three parts. Firstly, the hardware of the data transmission system is designed based on FPGA and W5100. Secondly, the reliable data communication under TCP Server mode is achieved by using Hardware Description Language (HDL). Finally, the upper computer monitoring interface is designed and realized by using Flash Builder platform. After a long time testing, the system runs stably and reliably, and the average data transmission rate reaches 11.32 Mbps. The system is capable of remote monitoring to the high frequency transmitters.
Cross Discipline
Surface Plasmon Resonances of Palladium Nanowire Arrays Prepared by Ion Track Technology
ZHAO Cong, HUANG Kejing, LYU Shuangbao, XU Guoheng, CHENG Hongwei, LIU Jie, YAO Huijun, SUN Youmei, XU Lijun, DUAN Jinglai
2018, 35(3): 313-320. doi: 10.11804/NuclPhysRev.35.03.313
Abstract:
Palladium nanowires with varied diameters were fabricated using ion-track templates coupled with electrochemical deposition. The morphology and crystallographic structure were characterized with Scanning Electron Microscopy, Transmission Electron Microscopy, X-ray diffraction (XRD). The plasmonic responses of the as-prepared nanowires were investigated by UV-Vis-NIR spectroscopy and the simulations based on the finite-difference time-domain algorithm. The results demonstrate that the surface plasmon resonances of Pd nanowire are sensitive to the wire geometry, but also influenced by the incidence angle of light. The frequency of the transverse dipolar plasmon resonance of nanowire arrays shifts within a wide range from visible to near infrared. With increasing of wires' diameter or length, the resonance peak shifts to the red. With increasing of incident angle, a new peak appears, which is possibly assigned to the excitation of the longitudinal resonance. In addition, numerical simulations disclose that propagating surface plasmon polaritons can be excited on the palladium nanowires and the wavelength of the resonance peak is in good agreement with the experimental results.
Feasibility Study on Whether Divergent Aperture can be Used on Proton Therapy Radiotherapy
LIU Chunbo, LIU Hongdong, HUO Wanli, PEI Xi
2018, 35(3): 321-326. doi: 10.11804/NuclPhysRev.35.03.321
Abstract:
Passive Scattering Proton Therapy (PSPT) is one of the main technologies for proton radiation therapy. The dose distribution in the patient deviates from the ideal state due to the edge scattering effect when the beam passes through the aperture. In this paper, TOPAS, a Monte Carlo software, was used to simulate the passive scattering treatment head. The influence of the edge scattering effect of the two aperture sets on the dose distribution was compared. The proton beam at 70, 110, 160, 200, 230 and 250 MeV was tested respectively. We found that the scattering effect of the conventional aperture is most obvious at 70 MeV, and the flatness and hetergeneity of the lateral dose curve at the inlet of 0.5 cm of the tank reach 4.63%, 108.05%, respectively. The dose shift caused by the edge scattering effect decreases with increasing water depth and disappears at the Bragg peak. After using the divergent aperture, the flatness and uniformity at 70 MeV are reduced to 1.28% and 101.31%, respectively, and the 100, 160, and 200 MeV proton beams are improved in different extents. For a proton beam with an energy close to 250 MeV, there is no advantage in the lateral dose curve of the divergent aperture. For all energy protons, the secondary neutrons are reduced with divergent aperture. The results show that the divergent aperture is effective for PSPT and this study provides data support for further application in clinical practice.
Theoretical Studies of Dielectronic Recombination Rate Coefficients for Re30+ Ions
TIAN Rui, FU Yanbiao, WEI Erlong, DONG Chenzhong
2018, 35(3): 327-334. doi: 10.11804/NuclPhysRev.35.03.327
Abstract:
Dielectronic recombination (DR) rate coefficients of complex ions are very important in some application research, such as extreme ultraviolet lithography and nuclear fusion. Based on the fully relativistic configuration interaction method, theoretical calculations are carried out to research the DR processes, in which Re30+ ions in the ground state 4p64d9 to (4p64d9)-1nln'l'(n=4~6, n'=4~23). Influence of excitation and radiation channels, configuration interaction, the effect of decays to autoionizing levels possibly followed by radiative cascades (DAC) are analyzed. The contributions through 4p subshell excitations to the total rate coefficient are 28.2%~44.9% in the whole temperature region. Hence the contributions from inner-shell electron excitation are very important. The contributions from the DAC transitions increase smoothly with the increasing temperature and are about 12.9% at 50 000 eV. The contributions of DAC can not be neglected. By means of compared total DR rate coefficients to radiative recombination rate coefficients and three-body recombination rate coefficients, it shows that the maximum value of the radiation recombination rate coefficient is 22.6% of the DR rate coefficient and the maximum value of the three-body recombination rate coefficient is only 0.3% of the DR rate coefficient. The total DR rate coefficient is greater than either the radiative recombination or three-body recombination coefficients in the whole temperature range. The corresponding DR process is very important for plasma ionization distribution, population level and spectrum simulation. In addition to facilitate the application, the total DR rate coefficients for the ground state and the first excited state are fitted to an empirical formula. These results will provide the reference for the further analyses of rhenium laser plasma spectrum simulation and the complex structures ions DR process.
Nuclear Energy and Nuclear Data
Comparison of the Thermal Neutron Scattering Cross Section of Water Based on ENDF/B-VIII.β and ENDF/B-VII.1
LI Zhifeng, CAI Jiejin
2018, 35(3): 335-338. doi: 10.11804/NuclPhysRev.35.03.335
Abstract(1337) PDF (480KB)(118)
Abstract:
This work takes the traditional moderator material H2O for example, the differences between ENDF/B-VⅢ.β and ENDF/B-VⅡ.1 versions from the ENDF/B nuclear evaluated library are analyzed. In order to compare the thermal neutron scattering data between ENDF/B-VⅢ.β and ENDF/B-VⅡ.1 versions under the same temperature, the interpolation method is used to obtain the thermal neutron scattering data under arbitrary temperatures. There are some differences between ENDF/B-VⅢ.β and ENDF/B-VⅡ.1 versions, the thermal neutron scattering cross sections of H bound in H2O within ENDF/B-VⅢ.β is different with that of ENDF/B-VⅡ.1, the scattering angle cosines of the neutron and target nuclei from the two libraries are slightly smaller than zero in lower energy range within thermal range. Moreover, the second scattering energy spectrum from ENDF/B-VⅢ.β is slightly harder than that from the ENDF/B-VⅡ.1 in higher energy range within thermal range when the temperature is higher than room temperature.