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2020 Vol. 37, No. 4

2020, (4): 1-2.
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2020, (4): 1-12.
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Nuclear Physics
Investigation of Diffusion Process in Deep Sub-barrier Fusion Reactions
Kaixuan CHENG, Chang XU
2020, 37(4): 809-815. doi: 10.11804/NuclPhysRev.37.2020039
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We introduce a new diffusion factor to describe the hindrance phenomenon in fusion reactions at deep sub-barrier energies based on the Pauli blocking effect after the projectile and target overlap. In this approach, the fusion cross sections are assumed to be the product of two parts: the tunneling factor to overcome the Coulomb barrier and the diffusion factor after two colliding nuclei contact. The former is described by coupled-channels approach and the latter depends on the colliding energies as well as the temperature of system. In total, 21 fusion systems with hindrance phenomenon are analyzed in details and it is found that the diffusion factor plays an important role near the experimental threshold energies of fusion hindrance. In addition, taking negative-Q-value system 64Ni+64Ni and positive-Q-value system 24Mg+30Si as examples, not only fusion cross sections but also two important representations, namely, astrophysical S factor and logarithmic derivative, are found to be in good agreement with experimental data.
Study Progress of the 25Mg(p, γ)26Al Experiments
Zhihong LI, Yunju LI, Jun SU, Hao ZHANG, Yangping SHEN, Shengquan YAN, Youbao WANG, Bing GUO, Gang LIAN, Sheng ZENG, Guozhu HE, Qiwei ZHANG, Long ZHANG, Fuqiang CAO, Xinyue LI, Tianli MA, Ding NAN, Baoqun CUI, Lihua CHEN, Weiping LIU
2020, 37(4): 816-824. doi: 10.11804/NuclPhysRev.37.2020028
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The long-lived radionuclide 26Al is one of the most important nuclide in the study of interstellar medium, \begin{document}$\gamma$\end{document}-ray astronomy and the formation of the solar system. The three celestial sites most likely to synthesize 26Al are related to the 25Mg (\begin{document}${\rm p},\,{\rm{\gamma }}$\end{document})26Al reaction, therefor the accurate measurement of the near-threshold level resonant strength and astrophysical reaction rates is of great significance to understand the origin of 26Al in the universe. This article reviews the experimental research methods and the recent progress in the 25Mg (\begin{document}${\rm p},\,{\rm{\gamma }}$\end{document})26Al experiment. Especially, the indirect measurement and direct measurement plan for this reaction in China is introduced. The current indirect measurement results have improved the experimental accuracy of the 25Mg (\begin{document}${\rm p},\,{\rm{\gamma }}$\end{document})26Al astrophysics reaction rates, which can help us estimate the yield of direct measurement and optimize the experimental design. The direct measurement results of high-energy level resonance are in good agreement with the existing experiments within the error bars, indicating that the designed detection system by this project is in good working condition and can be competent for the experiment of Jinping deep underground nuclear astrophysics.
Using Deep Learning to Study the Equation of State of Nuclear Matter
Fupeng LI, Yongjia WANG, Qingfeng LI
2020, 37(4): 825-832. doi: 10.11804/NuclPhysRev.37.2020017
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The equation of state (EOS) of nuclear matter is essential for studying the properties of nuclei and the evolution of universe and astro-objects. Heavy-ion collisions at intermediate energies permit creating nuclear matter with high density and temperature, by comparing transport model simulations with the corresponding experimental data offers one of the most important way to study the nuclear EOS. Unfortunately, different models do not always give the same results. In this work, a deep convolutional neural network (CNN) is used to identify the nuclear EOS from the spectra in transverse momentum and rapidity of protons. It is found that the network can be taken as a useful decoder to extract the nuclear EOS from the transverse momentum and rapidity distribution of protons. By using the Prediction Difference Analysis method, the most sensitive region of the transverse momentum and rapidity distribution to the nuclear EOS can be found out, which may offer an alternative strategy for experimental and theoretical studies of heavy-ion collisions. In addition, a gradient boosting framework (LightGBM) that uses tree based learning algorithms is also applied, and it is found that the accuracy obtained with the LightGBM is similar to that with CNN.
Operator Changing Between Two Vacua of the ϕ4 Quantum Field Theory
Hui LIU, Hengyuan GUO, Yao ZHOU, Evslin Jarah
2020, 37(4): 833-841. doi: 10.11804/NuclPhysRev.37.2020018
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In this note, we normal order the Hamiltonian of \begin{document}$\phi^4$\end{document} model to regularize the vacuum energy, based on canonical quantization. We perturbatively calculate the correction of the vacuum state to the second order, meanwhile at the first time get an operator that can change between two vacua of the \begin{document}$\phi^4$\end{document} quantum field theory. We believe this operator is at the same time the \begin{document}$\phi^4$\end{document} kink operator in a certain limit. In the end we give a brief introduction to the application of the vacuum energy.
Accelerator
Development and Validation of Lattice Adjustment Application Based on PACS under DC/Pulse Dual-mode
Guimei MA, Jie LIU, Jiancheng YANG, Weiping CHAI, Yunpeng ZHU, shuang RUAN
2020, 37(4): 842-847. doi: 10.11804/NuclPhysRev.37.2019057
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To reduce the amount of duplication efforts of physical and program developers, a portable, extensible and maintainable PACS (Physics-oriented Accelerator Control System) is proposed and implemented for heavy ion accelerator facilities by IMP (Institute of Modern Physics, Chinese Academy of Sciences). For testing the feasibility of the PACS, a lattice adjustment application and its new GUI for both DC and pulse modes is programmed by Python language. The DC mode, built with the SQL database and soft IOC of the EPICS, is performed in the HIRFL-CSRe. In addition, the pulse mode is tested in the HIRFL-CSRm. The testing results show that the tune adjustment and optics calculation in the two modes are implemented successfully, and the PACS can provide the interfaces between the modules and layers. Therefore, the framework of the PACS is feasible.
Simulation and Evaluation of Beam Loading Feedforward Compensation for CiADS Linac
Chengye XU, Zhijun WANG, Zheng GAO, Guirong HUANG, Ran HUANG, Jinying MA
2020, 37(4): 848-853. doi: 10.11804/NuclPhysRev.37.2020023
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For a high power superconducting proton linac, the transient beam loading effect is an important factor affecting the amplitude and phase stability of the electromagnetic field in a superconducting cavity. Based on the resonant cavity field model, a time-domain simulation code for the beam loading effect in a superconducting cavity was developed, and the simulation results were verified in the prototype injector II of C-ADS. It was then evaluated the influence of pulse width, feedforward timing jitter and beam ripple for CiADS. The simulation results, to meet the design specification, showed that the Radio frequency(RF) fluctuations for each cavity should be less than 0.1% in amplitude and \begin{document}$0.1^{\circ}$\end{document} in phase. And the feedforward timing jitter should not exceed 0.79 µs, the beam DC deviation should not exceed 0.9%. The relationship between the maximum ripple amplitude and the ripple frequency was given. These results will provide a basis for determining technical specifications of relevant sub-systems of CiADS.
Optimum Design of the Magnetic Mirror Structure for Testing Nb3Sn Sextupole Coil
Li ZHU, Wei WU, Shurong YU, Yuquan CHEN, Enming MEI, Peng MA, Qinggao YAO, Liangting SUN
2020, 37(4): 854-858. doi: 10.11804/NuclPhysRev.37.2020034
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The Institute of Modern Physics, Chinese Academy of Sciences is developing the new Nb3Sn superconducting magnet system for the fourth-generation 45 GHz ECR source(FECR). The FECR magnet coils includes six Nb3Sn superconducting sextuple coils and four Nb3Sn solenoid coils. Because of the technical difficulty of winding shaped sextupole coils (non-standard saddle type) from a single superconducting wire and the stress sensitivity of Nb3Sn superconductivity, a magnetic mirror structure based on an aluminum shell-based structure and Bladder & Key technology was devised to test whether the performance of a single Nb3Sn sextupole coil can meet the design specifications. This paper describes the detailed optimum design process of the magnetic mirror structure using the ANSYS Parameter Design language (APDL), presents the optimized mirror structure, the determination of the room-temperature prestress and gives the maximum equivalent stress during room temperature assembly, cool-down, and magnet excitation. Furthermore, the effects of the pre-stress applied to the sextupole coil in the mirror structure was also analyzed and assessed in the context of the sextupole coil fabrication tolerance (±0.1 mm).
Nuclear Technology
Design and Implementation of Modulation Driver Module in the Nuclear Signal Readout Method Based on Optical Fiber Sensor
Bowen LI, Chao LI, Ping CAO, Xiaohu WANG, Qi AN
2020, 37(4): 859-866. doi: 10.11804/NuclPhysRev.37.2020004
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In the nuclear signal readout method of optical phase modulation, the detector signal is modulated into optical phase to be transmitted along an optical fiber. In this readout scheme, the Modulation Driver Module, which generates and amplifies the carrier signal, plays an important role in the readout electronics. In order to generate high and adjustable amplitude carrier signals with low phase noise, this paper proposes a carrier generation and amplification method based on PLL and MMIC RF amplifier respectively, which has adventages of simple structure, small size and excellent performance. To evaluate this method, the loop filter for the carrier generation circuit is designed and simulated with the ADIsimPLL simulation software. Meanwhile, the carrier amplification circuit is designed and simulated with the ADS simulation software. Furthermore, test results show that the phase noise of the output carrier signal with 26 dBm amplitude is better than –110 dBc/Hz@ 100 kHz, which can be used for signal demodulation well.
Search Method of Radioactive Source Based on Particle Filter and Artificial Potential Field
Cheng ZHANG, Yufeng XIAO, Haojie LIU, Mingsheng WANG
2020, 37(4): 867-874. doi: 10.11804/NuclPhysRev.37.2020030
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In order to solve the problems of difficulty and low positioning accuracy in the process of radioactive source search, an autonomous source finding method suitable for mobile robot is proposed. In this method, the radiation counting value collected by the mobile robot equipped with the radiation detector is used to establish the radiation attenuation model according to the attenuation law of the gamma ray, and the particle filter algorithm is used to estimate the parameters of the radiation source in real time. The Gaussian distribution function is used to adaptively update the resampled particles to ensure the diversity of the resampled particles. The robot path planning model is established according to the radiation environment, and the artificial potential field law is used to draw the automatic source-seeking path of the robot. Experiments are carried out under matlab, and the results show that the method can find unknown single point source in the occluded environment, and the adaptive updating can improve the stability of the algorithm and reduce the source search error.
Cross Discipline
An Overview and Prospect of Nuclear Battery
Xiaoyi LI, Jingbin LU, Renzhou ZHENG, Xu XU, Yu WANG, Yumin LIU, Rui HE, Lei LIANG
2020, 37(4): 875-892. doi: 10.11804/NuclPhysRev.37.2019066
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The nuclear battery has many advantages, including high energy density, stable performance, no manual intervention etc., which can be widely utilized in cases requiring long-term reliable power supply. Among them, the Radioisotope Thermoelectric Generators (RTG) is the earliest used and the most technically matured one, while betavoltaic battery is now commercialized. However, there are still some problems including self-absorption effect, low energy conversion efficiency and severe radiation damage which restrict the application of betavoltaic batteries. Additionally, for an actual nuclear battery, it should be noticed that the component and density of the source will be changed because the radiation source decays continually, which leads to the electrical performance decline. In this review, the major events in nuclear battery development are listed on a timeline, and the principles and applications of different types of nuclear batteries are also introduced. For betavoltaic battery, the existence of self-absorption effect is pointed out as an important scientific problem, and for batteries with 63Ni and TiT2 source, the time-related electrical properties are also obtained. This paper also pointed out that, fine and precise calculations are very crucial in the optimized designing processes for a particular structure of the practical nuclear battery. Finally, researching assumptions including combining the source and the energy converting material and the use of energy converting structures with heavier isotopes are presented, which are benefit to solve the self-absorption problem, rise the output power of the nuclear battery and reduce the influence of radiation damage.
Study on Quality Diagnosis and Dose Measurement Accuracy Evaluation of 100 MeV Proton Beam
Qiaojuan WANG, Li SUI, Yihao GONG, Fuquan KONG, Jiancheng LIU, Yanwen ZHANG, Jinhua HAN
2020, 37(4): 893-900. doi: 10.11804/NuclPhysRev.37.2020029
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The biological effect of proton radiation is an important foundation of space radiobiology and proton radiotherapy, which can provide scientific basis for the estimation of risk to crews in space radiation and optimization design of proton therapy. It is necessary to establish irradiation technology for biological samples by accelerator. The protons with middle-energy generated by 100 MeV cyclotron established recently by the China Institute of Atomic Energy have the highest energy in China, particularly suitable for the research of space radiobiology and proton therapy. In present study, the methods of proton beam diagnosis and dose measurement were established. The beam quality, such as the size and uniformity of irradiation field, and the accuracy of dose measurement system, was analyzed and evaluated by means of in-beam and off-line methods. The results show that LiF(Mg, Ti) thermo-luminescence detector with good response to photon dose also has good dose response to 90 MeV protons, which can be used to evaluate the accuracy of dose of protons with middle-energy. The uniformity of 100 MeV proton beam is better than 90% in 5.0 cm×5.0 cm irradiation field. The accuracy of in-beam dose measurement system is better than 93%. The beam quality and dose measurement conditions of proton basically meet the requirements of radiobiology, which can provide reliable guarantee for the research of radiobiological effects.
Monte Carlo Study on the Method of Rapid Range Verification of Carbon Ion Beam
Yuhang CHE, Qianian MENG, Xiaofang ZHANG, Xinguo LIU, Zhongying DAI, Qiang LI
2020, 37(4): 901-907. doi: 10.11804/NuclPhysRev.37.2019064
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The depth dose distribution of an ion beam (protons and heavy ions) in the longitudinal direction can be converted into a lateral dose profile via wedge devices for rapid measurement and verification on the range of the ion beam. In this work, the GEANT4 kernel-based GATE Monte Carlo simulation platform was used to calculate the depth dose distributions of various energy carbon-ion beams in materials of copper (Cu), aluminum (Al), iron (Fe) and polymethyl methacrylate (PMMA), which are usually applied to make wedge devices. The relationships between the beam energy and corresponding penetration depth of the Bragg peak position for the carbon ion beams in the various materials were obtained. The lateral dose profiles of carbon ion beams with different energies passing through a single wedge plate, a double wedge plate, and a large and small combined wedge plate were simulated and calculated under different configurations. Therefore, the relationships between the position of the peak of lateral dose and the beam range for the various energy carbon ion beams were acquired. Thus, our Monte Carlo simulations provided a substantial basis for further development of rapid range verification methods and devices in heavy ion therapy.
Nuclear Energy and Nuclear Data
Experimental Progress of Key Nuclear Data in TMSR Photoneutron Source
Xiaohe WANG, Jifeng HU, Jianlong HAN, Xiangzhou CAI, Hongwei WANG, Longxiang LIU, Bing JIANG, Zian GUO, Jingen CHEN
2020, 37(4): 908-912. doi: 10.11804/NuclPhysRev.37.2020082
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The accuracy and reliability of Th-U fuel cycle nuclear data have an important impact on the safety and economy of thorium based molten salt reactor. However, the existing nuclear data, which are developed based on U-Pu fuel cycle, will arise high uncertainty in the nuclear design of thorium molten salt reactor. In order to improve the applicability of nuclear data for the physical design of thorium molten salt reactor, a compact photoneutron source (PNS) driven by a 15 MeV electron LINAC was designed and built up by Shanghai Institute of Applied Physics of CAS for the measurement of Th-U fuel cycle nuclear data. The PNS has passed the technical acceptance, and carried out a series of nuclear data measurement for key nuclides, which are used for verifying the reliability of existing nuclear data and providing the basic experimental data for the evaluation and improvement of nuclear data.
Study of Medical Radioisotopes Production by Accelerator Induced Reactions with FLUKA
Rui HAN, Zhiqiang CHEN, Guoyu TIAN, Fudong SHI, Xin ZHANG, Bingyan LIU, Hui SUN
2020, 37(4): 913-917. doi: 10.11804/NuclPhysRev.37.2020025
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The medical radioisotopes 99Mo/99mTc, 64,67Cu, 68Ge/68Ga, 82Sr/82Rb, 211At, 225Ac have been attracting a lot of attention in nuclear medicine. In this paper, the yields and product distributions of the above medical radioisotopes were studied with FLUKA code. The results show that the yield growth trend becomes slower with the increase of beam energy. The yield increased with the increase of irradiation time and decreased with the increase of cooling time. The change mainly depends on the half-life of the medical radioisotopes. The incident beam produces medical radioisotopes within the effective range in the isotope target. The reasonable target thickness can optimize the specific activity value of the medical radioisotopes. Moreover, the kinds and yields of impurity nuclides also increased with the increase of the beam energy. The reasonable irradiation energy and irradiation time can reduce the complexity of subsequent medical radioisotopes separation and purification. This work provides important information for the accelerator produced medical radioisotopes by FLUKA calculation.
Evaluation of Fission Yields with Bayesian Neural Networks
Ziao WANG, Yu QIANG, Junchen PEI
2020, 37(4): 918-923. doi: 10.11804/NuclPhysRev.37.2020027
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Nuclear fission data are important infrastructure data in nuclear applications and nuclear engineering. It is still challenging to obtain accurate and complete energy-dependent fission yields in experiments and theories. Bayesian Neural Network (BNN) is idea to treat inverse regression problems and can provide quantified uncertainties. We apply BNN to infer fission yields based on learning of existing fission yields. In particular, BNN is very useful for evaluations of fission yields when incomplete experimental data are available. We demonstrated that the BNN evaluations are quite satisfactory on mass distributions and energy dependencies of fission yields. This indicates that BNN is very promising in nuclear data community.
Reliability Analysis of Charging Function of Digital Chemistry and Volume Control System in Nuclear Power Plant
Yuanyuan WANG, Simin XU, Ting YANG, Hong QIAN, Xiaolei PAN
2020, 37(4): 924-934. doi: 10.11804/NuclPhysRev.37.2020072
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The technology of controlled, self-sustained chain fission reaction is one of the most important applications of nuclear power, among which the water-cooled, thermal spectrum nuclear reactor is the dominant technique. The digital I&C system of a water-cooled of nuclear power plants is the nerve center of nuclear power plants and improving its reliability is of great significance to nuclear safety. In order to solve the reliability problems of the dynamic behaviors such as standby automatic switching and startup failure realized by the nuclear power plant digital I&C system, this paper studies the dynamic fault tree analysis method of the chemical and volume system. According to the control system structure involved in the charging control and the control logic of the charging pump cold and hot standby, a dynamic fault tree model of the upper charging function failure is established. The minimum cut set method and Markov model are used for reliability quantitative analysis. Reliability analysis results show that redundancy and backup improve the reliability of the system. The result of importance analysis show that for system optimization design, priority should be given to electrical switch cabinets and junction boxes, and electrical switch cabinets and process control cabinets should be given priority to inspection and maintenance.