Chinese Spallation Neutron Source Research Articles

Neutron capture reaction cross-section data processing and resonance parameter analysis of <sup>197</sup>Au based on white light neutron source

Neutron capture reaction is one of the neutron reactions and plays an important role in using reactor control rods and shell materials, designing nuclear device structures, and studying nuclear astrophysics S processes and element origins. The 4π BaF<sub>2</sub> detection device has advantages such as high time resolution, low neutron sensitivity, and high detection efficiency, thus making it suitable for measuring neutron radiation capture reaction cross-section data. In order to fill the gap in our neutron capture reaction data in the keV energy range and improve their accuracy, the Key Laboratory of Nuclear Data at the Chinese Institute of Atomic Energy (CIAE) has established a Gamma Total Absorption Facility (GTAF), which consists of 28 hexagonal BaF<sub>2</sub> crystals and 12 pentagonal BaF<sub>2</sub> crystals to form a spherical shell with an external diameter of 25 cm and an internal diameter of 10 cm, covering 95.2% of the solid angles. The Back-n beam line of the Chinese Spallation Neutron Source (CSNS) is a back-streaming white beam line that covers neutron energy ranging from a few eV to several hundred MeV, making it suitable for measuring neutron capture cross-sections. The reaction cross-section data of <sup>197</sup>Au is measured by using GTAF on the Back-n beam line. The measurement data are preliminarily background deducted through energy screening, PSD method, and crystal multiplicity screening. Subsequently, the background is analyzed and deducted based on the measurement data of <sup>nat</sup>C and empty samples, and the yield of <sup>197</sup>Au capture reaction is obtained. Resonance parameters are a set of parameters extracted from experimental data to describe the resonance curve, which can eliminate the influence of experimental conditions on resonance data and are more important than the cross-section obtained from experiments. The resonance energy, neutron resonance width, and gamma resonance width parameters of <sup>197</sup>Au at 1–100 eV are fitted by using the SAMMY program. From the comparison between the resonance curves obtained from experimental measurements and the resonance parameters obtained from fitting with the ENDF/B-VIII.0 database, it can follow that the experimental measurement results are in good agreement with the database, nevertheless, there exist some differences in the resonance parameter, which may be due to the GTAF energy resolution, Back-n neutron spectrum measurement accuracy, and the experimental background deduction method. Our next work is to identify the sources of difference.

Accuracy improvement of longitudinal network in China Spallation Neutron Source using stretched wire

In order to improve the transverse alignment accuracy of the control network in Chinese Spallation Neutron Source (CSNS) Linac, a 200-m stretched wire-based system was established in the tunnel. A wire position sensor based on bi-telecentric technology (tWPS) was specially designed to obtain the offset with respect to the stretched wire. A control network adjustment algorithm with additional wire constraints has been developed. The laser tracker measured station by station in a free station way, and measured the control network and the fiducials of the tWPS at the same time. The offset observation equation was combined with the angle observation equation and distance observation equation of the laser tracker for joint solution. As a result, the transverse accuracy of the control network was improved from 0.061 mm without wire constraint to 0.028 mm with wire constraint, which indicates that the addition of wire constraints can indeed effectively improve the transverse accuracy of the longitudinal control network.

Comparative Research on Ventilation Characteristics of Scattering and Sample Room from Chinese Spallation Neutron Source

Ventilation design of the scattering room and sample room in the Chinese Spallation Neutron Source (CSNS) is of great significance to maintain good indoor air quality and ensure the health of radiation workers. Based on the computational fluid dynamics (CFD) theory, the three-dimensional models of the scattering and sample rooms were established and fourteen layout schemes were simulated. Subsequently, the best schemes were selected among three typical layout schemes. On this basis, the paper presents research about the influence of changing the height of the outlet on the ventilation quality. The results show that the trend of numerical simulation is consistent with experimental data, which verifies the reliability of the numerical method. The change of the exhaust port position has an apparent influence on indoor ventilation, which reduces the air age by 4–27%. When the position of the outlet descends 0.5 m, the air age decreases by 2–11%, and this study provides guidance and suggestions for the design of the scattering and sample rooms.

Operation and Maintenance of Chinese Spallation Neutron Source Stripper Foil

Operation and Maintenance of Chinese Spallation Neutron Source Stripper Foil

Heat Transfer Analysis in Supercritical Hydrogen of Decoupled Poisoned Hydrogen Moderator with Non-Uniform Heat Source of Chinese Spallation Neutron Source

The flow field distribution and thermal properties of supercritical hydrogen are crucial factors affecting the quality of neutrons output from spallation neutron source, which may contribute to the optimization design of the moderator. Several sensitivity studies on affecting heat transfer characteristics of liquid hydrogen inside a moderator were executed, and a choice was made to use a computational fluid dynamics method for numerical simulation. The sensitivity degree of factors affecting the heat transfer characteristics of liquid hydrogen are in sequence of inlet mass flow, beam power and operating pressure. Especially when the beam power is 500 kW (the temperature range of liquid hydrogen is about 20~30 K); where the effect of mass flow rate is remarkable, the cooling effect is best in the range of 60~90 g/s × 394 mm2. Meanwhile, the maximum temperature of liquid hydrogen is close to the bottom recirculation zone due to the influence of the flow field and the heat deposition distribution of the poisoned plate. The effect of variable pressure on the temperature of liquid hydrogen is not significant, whereas the sudden rise of wall temperature is observed near the large specific heat region of 15 bar.

Research on protection system of resonant network in CSNS magnet power supplies

Chinese Spallation Neutron Source (CSNS) is one of the key projects of China, in which the main magnet power supplies adopt the structures of resonant networks (Wang et al. in Sci China Phys Mech Astron 54(Suppl 2):239–244, 2011). Since each network contains a lot of components, and the working state of all the components will affect the whole accelerator, it is necessary to monitor the operation of each part in the resonant network. In this protections system, a supervision to 314 switch signals and 118 analog signals is realized using a chip of field programmable gate array (FPGA). The details about the hardware and software designs are introduced in this paper. This protection system has been used in CSNS project, and the result proves that the RCS has been well monitored by this system. This system is a self-developed protection system according to the engineering needs of CSNS. It can realize the real-time monitoring and protection of the working state of resonance network by processing a large number of data using FPGA.

Application and evaluation of Chinese spallation neutron source in single-event effects testing

Due to the lack of available spallation neutron source, the atmospheric neutron single event effect (SEE) in China were studied mainly by means of simulation and single energy neutron test. Since the Chinese spallation neutron source (CSNS) passed the national acceptance, it has become possible to carry out the research on atmospheric neutron SEE by using the CSNS. In this paper, the neutron SEE experiments of 3 kinds of SRAMs with different feature sizes are carried out for the first time by using the CSNS back-n. The application of CSNS back-n in the study of atmospheric neutron SEE is evaluated by comparing with the results of the earlier plateau experiment. The results show that the cross section of the single event upset is smaller than that of the plateau test, and the cross sections of different devices have no obvious monotonic relationship with feature size. The reason for the former result is that the energy spectrum of CSNS back-n is slightly softer than that of the atmospheric neutron. The reason for the second result is that small feature size means small critical charge and small sensitive volume, and these two factors compete with each other when they make the contribution to the cross section. According to the difference in energy spectrum and cross section among the SRAM devices, a correction factor is proposed to correct the test results based on CSNS back-n. For the difference in energy spectrum, different energy thresholds will produce different ratios between the cross sections by using CSNS back-n and atmospheric neutron. The neutrons of CSNS back-n are mainly concentrated around 1 MeV, which is close to the energy threshold of general SRAM devices. Thus, inaccurate energy threshold estimation will introduce a large error into the cross section of SEU. Thus, the relation between the correction factor and the energy threshold is analyzed. If 12 MeV is selected as the energy threshold to calculate the cross section, more consistent results could be obtained for our DUT in CSNS back-n and atmospheric neutron environment. In a word, the results show that the CSNS back-n can be used to speed up the atmospheric neutron SEE test, but the result should be corrected to evaluate the threat from atmospheric neutron. Fortunately, with the continuous increase of CSNS operating power, the neutron flux and the accelerated factor of CSNS will increase synchronously. Besides, other 3 white light neutron beams are planned in the CSNS project, the planned energy spectra are closer to those of atmospheric neutron. It is expected that the CSNS will be better applied to the study of atmospheric neutron SEE.

Experimental result of back-streaming white neutron beam characterization at Chinese spallation neutron source

The Chinese spallation neutron source was completed in May 2018 and then subsequently commissioned. The Back-streaming white neutron beam line can be used in neutron nuclear data measurement, neutron physics research, and nuclear technology. In these experiments, it is necessary to know the neutron energy spectrum, the neutron flux, and the neutron beam profile of the neutron beam. In this paper, we present the preliminary measurements of these parameters. The neutron energy spectrum and neutron flux are measured by the time-of-flight method with a fission chamber equipped with <sup>235</sup>U and <sup>238</sup>U samples and a <sup>6</sup>Li-Si detector. The neutron beam profile is measured by a scintillator-CMOS detection system. The preliminary experimental measurements of the beam line are obtained. Among them, the energy spectrum measurement range of white neutrons is from eV to more than 100 MeV, which also gives an uncertainty analysis; the neutron fluence rate gives the full power value of the two experimental halls; the collimated white neutron beam spot is given under a diameter of 60 mm. The future plan is also given. The results of these experimental parameters can serve as the foundation for the future nuclear data measurement and detector calibration experiments of the beam line.

Erratum: Experimental result of back-streaming white neutron beam characterization at Chinese spallation neutron source

摘要 关键词: 01.52.+r / 29.25.Dz / 28.20.–v / 28.20.Pr / 99.10.Cd Abstract Keywords: / / / / 作者及机构信息 鲍杰, 陈永浩, 张显鹏, 栾广源, 任杰, 王琦, 阮锡超, 张凯, 安琪, 白怀勇, 曹平, 陈琪萍, 程品晶, 崔增琪, 樊瑞睿, 封常青, 顾旻皓, 郭凤琴, 韩长材, 韩子杰, 贺国珠, 何泳成, 何越峰, 黄翰雄, 黄蔚玲, 黄锡汝, 季筱路, 吉旭阳, 江浩雨, 蒋伟, 敬罕涛, 康玲, 康明涛, 兰长林, 李波, 李论, 李强, 李晓, 李阳, 李样, 刘荣, 刘树彬, 刘星言, 马应林, 宁常军, 聂阳波, 齐斌斌, 宋朝晖, 孙虹, 孙晓阳, 孙志嘉, 谭志新, 唐洪庆, 唐靖宇, 王鹏程, 王涛峰, 王艳凤, 王朝辉, 王征, 文杰, 温中伟, 吴青彪, 吴晓光, 吴煊, 解立坤, 羊奕伟, 杨毅, 易晗, 于莉, 余滔, 于永积, 张国辉, 张旌, 张林浩, 张利英, 张清民, 张奇伟, 张玉亮, 张志永, 赵映潭, 周良, 周祖英, 朱丹阳, 朱科军, 朱鹏 Authors and contacts Bao Jie, Chen Yong-Hao, Zhang Xian-Peng, Luan Guang-Yuan, Ren Jie, Wang Qi, Ruan Xi-Chao, Zhang Kai, An Qi, Bai Huai-Yong, Cao Ping, Chen Qi-Ping, Cheng Pin-Jing, Cui Zeng-Qi, Fan Rui-Rui, Feng Chang-Qing, Gu Min-Hao, Guo Feng-Qin, Han Chang-Cai, Han Zi-Jie, He Guo-Zhu, He Yong-Cheng, He Yue-Feng, Huang Han-Xiong, Huang Wei-Ling, Huang Xi-Ru, Ji Xiao-Lu, Ji Xu-Yang, Jiang Hao-Yu, Jiang Wei, Jing Han-Tao, Kang Ling, Kang Ming-Tao, Lan Chang-Lin, Li Bo, Li Lun, Li Qiang, Li Xiao, Li Yang, Li Yang, Liu Rong, Liu Shu-Bin, Liu Xing-Yan, Ma Ying-Lin, Ning Chang-Jun, Nie Yang-Bo, Qi Bin-Bin, Song Zhao-Hui, Sun Hong, Sun Xiao-Yang, Sun Zhi-Jia, Tan Zhi-Xin, Tang Hong-Qing, Tang Jing-Yu, Wang Peng-Cheng, Wang Tao-Feng, Wang Yan-Feng, Wang Zhao-Hui, Wang Zheng, Wen Jie, Wen Zhong-Wei, Wu Qing-Biao, Wu Xiao-Guang, Wu Xuan, Xie Li-Kun, Yang Yi-Wei, Yang Yi, Yi Han, Yu Li, Yu Tao, Yu Yong-Ji, Zhang Guo-Hui, Zhang Jing, Zhang Lin-Hao, Zhang Li-Ying, Zhang Qing-Min, Zhang Qi-Wei, Zhang Yu-Liang, Zhang Zhi-Yong, Zhao Ying-Tan, Zhou Liang, Zhou Zu-Ying, Zhu Dan-Yang, Zhu Ke-Jun, Zhu Peng 文章全文 : translate this paragraph 参考文献 施引文献

Beamline design of EMuS - the first Experimental Muon Source in China

We report the beamline design of the Experimental Muon Source (EMuS) project in China. Based on the 1.6 GeV/100 kW proton accelerator at the Chinese Spallation Neutron Source (CSNS), EMuS will extract one bunch from every 10 double-bunch proton pulses to hit a stand-alone target sitting in a superconducting solenoid, and the secondary muons/pions are guided to the experimental area. The beamline is designed to provide both a surface muon beam and a decay muon beam, so that various experiments such as muSR applications and particle/nuclear physics experiments can be conducted. In this work we present the conceptual design and simulation of the beamlines, and discuss the future aspects of the project.

Study of wave form compensation at CSNS/RCS magnets

A method of wave form compensation for magnets of the Rapid Cycling Synchrotron (RCS), which is based on transfer function between magnetic field and exciting current, was investigated on the magnets of RCS of Chinese Spallation Neutron Source (CSNS). By performing wave form compensation, the magnetic field ramping function for RCS magnets can be accurately controlled to the given wave form, which is not limited to sine function. The method of wave form compensation introduced in this paper can be used to reduce the magnetic field tracking errors, and can also be used to accurately control the betatron tune for RCS.

Intelligent pulse light source in the performance calibration system of two-dimensional neutron detector

Chinese Spallation Neutron Source (CSNS) project will use numerous two-dimensional (2D) neutron detectors whose ZnS (Ag) scintillator is doped with 6Li. To ensure the consistency of all neutron detectors, a calibration system for the performance of 2D neutron detectors is designed. For radiation protection, the state control of the radiation source gets more and more strict. It is impossible to directly carry out experiments with massive radioactive particles. Thus, the following scheme has been designed. The controlled pulsed laser light source on a 2D mobile platform is used to replace the neutron bombardment to generate the photon. The pulse signal drives the laser diode to generate pulse light. The pulse light source located on the 2D platform is controlled by the core controller, and goes to the wavelength shift fiber through the optical fiber. The host computer (PC) receives the signal from the electronics system, processes data, and automatically calibrates the performance parameters. As shown by the experimental results, the pulse light source can perfectly meet all requirements of 2D neutron detector calibration system.

Collimator at end of ring to target beam transport

The collimator at the end of the ring to target beam transport (RTBT) line is one of the key devices in the Chinese Spallation Neutron Source (CSNS) project. Design reliability of the collimator is extremely important since the high radiation on it due to its closeness to the target station. According to the working principle of the collimator and CSNS physical design requirements, comparing the design experience of similar foreign accelerator, the collimator is designed. Considering strict requirements of thermal deposition, power loss and material performance in the design process, the specific scheme is expounded. Using the result compared between Bethe-Bloch formula and SRIM software to determine the reliability of the simulation tool and simulation methods. According to the result of ANSYS finite element software simulation, the reliability of the collimator structure design is verified. ©, 2015, Editorial Office of High Power Laser and Particle Beams. All right reserved.

Numerical simulation research of plasma characteristics in a multi-cusp proton source based on magnets layout

It is significant to study negative hydrogen ion source for the construction of Chinese national spallation neutron source (CSNS) and the implementation of the international thermonuclear experimental reactor (ITER) project. Numerical simulation is an indispensable research measure due to the physical characteristics of ion source. In view of the facts above, in this paper we first elaborate the self-developed three-dimensional particle-in-cell/Monte Carlo collisions (PIC/MCC) algorithm and then describe the mechanism of negative hydrogen ion (H-) volume production. Based on these, the multi-cusp proton source of the Chinese atomic energy research center is systematically simulated. In the cases of the same polarities and the opposite polarities of extraction magnetic fields, multi-cusp proton source discharge characteristics are discussed and analyzed respectively. The result shows that in the case of the opposite polarities of the two extraction magnets, magnetic drift directions near the two extraction magnets are the same and have great values, namely intense magnetic drift, which causes the total number of electrons to be big, and induces the high-energy electrons to become active in a specific area. And so, the volume production rate of H- ions is higher, that is to say, H- ions present Y drift. On the contrary, in the case of the same polarities of the two extraction magnets, the binding effect of electron is worse and the volume production rate of H- ions is lower, but spatial distribution of volume production H- is uniform.

Study of shielding design for SANS at CSNS

The small angle neutron scattering (SANS) instrument is presently being constructed at Chinese Spallation Neutron Source (CSNS) in China, and the biological shielding design is needed to prevent the instrument from causing excessive dose rates in accessible locations. In this paper, the study of shielding design for SANS that relies on Monte Carlo simulation is introduced. Beam line shielding calculations are performed considering both scenarios of closed versus open T0 chopper. The basic design scheme of the beam stop is discussed. The size of the T0 chopper rotor is also estimated.

Shielding calculation for the CSNS target station

In this paper we firstly calculate the one-dimension shielding models to give the basic data for the Chinese Spallation Neutron Source (CSNS) target station. Then the three-dimensional shielding calculations have been performed for the detailed design of the CSNS target station. The gaps and void spaces in the CSNS target station are considered for precise estimation. We find that 4.8-meter-radius steel adding 1.2-meter-thick magnetite concrete can satisfy the shielding requirement in the horizontal direction. The dose rate on the top of the ceiling is a little higher than 2.5μSv/h due to streaming effect, which originates from the moderator transfer lines. A thin sandwich structure will be adopted for decreasing residual radioactivity dose rate on the altitude directions after considering the engineering cost and maintenance. All these calculations lie on the Monte Carlo simulation code MCNPX2.5.0.

Validation of source biasing method for its use in CSNS beamline shielding calculation

The Chinese spallation neutron source (CSNS) is a high-performance pulsed neutron source, having 20 neutron beamlines for neutron scattering instruments. The shielding design of these beamlines is usually needed for Monte Carlo (MC) calculation, and the use of variance reduction methods is critical to carrying out an efficient, reliable MC shielding calculation. This paper discusses the source biasing method based on actual source term and geometry model of a CSNS neutron beamline. Dose distribution throughout the geometry model was calculated with the FLUKA MC code. Full analogue calculation and biased calculation were compared, and it was validated that the source biasing method can effectively promote the calculation efficiency.

Study of a position-sensitive scintillator neutron detector

The investigation of a novel thermal neutron detector is developed to fulfill the requirements of the high intensity power diffractometer (HIPD) at the Chinese Spallation Neutron Source (CSNS). It consists of two layers of 6LiF/ZnS(Ag) scintillators, two layers of crossed WLSF arrays, several multi-anode photo multiplier tubes (MA-PMT), and the matching readout electronics. The neutron detection efficiency of the scintilltors, the light transportation ability of the WLSF, and the spatial linearity of the readout electronics are measured and discussed in this paper. It shows that the sandwich structure and the compact readout electronics could fulfill the needs of the HIPD. A prototype with a 10 cm×10 cm sensitive area has been constructed to further study the characteristics of the neutron scintillator detector.

Research and Development of the AC Magnets for CSNS/RCS

Chinese Spallation Neutron Source (CSNS) is a facility planned to be built in China in the coming years. It is composed of 80 MeV Linac, 1.6 GeV Rapid Cycling Synchrotron (RCS) and target station. To accelerate the proton beam from 80 MeV to 1.6 GeV, the RCS requires the field of dipole and quadrupole magnets to change with sine waveform of 25 Hz plus a biased DC. For large amplitude AC magnets with large aperture, there are critical issues to be addressed, such as eddy current induced in the magnet yoke, coils and endplates, vibration of the yoke and coil, field tracking between dipoles and quadrupoles, and so on. To study these issues, one prototype dipole magnet and one prototype quadrupole magnet have been developed and tested. In this paper, the design, fabrication and tests of the two magnets will be described.

The expected radiation damage of CSNS target

The radiation damage to the tungsten target and its SS316 vessel for Chinese Spallation Neutron Source (CSNS) has been estimated with a Monte-Carlo simulation code MCNPX2.5.0. We compare the effects on the radiation damage due to two different proton beam profiles: a uniform distribution and a Gaussian distribution. We also discuss the dependence of the radiation damage estimation on different physics models. The results show the peak displacement productions in vessel and the fourth target plate are 2.5 and 5.5dpa/y, respectively, under a Gaussian proton beam. The peak helium productions in the vessel and the fourth target are 305 and 353appm/y, respectively, under the same proton beam. Based on these results and the allowable dpa values we have estimated the lifetime of the tungsten target and its vessel.