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A large area ^(3)He tube array detector with vacuum operation capacity for the SANS instrument at the CSNS

Nuclear Science and Techniques 2022年第7期33卷 83-92页

作者： Xing-Fen Jiang Jian-Rong Zhou Hong Luo Liang Xiao Xiao-Juan Zhou Hong Xu Yuan-Guang Xia Xiao-Guang Wu Lin Zhu Wen-Qing Yang Gui-An Yang Bei-Ju Guan Hong-Yu Zhang Yu-Bin Zhao Zhi-Jia Sun Yuan-Bo Chen State Key Laboratory of Particle Detection and Electronics Institute of High Energy PhysicsChinese Academy of SciencesBeijing100049China Spallation neutron source Science Center Dongguan523803China University of Chinese Academy of Sciences Beijing100049China

The small-angle neutron scattering(SANS)instrument,one of the first three instruments of the china Spallation neutron source(CSNS),is designed to probe the microscopic and mesoscopic structures of materials in the scale range 1–100 nm.A large-area ^(3)He tube array detector has been constructed and operates at the CSNS SANS instrument since August *** consists of 120 linear position-sensitive detector tubes,each 1 m in length and 8 mm in diameter,and filled with ^(3)He gas at 20 bar to obtain a high detection *** ^(3)He tubes were divided into ten modules,providing an overall area of 1000 mm×1020 mm with a high count rate *** each tube is installed independently,the detector can be quickly repaired in situ by replacing damaged *** reduce air scattering,the SANS detector must operate in a vacuum environment(0.1 mbar).An all-metal sealing technique was adopted to avoid high-voltage breakdown by ensuring a high-voltage connection and an electronic system working in an atmospheric environment.A position resolution of 7.8±0.1 mm(full width at maximum)is measured along the length of the tubes,with a high detection efficiency of 81±2% at *** over the past four years,the detector appears to perform well and with a high stability,which supports the SANS instrument to finish approximately 200 user scientific programs.

关键词： neutron detectors ^(3)He tubes Gaseous detectors Small-angle neutron scattering

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Morphology Evolution of Polystyrene-core/Poly(N-isopropylacrylamide)-shell Microgel Synthesized by One-pot Polymerization

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Chinese Journal of Polymer Science 2017年第9期35卷 1156-1164页

作者： Wen-tao Hu Hua Yang 程贺胡海青 Key Laboratory of Rubber-Plastics Ministry of Education/Shandong Provincial Key Laboratory of Rubber-PlasticsSchool of Polymer Science and EngineeringQingdao University of Science and TechnologyQingdao 266042China china Spallation neutron source(CSNS) Institute of High Energy Physics(IHEP)Chinese Academy of Sciences(CAS)Dongguan 523803China Dongguan Institute of neutron Science(DINS) Dongguan 523808China

One-pot polymerization with macroinitiator is supposed to be a robust, facile way to synthesize well-defined core- shell nanoparticles with fixed shell thickness. To testify this, we investigated the temperature-depending morphology evolution of polystyrene （PS） core/poly（N-isopropylacrylamide）（PNIPAM） shell microgel synthesized by one-pot polymerization with PNIPAM-RAFT as macroinitiator in dimethylformamide （DMF） by transmission electron microscopy （TEM）, dynamic/static light scattering （DLS/SLS） and small angle neutron scattering （SANS）. It is revealed that the microgel has a core-shell structure, i.e., the core is made of pure PS, but the shell is composed of both PNIPAM-RAFT macroinitiator and crosslinked PS. In fact, there are 92.0 wt% D20, 6.7 wt% PNIPAM and 1.3 wt% PS in the shell in its aqueous dispersion at 21 ℃; therefore, its shell thickness is much larger than the extended chain length of the macroinitiator as revealed by both SANS and DLS observations. Competitive growth of styrene, divinylbenzene and PNIPAM macroinitiator as well as possible chain transfer from amine proton of PNIPAM side chain may lead to the larger shell thickness, compared with the extended chain length of the macroinitiator. Our work can shed light on the real morphology control in one-pot polymerization.

关键词： One-pot PS-core/PNIPAM-shell TEM DLS SANS

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Mechanical design of a low β superconducting elliptical cavity for CSNS-II

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Radiation Detection Technology and Methods 2021年第3期5卷 315-323页

作者： Peihua Qu Huachang Liu Yun Wang Bo Li Xiaolei Wu Ahong Li Mengxu Fan Qiang Chen Jun Peng Institute of High Energy Physics Chinese Academy of Sciences(CAS)Beijing 100049China Spallation neutron source Science Center Dongguan 523803China

Background A lowβsuperconducting elliptical cavity was designed for the china Spallation neutron source phase II project(CSNS-II).Methods The method to improve the mechanical stability of the lowβsuperconducting elliptical cavity was introduced,and the corresponding mechanical design was *** software COMSOL Multiphysics and ANSYS APDL were used to calculate the static Lorentz force detuning factor k_(L)(LFD)and the helium pressure sensitivity factor k_(p)(DFDP)of the bare cavity,which were−4.71 Hz(MV/m)^(−2) and−21.1 Hz/mbar,*** double-ring stiffeners reinforcement scheme was *** The radii of the double-ring stiffeners were 70 and 135 mm,*** structure design of the helium vessel of the cavity was *** following is the mechanical parameters of the reinforced cavity,the tuning sensitivity is 199.8 kHz/mm,longitudinal stiffness is 4.76kN/mm,k_(L) and k_(p) were−1.39 Hz(MV/m)^(−2) and 4.67 Hz/mbar,respectively,which met the operating *** tuning sensitivity and stiffness of the reinforced cavity with different wall thicknesses were optimized,and the final wall thickness was selected as 4 *** The mechanical design of CSNS-II 648 MHz five-cell lowβsuperconducting elliptical cavity was introduced systematically in the *** LFD,DFDP,and the maximum surface stress of the cavity were reduced by optimizing the cavity wall thickness and the position of the double-ring *** reinforced cavity met operational requirements.

关键词： Lowβsuperconducting elliptical cavity Mechanical design LFD DFDP Tuning sensitivity Longitudinal stiffness

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Design and performance of the LLRF control system for CSNS linac

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Radiation Detection Technology and Methods 2020年第2期4卷 196-202页

作者： Linyan Rong Zhencheng Mu Jian Li Zhexin Xie Wenzhong Zhou Bo Wang Maliang Wan Meifei Liu Xinan Xu Institute of High Energy Physics Chinese Academy of SciencesBeijingChina Spallation neutron source Science Center DongguanChina

Objective The china Spallation neutron source(CSNS)linac is designed with beam energy of 80 MeV and a peak current of 15 mA in the first *** consists of RFQ,two bunchers of medium-energy beam transmission line,four DTL tanks and one debuncher of linac-to-ring beam transmission ***,eight online RF power sources are used to power these *** order to stabilize the amplitude,phase and resonant frequency of the RF accelerating field,and minimize beam loss,we have established digital low-level RF(LLRF)control *** The LLRF system includes RF reference line,analog module(AM),clock distribution module,digital control module(DCM),high-power protection module,timing and RF interlock module and so *** DCM is mainly responsible for the stability of the RF field amplitude and phase,and RF interlock module can quickly cut off the RF drive in case of arc in the RF transmission system,VSWR over threshold or cavity vacuum fault and so *** During beam commissioning,all of eight online units of LLRF control system were operating stably and *** amplitude and phase variations of the linac fields have been achieved about±0.4%and±0.15°with 10-mA beam loading,much better than the design requirements of±1%in amplitude and±1°in *** With the help of this system,we achieved stable operation under different beam ***,many important progresses have been achieved in the LLRF control system for amore convenient operation and a higher stability *** article describes the design and implementation of the LLRF for CSNS linac.

关键词： RF power source LLRF Reference system High-power protection Tracking resonant frequency of cavity

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Five-view three-dimensional reconstructionfor ultrafast dynamic imaging of pulsedradiation sources

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Matter and Radiation at Extremes 2024年第2期9卷 63-73页

作者： Jianpeng Gao Liang Sheng Xinyi Wang Yanhong Zhang Liang Li Baojun Duan Mei Zhang Yang Li Dongwei Hei Department of Engineering Physics Tsinghua UniversityBeijing 100084China National Key Laboratory of Intense Pulsed Radiation Simulation and Effect Northwest Institute of Nuclear TechnologyXi’an 710024China

Multiaxial neutron/x-ray imaging and three-dimensional (3D) reconstruction techniques play a crucial role in gaining valuable insights intothe generation and evolution mechanisms of pulsed radiation sources. Owing to the short emission time (∼200 ns) and drastic changes of thepulsed radiation source, it is necessary to acquire projection data within a few nanoseconds in order to achieve clear computed tomography3D imaging. As a consequence, projection data that can be used for computed tomography image reconstruction at a certain moment are oftenavailable for only a few angles. Traditional algorithms employed in the process of reconstructing 3D images with extremely incomplete datamay introduce significant distortions and artifacts into the final image. In this paper, we propose an iterative image reconstruction methodusing cylindrical harmonic decomposition and a self-supervised denoising network algorithm based on the deep image prior method. Weaugment the prior information with a 2D total variation prior and a 3D deep image prior. Single-wire Z-pinch imaging experiments have beencarried out at Qin-1 facility in five views and four frames, with a time resolution of 3 ns for each frame and a time interval of 40 ns betweenadjacent frames. Both numerical simulations and experiments verify that our proposed algorithm can achieve high-quality reconstructionresults and obtain the 3D intensity distribution and evolution of extreme ultraviolet and soft x-ray emission from plasma.

关键词： frames image sources

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Development of a ~3He Gas Filling Station at the china Spallation neutron source

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Chinese Physics Letters 2021年第5期38卷 16-20页

作者： Zecong Qin Chuyi Huang ZNBuck WKreuzpaintner SMAmir ASalman Fan Ye Junpei Zhang Chenyang Jiang Tianhao Wang Xin Tong Institute of High Energy Physics Chinese Academy of Sciences(CAS)Beijing 100049China Spallation neutron source Science Center Dongguan 523803China Oak Ridge National Laboratory Oak RidgeTN 37930USA

At the china Spallation neutron source(CSNS), we have developed a custom gas-filling station, a glassblowing workshop, and a spin-exchange optical pumping(SEOP) system for producing high-quality ^(3)He-based neutron spin filter(NSF) cells. The gas-filling station is capable of routinely filling ^(3)He cells made from GE180 glass of various dimensions, to be used as neutron polarizers and analyzers on beamlines at the CSNS. Performance tests on cells fabricated at our gas-filling station are conducted via neutron transmission and nuclear-magneticresonance measurements, revealing nominal filling pressures, and a saturated ~3He polarization in the region of 80%, with a lifetime of approximately 240 hours. These results demonstrate our ability to produce competitive NSF cells to meet the ever-increasing research needs of the polarized neutron research community.

关键词： NSF Development of a Gas Filling Station at the china Spallation neutron source

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Machine learning-based direct solver for one-to-many problems on temporal shaping of relativistic electron beams

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Frontiers of physics 2022年第6期17卷 15-24页

作者： Jinyu Wan Yi Jiao Key Laboratory of Particle Acceleration Physics and Technology Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China University of Chinese Academy of Sciences Beijing 100049China china Spallation neutron source Dongguan 523803China

To control the temporal profile of a relativistic electron beam to meet requirements of various advanced scientific applications like free-electronlaser and plasma wakefield acceleration,a widely-used technique is to manipulate the dispersion terms which turns out to be one-to-many *** to their intrinsic one-to-many property,current popular stochastic optimization approaches on temporal shaping may face the problems of long computing time or sometimes suggesting only one *** we propose a real-time solver for one-to-many problems of temporal shaping,with the aid of a semi-supervised machine learning method,the conditional generative adversarial network(CGAN).We demonstrate that the CGAN solver can learn the one-to-many dynamics and is able to accurately and quickly predict the required dispersion terms for different custom temporal *** machine learning-based solver is expected to have the potential for wide applications to one-to-many problems in other scientific fields.

关键词： beam shaping one-to-many problem machine learning

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Measurement of emittance at CSNS ion source without analyzing magnet

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Radiation Detection Technology and Methods 2022年第2期6卷 209-213页

作者： Shengjin Liu Yongjia Lv Fang Li Huafu ouyang Yongchuan Xiao Kangjia Xue Xiuxia Cao Weidong Chen Ruiyang Qiu Shunming Liu Hui Li Renli Zhu Institute of High Energy Physics Chinese Academy of SciencesBeijing 100049China Spallation neutron source Science Center Dongguan 523803.China

Purpose High current beam is required for CSNS update in *** 50 mA H-will be designed to deliver to the linac in CSNSⅡ.For the present state of CSNS ion source,the beam emittance cannot satisfy the requirement of RFQ entrance at the 50 mA *** order to improve the beam quality,CSNS ion source is required further *** Simulation shows emittance growth due to the space charge force in the intense H-beam when the beam transports through the analyzing *** considering the neutralization of space charge,the emittance growth could be *** analyzing magnet thus is considered to removed,which might destroy the neutralization of space *** beam emittance is measured at the revised CSNS ion *** Measured results show that beam emittance without the analyzing magnet becomes smaller than that of CSNS ion *** the requirement of 0.2πmm mrad,beam current is larger than 30 *** reveals that analyzing magnet could destroy space charge neutralization and result in the significant increase of *** Although the results presented are preliminary,it is important to improve the beam *** paper details the ion source improvement and measurement process.

关键词： CSNS ion source Beam emittance High current pulse beam Analyzing magnet

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The SLEGS beamline of SSRF

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Nuclear Science and Techniques 2024年第7期35卷 20-30页

作者： Long-Xiang Liu Hong-Wei Wang Gong-Tao Fan Hang-Hua Xu Yue Zhang Zi-Rui Hao Ai-Guo Li Shanghai Advanced Research Institute Chinese Academy of SciencesShanghai201210China

The Shanghai Laser Electron Gamma source(SLEGS, located in BL03SSID) beamline at the Shanghai Synchrotron Radiation Facility(SSRF) is a Laser Compton Scattering(LCS) gamma source used for the investigation of nuclear structure, which is in extensive demand in fields such as nuclear astrophysics, nuclear cluster structure, polarization physics, and nuclear energy. The beamline is based on the inverse Compton scattering of 10640 nm photons on 3.5 GeV electrons and a gamma source with variable energy by changing the scattering angle from 20° to 160°. γ rays of 0.25-21.1 MeV can be extracted by the scheme consisting of the interaction chamber, coarse collimator, fine collimator, and attenuator. The maximum photon flux for 180° is approximately 10~7 photons/s at the target at 21.7 MeV, with a 3-mm-diameter beam. The beamline was equipped with four types of spectrometers for experiments in( γ,γ'),( γ,n),( γ,p), and( γ,α). At present, Nuclear Resonance Fluorescence(NRF) spectrometry, Flat-Efficiency neutron Detector(FED) spectrometry, neutron Time-Of-Flight(TOF) spectrometry, and Light-Charged Particle(LCP) spectrometry methods have been developed.

关键词： Shanghai Synchrotron Radiation Facility SLEGS Nuclear astrophysics Nuclear structure

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Structure and magnetic properties of the S=3/2 zigzag spin chain antiferromagnet BaCoTe_(2)O_(7)

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Science china(Physics,Mechanics & Astronomy) 2021年第8期64卷 91-97页

作者： Lisi Li Xunwu Hu Zengjia Liu Jia Yu Benyuan Cheng Sihao Deng Lunhua He Kun Cao Dao-Xin Yao Meng Wang Center for neutron Science and Technology School of PhysicsSun Yat-sen UniversityGuangzhou 510275China Shanghai Institute of Laser Plasma Shanghai 201800China Center for High Pressure Science and Technology Advanced Research Shanghai 201203China Spallation neutron source Science Center Dongguan 523803China Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China Songshan Lake Materials Laboratory Dongguan 523808China

We report a study of the structure and magnetic properties of the S=3/2 zigzag spin chain compound BaCoTe_(2)O_(7).neutron diffraction measurements show that it crystallizes in the noncentrosymmetric space group Ama2 with a canted↑↑↓↓spin structure along the quasi-one-dimensional zigzag chain and a moment size of 1.89(2)μBat 2 *** magnetic susceptibility and specific heat measurements yield an antiferromagnetic phase transition at TN=6.2 K.A negative Curie-Weiss temperature,ΘCW=-74.7(2) K,and an empirical frustration parameter,f=|ΘCW|/TN≈12,are obtained by fitting the magnetic susceptibility,indicating antiferromagnetic interactions and strong magnetic *** ultraviolet-visible absorption spectroscopy and first-principles calculations,an indirect band gap of 2.68(2) eV is *** propose that the canted zigzag spin chain of BaCoTe_(2)O_(7) may produce a change in the polarization via the exchange-striction mechanism.

关键词： antiferromagnet zigzag spin chain magnetic frustration spin structure

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