In recent years,a new generation of storage ring-based light sources,known as diffraction-limited storage rings(DLSRs),whose emittance approaches the diffraction limit for the range of X-ray wavelengths of interest to...In recent years,a new generation of storage ring-based light sources,known as diffraction-limited storage rings(DLSRs),whose emittance approaches the diffraction limit for the range of X-ray wavelengths of interest to the scientific community,has garnered significant attention worldwide.Researchers have begun to design and build DLSRs.Among various DLSR proposals,the hybrid multibend achromat(H-MBA)lattice enables sextupole strengths to be maintained at a reasonable level when minimizing the emittance;hence,it has been adopted in many DLSR designs.Based on the H-7BA lattice,the design of the Advanced Photon Source Upgrade Project(APS-U)can effectively reduce emittance by replacing six quadrupoles with anti-bends.Herein,we discuss the feasibility of designing an APS-U-type H-MBA lattice for the Southern Advanced Photon Source,a mid-energy DLSR light source with ultralow emittance that has been proposed to be built adjacent to the China Spallation Neutron Source.Both linear and nonlinear dynamics are optimized to obtain a detailed design of this type of lattice.The emittance is minimized,while a sufficiently large dynamic aperture(DA)and momentum acceptance(MA)are maintained.A design comprising 36 APS-U type H-7BAs,with an energy of 3 GeV and a circumference of 972 m,is achieved.The horizontal natural emittance is 20 pm·rad,with a horizontal DA of 5.8 mm,a vertical DA of 4.5 mm,and an MA of 4%,as well as a long longitudinal damping time of 120 ms.Subsequently,a few modifications are performed based on the APS-U-type lattice to reduce the maximum value of damping time from 120 to 44 ms while maintaining other performance parameters at the same level.展开更多
Purpose High energy photon source is a 6 GeV diffraction-limited storage ring light source currently under construction in Beijing.A low-frequency fundamental radio-frequency(rf)system of 166.6 MHz was proposed to acc...Purpose High energy photon source is a 6 GeV diffraction-limited storage ring light source currently under construction in Beijing.A low-frequency fundamental radio-frequency(rf)system of 166.6 MHz was proposed to accommodate the accelerator physics design.Superconducting rf(srf)technologies were chosen for the storage ring rf accompanied by solid-state power amplifiers and digital low-level rf controls.The design of the rf system was completed,and the parameters are frozen.Elucidation of the rf design with key parameters is desired.Methods The requirements from the accelerator physics design will be presented followed by the detailed rf design.The logic behind the choice of key rf parameters is elaborated.The configuration of the entire rf system is presented.Results and conclusions The fundamental srf cavity of 166.6 MHz was designed to accelerate the ultrarelativistic electron beam.Heavy damping of higher-order modes in these cavities is required to avoid the coupled bunch instabilities.An active third harmonic srf of 499.8 MHz was adopted to realize the required rf gymnastics.Normal-conducting 5-cell cavities will be used for the booster rf.Solid-state amplifiers of 2.4 MW in total will be installed at HEPS to drive these cavities in the booster and the storage ring.A digital low-level rf system will be used to regulate rf field inside each cavity with high stabilities.The rf configuration during the commissioning and the operation scenarios are also presented.展开更多
In-line phase-contrast computed tomography（IL-PC-CT） imaging is a new physical and biochemical imaging method.IL-PC-CT has advantages compared to absorption CT when imaging soft tissues. In practical applications, r...In-line phase-contrast computed tomography（IL-PC-CT） imaging is a new physical and biochemical imaging method.IL-PC-CT has advantages compared to absorption CT when imaging soft tissues. In practical applications, ring artifacts which will reduce the image quality are commonly encountered in IL-PC-CT, and numerous correction methods exist to either pre-process the sinogram or post-process the reconstructed image. In this study, we develop an IL-PC-CT reconstruction method based on anisotropic total variation（TV） minimization. Using this method, the ring artifacts are corrected during the reconstruction process. This method is compared with two methods： a sinogram preprocessing correction technique based on wavelet-FFT filter and a reconstruction method based on isotropic TV. The correction results show that the proposed method can reduce visible ring artifacts while preserving the liver section details for real liver section synchrotron data.展开更多
POLAR is a compact space-borne detector initially designed to measure the polarization of hard X-rays emitted from Gamma-Ray Bursts in the energy range 50–500 ke V.This instrument was launched successfully onboard th...POLAR is a compact space-borne detector initially designed to measure the polarization of hard X-rays emitted from Gamma-Ray Bursts in the energy range 50–500 ke V.This instrument was launched successfully onboard the Chinese space laboratory Tiangong-2(TG-2) on 2016 September 15.After being switched on a few days later,tens of gigabytes of raw detection data were produced in-orbit by POLAR and transferred to the ground every day.Before the launch date,a full pipeline and related software were designed and developed for the purpose of quickly pre-processing all the raw data from POLAR,which include both science data and engineering data,then to generate the high level scientific data products that are suitable for later science analysis.This pipeline has been successfully applied for use by the POLAR Science Data Center in the Institute of High Energy Physics(IHEP) after POLAR was launched and switched on.A detailed introduction to the pipeline and some of the core relevant algorithms are presented in this paper.展开更多
Purpose A new in-vacuum three-dimensional Hall probe magnetic measurement system is under fabrication for characterizing the magnetic performance of the Cryogenic Permanent Magnet Undulator(CPMU).In order to fit the s...Purpose A new in-vacuum three-dimensional Hall probe magnetic measurement system is under fabrication for characterizing the magnetic performance of the Cryogenic Permanent Magnet Undulator(CPMU).In order to fit the small gap(5 mm)of magnetic structure and vacuum environment,a small three-dimensional Hall probe has been manufactured.The angular and positional misalignment errors of the Hall sensors play an important role in the measurement accuracy of the CPMU.In order to minimize the misalignment errors,a method of calibrating angle error and relative assembly displacements of a three-dimensional Hall probe is carried out.Methods The angle error of Hall sensors will be calibrated by a standard dipole magnet and a five-dimensional Hall bench.The standard dipole magnet will generate a single direction and uniform magnetic field.And the fivedimensional Hall bench is used to rotate the Hall probe which is put in the center of magnet.Based on the relationship between angle and magnetic field strength,the angle error of each Hall sensor will be obtained.The relative position between the sensitive areas of the Hall sensors will be calibrated by a two-dimensional magnetic field undulator section.Based on Maxwell’s equations,through the calculation of measurement magnetic field strength,the relative assembly displacements of the three Hall sensors can be derived.Results The details of the calibration methods and the data processing of angle error and relative assembly displacements of a three-dimensional Hall probe are presented.The three-dimensional magnetic fields of a cryogenic permanent magnet undulator can be received accurately by correcting these angle errors and position errors of Hall sensors.Conclusions This paper illustrates the relative position and angle calibration procedures and the data processing of a three-dimensional Hall probe.Now the design of a smaller Hall probe is in process.The calibration of the angle errors and position errors will be carried out after the fabrication of the standard dipole magnet.展开更多
The 10-MeV Accelerator-Driven Subcritical(ADS)system Injector-I test stand at the Institute of High Energy Physics(IHEP)is a testing facility dedicated to demonstrating the feasibility of the spoke-based super-conduct...The 10-MeV Accelerator-Driven Subcritical(ADS)system Injector-I test stand at the Institute of High Energy Physics(IHEP)is a testing facility dedicated to demonstrating the feasibility of the spoke-based super-conducting(SC)linear accelerator(linac)for the ADS project in China.The injector adopted a four-vane copper structure radio frequency quadrupole(RFQ)with an output energy of 3.2 MeV and an SC section accommodating 14 β_(g)=0.12 single spoke cavities,14 SC solenoids,and 14 cold beam position monitors(BPMs).A 10-MeV pulsed beam with a beam current of 10 mA and a 2-mA continuous wave(CW)beam were successfully shooting through.The commissioning results confirmed the feasibility of using a 325-MHz spoke-type cavity for accelerating the proton beam in the low β and medium β sections.This paper describes the results achieved,the difficulties encountered,and the experiences obtained during commissioning.展开更多
Purpose In order to achieve a high-precision measurement of the incident and the reflected power,a WR1800 rectangular waveguide directional coupler with high directivity and high power level has been in-house developed...Purpose In order to achieve a high-precision measurement of the incident and the reflected power,a WR1800 rectangular waveguide directional coupler with high directivity and high power level has been in-house developed.Multiple couplers will be installed in the 500-MHz high-power radio-frequency transmission lines delivering 200-kW continuous-wave power for the High Energy Photon Source(HEPS).Methods The directional coupler adopts the design scheme of primary and secondary transmission lines and coaxial coupling-head structure.The shape and dimensional parameters of the coupling head were carefully optimized by using microwave simulation codes.An optimum directivity of 64 dB was achieved in simulations.Results and conclusions A prototype coupler was subsequently manufactured,and its directivity was measured to be 48.2 dB following a rigorous calibration procedure,largely exceeding the design goal and the commercial product.The coupler was then connected to an existing 500-MHz klystron system,and a high-power test with short-circuit termination was conducted.The high directivity of the coupler was confirmed up to 200 kW.During the 6 hours of power aging with continuous-wave 200 kW in a standing-wave setup,no performance degradation was observed on the coupler.The coupler temperature was measured to be 20◦C above the ambient environment.The design requirements were comfortably fulfilled.These constitute thefirst in-house development of a large-size waveguide directional coupler with high directivity and high power level for HEPS.The design,fabrication,and performance tests of the directional coupler are presented.展开更多
The ATF2 project is the final focus system prototype for the ILC and CLIC linear collider projects, with the purpose of reaching a 37nm vertical beam size at the interaction point. In the nanometer beam size regime, h...The ATF2 project is the final focus system prototype for the ILC and CLIC linear collider projects, with the purpose of reaching a 37nm vertical beam size at the interaction point. In the nanometer beam size regime, higher order multipoles in magnets become a crucial point for consideration. The strength and rotation angle of the ATF2 QEA magnets were reconstructed from the IHEP measurements and compared with the KEK ones to be identical. Based on the study of the skew multipoles sensitivity, we report on the analysis of the possible mitigation of the measured multipoles. A suggestion is given which will benefit the ATF2 present commissioning to reach the goal beam size, and also the reduced β optics in future.展开更多
This paper presents the prospects of measuring σ(e^(+)e^(-)→ZH)× Br(H→γγ) in three Z decay channels Z→qq/μ^(+)μ^(-)/vv using the baseline detector with √s=240GeV at the Circular Electron Positron Collide...This paper presents the prospects of measuring σ(e^(+)e^(-)→ZH)× Br(H→γγ) in three Z decay channels Z→qq/μ^(+)μ^(-)/vv using the baseline detector with √s=240GeV at the Circular Electron Positron Collider(CEPC).Simulated Monte Carlo events were generated and scaled to an integrated luminosity of 5.6 ab^(-1) to mimic the data.Extrapolated results to 20 ab^(-1) are also reported.The expected statistical precision of these measurements after combining three channels of Z boson decay was 7.7%.With some preliminary estimation on the systematical uncertainties,the total precision is 7.9%.The performance of the CEPC electro-magnetic calorimeter(ECAL) was studied by smearing the photon energy resolution in simulated events in the e^(+)e^(-)→ZH→qqγγ channel.In the present ECAL design,the stochastic term in resolution plays the dominant role in the precision of Higgs measurements in the H→γγ channel.The impact of the resolution on the measured precision of σ(ZH)×Br(ZH→qqγγ) as well as the optimization of the ECAL constant and stochastic terms were studied for further detector design.展开更多
After the success of the Daya Bay experiment, the Jiangmen Underground Neutrino Observatory （JUNO） was launched to measure neutrino-mass hierarchy and oscillation parameters and to study other neutrino physics. Its ...After the success of the Daya Bay experiment, the Jiangmen Underground Neutrino Observatory （JUNO） was launched to measure neutrino-mass hierarchy and oscillation parameters and to study other neutrino physics. Its central detector is set for antineutrinos from reactors, the Earth, the atmosphere, and the Sun. The main requirements of the central detector are con- tainment of 20 kt of liquid scintillator, as the target mass, and 3% energy resolution. It is about a ball-shape detector of 38.5 m with -75% coverage of PMT on its inner surface. The design of such a huge detector is a big challenge because it must meet the requirements for several different types of physics measurement and possess the feasibility and reliability in its structure and engineering, all at reasonable time and cost. One option for the JUNO central detector is a hyper-scale acrylic ball sub- merged in the water to shield the background. This paper proposes a structural scheme for such an acrylic ball that is supported by a stainless-steel truss, inspired by point-supported glass-curtain walls in civil engineering. The preliminary design of the scheme is completed and verified by finite element （FE） method using ABAQUS. FE analysis shows that the scheme can con- trol the stress level of the acrylic ball within the limit of 5 to 10 MPa, in accordance with the demand of the design objective of the central detector. The scheme is of outstanding global stability and allows various chocces on local connections. We prove that the scheme is of good feasibility and should be a reasonable option for the central detector.展开更多
Very Small Angle Neutron Scattering （VSANS） is an upgrade of the traditional Small Angle Neutron Scattering （SANS） technique which can cover three orders of magnitude of length scale from one nanometer to one micr...Very Small Angle Neutron Scattering （VSANS） is an upgrade of the traditional Small Angle Neutron Scattering （SANS） technique which can cover three orders of magnitude of length scale from one nanometer to one micrometer. It is a powerful tool for structure calibration in polymer science, biology, material science and condensed matter physics. Since the first VSANS instrument, Dll in Grenoble, was built in 1972, new collimation techniques, focusing optics （multi-beam converging apertures, material or magnetic lenses, and focusing mirrors） and higher resolution detectors combined with the long flight paths and long incident neutron wavelengths have been developed. In this paper, a detailed review is given of the development, principles and application conditions of various VSANS techniques. Then, beam current gain factors are calculated to evaluate those techniques. A VSANS design for the China Spallation Neutron Source （CSNS） is thereby presented.展开更多
The China-ADS project is a strategic plan launched by the Chinese Academy of Sciences to solve the nuclear waste problem and the resource problem for nuclear power in China. Under its long-term plan, it will last unti...The China-ADS project is a strategic plan launched by the Chinese Academy of Sciences to solve the nuclear waste problem and the resource problem for nuclear power in China. Under its long-term plan, it will last until about 2040. In order to achieve the extremely high reliability and availability required for the C-ADS accelerator, a fault tolerant strategy has been implanted. The failure effects of key elements such as the RF cavities and focusing elements in different locations of the injector-I part have been studied and schemes of compensation based on the local compensation-rematch method have been proposed. In addition, error analysis has been carried out to check the reliability of this method compared with the uncompensated situation, and it is found to be very effective. As the injector-I testing facility is coming into operation, it is possible to check and improve the compensation-rematch method with the beam testing experiment before the main linac operation.展开更多
For proton linear accelerators used in applications such as accelerator-driven systems, due to the nature of the operation, it is essential for the beam failure rate to be several orders of magnitude lower than usual ...For proton linear accelerators used in applications such as accelerator-driven systems, due to the nature of the operation, it is essential for the beam failure rate to be several orders of magnitude lower than usual performance of similar accelerators. A fault-tolerant mechanism should be mandatorily imposed in order to maintain short recovery time, high uptime and extremely low frequency of beam loss. This paper proposes an innovative and challenging way for compensation and rematch of cavity failure using fast electronic devices and Field Programmable Gate Arrays （FPGAs） instead of embedded computers to complete the computation of beam dynamics. A method of building an equivalent model for the FPGA, with optimization using a genetic algorithm, is shown. Results based on the model and algorithm are compared with TRACEWIN simulation to show the precision and correctness of the mechanism.展开更多
In a Rapid Cycling Synchrotron （RCS）, power loss due to an eddy current on the metal vacuum chamber would cause heating of the vacuum chamber. It is important to study the effect for estimating eddy current induced ...In a Rapid Cycling Synchrotron （RCS）, power loss due to an eddy current on the metal vacuum chamber would cause heating of the vacuum chamber. It is important to study the effect for estimating eddy current induced power loss and temperature growth. Analytical formulas for eddy current power loss for various types of vacuum chambers are derived for dipole and quadrupole repeetively. By using the prototype of dipole of CSNS/RCS, an experiment was done to test the analytical formula. The derived formulas were applied to calculating the eddy current power loss on some special structures of an RCS vacuum chamber.展开更多
In this paper we will show a general method of how to make an optimized parameter design of a circular e＋e- Higgs factory by using analytical expression of maximum beam-beam parameter and beamstrahlung beam lifetime ...In this paper we will show a general method of how to make an optimized parameter design of a circular e＋e- Higgs factory by using analytical expression of maximum beam-beam parameter and beamstrahlung beam lifetime starting from a given design goal and technical limitations. A parameter space has been explored. Based on beam parameters scan and RF parameters scan, a set of optimized parameter designs for 50 km Circular Higgs Factory （CHF） with different RF frequency was proposed.展开更多
The vibrating wire alignment technique is a method which, by measuring the spatial distribution of a magnetic field, can achieve very high alignment accuracy. The vibrating wire alignment technique can be applied to f...The vibrating wire alignment technique is a method which, by measuring the spatial distribution of a magnetic field, can achieve very high alignment accuracy. The vibrating wire alignment technique can be applied to fiducializing magnets and the alignment of accelerator straight section components, and it is a necessary supplement to conventional alignment methods. This article gives a systematic summary of the vibrating wire alignment technique, including vibrating wire model analysis, system frequency calculation, wire sag calculation, and the relation between wire amplitude and magnetic induction intensity. On the basis of this analysis, this article outlines two existing alignment methods, one based on magnetic field measurement and the other on amplitude and phase measurements. Finally, some basic experimental issues are discussed.展开更多
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-depen...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.展开更多
A new H^- ion source has been installed successfully and will be used to serve the China Spallation Neutron Source （CSNS）. In this paper, we report various components of the ion source, including the discharge chamb...A new H^- ion source has been installed successfully and will be used to serve the China Spallation Neutron Source （CSNS）. In this paper, we report various components of the ion source, including the discharge chamber, temperature, cooling system, extraction electrodes, analyzing magnet, remote control system and so on. Compared to the previous experimental ion source, some improvements have been made to make the ion source more compact and convenient. In the present arrangement, the Penning field is generated by a pair of pole tip extensions on the 90° analyzing magnet instead of by a separate circuit. For the remote control system, F3RP61-2L is applied to the accelerator online control system for the first time. In the running of the ion source, a stable pulse H^- beam with a current of 50 mA at an energy of 50 keV is produced. The extraction frequency and pulse width is 25 Hz and 500 μs, respectively. Furthermore, an emittance scanner has been installed and measurements are in progress.展开更多
The monodisperse polystyrene spheres are assembled into the colloidal crystal on the glass substrate by vertical deposition method, which is aimed at the so-called photonic crystal applications. The structural informa...The monodisperse polystyrene spheres are assembled into the colloidal crystal on the glass substrate by vertical deposition method, which is aimed at the so-called photonic crystal applications. The structural information of the bulk colloidal crystal is crucial for understanding the crystal growth mechanism and devel- oping the various applications of colloidal crystal. Small-angle X-ray scattering （SAXS） technique was used to obtain the bulk structure of the colloidal crystal at Beamline lW2A of BSRF. It is found that the SAXS pattern is sensitive to the relative orientation between the colloidal sample and the incident X-ray direction. The crystal lattice was well distinguished and determined by the SAXS data.展开更多
Purpose To evaluate the prompt and induced dose rate in backscattering neutron hall for radiation protection and safety management.Method The dose rates were calculated by Monte Carlo code FLUKA,with the"multi-st...Purpose To evaluate the prompt and induced dose rate in backscattering neutron hall for radiation protection and safety management.Method The dose rates were calculated by Monte Carlo code FLUKA,with the"multi-step"simulation method based on traditional"two-step simulation"method.Conclusion Operation time of staff workers does not need to be restricted.But with the increase in beam power and irra-diation time,serious consideration might need to be taken as the dose rate of samples may be higher than the limit value.展开更多
基金This work was supported by the National Natural Science Foundation of China(No.11922512)the Youth Innovation Promotion Association of Chinese Academy of Sciences(No.Y201904)the Guangdong Basic and Applied Basic Research Foundation—Guangdong Dongguan Joint Foundation(No.2019B1515120069).
文摘In recent years,a new generation of storage ring-based light sources,known as diffraction-limited storage rings(DLSRs),whose emittance approaches the diffraction limit for the range of X-ray wavelengths of interest to the scientific community,has garnered significant attention worldwide.Researchers have begun to design and build DLSRs.Among various DLSR proposals,the hybrid multibend achromat(H-MBA)lattice enables sextupole strengths to be maintained at a reasonable level when minimizing the emittance;hence,it has been adopted in many DLSR designs.Based on the H-7BA lattice,the design of the Advanced Photon Source Upgrade Project(APS-U)can effectively reduce emittance by replacing six quadrupoles with anti-bends.Herein,we discuss the feasibility of designing an APS-U-type H-MBA lattice for the Southern Advanced Photon Source,a mid-energy DLSR light source with ultralow emittance that has been proposed to be built adjacent to the China Spallation Neutron Source.Both linear and nonlinear dynamics are optimized to obtain a detailed design of this type of lattice.The emittance is minimized,while a sufficiently large dynamic aperture(DA)and momentum acceptance(MA)are maintained.A design comprising 36 APS-U type H-7BAs,with an energy of 3 GeV and a circumference of 972 m,is achieved.The horizontal natural emittance is 20 pm·rad,with a horizontal DA of 5.8 mm,a vertical DA of 4.5 mm,and an MA of 4%,as well as a long longitudinal damping time of 120 ms.Subsequently,a few modifications are performed based on the APS-U-type lattice to reduce the maximum value of damping time from 120 to 44 ms while maintaining other performance parameters at the same level.
基金supported by High Energy Photon Source(HEPS),a major national science and technology infrastructure in China.Funding was also received from the Chinese Academy of Sciences and the National Natural Science Foundation of China(Grant No.12275285).
文摘Purpose High energy photon source is a 6 GeV diffraction-limited storage ring light source currently under construction in Beijing.A low-frequency fundamental radio-frequency(rf)system of 166.6 MHz was proposed to accommodate the accelerator physics design.Superconducting rf(srf)technologies were chosen for the storage ring rf accompanied by solid-state power amplifiers and digital low-level rf controls.The design of the rf system was completed,and the parameters are frozen.Elucidation of the rf design with key parameters is desired.Methods The requirements from the accelerator physics design will be presented followed by the detailed rf design.The logic behind the choice of key rf parameters is elaborated.The configuration of the entire rf system is presented.Results and conclusions The fundamental srf cavity of 166.6 MHz was designed to accelerate the ultrarelativistic electron beam.Heavy damping of higher-order modes in these cavities is required to avoid the coupled bunch instabilities.An active third harmonic srf of 499.8 MHz was adopted to realize the required rf gymnastics.Normal-conducting 5-cell cavities will be used for the booster rf.Solid-state amplifiers of 2.4 MW in total will be installed at HEPS to drive these cavities in the booster and the storage ring.A digital low-level rf system will be used to regulate rf field inside each cavity with high stabilities.The rf configuration during the commissioning and the operation scenarios are also presented.
基金supported by the National Natural Science Foundation of China(Grant Nos.61671004,61271012,81371549,81671683,and 11501415)the Natural Science Foundation of Tianjin City,China(Grant No.16JCYBJC28600)+4 种基金the WBE Liver Fibrosis Foundation of China(Grant No.CFHPC20131033)the Instrument Developing Project of the Chinese Academy of Sciences(Grant No.YZ201410)the Foundation of Tianjin University of Technology and Education(Grant Nos.KJ11-22 and J10011060321)SRF for ROCS,SEMthe IHEP-CAS Scientific Research Foundation(Grant No.2013IHEPYJRC801)
文摘In-line phase-contrast computed tomography（IL-PC-CT） imaging is a new physical and biochemical imaging method.IL-PC-CT has advantages compared to absorption CT when imaging soft tissues. In practical applications, ring artifacts which will reduce the image quality are commonly encountered in IL-PC-CT, and numerous correction methods exist to either pre-process the sinogram or post-process the reconstructed image. In this study, we develop an IL-PC-CT reconstruction method based on anisotropic total variation（TV） minimization. Using this method, the ring artifacts are corrected during the reconstruction process. This method is compared with two methods： a sinogram preprocessing correction technique based on wavelet-FFT filter and a reconstruction method based on isotropic TV. The correction results show that the proposed method can reduce visible ring artifacts while preserving the liver section details for real liver section synchrotron data.
基金financial support from the Joint Research Fund in Astronomy under a cooperative agreement between the National Natural Science Foundation of China and the Chinese Academy of Sciences (Grant No. U1631242)the National Natural Science Foundation of China (Grant Nos. 11503028 and 11403028)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB23040400)the National Basic Research Program (973 Program) of China (2014CB845800)
文摘POLAR is a compact space-borne detector initially designed to measure the polarization of hard X-rays emitted from Gamma-Ray Bursts in the energy range 50–500 ke V.This instrument was launched successfully onboard the Chinese space laboratory Tiangong-2(TG-2) on 2016 September 15.After being switched on a few days later,tens of gigabytes of raw detection data were produced in-orbit by POLAR and transferred to the ground every day.Before the launch date,a full pipeline and related software were designed and developed for the purpose of quickly pre-processing all the raw data from POLAR,which include both science data and engineering data,then to generate the high level scientific data products that are suitable for later science analysis.This pipeline has been successfully applied for use by the POLAR Science Data Center in the Institute of High Energy Physics(IHEP) after POLAR was launched and switched on.A detailed introduction to the pipeline and some of the core relevant algorithms are presented in this paper.
文摘Purpose A new in-vacuum three-dimensional Hall probe magnetic measurement system is under fabrication for characterizing the magnetic performance of the Cryogenic Permanent Magnet Undulator(CPMU).In order to fit the small gap(5 mm)of magnetic structure and vacuum environment,a small three-dimensional Hall probe has been manufactured.The angular and positional misalignment errors of the Hall sensors play an important role in the measurement accuracy of the CPMU.In order to minimize the misalignment errors,a method of calibrating angle error and relative assembly displacements of a three-dimensional Hall probe is carried out.Methods The angle error of Hall sensors will be calibrated by a standard dipole magnet and a five-dimensional Hall bench.The standard dipole magnet will generate a single direction and uniform magnetic field.And the fivedimensional Hall bench is used to rotate the Hall probe which is put in the center of magnet.Based on the relationship between angle and magnetic field strength,the angle error of each Hall sensor will be obtained.The relative position between the sensitive areas of the Hall sensors will be calibrated by a two-dimensional magnetic field undulator section.Based on Maxwell’s equations,through the calculation of measurement magnetic field strength,the relative assembly displacements of the three Hall sensors can be derived.Results The details of the calibration methods and the data processing of angle error and relative assembly displacements of a three-dimensional Hall probe are presented.The three-dimensional magnetic fields of a cryogenic permanent magnet undulator can be received accurately by correcting these angle errors and position errors of Hall sensors.Conclusions This paper illustrates the relative position and angle calibration procedures and the data processing of a three-dimensional Hall probe.Now the design of a smaller Hall probe is in process.The calibration of the angle errors and position errors will be carried out after the fabrication of the standard dipole magnet.
基金This work was supported by Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA03030201)the Key Laboratory of Particle Acceleration Physics and Technology Autonomous Foundation of CAS China(No.JSQ2017ZZ01).
文摘The 10-MeV Accelerator-Driven Subcritical(ADS)system Injector-I test stand at the Institute of High Energy Physics(IHEP)is a testing facility dedicated to demonstrating the feasibility of the spoke-based super-conducting(SC)linear accelerator(linac)for the ADS project in China.The injector adopted a four-vane copper structure radio frequency quadrupole(RFQ)with an output energy of 3.2 MeV and an SC section accommodating 14 β_(g)=0.12 single spoke cavities,14 SC solenoids,and 14 cold beam position monitors(BPMs).A 10-MeV pulsed beam with a beam current of 10 mA and a 2-mA continuous wave(CW)beam were successfully shooting through.The commissioning results confirmed the feasibility of using a 325-MHz spoke-type cavity for accelerating the proton beam in the low β and medium β sections.This paper describes the results achieved,the difficulties encountered,and the experiences obtained during commissioning.
文摘Purpose In order to achieve a high-precision measurement of the incident and the reflected power,a WR1800 rectangular waveguide directional coupler with high directivity and high power level has been in-house developed.Multiple couplers will be installed in the 500-MHz high-power radio-frequency transmission lines delivering 200-kW continuous-wave power for the High Energy Photon Source(HEPS).Methods The directional coupler adopts the design scheme of primary and secondary transmission lines and coaxial coupling-head structure.The shape and dimensional parameters of the coupling head were carefully optimized by using microwave simulation codes.An optimum directivity of 64 dB was achieved in simulations.Results and conclusions A prototype coupler was subsequently manufactured,and its directivity was measured to be 48.2 dB following a rigorous calibration procedure,largely exceeding the design goal and the commercial product.The coupler was then connected to an existing 500-MHz klystron system,and a high-power test with short-circuit termination was conducted.The high directivity of the coupler was confirmed up to 200 kW.During the 6 hours of power aging with continuous-wave 200 kW in a standing-wave setup,no performance degradation was observed on the coupler.The coupler temperature was measured to be 20◦C above the ambient environment.The design requirements were comfortably fulfilled.These constitute thefirst in-house development of a large-size waveguide directional coupler with high directivity and high power level for HEPS.The design,fabrication,and performance tests of the directional coupler are presented.
基金Supported by Agence Nationale de la Recherche of the French Ministry of Research(Programme Blanc,Project ATF2-IN2P3-KEK,contract,ANR-06-BLAN-0027)National Natural Science Foundation of China(11175192)support in part by the USDepartment of Energy(DE-AC02-76SF00515)
文摘The ATF2 project is the final focus system prototype for the ILC and CLIC linear collider projects, with the purpose of reaching a 37nm vertical beam size at the interaction point. In the nanometer beam size regime, higher order multipoles in magnets become a crucial point for consideration. The strength and rotation angle of the ATF2 QEA magnets were reconstructed from the IHEP measurements and compared with the KEK ones to be identical. Based on the study of the skew multipoles sensitivity, we report on the analysis of the possible mitigation of the measured multipoles. A suggestion is given which will benefit the ATF2 present commissioning to reach the goal beam size, and also the reduced β optics in future.
基金Supported by the IHEP Innovative Project on Sciences and Technologies (E2545AU210)。
文摘This paper presents the prospects of measuring σ(e^(+)e^(-)→ZH)× Br(H→γγ) in three Z decay channels Z→qq/μ^(+)μ^(-)/vv using the baseline detector with √s=240GeV at the Circular Electron Positron Collider(CEPC).Simulated Monte Carlo events were generated and scaled to an integrated luminosity of 5.6 ab^(-1) to mimic the data.Extrapolated results to 20 ab^(-1) are also reported.The expected statistical precision of these measurements after combining three channels of Z boson decay was 7.7%.With some preliminary estimation on the systematical uncertainties,the total precision is 7.9%.The performance of the CEPC electro-magnetic calorimeter(ECAL) was studied by smearing the photon energy resolution in simulated events in the e^(+)e^(-)→ZH→qqγγ channel.In the present ECAL design,the stochastic term in resolution plays the dominant role in the precision of Higgs measurements in the H→γγ channel.The impact of the resolution on the measured precision of σ(ZH)×Br(ZH→qqγγ) as well as the optimization of the ECAL constant and stochastic terms were studied for further detector design.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA10010200)the Tsinghua University Initiative Scientific Research Program(Grant No.20131089288)
文摘After the success of the Daya Bay experiment, the Jiangmen Underground Neutrino Observatory （JUNO） was launched to measure neutrino-mass hierarchy and oscillation parameters and to study other neutrino physics. Its central detector is set for antineutrinos from reactors, the Earth, the atmosphere, and the Sun. The main requirements of the central detector are con- tainment of 20 kt of liquid scintillator, as the target mass, and 3% energy resolution. It is about a ball-shape detector of 38.5 m with -75% coverage of PMT on its inner surface. The design of such a huge detector is a big challenge because it must meet the requirements for several different types of physics measurement and possess the feasibility and reliability in its structure and engineering, all at reasonable time and cost. One option for the JUNO central detector is a hyper-scale acrylic ball sub- merged in the water to shield the background. This paper proposes a structural scheme for such an acrylic ball that is supported by a stainless-steel truss, inspired by point-supported glass-curtain walls in civil engineering. The preliminary design of the scheme is completed and verified by finite element （FE） method using ABAQUS. FE analysis shows that the scheme can con- trol the stress level of the acrylic ball within the limit of 5 to 10 MPa, in accordance with the demand of the design objective of the central detector. The scheme is of outstanding global stability and allows various chocces on local connections. We prove that the scheme is of good feasibility and should be a reasonable option for the central detector.
基金Supported by National Natural Science Foundation of China(21474119,11305191)
文摘Very Small Angle Neutron Scattering （VSANS） is an upgrade of the traditional Small Angle Neutron Scattering （SANS） technique which can cover three orders of magnitude of length scale from one nanometer to one micrometer. It is a powerful tool for structure calibration in polymer science, biology, material science and condensed matter physics. Since the first VSANS instrument, Dll in Grenoble, was built in 1972, new collimation techniques, focusing optics （multi-beam converging apertures, material or magnetic lenses, and focusing mirrors） and higher resolution detectors combined with the long flight paths and long incident neutron wavelengths have been developed. In this paper, a detailed review is given of the development, principles and application conditions of various VSANS techniques. Then, beam current gain factors are calculated to evaluate those techniques. A VSANS design for the China Spallation Neutron Source （CSNS） is thereby presented.
基金Supported by National Natural Science Foundation of China(Projects 11235012,11475201)the China ADS Project(XDA03020000)
文摘The China-ADS project is a strategic plan launched by the Chinese Academy of Sciences to solve the nuclear waste problem and the resource problem for nuclear power in China. Under its long-term plan, it will last until about 2040. In order to achieve the extremely high reliability and availability required for the C-ADS accelerator, a fault tolerant strategy has been implanted. The failure effects of key elements such as the RF cavities and focusing elements in different locations of the injector-I part have been studied and schemes of compensation based on the local compensation-rematch method have been proposed. In addition, error analysis has been carried out to check the reliability of this method compared with the uncompensated situation, and it is found to be very effective. As the injector-I testing facility is coming into operation, it is possible to check and improve the compensation-rematch method with the beam testing experiment before the main linac operation.
基金Supported by China ADS Project(XDA03020600)Natural Science Foundation of China(11575216)
文摘For proton linear accelerators used in applications such as accelerator-driven systems, due to the nature of the operation, it is essential for the beam failure rate to be several orders of magnitude lower than usual performance of similar accelerators. A fault-tolerant mechanism should be mandatorily imposed in order to maintain short recovery time, high uptime and extremely low frequency of beam loss. This paper proposes an innovative and challenging way for compensation and rematch of cavity failure using fast electronic devices and Field Programmable Gate Arrays （FPGAs） instead of embedded computers to complete the computation of beam dynamics. A method of building an equivalent model for the FPGA, with optimization using a genetic algorithm, is shown. Results based on the model and algorithm are compared with TRACEWIN simulation to show the precision and correctness of the mechanism.
文摘In a Rapid Cycling Synchrotron （RCS）, power loss due to an eddy current on the metal vacuum chamber would cause heating of the vacuum chamber. It is important to study the effect for estimating eddy current induced power loss and temperature growth. Analytical formulas for eddy current power loss for various types of vacuum chambers are derived for dipole and quadrupole repeetively. By using the prototype of dipole of CSNS/RCS, an experiment was done to test the analytical formula. The derived formulas were applied to calculating the eddy current power loss on some special structures of an RCS vacuum chamber.
基金Supported by National Foundation of Natural Sciences(11175192)
文摘In this paper we will show a general method of how to make an optimized parameter design of a circular e＋e- Higgs factory by using analytical expression of maximum beam-beam parameter and beamstrahlung beam lifetime starting from a given design goal and technical limitations. A parameter space has been explored. Based on beam parameters scan and RF parameters scan, a set of optimized parameter designs for 50 km Circular Higgs Factory （CHF） with different RF frequency was proposed.
文摘The vibrating wire alignment technique is a method which, by measuring the spatial distribution of a magnetic field, can achieve very high alignment accuracy. The vibrating wire alignment technique can be applied to fiducializing magnets and the alignment of accelerator straight section components, and it is a necessary supplement to conventional alignment methods. This article gives a systematic summary of the vibrating wire alignment technique, including vibrating wire model analysis, system frequency calculation, wire sag calculation, and the relation between wire amplitude and magnetic induction intensity. On the basis of this analysis, this article outlines two existing alignment methods, one based on magnetic field measurement and the other on amplitude and phase measurements. Finally, some basic experimental issues are discussed.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.21474119 and 21674020)
文摘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.
文摘A new H^- ion source has been installed successfully and will be used to serve the China Spallation Neutron Source （CSNS）. In this paper, we report various components of the ion source, including the discharge chamber, temperature, cooling system, extraction electrodes, analyzing magnet, remote control system and so on. Compared to the previous experimental ion source, some improvements have been made to make the ion source more compact and convenient. In the present arrangement, the Penning field is generated by a pair of pole tip extensions on the 90° analyzing magnet instead of by a separate circuit. For the remote control system, F3RP61-2L is applied to the accelerator online control system for the first time. In the running of the ion source, a stable pulse H^- beam with a current of 50 mA at an energy of 50 keV is produced. The extraction frequency and pulse width is 25 Hz and 500 μs, respectively. Furthermore, an emittance scanner has been installed and measurements are in progress.
基金Supported by National Natural Science Foundation of China (10832011)Knowledge Innovation Program of Chinese Academy of Sciences (KJCX2-YW-L08)
文摘The monodisperse polystyrene spheres are assembled into the colloidal crystal on the glass substrate by vertical deposition method, which is aimed at the so-called photonic crystal applications. The structural information of the bulk colloidal crystal is crucial for understanding the crystal growth mechanism and devel- oping the various applications of colloidal crystal. Small-angle X-ray scattering （SAXS） technique was used to obtain the bulk structure of the colloidal crystal at Beamline lW2A of BSRF. It is found that the SAXS pattern is sensitive to the relative orientation between the colloidal sample and the incident X-ray direction. The crystal lattice was well distinguished and determined by the SAXS data.
基金supported by the National Key Research and Development Program of China(Project:2016YFA0401601)
文摘Purpose To evaluate the prompt and induced dose rate in backscattering neutron hall for radiation protection and safety management.Method The dose rates were calculated by Monte Carlo code FLUKA,with the"multi-step"simulation method based on traditional"two-step simulation"method.Conclusion Operation time of staff workers does not need to be restricted.But with the increase in beam power and irra-diation time,serious consideration might need to be taken as the dose rate of samples may be higher than the limit value.
