Molten Salt Reactor(MSR) was selected as one of the six innovative nuclear reactors by the Generation IV International Forum(GIF).The circulating-fuel in the can-type molten salt fast reactor makes the neutronics and ...Molten Salt Reactor(MSR) was selected as one of the six innovative nuclear reactors by the Generation IV International Forum(GIF).The circulating-fuel in the can-type molten salt fast reactor makes the neutronics and thermo-hydraulics of the reactor strongly coupled and different from that of traditional solid-fuel reactors.In the present paper,a new coupling model is presented that physically describes the inherent relations between the neutron flux,the delayed neutron precursor,the heat transfer and the turbulent flow.Based on the model,integrating nuclear data processing,CAD modeling,structured and unstructured mesh technology,data analysis and visualization application,a three dimension steady state simulation code system(MSR3DS) for the can-type molten salt fast reactor is developed and validated.In order to demonstrate the ability of the code,the three dimension distributions of the velocity,the neutron flux,the delayed neutron precursor and the temperature were obtained for the simplified MOlten Salt Advanced Reactor Transmuter(MOSART) using this code.The results indicate that the MSR3DS code can provide a feasible description of multi-physical coupling phenomena in can-type molten salt fast reactor.Furthermore,the code can well predict the flow effect of fuel salt and the transport effect of the turbulent diffusion.展开更多
We report the design of a wide-range energy material beamline(E-line) with multiple experimental techniques at the Shanghai Synchrotron Radiation Facility.The undulators consisted of an elliptically polarizing undulat...We report the design of a wide-range energy material beamline(E-line) with multiple experimental techniques at the Shanghai Synchrotron Radiation Facility.The undulators consisted of an elliptically polarizing undulator and in-vacuum undulator that generate the soft and hard X-rays, respectively. The beamline covered a wide energy range from 130 to 18 ke V with both a high photon flux([ 10^(12) phs/s with exit silt 30 lm in soft X-ray and [ 5 9 10^(12) phs/s in hard X-ray within 0.1%BW bandwidth) and promising resolving power(maximum E/DE [ 15,000 in soft X-ray with exit silt 30 lm and [6000 in hard X-ray). Moreover, the beam spots from the soft and hard X-rays were focused to the same sample position with a high overlap ratio, so that the surfaces, interfaces, and bulk properties were characterized in situ by changing the probing depth.展开更多
Sulfate, nitrate and ammonium （SNA） are the dominant species in secondary inorganic aerosol, and are considered an important factor in regional haze formation. Size-fractionated aerosol particles for a whole year we...Sulfate, nitrate and ammonium （SNA） are the dominant species in secondary inorganic aerosol, and are considered an important factor in regional haze formation. Size-fractionated aerosol particles for a whole year were collected to study the size distribution of SNA as well as their chemical species in Shanghai. SNA mainly accumulated in fine particles and the highest average ratio of SNA to particulate matter （PM） was observed to be 47% in the fine size fraction （0.49-0.95 ~tm）. Higher sulfur oxidation ratio and nitrogen oxidation ratio values were observed in PM of fine size less than 0.95 ~tm. Ion balance calculations indicated that more secondary sulfate and nitrate would be generated in PM of fine size （0.49-0.95 p.m）. Sulfur K-edge X-ray absorption near-edge structure （XANES） spectra of typical samples were analyzed. Results revealed that sulfur mainly existed as sulfate with a proportion （atomic basis） more than 73% in all size of PM and even higher at 90% in fine particles. Sulfate mainly existed as （NH4）2SO4 and gypsum in PM of Shanghai. Compared to non-haze days, a dramatic increase of （NH4）2SO4 content was found in fine particles on haze days only, which suggested the promoting impact of （NH4）2SO4 on haze formation. According to the result of air mass backward trajectory analysis, more （NH4）2SO4 would be generated during the periods of air mass stagnation. Based on XANES, analysis of sulfate species in size-fractionated aerosol particles can be an effective way to evaluate the impact of sulfate aerosols on regional haze formation.展开更多
Beam lifetime is dominated by Touschek scattering at the Shanghai Synchrotron Radiation Facility(SSRF).Touschek loss rate is affected by probability for scattering beyond the RF acceptance and the volume charge densit...Beam lifetime is dominated by Touschek scattering at the Shanghai Synchrotron Radiation Facility(SSRF).Touschek loss rate is affected by probability for scattering beyond the RF acceptance and the volume charge density of the bench.In the phaseⅡupgrade of the SSRF,a third harmonic superconducting cavity will be used to enhance the Touschek lifetime by lengthening the bunches.The Touschek lifetime improvement factor is affected by the voltage of a harmonic cavity.To stabilize the cavity voltage,a tuning control system was designed to control it.The design of the tuning control system was based on the SSRF third-generation low-level RF control system.Some hardware and specialized algorithms were redesigned to fit the harmonic cavity control.The design of the tuning control system is complete,and the control system has been tested.The test result shows that the fluctuation of amplitude is<±0.34%within 1.5 h,which satisfies the stability requirement.展开更多
To achieve high-efficiency operation of the highgain free-electron laser(FEL),the electron beams and radiated photon beams need to be overlapped precisely and pass through the entire undulator section.Therefore,a high...To achieve high-efficiency operation of the highgain free-electron laser(FEL),the electron beams and radiated photon beams need to be overlapped precisely and pass through the entire undulator section.Therefore,a high-resolution beam-position monitor(BPM)is required.A cavity BPM(CBPM)with a resonant cavity structure was developed and used in the Shanghai Soft X-ray FEL(SXFEL)test facility and can achieve a position resolution of<1μm.The construction and operation of the SXFEL user facility also bring about higher requirements for beamposition measurement.In this case,the factors that affect the performance of the CBPM system were further analyzed.These included the amplitude and phase stability of the local oscillator,stability of the trigger signal,performance of the radio frequency front-end,signal processing electronics,and signal processing algorithms.Based on the upgrade and optimization of the system,a beam test platform was built at the end of the linear acceleration section of the SXFEL,and the experimental results show that the position resolution of the system can reach 177 nm at a bunch charge of 500 pC,and the dynamic range is controlled within±300μm,and the relative measurement uncertainty of the bunch charge can reach 0.021%,which are significant improvements compared to the attributes of the previous system.展开更多
The Shanghai Advanced Proton Therapy facility employs third-integer slow extraction. In order to achieve accurate treatment, high-quality spill is needed. Therefore,parameters that may affect slow extraction should be...The Shanghai Advanced Proton Therapy facility employs third-integer slow extraction. In order to achieve accurate treatment, high-quality spill is needed. Therefore,parameters that may affect slow extraction should be investigated by simulation. A computer model of the synchrotron operation slow extraction was constructed with MATLAB~. By simulating the motion of the circulating protons, we could quantify the influence of machine and initial beam parameters on properties of the extracted beam, such as ripple, uniformity, stability, on-and off-time of the spill and spill width in the synchrotron.Suitable design parameters including the horizontal tunes,power supply ripple, longitudinal RF cavity voltage, RFKO and the chromaticities were determined.展开更多
In this article, we present the promise of a new method generating double electron pulses in picosecondscale pulse length and tunable interpulse spacing at several picoseconds. This has witnessed an impressive potenti...In this article, we present the promise of a new method generating double electron pulses in picosecondscale pulse length and tunable interpulse spacing at several picoseconds. This has witnessed an impressive potential of application in pump–probe techniques, two-color X-ray free electron laser, high-gradient witness bunch acceleration in a plasma, etc. Three-dimensional simulations are carried out to analyze the dynamic of the electron beam in a linear accelerator. Comparisons are made between the new method and existing ways.展开更多
Axial gas-liquid separators have been adopted in fission gas removal systems for the development of thorium molten salt reactors. In our previous study, we observed an unsteady flow phenomenon in which the flow patter...Axial gas-liquid separators have been adopted in fission gas removal systems for the development of thorium molten salt reactors. In our previous study, we observed an unsteady flow phenomenon in which the flow pattern is directly dependent on the backpressure in a gas-liquid separator; however, the underlying flow mechanism is still unknown. In order to move a step further in clarifying how the flow pattern evolves with a variation in backpressure, a large eddy simulation(LES) was adopted to study the flow field evolution. In the simulation, an artificial boundary was applied at the separator outlet under the assumption that the backpressure increases linearly. The numerical results indicate that the unsteady flow feature is captured by the LES approach, and the flow transition is mainly due to the axial velocity profile redistribution induced by the backpressure variation. With the increase in backpressure,the axial velocity near the downstream orifice transits from negative to positive. This change in the axial velocity sign forces the unstable spiral vortex to become a stable rectilinear vortex.展开更多
Free electron lasers provide high-power and ultrashort pulses with extreme brightness. In order to improve a facility's capabilities and explore the possibility of performing high-resolution time-resolved experime...Free electron lasers provide high-power and ultrashort pulses with extreme brightness. In order to improve a facility's capabilities and explore the possibility of performing high-resolution time-resolved experiments, a beam arrival time resolution under 100 fs is required. In this article, a novel beam arrival time monitor(BAM)equipped with two cavities has been designed and a beam flight time measurement scheme based on the BAM prototype has been proposed to estimate phase jitter in the signal measurement system. The two BAM cavities work at different frequencies and the frequency difference is designed to be 35 MHz. Therefore, a self-mixing intermediate frequency signal can be generated using the two cavities. The measured beam flight time shows a temporal deviation of 37 fs(rms).展开更多
Phase space is one of the most important parameters used to describe beam properties. Computer tomography, as a method for reconstructing phase space and measuring beam emittance, has been used in many accelerators ov...Phase space is one of the most important parameters used to describe beam properties. Computer tomography, as a method for reconstructing phase space and measuring beam emittance, has been used in many accelerators over the past few decades. In this paper, we demonstrate a transverse phase space reconstruction study in the Shanghai soft X-ray free electron laser facility. First,we discuss the basic principles of phase space reconstruction and the advantage of reconstructing beam distribution in normalized phase space. Then, the phase space reconstruction results by different computer tomography methods based on the maximum entropy(MENT) algorithm and the filtered back projection algorithm in normalized phase space are presented. The simulation results indicate that,with proper configuration of the phase advance between adjacent screens, the MENT algorithm is feasible and has good efficiency. The beam emittance and Twiss parameters are also calculated using the reconstructed phase space.展开更多
A proton therapy system is a large medical device to treat tumors.Its gantry is of large structure and high precision.A new half-gantry was designed in the Shanghai Advanced Proton Therapy(SAPT)project.In this paper,t...A proton therapy system is a large medical device to treat tumors.Its gantry is of large structure and high precision.A new half-gantry was designed in the Shanghai Advanced Proton Therapy(SAPT)project.In this paper,the weight of gantry in design is reduced significantly by size and structure optimizations,to improve its cost-effectiveness,while guaranteeing the functions and precision.The processes of physics optimization,empirical design optimization,topological optimization and size optimization,together with factors of consideration,are described.The gantry weight is reduced by 30%,with the same precision.展开更多
Fast reactors based on thorium fuel have enhanced inherent safety. Fluoride salt performs well as a coolant in high-temperature nuclear systems. In this paper,we present a reference core for a large fluoride-salt-cool...Fast reactors based on thorium fuel have enhanced inherent safety. Fluoride salt performs well as a coolant in high-temperature nuclear systems. In this paper,we present a reference core for a large fluoride-salt-cooled solid-fuel fast reactor(LSFR) using thorium–uranium fuel cycle. Neutronics physics of the LSFR reference core is investigated with 2D and 3D in-core fuel management strategy. The design parameters analyzed include the fuel volume fraction, power density level and continuous removal of fission products with 3D fuel shuffling that obtains better equilibrium core performance than 2D shuffling. A self-sustained core is achieved for all cases,and the core of 60% fuel volume fraction at 50 MW/m^3 power density is of the best breeding performance(average breeding ratio 1.134). The LSFR core based on thorium fuel is advantageous in its high discharge burn-up of 20–30% fissions per initial heavy metal atom, small reactivity swing over the whole lifetime(to simplify the reactivity control system), the negative reactivity temperature coefficient(intrinsically safe for all cases) and accepted cladding peak radiation damage. The LSFR reactor is a good alternative option for the deployment of a self-sustained thorium-based nuclear system.展开更多
The zero degree calorimeter(ZDC) at RHICSTAR was installed in the year 2000.After running for more than 10 years,the performance of the STAR-ZDC cannot maintain a proper status because of the radiation damage.The ZDC ...The zero degree calorimeter(ZDC) at RHICSTAR was installed in the year 2000.After running for more than 10 years,the performance of the STAR-ZDC cannot maintain a proper status because of the radiation damage.The ZDC on RHIC-BRAHMS had been moved to STAR in 2011 after some tests.We present here the result of the tests as well as the physical performance of those ZDC modules between the 2011 and 2015 RHIC runs.The excellent energy resolution of the ZDC in heavy ion collision provides a good candidate for future detector development,such as the CSR experiment at CAS-Lanzhou facility.展开更多
X-ray photon correlation spectroscopy(XPCS)has emerged as a powerful tool for probing the nanoscale dynamics of soft condensed matter and strongly correlated materials owing to its high spatial resolution and penetrat...X-ray photon correlation spectroscopy(XPCS)has emerged as a powerful tool for probing the nanoscale dynamics of soft condensed matter and strongly correlated materials owing to its high spatial resolution and penetration capabilities.This technique requires high brilliance and beam coherence,which are not directly available at modern synchrotron beamlines in China.To facilitate future XPCS experiments,we modified the optical setup of the newly commissioned BL10U1 USAXS beamline at the Shanghai Synchrotron Radiation Facility(SSRF).Subsequently,we performed XPCS measurements on silica suspensions in glycerol,which were opaque owing to their high concentrations.Images were collected using a high frame rate area detector.A comprehensive analysis was performed,yielding correlation functions and several key dynamic parameters.All the results were consistent with the theory of Brownian motion and demonstrated the feasibility of XPCS at SSRF.Finally,by carefully optimizing the setup and analyzing the algorithms,we achieved a time resolution of 2 ms,which enabled the characterization of millisecond dynamics in opaque systems.展开更多
In this paper,we report a MATLAB-based GUI tool,bodgui,which integrates functions of lattice editor,linear match,and nonlinear optimization,and visualized tracking functions for beam optics design.A user can switch hi...In this paper,we report a MATLAB-based GUI tool,bodgui,which integrates functions of lattice editor,linear match,and nonlinear optimization,and visualized tracking functions for beam optics design.A user can switch his/her design procedures one to another.Flexibilities are provided for adjusting or optimizing the lattice settings in commissioning or operation of the accelerators.The algorithm of the linear match and nonlinear optimization,and the GUI windows including the main functions and running status,are presented.The SSRF storage ring was employed as a test lattice.Several optics modes designed and optimized by the GUI tools were used for commissioning the storage ring.Functions of bodgui tool are machine-independent,and it can be well applied to modern light sources being built in other parts of the world.展开更多
A front-end electronics of dose monitor has been developed for measuring irradiation dose to the patient in Shanghai Advanced Proton Therapy Facility.The parallel plate ionization chamber is used for the dose monitori...A front-end electronics of dose monitor has been developed for measuring irradiation dose to the patient in Shanghai Advanced Proton Therapy Facility.The parallel plate ionization chamber is used for the dose monitoring.Unlike the traditional method of recycling capacitor integration and voltage-to-frequency conversion,this dose monitor electronics uses the trans-impedance amplifier and analog-to-digital conversion method.It performs satisfactorily,with the integral nonlinearity of less than ±0.04 nA in the range of-400 to 50 nA and the resolution of about±0.6 nA.展开更多
In this paper,we present the general design methods and parameter measurements of a 1-k W solidstate radio frequency(RF) power amplifier at 2856 MHz,for the soft X-ray free electron laser facility.Three-stage amplific...In this paper,we present the general design methods and parameter measurements of a 1-k W solidstate radio frequency(RF) power amplifier at 2856 MHz,for the soft X-ray free electron laser facility.Three-stage amplification with a 4-way combination is used.An RF switch module is integrated with the solid-state RF power amplifier to convert the continuous wave(CW) signal into pulse signal,with adjustable pulse width.The power gain is measured at 57.7 d B at 60 d Bm output.The RF phase noise,which is measured by the low-level RF system,is\0.015 degree(RMS),while the pulse frontier jitter is\5 ns.展开更多
By choosing parameters in the modulator, the dispersive section and the seed laser, the spatial bunching of the electron beam can be correlated to the n-th harmonic of the radiator radiation, instead of the fundamenta...By choosing parameters in the modulator, the dispersive section and the seed laser, the spatial bunching of the electron beam can be correlated to the n-th harmonic of the radiator radiation, instead of the fundamental radiation in conventional high-gain harmonic generation (HGHG). Thus, the radiator undulator is operated at high harmonic mode. In this paper, the possibility of harmonic operation of Shanghai deep ultraviolet (SDUV) free electron laser (FEL) is studied. Discussions on the principle of harmonic operation, the simulation code development, the simulation results, and the proposed experimental procedure for verification of harmonic operation at the SDUV FEL are also presented.展开更多
Frequency-modulation atomic force microscopy(FM-AFM) is a highly versatile tool for surface science.Besides imaging surfaces, FM-AFM is capable of measuring interactions between the AFM probe and the surface with high...Frequency-modulation atomic force microscopy(FM-AFM) is a highly versatile tool for surface science.Besides imaging surfaces, FM-AFM is capable of measuring interactions between the AFM probe and the surface with high sensitivity, which can provide chemical information at sub-nanometer resolution. This is achieved by deconvoluting the frequency shift, which is directly measured in experiments, into the force between the probe and sample. At present, the widely used method to perform this deconvolution has been shown to be accurate under high quality(high-Q) factor vacuum conditions. However, under low quality(low-Q) factor conditions, such as in solution, it is not clear if this method is valid. A previous study apparently verified this relation for experiments in solution by comparing the force calculated by this equation with that obtained in separate experiments using the surface force apparatus(SFA). Here we show that, in solution, a more direct comparison of the force calculated by this relation with that directly measured by the cantilever deflection in AFM reveals significant differences,both qualitative and quantitative. However, we also find that there are complications that hinder this comparison.Namely, while contact with the surface is clear in the direct measurements(including the SFA data), it is less certain in the FM-AFM case. Hence, it is not clear if the two methods are measuring the same tip-sample distance regimes. Thus, our results suggest that a more thorough verification of this relation is required, as application of this formulation for experiments in solution may not be valid.展开更多
Based on the service characteristics of fuel elements for molten salt reactors,they need to have a high power density,resistance to coolant infiltration,and excellent thermodynamic properties.To solve the problem of t...Based on the service characteristics of fuel elements for molten salt reactors,they need to have a high power density,resistance to coolant infiltration,and excellent thermodynamic properties.To solve the problem of the graphite used in the fuel element for these reactors being susceptible to molten salt infiltration,carbon black(CB)was added to increase the density of the graphite,and a fuel element(TRISO(tri-structural isotropic)fuel particles were randomly distributed in the modified graphite matrix)was prepared by cold isostatic pressing process.An out-of-pile performance study shows that the densification and pore structure of the modified graphite matrix were improved,as was the resistance to molten salt infiltration.The median pore size of the modified graphite was reduced from 673 to 433 nm and the threshold pressure for molten salt(FLiBe,66%(molar fraction)LiF and 34%BeF_(2))infiltration was increased from 0.88 to 1.37 MPa.The isotropic CB made the graphite matrix less anisotropic,while its thermal conductivity and compressive strength were reduced due to the difficult graphitization of CB.Fuel elements containing 20%(volume fraction)TRISO particles were prepared.Numerical simulations show that the power and temperature distribution of the fuel were in line with the design requirements.The modified graphite matrix had a higher density,smaller pores,a lower anisotropy and a greater resistance to FLiBe infiltration.展开更多
基金Supported by the"Strategic Priority Research Program"of the Chinese Academy of Science(No.XD02001004)
文摘Molten Salt Reactor(MSR) was selected as one of the six innovative nuclear reactors by the Generation IV International Forum(GIF).The circulating-fuel in the can-type molten salt fast reactor makes the neutronics and thermo-hydraulics of the reactor strongly coupled and different from that of traditional solid-fuel reactors.In the present paper,a new coupling model is presented that physically describes the inherent relations between the neutron flux,the delayed neutron precursor,the heat transfer and the turbulent flow.Based on the model,integrating nuclear data processing,CAD modeling,structured and unstructured mesh technology,data analysis and visualization application,a three dimension steady state simulation code system(MSR3DS) for the can-type molten salt fast reactor is developed and validated.In order to demonstrate the ability of the code,the three dimension distributions of the velocity,the neutron flux,the delayed neutron precursor and the temperature were obtained for the simplified MOlten Salt Advanced Reactor Transmuter(MOSART) using this code.The results indicate that the MSR3DS code can provide a feasible description of multi-physical coupling phenomena in can-type molten salt fast reactor.Furthermore,the code can well predict the flow effect of fuel salt and the transport effect of the turbulent diffusion.
基金supported by the National Development and Reform Commission(NDRC) of Chinathe National Natural Science Foundation of China(No.11505280)+1 种基金the Shanghai Youth Foundation(No.14YF1407500)the National Science Foundation of China(Nos.11475251,11225527)
文摘We report the design of a wide-range energy material beamline(E-line) with multiple experimental techniques at the Shanghai Synchrotron Radiation Facility.The undulators consisted of an elliptically polarizing undulator and in-vacuum undulator that generate the soft and hard X-rays, respectively. The beamline covered a wide energy range from 130 to 18 ke V with both a high photon flux([ 10^(12) phs/s with exit silt 30 lm in soft X-ray and [ 5 9 10^(12) phs/s in hard X-ray within 0.1%BW bandwidth) and promising resolving power(maximum E/DE [ 15,000 in soft X-ray with exit silt 30 lm and [6000 in hard X-ray). Moreover, the beam spots from the soft and hard X-rays were focused to the same sample position with a high overlap ratio, so that the surfaces, interfaces, and bulk properties were characterized in situ by changing the probing depth.
基金supported by the National Natural Science Foundation of China(No.11079049)the National Natural Science Foundation for Young Scholars(No.11005141,11005144,11105171,11305242)+1 种基金the Key Program of Basic Research of Shanghai Science and Technology Commission Foundation(No.10JC1417200)the Major Project of Knowledge Innovation Programof Chinese Academy of Sciences(No.KJCX3.SYW.N3)
文摘Sulfate, nitrate and ammonium （SNA） are the dominant species in secondary inorganic aerosol, and are considered an important factor in regional haze formation. Size-fractionated aerosol particles for a whole year were collected to study the size distribution of SNA as well as their chemical species in Shanghai. SNA mainly accumulated in fine particles and the highest average ratio of SNA to particulate matter （PM） was observed to be 47% in the fine size fraction （0.49-0.95 ~tm）. Higher sulfur oxidation ratio and nitrogen oxidation ratio values were observed in PM of fine size less than 0.95 ~tm. Ion balance calculations indicated that more secondary sulfate and nitrate would be generated in PM of fine size （0.49-0.95 p.m）. Sulfur K-edge X-ray absorption near-edge structure （XANES） spectra of typical samples were analyzed. Results revealed that sulfur mainly existed as sulfate with a proportion （atomic basis） more than 73% in all size of PM and even higher at 90% in fine particles. Sulfate mainly existed as （NH4）2SO4 and gypsum in PM of Shanghai. Compared to non-haze days, a dramatic increase of （NH4）2SO4 content was found in fine particles on haze days only, which suggested the promoting impact of （NH4）2SO4 on haze formation. According to the result of air mass backward trajectory analysis, more （NH4）2SO4 would be generated during the periods of air mass stagnation. Based on XANES, analysis of sulfate species in size-fractionated aerosol particles can be an effective way to evaluate the impact of sulfate aerosols on regional haze formation.
文摘Beam lifetime is dominated by Touschek scattering at the Shanghai Synchrotron Radiation Facility(SSRF).Touschek loss rate is affected by probability for scattering beyond the RF acceptance and the volume charge density of the bench.In the phaseⅡupgrade of the SSRF,a third harmonic superconducting cavity will be used to enhance the Touschek lifetime by lengthening the bunches.The Touschek lifetime improvement factor is affected by the voltage of a harmonic cavity.To stabilize the cavity voltage,a tuning control system was designed to control it.The design of the tuning control system was based on the SSRF third-generation low-level RF control system.Some hardware and specialized algorithms were redesigned to fit the harmonic cavity control.The design of the tuning control system is complete,and the control system has been tested.The test result shows that the fluctuation of amplitude is<±0.34%within 1.5 h,which satisfies the stability requirement.
基金supported by the National Key Research and Development Program of China(No.2016YFA0401903)National Natural Science Foundation of China(No.12175293)+1 种基金the Young and Middle-Aged Leading ScientistsEngineers and Innovators through the Ten Thousand Talent Program。
文摘To achieve high-efficiency operation of the highgain free-electron laser(FEL),the electron beams and radiated photon beams need to be overlapped precisely and pass through the entire undulator section.Therefore,a high-resolution beam-position monitor(BPM)is required.A cavity BPM(CBPM)with a resonant cavity structure was developed and used in the Shanghai Soft X-ray FEL(SXFEL)test facility and can achieve a position resolution of<1μm.The construction and operation of the SXFEL user facility also bring about higher requirements for beamposition measurement.In this case,the factors that affect the performance of the CBPM system were further analyzed.These included the amplitude and phase stability of the local oscillator,stability of the trigger signal,performance of the radio frequency front-end,signal processing electronics,and signal processing algorithms.Based on the upgrade and optimization of the system,a beam test platform was built at the end of the linear acceleration section of the SXFEL,and the experimental results show that the position resolution of the system can reach 177 nm at a bunch charge of 500 pC,and the dynamic range is controlled within±300μm,and the relative measurement uncertainty of the bunch charge can reach 0.021%,which are significant improvements compared to the attributes of the previous system.
基金supported by the Youth Innovation Promotion Association of Chinese Academy of Sciences(No.20150210)
文摘The Shanghai Advanced Proton Therapy facility employs third-integer slow extraction. In order to achieve accurate treatment, high-quality spill is needed. Therefore,parameters that may affect slow extraction should be investigated by simulation. A computer model of the synchrotron operation slow extraction was constructed with MATLAB~. By simulating the motion of the circulating protons, we could quantify the influence of machine and initial beam parameters on properties of the extracted beam, such as ripple, uniformity, stability, on-and off-time of the spill and spill width in the synchrotron.Suitable design parameters including the horizontal tunes,power supply ripple, longitudinal RF cavity voltage, RFKO and the chromaticities were determined.
基金partially supported by the Major State Basic Research Development Program of China(No.2011CB808300)the National Natural Science Foundation of China(Nos.11175240,11205234 and 11322550)
文摘In this article, we present the promise of a new method generating double electron pulses in picosecondscale pulse length and tunable interpulse spacing at several picoseconds. This has witnessed an impressive potential of application in pump–probe techniques, two-color X-ray free electron laser, high-gradient witness bunch acceleration in a plasma, etc. Three-dimensional simulations are carried out to analyze the dynamic of the electron beam in a linear accelerator. Comparisons are made between the new method and existing ways.
基金supported by the National Natural Science Foundation of China(Nos.11535009 and 51406114)
文摘Axial gas-liquid separators have been adopted in fission gas removal systems for the development of thorium molten salt reactors. In our previous study, we observed an unsteady flow phenomenon in which the flow pattern is directly dependent on the backpressure in a gas-liquid separator; however, the underlying flow mechanism is still unknown. In order to move a step further in clarifying how the flow pattern evolves with a variation in backpressure, a large eddy simulation(LES) was adopted to study the flow field evolution. In the simulation, an artificial boundary was applied at the separator outlet under the assumption that the backpressure increases linearly. The numerical results indicate that the unsteady flow feature is captured by the LES approach, and the flow transition is mainly due to the axial velocity profile redistribution induced by the backpressure variation. With the increase in backpressure,the axial velocity near the downstream orifice transits from negative to positive. This change in the axial velocity sign forces the unstable spiral vortex to become a stable rectilinear vortex.
基金supported by the National Natural Science Foundation of China(No.11575282)
文摘Free electron lasers provide high-power and ultrashort pulses with extreme brightness. In order to improve a facility's capabilities and explore the possibility of performing high-resolution time-resolved experiments, a beam arrival time resolution under 100 fs is required. In this article, a novel beam arrival time monitor(BAM)equipped with two cavities has been designed and a beam flight time measurement scheme based on the BAM prototype has been proposed to estimate phase jitter in the signal measurement system. The two BAM cavities work at different frequencies and the frequency difference is designed to be 35 MHz. Therefore, a self-mixing intermediate frequency signal can be generated using the two cavities. The measured beam flight time shows a temporal deviation of 37 fs(rms).
文摘Phase space is one of the most important parameters used to describe beam properties. Computer tomography, as a method for reconstructing phase space and measuring beam emittance, has been used in many accelerators over the past few decades. In this paper, we demonstrate a transverse phase space reconstruction study in the Shanghai soft X-ray free electron laser facility. First,we discuss the basic principles of phase space reconstruction and the advantage of reconstructing beam distribution in normalized phase space. Then, the phase space reconstruction results by different computer tomography methods based on the maximum entropy(MENT) algorithm and the filtered back projection algorithm in normalized phase space are presented. The simulation results indicate that,with proper configuration of the phase advance between adjacent screens, the MENT algorithm is feasible and has good efficiency. The beam emittance and Twiss parameters are also calculated using the reconstructed phase space.
基金Supported by the Shanghai Advanced Proton Therapy project(No.Y331061061)
文摘A proton therapy system is a large medical device to treat tumors.Its gantry is of large structure and high precision.A new half-gantry was designed in the Shanghai Advanced Proton Therapy(SAPT)project.In this paper,the weight of gantry in design is reduced significantly by size and structure optimizations,to improve its cost-effectiveness,while guaranteeing the functions and precision.The processes of physics optimization,empirical design optimization,topological optimization and size optimization,together with factors of consideration,are described.The gantry weight is reduced by 30%,with the same precision.
基金supported by the ‘‘Strategic Priority Research Program’’ of the Chinese Academy of Sciences(No.XDA02010200)the Frontier Science Key Program of Chinese Academy of Sciences(No.QYZDY-SSW-JSC016)
文摘Fast reactors based on thorium fuel have enhanced inherent safety. Fluoride salt performs well as a coolant in high-temperature nuclear systems. In this paper,we present a reference core for a large fluoride-salt-cooled solid-fuel fast reactor(LSFR) using thorium–uranium fuel cycle. Neutronics physics of the LSFR reference core is investigated with 2D and 3D in-core fuel management strategy. The design parameters analyzed include the fuel volume fraction, power density level and continuous removal of fission products with 3D fuel shuffling that obtains better equilibrium core performance than 2D shuffling. A self-sustained core is achieved for all cases,and the core of 60% fuel volume fraction at 50 MW/m^3 power density is of the best breeding performance(average breeding ratio 1.134). The LSFR core based on thorium fuel is advantageous in its high discharge burn-up of 20–30% fissions per initial heavy metal atom, small reactivity swing over the whole lifetime(to simplify the reactivity control system), the negative reactivity temperature coefficient(intrinsically safe for all cases) and accepted cladding peak radiation damage. The LSFR reactor is a good alternative option for the deployment of a self-sustained thorium-based nuclear system.
基金supported by the Major State Basic Research Development Program in China(2014CB845400)the National Natural Science Foundation of China(Nos.11421505,11520101004,11322547,and 11275250)
文摘The zero degree calorimeter(ZDC) at RHICSTAR was installed in the year 2000.After running for more than 10 years,the performance of the STAR-ZDC cannot maintain a proper status because of the radiation damage.The ZDC on RHIC-BRAHMS had been moved to STAR in 2011 after some tests.We present here the result of the tests as well as the physical performance of those ZDC modules between the 2011 and 2015 RHIC runs.The excellent energy resolution of the ZDC in heavy ion collision provides a good candidate for future detector development,such as the CSR experiment at CAS-Lanzhou facility.
基金This work was supported by National Natural Science Foundation of China(No.12075304)Natural Science Foundation of Shanghai(No.22ZR1442100)National Key Research and Development Program of China(No.2022YFB3503904).
文摘X-ray photon correlation spectroscopy(XPCS)has emerged as a powerful tool for probing the nanoscale dynamics of soft condensed matter and strongly correlated materials owing to its high spatial resolution and penetration capabilities.This technique requires high brilliance and beam coherence,which are not directly available at modern synchrotron beamlines in China.To facilitate future XPCS experiments,we modified the optical setup of the newly commissioned BL10U1 USAXS beamline at the Shanghai Synchrotron Radiation Facility(SSRF).Subsequently,we performed XPCS measurements on silica suspensions in glycerol,which were opaque owing to their high concentrations.Images were collected using a high frame rate area detector.A comprehensive analysis was performed,yielding correlation functions and several key dynamic parameters.All the results were consistent with the theory of Brownian motion and demonstrated the feasibility of XPCS at SSRF.Finally,by carefully optimizing the setup and analyzing the algorithms,we achieved a time resolution of 2 ms,which enabled the characterization of millisecond dynamics in opaque systems.
文摘In this paper,we report a MATLAB-based GUI tool,bodgui,which integrates functions of lattice editor,linear match,and nonlinear optimization,and visualized tracking functions for beam optics design.A user can switch his/her design procedures one to another.Flexibilities are provided for adjusting or optimizing the lattice settings in commissioning or operation of the accelerators.The algorithm of the linear match and nonlinear optimization,and the GUI windows including the main functions and running status,are presented.The SSRF storage ring was employed as a test lattice.Several optics modes designed and optimized by the GUI tools were used for commissioning the storage ring.Functions of bodgui tool are machine-independent,and it can be well applied to modern light sources being built in other parts of the world.
文摘A front-end electronics of dose monitor has been developed for measuring irradiation dose to the patient in Shanghai Advanced Proton Therapy Facility.The parallel plate ionization chamber is used for the dose monitoring.Unlike the traditional method of recycling capacitor integration and voltage-to-frequency conversion,this dose monitor electronics uses the trans-impedance amplifier and analog-to-digital conversion method.It performs satisfactorily,with the integral nonlinearity of less than ±0.04 nA in the range of-400 to 50 nA and the resolution of about±0.6 nA.
文摘In this paper,we present the general design methods and parameter measurements of a 1-k W solidstate radio frequency(RF) power amplifier at 2856 MHz,for the soft X-ray free electron laser facility.Three-stage amplification with a 4-way combination is used.An RF switch module is integrated with the solid-state RF power amplifier to convert the continuous wave(CW) signal into pulse signal,with adjustable pulse width.The power gain is measured at 57.7 d B at 60 d Bm output.The RF phase noise,which is measured by the low-level RF system,is\0.015 degree(RMS),while the pulse frontier jitter is\5 ns.
基金Key Project for Promoting Fundamental Research in China (Grant No. 2002CB713600)
文摘By choosing parameters in the modulator, the dispersive section and the seed laser, the spatial bunching of the electron beam can be correlated to the n-th harmonic of the radiator radiation, instead of the fundamental radiation in conventional high-gain harmonic generation (HGHG). Thus, the radiator undulator is operated at high harmonic mode. In this paper, the possibility of harmonic operation of Shanghai deep ultraviolet (SDUV) free electron laser (FEL) is studied. Discussions on the principle of harmonic operation, the simulation code development, the simulation results, and the proposed experimental procedure for verification of harmonic operation at the SDUV FEL are also presented.
基金the National Natural Science Foundation of China(Nos.991129000,11374207,31370750,21273148 and 11074168)
文摘Frequency-modulation atomic force microscopy(FM-AFM) is a highly versatile tool for surface science.Besides imaging surfaces, FM-AFM is capable of measuring interactions between the AFM probe and the surface with high sensitivity, which can provide chemical information at sub-nanometer resolution. This is achieved by deconvoluting the frequency shift, which is directly measured in experiments, into the force between the probe and sample. At present, the widely used method to perform this deconvolution has been shown to be accurate under high quality(high-Q) factor vacuum conditions. However, under low quality(low-Q) factor conditions, such as in solution, it is not clear if this method is valid. A previous study apparently verified this relation for experiments in solution by comparing the force calculated by this equation with that obtained in separate experiments using the surface force apparatus(SFA). Here we show that, in solution, a more direct comparison of the force calculated by this relation with that directly measured by the cantilever deflection in AFM reveals significant differences,both qualitative and quantitative. However, we also find that there are complications that hinder this comparison.Namely, while contact with the surface is clear in the direct measurements(including the SFA data), it is less certain in the FM-AFM case. Hence, it is not clear if the two methods are measuring the same tip-sample distance regimes. Thus, our results suggest that a more thorough verification of this relation is required, as application of this formulation for experiments in solution may not be valid.
文摘Based on the service characteristics of fuel elements for molten salt reactors,they need to have a high power density,resistance to coolant infiltration,and excellent thermodynamic properties.To solve the problem of the graphite used in the fuel element for these reactors being susceptible to molten salt infiltration,carbon black(CB)was added to increase the density of the graphite,and a fuel element(TRISO(tri-structural isotropic)fuel particles were randomly distributed in the modified graphite matrix)was prepared by cold isostatic pressing process.An out-of-pile performance study shows that the densification and pore structure of the modified graphite matrix were improved,as was the resistance to molten salt infiltration.The median pore size of the modified graphite was reduced from 673 to 433 nm and the threshold pressure for molten salt(FLiBe,66%(molar fraction)LiF and 34%BeF_(2))infiltration was increased from 0.88 to 1.37 MPa.The isotropic CB made the graphite matrix less anisotropic,while its thermal conductivity and compressive strength were reduced due to the difficult graphitization of CB.Fuel elements containing 20%(volume fraction)TRISO particles were prepared.Numerical simulations show that the power and temperature distribution of the fuel were in line with the design requirements.The modified graphite matrix had a higher density,smaller pores,a lower anisotropy and a greater resistance to FLiBe infiltration.
