最新刊期
卷 39 ， 期 7 ， 2016
- 摘要：Background:Time Projection Chamber (TPC) is a kind of high resolution gas detectors developed on the basis of Multi Wire Proportional Chamber (MWPC) and Multi Wire Drift Chamber (MWDC). TPC has an excellent position resolution that can achieve high momentum resolution. Prior to the CEE (Cooler-Storage-Ring (CSR) External-target Experiment)-TPC construction at Heavy Ion Research Facility in Lanzhou (HIRFL), it is necessary to simulate and estimate the performance of this detector.Purpose:This study aims to estimate the momentum resolution of the TPCviaa simulation according to designed parameters.Methods:A series of simulation codes including Geant4, Kalman Filter and other programs were applied to the evaluation of momentum resolution for CEE-TPC using corresponding parameters. Three particles, i.e., π meson, proton and deuteron, were used for simulation study and other influence factors on momentum resolution were analyzed.Results:It is found that the typical momentum resolution of these three particles is about 5%.Conclusion:According to the simulation results, CEE-TPC can meet the requirements in the heavy ion collisions experiment at CSR to identify three typical particles, i.e., π meson, proton and deuteron. It can provide referable technical parameters for the construction of the future CEE-TPC.关键词：TPC;Momentum resolution;Monte Carlo simulation
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发布时间：2021-05-24 - 摘要：Background:Due to the existence of transient beam loading effect in cavity, the energy of the bunch head is higher than the other part in 15-MeV linear accelerator (LINAC) designed for thorium molten salt reactor (TMSR) photo-neutron source. This uneven distribution of energy leads to high energy spread, thus depresses transmission efficiency of beam.Purpose:This study aims to develop a digital feedforward compensation to reduce the influence of beam loading effect and decrease energy spread of the beam.Methods:The Field Programmable Gate Array (FPGA) programming language VHDL (Very-High-Speed Integrated Circuit Hardware Description Language) was used to design the feedforward module. This module was added to the original FPGA modules of low level radio frequency (LLRF) control system to cut down the intensity of head of radio frequency (RF) field.Results:The experimental test shows that the feedforward function of LLRF control system suppressed the energy spread to an ideal level and the transmission efficiency of the beam current had also been significantly improved.Conclusion:The digital feedforward method overcomes the deflection of traditional beam compensation method which malfunctions in the situation of big bunch and high beam current.关键词：FPGA;First in first out(FIFO);Serial conversion;Feed-forward control;Low-level radio frequency;Linac
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发布时间：2021-05-24
NUCLEAR ELECTRONICS AND INSTRUMENTATION
- 摘要：Background:The nature of confined water adlayer at nanoscale under ambient is important in biology, material science, and nanofluidics. However, observing wetting and dewetting process of water adlayer on the interface directly is still a challenge.Purpose:This paper aims to reveal the nature of confined molecularly thin water layer between a graphene layer and a mica substrate.Methods:Room temperaturein-situAtomic Force Microscope (AFM) observation method was adopted here.Results:The results showed that the measured height of the monolayer water film was about 0.37nm, in agreement with the height of a monolayer of ice. The wetting and dewetting process of water adlayers was able to be controlled by changing the ambient humidity. The molecularly thin adlayers can wet the interface through increasing the humidity; otherwise it dewets by reducing the humidity.Conclusion:The flat graphene coating offers a novel size-adjustable nano channel, which suggests a new approach for high resolution imaging of confined molecularly thin fluid films. Furthermore, these results can potentially aid in the fabrication of novel nanofluidic devices.关键词：Graphene;Confined water adlayer at nanoscale;AFM
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发布时间：2021-05-24 - 摘要：Background:The long-lived fission product151Sm plays an important role in environmental science, life science, nuclear data,etc.It is interesting to establish a high precise and sensitivity measurement method with Accelerator Mass Spectra (AMS) and develop a series of standards of151Sm.Purpose:The aim is to develop a series of laboratory reference standards for151Sm AMS measurements.Methods:The long-lived radioactive nuclide151Sm was producedvianeutron capture reaction of150Sm by the irradiation of 52.6-mg Sm2O3(with150Sm enriched to 87.34%) in the Heavy Water Research Reactor (HWRR) at China Institute of Atomic Energy (CIAE). The151Sm/150Sm ratio in the irradiated Sm2O3sample was measured with Thermal Ionization Mass Spectrometry (TIMS) at the Nuclear Power Institute of China (NPIC). This standard151Sm sample was then diluted with the enriched154Sm2O3(154Sm is enriched to 98.61%) to obtain three other standards.Results:The151Sm/150Sm ratio in the irradiated Sm2O3sample is 3.75×10-3(the relative standard deviation is 0.06%) measured with TIMS. Three standards with151Sm/154Sm ratios of (9.25±0.08)×10-7, (8.87±0.08)×10-8and (8.08±0.08)×10-9, respectively, were prepared for the calibration in AMS measurement of151Sm. The concentrations of Sm in standard solution (I) and diluent solution were measured using isotopic dilution mass spectrometry.Conclusion:The measurement method of TIMS for isotope ratio of151Sm was established. A series of standards was prepared for the calibration in AMS measurement of151Sm.关键词：AMS;151Sm;Calibration standards;Thermal ionization mass spectrometry
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发布时间：2021-05-24 - 摘要：Background:The study of the ERL-FEL (Energy recoverylinac-Free electron laser) is in progress at IHEP (Institute of High Energy Physics). It's necessary to shield the radiation of the ERL-FEL.Purpose:This thesis mainly discusses how to use FLUKA to write the source file of the ERL-FEL to optimize shielding design.Methods:The discrete sampling method was used to integrate multiple lost sources in one source file and a comparison was made between the whole source simulation results and the accumulative total of all the independent source processing results.Results:The result shows that they are exactly similar.Conclusion:The discrete sampling method based on the beam loss source is suitable for the small electron linear accelerator shielding calculation, and it's also conducive to the expansion of the user program source in different devices.关键词：FLUKA;Source file;Discrete sampling;Extensible;ERL-FEL
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发布时间：2021-05-24
NUCLEAR PHYSICS, INTERDISCIPLINARY RESEARCH
- 摘要：Background:The plight of a large number of spent fuel accumulation can be effectively alleviated by constructing spent fuel dry storage facilities. Having been widely adopted in foreign countries, spent fuel dry storage technology has not yet been studied in our country.Purpose:The aim is to study the criticality safety of spent fuel dry storage facility.Methods:The research object is HI-STORM 100 spent fuel dry storage facility internal loading AFA-3G fuel assembly in this paper. Using the MCNP (Monte Carlo N Particle Transport Code) 4C code, criticality safety was studied by changing the density of the water inside and outside of the storage facilities.Results:The results indicate thatkeffis far below 0.93 in the normal condition, which is safety. But there would be some problems if the water density is greater than 0.8 g·cm-3under accident condition. Nuclides composition based on burnup credit can be got by using ORIGEN-ARP code. And then calculation study on the critical safety of dry storage facilities in the same model was carried out.Conclusion:It is possible to provide some proposals on the research of criticality safety.关键词：Dry storage;Burnup credit;Criticality safety;Spent fuel
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发布时间：2021-05-24 - 摘要：Background:Classical fault-tree link method is usually used in event-tree analysis to convert sequence/consequence into final sequence/consequence fault-tree models, during which boundary condition and success branch treatment are set to ensure the final model satisfying certain requirement.Purpose:This study aims to solve the structure redundancy problem caused by complex boundary setting in the final fault trees.Methods:Based on structure reuse, a processing method of complex boundary condition in event-tree is proposed.Results:Processing speed of this method is significantly improved for event tree analysis under the condition that the qualitative and quantitative result is identical.Conclusion:This complex boundary condition processing method provides an efficient solution for real time risk analysis of nuclear power plant.关键词：Probabilistic safety analysis;Event-tree;Boundary condition;RiskA
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发布时间：2021-05-24 - 摘要：Background:In a liquid fuel molten salt reactor, the fuel circulates in the primary loop, and it can be reprocessed and refueled online, therefore the fuel management of liquid fuel molten salt reactor differs from conventional solid fuel nuclear reactors.Purpose:This study aims to develope a new fuel management and burnup analysis code that considers the flow effect of molten salt and the online refueling and reprocessing for a small modular molten salt fast reactor.Methods:Based on the MCNP5 and ORIGEN2.1 code, a new fuel management code is developed to suit for liquid fuel molten salt reactor. Five operation modes for both the continuous online refueling and batch online refueling are studied. Thekeffand the burnup of some important nuclides during 30-a continuous operation with batch online refueling are analyzed.Results:The simulation results show that the small modular molten salt fast reactor can be operated within a smallkefffluctuation both under the continuous refueling scheme with variable feed rating and under the constant batch refueling scheme.Conclusion:The newly developed code can be applied to the research of liquid fuel molten salt reactors. And the presented schemes provide a reference for liquid fuel molten salt reactor design and fuel management analysis.关键词：Small modular reactor;Molten salt fast reactor;Burnup analysis;Fuel management
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发布时间：2021-05-24
NUCLEAR ENERGY SCIENCE AND ENGINEERING
- 摘要：BackgroundX-ray position sensitive detector is indispensable for beamlines at synchrotron radiation facilities. Synthetic single-crystal diamond position sensitive detectors have been developed to take advantage of next-generation synchrotron sources, which are trending toward use of high-flux beams and/or beams requiring enhanced stability and precise understanding of beam position and intensity from the front end of the beamline all the way to the sample in recent years.PurposeIt is aimed to provide accurate real-time position and flux for high-flux X-ray beams. Methods: Based on the principle of potentiometers, the transmission-mode diamond X-ray position sensitive detector works as a "solid" ionization chamber. When the X-ray beam comes into the detector's sensitive region, electronic-holes occur due to the effect of ionization and the charges or the current pulses on the electrodes of the detector are given. According to the collected currents on the electrodes, the location of the incident X-ray can be determined by the ratio between the current difference of electrodes and the total current.ResultsA signal/noise ratio of (S/N)>5×103 and a position resolution of σ=(136±11) nm for the synthetic single-crystal diamond position sensitive detector with an active area of 2.5 mm×2.5 mm, respectively, have been obtained. The measurement precisions for the X-ray beam intensity and position linearity are less than 0.1%.ConclusionWe have demonstrated the feasibility of building a transmission-mode synthetic single-crystal diamond X-ray position sensitive detector, which could measure X-ray beam intensity and position in real time. Its performance was determined on the macromolecular crystallography beamline (BL17U1) at SSRF. Experimental data show that the diamond detector has good linear response and measurement precision of beam intensity within the whole active area.关键词：Transmission-mode diamond X-ray position sensitive detector;Submicron position resolution
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发布时间：2021-05-24 - 摘要：BackgroundWith the increasing number of beamlines in Shanghai Synchrotron Radiation Facility (SSRF), the amount of the parameter records of the running state grows exponentially year by year, while the data processing method implemented at the beginning of the construction of beamlines could not meet new user requirements.PurposeThis study aims to solve this problem by using MATLAB. Methods: The fault pattern recognition system with strong nonlinear mapping ability was developed by using MATLAB, and the neural network was adopted to analyze the running data, which could get the result we want and give pre-warning informationvia the connection between the MATLAB and Archive database.ResultsAnalysis result of the two temperatures record data of the monochrometer at BL13W and BL17U beamlines demonstrated the efficiency of this method.ConclusionMATLAB can be used to improve analytical ability of running data and successfully identify pre-warning for each beamline in SSRF.关键词：MATLAB;Beamline;Archive database;Data analysis
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发布时间：2021-05-24 - 摘要：BackgroundThe dynamic field integral means the integrated magnetic field along the electron's trajectory in undulator, which will cause the tune shift, dynamic aperture reduction and beam lifetime shortening, etc. The effect is inversely proportional to the square of the electron energy and the filed transverse roll-off. The field of the APPLE-Ⅱ type Elliptical Polarization Undulator (EPU) has a very fast, intrinsic, transverse roll-off, especially for the vertical polarization mode, creating significant dynamic field integral effect to the beam motion. The research on the dynamic field integral effect of APPLE-Ⅱ type EPU and the corresponding magnetic field shimming method is the hotspot in the field of international particle accelerator.PurposeThe principle of "L-Shimming" method to reduce dynamic field integral effect for APPLE-Ⅱ type EPU is stated in this paper. Methods: The optimization design of "L-Shimming" for EPU148 dynamic field integral effect has been done with "RADIA Code".ResultsThe measurement results of flipping coil indicate that the magnetic field strength measured is coincident with the simulation result, and the error is less than 10% of the maximum shimming quantity. After shimming, the dynamic field integral effect of EPU148 will reduce an order of magnitude. The machine study has been done after EPU148 is installed in SSRF storage ring with the tune shift less than 0.001, and the beam injection efficiency has almost not been influenced with EPU148 in all operation polarization modes and all operation gaps.ConclusionIt is proved that the shimming to reduce EPU148 dynamic field integral effect is successful.关键词：Field shimming;Dynamic field integral;Undulator
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发布时间：2021-05-24 - 摘要：BackgroundHigh quality electronic beam is the key to produce high quality synchrotron radiation or free-electron laser (FEL). Microwave electronic LINAC plays the role of injector, whose performance influences the quality of electronic beam deeply.PurposeIn order to minimize the noise interference (temperature, microphonics, etc), we develop a universal, robust, efficient and extendible Low Level Radio Frequency (LLRF) control system, in which automatic frequency control (AFC) function is already implanted and more functions will be embedded in the future. Methods: This system, based on MicroTCA, adopts Experimental Physics and Industrial Control System (EPICS) structures, and develops in C/C++. The core algorithms are Proportion-Integral-Differential (PID) and Least-Squares method.ResultsTwo different ways of AFC were realized and the system was tested on Sirius-LINAC test facility.ConclusionThe result shows that the cavity is well tuned when the AFC system is on, and obvious differences are found. This system will be optimized and enlarged in the future.关键词：Microwave electronic LINAC;MicroTCA;EPICS;AFC;Least-Squares method;PID
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发布时间：2021-05-24
SYNCHROTRON RADIATION TECHNOLOGY AND APPLICATIONS
- 摘要：BackgroundIn the high voltage accelerating tube, the electronic load effect tends to cause a large amount of electrons flow in the tube, making it difficult to continuously increase the voltage, and thus needs to be avoided. Electronic load effect is related to the multiplication of the stray particles in the accelerating tube.PurposeThis study aims to propose a method to suppress the electronic load effect. Methods: The lens electric field is adopted to eliminate the spray particles. The formation of the lens electric field is built through the unequal gradient potential.ResultsThe lens electric field has no effect on the main beam on the central axis, but the stray particles that are far away from the central axis are dissipated. It effectively prevents the long distance movement of these stray particles, and weakens the doubling capacity of the stray particles.ConclusionThe lens electric field has an inhibitory effect on the electric load effect for the high voltage accelerating tube.关键词：Accelerating tube;Electronic load effect;Unequal gradient;Suppression;Lens field
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发布时间：2021-05-24 - 摘要：BackgroundFilters are important parts of α radioactive aerosol measurement system. The characters of different filters causing energy peak tailing will interfere the result of artificial radioactive aerosol measurement, or might even make results failure.PurposeThe work aims to test peak tailing of different filters in measuring α radioactive aerosol energy spectrum. Methods: The research collects α radioactive aerosol on different filters by aerosol sampling device and uses α spectrometer to measure peak tailing of 214Po (7.68 MeV).ResultsThe results show that the peak tailing is minimized when hybrid filters with pore size of 0.45 μm was adopted. When high-flow system is applied, the filters' pore size are expected to be reduced to 0.3 μm. Hybrid fibers are better than PTFE (Polytetrafluoroethylene) and PES (Polyethersulfone) filters in reducing peak tailing with the same pore size (0.45μm).ConclusionThe research provides important basis on how to select filters to reduce peak tailing in measuring α radioactive aerosol energy spectrum.关键词：Radioactive aerosol;Filter membrane;Peak tailing;α energy spectrum
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发布时间：2021-05-24 - 摘要：BackgroundNowadays, digital radiography is widely utilized in non-destructive testing. However, some issues concerning this new technique need to be addressed properly, and some key parameters of the imaging system need to be quantified by some measurement methods.PurposeTo evaluate a digital radiography system using linear detector array quantitatively and efficiently, and optimize the testing parameters accordingly, modulation transfer function (MTF) of the imaging system was calculated and analyzed. Methods: Edge tool, duplex wire image quality indicator (IQI) and resolution test card were used to measure MTF of the system under different testing parameters, which include focus size, magnification and object orientation.ResultsResults show that the contrast transfer function (CTF) measured by duplex IQI and resolution test card is almost identical, while signals from duplex IQI are easier to analyze quantitatively. CTF from duplex IQI is approximately a curve of second order, and the CTF can be used to transform to MTF, but the values are higher than that from edge tool, as movement during image acquisition process is unstable.ConclusionAfter analysis, we find that the system performance is affected by many factors together, but MTF can be used to evaluate these factors perfectly, thus to find out equivalent parameters combination or determine the optimum testing parameters.关键词：Digital radiography;Linear detector array;MTF;Edge tool;Diplex wire IQI;Resolution test card
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发布时间：2021-05-24 - 摘要：BackgroundMonte Carlo (MC) simulation method is often used to estimate various parameters for analyzing gamma-ray spectrum, but the deep penetration constrains its application in airborne detection.PurposeThis study aims to find a solution for the deep penetration problem in MC simulation of airborne gamma-ray spectrum. Methods: When many of same-sized airborne gamma-ray spectrometry (AGS) are placed in the same height and the distances between the center of each AGS and the boundary of stratum are greater than the detectable radius, the response laws of these AGSs are the same under infinite source particles. Based on the principle, a spherical shell model of MC simulation for an airborne gamma-ray spectrum is proposed to solve the above problem.ResultsAirborne gamma-ray spectrums of four calibration models are simulated by this spherical shell model on the MCNP (Monte Carlo N Particle) platform, which are in agreement with their respective observational average spectrums. Moreover, the estimated calibration factors of four radionuclides at 100-m altitude in the Vesivehmaa region of Finland are calculated by this method, which show an agreement within 20% error in comparison with the sampling methodology and simulation values of Allyson et al. ConclusionThe results verify that the spherical shell model has high simulation efficiency and can provide reliable parameters for inversing stratum information by airborne gamma-ray spectrum.关键词：Airborne gamma-ray spectrum;MC simulation;Spherical shell model
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发布时间：2021-05-24
LOW ENERGY ACCELERATOR, RAY AND APPLICATIONS
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