最新刊期
卷 0 ， 期 0 ， 2020
- 摘要：Background: Gas bremsstrahlung is one of the most important radiation sources that needs to be taken into consideration for shielding design of beamlines at the third generation synchrotron radiation light source. Shanghai Synchrotron Radiation Facility (SSRF) is one of the third generation synchrotron radiation light source in the world. The Protein Micro-crystallography Beamline (BL18U) is one of the commissioning beamlines and is a representative insertion device beamline at SSRF. Purpose: Estimation of radiation dose induced by scattering bremsstrahlung and photoneutrons at BL18U. Methods: Dose rate distribution induced by scattering bremsstrahlung and photoneutrons at BL18U are performed by Monte Carlo simulation code FLUKA. The radiation dose was analyzed with the variation of slits size, beam current at storage ring and the vacuum. Dose rate of photons and photoneutrons at the outside of the optical enclosure of BL18U were measured by using high sensitivity photon and neutron monitors. Results: The measurement results show that the reliability of the simulation. Conclusion: The simulation and measurement methods presented in this study can be applied to evaluate the dose rate level of other beamline stations at SSRF, and provide references to the shielding design for the following beamlines at SSRF in the near future. Abstract关键词：Synchrotron radiation;Beamline station;Monte Carlo method;FLUKA;Bremsstrahlung;Radiation measurement
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发布时间：2021-03-03 -
Influence of scintillator’s thickness on imaging quality of lens-coupled hard X-ray imaging detector
摘要：Background: Scintillator is an important component of synchrotron X-ray imaging detectors, which converts the incident X-rays into visible light to be imaged by visible light imaging detectors. The thickness of scintillators has a great impact on the spatial resolution and contrast of the images. When the thickness of the scintillator is matched with detector lens (NA), image quality of experimental results will be improved obviously. But in fact, users doing X-ray imaging experiments at Shanghai Synchrotron Radiation Facility (SSRF) don’t take into account this factor and it is difficult to obtain the best results with high image quality. Purpose: Matching thickness of scintillators with NA of objective can help us get good experimental results with high-quality images. Methods: We obtain the optimal thickness of scintillator for every objective lens by the way of mathematical computations of resolution theoretical curves and analysis of image contrast of experimental results. Results: Both of the results are nearly in accordance with each other. Conclusion: Users of SSRF will get better results of X-ray imaging experiment than before when they chose the optimal thickness of scintillator matched with the objective lens. Abstract关键词：X-Ray imaging detector;Scintillator;Spatial resolution;Contrast- 36
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发布时间：2021-03-03 - 摘要：Background: Multi-gap Resistive Plate Chamber (MRPC) is a kind of gas detector developed in 1995. Purpose: For its excellent time resolution and high efficiency, MRPC is used to detect thermal neutron by coating boron on the inner glass. Methods: The performances of the boron-coated MRPC thermal neutron detector are largely affected by the component or proportion of the working gas, so it is important to optimize the proportion of working gas. Then Garfield was used to simulate the gas parameter, such as Townsend coefficient ?, electron attachment coefficient ?, drift velocity v and diffusion coefficient D. Results: The time resolution ?t and detection efficiency ? of MRPC were calculated. Conclusion: Through the simulation, the proportion of working gas is optimized to provide necessary guidance for the fabrication of the detector. Abstract
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发布时间：2021-03-03 - 摘要：Background: There are several defects in traditional optical imaging such as background interference, toxic fluorescence stain, low stability etc. Similar problems can be avoided by use of Cerenkov light for optical imaging. Purpose: This work is to confirm the feasibility of Cerenkov light imaging in theory, find the shortage of Cerenkov light imaging, seek the feasible solution. Methods: Using the Monte Carlo method, (1) Simulate the condition that decay particles from three kinds of radioactive source (18F, 131I, 32P) produce Cerenkov light, analyze the relationship between thickness of the muscle and the number of Cerenkov photons; (2) Exchange the radioactive source to light source, analyze the penetration of photon in different wavelengths within Cerenkov light wavelength range. Results: The feasibility of Cerenkov light imaging is verified by using Monte Carlo method, penetrability of single Cerenkov light is poor, however, penetrability appears better of Cerenkov light in long wavelength. Conclusion: Cerenkov light imaging can be used as a novel imaging method, it has promising application. The problem of poor penetrability can be solved by giving a way to make the wavelength of Cerenkov light "red-shift". Abstract关键词：Monte Carlo method;Cerenkov light;Biological imaging
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发布时间：2021-03-03 - 摘要：Background: Traditional dual-energy X-ray inspection technology serves to classify different materials based on the proper value related with effective atomic number. Purpose: This paper aims to solve the problem of the relevance between the proper value and material’s thickness (thickness effect), which reduces the reliability of dual-energy inspection technology. Methods: A numerical method which combines Simpson formula and sequential quadratic programming (SQP) method is proposed to eliminate the thickness effect of dual-energy values. The process of X-ray inspection is simulated by Monte Carlo method based on MCNP. Probability-classification method is used to evaluate the effectiveness of diminishing error probability of material-classification, and classification boundaries of different materials. A practical X-ray inspection machine is used to verify this method. Results: The experimental results indicate that not only the thickness effect is diminished obviously by this method, but also the classification boundaries are effectively achieved. Conclusion: The dual-energy value of X-ray transmission image can be extracted by our proposed method with effectiveness and practical applicability. Abstract关键词：X-ray;Proper value;Thickness effect;Numerical method;MCNP
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发布时间：2021-03-03 - 摘要：Background: Super absorbent resin (SAR) is widely used to absorb ion solution, while its absorbency needs further improvement. Purpose: The aim is to synthesise a new salt resistance SAR by radiation crosslinking, and its performance and the post-processing are researched. Methods: A copolymer gel composed of polyvinyl alcohol, polyacrylate sodium and ethylene diamine tetraacetic acid was prepared by the electron beam radiation crosslinking. The copolymer gels were dipped into the washing liquid comprised of different proportions of methanol and deionized water for swelling and immersion. Then these gels were frozen at ?80 °C. After freeze-drying, crushing and screening, the new superabsorbent SAR was prepared. The factors may have influence on the ionic solutions absorption of the SAR which were investigated and optimized with orthogonal tests. The factors included the weight ratios of Poly vinyl alcohol (PVA) to Poly acrylate sodium (PAAS) to Ethylene diamine tetraacetic acid (EDTA) and the washing liquid. The performance of the SAR at home and abroad was tested. Results: The Suda3 SAR prepared under our optimized synthesis condition has excellent absorption rate and centrifugal liquid retaining capacity. The absorbency of the Suda3 SAR is (821.05±1.61) g?g?1 in deionized water and (72.57±3.01) g?g?1 in 0.9wt% NaCl solution respectively. These parameters are significantly better than that of the SAR of domestic and foreign famous companies (P<0.01). Conclusion: In this study, the new salt resistance SAR was prepared by radiation crosslinking and the post-processing. The SAR has excellent absorbency properties and could be used in the field of medicine and hygiene material. Abstract
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发布时间：2021-03-03 - 摘要：Background: Electron temperature is one of most important parameters in the controlled magnetic confinement fusion experiments. Purpose: We attempt to develop a set of soft X-ray energy spectrum diagnostic system for measuring the plasma soft X-ray (1?30 keV) spectra on Experimental Advanced Superconducting Tokamak (EAST). Methods: The diagnostic system is based on a 10-element Silicon Drift Detector (SDD) array and fast electronics, and basically views lower half-space of the plasma. Results: The diagnostic system can measure electron temperature under various plasma configuration conditions and the electron temperature obtained from the system is consistent with electron circle emission (ECE) and X-ray crystal spectrometer (XCS) diagnostic systems. And the system can monitor the middle and high Z impurities in the plasma as the good energy resolution of the system. Conclusion: The diagnostic system had been installed on EAST and verified its reliability and effectiveness and gained the good experimental results. Abstract
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发布时间：2021-03-03 - 摘要：Background: With the development of integrated circuits, the high-precision signal generator is always used in the process of simulation, testing, inspection and maintenance of electronic equipment in modern physics. The traditional signal generator generates signal by using oscillator, but the precision of oscillator is not high enough which becomes a bottleneck limiting the scope of application. Purpose: The aim is to address the needs of high-precision of signal generator, and design a programmable high-resolution signal generator. Methods: The direct digital frequency synthesizer technique and Sigma-Delta Digital to Analog Converter (DAC) were adopted to design this proposed high-precision signal generator. Digital chips CS5376 and CS4373 were employed together with the CompactRIO DAC to achieve the target of 110 dB signal-to-Noise Ratio (SNR) and ?110 dB Total Harmonic Distortion (THD). Programmable waveform was prepared in the mainframe using appropriate software platform such as Matlab, LabVIEW, etc. Results: After the actual measurement, the designed signal generator is proved to be with the noise ratio of SNR better than 110dB, and the total harmonic distortion THD less than ?110dB, and performs excellent in portability and stability. Conclusion: The performance of signal generator meets the need of our testing. Abstract关键词：Signal generator;Programmable;Sigma-Delta modulator;High-resolution
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发布时间：2021-03-03 - 摘要：Background: At present most radiation dose meters have the serious problem of energy response, and they just use the count rate plus relative correction method to measure the dose rate. This method has large error, and cannot distinguish the type of radionuclide, also cannot obtain the contribution of each radionuclide to the dose rate. Purpose: The research of new method is to measure the dose rate and improve the accuracy of measurement. Methods: The method of γ dose rate measurement through measuring full energy peak of γ spectrum was put forward, the angular response function of parallel γ ray injected into detector was defined. The average angular response over full space in the energy range from 0.02 MeV to 3 MeV was calculated by Monte Carlo simulation for ?50mm×50mm NaI(Tl) detector. Measurement tests have been done using standard radioactive sources of 137Cs, 60Co, 152Eu, 133Ba and in reference radioactive field of 137Cs, 60Co, 226Ra, 241Am in a national lab. Results: The test errors are smaller than 2% compared with the theoretical value for standard sources, and smaller than 3% compared with the value of PTW 10 L spherical chamber for reference radiation field. Conclusion: The results show that the method is suitable for the dose rate measurement for a wide range of energy without experimental calibration, can calculate the dose rate of different energy ray, and at the same time identify the radioactive nuclides in the radiation source. Abstract关键词：γ energy spectrum;Full energy peak;NaI(Tl) detector;Response function;Dose rate
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发布时间：2021-03-03 - 摘要：Background: Calibrating the detection efficiency accurately is the key process to the disc filter sample activity detected by High Purity Germanium (HPGe) gamma spectrometer, and the diameter of the disc filter source is varied with the specification of the sampler filter. Purpose: To study further the relation between detection efficiency and the source size, the HPGe detector peak efficiency (relative detective efficiency is 60%) was performed for disc sources with diameters of ?24mm, ?80mm and ?90mm, respectively. Methods: The efficiency and the solid angle for disc source with diameter ranging ?40–160mm were simulated using the MCNP and the Geant4. Results: The result shows that the detecting efficiency of three sources is consistent, and the efficiency gradually decreases with the increasing size of the disc source with diameter greater than ?90mm. Conclusion: The efficiency for disc sources with diameter less than ?90mm is directly calibrated by the standard point sources, while for disc sources with diameter larger than ?90mm which is needed to be calibrated by the standard disc sources. Abstract
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发布时间：2021-03-03 - 摘要：Background: Gel electrophoresis is a powerful biochemical separation technique. Most biological molecules are completely transparent in the visible region of light, so it is necessary to use staining to show the results after gel electrophoresis, and the general steps of conventional staining methods are time-consuming. Purpose: We try to develop a novel approach to simplify the gel electrophoresis: Pre-Staining Gel Electrophoresis (PSGE), which can make the gel electrophoresis results monitored in real time. Methods: Pre-stain the protein samples with Coomassie Brilliant Blue (CBB) for 30 min before loading the sample into the gel well. Results and Conclusion: PSGE can be successfully used to analyze the binding efficiency of Bovine Serum Albumin (BSA) and amphiphilic polymer via chemical coupling and physical absorption, and the double PSGE also shows a great potential in bio-analytical chemistry.Cited关键词：Gel electrophoresis;Pre-staining;Covalent coupling;Physical absorption;Protein;Amphiphilic polymer
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发布时间：2021-03-03 - 摘要：Background & Purpose: The China Spallation Neutron Source/Rapid Cycling Synchrotron (CSNS/RCS) primary collimator is to be transported from Hefei to Dongguan through truck transportation for more than 1200-km distance, and the vibration during the process is pre-studied. The brittle tungsten scraper slice is the weakest point of the machine, and it could break down due to the vibration during the transportation. Considering its cost is more than one million yuan (RMB) and manufacturing time is longer than one year, it is of extremely high necessity to evaluate the safety of its transportation process. Methods: In this paper, a virtual truck model is established using Matlab/Simulink to simulate the transit process, and an experiment that collects the vibration data of a real truck transportation process is conducted. Then the vibration excitation data is imported into ANSYS Workbench to study the stress of the scraper slice caused by vibration. Results & Conclusion: The validity of the two-degree-of-freedom truck model is verified, and a guidance of truck velocity is given. This research will benefit the safety transportation of other high energy physics machines.Cited关键词：Primary collimator;Tungsten scraper slice;Modal analysis;Ride comfort analysis;Spectral analysis;Random vibration analysis;Response spectrum analysis
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发布时间：2021-03-03 - 摘要：Background: The leak test temperature and startup and shutdown pressure-temperatue (P-T) limits for reactor pressure vessel are specified in the ASME code and in the U.S. Part 50 to Title 10 of the Code of Federal Regulations. The ASME Code Case N-629 has been integrated into the 2013 ASME code. The KIc curves indexed by RTNDT and RTT0 are both accepted by the ASME code. Purpose: The application of KIc-RTT0 curve to the determination of the P-T curve needs to be compared against the results using KIc-RTNDT and KIR-RTNDT curves. Methods: The P-T limit curves at the design life of 40 years and in the extended period are made for a home-made Reactor pressure vessel (RPV) which is taken as an example. Results: It is indicated that there exists great difference among results using the three methods. The P-T operating window based on KIc-RTT0 is widened. The brittle facture can not occur during the normal start-up and cool-down transients. The P-T limit curves from KIc-RTNDT curve are relatively conservative while the results based on KIR-RTNDT curve are too conservative. Conclusion: The analysis in this paper provides the technical support to the operation and the potentional of life extension for this RPV. Abstract关键词：Reactor pressure vessel;P-T limit curve;Master curve;ASTM E1921
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发布时间：2021-03-03 - 摘要：Background: The thermal hydraulics behavior of the Pebble Bed Advanced High Temperature Reactor (PB-AHTR) hot channel was studied. Purpose: We aim to analyze the thermal-hydraulics behavior of the PB-AHTR, such as pressure drop, temperature distribution of coolant and pebble bed as well as thermal removal capacity in the condition of loss of partial coolant. Methods: We used a modified FLUENT code which was coupled with a local non-equilibrium porous media model by introducing a User Defined Scalar (UDS) in the calculation domain of the reactor core and subjoining different resistance terms (Ergun and KTA) to calculate the temperature of coolant, solid phase of pebble bed and pebble center in the core. Results: Computational results showed that the resistance factor has great influence on pressure drop and velocity distribution, but less impact on the temperature of coolant, solid phase of pebble bed and pebble center. We also confirmed the heat removal capacity of the PB-AHTR in the condition of nominal and loss of partial coolant conditions. Conclusion: The numerical analyses results can provide a useful proposal to optimize the design of PB-AHTR. Abstract
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发布时间：2021-03-03 - 摘要：Background: As nuclear grade cable must endure harsh environment within design life, it is critical to predict cable thermal life accurately owing to thermal aging, which is one of dominant factors of aging mechanism. Purpose: Using time temperature superposition (TTS) method, the aim is to construct nuclear grade cable thermal life model, predict cable residual life and develop life model interactive interface under Matlab GUI. Methods: According to TTS, nuclear grade cable thermal life model can be constructed by shifting data groups at various temperatures to preset reference temperature with translation factor which is determined by non-linear programming optimization. Interactive interface of cable thermal life model developed under Matlab GUI consists of superposition mode and standard mode which include features such as optimization of translation factor, calculation of activation energy, construction of thermal aging curve and analysis of aging mechanism. Results: With calculation result comparison between superposition and standard method, the result with TTS has better accuracy than that with standard method. Furthermore, confidence level of nuclear grade cable thermal life with TTS is higher than that with standard method. Conclusion: The results show that TTS methodology is applicable to thermal life prediction of nuclear grade cable. Interactive Interface under Matlab GUI achieves anticipated functionalities. Abstract关键词：Nuclear grade cable;Thermal life model;Time temperature superposition;Elongation-at-break
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发布时间：2021-03-03 - 摘要：Background: Steam flow limiter is an important device of steam generator in nuclear power plant. It limits the steam flow during the event of steam line break. However, it is required that the steam flow limiter has low pressure loss during normal operation of steam generator. Purpose: The aim is to design a steam flow limiter with lower pressure loss. Methods: An improved design of steam flow limiter is developed by increasing the number of Venturies from 7 to 19. Two test models of steam flow limiters of traditional design and improved design are tested. Results: The pressure loss factor of the traditional design test model is 6.9. The pressure loss factor of the improved design test model is 4.4. Conclusion: Based on the same total throat flow area, it is verified by tests that the pressure loss of steam flow limiter containing 19 Venturis is significantly lower than that containing 7 Venturis. The pressure loss calculation method is verified simultaneously. Abstract关键词：Steam generator;Steam flow limiter;Venturi;Pressure loss
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发布时间：2021-03-03
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