最新刊期
卷 38 ， 期 8 ， 2015
- 摘要：Background: The metal wire used in pulsed taut-wire technique would sag for gravity, so the wire may not just at the geometrical axis of the solenoid, this would result in error. Purpose: This paper studies the wire sag and finds some methods to minimize this error. Methods: From theoretical analysis, we find an expression (Catenary) to describe the wire sag, and this has been verified by experiment. Based on the catenary and wave equation, a taut wire vibration model is established and wire’s vibration waveform is calculated. Results: The waveform shows that wire sag may lead to ?0.964 mm offset and ?0.162 mrad tilt measurement error. Conclusion: There are three ways which can reduce this error, i.e. (1) numerical correction, (2) the increasing of the tension on the wire, and (3) the building of a vertical experiment roof. Abstract关键词：Pulsed-taut wire;Solenoid coil;Wire sag;Catenary;Magnet axis measurement
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发布时间：2021-03-03 - 摘要：Background: Detail sensitivity is an important technical indicator in the fast neutron radiography. Purpose: The spatial resolution and contrast sensitivity have important effects on the fast neutron radiography. Methods: Using the control variable methods, we process the different depth and diameter aperture samples of the polyethylene and Pb. Results: Many fast photographic images are obtained under different conditions. Conclusion: Through digital image processing, the preliminary relationship between the detail sensitivity with spatial resolution and contrast sensitivity were given. When the diameter is small, spatial resolution plays an important role in the detail sensitivity; however, contrast sensitivity plays an important part when the diameter is bigger. At last, a preliminary reference conclusion about detail sensitivity is given. Abstract关键词：Fast neutron radiography;Detail sensitivity;Spatial resolution;Contrast sensitivity;Image processing
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发布时间：2021-03-03 - 摘要：Background: A good knowledge of gas gain properties is of importance for the development and operation of proportional counters. Spherical tissue equivalent proportional counters (TEPC) have been widely used in the protection dosimetry applications, thus it is necessary to investigate the gas gain characterization in TEPC detectors. Because of the extremely low pressure, gas gain in the TEPC is significantly influenced by the gradient of the electric field around the anode wire. Gradient-field model was proved to be accurate enough to predict the gas gain in the TEPC. However, the formula based on the gradient-field model comprises three gas dependent constants which make it impractical for TEPC design and applications. Purpose: This work aims to develop a technical routine for the simulation of the TEPC gas gain and implement validations of the simulated results. Methods: In this work, a Benjamin type TEPC was firstly developed, then ANSYS was employed to solve the electric field strength in the detector. Garfield was used to simulate the gas gain properties in the Benjamin type TEPC with different bias voltage. At last, an internal 241Am α source was adopted to measure the absolute gas amplification factor in the TEPC. Results: It is found that, Benjamin type TEPC has a uniform electric field intensity distribution along the anode wire, which could be employed in TEPC design. Garfield simulated results agreed well with the experimental values. The deviation between the measured and simulated values increases with the applied bias of the detector. Conclusion: Given the fact that the TEPC was usually operated with gas gain to be about 40, the Garfield simulation method could be used as reference in the TEPC development and operation. Abstract关键词：Spherical TEPC;Benjamin structure;ANSYS;Garfield;Absolute gas gain
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发布时间：2021-03-03 - 摘要：Background: The Peking University Neutron Imaging Facility (PKUNIFTY) was developed by using neutron sources generated by Radio Frequency Quadrupole (RFQ) accelerators. Purpose: This study aims to design a low level control system that meet the requirement of stable operation of the RFQ accelerator. Methods: Both the automatic gain control (AGC) and automatic frequency control (AFC) were designed to control the cavity frequency. The power fed into cavity by automatic and manual ways. In order to make it safe and stable, the standing wave ratio (SWR) and limit signal were constantly monitored. The human machine interface (HMI) was implemented in the remote computer using LabVIEW, it communicates with both the control system’ microcontroller unit (MCU) and the Programmable Logic Controller (PLC) via RS232 interface. Results: The control precision of the accelerating field is ±1% in amplitude and ±1° in phase in a 48-h closed loop test. Conclusion: Test results show that the low level control system meet the requirements for stable control of the power and cavity frequency of RFQ accelerator. Abstract关键词：RFQ accelerator;Low level control system
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发布时间：2021-03-03 - 摘要：Background: Zinc oxide has an extensive applied prospect on photoelectric devices, like light-emitting diodes and solar cells, due to its 3.37 eV optical band gap and 60 meV excition binding energy. Recently, doping ZnO with metal elements has become a popular research topic because of the dramatic improvement on photoelectricity, piezoelectric property and conductivity. Comparing with other elements, Ag is appropriate to act as acceptor dopant element because it has a shallow acceptor level in ZnO. Therefore, many coupling systems of ZnO-Ag nanostructures have been researched. Purpose: Various methods of incorporating Ag and ZnO have been researched but it is hard to control the uniformity of doped Ag in ZnO. The quality of ZnO thin films is also one of the key factors affecting the property of samples. This paper mainly focused on how to prepare high-quality ZnO thin films by magnetron sputtering technique and how to improve the photoluminescence property of ZnO via controlling the uniformity of Ag dopant. Methods: High-quality ZnO thin films were deposited on Al2O3 substrates by magnetron sputtering technique with combination of subsequent thermal annealing. The films were then implanted with Ag ions at different energies and ?uences. We discussed the structural and photoluminescence properties of implanted ZnO thin film by means of grazing incidence X-ray diffraction (GIXRD), photoluminescence (PL), UV-vis and scanning electron microscope (SEM). Results: The PL of prepared samples showed that two bands at 380 nm and 610 nm were observed for pure ZnO films and two new peaks at 400 nm and 430 nm appeared for the implanted ZnO. Ag ion implantation strongly enhanced the excition peak of ZnO and quenched the PL peak from oxygen defect of ZnO. However, the PL bands of implanted ZnO films at 400 nm and 430 nm have been quenched after thermal annealing at nitrogen atmosphere. Conclusion: In summary, Ag nanoparticles were formed in ZnO thin films after Ag ion implantation. Thus the surface plasma resonance absorption peak from Ag nanoparticles was observed. Furthermore, the formed Ag nanoparticles quenched the oxygen defect and enhanced the excition peak of ZnO. The existence of AgZn and Agi energy levels and synthesis of Ag nanoparticles made a great improvement on the PL property of ZnO. Abstract关键词：ZnO thin film;Ag nano-particles;Ion implantation;Defect;Photoluminescence
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发布时间：2021-03-03 - 摘要：Background: Networking technique is more and more widely integrated into digital instruments that connected with distributed digital control system (DCS). Purpose: This study aims to achieve direct network connection of a digital ultrasonic flowmeter to Experimental Physics and Industrial Control System (EPICS). An Ethernet interface for the TMS320F28335-based ultrasonic flowmeter was designed and implemented to realize real-time network communication with EPICS. Methods: The Ethernet chip, DM9000 was employed and extended to the ultrasonic flowmeter platform which was controlled by TMS320F28335. EPICS was configured to client/server architecture where the digital ultrasonic flowmeter was working as client and the uIP TCP/IP stack was integrated for data communication with the Input/Output Controller (IOC) server. The measured real-time flow rate data was dynamically displayed on the Operator Interface (OPI) console by EPICS Camonitor and Control System Studio. Results: Self-checking results showed reliable TCP communication between client and server was performed on the calibration platform. It was further verified by actual measurements on the flow calibration platform that the digital ultrasonic flowmeter realized real-time and reliable communication, which made the ultrasonic flowmeter equipped with networking functionality. Conclusion: This article presents a new digital communication method between the digital ultrasonic flowmeter and EPICS. It accelerates the digital and networking process of the measuring instrument in nuclear reactor. Abstract关键词：DCS;Ethernet interface;TMS320F28335;Ultrasonic flowmeter;DM9000
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发布时间：2021-03-03 - 摘要：Background: The activated carbon sorption is often used to reduce the concentration of the exhaust gas. But the ability of sorption is limited. If the concentration is high, the radioactive pollution may take place at the surroundings of radon chamber. In addition, natural decay of radon takes a long time because of the long half-life of radon. Purpose: The aim is to solve the problem of radioactive pollution and reduce the radon concentration in the radon chamber in a short time. Methods: The aim is to put forward a disposal system to bring the exhaust gas to storage chamber and keep the exhaust gas in the storage chamber for some time then let out. Results: By this way, the radon concentration of radon chamber can be reduced in a short time and the radioactive pollution can be solved. Conclusion: The disposal system can achieve the expected goals. Abstract关键词：Radon chamber exhaust gas;Exhaust gas emission;Exhaust gas pollution;Operation in safety
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发布时间：2021-03-03 - 摘要：Background: Plastic scintillator detector array (PSD), developed by Institute of Modern Physics, Chinese Academy of Sciences (IMPCAS), is one of the most important parts in the payload of Dark Matter Particles Explorer (DAMPE) which is mainly used for the study of dark matter. As an anti-coincidence detector, and a charged-particle identification detector, the PSD is composed by 82 plastic scintillator counters. Purpose: Due to the difference among a batch of scintillator counters, it is necessary to develop a test bench with high test efficiency and also to obtain their performance, such as uniformity of light output, light attenuation length, peak of Minimum Ionizing Particle (MIPs) and detection efficiency simultaneously. Methods: A high-efficiency test bench, including electronic modules, data acquisition, analysis system, etc, has been constructed to study the characteristics of 24 scintillator counters with cosmic rays. Individual trigger module with dimensions of 34 cm×2 cm×1 cm has been set up at different points of ±34 cm, ±17 cm and 0 cm. With this test bench, the light attenuation length and other main parameters of 20 counters have been investigated. Results and Conclusion: Through the high-efficiency test bench, data of 20 scintillator counters could be obtained simultaneously. After analysis of 185 counters’ data, we can select 82 counters which fulfill all technology parameters provided by DAMPE and use in PSD. Abstract关键词：Plastic scintillator counter;Attenuation length;Relative light yield;Detection efficiency
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发布时间：2021-03-03 - 摘要：Background: The aggregation of amyloid proteins leads to some serious diseases, such as Alzheimer’s disease, Parkinson’s disease; silicone oil is identified as biosafety material, and is widely used in industry and daily life, even implantation in vivo. Purpose: The aim is to study the influence of silicone oil on the aggregation of amyloid proteins and peptides. Methods: We measured the fluorescence of thioflavin T(ThT) in the samples and image the aggregated fibers by atomic force microscope (AFM). Results: Five kinds of amyloid proteins/peptides aggregated faster and more sufficiently in the samples containing silicone oil, and the fibers are longer and denser in silicone oil sample. Conclusion: A certain amount of silicone oil can promote the aggregation of these amyloid proteins and peptides. Abstract关键词：Silicone oil;Amyloid protein;Vibration;Aggregation
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发布时间：2021-03-03 - 摘要：Background: The D-T controllable neutron source is used to replace the chemical gamma source to measure the formation density in oil exploration. Purpose: The paper aims to study the effect of pair production on density measurement accuracy using the D-T neutron induced gamma ray. Methods: Firstly, the theory of traditional chemical source density logging method is analyzed, and the difference of the mass attenuation coefficient between Compton scattering and pair production is compared. In addition, the measurement accuracies of both traditional density log and neutron induced gamma density log are studied using Monte Carlo simulation method. And then the source of error and its correction are analyzed. Results & Conclusion: The measurement accuracy of neutron induced gamma density is worse than the traditional density log, the reason is that the contribution of gamma comes from not only the Campton scattering, which is employed in traditional density log, but also pair production. Moreover, the pair production of gamma ray is sensitive to the formation lithology, and the measurement accuracy could be increased if the lithology correction was added. Abstract关键词：Density log;Induced gamma ray source;Deuterium-Tritium controllable neutron source;Compton scattering;Pair production
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发布时间：2021-03-03 - 摘要：Background: Shanghai Advanced Proton Therapy (SAPT) is the first domestic proton therapy system independently developed by Shanghai Institute of Applied Physics, the gantry is the key component of SAPT. Purpose: This study aims to understand the vibration response caused by the drive motor of the gantry that affects the treatment accuracy. Methods: The drive motor harmonic analysis is conducted by ANSYS-harmonic module with the motor parameters provided by SAPT’s design company, Siemens. Data were collected by POST26 and analyzed by ORIGIN. Results: Max harmonic response amplitude (4.6×10?6 m) and corresponding motor frequency (44 Hz) of the isocenter were given on two typical positions of the gantry. Conclusion: The max amplitude is much less than the design specification (0.05 mm), and it will be tested in commissioning stage. Once verified, it will provide the reference data in maintaining stage. Abstract关键词：Proton therapy;Gantry;Isocenter;Harmonic response analysis
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发布时间：2021-03-03 - 摘要：Background: The application of gamma ray spectroscopy on the classification for the sedimentary rocks is helpful to solve the problem of small classification and the long cycle for chemical analysis of the sedimentary rocks. Purpose: This study aims to introduce a method of determining the content of natural radionuclides K, U, Th in the well drilling debris with the low background gamma ray spectroscopy for dipartition among dark gray ash mudstone, dark grey calcareous mudstone and grey calcareous mudstone. Methods: Count rates of K, U, Th in the energy ranges of 1.37–1.56 MeV, 1.66–1.86 MeV and 2.41–2.81 MeV were selected to represent the intensity of radioactivity of K, U, Th. The fisher discriminant criterion was applied to measured count rates of various samples for classification of sedimentary rocks using the Statistical Product and Service Solutions (SPSS) software. Results: According to the count rate of K, U, Th and total count rate of the three mudstones carry out the discriminant analysis of rock lithology by using SPSS software, the accuracy rate reached 100%, 76.47% and 60%, respectively. Conclusion: Gamma ray spectrometry method is of great significance for the division of sedimentary rocks in small class. It could be used to completely identify the dark gray mudstone and the identification effect for dark grey calcareous mudstone, and grey calcareous mudstone is good, but not distinguish them completely. Abstract关键词：Gamma ray spectrometer;Analysis of cores;Discriminant analysis
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发布时间：2021-03-03 - 摘要：Background: The Fluoride-salt-cooled high-temperature reactor (FHR) is a thermal reactor using molten salt (2LiF-BeF2, FLiBe) as coolant and TRISO (Tri-structural Isotropic) as fuel and graphite as moderator. Isotopes, such as 6Li, 7Li, 9Be and 19F in the FLiBe coolant, generate tritium under the neutron irradiation. Tritium can easily permeate through metal at high temperature and may be a radiation source to the workers and public. Tritium can also react with F and create TF, which is highly corrosive and may cause damage to the structural materials. Purpose: We used different versions of SCALE to calculate the tritium production of a typical FHR and analyzed the difference among the computational results. Methods: We have created 3D models using the same FHR design parameters in SCALE. Results: The results show that in the calculation of tritium production from lithium, the TRITON (Transport Rigor Implemented with Time-dependent Operation for Neutronic depletion) module of SCALE6 handles the lithium element incorrectly and introduces significant differences compared with the previous versions of SCALE. When we calculate the tritium production from 9Be and 19F, different versions of SCALE give different results because the reactions are defined differently. Conclusion: Our analyses show that when SCALE is used to calculate the tritium production of the FHR, SCALE6 is the preferred version. However, the temporary file, ft33f001, created by TRITON as the cross section library, and ORIGEN-S can be used to calculate the tritium production in order to correct the mishandling of lithium element in SCALE6. Abstract关键词：FHR;FLiBe;Tritium;SCALE;TRITON
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发布时间：2021-03-03 - 摘要：Background: The partitioning and transmutation (P&T) is considered as a feasible method to deal with nuclear waste. Lead-bismuth reactor is one of the most promising nuclear energy systems for Accelerator Driven System (ADS) and Generation-IV reactors. Transmutation fuel is concerned by both P&T and ADS system. Purpose: The aim is to select a suitable transmutation fuel for the lead-bismuth reactor. Methods: In this work, we analyzed characteristics of lead-bismuth reactor and ADS system, and summarized main features of transmutation fuels and design schemes of lead-bismuth reactors. Results: Most lead-bismuth reactors select nitride fuel, and features of nitride fuel are much more suitable than other fuels for the lead-bismuth system. Conclusion: Nitride fuel is currently the optimum selection of transmutation fuel in the lead-bismuth cooled reactor. Irradiation and transmutation experiments for nitride fuel in the Chinese Academy of Sciences ADS system are expected.Cited关键词：Lead-bismuth cooled reactor;Transmutation;Fuel;Minor actinides;Nitride fuel
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发布时间：2021-03-03 - 摘要：Background: Traveling wave reactor is a new-type advanced nuclear reactor utilizing depleted uranium or natural uranium as the fuel. However, there are few researches on the small traveling wave reactor with radial shuffling. Purpose: This study aims to design a small traveling wave reactor core and the corresponding radial shuffling schemeto achieve a long service life of 30 a at least and deep burnup of assemblies. Methods: A coupled code of MCNP code and ORIGEN2 was utilized as the means of core design. A conceptual core design of small traveling wave reactor was studied with emphasis on the influence factors of enrichment and distribution of fuel assemblies to the physical parameters of reactor, based on the China Experimental Fast Reactor (CEFR). Results: Study on the enrichment of burning assemblies shows that the small reactor needs appropriately enrichment. It cannot be critical if enrichment is too low and the breeding of the core decreases if it is too high. Compared the low leakage with the board type layout, it reveals that both of the power distribution are similar while the breeding assemblies in the latter own better breeding characteristic. Finally, the reactivity of the designed core varies slightly in the whole life and the discharge burnups of different fuel assemblies are relatively close to each other and the average burnup is about 238 MWD/kgHM. Conclusion: A small traveling wave reactor core with 30-a life is designed. The shuffling schemes with 8 a makes the discharge burnup of assemblies uniform and deep relatively. Abstract关键词：Traveling wave reactor;MCNP;ORIGEN2;Coupling;Core design;Small reactor
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发布时间：2021-03-03
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