最新刊期
卷 38 ， 期 7 ， 2015
- 摘要：Background: Indirect Charge Coupled Device (CCD) using scintillator as a convertor of X-ray is widely used in synchrotron radiation X-ray imaging system. High detection efficiency and high spatial resolution of the detector are required to take advantages of the third generation synchrotron radiation light source. It has been proved that patterning the scintillator with photonic crystal (PhC) could increase the light output of the scintillator, thus enhancing the detection efficiency of scintillator-based detector. Purpose: In order to exploit the application of PhC in scintillator-based X-ray imaging detector, it is necessary to investigate the effect of PhC on the spatial resolution of the imaging detector. Methods: Three kinds of PhC, Polystyrene (PS), Anodic Aluminum Oxide (AAO) and SiNx, were employed and superinduced on the Y3Al5O12:Ce scintillator basal. Imaging experiments with and without PhC were performed at the BL13W1 beamline of the Shanghai Synchrotron Radiation Facility (SSRF). The effect of PhC on the resolution was evaluated by comparing images of resolution bar taken by detector with and without PhC. Results: The homogeneity and the lattice type of the PhC, i.e., SiNx have great impact on the spatial resolution. Conclusion: PhC with homogeneous structure is preferred to achieve better spatial resolution. Triangular lattice PhC performs better than the square lattice one in imaging detector. Abstract关键词：Photonic crystals;Scintillator;Synchrotron radiation imaging;Detector;Spatial resolution
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发布时间：2021-03-03 - 摘要：Background: The intensive cooling method of inserting copper wire coils into the cooling fluid tube can improve the convective heat transfer coefficient of the cooling tube much, thus enhancing the cooling effect. This method has been already utilized in some synchrotron radiation facilities in the world. Purpose: The aim is to introduce such kind of intensive cooling method and provide forward-looking and useful exploration for the applications of such type of intensive cooling method. Methods: According to the related published papers, the critical structural parameters of the helical wire coils and the intensive cooling mechanism are explained, and its applications in some synchrotron radiation facilities are described. Simultaneously, the key technical problems and development trend of such type of technique are also depicted. Results: It is found that not only to enhance the cooling effect, but also to minimize the strengthening of the negative effects, such as reducing pressure loss and vibration, both are the critical issues for the development of the proposed intensive cooling method. Conclusion: This technique is expected to be used in some national synchrotron radiation facilities, especially the third generation high-energy & high-heat synchrotron radiation cooling systems. Abstract关键词：Helical wire coil;Intensive cooling;Synchrotron radiation
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发布时间：2021-03-03 - 摘要：Background: In collaboration with the National Synchrotron Radiation Laboratory, Huazhong University of Science and Technology is developing an oscillator-based THz free-electron laser (HUST THz-FEL). Purpose: In order to measure the magnetic field integrals of the undualtor accurately and quickly, a measurement system based on the stretch-wire method (SWM) was established. Methods: In the system, an eight and a half digital multimeter, Agilent 3458, was adopted to acquire the micro-volt voltage signal, and a Kohzu high precision positioning platform was employed to realize the high synchronized wire movement. The software of this system was implemented by LabVIEW programming Results: The field measurement system was tested in a prototype hybrid permanent undulator with 7 periods, which shows consistent results with the Hall probe mapping. The repeatability precision for first integral and second integral are better than 2.5?10?6 T?m and 2.5?10?6 T?m2 respectively. Conclusion: The system met the design requirements and will be applied to the compact THz FEL oscillator located in Huazhong University of Science and Technology.Cited关键词：Undulator;SWM;Magnetic field integral
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发布时间：2021-03-03 - 摘要：Background: Many issues such as beam dynamics and beam instability concerning machine performance and stability are being studied in accelerator facility. As a consequence, a Fast Beam Transverse Profile Monitor (FBPM) using visible synchrotron radiation is being developed and will be applied for the upgrade project of Hefei Light Source (HLS II). Purpose: This study aims to design a FBPM apparatus to measure beam position and size in electron storage ring. Methods: A Hamamatsu Multi-Anode Photo-Multiplier Tube (MAPMT) R5900U-00-L16 is applied to the development of FBMP. This MAPMT has a 0.8 mm?16 mm effective area per channel and 0.6 ns typical rise time which has enough spatial and temporal resolution. Logarithm processing technique with four successive channels is used to acquire beam parameters. Results: The test results show that measurement errors of focal length are within ?1 mm, bandwidth of low noise wideband amplifier is approximately 420 MHz, gain errors between all the four channels and the second channel are less than 0.2 dB, and peak signal errors among them are no more than 2%. Conclusion: The FBMP apparatus proposed in this paper meet the requirements of acquiring beam turn-by-turn transverse beam position and size with only four channels of MAPMT. Abstract关键词：FBPM;Turn-by-turn transverse size and position;MAPMT;Logarithm processing technique
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发布时间：2021-03-03 - 摘要：Background: In luminescence dating, dose rate is the irradiation dose a sample absorbed per unit time. The estimation of a dose rate affects the reliability of the burial age. Quadratic Propagation of Uncertainty (QPU) is routinely used to assess the standard error of a dose rate estimate. However, dose rate calculation involves lots of non-linear transformations between various parameters. This complicates the application of QPU method in dose rate error estimation. Purpose: In the current study, a detailed introduction to the calculation of the annual dose rate in case of coarse quartz sediments is given. A Monte Carlo technique (a “parametric bootstrap” method) is employed to simulate the propagation of uncertainty in dose rate calculation. Methods: An open source R program used for performing the simulation is developed. A practical application of this technique is illustrated using a measured data set. Results & Conclusion: The Monte Carlo method is more flexible and simple in comparison with the QPU approach in dose rate error assessment. The stochastic scheme described in this article can be applied to any field of the analytical sciences. Abstract关键词：Luminescence dating;Dose rate calculation;Error propagation;Monte Carlo technique
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发布时间：2021-03-03 - 摘要：Background: Some radiopharmaceuticals based on peptides have been applied in preclinical and clinical trials, in the meantime, a large number of peptides are to be exploited. After years of development, radiolabeling techniques of peptides have progressed to be a system method. Through these methods of radiolabeling, peptides’ physiological activities would be influenced. Purpose: In this paper, we summarized two current commonly used 18F labeling methods for preparation of radiopharmaceuticals based on peptides. Methods: By comparison of labeling conditions, radiochemistry yields, specific activity of labeling products, radiochemistry purity, stability and pharmacokinetics of final products, we evaluated advantages and disadvantages of the two methods, with the hope to provide reference data for future research of 18F-labeled peptide radiopharmaceuticals. Results: Both [18F]SFB and Al18F-NOTA could readily label RGDyk peptide with 18F, with a radiochemistry yield of about 8.5% and 15%, respectively. [18F]SFB could produce radiolabeled peptides with better specific activity, while Al18F-NOTA proved to be a more time-saving method. For stability test, more than 80% of both [18F]SFB and Al18F-NOTA could maintain intact in PBS (Phosphate Buffer Solution) or BSA (Bovine Serum Albumin) within 360 min, and about 50% radiolabeled peptides could survive in vivo. Conclusion: The in vitro and in vivo stability of [18F]-RGD obtained with both methods were excellent, and biodistribution pattern of radiolabeled products via two methods did not show obvious differences. Abstract关键词：18F;Radiolabeling of peptides;[18F]SFB;Al[18F]-NOTA
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发布时间：2021-03-03 - 摘要：Background: Nitrate natural circulation loop (NNCL) is one of experimental platform in thorium-based molten salt reactor (TMSR), which was designed to study the heat transfer behavior and corrosion behavior of direct reactor auxiliary cooling system (DRACS). Purpose: This study aims to implement a distributed control system (DCS) with functionalities of system control, online state monitor and experimental data acquisition in NNCL. Methods: An experimental physics and industrial control system (EPICS) based distributed control system was designed for this project. An optimized support module structure was designed for I/O operation with low-level PLCs to improve the performance of input/output controller (IOC) runtime database, and a PostgreSQL database was employed for data archive by RDB ChannelArchiver. A control system studio (CSS) interface and MATLAB was implemented in operator interface (OPI) computers, for visual operation and experimental data calculation. Results: Testing for online operation and history data acquisition in OPI interface proved that the control system satisfied all requirements of NNCL control and state monitor with long-term effective. Conclusion: The system could provide efficient and reliable routine for online operation and would well support advanced study of DRACS on this NNCL platform. Abstract关键词：NNCL;EPICS;On-line monitoring;DCS
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发布时间：2021-03-03 - 摘要：Background: Insulated Core Transformer (ICT) used in irradiation industry has many disadvantages on account of its low operating frequency, Planar Insulated Core Transformer (PICT) is developed for high-frequency high voltage direct current (H-V DC) generator. Purpose: This study aims to develop a novel PICT-based H-V DC for power supply less than 1 MeV, and investigate its output characteristics for the design and optimization of PICT. Methods: Preliminary test on self-designed PICT apparatus is carried out and the output characteristics under different loads are measured. Both theoretically and by Multisim PICT’s equivalent circuit and parametric model are built and the reason giving rise to voltage drop is analyzed. Emphatically, the influence of stray parameters to the output characteristics is discussed and experimental verification is also presented. Results & Conclusion: Leakage flux causes voltage drop when the load current is heavy. To eliminate the leakage flux, power coefficient must be rectified by compensation capacitor, and the relevant experimental verification shows satisfactory results. And Multisim simulation is considered to be practicable in physical design of PICT in view of good consistency with experimental result. Abstract关键词：PICT;Output characteristic;Leakage flux;Power coefficient
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发布时间：2021-03-03 - 摘要：Background: In inertial confinement fusion (ICF) experiments, the temperature and density of fusion plasma zone are extremely important parameters requiring to diagnose. Purpose: The aim is to design a circuit for diagnosing the temperature information of the plasma zone. Methods: In order to diagnose the temperature information of plasma zone, neutron time-of-flight method was adopted to measure the neutron energy spectrum, i.e., to measure the delay time between the signal of the detector and start signal. We designed a program to accurately measure the time-of-flight with constant fraction discrimination (CFD) method, and used the TDC-GP21 (Time Digital Conversion) produced by ACAM Company (Germany) to complete accurate time measurement. Results: Based on the program, the electronics time-resolution of the measurement circuit within 1 500 ns range is higher than 200 ps, and the measurement deviation is smaller than 0.06%. At the same time, the typical result of electronics time-resolution included detector time-resolution is 217.5 ps. Conclusion: The recording capability and measurement accuracy of the circuit designed can meet the needs of practical applications, which could be used in neutron diagnosing. Abstract关键词：ICF;Nuclear diagnostic;Neutron time-of-flight;TDC
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发布时间：2021-03-03 - 摘要：Background: Corrosion of the structural materials of Molten Salt Reactor (MSR) has been recognized as a challenge that prevents the MSR from long term operation. Oak Ridge National Laboratory (ORNL) has revealed that corrosion occurs predominantly through dealloying of Cr from the candidate nickel-based high temperature alloys. Therefore, a systematic study on the corrosion characteristics of candidate structural materials is needed to ensure their applications in MSR. Purpose: The present work is to evaluate the corrosion behaviors of some nickel-based alloys with different Cr content as well as to supply more corrosion data of materials in molten fluoride salts for reliable selection of structural materials. Methods: Static corrosion tests of five kinds of nickel-based high temperature alloys (Hastelloy B-2, Haynes 242, Hastelloy S, GH 3030 and Hastelloy X) were performed in purified molten FLiNaK salt at 700 °C for 400 h. The microstructural morphology and chemical composition of the samples were examined by Scanning Electron Microscope (SEM) and Electron Probe Microanalysis (EPMA). Results: Hastelloy B-2 and Haynes 242 with low Cr content exhibited better corrosion resistance, while the high Cr-content alloys, GH 3030 and Hastelloy X, exhibited severe corrosion after the corrosion tests. Conclusion: It was found that the corrosion was correlated with the original Cr-content of the alloys, and the weight-loss/area due to corrosion increased with the Cr-content of alloys. When the Cr content of alloys is higher than 20 wt.%, these alloys would suffer severe corrosion in molten fluoride salt environments. Abstract关键词：Nickel-based alloys;FLiNaK salt;Corrosion;Cr
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发布时间：2021-03-03 - 摘要：Background: As corrosion of processing equipment from the high aggressive reagent is a serious problem during the pyroprocessing, the molten salt frozen-wall is proposed as an option for protecting the metallic walls from corrosion by a layer of frozen salt. Purpose: In order to study this means of corrosion protection, the research on the formation and controlling of molten salt frozen-wall was carried out. Methods: Nitrate molten salt (melt point: 142 oC) was used as the research medium and heat transfer oil was adopted as coolant. An experimental platform for the research of molten salt frozen-wall was built, which contains an up-flow tapered test tank covered with heat exchange jacket. The frozen-wall was formed and maintained by controlling the internally heating and the cooling of outer part of the test tank. The thickness of frozen wall was directly measured by caliper and also figured out by the measured temperatures. Results: The operation temperature of molten salt ranges from 150 oC to 250 oC; the maximum flowrate of molten salt is 500 L?h?1; the operation temperature of heat transfer oil ranges from 5 oC to 120 oC; and the flowrate of oil ranges from 1.5 m3?h?1 to 15 m3?h?1. Under the expected operating conditions, a layer of frozen can be easily and predictably deposited and maintained on surfaces contacted by the salt. The molten salt frozen-wall was adherent and stable. The average formation rate ranges from 0.2 mm?min?1 to 0.5 mm?min?1. The heat flow decreases with the thickness increasing during the process of formation, at the same time temperature difference through frozen-wall layer gradually increased, and the change trends are all damped. The frozen-wall could reach static equilibrium by controlling the heat transfer rate. When frozen-wall is in a state of balance, the temperature gradient and the thickness of frozen-wall are constant; the decay heat of fission produces simulated by heating rod is equal to the heat flow through frozen-wall layer, and is also equal to the cooling power of heat transfer oil. We also simulated the real application scenarios to test the operation parameters and get some good results. Conclusion: All the research results would be helpful for the developing of fluoride molten salt frozen-wall technology. Abstract关键词：Molten salt;Reactor;Pyroprocessing;Frozen-wall;Heat transfer
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发布时间：2021-03-03 - 摘要：Background: The toroidal charge exchange recombination spectroscopy (CXRS) diagnostic was recently deployed on Experimental Advanced Superconducting Tokamak (EAST). The main purpose of this diagnostic system is the profiles of plasma temperature and velocity profiles. The system was calibrated preliminarily by using an integrating sphere lamp whose wavelength and intensity was checked precisely by the manufacturer. As the integrating sphere lamp can only be used before or after the experiment, the real time calibration for the CXRS diagnostic system becomes very important. Purpose: This study aims to use CXRS to measure impurity density, which requires the absolute intensity of the spectrum, so the system must be absolutely calibrated. Methods: The intensity of bremsstrahlung emitted from the plasma during the CXRS experiments was measured. Theoretical computations were performed using relevant parameters of EAST plasma. Results: Compared the measurement results of bremsstrahlung intensity to the theoretical calculation whose parameters were provided by other diagnostic systems, it is shown that errors were in the same order of magnitude and very common in the plasma diagnostic. Conclusion: The experimental results showed that absolute intensity calibration based on the bremsstrahlung is feasible and it gives a possible way for the real time calibration. In the future experiment, the CXRS diagnostic system will adopt this method. Abstract关键词：Plasma diagnostic;CXRS;Bremsstrahlung;Intensity calibration
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发布时间：2021-03-03 - 摘要：Background: Tungsten (W) is a promising candidate for future use in fusion reactors as plasma facing material. During operation it will be exposed to both particle irradiation and high heat flux (HHF) loads. Particle irradiation, especially helium (He), is expected to cause significant surface modifications of W, might leading to performance degradation. The effect of heat loading can accelerate such surface damage. Therefore, the performance of W under the combined action of both heat and particle fluxes has to be investigated in more detail. Purpose: The aim is to investigate the surface modifications of rolled W during exposure to combined heating and He particle flux depending on surface temperature, He flux and fluence. Methods: The He-flux/heating experiments were performed on rolled W samples using the neutral beam HHF test facility GLADIS at IPP Garching, Germany. HHF loads generated with He atoms of 2.4 MW?m?2 and 9.5 MW?m?2 were used. W samples were adiabatically loaded to peak surface temperatures of ~1000 K, ~2000 K and ~3000 K, close to melting. He fluences increased from about 1×1021m?2 to 6×1022 m?2. Results: During He-loading at a low surface temperature (~1000 K), with increasing fluence, defects appeared in grains first, and then blistering was observed on the sample surface, with many ruptured blisters to form lids and grooves. The largest blisters formed on grains with near <001> surface normal. As fluence was increased continuously, small holes were formed on the surface, and the grooves still existed. However, at intermediate surface temperature (~2000 K), with increasing fluence, the damage morphology changed from a porous structure with blisters, via a porous structure with grooves, to a small coral-like structure. At high surface temperature (~3000 K), an evolution from a porous structure to a coral-like structure with increasing fluence was observed, and the coral-like structure changed little as the increasing of fluence continuously. It is shown that the surface modification of rolled W is dependent on a competitive relationship between the formation of blisters and coral-like structures. To study the behaviour of such He damaged surfaces under fusion relevant transient heat loads, 0.9GW?m?2 Edge Localized Modes (ELMs)-like laser thermal shocks were applied. Local melting was observed on the coral-like structure after thermal shocks. Conclusion: The damage morphology of rolled W changes from blisters with a grain orientation dependence to a porous/coral-like structure with increasing temperature, because at high temperatures the Hen and HenVm (He-vacancy) clusters will be broken up and He will diffuse relatively deeply into the W bulk. This transformation of damage morphology can also be induced by the rise of He fluence. Abstract关键词：Tungsten;Helium;High heat flux;Surface modification
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发布时间：2021-03-03 - 摘要：Background: Hastelloy-N alloy is selected as the structural material for molten salt reactor (MSR), however, it is well-known that helium atoms play an important role in nickel-based materials after severe neutron irradiation, since they can drastically alter mechanical properties, potentially embrittle materials even at low concentration. Purpose: This study aims to understand the hardening of Hastelloy-N alloy material caused by helium irradiation. Methods: Samples were irradiated by helium ions of various energies and intensities at room temperature. After annealed at temperature of 773 K, 873 K and 973 K separately, and some typical samples annealed at 873 K were chosen as objects of investigation. Nano-indentation technique was used to obtain the hardness; elastic recoil detection (ERD) was used to detect the helium concentration; and positron annihilation spectroscopy (PAS) was used to investigate S parameter. The microstructure was characterized by transmission electron microscopy (TEM). Results: The hardness of the Hastelloy-N alloys irradiated by He+ increased with the dose whilst the S parameter first increased with irradiation dose, but decresed after reach certain incident depth. After annealing, both the hardness and the S parameters decreased. The TEM image showed lots of radiation-induced defects after irradiation. The small defects were annihilated and 1-nm small helium bubble was observed after annealing. Conclusion: The large radiation-induced defects were believed to be the causes of the hardening. While the recovery of hardening after 873 K annealing was ascribed to the annihilation of the small defects, the desorption of helium and the decreasing number of HenVm. Abstract关键词：Nickel-based alloy;Helium ions;Irradiation;Hardness
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发布时间：2021-03-03 - 摘要：Background: In safety analysis of pressurized water reactor (PWR), departure from nucleate boiling ratio (DNBR) is usually calculated by three codes: a system transient analysis code, a heat flux calculation code and a subchannel analysis code, or by simplified model through a partial derivative approximation of the core DNB limit lines, but either procedure has problems of cumbersome or low accuracy. Purpose: The aim of this study is to gain a simple DNBR calculation method with high accuracy. Methods: A 3-layers back propagation (BP) neural network was proposed with a training data set to quickly predict DNBR using four variables of reactor coolant system (nuclear power, core inlet temperature, mass flow rate and pressure). Results: The error of the developed BP network is very small, and has similar results compared with the subchannel code calculations in two typical events. Conclusion: The trained BP network is accurate enough to be used in predicting DNBR, even in transient conditions. Abstract关键词：DNBR;Neural network;BP algorithm;Accident analysis
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发布时间：2021-03-03
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