最新刊期
卷 0 ， 期 0 ， 2020
- 摘要：Background: The performance of permanent magnets at cryogenic temperature can be measured by using high-precision hall sensors. Purpose: Accurate calibration of high-precision hall sensor at cryogenic temperature is of great significance for the research on magnetic properties of cryogenic magnet. Methods: In Shanghai Synchrotron Radiation Facility (SSRF), we had the hall sensor placed at the helium temperature by using a cryo cooler based on the success of hall sensor calibration at room temperature. Several electric heaters mounted at the cold head are used to precisely adjust the test temperature (from 6.5 K to 300 K) and keep the temperature constant. The sensitivity of the Hall probes was measured at temperature range from 6.5 K to 300 K over a magnetic field range of ±1.8 T. Results: It was found that the sensitivity increased as the temperature decreased from 300 K to about 150 K and became flattened below 50K. The increase was 4% or so compared with the normal temperature sensitivity. Conclusion: The calibrated probe can be used to measure the performance of permanent magnet and meet the demand of permanent magnet property under low temperature environment.Cited关键词：Shanghai Synchrotron Radiation Facility (SSRF);Cryogenic Permanent Magnet Undulators (CPMU);Hall sensor;Calibration
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发布时间：2021-03-03 - 摘要：Background: The infrared beam line consists of many kinds of optical components that are susceptible to the external mechanical vibration, which will be further amplified by the long optical paths to seriously destroy the stability of infrared beam position. Purpose: The active feedback controller is used to stabilize the infrared beam position disturbed by the external environment. Methods: The design of the active feedback controller used in the infrared beam line of SSRF was proposed in this paper firstly, which included its background, light-path layout and operating process. Subsequently, the selections of the crucial components such as detector and actuator were discussed in details. Finally, the correction compensator design and its experimental test were also presented. The correction compensator design was realized by utilizing the frequency response method, and tested in time domain, frequency domain and mathematical model simulation of the controlled object. Results: The experimental tests included time domain step response signal of the controller, the time domain signal and its relevant magnitude spectrum in frequency domain due to the light source simulation vibration. Conclusion: The results show that the maximum effective operating band is 250 Hz and the maximum steady state error is 5 um.Cited关键词：Feedback controller;Correction compensator;Step response;Magnitude spectrum
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发布时间：2021-03-03 - 摘要：Background: China Spallation Neutron Source (CSNS) is a medium-sized high-flux spallation neutron source under construction with Rapid Cycling Synchrotron (RCS) of 25 Hz as the main accelerator. The RF cavity of RCS requires that the output bandwidth of bias current source is greater than 10 kHz, while the maximum output bandwidth of switching power supply prototype is only 3 kHz, which can’t meet the design requirements. Purpose: In order to improve the output bandwidth of the entire system, the linear adjustment branch is added to the switching power supply in a formal bias current source. Methods: This paper introduced the principle of selecting the linear adjustment branch, analyzed the advantages and disadvantages of the different methods and showed the test results of output bandwidth after adding linear adjustment branch. Results: The output bandwidth of the system after adding linear adjustment branch is greater than 10 kHz. Conclusion: Linear adjustment branch can compensate for the output bandwidth of the switching power supply.Cited关键词：Switching power supply;Linear adjustment branch;Bandwidth;Testing
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发布时间：2021-03-03 - 摘要：Background: A compact cyclotron with energy of 11 MeV and current of 50 ?A is under construction in Institute of Fluid Physics of China Academy of Engineering Physics. The compact cyclotron is developed for medical isotope production. Purpose: To minimize the cost and to shorten the time of the development of the compact cyclotron, a lot of efforts were dedicated to the physics design of the compact cyclotron. Methods: Physics design of the main magnet was performed using TOSCA software, and start-to-end beam dynamics design was performed using home-made software CYCDYN. Results: Physics design of the compact cyclotron was given in details. Design methods and results of the main subsystems (including ion source, radial sector focusing magnet, RF cavity, central region and extraction system) were also given in this paper. Conclusion: Now commissioning of this cyclotron has been finished, and the goal for extracting proton beams of 11 MeV and 50 uA on average has been achieved. Physics design of the cyclotron has been validated by the commissioning results.Cited关键词：Compact cyclotron;Ion source;Magnet;Central region;Extraction system
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发布时间：2021-03-03 - 摘要：Background: The metal vapor vacuum arc (MEVVA) ion source is a common source which provides strong metal ion flow. To trigger this ion source, a high-voltage trigger pulse generator and a high-voltage isolation pulse transformer are needed, which makes the power supply system complex. Purpose: To simplify the power supply system, a trigger method with a resistor was introduced, and some characteristics of this method were studied. Methods: The ion flow provided by different main arc current was measured, as well as the trigger current. The main arc current and the ion current were recorded with different trigger resistances. Results: Experimental results showed that, within a certain range of resistances, the larger the resistance value, the more difficult it was to success fully trigger the source. Meanwhile, the main arc rising edge became slower on the increasing in the trigger time. However, the resistance value increment had hardly impact on the intensity of ion flow extracted in the end. The ion flow became stronger with the increasing main arc current. Conclusion: The power supply system of ion source is simplified by using the trigger method with a resistor. Only a suitable resistor was needed to complete the conversion process from trigger to arc initiating.Cited关键词：Vacuum arc;Ion source;Trigger;Ion current
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发布时间：2021-03-03 - 摘要：Background: The accuracy of dosimeter measurement of X and γ rays needs to be resolved. Purpose: The aim is to study the correction term of the equivalent process of low-energy X-ray and the natural radioactive source. Methods: Instead of the standard sources, X-ray machine was adopted on the dose instrument calibration. The influence factors of the equivalence between low-energy X-ray and high-energy X or γ rays were simulated using Monte Carlo (MCNP) software. Results: The influences of distance, space scattering, response of detector on dose equivalence were obtained. The simulation results were also analyzed. Conclusion: The method can be used in dose equivalent correction for low-energy X-ray, high-energy X or γ rays, which is significant for the widespread use of X rays.Cited关键词：Monte Carlo (MCNP);Equivalence;Kerma rate;Influence factor;X and γrays
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发布时间：2021-03-03 - 摘要：Background: As one of the most attractive materials for the first wall or structural materials in fusion reactors, silicon carbide (SiC) is subjected to strong heat flux, neutron radiation and the bombardment by energetic ions. However, defects in material will be induced by high temperature and high radiation. Purpose: The analysis of irradiation damage behavior in SiC is important for the development of fusion reactors. Methods: 6H-SiC were irradiated by 100-keV He+ at 600 oC in doses of 5×1015ions?cm?2, 1×1016 ions?cm?2, 3×1016 ions?cm?2 and 8×1016ions?cm?2. Multi-mode scanning probe microscopy techniques, including tapping mode atomic force microscopy (AFM), and nano-indentation/scratch and conduction mode AFM techniques were used to analyze the irradiation damage. Results: He ion irradiation with the dose of 5×1015?1×1016 ions?cm?2 leads to an obvious change of surface topography. It can be clearly seen the surface swelling of irradiated samples. The surface roughness and root mean square roughness (RMS) value increased with increasing He+ doses. However, the nano hardness and scratching resistance decreased with increasing He+ doses. The distributions and morphologies of helium bubble could be clearly observed by conduction AFM. The surface swellings of the irradiated samples were mainly produced by the internal pressure of helium bubbles. Conclusion: We have performed multi-mode scanning probe microscopy techniques for detecting the He+ irradiated SiC samples. This technique can provide a comprehensive evaluation of irradiated fusion materials.Cited关键词：Silicon carbide (SiC);Irradiation damage;Nano-indentation/scratch;Multi-mode scanning probe microscope
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发布时间：2021-03-03 - 摘要：Background: According to the requirements of GB/T 16145-1995, the sample must be of the same mass density with standard source in the measurement of radiation activity with HPGe γ-ray spectrometer, but the density of the sample is hardly consistent with the standard source in laboratory. Purpose: The aim is to study the effect of the samples in different densities on measurement results. Methods: Firstly, the net count rates (n) of the six samples in various mass densities are measured using HPGe γ-ray spectrometer, and the respective self-absorption coefficients are calculated. Secondly, the sample-model is established using sourceless efficiency calibration software-Gammaclib. And then the detection efficiency and self-absorption coefficient are obtained. Results: The detection results show that with the raise of density, the self absorption coefficients are decreased. Conclusion: The results by both methods indicate that the differences of the density between sample and standard source have obvious influences on the measurement results and need self-absorption correction.Cited关键词：HPGe γ-ray spectrometer;Self-absorption correction;Sourceless efficiency calibration method;Detecting efficiency
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发布时间：2021-03-03 - 摘要：Background: Active reflector is the one of the crucial innovations of Five-hundred-meter Aperture Spherical radio Telescope (FAST) whose performance touches on that of the overall telescope. Purpose: A real time control system is needed for the active reflector system. Experimental Physics and Industrial Control System (EPICS) is a well-used framework over the world which has good performance in real time control. Methods: Based on Input/Output Controller (IOC) frame of EPICS, a new node record was designed to simplify the node management of IOC and improve the reusability of IOC codes by making full use of the excellent real-time performance of EPICS and large number of controlled nodes (more than 2 000) on FAST reflector. Results: The record type was used in design of active reflector control system of FAST Miyun model. And the new IOC controller was experimentally tested in laboratory together with the real node’s hardware board. Conclusion: Experimental results show that this new node record can be adapted to FAST control system to enhance the convenience of code reusability.Cited
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发布时间：2021-03-03 - 摘要：Background: In gamma spectral measurement, if the sample activity or detection efficiency of the detector is low, the most often used method to reduce the statistical fluctuation of the measurement data is to increase the measurement time and the detector dimensions. Purpose: Considering the economic factors as well as the matching problem with other nuclear electronics devices, both the size of the detector and the measurement time are limited. In this case, processing gamma spectrum data by the mathematical method to reduce statistical fluctuations for fast and accurate analysis of radionuclides received widespread attention at home and abroad. Methods: The basic principles of non-parametric Bootstrap method was described and applied to laboratory gamma spectrum data processing. The gamma spectrum of 241Am, 137Cs and 60Co were measured in different time periods by NaI(Tl) detectors. Results: The non-parametric Bootstrap method was used to process the gamma spectra measured in short time and the results were compared with the gamma spectra data measured in long time under the same conditions, and the calculated spectra agreed well with the measured spectra. Conclusion: It provides a feasible technique to quickly measure gamma spectrum at low activity levels.Cited关键词：Bootstrap method;Non-parametric method;Confidence interval;Gamma spectrum
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发布时间：2021-03-03 - 摘要：Background: The solid-state Nuclear Magnetic Resonance (NMR) is an effective method for the research of cement-based materials. Now it focuses on using solid 29Si and 27Al NMR to research the hydration structure of the cement-based materials in cement chemistry. Purpose: A theoretical guidance is proposed for solid 29Si and 27Al NMR technology used in cement chemistry research. Methods: We reviewed the application of solid 29Si and 27Al NMR in the cement-based materials and analyzed the problem among the researches. Results: This paper introduced an fundamental, relevant-conditions and basic parameters of NMR, and studied the technical parameters of solid 29Si and 27Al NMR together with the relationship among the hydration structure of cement-based material. Moreover, this paper reviewed the related domestic and overseas achievements in the research of hydration structure of the cement-based materials using solid 29Si and 27Al NMR. Conclusion: There were some problems in the research on cement-based materials by technology of solid 29Si and 27Al NMR. NMR will promote the Hydration theory of cement-based material greatly.Cited关键词：29Si;27Al;Nuclear Magnetic Resonance (NMR);C-S-H
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发布时间：2021-03-03 - 摘要：Background: Qimantage is an important tectonic metallogenic belt in western part of East Kunlun Mountain. It has experienced complex geological evolution, and significant mineralization. However, because of the plateau climate and inaccessibility, fewer research works have been done on this area, especially after Indo-sinian epoch. Purpose: Our work is to research tectonic activity, thermal history and uplifting around Bayinguole river in Qimantage belt. Methods: The apatite fission-track method was applied to research the tectonic setting, simulate the thermal history and calculate the uplift size and uplift speed. Results: A series of apatite fission track ages from granitoid samples in Bayinguole area of Eastern Kunlun Mountain were obtained, ranging from 120 Ma to 47 Ma that might be divided into three groups: 120?100 Ma, 67 Ma and 54?47 Ma. These ages reflected tectonic events in this area very well. Conclusions: The 120?100 Ma and 67 Ma ages present collision-convergences of Gangdese terrane and Himalayan terrane with their north-side terranes in Early Cretaceous and Late Cretaceous respectively. The ages of 54?47 Ma reflect post-orogenic stretching events in Eocene. Three stages of thermal evolution history are revealed by apatite fission track modeling in this area. Stage one 180?140 Ma is in the bottom temperature of apatite fission track anneal zone. Stage two 140?13 Ma records slow cooling. The last stage after 13 Ma records rapid cooling with temperature dropped 50 oC. The uplifting ranges for these three stages are 1.0 km, 0.6 km and 1.4 km, respectively. The cumulative amount of uplift is about 3.0 km. The formular calculations for the 3 samples have their rock uplifts of 3623 m, 3317 m and 3769 m, respectively, averaging 3570 m, in accordance with the results based on the 3 stage thermal history.Cited关键词：Fission track dating;Tectonic activities;Uplifting;Geological thermal history;Tibet Plateau
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发布时间：2021-03-03 - 摘要：Background: Fission product gas accumulation in Tri-structural iso-tropic (TRISO) coated fuel particles can cause the failure of TRISO fuel elements. Purpose: The aim is to study the fission product gases (xenon and krypton) accumulation in UO2 and ThO2 coated particles with respect to various neutron spectra and neutron flux. Methods: Calculations were conducted using ORIGEN code with the neutron databases of THERMAL.LIB, BWRU.LIB, CANDUSEU.LIB and PWRU.LIB as input. Results: It was found that, with the same neutron spectrum, neutron flux and running time, the production of xenon is about 7 times of that of krypton in the UO2 coated particles, and about 4.5 times in the ThO2 coated particles. For the ThO2 coated particles, both xenon and krypton reach saturation earlier when the neutron spectrum are softer, and the saturation values are smaller compared with those in the harder spectrum environment. Conclusion: Taking the fission product gas accumulation as the main factor of TRISO coated particles, the calculation implies that the ThO2 coated particles can have a longer lifetime than the UO2 coated particles under the same neutron environment.Cited
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发布时间：2021-03-03 - 摘要：Background: The Daya Bay neutrino experiment is designed to measure the mixing angle ?13 using anti-neutrinos produced by the reactors of the Daya Bay Nuclear Power Plant (NPP) and the Ling Ao NPP. The distance from nuclear reactors to experiment detectors is needed. Purpose: The aim is to introduce the way of building and measuring the control network during the distance surveying. Methods: The 3D distance was obtained by GPS, total station and laser tracker, and several software and different instruments were used for the combination of data adjustment and coordinate transformation, as well as the correctness checking. Results: Through the actual measurement and data processing, the accuracy of the distance is better than the designed requirement of ±40 mm. Conclusion: The success of the Daya Bay reactor neutrino experiment demonstrates that the result of 3D distance measurement is reasonable and correct, and the survey work makes an important contribution to the Daya Bay reactor neutrino experiment.Cited关键词：Daya Bay reactor;Neutrino;Distance measurement;Precision
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发布时间：2021-03-03 - 摘要：Background: Primary water stress corrosion cracking (PWSCC) is commonly produced in the dissimilar metal welded joints for connecting the pipe-nozzles of nuclear reactor pressure vessels to the safe ends. The technology to repair and mitigate PWSCC is usually to make the weld overlay of higher corrosion resistant Alloy52M on the pipe joints. Purpose: We need to assess the integrity of the welded overlay structures, and to make Leak-before-break (LBB) analyses. The effect of the weld overlay thickness on the LBB behavior needs to be studied. Methods: Based on the three-dimensional finite element fracture mechanics analyses, the ABAQUS software was applied to construct the LBB curves and ligament instability lines of the dissimilar metal welded overlay structures. The effects of the weld overlay thickness on the LBB curves and ligament instability lines were analyzed. Results: The results show that the LBB curves and ligament instability lines with the weld overlay are located above those without the weld overlay. With increasing weld overlay thickness, the LBB curves and ligament instability lines both shift upward. Conclusion: The weld overlay can increase the LBB safe margin of the dissimilar metal welded joints. With increasing weld overlay thickness, the LBB safe margin of the joint structure can be further increased.Cited关键词：Weld overlay;Leak-before-break (LBB) curves;Ligament instability lines;Nuclear safe end;Dissimilar metal welded joint
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发布时间：2021-03-03 - 摘要：Background: Transient curves are essential for the stress analysis of related equipments in nuclear power plant (NPP). The actually operating data or the design transient data of a NPP usually consist of a large number of data points with very short time intervals. To simplify the analysis, transient curves are generally piecewise linearized in advance. Up to now, the piecewise linearization of transient curves is accomplished manually. Purpose: The aim is to develop a method for the piecewise linearization of transient curves, and to implement it by programming. Methods: First of all, the fitting line of a number of data points was obtained by the least square method. The segment of the fitting line is set while the accumulation error of linearization exceeds the preset limit with the increasing number of points. Then, the linearization of subsequent data points was begun from the last point of the preceding curve segment to get the next segment in the same way, and continue until the final data point involved. Finally, averageing of junction points is taken for the segment connection. Results: A computer program named PLTC (Piecewise Linearization for Transient Curves) was implemented and verified by the linearization of the standard sine curve and typical transient curves of a NPP. Conclusion: The method and the PLTC program can be well used to the piecewise linearization of transient curves, with improving efficiency and precision.Cited关键词：Transient curves;Piecewise linearization;Least square method;Program
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