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Neutron imaging is a transmission imaging method, which has a wide range of applications in the fields of non-destructive testing of internal defects in materials, the distribution of light elements in samples, and the detection of radioactive samples due to the advantages of neutrons with deep penetration, ability to distinguish isotopes, and sensitivity to light elements. With the continuous development of various application fields, the requirements for the spatial resolution of neutron imaging are getting higher and higher, and improving the spatial resolution of neutron imaging and continuously approaching the micron level has become a key research direction in the field of neutron imaging. At present, the international advanced neutron imaging device has been able to complete the high-resolution neutron imaging test with spatial resolution at the micron level, and the domestic research in this field has also made some progress with the completion of the three major neutron sources, and is gradually approaching the international advanced level. The thermal neutron imaging device and the cold neutron imaging device of the China Advanced Research Reactor have been completed and put into use in recent years, and the maximum neutron flux density at the sample of the device can reach 4×109 cm−2·s−1, the optical path system has been greatly improved compared with the original neutron imaging device, and the spatial resolution of the detector has reached the sub-millimeter level, which has been widely used in aerospace, cultural relics and archaeology, hydrogen content characterization and other fields. The main factors affecting the spatial resolution of neutron imaging in neutron imaging devices are neutron sources, neutron optical path systems and neutron imaging detectors. In this study, based on the relevant test requirements in the fields of zirconium alloy hydrogen content and cultural relics production technology, the influencing factors of neutron imaging spatial resolution were studied, and a set of high-spatially resolved neutron imaging detectors based on the thermal neutron imaging device of China Advanced Research Reactor was built. At the same time, the spatial resolution of the detector was calculated theoretically, and the detector was debugged as a whole. Finally, the relevant band bundle commissioning of the detector system was completed on the thermal neutron imaging facility of China Advanced Research Reactor, and the syringe needle samples were tested. The test results show that the spatial resolution of the detector reaches 11.3 μm, and the actual available field of view size reaches 23.6 mm×28 mm, achieving a spatial resolution of 10 μm.

Neutron imaging can nondestructively detect the composition and structure of a sample, and has been used in many fields for quantitative analysis. Neutron imaging can be used to detect elements that are difficult to detect with X-rays, such as hydrogen. When neutron imaging is used for quantitative analysis of hydrogen-containing samples, the neutron beam decays because of scattering with hydrogen rather absorption. However, neutrons scattered in the direction of the neutron beam may still reach the detector, and these scattered neutrons can bring additional intensity to the sample and its edges, bring artifacts to the image, and cause serious interference to quantitative analysis. The elimination of scattering effect is one of the most important problems in the quantitative analysis of neutron imaging. Because samples with hydrogen have a larger total scattering than absorption cross section, the influence of the scattered neutrons on the transmitted image is not negligible. The results of neutron imaging quantitative analysis are also affected by the energy spectrum effect. Since the incident neutron beam is not unienergetic, the probability of interaction between the lower energy neutrons and the sample is high, resulting in the macroscopic cross section of the neutron varying with the thickness of the sample. Several existing scattering correction methods, such as increasing the distance between the sample and the detector, the point scattered functions method, using microchannel plates, and using the blackbody grids, are not applicable to all samples, or not applicable to dynamic neutron imaging, or will increase exposure time or complicate data processing. A new scattering correction method, the double-detector method was presented. The double-detector method used two detectors at two locations to image. The close detector can obtain a high-resolution image, but the image is affected by scattered neutrons. The far detector obtain images that are unaffected by scattered neutrons, but with poor resolution. The scattering neutron distribution can be obtained by processing the two images. By subtracting the scattering neutron distribution from the close image, an image with high resolution and free from scattering neutrons can be obtained to complete scattering correction. The method was used to correct the water steps sample images. And the macroscopic cross section was corrected by the energy spectrum correction factor. The results show that the thickness of the water steps in the close-position image differs greatly from the actual thickness due to the influence of scattered neutrons. And the thickness of the water steps corrected by the double-detector method is in good agreement with the actual thickness. The double-detector method is a feasible scattering correction method.

The texture of polycrystalline material is the preferred orientation distribution of its crystallites. As an intrinsic feature of metals, alloys, ceramics and polymers, texture strongly affects many properties of polycrystalline materials. It will make the material exhibit significant anisotropy in properties, consequently affecting its service performance. Therefore, texture is regarded as one of the essential parameters for describing a full microstructural characterization of polycrystalline materials. Texture determination is usually based on the pole figure measurements by X-ray, synchrotron radiation, electron back-scatter diffraction and neutron diffraction. Among these techniques, neutron diffraction offers many advantages in texture characterization due to the low absorption coefficient of neutrons. For example, it enables the use of sample environment devices to investigate texture evolution during in-situ high temperature or loading processes of materials. The first neutron texture diffractometer in China has been built at the China Advanced Research Reactor (CARR), due to strong demand for texture measurement with neutrons from the domestic user community. This instrument is mainly applied to study texture in commonly used industrial materials and engineering components. As the study of texture evolution during in-situ loading processes is extremely important for a deeper understanding of the deformation modes and performance evolution mechanisms of materials under various deformation processes and service environment. A specialized in-situ loading device was designed and developed based on the neutron texture diffractometer of CARR, capable of applying a maximum loading force of 10 kN, with a continuously adjustable loading rate ranging from 0.01 to 3 mm/min. In order to realize real-time measurement of the microstructure and bulk texture evolution in polycrystalline materials during in-situ tensile and compression processes, this loading device can be rotated around neutron texture diffractometer Euler cradle χ angle from 0° to 90° and along the tensile axis rotated from 0° to 360°. The texture evolution of hot-extruded Mg-1.2Al-0.3Ca-0.47Mn (MMK1) alloy during in-situ tensile process was studied using this device, and it was found that the intensity of the (0002) basal texture continuously increased with increasing of tensile displacement, indicating that the device’s capability to measure texture evolution of polycrystalline materials during in-situ loading processes. The design and development of this in-situ loading device at the CARR neutron texture diffractometer provide crucial technical support for investigating the relationship between microstructure and mechanical properties of polycrystalline materials, especially the laws and mechanisms of material structure evolution under external load condition.

Residual stress is a key factor that directly affects fatigue, stress corrosion, fretting wear and other performance of engineering materials and components. However, it is difficult to accurately obtain the distribution of the deep residual stress field of the components using theoretical analysis and traditional non-destructive testing methods, which greatly hinders the development of advanced components. Due to the high penetration ability of thermal neutrons, neutron diffraction is an excellent engineering tool for providing mapping of residual stresses nondestructively in bulk components. Therefore, neutron diffraction was the most suitable non-destructive technique to characterize the deep residual stresses distribution. Therefore, National Important Project on Scientific Instrument and Equipment “the Neutron Diffractometer for Residual Stress and Defect in Materials and Components” was funded to built Engineering and Scientific Stress Diffractometer at China Advanced Research Reactor (CARR), which will serve the development of national important equipments, provide testing technique for manufacturing process of large-scale component and accumulate technical data for new material design. In order to fully play the role of Engineering and Scientific Stress Diffractometer in residual stress characterization of the engineering components, the mostly used crystal planes and the required wavelength for diffraction angle of about 90° of steel, nickel, copper, aluminum and titanium were analyzed. Thus, the optimal wavelength of the diffractometer was chosen to be around 0.164 nm, which satisfies the residual stress measurement for most commonly used metal materials. With this wavelength, the error of Fe(211) diffraction peak position was used as figure of Merit for the optics optimization. Optimized optics was obtained by tuning the horizontal and vertical focusing parameters. The neutron flux at the sample position that measured at the optimized optics with wavelength of 0.164 nm is a key parameter for the intensity performance of diffractometer. The activation method is the most commonly used technique to measure the distribution of neutron flux, which has the advantages of flexibility, adaptability, wide sensitivity and small disturbance to neutron field. In this work, the neutron flux at the sample is 3.0×107 cm−2·s−1 (±4.5%) at full reactor power of 60 MW. The resolution at the diffraction angle of about 90° is 0.42% by analyzing Fe(211) diffraction peak. The position resolution of the area detector was tested using a cadmium plate with three slit with known size. The horizontal position resolution is (1.44±0.03) mm. In this work, the optical optimization and performance calibration of Engineering and Scientific Stress Diffractometer at CARR were completed, which provides an experimental foundation for the instrument operation.

The in-situ experimental study of the microstructure of materials under thermodynamic coupling under near-working conditions is very important for in-depth understanding of the evolution mechanism of material service performance. The microscopic distribution of nanostructures on the sample can be given. Based on the advantages of small-angle neutron scattering method with good statistics and large sampling volume, in-situ experiments can be carried out, based on the small-angle neutron scattering spectrometer of China Advanced Research Reactor, an in-situ experimental device with simultaneous loading of high temperature and tensile force was designed and developed, and the morphological changes of materials at the nanoscale were measured online at high temperature and high pressure. The test results of the inspection and calibration experiment show that the maximum load of the device can reach 20 kN, the maximum temperature is 800℃, and the temperature control accuracy is better than ±1℃. The device was used to carry out in-situ small-angle neutron scattering experiments on nickel-based single crystal superalloy samples, and the obvious changes in the internal nanostructure of the samples under temperature tension conditions were obtained, indicating that the device could carry out the experimental research ability of in-situ thermodynamic coupling loading small-angle neutron scattering. The device and its corresponding experimental methods can also be used for in-situ experimental research of various high-temperature structural materials such as nuclear power stainless steel to provide microstructure evolution data.

Metallic magnetic calorimetry holds significant promise in critical defense applications such as nuclear proliferation prevention, radionuclide classification, nuclear safety and anti-terrorism. Metallic magnetic calorimetry realizes energy resolution in the order of a few electron Volts by utilizing the significant contribution of heat capacity of a magnetic origin at milli-Kelvin temperatures in rare-earth doped Au films. For detecting gamma-ray photons with an energy of around 100 keV, the energy resolution is better than 0.1%, 10 times better than the high-purity germanium (HPGe) gamma spectrometer with the highest energy resolution. The metallic magnetic calorimeter can detect other radiation types than gamma rays such as alpha and beta emissions. Metallic magnetic calorimetry can also be used for precise measurement of astrophysical phenomena, cosmic rays and other high-energy physics phenomena. As an critical part of the metallic magnetic calorimeter, the pick-up coil plays a dual role in the sensor unit. It is not only responsible for converting magnetic flux changes into electrical signals, which is subsequently picked up by the SQUID chip, but also responsible for generating persistent excitation magnetic field and magnetizing the rare-earth doped sensor thin-film. The design configuration and electromagnetic parameters of pick-up coil can directly influence the energy resolution of the sensor. In the paper the influences of various parameters (e.g., number of turns of soil, duty ratio) on the electromagnetic characteristics using the finite element method was calculated. The actual pick-up coil size is in the order of micrometers. As direct measurement of such tiny devices is extremely difficult with conventional means and such measurements suffer high errors, in this paper scaled-up samples were measured, and the validity of the simulation model and parameters through comparison with measurement results was verified to provide a reliable foundation for design work of pick-up coils. The calculation results show that the influence of turn number of pick-up meander coil on inductance is more significant than other parameters such as duty ratio and loop pitch. With the increase of the duty ratio, the inductance shows a monotonic decrease trend. When the duty ratio increases from 30% to 70%, the inductance decreases by about 76.4%. On the other hand, with the increase of the turn number, the inductance shows an obvious increasing trend. When the turn number increases from 15 to 75, the inductance increases by about 253%. The simulation result also reveals the magnetic field distribution inside the metal magnetic calorimeter sensor pick-up coil, which provides critical information for the design of the sensor thin film.

Objective To analyze the clinical characteristics of patients in makeshift COVID-19 hospital and discuss how to establish and optimize the transfer system for a large number of critical cases. Methods From April 10 to May 24 of 2022, 659 patients with COVID-19 who needed to be transferred due to emergency in makeshift hospital located in National Convention and Exhibition Center were included, and their basic information, including the age, gender, underlying diseases and reasons for transfer, were analyzed. According to the key elements of the transfer process, a fast and efficient transfer system was established. Results Among the 659 transferred patients, 131 patients had respiratory system related diseases whose mean age was 58.47(95%CI: 55.62~61.33), with a male to female ratio of 1∶0.37(95/36). There were 528 patients had non-respiratory system diseases, whose mean age was 52.57(95%CI: 50.87~54.28), with a male to female ratio of 1∶1.01 (263/265). The types of diseases of the transferred patients mainly were 86 cases of endocrine diseases, 69 cases of cardiovascular system diseases, 34 cases of fever, 38 cases of nervous system diseases, 36 cases of tumor diseases, 34 cases of trauma, 32 cases of digestive system diseases and 199 cases of other diseases. Conclusion The effective treatment of patients in critical condition in makeshift hospital depends on the linkage mechanism run effectively, and the establishment of a fast, smooth, efficient and safe transport system can improve the treatment level of critical cases in large makeshift hospital.

The neutron texture diffractometer has unique advantage in the texture research for the key materials in the fields of aerospace, transportation, nuclear industry and so on. In order to improve the detection efficiency, the detection system of the neutron texture diffractometer at China Advanced Research Reactor (CARR) has been upgraded from a single 3He counter tube to a large-area two-dimensional position sensitive detector during 2020-2021. However, due to the difference of configuration and hardware design of the neutron texture diffractometer at the major neutron scattering laboratories in the world, the formats of obtained experimental data are also different, which results in the significant difference of the data analysis and processing. Therefore, the new method and software should be proposed to analyze the experimental data collected from two-dimensional position sensitive detector of neutron texture diffractometer at CARR.The results of texture measurement using neutron texture diffractometer generally were represented by pole figure. The pole figure window resolution of the texture diffractometer is an important factor affecting the results of texture measurement. Due to the diffraction signal of larger range angles along the longitudinal direction (α direction) can be detected by the two-dimensional position-sensitive detector, therefore, in order to meet the demand of texture measurement for resolution, the diffraction data should be firstly divided into several pieces in longitudinal direction to adjust the α direction resolution of the pole figure window. Then, during data preprocessing, it is key to accurately obtain the integral intensity of the diffraction peak for getting an accurate pole figure. However, the position of diffraction peaks may shift slightly due to the possible eccentricity during sample installation and uneven background of diffraction spectrum caused by noise, which result in the inaccurate fitting results. Moreover, generally the massive experimental data were collected by the two-dimensional sensitive detector during texture measurement. Thus, the parameters of background and peaks position should be strictly constricted for data corresponding to each-phi angle before fitting diffraction spectrum. The constrained parameters obtained through optimization of polynomial background function and peak shape function by fitting sum-phi data (the sum of intensity for all phi angle according to each chi angle) were used to fit each-phi data. Finally, the fitting integral intensity were converted and normalized for all each-phi data to get pole figure. Based on these design ideals, the data processing and analysis software was developed using Python language for neutron texture measurement with two-dimensional position sensitive detector. The experimental data of magnesium alloy was analyzed and processed with this software system, and the results verified the reliability of software.In a word, according to the experimental requirements of neutron texture diffractometer equipped with two-dimensional position sensitive detector at CARR, the experimental data analysis method has been established, and the data analysis and processing software has been developed. Especially, the resolution adjustment method of pole figure window along α direction has been achieved based on two-dimensional position sensitive detector. The batch processing of conversion from neutron counting to the integrated intensity of diffraction peaks is realized. In addition, the pole density normalization and the drawing of pole figures can be achieved smoothly. All of these meet the functional requirements of the upgraded neutron texture diffractometer and provide the guidance for the similar data analysis and processing.

BackgroundThe study of irradiated samples is of considerable importance. Owing to these samples being radioactive, the applicability of conventional characterization methods is limited. Because of the high sensitivity of 3He detectors to neutrons, the small-angle neutron scattering (SANS) technique is nearly unaffected by radiation such as gamma, beta rays, and sample preparation is simple.PurposeThis study aims to develop a device for SANS measurement of nanostructures in radioactive samples.MethodsThe shielding thickness of the device was optimized through Monte Carlo simulations. Experimental efficiency and safety of the device were improved by combining remote-control functionality and automated sample switching among up to 12 samples loaded simultaneously. Finally, the device was used to carry out a SANS experiment for characterizing the radioactive A508-III steel sample.ResultsThe optimized thickness of the lead shielding layer of the device is 7.5 cm, the corresponding maximum dose rate of the measurable radioactive sample is 1.4 mSv·h-1. The results of successful SANS experiment on a A508-III steel irradiation surveillance specimen indicate that low-dose, long-term irradiation has a minimal impact on the nanostructure of pressure vessel steel.ConclusionsThe device and associated technical methods can be applied for nanostructure characterization of radioactive samples.

Objective To investigate the structure characteristics, influencing factors and the correlation with clinical parameters of gastric microbiota in cirrhotic patients with portal hypertension. Methods Preoperative gastric mucosa and gastric juice samples were collected from cirrhotic patients undergoing transjugular intrahepatic portosystemic shunt (TIPS) in our hospital from November 2020 to November 2021, and relevant clinical parameters during hospitalization were also obtained. The composition and diversity of gastric microbiota in the patients were analyzed by 16S rRNA high-throughput sequencing. LEfSe analysis was used to search for different bacteria; Redundancy analysis (RDA) was performed to identify the main factors affecting the gastric microbiota community structure; and Spearman correlation analysis was adopted to explore the correlation between the abundance of gastric microflora and clinical parameters. Results Proteobacteria, Actinobacteria, Acidobacteria and Chloroflexi were enriched in gastric mucosa, while Firmicutes and Fusobacteria in gastric juice. The Chao1 index of species in gastric mucosa was significantly higher than that in gastric fluid (P < 0.01), however, the Shannon index of community between the 2 groups was not different (P>0.05). PCoA analysis showed that there was statistical difference in community composition between gastric mucosa and gastric juice (P < 0.05). Further analysis of the gastric microbiota indicated that Peptostreptococcus and Capnocytophaga were abundant in the gastric mucosa of patients with portal hypertensive gastropathy (PHG), but the α diversity and β diversity of gastric mucosal flora had no significance between PHG and non-PHG patients (P>0.05). RDA analysis suggested that portal pressure gradient (PPG) was the main factor affecting the community structure of gastric mucosa flora (r2=0.683, P < 0.001), and the abundance of Hamadaea and Eikenella were positively correlated with PPG (r=0.633, 0.618, respectively; P < 0.05). Conclusion The microflora structure between gastric mucosa and gastric juice is different in cirrhotic patients with portal hypertension, but there is no significant difference in the species diversity. The composition of gastric mucosal flora in patients with PHG has characteristic changes, and PPG plays an important role in the structure of gastric mucosa microbiota. The relatively increased abundance of Hamadaea and Eikenella in gastric mucosa may be associated with portal hypertension in cirrhosis.

The tumor microenvironment is highly immunosuppressive. The genetically modified oncolytic vaccinia virus (OVV) is a promising vector for cancer immunotherapy. The aim of the present study was to assess the antitumor effects of human interleukin-2 (hIL2)-armed OVV in vitro. The hIL2 gene was inserted into a thymidine kinase and the viral growth factor double deleted oncolytic VV (VVDD) to generate recombinant hIL2-armed OVV (rVVDD-hIL2). Viral replication capacity in A549 cells was quantified by plaque titration on CV-1 cells. Production of hIL2 in cancer cells infected by rVVDD-hIL2 was measured by enzyme-linked immunosorbent assay. Finally, 3-(4,5-dimethylthiazol-2-yl)-5-(3-arboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) assay was performed to assess the antitumor effects of rVVDD-hIL2. The results showed that rVVDD-hIL2 viral particles expressed increasing levels of hIL2 in human and murine cancer cell lines with growing multiplicities of infection (MOIs). The insertion of the hIL2 gene did not impair the replication capacity of VV, and the rVVDD-hIL2 virus killed cancer cells efficaciously. The lytic effects of the recombinant oncolytic virus on tumor cells increased with the growing MOIs. In conclusion, these findings suggest that hIL2-armed VVDD effectively infects and lyses tumor cells, with high expression of hIL2.