Efficiency calculation of the ⁿMCP with ¹⁰B doping based on mathematical models

Yang, Jianqing,Zhou, Jianrong,Zhang, Lianjun,Tan, Jinhao,Jiang, Xingfen,Zhou, Jianjin,Zhou, Xiaojuan,Hou, Linjun,Song, Yushou,Sun, XinLi,Zhang, Quanhu,Sun, Zhijia,Chen, Yuanbo Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.7

The ⁿMCP (Neutron sensitive microchannel plate) combined with advanced readout electronics is widely used in energy selective neutron imaging because of its good spatial and timing resolution. Neutron detection efficiency is a crucial parameter for the ⁿMCP. In this paper, a mathematical model based on the oblique cylindrical channel and elliptical pore was established to calculate the neutron absorption probability, the escape probability of charged particles and overall detection efficiency of ⁿMCP and analyze the effects of neutron incident position, pore diameter, wall thickness and bias angle. It was shown that when the doping concentration of the ⁿMCP was 10 mol%, the thickness of ⁿMCP was 0.6 mm, the detection efficiency could reach maximum value, about 24% for thermal neutrons if the pore diameter was 6 ㎛, the wall thickness was 2 ㎛ and the bias angle was 3 or 6°. The calculated results are of great significance for evaluating the detection efficiency of the ⁿMCP. In a subsequent companion paper, the mathematical model would be extended to the case of the spatial resolution and detection efficiency optimization of the coating ⁿMCP.

Optimization study of a clustering algorithm for cosmic-ray muon scattering tomography used in fast inspection

Hou, Linjun,Huo, Yonggang,Zuo, Wenming,Yao, Qingxu,Yang, Jianqing,Zhang, Quanhu Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.1

Cosmic-ray muon scattering tomography (MST) technology is a new radiation imaging technology with unique advantages. As the performance of its image reconstruction algorithm has a crucial influence on the imaging quality, researches on this algorithm are of great significance to the development and application of this technology. In this paper, a fast inspection algorithm based on clustering analysis for the identification of the existence of nuclear materials is studied and optimized. Firstly, the principles of MST technology and a binned clustering algorithm were introduced, and then several simulation experiments were carried out using Geant4 toolkit to test the effects of exposure time, algorithm parameter, the size and structure of object on the performance of the algorithm. Based on these, we proposed two optimization methods for the clustering algorithm: the optimization of vertical distance coefficient and the displacement of sub-volumes. Finally, several sets of experiments were designed to validate the optimization effect, and the results showed that these two optimization methods could significantly enhance the distinguishing ability of the algorithm for different materials, help to obtain more details in practical applications, and was therefore of great importance to the development and application of the MST technology.

A novel reconstruction algorithm based on density clustering for cosmic-ray muon scattering inspection

Hou, Linjun,Zhang, Quanhu,Yang, Jianqing,Cai, Xingfu,Yao, Qingxu,Huo, Yonggang,Chen, Qifan Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.7

As a relatively new radiation imaging method, the cosmic-ray muon scattering imaging technology can be used to prevent nuclear smuggling and is of considerable significance to nuclear safety. Proposed in this paper is a new reconstruction algorithm based on density clustering, aiming to improve inspection quality with better performance. Firstly, this new algorithm is introduced in detail. Then in order to eliminate the inequity of the density threshold caused by the heterogeneity of the muon flux in different positions, a new flux correction method is proposed. Finally, three groups of simulation experiments are carried out with the help of Geant4 toolkit to optimize the algorithm parameters, verify the correction method and test the inspection quality under shielded condition, and compare this algorithm with another common inspection algorithm under different conditions. The results show that this algorithm can effectively identify and locate nuclear material with low misjudging and missing rates even when there is shielding and momentum precision is low, and the threshold correcting method is universally effective for density clustering algorithms.

Numerical study on heterogeneous behavior of fine particle growth

FAN Fengxian,YANG Linjun,Yuan Zhulin,Yan Jinpei,Jo Young Min 한국입자에어로졸학회 2009 Particle and Aerosol Research Vol.5 No.4

PM2.5 is one of critical air pollutants due to its high absorbability of heavy metallic fumes, PAH and bacillary micro organisms. Such a fine particulate matter is often formed through various nucleation processes including condensation. This study attempts to find the nucleation behaviors of PM2.5 arisen from coal power stations using a classical heterogeneous Fletcher’s theory. The numerical simulation by C-language could approximate the nucleation process of PM2.5 from water vapor, of which approach revealed the required energy for embryo formation and embryo size and nucleation rate. As a result of the calculation, it was found that wetting agents could affect the particle nucleation in vapor condensation. In particular, critical contact angle relates closely with the vapor saturation. Particle condensation could be reduced by lowering the angles. The wetting agents aid to decrease the contact angle and surface tensions, thereby may contribute to save the formation energy. Key words : Particle nucleation, Fletcher’s theory, Particle wettability, Numerical simulation

Single-Crystalline Self-Branched Anatase Titania Nanowires for Dye-Sensitized Solar Cells

Zhenquan Li,Huang Yang,Fei Wu,Jianxun Fu,Linjun Wang,Weiguang Yang 대한금속·재료학회 2017 ELECTRONIC MATERIALS LETTERS Vol.13 No.2

The morphology of the anatase titania plays an important role in improving thephotovoltaic performance in dye-sensitized solar cells. In this work, singlecrystallineself-branched anatase TiO2 nanowires have been synthesized byhydrothermal method using TBAH and CTAB as morphology controlling agents. The obtained self-branched TiO2 nanowires dominated by a large percentage of(010) facets. The photovoltaic conversion efficiency (6.37%) of dye-sensitizedsolar cell (DSSC) based on the self-branched TiO2 nanowires shows a significantimprovement (26.6%) compared to that of P25 TiO2 (5.03%). The enhancedperformance of the self-branched TiO2 nanowires-based DSSC is due to heir largepercent of exposed (010) facets which have strong dye adsorption capacity andeffective charge transport of the self-branched 1D nanostructures.

Molecular Beam Epitaxy of Highly Crystalline Monolayer Molybdenum Disulfide on Hexagonal Boron Nitride

Fu, Deyi,Zhao, Xiaoxu,Zhang, Yu-Yang,Li, Linjun,Xu, Hai,Jang, A-Rang,Yoon, Seong In,Song, Peng,Poh, Sock Mui,Ren, Tianhua,Ding, Zijing,Fu, Wei,Shin, Tae Joo,Shin, Hyeon Suk,Pantelides, Sokrates T.,Zho American Chemical Society 2017 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.139 No.27

<P>Atomically thin molybdenum disulfide (MoS2), a direct-band-gap semiconductor, is promising for applications in electronics and optoelectronics, but the scalable synthesis of highly crystalline film remains challenging. Here we report the successful epitaxial growth of a continuous, uniform, highly crystalline monolayer MoS2 film on hexagonal boron nitride (h-BN) by molecular beam epitaxy. Atomic force microscopy and electron microscopy studies reveal that MoS2 grown on h-BN primarily consists of two types of nucleation grains (0 aligned and 60 degrees antialigned domains). By adopting a high growth temperature and ultralow precursor flux, the formation of 60 degrees antialigned grains is largely suppressed. The resulting perfectly aligned grains merge seamlessly into a highly crystalline film. Large-scale monolayer MoS2 film can be grown on a 2 in. h-BN/sapphire wafer, for which surface morphology and Raman mapping confirm good spatial uniformity. Our study represents a significant step in the scalable synthesis of highly crystalline MoS2 films on atomically flat surfaces and paves the way to large-scale applications.</P>