分类： 核科学技术 >> 粒子加速器 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： A C-band RF pulse compressor is in development at SINAP. It comprises of two resonant cavities, two mode convertors and a 3 dB power divider. TE0.1.15 mode is selected for obtaining higher quality factor Q0 of the RF pulse compressor cavities, so that the power gain factor can be 3.2, which is supposed to multiply the RF power from 50 MW to 160 MW. In this paper, we report our work on C-band RF pulse compressor, namely the design simulation and cold test results.
分类： 地球科学 >> 地理学 提交时间： 2023-06-13 合作期刊: 《干旱区科学》
Janisson B de JESUS
Tatiana M KUPLICH
Íkaro D de C BARRETO
Fernando L HILLEBRAND
Cristiano N da ROSA
摘要：The Caatinga biome is an important ecosystem in the semi-arid region of Brazil. It has significantly degraded due to human activities and is currently a region undergoing desertification. Thus, monitoring the variation in the Caatinga biome has become essential for its sustainable development. However, traditional methods for estimating aboveground biomass (AGB) are time-consuming and destructive. Remote sensing, such as optical and radar imaging, can estimate and correlate with vegetation. Nevertheless, radar imaging is still a novelty to be applied in estimating the AGB of this biome, which is an area with little research. Therefore, this study aimed to use Sentinel-1 images to estimate the AGB of the Caatinga biome in Sergipe State (northeastern Brazil) and to verify its influencing factors. Nineteen sample plots (30 m×30 m) were selected, and the stems of individuals with a circumference at breast height (1.3 m above the ground) equal to or greater than 6.0 cm were measured, and the AGB through an allometric equation was estimated. The Sentinel-1 images from 3 different periods (green, intermediate, and dry periods) were used to consider the phenological conditions of the Caatinga biome. All the pre-processing and extraction of attributes (co-polarized VV (vertical transmit and vertical receive), cross-polarized VH (vertical transmit and horizontal receive), and band ratio VH/VV backscatter, radar vegetation index, dual polarization synthetic aperture radar (SAR) vegetation index (DPSVI), entropy (H), and alpha angle (α)) were performed with Sentinel's Application Platform. These attributes were used to estimate the AGB through simple and multiple linear regressions and evaluated by the coefficients of determination (R2), correlation (r), and root mean squared error (RMSE). The results showed that the attributes individually had little ability to estimate the AGB of the Caatinga biome in the three periods. Combined with multiple regression, we found that the intermediate period presented the equation with the best results among the observed and estimated variables (R2=0.73; r=0.85; RMSE=8.33 Mg/hm2), followed by the greenness period (R2=0.72; r=0.85; RMSE=8.40 Mg/hm2). The attributes contributing to these equations were VH/VV, DPSVI, H, α, and co-polarized VV for the green period and cross-polarized VH for the intermediate period. The study showed that the Sentinel-1 images could be used to estimate the AGB of the Caatinga biome in the green and intermediate phenological periods since the SAR attributes highly correlated with the estimated variable (i.e., AGB) through multiple linear equations.
分类： 物理学 >> 核物理学 提交时间： 2024-12-30
Zhang, Mr. Yihao
Huang, Mr. Zhicheng
Wei, Dr. Yelong
Sun, Dr. Li
Cao, Mr. Zexin
Wang, Mr. Chengzhe
feng, Dr. guangyao
Faillace, Dr. Luigi
Alesini, Dr. David
摘要： To implement the linear injector for proposed Jinhua Light Source (JHLS) project, a 1-meter C-band constant gradient (CG) travelling wave (TW) accelerating structure is developed with the aim of to generate a gradient of ≥ 40 MV/m. This C-band structure works at a mode of 3π/4 with a relatively low group velocity varying from 0.016c to 0.009c to increase the accelerating gradient at a given input power. It employs a cell shape with elliptical irises and circular arc tops to reduce the surface electric and magnetic fields and to achieve an average shunt impedance of 94 MΩ/m through optimizations. This results in an accelerating gradient of 40 MV/m with an input power of 29.6 MW, which has an efficiency comparatively higher than those of previously-reported C-band structures. Moreover, a new technique is utilized for the design of couplers, significantly simplifying the whole optimization process and achieves high accuracy. After fabrication, the structure was precisely tuned, results from low-power radiofrequency (RF) measurements and the comparison with simulated values are also presented in this paper.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2025-05-19
摘要： The application of radiofrequency (RF) electron guns operating at cryogenic temperatures can enhance theperformance of a photoinjector. The low emittance and increased brightness of the electron beams resultingfrom the high gradient in the cryogenic photoinjector make it possible to improve the performance of new lightsources. As an upgrading scheme for the Shanghai Soft X-ray Free-Electron Laser (SXFEL), this study exploresa novel photocathode RF gun by introducing the TM02 mode into the cathode cell of a 2.6-cell electron gun,which improves the RF performance, particularly in terms of the monopole field. Furthermore, the optimizedcathode cell with the TM02 mode can reduce the errors resulting from installation and decrease the dark currentwith alternative cathodes. In this study, the beam dynamics in a photoinjector were optimized using a 500 pC,5 ps beam, and its feasibility was examined. This paper presents the entire RF design process, including theadjustment of the RF structure, coupler design, local field, and multipole mode suppression to provide theoreticalguidance for subsequent manufacturing and assembly.
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