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: Conditioning an accelerating structure is important, and its performance is limited by breakdown and vacuum degradation, hence the necessity of finding problem in the conditioning. In order to save time, a judging process built in the firmware layer is applied in this paper. The system using the embedded algorithm in the Field Programmable Gate Array (FPGA) locates the position of breakdown and displays the result in the user interface. Also, the system has the functions of automatic conditioning and interlock protection, which are useful during the conditioning process of an S-band accelerating structure.
分类: 物理学 >> 地球物理学、天文学和天体物理学 提交时间: 2024-01-09 合作期刊: 《Research in Astronomy and Astrophysics》
摘要: HD 222925 is a rare r-process enhanced star in the Milky Way because of its metal abundance ([Fe/H] =−1.46 ± 0.10) and Eu abundance ([Eu/Fe] = 1.32 ± 0.08). Based on the very complete set of elemental abundances of HD 222925, we use the abundance decomposition method to fit the observed abundances of 58 elements in the sample star, which is also the largest number of elemental abundances fitted at the same time for a fixed star. We analyze the astrophysical origins of elements in HD 222925 by its abundance ratios and component ratios. It is found that the light elements and the iron group elements in HD 222925 mainly originate from the primary process of the Type II supernovae (SNe II) with the progenitor mass M > 10 M⊙ and have no contribution from SNe Ia and the first generation of very massive stars. The contribution of the weak r-process to Ga, Ge, and As is superior to that of the other processes, and its contribution decreases linearly with increasing atomic number. The main r-process that is likely derived from a neutron star merger plays a key role in the formation of neutron-capture elements (Z ≥ 38) in HD 222925.
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: In this paper, we propose a two-mode polarizable deflecting structure, as a new concept for bunch measurement and beam control. With two modes of HEM11 and HEM12 operating in the same structure on horizontal and vertical directions, respectively, the operation status can be switched between the two polarization modes. They can be operated simultaneously with two independent input power sources. With two-mode deflecting structure, the bunch distortion caused by the geometric wake-fields in the accelerating structure can be measured by one structure.
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: For developing the X-ray Free Electron Lasers test facility (SXFEL) at Shanghai Institute of Applied Physics, Chinese Academy of Sciences (SINAP), ultra-short bunch is the crucial requirement for excellent lasing performance. It is a big challenge for deflecting cavity to measure the length of ultra-short bunch, and higher deflecting gradient is required for higher measurement resolution. X-band travelling wave deflecting structure has features of higher deflecting voltage and compact structure, which has good performance at ultra-short bunch length measurement. In this paper, a new X-band deflecting structure is designed to operate in HEM11-2/3 mode. For suppressing the polarization of deflecting plane of the HEM11 mode, two symmetrical caves are added on the cavity wall to separate two polarized modes.
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: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present analysis of the spatial density structure for the outer disk from 8$-$14 \,kpc with the LAMOST DR5 13534 OB-type stars and observe similar flaring on north and south sides of the disk implying that the flaring structure is symmetrical about the Galactic plane, for which the scale height at different Galactocentric distance is from 0.14 to 0.5 \,kpc. By using the average slope to characterize the flaring strength we find that the thickness of the OB stellar disk is similar but flaring is slightly stronger compared to the thin disk as traced by red giant branch stars, possibly implying that secular evolution is not the main contributor to the flaring but perturbation scenarios such as interactions with passing dwarf galaxies should be more possible. When comparing the scale height of OB stellar disk of the north and south sides with the gas disk, the former one is slightly thicker than the later one by $\approx$ 33 and 9 \,pc, meaning that one could tentatively use young OB-type stars to trace the gas properties. Meanwhile, we unravel that the radial scale length of the young OB stellar disk is 1.17 $\pm$ 0.05 \,kpc, which is shorter than that of the gas disk, confirming that the gas disk is more extended than stellar disk. What is more, by considering the mid-plane displacements ($Z_{0}$) in our density model we find that almost all of $Z_{0}$ are within 100 \,pc with the increasing trend as Galactocentric distance increases.