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北京大学正在设计β=0.09,频率为162.5 MHz taper型的二分之一波长射频超导谐振腔(HWR腔),这种腔针对高流强质子束(约100mA)和氘束(约50mA)的加速而设计。对于这种超导腔而言机械性能分析是十分重要的,可以通过机械性能分析来估计由于腔体的形变带来的频率偏移。用ANSYS分析了由于液氦压力不稳定造成的麦克风效应以及洛伦兹力造成的腔体失谐,并且对沿腔体轴线方向的调谐进行了分析。模拟结果显示这只腔压力敏感系数为31.1 Hz/kPa,洛伦兹力系数为-0.41Hz/(MV·m~(-1))~2。腔体的调谐范围达到±177kHz,足够补偿腔体可能的频率偏移。腔体的机械性能满足腔体正常运行的要求。 相似文献
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The maximum beam current that can be accelerated in an energy recovery linac (ERL) can be severely limited by the transverse multi-pass beam breakup instability (BBU), especially in future ERL light sources with multi-GeV high energy beam energy and more than 100 mA average current. In this paper, the multi-pass BBU of such a high energy ERL is studied based on the simulation of a 3-GeV ERL light source that is proposed by KEK. This work is expected to provide a reference for future high energy ERL projects. 相似文献
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Peking University is designing a new SRF gun that is composed of a quarter wave resonator (QWR) and an elliptical cavity. Compared to the elliptical cavity, the QWR is sufficiently compact at the same frequency and its electric field is quasi-DC. The RF parameters are determined by optimization of QWR cavity structure and the possible multipacting locations are analyzed by 2D MP simulation. The simulation results show that multipacting is not a critical issue for our optimized cavity structure. 相似文献
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基于超导器的连续波运行的高流强质子/氘束被越来越多的大科学装置所采用。在流强低于10 mA情况下,用于加速低段粒子的超导腔的高阶模影响基本可以忽略,但是对于加速百mA强流的低超导腔,其高阶模损耗情况有待研究。近期北京大学设计并加工了一支=0.09、运行频率162.5 MHz的超导半波长谐振腔,用于研究非相对论低超导半波长谐振腔加速100 mA强流质子束时可能涉及到的关键物理问题。重点研究了这支半波长谐振腔内部高阶模损耗的问题,用时域和频域两种方法分别计算了腔的高阶模损失因子,同时计算了考虑加工误差下腔内发生高阶模共振激发的概率。 相似文献
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Peking University is designing a new SRF gun that is composed of a quarter wave resonator (QWR) and an elliptical cavity. Compared to the elliptical cavity, the QWR is sufficiently compact at the same frequency and its electric field is quasi-DC. The RF parameters are determined by optimization of QWR cavity structure and the possible multipacting locations are analyzed by 2D MP simulation. The simulation results show that multipacting is not a critical issue for our optimized cavity structure. 相似文献
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For the purpose of producing high intensity, multiply charged metal ion beams, the dual hollow cathode ion source for metal ions (DUHOCAMIS) was derived from the hot cathode Penning ion source combined with the hollow cathode sputtering experiments in 2007. To investigate the behavior of this discharge geometry in a stronger magnetic bottle-shaped field, a new test bench for DUHOCAMIS with a high magnetic bottle-shaped field up to 0.6 T has been set up at the Peking University. The experiments with magnetic fields from 0.13 T to 0.52 T have indicated that the discharge behavior is very sensitive to the magnetic flux densities. The slope of discharge curves in a very wide range can be controlled by changing the magnetic field as well as regulated by adjusting the cathode heating power; the production of metallic ions would be much greater than gas ions with the increased magnetic flux density; and the magnetic field has a much higher influence on the DHCD mode than on the PIG mode. 相似文献
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现代光源的发展不断推动着人们从更深层次上理解物质的基本结构和动力学行为。X射线自由电子激光作为最先进的光源,其超高的峰值功率、超短的脉冲长度和优良的相干性,为人们以原子级时空分辨率探测和操控物质中的超快过程提供了可能。目前全世界已有多个X射线自由电子激光装置建成并投入使用,在原子分子物理、化学、生命科学、材料科学等各学科应用中都显示出了重要价值。同时大量的研究工作也集中于继续提高X射线自由电子激光的性能,包括把脉冲持续时间从fs量级进一步缩短至as量级,这将为超快科学的发展带来新突破。以超快脉冲产生为主线,综述了近年来超快X射线自由电子激光产生方案的研究进展,从产生原理、方案特性、最新成果等方面介绍了各类产生方案,总结对比了各方案的优缺点,最后对超快X射线自由电子激光的未来发展方向进行了展望。 相似文献
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Relative enhancement of photoluminescence intensity of passivated silicon nanocrystals in a silicon dioxide matrix 下载免费PDF全文
Photoluminescence (PL) intensity of passivated silicon nanocrystals (Si NCs) embedded in a SiO 2 matrix is compared with that of unpassivated Si NCs. We investigate the relative enhancement of PL intensity (I R ) as a function of annealing temperature and implanted Si ion dose. The I R increases simultaneously with the annealing temperature. This demonstrates an increase in the number of dangling bonds (DBs) with the degree of Si crystallization varying via the annealing temperature. The increase in I R with implanted Si ion dose is also observed. We believe that the near-field interaction between DBs and neighboring Si NCs is an additional factor that reduces the PL efficiency of unpassivated Si NCs. 相似文献
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用^1^4C-加速器质谱法(AMS)研究了香烟中尼古丁的亚硝基衍生物4-(甲基亚硝胺基)-1-(3-吡啶基)-1-丁酮(NNK)与小鼠体内血红蛋白(Hb)的加合作用,给出了加合剂量响应曲线。NNK剂量在0.01~0.1μg/kgb.w.范围内,加合水平基本上是一样的;而在0.1~3.0μg/kgb.w.范围内,加合物数量与NNK剂量之间呈1g/1g表示的线性关系。同时研究发现一次性给药的NNK-Hb加合物在小鼠体内的衰减表现为快、慢两个阶段,前3天内衰减很快,3天后衰减不明显。 相似文献